南沙海区礼乐盆地沉积地层与构造特征分析

通过对地震剖面、钻井及拖网采样资料的分析，认为礼乐盆地发育有海相的中

EFFECT OF IMAGE FORCES ON ELECTRONS CONFINED IN LOW-DIMENSIONAL STRUCTURES UNDER A MAGNETIC-FIELD

We consider the effect of image forces, arising due to a difference in dielectric permeabilities of the well layer and barrier layers, on the energy spectrum of an electron confined in a rectangular potential well under a magnetic field. Depending on the value and the sign of the dielectric mismatch, image forces can localize electrons near the interfaces of the well or in well centre and change the direct intersubband gaps into indirect ones. These effects can be controlled by variation of the magnetic field, offering possibilities for exact tuning of electronic devices.

低碳:国家可持续发展实验区建设的重要方向

<正>经过20多年的建设与发展,国家可持续发展实验区依靠科技进步、机制创新,在协调社会经济发展与环境资源关系、促进经济发展、提高居民生活质量、探索新型工业化道路等诸多方面进行了积极的探索和实践,极大地推动了区域经济社会的协调发展,已成为实施国家可持续发展战略的

土壤有机质模型的比较分析

土壤有机质作为土壤C库,其含量和动态变化对全球C循环、土壤肥力、土壤质量和健康起着重要作用.SOM模型利用经验性的假设和已有数据对土壤有机质含量和动态变化进行模拟,尤其是可以对无法取得足够必要数据的试验进行模拟,所以SOM模型成为定量研究土壤有机质积累分解的重要手段.利用SOM模型有助于对土壤有机质分解机理的研究,并且可通过SOM模型对土壤CO2排放量、植物生产量进行预测,同时也可对农业管理措施做出评估.文中对几种SOM模型进行了概述,尤其对有影响的RothC模型和CENTURY模型进行了比较分析。

Impedance study of (PEO)(10)LiClO4-Al2O3 composite polymer electrolyte with blocking electrodes

A composite solid polymer electrolyte (SPE) of (PEO)(10)LiClO4-Al2O3 was prepared and Pt and stainless steel(SS) blocking electrodes were used for an impedance study. It was found that the semicircle in the high frequency range and the straight line in the low frequency range depend upon different blocking electrodes and polarization potentials applied in the experiments. In the equivalent circuit. two constant phase elements (CPE) have been used instead of the pure geometrical and double layer capacitances. respectively. A theoretical line calculated from their estimated values has a good correlation with the experiment data. Moreover. the equivalent circuit also can be used to explain the impedance properties of Pt and stainless steel (SS) blocking electrodes both in the high and the low frequency ranges. (C) 2001 Elsevier Science Ltd. All rights reserved.

Periodical mixing of MORB magmas near East Pacific Rise 13N: evidence from modeling and zoned plagioclase phenocrysts

Thirty-six basalt samples from near East Pacific Rise 13N are analyzed for major and trace elements. Different types of zoned plagioclase phenocrysts in basalts are also backscatter imaged, and major element profiles scanned and analyzed for microprobe. Basalts dredged from a restricted area have evolved to different extents (MgO=9.38wt%-6.76wt%). High MgO basalts are modeled for crystallization to MgO of about 7wt%, and resulted in the Ni contents (28 ppm) that are generally lower than that in observed basalts (> 60 ppm). It suggests that low MgO basalts may have experienced more intensive magma mixing. High MgO (9.38wt%) basalt is modeled for self-"mixing-crystallization", and the high Ni contents in low MgO basalts can be generated in small scale and periodical self-mixing of new magma (high MgO). "Mixing-crystallization" processes that low MgO magmas experienced accord with recent 226Ra/230Th disequilibria studies for magma residence time, in which low MgO magmas have experienced more circles of "mixing-crystallization" in relatively longer residence time. Magma mixing is not homogeneous in magma chamber, however, low MgO magmas are closer to stable composition produced by periodical "mixing-crystallization", which is also an important reason for magma diversity in East Pacific Rise. Zoned plagioclase phenocrysts can be divided into two types: with and without high An# cores, both of which have multiple reversed An# zones, suggesting periodical mixing of their host magmas. Cores of zoned plagioclase in low MgO (7.45wt%) basalt differ significantly with their mantle in An#, but are similar in An# with microlite cores (products of equilibrium crystallization) in high MgO (9.38wt%) basalt, which further shows that plagioclase phenocryst cores in low MgO basalts may have formed in their parental magmas before entering into the magma chamber.

Origin and Pathway of Equatorial 13 degrees C Water in the Pacific Identified by a Simulated Passive Tracer and Its Adjoint

The origin and pathway of the thermostad water in the eastern equatorial Pacific Ocean, often referred to as the equatorial 13 degrees C Water, are investigated using a simulated passive tracer and its adjoint, based on circulation estimates of a global general circulation model. Results demonstrate that the source region of the 13 degrees C Water lies well outside the tropics. In the South Pacific, some 13 degrees C Water is formed northeast of New Zealand, confirming an earlier hypothesis on the water's origin. The South Pacific origin of the 13 degrees C Water is also related to the formation of the Eastern Subtropical Mode Water (ESTMW) and the Sub-Antarctic Mode Water (SAMW). The portion of the ESTMW and SAMW that eventually enters the density range of the 13 degrees C Water (25.8 < sigma(theta) < 26.6 kg m(-3)) does so largely by mixing. Water formed in the subtropics enters the equatorial region predominantly through the western boundary, while its interior transport is relatively small. The fresher North Pacific ESTMW and Central Mode Water (CMW) are also important sources of the 13 degrees C Water. The ratio of the southern versus the northern origins of the water mass is about 2 to 1 and tends to increase with time elapsed from its origin. Of the total volume of initially tracer-tagged water in the eastern equatorial Pacific, approximately 47.5% originates from depths above sigma(theta) = 25.8 kg m(-3) and 34.6% from depths below sigma(theta) = 26.6 kg m(-3), indicative of a dramatic impact of mixing on the route of subtropical water to becoming the 13 degrees C Water. Still only a small portion of the water formed in the subtropics reaches the equatorial region, because most of the water is trapped and recirculates in the subtropical gyre.

青藏高原不同海拔地区唐古特山莨菪叶片光合色素含量和抗氧化酶活性的比较研究

以青藏高原东北隅的西宁和海北（海拔分别为2 300 m和3 200 m）人工栽培唐古特山莨菪为材料,对两不同海拔地区间各叶层叶片光合色素含量和抗氧化酶活性等生理指标进行比较分析.结果显示：（1）生长在海北的唐古特山莨菪叶片厚度极显著高于西宁（P〈0.01）,且两地区植物的叶片厚度从第1层到第4层均呈显著增加趋势;海北唐古特山莨菪叶片的叶绿素a、叶绿素b、总叶绿素、类胡萝卜素含量以及紫外吸收物质的含量均显著高于西宁地区（P〈0.05）,从第1层到第4层,两地植株叶片的光合色素和紫外吸收物质的含量都呈降低的趋势,且两地区间差异显著;叶绿素a/b的层间差异显著（P〈0.05）,但两海拔地区间差异不显著;类胡萝卜素/叶绿素比值海北高于西宁,从第1层到第4层叶片呈降低趋势.（2）生长于海北的唐古特山莨菪叶片组织中的SOD、CAT活性和MDA含量比西宁的高,POD、APX则相反;从第1层叶片到第4层,西宁和海北唐古特山莨菪叶片中的SOD活性显著增高（P〈0.05）,但两地区各层间的CAT、POD、APX活性和MDA含量无明显的变化.研究表明,不同海拔对唐古特山莨菪叶片的生理特性有影响,同一海拔不同叶层叶片之间差异也较为明显;生长在高海拔地区的植物尽管表现出诸多生理适应特征,但膜系统依然有一定受损.