Shear horizontal surface waves in piezoelectric materials with surface stress

ABSTRACT

The propagation of shear horizontal (SH) surface waves in piezoelectric semi-infinite bodies is investigated theoretically. The surface stress exerting on the boundary is taken into account through surface piezoelectricity theory, and the velocity ranges and existence conditions of such surface waves for both electrically open and shorted cases are derived in detail. Analysis results show that the SH surface waves occurring with surface stress are dispersive in contrast to the classical situation, and the propagation characteristics strongly depend on the relative value of surface elasticity, surface piezoelectricity and surface density.     

The Community Child Health Network Life Stress Interview: a brief chronic stress measure for community health research

Background and Objectives: Chronic stress is implicated in many theories as a contributor to a wide range of physical and mental health problems. The current study describes the development of a chronic stress measure that was based on the UCLA Life Stress Interview (LSI) and adapted in collaboration with community partners for use in a large community health study of low-income, ethnically diverse parents of infants in the USA (Community Child Health Network [CCHN]). We describe the instrument, its purpose and adaptations, implementation, and results of a reliability study in a subsample of the larger study cohort. Design and Methods: Interviews with 272 mothers were included in the present study. Chronic stress was assessed using the CCHN LSI, an instrument designed for administration by trained community interviewers to assess four domains of chronic stress, each rated by interviewers. Results: Significant correlations ranging from small to moderate in size between chronic stress scores on this measure, other measures of stress, biomarkers of allostatic load, and mental health provide initial evidence of construct and concurrent validity. Reliability data for interviewer ratings are also provided. Conclusions: This relatively brief interview (15 minutes) is available for use and may be a valuable tool for researchers seeking to measure chronic stress reliably and validly in future studies with time constraints.     

On the dislocation mechanism of amorphization of Si by indentation

The formation of an amorphous phase underneath a Vickers indentation produced on a Si(001) surface at room temperature has been observed by cross-sectional transmission electron microscopy. Two types of location are observed for the amorphous phase. One is formed just underneath the image of the indentation and the other is parallel to the slip planes of Si. It is concluded that the latter type, at least, is formed as a result of activation of dislocations which is induced by an external shear stress combined with a hydrostatic pressure.     

Negative life events and symptoms of depression and anxiety: stress causation and/or stress generation

Background and Objectives: Stressful life events are known to contribute to development of depression; however, it is possible this link is bidirectional. The present study examined whether such stress generation effects are greater than the effects of stressful life events on depression, and whether stress generation is also evident with anxiety. Design: Participants were two large age cohorts (N = 732 aged 44 years; N = 705 aged 63 years) from the West of Scotland Twenty-07 study. Methods: Stressful life events, depression, and anxiety symptoms were measured twice five years apart. Cross-lagged panel analysis examined the mutual influences of stressful life events on depression and on anxiety over time. Results: Life events predicted later depressive symptomatology (p = .01), but the depression predicting life events relationship was less strong (p = .06), whereas earlier anxiety predicted life events five years later (p = .001). There was evidence of sex differences in the extent to which life events predicted later anxiety. Conclusions: This study provides evidence of stress causation for depression and weaker evidence for stress generation. In contrast, there was strong evidence of stress generation for anxiety but weaker evidence for stress causation, and that differed for men and women.     

Childhood exposure to emotional abuse and later life stress among Kenyan women: a mediation analysis of cross-sectional data

Background and objective: We explore whether perceived stress among Kenyan mothers is predicted by childhood exposure to emotional abuse – both witnessed among parents and experienced directly. Further, we explore whether this association is mediated by social support, family functioning and polygynous marriage.

Design: We used cross-sectional data from a systematic random sample (n?=?1974) of mothers in semi-rural Kenya.

Methods: Data were collected using validated scales and trained interviewers. Analyses were conducted using bootstrapped structural equation models and fixed-effects linear regression models, controlling for age and household wealth.

Results: Reported experience of emotional abuse – both directly experienced and observed among household adults – was high in the present population (72.5% and 69%, respectively). Perceived stress among women was significantly higher if they were exposed to more emotional abuse during childhood (p?<?.001). Lower social support, worse family functioning and higher rates of polygynous marriage mediated pathways between emotional abuse exposure during childhood and adult perceived stress.

Conclusion: Future research should investigate whether social integration, identity formation and self-esteem underlie observed dynamics in sub-Saharan Africa. Efforts to promote social integration and support should target children currently experiencing emotional abuse, and may include child-targeted high quality television programing and adult-targeted media and celebrity campaigns.     

Depression and stressful environments: identifying gaps in conceptualization and measurement

Background and Objectives: Stress is well known as a trigger of depressive reactions, fear, anxiety, and behavioral disorders. However, there are many gaps in the conceptualization and measurement of environmental stress. Results: Exciting developments in the neuroscience of stress have increasingly expanded our knowledge of mechanisms by which stress may affect emotional and behavioral adjustment. Ironically, environmental stress has often been a silent player in human studies of stress processes. There is a significant need for increased efforts to include environmental stress variables in models of internalizing and other disorders. Measurement and conceptualization issues are prominent, and this article makes the case for improved methods of measuring acute, chronic, and early life stress, and for additional conceptualization of the dynamically changing and bidirectional effects of stress on disorder over time. Conclusions: There is a critical need for greater focus on and better measurement of the environment and its impact on emotional and other disorders, with emphasis on developmentally informed hypotheses. Empirical findings and new perspectives may contribute enormously to our understanding of normal and abnormal outcomes, and also to the challenge of effective interventions to promote mental health and optimal functioning.     

Stress with parents and peers: how adolescents from 18 nations cope with relationship stress

Background and Objectives: We investigated how adolescents from five regions around the world perceived and coped with parent- and peer-related stress. Design: The study comprised N = 4957 adolescents (mean age of 15.2 years) from 18 countries. Methods: The study used self-report measures for stress perception and coping style. Results: Across countries, adolescents perceived parent-related stress to be considerably greater than peer-related stress. They coped less actively with parent-related stress than with peer-related stress. Significant differences emerged with respect to geographic region and key demographic indicators. Adolescents from Eastern European and Western countries had generally quite low levels of stress. Adolescents from Southern Europe exhibited the highest stress levels and the greatest coping activity in dealing with stress in both domains, whereas adolescents from Southern Emerging and Asian countries reported high levels of parent-related stress and dealt much less actively with parent-related stress than with peer-related stress. Conclusions: Adolescents from all countries were remarkably competent in dealing with relationship stressors. Cultural and regional differences have a stronger effect on stress perception and coping style than gender.     

Fireman's job stress: Integrating work/non-work conflict with Job Demand-Control-Support model

IntroductionHeavy working load and uncontrollable schedule often lead firemen to face to conflict between work and non-work life.ObjectiveThis study aims to examine the mediating role of work/non-work conflict between firemen's job stress and job demand, job control, job support and family support.MethodQuestionnaire survey was used for data collection. Four hundred and twenty-two firemen returned completed questionnaires. Structure equation modelling was employed for data analysis.ResultsWork/leisure conflict (WLC) and work/family conflict (WFC) mediate partially the relationship between job demand and job control, job support and job stress. The relationship between family support and job stress is fully mediated by WLC and WFC.ConclusionWFC and WLC are integrated into Job Demand-Control-Support model model in current research to narrow the gap of job stress theory.     

Elasto-hydrodynamics of quasicrystals with a crack under sudden impacts

ABSTRACT

In this paper, a mode-III crack in one-dimensional (1D) hexagonal quasicrystals subjected to anti-plane impact loading is analyzed. The elasto-hydrodynamics of quasicrystals is adopted, where the phonon field obeys wave equation, and the phason field obeys diffusion equation. By introducing a new auxiliary function, the coupled wave-diffusion equations are converted to a single higher-order partial differential equation. With the aid of the Laplace transform, an associated mixed initial-boundary value problem is reduced to two sets of dual integral equations, and then transformed into two coupled Fredholm integral equations of the second kind. Numerical results of transient phonon and phason stress intensity factors and crack-centre displacement jump are obtained through the numerical inversion of the Laplace transform and are presented graphically to show the influences of the phason.     

On French listeners’ ability to use stress during spoken word processing

Previous studies have suggested that French listeners experience difficulties when they have to discriminate between words that differ in stress. A limitation is that these studies used stress patterns that do not respect the rules of stress placement in French. In this study, three stress patterns were tested on bisyllabic words (1) the legal stress pattern in French, namely words that were unstressed compared to words that bore primary stress on their last syllable (/?u?i/-/?u’?i/), (2) an illegal stress location pattern, namely words that bore primary stress on their first syllable compared to words that bore primary stress on their last syllable (/’?u?i/-/?u’?i/) and (3) an illegal pattern that involves an unstressed word, namely words that were unstressed compared to words that bore primary stress on their first syllable (/?u?i/-/’?u?i/). In an ABX task, participants heard three items produced by three different speakers and had to indicate whether X was identical to A or B. The stimuli A and B varied in stress (/?u’?i/-/?u?i/-/?u’?i/), in one phoneme (/?u’?i/-/?u’???/-/?u’?i/) or in both stress and one phoneme (/?u’?i/-/?u???/-/?u’?i/). The results showed that French listeners are fully able to discriminate between two words differing in stress provided that the stress pattern included an unstressed word. More importantly, they suggest that the French listeners’ difficulties mainly reside in locating stress within words.     

Homogeneous nucleation of dislocation loops under stress in perfect crystals

We present an analysis and results on the homogeneous nucleation of a dislocation loop under stress in a perfect crystal. By using a variational boundary integral method in the Peierls-Nabarro framework, we have determined the saddle-point configurations of embryonic dislocation loops and their associated activation energies under stress levels up to the ideal shear strength. The high-energy barriers under the usual levels of applied shear stresses, differing markedly from the ideal shear strength, confirm the widely held view that thermal motion should play no role in such nucleation. The result provides means for more definitive solutions of fundamental problems involving homogeneous nucleation of dislocation loops and has significant implications for models based on the mechanism of nucleation of dislocations from a perfect crystal.     

Intrinsic goals for leisure-time physical activity predict children's daily step counts through autonomous motivation

ObjectivesThe present study tested a motivational sequence in which children's goals for leisure-time sport and physical activity (PA) from Goal Content Theory predicted pedometer-determined PA through behavioural regulation constructs from Self-Determination Theory.DesignQuantitative cross-sectional study.MethodsA sample of 1272 Flemish (Dutch speaking part of Belgium) sixth graders (M age = 11.42 years) filled in a questionnaire on PA goal content, behavioural regulations and pubertal status. Children's height and weight were measured to assess Body Mass Index (BMI). To measure daily PA behaviour, participants wore a pedometer for seven consecutive days. Structural equation modelling was performed to test the proposed motivational sequence and to examine the mediation effect of behavioural regulations towards leisure-time sport and PA on the relation between PA goal content and daily step counts.ResultsA structural equation model supported the hypothesized sequence in which intrinsic goals for leisure-time sport and PA predicted children's daily step counts through autonomous motivation towards leisure-time sport and PA. Multi-sample invariance testing revealed that the proposed model was largely invariant across BMI groups, pubertal status and gender.ConclusionsThe findings highlight the importance of emphasizing intrinsic goals for participation in leisure-time sport and PA in children aged 10–12 years. By stimulating children to participate in PA and sports by referring to intrinsic goals, children are more likely to enjoy PA, which in turn might increase the likelihood of a regular and long-term PA engagement.     

Selective attention as a protagonist in contemporary workplace stress: implications for the interruption age

Background and Objectives: The ubiquity of instant messages and email notifications in contemporary work environments has opened a Pandora's Box. This box is filled with countless interruptions coming from laptops, smartphones, and other devices, all of which constantly call for employees’ attention. In this interruption era, workplace stress is a pervasive problem. To examine this problem, the present study hypothesizes that the three-way interaction among the frequency with which interrupting stimuli appear, their salience, and employees’ deficits in inhibiting attentional responses to them impacts mental workload perceptions, ultimately leading to stress. The study, further, probes a related form of self-efficacy as a potential suppressor of interruption-based stress. Design: The study used a 2 (low vs. high frequency) × 2 (low vs. high salience) mixed model design. Methods: The 128 subjects completed a test of their inhibitory deficits and rated their mental workload perceptions and experiences of stress following a computer-based task. Results: Inhibitory deficits and increased interruption salience can alter the perception of mental workload in contemporary work environments for the worse, but interruption self-efficacy can help offset any resulting interruption-based stress. Conclusions: This study extends the literatures on work interruptions as well as on stress and coping in the workplace.     

Dimensions of distress tolerance and the moderating effects on mindfulness-based stress reduction

Background and Objectives: This study examined the relationship between distress tolerance and psychosocial changes among individuals participating in Mindfulness-Based Stress Reduction (MBSR). The objective of the analysis was to discern whether individuals with lower distress tolerance measured before MBSR showed larger reductions in perceived stress following MBSR. Design and Methods: Data were collected from a sample of convenience (n?=?372) using a quasi-experimental design. Participants completed self-report measures immediately prior to course enrollment and following course completion. Results: Perceived stress, distress tolerance, and mood states showed favorable changes from pre- to post-MBSR in the current study. Baseline distress tolerance significantly moderated reductions on perceived stress, supporting the primary hypothesis that individuals with lower baseline distress tolerance evidenced a greater decline in perceived stress following MBSR. For a one-unit increase on the self-reported baseline Distress Tolerance Scale, reported perceived stress scores decreased by 2.5 units (p?Conclusions: The finding that individuals with lower baseline distress tolerance evidenced a greater decline in perceived stress may offer hints about who is most likely to benefit from MBSR and other mindfulness-based treatments. Identifying moderators of treatment outcomes may yield important benefits in matching individuals to treatments that are most likely to work for them.     

Coping and care-related stress in parents of a child with autism spectrum disorder

Background and Objectives: Parenting a child with Autism Spectrum Disorder (ASD) is challenging and can result in elevated levels of parenting stress. This study investigated the relationship between parent-ratings of their child’s ASD symptoms and two conceptually different measures of parenting stress: One specific to the ASD context and the other a general stress measure applicable to the broader caregiving context. Additionally, the influence of coping style on the relationship between child’s ASD symptoms and parenting stress was investigated.

Design and Methods: Using an internet survey, parents (N?=?178) caring for a child with ASD reported on coping strategies, completed two measures of parenting stress, and assessed their child’s ASD symptoms.

Results: Parenting stress increased with severity of the child’s ASD symptoms, but the strength of this relationship depended on whether a general or disorder-specific measure of parenting stress was used. Regression analyses indicated that some coping strategies moderated the impact of ASD symptom severity on the parent’s care-related stress, but moderation depended on how stress was conceptualized.

Conclusion: This study reinforces the importance of identifying the coping strategies of parents of children with developmental disorders, and highlights the consequences of using different conceptual approaches to measure parenting stress.     

Early life adversity potentiates the effects of later life stress on cumulative physiological dysregulation

Background and Objectives: Previous research indicates that early life adversity may heighten stress reactivity and impair mechanisms for adaptive coping, suggesting that experience of stress in early life may also potentiate adults' physiological vulnerability to stress in later life. The study tested this hypothesis by investigating whether the experience of stressful events and circumstances (SEC) in childhood or adolescence amplified the effect of adulthood SEC on physiological dysregulation (allostatic load, AL) in later midlife. Design: Observational data were used in the present study. Physiological functioning was measured in later midlife (participants' age ranged from 49 to 63 years). Both childhood/adolescence and adulthood SEC were reported retrospectively on the same occasion. Methods: Participants were 5309 Danish men and women from Copenhagen Aging and Midlife Biobank (CAMB). SEC included socioeconomic and family factors. The AL index was based on nine cardiovascular, metabolic, and immune biomarkers. Results: Experience of SEC in both early life and adulthood independently predicted higher AL. In men, experience of SEC in early life also potentiated the effect of SEC in adulthood on AL. Conclusions: The results provide further insight into the mechanisms behind the “biological embedding” of childhood stress.     

Physical fitness and prior physical activity are both associated with less cortisol secretion during psychosocial stress

Background: Evidence linking fitness and decreased psychosocial stress comes from studies of athletes and typically relies upon self-report measures. Furthermore, there is little evidence regarding the impact of physical activity (PA) prior to a stressor. The aims of this study were to determine whether fitness and prior PA influence cortisol concentrations during psychosocial stress.

Methods: Seventy-five non-athletic participants took part in a submaximal walk prior to the Trier Social Stress Test for Groups (TSST-G). During the walk, fitness was assessed using heart rate (HR). A further 89 participants took part in the TSST-G without the walk. Stress responsiveness was assessed using salivary cortisol collected at 10-min intervals on seven occasions.

Results: Hierarchical multiple regression revealed that average walking HR accounted for 9% of the variance in cortisol secretion (P?=?.016), where a higher HR was associated with higher cortisol secretion. Between-subjects ANCOVA revealed that the walking group had a significantly lower cortisol secretion than the non-walking group (P?=?.009).

Conclusions: These findings indicate that fitter individuals have reduced cortisol secretion during psychosocial stress. They also indicate that prior PA can reduce cortisol concentrations during psychosocial stress and are suggestive of a role of PA in reducing the impact of stress on health.     

Experimental evidence of relaxation arising from the motion of geometrical kinks on screw dislocations in iron

Abstract

Internal friction measurements with a superimposed bias stress have provided evidence for geometrical kink migration on screw dislocations in iron. This intrinsic process causes a relaxation phenomenon in internal friction which has been identified with the occurrence of a subpeak (below 20 K) of the α-peak. The effect of different bias stress has allowed us to evaluate the kink migration energy, E ^m _k ? 0·001eV.     

Family support,family stress,and suicidal ideation in a combat-exposed sample of Operation Enduring Freedom/Operation Iraqi Freedom veterans

Background and Objectives: Deployment-related risk factors for suicidal ideation among Operation Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF) veterans have received a great deal of attention. Studies show that mental health symptoms mediate the association between most deployment stressors and suicidal ideation; however, family-related factors during deployment are largely unexplored. We examined posttraumatic stress disorder (PTSD) and depression symptoms as mediators of the associations between deployment family support and stress and post-deployment suicidal ideation in combat-exposed OEF/OIF veterans. Design: National cross-sectional mail survey. Methods: 1046 veterans responded to the survey. The sample for this study was 978 veterans who experienced combat. Regression-based path analyses were conducted. Results: Family support and stress had direct associations with suicidal ideation. When PTSD and depression symptoms were examined as mediators of these associations, results revealed significant indirect paths through these symptoms. Conclusions: This study contributes to the literature on suicidal ideation risk factors among OEF/OIF veterans. Deployment family support and family stress are associated with suicidal ideation; however these associations occur primarily through mental health symptomatology, consistent with findings observed for other deployment factors. This research supports ongoing efforts to treat mental health symptomatology as a means of suicide prevention.     

Assessment of job stress factors in a context of organizational change

IntroductionResearch consistently showed that stress and organizational change are closely related.ObjectiveThis study was conducted to identify the psychosocial job characteristics that are responsible for psychological stress in a context of organizational change.MethodAn expanded 30-item version of the Job Content Questionnaire was used to measure psychological demands, decision latitude, supervisor support, coworker support, and organizational difficulties. Online survey responses from 973 employees from the university of Strasbourg were analyzed.ResultsConfirmatory Factor Analyses indicated a poor fit of the five-factor model based on 30 items but an acceptable to good fit of a reduced five-factor model based on 26 items. Results from a stepwise regression showed that the organizational difficulties dimension was the second most important predictor of psychological stress.ConclusionThe implications of these findings for further work on health outcomes of organizational changes closed this study.