Influence of plastic strain localisation on the mechanical properties of metal matrix composites

The aim of the present study is to reveal the most critical underlying factor influencing the mechanical properties of metal matrix composites (MMCs). It is shown that the mechanical properties of MMCs are essentially governed by the degree of strain localisation during plastic deformation. In other words, the MMCs exhibit superior mechanical performance only if the strain localisation is obviously inhibited and the accumulated stresses can be effectively transferred out. The work provides a new perspective in guiding the design of next-generation high-performance MMCs by suppressing the strain localisation as far as possible.     

大鼠注意定势转移任务模型的深入研究：种系和检测程序的影响

注意定势转移任务(attentional set-shifting task, AST)可用于特异性检测啮齿类动物前额叶皮层及其皮层下神经通路介导的认知灵活性, 是目前研究认知灵活性及其障碍神经基础的重要模型。本研究系统调查了大鼠种系和检测程序差异对AST结果的影响。通过比较Wistar和Sprague Dawley (SD)两个种系大鼠在七阶段和五阶段两种AST检测程序中的认知表现, 研究发现：(1) SD和Wistar大鼠前额叶认知功能存在差异, 后者的总体认知表现优于前者。尤其是Wistar大鼠在逆反学习阶段的达标训练次数及错误率显著低于SD大鼠, 表明Wistar大鼠具有更高的策略转换灵活性。(2)在AST测试中逆反学习和外维度定势转移是认知灵活性评价的核心指标。这两种认知转换过程分别以前期策略和注意定势建立为基础。结果显示在两种AST检测程序中Wistar和SD大鼠在逆反学习和/或外维度定势转移等复杂学习阶段的达标训练次数和错误率均高于其它简单关联学习阶段, 表明在目前实验条件下大鼠均表现出定势形成和转换困难的反应模式, 不同认知反应间的结构关系具有稳定性。这些结果提示大鼠前额叶皮质介导的认知灵活性存在种系差异, AST各阶段认知反应间的结构效度不受目前使用的大鼠种系和检测程序差异的影响, 扩展了对AST模型的认识。     

Psychological strain and emotional labor among police-officers: A diary study

The authors examined the relationship between psychological strain, emotional dissonance and emotional job demands during a working day of 65 Dutch (military) police officers, using a 5-day diary design. We hypothesized that emotional dissonance partly mediated the relationship between psychological strain at the start and at the end of a work shift. We also tested the mediating role of emotional dissonance between emotional job demands and psychological strain at the end of a work shift. Results of structural equation modeling analyses showed that psychological strain at the start of a work shift had a positive effect on the experience of emotional dissonance and psychological strain at the end of a work shift. Emotional dissonance partly mediated the relationship between psychological strain at the start and psychological strain at the end of a work shift. Results are discussed in light of conservation of resources theory (Hobfoll, S. E. (1988). The ecology of stress. New York: Hemisphere Publishing Corporation).     

Perceived Social Support and Caregiver Strain in Caregivers of Children with Tourette’s Disorder

The research on Tourette’s disorder (TD), a neuropsychological disorder consisting of motor and phonic tics, has largely focused on individuals with TD and not on the caregivers of children with TD. We investigated the effects of several variables on caregiver strain of caregivers of children with TD, including perceived social support, caregiver characteristics, and characteristics of the child’s disorder. An online survey was completed by 140 caregivers of children with TD between the ages of 6 to 18 years. We performed a path analysis to examine the outcome of caregiver strain in relation to the research variables. Our results indicated that caregiver age, symptom severity of the child’s TD, and perceived social support accounted for variance in caregiver strain, and that perceived social support was a partial mediator of child’s symptom severity and caregiver strain. Symptom severity and caregiver strain were also related to the presence of other comorbid disorders, such as Oppositional Defiant Disorder (ODD), anxiety, or Attention Deficit Hyperactivity Disorder (ADHD) when compared to children either having no other comorbid disorders or other types of disorders.     

Psychological Distress in Caregivers of Liver and Lung Transplant Candidates

Although organ transplantation represents a stressful experience for the entire family, surprisingly little research has focused on the adjustment of caregivers. The purpose of this study was to examine what caregivers report to be the greatest benefits and stressors pretransplant, the prevalence of psychological distress and caregiver strain in pretransplant caregivers as compared to normative populations, and the physical, psychological, and demographic variables that predict distress. Fifty-two caregivers of transplant candidates (28 liver and 24 lung) completed a series of questionnaires, including the Psychosocial Adjustment to Illness Scale (PAIS-SR), SF-36 Health Survey, Caregiver Strain Index (CSI), and qualitative questions about benefits and stressors. The most commonly reported benefit of being a caregiver could be categorized as Helping the Patient, and the most common stressors were associated with Uncertainty/Waiting/Fears. Compared to normative samples of caregivers of patients with Alzheimer's disease, caregivers of liver transplant candidates reported more caregiver strain; there were no differences for lung transplant caregivers. Caregiver social functioning was found to be the only significant predictor of caregiver distress, with those caregivers who report greater distress also reporting extreme and frequent interference with normal social activities. Implications of these findings for psychological interventions are discussed.     

Social-relational exposures and well-being: Using multivariate twin data to rule-out heritable and shared environmental confounds

The aims of the present study were as follows: (1) Using a large sample of adults, estimate overlap between social-relational exposures measured at midlife and well-being measured at midlife and approximately 9-years later. (2) Using a subsample of twins, test for heritable variation in social-relational exposures, and (3) controlling for heritable and shared environmental variation, estimate overlap between social-relational exposures and well-being, both concurrently and approximately 9-years later. Results indicated small-to-moderate overlap between exposures and well-being (mean r = 0.29, range = 0.05–0.54). There was also evidence for heritable variation in exposures, and after accounting for these genetic factors, the degree of overlap between social-relational exposures and well-being decreased (mean r = 0.10, range = −0.07 to 0.33).     

The linear system theory's account of behavior maintained by variable-ratio schedules.

The mathematical theory of linear systems, which has been used successfully to describe behavior maintained by variable-interval schedules, is extended to describe behavior maintained by variable-ratio schedules. The result of the analysis is a pair of equations, one of which expresses response rate on a variable-ratio schedule as a function of the mean ratio requirement (n) that the schedule arranges. The other equation expresses response rate on a variable-ratio schedule as a function of reinforcement rate. Both equations accurately describe existing data from variable-ratio schedules. The theory accounts for two additional characteristics of behavior maintained by variable-ratio schedules; namely, the appearance of strained, two-valued (i.e., zero or very rapid) responding at large ns, and the abrupt cessation of responding at a boundary n. The theory also accounts for differences between behavior on variable-interval and variable-ratio schedules, including (a) the occurrence of strained responding on variable-ratio but not on variable-interval schedules, (b) the abrupt cessation of responding on occurrence of higher response rates on variable-ratio than on variable-interval schedules. Furthermore, given data from a series of variable-interval schedules and from a series of concurrent variable-ratio variable-interval schedules, the theory permits quantitative prediction of many properties of behavior on single-alternative variable-ratio schedules. The linear system theory's combined account of behavior on variable-interval and variable-ratio schedules is superior to existing versions of six other mathematical theories of variable-interval and variable-ratio responding.     

Role strain among South African seminarians in the Anglican Church: toward a typology of congregational support

This phenomenological study explored student value perceptions of religious participation among nontraditional South African distance learners who persisted in theological distance education. Four basic types of churches emerged including the Equipping Church, the Empowering Church, the Engaging Church, and the Endangering Church. However, in examining religious coping strategies among South African distance learners, it was discovered that the four women interviewed experienced a deep sense of loneliness in their calling and had to rely almost exclusively on resources outside their local church. These Black South African women’s sense of being called alone is both inconsistent with the theoretical framework of role theory and the theological framework of the Anglican Church as expressed by the official Prayer Book.     

The differential impact on carers dealing with clients with challenging behaviours

This study addresses the effects of organizational culture on the ways in which carers in small community homes cope with clients with challenging behaviours. Results indicated that carers socialized in a traditional setting (i.e. large institutions) responded to challenging behaviours by becoming more negative in their attitudes towards clients. Strain levels in carers socialized in the Social Services were related directly to client challenging behaviours, and unrelated to their attitudes which remained positive.     

Perceived employability and employee strain: A meta-analysis

This meta-analysis addresses the association between perceived employability (PE) and employee strain (k = 34). Consistent with expectations, PE was negatively related to strain (ρ = −.12, 95% CI = −.16 to −.08). Moderator analysis showed that this relationship was stronger post-2008 (ρ = −.20, 84% CI = −.23 to −.17) versus pre-2008 (ρ = −.06, 84% CI = −.08 to −.05) and in high (ρ = −.17, 84% CI = −.21 to −.14) versus low (ρ = −.07, 84% CI = −.09 to −.06) uncertainty avoidant cultures. Our results suggest that career competency development interventions can be effective for reducing employee strain and that national uncertainty avoidance need be incorporated into models of boundaryless careers, especially as it relates to employee health and well-being.