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

Tropical forest hydrology and the role of the UNESCO International Hydrological Programme

International audienceThe paper outlines a perspective on tropical forest hydrology within the context of an international hydrological programme. Experience in tropical forest hydrology research in North East Australia is a focal point for comparison with international activities elsewhere. The impacts of climate variability and change are considered briefly, as well as those of reforestation of degraded land on the land use hydrology, which requires a longer term vision and support of long term experimental catchments. Sadly, too few long term experimental catchments have been maintained in the humid tropics and there have been some significant closures even of these sites in recent years. Yet the case for long-term experiments is strengthened by the problematic issue of separating anthropogenic influences (such as land use change) on the hydrology of landscapes from the effects of climate variability at a time of escalation in population and related socio-economic pressures in the humid tropics. Particular emphasis is made of the need for greater consideration for the social and cultural dimensions of forest management within forest hydrology. Furthermore, scientists must be committed to incorporating ‘societal needs' in their planning of research projects, as well as in publicizing the applications of their results, within the framework of forest-land-water policy. Alarm is expressed at the extensive disregard for the application of existing forest hydrology ‘know how' in forest-land management manipulations associated with the humid tropics

Sexually transmitted infection risk exposure among black and minority ethnic youth in northwest London: findings from a study translating a sexually transmitted infection risk-reduction intervention to the UK setting.

OBJECTIVES: Young black women are disproportionately affected by sexually transmitted infections (STI) in the UK, but effective interventions to address this are lacking. The Young Brent Project explored the nature and context of sexual risk-taking in young people to inform the translation of an effective clinic-based STI reduction intervention (Project SAFE) from the USA to the UK. METHODS: One-to-one in-depth interviews (n = 37) and group discussions (n = 10) were conducted among men and women aged 15-27 years from different ethnic backgrounds recruited from youth and genitourinary medicine clinic settings in Brent, London. The interviews explored the context within which STI-related risks were assessed, experienced and avoided, the skills needed to recognise risk and the barriers to behaviour change. RESULTS: Concurrent sexual partnerships, mismatched perceptions and expectations, and barriers to condom use contributed to STI risk exposure and difficulties in implementing risk-reduction strategies. Women attempted to achieve monogamy, but experienced complex and fluid sexual relationships. Low risk awareness, flawed partner risk assessments, negative perceptions of condoms and lack of control hindered condom use. Whereas men made conscious decisions, women experienced persuasion, deceit and difficulty in requesting condom use, particularly with older partners. CONCLUSIONS: Knowledge of STI and condom use skills is not enough to equip young people with the means to reduce STI risk. Interventions with young women need to place greater emphasis on: entering and maintaining healthy relationships; awareness of risks attached to different forms of concurrency and how concurrency arises; skills to redress power imbalances and building self-esteem

Approaches to consent in public health research in secondary schools

OBJECTIVES: We assess different approaches to seeking consent in research in secondary schools. DESIGN: We review evidence on seeking active versus passive parent/carer consent on participant response rates and profiles. We explore the legal and regulatory requirements governing student and parent/carer consent in the UK. RESULTS: Evidence demonstrates that requiring parent/carer active consent reduces response rates and introduces selection biases, which impact the rigour of research and hence its usefulness for assessing young people's needs. There is no evidence on the impacts of seeking active versus passive student consent but this is likely to be marginal when researchers are directly in communication with students in schools. There is no legal requirement to seek active parent/carer consent for children's involvement in research on non-medicinal intervention or observational studies. Such research is instead covered by common law, which indicates that it is acceptable to seek students' own active consent when they are judged competent. General data protection regulation legislation does not change this. It is generally accepted that most secondary school students age 11+ are competent to provide their own consent for interventions though this should be assessed individually. CONCLUSION: Allowing parent/carer opt-out rights recognises their autonomy while giving primacy to student autonomy. In the case of intervention research, most interventions are delivered at the level of the school so consent can only practically be sought from head teachers. Where interventions are individually targeted, seeking student active consent for these should be considered where feasible

The relationship of soil and woodland cover on soil hydraulic conductivity at a hillslope scale and local flood management in the Scottish Borders

An important criteria in Natural Flood Management (NFM) is understanding and improving the surface soil permeability (or field, saturated hydraulic conductivity, Kfs; Talsma, 1987) of natural ground surfaces with the view of increasing rainfall infiltration and storage capacity (Marshall et al., 2009). At the local scale infiltrability and soil hydraulic conductivity (Ks) are key soil properties as they activate surface and near-surface flow paths that influence runoff generation (Elsenbeer, 2001; Bonell et al., 2010)

Natural flood management: does age of forest influence flood mitigation?

Forestry has the potential to alleviate flooding by delaying the downstream passage of flood flows, reducing the volume of runoff through interception (Calder et al. 2003) and promoting rainfall infiltration into the soil (Forest Research, 2010). However, it is difficult to predict how much a forest needs to grow, before there is any significant effect on soil properties to increase the capacity to 1) store water, 2) increase soil infiltration, 3) slow water and reduce water flow connectivity to rivers. The structural coupling between plant roots and soil environment determines flow paths through the soil, where root growth and die-back influences soil hydraulic properties, increasing macropore distribution (Bengough, 2012) and soil permeability. We test the hypothesis: as the forest grows soil permeability below forests will increase, due to increasing macropore structure

Development of soil hydraulic properties below grassland, ancient forest and plantation forests

Woodlands in particular have the potential to alleviate flooding by delaying the downstream passage of flood flows, reducing the volume of runoff through interception (Calder et al. 2003) and promoting rainfall infiltration into the soil (Thomas & Nisbet, 2006). The natural processes which occur below ground to enable a change in hydraulic pathways and storage are complex and are dependent not only on geology, but also on landuse. We focus this study on below-ground changes that influence soil water characteristics, such as soil hydraulic conductivity, soil water retention and soil structure, which are all important in understanding how the planting of trees can mitigate localised flooding

Is positive school climate and adolescent mental health: Longitudinal study of young people in England

Background and objectives: Studies suggest that individual student-reported connection to school is associated with better mental health. However, there is less evidence for associations between schools’ overall school climate and the mental health of their students. This may reflect limitations in which mental health outcomes have been examined. We conducted a large longitudinal study in schools, hypothesising that we would find associations at both the student and school levels between student-reported positive school climate, and reduced student conduct and emotional problems and improved mental wellbeing. // Methods: We tracked students in 20 English secondary schools from near the end of the first year of secondary school (age 11/12) over 3 years using reliable measures of school climate and mental health. // Results: We found associations between student-level reports of positive school climate at baseline, and reduced conduct and emotional problems and better mental wellbeing at 3-year follow-up adjusting for various potential confounders. We also found some evidence of adjusted associations between baseline school-level measures of overall positive climate and better student mental health at follow-up. However, these student- and school-level associations reduced considerably when also adjusting for baseline mental health. // Conclusions: Our findings suggest that there are associations between school climate and student mental health at both the student and school level but these associations are complex and not necessarily causal

Determining the optimal strategy for reopening schools, the impact of test and trace interventions, and the risk of occurrence of a second COVID-19 epidemic wave in the UK: a modelling study

Background: As lockdown measures to slow the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection begin to ease in the UK, it is important to assess the impact of any changes in policy, including school reopening and broader relaxation of physical distancing measures. We aimed to use an individual-based model to predict the impact of two possible strategies for reopening schools to all students in the UK from September, 2020, in combination with different assumptions about relaxation of physical distancing measures and the scale-up of testing. Methods: In this modelling study, we used Covasim, a stochastic individual-based model for transmission of SARS-CoV-2, calibrated to the UK epidemic. The model describes individuals' contact networks stratified into household, school, workplace, and community layers, and uses demographic and epidemiological data from the UK. We simulated six different scenarios, representing the combination of two school reopening strategies (full time and a part-time rota system with 50% of students attending school on alternate weeks) and three testing scenarios (68% contact tracing with no scale-up in testing, 68% contact tracing with sufficient testing to avoid a second COVID-19 wave, and 40% contact tracing with sufficient testing to avoid a second COVID-19 wave). We estimated the number of new infections, cases, and deaths, as well as the effective reproduction number (R) under different strategies. In a sensitivity analysis to account for uncertainties within the stochastic simulation, we also simulated infectiousness of children and young adults aged younger than 20 years at 50% relative to older ages (20 years and older). Findings: With increased levels of testing (between 59% and 87% of symptomatic people tested at some point during an active SARS-CoV-2 infection, depending on the scenario), and effective contact tracing and isolation, an epidemic rebound might be prevented. Assuming 68% of contacts could be traced, we estimate that 75% of individuals with symptomatic infection would need to be tested and positive cases isolated if schools return full-time in September, or 65% if a part-time rota system were used. If only 40% of contacts could be traced, these figures would increase to 87% and 75%, respectively. However, without these levels of testing and contact tracing, reopening of schools together with gradual relaxing of the lockdown measures are likely to induce a second wave that would peak in December, 2020, if schools open full-time in September, and in February, 2021, if a part-time rota system were adopted. In either case, the second wave would result in R rising above 1 and a resulting second wave of infections 2·0–2·3 times the size of the original COVID-19 wave. When infectiousness of children and young adults was varied from 100% to 50% of that of older ages, we still found that a comprehensive and effective test–trace–isolate strategy would be required to avoid a second COVID-19 wave. Interpretation: To prevent a second COVID-19 wave, relaxation of physical distancing, including reopening of schools, in the UK must be accompanied by large-scale, population-wide testing of symptomatic individuals and effective tracing of their contacts, followed by isolation of diagnosed individuals. Funding: None