A New Method of Identifying 3D Null Points in Solar Vector Magnetic Fields

Employing the Poincare index of isolated null-points in a vector field, we worked out a mathematical method of searching for 3D null-points in coronal magnetic fields. After introducing the relevant differential topology, we test the method by using the analytical model of Brown & Priest. The location of null-point identified by our method coincides precisely with the analytical solution. Finally we apply the method to the 3D coronal magnetic fields reconstructed from an observed MDI magnetogram of a super-active region (NOAA 10488). We find that the 3D null-point seems to be a key element in the magnetic topology associated with flare occurrence.     

A Differential Abundance Analysis of HD219175 A and B

The abundances of the wide binary pair HD 219175 A and B are determined and compared using a line-by-line differential analysis. No evidence for difference has been found in the abundances of Fe, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Ni, Cu and Ba. Our results support a physical relation between the two components of HD 219175.     

加拿大科学家研究表明——中国人身材比率最健康

加拿大安大略麦克马斯特大学教授领导的研究表明，使用测量人的腰臀围比率的方法，是预测一个人是否肥胖和是否面临患心脏病危险的最佳方法。这个方法比目前世界上医学界普遍使用的体重指数（体重除以身高的平方）的方法要准确3倍。加拿大科学家还指出，按照膜臀比，中国人身材的比率最健康。     

X Per新发射相的不寻常变化

对ＸＰｅｒ新发射相连续四年的光学光谱和近红外光度监测结果，ＸＰｅｒ近两年的变化不同寻常，主要表现以下两点：（１）尽管它的光学光度Ｖ星等只恢复至失去气壳前的亮度，但Ｈａ发射线等值宽度和近红外，Ｊ，Ｈ和Ｋ光度地超过了历史记录的最大值，分别达到了１６．３４Ａ和５．３＾ｍ，５．３＾ｍ和５．１＾ｍ，表明ＸＰｅｒ新发射相气南的密度和尺度较都大，（２）我们首次观测到ＸＰｅｒ近红外光度和Ｈα发射线等值宽度变化趋势     

Can the bump in the composite spectrum of GRB 910503 be an emission line feature of gamma-ray bursts？

Appearing in the composite spectral data of BATSE, EGRET and COMPTEL for GRB 910503, there is a bump at around 1600 keV. We perform a statistical analysis on the spectral data, trying to find out if the bump could be accounted for by a blue-shifted and significantly broadened rest frame line due to the Doppler effect of an expanding fireball surface. We made an F-test and adopted previously proposed criteria. The study reveals that the criteria are well satisfied and the feature can be interpreted as the blue shifted 6.4 keV line. Prom the fit with this line taken into account, we find the Lorentz factor of this source to be P = 116-9+9 (at the 68% confident level,△x2 = 1) and the rest frame spectral peak energy to be E0,p- 2.96-0.18+0.24 keV. Although the existence of the emission line feature requires other independent tests to confirm, the analysis suggests that it is feasible to detect emission line features in the high energy range of GRB spectra when taking into account the Doppler effect of fireball expansion.     

《物种起源》的起源

查尔斯·达尔文的《物种起源》一书，全名是《物竞天择，适者生存之物种起源论》，出版于1859年11月24日。这是一本科学著作当中的经典，被看作是进化生物学的奠基之作。在1872年出版第6版的时候，书名被简化为《物种起源》。达尔文通过这本著作介绍了生物种群经过一个漫长的自然选择过程而发生世代演化的理论，并在书中列举出了生命以分支进化和种系遗传的形式产生分异的大量例证，     

用Monte Carlo方法拟合超新星SN1993J的早期光谱

通过把从光球辐射出来的连续能谱能量分成大量的光子包，然后用ＭｏｎｇｅＣａｒｌｏ方法跟踪这些光子包从光球向超新星包层外运动的过程，这一方法能很好的解决超新星的光谱拟合中的谱线覆盖问题，由于同时编制了用于构造超新星包层中的密度结构和丰度分布的程序，以及大量的用比较观测和理论拟合的绘图和支持程序，使我们的ＭｏｎｔｅＣａｒｌｏ光谱拟合软件包能够很好的运用于超新星的早期光谱研究。本文给出了ＳＮ１９９３Ｊ在１     

Physical Parameters of a Flare Dervied from Multi—line 2D Spectroscopy

Time series of 2D spectra of Hα and CaⅡ λ8542 for a flare of 1999 December 22 are obtained and analyzed with a new fitting technique. The method we proposed can simultaneously yield the four parameters: the line source function, the optical thickness at line center, the line-of-sight velocity and the Doppler width. We present the spatial distributions of the physical parameters and their temporal evolutions determined from the 2D spectra. Our results are consistent with the general picture predicted by the flare dynamic models.