I'm going to take the queen and then two slides later, I'll give you the answer. Don't go to the answer before they finish the quiz. And it's this one right here at the top. Great. You can't read up something. No, I haven't. It's the one you just posted. Actually here, I'll give you your drive back. I have visited parents. No, I've gone up to Vancouver tonight. I just came back from chatting with Jim Simons in York, which after 10 minutes I had to leave because he started smoking. There's a lot of smoke coming into my face. Every time he says I'm sorry. Is he reasonably alert these days? You know, he was there for my talk and I chatted with him, and he missed most of the other meeting. You got quite tired and so on. But he's... No, I have to get in a plane. Yeah, sorry. Okay, let's get started here. So, last lecture on learning and memory. For me, before we move on to sort of the last component of the course, there's going to be a bit on emotion, autism, and other diseases of the brain and the mind to finish the course on. So, remember from the last lecture I gave, and also from Henry Lester's lecture, you know that memory consists of multiple stages, both psychologically and neurobiologically. So, there are events at the molecular level that require calcium influx through NMDA receptors and phosphorylation of various proteins that can happen pretty quickly. And then there are events that require gene expression through crept binding proteins and other mechanisms that can result in ultra-structural changes. So, there are multiple stages in time. And remember that psychologically there were multiple stages, short-term memory, long-term memory, iconic memory. And as well, there are multiple types of memory. And so far, we only looked at declarative memory. So, today we'll look at a couple of the different types of non-declared of memory, of which you'll remember there are several. So, remember this picture here just to remind you and see if people have any questions. That was sort of the broadest scheme for getting a memory in and coding. And then there was a set of long drawn-out processes that could go on for years that consolidated the memory. And then there were two types of retrieval, one of which is shown here, the two types of retrieval being recall and recognition. And one thing that I mentioned but didn't go much into that's quite important these days is this reconciliation. So, remember that when you remember a memory, it becomes a stimulus again in its own right. And you can re-encode and re-consolidate that memory. And so, every time you remember something, it becomes plastic and flexible to some extent, and it's re-consolidated. So, if you keep remembering something and talking about it, you can change the memory over time. You can have false memories over time. And this is one mechanism that people have looked at a lot for traumatic memories, phobias, post-traumatic stress disorder and so forth. That one mechanism for trying to help people with those kinds of traumatic memories is to have them recall the memory such that it becomes sort of plastic again and can be re-consolidated with a different memory trace. You have them re-consolidate, you have them recall very traumatic memories, and while they're doing that you can give them drugs or you can do behavioral interventions such that the new consolidation that is laid down can overwrite the previous one and can to some extent cure their traumatic memory.  So, again, to get a memory plastic and have a change, you need to retrieve it and then this re-consolidation mechanism can make it to some extent flexible. This scheme we had remember short-term memory which depends mostly on regions in the frontal lobe. There are neurons there that are highly correlated with holding something in working memory in humans and in monkeys. Limited capacity about seven items decays quickly after about a minute or less. And if you keep stuff in here, you keep rehearsing it, there is a bottleneck for transferring information from stuff you're currently thinking about, working memory, into long-term memory which is what you want to do when you memorize material for a course.  You have to offload it and stabilize it in long-term memory. If you're successful at doing that, so it takes a while, so doing this requires the hippocampus and it's effortful and it's subject to interference, it takes time, etc. But when you do it, in principle long-term memory has no known upper bound in humans and also no bound in terms of time. So you can remember things, an arbitrary number of things for an arbitrary amount of time in principle. And some people are very good at this, so some people seem to be able to remember every day of their lives and it's a big puzzle why not everybody is like that. Make it much easier for this course if you just remembered everything. There are also some people, just to mention it quickly, that either because they're born that way or because of a lot of practice, probably both, that typically are sort of performance artists in Vegas or something that seem to be able to merge working memory and long-term memory and they've done brain imaging studies on these people so they effectively are able to use their long-term memory as though it were working memory. And of course, if you do that, you have an unlimited storage capacity and you can just read, you know, 100 digits of pi or something and it's in there. So there are people that can do that and they seem to be able to not have the same bottleneck for transferring between these two types that you and I have. So there's all kinds of unusual features, but this is how it normally works and there are exceptional memory cases that still need to be explained. This is what we had last time. So remember that there was a graded retrograde amnesia, a complete anterograde amnesia if you have damage to the hippocampus like this patient HM had. One thing that's important to point out is that episodic memory, so remembering a particular autobiographical episode, like exactly what you had for breakfast this morning, where and with whom you went out to dinner last night so that your ability to consciously re-experience something in space and time and as happening to you, that depends on the hippocampus. But over time seems to be converted to another form of declarative memory called semantic memory, which is just memory for facts. So most of your memory eventually gets converted into facts. So I could ask you, what's the capital of France? You would say Paris, and that would just be semantic memory. But if I asked you, well, where did you learn that? What specific episode? Or who's the president of the US? Or even material for this course. After a while, you would know it as facts, even though initially it was encoded as an episodic memory. But so these traces seem to be recoded as semantic memory over time. We just put various types of declarative memory that people have studied up here. So semantic memory depends on your cortex, especially in the temporal lobe, and there are neurodegenerative diseases, for instance, that affects temporal cortex, which will result in semantic dementia and a loss of semantic memory. But this is memory for facts. Episodic memory is memory for specific autobiographical episodes, and that depends on the hippocampus as well as other regions. Your autobiographical memory is a mix. So a lot of it is episodic, but some of it, like just knowing your name or knowing when you're born, that's semantic. So it's a mix.  And we just put that up here so they've studied this. More recent studies have looked at 9-11, any sort of public, highly emotional event. And psychologists have then been fond of doing studies on that whenever something like that happens, or the latest incidents in Paris. I'm sure there's psychologists now studying how that's encoded in people's memories. And what you find when you ask people is that they're typically able to recollect a lot of autobiographical detail, much more so than, you know, if you ask them for non-emotional events. And so they've studied this both for real-life events and also in the lab. The basic idea is that emotion serves as a sort of, like a spotlight, as a sort of filter on your encoding and in particular consolidation of declarative memory. So if you look, it's a little hard to see here, if you look at some picture that's emotional or arousing in the middle here because I guess there's a surgery going on. What you will remember is the deep, if I asked you afterwards for your visual memory for this picture, you would remember a lot about the emotional stuff having to do with the surgery in the middle and probably less about people in the background, etc. People have studied this a lot in terms of eye-witness testimony at crime scenes. They'll remember details about the blood or the knife, but they won't remember who the bystanders were and things like that. And the same thing happens in time. If you have, for instance, a stream of words in an experiment, one of which is more emotional than the others, you will remember this word, but your memory for words in the vicinity of that is actually decreased. So it's like a center-surround mechanism, actually, in both space and time that serves to sharpen your memory for that material that's the most salient, in this case, most emotional. And as I said, people have studied this in quite some detail. This is how traumatic memories also arise. And it mostly operates in real life at the level of consolidation. So if people experience a very traumatic event, or if you have rats in a very traumatic event, you can, after the event, you can give them, for instance, protein synthesis inhibitors or drugs that would interfere with memory consolidation and they would not lay down an emotional memory for that event. Okay, so just to summarize, so we talked about declarative memory last time just to make the point that it's extremely complicated and it has lots of different ways in which it is modulated. So this was one example. It can be sharpened by emotional arousal, which is one mechanism that people have looked at a lot. We're going to move over now to considering some aspects of non-declared of memory. Remember, this is a heterogeneous category unlike declarative memory. So for declarative memory, you can say it's memory for facts and events. It's relational memory, spatial memory. It depends critically on the hippocampus at encoding and consolidation. So we know a lot in a fairly homogeneous system.  Before we do that, we're going to have a short quiz that Henry just gave me.  Alright, so we had types of memory. Now we're going to go on to talking about some types of non-declared of memory. So there are two broad types which are associative and non-associative. And here's the definition of these. So non-associative learning, you've probably heard about both of these before, is learning with respect to a single stimulus. You're not associating two stimuli. There's just one stimulus that's happening, but of course you have plasticity, and so learning in a very simple sense there. Does anybody know what kind of phenomenon you have that would count as learning in this very simple sense for just repetitions of a single stimulus? Any guess? Well, either increments or decrements in response. So some change. And decrements are habituation, and increments would be sensitization. So those two, those have been studied a lot. Associative learning is learning about relationships between two stimuli, that's Pavlovian conditioning. We'll take a look at that in a minute. Or between a behavior and an outcome or a stimulus and an outcome, which is instrumental learning. So those are the two big kinds, which just lists them here. So this just says what I said. Your book goes through non-associative learning in the sea slug, where Eric Candel, who's one of the co-authors of your book, and his colleagues did a lot of work and won the Nobel Prize for a lot of the work that they did. You can find these animals here if you go out to the tide pools in the ocean. So they're just little mollusks. They'll put out jets of ink. And I guess you could, while you pretty can't do this, take them apart a little bit to actually touch them. Well, you can probably touch them and you could see what happens. But you could do the same thing to a slug or a snail. Maybe you've done this when you were a little kid. If you touch part of the animal, it will withdraw parts of its body. If you do that again, it'll withdraw and it'll take even longer to come out. If you then wait a long time, you can start over again. So there are changes over time in the synaptic efficacy with which a sensory stimulus causes a motor response. And this has been worked out in some detail. Here's the little circuitry. And in particular, if you record from the sensory neuron, from the motor neuron, and look at what might happen in between those two, where you find the change is in the synaptic efficacy of the sensory motor onto the motor neuron. So the sensory neuron responds the same all the time. That's what's shown in this trace. If you keep touching the siphon on this aplasia, it will become habituated because there is less transmitter release. So you can ask very mechanistic questions about exactly where, at which synapse these plastic changes that define the change between stimulus and response actually occur in these simple nervous systems. So your book goes over that in detail and it has, of course, been mapped out. And one nice feature of this is that it also has this hold of molecular machinery here. This is for sensitization in aplasia. It has been worked out in a great detail and distinguishes the molecular mechanism for short-term memory, which depends on just phosphorylation of receptors and ion channels, like the serotonin receptor here. So that's not that permanent, but it can take place quite quickly. And long-term changes, which depend on changes in gene expression. So cyclic AMP has to bind to the cyclic AMP response element binding protein and bind to DNA. There's differential gene transcription. New protein synthesis is required for this. And new proteins can be made. New receptors can be inserted. There can be ultra-structural changes and so on. And you can manipulate these as you would expect. So in general, if you block short-term memory, you also block the induction of long-term memory. But you can have short-term memory going on. But if you have, for instance, a protein synthesis inhibitor, you will block the induction of long-term memory. And there are many different versions of this that initially behavioral psychologists have studied. And now we know a lot about the neural underpinnings of many of these. So there are associations between stimuli responses and outcomes, which is what these letters stand for. In terms of just basic things to know, these here, so an unconditioned stimulus, is a stimulus, the response to which you don't need to learn. So it's innate. And so if you see something dangerous, if you see a snake or something like that, or if you get electric shock, you don't need to learn to fear that. You would respond to that in an unconditioned way. So you have unconditioned responses to unconditioned stimuli. For which learning is not essential. And then conditioned stimuli are the opposite. For those, you have to learn the conditioned response. And so in typical, for instance, Pavlovian conditioning setups, you pair stimuli with unconditioned stimuli, with unconditioned stimuli, and you can learn about the value, good or bad, of a conditioned stimulus. I'll show you an example in a minute. Well, here's the first one. Ivan Pavlov, who won the Nobel Prize in 1904 for his work on what's now known as Pavlovian conditioning in order, in honor of him. This is a form, in his experiment, it was a form of appetitive conditioning, but you could also do this for aversive stimuli. So in his case, he measured a response in the dog, which was the secretion of saliva and gastric juice, in response to food. So that happens normally without any learning. So if you give the dog food, it will salivate and there will be gastric secretions in the stomach as an unconditioned response. So the food is an unconditioned stimulus. But in addition, you have a bell or some other stimulus that you pair with the presentation of food, as all pet owners know. Your pet will very quickly learn that this stimulus, the sound of the can being opened or any kind of stimulus that is regularly paired with the presentation of food, is predictive of the food and you will get salivation and gastric juice secretion to the tongue after learning. So initially the tongue does nothing. It's meaningless, but it acquires meaning through its regular relationship with the presentation of the food and that's what he measured here. So here's how that would go. These are slides from my colleague, John O'Doherty, who is part of this work or more complicated versions of this in humans with fMRI. But this is the basic idea. You have an unconditioned response to the unconditioned stimulus and if you regularly pair a number of times a conditioned stimulus with this, what will happen is that you get a conditioned response that anticipates the food. So in a sense, you can think of the conditioned response in this simple example being like the unconditioned response only moved forward in time. In fact, it's typically more complicated than that and conditioned responses do not need to mimic unconditioned responses. It's typically more complicated. But anyway, they're predictive responses to a stimulus that predicts a later unconditioned stimulus. Any questions about this? It's clear to people. The basic setup. There are various versions of this that you don't need to know. So we'll skip that one. One structure that's been studied in great detail for Pavlovian conditioning mostly for aversive Pavlovian conditioning so-called Pavlovian fear conditioning. So it's the same thing as what I showed you except that instead of food you have electric shock or some bad unconditioned stimulus but otherwise it's the same setup. Is the amygdala. And the amygdala in the human brain is shown here. This is a postmortem human brain. So it's like the brain that you had in the first discussion section that's been sectioned and stained from myelin. So myelin is black and you see the thalamus here. Here is part of the ventricle and down here where my cursor is circling right now is the medial temporal lobe and this structure here is the amygdala.  So it's a collection of nuclei. Here's how it looks in the structural MRI scan that's involved in a lot of different things but in particular a lot of different learning mechanisms and it interacts with many other brain structures to implement those. So for instance remember I talked briefly just a few minutes ago ago about highly emotional events like the explosion of the space shuttle or 9-11 etc. that you remember extremely well these so-called flash bulb memories the amygdala seems to be responsible for that. So it modulates how the hippocampus functions. It has projections to the hippocampus so that when there is some strongly emotional event hippocampal dependent declarative memory is sort of boosted up and you consolidate that stimulus with more detail. It's also interacts with the prefrontal cortex and the basal ganglia in various forms of instrumental learning and within the amygdala it's involved in Pavlovian fear conditioning and that's been worked out by quite a few people in particular Joe Ladoo and this is how it would work. So again you have a conditioned stimulus like a tone and instead of getting food as in Pavlov's case people typically because it's more efficacious use an aversive unconditioned stimulus so electric shock. So the rat will avoid and startle and have lots of stress responses to just the shock.  So it will freeze, its blood pressure will go up etc because it's expecting to get the shock. But so that's the acid test of a Pavlovian fear conditioning paradigm. You give the shock and the tone and the rat freezes and is unhappy. You give the shock and the tone and the rat does it again. You do that a bunch of times and then you only give the tone and the rat will freeze and show fear responses and compare to this learning the tone did nothing. That difference is the difference in learning that's Pavlovian fear conditioning. The difference in response that you see to a condition stimulus before versus after conditioning. The magnitude of that is the magnitude of your learning. And how does that work? Well you have to get the tone so sensory information from the tone through auditory thalamus, auditory cortex that has to get in to the amygdala and information from the shock has to get in through the somatosensory system so you remember which two from lectures you had in the past and then these have to converge on neurons that conform associations between the two and what kind, you might wonder what kind of molecular mechanism could implement this sort of convergence. Well it's exactly like what you heard about before. It's NMDA receptor dependent long-term potentiation in these neurons here in the lateral amygdala such that when they get coincident inputs about the tone from auditory channels and about the shock from somatosensory channels they encode that coincidence and subsequently either one of those alone if you just get the tone coming in is now sufficient to reactivate this memory trace and then the amygdala projects out to a whole bunch of other places that can affect the behavior like freezing blood pressure changes and so on. So that's the basic circuitry for Pavlovian fear conditioning. You can do, as in the case of declarative memory you can add on to this various embellishment and ways of modulating this simple circuit so that it can interact with other forms of memory. So for instance, if you now put the rat into a particular location in its cage and you only do this you only give it a shock when it's in that location well that's a form that requires a form of spatial relational memory which you'll remember depends on the hippocampus. So you can have contextual fear conditioning that the rat becomes afraid of being in a particular place because it always got shocked in that place that depends on the amygdala like Pavlovian fear conditioning but also on the hippocampus because it requires this relational spatial component so contextual fear conditioning if it requires linking a place to an unconditioned stimulus requires both the amygdala and the hippocampus. Okay so these are just some facts to know so Pavlovian fear conditioning in humans and in other animals is dissociable from declarative memory. The amygdala basically is essential for fear conditioning, the hippocampus for declarative. And there's people have done these studies, here's one done by my former colleague Antoine Basharra who's, when he was at the University of Iowa, now at USC in a human patient so here's the experiment, you do a Pavlovian fear conditioning paradigm and you measure two types of dependent measures in this, in people one is just just like what you would measure in the rat this is a measure of the emotional response to the conditioned stimulus skin conductance response that's shown over the left and the other one is a measure of declarative recall that is you ask the person which conditioned stimulus was matched with the aversive stimulus and when you do that you find in controls that there is learning both about Pavlovian fear conditioning so these bars over here are higher and in terms of declarative memory for which stimuli were paired you can dissociate these you can have a patient who has lesions of the amygdala that's shown in this panel here this patient has intact declarative memory for which conditioned stimuli were paired with shock, or in this case it was an aversive tone loud noise but fails to have Pavlovian fear conditioning so this shows you that the amygdala is necessary for Pavlovian fear conditioning but not for declarative memory conversely you can have another patient who has damaged the hippocampus in the bottom panel and he has intact Pavlovian fear conditioning and remember can't tell you anything about the stimuli so experiments like this so this would be considered a double dissociation with respect to the amygdala and the hippocampus show you what that previous slide just summarized the amygdala is necessary for Pavlovian fear conditioning the hippocampus for declarative memory let me show you an actual experiment for how this looks so this person here was a postdoc, former postdoc in Elizabeth Phelps Phelps's lab at NYU is undergoing the fear conditioning experiment so he has an electric shock bracelet on here and he's going to get shocked every once in a while and he's watching conditioned stimuli squares of different colors so he's been watching a yellow square nothing happened so he's not getting conditioned to that yellow square and they're measuring his skin conductance response and other responses and now he sees blue square and as you will see at the offset of this blue square he gets an unconditioned stimulus which was the shock and so this goes on for quite a while and so every time he sees the yellow square nothing happens when he sees the blue square he gets zapped and so he becomes Pavlovian conditioned he becomes fear conditioned to associating the blue square with the shock and so then you can measure that after he's gone through this a whole bunch of times the blue square was only got zapped but not with the yellow square you then unbeknownst to him have disconnected the shock things he's not going to get shocked at all and you only show the conditioned stimuli and measure his response to those so in the case of the yellow square you know there's nothing that's happening and so you will not measure any skin conductance response when he sees that but for the blue square his brain predicts that he would get the shock and so he will have a skin conductance response to the blue square because it was always paired with the shock and that passed and you can kind of you can't see unless I showed you a trace of the skin conductance response but you can tell something about his emotional state just from watching his face I guess he was expecting a shock if you measure this in his case he would have electrodes on the palms of his hands that measure skin conductance response as a measure sympathetic emotional arousal you find that the blue square is the conditioned stimulus that was paired with the shock the CS plus elicits a much larger skin conductance response when just shown by itself after training without the shock then does the yellow square the CS minus which is a conditioned stimulus that was not paired with the shock so that difference shows you that standard Pavlovian fear conditioning happened now what's interesting is I could take any of you having just watched this video and put skin conductance electrodes on you and show you those same stimuli the blue square the yellow square and I would find that you would show the same thing that you would also show a larger skin conductance response now to the blue square and to the yellow square even though you yourself never got any electric shock you just observed another person getting electric shock so this is called observational learning and most of what you learn about the world depends on that so it's not actual experience because for something like this like electric shock it would kill you but it depends on observing what happens to other people so a lot of learning is observational learning and there are aspects of this in other animals as well and then I can do something even more removed than that you don't even need to watch the person I can just tell you in the next experiment I can tell you when the blue square comes on you're going to get a shock and when the yellow square comes on you won't and if I do that just mere instruction again I see differences in skin conductance response so at least in humans you can induce Pavlovian fear conditioning through direct experience through observation and through instruction all of these depend well these two depend on the amygdala this last one may be more complicated but anyways this is one big point that most of what you learn is from observing what happens to other people rather than having to have direct experience yourself there also as you might imagine important constraints on what it is what kinds of associations it is that you can learn in the first place so there's certain stimuli that you can learn about and that you can learn associations for and that animals can learn associations for much more easily than others so it's not all the same it's not equally easy to associate electric shock with any kind of stimulus and depending on what the what the unconditioned stimulus is this can be quite quite narrow okay now let me skip this part here and go on okay so that's one form of non declarative memory Pavlovian conditioning which can be both appetitive like what Pavlov originally did if you have tasty dog food or it can be aversive as in Pavlovian fear conditioning either way you can have a unconditioned stimulus that is either strongly positive or negatively valenced and you can learn about that but you're not doing anything so you're not doing anything the animals not doing anything you're passive and you're simply your brain is just linking statistical associations between stimuli and effects that it sees out there in the world by contrast instrumental learning requires that you actually do stuff so your behavior determines the occurrence of an unconditioned stimulus this goes back to classic work by Thorndike who had these puzzle boxes for cats and so he made these boxes that if the cat pushed just the right kind of lever in here it would open this door and it could get out to what's pretty impossible for you to recognize here a vicious fish and so the cat wants to do this it wants to learn how to behave so that it gets this reward so there's an unconditioned stimulus out here the fish that's highly rewarding but there's not just Pavlovian learning the cat has to do something in order for that unconditioned repetitive stimulus to be obtained you can imagine the converse and the repetitive domain if you had a electric shock that was coming up so you have to push something to be able to escape from the electric shock in either case you have to do something and so animals will learn that that's what's shown here the time required to escape the box decreases over time because the cat learns just by random chance initially and it gets better and better at learning what to do in here in order to get the food reward okay let me just go on to this one here so there were a variety of different kinds of instrumental learning that people have studied some are like what you would see in the case of the cat where you just randomly you know keep learning and you get better over time gradually and so you essentially build up a habit to obtain a reward or escape a shock whatever the learning paradigm is and this is known to depend on parts of the basal ganglia nuclei within the brain that are involved for motor learning and this kind of habit learning there's a more complicated one for which you require the prefrontal cortex that's called gold directed instrumental learning and there you have more of a model of the world and it's more flexible and you can figure out how to get the food not only by sort of trial and error learning but in a more goal directed way this one is more flexible typically in many cases you do this this one first so learning instrumental learning can often be very effortful you have to know which you have to figure out what sequence of actions to do in order to get some effect after you do it a whole bunch of times it becomes habitized so it's a little bit like in the case of declarative memory where we saw that initially it's dependent on working memory and it's dependent on loops between working memory and the hippocampus but that over time it would get offloaded consolidated into long-term memory same thing here so you can have some instrumental learning that requires you to do a bunch of actions that might be quite complicated to achieve a goal if you do it a whole bunch of times it can develop into a habit and then you don't need to do that anymore but it becomes less flexible as a consequence so for instance if I had to learn how to drive to for my home to get here right and I've done it a whole bunch of times initially it was quite effortful I had a little map in my head of which streets to turn on and so on so it was goal directed instrumental learning after doing that a year I just drove an autopilot but now if I want to instead go to the gym or I want to go somewhere else I start driving and suddenly I'm at lab because this habit kicked in and I just sort of drive an autopilot so habits are less flexible once they're set up and I think this just says everything that I said here okay so Pavlovian fear conditioning again depends on the amygdala contextual fear condition remember depends on amygdala plus hippocampus this one I didn't mention so you don't need to know about it declarative memory depends on the hippocampus and relational and spatial memory remember depends on the hippocampus the storage and recall of declarative memory depends on many other brain regions and interactions between hippocampus and cortex so the main role of the hippocampus is in consolidation of declarative memory and you remember that from the lesions in this patient's HM's brain he didn't lose all of his declarative memory he still had to declare that this was the patient that had bilateral hippocampal lesions he still had memory for very remote events in his past but he had this graded great amnesia so that as long as there was consolidation still going on he needed the hippocampus and then we had these ones just down here that if you have habit based forms of instrumental learning that requires the basal ganglia whereas if it's goal directed it requires the frontal cortex so each of these can be a course and actually there is a course that talks about some of these CS102 CNS102A that isn't offered this year but will be offered next year but the point is that just like when we had the initial taxonomy of memory you can dissociate different types of memory so what you need to know about is Pavlovian fear conditioning declarative memory and instrumental learning and these depend on specific brain structures the full brain circuits are very complicated but these are the sort of essential brain structures if you have damage to the frontal cortex you have problems with goal directed learning if you have damage to the hippocampus you can't consolidate declarative memory if you have lesions of the amygdala you can't learn Pavlovian fear conditioning and so you could imagine a final exam question that would ask you if you had some lesions in various places in the brain what could a patient no longer do and you should be able to predict that from what you've learned here any questions about type the distinctions between these different types of memory and their links to some of these brain structures here it's worth pointing out that some learning can happen very very fast so some learning takes a long time many many trials but there are specialized mechanisms set up and again this shows you that you can learn about some you learn about some things in a certain way it's not that you can learn to associate anything with anything some good examples are for instance taste aversion conditioning so if you get very nauseated after eating something you can develop an aversion to that particular taste and that just requires one trial there's also one that I'll show you a little video of here because it's kind of interesting it's been mapped out in quite some detail depends on the amygdala in rodents in hamsters other rodents have a tube and it's thought to be an animal model of depression of sorts in humans and this is a one trial form of social learning that these animals have conditioned social defeat so what happens I didn't make these little animations here but from somebody else who studies this what happens is that you take a male hamster and you plop them in to the cage of the home cage of another hamster I'll show you a video of this in a second these two animals will fight in a very stereotyped way it doesn't take very long and one of them will establish itself as dominant and the other as subordinate so one stronger and one weaker and once that is set up the hamster that lost will never fight another male and as soon as you present it with another male it won't defend its home cage anymore and it will always try to escape and it seems like a very long term maybe close to permanent a switch in its behavior basically learned that it can't it's too weak as it were anthropomorphizing somewhat and it instead just chose a very large stress response to any other male hamster instead of trying to defend itself sorry let me just show you what it looks like so here what we're going to do we've just plopped in one hamster into another hamster's home cage both males and as I said they will always will immediately fight very quickly they will establish they will figure out it's hard for us to tell but they can figure out which one is stronger and weaker and you can tell that when that happens because one of them, the weaker one will suddenly stop fighting and instead try to escape so it's like a switch and when that switch happens after that switch that hamster will never fight another hamster so here they are initially and they're fighting around just it'll just take a few four seconds so initially this hamster fights and defends its home turf and there suddenly it figured out it was too weak and now it runs away and it won't ever fight another hamster and you can test this now so a week or months later you can take that same hamster that was that experienced conditioned defeat and you can drop in another hamster to its cage so that's what's done here it doesn't fight at all so this hamster was just dropped in wondering why there's nobody here to fight with and the one here that experienced defeat before instead just had the super high stress response and you can measure all these changes in cortisol, stress hormones in this animal and it seems like a permanent switch in behavior so it's just one particular model system but it's very striking it shows you essentially what seems like permanent changes in a single learning episode in a very specific social context and again it depends it depends on the amygdala if you infuse drugs into the amygdala block and endiator receptors this doesn't happen so you can do a lot of manipulations last few slides to end on to encourage you to get more sleep I think I alluded to this very briefly a few lectures ago sleep is extremely important it's essential whenever anybody has tried to deprive an animal of sleep those animals have died so lack of sleep will kill you it does happen in humans with a rare disease fatal familial insomnia but not volitionally but anyway this is how much the National Sleep Foundation says you need to sleep and you probably get a lot less and you might think well what sleep good for can I get by with less seems to subserve many complex homeostatic functions but one thing that it seems to do is to re-normalize the strength of your synapses so during the day there's lots of LTP going on and lots of synapses are potentiated and learning is going on you need to somehow re-normalize that and bring that down and to some extent stabilize certain memories while forgetting others so there's complex mechanisms that have to do with re-normalizing strength of synapses that have been potentiated through experience during the day and stabilizing memories that require sleep so when people have studied this maybe this is fairly clear in humans it depends on certain tasks but you can have people do various tasks so here's one particular motor sequence learning task in humans if you have the same time elapsed between learning the task and then testing and you're awake this is the improvement that you would see here between these two green bars for instance whereas if you have the same time elapsed but after training on this task you take a nap and then you test the person so the time interval is identical except in one case you slept and the other not that sleep leads to a big improvement in performance and this is a very reliable effect that people have found on certain tasks that there seems to be a requirement for sleep such that if you have consolidation of memory during sleep it greatly improves your performance on this is a non declarative memory task just a motor sequence learning task people have done it with other more complicated things let me just show you the last one this is a task the tower of Hanoi here where you have to figure out how to move all of these discs onto another peg here many of you have maybe done this and you can never have a smaller disc underneath a larger one so you have to figure out how to do that so it takes a while when you actually do this and it turns out the same thing happens so when you do this during the day and you wait for some time to elapse and you ask how good are you you are not really much better after several hours but if you sleep on it you get better so this is a much more complicated task that presumably involves elements both of declarative and non declarative learning that essentially is something like insight so insight or the ability to construct more abstract memory representations that can allow you to solve complex problems in humans does seem to require sleep as well so I wanted to end on that note to encourage you all to get sleep because it will help you consolidate what you learned in this course ok


good morning, you welcome you all to this session last class we have discussed the first law of thermodynamics we started discussing the first law of thermodynamics and then we defined a property enthalpy h which is the combination of intermolecular energy a part of the internal energy or in a stationary or closed system that is the internal energy plus the product of pressure and volume and we also recognize that this internal this enthalpy as a property of the system bears its physical significance relating to energy transfer in an open system or a flow process. So, today therefore, we will apply this first law for a flow system or a flow process or an open system and we will see how does enthalpy bear a physical significance with the energy transfer across the boundary of such an open system. So, for that what we do we just consider a flow system like this let us let us consider a device a flow device this is known as a flow device flow device well which has an inflow where there is continuously an inflow of fluid and continuously an outflow of fluid inflow and outflow of fluid and this flow device is connected with a shaft so that a shaft work is coming out in the form of the rotation of the shaft let us consider an infinite small amount of work d w d cut w as I explained earlier is coming over a time d t so that we can represent the d w d t as the rate at which the work is coming out from this flow device in the form of shaft work and also let us consider similar way infinite small amount of heat d cut q is added continuously over an interval of time d t so that we can represent the d q d t as a continuous rate of heat flowing or heat transfer into this flow device. Now, this flow device where there is a continuous flow of fluid at one section and continuous flow of fluid out another section it is flow in and flow out and developing both work and heat that means transferring in terms of work and heat with the surrounding is termed as an open system or a control volume in fact we consider a close a boundary circumscribing this flow device this way if we consider a boundary this way this this system within this fixed boundary is known as an open system or a control volume or a control volume which is characterized by this fixed boundary as I have already told you that a an open system is a control volume system or simply a control volume where where the boundary where the system or the control volume is characterized by the fixed boundary and across which the mass transfer takes place there is continuous in flow of fluid and there is continuous out flow of fluid. Now, if we want to make the conservation of energy statement for this open system or control volume it is very simple that we can write it like this the rate of rate of energy in flow to the control volume I write simply c v minus the rate of energy well out flow from c v must be equal to the rate of change of rate of change of energy within the control volume or the open system in in consideration within the c v this is the very simple and the preliminary statement of conservation of energy that the rate of energy in flow to control volume minus the out flow rate of energy out flow from control volume is equal to the rate of change of energy within the control volume now you see therefore we have to find out what are the in flow energy in flow quantities into the control volume and what are the out flow quantities very first case we see that we have considered the work is coming out in the form of the shaft work from the control volume this is one way the energy is coming out in the form of work and similarly the energy in the form of it is going into the control volume because we have considered this heat energy to be going into the control volume for the general deduction apart from this the energy quantities coming into the control volume due to the in flow of fluid mass across this section similarly the energy which is going out of the control volume are associated with the efflux of fluid mass from the control volume across this boundary so therefore we have to now recognize to know the different energies which are coming into the control volume or coming out of the control volume what are the energy quantities that are associated with the flow of a fluid stream so we have to first recognize that so what are the different quantity different energies different forms of energies that are associated with the flow of a fluid stream with the flow of a fluid stream the energy quantities or the different energies those are associated are first is intermolecular energy that is the kinetic and potential energy of the molecule intermolecular energy existing all substances under all conditions if it is at a temperature above than the absolute zero so this is the intermolecular energy number two is the kinetic energy this is because of the flow velocity though a fluid flow or fluid stream flowing stream possesses kinetic energy another energy is a very well known energy is the potential energy this is by virtue of its placement or virtue of its position in a conservative force field if there is no such external conservative force field so gravitational force field is there so gravitational potential energy is there apart from that there is another energy which is there in a flow of stream of fluid is the pressure energy that you have read in your fundamental fluid mechanics class what is that pressure energy or it may be termed as flow work this is because of the existence of pressure at a particular section in the flowing fluid as you know that it is because of the pressure a section a fluid layer at a section is capable of pushing the neighbouring layer to make its flow through the passage so therefore to maintain the flow the layer at any section the fluid layer at any section has to continuously push the neighbouring layer and by virtue of its pressure it can do so and it makes its way through so therefore we see to maintain a flow each and every section the fluid at each and every section does work on the neighbouring layer and that work is known as flow work whose magnitude is pressure times the specific volume per unit mass well that is the work per unit mass and if we look from this angle that this capability of doing this work by a particular layer of fluid at any section on its neighbouring layer to make its way through the flow is known as the energy which is inherent in the fluid or stored in the fluid layer and it is stored in the fluid layer in the form of pressure energy we tell it in the as pressure energy sometimes we refer it to as pressure energy or sometimes we refer it to as flow work so therefore we see what are the energy quantities that are associated with a flow of fluid stream one is the internal energy by virtue of its state thermodynamic state another is the kinetic energy by virtue of the flow velocity another is the potential energy by virtue of its position in a conservative force field and last one is the pressure energy by virtue of the pressure in the flow field so if we recognize this energy quantities then we can now come we can now recognize the energies which are coming into a into the control volume and going out of the control volume so therefore if we again see this one let us consider the rate of inflow of mass as d m 1 d t and let the outflow of mass as d m 2 d t the rate of outflow this is the rate of inflow of mass this is the rate of outflow of mass now to identify those energy quantities we will have to fix the state of the fluid at inlet let the inlet pressure is given by p 1 the corresponding specific volume is given by v 1 let the inlet velocity is given by v 1 and let from any arbitrary reference datum the elevation the vertical height at the inlet section is given by z 1 the corresponding quantity at outlet is given by p 2 with a subscript 2 v 2 that is the specific volume v 2 is the pressure velocity v 2 and also the elevation from a reference datum the vertical height as z 2 therefore with this nomenclature we can now write the rate of energy coming in to the control volume associated with the inflow of fluid as d m 1 d t that is the rate times the specific that is the per unit mass internal energy plus the flow work we write first that the pressure energy plus the kinetic energy per unit mass plus the potential energy we consider only the gravitational potential energy is present that means no other external conservative force field is there so this is the rate of energy coming into the control volume through the inflow of fluid mass well plus as we have already considered in this figure for this control volume this heat is being added at a rate of d q d t so we write d q d t so therefore this is the inflow of energy to the control volume similarly what is the outflow of energy from the control volume minus that is the energy quantities which are going out with the fluid stream at the outlet that is the outflow of fluid that becomes u 2 that is the internal energy at the outlet p 2 v 2 pressure energy per unit mass at the outlet fluid stream plus v 2 square by 2 plus g j 2 plus the work quantity because we have considered the for the control volume the shaft work is coming out then is control volume or the flow device or the open system develops work in the form that work is coming out in the form of the shaft work coming out to the surrounding so therefore we can write it this is equal to d w d t and difference d t minus very good minus and this will be equal to the rate of change of energy within the control volume where e c v is the energy in the control volume internal energy in the control volume at any instant internal energy in the control volume in the control volume in the c v at any instant ok this internal energy at any instant comprises all the energies in the control volume that is the intermolecular energy the kinetic energy due to the motions of fluid particles within the control volume plus the potential energy so this is the statement of the conservation of energy. So, now under a special and this you can consider as the general steady flow in a general sorry not steady general flow general energy equations for a flow process. We can consider this as the general energy equation general we can write it general energy equation general energy equation for a flow process for a flow process for a flow process or open system for an open or for an open system. Now for a special case when the flow process is steady as a special case for steady flow process for a steady flow process. When the flow process is steady that means we know the definition of a steady process or a steady flow field that means each and every point in this system the properties are invariant with time that means as a whole the properties within this control volume or the open system would be invariant with time this will happen when the mass flow rate at inlet and mass flow rate at outlet will be same. So, there will not be any mass accumulation within the control volume and at the same time the energy in flow to the control volume must be equal to the energy out flow from the control volume. So, that there is no change of energy within the control volume with time. So, that the energy quantity remains same the mass remains same. So, all the thermodynamic properties at each and every point within the control volume will remain same. So, this situation refers to a steady flow process. So, therefore we can write in those process first of all from mass point of view d m 1 d t is equal to d m 2 d t is equal to 0 that means the control volume mass will not increase sorry sorry sorry sorry I am sorry is constant let d m d t I am sorry this is constant otherwise for an general case we can write similar to energy conservation d m 1 d 2 minus d m 2 d 2 very correct d m c v d t which means the general conservation of mass the rate of mass in flow to the control volume minus rate of mass out flow from the control volume is equal to the rate of change of mass in the control volume. So, m c v is the mass of the control volume at any instant. So, for a steady flow this becomes 0 this is equal to d m d t. Similarly this becomes 0. So, if we now this is the general equation for a steady flow process, but conventionally this is written in a form like this if we divide the terms each and every term by the d m 1 d t or d m 2 d t which is equal to each other and let it be d m d t and divide each and every term by d m d t then we get an equation if we divide the terms on the left in the left hand side all the terms by d m d t then we get an equation in this form u 1 plus p 1 v 1 plus v 1 square by 2 plus g z 1 plus d q d m well is equal to what we can write u 2 plus p 2 v 2 plus v 2 square by 2 plus g z 2 plus d w d m difference is that here we what is seen what is implied by this equation the rate of energy in flow is equal to the rate of energy out from the control point each and every term represents the energy per unit mass it is more conventional to represents the energy quantities per unit mass this is the heat flow into the control volume per unit mass this is the workflow out of the control volume per unit mass this is the flow out of the control volume per unit mass this is the heat flow into the control volume per unit mass this is the workflow out of the control volume per unit mass in this equation this where the energy quantities on time basis the rate of energy coming in rate of heat coming in so rate of energy quantity going out rate of heat going rate of work coming out or going out but in general the for a steady flow process it is conventional to express this quantities in terms of mass so therefore each and every quantities energy per unit mass so energy coming in per unit mass is equal to energy going out per unit mass in the control volume and it is out of the control volume so this is known as steady flow energy equation the special case steady flow energy equation now you see that we have defined this summation of u plus p v as the enthalpy so specific internal energy plus pressure times specific volume can be defined as specific enthalpy since the enthalpy is defined as u plus p v you know u is an extensive property volume is an extensive property so if you define the corresponding intensive property by dividing it by the mass of the system we can define the specific enthalpy the sum of specific internal energy plus the product of pressure and specific volume so therefore we can write the equation in terms of the enthalpy quantities v one square by two plus g z one plus d q d m is equal to u two plus p two v two plus sorry we are writing h two plus v two square by two plus g z two plus d w d m this can be manipulated algebraically in this fashion that you can write this way that d q d m rather here you can write this way d w d m minus d q d m is equal to h one minus h two plus v one square minus v that means we are taking this here and we are writing this in the left hand side a simple algebraic manipulation h one minus h two d w m ok alright g z one minus z two divided oh ok this is g z one minus z two so you see that this is the final outcome of the steady flow energy equation but incidentally it happens that in all engineering devices all these things that heat transfer work transfer do not take place simultaneously and moreover the changes in potential energies and kinetic energies are sometimes neglected for example let us consider only the devices which have only work interactions which have only work interactions without any heat interactions let us consider turbine or compressor let us consider a turbine for example the simple case the turbine you know the turbine this is insulated let this is one this is two let this is insulated so in this case d w d t is there which is coming out whereas d q d t is zero or you can tell d w d m is there and d q d m is zero and if we neglect the change in the kinetic energy at the inlet and outlet of this turbine and also the changes in the potential energy then what we get we get from this equation you see that this becomes zero this becomes zero so simply and also this is zero that means the work coming out from the turbine in that case is h one minus h two therefore we see that for only work interacting devices for example in a turbine when work is coming out where the changes in kinetic and potential energies are negligible compared to the changes in the enthalpy it is the property enthalpy whose difference between the inlet and outlet state straight away give the work interaction quantity similarly in case of compressor if you see that is the reverse in case of a compressor if you see in case of a compressor see let us in case of a compressor if you see it is the same thing that if it is insulated let this is one and this is two and if it is insulated similar way d q d m is zero but it absorbs energy that means soft work is fading to the compressor that means it has d w d m but in this direction in that case also we can express the same equation that is in this case also d w d m is h one minus h two the same equation here h one is greater than h two always so that this quantity is positive work is coming out in this case h one is less than h two that means the enthalpy at the outlet is outlet section is more than that at inlet so that d w d m is negative which implies physically the work is going in similarly there are devices like heat exchanger where there is only heat input to a system for example a fluid flowing through a pipe flow and there is no work transfer that means d w d m is zero and if the flow area is uniform we can neglect the kinetic energy change that means v one is almost equal to v two and if we change the potential energies neglect the changes in the potential energy here also we can write from this equation you see this equation again we can write here making this zero minus d q d m is h one minus h two or d q d m is h two minus h one that means it is the difference of enthalpy which gives this heat transfer that means this is positive that means heat is added when h two is more than h one if h two is less than h one the heat is rejected so therefore we see now the physical significance of enthalpy is such that in flow devices steady flow devices the difference between the enthalpy at inlet and outlet section gives the net work and heat interactions by that device with the surroundings so for only work interacting devices it is in the work transfer is simply coming out as the difference in enthalpy provided the change in kinetic and potential energies are neglected and in all practical applications for those devices which interact in terms of either work or heat the changes in kinetic and potential energies are usually very small as compared to the changes in enthalpy so therefore it is the change in the enthalpy quantity which straight away giving the work so here you see the enthalpy in such system bears more or less the synonymous role as internal energy as if it is because of the release of enthalpy or absorption of enthalpy the work transfer takes place in a turbine the work is done because of the change in enthalpy so enthalpy bears the same physical significance or same physical entity as the internal energy does for a closed system similarly in a compressor the work is absorbed by virtue of which its enthalpy is raised because it is the difference of enthalpy which is giving the work quantity similarly in case of heat interacting devices where only heat interaction takes place it is by virtue of the change in enthalpy the heat energies coming out is equated with the change in enthalpy so therefore in this way we can tell that enthalpy bears a similar thing that is as internal energy does in a closed system but truly speaking it is not the internal energy it is a property of the system whose definition comes only by the mathematical expression h is equal to u plus p v now we see some more examples which may come in your compressible flow calculations that there is no heat and work interaction that means the flow takes place through a nozzle but there is a change in velocity for example the flow through a nozzle or a diffuser flow through a nozzle or a diffuser this is a nozzle this is a nozzle 1 and 2 and this is a diffuser flow through a nozzle and diffuser here what happens v2 is greater than v1 and here v2 is less than v1 that is 1 and 2 similarly the p1 here is greater than p2 here v2 is more less than v1 here p1 is less than p2 so pressure increases velocity decreases pressure decreases velocity increases in this case if you see the energy equation here again the common these two terms are zero so these terms we will take care of and if we neglect the potential energy changes to be zero because the there is no change or the change in the vertical heights at the inlet and outlet are small then here the equation tells like that h1 plus v1 square by 2 is equal to h2 plus v2 square by 2 now if you explicitly see it u1 plus p1 v1 plus v1 square by 2 that means this is the conservation of energy when heat and work quantities are not there the flow takes place in such a way the total energy comprising the enthalpy and the kinetic energies remains same that means here the kinetic energies created out of the enthalpies similarly here the kinetic energies are destroyed or kinetic energies are reduced the pressure energy the enthalpies are increased by virtue of the kinetic energy you see that this is the expression so this expression holds good for this type of flow now I will deduce the Bernoulli's equation which you have already read at your fluid mechanics class the Bernoulli's equation from this principle or from this equation of energy equation for a steady flow process what is Bernoulli's equation if you recall Bernoulli's equation is basically the equation for conservation of energy it is a mathematical statement for the conservation of energy for the flow of fluid but this is not the Bernoulli's equation perfectly this is the broad statement now what type of energy conservation in Bernoulli's equation we consider only the mechanical energy we see how the total mechanical energies conserved that is why it is known as mechanical energy equation this is the conservation of mechanical energy and we seek a simplified form of this conservation of energy in certain special cases of fluid that means in case of flow of an inviscid steady flow of fluid inviscid steady flow of fluid what we know that in Bernoulli's equation if you recapitulate your Bernoulli's equation Bernoulli's equation Bernoulli's equation we know that the pressure energy p by rho sometimes we can write it in terms of the specific volume or 1 by rho these are synonymous but usual convention is that in fluid mechanics we use it as 1 by rho we use density rather instead of specific volume but in thermodynamics we prefer this is a convention the specific volume so p by rho plus v square by 2 we know this expression g z is equal to constant what does it mean so this quantity as we have seen is the pressure energy of the flow work per unit mass this quantity is the kinetic energy per unit mass in a flow of fluid and this quantity is the potential energy unit mass so some of these three quantities give the total mechanical energy per unit mass in the flow of the fluid which are associated with the fluid stream and Bernoulli's equation tells that for an inviscid incompressible what are the conditions inviscid incompressible steady flow of a fluid these three things are constant and this is constant only along a streamline if the fluid is rotational and if the fluid is irrotational this constant is constant throughout the flow field this very important again I tell you this is the recapitulation in many times this question is asked in an interview or in a vahibhavoshi what is Bernoulli's equation and what are its restriction see if you tell the Bernoulli's equation it is basically the conservation of mechanical energy sort of those mechanical energies associated with the flow of a fluid stream this is the pressure energy or the flow work the kinetic energy and the potential energy usually we will consider the gravitational potential energy so some of these three energy will be constant provided there is no energy interactions from outside so first condition there is no heat and work interactions in the fluid flow from outside number two there is no change from mechanical energy to other form of energy or intermolecular energy which we physically call it as dissipation of energy or degradation of energy from the second law of thermodynamic because energy is converted from a higher grade to a lower grade so there is no such conversion which is only possible if the friction of the fluid is absent that means fluid is non viscous or inviscid see inviscid fluid and fluid is incompressible pressure remains same sorry and sorry density remains same density does not change in the flow so for an incompressible inviscid and steady flow of fluid without any work and heat interactions this three quantities p by rho represents the pressure energy per unit mass the phi square by two represents the kinetic energy per unit mass and gz represents the gravitational potential energy per unit mass some of these three quantities remain constant but this constant value remains same only along the streamline only along the streamline but for a rotational flow but for any rotational flow this is constant throughout now I like to tell you I do not know whether you know these things from your basic fluid mechanics class that why this is constant along streamline why in a rotational flow and what is the difference between rotational and irrotational flow from the energy concept from the energy viewpoint from the viewpoint of energy transfer you know the rotational and irrotational flow definition is that a flow is said to be irrotational when the rotation is 0 rotation of fluid element that is the curl of the velocity vector is 0 how do you define the rotation of a fluid element it is the average angular velocity of the two adjacent linear sides of a fluid element which are initially perpendicular and this is given by the curl of the velocity vector three rotation component in three coordinate directions so if the rotation is 0 flow is irrotational but if the rotation is not 0 the curl of the velocity vector is not 0 then the flow is rotational from the energy point of view in a rotational flow there is always a work interactions work is either given to the fluid from inside outside or work is extracted from the fluid from outside from the inside to the outside so because of this work given to the fluid or taken from the fluid the constant varies from streamline to streamline but if there is no work interaction along with no heat interaction then the fluid behavior is irrotational so it is both in visit and irrotational but it may be an in visit flow but rotational flow where the work interaction may take place from outside to the fluid or inside that means between the flow of fluid with the surrounding this is very important so if you discard the work interaction that means flow of an in visit fluid without any work interactions from the surroundings also no heat interactions from the surrounding then the fluid behaves as an irrotational in visit irrotational flow and in visit irrotational flow is synonymous to isentropic flow in thermodynamics isentropic flow without work interactions you can write isentropic flow without work interaction now let us immediately recapitulate hurriedly how we can derive these equations now from the steady flow energy equations now you see this is the steady flow energy equation general steady flow energy equations now if we apply this to a fluid irrotational flow of fluid irrotational in visit steady flow of fluid so we start with the steady flow energy equation so irrotational flow means there is no work or heat interaction this is 0 so therefore we can write that the steady flow energy equation takes the form h 1 plus v 1 square by 2 plus g z 1 is h 2 plus v 2 square by 2 plus g z 2 this it is very simple we can write from a differential in a differential form as d of we can write h rather we write this d h plus d v square by 2 plus d of g z is equal to 0 because if you integrate it between section 1 and 2 you get h 2 minus h 1 plus v 2 square by 2 minus v 1 square by 2 plus g z 2 minus z 1 you can write this thing now if we recollect the thermodynamic property relation which i will discuss again in this class that d d s is equal to d u plus p d v and we can write h is equal to u plus p v so d h is equal to d u plus p d v plus v d p sorry so if you replace the d u in terms of d h we can write d h is t d s minus v d p this is a very useful relationship which we get i will explain this in the next class also d h is t d s plus v d p yes d h is t d s plus v d p alright so if you substitute this we get that so for an isentropic flow so i have told you that in visit irrotational flow is synonymous to an isentropic flow without working direction d h is v d p so if i replace it we get v d p plus d v square by 2 plus d of g z is 0 so if we integrate this equation well if we integrate this equation we get integration of v d p plus integration of d v square by 2 plus integration of d g z is equal to 0 so far we have put the constraint of isentropicness of the flow isentropic that is the flow is isentropic that is in visit without any work interaction but incompressibility has not put into consideration if we put the incompressibility into fact that this v comes out from the integration plus sorry it is constant after integration it is constant very good d v square by 2 plus integration of d d z is equal to constant ok so therefore we can write after integration p by rho v can be written as 1 upon rho plus v square by 2 plus g z is simply constant and this is constant without the flow field and this is simply the mechanical energy equation for an in visit for an in visit steady irrotational irrotational these are the condition incompressible flow in gravitational full flow field in gravitational force field that means if a in visit steady irrotational incompressible flow in gravitational force field takes place the rotational flow means that there is from the energy point of view no energy interaction neither heat nor work this sum of this three energy quantities remain constant that means the mechanical total mechanical energy that is the pressure energy kinetic energy and this thing constant but if we we draw this constant of in visit that means the flow becomes real that is a real fluid that is which has got viscosity it may be steady it may be irrotational it may be incompressible because you know the flow of liquids are always incompressible they are changing density associated with the change in pressure is very small then what happens the sum of this three mechanical energy will not be constant because then a part of the mechanical energy either from the pressure of the velocities the agency friction of the fluid or friction between the fluid and the solid wall that is the consequence of fluid viscosity in that case also the conservation of energy will come into picture because energy is neither created not destroyed some form of the mechanical energy is converted into intermolecular energy through the friction which will be taken care of by this intermolecular energy which has been taken care of so therefore all the energy in the mechanical energy in the equation of conservation of energy for a real fluid we use a term as loss which is meant as the loss in mechanical energy so some form of mechanical energy is lost that means has disappeared but it has taken place in the other form as the intermolecular energy so this conversion with term is as a loss in the mechanical energy equation because this is a loss from the sense of mechanical energy that means the mechanical energy as a whole well this is because of the friction so this is all about the principle of application of first law conservation of energy to an open system any question thank you


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All right, so I spent the first part of my presentation discussing Bitcoin and doing an introductory conversation about Bitcoin and You may have heard this term blockchain In fact, it's on the poster. It's on all the posters Blockchain and cryptocurrency what on earth is a blockchain and what does it have to do with Bitcoin? So Bitcoin is the foundational technology. Bitcoin is the technology that started it all Bitcoin is the parent and it has spawned many trial because many children because it is successful and As successful technology it has created a number of other opportunities When people use the term blockchain, they're referring to one technology that is part of Bitcoin It is perhaps the most visible technology, which is the database that stores transactions the public ledger The list of all transactions that has happened. It's a decentralized replicated database For those of you who are interested in the technical terms that is what a blockchain is But people don't use it to mean that People use the term blockchain to mean things that are kind of like Bitcoin Things that do what Bitcoin does and then some and all of the other applications that have nothing to do with money And then the banks go and some of the things we do But we would like to call blockchain to seem like we're doing innovation and Then the consultants go to the banks and say and you can also call blockchain doing exactly what you used to do Business as usual without being disrupted at all and we're sure we can make it work for you if you pay us enough As a result nobody really knows what blockchain means Blockchain is an industry We have a saying that The most important meaning of blockchain is that if you go to Silicon Valley Go into your hotel room turn off all the lights Stand in front of the mirror and say blockchain blockchain blockchain three times Ten venture capitalists will jump out of the closet since for a millions of dollars at you And that is true That is true. I've seen it Blockchain in itself is meaningless Blockchain is what we use to say the technology behind Bitcoin Which is a bit like saying network is the technology behind the internet And of course if you're one of the industries that is being massively disrupted by the internet Maybe you want to say hey we can do network too We don't want to do the public messy open Not very profitable freedom bringing internet But we could do network all day as long as it's private controlled and profit-making and we can charge by the minute We can do network too And if you think that's fiction, that's exactly what happened on the internet in the 90s That's what the phone companies tried to do. They tried to create private internet Which was internet without any of the interesting things It was internet's way you needed a license and a registration and an account Well now a lot of companies are trying to do that with the Bitcoin space So blockchain means some interesting things But it also means some not so interesting things and it also means some things that are just Attempts by consultants to confuse enough to make some money on the side. I'm gonna focus on the interesting things So, how do you tell what a blockchain is and what a blockchain isn't? What are the things that are interesting about Bitcoin? What are the things that are interesting about the internet? Is the internet interesting because it offers you network is Bitcoin interesting because it does payments To me the interesting things are certain characteristics. What is Bitcoin? Bitcoin is a system of payments that is open What does open mean? Open means anyone can access it anyone can participate Anyone can innovate on the system without asking for permission. That's what open means It is borderless There are no borders. There are no borders on the internet. There are no borders in Bitcoin The protocol simply does not see distinctions between countries. They are meaningless It is neutral It doesn't care if the participant is male female Christian Muslim old young rich poor Browns black whites or whatever The protocol doesn't care. It's neutral. It validates transactions. It's decentralized There is no central point of control It is censorship resistance. You cannot Sensor freeze or cancel transactions. Those are the things that make Bitcoin interesting Arguably, those are the things that make the internet interesting Right, that's why it's powerful There are other blockchains that also share those characteristics In fact people have taken the basic recipe of Bitcoin and in the first year they created two or three alternative coins They were called altcoins since then every year more and more and more and more today. There are more than 1500 blockchain based systems that use the basic recipe of Bitcoin or variations of that Design principle to create systems of currency Systems of trade platforms and various other things. These are all blockchains. Most of them Share the interesting characteristics of Bitcoin their open borderless neutral censorship resistance some do not of the 1500 I Would say more than 90% are worthless And of those more than 90% are probably scams Their primary purpose is to enrich the people who created them They see something successful. They try to create it. In fact, we have seen the emergence of a very large number of scams Scams that are in essence Ponzi schemes. Who's familiar with the term Ponzi? Ponzi Did you know that's the name of a guy? Mr. Ponzi He inadvertently became famous Multi-layer marketing systems pyramid schemes, right So if you try to sell Bitcoin to someone and I don't I talk about it as an experimental technology That you should only invest in if you really understand how it works And you should primarily invest in learning and understanding the technical skills that can turn this into an innovative industry a Start-up business a career some opportunity for you as an individual It's not a stock investment and if you hear someone tell you that this system is an investment It's a sure investment It's a safe investment. It's a risk-free investment or even worse It is a system that is guaranteed to make you rich Quickly run away as fast as you can because those characteristics are shared by only one category of investments scams Nothing in life is easy risk-free and will make you rich So beware especially in Southeast Asia where you have very large numbers of new Middle-class investors for the first time entering investment markets Scam coins Ponzi schemes and multi-level marketing schemes are extremely popular When you hear this is like Bitcoin only will make you rich Girl away run away Bitcoin will not make you rich. It can't make you poor quickly It is a volatile experimental system that comes with risks I am advocating the understanding of this technology, which is enormously powerful Not the use of it as a speculative investment Unless you need to use it and know how to use it. It's not an investment Now let's talk about some of the other systems that are out there There are probably about a dozen other Cryptocurrencies crypto currencies is another term we use for these open blockchains these public systems of ledger That can be used to build systems of trust some of them are very explicitly Currencies I'll mention just a few you may have heard of them dash Monero Ethereum Zcash Light coin all of these are crypto currencies that are based on open public ledgers They represent interesting technologies that are developing a long-time Bitcoin many others are also growing I Do not Recommend you use those as speculative investments either but understand what they do and how they're different so that you can get a better Picture of this industry as it emerges My next focus on Ethereum Which I haven't talked about much How many people here are familiar with the theorem or have heard of it used it? Great a very large number of people so for those of you who have not heard about the theorem the theorem started Based on a paper published in 2013 by then 19-year-old Vitalik buttern I got a hold of that paper before it became public and called Vitalik up to get some information about this I was very skeptical, but I have been interested ever since and I'm writing my next book on it the idea behind the theorem is if we can have this public ledger that is Allowing us to trust and do computation at scale how about instead of using it for money We use it to run computer programs and these computer programs run everywhere and their results are recorded in a way That is immutable Persistent and trustworthy by all of the participants global secure decentralized computation not money And it has a system of money called ether, but what it really allows you to do interestingly is run smart contracts The idea here is taking contractual arrangements the kinds of things we would do in commercial contract law or transactional laws, it's known and encode relationships and contractual obligations in software programs if this happens then do this else do that the way you would write Contract in a human spoken language instead encoding it in software and then having that program of law execute on a global platform Not money But it is part of this System of trust that is based on the same global blockchain phenomenon. So blockchain isn't just money People have suggested using blockchain for a number of non financial applications mostly applications related to trust one very common application is the registration of assets or ownership of tangible or non tangible things For example, and this is a big problem in developing nations and an area where blockchain can have a very large impact is the registration of title over land and the ownership of assets like homes So the possibility of using a blockchain is Because if you record something on the blockchain It cannot be modified it is immutable once recorded on the blockchain the system of trust prevents anyone from Reversing that from overwriting that from changing the past So it creates a permanent Immutable record of history in a real estate transaction that is really important that allows you to pass title of a piece of land from person to person independently While no one being able to falsify that record or steal your land through paper One of the most common forms of theft of land are with the falsification of paper You don't have to Go into someone's land with guns and take it from them if you can go to the local land registry office Brite someone to change it into your name and send the police into their land with guns to take it from them on your behalf That kind of thing can really be affected by a blockchain Other things are the record the registration and access to assets You can for example have the title of a car a boat an aircraft registered on the blockchain We were having a discussion here in the waiting room with the gentleman from the airline industry and one of the interesting Applications we discussed is the ability to record maintenance records and parts in a blockchain in a way that they cannot be modified If a plane crashes, I'm a private pilot by the way, so this is an area of interest to me But if a plane crashes One of the first things you want to do is go back and look at the maintenance records and say was the left jet engine actually Inspected after 100 hours of operation as it's supposed to be how can you tell in Traditional forms if we have that written down on paper I Could write down today and put a date a month ago before the plane crash and say look It was inspected you falsified the record after the fact you could falsify a database after the fact and Witnesses are unreliable. How do you know what actually happens a? Blockchain allows you to record the fact that the inspection happens and it cannot be modified or falsified after the fact and it Cannot be inserted in the future and pretend to be in the past So these are elements where the same mechanism that's used to create trust from money and Transactions can be used to record the truth in a permanent immutable record These are the applications that most companies are fascinated by beyond money that have the general term blockchain That's the good now. Let's talk about the bad and the ugly That same term blockchain is used to mention a lot of things that do not have any basis in fact and don't actually work What has become very fashionable lately is this idea that you can do blockchain Without Bitcoin as in blockchain is good, but Bitcoin is bad. It's used by criminals gamblers degenerates It's just money one of the fundamental Mechanisms behind the blockchain is its security Bitcoin allows you to have a system that is decentralized without the central point of control by creating a competition In which those who provide security are rewarded in Bitcoin the currency So the currency in Bitcoin is not just a vehicle for doing value transactions It is the basis of the mechanism of security and That mechanism of security allows you to have a blockchain that is operated and secured by anonymous participants whose only claim to providing security is that they submit as A promise for their security and they risk energy and They may gain as a return a reward in Bitcoin unless they try to cheat in which case they lose everything That competition that game is the basis of Bitcoin security But what that system of security allows you to do is have the system managed by everyone so that no one is in charge Here's the problem if you take away the system of reward Then there is no mechanism for punishment. If you take away the system of punishment for cheating. There is no security Blockchains use a currency Because they use a system of security that is based on market forces on game theory To use a blockchain without a currency you have to find another way of doing security And this is where the traditional institutions come in and say I know how about We assign five trusted Institutions and they validate every block on the blockchain and Make it a private blockchain where we control who has access and since those five private institutions Assign trust on the blockchain if you trust those institutions you can trust the blockchain That is business as usual that is blockchain being used to perpetuate the system of Institutional trust that has failed That has failed to scale only worse if you use a blockchain in that kind of way as a private closed system where trust is Assigned to institutions If those institutions are compromised or their keys are stolen or hacked Because you've concentrated all of that power and just a few participants that system is no longer secure These are the same companies that get hacked every Timing read on the news That someone got hacked. This is who we're supposed to trust to run these blockchains the whole point of Bitcoin's open public blockchain is through a system of currency It creates security that does not depend on any one individual or institution If you take the currency away the security model disappears to and you're back to a Ledger that is controlled by a single entity or a few entities We have a name for that. It's called a database So this is the real question you should ask how do you evaluate? the difference between blockchain and As we would say in America bullshit They both start with a B One of them is real the other one isn't One of them is used as the basis of a 12 billion dollar global security centralized economy And the other thing is the thing the consultants trying to sell How can you tell the difference between real and not real? Ask the following questions Is it open? Is it public? Is it borderless? Is it censorship resistant? Is it neutral? Can anyone access it without permission? Can anyone use it without permission? Can anyone innovate on it without permission if the answer to all of those questions is yes Then it's giving you the values that we find so interesting in Bitcoins blockchain and you can say that for a number of other cryptocurrencies and blockchains. Yes to all of those things If you can take the entire brochure that describes this thing and do search and replace and for every mention of Blockchain you can replace it with a word database and then you read it and it still makes sense You're not being sold the blockchain.  Thank you


All right guys, it's now 12 o'clock. Let's see how far our hackers have gotten We've given them enough time to actually do something or at least learn enough to do something. Let's see what's happening All right, so yeah, that's right name and what you do? Vignesh, and I'm building a URL shortener. Mm-hmm And I'm not sure if I'm going to complete it. I'm learning a lot So I'm learning like I'm learning express and node.js like all so I'll see if I'm able to All right My name is Harsh and I've hardly complete 5% of what I'm supposed to do and which is I'm kind of Making a distributed Working environment like if I'll send a code and I'll send some data and the kind will run the code for me And send me the result back nice All right, man. What you doing? I'm just learning some words. Yes How far are you into that? Yeah, just started Next Next up net row.  How far are you in that? I am not doing good We'll come back to you. I'll come See all right So who you are and what you do? I'm Samyuk and we are working on a Google killer Okay, how far you into that? We are half it through Not bad. So who you are and what you do? I'm trying to learn some indie Some more So, how far you are what are you doing? Well, that's it. I'm learning in the And how far you do it? I'm I'm just started. I just start nice. That's it. Next up. We are and what you're doing? I am Pratik. I'm consuming Red Bull. Nice and in your spare time. Huh? In your spare time I'm trying to do my search engine project. Mm-hmm. I'm almost done with the client search Capacity now then we can we have with this spec for the server side. We can move to server side and I think we have Manga TV scheme also chopped up. All right. Nice. All right. Next up. We are and what you do? That's awesome. No, no, no, no So right and also who you are? Oh So You plug in so we're trying to capture your face We're trying to capture your face and we're going to use official recognition API to show which social networks you're on Just when you stand in front of the browser. Yeah, that's it Just for looking at your face, we're trying to retrieve the information And how far you guys into that just started Yeah, so you do you do you do so who you are and what's going on? So I'm at saying and I'm working on a WordPress plug-in as I had mentioned And I'm almost halfway through nice. So you finished by morning. Yes. I will be Okay, so guys one big circle. Yeah Okay, perfect. So who you guys are and then what you guys are doing? Okay Okay So, what are you guys doing so this is planning what to do So this is converging actually to an idea that we create a Board for rich content of Twitter Like if like p interest basically if you have visited p interest what it does is kind of present the entire content And a very rich format and in the board form basically, it's very easy to browse So we're trying to come combine p interest plus Twitter plus interesting content What's coming up? So all of us are going to work on that nice. So currently you're at like what minus five percent. Yeah So you think you guys how far do you guys think you'll get by morning? So who you are and what you do I am Jay, I am trying to create a In touch button like there is plus one button for Google plus and Okay In touch ID, okay So when some of the presses in touch button people get in touch with each other and stick nice nice. How far are you into that? 50% part has been done and rest of 50% I don't know how I'm going to do You think you might finish by morning? Think so I need some help, but nice. Let's check back in the morning.  It's a diff 2.0 spec draft number 16 draft number 22 And I need to figure out what has changed in the last few months so that I can go read all my code This is ready guys can't figure out how to get to a final spec So it's it's not pleasant, but pretty hell man There's a new version of the spec where they break something else in the past So if anyone from there is watching fix this, okay Down to final man It's been three years and so so how many hours have you spent reading and how many hours you think will take? I think it'll take longer to read this into implement changes because for all I know they just change the terms And they're not seeing the actual spec Read the damn thing to find out It's a 11-page document original and 11-page body for it Alright people you heard it here. This is hacker news at 12 o'clock. Let's see what happens in the morning Oh, yeah, right. Of course of what I'm doing. I'm pretty much doing nothing as usual But I'm trying to check up the specs of Kerberos totally unrelated Yeah, and getting him coffee sadly So let's check back in the morning. Let's see how far these people have gotten