CARNEGIE MELLON UNIVERSITY -
UNIVERSITY OF PITTSBURGH

Monday, November 9, 2009, Astro Coffee, 2:00 PM, 416 Allen Hall, PITT.

Monday, November 9, 2009, CMU/Pitt Joint Physics Colloquium, "Chemo and Phototactic Nano/Microbots." Dr. Ayusman Sen, Pennsylvania State University, 4:30 PM, 102 Thaw Hall, PITT

Abstract: One of the most interesting scientific challenges is the design of autonomous synthetic nano/micromotors which can be used for drug delivery, self-assembly of superstructures, roving sensors, and other emerging applications. We have demonstrated that one can build nanomotors “from scratch” that mimic biological motors by using catalytic reactions to create forces based on chemical gradients. In biological systems, microorganisms not only move autonomously, but also respond to their environment via the phenomenon of taxis: the movement towards or away from a chemical (chemotaxis) or light (phototaxis). We have recently observed the first examples of non-biological chemo and phototaxis. For example, when placed in a gradient of fuel, the motors spontaneously migrate up the concentration gradient. This behavior provides a novel way to direct particle movement towards specific targets. We have also explored self-diffusiophoresis as an alternative mechanism to power synthetic micro/nanomotors,. We have shown that particles that release ions under UV illumination exhibit the phenomenon of phototaxis. Further, the gradients produced by adjacent particles interact and the particles began to swarm into schools. Thus, the particles are reminiscent of quorum sensing organisms that swarm in response to a minimum threshold concentration of a signaling chemical.

Wednesday, November 11, 2009, Graduate Students/Undergraduate Students/Faculty/Staff Coffee Hour, 4:00 PM, 319 Allen Hall, PITT.

Thursday, November 12, 2009, Astro Coffee, 2:00 PM, 416 Allen Hall, PITT.

Thursday, November 12, 2009, Condensed Matter Seminar, "Free Energy Landscapes and Amyloidogenic Protein Aggregation", David Talaga, Rutgers University, 4:30 PM, WEH 7316, CMU.

Abstract: Proposed mechanisms of amyloid growth remain idiosyncratic to the precursor, conditions, and methods used for measurement. Our aim is to directly observe oligomeric intermediates and develop a detailed molecular model of amyloidogenesis. Such a model allows construction of an amyloidogenic aggregation free energy landscape and enables a more universal approach to evaluating the roles of different amyloid-related species. We combine atomic force microscopy particle size distribution measurements with earlier measurements on 1-anilino-8-naphthalene sulfonate, thioflavin T and dynamic light scat-tering to develop a quantitative kinetic model for the aggregation of ß-lactoglobulin into amyloid. We directly compare our simulations to the population distributions provided by dynamic light scattering and atomic force microscopy. We combine species in the simulation according to structural type to compare with the fluorescence fingerprint results. The kinetic model of amyloidogenesis leads to an aggregation free energy landscape. We define the roles of and propose a classification scheme for different oligomeric species based on their location on the aggregation free energy landscape. The relation of the different types of oligomers to the amyloid cascade hypothesis and the toxic oligomer hypothesis for amyloid-related diseases will be discussed. We will also discuss existing kinetic mechanisms in terms of the different types of oligomers and provide a possible resolution to the toxic oligomer-amyloid coincidence. Moreover, some of our recent work using nanopores, resistive pulse and electrochemical impedance electrical measurement to monitor protein conformations will be presented.

Thursday, November 12, 2009, Quantum Information Seminar, "Local implementation of multipartite nonlocal unitaries", Li Yu, CMU. 4:30 PM, WEH 6325, CMU.

Abstract: Nonlocal unitaries can be carried out at spatially separated parties using entanglement and classical communication as resources. I am going to introduce some of our protocols for implementation of multipartite unitaries with a graph state as the entanglement resource. The protocols have the corresponding bipartite versions which we have discussed in the past seminars. This work is done in collaboration with Profs. Griffiths and Cohen.

Friday, November 13, 2009, CMU/Pitt Astro-Lunch Seminar, Luc Dessart, Laboratoire d'Astrophysique de Marseille, Topic TBD 12:00 PM, 106 Allen Hall, PITT

Monday, November 16, 2009, Doctoral Defense, Patrick Irvin, Pitt, “Optical Investigations of Nanostructured Oxides and Semiconductors”, 9:00 AM, 316 Allen Hall, PITT.

Abstract: Semiconductors and oxides form the backbone of modern microelectronics with devices like the field-effect transistor. We are interested in taking advantage of additional properties that can be found in oxides (such as ferroelectricity, electro-optic effect, and metal-insulator transition) and integrating them with semiconductors. One potential application is a quantum computing architecture that uses spins in semiconductor quantum dots as qubits and a proximate ferroelectric oxide to control gate operations. In this talk I will describe our efforts to characterize single spins in GaAs quantum dots. I will also discuss the creation of rewritable nanoscale devices at the interface of two insulating oxides, LaAlO3 and SrTiO3, along with experiments demonstrating the photosensitivity in such devices.

Monday, November 16, 2009, CMU/Pitt Joint Physics Colloquium, Robert Suter, CMU, Topic TBD. 4:30 PM, WEH 7500, CMU.