Local structure of Sr2FeMoxW1-xO6 double perovskites across the composition-driven metal to insulator transition

Sr2FeMoO6 oxides exhibit a half-metallic ferromagnetic (HM-FM) ground state and peculiar magnetic and magnetotransport properties, which are interesting for applications in the emerging field of spintronics and attractive for fundamental research in the field of heavily correlated electron systems. Sr2FeWO6 is an insulator with an antiferromagnetic (I-AFM) ground state. The solid solutions Sr2FeMoxW1-xO6 also have peculiar properties-W doping enhances chemical order which allows stabilization of the HM-FM state; as the W content exceeds a certain value a metal to insulator transition (MIT) occurs. The role of W in determining the physical properties of Sr2FeMoxW1-xO6 systems has been a matter of intense investigation. This work deals with the problem of the structural and electronic changes related to the MIT from a local perspective by means of x-ray absorption spectroscopy (XAS). This technique allows one to probe in detail the local structure and electronic modifications around selected absorber ions (W, Mo, Fe and Sr in our case). The results of XAS analysis in the whole composition range (0 <= x <= 1), in the near edge (XANES) and extended (EXAFS) regions, demonstrate an abrupt change of the local structure around the Fe and Mo sites at the critical composition, x(c). This change represents the microstructural counterpart associated with the MIT. Conversely, the local structure and electronic configuration of W ions remain unaltered in the whole composition range, suggesting indirect participation of W in the MIT.

“We have to work within the system!”: Staff perceptions of organizational barriers to decision making for older adults with dementia in Australian aged care facilities

The current study explored the perceptions of direct care staff working in Australian residential aged care facilities (RACFs) regarding the organizational barriers that they believe prevent them from facilitating decision making for individuals with dementia. Normalization process theory (NPT) was used to interpret the findings to understand these barriers in a broader context. The qualitative study involved semi-structured interviews (N = 41) and focus groups (N = 8) with 80 direct care staff members of all levels working in Australian RACFs. Data collection and analysis were conducted in parallel and followed a systematic, inductive approach in line with grounded theory. The perceptions of participants regarding the organizational barriers to facilitating decision making for individuals with dementia can be described by the core category, Working Within the System, and three sub-themes: (a) finding time, (b) competing rights, and (c)not knowing. Examining the views of direct care staff through the lens of NPT allows possible areas for improvement to be identified at an organizational level and the perceived barriers to be understood in the context of promoting normalization of decision making for individuals with dementia.

A systematic review of studies identifying predictors of poor return to work outcomes following workplace injury

BACKGROUND: Injuries occurring in the workplace can have serious implications for the health of the individual, the productivity of the employer and the overall economic community. OBJECTIVE: The objective of this paper is to increase the current state of understanding of individual demographic and psychosocial characteristics associated with extended absenteeism from the workforce due to a workplace injury. METHODS: Studies included in this systematic literature review tracked participants' return to work status over a minimum of three months, identified either demographic, psychosocial or general injury predictors of poor return to work outcomes and included a heterogeneous sample of workplace injuries. RESULTS: Identified predictors of poor return to work outcomes included older age, female gender, divorced marital status, two or more dependent family members, lower education levels, employment variables associated with reduced labour market desirability, severity or sensitive injury locations, negative attitudes and outcome perceptions of the participant. CONCLUSIONS: There is a need for clear and consistent definition and measurement of return to work outcomes and a holistic theoretical model integrating injury, psychosocial and demographic predictors of return to work. Through greater understanding of the nature of factors affecting return to work, improved outcomes could be achieved.

Seamless journeys : enhancing accessibility to work through digital technologies for people with mobility-related impairments

Numerous disruptions and barriers are encountered by persons with mobility-related disabilities in their daily’s experience of going to work and the pressure these exert on gaining and maintaining their employment. The nature and extent of their difficulties to workforce participation entails a requirement for extensive planning and also strategies to address problems of being stranded (for example, when the bus they are waiting for is not accessible). This paper presents the conceptualisation and methods of understanding workforce participation as a journey, and a discussion on the role digital technologies play in helping people with mobility-related disabilities in their journeys to work and mitigating disruptions when these occur. This is presented through an initial case study that helped identify the sequence of supports needed to be in place to make the work journey possible. Importantly, the paper also highlights points of intervention for the use of digital technologies and where design can potentially help to enhance accessibility to work for people with mobility-related impairments by making journeys to work seamless.

Molecular dynamics insight to phase transition in n-alkanes with carbon nanofillers

The present work aims to investigate the phase transition, dispersion and diffusion behavior of nanocomposites of carbon nanotube (CNT) and straight chain alkanes. These materials are potential candidates for organic phase change materials(PCMs) and have attracted flurry of research recently. Accurate experimental evaluation of the mass, thermal and transport properties of such composites is both difficult as well as economically taxing. Additionally it is crucial to understand the factors that results in modification or enhancement of their characteristic at atomic or molecular level. Classical molecular dynamics approach has been extended to elucidate the same. Bulk atomistic models have been generated and subjected to rigorous multistage equilibration. To reaffirm the approach, both canonical and constant-temperature, constant-pressure ensembles were employed to simulate the models under consideration. Explicit determination of kinetic, potential, non-bond and total energy assisted in understanding the enhanced thermal and transport property of the nanocomposites from molecular point of view. Crucial parameters including mean square displacement and simulated self diffusion coefficient precisely define the balance of the thermodynamic and hydrodynamic interactions. Radial distribution function also reflected the density variation, strength and mobility of the nanocomposites. It is expected that CNT functionalization could improve the dispersion within n-alkane matrix. This would further ameliorate the mass and thermal properties of the composite. Additionally, the determined density was in good agreement with experimental data. Thus, molecular dynamics can be utilized as a high throughput technique for theoretical investigation of nanocomposites PCMs. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

Ductile To Brittle Transition In Dynamic Fracture Of Brittle Bulk Metallic Glass

We report an unusual transition from a locally ductile to a pure brittle fracture in the dynamic fracture of brittle Mg65Cu20Gd10 bulk metallic glass. The fractographic evolution from a dimple structure to a periodic corrugation pattern and then to the mirror zone along the crack propagation direction during the dynamic fracture process is discussed within the framework of the meniscus instability of the fracture process zone. This work might provide an important clue in understanding of the energy dissipation mechanism for dynamic crack propagation in brittle glassy materials. (C) 2008 American Institute of Physics.

Excitonic bright-to-dark transition induced by spin-orbit coupling

The center-of-mass motion of quasi-two-dimensional excitons with spin-orbit coupling is calculated within the framework of effective mass theory. The results indicate that the spin-orbit coupling will induce a controllable bright-to-dark transition in a quasi-two-dimensional exciton system. This procedure can work as a way to increase the lifetime of excitons. (c) 2008 American Institute of Physics.

High-School Students´ Summer Jobs and their Ensuing Labor Market Achievement : the Long Term Effect

In part because of high and persistent youth unemployment, adolescent students’ transition from school to work is an important policy and research topic. Many countries have implemented public programs offering summer jobs or work while in high-school as measures to smooth the transition. While the immediate effect of the programs on school attendance, school grades, and disposable income is well documented, their effect on the transition to the labor market remains an open question. Observational studies have shown strong positive effects of summer jobs, but also that the estimated effect is highly vulnerable to selection bias. In this paper, some 3700 high-school students applying for summer jobs in the period 1995-2003,via a program, are followed to 30 years of age. A quarter of the applicants were randomly offered a summer job each year. Among the remaining students, 50% had a (non-program related) summer job while in high-school. We find the income, post high-school, for the offered and non-offered groups to be similar and conclude that the effect of summer jobs on the transition to the labor market is inconsequential.

Soliton clusters inducing insulator-to-metal transition in polyacetylene: a Su-Schrieffer-Heeger model study

The Su-Schrieffer-Heeger (SSH) Hamiltonian has been one of most used models to study the electronic structure of polyacetylene (PA) chains. It has been reported in the literature that in the SSH framework a disordered soliton distribution can not produce a metallic regime. However, in this work (using the same SSH model and parameters) we show that this is possible. The necessary conditions for true metals (non-vanishing density of states and extended wavefunctions around the Fermi level) are obtained for soliton concentration higher than 6% through soliton segregation (clustering). These results are consistent with recent experimental data supporting disorder as an essential mechanism behind the high conductivity of conducting polymers. (C) 2001 Elsevier B.V. B.V. All rights reserved.

INSULATOR-TO-METAL TRANSITION IN POLYTHIOPHENE

In the present work, the electronic structure of polythiophene at several doping levels is investigated by the use of the Huckel Hamiltonian with sigma-bond compressibility. Excess charges are assumed to be stored in conformational defects of the bipolaron type. The Hamiltonian matrix elements representative of a bipolaron are obtained from a previous thiophene oligomer calculation, and then transferred to very long chains. Negative factor counting and inverse iteration techniques have been used to evaluate densities of states and wave functions, respectively. Several types of defect distributions were analyzed. Our results are consistent with the following: (i) the bipolaron lattice does not present a finite density of states at the Fermi energy at any doping level; (ii) bipolaron clusters show an insulator-to-metal transition at 8 mol% doping level; (iii) segregation disorder shows an insulator-to-metal transition for doping levels in the range 20-30 mor %.

The columnar to equiaxed transition of horizontal unsteady-state directionally solidified Al-Si alloys

Experiments were conducted to investigate the influence of thermal parameters on the columnar to equiaxed transition during the horizontal unsteady-state directional solidification of Al-Si alloys. The parameters analyzed include the heat transfer coefficients, growth rates, cooling rates, temperature gradients and composition. A combined theoretical and experimental approach is developed to determine the solidification thermal variables considered. The increasing solute content in Al-Si alloys was not found to affect significantly the experimental position of the CET which occurred for cooling rates in the range between 0.35 and 0.64 K/s for any of three alloy compositions examined. A comparative analysis between the results of this work and those from the literature proposed to analyze the CET during upward vertical solidification of Al-Si alloys is reported and the results have shown that the end of the columnar region during horizontal directional solidification is abbreviated as a result of about six times higher thermal gradient than that verified during upward unidirectional solidification of alloys investigated.

The impact of school year work on adolescent *development

In recent decades, work has become an increasingly common feature of adolescent life in the United States. Once assumed to be an inherently positive experience for youth, school year work has recently been associated with several adverse effects, especially as the number of hours of weekly work increases. The purpose of this dissertation was to describe the impact of school year work on adolescent development in a sample of high school students from rural South Texas, an area where economically-disadvantaged and Hispanic students are heavily represented.^ The first study described the prevalence and work circumstances of 3,565 10$\rm\sp{th}$ and 12$\rm\sp{th}$ grade students who responded to anonymous surveys conducted in regular classrooms. The overall prevalence of current work was 53%. Prevalence differed by grade, college-noncollege-bound status, and parent education. Fifty percent of employed students worked to support consumer spending.^ The second study examined the effects of four levels of work intensity on the academic, behavioral, social, mental and physical health of students. The following negative effects of intense work were reported: (1) decreased engagement in school, satisfaction with leisure time, and hours of weeknight and weekend sleep, and (2) increased health risk behaviors and psychological stress. The negative effects of intense work differed by gender, grade, ethnicity, but not by parent education.^ The third study described the prevalence of injury in the study population. A dose response effect was observed where increasing hours of weekly work were significantly related to work-related injury. The likelihood of being injured while employed in restaurant, farm/ranch, and construction work was greater than the probability of being injured while working in factory/office/skilled, yard, or retail work when compared to babysitting. Cuts, shocks/burns and sprains were the most common injuries in working teens.^ Students, parents, educators, health professionals and policymakers should continue to monitor the number of weekly hours that students work during the school year. ^

Impact of economic crisis on mental health of migrant workers: what happened with migrants who came to Spain to work?

Objectives: To assess changes in mental health in a sample of migrant workers after the eruption of the economic crisis in Spain. Methods: 318 migrant workers were interviewed. Mental health, sociodemographic, and economic crisis related variables were obtained through face-to-face (2008) and phone (2011) interviews. Prevalence of poor mental health (PMH) was compared (2011–2008) and multivariate logistic regression models were fitted. Results: Change in prevalence of PMH was higher in men (aOR 4.63; 95 % CI 2.11–10.16). Subgroups of men showing the largest detrimental mental health effects were: unemployed, with low salaries (≤1,200 euros) and those reporting family burden. An increase of PMH was found in women, without significant associations. Conclusions: Mental health of migrant workers in Spain has worsened during the economic crisis.