On a Problem of Allocation of Sample Size in Stratified Random Sampling

In this paper we shall consider the problem of judging how good an actual compromise allocation is compared to Neyman's optimum allocation for the case of stratified random sampling by obtaining a bound to the ratio of the corresponding variances. A solution to a more general version of the problem considered by COCHRAN (1977) and RAO (1983) has been obtained and the results have been empirically demonstrated.     

中国越桔属的研究

本文讨论了越桔属在杜鹃花科中的系统位置;报道了国产越桔属的已知种91种,归为15个组级类群,按组可划分为5个分布区类型;指出了本属植物在形态、习性上的变异趋向;并联系越桔亚科的分类与分布,讨论了本属区系起源问题,作出几点初步推论: 1.越桔亚科的基干类群极可能发源于古南大陆西北部,也即热带美洲位置偏北。 2.越桔属的原始类群是古南大陆西部山地区系的后裔,而不是从东亚起源。在南、北古陆接触的热带东南亚繁衍后,经中南半岛至我国西南、南部、东部渗入到中部,而后往北。 3.对本属温带成分的13个组的区系分析,认为北温带成分的根源是在热带高山,而北极-高山成分的越桔,来源于亚洲、美洲的亚热带、热带山地     

Monitoring the permeability profile of lipid membranes with spin probes

The rate of reaction of the ascorbate ion with the nitroxide group of spin probes intercalated in lipid bilayers has been studied to examine the mechanism of transport of solutes across membranes. The loss of electron spin resonance (ESR) signal follows first-order kinetics. For a given bilayer system, the half-time of the process increases with the distance of the reacting group from the aqueous interface, according to an approximately linear permeation profile. The dependence on phospholipid headgroup is that which would be predicted from the net charge; addition of negatively charged headgroups increases the half-time of reaction, and positively charged headgroups decrease it, compared with bilayers having no net charge. Addition of cholesterol, which is known to decrease the fluidity of the hydrocarbon core of the bilayer, is found to increase the half-time of reaction. The results have been analyzed in terms of a partition-diffusion mechanism. It is suggested that the rate-limiting step for partitioning the solute into the bilayer might be removal of water of hydration. Cholesterol increases the activation energy, most probably by increasing the height of the barriers to diffusion. Quantitation of the changes in reaction rates gives an estimate of the change in bilayer surface potential on changing the headgroup composition. Examination of the permeation profile supports a diffusive mechanism, from which it can be estimated that the diffusion coefficient is approximately halved on adding 35 mol% cholesterol to egg lecithin bilayers.     

High risk water pollution hazards affecting Aveiro coastal lagoon (Portugal) – A habitat risk assessment using InVEST

Anthropogenic pressures put at jeopardy ecosystem services (ES) provided by natural habitats. Ecosystem Based Management (EBM) approaches can support policymakers dealing with physical, chemical, and biological stresses caused by high-risk water pollution (HRWP) and sudden-accidental pollution (SAP). The objective of this study is to evaluate how alarming HRWP pressures might become in fragile marine, coastal, estuarine, and freshwater socio-ecological systems (MCEF-SES) surrounded by heavily industrialized and urbanized areas. To this end a spatially explicit analysis, using the InVEST-Habitat Risk Assessment (InVEST-HRA) model in combination with expert judgement from researchers from various fields, is performed. An application is provided for the case of the Ria de Aveiro (RdA) coastal lagoon in Portugal. Results show high spatial variance of HRWP hazards across RdA, with one major multi-layer risk hotspot at the center of the research area and a second patch of multiple risk hotspots towards the North of RdA. Salines emerge as the most threatened habitat followed by Intertidal flats and Saltmarshes. The most significant water pollution risk sources contributing to Salines cumulative risk are Fossil fuel processing, storage and sale units, Industrial units, Aquaculture, and the Marinas. Industries involving dangerous substances in the region threaten primarily Watercourses. This study confirms the InVEST-HRA model in combination with expert judgement is a transparent and easily replicable approach to build ES-based knowledge about habitat risks threatening MCEF-SES in a Natura 2000 site heavily pressured by HRWP hazards. After further valuation analysis, pondering gains and losses from regional development and environmental protection, this knowledge can support the planning and management of coastal areas and the prioritization of pollution abatement interventions. In particular, by estimating the loss that HRWP causes in the value of ecosystem services, defining HRWP abatement policies, assessing the effectiveness, costs and benefits of those abatement policies and, ultimately, evaluating the results for the well-being of local communities through global efficiency analysis, cost-benefit analysis or cost-effectiveness analysis. Hence, it bridges the gap between an informed EBM and the development policies of fragile regions.