Science 198: Perspectives on Science

2005-2006

Lecture Questions

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1) Various lineages of birds have evolved nanostructures with crystal-like order from primitive nanostrutures with quasi-order, or amorphous structure. How might selection on the optical properties of a structural color (e.g. hue, brilliance,iridescence, or saturation, or "breadth" of a reflectance spectrum) result in fundamental changes in nanostructure? How could you test these hypotheses?

2) Before the invention of the electron microscope, biologists hypothesized that non-iridescent structural colors were produced by incoherent, Rayleigh scattering (the same mechanism as the blue sky). For fifty years after the first electron microscope pictures of the quasi-ordered nanostructures in spongy keratin of feather barbs, most biologist were still satisfied that these materials were appropriate for Rayleigh scattering. What did they miss? Why were they wrong? Can you think of other examples in science were expectations appeared to be met, but turned out to wrong, and the data were staring us in the face all along?

3) What conditions might favor the evolution of structural colors? Are their optical effects that cannot be achieved with pigments? Under what conditions might structural colors be disadvantageous?

4) What is the fundamental difference between coherent and incoherent scattering? Assuming the average index of refraction in these tissues is about 1.5, what structural spacing would give rise to coherent scattering in the blue range? How does this compare to the dimensions of a typical cell?

1) Why is "Dark Energy" named that, and what is the evidence for it?

2) What is the principle observed effect of Dark Energy on our Universe today? Was the existence of Dark Energy predicted? (Should it have been?)

3) Currently there is no accepted theory explaining what Dark Energy is and no observations telling us how it behaves over cosmic time. How will we learn more about Dark Energy?

1. Dr. Barnett Rosenberg's experiments are great examples of hypothesis-driven research and the importance of control experiments. What was Rosenberg's hypothesis? What was his experimental design? Why did control experiments turn out to be so important?

2. Many a metalloprotein has been featured as the Protein Data Bank's Molecule of the Month (http://www.rcsb.org/pdb/molecules/molecule_list.html), including phenylalanine hydroxylase, alcohol dehydrogenase, Photosystem II, and others. What are the physiological roles and structural features of transferrin and ferritin?

3. Transferrin is being investigated as a delivery vehicle for several types of medicines, including metal-containing ones. Articulate at least two reasons why this strategy is promising, and two concerns about such an approach.

1. What is the largest decimal number that could be represented in a 32 bit classical register? What is this number for a quantum register?

2. What is meant by "superposition"?

3. How does quantum error correction work?

4. Describe the type of problem that quantum computers are envisioned to be used on. What makes this type of problem different from others? Why will a quantum computer be able to solve this type of problem when a classical computer can not?

1. What is somatic cell nuclear transfer and why do some people call it therapeutic cloning?

2. What is you opinion about, and your analysis of, the ethical principles involved in working with and creating new human embryonic stem cells?

3. Why are adult stem cells not good substitutes for embryonic stem cells?

Answer 3 of the following 4 questions:

1. An essential feature of the hydrated electron problem is that one of the electrons is not incorporated into the water molecules. Why does this happen?

2. What was the purpose of attaching argon atoms to the water clusters? Hint: The main experimental observable was the detection of sharp resonances in the absorption spectrum of infrared light. How does one usually detect such resonances, and why does this not work in the case of the ionic clusters important to the hydrated electron study?

3. What were the two types of motion that contributed to the observed resonances? What characteristic feature in the spectrum immediately signaled the presence of the "sacrificed" AA water molecule? What does "AA" stand for?

4. The "supersonic jet" was very important in the generation of the cluster ions. What property of this jet was used to grow the tiny ice crystals that were subsequently filtered using a mass spectrometer?