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341.
研究了4种成片分布的典型岩性(页岩、石灰岩、花岗岩、黄土)区域沉积物金属元素(Li、Na、K、Ca、Sr、Ba、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Al等共16种)总量与形态特征.结果表明:这4种岩性区域沉积物金属元素含量与形态均有显著的差别.与其它岩性相比,黄土地区易迁移元素含量高,而重金属含量显著较低;其金属元素残渣态含量高,而有机态、铁锰氧化物态和可交换态含量低.石灰岩地区重金属含量较高,而易迁移元素如Na,Sr等含量则较低;其重金属元素残渣态含量不偏低,表明经风化作用释放出来的重金属参与了次生矿物的形成过程而得以富集.花岗岩地区重金属含量居中,而Fe和Al含量较高;其金属元素残渣态含量不偏高则与风化作用较强有关.页岩地区元素含量与形态均居中,代表了各种岩性的平均水平.  相似文献   
342.
农田NO排放的自动观测   总被引:6,自引:2,他引:6  
详细介绍农田NO排放自动观测的方法原理,系统整体构造及电路和气路配置,并讨论了观测结果的可靠性。同地,还就已取得的一些初步研究结果进行了分析,对华东秋,冬季麦田的NO排放进行自动连续观测的结果表明,秋季麦田的NO排放具有与温度几乎完全同步的日变化规律。  相似文献   
343.
GeochemicalcharacteristicsofrareearthelementsinWuhansectionoftheYangtzeRiverWangLijun;ZhangShen;ZhangChaosheng(InstituteofGeo...  相似文献   
344.
于2013年4月至6月在杭州城市河道对微纳米气泡改善河道水生态环境进行了持续的原位监测实验.结果表明,与对照区相比,试验区水体温度平均升高0.7℃,pH增大0.2,溶解氧增加1.0 mg/L,而TDS浓度降低42 mg/L;水质污染指标高锰酸盐指数、总氮、氨氮、总磷平均浓度分别降低了8.45 mg/L、6.78 mg/L、8.90 mg/L和0.58 mg/L.由此可推测微纳米气泡在一定程度上能有效净化水质,为恢复良好水生生态环境提供新的方法和技术手段.  相似文献   
345.
Noroviruses are one of important agents that cause acute viral gastroenteritis worldwide. These viruses are belonging to Caliciviridae family and are genetically diverse. To date, there is no valuable data about prevalence of norovirus infection and the dominant genogroup/genotype among Iranian population. The objective of this study was to determine the frequency of norovirus infection in Iranian patients with gastroenteritis referred to three hospitals of Tehran and to specify the dominant genogroup/genotype of this virus among our study population. A total of 293 patients with acute gastroenteritis were included in the study. Detection of norovirus was performed using RT-PCR method and confirmed by direct sequencing with specific designed primers for capsid region of norovirus genome. Phylogenetic analysis was performed using the neighbor-joining method. Norovirus strains identified in our study were subsequently categorized according to previously defined genogroup/genotypes. Of these, norovirus GII was dominant genogroup. Sixty-five percent (17 of 26) of positive samples were determined as GII and 35% (9 of 26) were determined as GI, respectively, in 2008–2009. And among 8 sequenced strains of genogroup II the most frequent genotype was GII.3. The results of this study indicated that norovirus must be considered as one of the infectious causes of acute gastroenteritis among Iranian population. We also found that GII.3 is more prevalent in our study population. To the best of our knowledge there is limited data about the role of noroviruses in children and adults’ acute gastroenteritis among Iranian patients and this prevalence and genotyping report of norovirus infection could be remarkable for further studies.  相似文献   
346.
Although forest conservation activities, particularly in the tropics, offer significant potential for mitigating carbon (C) emissions, these types of activities have faced obstacles in the policy arena caused by the difficulty in determining key elements of the project cycle, particularly the baseline. A baseline for forest conservation has two main components: the projected land-use change and the corresponding carbon stocks in applicable pools in vegetation and soil, with land-use change being the most difficult to address analytically. In this paper we focus on developing and comparing three models, ranging from relatively simple extrapolations of past trends in land use based on simple drivers such as population growth to more complex extrapolations of past trends using spatially explicit models of land-use change driven by biophysical and socioeconomic factors. The three models used for making baseline projections of tropical deforestation at the regional scale are: the Forest Area Change (FAC) model, the Land Use and Carbon Sequestration (LUCS) model, and the Geographical Modeling (GEOMOD) model. The models were used to project deforestation in six tropical regions that featured different ecological and socioeconomic conditions, population dynamics, and uses of the land: (1) northern Belize; (2) Santa Cruz State, Bolivia; (3) Paraná State, Brazil; (4) Campeche, Mexico; (5) Chiapas, Mexico; and (6) Michoacán, Mexico. A comparison of all model outputs across all six regions shows that each model produced quite different deforestation baselines. In general, the simplest FAC model, applied at the national administrative-unit scale, projected the highest amount of forest loss (four out of six regions) and the LUCS model the least amount of loss (four out of five regions). Based on simulations of GEOMOD, we found that readily observable physical and biological factors as well as distance to areas of past disturbance were each about twice as important as either sociological/demographic or economic/infrastructure factors (less observable) in explaining empirical land-use patterns. We propose from the lessons learned, a methodology comprised of three main steps and six tasks can be used to begin developing credible baselines. We also propose that the baselines be projected over a 10-year period because, although projections beyond 10 years are feasible, they are likely to be unrealistic for policy purposes. In the first step, an historic land-use change and deforestation estimate is made by determining the analytic domain (size of the region relative to the size of proposed project), obtaining historic data, analyzing candidate baseline drivers, and identifying three to four major drivers. In the second step, a baseline of where deforestation is likely to occur–a potential land-use change (PLUC) map—is produced using a spatial model such as GEOMOD that uses the key drivers from step one. Then rates of deforestation are projected over a 10-year baseline period based on one of the three models. Using the PLUC maps, projected rates of deforestation, and carbon stock estimates, baseline projections are developed that can be used for project GHG accounting and crediting purposes: The final step proposes that, at agreed interval (e.g., about 10 years), the baseline assumptions about baseline drivers be re-assessed. This step reviews the viability of the 10-year baseline in light of changes in one or more key baseline drivers (e.g., new roads, new communities, new protected area, etc.). The potential land-use change map and estimates of rates of deforestation could be re-done at the agreed interval, allowing the deforestation rates and changes in spatial drivers to be incorporated into a defense of the existing baseline, or the derivation of a new baseline projection.  相似文献   
347.
Host selection and infection strategies of parasitoids often correlate with high parental investment and low numbers of progeny. In this study, we investigate how additional internal mechanisms might shape brood size and fitness of the offspring. Emblemasoma auditrix is a parasitoid fly in which about 38 larvae hatch simultaneously in utero. After host location, a single larva is deposited into the host, where it rapidly develops and pupates after about 5 days. The search for hosts can take several weeks, and during that time, the larvae arrest their development and remain in the first larval instar. Nevertheless, the larvae increase in weight within the uterus, and this growth correlates to a decrease in the number of larvae, although no larvae are deposited. Thus, our data indicate a first case of prenatal cannibalism in an invertebrate with larvae feeding on each other within the uterus of the adult.  相似文献   
348.
Numerous studies have focussed on the relationship between female choice and the multiple exaggerated sexual traits of males. However, little is known about the ability of males to actively enhance specific components of their display in response to the loss of one component. We investigated the capacity of male satin bowerbirds (Ptilonorhynchus violaceus) to respond to the loss of one of their sexual signals by performing an experiment in which we removed decorations at their bowers. We found that males compensated for decoration loss by increasing bower construction behaviour and decreasing their latency to bower painting. These results are novel because they suggest that males can assess the quality of their own display and make decisions about how to augment their displays. We discuss these results in the context of previous studies of mate choice in satin bowerbirds, as both of the supplementary behaviours we observed are known correlates of male mating success.  相似文献   
349.
Climate change programs have largely used the project-specific approach for estimating baseline emissions of climate mitigation projects. This approach is subjective, lacks transparency, can generate inconsistent baselines for similar projects, and is likely to have high transaction costs. The use of regional baselines, which partially addresses these issues, has been reported in the literature on forestry and agriculture projects, and in greenhouse gas (GHG) mitigation program guidance for them (e.g., WRI/WBCSD GHG Project Protocol, USDOE’s 1605(b) registry, UNFCCC’s Clean Development Mechanism). This paper provides an assessment of project-specific and regional baselines approaches for key baseline tasks, using project and program examples. The regional experience to date is then synthesized into generic steps that are referred to as Stratified Regional Baselines (SRB). Regional approaches generally, and SRB in particular explicitly acknowledge the heterogeneity of carbon density, land use change, and other key baseline driver variables across a landscape. SRB focuses on providing guidance on how to stratify lands into parcels with relatively homogeneous characteristics to estimate conservative baselines within a GHG assessment boundary, by applying systematic methods to determine the boundary and time period for input data.
Kenneth AndraskoEmail:
  相似文献   
350.
Symbiont-induced male-killing phenotypes have been found in a variety of insects. Conventionally, these phenotypes have been divided into two categories according to the timing of action: early male killing at embryonic stages and late male killing at late larval stages. In Drosophila species, endosymbiotic bacteria of the genus Spiroplasma have been known to cause early male killing. Here, we report that a spiroplasma strain normally causing early male killing also induces late male killing depending on the maternal host age: male-specific mortality of larvae and pupae was more frequently observed in the offspring of young females. As the lowest spiroplasma density and occasional male production were also associated with newly emerged females, we proposed the density-dependent hypothesis for the expression of early and late male-killing phenotypes. Our finding suggested that (1) early and late male-killing phenotypes can be caused by the same symbiont and probably by the same mechanism; (2) late male killing may occur as an attenuated expression of early male killing; (3) expression of early and late male-killing phenotypes may be dependent on the symbiont density, and thus, could potentially be affected by the host immunity and regulation; and (4) early male killing and late male killing could be alternative strategies adopted by microbial reproductive manipulators.  相似文献   
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