Events

Under fully developed flow conditions, the convective heat transfer coefficient is inversely proportional to the hydraulic diameter of the channel through which a coolant flows. In addition, inside a heat sink several smaller channels can be used in place of a single larger channel as a means of increasing the convective heat transfer area per unit volume. Based on this rationale, microchannels were proposed for high heat flux cooling applications. Unfortunately, for a given flow velocity the pressure drop is also inversely proportional to the square of the diameter of the flow channel.

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In this talk, I will describe our experiments of using non-contact atomic force microscopy (AFM) to probe local properties of nanostructures. The AFM tip is used as a mobile gate to perturb samples locally and at the same time a sensor to detect minute electrostatic forces due to single electron charging (~ 10 /f/N). This technique allows us to track the charging process of a semiconducting carbon nanotube with high spatial and energetic resolution and provide a map of its local potential fluctuations.

This isn't about solid state or optical physics, but should be of interest to current and prospective graduate students, and those who interact with them in any capacity. People who attended this conference promised to report back to their departments, and I'd like to take this opportunity to do so. An APS/AAPT-sponsored conference to focus national attention on graduate education in physics took place at the American Center for Physics (ACP) in College Park, MD from January 30 � February 2, 2008.

Solar energy has by far the largest potential of all renewable energy sources and photovoltaics is the key technology to utilize this potential. At present photovoltaics technology ranges from widely employed first generation silicon wafer based solar cells to third generation multijunction cells used in space.

Helimagnets are magnetically ordered materials in which the spin-orbit interaction leads to a spiral structure of the magnetization. I will review the phenomenology of MnSi as the prototypical and best studied helimagnet, in particular various phases or suspected phases identified by neutron scattering and other techniques. The most spectacular feature is a pronounced T^(3/2) behavior of the resistivity in a large region of parameter space. I will then review theoretical efforts to understand the observed effects.

Cosmological distance measurements are challenging but fundamental to our understanding of the expansion history of the Universe. With the more precise techniques developed in the last decade, we have determined that the expansion rate is accelerating. This strange and unexpected result is attributed to a new force dubbed �Dark Energy,� for lack of any deeper understanding. I will discuss a new method for measuring cosmic distances, Baryon Acoustic Oscillations, and an experiment that will bring this technique to a new level of precision in the ongoing effort to understand Dark Energy.

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Both liquid and ice clouds in the atmosphere form on small aerosol particles, which are produced by various sources. The effects of aerosols on cloud properties are complex and one of the most uncertain factors in predicting climate change. Some aerosol sources and how they act as cloud condensation nuclei (for liquid clouds) and ice nuclei (for ice clouds higher in the atmosphere) will be presented. Much of the data presented will be from in-situ cloud measurements taken from atmospheric research aircraft in different parts of the world.

In order to help understand the wide scatter in the reported fatigue properties reported for bulk metallic glasses, the roles of free volume and residual stress in affecting the fracture and fatigue behavior of a Zr44Ti11Ni10Cu10Be25 bulk metallic glass were examined. Different residual stress and free volume states were achieved by annealing below the glass transition temperature.