( i )

1. Phase Transitions Studied with Colloids: Effects of confinement on a cylindrical surfaceAnthony D. Dinsmore, University of Massachusetts Amherst, DMR 0907195 While the thermodynamics of bulk crystalline phases is well established, spatially confined systems raise interesting fundamental questions and opportunities for new properties. Here we study the behavior of discs or spheres that lie on the surface of a cylinder. We are motivated by biological structures (microtubules and cylindrical membrane/protein structures) and by the potential for coatings on fibers. Unlike flat surfaces, cylinders impose the topological constraint of periodicity around the circumference. For a range of inter-particle forces, we find that this constraint leads to rhombic crystalline phases that are not seen on flat surfaces; this leads to the possibility of new properties. There are also structures with a “seam” (already seen for hard spheres [1]), which resemble those in protein-based systems. We use computer simulations to explore this system. For visualization, the structure is “sliced” along the axis and “unrolled.” The left and right edges correspond to the same particles. As the circumference is increased, a hexagonal crystal (i) becomes rhombic (ii), then a chiral structure with a seam, called a “line-slip” [1] (iii). (i) (ii) (iii) [1] See, for example, Mughal, Chan,& Weaire , Phys. Rev. Lett. 106, 115704 (2011).

2. Training the Next Generation of ScientistsAnthony D. Dinsmore, University of Massachusetts Amherst, DMR 0907195 Graduate Students Jaime Hutchison, Liquan Pei, and Derek Wood contributed to and are supported by this research project. Dinsmore is also active in supporting undergraduate research through the UMass Commonwealth Honors College, as co-instructor of a Freshman research seminar (see left), and through individual research projects. For the past three years, Dinsmore has contributed to design of a new, 4-year undergraduate program at UMass: the Integrated Concentration in Science (iCons). The program will soon start its 3rd year. Education and outreach activities also included co-organization of the 5th annual, 1-week UMass Summer School on Complex Fluids and Soft Solids. First-year undergraduate students at UMass Amherst finish presenting their research on energy usage in their dorm. Their experience in designing and completing the project is an important step toward careers in science, engineering, or myriad other fields.