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691.
Curtis J. Saxton Kinwah Wu Helen Pongracic & Giora Shaviv 《Monthly notices of the Royal Astronomical Society》1998,299(3):862-876
The stand-off shock formed in the accretion flow on to a stationary wall, such as the surface of a white dwarf, may be thermally unstable, depending on the cooling processes which dominate the post-shock flow. Some processes lead to instability, while others tend to stabilize the shock. We consider competition between the destabilizing influence of thermal bremsstrahlung cooling, and a stabilizing process which is a power law in density and temperature. Cyclotron cooling and processes which are of order 1, 3/2 and 2 in density are considered. The relative efficiency and power-law indices of the second mechanism are varied, and particular effects on the stability properties and frequencies of oscillation modes are examined. 相似文献
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The process of cosmic ray acceleration up to energies in excess of 1020 eV at relativistic shock waves with large Lorentz factors, Γ≫1, requires ∼Γ2 particle energy gains at single reflections from the shock (cf. Gallant & Achterberg). In the present Letter , by applying numerical simulations we address an efficiency problem arising for such models. The actual efficiency of the acceleration process is expected to be substantially lower than the estimates of previous authors. 相似文献
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The prompt ( t ≲0.16 d) light curve and initial 9th-magnitude optical flash from GRB 990123 can be attributed to a reverse external shock, or possibly to internal shocks. We discuss the time decay laws and spectral slopes expected under various dynamical regimes, and the constraints imposed on the model by the observations, arguing that they provide strongly suggestive evidence for features beyond those in the simple standard model. The longer term afterglow behaviour is discussed in the context of the forward shock, and it is argued that, if the steepening after 3 d is due to a jet geometry, this is likely to be a result of jet-edge effects, rather than sideways expansion. 相似文献
698.
A Santulli A Modica C Messina L Ceffa A Curatolo G Rivas G Fabi V DAmelio 《Marine pollution bulletin》1999,38(12):173-1114
The paper reports the results of an experimental seismic survey in the open sea by an air gun, carried out to evaluate the effects of air gun acoustic waves on marine animals. Air gun blast exposition was found to have a marked influence on confined Dicentrarchus labrax. Our data, in fact, demonstrated a biochemical response to acoustic stress induced by air gun blasts. Variations of cortisol, glucose, lactate, AMP, ADP, ATP and cAMP in different tissues of D. labrax, indicate that fish have a typical primary and secondary stress response after air gun detonations. Radiography indicates that air gun blasts do not induce any macroscopic effect on skeletal apparatus. The variations of biochemical parameters returned within physiological values within 72 h indicating a rapid recovery of homeostasis after acoustic stress and no mortality was observed. 相似文献
699.
云南水汞的远震和近震前兆异常特征分析 总被引:2,自引:1,他引:1
本通过对云南西部7个水汞观测站,1990年 ̄1996年9月省内及邻区26次M≥5.0级地震的水汞资料进行异常时空强及其形态的分析研究,总结出云南水汞在远震和近震前的前兆异常特征,用这些前兆异常特征对1996年9月后1年内各观测站的水汞异常与所发生的地震进行检验,结果很好。此项研究,有助于对未来发震区的判定。 相似文献
700.
十足类甲壳动物多倍体育种进展 总被引:5,自引:1,他引:4
结合作者近期的研究,综述了近年来十足类甲壳动物多倍体育种的原理及诱导方法的进展,并对研究现状、存在问题和今后的发展方向进行了探讨。 相似文献