Land desertification and restoration in Middle East and North Africa (MENA) region

The Middle East and North Africa (MENA) region is characterized by high population growth, degraded and fragile nat-ural ecosystems, and a limited amount of arable lands. It is one of the most water-sc...     

Determination of allowable subgrade frost heave with the pavement roughness index in numerical analysis

Frost heave is an upward swelling of soil during cryogenic conditions in cold regions. It is caused by the accumulation of ice crystals in subgrade soil, which grow upwards when freezing temperatures penetrate into the subgrade. This study establishes the allowable soil subgrade frost heave based on the roughness standard of asphalt pavement in China, and aims to balance the pavement design and frost heave resistance of subgrades in cold regions. We formulated a mechanical model of pavement supported by the boundary conditions of differential frost heave, based on the elastic layered system theory. The differential soil subgrade frost heave was modeled as a sinusoidal function, and the allowable frost heave and the roughness index were modeled as the displacement boundaries for the top and bottom of the pavement structure. Then the allowable frost heave was back-calculated according to the roughness standard. Numerical results show that the allowable frost heave depends on the pavement structure, material properties, the highway grade, and other factors. In order to ensure that the actual soil subgrade frost heave is lower than the allowable frost heave, pavement structures and materials need to be selected and designed carefully. The numerical method proposed here can be applied to establish the frost heave resistance of subgrade when the pavement structure and materials are determined.     

东印度洋水体输运的季节变化及相关盐度变化

利用20年（1992-2012年）的ECCO2模式模拟数据,主要研究了东印度洋（EIO）水体输运的季节变化.在EIO选取3个断面,分别为赤道、80°E和6°N.研究结果表明,跨赤道和80°E的季节输运主体部分大致相补偿.跨赤道的大部分水体输运局限在上层100 m,80°E的水体输运具有复杂结构,与显著的季风流、Wyrtki Jets（WJs）、赤道潜流（EUC）等有关.6°N上层水体净输运较小,但存在较强的边界流和相对较弱的内区流.纬向流的显著变化发生在80°E.在季风盛行季节,由于WJs减弱,赤道附近的水体输运以西向的梯度流为主,上层100 m的其余区域则主要受季风流控制.同样,由于EUC减弱,西向的梯度流与次表层东向的EUC之间也存在转换.在季风转换季节,季风流减弱,WJs与EUC分别在上层100 m和次表层占主导地位.此外,本研究还讨论了与季风流、WJs和EUC相关的盐水和暖水交换,有助于了解研究区域内温度和盐度的水平和垂直结构.     

墨西哥与主流纹岩及有关岩石相伴的矿化作用

在流纹质熔岩的气孔和裂隙中出现黄玉，表明母岩浆中F及亲F元素（Sn、W、Mo、Be、Li、Ta、Nb等）的含量很高，因此可能伴生有这些元素的火山成因或次火山成因的矿床。在墨西哥中央高原上分布极为广泛的黄玉流纹岩，与美国西部黄玉流纹岩的不同之处在于：①它们在科迪勒拉东部边缘的高原上呈线性带状产出，而不像美国西部的盆岭区那样呈大面积分布；②它们的年龄范围较窄，代表了大约在30Ma以前发生的岩浆幕，而不像美国西部那样代表在50Ma期间发生的一系列事件；③黄玉流纹岩分布区未出露前寒武纪岩石，而在美国人们通常假定黄玉流纹岩下伏有前寒纪岩石；④它们与双峰火山作用的伴生关系远不如美国西部那样清楚，而且不涉及玄武质岩石；⑤似乎没有含石榴石的黄玉流纹岩；⑥它们伴有大量的锡矿化，但在美国，黄玉流纹岩伴有克莱马克斯型斑岩钼矿床；⑦与此相当的侵入岩特别富B。直接与喷出的黄玉流纹岩穹丘有关的矿床仅包括：（1)玻斑状顶盖角砾岩、陆倾斜流动条带、交叉断裂中的喷气孔锡石和木锡矿以及边缘砂矿；（2）充填裂隙的宝石黄玉和宝石黄玉砂矿。明显地与同期岩浆作用有关的地下矿床包括（3）产于碳酸盐岩中的Ag-Pb-Zn脉状矿床和交代矿床；（4）近地表花岗岩接触带中的含铀萤石矿床；（5）与更深处花岗岩有关的矽卡岩／萤石／Zn-Pb-Ag/Sn/Be矿床。在Pinos、Zac地区流纹熔岩下之很厚的火山泥矿床，可能是由于岩浆与地表水的相互作用而形成的，这些与岩浆相互作用的地下水后来在平流循环时引起碳酸盐岩围岩中出现银矿化。 Spor山型的铍矿床可能产于某些黄玉流纹岩熔岩流还未出露的底部，但这还没有得以证实。     

Logs and Snags in a Shola Forest of Kerala, India

Introduction Dead wood is an important structural and functional component of a forest ecosystem(Fridman and Welheim 2000). Recent studies also indicate that dead wood is important for maintaining both plant and animal diversity in different forest ecosystems (Grove 2001) as it serve as an energy source (Bray and Gorham 1964) and habitat for an array of organisms. Dead wood can also help reduce erosion, increase soil organic matters (McFee and Stone 1966), and suitable conditions for seedli…     

Effects of base analogues 5-bromouracil and 6-aminopurine on development of zebrafish Danio Rerio

Zebrafish （Danio rerio） genetic screens allow isolation of a wide array of problems in vertebrate biology. The effects of base analogues 5-bromouracil and 6-aminopurine on the development of zebrafish embryos are reported for the first time in this study. The early development of the zebrafish embryos was little affected by 5-bromouracil and 6-aminopurine, while the late development （organogenesis） was significantly impaired. Embryos exposed to 5-bromouracil mainly showed curled tail, wavy body, golden pigmentation and the mouth with protruding lower jaw. 6-aminopurine-treated embryos had defective anterior structures, curled tails and wavy body. RAPD analysis showed that the majority of 5-bromouracil-and 6-aminopurine-treated larvae and fish shared banding patterns in common with the control, suggesting that most mutagenesis induced by these agents are point mutations. However, some fish derived from 5-bromouracil-treated embryos had golden（gol） pigmentation; and RAPD analysis revealed that their band patterns differed from those of the control.Possibly, 5-bromouracil can occasionally cause relatively extensive changes in the fish genome. The results of this study may provide valuable help for detailed studies of mutagenesis.     

城市水文学

一、城市水文学的定义水文学可定义为研究地球上水的一门自然科学,它研究地球上水的流动、循环、分布;水的物理化学性质;以及水与环境、当然也包括与生物之间的相互关系(联合国教科文组织,1979)。这种表述意在强调该学科的两个特点:它的多学科性质,涉及到物理学、化学、生物学以及各种应用科学;它对自然界各种状态的水的空间和时间分布规律以及运动的关注。其中第二个特点在水循环概念中得到体现,水循环概念表明了降落于陆地上的水又流归海洋的各种途径,在海洋中,水的蒸发又为循环的再进行提供了水气来源。     

沉积有机氮的来源和成岩作用

这篇文章是有关沉积有机持（ＳＯＭ）中氮的保存和围变作用认识的概述，内容着重于油气形成体系，但也涉及到煤。