Majorana zero modes in gate-defined germanium hole nanowires

We theoretically study gate-defined one-dimensional channels in planar Ge hole gases as a potential platform for non-Abelian Majorana zero modes. We model the valence band holes in the Ge channel by adding appropriate confinement potentials to the 3D Luttinger-Kohn Hamiltonian, additionally taking into account a magnetic field applied parallel to the channel, an out-of-plane electric field, as well as the effect of compressive strain in the parent quantum well. Assuming that the Ge channel is proximitized by an $s$-wave superconductor (such as, e.g., Al) we calculate the topological phase diagrams for different channel geometries, showing that sufficiently narrow Ge hole channels can indeed enter a topological superconducting phase with Majorana zero modes at the channel ends. We estimate the size of the topological gap and its dependence on various system parameters such as channel width, strain, and the applied out-of-plane electric field, allowing us to critically discuss under which conditions Ge hole channels may manifest Majorana zero modes. Since ultra-clean Ge quantum wells with hole mobilities exceeding one million and mean-free paths on the order of many microns already exist, gate-defined Ge hole channels may be able to overcome some of the problems caused by the presence of substantial disorder in more conventional Majorana platforms

Trends in adult tobacco use from two South African demographic and health surveys conducted in 1998 and 2003

Introduction. Since peaking in the early 1990s in South Africa,tobacco use has declined significantly. The reduction has beenattributed to the governmentfs comprehensive tobacco controlpolicies that were introduced at the time.Objective. To assess the pattern of tobacco use in the SouthAfrican Demographic and Health Surveys of 1998 and 2003.Methods. Multi-stage sampling was used to select approximately 11 000 households in cross-sectional national surveys. Face-to-face interviews, conducted with 13 826 adults (41% men) aged .15 years in 1998, and 8 115 (42% men) in 2003, included questions on tobacco use according to the WHO STEP-wise surveillance programme. Logistic regression analysis was used to assess the independent effects of selected characteristics on smoking prevalence.Results. Daily or occasional smoking prevalence among women remained unchanged at 10 - 11%; it decreased among men from 42% (1998) to 35% (2003). The decline for men was significant among the poorest and those aged 25 - 44 years. Strong age patterns were observed, peaking at 35 - 44 years, which was reduced among men in 2003. Higher income and education were associated with low prevalence of smoking, while living in urban areas was associated with higher rates. Black men and women smoked significantly less than otherpopulation groups.Conclusion. Despite decreased smoking rates in some subgroups, a lapse exists in the efforts to reduce tobacco use, as smoking rates have remained unchanged among women, and also among young adults aged 15 - 24 years

Evaluation of savings from an underground fan replacement project

Abstract: The savings calculation methodology from a fan replacement project is presented in this paper. The fans replaced are part of the underground ventilation system in a platinum mine. Initially, 290 axial flow fans rated at 45kW were to be replaced with carbon fibre composite fans. According to the manufacturer, the carbon fibre construction allowed for an optimum blade shape which results in the carbon fibre fan being more energy efficient. However, after the first few fans were replaced, it was discovered that the mine’s blasting activities caused the carbon fibre fans to crack and eventually fail. Fortunately, the manufacturer was able to produce a steel fan with similar performance to that of the carbon composite fans and continue replacing old fans in the mine. The savings were independently verified according to the International Performance Measurement & Verification Protocol (IPMVP). This involved testing old and new fans in a BS848 test duct and comparing the old and new fans at various operating points on their fan curves and making adjustments for operating conditions such as air density underground vs at the test duct. It was found that the new fans saved 5kW on average, across a range of operating points

Validating homicide rates in the Western Cape Province, South Africa: Findings from the 2009 Injury Mortality Survey

Background. The Western Cape Province had the highest homicide rates in South Africa during the early 2000s. South African Police Service (SAPS) data suggested a significant decline in homicide rates in the Western Cape since 2007. It ranked second highest to the Eastern Cape Province until 2013 and ranked highest again at 52.1/100 000 in 2015. A recent national injury mortality survey offers an alternative data source to assess whether the decline in homicide rates in the Western Cape was real.Methods. A retrospective record review of autopsies was conducted from 45 state mortuaries in eight provinces for 2009. In addition, mortality data for the Western Cape were sourced from the Provincial Injury Mortality Surveillance System. Age-standardised mortality rates and crude homicide rates per 100 000 population were calculated to compare with the SAPS crude rates.Results. Our study found that the Western Cape had a provincial age standardised homicide rate of 40.1/100 000 in 2009 and ranked fourth highest among the nine provinces. The crude homicide rate of 43/100 000 for the Western Cape was similar to the SAPS provincial homicide rate of 42.4/100 000. The Northern Cape Province was the only notable exception to our provincial homicide rate ranking comparison with the SAPS for 2009.Conclusions. The Western Cape is fortunate to have alternative data sources to monitor trends in homicides over time. The latest release of the 2014/2015 SAPS crime statistics should be assessed in a similar manner, with a more recent data source, to validate accuracy of the provincial rates on a regular basis

RKKY interaction in one-dimensional flat band lattices

We study the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between two classical magnetic impurities in one-dimensional lattice models with flat bands. As two representative examples, we pick the stub lattice and the diamond lattice at half filling. We first calculate the exact RKKY interaction numerically and then compare our data to results obtained via different analytical techniques. In both our examples, we find that the RKKY interaction exhibits peculiar features that can directly be traced back to the presence of a flat band. Importantly, these features are not captured by the conventional RKKY approximation based on non-degenerate perturbation theory. Instead, we find that degenerate perturbation theory correctly reproduces our exact results if there is an energy gap between the flat and the dispersive bands, while a non-perturbative approach becomes necessary in the absence of a gap

Tracking mortality in near to real time provides essential information about the impact of the COVID-19 pandemic in South Africa in 2020

Background. Producing timely and accurate estimates of the impact of COVID-19 on mortality is challenging for most countries, but impossible for South Africa (SA) from cause-of-death statistics. Objectives. To quantify the excess deaths and likely magnitude of COVID-19 in SA in 2020 and draw conclusions on monitoring the epidemic in 2021. Methods. Basic details of deaths registered on the National Population Register by the Department of Home Affairs (DoHA) are provided to the South African Medical Research Council weekly. Adjustments are made to the numbers of weekly deaths to account for non-registration on the population register, as well as late registration of death with the DoHA. The weekly number of deaths is compared with the number predicted based on the Holt-Winters time-series analysis of past deaths for provinces and metropolitan areas. Excess deaths were calculated for all-causes deaths and natural deaths, using the predicted deaths as a baseline. In addition, an adjustment was made to the baseline for natural deaths to account for the drop in natural deaths due to lockdown. Results. We estimated that just over 550 000 deaths occurred among persons aged ≥1 year during 2020, 13% higher than the 485 000 predicted before the pandemic. A pronounced increase in weekly deaths from natural causes peaked in the middle of July across all ages except <20 years, and across all provinces with slightly different timing. During December, it became clear that SA was experiencing a second wave of COVID-19 that would exceed the death toll of the first wave. In 2020, there were 70 000 - 76 000 excess deaths from natural causes, depending on the base. Using the adjusted base, the excess death rate from natural causes was 122 per 100 000 population, with a male-to-female ratio of 0.78. Deaths from unnatural causes halved for both males and females during the stringent lockdown level 5. The numbers reverted towards the predicted number with some fluctuations as lockdown restrictions varied. Just under 5 000 unnatural deaths were averted. Conclusions. Tracking the weekly numbers of deaths in near to real time has provided important information about the spatiotemporal impact of the pandemic and highlights that the ~28 000 reported COVID-19 deaths during 2020 substantially understate the death toll from COVID-19. There is an urgent need to re-engineer the system of collecting and processing cause-of-death information so that it can be accessed in a timely way to inform public health actions

Effect of vitamin-enriched bread on the vitamin status of an isolated rural community - a controlled clinical trial

No Abstract

Issues in public health: Unnatural deaths, alcohol bans and curfews: Evidence from a quasi-natural experiment during COVID-19

Background. Coronavirus disease-19 (COVID-19) restrictions, particularly relating to the sale of alcohol and hours of curfew, have had a marked effect on the temporal pattern of unnatural deaths in South Africa. Methods. Death data were collected over 68 weeks from January 2020 to April 2021, together with information on the nature of restrictions (if any) on the sale of alcohol, and hours of curfew. Data were analysed using a simple ordinary least square (OLS) regression model to estimate the relative contribution of restrictions on the sale of alcohol and hours of curfew to the pattern of excess unnatural deaths. Results. The complete restriction on the sale of alcohol resulted in a statistically significant reduction in unnatural deaths regardless of the length of curfew. To the contrary, periods where no or limited restrictions on alcohol were in force had no significant effect, or resulted in significantly increased unnatural deaths. Conclusion. The present study highlights an association between alcohol availability and the number of unnatural deaths and demonstrates the extent to which those deaths might be averted by disrupting the alcohol supply. While this is not a long-term solution to addressing alcohol-related harm, it further raises the importance of implementing evidence-based alcohol control measures