用超速CT机检测99例无症状香港中国人降低钙指数

回顾分析Ｍａｔｉｌｄａ医院超速ＣＴ室筛选首批病人中９９例中国人资料，很明显从通常采用１３０－１００Ｈｏｕｎｓｆｉｅｌｄ单位作为检出冠状血管钙化的基数应用至中国人身上其阈值数目需要降低，同时，我们也发现如果病人年龄按每１０年范围分组（２１－３０，３０－４０，４１－５０，５１－６０）而计算其超速ＣＴ的钙化指数会较随机男女一起按平均计算更易区分其差异．进一步分析显示，男性中年时候超速ＣＴ指数已达最高值，而女性则晚１０年方达最高值，因此，为了更易探测冠脉循环内钙化倾向应作出超速ＣＴ检出钙化的指数数目．这些实践经验对动脉粥样硬化过程的预测或预防有实际意义．     

Effects of Young's modulus on fault displacement

Elastic crack models predict a linear relationship between displacement (u) and rupture (trace) length (L) during slip in a fault zone. Attempts to find universal-scaling laws for L/u, however, have generally failed. Here I propose that these attempts have failed because they do not take into account the changes in the mechanical properties, in particular Young's modulus (stiffness), of the fault zone as it evolves. I propose that Young's modulus affects fault displacement both spatially and temporally: spatially when the trace of a fault at a given time dissects host rocks of different stiffnesses, and temporally when the stiffness of the fault zone itself changes. During the evolution of an active fault zone, the effective Young's modulus of its damage zone and fault core normally decreases, and so does the L/u ratio of the fault. By contrast, during inactive periods sealing and healing of the damage zone and core may increase the stiffness, hence the L/u ratio in subsequent slips. This model predicts that not only will the scaling of L/u within a given fault population vary in space and time, but also that of individual faults. To cite this article: A. Gudmundsson, C. R. Geoscience 336 (2004).     

Modélisation du transport réactif en milieux poreux non saturés avec une méthode ELLAM en maillage variable

Modelling contaminant transfer with biological/chemical/radioactive processes needs appropriate numerical methods able to reproduce sharp concentration fronts. In this work, we develop a new Eulerian–Lagrangian Localized Adjoint Method (ELLAM) for solving the reactive transport equation with non-constant coefficients. To avoid interpolation (leading to errors), we use a moving grid to define the solution and test functions. The method is used to simulate first the infiltration of solute into a column of unsaturated porous medium and second the multispecies transport. The developed ELLAM gives accurate results without non-physical oscillations or numerical diffusion, even when using large time steps. To cite this article: A. Younes, C. R. Geoscience 336 (2004).     

Le Silurien de la région d'Oulad Abbou (Meseta occidentale,Maroc) : une sédimentation péritidale sous contrôle tectonique

In the Oulad Abbou syncline, western coastal Meseta, the Silurian deposits exhibit siliciclastic or mixed siliciclastic/carbonate tidal facies that recorded alkaline basalt flows and syn-sedimentary deformations. These facies are staked into peritidal shallowing upward sequences reflecting the evolution from an infratidal to a supratidal environment. These sequences recorded low-amplitude and high-frequency sea-level variations. The built-up of these rhythmic sequences is related to distensive tectonic that allowed the development of isolated platform from extensive siliciclastic influx. This tectonic event is well recorded in the palaeogeographic evolution of the northern Gondwana platform during the Lower Palaeozoic time. To cite this article: A. Attou, N. Hamoumi, C. R. Geoscience 336 (2004).     

Geological and SHRIMP II U-Pb constraints on the age and origin of the Breves Cu-Au-(W-Bi-Sn) deposit,Carajás,Brazil

The Breves deposit in the Carajás Copper-Gold Belt, Brazil, a member of the Cu-Au-(W-Bi-Sn) group of deposits, contains about 50 Mt of 1.22% Cu, 0.75 g/t Au, 2.4 g/t Ag, 1,200 g/t W, 70 g/t Sn, 175 g/t Mo and 75 g/t Bi. It is hosted by sandstones and siltstones of the Águas Claras Formation (minimum age of 2,681±5 Ma) in the roof zone of a complex, highly altered granite intrusion. The mineralisation is disseminated in a greisenized zone, resulting from alteration of probable monzogranites and syenogranites. The ore-bearing greisen contains abundant xenomorphic quartz in association with Fe-chlorite and muscovite. The gangue assemblage also includes fluorite, tourmaline, and minor amounts of monazite, xenotime, chlorapatite, thorite, zircon, calcite, siderite and bastnäesite. Copper mineralisation is dominated by chalcopyrite associated with pyrite, arsenopyrite, pyrrhotite and molybdenite. Gold particles, in equilibrium with native bismuth, are common as inclusions in chalcopyrite. The greisen contains sub-economic concentrations of tungsten and niobium that are related to the presence of ferberite, qitianlingite and Nb-rutile. SHRIMP II zircon dating of the host granites gives ²⁰⁷Pb/²⁰⁶Pb ages of 1,878±8 and 1,880±9 Ma for two phases, and a combined age of 1,879±6 Ma. SHRIMP II dating of monazite and xenotime grains in late- to post-mineralisation veins gives a combined ²⁰⁷Pb/²⁰⁶Pb age of 1,872±7 Ma, indistinguishable from the ages of the granites. This provides a genetic connection between the Breves deposit and the ca. 1.88 Ga A-type granite magmatism that typifies the Carajás Belt as part of a much larger, intracratonic magmatic province that extends over much of the Amazonian Craton. The recognition of this association has exploration implications, not only for the geophysical signature of the granite roof zones, but also for likely geochemical dispersion around the deposits of this type.Editorial handling: G. Beaudoin     

Settlement analysis of rectangular piles in nonhomogeneous soil using a Winkler model approach

An analytical approach using a Winkler model is investigated to provide analytical solutions of settlement of a rectangular pile subjected to vertical loads in nonhomogeneous soils. For a vertically loaded pile with a rectangular cross section, the settlement influence factor of a normal pile in nonhomogeneous soils is derived from Mindlin's solution for elastic continuum analysis. For short piles with rectangular and circular cross sections, the modified forms of settlement influence factors of normal piles are produced taking into account the load transfer parameter proposed by Randolph for short circular piles. The modulus of subgrade reaction along a rectangular pile in nonhomogeneous soils is expressed by using the settlement influence factor related to Mindlin's solution to combine the elastic continuum approach with the subgrade‐reaction approach. The relationship between settlement and vertical load for a rectangular pile in nonhomogeneous soils is available in the form of the recurrence equation. The formulation of settlement of soils surrounding a rectangular pile subjected to vertical loads in nonhomogeneous soils is proposed by taking into account Mindlin's solution and both the equivalent thickness and the equivalent elastic modulus for layers in the equivalent elastic method. The difference of settlement between square and circular piles is insignificant, and the settlement of a rectangular pile decreases as the aspect ratio of the rectangular pile cross section increases. The comparison of results calculated by the present method for a rectangular pile in nonhomogeneous soils has shown good agreement with those obtained from the analytical methods and the finite element method. Copyright © 2014 John Wiley & Sons, Ltd.     

The Cretaceous (Cenomanian) continental record of the Laje do Coringa flagstone (Alcântara Formation), northeastern South America

The fossil taxa of the Cenomanian continental flora and fauna of São Luís Basin are observed primarily in the bone bed of the Laje do Coringa, Alcântara Formation. Many of the disarticulated fish and tetrapod skeletal and dental elements are remarkably similar to the chronocorrelate fauna of Northern Africa. In this study, we present a summary of the continental flora and fauna of the Laje do Coringa bone-bed. The record emphasizes the existence of a trans-oceanic typical fauna, at least until the early Cenomanian, which may be interpreted as minor evolutionary changes after a major vicariant event or as a result of a land bridge across the equatorial Atlantic Ocean, thereby allowing interchanges between South America and Africa. The paleoenvironmental conditions in the northern Maranhão State coast during that time were inferred as forested humid areas surrounded by an arid to semi-arid landscape.     

古/中元古代界线:1.8Ga

年代地层表是我们描述地球历史演化的时间框架,也隐含着我们对地球演化过程的基本认识,承载着一系列核心科学问题。现有的国际前寒武纪地质年表存在不少问题,还没有被普遍接受的新方案。在现行国际地层年表(IUGS 1989—2004)中,20～18亿年被称为造山纪,18～16亿年被称为固结纪,16～14亿年被称为盖层纪,也即:造山运动结束到盖层发育之间的过渡时期为固结纪,而将盖层的广泛发育作为中元古代的开始。在我国,由于"吕梁运动"是华北克拉通结晶基底最终形成的标志性构造-热事件,此后发育以长城系-蓟县系-青白口系为代表的地台型沉积盖层,因此我国地质界一直以长城系的底界代表中元古代的开始,并根据"吕梁运动"结束时间,将古/中元古代的时间界线置于18亿年。2012年国际地层委员会提出了一份全新的全球前寒武纪地质年代表划分建议方案,其中2060～1780Ma阶段被称为古元古代哥伦比亚纪,主要以Columbia超大陆的聚合为特征;而之后17. 8～8. 5亿年的近10亿年间,则被定义为罗迪尼亚纪,代表了从Columbia超大陆裂解到Rodinia超大陆聚合的漫长阶段。即这一新建议方案的古/中元古代界线为17. 8亿年,与我国学者长期以来所坚持的古/中元古代分界是基本一致的。在华北克拉通,"吕梁运动"的结束时间在～18亿年,此后整体处于多期裂解的陆内伸展环境,长城系-蓟县系基本上属于连续的陆表海沉积。近年来的研究表明,燕山地区长城系的底界年龄约为17亿年,长城系与蓟县系的分界则为16亿年。如果一味按照现行国际地层划分方案,其古/中元古代的界线(16亿年)将对应于长城系-蓟县系的分界,华北克拉通这套盖层型沉积将被人为分割为两部分,这显然是很不合理的。值得注意的是,在华北克拉通中部吕梁地区发育的小两岭组火山岩和在其南部地区发育的、也是世界范围内同时期最大规模的火山活动——熊耳群火山-沉积岩系,是华北克拉通结晶基底之上最早发育的盖层沉积,其起始形成时间约为18亿年。这与新建议的古/中元古代分界非常接近。从全球地质演化来看,从18到16亿年,造山作用结束,Columbia超大陆开始裂解,岩浆作用方式和岩浆岩组合类型及其地球化学特征发生明显改变,如斜长岩、环斑花岗岩在世界主要克拉通均有发育。与此同时,稳定沉积盖层开始广泛发育,条带状铁建造(BIF)消失,代之以鲕状或粒状矿物集合体组成的浅海富铁沉积,另外海相硫化物沉积、有核原生生物等也首次出现。所有这些都标志着,在此前后,地球岩石圈、水圈和大气圈均发生了重大转折,生物圈也进入新的演化阶段,标志着地球进入"中年期"演化阶段。虽然地球演化发生重要转折的根本原因和细节还有待进一步深入探讨,但这一转变的起点或最重要的时间点,无疑就在18亿年前后,因此,本文认为,应将其作为全球古/中元古代的时间界线。     

Elastic properties of granulite facies rocks of Mahabalipuram, Tamil Nadu, India

Compressional and shear wave velocities and attenuation measurements have been carried out in some of the borehole samples of acidic, basic and intermediate granulites of Mahabalipuram, Tamil Nadu, India. The results have been obtained at ambient conditions using ‘time-of-flight’ pulse transmission technique at 1.0 MHz frequency. The results show linear relationships between velocity and density, and velocity and attenuation properties of the rocks. The acidic granulites show lower velocities and higher attenuation than the intermediate and basic granulites. The average values of the Poisson’s ratio of acidic, intermediate and basic granulites have been found to be 0.210, 0.241 and 0.279 respectively. The variations in velocities and attenuation in these low porosity crystalline rocks are found to be strongly influenced by their mineral composition. The laboratory velocity data (extrapolated to high pressure) of the present study and the published field velocity data from deep seismic sounding studies indicate that these granulite facies rocks may belong to mid-crustal depths only.     

构造带综放工作面支架异常压力机理探讨

针对多个综放采场出现的支架立柱压爆、油缸变形等异常矿压显现,通过对综放采场上覆岩层的运动范围及运动特点、顶板结构动态稳定性的分析,探讨了综放工作面异常压力产生的机理。得出了顶板结构局部铰接失稳（滑落失稳）是造成异常压力主要原因的结论。由于滑落失稳的原因不同,可分为水浸蚀型、地质构造型和顶板失稳型。通过对综放采场支架作用力的分析,给出了计算异常压力的公式。利用顶板结构动态稳定性判断准则,可对异常压力的类型进行判别,从而进一步确定异常压力的计算方法,为采场支架选型和现场控制异常压力提供理论依据。