1834 research outputs found
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Strategic queueing behavior for individual and social optimization in managing discrete time working vacation queue with Bernoulli interruption schedule
No full textIn this paper, we consider a discrete time working vacation queue with a utility function for the reward of receiving the service and the cost of waiting in the system. A more flexible switching mechanism between low and regular service states is introduced to enhance the practical value of the working vacation queue. Under different precision levels of the system information, namely observable, almost unobservable and fully unobservable cases, the utility function is studied from both the individual customer's and the system administrator's points of view. By analyzing the steady-state behavior of the system, the associated optimal joining decisions under different information scenarios are obtained. We find that for the fully observable queue, the joining threshold for individual optimization may be less than the one for social optimization in working vacation period. A similar situation also appears in almost unobservable case. Such phenomenon is not possible for the classic first come first served queue due to the fact that there is no vacation time and thus will not cause large fluctuations in customers' conditional waiting time. Additionally, we also conduct some numerical comparisons to demonstrate the effect of the information levels as well as system parameters on customer joining behaviorNational Research Foundation (South Africa
Are HIV and reproductive health services adapted to the needs of female sex workers? Results of a policy and situational analysis in Tete, Mozambique
No full textIn the context of an implementation research project aiming at improving use of HIV and sexual and reproductive health (SRH) services for female sex workers (FSWs), a broad situational analysis was conducted in Tete, Mozambique, assessing if services are adapted to the needs of FSWs.National Research Foundation (South Africa
Plasmid-mediated resistance and virulence mechanisms in the private health sector in KwaZulu- Natal, South Africa: An investigation of methicillin resistant Staphylococcus aureus (MRSA) clinical isolates collected during a three month period.
No full textOBJECTIVES: Due to the lack of information on the plasmid content of MRSA strains in South Africa (SA), this study investigated the resistance and virulence mechanisms of 27 clinical isolates from the private health care sector over a period of 3 months.
METHODS: Plasmids were extracted and the presence of MRSA confirmed by the presence of mecA. The isolates were subjected to antimicrobial susceptibility testing and molecular characterization of common resistance encoding genes and frequently encountered virulence factors by PCR using plasmid DNA as the template. The genetic relatedness between the isolates was determined by pulsed field gel electrophoresis (PFGE).
RESULTS: All isolates were plasmid positive, and displayed ampillicin, ciprofloxacin, gentamicin, rifampicin, tetracycline, erythromycin, and clindamycin resistance. They were all fully susceptible to daptomycin, linezolid, vancomycin, tigecycline and fusidic acid. Multidrug resistance (MDR) was found in 74.1% (20/27) of the MRSA isolates. The frequency of the resistance and virulence genes ranged from 100% to 0%. PFGE analysis revealed 10 pulsotypes, designated A-J, which showed correlation with resistance profile of the isolates in each group. Of note, 85.2% (23/27) of the isolates clustered into six major PFGE types giving an indication of similar circulating MRSA clones.
CONCLUSIONS: This study highlights the genetic diversity and resistance mechanisms in MRSA strains from the private health sector in SA hence the need for implementing effective infection control programs.National Research Foundation (South Africa
Crowned Eagle nest sites in an urban landscape: Requirements of a large eagle in the Durban Metropolitan Open Space System.
No full textGlobally, dramatic land use change typical of urbanisation negatively affects biodiversity, especially for top predators. The Durban Metropolitan Open Space System (D’MOSS), South Africa, faces the challenge of conserving biodiversity in a regional hotspot in the face of rapid urban growth in one of Africa's major commercial hubs. Consequently, we investigated nest site selection of crowned eagles (Stephanoaetus coronatus) on various spatial scales within this urban mosaic. Unexpectedly the inter-nest distances were small in this human-dominated landscape. However, breeding sites were not evenly distributed through the landscape and were closely associated with natural forest, while nest trees were most frequently in patches of exotic large riverine Sydney blue gum (Eucalyptus saligna, Smith 1797) within the D’MOSS planning zones. Crowned eagles showed a strong tendency to avoid informal settlement areas; however they were tolerant of proximity to established formal settlements and occupied dwellings. Consequently, continued protection of the D’MOSS system, and a considered approach to management of E. saligna are necessary for the persistence of the crowned eagle in this landscape. Future research should focus on food requirements, post-fledging survival, and recruitment to determine which nest sites are most productive and whether this population is acting as a source or a sinkNational Research Foundation (South Africa
We don’t play with gays, they’re not real boys..they can’t fight: Hegemonic masculinity and (homophobic) violence in the primary years of schooling
No full textWhenever masculinity and school violence are considered in South African research, the focus is often on the high school. In this paper, we consider a different direction by drawing on Connell’s (1995) concept of hegemonic masculinity to understand the workings of power and violence amongst a group of South African primary school boys. Little is known about how forces of hegemonic masculinity operate to shape every day gender relations amongst younger boys. Against this background, this paper focuses on a particular group of boys, between 10 and 13 years old, who attend a ‘black’, working-class primary school in South Africa. In addition, they identify themselves as ‘real boys’, where being a ‘real boy’ is inextricably linked to violent ‘performances’ of hegemonic masculinity on the school playground during break time. The paper explores how these boys use forms of violence to claim control of the playground space and to exclude, marginalise and denigrate the other group of boys whom they construct as ‘unmasculine’ and ‘gay’. The findings raise implications for ways of curbing the violence, such as working with the boys to promote non-violent interpretations of performing, being and becoming a ‘real boy’National Research Foundation (South Africa
Air pollution, pollens and childhood asthma – is there a link?
No full textWhile the interplay between ambient air pollutants and their role in the development of asthma continues to remain a subject of detailed study, a link appears to be postulated between ambient air pollutants and airborne pollens in the increasing prevalence of allergic airway disease. With an increasing focus on climate change and the effects of global warming, pollen allergy has become the focus of recent studies looking at the interrelationship between ambient air pollutants and pollen exposures in individuals with allergic respiratory disease. At the population level, little is known about the potential synergistic effects between pollen allergens and air pollutants since this type of association poses challenges in uncontrolled real-life settings. The current knowledge of the pathogenesis of allergies and asthma due to the combined exposure to biological agents such as pollens and air pollutants has been based primarily on animal or in vitro studies. This article highlights possible mechanisms involved in the interrelationship between air pollutants and pollen allergens with asthma, and summarises the evidence on the independent and/or co-effect of multiple environmental exposures (ambient air pollutants and pollens) on childhood asthma.National Research Foundation (South Africa
Relationship between pesticide metabolites, cytokine patterns, and asthma-related outcomes in rural women workers
No full textThe objective of this study was to investigate the relationship between exposure to organophosphate (OP) and pyrethroid (PYR) pesticides with serum cytokine patterns and asthma-related outcomes among rural women workers. A cross-sectional study was conducted among rural women (n = 211), including those working and living on farms and nearby town dwellers. Pesticide exposure was assessed using urinary metabolite concentrations of OP and PYR pesticides. Health outcome assessment was ascertained through the European Community Respiratory Health Survey (ECRHS) questionnaire, fractional exhaled nitric oxide (FeNO), and serum cytokines associated with asthma. The prevalence of doctor-diagnosed asthma was 11%, adult-onset asthma 9%, and current asthma 6%. In this population, the proportion of T helper type 2 (Th2) cytokines (interleukin (IL)-4, IL-5, and IL-13) detectable in subjects was between 18% and 40%, while the proportion of non-Th2 cytokines (IL-6, IL-8, IL-10, IL-17, and interferon gamma) was between 35% and 71%. Most Th2 and non-Th2 cytokines were positively associated with either OP or PYR metabolites. Non-Th2 cytokines showed much stronger associations with OP metabolites (Dimethyl phosphate OR = 4.23; 95% CI: 1.54–11.65) than Th2 cytokines (Dimethyl phosphate OR = 1.69; 95% CI: 0.83–3.46). This study suggests that exposure to most OP and some PYR pesticides may be associated with asthma-related cytokines, with non-Th2 cytokines demonstrating consistently stronger relationshipsNational Research Foundation (South Africa
Review of the literature on demographic determinants of chemical hazard information recall
No full textIn many low and middle income countries (LMIC), workers’ and consumers’ only access to risk and hazard information in relation to the chemicals they use or work with is on the chemical label and safety data sheet. Recall of chemical hazard information is vital in order for label warnings and precautionary information to promote effective safety behaviors. A literature review, therefore, was conducted on determinants of chemical hazard information recall among workers and consumers globally. Since comprehension and recall are closely linked, the determinants of both were reviewed. Literature was reviewed from both online and print peer reviewed journals for all study designs and countries. This review indicated that the level of education, previous training and the inclusion of pictograms on the hazard communication material are all factors that contribute to the recall of hazard information. The influence of gender and age on recall is incongruent and remains to be explored. More research is required on the demographic predictors of the recall of hazard information, the effect of design and non-design factors on recall, the effect of training on the recall among low literate populations and the examining of different regions or contexts..National Research Foundation (South Africa
A driving behaviour model of electrical wheelchair users
No full textIn spite of the presence of powered wheelchairs, some of the users still experience steering challenges and manoeuvring difficulties that limit their capacity of navigating effectively. For such users, steering support and assistive systems may be very necessary. To appreciate the assistance, there is need that the assistive control is adaptable to the user’s steering behaviour. This paper contributes to wheelchair steering improvement by modelling the steering behaviour of powered wheelchair users, for integration into the control system. More precisely, the modelling is based on the improved Directed Potential Field (DPF) method for trajectory planning. The method has facilitated the formulation of a simple behaviour model that is also linear in parameters. To obtain the steering data for parameter identification, seven individuals participated in driving the wheelchair in different virtual worlds on the augmented platform. The obtained data facilitated the estimation of user parameters, using the ordinary least square method, with satisfactory regression analysis results.National Research Foundation (South Africa
Exotic trees modify the thermal landscape and food resources for lizard communities
No full textIncreasing numbers of invasive plant species are establishing around the globe, and these species frequently form dense stands that alter habitat structure in critical ways. Nevertheless, little is known about the mechanisms underlying the impacts of invasive alien plant species on native fauna. We first ask whether alien pine trees impact lizard species richness in the Cape Floristic Region of South Africa, a world-renowned biodiversity hotspot, by examining differences in lizard species richness, abundance, and diversity between native mountain fynbos and exotic pine tree-dominated habitats. We then examine two mutually non-exclusive processes: (i) changes in the thermal quality of the habitat and (ii) changes in the availability of food resources, to explain differences in lizard assemblages among habitat types. Lizard richness, abundance, and diversity were greater in fynbos habitat than in fynbos heavily invaded by pine and in pine plantations. The thermal quality of the environment and food resources was consistently higher in native fynbos than in pine forests, but these responses were more varied when comparisons were made along an invasion gradient and among seasons. Our results suggest that management strategies must consider spatially and temporally detailed measurements of thermal regimes and resources to assess the impacts of invasive vegetation on reptile diversity.National Research Foundation (South Africa