Extinction of the trochid gastropod,Umbonium (Suchium) moniliferum (Lamarck), and associated species on an intertidal sandflat

On an intertidal sandflat in western Kyushu, Japan in 1979, the trochid gastropod,Umbonium (Suchium) moniliferum (Lamarck), and the thalassinidean ghost shrimp,Callianassa japonica Ortmann, densely inhabited the lower and upper zones, respectvely.Callianassa japonica subsequently expanded its distribution range considerably, having occupied almost the entire sandflat by 1983. Concurrently, theU. moniliferum population gradually declined, becoming extinct in 1986. Furthermore, the populations of 9 species associated withU. moniliferum (predators, an ectoparasite, and subsequent inhabitants of emptyU. moniliferum shells) had disappeared by the end of 1992. The extinction processes ofU. moniliferum and the two other most numerically dominant species, the ectoparasitic gastropod,Odostomia sp., and the hermit crab,Diogenes nitidimanus Terao, were described in detail. It is believed that the bioturbation of sediments byC. japonica was responsible for the extinctions, possible mechanisms involved being discussed. This is the first documented record of the extinction of a large part of a macrobenthic assemblage centering on a filter-feedingUmbonium species which is characteristic of the benthic communities on many intertidal sandflats extending from Japanese to Southeast-Asian waters.     

Effectiveness of second mating for two incompatible types of the citrus red mite,Panonychus citri (McGregor)

Summary Two types of the citrus red mite,Panonychus citri (M.) occur in some pear orchards in the intermediate latitudal areas in Japan during a certain period of the year (Takafuji andMorimoto, 1983): one is a diapausing type (DP) and the other a non-diapausing type (C). These two types are incompatible: no adult females are produced from the crosses between them (Takafuji andFujimoto, 1985). In the present study, females of each type were doubly crossed, first with a male of the other type, and then with a male of the same type, to examine the effectiveness of the second mating. In the females of the DP type, the second mating with a male of the same type was almost totally ineffective. In contrast, for the females of the C type the effectiveness of the second mating depended on the durations of the first and second matings: the famles produced female offspring only when the duration of the first copulation with a male of the DP type was brief and the second copulation with a male of the C type lasted relatively long. The results suggested that if the two types coexist, the intercrossing between them will favour the C type over the DP type.     

A sufficient condition for the MSE dominance of the positive-part shrinkage estimator when each individual regression coefficient is estimated in a misspecified linear regression model

In this paper, assuming that there exist omitted explanatory variables in the specified model, we derive the exact formula for the mean squared error (MSE) of a general family of shrinkage estimators for each individual regression coefficient. It is shown analytically that when our concern is to estimate each individual regression coefficient, the positive-part shrinkage estimators have smaller MSE than the original shrinkage estimators under some conditions even when the relevant regressors are omitted. Also, by numerical evaluations, we showed the effects of our theorem for several specific cases. It is shown that the positive-part shrinkage estimators have smaller MSE than the original shrinkage estimators for wide region of parameter space even when there exist omitted variables in the specified model.     

Theoretical considerations on the C-D effect in self-thinning plant populations

A model for describing the competition–density (C-D) effect in self-thinning populations was developed on the basis of the following three basic assumptions: (1) the growth of mean phytomass follows a general logistic equation; (2) final yield is independent of initial population density; and (3) there exists a functional relationship between actual and initial population densities at any given time. The resultant equation takes the same reciprocal form as the reciprocal equation of the C-D effect derived from Shinozaki–Kira's theory (i.e., the logistic theory of the C-D effect), which deals with the density effect in nonself-thinning populations. However, one of the two time-dependent coefficients is quite different in mathematical interpretation between the two reciprocal equations. The reciprocal equation for self-thinning populations is essentially the same as the reciprocal equation assumed in the derivation of the functional relationship between actual and initial population densities. The establishment of the reciprocal equation is supported by the empirical facts that the reciprocal relationship between mean phytomass and population density is discernible in not only nonself-thinning populations but also in self-thinning populations. The present model is expected to systematically interpret underlying mechanisms between the C-D effect, which is observed at a time constant among populations with various initial densities, and self-thinning, which is observed along a time continuum in a given population. Received: August 5, 1998 / Accepted: January 7, 1999     

日本电子企业扭亏 索尼领衔，松下跟进

索尼公司近日宣称,由于电视和视频游戏业务的好转,索尼在今年第二季度的利润达到257亿日元。 索尼的首席财务官表示,索尼公司“继续展开攻势”的时候到了,因为种种迹象显示,全球经济的复苏正在将这个日本电子工业巨人彻底拉出长期萧条的泥潭。     

日本制造企业新产品开发过程中模糊前端创新的效果分析

本文对日本制造企业新产品开发(NPD)过程中模糊前端(FFE)创新成功的关键因素进行了大样本分析,开发并构建了FFE创新要素与NPD项目绩效之间的因果关系模型.根据513家日本制造企业NPD项目的调查数据,运用AMOS验证因果关系模型,我们得出两个重要结论:在FFE阶段,技术和市场的不确定性减少越多,NPD项目的效率越高;开发前项目初始规划强度越大,开发过程中市场和技术的不确定性就越少.而且相对服务企业而言,制造企业的管理层更容易做出对降低市场不确定性有重大影响的初始规划.     

On the use of the Stein variance estimator in the double <Emphasis Type="Italic">k</Emphasis>-class estimator when each individual regression coefficient is estimated

In this paper we consider the double k-class estimator which incorporates the Stein variance estimator. This estimator is called the SVKK estimator. We derive the explicit formula for the mean squared error (MSE) of the SVKK estimator for each individual regression coefficient. It is shown analytically that the MSE performance of the Stein-rule estimator for each individual regression coefficient can be improved by utilizing the Stein variance estimator. Also, MSE’s of several estimators included in a family of the SVKK estimators are compared by numerical evaluations.     

Intergenerational interaction between old and young in creative task

By comparing intergenerational to same-generation interactions in creative activities, we aimed to reveal characteristic behaviors of older and younger adults in intergenerational interactions using a wooden block task. Four categories (“Proposal request”, “New proposal”, “Reactions to proposal”, “Assessments of partner’s behavior”) were extracted from conversations during task performance. In intergenerational groups, the ratio of utterances of “Proposal request” (encouraging a new proposal to partner) were higher than in same-generation groups for older adults. In intergenerational groups, older people assumed the role of encouraging younger people to suggest new ideas, and older people’s such empathic behaviors might provoke lively arguments.     

日本出版业的现状

日本出版业的现状是出版规模不断缩小,已经连续7年呈负增长.出版社的正常项目收益率低于1980年代,大经销商之间的"销售额竞争"激烈,书店营业额连续7年也呈负增长.出版流通机制分委托供销制和二次销售制两种.     

日本经济的尴尬

每天，在东京小田吉（Odakyu）的百货商店里，衣着得体的“电梯女孩”都在笑容满面地问候进出电梯的顾客。休息时，她们还要继续练习问候的技巧、精心整理衣饰和妆容。