Oblique Ion Two-Stream Instability in the Foot Region of a Collisionless Shock

Electrostatic behavior of a collisionless plasma in the foot region of high Mach number perpendicular shocks is investigated through the two-dimensional linear analysis and electrostatic particle-in-cell (PIC) simulation. The simulations are double periodic and taken as a proxy for the situation in the foot. The linear analysis for relatively cold unmagnetized plasmas with a reflected proton beam shows that obliquely propagating Buneman instability is strongly excited. We also found that when the electron temperature is much higher than the proton temperature, the most unstable mode is the highly obliquely propagating ion two-stream instability excited through the resonance between ion plasma oscillations of the background protons and of the beam protons, rather than the ion acoustic instability that is dominant for parallel propagation. To investigate nonlinear behavior of the ion two-stream instability, we have made PIC simulations for the shock foot region in which the initial state satisfies the Buneman instability condition. In the first phase, electrostatic waves grow two-dimensionally by the Buneman instability to heat electrons. In the second phase, highly oblique ion two-stream instability grows to heat mainly ions. This result is in contrast to previous studies based on one-dimensional simulations, for which ion acoustic instability further heats electrons. The present result implies that overheating problem of electrons for shocks in supernova remnants is resolved by considering ion two-stream instability propagating highly obliquely to the shock normal and that multi-dimensional analysis is crucial to understand the particle heating and acceleration processes in shocks.Comment: 20 pages, 9 figures, accepted for publication in Ap

Seismic Performance of Precast Column-Foundation Connection Assembled by Post-Tensioning

In order to develop design recommendations for column-foundation connection assembled by post-tensioning in seismic regions, cyclic loading tests were carried out on 14 test units simulating such kind of connections under earthquake loading. The tests were consisted of two series: Series A was mainly for comparison between precast reinforced and precast prestressed concrete column-foundation connections, and Series B for investigating differences between test units with grouted and ungrouted tendons. The main experimental parameter other than the above was an axial load level

Photoreactions of retinochrome at very low temperatures

AbstractRetinochrome is one of the retinal proteins found in the retina of cephalopods. It catalyses the light isomerization of retinal from the all-trans to the 11-cis form. On cooling to 25 K, the absorption peak of retinochrome (λmax 490 nm) was broadened with a shoulder, showing the spectrum steepened on the long wavelength side. On irradiation with yellow-green light (550 nm), retinochrome produced an intermediate with λmax at a shorter wavelength, around 465 nm, and a lower extinction coefficient than lumiretinochrome. It changed to lunuretinochrome (λmax 475 nm) in the dark on warming to liquid nitrogen temperature. We shall call this new intermediate prelunuretinochrome

Enhancement or Suppression of ACE Inhibitory Activity by a Mixture of Tea and Foods for Specified Health Uses (FOSHU) That Are Marketed as “Support for Normal Blood Pressure”

The ACE inhibitory activities of mixtures of FOSHUs (Healthya, Goma-Mugicha, Lapis Support and Ameal) were examined in order to identify any antihypertensive interactions. Among combinations of Healthya with other samples that contain active peptides, only that with Ameal was found to have no inhibitory activity. Enhanced activity was observed in 2 other mixtures. The activity of a mixture of tea polyphenols and the whey component extracted from an Ameal solution was significantly decreased, thus demonstrating that whey protein lowered the ACE inhibitory activity of Healthya. Although oral administration of tea polyphenols alone significantly decreased SBP in SHR at 2 and 4 hr, combined administration with Ameal failed to decrease SBP at the same time points. In conclusion, the simultaneous intake of tea and FOSHUs that contain active peptides might affect daily self-antihypertensive management via enhancement or suppression of ACE inhibitory activity