Accretion physics of AM Herculis binaries, I. Results from one-dimensional stationary radiation hydrodynamics

We have solved the one-dimensional stationary two-fluid hydrodynamic equations for post-shock flows on accreting magnetic white dwarfs simultaneous with the fully frequency and angle-dependent radiative transfer for cyclotron radiation and bremsstrahlung. Magnetic field strengths B = 10 to 100 MG are considered. At given B, this theory relates the properties of the emission region to a single physical parameter, the mass flow density (or accretion rate per unit area). We present the normalized temperature profiles and fit formulae for the peak electron temperature, the geometrical shock height, and the column density of the post-shock flow. The results apply to pillbox-shaped emission regions. With a first-order temperature correction they can also be used for narrower columns provided they are not too tall.Comment: 10 pages with 10 Postscript figures, accepted for publication in Astronomy & Astrophysics. The source file contains Table 1a/b in ASCII forma

Attitudes of Zimbabwean medical students to future practice

A medical research paper on the need for newly graduated medical students to engage in medical rural development in Zimbabwe.Zimbabwe, like many other developing and developed countries, experiences a significant mal-distribution of doctors in favour of urban areas. Out of a total of 1 295 registered medical practitioners in 1989, only 570 were in public service. A number of strategies in various countries have been attempted to address this problem, including preferential admission policies to medical schools and financial incentives to encourage location to under -served areas. In Zimbabwe, a bonding system has been introduced for new medical graduates to redress this imbalance. Additionally, students are trained on a new curriculum. This curriculum, introduced in 1987, aims to equip graduates with the knowledge and skills for them to be able to practise better in rural settings (University of Zimbabwe New Medical Undergraduate, unpublished). With this aim, it was also hoped that graduates’ attitudes towards rural deployment would be positive

Chandra High Energy Transmission Grating Spectrum of AE Aquarii

(Abridged) The results of a Chandra X-ray Observatory High-Energy Transmission Grating (HETG) observation of the nova-like cataclysmic binary AE Aqr are described. First, the X-ray spectrum is that of an optically thin multi-temperature thermal plasma; the X-ray emission lines are broad, with widths that increase with the line energy, from sigma~1 eV for O VIII to sigma~5.5 eV for Si XIV; the X-ray spectrum is reasonably well fit by a plasma model with a Gaussian emission measure distribution that peaks at log T(K)=7.16, has a width sigma=0.48, an Fe abundance equal to 0.44 times solar, and other metal (primarily Ne, Mg, and Si) abundances equal to 0.76 times solar; and for a distance d=100 pc, the total emission measure EM=8.0E53 cm^-3 and the 0.5-10 keV luminosity L_X=1.1E31 erg/s. Second, based on the f/(i+r) flux ratios of the forbidden (f), intercombination (i), and recombination (r) lines of the He alpha triplets of N VI, O VII, and Ne IX measured by Itoh et al. in the XMM-Newton Reflection Grating Spectrometer spectrum and those of O VII, Ne IX, Mg XI, and Si XIII in the Chandra HETG spectrum, either the electron density of the plasma increases with temperature by over three orders of magnitude, from n_e~6E10 cm^-3 for N VI to n_e~1E14 cm^-3 for SI XIII, and/or the plasma is significantly affected by photoexcitation. Third, the radial velocity of the X-ray emission lines varies on the white dwarf spin phase, with two oscillations per spin cycle and an amplitude K~160 km/s. These results appear to be inconsistent with the recent models of Itoh et al., Ikhsanov, and Venter & Meintjes of an extended, low-density source of X-rays in AE Aqr, but instead support earlier models in which the dominant source of X-rays is of high density and/or in close proximity to the white dwarf.Comment: 13 pages including 1 table and 11 encapsulated postscript figure (3 in color); uses emulateapj.cls and apjfonts.sty; accepted on 2009 October 1 for publication in The Astrophysical Journa

The use and perception of urban green spaces through the twentieth century: a case study of the Rondebosch Common

The aim of this research was to unpack and analyse the emergence of narratives around urban green spaces as sites of community interaction, social activity and cultural and conservational value. I used the case study of the Rondebosch Common in Cape Town, South Africa during the period 1900 to 2015 to accomplish these aims. The Rondebosch Common has been fixture of the southern suburbs of the city for over one hundred years and provided a public green space for community interactions. I was able to gather letters and memos sent and received from the Town Clerk's Office from the South African National Archives Repository in Cape Town as well as newspaper articles from the Cape Argus and Cape News newspapers. The archival materials were chosen because they provided the point of view of the local government, the residents of Rondebosch and other users of the Rondebosch Common during the twentieth century. The newspaper articles were used to understand these points of views in the twenty-first century. Public spaces such as the Rondebosch Common are constructed in different ways, i.e. socially, politically, and these constructions determine the appropriate behaviours for the spaces as well as the values and meanings attributed to them. A public open green space such as the Rondebosch Common, which has existed as such for so long, provides an opportunity to examine the inherent political and social nature of old green spaces within the Global South context. Cape Town's colonial and apartheid state added a tension to interactions in the twentieth century as well as a layer of aspiration towards the English or Western ideal. The post-apartheid Cape Town urban and suburban landscape is still fraught with racial and socio-economic divisions. The purpose of my research was to determine how socio-economic, political and ideological context of the Rondebosch Common, in terms of both its physical location and the historical time period, has affected the way in which has been perceived by various groups and how it has been contested by those groups. I also attempt to unpack some of the uses of the Rondebosch Common and how and why they changed over time. It is argued that the demands and claims placed over a public green space such as the Rondebosch Common are represented over broader issues such as belonging, identity and civic entitlements (Di Masso, 2012)