Malaria risk: estimating clinical episodes of malaria

Estimates of the disease burden caused by malaria are crucial for informing malaria control programmes. Snow and colleagues claim that their estimate of 515 million cases of malaria caused by Plasmodium falciparum globally is up to 50% higher than that reported by the World Health Organization (WHO), and 200% higher for areas outside Africa. However, this comparison refers to the WHO's estimates from 1990 and 1998, and not to the range of 300 million to 500 million that the WHO has used since 2000 (ref. 2). Both groups agree that the burden of malaria disease outside Africa, especially in South Asia, is greater than was estimated in the 1990s.     

The economic and social burden of malaria

Where malaria prospers most, human societies have prospered least. The global distribution of per-capita gross domestic product shows a striking correlation between malaria and poverty, and malaria-endemic countries also have lower rates of economic growth. There are multiple channels by which malaria impedes development, including effects on fertility, population growth, saving and investment, worker productivity, absenteeism, premature mortality and medical costs.     

风险容忍度的估算与求解

风险容忍度较好地反映了投资者的风险--回报偏好.首先提出用风险容忍度这一实际和近似的方法确定投资目标,代替寻找投资者的无差异曲线;接着,给出风险容忍度的估算和求解过程,并得出相应的结论; 最后,进一步讨论了风险容忍度在制定投资目标过程中的重要性.     

基于β值的风险测度模型选择

介绍了基于β值的现代投资组合理论及其演变模型,阐述了目前在我国证券市场上,由于交易费用不均、信息获取不对称等情况的存在,使得具有不同资金规模的投资者处于不同的风险水平。因此为了把握市场,不同的投资者必须采用不同的投资策略。最后运用具体的股票投资组合实例,分析了大中型机构投资者和中小投资者在投资组合方面的不同取向。     

Pareto风险模型中分位数保费的贝叶斯估计

分位数保费原理是非寿险精算中的一种重要的保费原理,在保险中有重要的应用.建立分位数保费原理的Pareto风险模型,通过引入损失函数,结合一些统计技巧,给出了分位数保费原理下风险保费的贝叶斯保费、贝叶斯估计、极大似然估计以及分位数估计.进而,讨论了这些估计的统计性质.最后,利用数值模拟的方法比较了这些估计的平均误差.     

Sugeno测度空间上局部风险最小化估计的界

在Sugeno测度空间上,为了将结构风险最小化原则应用于局部函数估计问题,给出了局部风险最小化估计问题的思想,并证明了局部风险最小化估计的界.     

Malaria parasites--discovery of the early liver form

Infections of mammalian malaria parasites start when sporozoites from an infected anopheline mosquito are injected into the bloodstream of the host. The sporozoites enter the hepatocytes and become transformed into exoerythrocytic schizonts. Since the discovery of the primate parasite Plasmodium cynomolgi in monkey hepatocytes and the rodent parasite Plasmodium berghei in hamster hepatocytes, the ultrastructure of these stages has been extensively studied both in primate and rodent plasmodia. These observations relate only to the development of the exoerythrocytic schizont 25 h after sporozoite injection until the final maturation (of P. berghei) 50 h post-inoculation. Recently, we have studied the route of entry of sporozoites across the cellular lining of liver sinusoids and invasion of the liver parenchymal cells by using transmission electron microscopy. The results of these studies in combination with other physiological experiments strongly suggested that the sporozoite was initially harboured by the Kupffer cell, from which the parasite escaped into the neighbouring hepatocyte. The migration of sporozoites from liver sinusoids to hepatocytes can be achieved within a few minutes. We present here the first ultrastructural observations on the natural transformation of intrahepatocytic sporozoites into exoerythrocytic forms in vivo, using the rodent malaria parasite P. berghei in a laboratory host, the Brown Norway rat. These observations complete the search for the final link in the life cycle of malaria parasites.