Hi, welcome to Nursing School Explained. This video on Acute Respiratory Distress Syndrome, also known as ARDS or ARDS. Now this is a syndrome that has got a lot of attention lately because this is the end of 2020 and we know that a lot of patients who have COVID are in danger for developing this. So let's take a look as to what the cause is. So ARDS can have a variety of causes such as aspiration, pneumonia, viral or bacterial, sepsis, severe massive trauma, PE and pulmonary embolism, near drowning when lungs get filled with water, acute pancreatitis because of all the inflammation that occurs on the left upper quadrant, coronary artery, bypass graft, surgery because of all the surgical changes, as well as DIC, disseminated intravascular coagulopathy, shock, etc. So as you can see there's a multitude of causes that can lead to this. So let's look at physiologically what is going on. So over here we have the normal pulmonary capillary alveolar structure. So we have the pulmonary artery that goes down into the pulmonary capillaries, CO2 diffuses into the alveolus, O2 diffuses into the pulmonary vein and then the oxygenated blood gets carried to the body and the cells. Now what happens in ARDS, there is an injury to this alveolar alveolar capillary membrane and whenever an injury occurs for any of these reasons up here, the immune system is triggered and this cascade of immune cells want to come and help fight whatever is the cause of the problem and so there's this cascade of cellular and biochemical changes that triggers these immune cells that are usually well intended such as neutrophils, macrophages, lymphocytes, monocytes and all of those produce cytokines and cytokines are basically cells that help promote the immune system to do its job and especially with COVID you have probably heard of the term cytokine storm. So now we have this massive immune response, all these cells that want to come fight any of these causes and therefore in order for these mediators to be released from the pulmonary capillaries, this permeability has to be opening up so they have to all be released and what happens when the cells are released, they're released in fluid and so then we have this interstitial edema that occurs between the alveolas and the pulmonary capillaries so this increased fluid that happens here and then if we have basically this alveolas that's now covered in fluid it's not going to be able to perform the oxygen and CO2 exchange as a normal alveolas would. Now this increased vascular permeability causes the interstitial edema and then the lungs get kind of stiff because they lose their compliance, their ability to open and contract as the chest wall expands and then recoils and then platelets also come to play they aggregate and release more chemical mediators which then means that more cells are being attracted to the alveolar capillary membrane and the fluid crosses that membrane and as you can see here this alveolas is swollen it's very puffy and now that fluid level is just increasing here so basically this alveolas you could think of is drowning in this fluid that all these chemical mediators from the immune system are causing and this alveola edema then does not allow for the oxygen and CO2 exchange and therefore the patient is going to have this acute respiratory distress syndrome so signs and symptoms as you can imagine when there is all this edema and the alveola are filling up with fluid the patient's respiratory rate is going to go up because they're going to have this air hunger there's going to be increased work of breathing and because fluid accumulates it's going to be audible with the set of scope in crackles and bronchi because now we have fluid here all this congestion that we can hear the patient will be restless because their O2 levels dropping and their CO2 is building up they might have altered level of consciousness because of the increased work of breathing and the distress that they're in their sympathetic nervous system will respond with tachycardia they might be cyanotic because we're now not perfusing so this oxygen exchange is not happening so the cells are starved of oxygen they might be have power and so be really pale and of course their oxygenation their O2 saddle will be low now diagnostic tests that are used to diagnose this is a chest SX-ray a very simple test and it usually shows diffuse bilateral infiltrates and remember that infiltrates usually mean fluid accumulation then on a chest X-ray air shows us black and fluid shows white and this is then called a white out on a chest X-ray because now you can't see any more air filled because the alveolar are drowning in this fluid and the fluid again is represented by these white patches that are just diffuse all over the patient's lungs now a chest CT can also be performed which is a much more detailed test or if we suspect a perfusion abnormality such as a pulmonary embolism and then certainly we'll need blood tests such as a blood count CMP arterial blood gases because we want to know exactly how our relationship between the O2 and CO2 are happening and maybe how the kidneys are compensating we want to get a urinalysis again checking for the kidney's ability to function and how they are able to concentrate because anything that concerns the respiratory symptom also can be damaged into the cardiac system we want to get an EKG and then certainly a blood or sputum culture because we have all this causes such as pneumonia or sepsis or trauma DIC shock that could be the underlying causes here now for complications so this is a severe severe critically ill patient who will require a lot of intensive care and complications include mods or multiple organ dysfunctional system which basically means because now none of the organs are being perfused this oxygen exchange is not happening so now we're not getting any oxygen in all our important organs and here specifically the kidneys the liver and the heart are not being perfused and that can lead to kidney liver and heart failure the patient can get ventilator associated pneumonia or VAP they can get burial trauma stress ulcers and then renal failure like I said from the decreased perfusion low blood pressure and it can lead to death and their trauma I'll come back to that so for treatment or nursing care because we are having trouble getting the body oxygenated we need to give the patient O2 oxygen administration and meticulous nursing care for anybody who's admitted with these signs and symptoms or diagnosis is very important because this is a process that happens not clearly it doesn't happen within a few minutes but it also doesn't happen over a few days so if we frequently assess our patients and want for these signs and symptoms specifically any changes in lung sounds we're able to hopefully prevent some of these changes and just put the patient on some oxygen get some of the diagnostic tests and get them treated so they can get better but a lot of times the patient will need to be intubated and so they will need positive pressure ventilation with PEEP which is positive end expiratory pressure and that is basically a ventilator setting and positive pressure ventilation basically means that when the patient is taken an inhalation that extra oxygen is being blown into the patient's lungs so these alveoli that are now all congested the air comes in and pushes out the fluid so that we can hopefully push some of that fluid back and then get that oxygenation get these capillaries oxygenated again that's what this positive end expiratory pressure here is with the positive pressure ventilation and that is a ventilator setting that I'll discuss in a different video but because we're now adding extra pressure to the lungs and these alveoli might already not be as elastic as they should be we can cause barotrauma basically blowing out or blowing up some of these alveoli so now air is escaping through the alveoli because there's this opening now and then it can get into that into that pleural cavity causing a pneumothorax or possibly even a tension pneumothorax so that's also another complication that can happen here from this barotrauma now as for nursing care because the patient is basically basically drowning in this fluid because of all these alveoli are filling up we need to position the patient and typically what we think about is we sit the patient up elevate the head of the bed but in ARDS this is not sufficient many times the patient will be positioned prone which means on their belly you've probably also heard about that with covid because the the change remember the fluid is always heavier and it will settle with the gravity so if we can now change the patient or turn them around now we can basically the fluid will come to the front of the alveoli and the back will be able to be profused so by kind of constantly rotating the patient we can ventilate different parts of the alveoli that are saturated in this fluid and there is front positioning there's lateral rotation where the patient will be maybe at 45 degrees and then rotated side to side and then there's also kinetic rotation and then the most important part here besides all the oxygenation is to maintain cardiac output and tissue perfusion because again the cells are starved of oxygen often there is decreased cardiac output because of this positive pressure that we're administering to the patient to keep the alveoli open but remember the more pressure we exert in that plural cavity the less room there is for that blood return from the superior inferior vena cava to return to the heart because now this positive pressure that we're trying to push into the lungs is taking up space there's only so much space available so because of this peak and decreased contractility the patient's cardiac output might be down so we'll require hemodynamic monitoring such as a central line central venous pressure pulmonary artery pressure and cardiac output monitoring as well as the patient will probably have an arterial line so that we can see exactly what their blood pressure is at any given time the patient will require IV fluids which might not be enough so they might also need positive inotropes to help with that contractility problem and those drugs are the butamine and dopamine that are most commonly used here and then if there is a problem with low blood volume or the patient is anemic for any of these reasons that we discussed over here then the patient will also require packed RBCs so that we now boost the patient's hemoglobin level so that they can the hemoglobin and the red blood cells can transport the O2 to the cells that that's so desperately needed so this concludes this video on ARDS I hope it has helped you gain a better understanding of how severe ARDS can be and how many different issues or underlying causes can cause ARDS and what happens physiologically and what we can do from a nursing perspective to keep an eye on these patients very closely so that hopefully they don't suffer and have to be placed on a ventilator or even if they do with all this meticulous monitoring and positioning particularly to help them get that oxygenation to their bodies and their tissues that's all desperately needed thanks for watching this video nursing school explain please give me a thumbs up if you liked it subscribe share with your friends and I'll see you soon


Welcome back team today. I have a book from Robert Green called The Daily Laws and I'm gonna try reading this every day I don't know if I'm gonna read it like this on video, but I'm gonna read it There was a point time where I did read another book every day. There were two books There was daily rituals or daily habits. I think it was daily rituals and The daily stoic so maybe I'll read from one of these three But every day I'll share a book with you and there'll be a link in the description to this book and on my website So let's get to it October 31st. You are the obstacle in This world where the game is played with loaded dice a man must have a temper of iron with armor proof With armor proof to the blow With armor proof to the blows of fate and weapons to make his way against men Life is one long battle. We have to fight at every step and Voltear very rightly says that if we succeed it is at the point of the sword and That we die with the weapon in our hand That is a quote from Arthur Schopenhauer and actually there is a Really good essay From Schopenhauer. Let's see if I can find it here It is on thinking for oneself is what it's called So what I'll do is I'm gonna add that to my notes for today And now when I go to my daily note It'll show up here is It'll be down here under thinking for oneself because I'll link to it And so then I can just go there then I can go here and I can listen to it So I'll include that link to if I remember And so actually we've got That and then we have our daily laws So if we go to daily laws, we could do the same thing open DIY laws And I may not have them in here So we'll just go to today and then we'll put in daily laws. So we'll get out here And then inside of here the parent concept is gonna be a book and The parent concept of the book is self-engineering and then there's sibling concepts that can go with it Like health wealth finance, whatever it is and if we put note type And then the note type will be a book note And these are all just links So what happens is when I click on any of these like if I click on self-engineering It'll take me to this page with all this information I have on self-engineering Then if I ever want to write something about self-engineering I have my references and all these links related to it. So Let's go back over to the camera view and continue on so Schopenhauer in that essay that I want to Take note of real quick He talks about thinking for oneself how most people don't think for themselves. So I just thought I would bring that up and Because most people don't think for themselves they end up following the follower and that creates a society where It creates an environment That is he doesn't he doesn't say this but in thinking about it. It's a magnetic environment It's a it's an electrically charged environment.  So basically Whatever the average is The average will pull Everyone into the average but even still the average will look out To something beyond itself and idolize it so you have stars in Hollywood and actors and actresses and things like that and you have people who Will not listen to the people in their immediate lives But they'll listen to the actors and actresses because they have this status But because they don't think for themselves They don't ask where did this status come from why are these people idolized or they idolize for having some sort of trait that is Superior to to others and if so, what is that trait? Is that trait supremely beneficial to me as an individual and to society as a whole is it going to propel Society forward but most people don't think like that and that's what Schopenhauer is talking about and to be honest If you're still watching this you don't think like one of those people and one of the most difficult things you if you're ever gonna encounter is Attempting to convey this philosophy to those people because you believe that if they understood what it is You understand that the world would operate and be an easier place to work in But that's not the case in this place You can only work on yourself because all of this is a reflection of you Everything that you've ever seen every quote that you've ever heard is created Specifically for you to deliver you a piece of information Now some people don't believe this but after they go through this a few thousand a few million times they understand and Hollywood attempts to tell us on a very regular basis exactly what's going on. There's a movie Groundhogs Day with Bill Murray and in this movie he relives the same day over and over and over again and Perhaps a feature that's maybe not a feature. There's something in the movie. That's missed is that he becomes very efficient at his days And so even though every day is the same he reaches a point where he's able to establish entire relationships and get Things done in the day that other people couldn't get done in a week now I can't remember right now at this moment exactly why Groundhogs Day ended for him But eventually it did and he went back into the regular world before a period of time What could have been years? He lived the same day over and over again where everyone Did the same thing and he be he was able to read what they were doing like clockwork And because he was able to read what they were doing like clockwork. He was able to Diffuse situations before they happened He was able to make bets and wagers because he knew was what was gonna happen next and then he could leverage those things to Impress people and he could leverage those those relationships to get favors and and he would just do this and Then he would go to sleep and he would wake up and it would all start over again That is how our lives are we operate on what we believe that we remember But we don't know if what is in our heads when we wake up was there when we went to bed the day before And we don't know what tomorrow is gonna be because we're creating it in the now. We're always in the now Now we can go deeper into this. I'm gonna finish this, but I'll tell you this that we are living in the dream state This is not this isn't even life Think about this place that we're in is opposite this place that you're in Because everything that is said everything you see is here for you. It's like it's your own personal video game And if you're watching this is because I came here is my purpose to tell you this and I'm saying this because it's my purpose to tell you this I was created by the creator and To be a vessel for the message that you're receiving right now This it's not a simulation This is an imagining you were imagining this Every day that you wake up you imagine all of this and sometimes you're able to Carry what it is that you desire into sleep and Then when you come back to this place You make it manifest if it's not manifest already And if you practice this night after night, eventually you become so good That you can't tell anybody what you're doing because they won't believe you And those that do believe you they're gonna want to know how to do it They're gonna become jealous and they're gonna become envious and they're gonna become greedy So the individuals that understand this stuff they typically keep it to themselves So I'm not giving you everything, but I'm telling you what this place is So you begin to go look for your own answers and on that note We'll finish this in the next broadcast team


And now stay tuned for the mystery program that is unique among all mystery programs Because even when you know who is guilty you always receive a startling surprise at the final curtain in the signal oil program The whistler the whistler and I know many things for I walk by night I know many strange tales hidden in the hearts of men and women who have stepped into the shadows Yes, I know the nameless terrors of which they dare not speak And now for the signal oil company the whistler's strange story a matter of courtesy Everybody loved Cressy Carlos everybody said they'd never known anyone quite like her heart They said was as big as she was and Cressy was a big woman She had a generous wide open frankness about it A hearty friendliness that penetrated the quick stinging with that made her famous Yes, everybody loved Cressy Carlos Everybody except perhaps her husband Matt The two of them owned and operated club Carlos the most successful and expensive of all the night spots in time A Julie Bradford featured singer at the club was singing her big number Cressy moved about and joked and kidded the customers and they ate it up Hi, yeah, come on in to count the suckers. Hello, Jack.  You're wrong Jack. We don't charge enough.  Make your way through the tightly packed tables until you reach your own Private tape yours and Matt No Matt, I want to talk to you about Looks like a good night. Yeah, yeah, it's fine You glance at Matt then with Julie the same The warm friendly smile remains fixed on your face But no one fooled you do they Chris you know all about Matt and Julie and you don't care She can have him catch Yes, you'd give Matt the Julie tonight, but there's the club Matt's half-owned and Club Carlos is the one thing you won't part. You won't really be satisfied until it all belongs to you No matter what price you have to pay That flame velvet nothing she called the costume doesn't hurt it she can sing too. Hey Julie Julie over here Come on Julie sit down with the bosses. You get better service Gotta take your math. Oh hi, Chrissy. Hello, Julie. You look good tonight. Hi Chrissy You'll turn my energy battery like that. Let me order your drink Julie. Oh, no, thanks. Remember. Oh, yes That's right. You never touch anything on the job. Well, I never do either Oh, I always have a drink before I come to the club just one at home. You do That's funny so do I you two ought to be able to build a great friendship on a coincidence like that I don't think so the customer is always right, but Chrissy doesn't think we're so right. Oh, that's where you're wrong Julie.  So you get up from the table move among your guests See that they get the best liquor the best food and that they pay the best prices for Later that night you stand behind the bar after closing time checking the register and chatting with Nick the bartender That's the last Nick. We can seal up the joint now. We had a good night. Yeah some ways So how was it bad? All right, I don't know. Good night Chrissy. Nick Yeah So how was it bad? Look, you know your own business. I don't have to tell you about That anything what do you know about Matt Julie? That's maybe I don't Okay, so we'll talk in the open you got to get rid of her. She's trouble. Come on. Let's have the rest of it Now she's sitting here with Matt tonight early. Nobody else is around. I don't see me cuz I'm under the bar fixing things. I Hear him talking and I don't dare move talking pretty personal Anyway, the wind up is this Julie saying to Matt.  She's just living it up Women do it all the time even She's not that good at actress.  That's no answer. What is it? I? Don't know With you a long time you've always been swell to me You made this place pull it through tough times now. It's all gravy. I don't like to see any cheap easy Nick Thanks, I know how you feel and I appreciate it But for now I'm just It's happened before and worn off. Yeah, but not this deep. I Have to see this and wear off before I believe it Night Chrissy night Nick. I'll believe it when I see it, too Chrissy Julie's a bigger fool than you thought she was isn't Maybe you can make it easy for her if she loves Matt as much as he says she does Yes, Chrissy if all she wants is Matt, maybe you and Julie can make a deal Mid-afternoon the next day you park your car on the side street next to the spacious apartment building where Julie lives As you take a shortcut through the adjacent parking lot a young man in mechanics overall Drive the car into the lot that hails the parking attempt Hey Matt We just Julie plant for its parking space, but this car from the garage number four is her space in your pocket No, I'll do it. You're gonna be here. I'll leave the keys in it. Okay. Oh, sure. Sure. Go ahead I'll be here You watch the mechanic park the car and Julie's parking place Then you enter the apartment building walk down the corridor leading to Julie's apartment You're about to press the bell when you hear voices coming from her apartment Matt's and Julie's You stop a moment then turn and walk back a few steps to another door Instinctively you try the knob open service entrance to Julie's kitchen You enter silently move quickly across the kitchen to a spot where you can hear better Now listen to me Cresce and me a crew. I told you that a hundred times But I still got a figure out a way of making the break with her and still hang on to my half of the crop That's how they told you that Yeah, what is it and God Except they grab us for murder and that's all Anybody know better that's not like Crescent We'll do it my One get a couple hours. I'm going home to do this. I'll come back at six. We'll have a drink All right Get some sleep now. Don't worry You wait until you hear Julie walk from the living room into the bedroom and close the door You're surprised that you're calm Suddenly it's as if you'd always known exactly what would happen and what you would be Wait until you're sure Julie's asleep Then move quietly into the living Cross to the low cable in front of the couch and pick up the small box The poison Julie intended for you Distant pastures they say usually look greener and that often goes for the other fellas car too But it needn't if you have to grind and grind on the starter Well, you see other cars start right off at the first touch. Don't envy the other fellow He's probably just using signal Apple When the traffic signal says go and the car next to you zooms out ahead leaving you with that glued to the spot feeling Don't envy him. He's probably just using signal Apple And when your car is laboring up a hill and another car breezes by easily smoothly in high Don't envy him.  You suddenly see a solution The bottle of poison Julie intended for you is in your hand and with it Julie's life and Matt's It's a perfect setup, isn't it Cressy? Nick the bartender at your club carless helped perfect it when he told you about Julie's conversation with Matt They're talking pretty personal Anyway, the wind up is Julie saying the Matt.  I always have a drink before I come to the club. Just one at home It is perfect, isn't it Cressy? Now Julie's asleep in her bedroom and the bottle of poison is held carefully in your gloved hand Only Julie's fingerprints will show on the table. You see a decanter filled with whiskey You quickly pour the poison into it Then you leave the empty poison bottle just under the edge of the couch where it can be found when anyone looks for evidence You've set the trap haven't you Cressy? And after a hurried survey you leave Julie's apartment quickly and quietly just the way you came When you reach your car you suddenly realized you left your car key in Julie's apartment You put the latch down on the kitchen door There's no way you can get it without waking Julie. You're stunned Then it hits you Just a single key on a chain.  What's the matter with you Cressy you got a beef with me? What would I have to beef about? I don't know only when you slide over a quick one like that last cracker Bigger things aren't exactly Rosie with us forget it Matt matter of fact I was just sitting here thinking that I don't know when you meant so much to me Yeah, how about us having a drink a short one for the short road huh gee I can't Cressy not tonight. I got a big appointment on the way to the club do there at six Probably have a drink with him. Oh Anyone I know No fellow wants to book an act in the club. I told him I talking over with him watch it Matt I don't want you auditioning any talent without me. Oh, no, this guy just wants to talk to me. That's all I Wouldn't set the deal along you know that Funny thing Before I went to sleep an hour or so ago. I was thinking about you to you in the club You're an awful smart operator Cressy Wasn't for you Club Carlos would be just annoyed in the region. Well, I'm glad to hear you say that Makes me feel wanted, you know, I sure couldn't swing it alone Couldn't make it click like you do Well, don't worry Matt. I got no plans for leaving you're the guy who's on his way out Huh, well a look at the time if you're gonna keep your six o'clock date. You better get going Oh, hey, you have to take a taxi though. I left our car at the garage the clutch was slipping. Why didn't you wait in the Lamarra morning? Well, okay, I'll grab a cap at the corner. See at the club. I Goodbye Matt That's it. Isn't it Cressy the last time you'll see Matt alive And you don't feel a shred of remorse about it as you walk to the window See him standing on the corner hail a taxi get in it and ride away Your only thought is that once your timetable plays out Club Carlos will be yours all yours You take up your vigil by the clock Allow Matt ample time to get the jewelry more time to have a lingering drink with it When you feel sure they've shared that last fatal drink from the poison whiskey to canter on Julie's table Go to the phone and place a very important call It's Cressy Julie. I thought you'd be on the way to the club by now Not going in tonight dressing. I not going in how come anything wrong I feel so strange I Got all dressed That's too bad Julie Is Matt there? No Don't give me that stuff Julie he's there isn't he no no Cressy honest look he was coming there and I know what he's got To be there. Okay, Chris. He was here Listen Julie listen carefully, this is important Did you and Matt have a drink together? Huh? Did you and Matt have a drink together? From the decanter on the table I'm gonna tell you Julie. Yes, sir. I think you deserve to know Never mind dear I'll do all the talking I'll do all the talking from here on in because your poison did my work for me Julie And I'm just real grateful to you. How did you know? Yeah that little green bottle. It's empty now Julie And I'm afraid it's out of your reach But I did I heard it all this afternoon you and Matt I was there So you see I had to call you Julie see how you were doing Just as a matter of courtesy And I got news for your kid You're dead. Hello. Hello They won't be calling the doctor now will she Chris No, Julie won't be calling anyone ever and you know now that Matt had a drink from the same decanter of poison whiskey Before he left Julie's apartment It's just a matter of time now isn't it Chris? As you wait for the call you know must come you change clothes Just as if everything were normal and you were going down to the club as usual You wonder who'll call how long it will take and then in the middle of your thoughts Hello, Chrissy. This is Nick. Oh, hi Nick. What's on your mind? Me and here from the distillery. Let's know if you want usual order. Oh Well, how does the stock look to you? Will the usual take care of it? Yeah, I think so. That's your answer then Want to check with you Chrissy after all you're the boss. Yeah Yeah, I am If you want to overlook Matt that is by the way, is he there yet? When he comes in no no, I'll be down after a while. I'll see you man Okay, sorry to bother you. Not at all.  Yes, yes, I am. My name's Branson Well, of course the time to come right in Won't you sit down? Yes, thanks. I Perhaps you'd better sit down too. Why is anything wrong? Yes, I'm afraid so.  When did he was driving a car and it rammed into an empty warehouse building? He had killed in an accident. Oh my I'm not sure Mrs. Carlos He he had an accident all right, but the ambulance attendant seems to think that death came as a result of poison Poison they're checking on that now Mrs. Carlos Another strange thing this car your husband was driving wasn't registered in his name not his car Well, then who's Lieutenant This car Matt was driving Was it a blue sedan? 1947 Olds move you what? Well, yes, it was That car belongs to Julie Bradford Singer at our club Matt's in mind Nick told me about her threats, but I wouldn't believe it. Oh, what threats Mrs. Carlos and who's Nick? Nick's a bartender at Club Carlos. I I Don't want to say anymore right now lieutenant If I were you I'd check on Julie Bradford and find out what really happened to Matt All right, Mrs. Carlos, I will check on Matt I'm sorry really sorry I leave you now. I have a hunch this investigation won't take long Believe me out of everything I can not to inconvenience you in any way Did you know that city traffic driving causes three times as much engine wear as highway driving? That's just one of the surprising facts proved by engineers during the development of signals amazing new premium motor oil Which reduces engine wear due to lubrication? 50% Using startling new scientific techniques never before available to the petroleum industry These engineers found a way to measure just how much engine wear was taking place Second by second at every different speed every different temperature Then they deliberately set out to develop an entirely new type of lubricant that would reduce engine wear under all the different Conditions encountered in driving the result is new signal premium a motor oil So superior it should keep that like new pep and power in your car twice as long Yet you pay no increase in price for the extra protection of this heavy-duty type signal oil So to protect your wallet and your car to get your next oil change at a signal service station Change to signal premium the amazing new motor oil that reduces engine wear due to lubrication 50% Well Cressy you're certain now that you've won aren't you? After police lieutenant Branson leads to investigate the details of your husband's death You reflect confidently on the steps. You've already taken You're sure Matt's death and Julie will appear as murder Once the lieutenant checks your story with Nick the bartender at Club Carlos And when lieutenant Branson finds Julie is dead He'll also find the key to yours and Matt's car at her apartment And you've already identified the car Matt was driving is Julie Yes, Cressy you're quite pleased with yourself aren't you're sure lieutenant Branson will return to confirm your story of the Double tragedy and the Club Carlos will be all yours just as you plan An hour or so later.  Yes, he repeated the conversation he overheard between Miss Bradford and your husband. I Didn't think she'd do it. I don't think she did do it, Mrs. Carlos What do you mean? Well, Miss Bradford was wearing a flamed velvet costume one that required a special skin makeup According to your bartender, that's why she dressed at home instead of at the club Well Looks to me as if she intended to go to the club tonight as usual In that case she wouldn't have poisoned the whiskey that she and your husband drank. What if Julie didn't that's just it If she didn't someone else did When did you last see Miss Bradford? Last night and she finished her act at the club and when was the last time you had heard apartment. I've never been there Your car keys were found So what? Matt probably no He was in his part Well, he probably took mine too with miss took it for his he left in a pretty big hurry. Mm-hmm. And what time was that? It was before six he took our car. He took your car and left here a little before six That's right. I'm afraid it isn't right. Mrs. Carlos Your husband couldn't have driven your car a little before six, but he did know mrs. Carlos Your car was parked on the side street near Julie Bradford's apartment most of the afternoon taken now.  Carlos You drove that car to Julie Bradford's apartment this afternoon And that's when you saw the blue sedan your husband was driving at the family's exit The car you identified as miss Bradford You couldn't have seen it anywhere else But I have I I've seen them together in it often. No mrs. Carlos Miss Bradford was never in the car you saw I'm afraid your lies are going to put you right in the gas chamber, but I'm not lying. Oh, yes, you are Miss Bradford's car is in the garage for repairs The car you saw delivered this afternoon to the parking lot attendant and identified as miss Bradford's Was a courtesy car the garage sent over while hers was being repaired That whistle be your signal for the signal oil program the whistler each sunday night at this same time Meantime signal oil company and the friendly independent dealers who help you go farther with signal gasoline hope you'll remember Regardless of what gasoline you use you'll enjoy more miles of happy driving If you drive at sensible speeds obey traffic regulations and avoid taking chances When you take a chance to save a moment You take a chance on that moment being your last featured in tonight's story were bill foreman Jeanette Nolan ted decorsia gg pierce and herbert litten and bill boucher The whistler was produced and directed by george w allen with story by charles wilson music by wilbur hash And was transmitted to our troops overseas by the armed forces radio service The whistler is entirely fictional and all characters portrayed on the whistler are also fictional Any similarity of names or resemblance to persons living or dead is purely coincidental Remember to tune in at the same time next sunday when the signal oil company will bring you another strange story by the whistler Marvin miller speaking for the signal oil company Stay tuned now for our miss brook starring eve arden which follows immediately over most of these stations This is cbs for columbia broadcasting system


Hello, hello everyone. My name is Laura and this is my channel Laura's Little Library and today's video is going to be my December TVR Started I will mention that my current read is deal with the devil by Kit Rocker. I am over halfway through I'm listening to the audiobook, but I'm gonna try and Follow along physically because I've just had such a struggle paying attention to the audiobook But that's because I have been listening to it at times where I can't concentrate It seems really good. I Have thoughts about it, but those will be in my reviews on Goodreads and at the end of November in my wrap-up So like stay tuned for that, but this is my current read and I hope to finish it Today would be nice, but tomorrow is more likely So this December I will most likely be participating in two readathons So my December TVR is going to be a mixture of the two readathons I am gonna try not to join any more readathons Just because one of them is a month long and the other is a week long so they do already overlap and I December much like October is a month where there are so many different readathons, and they're also fun and wonderful But I just can't do Too many of them so I'm going to go through both readathons and go through the prompts and My answers and that will kind of make up my December TVR. I don't plan on reading any books outside of the readathons for December because Both readathons have enough prompts. I don't think I could read any more of them even if I wanted to But I will also note to hear that I do have a winter TVR And that will be going up later in December when it's more closer to actually the winter solstice when it's actually officially winter and Those books I won't have a lot of overlap But that's because those are books that I'm reading during the season of winter So not just December, but January and February as well So keep an eye out for that video and the best way to do that is by Subscribing and clicking the bell so that you're notified, but that will be a video with different books on that TVR So the first readathon that I'll be participating in is the month-long one And that is the reindeer readathon and this is hosted by break even books And I'm not on the right page of my bullet journal The way this readathon works is that everyone is split up into teams and then each prompt is worth a certain amount of points I have been assigned to teams snowflake. I love it. I'm so excited And but the prompts are the same for everyone You have your set number of prompts and then you have three bonus prompts and then if you complete all the prompts Within the time then you may do one of the prompts again for extra points, but There are plenty of prompts so if I can get through all the prompts. I will be very proud So because it is the reindeer readathon all the prompts are named after the reindeer. So let's go Also another thing to note is that you can't use one book for multiple prompts So I do have a book for every prompt. All right, so the first one is dasher This is and it's to read a short story or novella. And so I decided to go with down among It is down among down among the six and buzz by Shona McGuire This is the second children in the wayward children series and I recently got this and I am really excited to read it So the next up we have dancer and this is to read a book by a favorite author And I'm gonna go with unravel the dusk by Elizabeth limb I am a big fan of Elizabeth limbs writing and I have the first one spin the dawn For some strange reason. I haven't read the second one. It's so stupid, but I do have the audiobook for us I'll be listening to it But hopefully I will be buying it shortly prompt number three is prancer and this is to read a book with travel And so I'm going with one by one by Ruth where? so this book is a Is a horror book actually is a thriller book and these bunch of co-workers travel to a cabin and then one by one they are murdered so It's a little bit of travel, but it's very wintry themed I was gonna read this in October and then I decided Let's save it for winter kind of break up the winter he reads while keeping still a winter setting so Then we have vixen what is a book recently caught your eye and I'm gonna go with the other side of perfect and this is by Marie go Turk and This book was just sent to me by a friend of mine Literally a couple days ago, and it is definitely caught my eye This is a dance ballet themed book and a lot of these books have like blue kind of gray blue covers And so it really fits in with that because I don't know. I think blue is just definitely a is the winter color So a lot of these books will have blue covers Moving on we have Comet and that is a five-star prediction. And so for that one. I have chosen spy X family volume four by Tatsuya and them and I Chose this because I love this manga, and I don't see myself I don't know if I can give any of these books less than a five-star unless it's like absolutely atrocious So I'm gonna keep going with this manga next up We have Cupid and that is to read a new author and so here's a book that does not have a blue cover Has an orange-ish cover and that is Hunt of the Gremal kid This is by Danny Swanson. I actually have the pleasure of meeting the author at the Twin Cities Comic Con And I am so excited to read this and it's nice and short, which is great for read-a-thons such as this one so and I mean she's got flames coming out of her hands, which is like it reminds me of a fireplace and makes Me think of warmth, which is what we need in the winter so This is gonna be my Cupid and then we have Donner and that is to read a book with a red or green cover And for that one, I am choosing In a Holidays by Christina Lauren. I have never read a Christina Lauren book This book was so popular Last year, I believe it was a book of the month book and everyone was loving it because everyone was reading a bunch of Christina Lauren and last year I just was not in the mood to read a Groundhog's Day type book But I think this year I'm gonna try and read as many like Christmas set books like actually in the holiday taking place during winter So I decided to give this one a try and this one I also have as an audiobook Then the next one is a fun one because for Blitzen It was have three books and have someone else choose it for you Whether it was put it up on your Instagram or Twitter or ask someone or do a pet thing and put treats on it and see Which one your pet picks, you know, whatever So I put polls up on my Twitter and Instagram and if you're not following me on social media My links are down below so you can follow those on all of the fun things fun bookish things that I post there and I the three books that I posted for people to choose was window shopping Happily ever actors and the 12 dates of Christmas I am interested in reading all three of them So none of them would have been a disappointment and it was really close like Like they were all within a few votes of each other But the one that did win out is the 12 dates of Christmas So I will be reading the 12 dates of Christmas I will have to see if I'm going to buy the physical copy or try and get it as an audiobook But I'm excited to read it. I think I would love to also read the other two books I've heard so many good things about the other two books and they caught my eye So I will for this readathon be reading the 12 dates of Christmas But that's not to say I didn't want to read the other books and then the last Prompt yes, and then the last prompt is Rudolph and that is to read a standalone and for this one I've chosen royal holiday by Jasmine Gullery Gullery Mm-hmm, and this is about a woman who goes to England with her daughter on a work trip and Ends up falling for I assume a royal or someone close to the royal family So again, you got the blue cover romance Christmas holidays So I will be reading all of these plus a few more for this readathon And since I planned this read-a-thon first those are all the books I'm gonna read and then this next read-a-thon I did my best to Incorporate as many of these books into that TBR because that one is only a week And it would just be a lot easier if I did the same books But for different read-a-thons, but what's fun about this second one that I'm doing which I should probably just tell you is the follow a lot on and And this one is partially reading but also has a little bit of just winter activities in general So that'll be a nice way to kind of change it up a little bit for me without adding too many more books onto my TBR I also did purchase a book work from the reindeer read-a-thon And so I'm really excited to use that As I'm going through my books because I am going to read one at a time. I'm not gonna do multiple at once So I can use the reindeer bookmark throughout the entire thing and I don't know why that makes me so happy, but it really does So now moving on to the follow a lot on follow a lot on I Can say it I promise the first prompt is to light a candle and read a book with blue on the cover and as we Saw and had been talking about majority of these books have blue on the cover, but Officially, I'm gonna choose royal holiday because it is the most holiday themed book with blue. It's almost like a blue-purple, but Yeah, I'm choosing this one And then the second prompt is to watch a movie and for this one. I'll probably watch the princess switch three with Vanessa Hudgens I Watched the first two. I'm not completely sure why I think I just like Vanessa Hudgens But it's really the only Christmas movie that has been advertised that is new this year that I've actually been like Yeah, I'll probably end up watching that. So that'll be the movie I watch for it Oh, and the nice thing about the follow a lot on is that you can overlapped Books and prompts so for the next one is to read a book with the holidays in them Um So I'm gonna read the royal holiday for that one is literally in the title So if there isn't winter holidays in here, I will be upset Then the next one is Secret Santa that is a book chosen for me And so that's gonna be the 12 days of Christmas because it's a book that other people chose for me to read for the reindeer Readathon for the prompt to read a gifted book I will be reading the other side perfect as it was recently gifted to me and has a blue cover So the next prompt is to take a picture of your book with Christmas decor or holiday decor I celebrate Christmas. So that's my natural inclination, but I do recognize that there are other holidays around this time. So It's it's to take a picture with whatever holiday decor And if you don't celebrate Christmas or any of the holidays around this time I'm sure you can find like a Christmas tree outside and put your book next to it and take a picture Moving on the next prompt is your newest book on your TBR. And if it's easier, it's the newest book on your physical TBR So that's what I'm choosing Which again is the other side of perfect as it is the most recently acquired book I have and therefore most recently added to my physical TBR The next prompt is an action is an action prompt and that is to do a random act of kindness And so I so I've been thinking in planning how I'm gonna do that But I am not gonna share the details because that is not something that I think should be publicized I think that random acts of kindness should be just small little things that you don't do for attention. So I'll do it but and then the last prompt for the follow a lot on is read an own voice book with diverse rep and Again, I will be reading the other side of perfect. Our main character is Japanese American as is our author and so Own voices diversity rep right here So that's kind of fun because that means I will have three books to read over that specific week Which by the way is the 12th to the 19th. I never said that. I'm sorry So it's these two and then listening to or reading the 12 dates of Christmas It's everything. It's just blue. I'm even wearing a blue sweater It looks really dark in the video But I am wearing a blue sweater because so much of this is blue and just winter December just seems blue So there you have it Those are all the books that I am going to try and read this December and for both of these readathons Let me know what you plan on reading this December and if you're doing any readathons And if there are any I need to check out even though I said I'm not gonna do another one We'll see because I will be going home halfway through December I'm gonna try and pre-film all of my videos so that we don't have to deal with no nice background or lighting issues and things like that. So I will try and pre-film, but I will be going home So that'll make it easier to read. Also, let me know if you want me to vlog anything I would definitely be willing to do reading vlogs either just for the month of December for the reindeer readathon or even just logging the week of the follow-all-off on Just having like a full week of being pure Christmas perfection. I will do my best But yeah, so comment down below what you're reading if you're interested in vlogs Yeah, otherwise as I said earlier click subscribe and hit the bell to be notified I post on Sundays and Wednesdays now. I did change my uploading schedule. It just fits better with my work schedule And oh my goodness, it gets so dark. It's so hard because I come home from work and I immediately start to film but it's already getting dark outside, but so that's why the ring light in my glasses is Visible. Otherwise if you like this video give it a thumbs up and until I see you all in the next one I wish you happy reading You


So, far we have focused our attention on a time correlated single photon counting which allows us to make measurements of lifetime from hundreds of picoseconds well maybe tens of picoseconds if you can have a very good instrument like we do and up to say hundreds of nanoseconds in some cases you might be able to go beyond that as well. Today we talk about a technique which allows you to go down further to hundreds of picoseconds at least if not better and this technique is called time resolved fluorescence up conversion or the name I like better is femtosecond optical gating the reason why I do not like the term fluorescence up conversion is that there are many people working in the area of material science who want to make up conversion materials materials in which two photons of smaller energy would join up to give you one photon of higher energy and the moment they see fluorescence up conversion technique they come and ask me is it possible for us to test our samples on your equipment of course it is not possible to test their sample on our equipment so I like femtosecond optical gating better just to avoid trouble. But then fluorescence up conversion technique is an absolutely valid commonly used name and we will see where this term up conversion comes from in this technique and how is it that we get accuracy in time up to femtosecond scale before proceeding further it is important to point out that none of these slides are made by me I do not know how to make such beautiful slides they are all prepared by my colleague for the Shobhan Shen from school of physical sciences Javalaner University he has kindly agreed to allow me to use these slides as many times as I want wherever I want. So let me start thanking Shobhan for these slides that are made with a lot of care as you will see so first of all let me show you a photograph of the up conversion spectrometer this is what it looks like this is actually photograph taken from top this is not our instrument it is the instrument that is there in JNU but then our instrument is pretty much the same and next day we are going to go to the lab and we are going to show you our instrument in real time and we will show you how the data is recorded so the idea is in this module we are going to tell you and try to make you understand without actually going to the lab how the data is recorded and what are the underlying principles and all and next day you will come to the lab and you will see what exactly is actually done right. So what you see here is this black flat surface with a lot of holes is a breadboard and if you go to any optics lab you will see breadboard like this in fact if you look carefully you will see that this black surface with holes is sitting on a shiny surface with holes that is an optical table top of the top of the optical table and the reason why we have so many screws the so many holes there is that it is possible to use bolts and screws and fix pieces of optics on this surface. Now whatever you see here is a piece of optics it may not be very clear from this photograph because it might be for many of us that we are seeing such apparatus for the first time but when you go to the lab and we see everything in front of our eyes I hope it will become clear and today's exercise is going to help us understand things that are there as well to start with let me try to give you from this figure a description of what is there in this spectrometer. So first thing that you have is what is written as SHG crystal SHG means second harmonic generation crystal we are going to have a couple of modules on nonlinear optical on nonlinear optics later on and there will learn that there are materials that allow two photons of they may be same energy they may be different energy but they allow two photons to combine and produce a photon of larger energy it is pretty much like two drops of water falling on a table coming together and forming a bigger drop it is just that the drops here are not drops of water they are drops of energy drops of light but not everything allows combination of photons there are very stringent conditions that have to be satisfied for a material to act as a nonlinear optical material and it that in itself is a very active field of research. So without going into that at this time just believe me when I say that the first thing we have here is a second harmonic generation crystal what is the purpose we will see in a while. Now why are we saying second harmonic because in this crystal at least what happens is you make incident laser light nominally of 800 nanometer but whatever laser light you might want to use and two photons of the same laser join up to produce a photon of double the energy this photon of double the energy that is called second harmonic or if I put it in another way suppose the frequency of the incident light is omega then two photons of frequency omega join up to produce another photon of 2 omega this 2 omega is a second harmonic of omega it is as simple as that. So what we do here is that you make incident this red light which is from a laser in our case it is a femtosecond pulsed titanium sapphire laser later on we will have occasion to talk a little more about what is there in the laser and how femtosecond pulses are produced for now let us just accept that this red light is the output of a femtosecond pulsed second harmonic sorry femtosecond pulse titanium sapphire laser and wavelength of this laser that the one that we have can be tuned from say 700 nanometer to 1000 nanometer or so let us say that this red light that we are showing you here is has a wavelength of 800 nanometer of course if I say wavelength of 800 nanometer it is not very difficult for you to work out what the frequency is because frequency and wavelength are related by lambda nu equal to c. Now what happens in the second harmonic generation crystal is that as I said two photons join up to give you one photon so suppose I am using 800 nanometer light what will be the wavelength of the some frequency photon this one is very easy it is going to be half right 800 by 2 400 but while doing this thing please remember one thing that you have to add frequencies not wavelength wavelength is actually in reciprocal scale. So the right way of doing it is to convert whatever you have to frequency at the frequencies and then go ahead you will see when we talk about some frequency generation later on rather than second harmonic generation that will become a little important second harmonic generation is easy because the wavelength of the output is just the half of the wavelength of input light. Now here let me tell you something it is a little easier to produce second harmonic of femtosecond pulse laser short pulse lasers why because when you do second harmonic generation what are you doing the first photon takes the material from its ground state to what is called a virtual state a virtual state is a non stationary state associated with the lifetime of 0 and it is usually described as a linear combination of these stationary states of the system. So requirement for second harmonic generation is that you take the system from the ground state to the first stationary state then there must be another photon of the same energy which will take it to another virtual state okay. So first frequency takes it to an energy of say nu well I am stating energy in terms of frequency here omega second one second photon also of omega frequency takes it to a virtual state whose energy gap between whose energy gap with the ground state is equivalent to a frequency of 2 omega and now there is no memory the system does not remember that it had gone up in two steps and it cannot stay in virtual state for any finite amount of time. So it has to emit a photon and comes down and since the energy gap between that virtual state and the ground state is equivalent to frequency of 2 omega it actually emits a photon of 2 omega and that is what you see as the sum frequency or in this case second harmonic it may be a little difficult to follow it in this way when I speak but then later on when we talk about non-linear optics will actually draw diagrams and then I hope it will become a little easier for now all we need to understand is that this red light falls on the second harmonic generation crystal SHG crystal and blue light is produced and what you have seen is the path of the blue light I will go back a little and I show you the path of the blue light but before that let me tell you you could see what happened right blue light gets produced here at the second harmonic generation crystal it hits what we have here is a dichroic beam splitter dichroic beam splitter means it reflects one color and transmits another color in this case you use a dichroic beam splitter which reflects blue light but transmits red light it could be the other way round as well you have dichroic beam splitter of both the variety then having been reflected from this dichroic beam splitter the blue light comes to another dichroic beam splitter this one dumps the residual red light residual red light goes through and blue light gets reflected in this way where it gets focused on the sample which is kept here by a mirror by a lens alright that is the path of blue light I will just show you the animation once more blue light is produced at second harmonic generation crystal it is the first beam splitter second one and now is focused on to the sample using a lens in our case we use a lens but there is a better option as we will come to later on now then the sample fluoresces and this is why you need blue light as we have discussed in one of the first modules fluorescence spectrum always comes at a lower energy compared to the excitation light unless you have an up conversion material right but normally when you talk about normal fluorescence emission always has emission is always at a lower energy because you cannot have more energy than what you put in unless something like this is going on that is why you need blue light because suppose you excite using 800 nanometer light where is it going to emit the only hope is NIR in fact materials emitting NIR are very useful but most of the things do not most of the things actually emit invisible range sometimes in UV range for that you need higher energy light and that is what is produced by the second harmonic generation crystal. So red light second harmonic generation crystal is sized to blue light that is deflected through a lens onto the sample and then from the sample you get a fluorescence that is shown by this line. Now fluorescence occurs in all directions the fluorescent light is sort of like the light that comes out of the regular lamps that we have it is in all directions and what we do here is that we collect the fluorescence by using this lens so you can understand this is the sample this is the lens. So the only fluorescence it can collect is something that comes from this point on the sample on which the excitation light has been focused and is within this solid angle that can be captured by the lens. So here something that becomes very important is numerical aperture ratio between the focal length of the lens and the diameter of the lens. If your focal lens is large in this case is it good or is it bad do I want to use a large focal length lens or a small focal length lens definitely small focal length lens in fact there are instruments in which they use a microscope objective you want the lens to be as close to the sample as possible because the further away you go more is the loss of light if you are here then you are catching say this solid angle if this is suppose this is your lens cross section of your lens you keep it here this is the solid angle that you catch you go here this line goes in this direction this way goes in this direction so you end up catching a much smaller solid angle right that means light collection is less efficient and fluorescence in any case the number of photons emitted is not all that great especially when you are talking about femtosecond time scale your lifetime is small and what we learned in the previous module is that lifetime is proportional to the fluorescence intensity pi f is equal to k r into tau f. So small lifetime would usually imply a small quantum yield as well now out of that if you are going to reject most of it then what will you see so that is why you want to capture as much of the solid angle as possible if you can capture 180 360 is never possible if you could capture 180 degrees it would be great but 180 is not possible so you want a lens with high numerical aperture so that you can go as close as possible and capture as much of the fluorescence light as possible are you clear about that and the other thing that is also implicit here is that the sample is kept at the focus of the collecting lens that is the configuration for best collection so you told me you do not want a long focal length lens and we discussed why do you want a small wider lens or do you want a narrower lens I mean diameter of the actual optic should it be small should it be large it should actually be as large as possible but there is a practical problem to that because your focal length is small if you want a very large lens then it is going to be a very huge curved surface like that cannot be very large actually right so there is a limitation that is why numerical aperture is the quantity that determines what kind of lens you are going to use alright so let us see what is happening here we have some labels here omega 2 is the frequency of fluorescence as we are denoting here what is omega 1 will come to that shortly so this fluorescent light is captured by the lens with small focal length then here we have a filter what is the purpose of this filter you see you are doing a collinear collection you are collecting in the same direction as the direction of propagation of the incident light so of course there will be not only this fluorescence light a lot of excitation light will also be there in the same path but then you do not want it right because if excitation light gets into the detection channel then your instrument is going to get messed up so you want to cut out an excitation light cut out the excitation light and you want only the fluorescence light to reach wherever it is going to reach later so now tell me how do I cut out the excitation light and allow only fluorescence to go through what should I use I we should use a filter that is right what kind of a filter a filter that cuts out high frequency high energy short wavelength light and transmits low frequency low energy long wavelength light what is that kind of a filter called it is called a long pass filter that is right so in equipment like this you have to actually use many different kinds of filters here you use a long pass filter and the purpose of that filter is to cut the excitation light while allowing the fluorescence to go through here you if you look carefully you will see there is another something here also you have some filters these are a different kind of filter they are called neutral density filter what is the meaning of a neutral density filter something that ideally cuts down a lot of the light going through irrespective of wavelength so if you plot absorbance or rather percentage transmittance against wavelength then you expect to see a flat line in case of neutral density filters a flat line that is at 50% 20% 10% 1% depending on your need why do you have neutral density filters here because we do not want too much of light to fall on the sample they are using a 100 femtosecond pulse so that is putting a lot of energy in to the sample in a very very small time so sample is going to burn that is why you always want to work at minimum excitation energy possible if you put in more excitation energy perhaps you will get stronger fluorescence but that comes at a cost and the cost is your sample might get damaged and if you are not careful you might not even understand that your sample is getting damaged so the problem with that is that once we are done with this discussion we can come back to it the problem with that is actually get incorrect result the lifetime you record can actually be different from what it what it is that problem is not there in TCSPC in TCSPC first of all not much of damage is there if you use diode less as an all secondly it does not matter if the sample degrades even during the experiment unless another fluorescence species is produced lifetime will remain unaffected not so in up conversion not so in optical gating in this case if the sample degrades even if it becomes something that is not fluorescent then your measurement can be affected and we will discuss why once we are done with the remaining part of the experiment of the discussion all right so what do we have we have this fluorescence going through the long pass filter then that cuts out all the blue light only fluorescence light goes through here you have a lens perhaps you will understand better when we show it to you in three dimensions next day here you have a lens and this lens focuses the fluorescence light on to another nonlinear crystal but here you see this one was SHG crystal the first one the second one is called SFG crystal because here it means some frequency generation crystal not second harmonic generation crystal why do we need on nonlinear crystal what is it doing there what is the function how does it help we will come to that shortly but for now we need to remember that this is a some frequency generation crystal now you see here when I say long pass filter you might actually have to use a different filter for a different sample that is why in this kind of an instrument you always need a set of filters what you see here you can see some color there they are all colored glass a set of filter mostly long pass which allow only the fluorescence light to go through but actually not all are long pass some short pass filters also there we will come to that all right so are we all okay with this path fundamental red light getting frequency double producing blue light which is directed on to the sample focused on to the sample then fluorescence light goes through a long pass filter whereby the excitation light is eliminated and then the fluorescence is focused by a lens on to a some frequency generation crystal are you okay with this arm but this is only one arm of the instrument only half of the story the remaining half of the story and that is where omega one comes in is in this side remember what is this optic here is it a plain is a simple mirror it is actually a dichroic right and dichroic reflects blue light and transmits red light what you see now is the path of the red light which is omega one I will show you the animation once again but then I am afraid I cannot speak fast enough to keep up with the animation after all we are trying to animate light which is the fastest thing in the in well in the universe so let us see so red light goes through the dichroic it is a mirror another mirror goes to and if retro reflector comes back see I could not keep up with it so now let me try to do it in a static mode so this is where your red light goes through where is it produced in the laser outside the spectrometer it is there if you see carefully you can see two beams one blue and one red the red light goes to the dichroic it is this mirror then this mirror comes back and here you have a retro reflector retro reflector means it can even be a pair of mirrors something that turns light back okay light does an about turn at the retro reflector what we have in our lab and in these instruments which are marketed by CDP corporation what they always have is they have a three sides of a cube front coated with gold there are some advantage with having three sides of a cube the advantage is that the light that comes out from the retro reflector is exactly parallel to the light that goes in that helps it alignment so if light goes in like this it will come out like this if it goes in like this it will come out like this so having a retro reflector which is three sides of a cube helps us in the alignment a little bit but after that again you have another mirror which takes the light to this mirror which focuses it through the same lens on to this some frequency generation crystal and we are saying that this red light has a frequency of omega 1 okay and this light also goes by the name of gate light remember one of the names is femtosecond optical gating this omega 1 serves as the gate before going any further let us make sure that we have not forgotten what kind of a light is that red light is it continuous light or is it pulse light it is pulse light right where remember it is the output of femtosecond pulse titanium sapphire laser it is pulse light full width of maximum of the pulse would be something like 100 femtosecond in our case it can be even smaller okay pulse light omega 1 is pulsed so what does it look like if the x axis time it looks something like this what about omega 2 if I look at it in time domain what is the time evolution of omega 2 is from fluorescence right so it is a decay okay this is a point that we are going to come back to shortly right but before that let us think in a little simple manner not worrying about time at the moment now you see what we have done we have focused light of two different frequencies omega 1 and omega 2 onto the some frequency generation crystal what should happen it is a non-linear crystal it is called a some frequency generation crystal so it would better give rise to some frequency what is the meaning of some frequency omega 1 plus omega 2 right so the some frequency is generated here and actually it is this some frequency that is detected how do we ensure that after here what we have not shown is we have a monochromator like the ones that we have discussed earlier while talking about steady state measurement but generally here you use a double monochromator there are two great things because you need very high precision in this case and then you have a regular photomultiplier tube or some other photodiode detector like what you have in your say fluorescence spectrometer okay so you are going to see omega 1 plus omega 2 and if you just measure the photo current out of the photomultiplier tube then you can get an idea about the intensity of the some frequency omega 1 plus omega 2 are we clear but what does all this have to do with femtosecond time resolution femtosecond optical gating we have understood the optical gating part perhaps because we said that this omega 1 light is called optical gate but why is it called a gate and we have understood femtosecond upconversion because here we are doing upconversion so this crystal is also called the upconversion crystal okay but how does that give us femtosecond time resolution that is what we are going to discuss in the next module before that let us do simple arithmetic I have 800 nanometer light right that is omega 1 okay and 600 nanometer light here of course fluorescence is broadband let us say we are focusing on the 600 nanometer fluorescence light okay so what wavelength is obtained upon mixing 600 nanometer and 800 nanometer light so what I have written is 800 nanometer and 600 nanometer light can we work it out of course maybe I can do a little bit of mental arithmetic it is upconversion right so you have to add 600 plus 800 1400 nanometer is the wavelength of the are we going to get 1400 nanometer when we combine 600 and 800 nanometer light in some frequency generation crystal why not because see 1400 nanometer is actually lesser energy than both 600 and 800 right and let us not forget that when you so go back to the fusion of drops analogy when 2 drops fuse 2 drops of water their masses add up when 2 drops of light when 2 photons fuse their energies should add up right E equal to h nu or E equal to hc by lambda so what you need to do is E 1 plus E 2 you cannot do lambda 1 plus lambda 2 right so E 1 plus E 2 would be hc 1 by lambda 1 plus 1 by lambda 2 so lambdas are you cannot add lambdas just like that you have to add frequencies so who can tell me what is the wavelength will obtain when we mix 800 nanometer with 600 nanometer yet work it out I do not think you are so good at mental arithmetic that you will be able to do it just like that I am not what you actually have to use is 1 by lambda equal to 1 by lambda 1 plus 1 by lambda so if you do not believe in taking LCM and all it is 600 plus 800 divided by 600 to 800 but reciprocal of that it turns out to be 344 nanometer now tell me this 344 nanometer light is it UV is it visible is it ultraviolet is infrared what is it UV right so now suppose your 800 nanometer is a nominal value for omega 1 if omega 2 is less than 600 nanometer it will be even more higher energy some frequency will have even higher energy more into UV what is the best case scenario if this is 800 the second one can be at most 800 actually cannot it has to be longer than 800 nanometer right so if it is 800 nanometer no what am I saying it can be anything actually because you are exciting by 400 nanometer sorry my mistake but suppose it is 800 nanometer then it will be 400 so typically well the point I am trying to drive at is that now when you choose at the monochromator and you choose the detector you want a monochromator and a detector that work well in the ultraviolet range we have not had the scope of discussing the blazing of monochromators unless you are using monochromators that use your holographic grating they are usually blazed at some wavelength or the other that means they are optimized the performance is based at that wavelength if you have grating that is blazed at 600 nanometer that means you will get maximum light coupling at 600 nanometer if you have something that is blazed at 300 nanometer that is what it means okay so typically and same is true for detectors and you do not have one ring to rule them all usually so you have a detector that works well in a particular range so when you do the up conversion measurement you might think that you need a rate sensitive detector you do not because you are looking at some frequency higher energy you will always need a higher energy you will need a detector that works well in UV region so that is another point to remember that you are actually detecting UV so the instrument would better be such that it can detect UV nicely okay but we are still not answered the question where is femtosecond in all this where is the question of grating that is what we want to do in the next module when instead of using the photograph we are going to use this schematic and we will show you where femtosecond time resolution comes from.