Quantitative structure-toxicity relationships of organophosphorous pesticides to fish (Cyprinus carpio)

This study was conducted to determine the relationships between 1381 chemical and structural parameters of 43 organophosphorus pesticides (OPs) and their toxicity to fish, Cyprinus carpio, using ChemOffice 8.03 and Dragon 2.1. By multivariate linear regression and intervariable regression analyses, various equations have been derived to calculate the lethal toxicity value, LC(50), for 43 OPs found in fish with different levels of toxicity. Results show that for all selected OPs, especially those of low toxic OPs (LC(50)< 2.5 mM), the equation, LC(50) = 56.259 - 13.071 lg K(ow)+17.510 MATS8P-17.455 Mor24u - 0.085 MW + 1.706 (lg K(ow))(2) + 2.306 (Mor14e)(2) + 6.849 Mor20 m (n = 43, F = 36.815, r = 0.942, r(adj)(2) = 0.862, SE = 2.899, p < 10(-6)), could account for 86.2% of the variability of the toxic effect. The steric and electronic characteristics and the hydrophobicity of OPs, in particular, are among the most important parameters determining the toxicity of OPs to fish. For the OPs with high toxicity, different structural parameters were introduced into the following two equations: LC(50)=3.795-1.195 (H1p)(2)-0.037 U-2.225 MATS3v-19.593 Tcon (n = 16, F = 56.820, r = 0.977, r(adj)(2) = 0.937, SE = 0.143, p < 10(-6)), where LC(50) is less than 2.5 mM, and LC(50) = 0.341-0.561 (HOMA)(2) + 0.231 HOMA (n = 3,r(adj)(2) = 1), where LC(50) is less than 0.3 mM. These results suggest that chemical and structural parameters could be useful in modeling chemical reactivity within homologous series of OP compounds and elucidating possible mechanisms associated with different levels of toxicity to fish.     

Air-substrate mercury exchange associated with landfill disposal of coal combustion products

Previous laboratory studies have shown that lignite-derived fly ash emitted mercury (Hg) to the atmosphere, whereas bituminous- and subbituminous-derived fly ash samples adsorbed Hg from the air. In addition, wet flue gas desulfurization (FGD) materials were found to have higher Hg emission rates than fly ash. This study investigated in situ Hg emissions at a blended bituminous-subbituminous ash landfill in the Great Lakes area and a lignite-derived ash and FGD solids landfill in the Midwestern United States using a dynamic field chamber. Fly ash and saturated FGD materials emitted Hg to atmosphere at low rates (-0.1 to 1.2 ng/ m2hr), whereas FGD material mixed with fly ash and pyrite exhibited higher emission rates (approximately 10 ng/m2hr) but were still comparable with natural background soils (-0.3 to 13 ng/ m2hr). Air temperature, solar radiation, and relative humidity were important factors correlated with measured Hg fluxes. Field study results were not consistent with corresponding laboratory observations in that fluxes measured in the latter were higher and more variable. This is hypothesized to be partially an artifact of the flux measurement methods.     

The use of magnetic resonance imaging in the prediction of birthweight

Extremes of fetal growth can increase adverse pregnancy outcomes, and this is equally applicable to single and multiple gestations. Traditionally, these cases have been identified using simple two-dimensional ultrasound which is quite limited by its low precision. Magnetic resonance imaging (MRI) has now been used for many years in obstetrics, mainly as an adjunct to ultrasound for congenital abnormalities and increasingly as part of the post-mortem examination. However, MRI can also be used to accurately assess fetal weight as first demonstrated by Baker et al in 1994, using body volumes rather than standard biometric measurements. This publication was followed by several others, all of which confirmed the superiority of MRI; however, despite this initial promise, the technique has never been successfully integrated into clinical practice. In this review, we provide an overview of the literature, detail the various techniques and formulas currently available, discuss the applicability to specific high-risk groups and present our vision for the future of MRI within clinical obstetrics.     

Future private car stock in China: current growth pattern and effects of car sales restriction

Mitigation and Adaptation Strategies for Global Change - Car stock projection is essential to evaluating the energy and environmental impacts of private cars in China. Since the private car...     

旅游开放度对摩梭文化的影响研究

泸沽湖地区以其独特的摩梭文化吸引着越来越多的游客,这种蓬勃发展的旅游业对当地文化的影响成为人们关注的焦点.本文提出了旅游开放度的概念及其测度方法,通过对摩梭家庭的走访和问卷调查.深入分析了旅游开放度对摩梭传统文化的影响.结果表明:旅游开放度的增加在一定程度上影响了当地摩梭人对自身传统文化的看法,这种看法的改变在旅游业相对发达的地区表现尤为突出.同时,对摩梭传统走婚制度影响因素进行相关分析的结果显示,外出打工是影响摩梭人的走婚观念的主要因素.     

20世纪90年代以来沈阳市人口、经济、空间与环境的协调度分析

在中国城市化迅速发展的背景下．城市人口、经济、空间与城市环境的矛盾日益复杂和激化，从可持续发展的角度出发．迫切需要研究城市人口、经济、空间与城市环境之闻的协调关系。运用主成分分析和回归分析等方法。在市区尺度上构建城市人口、经济、空阃与城市环境的协调评价体系，并以老工业城市沈阳为例，进行实证分析。分析结果表明：沈阳城市人口经济空间的综合发展于1993—1999年处于困境．2000年以后城市综合发展逐步好转；沈阳城市环境在1998年以后稳定上升；沈阳城市综合发展与城市环境的静态协调度具有明显的阶段性和波动性特征，动态协调度具有平滑和滞后性的特点；静态协调度于1993—1994年属于基本不协调阶段．1995—2005年基本处于协调状态。于1999年出现了低谷。并存在着下降的趋势；动态协调度于1993—1996年属于基本不协调阶段。1997年以后总体上属于基本协调阶段。     

热盐腐蚀环境对TC11钛合金高温寿命影响规律试验研究

目的 针对发动机钛合金部件在热盐环境与工作载荷下的寿命衰减问题，开展TC11钛合金热盐腐蚀疲劳与应力腐蚀试验，研究腐蚀环境下TC11的高温寿命衰减规律与失效机理。方法 利用喷盐法制备TC11钛合金试验件，研究不同温度与应力水平对TC11腐蚀疲劳以及应力腐蚀的影响规律。利用SEM等观测手段，开展腐蚀疲劳以及应力腐蚀试样断口与表面的形貌分析，分析腐蚀环境下的失效机理。结果 热盐腐蚀环境导致TC11的寿命显著降低，对比450 ℃下无腐蚀寿命，腐蚀疲劳寿命下降了2个数量级，应力腐蚀寿命下降到不足1%，且分散性较大。观察腐蚀疲劳和应力腐蚀的试样可以发现，表面有明显的腐蚀坑，腐蚀坑底发现裂纹。结论 热盐环境下，TC11腐蚀疲劳寿命和应力腐蚀寿命都会明显下降。由于腐蚀导致钛合金试样表面产生许多腐蚀坑，在腐蚀坑局部形成近似缺口，缺口部位的应力集中是导致腐蚀疲劳寿命衰减的重要因素。腐蚀疲劳的寿命低于Kt=1的无腐蚀疲劳寿命，但是要大于Kt=3的无腐蚀疲劳寿命。     

高压水射流计算机模拟可视化初探

在分析射流参数解析解的基础上,结合前人提出的有关经验公式,利用可视化软件工具和可视化图形工具,对高压水射流的射流结构和射流参数进行可视化模拟。阐明了模拟可视化的必要性和可行性,提出了可视化模拟在高压水射流技术研究上的几个可能的发展方向。     

马尔柯夫法在耕地质量动态评价中的应用

根据随机过程原理,构建了新的转移矩阵,建立了一个马尔柯夫链综合耕地质量评价模型.通过实例的应用,分析证明了其模型的可靠性,从而为耕地质量动态评价的科学化提供了依据.