The shear-transformation-zone (STZ) theory of plastic deformation predicts that sufficiently soft, noncrystalline solids are linearly unstable against forming periodic arrays of microstructural shear bands. A limited nonlinear analysis indicates that this instability may be the mechanism responsible for strain softening in both constant-stress and constant-strain-rate experiments. The analysis ...

The development of zeolite-like structures with extra-large pores (>12-membered rings, 12R) has been sporadic and is currently at 30R. In general, templating via molecules leads to crystalline frameworks, whereas the use of organized assemblies that permit much larger pores produces noncrystalline frameworks. Synthetic methods that generate crystallinity from both discrete templates and organiz...

Enzymes that catalyze the oxidation of amino acids have been found in microorganisms, mammals, and lower animals. As yet, few of these have been obtained in a state of high purity, and many studies on these enzymes have therefore been carried out with relatively crude preparations. The detailed mechanism of the flavoprotein-cat.alyzed oxidative dcamination of amino acids remains to be <Jlucidat...

The development of short-to-medium-range order in atomic arrangements has generally been observed in noncrystalline solid systems such as metallic glasses. Whether such medium-range order (MRO) can exist in materials at well above their melting or glass-transition temperature has been a long-standing important scientific issue. Here, using ab initio molecular dynamics simulations, we show that ...

We introduce the concept of computerized tomographic microscopy in magnetic resonance imaging using the magnetic fields and field gradients from a ferromagnetic probe. We investigate a configuration where a two-dimensional sample is under the influence of a large static polarizing field, a small perpendicular radio-frequency field, and a magnetic field from a ferromagnetic sphere. We demonstrat...

Heterogeneous catalysis performed in the liquid phase is an important type of catalytic process which is rarely studied in situ. Using microfocus X-ray fluorescence and X-ray diffraction computed tomography (μ-XRF-CT, μ-XRD-CT) in combination with X-ray absorption near-edge spectroscopy (XANES), we have determined the active state of a Mo-promoted Pt/C catalyst (NanoSelect) for the liquid-phase...

Chien-Chun Chen,1 Jianwei Miao,2 C. W. Wang,3 and T. K. Lee1 1Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan 2Department of Physics and Astronomy and California NanoSystems Institute, University of California, Los Angeles, California 90095, USA 3Department of Physics, University of Florida, Gainesville, Florida 32611, USA Received 9 March 2007; revised manuscript received ...