Rapid deconvolution of low-resolution time-of-flight data using Bayesian inference

The deconvolution of low-resolution time-of-flight data has numerous advantages, including the ability to extract additional information from the experimental data. We augment the well-known Lucy-Richardson deconvolution algorithm using various Bayesian prior distributions and show that a prior of second-differences of the signal outperforms the standard Lucy-Richardson algorithm, accelerating the rate of convergence by more than a factor of four, while preserving the peak amplitude ratios of a similar fraction of the total peaks. A novel stopping criterion and boosting mechanism are implemented to ensure that these methods converge to a similar final entropy and local minima are avoided. Improvement by a factor of two in mass resolution allows more accurate quantification of the spectra. The general method is demonstrated in this paper through the deconvolution of fragmentation peaks of the 2,5-dihydroxybenzoic acid matrix and the benzyltriphenylphosphonium thermometer ion, following femtosecond ultraviolet laser desorption

Synthesis of triazole-linked 2-trichloromethylquinazolines and exploration of their efficacy against P. falciparum

Using 2-trichloromethylquinazoline as scaffold, seven novel triazole-linked compounds have been synthesized using CuAAC chemistry. The in vitrobiological activity of four of the compounds on the Plasmodium falciparumchloroquine-sensitive strain NF54 was then determined. The compounds which were tested showed moderate activity with 1.45 /iM as the lowest inhibitory concentration

The development of a toxicity database using freshwater macroinvertebrates, and its application to the protection of South African water resources

There is a growing international trend towards the protection of freshwater resources from pollution by imposing instream guidelines and specified waste-discharge conditions. Current methods for devising freshwater quality guidelines are based on species sensitivity distributions (SSDs) that are used to identify pollutant concentrations, ensuring the protection of a modelled percentage of species (95% protection is a common goal). SSDs are derived from the toxicity test results of as many taxa as possible for each polluting substance. Waste-discharge licences can be for single substances, specified in terms of chemical concentrations, and derived in conjunction with instream guidelines; or for complex mixtures, specified in terms of toxic units. In both cases toxicity test results are the core data used. The emphasis on SSDs calls into question the species constituting the test populations. It is likely that SSDs based in part on the responses of local organisms will achieve superior site-specific ecological protection. Until the early 1990s, there were very few data on the tolerances of South African freshwater organisms. In the intervening decade, the Unilever Centre for Environmental Water Quality at Rhodes University has developed a toxicity database that, to date, records the responses of 21 South African freshwater taxa to 26 single-substance pollutants or mixtures. This is the most comprehensive database of South African toxicity responses available and has been used in the drawing up of methods and guidelines to protect water resources. This paper aims to make these data available and to describe applications of the data using selected case studies

Evaluating the potential for the environmentally sustainable control of foot and mouth disease in Sub-Saharan Africa

Strategies to control transboundary diseases have in the past generated unintended negative consequences for both the environment and local human populations. Integrating perspectives from across disciplines, including livestock, veterinary and conservation sectors, is necessary for identifying disease control strategies that optimise environmental goods and services at the wildlife-livestock interface. Prompted by the recent development of a global strategy for the control and elimination of foot-and-mouth disease (FMD), this paper seeks insight into the consequences of, and rational options for potential FMD control measures in relation to environmental, conservation and human poverty considerations in Africa. We suggest a more environmentally nuanced process of FMD control that safe-guards the integrity of wild populations and the ecosystem dynamics on which human livelihoods depend while simultaneously improving socio-economic conditions of rural people. In particular, we outline five major issues that need to be considered: 1) improved understanding of the different FMD viral strains and how they circulate between domestic and wildlife populations; 2) an appreciation for the economic value of wildlife for many African countries whose presence might preclude the country from ever achieving an FMD-free status; 3) exploring ways in which livestock production can be improved without compromising wildlife such as implementing commodity-based trading schemes; 4) introducing a participatory approach involving local farmers and the national veterinary services in the control of FMD; and 5) finally the possibility that transfrontier conservation might offer new hope of integrating decision-making at the wildlife-livestock interface

Afrikaans adaptation of the children’s hope scale: Validation and measurement invariance

The overarching aim of this study was to validate the Afrikaans version of Snyder’s (1997) Children’s Hope Scale in a sample of children from Cape Town, South Africa. Within this process, the study aimed to test the measurement invariance across the English and Afrikaans language versions. The study used a cross-sectional survey design, with a two-stage stratified random sample of 1022 children between the ages of 11- to 12-years-old. We selected the participants from 15 schools located in low and middle socio-economic status communities in the Cape Town Metropole. We used confirmatory factor analysis to analyse the data. The results indicated a good fit for the overall model using the pooled sample (X2 = 35.692; df = 7; p =.00; CFI =.984; RMSEA =.063; SRMR =.023). Multi-group confirmatory factor analysis further demonstrated the tenability of metric and scalar invariance