Attitudes of private general practitioners towards health care in South Africa

The need for health care reform in South Africa is acknowledged by the govermnent as well as by the non-governmental health sector. There is, however, no unanimity regarding the nature of the envisaged reform. A country-wide postal survey of 700 private sector general practitioners (GPs) from a commercial database of 5 000 was conducted to explore attitudes towards health care. A response rate of 67,4% was obtained. Respondents were mostly male (92%) and urban-based (64%). The median age was 42 years. Most respondents:(i) believed health care to be a right for all citizens; (ii) favoured private or a combination of private and public funding mechanisms with fee-for-service arrangements; (iii) opposed cost-containment measures imposed by funders, e.g. medical aids; and (iv) believed doctors should be responsible for primary care in under-served areas. After sex, age, location (urban versus rural) and GP postgraduate qualification had been controlled for by means of logistic regression techniques, the university at which a respondent's basic degree was obtained emerged as the only independent predictor of attitudes to the following: (i) comprehensive care as a right; (ii) integration of the public and private sectors; (iii) preferred funding source for a future health system; and (iv) preference for fee-for-service remuneration. Both university and gender independently predicted attitudes on GPs' income. Graduates of white, Afrikaans-medium universities were strongly in favour of a privately funded and fee-for-service orientated system. Those who qualified at black universities, on the other hand, favoured public funding with less emphasis on fee-for-service. White, English university graduates, while expressing a preference for fee-for-service remuneration, were less enthusiastic about private funding, favouring a mixed funding approach (private and public) instead. This is the first systematic study of GP attitudes to health care in South Africa. Further research is recommended to understand the significance of the attitudes expressed and to investigate the role of the university medical school and other factors in practitioners' attitudes to health care

Ultrafiltration of municipal wastewater: study on fouling models and fouling mechanisms

Ultrafiltration (UF) with hollow fiber membranes is a proven membrane technique that can achieve high water quality standards as a tertiary treatment in municipal wastewater treatment plants. However, UF has a major drawback, membrane fouling, which causes losses of productivity and increases operation costs. Thus, the aim of this work is to model membrane fouling in the UF of a secondary treatment effluent. The tests were carried out with a model wastewater solution that consisted of bovine serum albumin and dextran. Three different transmembrane pressures and three different crossflow velocities were tested. Several fouling models available in the literature, and new models proposed, were fitted to permeate flux decline experimental data. The models studied by other authors and considered in this study were: Hermia s models (complete, intermediate, standard pore blocking and gel layer) and Belfort s model. The new models proposed in this work were: modified Belfort s model, quadratic exponential model, logarithmic inversed model, double exponential model and tangent inversed model. The fitting accuracy of the models was determined in terms of the R-squared and standard deviation. The results showed that the model that had the higher fitting accuracy was the logarithmic inversed model. Among the Hermia s models, the model that had the higher fitting accuracy was the intermediate pore blocking model. Therefore, the predominant fouling mechanism was determined and it was the intermediate pore blocking modelThe authors wish to gratefully acknowledge the financial support of the Generalitat Valenciana through the project "Ayudas para la realizacion de proyectos I+D para grupos de investigacion emergentes GV/2013".Soler Cabezas, JL.; Tora Grau, M.; Vincent Vela, MC.; Mendoza Roca, JA.; Martínez Francisco, FJ. (2014). 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Analysis of membrane pore blocking models adapted to crossflow ultrafiltration in the ultrafiltration of PEG. Chemical Engineering Journal, 149(1-3), 232-241. doi:10.1016/j.cej.2008.10.027Hasan, A., Peluso, C. R., Hull, T. S., Fieschko, J., & Chatterjee, S. G. (2013). A surface-renewal model of cross-flow microfiltration. Brazilian Journal of Chemical Engineering, 30(1), 167-186. doi:10.1590/s0104-66322013000100019ANG, W., & ELIMELECH, M. (2007). Protein (BSA) fouling of reverse osmosis membranes: Implications for wastewater reclamation. Journal of Membrane Science, 296(1-2), 83-92. doi:10.1016/j.memsci.2007.03.018Muthukumaran, S., & Baskaran, K. (2013). Comparison of the performance of ceramic microfiltration and ultrafiltration membranes in the reclamation and reuse of secondary wastewater. Desalination and Water Treatment, 52(4-6), 670-677. doi:10.1080/19443994.2013.826333Tasselli, F., Cassano, A., & Drioli, E. (2007). Ultrafiltration of kiwifruit juice using modified poly(ether ether ketone) hollow fibre membranes. Separation and Purification Technology, 57(1), 94-102. doi:10.1016/j.seppur.2007.03.007Chung, T.-S., Qin, J.-J., & Gu, J. (2000). Effect of shear rate within the spinneret on morphology, separation performance and mechanical properties of ultrafiltration polyethersulfone hollow fiber membranes. Chemical Engineering Science, 55(6), 1077-1091. doi:10.1016/s0009-2509(99)00371-1Swaminathan, T., Chaudhuri, M., & Sirkar, K. K. (1979). Anomalous flux behavior in initial time stirred protein ultrafiltration through partially permeable membranes. Journal of Applied Polymer Science, 24(6), 1581-1585. doi:10.1002/app.1979.070240620Ahmad, A. L., & Hairul, N. A. H. (2009). Protein–membrane interactions in forced-flow electrophoresis of protein solutions: Effect of initial pH and initial ionic strength. Separation and Purification Technology, 66(2), 273-278. doi:10.1016/j.seppur.2008.12.027Gu, Z. 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A Nonlinear Force-Free Magnetic Field Approximation Suitable for Fast Forward-Fitting to Coronal Loops. I. Theory

We derive an analytical approximation of nonlinear force-free magnetic field solutions (NLFFF) that can efficiently be used for fast forward-fitting to solar magnetic data, constrained either by observed line-of-sight magnetograms and stereoscopically triangulated coronal loops, or by 3D vector-magnetograph data. The derived NLFFF solutions provide the magnetic field components $B_x({\bf x})$, $B_y({\bf x})$, $B_z({\bf x})$, the force-free parameter $\alpha({\bf x})$, the electric current density ${\bf j}({\bf x})$, and are accurate to second-order (of the nonlinear force-free $\alpha$-parameter). The explicit expressions of a force-free field can easily be applied to modeling or forward-fitting of many coronal phenomena.Comment: Solar Physics (in press), 26 pages, 11 figure

Nonlinear force-free reconstruction of the global solar magnetic field: methodology

We present a novel numerical method that allows the calculation of nonlinear force-free magnetostatic solutions above a boundary surface on which only the distribution of the normal magnetic field component is given. The method relies on the theory of force-free electrodynamics and applies directly to the reconstruction of the solar coronal magnetic field for a given distribution of the photospheric radial field component. The method works as follows: we start with any initial magnetostatic global field configuration (e.g. zero, dipole), and along the boundary surface we create an evolving distribution of tangential (horizontal) electric fields that, via Faraday's equation, give rise to a respective normal field distribution approaching asymptotically the target distribution. At the same time, these electric fields are used as boundary condition to numerically evolve the resulting electromagnetic field above the boundary surface, modelled as a thin ideal plasma with non-reflecting, perfectly absorbing outer boundaries. The simulation relaxes to a nonlinear force-free configuration that satisfies the given normal field distribution on the boundary. This is different from existing methods relying on a fixed boundary condition - the boundary evolves toward the a priori given one, at the same time evolving the three-dimensional field solution above it. Moreover, this is the first time a nonlinear force-free solution is reached by using only the normal field component on the boundary. This solution is not unique, but depends on the initial magnetic field configuration and on the evolutionary course along the boundary surface. To our knowledge, this is the first time that the formalism of force-free electrodynamics, used very successfully in other astrophysical contexts, is applied to the global solar magnetic field.Comment: 18 pages, 5 figures, Solar Physic

All-optical switching and strong coupling using tunable whispering-gallery-mode microresonators

We review our recent work on tunable, ultrahigh quality factor whispering-gallery-mode bottle microresonators and highlight their applications in nonlinear optics and in quantum optics experiments. Our resonators combine ultra-high quality factors of up to Q = 3.6 \times 10^8, a small mode volume, and near-lossless fiber coupling, with a simple and customizable mode structure enabling full tunability. We study, theoretically and experimentally, nonlinear all-optical switching via the Kerr effect when the resonator is operated in an add-drop configuration. This allows us to optically route a single-wavelength cw optical signal between two fiber ports with high efficiency. Finally, we report on progress towards strong coupling of single rubidium atoms to an ultra-high Q mode of an actively stabilized bottle microresonator.Comment: 20 pages, 24 figures. Accepted for publication in Applied Physics B. Changes according to referee suggestions: minor corrections to some figures and captions, clarification of some points in the text, added references, added new paragraph with results on atom-resonator interactio

Coherent matter wave inertial sensors for precision measurements in space

We analyze the advantages of using ultra-cold coherent sources of atoms for matter-wave interferometry in space. We present a proof-of-principle experiment that is based on an analysis of the results previously published in [Richard et al., Phys. Rev. Lett., 91, 010405 (2003)] from which we extract the ratio h/m for 87Rb. This measurement shows that a limitation in accuracy arises due to atomic interactions within the Bose-Einstein condensate

First Observation of Coherent π0\pi^0 Production in Neutrino Nucleus Interactions with Eν<E_{\nu}< 2 GeV

The MiniBooNE experiment at Fermilab has amassed the largest sample to date of $\pi^0$s produced in neutral current (NC) neutrino-nucleus interactions at low energy. This paper reports a measurement of the momentum distribution of $\pi^0$s produced in mineral oil (CH$_2$) and the first observation of coherent $\pi^0$ production below 2 GeV. In the forward direction, the yield of events observed above the expectation for resonant production is attributed primarily to coherent production off carbon, but may also include a small contribution from diffractive production on hydrogen. Integrated over the MiniBooNE neutrino flux, the sum of the NC coherent and diffractive modes is found to be (19.5 $\pm$1.1 (stat) $\pm$2.5 (sys))% of all exclusive NC $\pi^0$ production at MiniBooNE. These measurements are of immediate utility because they quantify an important background to MiniBooNE's search for $\nu_{\mu} \to \nu_e$ oscillations.Comment: Submitted to Phys. Lett.

Long term intrinsic cycling in human life course antibody responses to influenza A(H3N2): an observational and modeling study

Background: Over a life course, human adaptive immunity to antigenically mutable pathogens exhibits competitive and facilitative interactions. We hypothesize that such interactions may lead to cyclic dynamics in immune responses over a lifetime. Methods: To investigate the cyclic behavior, we analyzed hemagglutination inhibition titers against 21 historical influenza A(H3N2) strains spanning 47 years from a cohort in Guangzhou, China, and applied Fourier spectrum analysis. To investigate possible biological mechanisms, we simulated individual antibody profiles encompassing known feedbacks and interactions due to generally recognized immunological mechanisms. Results: We demonstrated a long-term periodicity (about 24 years) in individual antibody responses. The reported cycles were robust to analytic and sampling approaches. Simulations suggested that individual-level cross-reaction between antigenically similar strains likely explains the reported cycle. We showed that the reported cycles are predictable at both individual and birth cohort level and that cohorts show a diversity of phases of these cycles. Phase of cycle was associated with the risk of seroconversion to circulating strains, after accounting for age and pre-existing titers of the circulating strains. Conclusions: Our findings reveal the existence of long-term periodicities in individual antibody responses to A(H3N2). We hypothesize that these cycles are driven by preexisting antibody responses blunting responses to antigenically similar pathogens (by preventing infection and/or robust antibody responses upon infection), leading to reductions in antigen-specific responses over time until individual's increasing risk leads to an infection with an antigenically distant enough virus to generate a robust immune response. These findings could help disentangle cohort effects from individual-level exposure histories, improve our understanding of observed heterogeneous antibody responses to immunizations, and inform targeted vaccine strategy

4pi Models of CMEs and ICMEs

Coronal mass ejections (CMEs), which dynamically connect the solar surface to the far reaches of interplanetary space, represent a major anifestation of solar activity. They are not only of principal interest but also play a pivotal role in the context of space weather predictions. The steady improvement of both numerical methods and computational resources during recent years has allowed for the creation of increasingly realistic models of interplanetary CMEs (ICMEs), which can now be compared to high-quality observational data from various space-bound missions. This review discusses existing models of CMEs, characterizing them by scientific aim and scope, CME initiation method, and physical effects included, thereby stressing the importance of fully 3-D ('4pi') spatial coverage.Comment: 14 pages plus references. Comments welcome. Accepted for publication in Solar Physics (SUN-360 topical issue

Observation of hard scattering in photoproduction events with a large rapidity gap at HERA

Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a function of the $\gamma p$ centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a two-jet structure with each jet having a transverse energy greater than 4 GeV. For the two-jet events, little energy flow is found outside the jets. This observation is consistent with the hard scattering of a quasi-real photon with a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil