Events

Moore's Law has set great expectations that the performance/price ratio of commercially available semiconductor devices will continue to improve exponentially at least until the end of the next decade. Although the physics of nanoscale silicon transistors alone would allow these expectations to (almost) be met, the physics of the metal wires that connect these transistors will soon place stringent limits on the performance of integrated circuits.

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The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2008 with one half to Yoichiro Nambu "for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics," and the other half jointly to Makoto Kobayashi and Toshihide Maskawa "for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature." Nambu's early work began a "paradigm shift" in particle theory in which we think of the "vacuum" not as a state of absolute nothingness but

Protein trafficking is critical in neurons since neurons must orchestrate the movement of a plethora of discrete intracellular signaling proteins from the cell body to the ends of their axons, over distances that may span up to several meters. A problem in studying protein trafficking has been a lack of tools to visualize the movement of discrete proteins inside live neurons, in real time. An integrated understanding of endocytic trafficking at the level of single or small numbers of receptor complexes inside live cells is currently hampered by technical limitations.

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The Biomedical Optics Laboratory is devoted to the development of new uses of lasers and light in medicine and biology. The research topics fall into two categories: (1) LASER/LIGHT-TISSUE INTERACTIONS where the photon affects the tissue, which covers therapies, surgical techniques and tissue machining applications, and (2) OPTICAL DIAGNOSTICS where the tissue affects the photon, which covers diagnostics such as imaging, spectroscopy, characterization and detection.

A model-based framework for teaching and learning physics suggests that pedagogical activities should highlight the modelling nature of physics and allow students opportunities to construct their own mental models and explore the relationships between them.

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The optical response of semiconductor quantum-wells often displays excitonic resonances with a typical energy spacing of 1 to 100 meV. To directly access transitions between these resonances, one can apply electro�magnetic fields in the terahertz frequency range. The resulting quantum dynamics and associated nonlinear optical effects are of great interest. They both manifest fundamental physical processes, such as many-body interactions and Coulomb correlations; and also have broad applications for optoelectronic devices.

I will describe recent experimental results, where we realize an asymmetric optical potential barrier for ultracold Rb 87 atoms using laser light tuned near the D2 optical transition. Such a one-way barrier, where atoms impinging on one side are transmitted but reflected from the other, is a realization of Maxwell's demon and has important implications for cooling atoms and molecules not amenable to standard laser-cooling techniques. In our experiment, atoms are confined to a far-detuned dipole trap consisting of a single focused Gaussian beam, which is divided near the focus by the barrier.