The effects of drugs on nutrition

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Magnetoplasmon excitations in an array of periodically modulated quantum wires

Motivated by the recent experiment of Hochgraefe et al., we have investigated the magnetoplasmon excitations in a periodic array of quantum wires with a periodic modulation along the wire direction. The equilibrium and dynamic properties of the system are treated self-consistently within the Thomas-Fermi-Dirac-von Weizsaecker approximation. A calculation of the dynamical response of the system to a far-infrared radiation field reveals a resonant anticrossing between the Kohn mode and a finite-wavevector longitudinal excitation which is induced by the density modulation along the wires. Our theoretical calculations are found to be in excellent agreement with experiment.Comment: 9 pages, 8 figure

Farmers' perceptions of the lay health worker on farms in the Western Cape, South Africa

This study is focussed on farms situated in the Boland health district of the Cape Winelands, South Africa. The aim was to explore, understand, and describe the perceptions of farmers of having a trained lay health worker (LHW) on the farm. A qualitative study design was applied. Data were collected during six in-depth interviews and two focus group discussions with participating farmers. The results show that farmers remained positive about the concept of having a trained LHW on the farm, but became frustrated with the lack of recognition of their and the LHWs' contribution by the public health service. Farmers who are willing to participate and remain active are key to introducing a farm community-based LHW intervention. Sustainable LHW interventions are dependent on public health sector support and recognition of all role players.Farm Management,

The outcome at 12 months of very-Iow-birth-weight infants ventilated at Tygerberg Hospital

Objective. To determine the outcome at 1 year of age of a group of very-Iow-birth-weight (VLBW) infants, from urban and rural communities, ventilated at Tygerberg Hospital, W. Cape. Study design. Prospective descriptive study in which the prevalence of bronchopulmonary dysplasia (BPD), sensorineural deafness, intraventricular haemorrhage (IVH), retinopathy of prematurity (ROP) and abnormal motor developmental outcomes were determined in 153 ventilated VLBW infants from rural and urban areas. Of these, 69% were from lower socio-economic backgrounds. Main outcome measures. Attrition rates for rural and urban babies, BPD, ROP, IVH and abnormal motor development. Study population and setting. All ventilated VLBW infants discharged from the neonatal intensive care unit at Tygerberg Hospital over a 1-year period were followed up at 3-monthly intervals for 12 months. Results. BPD was diagnosed in 19% of the babies, with significantly more babies with birth weights under 1 000 g and gestational ages under 28 weeks having BPD. Of the babies with BPD, 25% had abnormal motor development at 1 year of age. Seven per cent of the babies had grade 3 or 4 ROP and 2,6% had sensorineural hearing loss. One hundred and seventeen (79%) of the infants attended the follow-up clinic until 12 months of age (corrected for prematurity). There were no significant differences in the number of babies followed up from rural or urban areas. Fourteen (11,9%) of the babies had abnormal motor development. A disturbing finding was that so many babies had spastic qiJadriplegia (8; 57%) versus diplegia (6; 43%).S Afr Med J 1995; 8

Exact results for a charged, harmonically trapped quantum gas at arbitrary temperature and magnetic field strength

An analytical expression for the first-order density matrix of a charged, two-dimensional, harmonically confined quantum gas, in the presence of a constant magnetic field is derived. In contrast to previous results available in the literature, our expressions are exact for any temperature and magnetic field strength. We also present a novel factorization of the Bloch density matrix in the form of a simple product with a clean separation of the zero-field and field-dependent parts. This factorization provides an alternative way of analytically investigating the effects of the magnetic field on the system, and also permits the extension of our analysis to other dimensions, and/or anisotropic confinement.Comment: To appear in Phys. Rev.

The PRIME model: a management solution in academic medicine

Background: The Health Sector and the rendering of health services in South Africa have undergone substantial adjustment since the political change in 1994, filtering through to academic medicine. The managerial responsibilities of the Heads of Department at Medical Schools multiplied. In order to improve their management skills; decrease their frustration; and optimally utilize the highly skilled person-power available, this study endeavoured to establish a management model for use by experienced as well as new Heads of Department in a School of Medicine, measured against the background of good management practices. Methods: A descriptive, explanatory survey comprising a literature review, a questionnaire survey and a Delphi process was performed. The literature study covered a few aspects, including assessing the possible needs of Heads of Department, exploring factors impacting on their environment, as well as the difference between management and leadership, and the difference between various management models that may be applicable to management in an academic setting such as a Medical School. The second part of the empirical study was the Delphi process, which involved six experts from the areas of management, health management, and education. A quantitative approach with open-ended questions was followed, focusing on measurement of experts' feelings about these areas. Results: Heads of Department are appointed in the academic environment with the primary focus on their educational achievements. Throughout the process, it was demonstrated that this is still relevant and needs to be part of the appointment process of Heads of Department in a School of Medicine. It was also indicated throughout this study that there is an increasing expectation from Heads of Department to take on sole responsibility for the management of their departments. In view of these developments, it was important to consider assisting them through establishing a management model, thus empowering them to manage their departments in the future. The main findings from the questionnaire to Heads of Department, the Delphi technique, and information obtained via the literature study enabled the researcher to make a recommendation on a management model that is flexible, individualized, relevant, and adaptable for Heads of Department at the School of Medicine at the UFS. Conclusion: Resources and services are spread thin by challenges from political changes and other challenges such as the AIDS pandemic and tuberculosis. Emphasis has shifted from hospital-based care to primary health care adding another dimension to the management strategy of academic institutions. A management model, the PRIME model, was developed that is simple, flexible, allows for individuality, integration and efficiency and should be easy to implement. It adds quality to management tasks but also to lives. It embraces multi-tasking and still focuses on the key position of the leader, while allowing growth and development of new talent. It is adjustable and should be the model of choice to address the ever changing environment of health management. It is recommended that a future study be conducted evaluating the possibility of utilising the principles of the PRIME model in other Medical Schools in South Africa in order to assist them with the managerial problems they might be experiencing. South African Family Practice Vol. 50 (1) 2008: pp. 71-71

Optimising water distribution systems using a weighted penalty in a genetic algorithm

Genetic algorithms (GAs) have become the preferred water system design optimisation technique for many researchers and practitioners. The main reason for using GAs is their ability to deal with nonlinear complex optimisation problems. The optimal decision in terms of designing, expansion/extending, addition or rehabilitation of water supply systems has to review possible options and select a cost-effective and efficient solution. This paper presents a new approach in determining a penalty value depending on the degree of failure, of the set pressure criteria, and the importance of the link supplying a specific node. Further modifications are also made in the cross-over and mutation procedures to ensure an increase in algorithm convergence. EPANET, a widely used water distribution network simulation model, is used in conjunction with the proposed newly developed GA for the optimisation of water distribution systems. The developed GA procedure has been incorporated in a software package called GANEO, which can be used to design new networks, analyse existing networks and prioritise improvements on existing networks. The developed GA has been tested on several international benchmark problems and has proved to be very efficient and robust. The EPANET hydraulic modelling software as well as the developed GANEO software, which performs the optimisation of the water distribution network, is freeware. The software provides a tool for consulting engineers to optimise the design or rehabilitation of a water distribution network.Keywords: optimising, water distribution system, genetic algorith

HST Spectra of GW Librae: A Hot Pulsating White Dwarf in a Cataclysmic Variable

We have obtained Hubble Space Telescope UV spectra of the white dwarf in GW Lib, the only known non-radially pulsating white dwarf in a cataclysmic variable, and the first known DAZQ variable. The UV light curve reveals large amplitude (10%) pulsationsin the UV with the same periods (646, 376 and 237 s) as those seen at optical wavelengths, but the mean spectrum fits with an average white dwarf temperature (14,700K for a 0.6M_{odot} white dwarf) that is too hot to be in the normal instability strip for ZZ Ceti stars. A better fit is achieved with a dual temperature model (with 63% of the white dwarf surface at a temperature of 13300K and 37% at 17100K), and a higher mass (0.8M_{odot}) white dwarf with 0.1 solar metal abundance. Since the blue edge of the instability strip moves to higher temperature with increasing mass, the lower temperature of this model is within the instability strip. However, the presence of accretion likely causes abundance and atmospheric temperature differences in GW Lib compared to all known single white dwarf pulsators, and the current models that have been capable of explaining ZZ Ceti stars may not apply.Comment: 13 pages, 4 figure