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How to Structure your Presentation, with Examples

August 3, 2018 - Dom Barnard

For many people the thought of delivering a presentation is a daunting task and brings about a  great deal of nerves . However, if you take some time to understand how effective presentations are structured and then apply this structure to your own presentation, you’ll appear much more confident and relaxed.

Here is our complete guide for structuring your presentation, with examples at the end of the article to demonstrate these points.

Why is structuring a presentation so important?

If you’ve ever sat through a great presentation, you’ll have left feeling either inspired or informed on a given topic. This isn’t because the speaker was the most knowledgeable or motivating person in the world. Instead, it’s because they know how to structure presentations – they have crafted their message in a logical and simple way that has allowed the audience can keep up with them and take away key messages.

Research has supported this, with studies showing that audiences retain structured information  40% more accurately  than unstructured information.

In fact, not only is structuring a presentation important for the benefit of the audience’s understanding, it’s also important for you as the speaker. A good structure helps you remain calm, stay on topic, and avoid any awkward silences.

What will affect your presentation structure?

Generally speaking, there is a natural flow that any decent presentation will follow which we will go into shortly. However, you should be aware that all presentation structures will be different in their own unique way and this will be due to a number of factors, including:

• Whether you need to deliver any demonstrations
• How  knowledgeable the audience  already is on the given subject
• How much interaction you want from the audience
• Any time constraints there are for your talk
• What setting you are in
• Your ability to use any kinds of visual assistance

Before choosing the presentation’s structure answer these questions first:

• What is your presentation’s aim?
• Who are the audience?
• What are the main points your audience should remember afterwards?

When reading the points below, think critically about what things may cause your presentation structure to be slightly different. You can add in certain elements and add more focus to certain moments if that works better for your speech.

What is the typical presentation structure?

This is the usual flow of a presentation, which covers all the vital sections and is a good starting point for yours. It allows your audience to easily follow along and sets out a solid structure you can add your content to.

1. Greet the audience and introduce yourself

Before you start delivering your talk, introduce yourself to the audience and clarify who you are and your relevant expertise. This does not need to be long or incredibly detailed, but will help build an immediate relationship between you and the audience. It gives you the chance to briefly clarify your expertise and why you are worth listening to. This will help establish your ethos so the audience will trust you more and think you’re credible.

Read our tips on  How to Start a Presentation Effectively

2. Introduction

In the introduction you need to explain the subject and purpose of your presentation whilst gaining the audience’s interest and confidence. It’s sometimes helpful to think of your introduction as funnel-shaped to help filter down your topic:

• Introduce your general topic
• Explain your topic area
• State the issues/challenges in this area you will be exploring
• State your presentation’s purpose – this is the basis of your presentation so ensure that you provide a statement explaining how the topic will be treated, for example, “I will argue that…” or maybe you will “compare”, “analyse”, “evaluate”, “describe” etc.
• Provide a statement of what you’re hoping the outcome of the presentation will be, for example, “I’m hoping this will be provide you with…”
• Show a preview of the organisation of your presentation

In this section also explain:

• The length of the talk.
• Signal whether you want audience interaction – some presenters prefer the audience to ask questions throughout whereas others allocate a specific section for this.
• If it applies, inform the audience whether to take notes or whether you will be providing handouts.

The way you structure your introduction can depend on the amount of time you have been given to present: a  sales pitch  may consist of a quick presentation so you may begin with your conclusion and then provide the evidence. Conversely, a speaker presenting their idea for change in the world would be better suited to start with the evidence and then conclude what this means for the audience.

Keep in mind that the main aim of the introduction is to grab the audience’s attention and connect with them.

3. The main body of your talk

The main body of your talk needs to meet the promises you made in the introduction. Depending on the nature of your presentation, clearly segment the different topics you will be discussing, and then work your way through them one at a time – it’s important for everything to be organised logically for the audience to fully understand. There are many different ways to organise your main points, such as, by priority, theme, chronologically etc.

• Main points should be addressed one by one with supporting evidence and examples.
• Before moving on to the next point you should provide a mini-summary.
• Links should be clearly stated between ideas and you must make it clear when you’re moving onto the next point.
• Allow time for people to take relevant notes and stick to the topics you have prepared beforehand rather than straying too far off topic.

When planning your presentation write a list of main points you want to make and ask yourself “What I am telling the audience? What should they understand from this?” refining your answers this way will help you produce clear messages.

4. Conclusion

In presentations the conclusion is frequently underdeveloped and lacks purpose which is a shame as it’s the best place to reinforce your messages. Typically, your presentation has a specific goal – that could be to convert a number of the audience members into customers, lead to a certain number of enquiries to make people knowledgeable on specific key points, or to motivate them towards a shared goal.

Regardless of what that goal is, be sure to summarise your main points and their implications. This clarifies the overall purpose of your talk and reinforces your reason for being there.

Follow these steps:

• Signal that it’s nearly the end of your presentation, for example, “As we wrap up/as we wind down the talk…”
• Restate the topic and purpose of your presentation – “In this speech I wanted to compare…”
• Summarise the main points, including their implications and conclusions
• Indicate what is next/a call to action/a thought-provoking takeaway
• Move on to the last section

5. Thank the audience and invite questions

Conclude your talk by thanking the audience for their time and invite them to  ask any questions  they may have. As mentioned earlier, personal circumstances will affect the structure of your presentation.

Many presenters prefer to make the Q&A session the key part of their talk and try to speed through the main body of the presentation. This is totally fine, but it is still best to focus on delivering some sort of initial presentation to set the tone and topics for discussion in the Q&A.

Other common presentation structures

The above was a description of a basic presentation, here are some more specific presentation layouts:

Demonstration

Use the demonstration structure when you have something useful to show. This is usually used when you want to show how a product works. Steve Jobs frequently used this technique in his presentations.

• Explain why the product is valuable.
• Describe why the product is necessary.
• Explain what problems it can solve for the audience.
• Demonstrate the product  to support what you’ve been saying.
• Make suggestions of other things it can do to make the audience curious.

Problem-solution

This structure is particularly useful in persuading the audience.

• Briefly frame the issue.
• Go into the issue in detail showing why it ‘s such a problem. Use logos and pathos for this – the logical and emotional appeals.
• Provide the solution and explain why this would also help the audience.
• Call to action – something you want the audience to do which is straightforward and pertinent to the solution.

Storytelling

As well as incorporating  stories in your presentation , you can organise your whole presentation as a story. There are lots of different type of story structures you can use – a popular choice is the monomyth – the hero’s journey. In a monomyth, a hero goes on a difficult journey or takes on a challenge – they move from the familiar into the unknown. After facing obstacles and ultimately succeeding the hero returns home, transformed and with newfound wisdom.

Storytelling for Business Success  webinar , where well-know storyteller Javier Bernad shares strategies for crafting compelling narratives.

Another popular choice for using a story to structure your presentation is in media ras (in the middle of thing). In this type of story you launch right into the action by providing a snippet/teaser of what’s happening and then you start explaining the events that led to that event. This is engaging because you’re starting your story at the most exciting part which will make the audience curious – they’ll want to know how you got there.

• Great storytelling: Examples from Alibaba Founder, Jack Ma

Remaining method

The remaining method structure is good for situations where you’re presenting your perspective on a controversial topic which has split people’s opinions.

• Go into the issue in detail showing why it’s such a problem – use logos and pathos.
• Rebut your opponents’ solutions  – explain why their solutions could be useful because the audience will see this as fair and will therefore think you’re trustworthy, and then explain why you think these solutions are not valid.
• After you’ve presented all the alternatives provide your solution, the remaining solution. This is very persuasive because it looks like the winning idea, especially with the audience believing that you’re fair and trustworthy.

Transitions

When delivering presentations it’s important for your words and ideas to flow so your audience can understand how everything links together and why it’s all relevant. This can be done  using speech transitions  which are words and phrases that allow you to smoothly move from one point to another so that your speech flows and your presentation is unified.

Transitions can be one word, a phrase or a full sentence – there are many different forms, here are some examples:

Moving from the introduction to the first point

Signify to the audience that you will now begin discussing the first main point:

• Now that you’re aware of the overview, let’s begin with…
• First, let’s begin with…
• I will first cover…
• My first point covers…
• To get started, let’s look at…

Shifting between similar points

Move from one point to a similar one:

• In the same way…
• Likewise…
• Equally…
• This is similar to…
• Similarly…

Internal summaries

Internal summarising consists of summarising before moving on to the next point. You must inform the audience:

• What part of the presentation you covered – “In the first part of this speech we’ve covered…”
• What the key points were – “Precisely how…”
• How this links in with the overall presentation – “So that’s the context…”
• What you’re moving on to – “Now I’d like to move on to the second part of presentation which looks at…”

Physical movement

You can move your body and your standing location when you transition to another point. The audience find it easier to follow your presentation and movement will increase their interest.

A common technique for incorporating movement into your presentation is to:

• Start your introduction by standing in the centre of the stage.
• For your first point you stand on the left side of the stage.
• You discuss your second point from the centre again.
• You stand on the right side of the stage for your third point.
• The conclusion occurs in the centre.

Key slides for your presentation

Slides are a useful tool for most presentations: they can greatly assist in the delivery of your message and help the audience follow along with what you are saying. Key slides include:

• An intro slide outlining your ideas
• A  summary slide  with core points to remember
• High quality image slides to supplement what you are saying

There are some presenters who choose not to use slides at all, though this is more of a rarity. Slides can be a powerful tool if used properly, but the problem is that many fail to do just that. Here are some golden rules to follow when using slides in a presentation:

• Don’t over fill them  – your slides are there to assist your speech, rather than be the focal point. They should have as little information as possible, to avoid distracting people from your talk.
• A picture says a thousand words  – instead of filling a slide with text, instead, focus on one or two images or diagrams to help support and explain the point you are discussing at that time.
• Make them readable  – depending on the size of your audience, some may not be able to see small text or images, so make everything large enough to fill the space.
• Don’t rush through slides  – give the audience enough time to digest each slide.

Guy Kawasaki, an entrepreneur and author, suggests that slideshows should follow a  10-20-30 rule :

• There should be a maximum of 10 slides – people rarely remember more than one concept afterwards so there’s no point overwhelming them with unnecessary information.
• The presentation should last no longer than 20 minutes as this will leave time for questions and discussion.
• The font size should be a minimum of 30pt because the audience reads faster than you talk so less information on the slides means that there is less chance of the audience being distracted.

Here are some additional resources for slide design:

• 7 design tips for effective, beautiful PowerPoint presentations
• 11 design tips for beautiful presentations
• 10 tips on how to make slides that communicate your idea

Group Presentations

Group presentations are structured in the same way as presentations with one speaker but usually require more rehearsal and practices.  Clean transitioning between speakers  is very important in producing a presentation that flows well. One way of doing this consists of:

• Briefly recap on what you covered in your section: “So that was a brief introduction on what health anxiety is and how it can affect somebody”
• Introduce the next speaker in the team and explain what they will discuss: “Now Elnaz will talk about the prevalence of health anxiety.”
• Then end by looking at the next speaker, gesturing towards them and saying their name: “Elnaz”.
• The next speaker should acknowledge this with a quick: “Thank you Joe.”

From this example you can see how the different sections of the presentations link which makes it easier for the audience to follow and remain engaged.

Example of great presentation structure and delivery

Having examples of great presentations will help inspire your own structures, here are a few such examples, each unique and inspiring in their own way.

How Google Works – by Eric Schmidt

This presentation by ex-Google CEO  Eric Schmidt  demonstrates some of the most important lessons he and his team have learnt with regards to working with some of the most talented individuals they hired. The simplistic yet cohesive style of all of the slides is something to be appreciated. They are relatively straightforward, yet add power and clarity to the narrative of the presentation.

Start with why – by Simon Sinek

Since being released in 2009, this presentation has been viewed almost four million times all around the world. The message itself is very powerful, however, it’s not an idea that hasn’t been heard before. What makes this presentation so powerful is the simple message he is getting across, and the straightforward and understandable manner in which he delivers it. Also note that he doesn’t use any slides, just a whiteboard where he creates a simple diagram of his opinion.

The Wisdom of a Third Grade Dropout – by Rick Rigsby

Here’s an example of a presentation given by a relatively unknown individual looking to inspire the next generation of graduates. Rick’s presentation is unique in many ways compared to the two above. Notably, he uses no visual prompts and includes a great deal of humour.

However, what is similar is the structure he uses. He first introduces his message that the wisest man he knew was a third-grade dropout. He then proceeds to deliver his main body of argument, and in the end, concludes with his message. This powerful speech keeps the viewer engaged throughout, through a mixture of heart-warming sentiment, powerful life advice and engaging humour.

As you can see from the examples above, and as it has been expressed throughout, a great presentation structure means analysing the core message of your presentation. Decide on a key message you want to impart the audience with, and then craft an engaging way of delivering it.

By preparing a solid structure, and  practising your talk  beforehand, you can walk into the presentation with confidence and deliver a meaningful message to an interested audience.

It’s important for a presentation to be well-structured so it can have the most impact on your audience. An unstructured presentation can be difficult to follow and even frustrating to listen to. The heart of your speech are your main points supported by evidence and your transitions should assist the movement between points and clarify how everything is linked.

Research suggests that the audience remember the first and last things you say so your introduction and conclusion are vital for reinforcing your points. Essentially, ensure you spend the time structuring your presentation and addressing all of the sections.

Presentation Structures: Everything You Need to Organize Your Talk

Hrideep barot.

• Presentation , Public Speaking , Speech Writing

A presentation structure includes an introduction, context, main body, conclusion, and scope for questions. Depending on the type of presentation you’re doing, this format can change. The article discusses various considerations for each section of a presentation structure.

For presentations to be understood and create a good impression, they can’t be haphazard. It has to have some sort of pre-planned presentation structure that is both logical and simple enough. Depending on the type of presentation you’re doing, there are likely some basic frameworks available that people tend to follow. Before we delve into the format, let’s consider key points to consider when planning a presentation.

How do you structure and plan a presentation?

We plan a presentation by considering the type of presentation, who our audience is, ideating the purpose, and formulating subtopics through research.

Consider the type of presentation

This leads to understanding the ideal flow to convey your content best. For instance, for persuasive presentations, you could use creative ways to convey what is best about a product, such as starting with a story about how it has helped many people achieve something.

On the other hand, for a progress presentation at your workplace, you might have conventions about what is expected, which must be followed precisely.

A few other types of presentations include:

• Informative presentations
• Instructive presentations
• Motivational presentations
• Analytical presentations

You might also want to consider if you want audience interaction and put that into the structure accordingly. While some allow questions mid-presentation for smaller audiences, it is typically left towards the end.

Consider your audience’s knowledge level and interests

This will determine if you can assume a particular knowledge base and not include it in your presentation structure or if you have to start off with basics and build up on that.

For instance, if you’re teaching 1st-year students about something, you might start with basics. But for graduates, a similar format would be unnecessary as they might have already learned about it.

Similarly, if your purpose is to deliver something entertaining, knowing about the interests and values of your audience helps a ton.

The most simple way is demographics. It’s typically quite easy to find out the expected age group, gender, etc of the audience. This information can help you have a basic idea of the sort of experiences they go through, which helps formulate an understanding.

Consider the purpose of your presentation

While this may seem obvious, many of us lose track of the main purpose and spend too much time on remotely related content. This diverts attention from the topic and might even cause boredom.

For example, if you’re advocating for some social action, it would be beneficial to stay on the topic itself, like the pros, cons, what can be done practically, etc. Instead, if the presenters spend more time criticizing others, the presentation will fall short of its purpose.

Few other examples of different purposes your presentation could have:

• Entertainment
• Providing information
• Telling your story
• Proposing ideas
• Discussing future plans for the company

Research your topic and start noting down the subtopics

Skip this if you already know exactly what needs to be a part of your presentation, and plan to include just that. While looking up your topic, you’ll discover the various sub-topics within that field. After you start noting them down, you can organize later what comes under which to build a structure.

Here is a guide on short presentations that you might be interested in.

So with these three considerations and subtopics in mind, we’re good to go over to decide our final structure.

What is the best presentation form?

The best presentation format is one that includes the introduction, context, main body, conclusion, and questions.

Here, we will discuss a template or structure for a typical presentation.

Introduction

• Greet the audience and introduce yourself, e.g., what you do and why you’re here
• The purpose of your presentation
• The flow or outline gives a sense of what they can expect
• Depending on the topic and audience, you might have to provide more or less context about your topic
• This could include a brief history, terminologies, the current market status, the current status of the field, etc.
• Includes the full depth of the primary purpose of the presentation
• All major chunks of data, including examples, evidence like research studies, etc, are included here
• Care needs to be taken at times to ensure that your introduction and context are not taking up so much time that the main body isn’t receiving enough attention. Ever wonder if a presentation can be too short? Check out this article .
• Bring emphasis to the main takeaways
• Thank your audience if they have been a good one
• Take questions and encourage healthy discussion
• End with sharing ways they can address their questions later

To make sure that the structure works out, it is important that you practice your presentation. This will also tell you if you’re falling within the time constraints. Here is a guide on how you can go about practicing your presentation.

5 Ways to Structure Your Presentation

The five ways include ordered, problem-solution, comparative, storytelling, and demonstrating structures.

1. Ordered Structure

The presentation follows a logical sequence starting with an introduction, main points, and then conclusions. This is what this article has focused on, as it’s the most straightforward method and tends to be very clear for the audience. However, for presentations that do not follow a clear progression, this may not be useful.

2. Problem-Solution Structure

This is useful when persuading the audience. You explain the problem (+ its importance and impact) and then provide a solution that motivates the audience to take it. This could be in the form of a product, a particular method of communication, some technical thing, etc. There should be a decent amount of time spent on the benefits of the solution as well as the exact “How?” to implement it to make the audience convinced. It helps to address any questions or barriers you expect them to have during the speech itself.

3. Comparative Method

This is useful when you want to highlight the benefits of something over alternatives . It is ideal to first fully address the alternatives by talking about their benefits and limitations. Then you lastly talk about the solution that you possess that effectively addresses the other limitations or is in some way a better choice than others, based on your arguments.

Alternatively, if you do not want to highlight the benefits of something particular and just form a comparison that demonstrates the pros and cons of different subjects in an unbiased manner, this technique is still used. For instance, how the main benefit of a product is practically useful for the consumer in comparison to the main benefit of another product can be discussed.

4. Storytelling Structure

This is useful when your goal is just to tell a story. This could be to explain the context or history of a company. It could also serve to talk about yourself and how you got there. A story will typically have an introduction, a complicating factor that introduces some challenges, and then an ending that highlights the importance of some action or belief. 

You may also go in a timewise order when explaining a story. This might take away from the thrill but is useful nonetheless when it is required for the audience to properly understand what is being conveyed. Storytelling can be done in various ways, so feel free to find your own structure.

5. Demonstration Structure

This is useful when demonstrating products or services . The benefits of the product/service are highlighted and it is demonstrated showing those capabilities. The goal should be on persuading the audience that it is useful to them for their needs.

How to structure a scientific presentation?

Structuring a scientific presentation typically includes an introduction, methods, results, and discussion.

This typically follows the below format, but depending on the university/conference guidelines, you’ll have to adjust accordingly. The rest of the sub-topics revolves around these sections.

• Introduction/Background 
• Literature review (if applicable)
• Acknowledgments (often optional)

After this, time is given to take questions.

How do you structure a presentation script?

The presentation never includes the full extent of the information. It’s just a concise version of what you’re speaking that adds as a visual aid at times while also highlighting major points. 

The script is where the major content lies. The structure remains the same, but the content is greater in depth .

Sample Presentation Script

To make it easier for you to understand how you can structure your presentation script, here is a sample script for a presentation on the topic: Importance of Public Speaking.

This follows the same flow introduced earlier- introduction, context, main body, conclusion, and questions.

Title: Importance of Public Speaking

Slide 1: Why is Public Speaking Important?

Greetings, ladies, and gentlemen. Today, I will be exploring the importance of public speaking. My name is John, and I’m thrilled to discuss with you how improving our public speaking abilities may make a significant difference in our quality of life in the personal, social, and professional domains.

Slide 2: Introduction

Public speaking involves persuading an audience with a well-organized message. It is an essential part of our daily lives. We use it when we make conversation in social groups as well as when we address enormous crowds at social gatherings. It is a highly multifaceted and effective tool.

I will start off by giving some information about the context, moving on to its benefits, which is the main crux of our presentation, and then we will spend some time concluding.

Slide 3: Context

Effective communication is essential in our globally interconnected society. Speaking in front of an audience enables us to express our views and thoughts clearly and firmly. It facilitates the development of solid bonds and influences others, and acts as a catalyst for constructive change. Public speaking may open doors of opportunity and propel achievement for anyone, whether they are a student, professional, or member of the community.

Slide 4: Personal Development

Public speaking increases self-esteem and confidence, which are quite rudimentary to our self-efficacy. Effective communication skills help us to be more assertive and feel more in control of our lives. Research suggests that having an internal locus of control (i.e., feeling in control) leads to better outcomes in our personal lives as well as greater mental health.  As we organize our ideas and arguments through public speaking, it improves critical thinking and organizational abilities. Furthermore, as we interact with others during talks and Q&A sessions, public speaking also enhances our listening abilities.

Slide 5: Professional Advancement

The ability to speak in front of an audience effectively is highly essential in most workplaces.

You ask Why? Well, it is because we are better able to communicate our qualifications and worth to potential employers, which enhances our performance in job interviews. Secondly, our influence within organizations grows when we can make a strong case for our points in meetings and conferences.

Next, for leadership positions, where success depends on inspiring and motivating others, public speaking is critical. And in general, you’ll need public speaking in any meeting or any talk you would typically deliver in front of a bunch of people. 

Slide 6: Conclusion

Public speaking is a sought-after, multifaceted, and handy skill across many settings. It gives us the ability to inspire others, tell our stories, and make a lasting impression. Strong public speaking abilities help us communicate clearly and lead with influence in many facets of our lives.

Slide 7: Questions

I appreciate everyone here for being a great audience and cooperating wonderfully throughout the presentation. Now I will be taking any questions you all have. Feel free to discuss this now or reach out to me after the session is over.

Slide 8: Thank you

I want to thank you all for being here today.

I hope that the presentation did well to emphasize the importance of public speaking and perhaps motivated at least some of you to work on improving your abilities. We will end here.

[End of presentation]

Here are some tips for delivering an effective presentation.

We considered a few key points for presentation structure and the typical format that can be followed. We also covered five ways you can structure your presentation and the format for a scientific presentation. Lastly, we covered a sample script for presentations.

Public speaking coaching is a great way to increase your skills and get better at presentations as well.

Enroll in our transformative 1:1 Coaching Program

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How To Make a Good Presentation [A Complete Guide]

By Krystle Wong , Jul 20, 2023

A top-notch presentation possesses the power to drive action. From winning stakeholders over and conveying a powerful message to securing funding — your secret weapon lies within the realm of creating an effective presentation .  

Being an excellent presenter isn’t confined to the boardroom. Whether you’re delivering a presentation at work, pursuing an academic career, involved in a non-profit organization or even a student, nailing the presentation game is a game-changer.

In this article, I’ll cover the top qualities of compelling presentations and walk you through a step-by-step guide on how to give a good presentation. Here’s a little tip to kick things off: for a headstart, check out Venngage’s collection of free presentation templates . They are fully customizable, and the best part is you don’t need professional design skills to make them shine!

These valuable presentation tips cater to individuals from diverse professional backgrounds, encompassing business professionals, sales and marketing teams, educators, trainers, students, researchers, non-profit organizations, public speakers and presenters. 

No matter your field or role, these tips for presenting will equip you with the skills to deliver effective presentations that leave a lasting impression on any audience.

Click to jump ahead:

What are the 10 qualities of a good presentation?

Step-by-step guide on how to prepare an effective presentation, 9 effective techniques to deliver a memorable presentation, faqs on making a good presentation, how to create a presentation with venngage in 5 steps.

When it comes to giving an engaging presentation that leaves a lasting impression, it’s not just about the content — it’s also about how you deliver it. Wondering what makes a good presentation? Well, the best presentations I’ve seen consistently exhibit these 10 qualities:

1. Clear structure

No one likes to get lost in a maze of information. Organize your thoughts into a logical flow, complete with an introduction, main points and a solid conclusion. A structured presentation helps your audience follow along effortlessly, leaving them with a sense of satisfaction at the end.

Regardless of your presentation style , a quality presentation starts with a clear roadmap. Browse through Venngage’s template library and select a presentation template that aligns with your content and presentation goals. Here’s a good presentation example template with a logical layout that includes sections for the introduction, main points, supporting information and a conclusion: 

2. Engaging opening

Hook your audience right from the start with an attention-grabbing statement, a fascinating question or maybe even a captivating anecdote. Set the stage for a killer presentation!

The opening moments of your presentation hold immense power – check out these 15 ways to start a presentation to set the stage and captivate your audience.

3. Relevant content

Make sure your content aligns with their interests and needs. Your audience is there for a reason, and that’s to get valuable insights. Avoid fluff and get straight to the point, your audience will be genuinely excited.

4. Effective visual aids

Picture this: a slide with walls of text and tiny charts, yawn! Visual aids should be just that—aiding your presentation. Opt for clear and visually appealing slides, engaging images and informative charts that add value and help reinforce your message.

With Venngage, visualizing data takes no effort at all. You can import data from CSV or Google Sheets seamlessly and create stunning charts, graphs and icon stories effortlessly to showcase your data in a captivating and impactful way.

5. Clear and concise communication

Keep your language simple, and avoid jargon or complicated terms. Communicate your ideas clearly, so your audience can easily grasp and retain the information being conveyed. This can prevent confusion and enhance the overall effectiveness of the message. 

6. Engaging delivery

Spice up your presentation with a sprinkle of enthusiasm! Maintain eye contact, use expressive gestures and vary your tone of voice to keep your audience glued to the edge of their seats. A touch of charisma goes a long way!

7. Interaction and audience engagement

Turn your presentation into an interactive experience — encourage questions, foster discussions and maybe even throw in a fun activity. Engaged audiences are more likely to remember and embrace your message.

Transform your slides into an interactive presentation with Venngage’s dynamic features like pop-ups, clickable icons and animated elements. Engage your audience with interactive content that lets them explore and interact with your presentation for a truly immersive experience.

8. Effective storytelling

Who doesn’t love a good story? Weaving relevant anecdotes, case studies or even a personal story into your presentation can captivate your audience and create a lasting impact. Stories build connections and make your message memorable.

A great presentation background is also essential as it sets the tone, creates visual interest and reinforces your message. Enhance the overall aesthetics of your presentation with these 15 presentation background examples and captivate your audience’s attention.

9. Well-timed pacing

Pace your presentation thoughtfully with well-designed presentation slides, neither rushing through nor dragging it out. Respect your audience’s time and ensure you cover all the essential points without losing their interest.

10. Strong conclusion

Last impressions linger! Summarize your main points and leave your audience with a clear takeaway. End your presentation with a bang , a call to action or an inspiring thought that resonates long after the conclusion.

In-person presentations aside, acing a virtual presentation is of paramount importance in today’s digital world. Check out this guide to learn how you can adapt your in-person presentations into virtual presentations . 

Preparing an effective presentation starts with laying a strong foundation that goes beyond just creating slides and notes. One of the quickest and best ways to make a presentation would be with the help of a good presentation software . 

Otherwise, let me walk you to how to prepare for a presentation step by step and unlock the secrets of crafting a professional presentation that sets you apart.

1. Understand the audience and their needs

Before you dive into preparing your masterpiece, take a moment to get to know your target audience. Tailor your presentation to meet their needs and expectations , and you’ll have them hooked from the start!

2. Conduct thorough research on the topic

Time to hit the books (or the internet)! Don’t skimp on the research with your presentation materials — dive deep into the subject matter and gather valuable insights . The more you know, the more confident you’ll feel in delivering your presentation.

3. Organize the content with a clear structure

No one wants to stumble through a chaotic mess of information. Outline your presentation with a clear and logical flow. Start with a captivating introduction, follow up with main points that build on each other and wrap it up with a powerful conclusion that leaves a lasting impression.

Delivering an effective business presentation hinges on captivating your audience, and Venngage’s professionally designed business presentation templates are tailor-made for this purpose. With thoughtfully structured layouts, these templates enhance your message’s clarity and coherence, ensuring a memorable and engaging experience for your audience members.

Don’t want to build your presentation layout from scratch? pick from these 5 foolproof presentation layout ideas that won’t go wrong. 

4. Develop visually appealing and supportive visual aids

Spice up your presentation with eye-catching visuals! Create slides that complement your message, not overshadow it. Remember, a picture is worth a thousand words, but that doesn’t mean you need to overload your slides with text.

Well-chosen designs create a cohesive and professional look, capturing your audience’s attention and enhancing the overall effectiveness of your message. Here’s a list of carefully curated PowerPoint presentation templates and great background graphics that will significantly influence the visual appeal and engagement of your presentation.

5. Practice, practice and practice

Practice makes perfect — rehearse your presentation and arrive early to your presentation to help overcome stage fright. Familiarity with your material will boost your presentation skills and help you handle curveballs with ease.

6. Seek feedback and make necessary adjustments

Don’t be afraid to ask for help and seek feedback from friends and colleagues. Constructive criticism can help you identify blind spots and fine-tune your presentation to perfection.

With Venngage’s real-time collaboration feature , receiving feedback and editing your presentation is a seamless process. Group members can access and work on the presentation simultaneously and edit content side by side in real-time. Changes will be reflected immediately to the entire team, promoting seamless teamwork.

7. Prepare for potential technical or logistical issues

Prepare for the unexpected by checking your equipment, internet connection and any other potential hiccups. If you’re worried that you’ll miss out on any important points, you could always have note cards prepared. Remember to remain focused and rehearse potential answers to anticipated questions.

8. Fine-tune and polish your presentation

As the big day approaches, give your presentation one last shine. Review your talking points, practice how to present a presentation and make any final tweaks. Deep breaths — you’re on the brink of delivering a successful presentation!

In competitive environments, persuasive presentations set individuals and organizations apart. To brush up on your presentation skills, read these guides on how to make a persuasive presentation and tips to presenting effectively . 

Whether you’re an experienced presenter or a novice, the right techniques will let your presentation skills soar to new heights!

From public speaking hacks to interactive elements and storytelling prowess, these 9 effective presentation techniques will empower you to leave a lasting impression on your audience and make your presentations unforgettable.

1. Confidence and positive body language

Positive body language instantly captivates your audience, making them believe in your message as much as you do. Strengthen your stage presence and own that stage like it’s your second home! Stand tall, shoulders back and exude confidence. 

2. Eye contact with the audience

Break down that invisible barrier and connect with your audience through their eyes. Maintaining eye contact when giving a presentation builds trust and shows that you’re present and engaged with them.

3. Effective use of hand gestures and movement

A little movement goes a long way! Emphasize key points with purposeful gestures and don’t be afraid to walk around the stage. Your energy will be contagious!

4. Utilize storytelling techniques

Weave the magic of storytelling into your presentation. Share relatable anecdotes, inspiring success stories or even personal experiences that tug at the heartstrings of your audience. Adjust your pitch, pace and volume to match the emotions and intensity of the story. Varying your speaking voice adds depth and enhances your stage presence.

5. Incorporate multimedia elements

Spice up your presentation with a dash of visual pizzazz! Use slides, images and video clips to add depth and clarity to your message. Just remember, less is more—don’t overwhelm them with information overload. 

Turn your presentations into an interactive party! Involve your audience with questions, polls or group activities. When they actively participate, they become invested in your presentation’s success. Bring your design to life with animated elements. Venngage allows you to apply animations to icons, images and text to create dynamic and engaging visual content.

6. Utilize humor strategically

Laughter is the best medicine—and a fantastic presentation enhancer! A well-placed joke or lighthearted moment can break the ice and create a warm atmosphere , making your audience more receptive to your message.

7. Practice active listening and respond to feedback

Be attentive to your audience’s reactions and feedback. If they have questions or concerns, address them with genuine interest and respect. Your responsiveness builds rapport and shows that you genuinely care about their experience.

8. Apply the 10-20-30 rule

Apply the 10-20-30 presentation rule and keep it short, sweet and impactful! Stick to ten slides, deliver your presentation within 20 minutes and use a 30-point font to ensure clarity and focus. Less is more, and your audience will thank you for it!

9. Implement the 5-5-5 rule

Simplicity is key. Limit each slide to five bullet points, with only five words per bullet point and allow each slide to remain visible for about five seconds. This rule keeps your presentation concise and prevents information overload.

Simple presentations are more engaging because they are easier to follow. Summarize your presentations and keep them simple with Venngage’s gallery of simple presentation templates and ensure that your message is delivered effectively across your audience.

1. How to start a presentation?

To kick off your presentation effectively, begin with an attention-grabbing statement or a powerful quote. Introduce yourself, establish credibility and clearly state the purpose and relevance of your presentation.

2. How to end a presentation?

For a strong conclusion, summarize your talking points and key takeaways. End with a compelling call to action or a thought-provoking question and remember to thank your audience and invite any final questions or interactions.

3. How to make a presentation interactive?

To make your presentation interactive, encourage questions and discussion throughout your talk. Utilize multimedia elements like videos or images and consider including polls, quizzes or group activities to actively involve your audience.

In need of inspiration for your next presentation? I’ve got your back! Pick from these 120+ presentation ideas, topics and examples to get started. 

Creating a stunning presentation with Venngage is a breeze with our user-friendly drag-and-drop editor and professionally designed templates for all your communication needs. 

Here’s how to make a presentation in just 5 simple steps with the help of Venngage:

Step 1: Sign up for Venngage for free using your email, Gmail or Facebook account or simply log in to access your account. 

Step 2: Pick a design from our selection of free presentation templates (they’re all created by our expert in-house designers).

Step 3: Make the template your own by customizing it to fit your content and branding. With Venngage’s intuitive drag-and-drop editor, you can easily modify text, change colors and adjust the layout to create a unique and eye-catching design.

Step 4: Elevate your presentation by incorporating captivating visuals. You can upload your images or choose from Venngage’s vast library of high-quality photos, icons and illustrations. 

Step 5: Upgrade to a premium or business account to export your presentation in PDF and print it for in-person presentations or share it digitally for free!

By following these five simple steps, you’ll have a professionally designed and visually engaging presentation ready in no time. With Venngage’s user-friendly platform, your presentation is sure to make a lasting impression. So, let your creativity flow and get ready to shine in your next presentation!

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• an informative
• an entertaining
• an inspiring
• or a persuasive presentation?

Typical Presentation Structure

The basic structure of a presentation is actually always the same and should consist of:

Introduction

Make sure that the structure of your presentation is not too complicated. The simpler it is, the better the audience can follow.

Personal Introduction

It is best to start your presentation by briefly introducing yourself which helps to build a connection with your audience right away.

Introduce the topic

Then introduce the topic, state the purpose of the presentation and provide a brief outline of the main points you will be addressing.

Mention the length

In the introduction, mention the approximate length of the talk and then also make sure you stick to it.

The introduction should be no longer than two slides and provide a good overview of the topic.

Icebreaker Polls

According to studies, people in the audience only have an average attention span of 10 minutes, which is why it is important to increase their attention right at the beginning and to arouse the audience's interest. You could make a good start with a few icebreaker polls for example. They lighten the mood right at the beginning and you can secure your audience's attention from the start.

For example, you could use SlideLizard to have all the answers at a glance and share them with your audience. In addition, the audience can try out how the polls work and already know how it works if you include more polls in the main part.

Get to know your audience

As mentioned earlier, it is always useful to think about who your audience actually is. Ask them questions at the beginning about how well they already know the topic of your presentation. Use SlideLizard for this so that you have a clear overview about the answers. You can use both single- and multiple-choice questions or also open questions and display their results as a WordCloud in your presentation, for example.

Include a quote

To make the beginning (or the end) of your presentation more exciting, it is always a good idea to include a quote. We have selected some powerful quotes for PowerPoint presentations for you.

Present your topic

The main part of a presentation should explain the topic well, state facts, justify them and give examples. Keep all the promises you made earlier in the introduction.

Length and Structure

The main part should make up about 70% of the presentation and also include a clear structure. Explain your ideas in detail and build them up logically. It should be organized chronologically, by priority or by topic. There should be a smooth transition between the individual issues. However, it is also important to use phrases that make it clear that a new topic is starting. We have listed some useful phrases for presentations here.

Visualize data and statistics and show pictures to underline facts. If you are still looking for good images, we have selected 5 sources of free images for you here.

Focus on the essentials

Focus on what is most important and summarize a bit. You don't have to say everything about a topic because your audience won’t remember everything either. Avoid complicated sentence structure, because if the audience does not understand something, they will not be able to read it again.

Make your presentation interactive

Make your presentation interactive to keep the attention of your audience. Use SlideLizard to include polls in your presentation, where your audience can vote directly from their smartphone and discuss the answers as soon as you received all votes. Here you can also find more tips for increasing audience engagement.

Repeat the main points

The conclusion should contain a summary of the most important key points. Repeat the main points you have made, summarize what the audience should have learned and explain how the new information can help in the future.

Include a Q&A part

Include a Q&A part at the end to make sure you don't leave any questions open. It's a good idea to use tools like SlideLizard for it. Your audience can ask anonymous questions and if there is not enough time, you can give them the answers afterwards. You can read more about the right way to do a question slide in PowerPoint here.

Get Feedback

It is also important to get feedback on your presentation at the end to keep improving. With SlideLizard you can ask your audience for anonymous feedback through star ratings, number ratings or open texts directly after your presentation. You can then export the responses and analyse them later in Excel.

Presentation style

Depending on the type of presentation you give, the structure will always be slightly different. We have selected a few different presentation styles and their structure for you.

Short Presentation

If you are one of many presenters on the day, you will only have a very limited time to present your idea and to convince your audience. It is very important to stand out with your presentation.

So you need to summarize your ideas as briefly as possible and probably should not need more than 3-5 slides.

Problem Solving Presentation

Start your presentation by explaining a problem and giving a short overview of it.

Then go into the problem a little more, providing both intellectual and emotional arguments for the seriousness of the problem. You should spend about the first 25% of your presentation on the problem.

After that, you should spend about 50% of your presentation proposing a solution and explaining it in detail.

In the last 25%, describe what benefits this solution will bring to your audience and ask them to take a simple but relevant action that relates to the problem being discussed.

Tell a Story

A great way to build an emotional connection with the audience is to structure a presentation like a story.

In the introduction, introduce a character who has to deal with a conflict. In the main part, tell how he tries to solve his problem but fails again and again. In the end, he manages to find a solution and wins.

Stories have the power to win customers, align colleagues and motivate employees. They’re the most compelling platform we have for managing imaginations. - Nancy Duarte / HBR Guide to Persuasive Presentations

Make a demonstration

Use the demonstration structure to show how a product works. First talk about a need or a problem that has to be solved.

Then explain how the product will help solve the problem and try to convince your audience of the need for your product.

Spend the end clarifying where and when the product can be purchased.

Chronological structure

When you have something historical to tell, it is always good to use a chronological structure. You always have to ask yourself what happens next.

To make it more interesting and exciting, it is a good idea to start by telling the end of something and after that you explain how you got there. This way you make the audience curious and you can gain their attention faster.

Nancy Duarte TED Talk

Nancy Duarte is a speaker and presentation design expert. She gives speeches all over the world, trying to improve the power of public presentations.

In her famous TED Talk "The Secret Structure of Great Talks" she dissects famous speeches such as Steve Jobs' iPhone launch speech and Martin Luther King's "I have a dream" speech. In doing so, she found out that each presentation is made up of 4 parts:

• What could be
• A moment to remember
• Promise of “New Bliss”

Related articles

About the author.

Helena Reitinger

Helena supports the SlideLizard team in marketing and design. She loves to express her creativity in texts and graphics.

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Process questions are similar to recall questions but they need some deeper thoughts and maybe also analysis.

An e-lecture is a lecture that is held online. Many schools and universities offer e-lectures as technical opportunities improve.

Internal Communication

Internal communication is particularly important for corporate communication. It communicates important information from leadership to staff so that they can do their jobs in the best possible way and work processes run well.

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Home Blog Business Presentation Structure Guidelines for Effective Communication

Presentation Structure Guidelines for Effective Communication

In the business world, a presentation is so much more than just a bunch of slides or points—it’s a golden opportunity. It can sway decisions, propel change, or bring people together. How you structure your presentation is absolutely critical in getting your ideas across clearly and compellingly. 

When you’ve got a structured presentation just right, it’s like you’re taking your audience by the hand and guiding them through your thoughts, making sure they pick up all the important bits along the way. Moreover, it speaks of your degree of professionalism and how much knowledge you bear on the topic in question. 

Therefore, nailing your presentation structure isn’t just helpful; it’s downright necessary to get the results you’re after. Whether you’re pitching a new concept to the investors, sharing the latest findings with your team, or taking the stage at a conference, how you lay out your content becomes the language you use to interact with your audience. Get to know all that’s required to create a powerful presentation structure that will guarantee success in business meetings, academic dissertations, or motivational talks .

Table of Contents

What is a Presentation Structure

Introduction, techniques to structure your presentation, common mistakes to avoid when designing a presentation structure, final words.

Let’s compare a presentation structure to a business plan . Just as a business plan is essential for guiding a company’s strategy and ensuring all aspects of the business are aligned toward common goals, a presentation structure is crucial for organizing the content and delivery of your talk. 

The presentation structure lays out a clear and logical sequence of information, akin to the sections of a business plan that outline the company’s mission , market analysis , and financial projections. This clear sequence ensures that your audience can easily follow and understand your message, maximizing the impact your speech can deliver and influencing your target audience. 

Key Elements of a Presentation Structure

The easiest way to study a presentation structure is to subdivide it into sections. Basically, every presentation has a structure that follows this formula: Introduction > Body > Conclusion.

The introduction is the first section of the presentation and sets the tone for the rest of the presentation. It should be attention-grabbing and make the audience want to listen to the rest of the presentation.

When defining how to start a presentation , these are the best tips we recommend you implement.

Start with a Hook

Kick off your introduction with a strong hook that grabs your audience’s attention. This could be an intriguing fact, a thought-provoking question, or a compelling story related to your topic. A captivating opening will make your audience want to listen and engage with your presentation.

Clearly State Your Topic

Be clear and concise when stating your topic. Your audience should immediately understand what your presentation is about and what they can expect to learn. A clear statement of your topic sets the stage and provides a roadmap for the rest of your presentation.

Establish Credibility

Take a moment to establish your credibility by briefly sharing your qualifications or experience related to the topic. This helps to build trust and rapport with your audience, and it shows that you are knowledgeable and well-prepared.

Engage Your Audience

Make your audience part of the presentation by engaging them from the start. Ask a question, encourage participation, or invite them to think about how the topic relates to their own experiences. Engagement helps to create a connection between you and your audience. Using a surprise factor is an alternative if you feel the topic you’re about to present may not fully resonate with the target audience.

Preview Main Points

End your introduction by briefly previewing the main points you will cover in your presentation. This provides a clear structure for your audience to follow and helps them understand what to expect in the body of your presentation. An agenda slide is the perfect tool for this purpose.

The body is the main part of the presentation and provides the content and information that the audience came to hear. It should feature the main points and details supporting your presentation’s objective. Depending on your topic, this could include data, arguments, case studies, examples, or demonstrations. Each main point should be clear and distinct, with evidence or examples substantiating it. The content should be tailored to your audience’s level of knowledge and interest.

Different presentations call for various structures. For example, a Product Presentation ’s structure should start by dividing the content into clear sections or headings. For instance, if presenting a new software tool, sections could include its features, benefits, and user feedback.

On the other hand, a Persuasive Presentation begins with stating the current situation or problem, followed by proposed solutions, evidence supporting those solutions, and the benefits of adopting your proposition.

Workshop or Training Presentations begin with an overview of what will be taught, followed by step-by-step instructions, examples, demonstrations, and summaries or quizzes after each major section.

One essential aspect is to plan the multimedia elements to include in your presentation, including audio, images, and video, depending on the presentation style you aim to deliver. Through our expertise, we want to share some tips on how to plan this kind of content:

• Using relevant content: Each image should be related to its accompanying content. Avoid using images just for decoration. If using videos, dedicate an entire slide to them rather than sticking them to a corner of your slide. Plan a powerful hook to connect your thoughts with these visual aids.
• Quality: Ensure all images are of high resolution and can be clearly viewed, even from a distance. Avoid pixelated or distorted images.
• Simplicity: Infographics and diagrams should be easy to understand. If presenting data, use simple charts or graphs instead of complex tables. Limit the amount of text on each slide to ensure clarity. This rule of simplicity also applies to written content and the structure of your speech. Use the Feynman Technique as a time-saver approach to simplify content to reach any knowledgeable audience.
• Consistency: A common cause of presentation failures is to distract the audience with an unprofessional look. Maintain a consistent style and color scheme for all images to give your presentation a polished and professional feel.

Along the path of creating these media elements, you can rethink your strategy for disclosing content. In general lines, you should present your points in a logical order, often from the most to least important or in a chronological sequence. This helps the audience follow along and build understanding step by step. Well-known practices like the storytelling technique follow this approach to maximize audience engagement. 

Transition smoothly between points. Phrases like “moving on,” “in addition,” or “on the other hand” can guide your audience through your narrative. Break up long sections of spoken content with anecdotes, questions, or short videos. Such an approach adds variety and keeps the audience engaged.

A well-structured conclusion is the linchpin that holds your presentation together, reinforcing your main points and leaving a lasting impression on your audience. It is your final opportunity to communicate your message and encourage audience engagement. So, before you consider how to end a presentation , here are some powerful tips to ensure you conclude your presentation with impact.

End with a Strong Statement or Quote

This technique is commonly used in motivational presentations, where the speaker leaves the audience with a slide containing a quote related to the topic of the presentation, something that evokes inner reflection about the topic discussed. 

Conclude your presentation with a strong, memorable statement or a powerful quote that ties back to your main message. This adds weight to your argument and leaves a lasting impression on your audience. If you aim to surprise your audience, silence can also be a strong statement if your presentation has to raise awareness about a problem.

Incorporate a Call-to-Action

Clearly communicate to your audience what you want them to do next. Whether it’s to adopt a new perspective, take specific action, or continue the conversation outside of the presentation, a clear call to action drives engagement and encourages your audience to act upon your message.

Ask Thought-Provoking Questions

Pose thought-provoking questions that stimulate reflection and discussion. This opens the door for audience participation and engagement and allows you to interact with the audience in a Q&A session, or reach after your presentation concluded to network.

Additional Resources and Contact Info

Offer resources such as articles, websites, or books for those interested in exploring your topic further. This not only adds value to your presentation but also encourages the audience to engage with the content beyond the presentation itself.

Consider the way you leave a communication channel open with your audience. This can be in the format of a deliverable, writing down your contact data in the “Thank You” slide , or simply via speech to inform where they can know more about you and your work.

We already discussed the basic Introduction-Body-Conclusion framework for a presentation, but there are alternative approaches that can help you structure your talk.

Problem-Solution Framework

The Problem-Solution Framework is a compelling method to structure presentations, particularly when aiming to persuade or inform an audience about addressing specific challenges. The framework operates on a simple yet impactful premise: initially, highlight a problem or challenge that needs addressing and subsequently propose a viable solution or set of solutions.

Starting with the problem establishes a context, engages the audience by highlighting pain points or challenges they may recognize, and creates a desire for resolution. It sets the stage for the solution to be perceived as necessary and valuable.

The solution phase offers that much-needed resolution. By presenting a clear, actionable solution or set of recommendations, the presenter provides a pathway to overcome the identified challenge. This structure is not only logical but also highly persuasive, as it appeals to the audience’s desire for resolution and improvement. In essence, the Problem-Solution Framework is both a guide for content organization and a psychological tool for persuasion.

Chronological Structure

The Chronological Structure is an intuitive and organized approach to presenting information based on a sequence of events or a progression in time. Whether recounting historical events, outlining the stages of a project, or narrating a personal story, this structure follows a clear beginning, middle, and end sequence. By presenting details in the order they occurred, the audience can easily follow the narrative, making connections between events and understanding causality.

This structure is especially effective when the timeline of events is crucial to the narrative or when showcasing developments, evolutions, or growth over time. It provides clarity and eliminates confusion that might arise from a non-linear presentation. Moreover, by anchoring information on a timeline, the Chronological Structure aids memory retention, as the audience can mentally “map out” the journey of events. In sum, this method offers clarity and a compelling narrative arc, ensuring audience engagement from start to finish.

Comparative Structure

The Comparative Structure is a strategic approach to presentations that hinges on juxtaposing two or more elements, ideas, or solutions side by side. By examining similarities and differences, this method illuminates unique qualities, advantages, or drawbacks inherent in each element. Often employed in business scenarios like product comparisons, market analysis, or debates, the comparative structure helps audiences critically analyze options and make informed decisions.

Presenters utilizing this structure typically start by introducing the elements for comparison. They then delve into detailed analysis, often using criteria or metrics to maintain objective evaluations. Visual aids like Venn diagrams or comparison charts can enhance clarity and visual appeal.

The strength of the Comparative Structure lies in its ability to foster critical thinking. By directly contrasting items, audiences are engaged, encouraged to weigh pros and cons, and ultimately arrive at a deeper understanding or more nuanced perspective on the subject matter.

Matrix Structure

The Matrix Structure offers an approach to organizing presentations by segmenting information into distinct categories or sections, akin to a grid or matrix. Instead of a linear flow, topics are grouped by themes, criteria, or any relevant classification, allowing for simultaneous exploration of multiple facets of a subject. Think of it as viewing a topic through various lenses concurrently.

For instance, in a business setting, a product might be examined in terms of design, functionality, market positioning, and customer feedback. Each of these constitutes a segment in the matrix.

Visually, the matrix can be represented using tables, grids, or quadrant charts, making the content easily digestible and engaging. A key advantage of this structure is its flexibility; presenters can delve deep into one segment or provide a broader overview of all areas, depending on the audience’s needs. Ultimately, the Matrix Structure ensures a comprehensive and multifaceted examination of a topic, providing depth and breadth in analysis.

Modular Structure

The final model we will study is the Modular Structure. It takes content and packs it into modules, which can be arranged at any other the presenter requires them to be. Each module addresses a specific topic or idea and is designed to be self-contained, ensuring clarity even if presented independently or in a different order. This adaptability makes the modular approach especially valuable in dynamic settings, such as workshops or conferences, where audience feedback or time constraints might necessitate adjustments on the fly.

For example, in a corporate training session, different modules could cover distinct skills or topics. Based on the attendees’ prior knowledge or the session’s time limit, the presenter can prioritize, omit, or rearrange modules without compromising the integrity of each segment.

By adopting the Modular Structure, presenters gain flexibility without sacrificing depth. This approach fosters a responsive presentation style, allowing speakers to tailor content in real-time, ensuring maximum relevance and engagement for their audience.

Even well-seasoned presenters can fall prey to these common mistakes in terms of presentation structure. Let’s learn how to prevent them.

Overloading with Information

It’s tempting to include every bit of knowledge you have on a topic. Still, information overload can quickly disengage an audience. Prioritize key points and leave out extraneous details. As famous architect, Mies van der Rohe famously coined, “Less is More.”

Weak Transitions

Jumping abruptly from one point to another can disrupt the flow and confuse listeners. Ensure smooth transitions between sections, signaling shifts in topics or ideas to keep the narrative cohesive.

Dull Design

While content is king, visual appeal matters. Relying solely on walls of text or bland slides can lose your audience’s interest. Incorporate engaging visuals, charts, and multimedia elements to enhance your message and retain attention.

Ignoring the Call to Action

Concluding your presentation without guiding the audience on the next steps or what’s expected of them can be a missed opportunity. Whether it’s seeking feedback, prompting a discussion, or encouraging an action, always have a clear call to action.

Good communication is all about making your point clear, especially in presentations. We’ve talked about how the right structure can keep your audience hooked. But there’s more to it. Think about your presentation. Is it telling your story the way you want? Is it reaching your audience? Take a step back and really look at how you’re laying it out. Don’t just go with the flow – choose your format wisely. Remember, every presentation tells a story, and how you set it up matters a lot.

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From Madmen to TedTalks: The Evolution of the Presentation

In the Don Draper days of 1960s Manhattan, the concept of a "presentation" was very different than it is today. At that time, presentations consisted of a series of hand-rendered drawings (or storyboards) that were first glued to a piece of foam core and then proudly displayed on metal easels for the audience’s viewing pleasure (or frustration, if they happened to be nearsighted). Or, in less sexy industries, paper memos were typed up on typewriters and distributed for people to read during meetings — usually accompanied verbally by an equally lackluster presenter. Today, it’s a totally different world. ‍ From the ubiquitous PowerPoint, to the many expensive and free Powerpoint alternatives , there is no shortage of presentation software options out there that help bring stories to life in boardrooms the world over.

With technological advances in sound, projection, high-def screens, animations, and more, everything today is digitalized, zoomable, easily prepared and easily digestible. But have we reached the golden age of presentation software yet?

Let’s see how we got here and what we can still improve.

If you had a brilliant idea to present to your boss or your team in 1960s, you didn’t have the option to open your trusty PowerPoint. No, all you had at your disposal was a large physical easel with built-in oversized pads of paper — where you built your presentation sheet by sheet, praying that it wouldn't get ripped, eaten by your dog, or rained on while on your way to the office.

When presenting, you may have used a "pointer" stick to direct your audience’s attention to the parts of the presentation currently under discussion.

Maybe if you were exceptionally well-organized — or if the presentation was super important — you mounted your hand-written memos to foam boards to display on (often flimsy) easels. Now that was impressive.

In the 1970s, giving an effective presentation meant using slides. But not the digital kind, since the world was still PowerPoint free.

We are talking about those tiny delicate 35mm transparent slides that were inserted into the slide projector and projected onto the white ‘screen’ on the wall. If you’re reading this and are getting nostalgic flutters reminiscing how your aunt came to visit once and gave your family a slide show about her recent Hawaii vacation while you and your toddler sibling were fighting over the last cookie on the floor, then yes, you’re thinking about the right device. (And yes, you’re officially ancient).

Fun Fact: The slide projector was actually around since 1950s and was a descendent of an even earlier device that was used as early as late 19th century. The tiny slides were crafted by professionals and took days in advance to make. Forget about pulling an all nighter at your laptop the day before the conference — you needed weeks, if not months, to pull a presentation off.

If you wanted to impress an audience in the 1980s, you might have used an overhead projector and transparencies (Or you still had the slide projector option, of course. Or the paper pad option. Paper was always free. PowerPoint still wasn’t around though.)

Unlike the slide projector, where the image was put in front of the light source, with an overhead projector, the transparent slide was put on top of the light source. These slides were bigger, too. They were also prepared in advance but the presenter could modify them and add material during the presentation using a marker. These projectors were especially widely used in the classroom , but were also the standard option for sales meetings and conferences.

If you were a diehard fan of the 35mm slide business, you were also in luck. Carousel slide projectors , which were capable of holding 80 to 140 slides and rotating them came into wide use. The slides still had to be made days in advance and, unlike transparencies, were not modifiable. But the device was more portable than the overhead slide projector.

The 1990s are where things changed drastically in the presentation world. PowerPoint, which was created by the startup Forethought in 1987, and almost immediately acquired by Microsoft , releases its first version for Windows in 1990 (the original version was made for Macintosh), and slowly begins to conquer the world.

The original version of PowerPoint was actually used for preparing the presentation slides and previewing them on the computer but not delivering the presentation. By the third version (PowerPoint 3.0, released in 1992 and later renamed PowerPoint 1992), the functionality of the software was extended to enable direct video output to digital projectors, eventually replacing the physical transparencies.

PowerPoint has revolutionized the way people did presentations. Suddenly, you could add text and graphics to slides (and remove them at will), and organize and re-organize the slides through the slide sorter.

PowerPoint 3.0 also introduced some features that made it look similar to the PowerPoint we know today - for instance, TrueType font support, transition effects, and drawing tools. These advances, as well as the eventual integration of PowerPoint with the rest of the Microsoft Office suit (in 1994 ) have sealed its position as the leading presentation software of the time.

By now, the concept of the "presentation" was improving. People no longer had to drag heavy projectors with them to conference rooms. The introduction of the PowerPoint software made creating presentations exponentially easier.

But the demands also started to change. Now that the process of preparing and presenting was easier than ever, people started expecting something else: better design.

A few powerpoint alternatives started popping up. Concurrence , a presentation software developed by Lighthouse Design, was released in late 1990s (for NeXTSTEP and OpenStep platforms). Concurrence was an integrated outlining and presentation software and was what Steve Jobs used for his first presentations. In 2003, Apple released Keynote , which was originally developed as a software for Steve Jobs to use at Apple keynote events, and soon became the most popular PowerPoint alternative at the time.

By 2010, presentation software programs started to roll out all kinds of bells and whistles (aka “product features”). Keynote (now part of iWork) introduced official HD compatibility, and new features such as group scaling, 3D charts, multi-column text boxes, auto bullets in any text field, image adjustments, free form masking tools, and three-dimensional transitions.

PowerPoint added all kinds of plug-ins, animations and pre-built templates.  Prezi launched, complete with a robust set of sophisticated, interactive “zooming” transitions between subtopics and slides. New rival presentation software programs started popping up. The competition was heating up, and the bar continued to rise on what people expected from “the presentation” on both ends: the production end (what presentation software let them create better presentations, quickly) as well as the receiving end (or what action or reaction they wanted their audience to have). By 2010, presentations were expected to be “presented” on a white screen or large TV monitor; paper printouts were unacceptable. Secondly, It had to clear and legible. It had to feature inspiring visuals. And more and more attention began to shift towards the design of each slide; how a presentation looked was a direct (positive or negative) reflection of the person presenting.

Presentations Today

We have undoubtedly made some strides since the age of the metal easels. No longer do we have to spend weeks in advance preparing the slides (that may be a good thing or not so good, depending on how you look at it). Whatever presentation software you use, the process is quick and easy.

Today everything is digital - projected onto a screen, sync'd with a large TV monitor, and so on. But we have also made significant advancements in the brain science of how we perceive, learn and retain visual information, which also has to be taken into account. That means it’s not longer enough to make your slide transitions look like you’re turning a physical page (actually, try to avoid that kind of thing if you’re intent on not annoying your audience). Presentations these days have to be beautiful and easily digestible.

Thankfully, PowerPoint is no longer the only presentation software on the block. If you do use it, you’d do better not to overuse its initially much lauded bells and whistles. Seriously, nobody is impressed by your ability to insert clever animations anymore. At best, they’ll be distracting and at worst - highly annoying.

The Future of Presenting

In a world where people are constantly bombarded with tons of visual (as well as textual) information every day — or every single time they open any kind of device — the design bar is steadily rising. Which means visual stories and presentations have to follow suit in order to remain a successful form of professional communication.

Yes, we’ve come a long way, but there is still room for improvement. With "blank slate" authoring tools like PowerPoint, most presenters still have work to do when it comes to creating truly beautiful presentations that engage but don’t overwhelm the viewer. If you want to move away from the "old standbys" completely—into the world of easy-to-use and viewer-friendly presentation software—PowerPoint alternatives today include non-linear, web-based and collaborative presentation programs. Luckily, creating beautiful presentations today does not have to be hard work, and it can even be fun! After all, that’s why we built Beautiful.ai . With its smart templates and design a.i., Beautiful.ai is taking the work out of the equation and still maintaining the most professional of presentation appearances. Try it for free today .

Tanya Mozias Slavin

Recommended articles, 15 simple reasons to be thankful this year from the beautiful.ai team, why we built beautiful.ai, the best and worst of presentations in 2020, how your content can directly impact your brand.

Crafting an Effective Presentation Structure: From Introduction to Conclusion

Crafting an Effective Presentation Structure, from introduction to conclusion, is daunting and brings about a great deal of work. A great presentation leaves the audience feeling either inspired or informed on a specific topic. It generally is not because the speaker was knowledgeable or motivating. 

Instead, they are aware of how to structure presentations logically and simply, allowing the audience to keep up with them and take away the key aspects of the presentation. A good structure helps the speaker deliver a presentation calmly, stay on topic and avoid any awkward silence between the presentations. This is precisely why individuals should look to enhance and develop effective presentation skills .

Factors that Determine the Presentation Structure

Before choosing and designing a presentation structure, the speaker should address a variety of factors, including: 

• Who is the audience, and how knowledgeable are they already?
• Time duration of the presentation.
• The kind of setting in which the presentation is being delivered.
• Aim of the Presentation.
• What are the key points the audience should take away from the presentation? 

Typical Presentation Structure 

In general, the contents of a presentation include an introduction, body, and conclusion. At times, it may include visual aids. This is the usual flow for crafting an effective presentation structure: from introduction to conclusion, which covers all the necessary sections and allows the audience to follow along easily. 

When designing a presentation, 

• Create a solid, organized structure for the entire presentation. 
• Keep the slides simple and clear to follow. 
• Remember to be concise and do not confuse the audience. 
• Make sure to add style and visual elements consistently in the presentation. 

The Introduction – Greeting the audience & introducing the speaker

Be sure to create a positive environment by welcoming the audience with a friendly greeting. This allows the audience to arrive, settle down, and prepare for the presentation to start. The introduction is essential to establish a relationship between the speaker and the audience and gather their attention .  

The introduction should help the audience comprehend and understand the subject and objective of the presentation as well as gain their attention and confidence . It should narrow down from a broad topic to the specifics of the talk. 

• Stating the general topic.
• Narrowing to the area of interest/ subject of the presentation.
• Stating the problems/ challenges in the area being discussed. 
• Stating the objective and purpose of the presentation. 
• Providing a statement of the outcome of the presentation. 
• Showing a preview of the content of the presentation.

This is a great time also to explain the length of the talk, indicate if the speaker wants an audience interaction, and inform the audience if they need to jot down the important points from the presentation. With effective presentation skills, people can keep the audience engaged and interested throughout the entire tenure of the presentation.

The Body 

The body of the presentation should meet the objective and the information indicated in the introduction. This is an integral part of crafting an Effective Presentation Structure: From the Introduction to the Conclusion should make up about 75% of the total duration of the presentation. 

• The topics should be segmented considering the nature of the presentation and then working through them individually for the audience to understand fully. 
• The main points should be concise with relevant supportive evidence, statistics, and examples. 
• Critical points should be indicated with reasons. Each important idea could be presented several times in different ways to help the audience fully absorb the meaning. 
• State clear links between the ideas and internal summaries and always signal when moving on to the next point. 
• Allow the audience to make relevant notes. Always remember to summarize the talk’s body and remind the audience of the topic. 

After the main part of the presentation, the audience should understand the information and arguments clearly. 

The Conclusion 

The conclusion is frequently underdeveloped, and a poorly executed closing can completely undermine a successful presentation. However, the best section is to reflect more power onto the messages and create a lasting impression in the audience’s minds. The conclusion determines whether the speaker has achieved the presentation goal. 

While crafting an Effective Presentation Structure: From Introduction to Conclusion, keep in mind that the conclusion should make up about 1/3 of the entire presentation and should contain the following elements: 

• Summarize the key points: Keeping in mind the goal of the presentation, remember to summarise the main points and their implications. This is a good way to ensure the audience walks away with the precise information the speaker intended to convey. 
• Repeating the core message: Repeating the core theme or message of the presentation can create a powerful conclusion. This will signal the end of the talk and will provide an overview of the argument, findings, and overall purpose of the talk. 
• Offering a thought-provoking takeaway: Use a powerful and effective quote or saying that relates to the presentation’s theme and resonates with the audience. 
• Visuals: Visuals can leave a lasting impression on the audience while the closing remarks are emphasized. 

Final Steps – Thanking the audience and inviting questions 

Conclude the talk by acknowledging and thanking the people present in the audience. Show them appreciation for their interest and the time that they have invested in the presentation. After this, the audience may be invited to ask any questions. It is best to focus on initially delivering the presentation to set the tone and topics for discussion in the Q&A. 

After finishing the entire presentation, the speaker should have built a relationship with their audience such that: 

• The audience follows through on the presentation. 
• It acts in the direction of the presentation’s goal. 
• The audience remembers the presentation. 

Collaborate with the expert Orator Academy team to gain more knowledge about this concept and enhance presentation skills. Check the official website of Orator Academy to develop your public speaking skills .

Vineeta Khanna

Vineeta Khanna is one of the most well known and successful public speaking coaches In New York and New Jersey. As the founder of Orator Academy, she has helped hundreds of young students and working professionals to become confident speakers.

Vineeta has worked with hundreds of students of all ages: elementary school students, college students, interns, job seekers, Wall Street professionals, home makers, IT professionals, teachers and more.

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Stellar Structure and Evolution

Stars are the source of almost all of the light our eyes see in the sky. Nuclear fusion is what makes a star what it is: the creation of new atomic nuclei within the star’s core. Many of stars’ properties — how long they live, what color they appear, how they die — are largely determined by how massive they are. The study of stellar structure and evolution is dedicated to understanding how stars change over their lifetimes, including the processes that shape them on the inside.

Center for Astrophysics | Harvard & Smithsonian researchers study stellar structure and evolution in many ways:

Studying fluctuations in light on nearby stars to determine their internal processes. While most stars appear too small to distinguish surface features, astronomers can infer variations in their interiors by how their light fluctuates. Those changes are due to “ starspots ” — dark spots created by magnetic variations in a star — and starquakes. For example, astronomers recently discovered that Proxima Centauri, the nearest star to the Sun, has starspots. That discovery was surprising, because researchers previously thought red dwarf stars like Proxima Centauri don’t have strong magnetic fluctuations. Proxima Centauri Might Be More Sunlike Than We Thought

Monitoring sound waves running through the interiors of Sun-like stars. These starquakes produce variations in the star’s light. Much like earthquakes provide hints about Earth’s, these sound waves allow astronomers to measure what’s going on inside stars. Using NASA’s Kepler observatory and other telescopes monitoring stars for exoplanet signals, researchers measure the fluctuations of light caused by starquakes. Solar-Like Oscillations in Other Stars

Studying stars that are similar to the Sun at other stages in evolution. We can only observe our Sun at this particular time of its life, but astronomers can see its past and future by looking at similar stars earlier or later in their cycle. Astronomers observe newly born Sun-like stars to determine what ours may have been like, and the effect that had on planet formation. Young Sun-like Star Shows a Magnetic Field Was Critical for Life on the Early Earth

Observing stars in the final stages of their lives. These giant stars pulsate and shed huge amounts of matter. Studying them reveals how they enrich interstellar space with new atoms, and how pulsation relates to physical processes deep in the star’s interior. Using the National Radio Astronomy Observatory’s Atacama Large Millimeter/submillimeter Array (ALMA) and other observatories, astronomers can identify the composition of the “winds” from aging stars. Pulsation-Driven Winds in Giant Stars

Identifying stars at all stages of life — including places where both dying and newborn stars coexist. Using NASA’s Chandra X-ray Observatory and other telescopes, astronomers have learned that the violent final stages of a star’s life can spur the creation of new stars, by compressing interstellar gas until it collapses under its own gravity to make protostars. In other instances, X-ray light from a binary system with a black hole or neutron star illuminates a star-forming region, which is opaque to visible light, but transparent to X-rays. A Stellar Circle of Life

Measuring the ages of stars to understand how they change over the course of their lives. Stars begin their lives spinning fast, and slow down gradually over time. Researchers want to know exactly how that rate changes, and how it reflects the aging of the star itself. Using NASA’s Kepler observatory and other instruments, astronomers have tracked starspots to measure the spinning of stars in a single cluster . Stars' Spins Reveal Their Ages  

Studying YSOs and their environments, as a way to determine how stars have the masses they do. The mass of a star dictates its life cycle, and that mass is set during its growth period before it’s even a star. Using the CfA’s Submillimeter Array (SMA) and other telescopes capable of seeing through the gas and dust around newborn stars, astronomers can track the evolution from protostar to star. SMA Unveils How Small Cosmic Seeds Grow Into Big Stars

This NASA's Solar Dynamics Observatory image reveals two large sunspot groups on the surface of the Sun. Sunspots and starspots are produced by magnetic activity, providing information about the internal structure of stars.

A Star Is Born

All stars begin their lives in dense interstellar clouds of gas and dust . Even before they become stars, though, much of their future life and structure is determined by the way they form.

A star is defined by nuclear fusion in its core. Before fusion begins, an object that will become a star is known as a young stellar object (YSO), and it passes through two major stages of development.

During the protostar phase, the YSO is still gathering mass onto itself in the form of gas and dust. Protostars are completely hidden in visible light, so all the information we have about them comes from infrared, submillimeter, and X-ray observations. The protostar’s gravity gathers mass into a spinning circumstellar disk, and some of the matter is funneled into powerful jets shooting away from the YSO. These processes help determine the mass of the eventual star, and as such dictate much of the rest of the star’s life.

During the pre-main-sequence (PMS) phase, the YSO contracts and heats up. New planets form out of the remains of the circumstellar disk. The specific way the YSO behaves depends on how much mass it gathers. Lower mass stars like the Sun pass through a stage of wild fluctuations as they lose their shrouds of gas and dust, during which they are called “T Tauri stars”. Higher mass PMS stars produce huge amounts of radiation, which can drive the surrounding gas away. This can throttle the formation of other stars, either preventing them from forming or keeping them at lower masses.

The jets and outflows of particles from YSOs can have a profound influence on the surrounding nebula. Since many stars form in a cluster from the same pool of gas and dust, they affect each other’s growth and development in profound ways.

All About Mass

Once YSOs have contracted and heated enough, fusion of hydrogen into helium begins in their cores and they become main sequence stars. The rate of that fusion increases with the mass of the star, so the most massive stars are the shortest-lived. 

The lowest-mass stars are known as red dwarfs or M dwarfs. These experience convection — the circulation of matter — throughout their interior. That means they burn for a very long time, giving them lifetimes much longer than the 13.8 billion years the universe has been around. None of these stars have lived through their entire lifecycle yet.

The Sun is a moderate mass star with a lifetime of roughly 10 billion years; we’re currently about halfway through the Sun’s main sequence. Stars in this middle range of mass have a distinct core where fusion takes place, and that limits the available supply of hydrogen to fuse into helium. Once that supply is exhausted, the star leaves the main sequence and swells into a red giant. The core then collapses slightly as it begins fusing helium into carbon and oxygen. Once the available helium supply is used up, the star sheds its outer layers , exposing the remnant of its core. This remnant is a white dwarf .

The highest mass stars consume their available hydrogen even more quickly, passing through the main sequence and helium-fusion phase in a much shorter amount of time. However, these stars have enough mass to keep fusion going, producing heavier elements up to iron. Elements beyond iron on the periodic table require more energy to fuse than is released by the fusion process, so the core of these stars can’t keep up the work. The core collapses under gravity, and the outer layers of the star are blown off in a supernova explosion. For the most massive stars, the cores collapse into black holes ; the slightly less massive stars leave behind neutron stars .

Aging Stars

During the post-main-sequence evolution when stars grow huge, they may also pulsate in and out due to instabilities in the outer layers of the stellar envelope. These pulsating stars include the Cepheid variables , used in measuring distances within the Milky Way and to nearby galaxies. In addition, massive stars in the last stages of life are the source of new elements. Fusion during the giant phases of stellar evolution produces elements like carbon, oxygen, and silicon that may be cycled toward the outer layers of the star. For the most massive stars, neutrons from fusion bombard atoms in the star to make yet more elements, including technetium, a rapidly-decaying element that doesn’t exist naturally on Earth. The more stable atoms from the dying star appear in the spectrum of its light, and are shed into interstellar space as the star dies.

The Seismology of Stars

We can’t see directly into a star’s interior. However, just as earthquakes on Earth’s surface reveal what’s going on inside the planet, the behavior of material on the surface of stars provides researchers with information about the interior. Asteroseismology is the study of vibrations of a star.

Naturally, the Sun is the star easiest to study. Researchers have measured the patterns of waves on the surface set up by the flow of atoms and energy deep inside the Sun. For more distant stars, astronomers observe variations in light from these processes. In some stars, the churn of hot matter is enough to produce “starquakes”: more violent fluctuations in the star’s behavior.

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Extreme eruption on young sun-like star signals savage environment for developing exoplanets, extreme weight loss: star sheds unexpected amounts of mass just before going supernova, stellar surf's up: monster waves as tall as three suns are crashing upon a colossal star, streamlining the search for black holes, 'black hole police' discover a dormant black hole outside of the milky way galaxy, scientists explain mysterious finger-like features in solar flares, spacecraft enters the sun's corona for the first time in history, astronomers observe a new type of binary star long predicted to exist, planetary remnants around white dwarf stars, mystery solved: dust cloud led to betelgeuse's 'great dimming', sensing the dynamic universe, telescopes and instruments, 1.5-meter tillinghast (60-inch) telescope, hungarian-made automated telescope network (hatnet), miniature exoplanet radial velocity array (minerva), transiting exoplanet survey satellite (tess).

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The structure and evolution of stars

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Presentation on theme: "The structure and evolution of stars"— Presentation transcript:

Prof. D.C. Richardson Sections

Life as a Low-mass Star Image: Eagle Nebula in 3 wavebands (Kitt Peak 0.9 m).

Stellar Evolution. The Mass-Luminosity Relation Our goals for learning: How does a star’s mass affect nuclear fusion?

Chapter 17 Star Stuff.

Factors affecting Fusion Rate Density –Since protons are closer together, the mean free path between collisions will be smaller Temperature –At higher.

Asymptotic Giant Branch. Learning outcomes Evolution and internal structure of low mass stars from the core He burning phase to the tip of the AGB Nucleosynthesis.

Chapter 12 Stellar Evolution. Infrared Image of Helix Nebula.

Today: How a star changes while on the main sequence What happens when stars run out of hydrogen fuel Second stage of thermonuclear fusion Star clusters.

Susan CartwrightOur Evolving Universe1 The Lives of Stars n From studying nearby stars and stellar clusters l most stars are on the main sequence l stars.

Stellar Structure and evolution

The Lives of Stars Chapter 12. Life on Main-Sequence Zero-Age Main Sequence (ZAMS) –main sequence location where stars are born Bottom/left edge of main.

Chapter 21: Stars: From Adolescence to Old Age

Post Main Sequence Evolution PHYS390 (Astrophysics) Professor Lee Carkner Lecture 15.

The Formation and Structure of Stars Chapter 9. Stellar Models The structure and evolution of a star is determined by the laws of: Hydrostatic equilibrium.

Finally, fusion starts, stopping collapse: a star! Star reaches Main Sequence at end of Hayashi Track One cloud ( M Sun ) forms many stars,

Stellar Structure Section 6: Introduction to Stellar Evolution Lecture 16 – Evolution of core after S-C instability Formation of red giant Evolution up.

Stellar Evolution Astronomy 315 Professor Lee Carkner Lecture 13.

Lecture 15PHYS1005 – 2003/4 Lecture 16: Stellar Structure and Evolution – I Objectives: Understand energy transport in stars Examine their internal structure.

Astronomy 1 – Fall 2014 Lecture 12; November 18, 2014.

STELLAR EVOLUTION HR Diagram

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The structure and evolution of stars

Title: msci astrophysics 210phy412 author: stephen smartt last modified by: smartt stephen created date: 11/11/2004 9:46:16 am document presentation format – powerpoint ppt presentation.

• Lecture 4 The equations of stellar structure
• For our stars which are isolated, static, and spherically symmetric there are four basic equations to describe structure. All physical quantities depend on the distance from the centre of the star alone
• Equation of hydrostatic equilibrium at each radius, forces due to pressure differences balance gravity
• Conservation of mass
• Conservation of energy at each radius, the change in the energy flux local rate of energy release
• Equation of energy transport relation between the energy flux and the local gradient of temperature
• These basic equations supplemented with
• Equation of state (pressure of a gas as a function of its density and temperature)
• Opacity (how opaque the gas is to the radiation field)
• Core nuclear energy generation rate
• The theme of this lecture is to discuss the energy generation in stars and
• how that energy is transported from the centre. The student will
• Learn how to determine the likely form of energy generation
• Derive the equation of conservation of energy. Which is formula
• number (3) of the stellar structure equations
• Before deriving the final formula, student will learn how to determine how energy is transported in the sun. This will include deriving the criterion for convection to occur.
• What is the source of this energy ? Four possibilities
• Cooling or contraction
• Chemical Reactions
• Nuclear Reactions
• Cooling and contraction
• These are closely related, so we consider them together. Cooling is simplest idea of all. Suppose the radiative energy of Sun is due to the Sun being much hotter when it was formed, and has since been cooling down .We can test how plausible this is.
• Or is sun slowly contracting with consequent release of gravitational potential energy, which is converted to radiation ?
• There are three ways energy can be transported in stars
• Convection energy transport by mass motions of the gas
• Conduction by exchange of energy during collisions of gas particles (usually e-)
• Radiation energy transport by the emission and absorption of photons
• Conduction and radiation are similar processes they both involve transfer of energy by direct interaction, either between particles or between photons and particles.
• Which is the more dominant in stars ?
• Energy carried by a typical particle 3kT/2 is comparable to energy carried by typical photon hc/?
• But number density of particles is much greater than that of photons. This would imply conduction is more important than radiation.
• Whether or not this condition is satisfied depends on two things
• The rate at which the element expands due to decreasing pressure
• The rate at which the density of the surroundings decreases with height
• Lets make two assumptions
• The element rises adiabatically
• The element rises at a speed much less than the sound speed. During motion, sound waves have time to smooth out the pressure differences between the element and the surroundings. Hence ?P ?P at all times
• Write a report describing the solar neutrino problem. You should read the introductory articles provided, and supplement this with your own reading. You should attempt to clarify the problem for yourself and understand its importance. In particular you should discuss the following
• Why and how have solar neutrinos been observed ?
• What is their importance
• Define and describe the solar neutrino problem
• Has it been resolved and if so how ?
• Approximately 1500-2000 words. Aim to read at least one of the original papers in the field (references given in the Bahcall article), and summarise its results in your essay. It should be a status report of the current knowledge in the field.
• Learning aim to understand the importance and status of one of the most fundamental tests of the theories of stellar structure and nuclear physics.
• Submission deadline Friday April 29th 4pm

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The structure and evolution of stars

Apr 06, 2019

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The structure and evolution of stars. Lecture 12:White dwarfs, neutron stars and black holes. Learning Outcomes. The student will learn How to derive the equation of state of a degenerate gas How polytropic models can be applied to degenerate stars - white dwarfs

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• magnetic field axis
• similar mass radius relation
• opposite spin
• initial rotation period

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The structure and evolution of stars Lecture 12:White dwarfs, neutron stars and black holes

Learning Outcomes The student will learn • How to derive the equation of state of a degenerate gas • How polytropic models can be applied to degenerate stars - white dwarfs • How to derive the stable upper mass limit for white dwarfs • How the theoretical relations compare to observations • What a neutron star is and what are their possible masses • How to measure the masses of black-holes and what are the likely production mechanisms

Introduction and recap So far have assumed that stars are composed of ideal gases In lecture on low mass stars: • Several times have mentioned degeneracy pressure - in the case of low-intermediate mass stars, they develop a degenerate He core. • Degeneracy pressure can resist the gravitational collapse • Will develop this idea in this lecture • Will use our knowledge of polytropes and the Lane-Emden equation In lecture on high mass stars: • Saw that high mass stars develop Fe core at the end of their lives • What will happen when core is composed of Fe ?

Equation of state of a degenerate gas At high densities, gas particles may be so close, that that interactions between them cannot be neglected. What basic physical principle will become important as we increase the density and pressure of a highly ionised ideal gas ? The Pauli exclusion principle - the e– in the gas must obey the law: No more than two electrons (of opposite spin) can occupy the same quantum cell The quantum cell of an e– is defined in phase space, and given by 6 values: x, y, z, px, py, pz The volume of allowed phase space is given by The number of electrons in this cell must be at most 2

Consider the centre of a star, as the density increases The e– become crowded, eventually 2 e– occupy almost same position Volume of phase space “full” (from exclusion principle) Not possible for another e– to occupy space, unless p significantly different Consider a group of electrons occupying a volume V of position space which have momenta in the range p+p. The volume of momentum space occupied by these electrons is given by the volume of a spherical shell of radius p, thickness p: Volume of phase space occupied is volume occupied in position space multiplied by volume occupied in momentum space Number of quantum states in this volume is Vph divided by volume of a quantum state (h3)

Define Npp = number of electrons with momenta V in the range p+p. Pauli’s exclusion principle tells us: Define a completely degenerate gas : one in which all of momentum states up to some critical value p0are filled, while the states with momenta greater than p0are empty.  The pressure P is mean rate of transport of momentum across unit area (see Appendix C of Taylor) Where vp= velocity of e– with momentum p

Use relation between p and vpfrom theory of special relativity Where me=rest mass of e– Combining the three expressions for N, P, and vp, we obtain pressure of a completely degenerate gas Non-relativistic degenerate gas (p0 <<mec)

By defining ne=N/V and recalling The electron degeneracy pressure for a non-relativistic degenerate gas: Relativistic degenerate gas (p0 >> mec ; when v approaches c and momentum  ∞ )

Aim is to obtain equation of state for a degenerate gas. We must convert ne to mass density  (using similar arguments to derivation of mean molecular weight: lecture 7). For each mass of H (mH) there is one e– . For He and heavier elements there is approximately 1/2 e– for each mH. Thus: In a completely degenerate gas the pressure depends only on the density and chemical composition. It is independent of temperature Suggested further reading: See Prialnik (Chapter 3), Taylor (Appendix 3) for full discussions of derivation

Thin non-degenerate surface layer of H or He Isothermal degenerate C/O core Degenerate stars There is not a sharp transition between relativistically degenerate and non-relativistically degenerate gas. Similarly there is no sharp transition between an ideal gas and a completely degenerate one. Partial degeneracy situation requires much more complex solution. White dwarfs Intrinsically faint, hot stars. Typical observed masses 0.1-1.4M Calculate typical radius and density of a white dwarf (=5.67x10-8 Wm-2K-4)

Example of WD discovered in Globular cluster M4 • Cluster age ~ 13Myrs • WDs represent cooling sequence • Similar intrinsic brightness as main-sequence members, but much hotter (hence bluer)

A polytrope of index n=1.5 with K=K1would describe non-relativistic case, and n=3, K=K2would describe relativistic case. Now recall from Lecture 7, the mass of a polytropic star is given by The Chandrasekhar mass Recall the equations of state for a degenerate gas - what could these be used for ?

Using this, and eliminating c and substituting in for  (as from Lecture 7). We obtain a relation between stellar mass and radius: Mn and Rn are constants that vary with polytropic index n (from solution of Lane-Emden equation shown in Lecture 7). For n=1.5, the relation between mass - radius, and mass density become Imagine degenerate gaseous spheres with higher and higher masses, what will happen ?

 Density becomes so high that the degenerate gas becomes relativistic, hence the degenerate gaseous sphere is still a polytrope but with index n=3 Substituting in for K2, gives us this limiting mass. First found by Chandrasekhar in 1931, it is the Chandrasekhar mass Inserting the values for the constants we get For X~0 ; MCh = 1.46M(He, C, O…. composition)

N Measured WD masses Mass estimates for 129 white dwarfs From Bergeron et al. 1992, ApJ Mean M = 0.56  0.14M How is mass determined ? Note sharp peak, and lack of high mass objects.

Observed mass-radius relation Mass/radius relation and initial mass vs. final mass estimate for WD in stellar clusters. How would you estimate the initial mass of the progenitor star of a WD ? Koester & Reimers 1996, A&A, 313, 810 White dwarfs in open clusters (NGC2516)

Neutron stars Will see in next lecture that the collapse of the Fe core of a massive star results in neutron star formation. Landau (1932) - postulated formation of “one gigantic nucleus” from stars more compact than critical value. Walter Baade and Fritz Zwicky (1934) suggested they come from supernovae Neutrons are fermions - neutron stars supported from gravitational collapse by neutron degeneracy. NS structure can be approximated by a polytrope of n=1.5 (ignoring relativistic effects) which leads to similar mass/radius relation. But constant of proportionality for neutron star calculations implies much smaller radii. 1.4MNS has R~10-15 km  ~6 x 1014 gm cm-3 (nuclear density)

Relativistic treatment of the equation of state imposes upper limit on NS mass. Above this mass, degeneracy pressure unable to balance self-gravity. • Complications: • General Theory of Relativity required • Interactions between neutrons (strong force) important • Structure and maximum mass equations too complex for this course Outer Crust: Fe and n-rich nuclei, relativistic degenerate e– Inner Crust: n-rich nuclei, relativistic degenerate e– Interior: superfluid neutrons Core: unknown, pions ?quarks ? Various calculations predict Mmax=1.5 – 3Msolar

Neutron star properties Neutron stars are predicted to rotate fast and have large magnetic fields. Simple arguments: Initial rotation period uncertain, but lets say similar to typical WDs (e.g. 40Eri Bhas PWD=1350s). Hence PNS ~ 4 ms Magnetic field strengths in WDs typically measured at B=5x108 Gauss, hence BNS~1014 Gauss (compare with B ~2 Gauss!) Similar luminosity to Sun, but mostly in X-rays (optically very faint)

Discovery of neutron stars 1967: Hewish and Bell discovered regularly spaced radio pulses P=1.337s, repeating from same point in sky. Approx. 1500 pulsars now known, with periods on range 0.002 < P < 4.3 s Crab pulsar - embedded in Crab nebula, which is remnant of supernova historically recorded in 1054AD Crab pulsar emits X-ray, optical, radio pulses P=0.033s Spectrum is power law from hard X-rays to the IR  Synchrotron radiation: relativistic electrons spiralling around magnetic field lines.

Pulsar mechanism Rapidly rotating NS with strong dipole magnetic field. Magnetic field axis is not aligned with rotational axis. Spectrum of Crab pulsar is non-thermal. Suggestive of synchrotron radiation - relativistic charged particles emit radiation dependent on particle energy. Charged particles (e-) accelerated along magnetic field lines, radiation is beamed in the the acceleration direction. If axes are not aligned, leads to the “lighthouse effect”

Black Holes Description of a black hole is entirely based on theory of General Relativity - beyond scope of this course. But simple arguments can be illustrative: Black holes are completely collapsed objects - radius of the “star” becomes so small that the escape velocity approaches the speed of light: Escape velocity for particle from an object of mass M and radius R If photons cannot escape, then vesc>c. Schwarzschild radius is

Size of black holes determined by mass. Example Schwarzschild radius for various masses given by: The event horizon is located at Rs - everything within the event horizon is lost. The event horizon hides the singularity from the outside Universe. Two more practical questions: What could collapse to from a black hole ? How can we detect them and measure their masses ?

“How massive stars end their life”Heger et al., 2003, ApJ, 591, 288

Black hole and neutron star masses from binary systems From J. Caseres, 2005, astro-ph/0503071

How to determine compact object masses P = orbital period Kc = semiamplitude of companion star i = inclination of the orbit to the line of sight (90o for orbit seen edge on) MBH and Mc = masses of invisible object and companion star Keplers Laws give: The LHS is measured from observations, and is called the mass function f(m). f(m) < MBH always, since sin i <1 and Mc>0 Hence we have firm lower limit on BH mass from relatively simple measurements

Summary • There is an upper limit to the mass of a white dwarf - we do not see WDs with masses > 1.4 M • We will see in next lectures what the implications of this are for other phenomena in the Universe. It actually led to the discovery of dark energy! • The collapse of massive stars produces two types of remnants - neutron stars and black holes. • Their masses have been measured in X-ray emitting binary systems • NS masses are clustered around 1.4 M • The maximum limit for a stable neutron star is 3-5M • Hard lower limits for masses of compact objects have been determined which have values much greater than this limit • These are the best stellar mass black hole candidates - with masses of 5-15 M they may be the collapsed remnants of very massive stars.

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State Of The Union

Scientists discover gigantic 'structure' under the surface of the Moon

Posted: April 29, 2024 | Last updated: April 29, 2024

Mysterious qualities

For centuries, the Moon has captivated people with its mysterious qualities and ever-changing appearance.

Untapped potential

Despite humans setting foot on its surface, there is still much to learn about its mysteries and untapped potential.

Recently, scientists have made a remarkable discovery hidden within the Moon's South Pole-Aitken basin, a colossal structure weighing over 2.18 billion kilograms and stretching more than 300km in depth and 2,000km in length.

This finding sheds light on a previously unknown aspect of the Moon, showcasing its immense size and weight in a region known for its vast craters.

Unusual discovery

The team of researchers, all based in the United States, proposed that the unusual discovery could be composed of metal from an asteroid's core or oxides formed from a magma ocean's crystallization.

Lead author Peter B. James from Baylor University in Houston suggested that one possible explanation for this additional mass is that the asteroid's metal remains embedded in the Moon's mantle.

Underground

To emphasize the enormity of this finding, James likened it to burying a pile of metal five times larger than the Big Island of Hawaii underground, highlighting the significant and unexpected mass they detected.

NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission played a crucial role in uncovering this significant discovery by monitoring fluctuations in the Moon's gravitational field.

Internal structure

The data obtained through GRAIL enables researchers to analyze the Moon's internal structure in detail.

Exceptional

The South Pole-Aitken Basin has long been a focal point of scientific interest due to its exceptional characteristics.

This region not only provides insights into the Moon's internal makeup and historical evolution but also hints at the possibility of uncovering more enigmatic secrets yet to be revealed.

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ORIGINAL RESEARCH article

This article is part of the research topic.

Investigation, Monitoring, Stability and Risk Assessment of Geohazards

Pore Structure Expansion and Evolution in Sandstone with Prefabricated Crack under Freeze-Thaw Cycles Based on CT Scanning Provisionally Accepted

• 1 College of Engineering, China University of Geosciences Wuhan, China

The final, formatted version of the article will be published soon.

In cold regions, rocks undergo periodic temperature fluctuations, resulting in deterioration in pore structure and mechanical behavior. This degradation can lead to instability in rock masses and contribute to landslides. While many studies have investigated the effects of freeze-thaw (F-T) cycles on the mechanical behavior of rocks, the micro-level mechanisms of deterioration remain less understood. In this study, the evolution of the pore structure of a prefabricated sandstone with 30 freeze-thaw cycles ranging from -20°C to 20°C is explored using CT scanning. The influence of the prefabricated crack is highlighted. The results indicate a significant impact of freeze-thaw cycles on large pores, with their proportion increasing from 15.28% to 38.72% after 30 F-T cycles. Within the initial 10 F-T cycles, pore structure changes occur without the expansion of prefabricated crack. However, after 15 F-T cycles, prefabricated crack begins extending downward, eventually becoming nearly continuous after 30 F-T cycles. Prefabricated crack notably influences pore distribution during freeze-thaw cycles, with higher porosity near the fracture, where pores initially expand and connect. These findings provide insights into the damage mechanism in sandstone under F-T cycles.

Keywords: freeze-thaw (F-T) cycles, landslide, CT scanning, Prefabricated crack, Pore structure

Received: 02 Mar 2024; Accepted: 29 Apr 2024.

Copyright: © 2024 Zhang, Luo and Niu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Xuedong Luo, College of Engineering, China University of Geosciences Wuhan, Wuhan, China

People also looked at

• Open access
• Published: 22 April 2024

Dynamic changes in the plastid and mitochondrial genomes of the angiosperm Corydalis pauciovulata (Papaveraceae)

• Seongjun Park 1 ,
• Boram An 2 &
• SeonJoo Park 2  

BMC Plant Biology volume  24 , Article number:  303 ( 2024 ) Cite this article

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Corydalis DC., the largest genus in the family Papaveraceae, comprises > 465 species. Complete plastid genomes (plastomes) of  Corydalis  show evolutionary changes, including syntenic arrangements, gene losses and duplications, and IR boundary shifts. However, little is known about the evolution of the mitochondrial genome (mitogenome) in Corydalis . Both the organelle genomes and transcriptomes are needed to better understand the relationships between the patterns of evolution in mitochondrial and plastid genomes.

We obtained complete plastid and mitochondrial genomes from  Corydalis pauciovulata  using a hybrid assembly of Illumina and Oxford Nanopore Technologies reads to assess the evolutionary parallels between the organelle genomes. The mitogenome and plastome of  C. pauciovulata  had sizes of 675,483 bp and 185,814 bp, respectively. Three ancestral gene clusters were missing from the mitogenome, and expanded IR (46,060 bp) and miniaturized SSC (202 bp) regions were identified in the plastome. The mitogenome and plastome of  C. pauciovulata  contained 41 and 67 protein-coding genes, respectively; the loss of genes was a plastid-specific event. We also generated a draft genome and transcriptome for C. pauciovulata . A combination of genomic and transcriptomic data supported the functional replacement of acetyl-CoA carboxylase subunit β ( accD ) by intracellular transfer to the nucleus in  C. pauciovulata . In contrast, our analyses suggested a concurrent loss of the NADH-plastoquinone oxidoreductase ( ndh ) complex in both the nuclear and plastid genomes. Finally, we performed genomic and transcriptomic analyses to characterize DNA replication, recombination, and repair (DNA-RRR) genes in  C. pauciovulata as well as the transcriptomes of  Liriodendron tulipifera and Nelumbo nuicifera . We obtained 25 DNA-RRR genes and identified their structure in C. pauciovulata . Pairwise comparisons of nonsynonymous ( d N ) and synonymous ( d S ) substitution rates revealed that several DNA-RRR genes in C. pauciovulata have higher d N and d S values than those in N . nuicifera.

Conclusions

The C. pauciovulata genomic data generated here provide a valuable resource for understanding the evolution of Corydalis organelle genomes. The first mitogenome of Papaveraceae provides an example that can be explored by other researchers sequencing the mitogenomes of related plants. Our results also provide fundamental information about DNA-RRR genes in Corydalis and their related rate variation, which elucidates the relationships between DNA-RRR genes and organelle genome stability.

Peer Review reports

Mitochondria and plastids originate from alphaproteobacterial and cyanobacterial endosymbionts, respectively [ 1 , 2 ]. The genomes of both are highly reduced relative to the ancestral genome because substantial numbers of genes were lost, and many essential genes were transferred into the nuclear genome of a host cell over evolutionary time [ 3 ]. In angiosperms, the mitochondrial and plastid genomes (mitogenomes and plastomes) are critical in respiration and photosynthesis, encoding only 41 and 79 proteins, respectively [ 4 , 5 ]. Thus, coordination between nuclear-encoded organelle-targeted and organelle-encoded proteins is essential for their function [ 6 ]. This process involves the import of nuclear-encoded organelle-targeted proteins, which contributes to organelle genome stability [ 7 ]; DNA replication, recombination, and repair (RRR) system [ 8 ]; posttranscriptional regulation, and translation initiation [ 9 ]. Many nuclear-encoded organelle-targeted proteins are dual-targeted to mitochondria and plastids [ 10 ]. Dysfunction of DNA-RRR genes, such as RECA and MSH1 , has been suggested to be a mechanism for rate acceleration of angiosperm organelle genomes [ 11 , 12 ]. These genes also regulate recombination activity in mitogenomes [ 13 , 14 ]. Researchers examined the relationship between dysfunction in DNA-RRR systems and plastome complexity in Geraniaceae and revealed a significant correlation between substitution rates and three DNA-RRR genes ( GYRA , WHY1 , and UVRB/C ) [ 15 ]. Thus, a comprehensive understanding of organelle genome evolution in plants requires a combination of organelle genomics and transcriptomics approaches.

The mitogenome and plastome of angiosperms vary in size, structure, and gene content, although the organelle genomes exhibit parallel evolutionary relics. For example, angiosperm mitogenomes range from 65.7 kb in Viscum scurruloideum [ 16 ] to 11.3 Mb in Silene conica [ 12 ], containing variable protein-coding genes ranging from 19 in V. scurruloideum [ 16 ] to 41 in Liriodendron tulipifera [ 17 ]. They exhibit multipartite organization, mapping as circular, linear, or branched molecules due to active recombination associated with repeats [ 18 ]. In contrast, angiosperm plastomes generally exhibit a circular quadripartite structure with large single-copy (LSC) and small single-copy (SSC) regions separated by two copies of an inverted repeat (IR) region, varying from 11.3 kb to 242.5 kb in size with 5–79 protein-coding genes [ 5 , 19 ]. However, the plastomes of some lineages of angiosperms exhibit structural changes, including IR loss and genome rearrangements [ 20 ]. In both genomes, several organelle genes have been successfully transferred to the nucleus through direct intracellular gene transfer (IGT) or substitution by a nuclear homolog [ 21 ]. In addition to IGT to the nucleus, intercompartmental transfers between organellar counterparts have been observed (mitochondrial DNA of plastid origin, MIPTs; plastid DNA of mitochondrial origin, PLMTs) [ 22 ]. MIPTs are a common feature of the mitogenome in angiosperms, while PLMTs are rare.

The genus Corydalis DC. consists of annual or perennial herbaceous plants and belongs to Papaveraceae Juss. It comprises approximately 465 species distributed throughout the Northern Hemisphere and tropical eastern Africa [ 23 ]. The plastomes of 72 Corydalis species have been sequenced (the NCBI database, accessed on May 24, 2023), representing only 15.5%. The sequenced Corydalis plastomes ranged in size from 149.9 kb in C. mucronifera (BK063233) to 218.8 kb in C. hendersonii (OP747311) with a quadripartite organization. The variation in plastome sizes within the genus is due to IR expansions, ranging from 22.7 kb to 54.9 kb. The Corydalis plastomes also exhibit divergent structural evolution, including multiple inversions and gene losses [ 24 , 25 , 26 , 27 ]. In particular, the losses of acetyl-CoA carboxylase subunit β ( accD ), ATP-dependent Clp protease proteolytic subunit gene ( clpP ), or all 11 subunits of NADH-plastoquinone oxidoreductase ( ndh ) are lineage-specific events within the genus [ 27 , 28 ].

Corydalis organelle genomes can provide excellent examples for studying the evolution of genome architecture, gene losses, mutation rates, and cytonuclear interactions. However, no complete mitogenome has been assembled and analyzed for the genus Corydalis , even at the level of the family Papaveraceae. We also have limited knowledge about DNA-RRR proteins in the Corydalis nuclear genome. In this study, we sequenced, assembled, and analyzed the complete sequences of the plastid and mitochondrial genomes of C. pauciovulata Ohwi and generated a draft nuclear genome and transcriptome. Corydalis pauciovulata Ohwi is an annual or biennial herb native to moist regions near streams and mountain valleys in Korea and Japan [ 29 ]. Our purpose of this study was to 1) explore the evolutionary characteristics of the C. pauciovulata plastid and mitochondrial genomes, 2) determine the nuclear-encoded DNA-RRR proteins, 3) identify the evolutionary fate of the lost genes in the organelle genomes, and 4) understand the driving factors of the dynamic genomic features of C. pauciovulata organelle genomes. For do that, we compared them to those of Nelumbo nucifera (since none of the Corydalis has a published mitogenome), as well as L. tulipifera as an outgroup, for which both organelle genomes and the transcriptome are available, to better understand the evolution of gene content, structure, and substitution rates.

Organelle genome assemblies and genome organization

The newly sequenced plastid and mitochondrial genomes of C. pauciovulata were assembled into circular molecules with lengths of 185,814 bp and 675,483 bp, respectively (Table  1 and Figs. 1 and 2 ). Depth of coverage analyses revealed that the organelle genomes were deeply (PE/MP/ONT; plastome: 3,092 × /1,932 × /280 × , mitogenome: 170 × /155 × /26 ×) covered (Figure S 1 ), supporting the accuracy of the assemblies.

The Corydalis pauciovulata plastome. Thick lines on the genome map indicate the inverted repeats (IRa and IRb: 46,060 bp), which separate the genome into small (SSC: 202 bp) and large (LSC: 92,155) single-copy regions. Genes on the inside and outside of the map are transcribed in clockwise and counterclockwise directions, respectively. Asterisks indicate genes transferred from single-copy regions to the IR, and ψ denotes a pseudogene. The red lines on the inner circle indicate tandem repeats. The black and red arrows on the outside of the map indicate contraction and expansion events, respectively. The colored boxes on the map correspond to the locally collinear blocks inferred by Mauve (see Fig.  3 ). The green lines within the inner circle indicate the positions of the pairs of repeats, with crossed connecting lines denoting reverse repeats

The Corydalis pauciovulata mitogenome. Genes on the inside and outside of the map are transcribed in clockwise and counterclockwise directions, respectively. The red lines on the inner circle indicate tandem repeats, and ψ denotes a pseudogene. The blue lines within the inner circle indicate the positions of the pairs of repeats, with crossed connecting lines denoting reverse repeats

The C. pauciovulata plastome had a general quadripartite structure; however, it contained expanded IR (46,060 bp) and miniaturized SSC (202 bp) regions (Fig.  1 ). An analysis of genome rearrangements with L. tulipifera and N. nucifera suggested that the C . pauciovulata plastome has experienced three inversions with eight breakpoints: trnK-rps16 , ndhC-trnV , accD-psaI , ndhB , trnR-trnN , trnN-ndhF , ndhF, and ndhA (Fig.  3 A). The first inversion (yellow box) with the rbcL-atpB-atpE-trnM region was relocated (Figs. 1 and 3 A). Compared to the published L. spectabilis plastome, which is from a related genus in the same subfamily, the second inversion (purple box) involving a pair of breakpoints ( ndhB and trnR-trnN ) in the IR region suggests a lineage-specific event (Fig.  1 and Figure S 2 ). The third inversion (blue box) with the ycf1-rps15-ndhH-ndhA region was the result of the expansion of the IR B (Figs. 1 and 3 A).

Structural alignments of the organelle genome arrangements in Corydalis pauciovulata . Blocks drawn below the horizontal line indicate sequences found in an inverted orientation. A The colored blocks represent collinear sequence blocks shared by all plastomes. Individual genes and strandedness are represented below the Liriodendron genome block. Only one copy of the inverted repeat (IR) is shown for each plastome, and the pink box below each plastome block indicates its IR. B The colored blocks represent collinear sequence blocks shared by all mitogenomes. The red boxes indicate the conserved gene clusters

The C. pauciovulata mitogenome showed high levels of structural divergence in comparison to the L. tulipifera and N. nucifera mitogenomes (Fig.  3 B). However, 11 conserved gene clusters were present in the C. pauciovulata mitogenome among the 14 ancestral gene clusters. Three ancestral gene clusters were missing in Corydalis : nad5 exon 3- nad1 exon 5, sdh3-trnP-UGG , and trnP-UGG(cp)-trnW-CCA(cp) (Fig.  3 B). In the N. nucifera conserved gene clusters, only one gene cluster was missing ( nad5 exon 3- nad1 exon 5; Fig.  3 B). The C. pauciovulata mitogenome contained 459 repeat pairs, including three large (> 1 kb), 77 intermediate (100–1000 bp), and 379 small (< 100 bp) repeats (Table  1 and Fig.  2 ). Among these repeats, seven repeat pairs (R1 to R7) were identified as potentially recombinationally active based on a thorough analysis of corrected long reads and other contigs (Figure S 3 ). These contigs displayed conflicts with the master circle and spanned predicted recombination boundaries, providing evidence to support the determination of their recombination activity. Assuming recombination across each IR (excluding R3 and R7), 19 additional genomic conformations could be predicted (Fig.  4 ), all containing the same genomic information.

Mitogenome rearrangements in Corydalis pauciovulata . Alternative genomic conformations based on five repeat pairs (R1, R2, R4, R5, and R6). MC: master circle corresponding to the mitogenome in Fig.  2

Gene content in organelle genomes

The C. pauciovulata plastome contains 67 proteins, 29 tRNAs, and four rRNAs (Table  1 and Table S 1 ). The functions of all 11 NADH-plastoquinone oxidoreductases ( ndh ) in the plastome were lost due to frameshift mutations ( ndhJ , ndhK , and ndhG ), premature stop codons ( ndhC , ndhD , ndhE , and ndhH ), degradation ( ndhA and ndhB ), or complete loss ( ndhI and ndhF ). In addition to the functional loss of the 11 ndh genes, the accD and trnV-UAC genes were also absent from the C. pauciovulata plastome. Multiple genes were duplicated, including sequences from the rpl32 , trnL-UGA , ccsA , ψndhD , psaC , ψndhE , ψndhG , ycf1 , rps15 , ψndhH , and ψndhA genes, due to IR boundary shifts (Fig.  1 ). Triplication of trnfM-CAU was observed in the C. pauciovulata plastome (Fig.  1 ). The plastome of C. pauciovulata contained 99 repeat pairs, covering 7.53% of the genome (Table  1 and Fig.  1 ).

The C. pauciovulata mitogenome contained a full set of 41 protein-coding genes, 12 tRNAs, and three rRNAs (Table  1 ). Twelve plastid-derived tRNAs were identified, and two of those tRNAs were pseudogenes (Table  1 and Fig.  2 ). Two copies of rps7, trnP-UGG, and trnI-CAU were identified in the C. pauciovulata mitogenome, but one copy of trnP-UGG appeared to be a pseudogene (Fig.  2 ). Thirty-six MIPTs were identified in the C. pauciovulata mitogenome, ranging from 64 to 6,500 bp and covering 4.21% of the genome (Table S 2 ). PREP-Mt predicted 738 putative C-to-U RNA editing sites to 41 C. pauciovulata mitochondrial protein-coding genes, more than in N. nucifera (715 sites) but fewer than in L. tulipifera (784 sites) (Table S 3 ). The available transcriptome data for 21 mitochondrial genes revealed 357 sites, and of the 328 sites predicted by PREP-Mt for these genes, 299 (91%) were edited (Table S 4 ). Nine hundred thirteen ORFs (≥ 150 bp in length) were identified in intergenic regions of the C. pauciovulata mitogenome. CD-search identified several ORFs harboring a partial or intact sequence homologous to RNase H ( Ty1/Copia and Ty3/Gypsy ), integrase, reverse transcriptase, mitovirus RNA-dependent RNA polymerase, DNA polymerase type B, and endonuclease/exonuclease/phosphatase families (Table S 5 ). Twelve ORFs (≥ 150 bp in length) were identified that contained small fragments (> 30 bp) of one or two mitochondrial genes (e.g., atp1 , rps19 , rpl2 , rpl5 , ccmFc , rps7 , cob , nad5 , sdh3 , and sdh4 ) (Table S 6 ). Seven of these ORFs ( orf457a/b , orf244 , orf234, orf146, orf56 , and orf54 ) were predicted to encode one or three transmembrane helices (Table S 6 ). Among them, orf457a/b was immediately downstream from a repeat (R1) that overlapped with the atp1 gene; the first 701 bp of orfs and atp1 were identical. Multiple transcripts had a sequence identical to that of the ORFs (Table S 6 and Figure S 4 ). The orf146 that contained a fragment of rpl5 was also associated with repeats (R5-R6) and was upstream of rps2 and orf244 (Figure S 4 ).

Evolutionary fate of organelle genes

To identify potential organelle-to-nucleus functional transfers (including an intermediate stage), we assembled a de novo transcriptome of C . pauciovulata . The completeness of the gene sets was assessed using BUSCO with the eudicot database of 2,236 conserved genes: 89.9% had complete gene coverage, 2.3% were fragmented, and only 7.8% were missing (Figure S 5 ). All 79 plastid and 41 mitochondrial protein-coding genes were used to query the C . pauciovulata transcriptome. We found a nuclear-encoded accD -like ORF with 88.8% nucleotide sequence identity to the Lamprocapnos spectabilis plastid accD gene. TargetP predicted the first 84 amino acids of this ORF to be a cTP (chloroplast = 0.975). PCR and Sanger sequencing identified the nuclear-encoded plastid-targeted ACCD , and the nucleotide sequence alignments of both copies confirmed the presence of an intron (Fig.  5 and Figure S 6 ). Using all 11 plastid ndh gene sequences from the L. spectabilis plastome as BLAST queries, we found no ndh -like gene sequences in the C . pauciovulata transcriptome. To address potential parallel loss of the plastid-encoded ndh genes and nuclear-encoded NDH-related genes in C. pauciovulata , we queried the amino acid sequences of the nuclear-encoded NDH-related protein complexes (Table S 7 ) with the translated C . pauciovulata transcriptome. Among the 20 nuclear NDH-related genes, we found only the nuclear-encoded ndhT from subcomplex EDB, pnsB3 from subcomplex B, all subcomplex L genes ( psnL1 - 5 ), and two linkers ( lhca5 and lhca6 ) (Fig.  5 ).

Schematic diagram of the organelle gene transfer to the nucleus and the NDH-PSI supercomplex. The colored blocks represent collinear sequence blocks shared by all plastomes. Blocks drawn below the horizontal line indicate sequences found in an inverted orientation. Individual genes and strandedness are represented below the Euptelea genome block. Only one copy of the inverted repeat (IR) is shown for each plastome, and the pink box below each plastome block indicates its IR

Substitution of the duplicated nuclear ACCase , RPL20 , RPL23 , and RPS16 gene sequences for the plastids was not detected in the C . pauciovulata transcriptome; one copy of a cytosolic homolog of eukaryotic ( ACCase ) and mitochondrial ( RPS16 ) origin was identified; and two copies of a cytosolic homolog of eukaryotic ( RPL23 ) and mitochondrial ( RPL20 ) origin were identified, but no transit peptides were predicted (Figure S 7 ).

Identification and characterization of nuclear DNA-RRR genes

To identify C . pauciovulata DNA-RRR genes, we queried the amino acid sequences of the 32 selected DNA-RRR genes from A. thaliana , which were classified into nine categories (Table S 8 ), with the translated C . pauciovulata transcriptome. A total of 25 DNA-RRR transcripts were identified in the transcriptome data (Table S 8 ). We failed to find seven DNA-RRR genes, POLIB , GYRBM , SSB2 , OSB3 , OSB 4 , WHY3 , or NTH2 . The predicted ORF sizes of the DNA-RRR genes ranged from 612 bp in ODB1 to 3,618 bp in Topol . We assembled a draft nuclear genome to determine the structure of DNA-RRR genes from C . pauciovulata . The frequency of 21-mers in the Illumina data was calculated using Jellyfish followed by GenomeScope (Figure S 8 ). The proportion of homozygosity in C . pauciovulata was evaluated to be 99.2%, and the genome size was estimated to be 236.3 Mb (Figure S 8 ). The hybrid genome assembly (PE, MP, and ONT reads) generated a draft nuclear genome of C . pauciovulata containing 3,821 contigs with a total length of 203.3 Mb. The completeness of the draft nuclear genome was also assessed using BUSCO with the eudicot database: 90.9% had complete gene coverage, 3.2% were fragmented, and only 5.9% were missing (Figure S 8 ). The 25 DNA-RRR CDSs of C . pauciovulata were used as queries in “BLASTN” against the draft de novo nuclear genome sequence of C . pauciovulata . Available nuclear genome data for 25 genes confirmed the exon/intron patterns of the Corydalis DNA-RRR genes (Fig.  6 ). The number of exons in 25 genes ranged from one ( GYRBC ) to 27 ( GYRA ).

Structure of 25 DNA replication, recombination, and repair system genes in Corydalis pauciovulata . Exons and introns are represented by boxes and lines, respectively

Nucleotide substitution rates

The C . pauciovulata and N. nucifera plastomes shared 67 plastid-encoded and 41 mitochondrial-encoded genes. To examine the rate variation in 108 organellar genes from C . pauciovulata , nonsynonymous ( d N ) and synonymous ( d S ) substitution rates were estimated and compared to those of N. nucifera (Figure S 9 ). An examination of the rate variation in individual organelle genes revealed gene-specific acceleration in C . pauciovulata. The mitochondrial-encoded nad6 and the plastid-encoded atpE , clpP , petD , petG , petL , petN , rpl20 , rpl23 , rpl32 , rps15 , rps16 , ycf1 , ycf2 , and ycf4 genes showed high levels of sequence divergence compared to the patterns of nucleotide substitutions in N. nucifera . Among them, the d N / d S values for the plastid-encoded clpP gene of C . pauciovulata were greater than one.

The estimates of nucleotide substitution rates in C . pauciovulata organelle genomes showed that plastid genes evolved significantly faster than mitochondrial genes in terms of d N and d S ( C . pauciovulata , d N : 3.05-fold, d S : 5.3-fold; Fig.  7 ). The mitochondrial rates of C . pauciovulata were very similar to that of N. nucifera ( d N : 1.16-fold, d S : 1.3-fold; Fig.  7 ). However, the plastid rates of C . pauciovulata were 2.11 times greater for d N and 2.04 times greater for d S than for N. nucifera (Fig.  7 ).

Boxplots of d N and d S values for plastid and mitochondrial genes in Corydalis pauciovulata and Nelumbo nucifera . The box represents values between quartiles, the solid lines extend to the minimum and maximum values, and the horizontal lines in the boxes show the median values. The numbers below the boxes represent the mean values

To investigate the differences between DNA-RRR genes from C . pauciovulata and N.   nuicifera , substitution rates were calculated. Among the 25 nuclear-encoded genes, many C . pauciovulata genes (except RECA1 , SSB1 , ODB1 , MSH1 , OGG1 , and LIG1 ) had slightly greater d N values than those of N. nucifera (Fig.  8 A). The Twinkle , GYRB , Topol , RECG , RECX , SSB1 , WHY1 , WHY2 , ODB1 , ODB2 , UNG , OGG1 , ARP , APE1L , and APE2 genes from C . pauciovulata had relatively high d S values (Fig.  8 A). In the C . pauciovulata comparison of d N and d S among the nuclear-encoded genes, there was no significant difference between the targeted groups (Fig.  8 B).

Sequence divergence of 25 DNA replication, recombination, and repair system genes. A Nonsynonymous ( d N ) and synonymous ( d S ) divergence values for 25 individual genes are plotted for C . pauciovulata and N. nucifera. Dual-targeted, plastid-targeted, and mitochondrial-targeted genes are indicated in red, green, and blue, respectively. The DNA-RRR genes are grouped into nine categories by gray parallelograms. B Boxplots of d N and d S values for the target groups. The box represents values between quartiles, the solid lines extend to the minimum and maximum values, and the horizontal lines in the boxes show the median values. The numbers below the boxes represent the mean values. The colors corresponding to the target groups (red, dual-targeted; green, plastid-targeted; and blue, mitochondrial-targeted genes)

In plant cells, organelle genomes require the import of nuclear-encoded organelle-targeted proteins involved in organelle genome stability, including DNA-RRR proteins [ 7 , 8 ], due to endosymbiotic gene transfers [ 3 , 30 ]. Modification of DNA-RRR genes is a potential cause of genome complexity [ 14 , 30 , 31 ]. To fully explore the correlations between the modifications of DNA-RRR genes and organelle genome complexity, it is important to produce a high-quality reference genome. However, it is challenging to assemble plastid and mitochondrial genomes that harbor repeats longer than the read length of a single-type platform for short reads [ 32 ]. Long reads generated by the ONT or PacBio platform can improve the accuracy and reliability of organelle genome structure compared with those generated by a short-read-based assembly [ 33 , 34 ].

Structural variations in Corydalis pauciovulata organelle genomes

In this study, we generated high-quality assemblies of the complete plastid and mitochondrial genomes of C . pauciovulata by combining two different Illumina libraries (one paired end and one mate pair) and ONT reads. In addition, we identified 25 DNA-RRR genes from C. pauciovulata and estimated substitution rate variations in each DNA-RRR gene, and the findings provide numerous opportunities for research on organelle genome stability in the family Papaveraceae. We have shown that the C . pauciovulata plastome has undergone dynamic changes that distinguish it from most angiosperm plastomes, similar to the findings for other members of the same genus. Many Corydalis species have been identified as having rearranged plastomes, including IR expansions and gene losses [ 24 , 27 , 28 ]. Our plastome showed conflicting structures and sizes with those of the two published plastomes of C. pauciovulata (MK264352; 161,773 bp and NC_072192; 159,167 bp), although we cannot rule out the possibility of heterogeneous divergence in the plastomes of  C .  pauciovulata . For example, our plastome contained an expanded IR (46,060 bp), whereas the two published plastomes contained IRs of typical sizes (MK264352; 22,719 bp and NC_072192; 22,777 bp). Nucleotide sequence alignment of three plastomes with one IR showed that our plastome was highly similar to that of MK264352 with 98.6% identity, whereas NC_072192 was divergent, with 91.9% identity, from our plastome. These conflicting findings are difficult to interpret because of the lack of a detailed assembly method, and whether the plastome was generated using a reference or de novo approach has not been reported. Notably, the two published plastomes were generated using only short reads and different assembly tools, which may have contributed to the observed differences in plastome structure and size compared with our assembly. In plant mitogenomes, recombination with repeats results in multiple isomeric master and subgenomic circles. The  C. pauciovulata  mitogenome exhibits a dynamic genome structure that can be shaped by intramolecular recombination, and we demonstrated that homologous recombination is associated with five repeats, resulting in multiple isomeric master circles (Fig.  8 ). However, additional configurations, including subgenomic circles, may be present in the mitochondria of C. pauciovulata . Recombination activity in the mitogenome can disrupt conserved gene clusters. Comparative gene cluster analysis showed that the  C. pauciovulata  mitogenome may have undergone more rearrangements than the N. nuicifera mitogenome because two additional more missing gene clusters were inferred for  C. pauciovulata .

Evolutionary dynamics of organelle genes

A comprehensive comparison of the nuclear and organelle genomes could help identify fates or factors that impact the evolution of mitogenomes and plastomes, including gene losses, rearrangements, and accelerated substitution rates. Although the loss of several plastid-encoded genes in Corydalis plastomes has been documented [ 24 , 25 , 27 , 28 ], the evolutionary fates of these genes are unclear. Our results showed that the C. pauciovulata plastome lacked 12 protein-coding genes ( accD and 11 ndh genes), but the mitogenome contained 41 protein-coding genes that are ancestral in angiosperms. The plastid accD gene was independently lost during angiosperm evolution, and two mechanisms of functional replacement to the nucleus have been documented for accD : 1) IGT in some Geraniaceae [ 35 ] and Trifolium [ 36 , 37 ] and 2) gene substitution by a cytosolic homolog of eukaryotic origin in Brassicaceae [ 38 , 39 ], Geraniaceae except for Hypseocharis [ 35 ], and Poaceae [ 40 , 41 ]. Nuclear genome and transcriptome data revealed that IGT of accD from plastids to the nucleus occurred in C . pauciovulata instead of as a gene substitution, and the nuclear-encoded ACCD gene acquired an intron (Fig.  6 ). A previous study showed that the loss of accD occurred in the common ancestor of Corydalis [ 28 ]. Taken together, these results suggest a single ancient transfer from plastids to the nucleus in this lineage.

In contrast to accD , there is no evidence of functional replacement of the plastid-encoded ndh genes in the nucleus, although the ndh complex plays a role in electron transport during photosynthesis [ 42 ]. A suite of nuclear-encoded NDH-related protein complexes that assemble plastid-localized ndh genes is required for photosynthesis [ 43 ]. The parallel loss of NDH-related protein complexes from nuclear and plastid genomes has been reported [ 44 , 45 ]. These results suggest that the plastid NDH complex has been lost in cells or that it has been functionally replaced by alternative factors. The loss of plastid ndh genes has been observed not only in parasitic [ 46 , 47 , 48 ], mycoheterotrophic [ 45 ], and carnivorous plants [ 49 , 50 ] but also in multiple photoautotrophic lineages [ 51 , 52 , 53 , 54 , 55 , 56 ]. Multiple losses or degradations of plastid ndh genes have occurred during Corydalis plastome evolution [ 24 , 25 , 27 , 28 ]. Although it is still unclear which factors contribute to the loss of the plastid ndh gene, possible explanations for this loss have been suggested through evolutionary adaptation during the transition to heterotrophic lifestyles [ 45 , 57 ] or arid conditions. In the C. pauciovulata transcriptome, we also detected no transcripts of the nuclear-encoded ndh gene for plastids and only a few nuclear-encoded NDH-related genes, suggesting potential losses in C. pauciovulata .

The clpP gene was previously annotated as a pseudogene or was lost [ 27 , 28 ]; however, we found that all the sequenced Corydalis, including our C. pauciovulata plastome, contained the clpP gene in their plastomes. The clpP , encoded by plastids, is crucial in protein metabolism, functioning in the degradation and turnover of damaged or misfolded proteins within the organelle [ 58 , 59 ]. This gene typically contains two introns, which are conserved across many plant lineages. In some cases, angiosperm lineages have been found to lack one or both introns within the clpP gene, revealing a correlation between increased substitution rates and structural changes in clpP genes [ 35 ]. The plastid-encoded clpP gene of C. pauciovulata exhibited d N / d S values greater than one, but its characteristic structure contained two introns. The increased substitution rates and the presence of introns in clpP genes observed in C. pauciovulata raise intriguing questions about the evolutionary dynamics of this gene. The identification of a large insertion in the first exon of the clpP gene of C. pauciovulata adds to our knowledge of plastid genome diversity and structural variation within this species. However, further investigation are needed to assess the functional consequences of any structural alterations, such as the large insertion in the first exon, and whether they impact the functionality of the gene.

Impact of DNA replication, recombination, and repair genes on organelle genome stability in Corydalis pauciovulata

Angiosperm organelles do not encode genes associated with the DNA repair system; thus, DNA-RRR genes must be imported into plastids or mitochondria to maintain the organelle genome stability [ 7 ]. The modification of DNA-RRR genes has also been proposed to drive genome rearrangements and rate accelerations in the organelle genomes of angiosperms [ 15 ]. We also suggest that the dynamic structure of the C. pauciovulata plastome may result from mutations in some of the DNA-RRR genes. Our analyses showed that some specific DNA-RRR genes of C. pauciovulata , which target mitochondria ( WHY2 , ODB1 , and UNG ), plastids ( WHY1 , ODB2 , ARP , and APE1L ), and both ( Twinkle , GYRB , Topol , RECG , and RECX ), had higher d N and d S values than those of N. nuicifera . An increase was found for the d N and d S of dual-targeted, d N of plastid-targeted, and d S of mitochondrial-targeted gene groups relative to those in N. nuicifera . Previous studies revealed that plastid-targeted WHY1 and dual-targeted RECG and MSH1 proteins help maintain plastid genome stability by preventing illegitimate recombination [ 30 , 31 , 60 ], showing that knockouts or high mutation rates of these genes increase the frequency of recombination in both mitochondria and plastids. However, MSH1 in C. pauciovulata displayed lower d N and d S values than that in N. nuicifera . MSH1 affects the genomes of both organelles; therefore, additional mitochondrial genome sequences are needed to explain this phenomenon. To better address the fundamental question about the correlation between the modification of DNA-RRR genes and organelle genome stability, additional genomic resources from other members of the family Papaveraceae are needed to examine distinct patterns of sequence divergence between the conserved and dynamic genome groups.

Our results provide a valuable resource for better understanding the evolution of Corydalis organelle genomes. In particular, the first mitogenome of Papaveraceae provides an example that other researchers can explore by sequencing the mitogenomes of related plants. Mutation or dysfunction of DNA-RRR systems has been hypothesized to cause plant organelle genome instability [ 7 ]. Our results provide fundamental information about DNA-RRR genes in Corydalis and their related rate variation, shedding light on the relationships between DNA-RRR genes and organelle genome stability. This highlights the importance of further research to elucidate the mechanistic underpinnings of DNA-RRR function and its impact on the evolutionary trajectories of organelle genomes across plant lineages.

Future research could focus on investigating the specific mechanisms by which DNA-RRR systems influence organelle genome stability in Corydalis and related taxa. In addition, comparative studies across a broader range of Papaveraceae species could provide valuable insights into the evolutionary conservation or divergence of DNA-RRR gene function and its implications for plant adaptation and diversification.

DNA extraction and genome sequencing

Corydalis pauciovulata individual was collected from Mt. Bohyeon in Yeongcheon-si, South Korea [voucher Seongjun Park 2018 (YNUH)]. Total genomic DNA (11.4 μg) was extracted from fresh leaves using the DNeasy Plant Mini Kit (Qiagen, Hilden, Germany) following the manufacturer’s protocol. The Corydalis DNA was sequenced using the Illumina HiSeq2000 platform (Illumina, San Diego, CA, USA) with two libraries: 100 bp × 2 paired-end (PE) reads from a 550 bp library and 100 bp × 2 mate-pair (MP) reads from a 3,000 bp library. In addition, long reads were generated using the Oxford Nanopore Technologies (ONT) GridION platform (ONT, Oxford, United Kingdom).

Organelle genome assemblies and annotation

The organelle genomes of C. pauciovulata were assembled using three approaches: 1) A standard method using Illumina PE reads, 2) a combined method using the Illumina PE and MP reads, and 3) a hybrid method using both Illumina and ONT data. For the standard and combined methods, Velvet v1.2.10 [ 61 ] was used to assemble the genomes with multiple k -mers (69 to 95) and expected coverage values (100, 200, 300, 400, 500, and 1000). For the hybrid method, SPAdes v3.13.1 [ 62 ] was used with multiple cutoff (0, 25, 50, 100, 200, and 300) values and the “careful” option. The de novo organelle genome assemblies were performed on a 32-core 3.33 GHz Linux workstation with 512 GB of memory. Circular plastid and mitochondrial genomes were assembled in Geneious Prime 2021.1.1 ( www.geneious.com ) by mapping contigs onto the longest contigs and merging, and the overcollapsed contigs were used to infer boundaries of repeat regions. To assess the depth of coverage for the completed genomes, Illumina PE/MP reads were mapped to the whole plastome and mitogenome sequences with Bowtie v2.2.9 [ 63 ], and ONT reads were mapped to the genomes with BWA v0.7.17 [ 64 ]. The C . pauciovulata plastid and mitochondrial genomes were annotated using a BLAST-like algorithm (50% similarity) in Geneious Prime with the protein-coding genes from Liriodendron tulipifera organelle genomes (NC_008326 and NC_021152), and their open reading frame (ORF) was confirmed using “Find ORFs” in Geneious Prime. All tRNA genes in the organelle genomes were predicted using tRNAscan-SE v2.0.9 [ 65 ] and ARAGORN v1.2.38 [ 66 ]. Circular organelle genomes were drawn with OGDRAW v1.3.1 [ 67 ]. The genomes were deposited in GenBank (accession numbers OR100521 and OR100522).

Comparative analyses

Dispersed repeat sequences in organelle genomes were identified by performing “BLASTN” searches against themselves using BLAST + v2.12.0 [ 68 ], with a word size of 16 and an e -value of 1 × 10 –6 . Mitochondrial DNAs of plastid origin (MIPTs) were identified by performing “BLASTN” searches of the C. pauciovulata plastome against its mitogenome with an e -value cutoff of 1 × 10 –6 , at least 80% sequence identity and a minimum length of 50 bp. Additionally, “BLASTN” searches of all 11 ndh and accD genes from the Lamprocapnos spectabilis plastome (NC_039756) against the C. pauciovulata mitogenome were also performed because the 12 plastid genes were lost or pseudogenes in the C. pauciovulata plastome. ORFs longer than 150 bp in the mitochondrial genome were predicted using the “Find ORFs” option with the ATG start codon in Geneious Prime. Any ORFs that overlapped with the annotated mitochondrial genes and MIPTs were excluded. To identify a conserved domain (CD), ORFs were translated, and CD searches were performed against the Conserved Domain Database (CDD) v3.19 [ 69 ]. To search for potential CMS-type ORFs in the C. pauciovulata mitogenome, all ORFs were compared with the annotated mitochondrial genes using “BLASTN” with an e -value cutoff of 1e-3, a minimum length of 30 bp, and at least 90% sequence identity. The TMHMM Server v.2.0 [ 70 ] was used to predict transmembrane helices in selected ORFs. Forty-one mitochondrial genes were searched using PREP-Mt [ 71 ] with a cutoff value of 0.5 to predict RNA editing sites. The available mitochondrial transcripts in the C . pauciovulata transcriptome (see below) were identified using BLAST + and aligned with the genomic gene sequences to verify the empirical RNA editing sites on the protein-coding genes. In addition, we mapped the corrected reads (see below) to the genomic gene sequences using Bowtie2 to confirm the sites.

Identification of organelle-targeted genes in the nucleus

Total RNA was isolated from fresh leaves using the methods of Breitler et al. [ 72 ]. The Corydalis RNA was sequenced using the Illumina HiSeq2000 platform with PE reads, and error correction for the PE reads was performed using Rcorrector v1.0.4 [ 73 ]. To identify organelle-targeted genes in the nucleus, transcriptomes from C . pauciovulata were assembled de novo using Trinity v2.13.2 [ 74 ] with the “trimmomatic” option. The transcripts were examined for completeness of the assembly using Benchmarking Universal Single-Copy Orthologs (BUSCO) v5.2.2 [ 75 ] with the lineage “eudicots_odb10”. The IGT events were identified using “BLASTN” ( e -value cutoff of 1e-10) of the 41 mitochondrial-encoded genes of the L. tulipifera mitogenome and the 79 plastid-encoded genes of the L. spectabilis plastome as queries. Four plastid-encoded genes, accD , rpl20 , rpl23, and rps16, have been substituted by a cytosolic homolog of an eukaryotic or mitochondrial origin [ 35 , 38 , 39 , 40 , 41 , 76 , 77 , 78 , 79 , 80 , 81 , 82 ]. To investigate the possible substitution of these genes in C . pauciovulata , the amino acid sequences of nuclear eukaryotic acetyl-CoA carboxylase ( ACC ) (AT1G36180 from Arabidopsis thaliana ), RPL20 (AT1G16740 from A. thaliana ), RPL23 (Q9LWB5 from Spinacia oleracea ), and RPS16 (AB365526 from Medicago truncatula ) were used to perform a “BLASTP” ( e -value cutoff of 1e-6) search against the translated Corydalis transcriptome. To detect the nuclear-encoded NDH complex in the nucleus, protein sequences from Arabidopsis thaliana were downloaded from The Arabidopsis Information Resource (TAIR) [ https://www.arabidopsis.org/ ] as references. The reference protein sequences were aligned to the Aquilegia coerulea v3.1 transcriptome from the genomics portal Phytozome v12.1.6 ( https://phytozome.jgi.doe.gov/pz/portal.html ) using “BLASTP” to extract the nuclear-encoded NDH complex of A. coerulea (Table S 5 ). The protein sequences from both A. thaliana and A. coerulea were used as queries against the translated Corydalis transcriptome. The chloroplast transit peptide (cTP), mitochondrial targeting peptide (mTP) and its cleavage site were predicted using TargetP v1.1 [ 83 ].

For the DNA-RRR genes, we focused on 32 nuclear genes from A. thaliana that were found to target plastids, mitochondria, or both [ 84 ] and used them as queries for “BLASTP” searches against the translated C. pauciovulata transcriptome (Table S 6 ). Transcriptomes from L. tulipifera (SRR8298316) and N. nucifera (SRR8298325) were also assembled de novo using the Sequence Read Archive (SRA) with Trinity to retrieve the DNA-RRR gene sequences.

Estimation of structure and substitution rate variation

The C . pauciovulata organelle genomes were aligned with the published N. nucifera plastid (KM655836) and mitochondrial (NC_030753) genomes from Proteales, which are available for comparison based on complete organelle genomes, using the “progressiveMauve” algorithm in Mauve v2.3.1 [ 85 ] in Geneious Prime. Organelle genomes from L. tulipifera were used as a reference. The nonsynonymous ( d N ) and synonymous substitution ( d S ) rates of organelle genes from C . pauciovulata and N. nucifera were calculated in KaKs_calculator v2.0 [ 86 ], employing the GY-HKY substitution model. Protein-coding genes from the L. tulipifera organelle genomes were used as a reference. Individual protein-coding genes were aligned based on the back-translation approach with MAFFT v7.017 [ 87 ] in Geneious Prime. Statistical analyses were conducted with R v4.1.2 [ 88 ].

The d N and d S rates of DNA-RRR genes from C . pauciovulata and N. nucifera were also calculated as described above. DNA-RRR genes from the L. tulipifera transcriptome were also used as a reference. To identify introns and exons in the DNA-RRR genes, a draft nuclear genome for C . pauciovulata was assembled using MaSuRCA v4.0.1 [ 89 ]. Nucleotide sequences of DNA-RRR genes from C . pauciovulata were used as queries against the draft genome of C . pauciovulata and aligned with identified nuclear contigs using MUSCLE [ 90 ] to determine the intron/exon boundaries.

Availability of data and materials

The data sets supporting the results of this article are included in additional files. Complete mitochondrial and plastid genome sequences are available in GenBank ( https://www.ncbi.nlm.nih.gov/nuccore/OR100521 , OR100522).

Abbreviations

Number of substitutions per nonsynonymous site

Number of substitutions per synonymous site

Large single copy

Small single copy

Inverted repeat

Intracellular gene transfer

Mitochondrial DNAs of plastid origin

Plastid DNAs of mitochondrial origin

DNA replication, recombination, and repair

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This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2017R1A6A3A11034431 to SP).

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SP contributed to the design of the project and assembled, finished, and annotated the plastid and mitochondrial genomes, generated the draft nuclear genome and transcriptomes, performed all analyses, prepared the figures and tables, and drafted the manuscript; BA designed and performed the experiments and read/edited the manuscript; and SJP contributed to the design of the project and read/edited the manuscript. All the authors read and approved the final draft of the manuscript.

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Park, S., An, B. & Park, S. Dynamic changes in the plastid and mitochondrial genomes of the angiosperm Corydalis pauciovulata (Papaveraceae). BMC Plant Biol 24 , 303 (2024). https://doi.org/10.1186/s12870-024-05025-4

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• Kenji Watanabe   ORCID: orcid.org/0000-0003-3701-8119 4 ,
• Takashi Taniguchi   ORCID: orcid.org/0000-0002-1467-3105 5 ,
• Jose Avila   ORCID: orcid.org/0000-0003-1027-5676 6 ,
• Pavel Dudin   ORCID: orcid.org/0000-0002-5971-0395 6 ,
• Qunyang Li   ORCID: orcid.org/0000-0002-6865-3863 3 ,
• Pu Yu   ORCID: orcid.org/0000-0002-5513-7632 1 , 7 ,
• Wenhui Duan   ORCID: orcid.org/0000-0001-9685-2547 1 , 7 , 8 ,
• Zhida Song 2 &
• Shuyun Zhou   ORCID: orcid.org/0000-0002-9841-8610 1 , 7  

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Magic-angle twisted bilayer graphene exhibits correlated phenomena such as superconductivity and Mott insulating states related to the weakly dispersing flat band near the Fermi energy. Such a flat band is expected to be sensitive to both the moiré period and lattice relaxations. Thus, clarifying the evolution of the electronic structure with the twist angle is critical for understanding the physics of magic-angle twisted bilayer graphene. Here we combine nano-spot angle-resolved photoemission spectroscopy and atomic force microscopy to resolve the fine electronic structure of the flat band and remote bands, as well as their evolution with twist angle from 1.07° to 2.60°. Near the magic angle, the dispersion is characterized by a flat band near the Fermi energy with a strongly reduced band width. Moreover, we observe a spectral weight transfer between remote bands at higher binding energy, which allows to extract the modulated interlayer spacing near the magic angle. Our work provides direct spectroscopic information on flat band physics and highlights the important role of lattice relaxations.

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Acknowledgements

This work is supported by the National Key R&D Program of China (nos 2021YFA1400100 and 2020YFA0308800), the National Natural Science Foundation of China (nos 12234011, 52025024, 92250305, 52388201, 12327805 and 12304226) and the Basic Science Center Program of NSFC (no. 52388201). H.Z. acknowledges support from the Shuimu Tsinghua Scholar project and the project funded by China Postdoctoral Science Foundation (grant no. 2022M721887). Z.S. and Y.W. were supported by the National Natural Science Foundation of China (General Program no. 12274005), National Key Research and Development Program of China (no. 2021YFA1401900) and Innovation Program for Quantum Science and Technology (no. 2021ZD0302403). K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT (grant no. JPMXP0112101001), JSPS KAKENHI (grant no. JP20H00354) and the CREST (JPMJCR15F3), JST. We acknowledge SOLEIL for the provision of synchrotron radiation facilities of beamline ANTARES.

Author information

These authors contributed equally: Qian Li, Hongyun Zhang.

Authors and Affiliations

State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, People’s Republic of China

Qian Li, Hongyun Zhang, Wanying Chen, Changhua Bao, Qinxin Liu, Tianyun Lin, Haoxiong Zhang, Pu Yu, Wenhui Duan & Shuyun Zhou

International Center for Quantum Materials, School of Physics, Peking University, Beijing, People’s Republic of China

Yijie Wang & Zhida Song

AML, CNMM, Department of Engineering Mechanics, Tsinghua University, Beijing, People’s Republic of China

Shuai Zhang & Qunyang Li

Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan

Kenji Watanabe

International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan

Takashi Taniguchi

Synchrotron SOLEIL, L’Orme des Merisiers, Gif sur Yvette, France

Jose Avila & Pavel Dudin

Frontier Science Center for Quantum Information, Beijing, People’s Republic of China

Pu Yu, Wenhui Duan & Shuyun Zhou

Institute for Advanced Study, Tsinghua University, Beijing, People’s Republic of China

Wenhui Duan

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Contributions

S. Zhou designed the research project. Qian Li and Hongyun Zhang prepared the samples. Hongyun Zhang, Qian Li, W.C., C.B., Q. Liu, T.L., Haoxiong Zhang, J.A., P.D. and S. Zhou performed the NanoARPES measurements and analysed the ARPES data. Qian Li performed the AFM measurements, with assistance from S. Zhang, Qunyang Li and P.Y. K.W. and T.T. grew the BN crystals. Y.W., W.D. and Z.S. performed the numerical calculations. Qian Li, Hongyun Zhang, P.Y. and S. Zhou wrote the manuscript, and all authors commented on the manuscript.

Corresponding author

Correspondence to Shuyun Zhou .

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Nature Materials thanks Petr Stepanov and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data

Extended data fig. 1 sample preparation..

a, Monolayer graphene exfoliated on SiO2/Si. b, The bottom graphene is picked up by BN attached to PDMS stamp. c, The twist angle between two layers of graphene is achieved by rotating the other half of graphene on the SiO2/Si. Then the top graphene is picked up by the PDMS/BN/G heterostructure. d, The heterostructure is flipped over, and the BN/tBLG sample is picked up by another PDMS stamp (see the live video in the Supplementary information ). e, The heterostructure is transferred onto a gold-coated substrate. f, Two narrow pieces of graphite are used to connect graphene and the gold-coated substrate. The scale bars in a-f are 100 μ m.

Extended Data Fig. 2 Determination of twist angle from ARPES and AFM measurements.

a, Optical image of 1.93 ∘ tBLG sample. The red dot indicates the measurement position. Red and orange curves indicate the top and bottom graphene layers, respectively. b, AFM image to show the measurement position as indicated by the red oval. c, d, L-AFM image and the fast Fournier transform (FFT) filtered image measured before the NanoARPES experiment. The scale bar is 20 nm. e, f, C-AFM image and the FFT-filtered image measured after NanoARPES experiment. g, Extracted line profiles from d and f along the blue and red lines, which suggests that the moiré period of 7.3 nm not change during the NanoARPES measurement. h, Fermi surface measured at the red dot in a, from which the separation between Kt and Kb points agrees well with the extracted moiré period from AFM measurement.

Extended Data Fig. 3 AFM characterization of the moiré superlattices for twist angles θ ranging from 1.07 ∘ to 2.60 ∘ .

a-i, AFM characterization for P1 ( θ = 1.07 ∘ ) and P2 ( θ = 1.31 ∘ ) on sample S1. The white scale bar in a is 20 nm. j-r, AFM characterization for P3 ( θ = 1.93 ∘ ) and P4 ( θ = 2.22 ∘ ) on sample S2. s-w, AFM characterization for P5 ( θ = 2.60 ∘ ) on sample S3. The first four columns are the AFM images, and fast Fourier transform (FFT) of AFM images, and FFT-filtered images, and ARPES spatial images with P1-P5 marked by red spots. The fifth column shows the optical images of the three samples S1-S3. The scale bars in a, e, j, n and s are 20 μ m.

Extended Data Fig. 4 Extracting the bandwidth of the flat band from experimental dispersion images at different twist angles.

a-e, Measured dispersion images from 1.07 ∘ to 2.60 ∘ tBLG along the cut H direction as indicated by the black line in the inset. f-j, Calculated dispersion images from 1.07 ∘ to 2.60 ∘ . The gray broken lines indicate the momentum range of the flat band edge, where gaps open between the flat band and remote bands. k-o, EDCs from a-e. The red tick marks indicate the peak positions, which are used for extracting the flat band dispersion.

Extended Data Fig. 5 Dependence of the momentum separation between the remote bands and momentum position of the vHS on the interlayer tunneling parameters ω AB and α.

a, Experimental energy contour at -0.5 eV for the 2.22 ∘ tBLG. The red arrow indicates the momentum separation between remote bands p1 and p2. b-d, Calculated energy contours using ω AB of 80, 120 and 160 meV, respectively. The energy separation gradually increases with increasing of ω AB , from which the calculated result at ω AB = 120 meV agrees well with the experiment result. e, Experimental energy contour at -0.1 eV for the 2.22 ∘ tBLG. f-h, Calculated energy contours using α of 0.5, 0.8 and 1.0, respectively. The position of the vHS shifts away from the moiré Brillouin zone border (gray dashed hexagons), from which the calculated results at α = 0.8 agrees well with the experimental results.

Extended Data Fig. 6 Evolution of the energy separation between remote bands p1 and p2 with twist angle.

a, Dispersion image at twist angle of 1.07 ∘ measured along the cut V direction as indicated by the black line in the inset. b, c, The comparison of the extracted ΔE1 and ΔE2 from experimental results with calculations using different parameters of ω AB and α . d, The comparison of energy separation between experimental and calculated results at different ky under the twist angle of 1.07 ∘ . The gray broken line indicates that overall linear scaling of the energy separation with ky. The error bar of experimental results in b-d is 3-4 meV, which is too small to see. Data in b, c are presented as difference between fitting values from 5 samples with different twist angles, with error bars representing the standard error.

Extended Data Fig. 7 Reproducibility of the experimental spectral weight ratio between p1 and p2 at different sample positions and after different beam exposure time.

a, ARPES spatial intensity image to show the two different positions A and B on sample 1, indicated by red and blue marks. b, c, ARPES energy contours at -0.5 eV for positions A and B. d, ARPES spatial intensity image to show the position C on sample 2, indicated by the green mark. e, ARPES measured energy contours at -0.5 eV for position C. f, Extracted momentum distribution curves (MDCs) from b, c, e along the red, blue and green broken lines. The extracted ratio between p1 and p2 from these three positions gives the same value, showing that the ratio is reproducible on different sample positions and different samples with the same twist angle. g, h, The dispersion images measured along the direction shown in inset of h at the beginning and after 6 hours measurement. i, j, ARPES intensity maps measured at the beginning of NanoARPES experiment and after 6 hours beam exposure. k, Extracted MDCs from i and j along the blue and red broken lines. The spectral weight ratio between p1 and p2 does not change with the beam exposure time.

Extended Data Fig. 8 Extracting the interlayer spacing of 1.07 ∘ tBLG from the spectral weight ratio.

a, Energy contour measured at -0.6 eV in 1.07 ∘ tBLG. b-e Calculated energy contours by using interlayer spacing c = 3.35 Å, 3.40 Å, 3.42 Å and 3.50 Å, respectively. f-j, Extracted MDCs from the calculated dispersion images in a-e along the black dashed lines at -0.6 eV.

Extended Data Fig. 9 Extracting the interlayer spacing for tBLG at twist angles ranging from 1.07 ∘ to 2.60 ∘ .

a-e, ARPES intensity maps measured at -0.60 eV at twist angles from 1.07 ∘ to 2.60 ∘ . f-j, Calculated energy contours after adjusting the interlayer spacing to fit the spectral ratio in a-e. k, Extracted MDCs at -0.6 eV, as indicated by the black dashed line in a, from which the interlayer spacing is obtained.

Extended Data Fig. 10 Lattice relaxation revealed by local vertical conductivity from C-AFM measurements.

a-d, C-AFM images measured at twist angles of 2.18 ∘ , 1.27 ∘ , 1.07 ∘ and 0.51 ∘ . e-h, Current profiles measured along the colored lines in a-d, which are normalized by the local current at AA-stacking (maximum current). The dashed line marks the minimum current.

Supplementary information

Supplementary information.

Supplementary Figs. 1–4 and discussion.

Supplementary Video 1

A video showing the flipping process whereby the PDMS/BN/tBLG structure was flipped over and picked up by another PDMS stamp.

Source data

Source data fig. 1.

Statistical source data.

Source Data Fig. 2

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Li, Q., Zhang, H., Wang, Y. et al. Evolution of the flat band and the role of lattice relaxations in twisted bilayer graphene. Nat. Mater. (2024). https://doi.org/10.1038/s41563-024-01858-4

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Received : 27 May 2023

Accepted : 11 March 2024

Published : 24 April 2024

DOI : https://doi.org/10.1038/s41563-024-01858-4

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