The relevance of shared experiences : a multi-level study of collective efficacy as a moderator of job control in the stressor-strain relationship

Karasek's Job Demand-Control model proposes that control mitigates the positive effects of work stressors on employee strain. Evidence to date remains mixed and, although a number of individual-level moderators have been examined, the role of broader, contextual, group factors has been largely overlooked. In this study, the extent to which control buffered or exacerbated the effects of demands on strain at the individual level was hypothesized to be influenced by perceptions of collective efficacy at the group level. Data from 544 employees in Australian organizations, nested within 23 workgroups, revealed significant three-way cross-level interactions among demands, control and collective efficacy on anxiety and job satisfaction. When the group perceived high levels of collective efficacy, high control buffered the negative consequences of high demands on anxiety and satisfaction. Conversely, when the group perceived low levels of collective efficacy, high control exacerbated the negative consequences of high demands on anxiety, but not satisfaction. In addition, a stress-exacerbating effect for high demands on anxiety and satisfaction was found when there was a mismatch between collective efficacy and control (i.e. combined high collective efficacy and low control). These results provide support for the notion that the stressor-strain relationship is moderated by both individual- and group-level factors.

Failure of discontinuous railhead edges due to plastic strain accumulation

Railhead is perhaps the highest stressed civil infrastructure due to the passage of heavily loaded wheels through a very small contact patch. The stresses at the contact patch cause yielding of the railhead material and wear. Many theories exist for the prediction of these mechanisms of continuous rails; this process in the discontinuous rails is relatively sparingly researched. Discontinuous railhead edges fail due to accumulating excessive plastic strains. Significant safety concern is widely reported as these edges form part of Insulated Rail Joints (IRJs) in the signalling track circuitry. Since Hertzian contact is not valid at a discontinuous edge, 3D finite element (3DFE) models of wheel contact at a railhead edge have been used in this research. Elastic–plastic material properties of the head hardened rail steel have been experimentally determined through uniaxial monotonic tension tests and incorporated into a FE model of a cylindrical specimen subject to cyclic tension load- ing. The parameters required for the Chaboche kinematic hardening model have been determined from the stabilised hysteresis loops of the cyclic load simulation and imple- mented into the 3DFE model. The 3DFE predictions of the plastic strain accumulation in the vicinity of the wheel contact at discontinuous railhead edges are shown to be affected by the contact due to passage of wheels rather than the magnitude of the loads the wheels carry. Therefore to eliminate this failure mechanism, modification to the contact patch is essential; reduction in wheel load cannot solve this problem.

Swelling induced finite strain flexure in a rectangular block of an isotropic elastic material

The deformation of a rectangular block into an annular wedge is studied with respect to the state of swelling interior to the block. Nonuniform swelling fields are shown to generate these flexure deformations in the absence of resultant forces and bending moments. Analytical expressions for the deformation fields demonstrate these effects for both incompressible and compressible generalizations of conventional hyperelastic materials. Existing results in the absence of a swelling agent are recovered as special cases.

Determination of strain-rate-dependent mechanical behavior of living and fixed osteocytes and chondrocytes using atomic force microscopy and inverse finite element analysis

The aim of this paper is to determine the strain-rate-dependent mechanical behavior of living and fixed osteocytes and chondrocytes, in vitro. Firstly, Atomic Force Microscopy (AFM) was used to obtain the force-indentation curves of these single cells at four different strain-rates. These results were then employed in inverse finite element analysis (FEA) using Modified Standard neo-Hookean Solid (MSnHS) idealization of these cells to determine their mechanical properties. In addition, a FEA model with a newly developed spring element was employed to accurately simulate AFM evaluation in this study. We report that both cytoskeleton (CSK) and intracellular fluid govern the strain-rate-dependent mechanical property of living cells whereas intracellular fluid plays a predominant role on fixed cells’ behavior. In addition, through the comparisons, it can be concluded that osteocytes are stiffer than chondrocytes at all strain-rates tested indicating that the cells could be the biomarker of their tissue origin. Finally, we report that MSnHS is able to capture the strain-rate-dependent mechanical behavior of osteocyte and chondrocyte for both living and fixed cells. Therefore, we concluded that the MSnHS is a good model for exploration of mechanical deformation responses of single osteocytes and chondrocytes. This study could open a new avenue for analysis of mechanical behavior of osteocytes and chondrocytes as well as other similar types of cells.

E-mail in the workplace : the role of stress appraisals and normative response pressure in the relationship between email stressors and employee strain

In many organizations, e-mail is an effective and dominant workplace application tool; however, research identifying its role as a potential workplace stressor remains limited. Utilizing the Transactional Model of Stress (Lazarus & Folkman, 1984), 215 full-time administrative and academic staff at a university were surveyed about workplace e-mail. The aim was to study the effects of potential e-mail stressors on emotional exhaustion as mediated and moderated by person and situation variables. Results indicated that 2 distinct e-mail stressors—high quantity and poor quality (in terms of high emotionality and ambiguity) of workplace e-mail—were associated both with stress appraisals (e-mail overload and e-mail uncertainty) and with emotional exhaustion. Furthermore, the effects of the 2 e-mail stressors on emotional exhaustion were mediated by appraised e-mail overload. Perceived normative response pressure—a relevant aspect of the specific work environment—added to the explanation of emotional exhaustion and accentuated the positive effect of e-mail ambiguity on emotional exhaustion, although effects involving normative response pressure were not explained by the stress appraisals.

A novel method of Fiber Bragg Grating (FBG) strain modulation and its application in FBG accelerometers

This thesis has systemically investigated the possibility of improving one type of optical fiber sensors by using a novel mechanism. Many parameters of the sensor have been improved, and one outcome of this innovation is that civil structures, such as bridges and high-rise buildings, may be operated more safely and used longer.

Heat strain evaluation of overt and covert body armour in a hot and humid environment

The aim of this study was to elucidate the thermophysiological effects of wearing lightweight non-military overt and covert personal body armour (PBA) in a hot and humid environment. Eight healthy males walked on a treadmill for 120 min at 22% of their heart rate reserve in a climate chamber simulating 31 °C (60%RH) wearing either no armour (control), overt or covert PBA in addition to a security guard uniform, in a randomised controlled crossover design. No significant difference between conditions at the end of each trial was observed in core temperature, heart rate or skin temperature (P > 0.05). Covert PBA produced a significantly greater amount of body mass change (−1.81 ± 0.44%) compared to control (−1.07 ± 0.38%, P = 0.009) and overt conditions (−1.27 ± 0.44%, P = 0.025). Although a greater change in body mass was observed after the covert PBA trial; based on the physiological outcome measures recorded, the heat strain encountered while wearing lightweight, non-military overt or covert PBA was negligible compared to no PBA. Practitioner summary The wearing of bullet proof vests or body armour is a requirement of personnel engaged in a wide range of occupations including police, security, customs and even journalists in theatres of war. This randomised controlled crossover study is the first to examine the thermophysiological effects of wearing lightweight non-military overt and covert personal body armour (PBA) in a hot and humid environment. We conclude that the heat strain encountered while wearing both overt and covert lightweight, non-military PBA was negligible compared to no PBA.

Experimental colonization of the canine urinary tract with the asymptomatic bacteriuria Escherichia coli strain 83972

Establishment of asymptomatic bacteriuria (ABU) with Escherichia coli 83972 is a viable prophylactic alternative to antibiotic therapy for the prevention of recurrent bacterial urinary tract infection in humans. Approximately 2 x 108 viable E. coli 83972 cells were introduced into the bladder of six healthy female dogs via a sterile urinary catheter. The presence of pyuria, depression, stranguria, pollakiuria and haematuria was documented for 6 weeks and urinalysis and aerobic bacterial cultures were performed every 24–72 h. Pyuria was present in all dogs on day 1 post-inoculation and 4/6 dogs (67%) had a positive urine culture on this day. Duration of colonization ranged from 0 to 10 days (median 4 days). Four dogs were re-inoculated on day 20. Duration of colonization following the second inoculation ranged from 1 to 3 days. No dog suffered pyrexia or appeared systemically unwell but all dogs initially exhibited mild pollakiuria and a small number displayed gross haematuria and/or stranguria. By day 3 of each trial all clinical signs had resolved. Persistent bacteriuria was not achieved in any dog but two dogs were colonized for 10 days following a single inoculation. Further research is required to determine whether establishment of ABU in dogs with recurrent urinary tract infection is a viable alternative to repeated doses of antimicrobial agents.

A new Salmonella typhimurium NM5004 strain expressing rat glutathione S-transferase 5-5 : use in detection of genotoxicity of dihaloalkanes using an SOS/umu test system

The Escherichia coli mu operon was subcloned into a pKK233-2 vector containing rat glutathione S-transferase (GST) 5-5 cDNA and the plasmid thus obtained was introduced into Salmonella typhimurium TA1535. The newly developed strain S.typhimurium NM5004, was found to have 52-fold greater GST activity than the original umu strain S.typhimurium TA1535/pSK1002. We compared sensitivities of these two tester strains, NM5004 and TA1535/ pSK1002, for induction of umuC gene expression with several dihaloalkanes which are activated or inactivated by GST 5-5 activity. The induction of umuC gene expression by these chemicals was monitored by measuring the cellular P-galactosidase activity produced by umuC'lacZ fusion gene in these two tester strains. Ethylene dibromide, 1-bromo-2-chloroethane, 1,2-dichloroethane, and methylene dichloride induced umuC gene expression more strongly in the NM5004 strain than the original strain, 4-Nitroquinoline 1-oxide and N-methyl-N'-nitro-N-nitrosoguanidine were found to induce umuC gene expression to similar extents in both strains. In the case of 1-nitropyrene and 2-nitrofluorene, however, NM5004 strain showed weaker umuC gene expression responses than the original TA1535/ pSK1002 strain, 1,2-Epoxy-3-(4'-nitrophenoxy)propane, a known substrate for GST 5-5, was found to inhibit umuC induction caused by 1-bromo-2-chloroethane. These results indicate that this new tester NM5004 strain expressing a mammalian GST theta class enzyme may be useful for studies of environmental chemicals proposed to be activated or inactivated by GST activity.

Temperature and strain-rate dependent fracture strength of graphynes

Graphyne is an allotrope of graphene. The mechanical properties of graphynes (α-, β-, γ- and 6,6,12-graphynes) under uniaxial tension deformation at different temperatures and strain rates are studied using molecular dynamics simulations. It is found that graphynes are more sensitive to temperature changes than graphene in terms of fracture strength and Young's modulus. The temperature sensitivity of the different graphynes is proportionally related to the percentage of acetylenic linkages in their structures, with the α-graphyne (having 100% of acetylenic linkages) being most sensitive to temperature. For the same graphyne, temperature exerts a more pronounced effect on the Young's modulus than fracture strength, which is different from that of graphene. The mechanical properties of graphynes are also sensitive to strain rate, in particular at higher temperatures.

Multiscale features and information extraction of online strain for long-span bridges

The strain data acquired from structural health monitoring (SHM) systems play an important role in the state monitoring and damage identification of bridges. Due to the environmental complexity of civil structures, a better understanding of the actual strain data will help filling the gap between theoretical/laboratorial results and practical application. In the study, the multi-scale features of strain response are first revealed after abundant investigations on the actual data from two typical long-span bridges. Results show that, strain types at the three typical temporal scales of 10^5, 10^2 and 10^0 sec are caused by temperature change, trains and heavy trucks, and have their respective cut-off frequency in the order of 10^-2, 10^-1 and 10^0 Hz. Multi-resolution analysis and wavelet shrinkage are applied for separating and extracting these strain types. During the above process, two methods for determining thresholds are introduced. The excellent ability of wavelet transform on simultaneously time-frequency analysis leads to an effective information extraction. After extraction, the strain data will be compressed at an attractive ratio. This research may contribute to a further understanding of actual strain data of long-span bridges; also, the proposed extracting methodology is applicable on actual SHM systems.

Thermal conductivity of configurable two-dimensional carbon nanotube architecture and strain modulation

We reported the thermal conductivity of the two-dimensional carbon nanotube (CNT)-based architecture, which can be constructed through welding of single-wall CNTs by electron beam. Using large-scale nonequilibrium molecular dynamics simulations, the thermal conductivity is found to vary with different junction types due to their different phonon scatterings at the junction. The strong length and strain dependence of the thermal conductivity suggests an effective avenue to tune the thermal transport properties of the CNT-based architecture, benefiting the design of nanoscale thermal rectifiers or phonon engineering.

Tendinopathy alters cumulative transverse strain in the patellar tendon postexercise.

Introduction This research evaluated the effect of tendinopathy on the cumulative transverse strain response of the patellar tendon to a bout of resistive quadriceps exercise. Methods Nine adults with unilateral patellar tendinopathy (age 18.2±0.7 years, height 1.92±0.06 m and weight 76.8±6.8 kg) and ten healthy adults free of knee pain (age 17.8±0.8 years, height 1.83±0.05 m and weight 73.2±7.6 kg) underwent standardised sagittal sonograms (7.2–14 MHz linear–array transducer) of both patellar tendons immediately prior and following 45 repetitions of a double–leg decline–squat exercise performed against a resistance of 145% bodyweight. Tendon thickness was determined 5–mm and 25–mm distal to the patellar pole. Transverse Hencky strain was calculated as the natural log of the ratio of post– to pre–exercise tendon thickness and expressed as a percentage. Measures of tendon echogenicity were calculated within the superficial and deep aspects of each tendon site from gray–scale profiles. Intratendinous microvessels were evaluated using power Doppler ultrasound. Results The cumulative transverse strain response to exercise in symptomatic tendinopathy was significantly lower than that of asymptomatic and healthy tendon (P<.05). There was also a significant reduction (57%) in the area of microvascularity immediately following exercise (P=.05), which was positively correlated (r=0.93, P<.05) with VISA-P score. Conclusions This study is the first to show that patellar tendinopathy is associated with an altered morphological and mechanical response of the tendon to exercise, which is manifest by a reduction in cumulative transverse strain and microvascularity, when present. Research directed toward identifying factors that influence the acute microvascular and transverse strain response of the patellar tendon to exercise in the various stages of tendinopathy is warranted.

Supervisor conflict management, justice and strain : multi-level relationships

Purpose The purpose of this paper is to test a multilevel model of the main and mediating effects of supervisor conflict management style (SCMS) climate and procedural justice (PJ) climate on employee strain. It is hypothesized that workgroup-level climate induced by SCMS can fall into four types: collaborative climate, yielding climate, forcing climate, or avoiding climate; that these group-level perceptions will have differential effects on employee strain, and will be mediated by PJ climate. Design/methodology/approach Multilevel SEM was used to analyze data from 420 employees nested in 61 workgroups. Findings Workgroups that perceived high supervisor collaborating climate reported lower sleep disturbance, job dissatisfaction, and action-taking cognitions. Workgroups that perceived high supervisor yielding climate and high supervisor forcing climate reported higher anxiety/depression, sleep disturbance, job dissatisfaction, and action-taking cognitions. Results supported a PJ climate mediation model when supervisors’ behavior was reported to be collaborative and yielding. Research limitations/implications The cross-sectional research design places limitations on conclusions about causality; thus, longitudinal studies are recommended. Practical implications Supervisor behavior in response to conflict may have far-reaching effects beyond those who are a party to the conflict. The more visible use of supervisor collaborative CMS may be beneficial. Social implications The economic costs associated with workplace conflict may be reduced through the application of these findings. Originality/value By applying multilevel theory and analysis, we extend workplace conflict theory.