General Relativistic MHD Simulations of the Gravitational Collapse of a Rotating Star with Magnetic Field as a Model of Gamma-Ray Bursts

We have performed 2.5-dimensional general relativistic magnetohydrodynamic (MHD) simulations of the gravitational collapse of a magnetized rotating massive star as a model of gamma ray bursts (GRBs). This simulation showed the formation of a disk-like structure and the generation of a jet-like outflow inside the shock wave launched at the core bounce. We have found the jet is accelerated by the magnetic pressure and the centrifugal force and is collimated by the pinching force of the toroidal magnetic field amplified by the rotation and the effect of geometry of the poloidal magnetic field. The maximum velocity of the jet is mildly relativistic ($\sim$ 0.3 c).Comment: 4 pages, 1 figure, aipTEX, contribution to the 2003 GRB Conference, held at Santa Fe, N

太陽の捩じれた磁気ループでのリング状のエネルギー解放

We investigate the magnetohydrodynamic (MHD) instability of the magnetic loop in association with the solar flare. We use \u27safety factor\u27 q to describe the local twist of the magnetic loop where low q value means the strong twist, then it becomes more unstable for the MHD instability.We present the q profile on the equilibrium for two types which may correspond to small and large flare. One type corresponding to small flare is the slim cylindrical untwisted magnetic loop in initial stage. When the tube is twisted, low q region is localized around the axis of the center of the loop. We conclude that the localized low q region must be ring shaped. The energy release by MHD instability can be localized with the ring shaped region. The other type is barrel shaped untwisted magnetic loop which may correspond to the large flare. After the twist, low q region is wide along the axis. The MHD instability is caused on the whole magnetic loop, therefore the energy release is global

6種類の血中膵酵素値に及ぼす加齢および性の影響

The serum levels of some pancreatic enzymes have been reported to be affected by age and gender. Currently, serum total amylase, pancreatic isoamylase (P-amylase) , lipase , trypsin (ogen) , pancreatic phospholipase A(2) (PLA(2)) , and elastase I are utilized in diagnosing pancreatic diseases. We here compared age and gender-related alterations of these six pancreatic enzymes in healthy subjects to delineate different properties among the enzymes. Subjects were 155 males and 172 females between ages 20 and 79 years who were apparently healthy, and were stratified by age and sex. PLA(2) and elastase I were assayed by RIA, trypsin (ogen) by EIA and others by activity. The pancreatic enzymes, except PLA(2), were significantly elevated with age, although they declined in males in the 260 age group. There were significant sex differences in total amylase and P-amylase. Total amylase was significantly higher in females than in males in the 260 age group, P-amylase in the 40-49 age group. Age should be considered in the valuation of serum enzymes except PLA(2), sex difference should be considered in the valuation of amylase (total and P-amylase).ある種の血中膵酵素値は加齢や性により影響を受けることが知られている。現在膵疾患の診断に利用されている6種類の膵酵素，アミラーゼ，P－アミラーゼ，リパーゼ，トリプシン，フォスフォリパーゼA(2)（PIA(2)），そしてエラスターゼⅠの血中値に及ぼす加齢および性の影響を比較検討した。健常者327名（男性：155名，女性：172名，年齢：20－79歳）を対象として，年齢および性により層別化して検討した。PLA(2)とエラスターゼⅠはRIA，トリプシンはEIA，そして他の酵素は活性を測定した。PLA(2)以外の血中月率酵素値は加齢とともに有意に上昇した。しかし男性では60代以降低下した。性差はアミラーゼとP－アミラーゼとに有意差が認められた。すなわち，アミラーゼは60代以降に，P－アミラーゼは40－49歳群でそれぞれ男性より女性において有意の高値を示した。PLA(2)以外の血中膵酵素値を評価する際には加齢による影響を考慮すべきであり，アミラーゼおよびP－アミラーゼの血中値を評価する際には性を考慮すべきである

Group velocity and causality in standard relativistic resistive magnetohydrodynamics

Group velocity of electromagnetic waves in plasmas derived by standard relativistic resistive MHD (resistive RMHD) equations is superluminal. If we assume that the group velocity represents the propagation velocity of a signal, we have to worry about the causality problem. That is, some acausal phenomena may be induced, such that information transportation to the absolute past and spontaneous decrease in the entropy. Here, we tried to find the acausal phenomena using standard resistive RMHD numerical simulations in the suggested situation of the acausal phenomena. The calculation results showed that even in such situations no acausal effect happens. The numerical result with respect to the velocity limit of the information transportation is consistent with a linear theory of wave train propagation. Our results assure that we can use these equations without problems of acausal phenomena.Comment: 28 pages, 10 figure

A relativistic two-stream instability in an extremely low-density plasma

A linear analysis based on two-fluid equations in the approximation of a cold plasma, wherein the plasma temperature is assumed to be zero, demonstrates that a two-stream instability occurs in all cases. However, if this were true, the drift motion of electrons in an electric current over a wire would become unstable, inducing an oscillation in an electric circuit with ions bounded around specific positions. To avoid this peculiar outcome, we must assume a warm plasma with a finite temperature when discussing the criterion of instability. The two-stream instability in warm plasmas has typically been analyzed using kinetic theory to provide a general formula for the instability criterion from the distribution function of the plasma. However, the criteria based on kinetic theory do not have an easily applicable form. Here, we provide an easily applicable criterion for the instability based on the two-fluid model at finite temperatures, extensionally in the framework of special relativity. This criterion is relevant for analyzing two-stream instabilities in low-density plasmas in the universe and in Earth-based experimental devices.Comment: 18pages, 4 figures, accepted for pubblication on Po