On convergence of the generalized Maxwell scheme: conductivity of composites containing cubic arrays of spherical particles

The Maxwell concept of equivalent inhomogeneity generalized to account for the interactions between the particles in the cluster and combined with recently reported results on the polarizability of a cube is used to evaluate the effective conductivities of the materials reinforced by cubic arrays of spherical particles. New numerical results demonstrate that the estimates of the effective properties based on the generalized Maxwell scheme with the equivalent inhomogeneity of cubic shape converge to the accurate periodic benchmark solutions, unlike spherical shape-based estimates.     

Infanticide and maternal aggression: Synchrony of male and female reproductive strategies in mice

Thirty-six percent of male mice from three strains attacked newborn pups sired by another male. No male attacked its own offspring. Females did not show differential aggression toward males likely (strangers) or unlikely (sires) to attack their pups. Both forms of aggression were unaffected by housing in rooms which did or did not contain the aggression targets. The three strains differed in strength of maternal aggression but not in the incidence of infanticide. Females showed more aggression when mated with males of the same, rather than a different, strain but no differences with intruders of the same or a different strain. Infanticide by males is best viewed as a postcopulatory, intermale-competition strategy, and maternal aggression as a counter strategy.     

A matter of style? Testing the moderating effect of driving styles on the relationship between job strain and work-related crashes of professional drivers

Different empirical studies suggest that both job strain and driving styles are significant contributors to the work-related traffic crashes suffered by professional drivers. Nevertheless, the current evidence falls considerably short when explaining why driving styles may modify (or not) the relationship between occupational stressors and professional drivers’ safety outcomes. The aim of this study was to examine whether driving styles moderate the effect of job strain on professional drivers’ Work Traffic Crashes (WTCs). This research was performed using the data collected from a sample of 753 professional drivers, responding to a self-report questionnaire on job strain (work stress indicator of the Job Demand-Control model), driving styles and work-traffic safety outcomes suffered in the past two years. Regression-based moderation analyses suggest that the job strain of professional drivers is positively associated with the occupational traffic crashes they suffer, and that such association is stronger in drivers with “reckless & careless”, “anxious”, and “angry & hostile” driving styles. Meanwhile, the “patient & careful” (positive) driving style was not associated with a lower risk of suffering a WTC, nor with a lower vulnerability to stress-related WTCs. The results of this study support the hypothesis that driving styles exert a statistical moderation between the job strain and the occupational traffic crashes suffered by professional drivers. These findings may support the design of evidence-based interventions in both the organizational and individual levels, focused stress-related factors and driving styles as predictors of work traffic crashes.     

On portfolio management with value at risk and uncertain returns via an artificial neural network scheme

This paper focuses on the computation issue of portfolio optimization with scenario-based Value-at-Risk. The main idea is to replace the portfolio selection models with linear programming problems. According to the convex optimization theory and some concepts of ordinary differential equations, a neural network model for solving linear programming problems is presented. The equilibrium point of the proposed model is proved to be equivalent to the optimal solution of the original problem. It is also shown that the proposed neural network model is stable in the sense of Lyapunov and it is globally convergent to an exact optimal solution of the portfolio selection problem with uncertain returns. Several illustrative examples are provided to show the feasibility and the efficiency of the proposed method in this paper.     

The direct product model for the mtmm matrix parameterized as a second order factor analysis model

The composite direct product model for the multitrait-multimethod matrix is reparameterized as a second-order factor analysis model. This facilitates the use of widely available computer programs such as LISREL and LISCOMP for fitting the model.Bruce Bloxom. Paul Horst and Karl Jöreskog contributed helpful comments to an earlier version of this paper. Their suggestions are gratefully acknowledged.     

Equivalent models in covariance structure analysis

Defining equivalent models as those that reproduce the same set of covariance matrices, necessary and sufficient conditions are stated for the local equivalence of two expanded identified modelsM ₁ andM ₂ when fitting the more restricted modelM ₀. Assuming several regularity conditions, the rank deficiency of the Jacobian matrix, composed of derivatives of the covariance elements with respect to the union of the free parameters ofM ₁ andM ₂ (which characterizes modelM ₁₂), is a necessary and sufficient condition for the local equivalence ofM ₁ andM ₂. This condition is satisfied, in practice, when the analysis dealing with the fitting ofM ₀, predicts that the decreases in the chi-square goodness-of-fit statistic for the fitting ofM ₁ orM ₂, orM ₁₂ are all equal for any set of sample data, except on differences due to rounding errors.This research was supported by the Foundation of Social-Cultural Sciences which is subsidized by the Dutch Scientific Organization (N.W.O.) under project number 500-278-003. The author wishes to thank Anne Boomsma, Ivo Molenaar, Albert Satorra, and Tom Snijders for their stimulating and crucial comments during the research, and the Editor, Paul Bekker, Henk Broer, and anonymous reviewers for their helpful suggestions.     

教育价值观和逆境信念在家庭经济压力与初中生学业成就之间的作用

大量研究表明,家庭经济压力对青少年学业成就具有显著的不利影响。但是,目前学界对家庭经济压力“怎样”（中介机制）以及“何时”（调节机制）影响青少年学业成就仍知之甚少。本研究在整合贫困文化模型及心理韧性理论的基础上构建一个有调节的中介模型,考察青少年教育价值观（读书是否有用）在家庭经济压力与学业成就之间的中介作用,同时检验中国文化逆境信念对该中介路径的调节作用。采用随机整群抽样,选取四川省9所普通中学1613名初中生（平均年龄13.42岁,SD = 1.22）作为研究对象。被试匿名填写家庭经济压力问卷、教育价值观问卷、中国文化逆境信念量表以及学业成就问卷。结果表明：（1）在控制了性别、年龄等人口学变量后,家庭经济压力显著负向预测学业成就。（2）教育价值观在家庭经济压力与学业成就之间具有部分中介作用。（3）积极逆境信念能缓冲家庭经济压力对教育价值观的消极作用,进而减少对学业成就的不利影响。本研究证实了“读书无用论”是经济困难与学业成就的重要联系机制,并肯定了中国文化逆境信念对经济困难青少年的保护作用。这一内在保护机制的揭示对教育实践有一定的启示。     

Relations between stress and work outcomes: The role of felt challenge, job control, and psychological strain

Recent research on reported work stress indicates stress may not always be deleterious for an individual or organization. Research in this area, however, has not yet examined a variety of work outcomes, the mechanism by which stress leads to such outcomes, and the moderators of this effect. The present study hypothesized that two types of reported stress (challenge- and hindrance-related) have a divergent relationship with work outcomes (relating to desirable and undesirable outcomes, respectively) and a similar (positive) relationship with psychological strain. We also hypothesize felt challenge as a mechanism through which challenge stress relates to desirable outcomes and job control as a moderator of the effect. Results from a heterogeneous sample of university staff employees (N=461) supported many of the hypotheses. The two types of stress differentially related to work outcomes yet both positively related to psychological strain. In addition, felt challenge mediated the relationship between challenge-related stress and work outcomes, yet the effect of challenge-related stress did not depend on job control.     

Exploring links between polychronicity and well-being from the perspective of person–job fit: Does it matter if you prefer to do only one thing at a time?

This research examined polychronicity, which refers to an individual’s preference for working on many things simultaneously as opposed to one at a time. It was hypothesized that supplies–values fit on this temporal variable is related to well-being. Specifically, it was predicted that deficient and excess polychronicity supplies are associated with poorer well-being, and that well-being is uniformly high along the continuum of polychronicity fit. It was also hypothesized that fit effects are stronger for individuals who place high importance on how their time is allocated than for individuals who place low importance on that dimension. Participants in Study 1, a laboratory experiment, were students (N = 266); participants in Study 2, conducted in a field setting, were employees of Canadian organizations (N = 746). No fit effects were observed in Study 1. Consistent with the hypotheses, however, fit on the dimension of polychronicity was related to job satisfaction, self-efficacy, and psychological strain in Study 2. The role of value importance as a moderator of the relation between supplies–values fit and well-being was not supported.