University of South Africa

About: University of South Africa is a education organization based out in Pretoria, South Africa. It is known for research contribution in the topics: Context (language use) & Population. The organization has 8478 authors who have published 19960 publications receiving 237688 citations. The organization is also known as: Unisa.

Influence of urbanization-driven land use/cover change on climate: The case of Addis Ababa, Ethiopia

Abstract: Land use change is the second most important anthropogenic influence on climate beside the emission of greenhouse gases. Urbanization is leading to significant land use changes in Africa since the continent is undergoing rapid urbanization and population growth in recent decades. Addis Ababa is one of these fast growing cities in the continent. Therefore, detection of land use change is very important to identify its impact on climate and sustainable land use management of the city. The study used Landsat images to generate land use/land cover change map for the city. The normalized difference vegetation index (NDVI) is used to detect the major changes of vegetation cover occurred between 1986 and 2011 as a result of land use and land cover change. Downscaled HadCM3 simulations under A2 and B2 emission scenarios is used to investigate future urban heat island (UHI) over the city of Addis Ababa. In the city, the analysis of Landsat images has shown that the built-up areas have increased by 121.88 km2 within the last 25 years. This finding is consistent with NDVI images taken over the same period that reveal a decline in vegetation cover. The impact of the urbanization-driven land use/cover change has resulted in notable nocturnal urban heat island (UHI) as revealed from an average increase in minimum temperature of 1.5 ° C at the centre of the city relative to rural site over the 1960–2001 period. The mean of the 2006–2010 spatial minimum temperature anomaly with respect to the base period mean of 1981–2005 is consistent with the observed UHI. The temperature in the central areas (both commercial and residential sectors) of Addis Ababa is warmer than the surrounding areas. The thermal gradient increase from about 1.44 ° C at the centre (Arada, Addis Ketema, Lideta and Kirkos) to 0.21 ° C at the peripheral parts of the city (Gulele, Bole, Nefasilk-Lafto, Kolfe Keranio and east of Yeka sub-cities) transecting across the hot (high-density urban) to moderately warm to cool (non-built-up) areas. However, the maximum temperature and rainfall exhibit variability that follows topographic differences. Future urban climate change projections of urban heat island formation under A2 and B2 emission scenarios show that the nocturnal UHI will be intense in winter or dry season episodes in the city. The highest urban warming is from October to December (2.5 ° C to 3.2 ° C ) during 2050s and 2080s.

Environmental Effects on the Electrical Characteristics of Back-Gated WSe2 Field-Effect Transistors

Abstract: We study the effect of polymer coating, pressure, temperature, and light on the electrical characteristics of monolayer WSe 2 back-gated transistors with Ni / Au contacts. Our investigation shows that the removal of a layer of poly(methyl methacrylate) (PMMA) or a decrease of the pressure change the device conductivity from p- to n-type. From the temperature behavior of the transistor transfer characteristics, a gate-tunable Schottky barrier at the contacts is demonstrated and a barrier height of ~ 70 meV in the flat-band condition is measured. We also report and discuss a temperature-driven change in the mobility and the subthreshold swing that is used to estimate the trap density at the WSe 2 / SiO 2 interface. Finally, from studying the spectral photoresponse of the WSe 2 , it is proven that the device can be used as a photodetector with a responsivity of ~ 0.5 AW − 1 at 700 nm and 0.37 mW / cm 2 optical power.

Home environment and cognitive development of black infants in impoverished South African families

Abstract: This study examined the interrelationships between home environment, mental and psychomotor development, growth, and educational and occupational indices of socioeconomic status among an urban sample of 305 African infants aged 2 to 30 months. The infants were assessed on the Bayley Scales of Infant Development and the Home Screening Questionnaire, and their heights and weights were recorded. Information regarding the family's socioeconomic status was obtained during interviews with caretakers. No significant relationships were found between parental education and occupation and infant cognitive development, but quality of the home environment was positively correlated with these indices of parental socioeconomic status. On the other hand, home environment scores were found to be significantly related to mental development, independent of parental education and occupation. There was considerable variation in home environments in the sample, which was drawn from generally impoverished urban communities. These findings from an African cultural group support the generalizability of the importance of the quality of the home environment for infant development. Cette ttude examina les relations entre le milieu familial, le developpement psychomoteur et mental, la croissance, et les indices de statut socio-economique (indices ayant rapport a la profession et a l'education) dans un echantillon urbain de 305 bebes africains ǎges de 2 a 30 mois. Les bebes furent evalues a partir des Echelles Bayley de Developpement Infantile (“Bayley Scales of Infant Development”) et du Questionnaire de Depistage Familial (“Home Screening Questionnaire”). Leur taille et de leur poids furent notes. Les informations concernant le statut socio-economique de la famille furent obtenues au cours d'entretiens avec des responsables sociaux. Aucune relation importante 'a ete decelee entre l'education et la profession parentales et le developpement cognitif du bebe, mais la qualite du milieu familial correspondait indeniablement a ces indices de statut socio-economique parental. D'autre part, le milieu familial s'avera ětre particulierement lie au developpement mental, independamment de l'education et de la profession parentales. L'on a enregistre des variations considerables entre les milieux familiaux dans l'echantillon qui fut pris de communautes urbaines generalement pauvres. Ces resultats, obtenus a partir d'un groupe culturel africain, viennent appuyer la generalisation possible de l'importance de la qualite du milieu familial pour le developpement de l'enfant.

[Clinical-epidemiological study of toxocariasis in a pediatric population].

Abstract: OBJECTIVE: The variety of toxocariasis clinic manifestations and its relationship with asthma motivated this study. The aim was to study T.canis seropositivity at a public pediatric service and its association with laboratory, epidemiological and clinical factors. METHODS: This study was cross-sectional and controlled. Two hundred and eight children, from 1 to 14 years old and treated at the University of Santo Amaro Pediatric Department s Immunology and Pneumology clinic between January 2000 and January 2001, underwent serology testing. Antibodies were detected by ELISA testing for the larval excretory-secretory antigen of T. canis. We used the chi-square test for T.canis seropositivity (titers > or = 1:320) associations with: puppies at home, contact with soil, geophagia, onicophagia, mother's educational level, asthma, chronic cough, repetitive pneumonia, skin manifestations, rhinitis, hepatomegaly, splenomegaly, abdominal pain, anemia, eosinophilia, immunoglobulins, parasitosis and stunted growth. The Kruskal-Wallis variance analysis method was used for mean comparisons between seropositive and seronegative groups. Significance was set at p < or = 0.05. RESULTS: Seroprevalence was 54.8%, with a mean age of 6.5 years while for seronegative children the mean age was 5.8 years, showing no significant difference. There was also no difference between sexes. Seropositivity was significantly associated with puppies at home, contact with soil, hepatomegaly, asthma, eosinophilia, increased serum immunoglobulin (Ig) E levels and stunted growth. CONCLUSION: Seroprevalence was elevated in this study . T.canis infection must be considered in at-risk children, such as those with puppies at home, who have had contact with soil, who have hepatomegaly and/or asthma with eosinophilia and increased serum IgE.