Choice of speciality amongst first-year medical students in the Nelson R. Mandela School of Medicine, University of KwaZulu-Natal

Background: Trends in career choice amongst medical graduates have considerable implications for the percentage of the workforce available for training. Objective: To investigate and review factors affecting career choice by undergraduate firstyearmedical students. Method: This was a cross-sectional study using a closed-ended, semi-structured surveyinstrument. Two hundred and four questionnaires were administered to all first-year medical students at the Nelson R. Mandela School of Medicine in the first term of the 2012 academic session. Results: The questionnaire was completed by 167 out of 204 students (81.8% response rate). Most of the respondents were South Africans (91%) and blacks (72%), with a higher proportion of women to men (2:1). The majority (86%) intended to undertake their postgraduate training in surgical specialties (53%), general surgery (50%) and cardiology (46%). Few were interested in an academic career in basic sciences (27.6%), either because they were not interested in research and/or teaching (48%), not clinically-orientated (20%), or found it to be an unattractive choice (12.3%). The top perceived career-related factors favouring choice of speciality were personal interest and benefits to patients as many (83%) respondents still viewed the medical profession as having a bright future in South Africa. Conclusions: Our study highlighted the fact that self and patient interests were strong determinants of speciality choices by the students and the role of parents and practice inrural areas were considered least as potential influencing factors. This would appear to be a good indicator that the healthcare sector may be boosted in the future by doctors who are wholeheartedly committed to the service of the communities with the greatest disease burden

Determination of drinking water and wastewater quality in cattle farms

Water plays an important role in any livestock production system as it as an essential medium for animal metabolism as well as an important cleaning medium. It is important that the quality of the drinking water is maintained at a certain level so as to lessen the possible adverse effects on the animals. According to the National Water Quality Standards, any water source with a classification of Class III and less is deemed suitable for animal consumption. At the same time, most cattle farms in Malaysia do not do proper treatment of their wastewater before releasing them into water bodies such as drains, rivers and lakes. In this study 7 cattle farms were selected and both drinking water and wastewater samples were collected for analysis. The water samples were analysed in-situ and at the lab for the following 15 parameters; dissolved oxygen, pH, salinity, electrical conductivity, turbidity, biological oxygen demand, chemical oxygen demand, total suspended solid, total dissolved solid, ammoniacal nitrogen, nitrate, phosphates, total coliform, iron and magnesium content. The results were then compared with the National Water Quality Standards and the overall classification for each water sample was decided. The results for drinking water were as follows; 1 (14.29%) Class II, 2 (28.57%) Class III, 2 (28.57%) Class IV and 2 (28.57%) Class V. Meanwhile, all the wastewater samples were categorized as Class V

A Diffuse Metal-Poor Component of the Sagittarius Stream Revealed by the H3 Survey

The tidal disruption of the Sagittarius dwarf galaxy has generated a spectacular stream of stars wrapping around the entire Galaxy. We use data from $Gaia$ and the H3 Stellar Spectroscopic Survey to identify 823 high-quality Sagittarius members based on their angular momenta. The H3 Survey is largely unbiased in metallicity, and so our sample of Sagittarius members is similarly unbiased. Stream stars span a wide range in [Fe/H] from $-0.2$ to $\approx -3.0$, with a mean overall metallicity of $\langle$[Fe/H]$\rangle=-0.99$. We identify a strong metallicity-dependence to the kinematics of the stream members. At [Fe/H]$\gt -0.8$ nearly all members belong to the well-known cold ($\sigma_v \lt 20$ km/s) leading and trailing arms. At intermediate metallicities ($-1.9 \lt$[Fe/H]$\lt -0.8$) a significant population (24$\%$) emerges of stars that are kinematically offset from the cold arms. These stars also appear to have hotter kinematics. At the lowest metallicities ([Fe/H]$\lesssim-2$), the majority of stars (69$\%$) belong to this kinematically-offset diffuse population. Comparison to simulations suggests that the diffuse component was stripped from the Sagittarius progenitor at earlier epochs, and therefore resided at larger radius on average, compared to the colder metal-rich component. We speculate that this kinematically diffuse, low metallicity, population is the stellar halo of the Sagittarius progenitor system.Comment: 18 pages, 12 figures, 1 table. Submitted to Ap

Discovery of the Magellanic Stellar Stream Out to 100 Kiloparsecs

The Magellanic Stream (MS) - an enormous ribbon of gas spanning $140^\circ$ of the southern sky trailing the Magellanic Clouds - has been exquisitely mapped in the five decades since its discovery. However, despite concerted efforts, no stellar counterpart to the MS has been conclusively identified. This stellar stream would reveal the distance and 6D kinematics of the MS, constraining its formation and the past orbital history of the Clouds. We have been conducting a spectroscopic survey of the most distant and luminous red giant stars in the Galactic outskirts. From this dataset, we have discovered a prominent population of 13 stars matching the extreme angular momentum of the Clouds, spanning up to $100^\circ$ along the MS at distances of $60-120$ kpc. Furthermore, these kinemetically-selected stars lie along a [$\alpha$/Fe]-deficient track in chemical space from $-2.5 < \mathrm{[Fe/H]} < -0.5$, consistent with their formation in the Clouds themselves. We identify these stars as high-confidence members of the Magellanic Stellar Stream. Half of these stars are metal-rich and closely follow the gaseous MS, whereas the other half are more scattered and metal-poor. We argue that the metal-rich stream is the recently-formed tidal counterpart to the MS, and speculate that the metal-poor population was thrown out of the SMC outskirts during an earlier interaction between the Clouds. The Magellanic Stellar Stream provides a strong set of constraints - distances, 6D kinematics, and birth locations - that will guide future simulations towards unveiling the detailed history of the Clouds.Comment: 21 pages, 12 figures. Submitted to Ap

A review: drinking water and wastewater quality assessment in ruminant farms

Water is an essential part in any livestock production and it is more so in ruminant production that is highly water intensive. Water is not only essential as a medium of animal metabolism, but it is also an important cleaning medium. Therefore, it is important that the quality of drinking water is maintained at a certain level so as to lessen the possible adverse effects on the animals. Despite there has being some standards set by the various agencies on the minimal water quality deemed suitable for livestock consumption, they are still vague and this, combined with poor compliance and the water sourcing of dubious sources in ruminant farms makes it hard to regulate the drinking water quality in ruminant farms. This, in turn, might lead to possible adverse effects in livestock production due to water contaminants. At the same time, most ruminant farms in Malaysia do not do proper treatment of their wastewater before releasing them into water bodies such as drains, rivers and lakes which could lead to possible adverse effects to the environment

Timing the Early Assembly of the Milky Way with the H3 Survey

The archeological record of stars in the Milky Way opens a uniquely detailed window into the early formation and assembly of galaxies. Here we use 11,000 main-sequence turn-off stars with well-measured ages, $[\mathrm{Fe}/{\rm{H}}]$, $[\alpha /\mathrm{Fe}]$, and orbits from the H3 Survey and Gaia to time the major events in the early Galaxy. Located beyond the Galactic plane, $1\lesssim | Z| /\mathrm{kpc}\lesssim 4$, this sample contains three chemically distinct groups: a low-metallicity population, and low-α and high-α groups at higher metallicity. The age and orbit distributions of these populations show that (1) the high-α group, which includes both disk stars and the in situ halo, has a star formation history independent of eccentricity that abruptly truncated 8.3 +- 0.1 Gyr ago (z sime 1); (2) the low-metallicity population, which we identify as the accreted stellar halo, is on eccentric orbits and its star formation truncated $10.2{.}_{-0.1}^{+0.2}$ Gyr ago (z sime 2); (3) the low-α population is primarily on low-eccentricity orbits and the bulk of its stars formed less than 8 Gyr ago. These results suggest a scenario in which the Milky Way accreted a satellite galaxy at z ≈ 2 that merged with the early disk by z ≈ 1. This merger truncated star formation in the early high-α disk and perturbed a fraction of that disk onto halo-like orbits. The merger enabled the formation of a chemically distinct, low-α disk at z lesssim 1. The lack of any stars on halo-like orbits at younger ages indicates that this event was the last significant disturbance to the Milky Way disk

The fastest stars in the Galaxy

We report a spectroscopic search for hypervelocity white dwarfs (WDs) that are runaways from Type Ia supernovae (SNe Ia) and related thermonuclear explosions. Candidates are selected from Gaia data with high tangential velocities and blue colors. We find six new runaways, including four stars with radial velocities (RVs) $>1000\,\rm km\,s^{-1}$ and total space velocities $\gtrsim 1300\,\rm km\,s^{-1}$. These are most likely the surviving donors from double-degenerate binaries in which the other WD exploded. The other two objects have lower minimum velocities, $\gtrsim 600\,\rm km\,s^{-1}$, and may have formed through a different mechanism, such as pure deflagration of a WD in a Type Iax supernova. The four fastest stars are hotter and smaller than the previously known "D$^6$ stars," with effective temperatures ranging from $\sim$20,000 to $\sim$130,000 K and radii of $\sim 0.02-0.10\,R_{\odot}$. Three of these have carbon-dominated atmospheres, and one has a helium-dominated atmosphere. Two stars have RVs of $-1694$ and $-2285\rm \,km\,s^{-1}$ -- the fastest systemic stellar RVs ever measured. Their inferred birth velocities, $\sim 2200-2500\,\rm km\,s^{-1}$, imply that both WDs in the progenitor binary had masses $>1.0\,M_{\odot}$. The high observed velocities suggest that a dominant fraction of the observed hypervelocity WD population comes from double-degenerate binaries whose total mass significantly exceeds the Chandrasekhar limit. However, the two nearest and faintest D$^6$ stars have the lowest velocities and masses, suggesting that observational selection effects favor rarer, higher-mass stars. A significant population of fainter low-mass runaways may still await discovery. We infer a birth rate of D$^6$ stars that is consistent with the SN Ia rate. The birth rate is poorly constrained, however, because the luminosities and lifetimes of $\rm D^6$ stars are uncertain.Comment: 26 pages, 17 figures. Accepted to OJ

Change in immune biomarkers of laboratory mice responding to experimental inoculation of different drinking water quality from selected dairy farms

Current knowledge of abnormal physiological responses in livestock due to consumption of substandard water is limited. This study was designed to explore the host cell responses in mice orally inoculated with different drinking water qualities from selected dairy cattle farms. A total of 28 female mice used in this study were divided into Group 1- negative control (treated with sterile deionized distilled water), Group 2 - treated with good quality water sample, Group 3 - treated with moderate quality water sample, and Group 4 - treated with unsatisfactory quality water sample. All the mice were given 0.25 mL of water samples three times daily for 30 days. Blood samples were collected from all mice before euthanasia at 30 days post-inoculation for reproductive hormones and biomarkers analyses. All treatment groups showed significant (p<0.05) weight loss compared to the control group. There was a significant difference in the serum immunoglobulin-G (IgG), , immunoglobulin-M (IgM), interleukin-12 (IL-12), haptoglobin (Hp), and serum amyloid A (SAA) profiles of mice among the different water quality treatments as compared to the control group (p<0.05). In conclusion, the host cell responses exhibited by the mice in the treatment groups indicates a high risk of potential negative effect on the production and health of the livestock due to long-term consumption of drinking water with subpar quality

Federated Learning for Breast Density Classification: A Real-World Implementation

Building robust deep learning-based models requires large quantities of diverse training data. In this study, we investigate the use of federated learning (FL) to build medical imaging classification models in a real-world collaborative setting. Seven clinical institutions from across the world joined this FL effort to train a model for breast density classification based on Breast Imaging, Reporting & Data System (BI-RADS). We show that despite substantial differences among the datasets from all sites (mammography system, class distribution, and data set size) and without centralizing data, we can successfully train AI models in federation. The results show that models trained using FL perform 6.3% on average better than their counterparts trained on an institute's local data alone. Furthermore, we show a 45.8% relative improvement in the models' generalizability when evaluated on the other participating sites' testing data.Comment: Accepted at the 1st MICCAI Workshop on "Distributed And Collaborative Learning"; add citation to Fig. 1 & 2 and update Fig.