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61.
Climate Suitability: For Stable Malaria Transmission in Zimbabwe Under Different Climate Change Scenarios 总被引:1,自引:0,他引:1
Jessica Hartman Kristie Ebi K. John McConnell Nathan Chan John Weyant 《Global Change & Human Health》2002,3(1):42-54
As climate is one factor determining the potential range of malaria, climate change may work with or against efforts to bring
malaria under control. We developed a model of future climate suitability for stable Plasmodium falciparum malaria transmission in Zimbabwe. Current climate suitability for stable malaria transmission is based on the MARA/ARMA model
of climatic constraints on the survival and development of the Anopheles vector and the Plasmodium falciparum malaria parasite. We explored potential future geographic distributions of malaria using sixteen projections of climate in
2100. The results suggest that, assuming no future human-imposed constraints on malaria transmission, changes in temperature
and precipitation could alter the geographic distribution of malaria in Zimbabwe, with previously unsuitable areas of dense
human population becoming suitable for transmission. Among all scenarios, the highlands become more suitable for transmission,
while the lowveld and areas currently limited by precipitation show varying degrees of change, depending on climate sensitivity
and greenhouse gas emission stabilization scenarios, and depending on the general circulation model used. The methods employed
can be used within or across other African countries.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
62.
Ocean Drilling Program (ODP) Hole 504B near the Costa Rica Rift is the deepest hole drilled in the ocean crust, penetrating a volcanic section, a transition zone and a sheeted dike complex. The distribution of Li and its isotopes through this 1.8-km section of oceanic crust reflects the varying conditions of seawater alteration with depth. The upper volcanic rocks, altered at low temperatures, are enriched in Li (5.6-27.3 ppm) and have heavier isotopic compositions (δ7Li=6.6-20.8‰) relative to fresh mid-ocean ridge basalt (MORB) due to uptake of seawater Li into alteration clays. The Li content and isotopic compositions of the deeper volcanic rocks are similar to MORB, reflecting restricted seawater circulation in this section. The transition zone is a region of mixing of seawater with upwelling hydrothermal fluids and sulfide mineralization. Li enrichment in this zone is accompanied by relatively light isotopic compositions (−0.8-2.1‰) which signify influence of basalt-derived Li during mineralization and alteration. Li decreases with depth to 0.6 ppm in the sheeted dike complex as a result of increasing hydrothermal extraction in the high-temperature reaction zone. Rocks in the dike complex have variable isotopic values that range from −1.7 to 7.9‰, depending on the extent of hydrothermal recrystallization and off-axis low-temperature alteration. Hydrothermally altered rocks are isotopically light because 6Li is preferentially retained in greenschist and amphibolite facies minerals. The δ7Li values of the highly altered rocks of the dike complex are complementary to those of high-temperature mid-ocean ridge vent fluids and compatible to equilibrium control by the alteration mineral assemblage. The inventory of Li in basement rocks permits a reevaluation of the role of oceanic crust in the budget of Li in the ocean. On balance, the upper 1.8 km of oceanic crusts remains a sink for oceanic Li. The observations at 504B and an estimated flux from the underlying 0.5 km of gabbro suggest that the global hydrothermal flux is at most 8×109 mol/yr, compatible with geophysical thermal models. This work defines the distribution of Li and its isotopes in the upper ocean crust and provides a basis to interpret the contribution of subducted lithosphere to arc magmas and cycling of crustal material in the deep mantle. 相似文献
63.
64.
基于DEM的分布式水文模型构建方法 总被引:52,自引:4,他引:52
基于 DEM的分布式水文模型是现代水文学同高科技 (如计算机技术、 3S技术等 )相结合的产物 ,是研究变化环境下水文循环与水资源演化规律的理想工具 ,代表了水文模型的最新发展方向。从 DEM的特性出发 ,本文探讨并总结了分布式水文模型的特点、建模思路和模型基本结构框图。在流域离散化方面 ,重点介绍了分布式水文模型常用的三种单元划分方法 ;最后 ,针对分布式水文模型构建问题 ,从“输入模块”、“单元水文模型”、“河网汇流模型”三方面 ,阐述了分布式水文模型微结构构建方法。 相似文献
65.
灌淤土壤可溶性盐分空间变异性与棉花生长关系研究 总被引:8,自引:3,他引:8
运用地统计学方法,在灌淤土壤上进行了棉田土壤可溶性盐分的空间变异规律与棉花生长关系系统研究。传统统计学分析表明土壤盐分测试数据基本符合正态分布;在一定取样间距下,土壤可溶性盐分的田间合理取样数目为27。半方差分析显示:土壤可溶性盐分具中等的水平变异性,但随着聚样深度的增加未表现出明显的垂直变异特性;随着棉花的生长发育,土壤可溶性盐分呈现出逐渐减弱的时间变异规律,采用直线或曲线拟合方程估计了可溶性盐分的半方差图及其参数,并绘制了其相应的等值线图。土壤可溶性盐分与棉花产量之间的相关分析表明:可溶性盐分含量与棉花产量之间呈显著负相关关系,且花铃期的相关性较播前显著。研究结果为提高田间试验有效性以及盐渍化土壤改良提供了科学依据与基础资料。 相似文献
66.
在对中国农村剩余劳动力现状描述的基础上 ,对剩余劳动力形成的原因进行了分析与阐述 ;结合目前形势 ,指出未来农村剩余劳动力的转移前景不容乐观 ;并在此基础上阐述了中国剩余劳动力转移途径和主要措施 相似文献
67.
68.
An Efficient Numerical Method for Computing Synthetic Seismograms for a Layered Half-space with Sources and Receivers at Close or Same Depths 总被引:1,自引:0,他引:1
— It is difficult to compute synthetic seismograms for a layered half-space with sources and receivers at close to or the same depths using the generalized R/T coefficient method (Kennett, 1983; Luco and Apsel, 1983; Yao and Harkrider, 1983; Chen, 1993), because the wavenumber integration converges very slowly. A semi-analytic method for accelerating the convergence, in which part of the integration is implemented analytically, was adopted by some authors (Apsel and Luco, 1983; Hisada, 1994, 1995). In this study, based on the principle of the Repeated Averaging Method (Dahlquist and Björck, 1974; Chang, 1988), we propose an alternative, efficient, numerical method, the peak-trough averaging method (PTAM), to overcome the difficulty mentioned above. Compared with the semi-analytic method, PTAM is not only much simpler mathematically and easier to implement in practice, but also more efficient. Using numerical examples, we illustrate the validity, accuracy and efficiency of the new method. 相似文献
69.
随着郑州市城市化进程的飞速发展和规模的不断扩大,尤其是郑东新区的建设,需水量急剧增加。为缓解郑州市供水紧张状况,调整引黄水量与地下水开采量的比例,确保郑州供水安全,需在黄河岸边开采地下水,水源地开采后,地下水流场范围内水位将下降,地下水流场的改变对黄河堤防稳定性是否产生影响,对此进行了初步研究和探讨。研究结果表明,开采浅层地下水,不会对黄河大堤造成危害。 相似文献
70.
由卫星和航空磁测成果推断中国岩石圈的磁性特征 总被引:11,自引:2,他引:11
根据前人所得卫星和航磁异常解释结果,作者的综合研究表明:(1)在塔里木、四川和松辽盒地,地壳呈强磁性,至少可分为两层,上层磁化强度为1A/m,下层为2A/m或更强一些。在上述盆地中央,地幔顶部约10km厚,也是强磁性的,此外,在南中国海,地壳和地幔顶部也是强磁性的,卫星磁异常的源位于上述部位。(2)西藏高原,中国东南沿海一带以及其他一些褶皱带之下,地壳是弱磁性的,磁性层在地表以下30km以内,磁化强度约0.66A/m。特别要指出的是,在东南沿海一带,磁性层底面和莫霍面重合,而居里等温面恰在莫霍面之下,因此这个带可能是Wasilewsky PJ等提出的“莫霍面是一个磁性界面”的一例。 相似文献