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[SQUEAKING][RUSTLING][CLICKING] RICHARD DE NEUFVILLE: Right. Richard de Neufville here again. Pleasure to talk with you, and for this session, I'm going to talk about porcupine graphs. It's all part of this topic of the forecast being always wrong, not every single time, but in general, we can't count on it being right. And we just expect it, the reality that we face during the-- our project lifetime is not what we anticipated. Now, what's a porcupine graph? Well, let me first describe what a porcupine animal is in case you don't know it or haven't seen it. The porcupine is a North American animal. It maybe exists elsewhere also. I think it does, but I'm not an expert in the area. But the important thing about a porcupine is that it is an animal, four-footed, small, about the size of a small dog, and it has a lot of spikes on it that go up from its back. And as you can see in this example here, they go all back in a variety of ways in many diff...

HAZEL SIVE: All right. Let's move on to the second topic of our discussion today, which we will start today and then continue on Friday. And this is a discussion of the proteins. The proteins, probably the most fascinating class of macromolecules, 55% of the dry mass of a cell, and proteins function everywhere. They do almost everything. Strictly speaking, proteins are not hereditary information, although Professor Jacks will talk with you about a class of proteins called prions, which kind of are hereditary information. So not hereditary info, but they do almost everything else. They form the structure of the cell. They form a major class of catalysts called enzymes that we will talk about on Friday. They function in defense as in the immune system. They allow cells to move, dot, dot, dot. Okay? We'll talk about proteins on and on and on as major players in the fabric of life. Their monomer is an amino acid that is abbreviated AA or little aa. And it has a partic...

PROFESSOR: All right. The end of this lecture generated so much excitement that we've continued on into the start of the next segment. So I think we'd better begin. What I told you, as several people were clever enough to observe, that the number of planes between the origin and intercept plane is equal to A times B times C, where the intercept is A T1 out plus B T2 out equals C T3 out. That is true only if the numbers A, B, and C are mutually prime. If it's something like 4, 2, 1, you won't get that number of planes. You'll get a submultiple. And the reason for that is that some of the planes, when you generate them by these three different translations in different directions, some of them are mapped on top of existing planes. And I'm not going to attempt to prove this, but let me just tell you the result, that if A and B contain some common factor, p, and B and C contain some common factor, q, and in the worst possible case, A and C contains som...

PHILIP GREENSPUN: All right. We're going to go in and outline, how do you navigate an airplane? It's become a lot easier now in the GPS age, but you still have to know a little bit about how people used to do it in the old days, partly to pass the exam, and partly because it's interesting. All right. So we're going to talk about looking out the window. That's called pilotage, planning your flight and then looking out the window. We'll talk about the old non-directional beacons, basically homing in on a radio station. In the 1950s, there was something called the VOR that we'll talk about that lets you figure out exactly your magnetic heading to or from a radio station. And finally, the way that most people get around these days, the GPS and the moving map. OK. So when you're doing pilotage, you come up in advance with a bunch of visual landmarks that you think you'll be able to see from the air. You're going to cross a river. You...

HAZEL SIVE: All right. After your class exercise that has to do with vectors and ligation, you should be able to find compatible ends and figure out whether or not they will ligate or not. And you should understand the concept of a vector and how this is used to carry a piece of DNA and to amplify a piece of DNA that you are interested in. I want now to move to our last topic in this discussion today. And that has got the acronym, or the abbreviation, PCR. PCR stands for polymerase chain reaction, polymerase chain reaction, PCR. And it is a very cool technique that allows one to exponentially amplify DNA in a test tube in the lab. Exponential amplification or synthesis of DNA in the lab-- why do we care about this? Why is PCR of interest? It's of interest because it means that you can take a tiny, tiny amount of starting DNA and you can make lots, and lots, and lots, and huge amounts of it. When we talked about molecular cloning, you also amplify DNA a great deal. But...

PROFESSOR: All right. Let's get started. So we have a fun lecture today about efficient origami design. Last Monday, we did inefficient origami design, but it was universal. We could fold anything. And let's see, Thursday, we talked about some basic foldability, crease patterns, what make the valid. That'll ground us a little bit today when designing some crease patterns. Although, we're going to stay fairly high level today because there are two big methods I want to talk about. One is tree method which is hit it pretty big in the impractical origami design. Lot of modern complex origami designers use it either in their head or occasionally on a computer. I demoed it quickly last time. So we are going to see some level of detail how that works. And then, I want to talk about Orgamizer which is one of the latest techniques for designing crazy, arbitrary, three-dimensional shapes that seems to be pretty efficient. Although we don't have a formal sense i...