武汉东湖的透明薄皮溞

本文报道了东湖大型肉食性枝角类——透明薄皮溞（Leptodora kindti）种群的周年变动昼夜垂直迁移及体长-体重回归方程。在I站1984年的高峰出现在8月, 1985年出现在7月, 数量分别为1.775和0.313 ind./L;且站均出现在9月, 数量分别为1.214和1.547 ind./L。透明薄皮溞有明显的昼夜垂直移动现象, 衣层的数量变动更明显, 通常以日出及日落前后1小时, 衣层数量最多, 用直接测重法测定了不同体长组的湿重、干重, 经统计处理获得了各自的回归方程。     

Zhang Heng's Seismoscope( 1):Its Emergence

The emergence of Zhang Heng's seismoscope has a profound historical background. This paper intends to explore the formation and material basis of Zhang Heng's scientific thought. It appears that the simple intention of "observing visions and distinguishing good fortune or misfortune"was his motivation to develop the seismoscope. Tracing its historical background,the authors proposed in this paper that the development of this seismoscope started around 128 A. D., and based on perceptual knowledge, two ideas about earthquakes came into being,i. e.,earthquake location could be judged according to the instrument shaking direction, and the earthquake and earth split were essentially different. In the instrument manufacture,Zhang Heng advocated a principle of "making utensils to imitate cosmos". By this principle,the following three problems were readily solved: the seismoscope imitated the response of the suspension system to earthquakes( i. e. natural seismoscope). Technically,the trigger mechanism of the latch was used for reference,and it recorded the physical evidence of earthquake occurrence by an ingenious way of a ball dropping from a dragon's mouth. The solution of these three key problems lead to the emergence of the seismoscope in 132 A. D. and the successful detection of an earthquake in 134 A. D. His invention deepened humanity's knowledge of natural laws, and promoted the development of science and technology in that time and later.     

Breakdown of boundary layers: (i) on moving surfaces; (ii) in semi-similar unsteady flow; (iii) in fully unsteady flow

Abstract

The breakdown and separation or reattachment of boundary layers adjoining a mainstream are studied in the three related situations (i)-(iii) of the title. For (i) the classical steady boundary layer generally admits a logarithmic singularity in the displacement when breakdown occurs on a downstream-moving surface whereas the corresponding singularity for an upstream-moving surface can be logarithmic or of minus-one-sixth form. Conversely, the breakdown can be delayed to the onset of zero mainstream flow, in which case the displacement singularity is again logarithmic. In certain flows these singularities prove to be removable locally, yielding a breakaway separation or reattachment and including the first known successes of a classical strategy in describing large-scale separation. Other flows, by contrast, require an interactive strategy. Again, even on a fixed surface a breakdown different from Goldstein's can be produced if there is a moving section of surface further upstream. The application to (ii), semi-similar unsteady boundary layers, e.g. near an impulsively started wedge-like trailing edge, then follows readily and predicts analogous forms of singularity. The corresponding singularity in displacement predicted for fully unsteady classical boundary layers, (iii), occurs within a finite time and, like (i) (usually) and (ii), a three-tiered breakdown is involved at first. Subsequently interaction comes into play. Comparisons with numerical and/or earlier work are noted. In all three situations (i)-(iii), although the dynamics involved near breakdown, separation or reattachment are predominantly inviscid, the presence of small viscosity is of significance in enforcing smoothness of the local velocity profiles.     

Biosorption of Cd(II) and Zn(II) by Nostoc commune: Isotherm and Kinetics Studies

In this study, Nostoc commune (cyanobacterium) was used as an inexpensive and efficient biosorbent for Cd(II) and Zn(II) removal from aqueous solutions. The effect of various physicochemical factors on Cd(II) and Zn(II) biosorption such as pH 2.0–7.0, initial metal concentration 0.0–300 mg/L and contact time 0–120 min were studied. Optimum pH for removal of Cd(II) and Zn(II) was 6.0, while the contact time was 30 min at room temperature. The nature of biosorbent and metal ion interaction was evaluated by infrared (IR) technique. IR analysis of bacterial biomass revealed the presence of amino, carboxyl, hydroxyl, and carbonyl groups, which are responsible for biosorption of Cd(II) and Zn (II). The maximum biosorption capacities for Cd(II) and Zn(II) biosorption by N. commune calculated from Langmuir biosorption isotherm were 126.32 and 115.41 mg/g, respectively. The biosorption isotherm for two biosorbents fitted well with Freundlich isotherm than Langmuir model with correlation coefficient (r² < 0.99). The biosorption kinetic data were fitted well with the pseudo‐second‐order kinetic model. Thus, this study indicated that the N. commune is an efficient biosorbent for the removal of Cd(II) and Zn(II) from aqueous solutions.     

CT淋巴管成像对不同分型的原发性小肠淋巴管扩张症患者的比较研究

目的：探讨CT淋巴管成像（CTL）在不同分型的原发性小肠淋巴管扩张症（PIL）患者的临床与影像特征比较和应用价值。方法：收集2016年1月至2019年12月确诊为PIL的所有患者,回顾分析其CTL图像,由两名放射科医师盲法评价,评价指标包括：性别、首发年龄、临床症状和体征、血清白蛋白、肠壁是否增厚、肠系膜密度增高、浆膜腔是否积液、异常淋巴管分布的部位及范围、淋巴液是否返流、淋巴瘘的有无,腹腔内是否有淋巴结和颈部是否有异常扩张的淋巴管。基于对比剂是否分布于小肠壁和肠系膜这一特异影像学征象,首次提出将PIL分型为Ⅰ型（阳性组）与Ⅱ型（阴性组）,比较两组患者的临床和影像学特征。结果：34例PIL患者中,Ⅰ型15例,Ⅱ型19例。Ⅰ型首次发病年龄较大（15.3±9.4 vs.8.3±3.8）,腹泻发生率较高,而肢体和/或颜面部肿胀的比例低于Ⅱ型,两组性别比和白蛋白水平差异无统计学意义;影像征象方面,Ⅰ型腹膜后异常扩张淋巴管和淋巴瘘的比例高于Ⅱ型,肠系膜密度增高和腹腔淋巴结出现的比例低于Ⅱ型。两组间肠壁增厚、浆膜腔积液、返流样表现和颈部异常扩张淋巴管的差异无统计学意义。结论：CTL可以评价PIL患...     

地震孕育体源流变模型(三)--前兆场

在三维流变介质体源孕震模型的粘弹性位移场与应变场理论基础上,建立了流变介质体源孕震模型的前兆场理论解,导出了流变介质中任意一点（x,y,z）的地倾斜、地下水位、电阻率的粘弹性解析解,并对地电阻率的应用作了初步分析,为地震孕育过程中前兆分析提供了一定的理论基础.      

2001年1月26日印度7.7级地震

20 0 1年 1月 2 6日 ,印度西部发生一次大地震 ,当时正值印度全国庆祝共和日。这次地震对独立的印度来说 ,无疑是一次破坏极其惨重的地震。自地震发生后 ,救援人员一直在努力清理废墟 ,并从倒塌的瓦砾中救出可能的幸存者。政府也已承认这次地震给印度造成的损失惨重。科学家们认为 ,过去没有对这一地区进行过全面的研究 ,最近几年才开始对该地区的古地震活动性进行了一些研究。其中一项研究是在卡奇沼泽地进行卡奇地区的地震历史研究。这里有一份关于卡奇地震带形变特征的详细报告的摘要。 1 81 9年发生在印度西北部的卡奇地震 ,是最显著的…     

趣味地震学(2):世界海啸意识日

现在的“世界日”愈来愈多。除却卫生日、野生动物日、气象日、地球母亲日、环境日、减灾日(10 月13 日)等几十项外,近两年又增加了一项?海啸意识日。海啸并不常有,却是致命的。根据联合国2018 年公布的数据[1](http://www.un.org/en/events/tsunamiday/),在过去100 年里,58 场海啸夺走逾26 万人的生命,平均每场海啸丧生4 600 人,超过其他任何自然灾害,尤以2004年印度洋海啸的死亡人数最多.     

Big difference in ~(87)Sr/ ~(86)Sr ratios of basalt and basin water: higher ~(87)Sr/ ~(86)Sr ratios in plagioclase

We analyzed the ~(87)Sr/~(86)Sr ratios of basaltic rocks and basin water in Xuyi,China,and found a big difference,which may challenge conventional wisdom on the contribution of basalt weathering in end-member analysis.Results of an in-house weathering experiment suggest that rainwater and dust are not responsible for the difference.By isolating the major minerals in basalt,we found that plagioclase has much higher ~(87)Sr/~(86)Sr ratios than bulk basalt and basin water,which might explain the difference in ~(87)Sr/~(86)Sr ratios of basalt and basin water.We inferthatlow-temperaturehydrothermalalteration increased the ~(87)Sr/~(86)Sr ratios of plagioclase.Future analyses of end-member contribution in a mixed-rock basin should take into account that basin water and plagioclase have higher ~(87)Sr/~(86)Sr ratios than basaltic rocks.     

Bedload transport in shallow water models: Why splitting (may) fail, how hyperbolicity (can) help

In this paper, we are concerned with sediment transport models consisting of a shallow water system coupled with the so called Exner equation to describe the evolution of the topography. We show that, for some bedload transport models like the well-known Meyer-Peter and Müller model, the system is hyperbolic and, thus, linearly stable, only under some constraint on the velocity. In practical situations, this condition is hopefully fulfilled. Numerical approximations of such system are often based on a splitting method, solving first shallow water equation on a time step and, updating afterwards the topography. It is shown that this strategy can create spurious/unphysical oscillations which are related to the study of hyperbolicity. Using an upper bound of the largest eigenvector may improve the results although the instabilities cannot be always avoided, e.g. in supercritical regions.     

Lead isotopic study of the Xigaze ophiolite (Tibet): the problem of the relationship between magmatites (gabbros,dolerites, lavas) and tectonites (harzburgites)

The Pb isotopic study of the Xigaze ophiolite (Tibet) shows that the tectonic (harzburgites) and magmatic (gabbros, dolerites, lavas) units bear different isotopic signatures, the harzburgitic rocks show much higher²⁰⁷Pb/²⁰⁴Pb values than the samples from the magmatic unit. Analyses of primary magmatic clinopyroxenes separated from the harzburgites confirmed that this difference is real and not due to secondary alteration processes. UPb analysis allowed determination of the crystallization age of the magmatites at 120 ± 10 m.y. This age is compatible with paleontological age determinations and thus demonstrates that UPb behaved more or less as a closed system since formation of the ophiolite. If an exchange with seawater has occurred, it must necessarily have happened shortly after crystallization of the Xigaze oceanic crust. Dolerite dykes crossing the harzburgites show similar Pb isotopic composition as the magmatites, indicating that they were emplaced when the ultramafic rocks were already brittle; however, the time difference of the emplacement was probably not larger than 280 m.y. This makes it evident that two sources with different isotopic signatures, one similar to normal MORB, the other with much higher²⁰⁷Pb/²⁰⁴Pb ratios, were active in the immediate neighborhood. One possible environment which can account for this association is a propagating ridge.