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排序方式: 共有50条查询结果,搜索用时 31 毫秒
1.
早期的地理信息系统(GIS)GIS局限于数据的输入、输出及其分析,发展到今天,GIS的内涵从狭义的管理地理信息的计算机系统逐步发展为到更广泛的空间信息系统,并逐渐形成了地球信息科学这门新兴的边缘科学.当前的GIS正朝向三维地理信息系统(3DGIS)、时态地理信息系统(TGIS)、无尺度地理信息系统(NSGIS)、网络地理信息系统(Web-GIS)、组件式地理信息系统(Com-GIS)、开放式地理信息系统(Open-GIS)等重要方向发展.从而,为推动其它领域信息化的进度提供了有力的保障. 相似文献
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We are investigating the effects of in vivo exposure of prototypical enzyme inducing agents on hepatic biotransformation enzyme expression in largemouth bass (Micropterus salmoides), a predatory game fish found throughout the United States and Canada. The current study targeted those genes involved in biotransformation and oxidative stress that may be regulated by Ah-receptor-dependent pathways. Exposure of bass to beta-naphthoflavone (beta-NF, 66 mg/kg, i.p.) elicited a 7-9-fold increase in hepatic microsomal cytochrome P4501A-dependent ethoxyresorufin O-deethylase (EROD) activities, but did not affect cytosolic GST catalytic activities toward 1-chloro-2,4-dinitrobenzene (CDNB) or 5-androstene-3,17-dione (ADI). Glutathione S-transferase A (GST-A) mRNA expression exhibited a transient, but non-significant increase following exposure to beta-NF, and generally tracked the minimal changes observed in GST-CDNB activities. Expression of the mRNA encoding glutamate-cysteine ligase catalytic subunit (GCLC), the rate-limiting enzyme in glutathione (GSH) biosynthesis, was increased 1.7-fold by beta-NF. Changes in GCLC mRNA expression were paralleled by increases in intracellular GSH. In summary, largemouth bass hepatic CYP1A-dependent and GSH biosynthetic pathways, and to a lesser extent GST, are responsive to exposure to beta-NF. 相似文献
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云南思茅——景谷地区中生界储集层特征 总被引:1,自引:0,他引:1
云南思茅-景谷地区有两类储集层:碎屑岩储集层和碳酸盐岩储集层,其中碎屑岩储集层要优于碳酸盐岩储集层。孔隙类型主要为次生溶孔,偶见剩余原生粒间孔。它们的储集性能基本上属低孔渗性储集层,强烈的压实作用、压溶作用、胶结作用、充填作用、碳酸盐化作用及重结晶作用是导致该区储集层孔隙性差的主要原因。但在有利的构造部位有可能找到孔渗性较好的区块。文中还论证了地表样品中识别埋藏古溶蚀的标志。 相似文献
4.
Comparative oxygen radical formation and toxicity of BDE 47 in rainbow trout cell lines 总被引:2,自引:0,他引:2
The polybrominated diphenyl ethers (PBDEs) constitute a class of flame retardants whose residues have markedly increased in fish and human tissues during the last decade. In particular, the levels of certain PBDE congeners in salmon have raised concern regarding potential risks associated with dietary PBDE exposures. However, little is known regarding PBDE-mediated cell injury in relevant in vitro cell models. We conducted a comparative study of oxyradical production and cell injury in rainbow trout gill (RTgill-W1) and trout liver cells (RTL-W1) exposed to 2,2',4,4'-tetrabromodiphenyl ether (BDE 47), a predominant BDE residue found in fish tissues such as salmonids. Exposure to low micromolar concentrations of BDE 47 elicited a significant loss in RTgill-W1 and RTL-W1 cell viability as measured by alamarBlue assay. The dose-response of BDE toxicity differed among the two cell lines, with the RTL-W1 liver cells showing greater resistance to toxicity at lower BDE 47 doses, but a more dramatic loss of viability relative to gill cells when challenged with higher (50 microM) doses. The sensitivity of the trout liver cells at higher BDE 47 exposures was reflected by a higher basal production of oxygen radical production by 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) fluorescence that was markedly enhanced in the presence of BDE 47, suggesting an overwhelming of trout liver cell antioxidant defense pathways. Collectively, our data indicate that RTgill-W1 and RTL-W1 liver cells are sensitive to BDE 47-mediated cell injury through a mechanism that may involve oxidative stress. Our data also provide an in vitro basis for potential tissue differences in BDE 47-mediated cell injury. 相似文献
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西昆仑库科西力克一带多金属矿地质及地球化学特征的初步研究 总被引:1,自引:0,他引:1
新疆阿克陶县恰尔隆一带1:5万区调工作中曾在库科西力克一带发现数个具有一定工业价值的矿点,这些矿点位于西昆仑铜钼多金属元素富集带,其矿种齐全,涉及Au、Ag、Cu、Pb—Zn、M0、W和Fe等,分布较为集中,资源前景较好,找矿潜力巨大。本文从矿床地质及元素地球化学的角度对一些典型矿点进行了系统调查、采样、分析及研究,发现库尔尕斯金铜矿点主成矿元素中Ag、Cu和Pb具有一致的成矿阶段,而Au受后期构造作用可能滞后富集成矿。同时各矿点间REE含量及分布模式存在较大的差异。除库尔尕斯金铜矿点外,各矿点中矿石和围岩REE总量和分布模式差别也较为明显。认为库科西力克一带各矿点在成矿地质条件上具有一定的联系,成矿物质可能主要来源于深部,主要受区域性断裂(库科西力克断裂)及岩浆活动的影响,但各矿点之间具有各自的成矿特点,这与各矿点不同的矿床类型相关。 相似文献
10.
大西洋和太平洋海水在北冰洋表层的分布:循环的意义E.PeterJones等北冰洋、Nordic海和拉布拉多海的淡水平衡对北半球深水生产力是至关重要的。北冰洋表层水和冰通过弗拉母海峡排出,它们有助于测定格陵兰和冰岛海域的对流区域的表层情况,表层水也通过... 相似文献