非饱和土中镉离子传输模型参数反演

使用自行设计的的真空实验装置,采用一维实验室土柱实验方法在不同实验条件下进行了15组实验,并基于实验所得的穿透曲线,使用梯度正则化方法反演得到了镉离子在8种葡萄牙土样和1种比利时土样中相应的传输模型参数.同时通过数值模拟实验验证了梯度正则化方法的有效性和可靠性,进而证明所得结果是有效的.

Refractive-index change and sensitivity improvement in holographic recording in LiNbO3:Ce:Cu crystals with green light

Nonvolatile holographic recording is performed with green light in LiNbO3:Ce:Cu crystals. The refractive-index change and the recording sensitivity are times better than those obtained by recording with red light, and higher optical fixing efficiency is obtained. Correspondingly, theoretical investigations are given.

S-DABO类化合物、其合成方法和用途

S-DABO类化合物、其合成方法和用途，属药物技术领域。本发明涉及一种5-烷基-6-苯基-2-(取代芳基羰基甲基硫)尿嘧啶类化合物，该类化合物具有如下通式：其中： R1为C1-3的烷基； R2＝C1-6的烷基、取代呋喃环、噻吩环、苯环(芳环上的取代基为H、OH、C1-3 的烷氧基)。以5-烷基-6-苯基硫尿嘧啶为反应物，与a-卤代酮在K2CO3催化下反应获得本发明产物。合成方法简便易行，产物具有显著的抗HIV病毒活性，且毒性较小，选择性指数高，可作为抗HIV药物候选物。

根足类原生动物半圆表壳虫壳体生物矿化特征

以有壳阿米巴类原生动物 (肉鞭门 ,叶足纲 )半圆表壳虫 (Arcellahemisphaerica)为研究对象 ,利用光镜和扫描电镜研究了其壳体生物矿化的特征。结果显示 :矿化前期 ,壳体为无色透明且柔软易变形 ;中期 ,为黄色较坚硬 ;后期 ,为褐色坚硬。通过X 射线显微分析术鉴定不同矿化时期壳体的无机元素 ,结果表明 ,与矿化前期相比矿化中期和后期壳体中Si、Mn和Fe的比例增加 ,Cl、K、S和Na的比例减少。由此推测 ,⑴半圆表壳虫矿化过程中壳体坚硬的原因是Si、Mn和Fe的比例增加导致 ,黄色

Long-term changes of Copepoda community (1957-1996) in a subtropical Chinese lake stocked densely with planktivorous filter-feeding silver and bighead carp

In contrast to the relatively well documented impact of particulate-feeding fish on zooplankton communities, little attention has been devoted to the impact of filter-feeding fish. Filter-feeding silver and bighead carp are the most intensively cultured fish species in Asia and comprise much of the production of Chinese aquaculture. However, little information is known about the impact of either fish on the zooplankton community. Long-term changes in the Copepoda community (1957-1996) were studied at two sampling stations of a subtropical Chinese lake (Lake Donghu) dominated by silver and bighead carp. For both calanoids and cyclopoids, the littoral station (I) was much more resource profitable than the pelagic station (II). There has been a tremendous increase in the annual fish catch over the past 30 years due to the increased stocking with fingerlings of the two carp species. There was a notably higher fish density at Station I than at Station II. Cyclopoid abundance was notably higher at Station I than at Station II during the 1950s to the 1980s, while the reverse became true in the 1990s. This is probably because when fish abundance increased to an extremely high level, the impact of fish predation on the cyclopoids became more important than that of food resources at the littoral station. At both stations, cyclopoid abundance was relatively low in spite of the presence of abundant prey. Similarly, calanoid density did not differ significantly between the two stations in the 1950s and 1960s, but was significantly lower at Station I than at Station II during the 1980s and 1990s. Such changes are attributed to the gradient of fish predation between the stations and an increasing predation pressure by the fish. The increased fish predation also correlated with a shift in summer-dominant calanoids from larger species to smaller ones. In conclusion, the predaceous cyclopoids are affected by fish predation to a much lesser extent than the herbivorous calanoids, and therefore increased predation by filter-feeding fish results in a definite increase in the cyclopoid/calanoid ratio. Predation by filter-feeding fish has been a driving force in shaping the copepod community structure of Lake Donghu during the past decades.

中国的海滩岩研究与进展

海滩岩作为海陆交互作用的直接产物之一，对于研究古海平面变化、海岸带演化以及古气候变化等海陆相互作

VGF法生长的低位错掺Si-GaAs单晶的缺陷和性质

研究了垂直梯度凝固法（VGF法）生长的掺Si低阻GaAs单晶材料的晶格缺陷和性质,并将VGF法和LEC法生长的非掺半绝缘GaAs单晶进行了比较.利用A-B腐蚀显微方法比较了两种材料中的微沉积缺陷,对其形成原因进行了分析.利用荧光光谱研究了掺Si-GaAs单晶中Si原子和B原子的占位情况和复合体缺陷.Hall测量结果表明,掺Si低阻VGF-GaAs单晶中存在很强的Si自补偿效应,造成掺杂效率降低.VGF-GaAs单晶生长过程中高的Si掺杂浓度造成晶体中产生大量杂质沉积,而杂质B的存在加重了这种现象.对降低缺陷密度,提高掺杂效率的途径进行了分析.

纳米尺度表/界面力电耦合的分子动力学/第一原理模拟

<正>在纳米尺度下,表/界面上力、电行为相互影响、密不可分。这种表/界面力电耦合的属性显著地影响着纳米器件的设计、制备和应用。本报告主要从固气、固液界面等方面讨论纳米尺度表/界面动力学的力电耦合属性对于纳米器件的影响。主要内容如下:

土地利用变化对流域面源污染的累积生态效应影响

从土地利用景观生态结构与面源污染的关系入手,分析大伙房水库流域土地利用景观结构及其变化过程,特别是农业景观结构变化对面源污染发生发展的累积生态效应影响。研究内容主要有三个方面:随着农业景观面积的增加,相应的化肥、农药施用量加大,造成面源污染加重;农业景观大多分布在河流的两侧,高差较大,这样极其容易引起水土流失,把土壤及其土壤中的有机物带入水库,加深面源污染的程度;农业内部结构的调整,如种植业向畜禽养殖业的转变对流域面源污染影响加大。

Synthesis of isotactic polystyrene with a rare-earth catalyst

Polymerization of styrene with the neodymium phosphonate Nd(P-507)/H2O/Al(i-Bu)(3) catalytic system has been examined. The polymer obtained was separated into a soluble and an insoluble fraction by 2-butanone extraction. C-13-NMR spectra indicate that the insoluble fraction is isotactic polystyrene and the soluble one is syndiotactic-rich atactic polystyrene. The polymerization features are described and discussed. The optimum conditions for the polymerization are as follows: [Nd] = (3.5-5.0) x 10(-2) mol/L; [styrene] = 5 mol/L; [Al]/[Nd] = 6-8 mol/mol; [H2O]/[Al] = 0.05-0.08 mol/mol; polymerization temperature around 70 degrees C. The percent yield of isotactic polystyrene (TY) is markedly affected by catalyst aging temperature. With increase of the aging temperature from 40 to 70 degrees C, TY increases from 9% to 48%. Using AlEt3 and Al(i-Bu)(2)H instead of Al(i-Bu)(3) decreases the yield of isotactic polystyrene. Different neodymium compounds give the following activity order: Nd(P-507)(3) > Nd(P-204)(3) > Nd(OPri)(3) > NdCl3 + C2HF5OH > Nd(naph)(3). With Nd(naph)(3) as catalyst, only atactic polystyrene is obtained. (C) 1998 John Wiley & Sons, Inc.

稀土对3’,5’-环腺嘌呤单核苷酸与3’,5’-环鸟嘌呤单核苷酸的快速断裂作用

在温和条件下能快速切断核酸的人工酶有许多重要的潜在应用价值,如作为模拟的限制性内切酶并发展到新的抗癌药物,因此,长期以来人们致力于研究具有高效率及高选择性的人工酶.关于稀土对核酸断裂作用的研究尚不多,而稀土对环核苷酸的催化水解作用只有Sumaoka等曾报道Ce~(3+)对3’,5’-环腺嘌呤单核苷酸(cAMP)有快速的水解作用,稀土对不同环核苷酸的催化水解作用尚未见报道.3’,5’-环腺嘌呤单核苷酸与3’,5’-环鸟嘌呤单核苷酸(cGMP)具有调节细胞应答及细胞间信息传递的作用,且细胞内不同环核苷酸的变化与某些心血管疾病的发病机理有关.本文用高压液相色谱(HPLC)和核磁共振(NMR)研究了稀土对cAMP与cGMP的断裂作用,并深入探索了其机理,这对于寻找高效率及高选择性的核酸催化体系,阐明稀土在生物体内的作用具有重要的意义.

Long-Wave Dynamics of Sea Level Variations during Indian Ocean Dipole Events

Long-wave dynamics of the interannual variations of the equatorial Indian Ocean circulation are studied using an ocean general circulation model forced by the assimilated surface winds and heat flux of the European Centre for Medium-Range Weather Forecasts. The simulation has reproduced the sea level anomalies of the Ocean Topography Experiment (TOPEX)/Poseidon altimeter observations well. The equatorial Kelvin and Rossby waves decomposed from the model simulation show that western boundary reflections provide important negative feedbacks to the evolution of the upwelling currents off the Java coast during Indian Ocean dipole (IOD) events. Two downwelling Kelvin wave pulses are generated at the western boundary during IOD events: the first is reflected from the equatorial Rossby waves and the second from the off-equatorial Rossby waves in the southern Indian Ocean. The upwelling in the eastern basin during the 1997-98 IOD event is weakened by the first Kelvin wave pulse and terminated by the second. In comparison, the upwelling during the 1994 IOD event is terminated by the first Kelvin wave pulse because the southeasterly winds off the Java coast are weak at the end of 1994. The atmospheric intraseasonal forcing, which plays an important role in inducing Java upwelling during the early stage of an IOD event, is found to play a minor role in terminating the upwelling off the Java coast because the intraseasonal winds are either weak or absent during the IOD mature phase. The equatorial wave analyses suggest that the upwelling off the Java coast during IOD events is terminated primarily by western boundary reflections.