Mobile HIV testing in South Africa: maximizing yield through data-guided site selection

BACKGROUND: Mobile community HIV testing can effectively reach undiagnosed people living with HIV in southern Africa. Variable yield in HIV test positivity has been a challenge with high- and low-yield sites often being closely situated. We sought to test whether easy-to-identify, site-level characteristics were associated with HIV positivity yield in a routine mobile HIV testing program.METHODS: We used routine testing program test data augmented with site-level characterization, either of the community or shopping site at which HIV testing was offered. Specifically, we described the local environment and interviewed key informants to gain additional information regarding the availability of HIV and other services in the locale.RESULTS: We included 122 residential and 26 shopping sites with median HIV-positive test yields of 7.6% and 6.9%, respectively. The range for community sites was from 2 to 55% with high and low yields at geographically proximal sites. Factors related to lower income and marginalization, including informal housing and the absence of name-brand stores in shopping venues, were associated with higher HIV-positive testing yield.CONCLUSIONS: Characterization of sites, particularly identifying factors related to marginalization, lack of services, and poverty, can aid in identifying sites with higher HIV-positive yield.

Correlation between the emulsion oligomerization parameters for C9 fraction and the characteristics of hydrocarbon resins

This paper investigates the production of hydrocarbon resins by emulsion oligomerization of the С9 fraction hydrocarbons in liquid by-products of oil refining. Such oligomers have a wide range of applications as film-forming agents in paints and anti-color coatings. Emulsion oligomerization was carried out using emulsifiers of the first and second kind. The study was performed at different values of the reaction temperature of the reaction duration, the intensity of agitation; concentrations of the emulsifier; С9:water fraction ratio. The resulting products were estimated according to the following indicators: the yield, unsaturation degree, softening temperature, mean molecular weight, color. Statistical analysis was carried out, the correlation of parameters of emulsion oligomerization and the yield and characteristics of oligomers was established. Given that, it would be possible to establish the optimal conditions for emulsion oligomerization and predict the properties of the products obtained. Specifically, it was established that the yield of hydrocarbon resins does not correlate with the reaction temperature (0.15 and 0.30) and the concentration of emulsifiers (0.08 and 0.03). It was proven that in the intervals studied the variable yield of oligomers depends on the duration of the reaction (correlation 0.88 and 0.81). In the case of oligomerization in the reverse emulsion, a significant correlation with the yield is also demonstrated by agitation intensity (0.51) and a С9:water fraction ratio (0.51). That has made it possible to derive an equation of the yield multiple linear regression dependent on the most significant process parameters. The high values of the yield and bromine number correlation (0.94 and 0.93) give grounds to argue about the progress of oligomerization reaction. The relationship among the characteristics of oligomers has been confirmed. This indicates the possibility of directed adjustment of certain characteristics of hydrocarbon resins.

Natural Grasslands as Lignocellulosic Biofuel Resources: Factors Affecting Fermentable Sugar Production

Semi-natural grassland habitats are most often limited to animal grazing and low intensity farming. Their potential in bioenergy production is complicated due to the heterogeneity, variation, accessibility, and need for complex pre-treatment/hydrolysis techniques to convert into valuable products. In this research, fermentable sugar production efficiency from various habitats at various vegetation periods was evaluated. The highest fermentable sugar yields (above 0.2 g/g volatile solids) over a period of 3 years were observed from habitats “xeric and calcareous grasslands” (Natura 2000 code: 6120) and “semi-natural dry grasslands and scrubland facies on calcareous substrates” (Natura 2000 code: 6210). Both had a higher proportion of dicotyledonous plants. At the same time, the highest productivity (above 0.7 t sugar/ha) was observed from lowland hay meadows in the initial stage of the vegetation. Thus, despite variable yield-affecting factors, grasslands can be a potential resource for energy production.

Comparison of the thermo-oxidative stability of murici oil (Byrsonima crassifolia L. Kunt) obtained by enzymatic hydrolysis assisted by ultrasound and classical method

The extraction of oil from various raw materials by enzymatic process has received great importance for being considered clean technology. In addition, the product obtained by enzymatic action has better yields as well as better chemical quality parameters, also better stability conditions. Thus, the objective of the present work was to optimize the murici pulp oil extraction process by enzymatic hydrolysis and to compare the thermo-oxidative stability of murici oil extracted by ultrasound-assisted enzymatic hydrolysis and the oil obtained by the classic method (Soxhlet). The results obtained showed a dependence on the dependent variable - yield (%) - as a function of the independent variables - enzyme concentration (%) and exposure time on ultrasound (min). From the applied statistical analysis, it was observed that the oil extracted by enzymatic hydrolysis showed greater thermal stability (400 °C) compared to that obtained by the classical method (384 °C). The analysis of oxidative stability showed greater propensity to oxidation the oil obtained by classical method compared to that obtained by enzymatic hydrolysis in 6 hours of induction at 110 °C. Thus, the oil obtained by enzymatic hydrolysis has properties superior to that obtained by the classical method and, thus, with better thermo-oxidative stability.

Stochastic Characteristics and Optimal Control for a Stochastic Chemostat Model with Variable Yield

In this paper, a stochastic chemostat model with variable yield and Contois growth function is investigated. The yield coefficient depends on the limiting nutrient, and the environmental noises are given by independent standard Brownian motions. First, the existence and uniqueness of global positive solution are proved. Second, by using stochastic Lyapunov function, Itô’s formula, and some important inequalities, stochastic characteristics for the stochastic model are studied, including the extinction of micro-organism, the strong persistence in the mean of micro-organism and, the existence of a unique stationary distribution of the stochastic model. Third, the necessary condition of an optimal stochastic control for the stochastic model is established by Hamiltonian function. In addition, some numerical simulations are carried out to illustrate the theoretical results and the influence of the variable yield on the microorganism.