Evidence for thermal spin transfer torque

Large heat currents are obtained in Co/Cu/Co spin valves positioned at the middle of Cu nanowires. The second harmonic voltage response to an applied current is used to investigate the effect of the heat current on the switching of the spin valves. Both the switching field and the magnitude of the voltage response are found to be dependent on the heat current. These effects are evidence for a thermal spin transfer torque acting on the magnetization and are accounted for by a thermodynamic model in which heat, charge and spin currents are linked by Onsager reciprocity relations.Comment: 4 pages, 4 figure

Parallelization of a two-dimensional flood inundation model based on domain decomposition

Flood modelling often involves prediction of the inundated extent over large spatial and temporal scales. As the dimensionality of the system and the complexity of the problems increase, the need to obtain quick solutions becomes a priority. However, for large-scale problems or situations where fine resolution data is required, it is often not possible or practical to run the model on a single computer in a reasonable timeframe. This paper presents the development and testing of a parallelized 2D diffusion-based flood inundation model (FloodMap-Parallel) which enables largescale simulations to be run on distributed multi-processors. The model has been applied to three locations in the UK with different flow and topographical boundary conditions. The accuracy of the parallelized model and its computational efficiency have been tested. The predictions obtained from the parallelized model match those obtained from the serialized simulations. The computational performance of the model has been investigated in relation to the granularity of the domain decomposition, the total number of cells and the domain decomposition configuration pattern. Results show that the parallelized model is more effective with simulations of low granularity and a large number of cells. The large communication overhead associated with the potential loadimbalance between sub-domains is a major bottleneck in utilizing this approach with higher domain granularity

Observation of vacancy-induced suppression of electronic cooling in defected graphene

Previous studies of electron-phonon interaction in impure graphene have found that static disorder can give rise to an enhancement of electronic cooling. We investigate the effect of dynamic disorder and observe over an order of magnitude suppression of electronic cooling compared with clean graphene. The effect is stronger in graphene with more vacancies, confirming its vacancy-induced nature. The dependence of the coupling constant on the phonon temperature implies its link to the dynamics of disorder. Our study highlights the effect of disorder on electron-phonon interaction in graphene. In addition, the suppression of electronic cooling holds great promise for improving the performance of graphene-based bolometer and photo-detector devices.Comment: 13 pages, 4 figure

Evaluating the importance of catchment hydrological parameters for urban surface water flood modelling using a simple hydro-inundation model

The influence of catchment hydrological processes on urban flooding is often considered through river discharges at a source catchment outlet, negating the role of other upstream areas that may add to the flooding. Therefore, where multiple entry points exist at the urban upstream boundary, e.g. during extreme rainfall events when surface runoff dominates in the catchment, a hydro-inundation model becomes advantageous as it can integrate the hydrological processes with surface flow routing on the urban floodplain. This paper uses a hydro-inundation model (FloodMap-HydroInundation2D) to investigate the role of catchment hydrological parameters in urban surface water flooding. A scenario-based approach was undertaken and the June 2007 event occurred in Kingston upon Hull, UK was used as a baseline simulation, for which a good range of data is available. After model sensitivity analysis and calibration, simulations were designed, considering the improvement of both the urban and rural land drainage and storage capacities. Results suggest the model is sensitive to the key hydrological parameter soil hydraulic conductivity. Sensitivity to mesh resolution and roughness parameterisation also agrees with previous studies on fluvial flood modelling. Furthermore, the improvement of drainage and storage capacity in the upstream rural area is able to alleviate the extent and magnitude of flooding in the downstream urban area. Similarly urban drainage and storage upgrade may also reduce the risks of flooding on site, albeit to a less extent compared to rural improvements. However, none of the improvement scenarios could remove the flow propagation completely. This study highlights that in some settings, urban surface water flood modelling is just as strongly controlled by rural factors (e.g. infiltration rate and water storage) as internal model parameters such as roughness and mesh resolution. It serves as an important reminder to researchers simulating urban flooding that it is not just the internal parameterisation that is important, but also the use of correct inputs from outside the area of study, especially for catchments with a mixture of urban and rural areas

Gate-Tunable Tunneling Resistance in Graphene/Topological Insulator Vertical Junctions

Graphene-based vertical heterostructures, particularly stacks incorporated with other layered materials, are promising for nanoelectronics. The stacking of two model Dirac materials, graphene and topological insulator, can considerably enlarge the family of van der Waals heterostructures. Despite well understanding of the two individual materials, the electron transport properties of a combined vertical heterojunction are still unknown. Here we show the experimental realization of a vertical heterojunction between Bi2Se3 nanoplate and monolayer graphene. At low temperatures, the electron transport through the vertical heterojunction is dominated by the tunneling process, which can be effectively tuned by gate voltage to alter the density of states near the Fermi surface. In the presence of a magnetic field, quantum oscillations are observed due to the quantized Landau levels in both graphene and the two-dimensional surface states of Bi2Se3. Furthermore, we observe an exotic gate-tunable tunneling resistance under high magnetic field, which displays resistance maxima when the underlying graphene becomes a quantum Hall insulator

From flooding to finance: NHS ambulance‐assisted evacuations of care home residents in Norfolk and Suffolk, UK

Focusing on the counties of Norfolk and Suffolk (UK), this investigation examines the effect of coastal and fluvial flooding on the use of ambulance service vehicles in the assisted evacuation of care home residents and quantifies the cost of this service to the NHS under flood conditions. This was completed using GIS Network Analyst functions to identify the impacts of flood probability (high: 1 in 30, medium: 1 in 30 to 1 in 100, and low: 1 in 100 to 1 in 1000) and target ambulance response-times (7, 18, 120, and 180 min) on ambulance service area, road network accessibility, the number of vulnerable care homes and their accessibility, the appropriateness of pre-identified evacuation routes, and the drive-time based evacuation cost to the National Health Service (NHS). The results indicate that approximately 68 care homes and 2,320 residents in Norfolk and Suffolk are at risk of inundation, and care home accessibility, in addition to ambulance service area, decreases with shorter ambulance response-times and lower flood probabilities. Additionally, the use of pre-identified evacuation routes, by the ambulance service, promotes efficient navigation between ambulance stations, care homes, and rest centres, but can unfavourably cause network clustering if unmanaged. In association with these routes, an estimated cost of evacuation based on ambulance drivetime was calculated at £34,000–£42,000 depending on flood probability. The importance of this research is highlighted by the current lack of identified flood evacuation and accessibility maps for emergency responder use, and the associated lack of evacuation cost estimations to be used by the government and NHS to budget for aid assistance during these natural disasters. Therefore, the application of this approach at a national level in the flood emergency planning process would be beneficial to promote strategic efficiency and financial preparedness of ambulance services for the purpose of ambulance-assisted flood evacuations