Droplet shapes on structured substrates and conformal invariance

We consider the finite-size scaling of equilibrium droplet shapes for fluid adsorption (at bulk two-phase co-existence) on heterogeneous substrates and also in wedge geometries in which only a finite domain $\Lambda_{A}$ of the substrate is completely wet. For three-dimensional systems with short-ranged forces we use renormalization group ideas to establish that both the shape of the droplet height and the height-height correlations can be understood from the conformal invariance of an appropriate operator. This allows us to predict the explicit scaling form of the droplet height for a number of different domain shapes. For systems with long-ranged forces, conformal invariance is not obeyed but the droplet shape is still shown to exhibit strong scaling behaviour. We argue that droplet formation in heterogeneous wedge geometries also shows a number of different scaling regimes depending on the range of the forces. The conformal invariance of the wedge droplet shape for short-ranged forces is shown explicitly.Comment: 20 pages, 7 figures. (Submitted to J.Phys.:Cond.Mat.

Growth studies on Si0.8Ge0.2 channel two-dimensional hole gases

We report a study of the influences of MBE conditions on the low-temperature mobilities of Si/Si0.8Ge0.2 2DHG structures. A significant dependence of 2DHG mobility on growth temperature is observed with the maximum mobility of 3640 cm2 V−1 s−1 at 5.4 K being achieved at the relatively high-growth temperature of 640 °C. This dependence is associated with a reduction in interface charge density. Studies on lower mobility samples show that Cu contamination can be reduced both by growth interruptions and by modifications to the Ge source; this reduction produces improvements in the low-temperature mobilities. We suggest that interface charge deriving from residual metal contamination is currently limiting the 4-K mobility

The effect of lockdown on intentional and nonintentional injury during the COVID-19 pandemic in Cape Town, South Africa: A preliminary report

Background. In response to the coronavirus pandemic, lockdown restrictions and a ban on alcohol sales were introduced in South Africa. Objectives. To investigate the impact of lockdown measures on the number of patients who visited a tertiary urban trauma centre. Methods. The period of investigation was from 1 February to 30 June 2020 and was segmented into three intervals: pre-lockdown (February and March 2020), hard lockdown (April and May 2020) and immediately post lockdown (June 2020). The electronic HECTIS health record registry was interrogated for the total number of patients that were seen per month. These were further categorised according to mechanism of injury (stab, gunshot, blunt assault and road traffic injuries). Penetrating (stab and gunshot) and blunt assault victims were collectively grouped as violent trauma. Results. The mean total number of patients seen decreased by 53% during the hard lockdown period. There was a moderate reduction (15%) in patients with gunshot injuries seen during the hard lockdown phase, but there was an 80% increase in the post-lockdown period. The proportion of patients injured in road traffic collisions pre lockdown, hard lockdown and immediate post lockdown was 16.4%, 8.9% and 11.1%, respectively. Patients injured in road traffic collisions decreased by 74% during the hard lockdown period and maintained a reduction of 32% during the immediate post-lockdown period. The mean total number of patients who visited the trauma unit returned to pre-lockdown levels in June. Conclusions. There was an overall trend of reduced number of patients who visited the trauma unit during the hard lockdown period; however, these numbers returned to pre-lockdown levels during the immediate post-lockdown period. The number of road traffic injury admissions remained reduced during all three phases of lockdown, while the number of gunshot victims increased substantially during the post-lockdown period

Methamphetamine use and sexual risk behaviour in Cape Town South Africa: A review of data from 8 studies conducted between 2004 and 2007

Community studies and studies of admissions to drug treatment centers indicate a dramatic increase in the prevalence of methamphetamine use in Cape Town since 2003. There has also been a substantial increase over this time period in the prevalence of HIV infection among women attending public antenatal clinics in the Western Cape province. This study aimed to review research conducted in Cape Town on the link between methamphetamine use and sexual risk behaviour. Method:A review of published research conducted in Cape Town between 2004 and 2007 was undertaken using PubMed, EBSCOhost and Science Direct. Results:Eight studies were identified, both quantitative and qualitative, and focusing on diverse populations, such as learners in school, out of school youth, adults in the community, men who have sex with men and sex workers. The total sample across the studies was 8153. Across multiple studies methamphetamine was fairly consistently associated with early vaginal sex, condom use during sex, having casual sex and other HIV risk behaviours. For some sub-groups the direction of the relationship was in an unexpected direction. Conclusion: The consistency of the findings across studies highlights the increased risk for contracting HIV among methamphetamine users, and reinforces the importance of interventions addressing both methamphetamine use and unsafe sexual behaviour among young people and other sectors of the population. The need for further research is also considered, particularly research that will explain some of the racial differences that were found

Collaboration and contestation in further and higher education partnerships in England: a Bourdieusian field analysis

Internationally, ‘College for All’ policies are creating new forms of vocational higher education (HE), and shifting relationships between HE and further education (FE) institutions. In this paper, we consider the way in which this is being implemented in England, drawing on a detailed qualitative case study of a regional HE–FE partnership to widen participation. We focus on the complex mix of collaboration and contestation that arose within it, and how these affected socially differentiated groups of students following high- and low-status routes through its provision. We outline Bourdieu’s concept of ‘field’ as a framework for our analysis and interpretation, including its theoretical ambiguities regarding the definition and scale of fields. Through hermeneutic dialogue between data and theory, we tentatively suggest that such partnerships represent bridges between HE and FE. These bridges are strong between higher-status institutions, but highly contested between lower-status institutions competing closely for distinction. We conclude that the trajectories and outcomes for socially disadvantaged students require attention and collective action to address the inequalities they face, and that our theoretical approach may have wider international relevance beyond the English case

Local functional models of critical correlations in thin-films

Recent work on local functional theories of critical inhomogeneous fluids and Ising-like magnets has shown them to be a potentially exact, or near exact, description of universal finite-size effects associated with the excess free-energy and scaling of one-point functions in critical thin films. This approach is extended to predict the two-point correlation function G in critical thin-films with symmetric surface fields in arbitrary dimension d. In d=2 we show there is exact agreement with the predictions of conformal invariance for the complete spectrum of correlation lengths as well as the detailed position dependence of the asymptotic decay of G. In d=3 and d>=4 we present new numerical predictions for the universal finite-size correlation length and scaling functions determining the structure of G across the thin-film. Highly accurate analytical closed form expressions for these universal properties are derived in arbitrary dimension.Comment: 4 pages, 1 postscript figure. Submitted to Phys Rev Let

Conflict of interest: A tenacious ethical dilemma in public health policy not only in clinical practice/research

In addition to the ethical practice of individual health professionals, bioethical debate about conflict of interest (CoI) must include the institutional ethics of public policy-making, as failure to establish independence from powerful stakeholder influence may pervert public health goals. All involved in public policy processes are accountable for CoI, including experts, scientists, professionals, industry and government officials. The liquor industry in South Africa is presented as a case study. Generic principles of how to identify, manage and address CoI are discussed. We propose that health professionals and policy makers should avoid partnering with industries that are harmful to health. Regarding institutional CoI, we recommend that there should be effective policies, procedures and processes for governing public-private joint ventures with such industries. These include arms-length funding, maintaining the balance between contesting vested interests, and full disclosure of the identity and affiliations of all participants in structures and reports pertaining to public policy-making