Population fluctuation and persistence of one-host–two-parasitoid systems depending on resource distribution: from parasitizing behavior to population dynamics

Population dynamics and variability were examined in one-host–two-parasitoid experimental systems with different resource distributions: resource-clumped and resource-sparse conditions. The system consists of a seed beetle host, Callosobruchus chinensis, and two parasitoid wasps, Anisopteromalus calandrae (Pteromalidae) and Heterospilus prosopidis (Braconidae). In the resource-clumped condition, suitable hosts for parasitism (the late fourth-instar larvae and pupae) were clumped in 1 large resource patch, but they were scattered evenly among 16 small patches in the resource-sparse condition. Population censuses were conducted at 10-day intervals in long-term cultures, renewing 10 g of azuki beans (Vigna angularis). In both resource conditions, the first period was a single-species system of C. chinensis only, and A. calandrae was added in the second period. The one-host–one-parasitoid system with C. chinensis and A. calandrae showed stable population dynamics with small fluctuations. After addition of H. prosopidis in the third period, two of three replicates persisted to day 800 in each resource condition, although one replicate in each went to extinction at an immediate outbreak of the H. prosopidis population after the introduction. Population variabilities of C. chinensis and H. prosopidis were significantly higher and the mean population size of A. calandrae was significantly smaller in the resource-sparse condition than that in the resource-clumped one. A short-term experiment on parasitism efficiencies revealed that H. prosopidis parasitized significantly more at a low host density in the resource-sparse condition than in the resource-clumped one. Mutual interference of H. prosopidis was weak enough at low parasitoid densities but became abruptly stronger with high densities. Providing fresh hosts in a mixture of already parasitized ones, host-searching behaviors of a parasitoid were recorded by video for 3 h and were compared between the two wasp species. H. prosopidis could parasitize fresh hosts more efficiently than A. calandrae through frequent long-distance walks (walking to distant beans at one bout or outside a clump of beans with hosts and back soon on a distant bean of the clump) after reencounters with parasitized hosts. Considering all the experimental results, populations were judged to be more fragile and more likely to go to extinction in the resource-sparse condition than in the resource-clumped one. A higher attacking efficiency of H. prosopidis destabilized population dynamics more in the resource-sparse condition. Received: December 23, 1998 / Accepted: January 20, 1999     

俄语法律术语初探

法律语言学是研究法律语言的科学,作为一门新兴学科近年来受到了较多学者的关注。本文梳理俄语中的法律术语,分析俄语法律术语的特点、来源、分类以及翻译法律术语时应注意的事项,认为随着中俄法律交流的日益频繁,研究俄语法律术语对语言学和法学理论都具有一定的意义。     

第二类Stirling数的新表示式

以组合分析方法引入指数型生成函数，利用正交关系通过迭代给出第二类Ｓｔｉｒｌｉｎｇ数的两个新的解析表示式．     

中国开放式基金基准组合正交特性的实证研究

基准组合具有某种正交特性（orthogonality properties）。把管理者组合（P）分解为基准组合（B）和积极管理的组合（A），其中基准组合不包含管理者的私人信息。用M代表市场组合，研究得出：cov（B，A）=0，cov（A，M）=0。进一步推导得出：β[P，B]=1，β[P，M]=β[B，M]。本文通过对中国开放式基金市场各基金所声称的基准进行实证检验，得出了我国基金市场开放式基金基准组合并不具有正交特性的结果。     

Constructing estimators of a mean vector through orthogonal reparametrization and differential equations

The simultaneous estimation of a mean vector is explored by reparametrizing it into its direction and norm components. A type of Pythagorean relation is employed to construct an estimate of the norm component, which results in solving an ordinary amerenuai equation, me james-Diem estimator is snown to be optimum in a class of estimators derived from general solutions of the ordinary differential equation. A new Stein-type estimator in the case of the inverse Gaussian distribution is constructed.     

Some adjusted orthogonal,variance balanced,multidimensional block designs

A multidimensional block design (MBD) is an experimental design with d > 1 blocking criteria geometrically represented as a d-dimensional lattice with treatment varieties assigned to some or all nodes of the lattice. Intrablock analysis of variance tables for some special classes of two- and three-dimensional block designs with some empty nodes are given. Design plans and efficiencies for 31 two-dimensional designs, each universally optimal in defined classes of designs, and 7 three-dimensional designs, each nearly optimal in defined classes of designs, are listed in the appendices. A need for such designs is apparent when the blocking criteria are implemented successively and empty nodes do not represent wasted experimental units.     

八连儿童道德行为观念的养成教育

八连村民非常重视团结、协作、互助等传统.乐群、诚实、朴实、踏实、认真、实干、内敛、稳重、自尊自重、自强、宽容、礼貌、谦让,是长辈们教育晚辈的重要内容.同时,村民们要求孩子要尊重长者,对父母要知道感恩,要养成勤问候、勤招呼、勤劳、节俭等等行为习惯.     

《尔雅》在训诂学史上的开创意义

<尔雅>是我国最早的按照词义系统和事物分类来沟通"正统语言"与其他语言系统问的词义关系的词学专著.它在语词训释实践中,反映了诸多训诂原则和训诂方法,开创了中国训诂中的"词义互释"方法和"义界释词"方法,为训诂学的产生奠定了理论基础.     

Leadership and emerging cultural patterns in a new television station

This longitudinal case study explores cultural patterns in a new British television company, tracking it from its inception into its third year. Qualitative research methods provide evidence to suggest that despite formal leaders’ intentions to achieve control and consensus, organisation members produce their own, diverse interpretations of leaders’ deliberate (and unintentional) messages. By drawing on inherited expectations and professional associations, members construct their own cultural worlds. Yet, the same professional norms and associations, which the literature suggests are salient in all media organisations, also provide legitimacy for individual leaders’ actions and therefore reinforce their cultural integrating role. Therefore, it is suggested that although organisation members are active in shaping culture, leaders of new media organisations of this nature are significant as sources of cultural cohesion, division and ambiguity, and thus they are influential in encouraging the formation of complex cultural patterns.     

Group Work Practice with Australia's Asylum Seekers

Abstract

Australia's asylum seekers have been rendered voiceless by the circumstances in which they find themselves, circumstances that include being subjected to punitive government policies, denial of basic rights and needs, economic impoverishment and social disadvantage. The Asylum Seekers Centre (ASC) in Sydney provides an individualised casework service to asylum seekers. The ASC also provides opportunities for asylum seekers to improve their circumstances through attending English classes and participating in other educational and social group programmes. The present paper is concerned with small group facilitation of mutual aid processes at the ASC. It focuses on one group programme, ‘Open Forum’, to illustrate a strengths-based empowerment practice. The paper concludes with some suggestions for extending group work practice with and on behalf of asylum seekers.