抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Freshwater biodiversity is the over-riding conservation priority during the International Decade for Action - 'Water for Life' - 2005 to 2015. Fresh water makes up only 0.01% of the World's water and approximately 0.8% of the Earth's surface, yet this tiny fraction of global water supports at least 100000 species out of approximately 1.8 million - almost 6% of all described species. Inland waters and freshwater biodiversity constitute a valuable natural resource, in economic, cultural, aesthetic, scientific and educational terms. Their conservation and management are critical to the interests of all humans, nations and governments. Yet this precious heritage is in crisis. Fresh waters are experiencing declines in biodiversity far greater than those in the most affected terrestrial ecosystems, and if trends in human demands for water remain unaltered and species losses continue at current rates, the opportunity to conserve much of the remaining biodiversity in fresh water will vanish before the 'Water for Life' decade ends in 2015. Why is this so, and what is being done about it? This article explores the special features of freshwater habitats and the biodiversity they support that makes them especially vulnerable to human activities. We document threats to global freshwater biodiversity under five headings: overexploitation; water pollution; flow modification; destruction or degradation of habitat; and invasion by exotic species. Their combined and interacting influences have resulted in population declines and range reduction of freshwater biodiversity worldwide. Conservation of biodiversity is complicated by the landscape position of rivers and wetlands as 'receivers' of land-use effluents, and the problems posed by endemism and thus non-substitutability. In addition, in many parts of the world, fresh water is subject to severe competition among multiple human stakeholders. Protection of freshwater biodiversity is perhaps the ultimate conservation challenge because it is influenced by the upstream drainage network, the surrounding land, the riparian zone, and - in the case of migrating aquatic fauna - downstream reaches. Such prerequisites are hardly ever met. Immediate action is needed where opportunities exist to set aside intact lake and river ecosystems within large protected areas. For most of the global land surface, trade-offs between conservation of freshwater biodiversity and human use of ecosystem goods and services are necessary. We advocate continuing attempts to check species loss but, in many situations, urge adoption of a compromise position of management for biodiversity conservation, ecosystem functioning and resilience, and human livelihoods in order to provide a viable long-term basis for freshwater conservation. Recognition of this need will require adoption of a new paradigm for biodiversity protection and freshwater ecosystem management - one that has been appropriately termed 'reconciliation ecology'.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/96AA265E3D88C95FB802E7A73CCB4332/S1464793105006950a.pdf/div-class-title-freshwater-biodiversity-importance-threats-status-and-conservation-challenges-div.pdf

Freshwater biodiversity: importance, threats, status and conservation challenges

The most unique feature of Earth is the existence of life, and the most extraordinary feature of life is its diversity. Approximately 9 million types of plants, animals, protists and fungi inhabit the Earth. So, too, do 7 billion people. Two decades ago, at the first Earth Summit, the vast majority of the world's nations declared that human actions were dismantling the Earth's ecosystems, eliminating genes, species and biological traits at an alarming rate. This observation led to the question of how such loss of biological diversity will alter the functioning of ecosystems and their ability to provide society with the goods and services needed to prosper.

/pdf/biodiversity-loss-and-its-impact-on-humanity-2d0fgc88mg.pdf

Biodiversity loss and its impact on humanity

This paper discusses the discounted utility (DU) model: its historical development, underlying assumptions, and "anomalies" - the empirical regularities that are inconsistent with its theoretical predictions. We then summarize the alternate theoretical formulations that have been advanced to address these anomalies. We also review three decades of empirical research on intertemporal choice, and discuss reasons for the spectacular variation in implicit discount rates across studies. Throughout the paper, we stress the importance of distinguishing time preference, per se, from many other considerations that also influence intertemporal choices.

/pdf/time-discounting-and-time-preference-a-critical-review-47don96ek5.pdf

Time Discounting and Time Preference: A Critical Review

Changes in Atmospheric Constituents and in Radiative Forcing

Does temperature affect economic performance? Has temperature always affected social welfare through its impact on physical and cognitive function? While many studies have explored the indirect links between climate and welfare (e.g. agricultural yield, violent conflict, or sea-level rise), few address the possibility of direct impacts operating through human physiology. This paper presents a model of labor supply under thermal stress, building on a longstanding physiological literature linking thermal stress to health and task performance. A key prediction is that effective labor supply – defined as a composite of labor hours, task performance, and effort – is decreasing in temperature deviations from the biological optimum. We use country-level panel data on population-weighted average temperature and income (1950-2005), to illustrate the potential magnitude of the effect. Using a fixed effects estimation strategy, we find that hotter-than-average years are associated with lower output per capita for already hot countries and higher output per capita for cold countries: approximately 3%-4% in both directions. We then use household data on air conditioning and heating expenditures from the US to provide further evidence in support of a physiologically based causal mechanism. This more direct causal link between climate and social welfare has important implications for both the economics of climate change and comparative development.

/pdf/feeling-the-heat-temperature-physiology-the-wealth-of-2otm9vfc9j.pdf

Feeling the Heat: Temperature, Physiology & the Wealth of Nations

The choices made by different individuals can reinforce each other. Network externalities provide an obvious example. Explanations for Microsoft’s domina tion of the operating system market, eBay’s domination of the online auction market, and the permanence of the QWERTY keyboard layout have been based on network effects. 1 The rapid growth in popularity of social networking sites such as Facebook and MySpace also illustrates the importance of social reinforcement. People join because their friends have already done so. In his theory of entrapment, Avinash Dixit (2003) exploits reinforcing effects of people’s choices to show how some may be entrapped into joining a club in spite of the fact that its existence makes them worse off. 2 There is an early precedent for the importance of social reinforcement in the work of Harvey Leibenstein (1950). Citing, as a precedent, the work of John Rae (1834), Leibenstein analyses situations in which one’s demand for a good increases with the number of others also buying it, using the term “bandwagon effects” to describe such situations. This is an early theory of fads and fashions, and is based on the recognition that other people’s actions can reinforce one’s own choices. Thomas Schelling’s (1978) work on tipping exemplifies the same insights. His iconic example

/pdf/social-reinforcement-cascades-entrapment-and-tipping-32cfd7jzwl.pdf

Social Reinforcement: Cascades, Entrapment, and Tipping

Focuses on a study which examined economic equilibria involving increasing returns and optimality. Description of the model; Geometrical and mathematical derivation of the model; Conditions involved in economies with efficient equilibria. (From Ebsco)

/pdf/equity-efficiency-and-increasing-returns-bmej6qk92y.pdf

Equity, Efficiency and Increasing Returns

The need to manage climate risks is not a new: it has shaped social institutions for many centuries In medieval England, a peasant farmer’s land was broken into many widely-dispersed parcels Economic historians interpret this as a way of hedging climate risk (see references in Bromley [9]) Land in different locations would be affected differently by droughts, floods and frosts By spreading land holdings over different locations, as well as by organizing agricultural cooperatives and buying insurance, farmers have managed climate risk for many centuries

/pdf/global-environmental-risks-2z04x8z9i2.pdf

Global Environmental Risks

We study the formation of emission abatement coalitions. A necessary condition for a coalition to be viable is that all of its members are net gainers. For this to happen, a coalition has to be at least of a certain size, the minimum critical size. We show that if there are fixed costs associated with abatement programs, or if there are “reinforcement effects”, then under certain conditions coalitions in excess of the minimum critical size are not vulnerable to “free riding” or to prisoners’ dilemma problems.

Formation of International Environmental Agreements

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