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

In an interdependent world the risks faced by any one agent depend not only on its choices but also on those of all others. Expectations about others' choices will influence investments in risk-management, and the outcome can be sub-optimal investment all round. We model this as the Nash equilibrium of a game and give conditions for such a sub-optimal equilibrium to be tipped to an optimal one. We also characterize the smallest coalition to tip an equilibrium, the minimum critical coalition, and show that this is also the cheapest critical coalition, so that there is no less expensive way to move the system from the sub- optimal to the optimal equilibrium. We illustrate these results by reference to airline security, the control of infectious diseases via vaccination and investment in research and development.

Interdependent Security: A General Model

This paper proposes a notion of equilibrium for an economy with increasing returns to scale and gives sufficient conditions for its existence and local uniqueness. The optimality properties of this equilibrium notion follows from our previous investigations on economies with increasing returns.
The notion of equilibrium used in this paper, i.e. a marginal cost pricing equilibrium, is a family of consumption plans, production plans, prices and lump sum taxes such that: all the first order conditions are satisfied in equilibrium; the lump sum taxes cover the aggregate losses of firms with increasing returns to scale; all markets for goods and services clear.
The intended model is an economy with a regulated natural monopoly and a large number of unregulated competitive firms.

Existence, Local Uniqueness, and Optimality of a Marginal Cost Pricing Equilibrium in an Economy with Increasing Returns

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.

https://papers.ssrn.com/sol3/Delivery.cfm/nber_w19725.pdf?abstractid=2367136&type=2

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

A standard normative model of optimal regulated pricing is Ramsey pricing. Ramsey prices are those prices which maximise the indirect social welfare function subject to the regulated firm breaking even at those prices. Faulhaber (1975), first observed that requiring a regulated multi-product monopoly to use Ramsey pricing may be incompatible with allowing free entry into some of the regulated firm’s markets. He argues that, in general, Ramsey prices produce cross-subsidisation in that if the cost function describing the monopolist’s technology is additively separable — hence the average cost of production for each product is well defined — then in some markets the Ramsey prices exceed the average cost of production and in other markets (the subsidised markets) the Ramsey prices are less than the average cost of production. Consequently, firms will enter those markets which are being taxed relative to the average cost of production and produce those commodities at a price less than the Ramsey price. This will leave the regulated firm with insufficient revenue to subsidise consumption in those markets where it is pricing below average cost. The resulting mix of regulated prices and market prices will not be socially optimal.

Ramsey Pricing in Telecommunications Markets with Free Entry

We consider here optimal use patterns for renewable resources and address the problem of optimal use of renewable resources under a variety of assumptions both about the nature of the economy in which these resources are embedded and about the objective of that economy. Although we focus here on the technical economic issues of defining and characterizing paths which are optimal in various senses, in the presence of renewable resources, one should not loose sight of the very real motivation underlying these exercises: many of the earth's most important biological and ecological resources are renewable, so that in their management we confront the fundamental choice which underlies this paper, namely their extinction, or their preservation as viable species.

Sustainable use of renewable resources, Chapter 2.1

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