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Chilean students and their projects, Winter, 2005

Cristobal Arratia and Eva Chi

Cristobal is working with chemistry postoc Eva Chi on how surfactant monolayers incorporate long-chain polymers. The polymers are "triblocks" with two sections that are hydrophobic and one that is hydrophilic. These polymers can readily go into a lipid monolayer made of the same kind of material as cell membranes. If the monolayer is compressed, though, the polymers get squeezed out. This squeeze-out phenomenon may be important for physiological effects. Thus it is important to see how it depends on the molecules involved -- both the polymer and the lipid. Cristobal is exploring the effect of replacing the normal lipids with different lipids having an enlarged polar head group. He is using one with a sugar headgroup. Remarkably, these lipids admit the polymers more easily than the normal lipids. It requires greater pressure to expel the polymers.

Loreto Barcos and Lei Xu

Loreto is working with physics grad student Lei Xu in Prof. Nagel's lab. Lei and Nagel recently discovered something anomalous about drops falling from high above a solid surface. Normally such drops splash into many droplets, as everyday experience shows. But when the impact takes place in a partial vacuum, the splashing stops. Instead drop spreads evenly on the surface and stays in one piece. Loreto and Lei are working to explore the conditions necessary for the splashing to stop.

Victor Romero and Ward Lopes

Victor is working with UC/Argonne postdoc Ward Lopes. Ward has just come out of the MRSEC clean room. Victor is holding some of his samples. They are studying the spontaneous stripe patterns formed when a thin film of certain "diblock copolymers" is deposited on a surface. The stripes differ in chemical composition. The stripes are formed from two alternating compositions. Metal atoms prefer one of these two compositions. Using this preference Ward was able to make silver atoms segregate along the stripes to make continuous wires. Many other metals were shown to segregate, too, but they make clusters of spherical droplets instead of wires. Victor's job is to vary the conditions in order to make gold atoms form wires as the silver ones do.

Maria-Luisa Cordero and Peter Eng

Maria-Luisa is working with staff scientst Peter Eng at Argonne Lab's Advanced Photon Source. The project is a collaboration between Peter and Prof. Jaeger's group at the University, handled by students Eric Corwin and John Royer. They are studying what happens when a heavy ball falls into loose sand. Like other researchers, they see a dramatic spout rebounding from the sand after the ball has fallen in. At Argonne the group plans to take an x-ray movie of the process to see what is happening within the granular material as it forms the spout.

T. Witten, February, 2005