T-2毒素的毒性效应及致毒机制研究进展

T-2毒素是由多种镰刀菌产生的单端孢霉烯族化合物中毒性较强的一种毒素,广泛存在于谷物和谷类食品中.经食物连续摄入T-2毒素会对人类和动物的健康造成潜在危害.目前,T-2毒素对人和动物健康的影响受到了社会的广泛关注,已成为毒理学领域研究的热点课题之一.在综述了T-2毒素的生物转化、代谢途径及其毒理学效应与机制基础上,对现...     

新烟碱类杀虫剂污染特征及其毒性效应

综述了新烟碱类杀虫剂在土壤、水体和大气中的赋存现状及其对无脊椎动物、脊椎动物和人类的毒性效应.新烟碱类杀虫剂普遍存在于多介质环境中,特别在农业种植区具有较高的残留浓度.新烟碱类杀虫剂对非靶标动物的影响主要表现在氧化应激、抑制活动能力、损伤DNA和生育功能;亦会对人类的生育、生殖、神经以及脏器功能带来风险.因此,今后亟需系统研究新烟碱类杀虫剂在多环境介质中的赋存及污染状况,深入探讨新烟碱类杀虫剂对非靶标生物的健康危害,以便全面了解此类杀虫剂对生态环境及非靶标生物造成的潜在风险.     

绿狐尾藻对铜绿微囊藻和羊角月牙藻的抑藻效应

分别将不同起始浓度(10~5、10~6、10~7、10~8和10~9ind.·L~(-1))的铜绿微囊藻和羊角月牙藻分组与绿狐尾藻进行共培养,连续10 d,每天测定各组铜绿微囊藻或羊角月牙藻的光密度值,用以确定绿狐尾藻对两种藻类不同浓度的生长抑制情况.结果表明,2. 5 g·(200 m L)~(-1)的绿狐尾藻对起始浓度为10~7ind.·L~(-1)和10~8ind.·L~(-1)的铜绿微囊藻具有明显的抑制作用;而对实验所设的所有起始浓度的羊角月牙藻生长均没有显著的抑制作用.并且,采用溶剂浸提与气相色谱-质谱联用(GC-MS)测定的方法,分析了绿狐尾藻粉末浸提液和绿狐尾藻生长液中可能存在的化感物质,通过分析,确定棕榈酸是绿狐尾藻分泌的化感物质之一,并且发现了3种可能是绿狐尾藻分泌的新型化感物质:3-乙基-3-甲基庚烷、磷酸三乙酯和酞酸二丁酯.     

双酚A对青岛大扁藻的干扰效应

为了探讨双酚A(bisphenol A,BPA)对海洋微藻的生态毒性效应,实验选择了以青岛大扁藻(Platymonas helgolanidica)作为受试物种,设置6个实验浓度(即0、2、4、6、8、10 mg·L-1)对微藻进行了96 h暴露处理,测定了不同浓度暴露下对青岛大扁藻的生长以及抗氧化系统酶活性等指标。研究结果表明,BPA对青岛大扁藻的96h-EC50为9.32 mg·L-1,属高毒类污染物。青岛大扁藻经过BPA暴露处理后,细胞密度下降,细胞色素含量降低,并且呈现明显的剂量-效应关系;细胞抗氧化系统中超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)、单脱氢抗坏血酸还原酶(MDHAR)、脱氢抗坏血酸还原酶(DHAR)、谷胱甘肽还原酶(GR)活性均受到干扰。     

基坑开挖与邻近高层建筑施工耦合模拟研究

以一邻近在建观光楼的基坑工程为背景,采用有限元软件MIDAS GTS-NX对其进行基坑开挖及邻近观光楼全过程数值模拟分析,结合模拟计算分析了邻近在建高层建筑的基坑开挖的耦合作用。模拟结果表明:在邻近在建建筑物的基坑开挖情况下,两者间的耦合作用明显;在邻近在建高层建筑物影响下,基坑支护结构水平位移差为10.1 mm;土体应力受邻近建筑动态影响在前期变化明显,到后期影响趋于稳定;在临近高层建筑施工处,地连墙角点和非角点处应力差异明显,地连墙角点应力受到邻近建筑施工影响较小,但非角点位置受到影响较为明显,在设计中应充分考虑该因素。     

Evaluating unintended consequences of intentional species introductions and eradications for improved conservation management

Increasingly intensive strategies to maintain biodiversity and ecosystem function are being deployed in response to global anthropogenic threats, including intentionally introducing and eradicating species via assisted migration, rewilding, biological control, invasive species eradications, and gene drives. These actions are highly contentious because of their potential for unintended consequences. We conducted a global literature review of these conservation actions to quantify how often unintended outcomes occur and to elucidate their underlying causes. To evaluate conservation outcomes, we developed a community assessment framework for systematically mapping the range of possible interaction types for 111 case studies. Applying this tool, we quantified the number of interaction types considered in each study and documented the nature and strength of intended and unintended outcomes. Intended outcomes were reported in 51% of cases, a combination of intended outcomes and unintended outcomes in 26%, and strictly unintended outcomes in 10%. Hence, unintended outcomes were reported in 36% of all cases evaluated. In evaluating overall conservations outcomes (weighing intended vs. unintended effects), some unintended effects were fairly innocuous relative to the conservation objective, whereas others resulted in serious unintended consequences in recipient communities. Studies that assessed a greater number of community interactions with the target species reported unintended outcomes more often, suggesting that unintended consequences may be underreported due to insufficient vetting. Most reported unintended outcomes arose from direct effects (68%) or simple density-mediated or indirect effects (25%) linked to the target species. Only a few documented cases arose from more complex interaction pathways (7%). Therefore, most unintended outcomes involved simple interactions that could be predicted and mitigated through more formal vetting. Our community assessment framework provides a tool for screening future conservation actions by mapping the recipient community interaction web to identify and mitigate unintended outcomes from intentional species introductions and eradications for conservation.     

Impact of bias in predicted height on tree volume estimation: A case-study of intrinsic nonlinearity

Bias originating from intrinsic nonlinearity in nonlinear models is caused by excess curvature in the solution locus of parameter estimates derived from least squares procedures. Bias due to intrinsic nonlinearity varies according to sample size as well as model specification. This paper analyses consequences of fractionising data into smaller sub-samples. Based on measurements of stem diameter and total tree height from the first Danish national forest inventory, it is demonstrated how data splitting at random may cause the intrinsic nonlinear curvature to exceed the critical F-value. Application of a Taylor-series expansion shows that, for all practical purposes, the bias in predictions of individual tree volume (based on stem diameter and tree height) is negligible. To minimize residual variance, intrinsic curvature and, in turn, prediction bias, it is recommended that data be stratified according to site conditions, stand characteristics or other relevant criteria. Finally, the preferred model should exhibit close-to-linear behaviour.     

Simulating dynamic and mixed-severity fire regimes: A process-based fire extension for LANDIS-II

Fire regimes result from reciprocal interactions between vegetation and fire that may be further affected by other disturbances, including climate, landform, and terrain. In this paper, we describe fire and fuel extensions for the forest landscape simulation model, LANDIS-II, that allow dynamic interactions among fire, vegetation, climate, and landscape structure, and incorporate realistic fire characteristics (shapes, distributions, and effects) that can vary within and between fire events. We demonstrate the capabilities of the new extensions using two case study examples with very different ecosystem characteristics: a boreal forest system from central Labrador, Canada, and a mixed conifer system from the Sierra Nevada Mountains (California, USA). In Labrador, comparison between the more complex dynamic fire extension and a classic fire simulator based on a simple fire size distribution showed little difference in terms of mean fire rotation and potential severity, but cumulative burn patterns created by the dynamic fire extension were more heterogeneous due to feedback between fuel types and fire behavior. Simulations in the Sierra Nevada indicated that burn patterns were responsive to topographic features, fuel types, and an extreme weather scenario, although the magnitude of responses depended on elevation. In both study areas, simulated fire size and resulting fire rotation intervals were moderately sensitive to parameters controlling the curvilinear response between fire spread and weather, as well as to the assumptions underlying the correlation between weather conditions and fire duration. Potential fire severity was more variable within the Sierra Nevada landscape and also was more sensitive to the correlation between weather conditions and fire duration. The fire modeling approach described here should be applicable to questions related to climate change and disturbance interactions, particularly within locations characterized by steep topography, where temporally or spatially dynamic vegetation significantly influences spread rates, where fire severity is variable, and where multiple disturbance types of varying severities are common.     

农业资源开发中的耦合效应

论文研究了农业系统的耦合效应,以达到提高农业资源利用率的目的。基于对农业资源特性的分析,肯定了农业资源开发进行系统耦合的必要性。重点论述了农业系统的涵义,并将其分为6个生产层,表述了每个生产层的特点,这为农业系统耦合提供某些理论基础。设计了农业系统耦合的结构要素,通过各结构要素在时序性、空间格局和生态过程上的相互联系和相互作用,将其结构要素耦合成为一个优势互补的农业系统。这个设计在马坪镇实施,取得显著的耦合效应。由此,讨论了在农业资源开发中如何发挥耦合效应的问题。     

Maternal investment in eggs is affected by male feet colour and breeding conditions in the blue-footed booby, <Emphasis Type="Italic">Sula nebouxii</Emphasis>

Females are expected to vary investment in offspring according to variables that may influence the offspring fitness in a way that optimises her inclusive fitness for a particular context. Thus, when sexual ornaments signal the quality of the male, females might invest in reproduction as a function of the attractiveness of their mate. We tested whether breeding conditions and male feet colour influence reproductive decisions of blue-footed booby females. In the blue-footed booby, male feet colour is a dynamic condition-dependent sexually selected trait that is related to paternal effort. During two consecutive years, an El Niño year (poor breeding conditions) and a year with good breeding conditions, we experimentally reduced male attractiveness by modifying their feet colour after the first egg was laid and recorded female investment in the second egg. We found that, relative to the first egg in the clutch, females laid heavier second eggs during the poor year than during the good year. Females paired with males with duller feet colour reduced second-egg mass and volume and delayed the laying of the second egg, independently of the year. Absolute yolk androstenedione (A4) concentration (but not testosterone, T) in second eggs was higher during a poor year than during a good year. Only during a year with poor breeding conditions, females paired with experimental males decreased the relative A4 concentration (but not T) in the second egg compared to control females. Thus, blue-footed booby females probably favour brood reduction by decreasing egg quality and increasing size asymmetry between chicks when the breeding and the mate conditions are poor.