Gender and race distribution of dental graduates (1985 - 2004) and first year dental students (2000 - 2005) in South Africa

This paper, written at the close of a decade of democracy in South Africa, sets out to analyse the demographic profile of dental graduates from 1985-2004 at the five Faculties/Schools of Dentistry in South Africa. A comparison of the profiles for the pre-democracy (1985-1994) and post-apartheid (1995-2004) periods has been made. The demographic profile of first year dental students from 2000-2005 is also presented. From 1985-1994, most dental graduates were male (79%), but this changed substantially from 1995-2004, with females comprising 46% of those graduating. In the pre-democracy period, more than three-quarters of all graduates were White (78%), decreasing to 46% in the post-apartheid period under review. Black graduates increased from 6% to 24% across the two study periods. Amongst the first year dental student intake from 2000- 2005, females comprised 57%. There was an almost equal distribution across the White, Black and Asian groups. Dental faculties/schools have made important strides in transforming the demographic profile of their students. The percentage of Black graduates, however, needs to be significantly increased if it is to reflect the national population. Faculties/schools must further ensure that able students from working class background are identified and considered for acceptance into the undergraduate dental programme, and should then be offered the necessary academic and mentoring support to enable success

Measurements of Scintillation Efficiency and Pulse-Shape for Low Energy Recoils in Liquid Xenon

Results of observations of low energy nuclear and electron recoil events in liquid xenon scintillator detectors are given. The relative scintillation efficiency for nuclear recoils is 0.22 +/- 0.01 in the recoil energy range 40 keV - 70 keV. Under the assumption of a single dominant decay component to the scintillation pulse-shape the log-normal mean parameter T0 of the maximum likelihood estimator of the decay time constant for 6 keV < Eee < 30 keV nuclear recoil events is equal to 21.0 ns +/- 0.5 ns. It is observed that for electron recoils T0 rises slowly with energy, having a value ~ 30 ns at Eee ~ 15 keV. Electron and nuclear recoil pulse-shapes are found to be well fitted by single exponential functions although some evidence is found for a double exponential form for the nuclear recoil pulse-shape.Comment: 11 pages, including 5 encapsulated postscript figure

Theory of asymmetric non-additive binary hard-sphere mixtures

We show that the formal procedure of integrating out the degrees of freedom of the small spheres in a binary hard-sphere mixture works equally well for non-additive as it does for additive mixtures. For highly asymmetric mixtures (small size ratios) the resulting effective Hamiltonian of the one-component fluid of big spheres, which consists of an infinite number of many-body interactions, should be accurately approximated by truncating after the term describing the effective pair interaction. Using a density functional treatment developed originally for additive hard-sphere mixtures we determine the zero, one, and two-body contribution to the effective Hamiltonian. We demonstrate that even small degrees of positive or negative non-additivity have significant effect on the shape of the depletion potential. The second virial coefficient $B_2$, corresponding to the effective pair interaction between two big spheres, is found to be a sensitive measure of the effects of non-additivity. The variation of $B_2$ with the density of the small spheres shows significantly different behavior for additive, slightly positive and slightly negative non-additive mixtures. We discuss the possible repercussions of these results for the phase behavior of binary hard-sphere mixtures and suggest that measurements of $B_2$ might provide a means of determining the degree of non-additivity in real colloidal mixtures

The ZEPLIN II dark matter detector: data acquisition system and data reduction

ZEPLIN-II is a two-phase (liquid/gas) xenon dark matter detector searching for WIMP-nucleon interactions. In this paper we describe the data acquisition system used to record the data from ZEPLIN-II and the reduction procedures which parameterise the data for subsequent analysis.Comment: 11 pages, 10 figure

The ZEPLIN II dark matter detector: data acquisition system and data reduction

ZEPLIN-II is a two-phase (liquid/gas) xenon dark matter detector searching for WIMP-nucleon interactions. In this paper we describe the data acquisition system used to record the data from ZEPLIN-II and the reduction procedures which parameterise the data for subsequent analysis.Comment: 11 pages, 10 figure

Limits on spin-dependent WIMP-nucleon cross-sections from the first ZEPLIN-II data

The first underground data run of the ZEPLIN-II experiment has set a limit on the nuclear recoil rate in the two-phase xenon detector for direct dark matter searches. In this paper the results from this run are converted into the limits on spin-dependent WIMP-proton and WIMP-neutron cross-sections. The minimum of the curve for WIMP-neutron cross-section corresponds to 0.07 pb at a WIMP mass of around 65 GeV.Comment: 12 pages, 2 figures, to be published in Physics Letters

The ZEPLIN-III dark matter detector: performance study using an end-to-end simulation tool

We present results from a GEANT4-based Monte Carlo tool for end-to-end simulations of the ZEPLIN-III dark matter experiment. ZEPLIN-III is a two-phase detector which measures both the scintillation light and the ionisation charge generated in liquid xenon by interacting particles and radiation. The software models the instrument response to radioactive backgrounds and calibration sources, including the generation, ray-tracing and detection of the primary and secondary scintillations in liquid and gaseous xenon, and subsequent processing by data acquisition electronics. A flexible user interface allows easy modification of detector parameters at run time. Realistic datasets can be produced to help with data analysis, an example of which is the position reconstruction algorithm developed from simulated data. We present a range of simulation results confirming the original design sensitivity of a few times $10^{-8}$ pb to the WIMP-nucleon cross-section.Comment: Submitted to Astroparticle Physic

Gender and race distribution of dental graduates (1985-2004) and first year dental students (2000-2005) in South Africa.

This paper, written at the close of a decade of democracy in South Africa, sets out to analyse the demographic profile of dental graduates from 1985-2004 at the five Faculties/Schools of Dentistry in South Africa. A comparison of the profiles for the pre-democracy (1985-1994) and post-apartheid (1995-2004) periods has been made. The demographic profile of first year dental students from 2000-2005 is also presented. From 1985-1994, most dental graduates were male (79%), but this changed substantially from 1995-2004, with females comprising 46% of those graduating. In the pre-democracy period, more than three-quarters of all graduates were White (78%), decreasing to 46% in the post-apartheid period under review. Black graduates increased from 6% to 24% across the two study periods. Amongst the first year dental student intake from 2000-2005, females comprised 57%. There was an almost equal distribution across the White, Black and Asian groups. Dental faculties/schools have made important strides in transforming the demographic profile of their students. The percentage of Black graduates, however, needs to be significantly increased if it is to reflect the national population. Faculties/schools must further ensure that able students from working class background are identified and considered for acceptance into the undergraduate dental programme, and should then be offered the necessary academic and mentoring support to enable success