Reversion phenomena of Cu-Cr alloys

Cu-Cr alloys which were given various aging and reversion treatments were investigated in terms of electrical resistivity and hardness. Transmission electron microscopy was one technique employed. Some results obtained are as follows: the increment of electrical resistivity after the reversion at a constant temperature decreases as the aging temperature rises. In a constant aging condition, the increment of electrical resistivity after the reversion increases, and the time required for a maximum reversion becomes shorter as the reversion temperature rises. The reversion phenomena can be repeated, but its amount decreases rapidly by repetition. At first, the amount of reversion increases with aging time and reaches its maximum, and then tends to decrease again. Hardness changes by the reversion are very small, but the hardness tends to soften slightly. Any changes in transmission electron micrographs by the reversion treatment cannot be detected

Generalized Cheeger-Gromoll Metrics and the Hopf map

We show, using two different approaches, that there exists a family of Riemannian metrics on the tangent bundle of a two-sphere, which induces metrics of constant curvature on its unit tangent bundle. In other words, given such a metric on the tangent bundle of a two-sphere, the Hopf map is identified with a Riemannian submersion from the universal covering space of the unit tangent bundle onto the two-sphere. A hyperbolic counterpart dealing with the tangent bundle of a hyperbolic plane is also presented.Comment: 17 pages, Dedicated to Professor Udo Simon on his seventieth birthda

Systematic description and key to streptomyces isolants from Chile-Atacama Desert, Hawaii, and Oregon soils

Systematic description and key to Streptomycetes isolants from Chile-Atacama Desert, Hawaii, and Oregon soil

Systematic description and key to Streptomyces isolants from Chile, Mexico and Arizona desert soils Progress report

Streptomycetes isolants from Chile, Mexico, and Arizona desert soil

Flavor Mass and Mixing and S_3 Symmetry -- An S_3 Invariant Model Reasonable to All --

We assume that weak bases of flavors (u, c)_{L,R}, (d,s)_{L,R}, (e, \mu) _{L,R}, (\nu_e, \nu_\mu)_{L,R} are the S_3 doublet and t_{L,R}, b_{L,R}, \tau_{L,R}, {\nu_\tau}_{L,R} are the S_3 singlet and further there are S_3 doublet Higgs (H_D^1, H_D^2) and S_3 singlet Higgs H_S. We suggest an S_3 invariant Yukawa interaction, in which masses caused from the interaction of S_3 singlet flavors and Higgs is very large and masses caused from interactions of S_3 doublet flavors and Higgs are very small, and the vacuum expectation value _0 is rather small compared to the _0. In this model, we can explain the quark sector mass hierarchy, flavor mixing V_{CKM} and measure of CP violation naturally. The leptonic sector mass hierarchy and flavor mixing described by V_{MNS} having one-maximal and one-large mixing character can also be explained naturally with no other symmetry restriction. In our model, an origin of Cabibbo angle is the ratio \lambda=_0 /_0 and an origin of CP violation is the phase of H_D^1.Comment: 16 page

3-D General Relativistic MHD Simulations of Generating Jets

We have performed a first fully 3-D GRMHD simulation with Schwarzschild black hole with a free falling corona. The initial simulation results show that a jet is created as in previous axisymmetric simulations. However, the time to generate the jet is longer than in the 2-D simulations. We expect that due to the additional azimuthal dimension the dynamics of jet formation can be modified.Comment: 4 pages Proc. Oxford Radio Galaxy Workshop ed. R. Laing & K. Blundell (San Francisco: PASP) in press (revised

Determining physical properties of the cell cortex

Actin and myosin assemble into a thin layer of a highly dynamic network underneath the membrane of eukaryotic cells. This network generates the forces that drive cell and tissue-scale morphogenetic processes. The effective material properties of this active network determine large-scale deformations and other morphogenetic events. For example,the characteristic time of stress relaxation (the Maxwell time)in the actomyosin sets the time scale of large-scale deformation of the cortex. Similarly, the characteristic length of stress propagation (the hydrodynamic length) sets the length scale of slow deformations, and a large hydrodynamic length is a prerequisite for long-ranged cortical flows. Here we introduce a method to determine physical parameters of the actomyosin cortical layer (in vivo). For this we investigate the relaxation dynamics of the cortex in response to laser ablation in the one-cell-stage {\it C. elegans} embryo and in the gastrulating zebrafish embryo. These responses can be interpreted using a coarse grained physical description of the cortex in terms of a two dimensional thin film of an active viscoelastic gel. To determine the Maxwell time, the hydrodynamic length and the ratio of active stress and per-area friction, we evaluated the response to laser ablation in two different ways: by quantifying flow and density fields as a function of space and time, and by determining the time evolution of the shape of the ablated region. Importantly, both methods provide best fit physical parameters that are in close agreement with each other and that are similar to previous estimates in the two systems. We provide an accurate and robust means for measuring physical parameters of the actomyosin cortical layer.It can be useful for investigations of actomyosin mechanics at the cellular-scale, but also for providing insights in the active mechanics processes that govern tissue-scale morphogenesis.Comment: 17 pages, 4 figure