Hey everyone, good morning, good afternoon, and good evening for wherever you are today. I'm here from Harness and I'm here to talk to you about building continuous resilience in the software delivery lifecycle with Chaos Engineering. Ultimately, cloud native development has enabled teams to move quickly, but it also introduces new ways for software to fail quickly. SREs, QA engineers and developers need to work together to optimize reliability and resilience to improve developer productivity. My name is Matt Shilisham and I'm a product marketing manager at Harness. We are a modern software delivery platform for continuous integration, continuous delivery, security testing, feature flags, service reliability management with service level objectives, cloud cost management, and Chaos Engineering. For the past 20 years, I have been helping teams build reliable and resilient systems and teams across the nuclear power industry, retail and e-commerce, as well as nonprofit groups that I've been a part of locally in Minnesota. I've enjoyed being a software engineer, product manager and product marketing manager and hope you enjoy this presentation today. Why am I here? I'm part of the Lytnis Chaos open source community, which is an incubating CNCF project. Harness as a sponsor is also part of the CNCF as a silver sponsor. You may have seen me at QCon plus cloud native Con Detroit, where we had our first ever chaos day in October 2022. Please feel free to contact me via email, Twitter or LinkedIn. Ultimately, we are here because we are building and making things better. As engineers and leaders, we are always seeking to understand and learn how the world works. I talk about how building for resilience is in fact chaos engineering. Ultimately, this discipline is simply allowing us to understand how the system works and operates. This is one of my favorite quotes from Twitter, from Andy Stanley, who has a podcast, where he just says, if you don't know why it's working when it's working, you won't know how to fix it when it breaks. And for me as a prior IT administrator, this is great, because you know, like when I had incidents and I had to respond, if it was a brand new issue that I didn't know what it was, it was hard. I had to dig around, I was stressed, nervous, but when I was able to practice failure and prepare for it, I was more confident. And ultimately, less failure occurred because I proactively planned for it. Another thing here, so why does chaos engineering even exist? So like, we get this little logo from bytebitego.com, resilience mechanisms were developed in the code and as architecture to help the system recover, fail gracefully, or simply display an error message to the user. Not everything has to be perfect, but an error message can instruct the user why something failed or help, you know, the IT person solve the problem. Chaos engineering can be used to validate and tune these mechanisms to make sure they work. Now at the end of the day, you say, why does chaos engineering exist here? Another way to phrase this is, you know, like, what failure modes does my system have, you know, and what mechanisms am I using to prevent that? And like, how do I test it? Do I wait for an incident to happen to prove it? Or can I test it proactively? Some common, you know, Kubernetes failure modes. This image is great to think through. I got these failure modes or stuff at the Kubernetes website. System instability, resource contention, scaling issues, configuration errors, resource exhaustion. Now Kubernetes is self healing to an extent, but the application that you put onto the container isn't necessarily always self healing. And you have to know how to handle these failures that happen. Now chaos engineering, the experience today, it's basically like, you know, a shopping cart on an e-commerce website. You can basically click around. This is an example from the litmus chaos open source project from the CNCF.  And there's a button you can click and there's experiments that you can pull from, right? But ultimately, you know, that works well. And like, when you click in here, you can see experiments that are basically, you know, easy to understand and self service.  So like today, a CAS experiment might just look like this, which is a declarative YAML file. You know, in here, all we're trying to do is delete like a pod from a Kubernetes deployment to see how my application behaves when it restarts or when that pod gets disrupted. You know, does my user on the other end of the application, you know, get an error message? Or does it gracefully degrade? Or is it a seamless transition to the restart application? So that's basically it, right? Now, if I dive into what we're trying to do with continuous resilience, you know, let's break this down on how reliability and resilience can help development teams. So improving resilience across the software delivery lifecycle, ultimately giving customers improved experience. Now, generally speaking, SREs, Q engineers and developers are a team, but they do work siloed, right? They hand off work to each other, whether it's through a PR, through a test, or, you know, through an incident. But what we're trying to do here, right, is, you know, SREs can leverage chaos engineering, maybe after an incident to recreate that incident to see, you know, how they can fix it, if they can fix it, or perhaps increase the blast radius of that incident in a simulated environment, right? And then you can validate that the experiment, the fix that you put in for the experiment resolves, and then they can shift that learning that test, if you will, left to the QA environment. So now the QA team can run that same experiment to see if there's any, you know, failure in that environment to see if the system, the configuration drifted. And ultimately that QA person, you can shift that to the left of the developer, so the developer can run that chaos experiment, you know, in that CI pipeline or that QA test environment. So now you have protection across the pipeline, and you're not waiting for a random incident, you know, that can happen. Now you can actually avoid that incident. So if I think about this at the business level, you know, innovation in software is a continuous process, and it has to be. And it can help us improve multiple aspects of the business, but more importantly, the developer and customer experience itself. So let's talk about innovation and achieving reliability and resilience. You know, it's challenging to solve everything at the same time, but this year in 2023, we need to not only move fast with high velocity, but we also need to do it efficiently at a low cost and with the highest reliability and resilience needed for the best customer experience. It's a mouthful, but how do we solve this, you know, automatic automation is key in a pipeline. So let's talk a little bit about the cost of software development. So right now, you know, there's approximately 27 million software developers globally with an average salary of 100,000 in the annual payroll equivalent to 2.7 trillion. You know, that's a lot of money, right?   Right, there's meetings, there's other toil, there's watching the deployment like babysitting it, right, there's security testing, there's all these things, you know, the toil that's preventing development teams to be productive. And not that you have to code for eight hours a day, but you can't be creative, you can't innovate. And if you're being, again, bogged down by all these toils in the deployment process, then you're not being as productive. So if we look at the math behind this opportunity, again, the annual payroll of 2.7 trillion, you know, what does that look like? So if we can cut developer toil in half, which is doable, right, then ultimately, like, you can look at your developer budget increasing as well. And then you can redirect that to development, right, whether that's being more productive with the same amount team or hiring more to do more capabilities, right, you don't always have to do more or less, but you can do more with cutting down this toil, you know, and I just wanted to point out as well, code isn't always the best way to solve a problem. But if the toil around building a prototype or testing a small unit of code is complicated, a development team won't feel comfortable testing out new ideas. So again, if you're able to quickly, you know, write code to solve a problem to test it to prototype it, and you can if you can deliver that, you know, to non production or production quickly and test it with a few customers, like that's an ability of a development team to task it feedback, you know, and iterate. So ultimately, like, innovate, you need to innovate to increase developer productivity and saved costs. And so like, where can you increase developer productivity? Right, let's break that down for reliability and resiliency. So you can reduce the software build time. You can reduce software deployment time, and you can reduce software to bug time. So let's dig into that last one a little bit more. Why do why developers spend more time in debugging right now?   Dependencies have not been tested. You know, it's very normal to not understand all that goes in and goes out of your system, especially in these managed service environments, you know, so you can't test everything, right? Sometimes you sometimes you wait for an incident to uncover that dependency, you know, retroactively, but you would rather be proactive, then, you know, a lack of understanding of the product architecture in today's world with thousands of microservices, you know, can a human understand the map of everything, you know, it's very hard to memorize that in the old school days of, you know, monolithic applications, sure, but microservices today are challenging. And then, you know, sometimes the developer, you know, their code is running in a new environment. And again, your code should be written in a way to kind of move around the workload to different clouds, but sometimes, again, there's dependencies that are intertwined that you just don't know about. So software developers are spending a lot more time debugging, right? And if you think about it, debugging in production, right, is the worst possible experience. If you think about responding to an incident, right, it's very stressful. It's painful for the customers. People are hunting and digging through the problem. And ultimately, the cost of that is expensive, because now you have production code that's broken, you have to go back, fix it, test it. And that's time that could have been spent on, you know, a new feature development, right? So and it's also like the loss opportunity costs of that customer, because maybe you lost that customer with that transaction that they weren't able to get. So that's where going back to that other slide where we're shifting left to QA and shifting left, you know, to non production and the code for the developer. If you can actually find these, you know, infrastructure failures and application failures early on, it's cheaper.  So if you look at this, it may cost $10 instead of $100. And if you fix it, you know, in the code right away before you even push it to QA, that can be up 100 times different than actually fixing it in production. So these are real values, right, that you can apply to kind of show why it's important to test more up front. Now, if you look at cloud native developers, they're focusing on the container itself and, you know, the consumable API is that it's using, right cloud native developers experience this at a rapidly increased pace because we are making it easier to deliver software, you know, they're experiencing more failures because it's easier to deliver software. Containers are helping developers focus on their application and API not worry so much about the stack underneath chances. You know, the chance of lack of understanding the lack of testing can cause issues across the whole infrastructure stack. And again, if you look back at, you know, even common Kubernetes failures, right, the system instability, the resource contention, right, these occur when Kubernetes cluster run out of resources such as CPU or memory configuration errors occur when a Kubernetes cluster is not properly configured. Resource contention occurs when multiple components compete for the same resources, system instability occurs when the Kubernetes cluster is not stable, and is regulated crashing or restarting. And chaos experiments that should be automated in the CD pipeline, for example, include testing for this resource exhaustion configuration errors, resource contention. And additionally, you can automate the testing for the ability to recover from these unexpected events and errors, as well as the ability to scale up and down as needed. And then ultimately, this can help you automate testing for the ability to detect, diagnose, and mitigate security vulnerabilities. So as develop, you know, as developers dig into these problems and debug, you know, they shouldn't have to like dig too far to find that issue, right? You're testing code as fast as possible and shipping code as fast as you can, but not looking at the overall system. And as that container sits in an application that consumes APIs and resources on infrastructure, the impact of the outage can greatly, you know, extend just beyond that container, right? So you have to ask yourself, are containers, are they tested for the functionality of these faults occurring? And is it revealing the deep dependencies in that infrastructure stack? So if you look at the faults of these deep dependencies, the problem is that happens is that customer face application is impacted, and the developer jumps in to resolve the issue, and they find out that there are multiple dependencies that are causing an issue. And this ends up increasing the cost of development, right? So now we have a service resilience is impacted, developers are debugging it, you know, dependency fault is discovered, and then new resilience issues discovered as well. So this is the case of the 10x to 100x costs and bug fixes. If we look at dependent fault testing, and what's required, what we can think through here is, you know, test your code for faults that are happening in like the code itself, the API consumed external resources, dependent infrastructure. And then again, this can apply over the container code, the application, API resources and infrastructure. This means that cloud native developers need fault injection and chaos experimentation. So if we look at revisiting the original use case of chaos engineering, we introduce controlled faults to reduce expensive outages. Seems important. But ultimately, we introduce controlled faults to reduce expensive outages. You know, we recommend recommended production chaos testing. And then it was very high barrier to entry. And then it was more so on a game day model. And then traditional chaos engineering has been more so a reactive approach driven by regulations like a requirement. But the new patterns driven by chaos engineering are the need to increase developer productivity, right, to remove that toil so they don't have to dig for answers and the need to increase quality in cloud native environments and the need to guarantee reliability in club in move to cloud native. So this this need leads the emergence of the new continuous resilience, which is basically verifying resilience through automated chaos testing continuously. And all that means is, you know, have a known failure mode that you need to protect against, you know, you're using a resilience mechanism, you can have a chaos tests to validate that that resilience mechanism still works as expected. Right, whether that's alerting you or, you know, triggering a failover, or just an error message, right, but if you can do this continuously, you can know your system is protected across the pipeline. So again, continuous resilience is chaos engineering across development, QA, pre prod and production. And one way we look at this is we measure it with resilience metrics, because if you can't measure something, you don't know if you're improving it. So the resilience score, it's the average success of the percent of steady state, given an experiment or component or a service. And then what that means is basically like my, your expected system is supposed to behave a certain way during a disruption. So then you can have a score associated with, you know, did it change or not change? Is it good? Is it bad? Is it up or down? And if you map that to resilience coverage, that's basically the number of chaos tests executed divided by the total number of possible chaos tests times 100. So if you think about building resilience for a system, maybe you have 10 failure modes you're trying to protect against that equate to five, you know, five to 10 tests that could be ran. So as you onboard a new system to get production ready, maybe you can start off by running 10 out of 10 to get that 100% coverage, or maybe you're just doing five out of 10 because, you know, every deployment you only need to do like most common ones, but then once a month, there once a quarter you're doing the other five. But basically continuous resilience and the developer pipeline is a way to achieve that resilience. So again, if we look at, you know, the game day approach versus pipeline approach, chaos experiments are executed on demand with a lot of preparation versus in pipelines chaos experiments are executed continuously and without much preparation. And then, you know, primary, primarily retarget SREs in the persona with a game day model versus with chaos and pipelines, all personas are executing the chaos experience. And then again, chaos with game days, the adoption barrier is very high because they're manual, right, they're events, whereas chaos and pipelines adoption barrier is much less because every time you're running a deployment or at a certain frequency, you're automatically running the tests. So again, traditionally, you know, developing chaos experiments has been a challenge code is always changing bandwidth is not budgeted to creating that. And the responsibility is typically not identified, you know, SREs are usually pulled into the incident and corresponding action tracking and then pulling the QA or developer. And then ultimately, like from, you know, identify identification to fix, it's not tracked to completion. So no idea how many more experiments develop or what failure modes of protect against, but a continuous resilience, you know, developing chaos experiment is a team sport across the delivery life cycle. And it's typically is attributed to an extension of regular tests, you know, chaos, hub or experiment repositories are maintained as code and get it. So you can have version control and historical information on how systems were configured. Then you can know exactly like how many tests need to be completed because you have the resilience coverage metric. So it's never an unknown that you're talking to leadership about what tests you're running or how how it's performing. You can actually just say, here's the test I'm running and here's the trend. So in summary, resilience is a real challenge in the modern or cloud native system because of nature of the development, use fault injection and chaos experimentation to get ahead of the resilience challenge and push chaos experimentation as a development culture into the organization rather than a game day culture. Thanks for listening today. I appreciate your time. Just wanted to let you know of a community event, Chaos Carnival, it's happening March 15th and 16th. It's a two day virtual event that's entirely free.  And if you have any questions, again, you can reach out to me at my hardest email or on Twitter or on LinkedIn. Thank you very much. Have a great day.


All right, so what mistakes in her understanding Vishal she had?   And then the uat is there's no requirements and stuff like that because the uat is the last testing before you deploy in the product. So it's the meat, it's the the uat testing is with stakeholders and representatives. I think that's that's what she that's where that's what she missed. For rest, she was okay. Okay, so you got that Amado. I got it. Thank you. The uat is just with the stakeholders not at that point they don't have any requirements anymore. Yeah, the b it rolls. Yeah, the b it rolls doesn't end. So the product is deployed, like, you know, it's just, yeah. So the uat test user except in testing is like, you know, it's the last thing and if there's something, if there's like, you know, the BA asked the stakeholders and stuff like that who's rep like, you know, who's going to be the main main person or main, you know, who will be the doing uat testing. You know, there could be stakeholders or representatives. But if there's anything needs to be changed, the BA has to go back and forth with the developers. Yeah, you know, if it's if it's changeable. Okay. Yeah. Thank you. You're welcome. Okay. So then user acceptance testing. So who leads the user acceptance testing and how they do that. That is a question to you. The user, from what I just said, the user as acceptance testing is still needed by by the BA, but it should be done by the stakeholders. The BA is also the leading the meeting. So, BA is leading to how we do that like that is basically the question. Okay. How do we do the user acceptance testing? Let's say they are done with the user acceptance testing is definitely to let them. The final part of the project. So the BA will send a meeting invite to the stakeholders and the testers that needs to be there. They will send out a meeting invite. The BA will call all of them to a meeting. Do an introduction in the, how do we say to the invites like the body and stop the reason for the meeting is user acceptance testing. And then the BA will go ahead and present the whole thing like, hey, this is the end of our project is our testing and all the rest. Now pass it over to the stakeholders or the person's responsible to do the user acceptance testing. Okay. So pass it to the stakeholders. So like how? I don't know how to explain it. I don't know if I'm saying. Okay, so I'm going to, I'm going to try to go over again. Let me tell you. So when, when the whole product was ready, right before deployment, there's a final testing that is called a user accepting testing.  It's the stakeholders representatives of stakeholders. It's called UAT testers be a works with the stakeholders and ask them to identify the user accepting testers, the UAT testers, and he gets the list from them, and then he invites them to give them an overview of the test cases.  But there's a there's another thing I just remembered that QA lead is a helper to a be a to provide him needed access to the test environment. And that's how the user accepting testing is done. That's the process of it. I don't know if I'm explaining right or wrong, but Right. Yeah. So now it, like what you understood. For he said the be a leads the user accepting testing, but before that they need to get through the stakeholders to identify. How do we say the people that would do the you the UAE testing right user acceptance testing. The user acceptance can seem like they need to get the leads of those people from the stakeholders. And then when you get the list from the stakeholders, you're going to send out the invites to them for the user acceptance testing session. So there's no invite. Or I mean, you can have a meeting and how are you going to basically. Yeah, exactly. Okay. Okay. Yeah. Yep. So sending an invite and then then what Get with them. So a meeting. So because we already have the leads from the stakeholders, the list of the people that would actually do the user acceptance testing. You got them. So you got it from the stakeholders and you go into the meeting. Now a day as a day of the meeting. Right. Okay. Yep. So that that was good. So again, let me quickly explain the user acceptance testing again. Yeah. So that you guys would. So what is user acceptance testing. So user acceptance testing is the last activity of of the project. Okay.  And then user acceptance testing be like why we do the user acceptance testing. So now you are the stakeholder. Okay. Now imagine that you are the stakeholder.  Okay. That some project you invested a million dollar. Okay. And that project is ready. And you have that product basically for your users. So. Will that be will not, will that not be wise that first at least test yourself so you don't get embarrassed in front of users. Because if you, you know, applied that product for the user and user started getting like a lot of problems, then not only you're going to be embarrassed on that, but you might be, you know, losing your users. Right.  Right. There would be a negative impact. Okay. Everyone will be kind of pretty hard, but there would be a negative impact. So that's why, you know, before deploying, deploying anything for the users, the business stakeholders who have invested, they have to do the user acceptance testing. So they have to test with the user perspective, all the functionality that will be related to user. Okay. So they, they have to test that before the go ahead for deployment will be like, you know, granted. Okay. So make sense. Any question? Why? There is like the UAT. So that is the answer for that. Okay. Because this is like the investor, the stakeholders who had invested in the product, they have to give a go ahead before the deployment for the user will happen. Okay. So that's why it's like user testing is done. So now, so then who will be user acceptance tester? The logical answer, if you understand what the user acceptance testing is, would be like either they would be stakeholder or representative of the stakeholders who have the right to decide who will test that product. Certainly stakeholders who have invested the money, right? Yeah. So either they will. So now, from the team, which I mean like a BA developer QA, all those like IT team, who is the person who have a closest relationship or longest relationship with the stakeholders? The BA. Exactly. So it would be more logical for the BA and BA is also vice of users, right? Yes. Okay. And BA when doing the testing with the testing team, also partnering with them and testing them all the test cases, which are user perspective test cases. Okay. So that user perspective test cases, BA does with the testing team, that is basically BA is a pre-run for the UAT. So basically that's when BA is learning the UAT. What are the test cases and what are the outcomes? And basically testing himself, okay, with the testers. Testers have definitely tested on their end, but BA is just learning that, like the testing that, you know, getting basically same the credential username and all those test scripts related to the user with the user perspective and then executing those.  Okay. So they would be like a pretty much, you know, very simple and easy to understand. Okay. So, for example, like, you know, this is how would be the UAT test scripts. Okay. So this is the actual test scripts for user acceptance testing, that real-time document. Okay. So that is a basically template. In that template, these things already would be explained like introduction, task, what that means, UAT is intended to test the functionality include, you know, data, this is whatever would be there, you know, and browser, which browser you can use it because you are testing for the user. So basically internet browser that you will be using if it is like Internet based and if it is like mobile based, then that then test account means like, you know, these would be like user ID, common user ID will be like this password will be, you know, this is with the password, this, this, this, and then, you know, the first time you use the dashboard login, we will ask to answer some security question means when you are first time login in security answer to first, first phone number answer one that is basically answer, you know, you have to write answer one, best friend answer to your favorite color, answer three and favorite sport team answer three, you know something like that. So to write answering the security question at each login click on yes radio button means like save it. So this is how it is being like the instructions are being given to the users. Okay. Like you are teaching each other how to use the Internet. Okay. Then test data.   Then these are the test scripts. Okay. Task one provided dashboard login. Okay. So login to ABC car dashboard. Click sign in using ABC car ID, which is definitely you will use this car ID and then enter the username, you know, respond to the security question. This is would be then under a recognized computer select yes to buy. I'm sorry. I'm sorry guys. My connection dropped. No worries. So bypass the security, you know, do this. So user data username password, which you already have, you know, you enter it. And what would be possible criteria? So it's an existing functionality means it's not a new functionality. It is existing. So, you know, expect a result successfully login to ABC car cloud dashboard application homepage opens in a new browser or start start here button gets displayed corporate information gets like. So this is the expected result. And then what next car corporate search. So intermember pin value to the test data sheet in the step one and click, you know, search button. Select text ID, number corresponding the members pin value enter from the drop down list on September to field. Then, you know, expect a result. Repeat for each of this as such, you know, they because there were multiple like, you know, cloud facet cosmos and nice. So for each members, you just have to repeat. Like, you know, you're testing multiple number. You just have to repeat that. Okay. And exactly what is what is that? What are we doing right now? I know I probably miss something in the beginning. This these are the test scripts basically for user acceptance testing. I'm giving you example how the, you know, user acceptance testing tasks look like. Okay. Okay. So I'll share this, you know, document with you guys too. Okay. So yeah. So that that is so simple. But you get these, you know, test scripts from the, you know, like the key way. Okay. So when the key way is doing their testing, they would have the user test cases too. You just have to ask the key way. Hey, can you give me that list of user test cases that you have prepared? And then you just have to prepare your and there might be a UAT template to just like this. But a UAT template in that template, these information was already there. I just like basically, you know, added and deleted. Okay. And this information, this UAT test account. I got these accounts from basically QA lead. He made that account. Okay. Test account and then test data got it from the key way because the testing would be done in like like a UAT server or test Q testing server. So they have to create those user in there because those user, if they would be in there, then you can do that. If the user is not there, then you won't be able to kind of test them. Okay. You won't get access. And similarly, like, you know, test data, they would have these test data user and all their information in the system. Okay.  Okay. But in test server or other, they create replica of those real users. Okay. So that's why you need this test data, that information that if you need to, you know, put, if you are searching some member, so you need to put that information member ID or something, and that data is basically the test data. So basically, you are getting test account created by QA test data from QA and these scripts from the QA. And if the QA don't have that, you know, script, then you create that yourself. Okay. Because these are just the basically translated of a translation of the requirement.  So you can create these basically like, so in this, basically, this is existing functionality. This is existing functionality. This is existing functionality. This is existing functionality. Only this little change was in this project that was happened. Okay. Test more information link on the claim detail page. So this is a user story. Okay. So even the requirement ID is like written over. So this was, you know, what happened. Okay. So there might be like, you know, few changes in there and the rest will be existing functionality. Okay. So this is what, you know, UAT test scripts look like.  All right. This is the data that you will put. And, you know, task one is this. You will like go to this URL. You will log in and then click sign in, enter username password, click sign in, username password, respond to if there is a security question, ask these, put these answer in and then save it so that next time you will be doing, going, it will not, you know, bypass the security question. If you won't save or won't select yes, then every time it will ask those security questions. Okay. So then when you will be in there on the dashboard, there will be a list of application. Okay. Select application claim management or claim claims management. Okay. App claim management or claim management simple. Select this and click start here button on the welcome page. Okay. So what you will see, so these like steps will let you log in and application homepage open in a new browser, started button get displayed and when you will like click on that corporate information get displayed. Okay. So this is our expected result and this is existing functionality. So we didn't, which means like we didn't build this. So, and why we have pass fail and this in functionality we mentioned because our scope is only like, you know, this that we are touching. If there would be anything happens over here, that is not our project scope. Okay. So that would be like some other team will be doing. We just have to notify that, you know, hey, login is not working. So we will not be able to, you know, proceed with until that will be working, which is mostly like pretty quick existing functionality. So already support team has that. Okay. So we have to only like the scope of this is new functionality that is being built. Okay. Like from claims summary page should display that is a new functionality. Okay. And in the claims summary page, what would be that, you know, such function will expect a result will be this. So it's so simple. Any question? No. All right. So then UAT is the last step. So again, expectation from you guys like, say, you know, tomorrow expectation is that you will have like, you know, two to three projects and explain end to end your role as a BA. Okay. So that is basically like, you know, expectation that as a BA. Okay. You will have for each project, your kind of, you know, role like that. For example, as a BM, I mean, this is a role.  And then as a role, as a BA, my main role was to gather document requirement. This is this, this is this and whole story end to end. Okay. So this will be like project one. So project one, you can basically get any, maybe like, you know, best buy. Okay. And the project to maybe Wells Fargo. Okay. Maybe you can and anything you can choose. Okay. Wells Fargo, investment, small businesses, like, you know, some project of it.  They were introducing, you know, business liens for credit, new functionality. And I work, you know, with that team. And so as a BA what I did then from, from there. So select any project from, you know, any industry.  In your words, just like that, you know. Okay. Make sense. Yeah. All right. So yeah. So that would be it. And I want you guys to basically like, you know, do it at least four projects. I'm, you know, asking that, you know, prepare end to end BA and it would be in your own basically like, you know, like first person account. Okay. Means like you will speak it as like right is that your own, like as a BA, my main role was to gather and document the requirement. So I started the project understanding and stakeholder analysis to understand the project I did. I looked at the project charter understood a high level requirement. I talked with the subject matter expert and created a business area context diagram at the same time. When I was doing the stakeholder analysis, I got the list of the stakeholder from the project charter and spoke with them for spoke with the project manager and ask that if he has some list after making a list of the stakeholder, I schedule a meeting with them, identify who is primary, who is secondary. After that I scheduled a business requirement gathering session with them after organizing multiple sessions. I created the business requirement document and I get it signed up from the primary stakeholder. After getting the BRD, I given a walkthrough to the solution team. I've given the walkthrough of the document to the solution team. So here, see somebody who made the would gave. Now that is basically, you know what I'm saying, that is wrong. Okay. So because then it's not like a first person. Okay. So a first person account that I have given a walkthrough to the solution team and I would all that would should will is will not be. It would be a past tense account, first person account. Okay. So that's what you, you will like it. And then working with the, how you work with the, you know, developers, how would you work with the tester and how you would, you know, UAT all that, that's what you will like basically do. And you will do at least for four, four project. So, and that is kind of, you know, must have for tomorrow. Okay. And one more thing. Do you do that meeting like an hour later or that's going to be an issue. I mean, if you guys are okay, I'm okay with that. So it's up to you. Amado, are you okay with that? Or it's going to an hour later does five p.m. Yes. Central. Yeah. Five central. Yeah. Then it'll be six Eastern on mine. Oh yeah. That's okay. Okay. All right. Thank you. You're welcome. Okay.   I'm not sending you this. Okay. Okay. So, and success criteria, if you would be able to create that for, for, for four projects, then I can basically guarantee you that, you know, in next, you know, six to eight weeks, you will have job. How that. Yeah. Because I really need this job. Right. Right.  Okay. Yeah. And that's why you have to, you know, get that I'll send you this, like a session for today. So, you know, let's go from there. Okay. All right. Sometimes I just feel like even the job are no more out there. I just be like, Oh my God, am I going to be able to make it through a job? So I think that I can guarantee that you would be make it through the first thing is to getting inside the door.  It's always another person. You will not have a problem in doing the job. You will do that. And I'll support you whenever you need it. And I'm pretty sure that, you know, after two, three weeks on the job, you will be totally fine. You will not, you know, initially definitely the, you will be scared and all that, that, but, you know, as two, three weeks will pass and, you know, I can, you know, get every day some time to you after your work that, you know, what you can expect and but give you the plan at that time. So you don't need to worry about that. You know, this point of time, this point of time, just focus to, you know, be prepared to get into the door, interview preparation. They, they can ask anyone question. They can ask you and what the answer would be and, you know, worry about that and prepare those. And that's why this exercise that you're doing, it's like kind of a basically interview preparation. Okay. Yes. Okay. So that's why I'm focusing forcing you two guys to do in your first hand account past tense. Okay. Yeah. Or you will get used to when you are describing the project that I did this, I did that, and this is how it happened. So you will get used to that. Okay. Because that's how when you have done something, that's how you explain, right? Yes. But when you have learned something, then you don't explain like that, right? Yep. So we are basically bridging that gap. Okay. So you are explaining. So these projects that you are explaining, that's how you are basically like, you know, you're deep diving, deep diving, which we already did. And, you know, basically did start to end. And that's why you know how you perform that role. Yeah. Okay. Thank you. All right. Okay. Bye. Bye.


Another important feature of geometric objects is known as symmetry. We say a geometric object has symmetry if a transformation of part of the object can be used to produce all of the object. The type of symmetry is determined by the type of transformation. For example, let's consider these symmetries of a line. So if I have a line, I can take part of it, and I can translate it to produce the rest of it. Since we can take part of a line and translate it to form all of the line, the line has translational symmetry. How about the circle? One of the things we can do is we can rotate part of the circle to produce the whole circle, and so the circle has rotational symmetry. Now, most discussion of symmetry centers around the idea of a reflection symmetry, so let's consider the following. Suppose a graph is symmetric about the y-axis. So let's consider a point on the graph with horizontal coordinate x and vertical coordinate y. When x, y is a point on the graph, then, because the graph is symmetric about the y-axis, we can reflect across the y-axis to get another point on the graph where our horizontal coordinate is negative x and our vertical coordinate is still y. So the coordinates are negative x, y. Now, since x, y is on the graph, it satisfies the equation. And since minus x, y is also on the graph, it also satisfies the equation. Conversely, if both x, y and minus x, y satisfy the equation, the graph is symmetric about the y-axis. So let's determine whether this graph is symmetric about the y-axis. So suppose x, y is a point on the graph, then we know that x and y satisfy the equation. What we'd like to know is if negative x, y also satisfies the equation. Well, let's check it out, making our replacement, and we'll do a little bit of algebra. Now, we know this statement is true, and this is the same thing, so we know that this statement is also true, which means that negative x, y also satisfies the equation. So negative x, y is also on the graph. And we can summarize our results. For any point on the graph, we know that the equation x to the fourth minus x squared equals y cubed plus y is true. Since minus x, y also satisfies this equation, minus x, y is also a point on the graph, and the graph is symmetric about the y-axis. What if our graph is symmetric about the x-axis? When x, y is a point on the graph, so is x negative y. And again, since x, y is on the graph, it satisfies the equation of the graph. Since x and negative y is also on the graph, it also satisfies the equation. And so conversely, if both x, y and x negative y satisfy the equation, the graph is symmetric about the x-axis. So let's see if our graph is symmetric about the x-axis. Again, suppose x, y is a point on the graph, then we know that the x and y coordinates have to satisfy the original equation. We want to know if x negative y also satisfies the equation. So let's substitute and check. And while we know that this equation is true, we don't know whether this equation is true. We have no guarantee that this equation is true. And I don't know about you, but without that guarantee, I'm not willing to commit. And so we might summarize our result. For any point x, y on the graph, we have x and y satisfying the equation of the graph, but since x and negative y does not in general satisfy this equation, x negative y is not in general a point on the graph, and the graph is not symmetric about the x-axis. And let's do some final reflections. Suppose the graph is symmetric about the origin. When x, y is a point on the graph, so is negative x and negative y. Since x, y is on the graph, it satisfies the equation. Since negative x, negative y is also on the graph, it also satisfies the equation. And so if both x, y and negative x, negative y satisfy the equation, the graph is symmetric about the origin. So let's put those all together to determine the symmetries of the graph, y squared equals x cubed plus x minus 8. So again, let's suppose x, y is a point on the graph. Remember, for any point x, y on the graph, y squared equals x cubed plus x plus 8, guaranteed true. We'll check to see if negative x, y is on the graph. So we'll substitute and simplify a little bit. We have this guaranteed true statement, but it doesn't look like this, so we have no guarantee that this is a true statement, so the graph is not symmetric about the y-axis. What about symmetry across the x-axis? We'll check to see if x and negative y is on the graph, so we'll substitute and simplify. And since we know that this statement is true, this, which is the same statement, is guaranteed true, so the graph is symmetric about the x-axis. And finally, we'll check for symmetry about the origin. Suppose x, y is a point on the graph. We'll check to see if minus x minus y is on the graph. So we'll substitute and simplify. Again, we're guaranteed that this equation is true, but this equation is nothing like that, so we don't have a guarantee of this, so the graph is not symmetric about the origin.


We're grateful for the opportunity to talk a little bit about our paper. I am Mikkel Deerey. I'm a physician scientist, a medical oncologist, a professor at Brown University, director of the Cancer Center at Brown University and associate dean at the Warren Alpert Medical School. And I'm here with my colleague Marie Ralph. We'll introduce herself as well. Hi, my name is Marie Ralph. I'm an MD-PhD student. I just graduated from Temple a couple weeks ago, and I was in Dr. Al Deerey's lab from 2015 to 2019. And this paper is a result of some of the work that I did there. Thank you, Marie. So the paper we're going to discuss today is entitled Trail Receptor Agonists Convert the Response of Breast Cancer Cells to Ankh 201, from antiproliferative to apoptotic. And the first author is Dr. Ralph. And Marie said we started this work at Fox Chase Cancer Center and we finalized some experiments after we moved to Brown University right at the beginning of 2019. And before we get into the details of the actual experiments we did in this manuscript, let me just take you back a little bit to provide some background that sort of sets the stage for the work that we pursued. And so, as I said earlier, I am a medical oncologist. And so for years, I've been interested in understanding the process of cell death as it relates to cancer and the effects of cancer treatments that we use, whether that is chemotherapy or radiation or other targeted therapies. And so in the process of trying to learn about that, going back now to the mid to late 90s, my laboratory discovered a gene that encodes a protein called death receptor 5. And death receptor 5 is a protein that sits in the cell membrane and is engaged by a ligand, a protein that circulates, that is made by natural killer cells, for example. And it's part of our innate immune system for how our body suppresses cancer and its metastases. And so for almost 25 years now, we have been interested in this cell death immune mechanism that suppresses cancer in our body and how various therapeutics interact with this pathway to have anti-cancer effects in patients or in the laboratory in the different models that we study. And because this is a powerful way that cancer can be suppressed along the way, we had the idea of looking for small molecule drugs that can activate this immune mechanism of cancer suppression. And so back in 2007, while we were at University of Pennsylvania, we carried out a chemical library screen in my laboratory looking for small molecules that upregulate the trail gene with the idea that the increased production of trail by small molecules, whether they're normal cells or tumor cells, could have a therapeutic benefit in the treatment of cancer. And we found a number of small molecules at the time, one of which has come to be known as TIC-10 for trail inducing compound number 10. And this compound entered clinical trials under the name of ONC 201. And interestingly, the compound has been having effects on tumors in patients, including patients with aggressive brain tumors, midline brain tumors with a specific epigenetic defect, H3K27M, and has been under study in other clinical trials. There have been some effects of the compound seen in patients with prostate cancer where bone metastases have shrunk or visceral metastases have lost their pet avidity. And some patients with metastatic endometrial cancer have had responses in their lymph nodes or in lung metastases. And so the drug continues to be studied in the clinic. So we have been interested to understand more about exactly how this drug is working in patients as well as in our preclinical models, trying to think of ways of getting the drug to work better in combination with other therapeutics, and trying to gain insights into, you know, when we use this drug. Why doesn't it work across the board for all tumors in the same way? You know, we appreciate there's a heterogeneity in cancer that we are learning about the whole field is learning about this. But the question is with this specific drug, what is the pattern of response? What determines that? And how can we get it to work a little bit better? So by way of just a little bit more background, while we originally described the discovery of this compound in a science translational medicine paper we published in 2013, in that paper, we describe PIC-10, trail-inducing compound number 10, is able to activate the trail gene by effects on some kinases within the cells such as AKT and ERC, which individually phosphorylate a transcription factor called FOXO3A. And when this transcription factor is phosphorylated, it is retained in the cytoplasm. And when these kinases are inhibited, the transcription factor then translocates to the nucleus, binds to the trail gene and activates trail. So, you know, we showed these effects early on, including some in vivo effects. And one of the interesting things that we observed early on was that the timing of cell death culture or in vivo was somewhat delayed. It took two to four days to see significant cell death. And we knew from our earlier studies with trail, you know, if you add trail to tumor cells, if they're sensitive, they just melt away and are obliterated within just a few hours, like three to four hours in many systems. Those cells are dead and gone. And so, we were interested in what, why was it taking so long? What are some of the earlier events? And so, we published a second paper in 2016 in Science Signaling, where we gained insights into some of those early events. And the insight that we gained was that 2.01-10 activates what's referred to as an integrated stress response in tumor cells and that this involves kinases. And we looked at a bunch of kinases that mediate this signaling and we uncovered HRI and PKR as relevant kinases that are involved in in activation of EIF2-alpha, ETF4, CHOP, transcription factors, and then ultimately, production of death receptor 5 as a transcriptional target. And so this was interesting for several reasons. One of the main reasons is that the original discovery of TIC-10-ONK-201 was based on its ability to upregulate trail. This part of the host immune system that suppresses cancer and its metastases. And here we just also discovered that this small molecule can upregulate the integrated stress response leading to production of death receptor 5, the receptor 4 trail. And so we think that the regulation of trail and death receptor 5 is relevant and significant part of the mechanism of action of this new anti-cancer compound. Recognizing, and I'll ask Marie to set the stage for her paper and then sort of get into our findings. But one of the observations we made in that 2016 science signaling paper is that the effects of ONK-201 TIC-10 on a large number of human tumor cell lines shows heterogeneity. So do you see pro-apoptotic effects in a number of human tumor cell lines? But in other cases, we saw anti-proliferative effects. And that was interesting. When you discover a candidate therapeutic, you want to learn more about it in terms of its effects. And just so that everyone understands what it does and how it does it, but also issues with how could we modulate these responses, for example, from anti-proliferative to pro-apoptotic, which would be a desirable thing in a clinical context where one would hope to see tumor shrink and an anti-tumor effect without much toxicity. So in drug development, we want to make sure we're having an effect on the tumor without much toxicity. One of the interesting aspects of ONK-201 is that the drug is extremely well tolerated. When it entered clinical trials, it's a pill that started in the clinic on an every three-week schedule and was having effects on brain tumors under that schedule. Later on, we published a second paper in the Journal of Clinical Investigation in 2018 where we intensified the dose of ONK-201 and were able to show an effect on metastasis as well as prolonged pathway suppression in vivo along the lines of the AKT and ERC suppression that I described earlier. And those results led to a modification of how the drug is being tested in clinical trials on a weekly schedule. And the drug was being developed by a company called Oncusutix that I founded over 12 years ago that has been taking this compound into the clinic and testing its effects in various tumor types. So a little bit of background about trail in breast cancer because this is the focus of our paper here and just to set the stage for a read. Trail was discovered around 1994, 95. And that discovery provided a new way to potentially treat cancer. Trail is part of the tumor necrosis family of cytokines and years ago when I was in clinical training at Johns Hopkins, there were clinical trials testing TNF or tumor necrosis factor in combination with other drugs for patients with cancer. And the problem was not that TNF is not effective. TNF is really an effective therapeutic. However, it's also incredibly toxic because of its effects on NFCapa B and has really been abandoned for systemic administration. But when trail came along, it doesn't have much of an effect on NFCapa B and it preferentially kills tumor cells or transform cells or by the way, virally infected cells, but not normal cells. And so that was part of its excitement, lack of toxicity, lack of this systemic inflammatory response. And trail was tested in the clinic for a number of years. And there were some responses and some tumors, but overall the signal from trail as an effective therapeutic was fairly weak. In part, we think because trail has a short half-life. And so, you know, we were excited with the discovery of TIC-10 that we could increase trail production in our mouse models or in vivo or in humans to potentially upregulate this trail pathway and boost the immune system to have anti-tumor effects. As anyone who has treated cancer knows, cancer is complex. And again, going back to this major heterogeneity of what we see when we treat tumor cells with drugs, we do see this heterogeneity with Antoine. And so we've wanted to understand that in terms of what happens in different cells and what could we do about it to get a more favorable therapeutic outcome. So with that very long-winded introduction, I hope you have an understanding where we have been with the work on the trail pathway and on to a one TIC-10 discovery and development. And I'll turn it over to Marie to talk about her work in the lab, including a prior paper that sort of led us to the current paper. So Marie? Yeah, thanks, Dr. Elderia. That was really helpful. So now hopefully everyone can get an idea of some of the history of trail and the history of Octo1 in the lab. So yeah, so I joined the lab as a PhD student in 2015 and I picked up a project that focused specifically on the effects of Octo1 in breast cancer. And Dr. Elderia was alluding to my first paper published in 2017 in molecular cancer therapeutics. This was the first paper to demonstrate the efficacy of Octo1 in breast cancers from a wide range of molecular subtypes. So breast cancers in general are a pretty trail resistant tumor type. There's only a small subset of the triple negative breast cancers which actually show sensitivity to trail. Majority are very resistant. So it was promising to see that when we treated breast cancers from a variety of different molecular subtypes with Octo1, the compound had efficacy. And looking a little bit more closely into that, some of these tumor types, the triple negative one specifically, the compound was having a proepoptotic effect and in other tumor types, it was having an anti-proliferative effect. And the anti-proliferative effect involved an arrest in the G1 phase of the cell cycle. And when we looked in vivo, we saw that while the proepoptotic effect translated into efficacy in a mouse model of breast cancer, the anti-proliferative effect did not. So this got us thinking that we should search for a strategy that could be used to convert this anti-proliferative effect into an apoptotic one. Now, Dr. Aldiri talked a little bit about the effects of Octo1 on DR5, the cell surface trail receptor, one of the death receptors. And I don't believe that he mentioned, but there are also effects of the compound on anti-apoptotic proteins. And so our knowledge of these two things, two known mechanisms of trail resistance in breast cancer led us to hypothesize that the combination of Octo1 and a trail receptor agonist may be highly efficacious.  So if we then add in a trail receptor agonist, it induces apoptosis in a very poet way. Yeah, so sort of I think the highlights that I would like you to go through, Marie, would be the issue of trying to convert anti-apoptotic the concept of priming the cells. So think about it this way. DR5 goes up, the anti-apoptotic proteins go down, but the cells are not really sensitive to the drug and they're not really sensitive to the trail. So we wondered at some point why the cells are not responding to the drug. We suspected, well, maybe they don't make enough trail. We described this as a trail inducing compound. And so we started to think, okay, well, what if we add some trail or a death receptor agonist to anybody? So we did that.  And I think it's important to point out that there's a dependence on death receptor 5. So there are a couple of points that I think are really nice to make, and I would love to do that. One is this idea of a switch. And we've talked about this in the past and the idea of flipping a switch. So the concept is cells are treated with a small molecule compound, not a whole lot is happening. Cells are treated with trail, not a whole lot is happening. You put them together and it's like flipping a switch. The cells now undergo potent cell death. Your cell culture data shows this beautifully in at least four different human breast cancer cell lines. I think that's important to say. I think the idea that it's not toxic to the fibroblasts is worth mentioning. I think the idea that the natural killer cells are active against the breast cancer cells that have been exposed to onto one is nice. And then the in vivo study. So I would just kind of review all of that, take your time because all of these are nice points to make to illustrate the progression of thinking, the idea of this combination therapy, the potential efficacy, open clinical trials, for example, at the National Cancer Institute to look at onto one in breast cancer. And our work would basically predict that it would be a rare patient with breast cancer who might just outright respond to this drug. And again, this goes back to cancer is complex and drug development is also very hard. And our colleagues, including at places like the National Cancer Institute, may be discouraged by single agent activity or the lack thereof in breast cancer. And here we are with this very nice preclinical data that provides hope for actually moving this forward. And we'll get to sort of the future directions, but I think we build on what we know there are hurdles, challenges. And I see this work as sort of an overcoming of some of those challenges through basic science and rational thinking and rational combination of therapeutics based on molecular pathways. So I would say all of that. We also showed that this combination of onc 201 with trial receptor agonist was non-toxic to human fibroblasts and our in vivo studies as well, confirmed that the combination was very safe in mice. Talk about the dependence on DR5 and also the efficacy on tumor growth in vivo besides the safety. Yeah, yeah, yeah. So we showed that the upregulation of DR5 by onc 201 was necessary for this sensitization to trial receptor agonist. The benefit here was that onc 201 alone had the potential to have efficacy in the triple negatives, but onc 201 alone was never gonna work in non-triple negatives, whether it be her to amplified or ERP or positive. So I- Well, you know, that's only partially correct because in some of the triple negatives, it doesn't do anything. And I strongly suspect that in those other triple negatives the combo will bring out an effect. I know you're thinking there is that there's less treatment options for triple negative in general. So it's like a way to, you know. Anyways, the fact is your paper is done. I mean, that figure in your paper is with non-ERPR positive. They have her too.  And as you know, hormone receptor positive breast cancer generally has much better outcomes and lots of treatment options. And, you know, like you said, the triple negative is where we really need to make important progress. But I think progress in breast cancer in general will ultimately be very helpful. Thank you, Marie, for that great summary of the data in the paper. And so just to summarize, we find that the combination of onto one with trail or trail receptor agonist antibodies is a potent synergistic combination that peers will have preclinical efficacy in breast cancer and does have some immune stimulatory effects that we showed in this paper. And so this is a novel therapeutic strategy that we plan to pursue and try to bring into the clinic because it could make a difference, you know, based on our preclinical results. It isn't clear how onto one monotherapy will play out in clinical trials and that consideration of combination therapies such as with this one might increase the chances for therapeutic efficacy in the clinic in different breast cancer subtypes. This type of insight is coming from detailed molecular analysis of breast cancer, cell lines and vivo models. And with an understanding of the mechanism of action of onto a one take 10 that involves upregulation of trail and death receptor five. Although in a number of human cell lines there isn't enough trail production. And so the addition of extra trail helps trigger apoptotic cell death.  I should say that at this point I wanna make a couple of comments. One, to acknowledge the funding of our work through the NIH and the National Cancer Institute and through the American Cancer Society support of our work, I would like to acknowledge our co-authors Akash Jabari, Jocelyn Ray, Landland Zoo, Tali Lev, Harry Campbell, Dave Dicker and Eric Cross. Some of our colleagues are Fox Chase Cancer Center where the work was started and largely completed by Marie who is the first author. And because we have seen these effects of the combination of trail plus onto a one as a promising therapeutic combination one of the extensions of the work that follows naturally is the question of how does this work in other tumor types? What has been observed in the clinic with onto one monotherapy are these remarkable responses and brain tumors, but not so much in other solid tumor types. So could a combination like onto a one and trail or trail receptor agonist be worth pursuing in the clinic to achieve synergistic anti-tumor efficacy? And so we have a number of other results and other systems, some by our co-authors here. So Akash Jabari as part of his master's thesis work at Brown University looked at combinations of onto a one with trail or another investigational drug called TLY-012 as well as some combinations of the onto one analog onto one two with TLY-012 in pancreatic cancer models. Jocelyn Ray who is in the GYN oncology residency program at Temple Fox Chase looked at the efficacy in preclinical models of the onto a one trail combination endometrial cancer models. And so we have a couple of manuscripts that are on the way we presented this work at national meetings such as ACR and some other society meetings. And we do see efficacy in other systems and we do have some ongoing work at Brown University being conducted by Dr. Cassandra Parker who's a resident in the department of surgery looking at gastric cancer models where we are seeing similar synergy between onto a one and trail and similar in vivo synergy in gastric cancer with the combination of onto a one and TLY. So we think that the insights gained in the work done by Dr. Ralph as presented in this paper sets the stage for future translational clinical trials in the area of breast cancer as well as other tumors where we could trigger activation of the death receptor pathway that is part of the innate immune system for suppression of cancer and its metastases. So we thank you for your attention to our presentation this afternoon and we look forward to seeing our own progress as well as collaboration with colleagues around the country and around the world as we bring these therapeutics into clinical translation. Thank you.


In previous lectures, I discussed the basic requirement for the observation of interference fringes in the laboratory and discuss some important experimental arrangement to observe the interference fringes in the laboratory. In this lecture, I am going to describe some possible engineering applications of interference phenomena of light. We have already seen that neutral rings experiment can be used to determine the wavelength of monochromatic light, refractive index of liquids and to study the flatness of glass plate. The Michelson interferometer may be used to measure accurately wavelength of light and wavelength difference between the two closely spaced spectral line of certain sources like sodium. In addition to this, it is also used for evaluation of a standard meter in terms of wavelength of light. Similarly, Fabry-Parrot interferometer can be used for similar applications. Here, I am going to describe few other possible engineering applications of interference of light. One important application of interference of thin film is the coating of non-reflecting films. When these films are coated on surfaces of optical elements like lens or prism, the reflectivity of surfaces is very much reduced. Therefore, the loss of light by reflection at various surfaces of a system of lenses or prisms is appreciably reduced. The main idea behind the non-reflecting film is the destructive interference between the waves reflected from the air film interface and film glass interface by properly adjusting the thickness and refractive index of the film material. Suppose, the refractive index of the film material mu r is less than the refractive index of glass mu g and greater than the refractive index of air mu a. In this case, if a beam of light of wavelength lambda is incident at air film interface, then phase change of pi occurs on reflections at both air film and film glass interfaces. Therefore, if the film thickness t is adjusted such that the condition to mu f t is equal to lambda by 2 is satisfied for normal incidence, then the condition for destructive interference is satisfied for the reflected light. Thus, if film thickness t is lambda upon 4 mu f, the light of wavelength lambda is not reflected. As we have discussed earlier, there is no loss of energy in interference phenomena. Therefore, there is merely a redistribution of energy. So, in this case, the energy mostly appears in the transmitted beam. In case of white light, lambda is generally chosen near the middle of the visible spectrum that is lambda around 5000 angstrom. At angles other than normal incidence, the part difference will change because of the factor cosine theta. However, since cos theta does not change very much near 0 degree, so reflection remains quite low over a fair range of small angle about the normal. Furthermore, the film is non-reflecting only for a particular value of lambda. For a polychromatic light, the film's non-reflecting property will be falling off when wavelength is less or greater than 5000 angstrom. However, there is not much increase in reflectivity when we go towards red and violet ends of the visible spectrum. Here, it should be noted that although the destructive interference will be observed for film thickness lambda upon 4 mu f or 3 lambda upon 4 mu f or 5 lambda upon 4 mu f, the lowest thickness lambda upon 4 mu f is preferred. For this thickness, reflectivity is small for entire range of visible spectrum. Above, we have seen that a film of thickness lambda upon 4 mu f where lambda is the wavelength of light and mu f is the film refractive index which lies between the refractive indices of the two surrounding media acts like an anti-reflecting layer. This happens due to destructive interference occurring between the waves reflected from the top and the bottom interfaces. However, if the refractive index of the film is smaller or greater than both the surrounding media, then in such a case in addition to the phase difference due to the additional part travelled by the wave reflected from the lower interface, there would also be an extra phase difference of pi between the two reflected waves. In this case, a film of thickness lambda upon 4 mu f therefore, would increase the reflectivity rather than reducing it. Now, if you consider a medium consisting of alternate layers of high and low refractive indices of mu naught plus delta mu and mu naught minus delta mu of equal thickness T, such medium is called a periodic medium and the special period of variation of the refractive index is 2 T. Suppose, delta mu is much smaller than mu naught and we choose the thickness of each layer to be T equal to lambda upon 4 mu naught which we can take approximately equal to lambda upon 4 mu naught plus delta mu or approximately equal to lambda upon 4 mu naught minus delta mu. In this case, the reflection arising out of individual reflections from the various interfaces would all be in phase and should result in a strong reflection. Thus, for a strong reflection at a chosen wavelength lambda b, the period of the refractive index variation should be 2 T is equal to lambda b upon 2 mu naught. This condition is similar to the Bragg's diffraction of x-rays from various atomic layer for normal incidence and therefore, is referred to as the Bragg's condition. The quantity lambda b is often referred to as the Bragg wavelength. As we move away from the wavelength lambda b, the reflectivity of the periodic medium falls off sharply. We can obtain an approximate expression for the wavelength deviation delta lambda from lambda b which will produce a zero reflectivity. In order to do this, we first note that at lambda b, the waves reflected from each of the n individual layer are all in phase leading to a strong reflection. If we move away from lambda b, then the individual waves reflected from the various layers will not be in phase and thus reflectivity reduces. If we choose a wavelength lambda b plus delta lambda such that the reflection from layer 1 and layer n by 2 plus 1 from layer 2 and n plus 2 plus 2 and so on up to reflection from layer n by 2 and n are out of phase, then the reflectivity will be zero. For reflection from each of the top n by 2 layer, there is a reflection from a corresponding lower n by 2 layer which is out of phase. Thus when we move from lambda b to lambda b plus delta lambda, the waves reflected from the first and n by 2 plus 1 th layer should have an additional phase difference of pi. Thus we have 2 pi by lambda b into mu naught into n by n into 2 t by 2 minus 2 pi by lambda b plus delta lambda into mu naught n into 2 t upon 2 is equal to pi. Here the first term on the LHS left hand side is simply the phase difference at lambda b between reflection first and n by 2 plus 1 due to the extra part travelled by the later wave and second term is that at lambda b plus delta lambda. Assuming delta lambda much smaller than lambda b, we have 2 pi divided by lambda b square into mu naught into n into 2 t by 2 into delta lambda is equal to pi and from this we get delta lambda upon lambda b is equal to lambda b upon mu naught n into 2 t which we can write equal to 2 t upon L where L is equal to t into n is the total thickness of the periodic medium. Thus if the incident wave is polychromatic like white light, the reflected light may have a high degree of monochromatic city. This principle is used in white light holographic. Thus the periodic medium discussed above finds wide application in high reflectivity multi layers coating. So, now I am going to describe the working of interference filter. So, working of this interference filter can be understood with the help of Fabry-Parrot interferometer. I have already discussed the construction of this interferometer. If this interferometer is placed in a parallel beam of white light, interference will occur for all the monochromatic component of such light, but this will not manifest itself until the transmitted beam is dispersed by an auxiliary spectroscope. We then observe a series of bright fringes in the spectrum each formed by a wavelength somewhat different from the next. The maxima will occur at wavelength given by lambda is equal to 2 t cos theta divided by m where m is any whole number. If t is a separation of a few millimeter there will be very narrow fringes and high dispersion is necessary in order to separate them. Such fringes are known as channel spectrum or as itself butler bands and have been used for example in calibration of spectroscopes for the infrared and in accurate measurements of wavelength of the absorption lines in the solar spectrum. An application of these fringes having considerable practical importance uses the situation where t is extremely small so that only 1 or 2 maxima occur within the visible range of wavelengths. With white light incident only 1 or 2 narrow bands of wavelength will then be transmitted the rest of the light being reflected. So, a pair of semi transparent metallic film can act as a filter passing nearly monochromatic light. For maxima to be widely separated m must be small number this is attained only by having the reflecting surfaces very close together. If we wish to have the maxima for m is equal to 2 occur at a given wavelength lambda the metal films would have to be a distance lambda apart. The maxima m is equal to 1 will then appear at a wavelength of 2 lambda such minute separation can be attained however with modern techniques of thin film deposition for this a semi transparent metal is first deposited on a glass plate next a thin layer of some dielectric material such as cryolite is deposited on the top of this and then the dielectric layer is in turn coated with another similar film of metal. Finally, another plate of glass is placed over the film for mechanical protection. The completed filter then has the cross section as shown in this figure since the part difference is now in the dielectric of index and the wavelength of maximum transmission for normal incidence are given by lambda is equal to 2 n t upon m. If there are 2 maxima in the visible spectrum one of these can easily be eliminated by using colored glass for protecting cover plate. So, up till now we have discussed some important engineering application of interference now I am going to discuss about the coherence of light wave. So, first I will discuss about the temporal coherence and then I will discuss about the spatial coherence. In all the experimental arrangement for the formation of interference fringes discussed earlier it was assumed that the displacement that is the electric field associated with light wave remained sinusoidal for all values of time. Thus the displacement was assumed to be given by e is equal to a cos k x minus omega t plus 5 this equation predicts that at any position x the displacement is sinusoidal for all time varying from minus infinity to plus infinity. For example, at x is equal to 0 we have e is equal to a cos omega t minus 5 and variation of e bit time forms infinite wave trends as shown in this figure. However, this will result only from perfectly monochromatic source and this corresponds to an idealized situation because the radiation from an ordinary light source consist of finite size wave trend. The average duration of the wave trend is tau c that is the electric field remains sinusoidal for times of the order of tau c. Thus at a given point the electric field at a time t and t plus delta t will in general have a definite phase relationship if delta t is much smaller than tau c and do not have any phase relationship if delta t is much greater than tau c. The time duration tau c is known as the quarence time of the source and the field is set to remain quarence for time tau c. The length l of the wave trend is given by l is equal to c into tau c where c is the velocity of light. This is referred to as quarence length for example, for neon light tau c is of the order of 10 to the power minus 10 second and for the red cadmium line it is of the order of 10 to the power minus 9 second and so the corresponding quarence length will be 3 centimeter and 30 centimeter respectively. The correlation between a wave at a given time and a certain time later is known as the temporal quarence. Again let us consider here the Young's double slit experiment.  If r 2 minus r 1 upon c is much smaller than tau c then the wave arriving at p from S 1 and S 2 will have a definite phase relationship and an interference pattern of good controls will be observed. On the other hand if the power difference r 2 minus r 1 is large enough such that r 2 minus r 1 upon c is much greater than tau c then the waves arriving at p from S 1 and S 2 will have no fixed phase relationship and no interference pattern will be observed. Thus the central fringe for which r 1 is equal to r 2 will in general have a good contrast and as we move towards higher order fringes the contrast of the fringes will gradually become poorer. Similarly, in the Michelson interferometer experiment if d is the distance between mirror m 1 and m 2 prime virtual image of mirror m 2 then for definite phase relationship between the beam reflected from m 1 and m 2 that is 2 d upon c much less than 2 d upon c than tau c and well defined fringes will be observed in this case. On the other hand if 2 d upon c is much greater than tau c then in general there is no definite phase relationship between the two beams and no interference pattern is observed. It may be mentioned that there is no definite distance at which the interference pattern disappears. As the distance increases the contrast of the fringes becomes gradually poorer and eventually the fringe system disappears. The coherence time for a laser beam is usually much larger than in comparison to ordinary light sources. For example, for a helium neon laser coherence time as large as 50 milliseconds have been obtained this would imply a coherence length of 15,000 kilometer. Commercially available helium neon laser have coherence time of the order of 15 nanosecond this means the coherence length is about of the order of 15 meter. Thus, using such as laser beam high contrast interference fringes can be obtained even for a part difference of few meters. In the Michelson interferometer experiment the decrease of degrees in contrast of the fringes can also be interpreted as being due to the fact that the source is not emitting at a single frequency. But over a narrow band of frequency as shown here when the part difference between the two interfering beams is 0 or very small the different wavelength components produce fringes superimposed on one another and the fringe contrast is good. On the other hand when the part difference is increased different wavelength component produce fringes fringe patterns which are is slightly displaced with respect to one another and the fringe contrast becomes poorer. We can equally well say that the poor fringe visibility for a large optical part difference is due to the non monochromaticity of the light source. It can be shown that the temporal coherence tau c of the beam is directly related to the spectral with delta lambda. The relation is given by this equation delta lambda is equal to lambda square upon c tau c or delta lambda is equal to lambda square upon l. Since frequency is related to wavelength by equation nu is equal to c upon lambda we can write spectral width in terms of frequency delta nu is equal to c by l which is approximately equal to 1 over tau c. Thus the frequency spread of a spectral line is inverse of the coherence length. If the coherence time tau c is large then the value of delta nu will be small that is the wave will be more monochromatic. So, now I am going to describe the spatial coherence that is the correlation between the two points at a certain distance away. So, earlier we considered the coherence of the field arriving at a particular point in space from a point source through two different optical paths. Now, let us discuss the coherence property properties of the field associated with the finite dimension of the source. We consider the young double hole experiment with the point source S being equidistant from S 1 and S 2. We assume S to be nearly monochromatic so that it produces interference fringes of good contrast on the screen P p prime. The point O on the screen is such that S 1 O is equal to S 2 O. Clearly the point source S will produce an intensity maxima around the point O. We next consider another similar source S prime at a distance l from S. We assume that the waves from S and S dash have no definite phase relationship. Thus the interference pattern observed on the screen P p prime will be superposition of the intensity distribution of the interference pattern formed due to S and S dash. If the separation l is slowly increased from 0, the contrast of the fringes on the screen P p prime becomes poorer because of the fact that interference pattern produced by S dash is slightly shifted from that produced by S. Clearly if S dash S 2 minus S dash S 1 equal to lambda by 2 the minima of the interference pattern produced by S will fall on the maxima of the fringe pattern produced by S dash and no fringe pattern will be observed. With the help of this figure it can be shown that the fringe pattern will disappear when l is of the order of lambda a upon 2 d. Now, if we have an extended incoherent source whose linear dimension is of the order of lambda a upon d. Then for every point on the source there is a point at a distance of lambda a upon 2 d which produces fringes which are shifted by half a fringe width. Therefore the interference pattern will not be observed. Thus for an extended incoherent source interference fringes of good contrast will be observed only when l is much smaller than lambda a upon d or d is much smaller than lambda a upon l. Equivalently for a given source of width l interference fringes of good contrast will be formed by interference of light from 2 point S 1 and S 2 separated by a distance d much smaller than lambda a upon l. Now, if theta is the angle subtended by the source at the slit then theta approximately lambda upon a and above condition for obtaining the fringe of good contrast takes the form d much less than lambda a upon l or d is much smaller than lambda upon theta. On the other hand if d is approximately lambda by theta the fringes will be of poor contrast. The distance lambda by theta gives the distance over which the beam may be assumed to be specially coherent and is referred to as the lateral coherence width l w.


The Roseau girls basketball team is coming off their second straight trip to state and a third place title a season ago And with a more majority of their roster returning they're eyeing even bigger goals Our goal is to win state coming off two straight-class two-way state tournament appearances There's no denying the Rams confidence is high But they still aren't satisfied after falling short of their goal of a state title a year ago Knowing that we were it within like eight points of the first-place team and that we should have been in the championship game I think it's really gonna push us to work even harder They know they'll be playing with an X on their back this season It's it puts a lot of pressure on us But it's also really motivating to know that people respect us and respect how well our team plays teams Definitely come with their best game, you know when we come to town or when they come to our gym But I just feel like we're composed. We're confident. We're mature And I think we're seeing the rewards of that now where they just they just seem like veterans They are a veteran group returning all but two players from a season ago Including the state's fourth leading scorer Kylie Borovic who averaged just over 26 points per game for the Rams last year We want her going to the basket and looking to attack the rim and and score off layups They're getting herself to the free throw line drying falls things like that And if that's not there looking to kick and then the options are really unlimited whether it's Ivy or Halsey for Three out to one of her sisters, you know for three or an attack or dumping it to one of our posts down low We just we have weapons all over the place and with those weapons They believe this is the team to bring home a state title I think they're very very driven and motivated and and like I said I think just now have the maturity and the poise and the experience to To make that happen if you've enjoyed this segment of Lakeland news Please consider making a tax deductible contribution to Lakeland public television


update. Welcome folks we have the Dow industrials finish up a hundred and three Nasdaq up 10 S&Ps flat a little selling coming into close out here folks. Dow, Dow industrials right now up nine bucks and then a Dow. Gold contract up nine bucks straight in at 18.25 an ounce we have silver up 39 cents 24 dollars 55 cents an ounce late sweet crude up a buck and they $82.26 a barrel notes and bonds the 10 year down 16 ticks trade in 130 110 the 30 year off 26 at 162.08 and King dollar King dollar down 285 ticks trade in 93035 Euro 115 yen 113.21 on the British pound at 135 to one US dollar we get open we take a look at the spy what you're gonna have out here you get the sideways market flat market spy up 42 cents 468 and the X100 we take a look at the three Q's it's going to be the same deal you're down 53 cents but bottom line you got a sideways move you get shot volume inside of that three Q's we hit a high on Friday with the four to 43 million chairs you down well you down 53 53 cents your sideways today over 28 million gold gold contract is going to get really interesting this week I like what we have on a Monday folks bottom line gold is approaching that 1836 and this is where this is caught monster flag three separate times we're up there three separate times it's failed three it's 1836 to 1839 folks that's the number we'll see what it can blow by at this time it blows by it you're going to see the gold up to 819 22 and the way that it would blow by it my take is that if the dollar got back under 93 729 it was fighting about that in a big way it overtook that in a broke out huge on the 20th of September 29th of September then came right back down that was the false breakdown town came back inside the range and popped right above the range again so bottom line is that this is a big number this is absolutely a big number because what does happen is this when you have a false break whether it's downtown or uptown then you get on the other side of it most times that's the end of the move meaning you're really going to move higher and that's what I mean by gold I mean the dollar that it fought over the 93 729 came down once and then took off that normally means that you're going top side so if it gets underneath that leverage number again gonna be a big move inside the commodity market folks have a great one have a safe one come back and visit Tommy tomorrow morning kicks us off nine o'clock in the morning great show folks


You need a financial advisor with the freedom to focus on your specific needs. Whatever your goals, Reid Potter can create a game plan tailored to you. Call Reid at 432-0777 at Pikeville, Kentucky to learn more. The University of Pikeville announced that they reached a purchase agreement with the Appalachian News Express for the A&E facility on Caroline Avenue in downtown Pikeville. The building currently houses the newspaper's offices and printing presses but will soon be converted into the University's new College of Dental Medicine. In a press release issued by the University of Pikeville, Jeff Vanderbeck, publisher at the Appalachian News Express is quoted as saying, the anticipation of more than 250 students and staff to become part of the community requires a lot of space. This arrangement is great for us, the city, and the University and secures and solidifies our ongoing relationship. The Appalachian News Express will be relocating its facility but it is unclear at this time where the new location will be. For Mountain Top News, I'm Kelsey Dean.


Thanks for watching this GitLab video. Today, I want to share a little bit about the remote stack. We'll discuss the tools required to build and run a business in a remote environment. My name is Brennan O'Leary, and I'm a developer evangelist at GitLab. You can find me on Twitter at O'Leary Crew, and I'll be happy to discuss anything in this video in more detail if you have questions. GitLab is the largest all-remote company in the world. As such, we've chosen tools built for that purpose, and we'll discuss how and why we made those decisions throughout this video. You can also use the hashtag all remote to learn more about how GitLab and other companies look at remote work. As with everything GitLab does, how we make our decisions about our tech stack must align with our values as a company. Those values – collaboration, results, efficiency, diversity and inclusion, iteration and transparency – color every decision we make, including about what tools we use. Tools must enable our way of collaborating, allowing us to share transparently with the world or at least within the company our decision-making process and the outcomes of those decisions. They must be efficient tools, and we often end up with what we lovingly call boring solutions. And every GitLab team member is encouraged to spend company money like it's their own, so any tool purchase is carefully considered and examined to ensure that it is a prudent investment. Efficiency is at the heart of everything we do. While functioning remotely as an experiment or for an extended period of time, you should try and minimize your tool stack. A collaborative documentation platform such as Google Docs, a company-wide chat tool like Microsoft Teams or Slack, and video chat like Zoom are all you need to get started. If your team also needs access to internal systems through VPN, it's critical to ensure that everyone has easy access and the instructions on their usage are very clear. At GitLab, our technology stack mirrors a very similar, simple set of tools that every team member has access to, which allow us to collaborate and get work done. These tools help us to tightly integrate our values into our work by writing things down, optimizing for the entire company rather than specific departments, keeping a single source of truth for all decision-making. Let's take a quick look at each of these aspects of our remote stack and how we decided to incorporate those tools into our stack.  For this purpose, we have chosen to have mostly MacBooks as our computer of choice. While some more technically advanced folks may use Linux on their laptop, the majority of GitLab team members run macOS on a company-provided MacBook. This allows us to have a consistent user experience and provides a boring solution for top-tier hardware reliability for every team member. Almost as critical as the computers we use is the office equipment surrounding your computer. GitLab provides employees the freedom to purchase the equipment they need, but recommends a few essentials. These include a comfortable desk and chair, external monitor and keyboard and mouse, as well as a dedicated microphone for video calls. Other equipment that a team member needs can be purchased and expensed so that they are not limited in their productivity and can be managers of one to understand what they need to get their job done. For video conferencing, we use the world-leading business video conferencing app Zoom. Zoom provides reliable meetings with audio and video to help team members interact in a more natural way than the traditional conference call. Zoom also allows us to host webinars with outside participants, share our screens, and even livestream many meetings directly to our YouTube channel. Zoom also integrates directly with our main enterprise chat application, Slack. Slack allows us to communicate between team members either synchronously or asynchronously. Channels exist at GitLab for a large variety of topics. This could be an event or a project that a team is working on, a long-standing team channel for answering questions, or even channels that are strictly about socializing with one another. In an all-remote environment, having these various methods of communication is critical for connecting team members. And GitLab is public by default and thus encourages most decisions to happen in public channels. That way, if another team member's input is needed with a problem or decision, they can easily be pulled into the conversation with a simple ad mention. For other documentation and communication, Google Docs provides an excellent multiplayer capability that lets team members take notes and share ideas quickly. Every single meeting at GitLab has at least two things, a Zoom link and a Google Doc with an agenda. These are the basic requirements of any meeting, and they help to ensure that those meetings are both effective and efficient. All team members are encouraged to take notes, ask questions via the Google Doc, or collaborate on slides or spreadsheets in Google Docs as well. And lastly, we'd be remiss to not point out another tool that is critical to our collaboration, GitLab. At GitLab, we believe that eating your own dog food or drinking your own champagne, depending on your preference, is one of the most critical things that we can do to make our products better. GitLab, the software, was born out of the need to have a collaboration tool that developers could also build and collaborate on together. Hence, it's a natural extension that we use GitLab to make GitLab. But it's not only our engineering department that uses GitLab. Everyone, from marketing to legal to customer success, uses GitLab in some capacity. If it's to edit a process, then we'll update the handbook using our web IDE. If it's organizing an event or content calendar, that will happen in issues and milestones. Or even if it comes to operating GitLab.com itself at scale, we use GitLab to build, test, and deploy GitLab. It's very meta.