Cosmological constraints from Chandra X-ray observations of galaxy clusters

Chandra X-ray observations of rich, dynamically relaxed galaxy clusters allow the properties of the X-ray gas and the total gravitating mass to be determined precisely. Here, we discuss how Chandra observations may be used as a powerful tool for cosmological studies. By combining Chandra X-ray results on the X-ray gas mass fractions in clusters with independent measurements of the Hubble constant and the mean baryonic matter density of the universe, we obtain a tight constraint on the mean total matter density of the universe, Ο_m, and an interesting constraint on the cosmological constant, Ο_Λ. Using these results, together with the observed local X-ray luminosity function of the most X-ray luminous galaxy clusters, a mass-luminosity relation determined from Chandra and ROSAT X-ray data and weak gravitational lensing observations, and the mass function predicted by numerical simulations, we obtain a precise constraint on the normalization of the power spectrum of density fluctuations in the nearby universe,σ₈. We compare our results with those obtained from other, independent methods. This revised version was published online in July 2006 with corrections to the Cover Date.     

Deep Processes of Basin Evolution:A Case Study of the Southern Songliao Basin and Adjacent Area,NE China in Mesozoic-Cenozoic

1IntroductionOne of the key factors related to basin geody-namics is deep process controlling formation and evolution of sedimentary basin. Depth and tempera-ture of asthenosphere,existence of mantle plume,occurrence of mantle melting,and amounts of melts under depressurization during thinning of lithosphere are controlling factors influenced formation and characteristics of extensional basin directly (Li,1994). Rifting is probably governed by frictional forces exerted on the base of litho…     

长江三峡工程地壳形变监测网络

长江三峡工程地壳形变监测网络，采用了当今高精度GPS、INSAR空间大地测量技术，并与精密水准测量，精密重力测量，精密激光测距和峒体连续形变监测等技术相结合，构成一个空间上点、线、面结合，时间上长、中、短兼顾的高精度，高时空分辨率的地壳形变监测网络。该网络既可获取三峡库区特别是库首区区域形变场和区域应变场的动态变化，监测库区主要断层活动，为水库诱发地震预测及研究服务，又可用于气象、滑坡地质灾害监测等，该监测网络于1997年底开始建设，2001年6月建成，到目前为止，已获得大量宝贵的观测资料，必将产生显著的经济效益和社会效益。     

银河系运动学参数的确定

利用 2 0 2个太阳附近疏散星团的视向速度和自行观测资料 ,对太阳的运动和银河系的运动学参数进行了研究。其中 ,距离在 0 .5kpc到 2kpc之间的 12 8个疏散星团对平均太阳运动分量的解算结果是 (u0 ,v0 ,w0 ) =(- 13.8± 1.4 ,- 5 .0± 1.6 ,- 11.6± 2 .9)km/s ;Oort常数和银河系径向运动参数的解算结果分别为 (A ,B) =(16 .9± 1.1,- 11.6± 2 .6 )km·s- 1·kpc- 1及 (C ,D) =(2 .5± 1.1,- 2 .1± 0 .9)km·s- 1·kpc- 1。     

Seismic rays in an ellipsoidal earth model: theoretical analysis and estimation of deviations due to the ellipticity

Summary. A first-order form of the Euler's equations for rays in an ellipsoidal model of the Earth is obtained. The conditions affecting the velocity law for a monotonic increase, with respect to the arc length, in the angular distance to the epicentre, and in the angle of incidence, are the same in the ellipsoidal and spherical models. It is therefore possible to trace rays and to compute travel times directly in an ellipsoidal earth as in the spherical model. Thus comparison with the rays of the same coordinates in a spherical earth provides an estimate of the various deviations of these rays due to the Earth's flattening, and the corresponding travel-time differences, for mantle P -waves and for shallow earthquakes. All these deviations are functions both of the latitude and of the epicentral distance. The difference in the distance to the Earth's centre at points with the same geocentric latitude on rays in the ellipsoidal and in the spherical model may reach several kilometres. Directly related to the deformation of the isovelocity surfaces, this difference is the only cause of significant perturbation in travel times. Other differences, such as that corresponding to the ray torsion, are of the first order in ellipticity, and may exceed 1 km. They induce only small differences in travel time, less than 0.01s. Thus, we show that the ellipticity correction obtained by Jeffreys (1935) and Bullen (1937) by a perturbational method can be recovered by a direct evaluation of the travel times in an ellipsoidal model of the Earth. Moreover, as stated by Dziewonski & Gilbert (1976), we verify the non-dependence of this correction on the choice of the velocity law.     

Magnetic susceptibility variations of the Edicaran cap carbonates in the Yangtze platform and their implications for paleoclimate

1 INTRODUCTION One of the most intriguing phenomena in the late Neoproterozoic (~750 to 543 Ma) is the globa occurrence of thin carbonates that directly overlie glacial deposits in almost every continent (Kennedy 1996; Hoffman et al., 1998; Hoffman and Schrag 2002; Brasier and Shields, 2000; James et al., 2001 Jiang et al., 2003; Nogueira et al., 2003). These “cap carbonates”, commonly several to tens of meters thick, have attracted enormous interests because o their unusually negati…     

岩体三维节点偶对分析及其应用

本文讨论了节点偶对分析的三维扩展。节点偶对分析是针对摩擦滑动节理单元的约束边界进行的序列矢量判定。在三维节理单元的分析中,几何约束和相应的力学判据极为复杂,采用节点偶对等效结合力方法才能迎刃而解。文中对三维转向节理模型的分析得到合理的结果,它表明本文所提出的方法可成功地应用于节理岩体的有限元分析。     

1966年邢台7.2级地震的构造背景和发震构造

本文根据石油地质勘探的最新资料和元-济人工地震地壳测深剖面相应地段重新解释的结果,分析了邢台7.2级地震的构造背景和发震断裂。研究结果表明,7.2级地震震中位于束鹿断陷盆地南部次凹的东缘,该次凹发育在由新河断裂等4条缓倾铲形正断裂分制围限地台盖层而成的“斛”状构造块体上,块体之下的地壳中存在两条倾向相反的高角度断裂;地震与断陷主断裂及其控制的断陷盆地并非是简单的对应关系,7.2级地震的发震断裂不是单一的缓倾铲形新河断裂或其下方的高角度的F_3断裂和深部的东断裂,而是它们的组合,且高角度断裂是发震断裂的主要部分     

渭河盆地北缘断裂带活动特征的初步研究

本文从渭河盆地北缘断裂的形成和活动时代,活动特征等资料出发,结合北缘断裂带及整个盆地历史地震活动和新生界地层发育特征的综合分析,对北缘断裂带的活动期次,主要断层的运动幅度和滑动速率及其时空演变规律和机制等问题进行了探讨。文章指出,北缘断裂带的形成是一个由盆地中心向北逐渐扩展的过程,自上新世起,断层活动明显有东强西弱的变化特征,而且扩展方向也发生了偏转。这一转变及活动强度的东西差异与山西剪切带对渭河盆地的影响密切相关