Baryte and calcite cements in the 'breccias' of Ogmore-by-Sea, South Wales

Each year many hundreds, if not thousands, of Earth-science students visit the coastline at Ogmore-by-Sea, mid-Glamorgan. They study the excellent exposures of Lower Carboniferous Limestone, with their well-preserved coral and other shelly faunas, together with the presumed late Triassic 'breccias'* that rest unconformably on top. A study of the cements within the breccias may give an insight into syndepositional mineralization and the formation of sedimentary basins linked to the opening of the Atlantic in early Mesozoic times.     

Interdecadal Variability of East Asian Summer Monsoon Precipitation over 220 Years （1777-1997）

In this study, long-term (1777–1997) precipitation data for Seoul, Korea, wetness indices from eastern China, and modern observations are used to identify the interdecadal variability in East Asian summer monsoon precipitation over the last 220 years. In the East Asian monsoon region, two long-term timescales of dry–wet transitions for the interdecadal variability and quasi-40-and quasi-60-year timescales are dominant in the 220-year precipitation data of Seoul, as well as in the wetness indices over China....     

玩具业中重金属的等离子体发射光谱分析

为了支持玩具业,许多实验室需要分析各种复杂基体中的金属含量。人们关心的主要元素是铅,但很多其他有毒元素也具有潜在的威胁,尤其对于儿童。这些重金属元素包括锑、砷、钡、镉、铬、硒、汞和铅,累积在人体中将产生不利的影响。一些塑料和木制玩具,特别是表面色彩鲜艳的玩具被证实含有更高水平的铅和其他元素,儿童因接触易摄入,相关法规对产品表面含有这些元素的材料作了一些限制。为了保证玩具和其他物品的生产、流通和销售,有必要检测其中的重金属含量。不同的管理机构对各类样品中的元素提供了限量要求。在玩具安全性的欧洲标准EN71第3部分(已纳入ISO8124-3),其中在“特定元素的迁移”一节给出了玩具材料中元素迁移的     

岩质边坡稳定性的工程地质研究

岩质边坡稳定问题是工程地质学的一个重要研究課题,也是工程实践中迫切要求解决的问题。但是,对这个问题的研究,无论是国內国外都在进行探讨,还沒有形成一套完整的理论体系。为了推动这一方面的研究工作和解决生产实践中所提出的问题,本文试图从工程地质观点,并结合力学概念作一初步探讨,不妥和错误之处,希读者批评指正。     

边坡开挖破坏过程的离心模型试验研究

边坡开挖是工程中经常遇到的问题。在清华大学土工离心机上,开发了一种离心机运转过程中的边坡开挖模拟技术。进行了土坡开挖的离心模型试验,测量了开挖过程中边坡的位移场变化。结果表明,边坡的破坏过程是从坡体下部开始的剪切带逐渐向上发展贯通的过程,并经历了滑裂面贯通前的平缓变形和贯通后变形迅速增大两个阶段。坡顶裂缝最初均是由受拉引起的,但随着剪切带的不断向上发展,裂缝的扩展是由拉伸和剪切两种作用综合引起的。     

Ripple formation in combined transdirectional steady and oscillatory flow

Measurements are described of the geometry of ripples formed on beds of sand exposed to a steady current at right angles to an oscillatory flow. Four different sands were studied. The oscillation was produced by an oscillating tray set into the bed of a steady-flow flume. It was observed that straight-crested ripples formed by oscillatory flow would usually develop a ‘serpentine’ form when the superimposed steady current exceeded a certain limit. For amplitudes of the tray velocity U_∞ less than about 0.38 m s^-1 this limit corresponded to U_∞/ū_*c>31, where ū_*c is the shear velocity measured just upstream of the oscillating tray. It is suggested that the serpentine form is caused by the interaction of vortices carried back and forth between adjacent ripples. On this assumption, the wavelength of the serpentine form would be proportional to the product of period of oscillation and near-bed steady current velocity. The present measurements appear to support this hypothesis although there is also evidence that the wavelength is influenced by preferred spacing patterns between vortices. The measurements also show the ratio of the amplitude of the serpentine form to its wavelength to be approximately constant. Empirical relationships are derived relating ripple geometry to flow and sediment properties. It is observed that the influence of Reynolds number and sediment properties on the geometry is very weak. It is suggested that this is typical of ripples formed with relatively low sediment transport rates. It is also found that, under the present experimental conditions, the ripple spacing in the direction of oscillation is almost independent of the magnitude of the steady current and in close agreement with the wavelengths previously measured in an oscillating water tunnel. This suggests that the additional inertia effects associated with oscillating tray rigs were not sufficient to affect bed geometry under the present test conditions.     

The influence of thermohaline fronts on chlorophyll a concentrations during spring and summer in the southeastern Yellow Sea

A spatial and temporal variation in physiochemical parameters in the southeastern Yellow Sea(YS) is investigated in the spring and summer of 2009 to 2011.Nutrient show a strong negative relationship with chlorophyll a(Chl a) concentration in spring,and the subsurface chlorophyll a maxima(SCM) layer was associated with the nitracline in summer.In summer,the SCM was usually found within or above the pycnocline and at the depths of shoals from the open sea to the coastal sea due to tidal and/or topographical fronts in the southernmost study area.High Chl a concentrations were found in the central southern YS,where the YS cold water layer expanded under the pycnocline and encountered water masses during spring and summer.After a typhoon in the summer of 2011,Chl a concentration increased,especially in the central southern YS,where cold waters occurred below the pycnocline.The results suggest that the development of thermohaline fronts may play an important role in the growth and accumulation of phytoplankton biomass in the upper layer of the southeastern YS during spring and summer.     

日本凋毛藻碳酸酐酶基因及其编码的蛋白特征

碳酸酐酶CA(EC 4.2.1.1)是含锌原子的金属蛋白酶,该酶的基本功能是催化CO₂与HCO₃-间的相互转换[1].该反应在许多生物过程中都发挥着重要的作用,例如离子交换、呼吸作用、pH稳定性、捕获CO₂和光合作用等[2~5].CA广泛分布于各种生物中,已知的CA酶根据氨基酸序列被分为-αCA,-βCA和γ-CA三种类型[5~7].这3种类型的CA酶序列间的相似性很低,被认为是由不同的途径进化而来的[7].α-型的CA酶在动物、植物、绿藻、细菌和蓝细菌中都有发现[7],在藻类中报道的α-型CA还很少.迄今为止只在衣藻中发现2种异构体,在盐藻中发现3种[8,9],在红藻中还未见报道.     

Geochemistry and Origin of Layers in Single Manganese Nodule from the Philippine Sea and Manganese Nodules from Offshore Minami-Torishima,Western Pacific

Layers from one manganese nodule dredged from the Philippine Sea(16°56'N, 129°48'E; water depth, 5700 m) and 45 bulk nodules from offshore Minami-Torishima Island, Japan(23°3'N, 153°22'E; water depth, 1200 m) were analyzed chemically and their origin is discussed based on geochemical constraints. In general, Cu, Ni, Zn and Mo tend to increase with increasing Mn content, while Co, Pb, Ba, V, Sc, Th, and the rare earth elements(REEs) show less variation with increasing Mn content. Nodule 42 H from the Philippine Sea has an average Mn/Fe ratio close to 1 and shows a positive Ce anomaly, suggesting a predominant hydrogenous origin. Profiles of 230Th230 ex and Thex/232 Th ratios in the outer ~0.3 mm of nodule 42 H indicate a steady growth rate of ~1.7 mm/Myr. Nodule E30 from offshore Minami-Torishima is characterized by lower Mn, Fe, Mn/Fe(0.53) and Mo/V(0.2) ratios but higher P and Cu/Ni(0.31) ratio relative to other nodules from that area. The Ce content of E30 is unusually low(82 ppm) when compared with other nodules from the area and it is the only nodule analyzed with a negative Ce anomaly(-0.64). Based on the geochemical data we suggest that most nodules from offshore Minami-Torishima are primarily of hydrogenous origin except E30, which is dominated by hydrothermal input, and E45, which has about a 35% hydrothermal contribution.