CFD Simulation of Low Reynolds-number Turbulence Models in Coral Thermal Microenvironment

The increasing frequency and severity of mass bleaching events in the past few decades has raised considerable concerns. Here we report on the numerical simulations of Low Reynolds turbulence models coral microenvironments to determine surface temperature rise in reef corals and test whether our model is capable to estimate of the extent of warming likely to be en-countered in the nature during calm conditions. The Computational Fluid Dynamics (CFD) simulation uses the OpenFOAM CFD libraries to implement a steady-state turbulent flow porous medium model, with heat transfer accounted for using a transport equation for temperature. We validated the model using controlled laboratory experiment observations

Sexual abuse and the grooming process in sport: Learning from Bella's story

Through a process of collaborative autoethnography, we explore the experiences of one female athlete named Bella who was groomed and then sexually abused by her male coach. Bella’s story signals how the structural conditions and power relationships embedded in competitive sporting environments, specifically the power invested in the coach, provide a unique sociocultural context that offers a number of potentialities for sexual abuse and exploitation to take place. We offer Bella’s story as a pedagogical resource for those involved in the world of sport to both think about and with as part of a process of encouraging change at the individual and institutional levels

Heat transfer enhancement in single impinging jets due to surface cavities

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.This paper presents an assessment of a novel technique that further enhances the heat transfer potential of a single impinging jet. The method entails a geometrical modification to the jet impingement surface wherein the jet is directed into a cylindrical cavity located coaxially beneath the jet orifice. A numerical study is performed to examine the parametric influence on heat dissipation and flow characteristics of this modified jet impingement process. The results indicate a very significant increase in heat transfer, which is primarily dependent on cavity depth and jet Reynolds number.cs201

Effect of nuclear motion on the critical nuclear charge for two-electron atoms

A variational method for calculating the critical nuclear charge, Zc, required for the binding of a nucleus to two electrons is reported. The method is very effective and performs well compared to the traditional variational principle for calculating energy. The critical nuclear charge, which corresponds to the minimum charge required for the atomic system to have at least one bound state, has been calculated for helium-like systems both with infinite and finite nuclear masses. The value of $Z_C=$ 0.911 028 2(3) is in very good agreement with recent values in the literature for two-electron atoms with an infinite nuclear mass. When nuclear motion is considered, the value for Zc varies from 0.911 030 3(2) for that with a nuclear mass of Ne (the largest heliogenic system considered) to 0.921 802 4(4) for a system with the nuclear mass of a positron. In all cases the energy varies smoothly as $Z \rightarrow 0$. It is found that for the finite nuclear mass case, in agreement with previous work for the fixed nucleus mass system, the outer electron remains localised near the nucleus at Z = Zc. Additionally, the electron probability distribution is calculated to determine the behaviour of the electrons at low Z

Soil Microbial Networks Shift Across a High-Elevation Successional Gradient.

While it is well established that microbial composition and diversity shift along environmental gradients, how interactions among microbes change is poorly understood. Here, we tested how community structure and species interactions among diverse groups of soil microbes (bacteria, fungi, non-fungal eukaryotes) change across a fundamental ecological gradient, succession. Our study system is a high-elevation alpine ecosystem that exhibits variability in successional stage due to topography and harsh environmental conditions. We used hierarchical Bayesian joint distribution modeling to remove the influence of environmental covariates on species distributions and generated interaction networks using the residual species-to-species variance-covariance matrix. We hypothesized that as ecological succession proceeds, diversity will increase, species composition will change, and soil microbial networks will become more complex. As expected, we found that diversity of most taxonomic groups increased over succession, and species composition changed considerably. Interestingly, and contrary to our hypothesis, interaction networks became less complex over succession (fewer interactions per taxon). Interactions between photosynthetic microbes and any other organism became less frequent over the gradient, whereas interactions between plants or soil microfauna and any other organism were more abundant in late succession. Results demonstrate that patterns in diversity and composition do not necessarily relate to patterns in network complexity and suggest that network analyses provide new insight into the ecology of highly diverse, microscopic communities

Brain-computer interface controlled functional electrical stimulation device for foot drop due to stroke.

Gait impairment due to foot drop is a common outcome of stroke, and current physiotherapy provides only limited restoration of gait function. Gait function can also be aided by orthoses, but these devices may be cumbersome and their benefits disappear upon removal. Hence, new neuro-rehabilitative therapies are being sought to generate permanent improvements in motor function beyond those of conventional physiotherapies through positive neural plasticity processes. Here, the authors describe an electroencephalogram (EEG) based brain-computer interface (BCI) controlled functional electrical stimulation (FES) system that enabled a stroke subject with foot drop to re-establish foot dorsiflexion. To this end, a prediction model was generated from EEG data collected as the subject alternated between periods of idling and attempted foot dorsiflexion. This prediction model was then used to classify online EEG data into either "idling" or "dorsiflexion" states, and this information was subsequently used to control an FES device to elicit effective foot dorsiflexion. The performance of the system was assessed in online sessions, where the subject was prompted by a computer to alternate between periods of idling and dorsiflexion. The subject demonstrated purposeful operation of the BCI-FES system, with an average cross-correlation between instructional cues and BCI-FES response of 0.60 over 3 sessions. In addition, analysis of the prediction model indicated that non-classical brain areas were activated in the process, suggesting post-stroke cortical re-organization. In the future, these systems may be explored as a potential therapeutic tool that can help promote positive plasticity and neural repair in chronic stroke patients

Gamma-ray bursts: Restarting the Engine

Recent gamma-ray burst observations have revealed late-time, highly energetic events which deviate from the simplest expectations of the standard fireball picture. Instead they may indicate that the central engine is active or restarted at late times. We suggest that fragmentation and subsequent accretion during the collapse of a rapidly rotating stellar core offers a natural mechanism for this.Comment: 8 pages, 1 figure; accepted by ApJ Letter