A comparative evaluation of two interventions for educator training in HIV/AIDS in South Africa

The purpose of this study was to compare two different methods to teach educators about HIV/AIDS. Sixty educators were selected from eight schools in KwaZulu-Natal Province, South Africa, to undergo HIV/AIDS training using an interactive CD-ROM intervention. Another sixty educators from other schools were selected to undergo a two-day Life Skills Training Programme provided by the Department of Education. The outcomes both before and after the interventions were measured by surveying the educators’ knowledge and attitudes related to HIV/AIDS, as well as their self-efficacy with respect to dealing with HIV/AIDS in the classroom setting. Both interventions resulted in significant changes in knowledge and attitudes as well as in the selfefficacy with respect to ability to teach about HIV/AIDS and to deal with classroom situations involving HIV and blood. The Life Skills Training Programme proved superior in enhancing basic knowledge about HIV, and the CD-ROM was superior in teaching about HIV transmission risks

Diffusion and Concentration of Solids in the Dead Zone of a Protoplanetary Disk

The streaming instability is a promising mechanism to drive the formation of planetesimals in protoplanetary disks. To trigger this process, it has been argued that sedimentation of solids onto the mid-plane needs to be efficient, and therefore that a quiescent gaseous environment is required. It is often suggested that dead-zone or disk-wind structure created by non-ideal magnetohydrodynamical (MHD) effects meets this requirement. However, simulations have shown that the mid-plane of a dead zone is not completely quiescent. In order to examine the concentration of solids in such an environment, we use the local-shearing-box approximation to simulate a particlegas system with an Ohmic dead zone including mutual drag force between the gas and the solids. We systematically compare the evolution of the system with ideal or non-ideal MHD, with or without backreaction drag force from particles on gas, and with varying solid abundances. Similar to previous investigations of deadzone dynamics, we find that particles of dimensionless stopping time ts = 0.1 do not sediment appreciably more than those in ideal magnetorotational turbulence, resulting in a vertical scale height an order of magnitude larger than in a laminar disk. Contrary to the expectation that this should curb the formation of planetesimals, we nevertheless find that strong clumping of solids still occurs in the dead zone when solid abundances are similar to the critical value for a laminar environment. This can be explained by the weak radial diffusion of particles near the mid-plane. The results imply that the sedimentation of particles to the mid-plane is not a necessary criterion for the formation of planetesimals by the streaming instability

A GENERALIZED STOCHASTIC DOMINANCE PROGRAM FOR THE IBM PC

A microcomputer program to perform Generalized Stochastic Dominance (GSD), Quasi-Second Degree Dominance (SSD), and Quasi-First Degree Stochastic Dominance (FSD) is described. The program is designed to run on IBM-compatible personal computers with a Hercules or CGA graphics adapter. It is menu-driven and has options for GSD, quasi-FSD, quasi-SSD, graphics, and calculations of premiums associated with use of dominant distributions.Research and Development/Tech Change/Emerging Technologies,

Time Preference and Its Relationship with Age, Health, and Survival Probability

Although theories from economics and evolutionary biology predict that one’s age, health, and survival probability should be associated with one’s subjective discount rate (SDR), few studies have empirically tested for these links. Our study analyzes in detail how the SDR is related to age, health, and survival probability, by surveying a sample of individuals in townships around Durban, South Africa. In contrast to previous studies, we find that age is not significantly related to the SDR, but both physical health and survival expectations have a U-shaped relationship with the SDR. Individuals in very poor health have high discount rates, and those in very good health also have high discount rates. Similarly, those with expected survival probability on the extremes have high discount rates. Therefore, health and survival probability, and not age, seem to be predictors of one’s SDR in an area of the world with high morbidity and mortality.subjective discount rate; delay discounting; expected survival probability; health; age; South Africa

Joint Reconstruction of Absorbed Optical Energy Density and Sound Speed Distribution in Photoacoustic Computed Tomography: A numerical Investigation

Photoacoustic computed tomography (PACT) is a rapidly emerging bioimaging modality that seeks to reconstruct an estimate of the absorbed optical energy density within an object. Conventional PACT image reconstruction methods assume a constant speed-of-sound (SOS), which can result in image artifacts when acoustic aberrations are significant. It has been demonstrated that incorporating knowledge of an object's SOS distribution into a PACT image reconstruction method can improve image quality. However, in many cases, the SOS distribution cannot be accurately and/or conveniently estimated prior to the PACT experiment. Because variations in the SOS distribution induce aberrations in the measured photoacoustic wavefields, certain information regarding an object's SOS distribution is encoded in the PACT measurement data. Based on this observation, a joint reconstruction (JR) problem has been proposed in which the SOS distribution is concurrently estimated along with the sought-after absorbed optical energy density from the photoacoustic measurement data. A broad understanding of the extent to which the JR problem can be accurately and reliably solved has not been reported. In this work, a series of numerical experiments is described that elucidate some important properties of the JR problem that pertain to its practical feasibility. To accomplish this, an optimization-based formulation of the JR problem is developed that yields a non-linear iterative algorithm that alternatingly updates the two image estimates. Heuristic analytic insights into the reconstruction problem are also provided. These results confirm the ill-conditioned nature of the joint reconstruction problem that will present significant challenges for practical applications.Comment: 13 pages, submitted to IEEE Transactions on Computational Imagin