基于Landsat TM的西安市城市热岛效应研究

IEECAS SKLLQG

基于TM的渤海海岸带1988~2000年生态环境变化

海岸带作为海陆之间的过渡地带,是全球生态环境最为复杂和特殊之处。研究海岸带土地利用变化对于了解该区域生态环境演变具有重要意义。利用1988和2000年的Landsat-TM数据,在GIS技术支持下,通过一系列空间分析,得到渤海海岸带土地利用/土地覆盖变化,结合社会经济统计资料分析该区域生态环境的动态变化情况及其驱动因素。结果表明,1988~2000年,由于渤海海岸带社会经济的快速发展,海岸带土地利用格局发生了巨大的变化。耕地大面积减少,城乡工矿用地、养殖池塘、盐田急剧扩张;林地、湿地等具有重要生态价值的土地类型面积显著下降。表明强烈的人类活动已经使自然生态系统受到破坏,渤海海岸带生态环境质量总体上呈现下降趋势。

基于TM影像的表层土壤有机碳空间格局

土壤有机碳是土壤肥力的核心指标之一,理解其空间分布格局对促进精准农业的发展和科学施肥具有重要意义。本研究旨在检验TM影像结合地面采样数据分析黑龙江省黑土分布区表层土壤有机碳空间分布格局的可行性。结果表明:1)表层土壤有机碳浓度与TM5波段呈显著正相关(r=0.553,P<0.01),与TM4、TM5波段影像像素值之间满足二次多项式回归关系(R2=0.6791,P<0.05);2)回归模型对表层土壤有机碳空间分布格局具有较好的预测效果(R2=0.7097,P<0.05);3)海拔高于200m的地区表层土壤有机碳浓度显著高于海拔低于200m的地区(P<0.05)。

基于TM影像和统计分析的林分参数估测研究(英文)

林业研究中的主要兴趣点之一在于通过经验或半经验模型建立林分参数与遥感影像数据间的相互关系来估测林分参数。基于覆盖美国佛罗里达州东北Duval县的遥感数据和两块样地清查数据,论文探讨了所选林分参数与TM影像光谱DN值间的相关性。相关性分析结果表明,单波段或植被指数对林分参数的解释能力低于50%,为此构建了林分参数与影像多波段间多元回归模型来估测林分参数。预测结果通过另一组数据验证,除林分密度外,其它参数估测可信度达75%以上。论文最后探讨了预测模型不足和需改进的地方,并指出该研究有助于更好地理解影像光谱值和林分参数间的关系。图1表2参9。

Separation of enantiomers of drugs by capillary electrophoresis with permethyl-gamma-cyclodextrin as chiral solvating agent

High-throughput screening is a promising new approach in analytical chemistry. Within the framework of an extended screening program (The German-Chinese Drug Screening Program), the enantioseparation of 86 drugs was investigated by capillary zone electrophoresis in the presence of the chiral solvating agent (CSA) octakis-(2,3,6-tri-O-methyl)-gamma-cyclodextrin (TM-gamma-CD). By this means, 15 drugs could be separated into enantiomeric pairs. Approximate measures for the degree of interaction (migration retardation factor, R-m) and for the degree of enantiomer recognition (migration separation factors, alpha(m)) revealed intriguing patterns that were compared with those found for native gamma-cyclodextrin (gamma-CD). Although there is a distinct influence of the analyte structure on the electrophoretic data, interpretation remains difficult. Most remarkably, permethylation of gamma-CD leads neither to a higher affinity nor to better chiral recognition, in contrast to the findings with alpha-CD.

Transient state of chiral recognition in a binary mixture of cyclodextrins in capillary electrophoresis

The transient state (as the defined point where no enantioseparation is obtained in a dual chiral selector system) of chiral recognition of aminoglutethimide in a binary mixture of neutral cyclodextrins (CDs) was studied by capillary electrophoresis (CE). The following three dual selector systems were used: alpha-cyclodextrin (alpha-CD) and beta-cyclodextrin (beta-CD); alpha-CD and heptakis(di-O-methyl-beta-cyclodextrin) (DM-beta-CD); alpha-CD and heptakis(tri-O-methyl-beta-cyclodextrin) (TM-beta-CD). The S-(-) enantiomer of the analyte was more strongly retained in the presence of either alpha-CD or TM-beta-CD at pH 2.5, 100 mM phosphate buffer, while the R-(+) enantiomer was more strongly retained in the presence of either P-CD or DM-P-CD. In the more simple case, the elution order is invariably kept if the enantiomers have the same elution order in either one of the two hosts of the binary mixture. In contrast, the elution order may be switched by varying the concentration ratio of two hosts that produce opposite elution order for this particular analyte. In such a dual selector system, the enantioselectivity will disappear at the transient state at a certain ratio of host,:host, Moreover, the migration times of the two enantiomers with host, alone (diluted in buffer) is approximately equal to the migration times at the corresponding concentration of host, alone (diluted in buffer), where the ratio of concentrations of host,:host, is the same as in the binary mixture at the transient state. As found by nuclear magnetic resonance experiments, the analyte is forming a 1:1 complex with either one of the CDs applied. From this finding, a theoretical model based on the mobility difference of the two enantiomers was derived that was used to simulate the transient state. (C) 2000 Elsevier Science B.V. All rights reserved.

Separation of drug enantiomers by capillary electrophoresis in the presence of neutral cyclodextrins

This is a selected review, highlighting our results obtained in an extended screening program ("The German-Chinese Drug Screening Program"), with a focus on a set of original data obtained with heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin(TM-beta-CD) as the chiral solvating agent (CSA). The enantioseparation of 86 drugs by capillary zone electrophoresis in the presence of this CSA was successful for 47 drugs. The migration separation factors (alpha(m)) and the migration retardation factors (R-m) were compared with those found for native beta-cyclodextrin (beta-CD). The patterns thus obtained were also compared with those observed for hexakis(2,3,6-tri-O-methyl)-alpha-CD (TM-alpha-CD) and octakis(2,3,6-tri-O-methyl)-gamma-CD (TM-gamma-CD), respectively. From the statistical data, it can be concluded that there is a remarkable influence of the analyte structure on the electrophoretic data. A substructure 4H was found in the analyte structure that has a significant influence on the analytes' behaviour. Thus, analytes bearing the substructure 4H do not only have a strong affinity to the CDs but also a high rate of success of chiral separation in all systems reviewed. In light of this, the different ring sizes of native cyclodextrins (alpha-, beta- and gamma-CD) readily explain their behaviour towards a limited test set of chiral drugs. Sterical considerations point to the significance of side-on-binding versus inclusion in the cavity of the host. In addition to the findings from the screening program, numerous references to the Literature are given. (C) 2000 Elsevier Science B.V. All rights reserved.

21世纪初中国生态退耕的空间格局及黄土高原典型区退耕的生态位适宜性分析(英文)

自1999年我国开始试行以"退耕还林"工程为主的生态退耕以来,到目前已历时十年。特别是进入21世纪,工程实施强度较大,因此从国家尺度上进行宏观生态退耕格局的分析对于评估生态退耕政策和确定未来政策导向具有重要意义。本研究以TM遥感监测的土地利用变化数据库为基础分析2000-2005年生态退耕的时空格局。在此基础上,以黄土高原典型地区陕西中北部为研究区,采用生态位适宜度评价模型探讨了生态退耕工程实施的合理性。研究结果表明:(1)2000-2005年间,生态退耕主要集中在中国中部地区,尤其是在黄河和长江的中上游地区,生态退耕面积与建设占用面积基本持平。在各生态类型区中,黄土高原土壤侵蚀区生态退耕面积最大,达到了1162.50km~2,主要用于还林;(2)整体看来,研究区内生态退耕的空间格局是合理的,即适宜性越差的耕地退耕比例越大。从退耕区域的适宜性水平来看,有77.35%的地区属于勉强适宜区,其中退为林地的面积为603.32km~2,退为草地的面积为528.94km~2。整个研究区内前者大于后者。然而,退耕地中仍有19.38%属于中度适宜区,原因可能来自于退耕指标分配等管理因素,另外,当地农民外出务工从而将中等适宜度的耕地退耕。结果表明,当前仍有大面积不适宜和勉强适宜的耕地存在,在未来工程实施过程区应该首先考虑该类地区。