A cooperative binomial ascertainment model.

It has been shown that the classical binomial form of ascertainment, assuming a constant probability pi that any affected individual may become a proband for his pedigree, cannot describe a rather wide range of ascertainment procedures that might arise in practice. Some more general heuristic ascertainment formulas might then be preferred, and in this paper we consider the probabilistic basis for these formulas. We retain the binomial assumption of the classical scheme but allow the ascertainment probability to depend on the number of potential probands per pedigree. This probability can be expressed by an increasing or a decreasing function of that number. Various illustrations are given and situations where the "cooperative" binomial scheme should be valuable are discussed.     

Chain binomial models and binomial autoregressive processes

Summary We establish a connection between a class of chain‐binomial models of use in ecology and epidemiology and binomial autoregressive (AR) processes. New results are obtained for the latter, including expressions for the lag‐ conditional distribution and related quantities. We focus on two types of chain‐binomial model, extinction–colonization and colonization–extinction models, and present two approaches to parameter estimation. The asymptotic distributions of the resulting estimators are studied, as well as their finite‐sample performance, and we give an application to real data. A connection is made with standard AR models, which also has implications for parameter estimation.     

科学研究五十年的点滴体会

邹承鲁教授是中国科学院院士。本文是作者在 50多年科学研究工作中的经验、心得和体会 ,是难得的一篇好文章。我们推荐给读者 ,相信会得到读者的好评。     

A generalized chain binomial model with application to HIV infection

The original Reed-Frost formulation of the chain binomial model is mathematically equivalent to a stochastic model allowing a Poisson number of effective contacts in a time interval. Their formulation cannot accommodate survey data that necessarily correspond to more complex distributions of partners or contacts, or to large populations where complete random mixing is unlikely. This paper generalizes the Reed-Frost model to accommodate these situations in both the one- and two-population settings. The extension to multiple populations is also outlined. Using the model to predict HIV incidence in San Francisco's homosexual population, we show that the total number of contacts over all partners is more important than the distribution of contacts among partners in determining the number of infected.     

Comparing strategies to preserve evolutionary diversity

The likely future extinction of various species will result in a decline of two quantities: species richness and phylogenetic diversity (PD, or ‘evolutionary history’). Under a simple stochastic model of extinction, we can estimate the expected loss of these quantities under two conservation strategies: An ‘egalitarian’ approach, which reduces the extinction risk of all species, and a ‘targeted’ approach that concentrates conservation effort on the most endangered taxa. For two such strategies that are constrained to experience the same expected loss of species richness, we ask which strategy results in a greater expected loss of PD. Using mathematical analysis and simulation, we describe how the strategy (egalitarian versus targeted) that minimizes the expected loss of PD depends on the distribution of endangered status across the tips of the tree, and the interaction of this status with the branch lengths. For a particular data set consisting of a phylogenetic tree of 62 lemur species, with extinction risks estimated from the IUCN ‘Red List’, we show that both strategies are virtually equivalent, though randomizing these extinction risks across the tip taxa can cause either strategy to outperform the other. In the second part of the paper, we describe an algorithm to determine how extreme the loss of PD for a given decline in species richness can be. We illustrate the use of this algorithm on the lemur tree.     

A simple method to preserve oceanic phytoplankton for flow cytometric analyses

A simple method was developed to preserve marine phytoplankton populations so that delayed flow cytometric analyses could be performed. The method consisted of immediate fixation with 1% glutaraldehyde (final concentration) followed by storage in liquid nitrogen. The method was tested on individual algal species and on natural samples from both coastal and pelagic waters. In most cases, it caused little cell loss and preserved well both forward angle light scatter and chlorophyll fluorescence, but phycoerythrin fluorescence sometimes was significantly increased. The technique performed best for the small-sized picoplankton (below 2 microns) such as Synechococcus cyanobacteria or the newly discovered oceanic prochlorophytes. For larger-sized cells it had to be applied on a case by case basis as some fragile species, particularly dinoflagellates and cryptophytes, were poorly preserved.     

A method to preserve extracellular surfactant-like phospholipids on the luminal surface of rodent gastric mucosa.

Previous results from our laboratory employing the phospholipid-selective cytochemical stain iodoplatinate (IP) suggest that surfactant-like phospholipids (SLPL) are intracellularly contained within rodent gastric mucous cells and are occasionally seen extracellularly within the mucous gel layer. This hydrophobic lipid coating may provide the stomach with a protective water-repellent lining against the corrosive gastric juice in the lumen. Extracellular SLPL are frequently removed during tissue processing for electron microscopy. In this study, we developed a simple method employing an agarose-embedding technique to retain these extracellular SLPL in gastric mucosa excised from rats pre-treated with prostaglandin (to stimulate gastric surfactant/mucus secretion). With the help of polypropylene supporting screens and cassette carriers, thin slices of agarose-embedded gastric mucosa were well preserved and uniformly stained with IP. Extracellular myelin figures were well retained over the interfoveolar surface as well as in the pit region. The IP-reactive substances were seen within or coating the surface of the mucous gel. Our results also indicate that agarose is useful not only for supporting soft tissue while preparing sections with a microslicer but also for preservation of extracellular lipoidal material for electron microscopic observation.     

我的科研和科研管理生涯

陆如山教授为中国医学科学院医学信息所名誉所长、卫生部国际卫生咨询委员会副主任、中华医学会医学信息学分会顾问,曾致力创建我国的放射医学研究基地,担任医学科学院放射医学研究所所长。在任世界卫生组织（WHO）助理总干事时,为国际卫生事业作出了重要贡献。他曾作为我国医学信息工作的牵头人,指导和协调全国医学信息工作,积极组建并参与中国医学信息网络和中文生物医学文献库等医学信息领域的基础建设,在放射医学和医学信息学方面发表论文近百篇。陆教授服从大局,敢为人先的精神,值得我们学习。[编者按]     

Ethical muscle and scientific interests: a role for philosophy in scientific research

Ethics, a branch of philosophy, has a place in the regulatory framework of human subjects research. Sometimes, however, ethical concepts and arguments play a more central role in scientific activity. This can happen, for example, when violations of research norms are also ethical violations. In such a situation, ethical arguments can be marshaled to improve the quality of the scientific research. I explore two different examples in which philosophers and scientists have used ethical arguments to plead for epistemological improvements in the conduct of research. The first example deals with research dishonesty in pharmaceutical development. The second example is concerned with neuropsychological research using fMRI technology.