Universal single level implicit algorithm for gasdynamics

A single level effectively explicit implicit algorithm for gasdynamics is presented. The method meets all the requirements for unconditionally stable global iteration over flows with mixed supersonic and supersonic zones including blunt body flow and boundary layer flows with strong interaction and streamwise separation. For hyperbolic (supersonic flow) regions the method is automatically equivalent to contemporary space marching methods. For elliptic (subsonic flow) regions, rapid convergence is facilitated by alternating direction solution sweeps which bring both sets of eigenvectors and the influence of both boundaries of a coordinate line equally into play. Point by point updating of the data with local iteration on the solution procedure at each spatial step as the sweeps progress not only renders the method single level in storage but, also, improves nonlinear accuracy to accelerate convergence by an order of magnitude over related two level linearized implicit methods. The method derives robust stability from the combination of an eigenvector split upwind difference method (CSCM) with diagonally dominant ADI(DDADI) approximate factorization and computed characteristic boundary approximations

Termination of the solar wind in the hot, partially ionized interstellar medium

Theoretical foundations for understanding the problem of the termination of the solar wind are reexamined in the light of most recent findings concerning the states of the solar wind and the local interstellar medium. The investigation suggests that a simple extention of Parker's (1961) analytical model provides a useful approximate description of the combined solar wind, interstellar wind plasma flowfield under conditions presently thought to occur. A linear perturbation solution exhibiting both the effects of photoionization and charge exchange is obtained for the supersonic solar wind. A numerical algorithm is described for computing moments of the non-equilibrium hydrogen distribution function and associated source terms for the MHD equations. Computed using the algorithm in conjunction with the extended Parker solution to approximate the plasma flowfield, profiles of hydrogen number density are given in the solar wind along the upstream and downstream axes of flow with respect to the direction of the interstellar wind. Predictions of solar Lyman-alpha backscatter intensities to be observed at 1 a.u. have been computed, in turn, from a set of such hydrogen number density profiles varied over assumed conditions of the interstellar wind

The influence of Instagram usage intensity and electronic word-of-mouth (ewom) on conspicuous consumption - a Generation Y perspective in an emerging economy

Abstract

The size of two-body weakly bound objects : short versus long range potentials

The variation of the size of two-body objects is investigated, as the separation energy approaches zero, with both long range potentials and short range potentials having a repulsive core. It is shown that long range potentials can also give rise to very extended systems. The asymptotic laws derived for states with angular momentum l=1,2 differ from the ones obtained with short range potentials. The sensitivity of the asymptotic laws on the shape and length of short range potentials defined by two and three parameters is studied. These ideas as well as the transition from the short to the long range regime for the l=0 case are illustrated using the Kratzer potential.Comment: 5 pages, 3 figures, submitted to Physical Review Letter

From research to policy in chronic disease prevention: mandatory salt reduction in South Africa

Abstract of a poster that presented at 20th International Congress of Nutrition, Granada, Spain, September 15-20, 2013

Re-aligning the cutting sequence with general support work and drafting a support sequence at Simunye Shaft

‘Roof support awaiting time’ (RSAT) is a term used at Goedehoop Colliery’s Simunye Shaft to describe the potential production time lost due to the continuous miner (CM) standing idle waiting for roof support to catch up. Investigations revealed that in 2013, Simunye Shaft had approximately 1400 hours of RSAT, which suggests that the mine could have potentially produced an additional 280 000 t of coal. This project consisted of two parts. Firstly, the causes of the high RSAT and means to improve the situation were investigated. Secondly, as insisted by mine management, the CM cutting sequence was investigated as a possible cause of high RSAT. Machine-related challenges due to the roofbolter installing support too slowly, geological conditions (mostly hard roof conditions and slips), logistical challenges pertaining to the CM cutting sequence, man-related challenges related to operator fatigue, re-support, operator inexperience, and the absence of support targets were identified as main contributors to RSAT. Furthermore, results showed that the roofbolters in the sections at Simunye Shaft are slower than the CMs. A target of 28% reduction in RSAT was set. Experts from Kennametal and Fletcher were consulted to find solutions for the identified causes. In total, eight solutions for RSAT were identified, but the solution that contributed most significantly to reducing RSAT was to use hard roof drill bits as a standard product at Simunye Shaft. Calculations showed that by using hard roof drill bits, RSAT can be reduced by 43%, which is more than the specified 28% target. The cutting sequences at Kriel, Greenside, and Simunye Shaft, together with three newly developed cutting sequences, were simulated using the UCMS (Underground Coal Mining Simulation) program. A re-aligning principle was incorporated into the newly developed cutting sequences to align the cutting sequences to general support work and to reduce RSAT. A decision matrix revealed that a cutting sequence in which boxing takes place in R3 (third road to the right of the belt road) and in which the realigning principle has been incorporated will be the best option for Simunye Shaft. The recommended cutting sequence will lead to a 5% increase in production.The work presented in this paper was carried out as partial fullfilment for the degree BEng (Mining Engineering)I would like to thank L.M. Mphasha, my mentor at the mine, and J.A. Maritz, my supervisor at the University of Pretoria, for their guidance and support.http://www.saimm.co.za/journal-papersam201

Students get wise about AIDS - The acceptability, feasibility and impact of an AIDS education programme in a suburban school in Cape Town

Objectives. The study assessed the acceptability and feasibility of an AIDS education programme for South African high-school students.Design, setting and sUbjects. A 'before-after' study was conducted in a suburban high school in Cape Town. All 232 standard 8 students were included, and were exposed to the programme over 9 months.Outcome measures. Students' knowledge about AIDS and sexually transmitted diseases (SIDs), attitudes towards people with AIDS and towards AIDS prevention, perceptions of self-efficacy with regard to risk reduction, self-reported behaviour and opinions on the programme were measured using questionnaires. In addition, teachers' opinions of and experiences with the programme were assessed.Results. After the programme, significantly more students knew how to protect themselves from HIV, could identity the symptoms of STOs and understood why people with STOs had a higher risk of becoming infected with HIV. After the programme, significantly more students believed that they knew how to use a condom (77% at baseline, 88.6% at follow-up; P < 0.01). Prior to the programme only 20.8% of the students reported ever having had sexual intercourse. After the programme, significantly more students (32.8%) reported having had sexual intercourse. Most students (80.5%) reported that the programme had helped them to make plans to protect themselves from HIV infection. Teachers found the programme valuable and easy to use.Conclusions. There are severaJ South African school programmes such as 'Get Wise about AIDS' which have been shown to be acceptable and feasible, and which seem to be effective. Randomised controlled trials are now needed to provide conclusive evidence of their effectiveness

Retrospective file review shows limited genetic services fails most patients – an argument for the implementation of exome sequencing as a first-tier test in resource-constraint settings

Background: Exome sequencing is recommended as a first-line investigation for patients with a developmental delay or intellectual disability. This approach has not been implemented in most resource-constraint settings, including Africa, due to the high cost of implementation. Instead, patients have limited access to services and testing options. Here, we evaluate the effectiveness of a limited genetic testing strategy and contrast the findings to a conceivable outcome if exome sequencing were available instead. Results: A retrospective audit of 934 patient files presenting to a medical genetics clinic in South Africa showed that 83% of patients presented with developmental delay as a clinical feature. Patients could be divided into three groups, representing distinct diagnostic pathways. Patient Group A (18%; mean test cost $131) were confirmed with aneuploidies, following a simple, inexpensive test. Patient Group B (25$140) presented with clinically recognizable conditions but only 39% received a genetic diagnostic confirmation due to limited testing options. Patient Group C – the largest group (57%; mean test cost $337) – presented with heterogenous conditions and DD, and 92% remained undiagnosed after limited available testing was performed. Conclusions: Patients with DD are the largest group of patients seen in medical genetics clinics in South Africa. When clinical features are not distinct, limited testing options drastically restricts diagnostic yield. A cost- and time analysis shows most patients would benefit from first-line exome sequencing, reducing their individual diagnostic odysseys

A photometric monitoring of bright high-amplitude delta Scuti stars. II. Period updates for seven stars

We present new photometric data for seven high-amplitude delta Scuti stars. The observations were acquired between 1996 and 2002, mostly in the Johnson photometric system. For one star (GW UMa), our observations are the first since the discovery of its pulsational nature from the Hipparcos data.The primary goal of this project was to update our knowledge on the period variations of the target stars. For this, we have collected all available photometric observations from the literature and constructed decades-long O-C diagrams of the stars. This traditional method is useful because of the single-periodic nature of the light variations. Text-book examples of slow period evolution (XX Cyg, DY Her, DY Peg) and cyclic period changes due to light-time effect (LITE) in a binary system (SZ Lyn) are updated with the new observations. For YZ Boo, we find a period decrease instead of increase. The previously suggested LITE-solution of BE Lyn (Kiss & Szatmary 1995) is not supported with the new O-C diagram. Instead of that, we suspect the presence of transient light curve shape variations mimicking small period changes.Comment: 11 pages, 15 figures, accepted for publication in A&

Fungi Associated with Decay in Treated Southern Pine Utility Poles in the Eastern United States

Approximately 1,320 fungi were isolated and studied from 246 creosote- or pentachlorophenol-treated southern pine poles in service in the eastern United States. The fungi identified were Basidiomycete decayers, soft rotters, and microfungi. White rot fungi predominated in the 262 Basidiomycete decayers isolated from 180 poles. The major Basidiomycetes isolated by radial position from poles of varying service ages appeared to develop initially in the outer treated zones and were often associated with seasoning checks. Some decay origins, however, appeared to be cases of preinvasion and escapes of preservative treatment. Five species of soft rot fungi comprised nearly 85% of 211 isolates obtained from 131 poles. They were isolated primarily from creosote-treated poles in outer treated zones at the groundline. Dissection analysis of 92 poles indicated that six developmental decay patterns and certain fungi were associated commonly with a pattern. The pole mycoflora isolated was relatively uniform in distribution in the eastern United States. The soft rotters and white rot group of Basidiomycete decayers appear to be a more important component of the treated southern pine pole mycoflora than has been recognized previously