Open course ware

[MUSIC PLAYING] PRESENTER: It is used to determine the concentrations of various solutions. In this video, we'll take you through the proper procedure. The number one rule of titration. [ALARM BLARING] A quick review of burette preparation. Please see the volumetric techniques video for more information. Here is the titrant you'll be using. Take your burette and fill it with a few milliliters of titrant. Then tilt and rotate the burette to coat the interior surface with titrant. Finally, allow the burette to drain completely, then fill to above the 0 mark. Firmly and securely clamp the burette to its stand. Hold on a minute, there are air bubbles in the tip. We can't have those. In order to get rid of them, quickly rotate the valve back and forth, letting small amounts of liquid pass through the tip intermittently, then slowly drain your burette to 0, or at least close to it. It is not vital that you drain to exactly 0 so don't spend all your lab time doin...

PROFESSOR: Determinism. And it all begins with photons. Einstein reluctantly came up with the idea that light was made of quanta-- quanta of light called photons. Now when you think of photons, we think of a particle. So everybody knew that light was a wave. Maxwell's equations had been so successful. Nevertheless, photoelectric effect-- Planck's work-- all were leading to the idea that, in some ways, photons were also particles. So when you think of a particle, however, there is an important difference between a particle in the sense of Newton, which is an object with zero size that carries energy and has a precise position and velocity at any time, and the quantum mechanical idea of particle, which is just some indivisible amount of energy or momentum that propagates. So light was made of photons-- packets of energy. And a photon is a particle-- a quantum mechanical particle. Not in the sense that maybe it has position and velocity determined or it's a point...

It comes acquainted with different antigens. And recall that what we were talking about was the following, that there were several kinds of phagocytic cells. Phagocytic cells are cells that chew up other things, both macrophages and even more frequently, dendritic cells, many of which hang around lymph nodes by the way. They process antigens into oligopeptides. The oligopeptides get presented on the surface of these cells. Let's say, here's a macrophage, in the form of through the class 2 MHC molecules which are displayed on the surfaces of the cells. And, here's a typical oligopeptide that has been chewed up from one of the antigens that was previously internalized, eaten up by the macrophage, a dendritic cell, and then presented on the surface. Recall, then, we have an itinerant macrophage or dendritic cell. Could we turn up the sound just a little, just a notch? Thank you. And this dendritic cell or macrophage...

Good morning. It can't go without at least some acknowledgement dimension. If you should ever find yourself in life in a situation where you have or are about to give up all hope, you think things are utterly impossible and there's no way, you will remember this week that nothing is impossible. It is possible to come back three games down in the bottom of the ninth inning, you've got to believe you can do it, and remember to have Dave Roberts pinch run. Just a general bit of good advice. What an amazing week, just absolutely amazing week. Wow. There are lessons in life to be taken from it. Please do take them. You know, there really are. I mean I'd given up hope by that point, I confess. I wish I could say oh, I knew they were going to pull it out, but I didn't. And, boy, they pulled it out one game at a time. So, all of you think good thoughts this week. This could be a historic week, you know, you...

It was quite an experience for all of us to get to hear him. And it is equally very fortunate now to have Wayne Hale who has had a very illustrious career at NASA. Wayne came to NASA the same year I did in 1978, worked his way up as an engineer through the propulsion system, the integrated communication systems. Became a flight director in 1988 and served there for 15 years. He was flight director both for the orbit phase and then the most really kind of intense flight control phase as ascent and entry. And Wayne was ascent and entry flight director and then lead flight director for many flights, including-- we were trying to figure out before. But I think he actually served for all of my last four flights. So we've known each other for a long time. In 2003, he was sent to the Kennedy Space Center to be head of launch operations. But he didn't get to spend very much time in the Florida sunshine because they asked him to come back to Houston the next year as deputy...