Electron diffraction study of a noncrystalline Zr−Ni phase

Metastable noncrystalline phases were retained by rapid quenching Zr?Ni alloys from the liquid state over the composition range 25 to 70 at. pct Ni. The X-ray and electron diffraction patterns of the metastable phases showed broad diffraction maxima indicating absence of long range crystalline order in them. The pair function of the metastable noncrystalline phase in a splat cooled Zr_0.7Ni_0.3 alloy was determined from the electron diffraction data. The various interatomic distances corresponding to the positions of the peaks in the pair function curve were determined. The nearest-neighbors coordination number was computed from the area under the first peak. The radius of the first near neighbor shell is 2.95 Å and the ratio of the second to the first interatomic distance is equal to 1.41 which is significantly lower than that observed in most metallic liquids. The local atomic arrangement in the non-crystalline Zr_0.7Ni_0.3 alloy was shown to be based on simple fcc coordination.     

On the characteristics of the threshold stress for superplastic flow in Zn-22 Pct Al

Formerly Graduate Research Assistant, Department of Chemical and Biochemical Engineering, Materials Science and Engineering, University California-Irvine.     

The kinetics and shear threshold of transient and rolling interactions of L-selectin with its ligand on leukocytes

The kinetics of rolling and transient adhesions through selectins may depend on the kinetics and mechanical properties of the selectin:ligand bond, as well as on cellular properties including receptor-anchoring to the cell membrane and cytoskeleton. Kinetics are known to depend on the selectin and may also be ligand dependent. Here, we study the kinetics of transient and rolling interactions of leukocytes with L-selectin immobilized on a substrate. Remarkably, all properties examined are similar to those seen when the sidedness is opposite, i.e., when the L-selectin ligand is on the substrate and when the ligand is isolated from HEV rather than present on leukocytes. The similar properties include rolling velocity, a threshold shear stress above 0.4 dyn/cm2 required to support rolling, a k degreesoff of 7.0 to 6.8 s-1 for the L-selectin tether bond, and a mechanical bond length of 0.24 to 0.20 A. Our results argue against a model in which L-selectin shedding mediates rolling. Furthermore, the fast and force-resistant kinetic properties suggest that L-selectin is specialized dynamically for tethering leukocytes to vessel walls and adherent leukocytes.     

Is the intracellular pH threshold an anaerobic threshold from the view point of intracellular events?: a brief review

Intracellular biochemical changes could be monitored noninvasivery and continuously by using nuclear magnetic resonance (NMR). In about the last decade, intracellular behavior of phosphorus compounds and pH during muscle contraction in man have been studied by 31P nuclear magnetic resonance spectroscopy (31P-MRS). During incremental load, lactic acidosis was followed by a decline in intracellular pH. 31P-MRS studies has been definitely proved that this change in intracellular pH shows the threshold behavior. Some reports discussed the intracellular pH threshold (pHT) as an anaerobic threshold (AT) from the view point of intracellular events. However, our studies revealed that pHT did not reflect the onset of lactate production. In this article, studies of intracellular pH of working muscle were reviewed in relation to an anaerobic threshold.