An Improved Red Spectrum of the Methane or T Dwarf SDSS 1624+0029: The Role of the Alkali Metals

The blast-wave model for gamma-ray bursts (GRBs) has been called into question by observations of spectra from GRBs that are harder than can be produced through optically thin synchrotron emission. If GRBs originate from the collapse of massive stars, then circumstellar clouds near burst sources will be illuminated by intense gamma radiation, and the electrons in these clouds will be rapidly scattered to energies as large as several hundred keV. Low-energy photons that subsequently pass through the hot plasma will be scattered to higher energies, hardening the intrinsic spectrum. This effect resolves the "line-of-death" objection to the synchrotron shock model. Illuminated clouds near GRBs will form relativistic plasmas containing large numbers of electron-positron pairs that can be detected within approximately 1-2 days of the explosion before expanding and dissipating. Localized regions of pair annihilation radiation in the Galaxy would reveal past GRB explosions.     

利用层析成像的结果探讨安徽及邻区中强地震深部构造背景

利用层析成像的最新成果,对研究区(28°～39°N,112°～124°E)的中强地震深部构造环境进行了研究,结果表明:(1)研究区中强震位置、地表地质构造和活动构造单元的划分与上地壳速度结构之间存在一定的关联性。M≥6.0地震大多数分布在上地壳高速区与低速区的交接地带或高速区,低速区内的地震活动相对较少;分布在高速区的地震,主要活动在高速区内的速度变异地带。华北平原断块的边界带及其内部是研究区内主要的中强地震活动场所,该断块西、北部的裂陷盆地带在上地壳以间断的大片低速区为特征,在与高速区的交接地带,中强地震呈带状活动,并有活动断裂带的发育。北西向展布的周口-合肥-宣城低速条带分隔大别山、鲁西-安徽高速区,北侧与高速区的交接地带中强地震活动较为活跃,可能是华北、华南两大构造区在深部构造和现代活动构造上的一条重要分界线。(2)霍山-六安地区历史中强地震和近代小震活动频繁与东大别山中部在中地壳发育低速层及存在切穿地壳的两组深断裂有关。(3)安徽的中强地震活动在深部构造上分区特征明显,依据历史地震活动重演和发震构造条件(深部)类比的原则,对安徽未来存在发生5级左右地震的危险区进行了初步判定。     

The significance of imposex levels and TBT contamination in the red whelk, Neptunea antiqua (L.) from the offshore Irish Sea

The extent to which open seas and oceanic waters have been contaminated by TBT is unclear since most sampling programmes have concentrated on inshore areas, particularly near harbours. Accordingly, the red whelk, Neptunea antiqua L. (Mollusca: Prosobranchia), a sublittoral and dioecious prosobranch species, was selected to investigate the potential effects of TBT-induced imposex in the central western Irish Sea. The presence of imposex was noted in > 90% of all female whelks that were examined on a monthly basis over a 12-month period. However, the proliferation of the vas deferens was not considered severe enough to affect the reproductive capabilities of the population. Low concentrations of butyltins were detected in the soft tissues of all whelks examined, ranging from 0.009 to 0.112 microg g(-1) Sn dry wt There was no significant correlation between the documented imposex stages and total butyltin contamination, indicating that the species is not a reliable bioindicator species of the effects of this contaminant.