Spacelike surfaces with free boundary in the Lorentz-Minkowski space

We investigate a variational problem in the Lorentz-Minkowski space \l^3 whose critical points are spacelike surfaces with constant mean curvature and making constant contact angle with a given support surface along its common boundary. We show that if the support surface is a pseudosphere, then the surface is a planar disc or a hyperbolic cap. We also study the problem of spacelike hypersurfaces with free boundary in the higher dimensional Lorentz-Minkowski space \l^{n+1}.Comment: 16 pages. Accepted in Classical and Quantum Gravit

Electronic learning can facilitate student performance in undergraduate surgical education: a prospective observational study

BACKGROUND: Our institution recently introduced a novel internet accessible computer aided learning (iCAL) programme to complement existing surgical undergraduate teaching methods. On graduation of the first full cycle of undergraduate students to whom this resource was available we assessed the utility of this new teaching facility. METHOD: The computer programme prospectively records usage of the system on an individual user basis. We evaluated the utilisation of the web-based programme and its impact on class ranking changes from an entry-test evaluation to an exit examination in surgery. RESULTS: 74.4% of students were able to access iCAL from off-campus internet access. The majority of iCAL usage (64.6%) took place during working hours (08:00–18:00) with little usage on the weekend (21.1%). Working hours usage was positively associated with improvement in class rank (P = 0.025, n = 148) but out-of hours usage was not (P = 0.306). Usage during weekdays was associated with improved rank (P = 0.04), whereas weekend usage was not (P = 0.504). There were no significant differences in usage between genders (P = 0.3). Usage of the iCAL system was positively correlated with improvement in class rank from the entry to the exit examination (P = 0.046). Students with lower ranks on entry examination, were found to use the computer system more frequently (P = 0.01). CONCLUSION: Electronic learning complements traditional teaching methods in undergraduate surgical teaching. Its is more frequently used by students achieving lower class ranking with traditional teaching methods, and this usage is associated with improvements in class ranking

Association between knowledge, risk behaviours, and testing for sexually transmitted infections among men who have sex with men: findings from a large online survey in the United Kingdom.

OBJECTIVES: In the UK, men who have sex with men (MSM) bear a disproportionate sexually transmitted infection (STI) burden. We investigated MSM's STI knowledge; whether their STI testing behaviour met national guidelines (annually if sexually active; 3-monthly if engaging in STI risk behaviours); and the relationship between STI testing in the last 3 months, STI knowledge and STI risk behaviours by HIV status. METHODS: Sexually active (in the last year) men aged > 15 years who were UK residents and were recruited from gay-orientated online dating platforms completed an anonymous online survey about STI knowledge, STI risk behaviours, and STI testing (March-May 2017). This included 11 true statements about STIs. Respondents scored 1 for each statement they 'knew', with those scoring < 6 overall treated as having 'poor' STI knowledge. Descriptive and multivariable analyses were conducted, separately by HIV status, to test our hypothesis and calculate adjusted odds ratios (AORs) with 95% confidence intervals (CIs). RESULTS: Compared to HIV-positive men (n = 489), the proportion of HIV-negative/unknown-status men (n = 3157) with 'poor' STI knowledge was significantly higher (46.4% versus 22.9% for HIV-positive men) and the proportion with STI testing in the last 12 months was lower (71.6% versus 87.2%, respectively). In the last 3 months, 56.9% of HIV-negative/unknown-status and 74.1% of HIV-positive men reported STI risk behaviours, of whom 45.8% and 55.1%, respectively, had been tested for STIs during this time. Among HIV-negative/unknown-status men, those reporting STI risk behaviours were more likely (AOR 1.52; 95% CI 1.26-1.84) and those with poor STI knowledge less likely (AOR 0.73; 95% CI 0.61-0.89) to have been tested during the last 3 months. However, neither factor was independently associated with 3-monthly testing among HIV-positive men. CONCLUSIONS: Improving STI knowledge, especially among HIV-negative/unknown-status men, and promoting frequent STI testing among men engaging in STI risk behaviours are vital to address the poor sexual health of MSM

HIV-1 co-receptor usage:influence on mother-to-child transmission and pediatric infection

Viral CCR5 usage is not a predictive marker of mother to child transmission (MTCT) of HIV-1. CXCR4-using viral variants are little represented in pregnant women, have an increased although not significant risk of transmission and can be eventually also detected in the neonates. Genetic polymorphisms are more frequently of relevance in the child than in the mother. However, specific tissues as the placenta or the intestine, which are involved in the prevalent routes of infection in MTCT, may play an important role of selective barriers

Mupirocin-resistant Staphylococcus aureus in Africa: a systematic review and meta-analysis

Background Mupirocin is widely used for nasal decolonization of Staphylococcus aureus to prevent subsequent staphylococcal infection in patients and healthcare personnel. However, the prolonged and unrestricted use has led to the emergence of mupirocin-resistant (mupR) S. aureus. The aim of this systematic review was to investigate the prevalence, phenotypic and molecular characteristics, and geographic spread of mupR S. aureus in Africa. Methods We examined five electronic databases (EBSCOhost, Google Scholar, ISI Web of Science, MEDLINE, and Scopus) for relevant English articles on screening for mupR S. aureus from various samples in Africa. In addition, we performed random effects meta-analysis of proportions to determine the pooled prevalence of mupR S. aureus in Africa. The search was conducted until 3 August 2016. Results We identified 43 eligible studies of which 11 (26%) were obtained only through Google Scholar. Most of the eligible studies (28/43; 65%) were conducted in Nigeria (10/43; 23%), Egypt (7/43; 16%), South Africa (6/43; 14%) and Tunisia (5/43; 12%). Overall, screening for mupR S. aureus was described in only 12 of 54 (22%) African countries. The disk diffusion method was the widely used technique (67%; 29/43) for the detection of mupR S. aureus in Africa. The mupA-positive S. aureus isolates were identified in five studies conducted in Egypt (n = 2), South Africa (n = 2), and Nigeria (n = 1). Low-level resistance (LmupR) and high-level resistance (HmupR) were both reported in six human studies from South Africa (n = 3), Egypt (n = 2) and Libya (n = 1). Data on mupR-MRSA was available in 11 studies from five countries, including Egypt, Ghana, Libya, Nigeria and South Africa. The pooled prevalence (based on 11 human studies) of mupR S. aureus in Africa was 14% (95% CI =6.8 to 23.2%). The proportion of mupA-positive S. aureus in Africa ranged between 0.5 and 8%. Furthermore, the frequency of S. aureus isolates that exhibited LmupR, HmupR and mupR-MRSA in Africa were 4 and 47%, 0.5 and 38%, 5 and 50%, respectively. Conclusions The prevalence of mupR S. aureus in Africa (14%) is worrisome and there is a need for data on administration and use of mupirocin. The disk diffusion method which is widely utilized in Africa could be an important method for the screening and identification of mupR S. aureus. Moreover, we advocate for surveillance studies with appropriate guidelines for screening mupR S. aureus in Africa

Cathodoluminescence of epitaxial GaN laterally overgrown on (0001) sapphire substrate. Time evolution with low energy electron beam

The evolution of GaN luminescence under electron beam injection has been studied by means of in situ cathodoluminescence experiments on various epitaxial lateral overgrown samples. It is shown that the ultraviolet (UV) peak of undoped materials experiences a decrease of its intensity as well as a noticeable redshift, while the other extrinsic peaks only experience an intensity decrease. However, in Mg doped materials the UV peak intensity decrease is followed by an increase of its intensity which can even reach larger values than the initial one. We suggest that all these features are self-consistently explained by the occurrence of strain relaxation resulting from the beam enhanced diffusion of vacancies from the free surface, and from the coalescence boundaries towards the bulk. (C) 2001 American Institute of Physics