Integrated Calendar

Aberration-correction in transmission electron microscopy (TEM) has seen an enormous boom during thelast decade, not just because of the formidable advancement of resolution. Improved contrast and imaging oflight atoms opens the possibilty of picometer scale mapping of atomic positions and more accurate chemicalquantification, increased probe currents allow for shorter acquisition times and higher signal-to-noise ratio for spectroscopy. The recent addition of chromatic aberration correction adds new capabilities improving the temporaldamping envelope of the objective lens. “Gentle” low voltage microscopy for carbon-based and organic materials and field-free imaging of magnetic materials with a Lorentz lens with a resolution close to atomic spatial resolution are key advantages of Cc-correction. Materials applications presented in this talk will be complemented by most recent results obtained onEurope's first chromatically and spherically corrected electron microscope. Besides the picometer preciselocalization of atoms in perovskite crystals, high-resolution spectroscopy both in scanning TEM and Cc¬corrected energy-filtered TEM provide element sensitive image maps for oxide hetero-interfaces on thelattice scale. Cc-corrected in-situ TEM at a specimen temperature higher than 600°C with atomic resolutionand nanomanipulation of single graphene layers are further examples.

It is well known that the amount of solar energy striking a 500500 kilometer portion of the earth is sufficient to meet the current energy demand of the entire planet. As such, the U.S. National Academy of Engineering has cited the economical capture and utilization of solar energy as one of the National Grand Challenges. Making fuels from sunlight is one of the strategic goals in the Department of Energy’s report, New Science for a Secure and Sustainable Energy Future. Because solar energy is an intermittent power source and the most suitable locations for solar power collection are desert regions and generally away from urban centers, it is essential that solar energy collection be coupled with energy storage technologies to be economical. Numerous storage solutions are being pursued, but the chemical storage of solar energy as a fuel is a superior concept due to the high energy density and the existing global infrastructure for fuel transport and storage. This talk will discuss a novel dual cavity, windowless, high temperature chemical reactor that converts concentrated solar thermal energy to Syngas, which is currently under development at the University of Florida. The cost effective, solar thermochemical production of Syngas, using an iron-based non-volatile metal oxide looping processes as a precursor for clean and carbon neutral synthetic hydrocarbon fuels such as methanol, methane, or synthetic petroleum, is the overarching project goal. The reactor uses water and recycled CO2 as the sole feed-stock and concentrated solar radiation as the sole energy source. Thus, the solar fuel is completely renewable and carbon neutral. A highly reactive, high surface area iron-based porous structure has been synthesized using a magnetically stabilized bed sintering technique. A hybrid reactor kinetic model has been developed and validated over a number of cycles in laboratory scale reactors. A 5000 sun solar simulator has been developed as an energy driver for the thermochemical reactions. Ongoing work involving the high temperature looping process to convert coal to hydrogen will also be considered.

After briefly reviewing past works on holographic computations of transport coefficients, I will show how one can derive a new and simple formula for bulk viscosity in the setting of the fluid-gravity correspondence using the null focusing equation for the horizon. The formula involves derivatives of the horizon values of bulk scalar fields with respect to the entropy and charge density. Using this formula one can straightforwardly reproduce several results in the literature that previously required numerical methods. I will conclude by showing our formula is exact, even though it apparently only involves horizon data. Our proof uses the fact that the hydrodynamics equations and transport coefficients are the same on any constant r holographic screen in the bulk.

Recently, anomalous superdiusion of ultra cold 87Rb atoms in an optical lattice has been observed along with a fat-tailed, Levy type, spatial distribution (Sagi et al PRL 108, 093002 (2012)). The anomalous exponents were found to depend on the depth of the optical potential. We find, within the framework of the semiclassical theory of Sisyphus cooling, three distinct phases of the dynamics, as the optical potential depth is lowered: normal diusion; Levy diusion; and x t3=2 scaling, the latter related to Obukhov's model (1959) of turbulence. The process can be formulated as a Levy walk, with strong correlations between the length and duration of the excursions. We show how an infinite covariant density describes the the momentum distribution, and explain how this non normalizable density plays a dual role to the stationary Boltzmann like equilibrium density.

Joint work with David Kessler.