Spin precession and spin Hall effect in monolayer graphene/Pt nanostructures

Spin Hall effects have surged as promising phenomena for spin logics operations without ferromagnets. However, the magnitude of the detected electric signals at room temperature in metallic systems has been so far underwhelming. Here, we demonstrate a two-order of magnitude enhancement of the signal in monolayer graphene/Pt devices when compared to their fully metallic counterparts. The enhancement stems in part from efficient spin injection and the large resistivity of graphene but we also observe 100% spin absorption in Pt and find an unusually large effective spin Hall angle of up to 0.15. The large spin-to-charge conversion allows us to characterise spin precession in graphene under the presence of a magnetic field. Furthermore, by developing an analytical model based on the 1D diffusive spin-transport, we demonstrate that the effective spin-relaxation time in graphene can be accurately determined using the (inverse) spin Hall effect as a means of detection. This is a necessary step to gather full understanding of the consequences of spin absorption in spin Hall devices, which is known to suppress effective spin lifetimes in both metallic and graphene systems.Comment: 14 pages, 6 figures. Accepted in 2D Materials. https://doi.org/10.1088/2053-1583/aa882

How can schools help to reduce the harm associated with teenage substance use? Development of a theoretically-driven whole-school approach

Purpose Substance use prevalence varies considerably between schools, but to date, whole school approaches for reducing substance use have only been moderately effective. The purpose of this paper is to develop a novel multifaceted whole-school approach to reduce substance use primarily among teenagers aged 11-14 years. Design/methodology/approach The outlined approach is premised on the proposal that schools can reduce the harms associated with substance use by promoting school connectedness and improving the school-related experiences of weakly connected and disconnected students. The aim of this approach is to develop students’ autonomy so that they may act in their real and long-term interests. This may be attained by promoting the realisation of essential human capacities for: practical reasoning – through valued opportunities for cognitive development and affiliation – through valued opportunities for affective development that advance students sense of acceptance within school. Schools may achieve this, it is proposed, by providing outlined forms of appropriate formal support and formal control that are augmented by particular features of school organisation, curriculum and pedagogic practice, which are also described. Findings A theoretically driven understanding of a whole school approach for reducing teenage substance use is outlined. Originality/value The outlined approach may usefully inform the development of future whole school interventions aiming to reduce problematic substance use among school students. Additional potential benefits include more successful student life trajectories

Coupling of groundwater, river level and rainfall in an upland floodplain

Upland floodplains provide an important function in regulating river flows and controlling the coupling of hillslope runoff with rivers. To investigate the responses of floodplain groundwater to river flows and rainfall events, a small floodplain in an upland area of the River Tweed catchment, Scotland, was characterised using geophysics, 3D geological mapping and hydrogeological testing; and monitoring undertaken from September 2011 to February 2013 of: groundwater levels in five pairs of piezometers; river stage and flow at the upstream and downstream limits of the study site; soil moisture on the adjacent hillslope; and meteorological parameters. Periodical groundwater chemistry and residence data were also collected. The floodplain aquifer is permeable throughout but partially stratified, comprising dominantly alluvial and glaciofluvial sandy gravels between 8 and 15m interspersed with thin, intermittent layers of low permeability silts, clays and peats. Overlying the gravel aquifer is a partial thin cover of low permeability alluvial silts, and it is underlain dominantly by low permeability glaciolacustrine silts and clays. High permeability solifluction deposits mantle much of the adjacent hillslope and provide a rapid connection to the floodplain aquifer. The unusually wet year of 2012 provides a good example of how a temperate upland floodplain responds to consistently high rainfall. Statistical analysis and graphical interpretation of groundwater level, rainfall, soil moisture and river stage demonstrates that: 1) dominant groundwater flow within the floodplain is in the same direction as the river, from up-valley to down-valley; 2) soil moisture in the hillslope is strongly correlated with local rainfall, but groundwater across much of the floodplain is more strongly influenced by river stage; except 3) groundwater near the edge of floodplain, which responds more slowly to local rainfall and river stage changes ; and 4) subsurface flow from the hillslope to the floodplain occurs during high rainfall events. A detailed investigation of three flood events, when the river rose above bank level and flooded adjacent fields and groundwater became artesian in parts of the floodplain, suggests that antecedent moisture conditions can partly explain the differences in groundwater response during different flood events, where high intensity or long duration rainfall can cause saturated soil conditions, reducing soil water storage capacity and hence promoting flood conditions. A conceptual model based on field data of groundwater flow after storm events during antecedent unsaturated and saturated soil conditions is presented

A new measure of unhealthy school environments and its implications for critical assessments of health promotion in schools

The theory of human functioning and school organisation informed by Basil Bernstein’s sociology of education suggests that to gain the commitment and promote the health of students, particularly those from disadvantaged backgrounds, schools require radical transformations eroding various ‘boundaries’: between and among staff and students; between students’ academic learning and broader social development and welfare; and between schools and their local communities. Existing research examining this theory has reported associations between school-level proxy measures of student commitment and lower rates of student smoking, drinking alcohol, use of drugs and violence. But this research has not directly assessed whether reduced school boundaries explain this. We piloted a new scale derived from teacher reports to measure unhealthy school boundaries and examined its inter-item reliability and its criterion validity in terms of associations with various measures of school commitment and smoking. Data on boundaries came from 101 teachers across 40 schools. Data on student commitment and smoking came from 6667 students. We assessed reliability by examining correlations between scale-items and criterion validity in terms of associations with student-reported commitment and smoking. Inter-item reliability was sub-optimal but better within the subscales about boundaries between academic/broader learning and schools/local communities. The scale had good criterion validity, strongly associated with reduced student-reported school commitment and increased student-reported smoking. We reflect on the implications of these findings in terms of critical perspectives on health promotion in schools and the strengths and limitations of quantitative research in examining health behaviours as opposed to practices

Geological structure as a control on floodplain groundwater dynamics

Groundwater in upland floodplains has an important function in regulating river flows and controlling the coupling of hillslope runoff with rivers, with complex interaction between surface waters and groundwaters throughout floodplain width and depth. Heterogeneity is a key feature of upland floodplain hydrogeology and influences catchment water flows, but it is difficult to characterise and therefore is often simplified or overlooked. An upland floodplain and adjacent hillslope in the Eddleston catchment, southern Scotland (UK), has been studied through detailed three-dimensional geological characterisation, the monitoring of ten carefully sited piezometers, and analysis of locally collected rainfall and river data. Lateral aquifer heterogeneity produces different patterns of groundwater level fluctuation across the floodplain. Much of the aquifer is strongly hydraulically connected to the river, with rapid groundwater level rise and recession over hours. Near the floodplain edge, however, the aquifer is more strongly coupled with subsurface hillslope inflows, facilitated by highly permeable solifluction deposits in the hillslope–floodplain transition zone. Here, groundwater level rise is slower but high heads can be maintained for weeks, sometimes with artesian conditions, with important implications for drainage and infrastructure development. Vertical heterogeneity in floodplain aquifer properties, to depths of at least 12 m, can create local aquifer compartmentalisation with upward hydraulic gradients, influencing groundwater mixing and hydrogeochemical evolution. Understanding the geological processes controlling aquifer heterogeneity, which are common to formerly glaciated valleys across northern latitudes, provides key insights into the hydrogeology and wider hydrological behaviour of upland floodplains

How Do Contextual Factors Influence Implementation and Receipt of Positive Youth Development Programs Addressing Substance Use and Violence? A Qualitative Meta-Synthesis of Process Evaluations

Objective:Positive youth development (PYD) often aims to prevent tobacco, alcohol, and drugs use and violence. We systematically reviewed PYD interventions, synthesizing process, and outcomes evidence. Synthesis of outcomes, published elsewhere, found no overall evidence of reducing substance use or violence but notable variability of fidelity. Our synthesis of process evaluations examined how implementation varied and was influenced by context.Data Source:Process evaluations of PYD aiming to reduce substance use and violence.Study Inclusion Criteria:Overall review published since 1985; written in English; focused on youth aged 11 to 18 years; focused on interventions addressing multiple positive assets; reported on theory, process, or outcomes; and concerned with reducing substance use or violence. Synthesis of process evaluations examined how implementation varies with or is influenced by context.Data Extraction:Two reviewers in parallel.Data Synthesis:Thematic synthesis.Results:We identified 12 reports. Community engagement enhanced program appeal. Collaboration with other agencies could broaden the activities offered. Calm but authoritative staff increased acceptability. Staff continuity underpinned diverse activities and durable relationships. Empowering participants were sometimes in tension with requiring them to engage in diverse activities.Conclusion:Our systematic review identified factors that might help improve the fidelity and acceptability of PYD interventions. Addressing these might enable PYD to fulfill its potential as a means of promoting health

Student- and school-level belonging and commitment and student smoking, drinking and misbehaviour

Objectives: It has been suggested that students are healthier in schools where more students are committed to school. Previous research has examined this only using a proxy measure of value-added education (a measure of whether school-level attendance and attainment are higher than predicted by students’ social profile), finding associations with smoking tobacco, use of alcohol and illicit drugs, and violence. These findings do not provide direct insights into the associations between school-level aggregate student commitment and health behaviours, and may simply reflect the proxy measure being residually confounded by unmeasured student characteristics. We examined the previously used proxy measure of value-added education, as well as direct measures at the level of the school and the student of lack of student commitment to school to see whether these were associated with students’ self-reported smoking tobacco, alcohol use and school misbehaviour. Design: Cross-sectional survey. Setting: A total of 40 schools in south-east England. Methods: Multi-level analyses. Results: There were associations between school- and student-level measures of lack of commitment to school and tobacco smoking, alcohol use and school misbehaviour outcomes, but the proxy measure of school-level commitment, value-added education, was not associated with these outcomes. A sensitivity analysis focused only on violent aspects of school misbehaviour found a pattern of associations identical to that found for the measure of misbehaviour. Conclusion: Our study provides the first direct evidence in support of the Theory of Human Functioning and School Organisation

The possibility of critical realist randomised controlled trials.

BACKGROUND: Some realists have criticised randomised controlled trials for their inability to explain the causal relations that they identify; to take into account the influence of the social context of the interventions they evaluate; and to account for individual difference. However, among realists, there is controversy over whether it is possible to improve trials by making them realist, or whether realism and the philosophical assumptions underlying trials are incompatible. This paper contributes to the debate in Trials on this issue. The debate thus far has concentrated on the possibility of combining trial methodology with that of realist evaluation. MAIN BODY: We concur with the contention that it is not feasible to combine randomised controlled trial design with the realist evaluation approach. However, we argue that a different variant of realism, critical realism, provides a more appropriate theoretical grounding for realist trials. In contrast to realist evaluation, which regards social mechanisms as an amalgam of social resources and people's reasoning, critical realism insists on their distinction. It does so on the basis of its assertion of the need to distinguish between social structures (in which resources lie) and human agency (which is at least partly guided by reasoning). From this perspective, conceiving of social mechanisms as external to participants can be seen as a valid methodological strategy for supplementing the exclusive concentration of trials on outcomes. While accepting realist evaluation's insistence that causality in open systems involves a configuration of multiple generative mechanisms, we adopt the critical realist interpretation of the experimental method, which sees it as creating artificial closure in order to identify the effects of specific causal mechanisms. If randomised controlled trials can be regarded as epidemiological proxies that substitute probabilistic controls over extraneous factors for closed experiments, their examination of the powers of discrete mechanisms through observation of the variation of outcomes is appropriate. CONCLUSION: While there are still issues to be resolved, critical realist randomised controlled trials are possible and have the potential to overcome some of the difficulties faced by traditional trial designs in accounting for the influence of social context and individual interpretation