Relationships between a cognitive testing instrument, academic points scores and average academic results of National Diploma Students at a University of Technology.

Higher education in South Africa faces a variety of challenges including poor pass rates, large numbers of students dependent on the National Student Financial Aid Scheme, intrapersonal and socioeconomic challenges of students and vast numbers of applicants vying for limited places in institutions. The primary method of selection and screening of applicants is the Academic Points Score (APS), calculated on Grade 12 achievement levels. However, large numbers of applicants exhibit similar or identical scores which meet minimum requirements. This makes effective selection difficult in terms of potential to succeed in the tertiary education context. Therefore, additional selection instruments may be useful in determining high from low potential candidates. Cognitive instruments are one option available to institutions and have been investigated to a certain extent, particularly in conjunction with alternative achievement based assessments. The present study examined a cognitive instrument utilised for selections at a University of Technology. The instrument is based on verbal and non-verbal reasoning skills, basic calculative ability, reading comprehension, memory and spatial reasoning. The results on the sub-tests of this instrument were examined in relation to APS and average mark achieved during study for National Diploma courses at the institution. Although statistically significant relationships did exist, as well as some demographic differences, effect sizes and correlation coefficients were small. Concerningly, APS did not explain a large percentage of variance in average mark. This finding is important in light of current selection procedures. Multiple regression and logistic regression models indicated that two specific sub-tests, in combination with APS, did contribute to predictive power in determining average mark. A number of themes in terms of this prediction are explored. These include English language ability, gender differences, specific cognitive skills and the general validity of utilisation of APS and/or cognitive testing as predictors of tertiary education success. In light of poor success rates in tertiary institutions across South Africa, further research into effective selection procedures should be prioritised

Molecular mechanism of MBX2319 inhibition of Escherichia coli AcrB multidrug efflux pump and comparison with other inhibitors

Efflux pumps of the resistance nodulation division (RND) superfamily, such as AcrB, make a major contribution to multidrug resistance in Gram-negative bacteria. The development of inhibitors of the RND pumps would improve the efficacy of current and next-generation antibiotics. To date, however, only one inhibitor has been cocrystallized with AcrB. Thus, in silico struc- ture-based analysis is essential for elucidating the interaction between other inhibitors and the efflux pumps. In this work, we used computer docking and molecular dynamics simulations to study the interaction between AcrB and the compound MBX2319, a novel pyranopyridine efflux pump inhibitor with potent activity against RND efflux pumps of Enterobacteriaceae species, as well as other known inhibitors (D13-9001, 1-[1-naphthylmethyl]-piperazine, and phenylalanylarginine-ß-naphthyl-amide) and the binding of doxorubicin to the efflux-defective F610A variant of AcrB. We also analyzed the binding of a sub- strate, minocycline, for comparison. Our results show that MBX2319 binds very tightly to the lower part of the distal pocket in the B protomer of AcrB, strongly interacting with the phenylalanines lining the hydrophobic trap, where the hydrophobic por- tion of D13-9001 was found to bind by X-ray crystallography. Additionally, MBX2319 binds to AcrB in a manner that is similar to the way in which doxorubicin binds to the F610A variant of AcrB. In contrast, 1-(1-naphthylmethyl)-piperazine and phenylalanylarginine-ß-naphthylamide appear to bind to somewhat different areas of the distal pocket in the B protomer of AcrB than does MBX2319. However, all inhibitors (except D13-9001) appear to distort the structure of the distal pocket, impairing the proper binding of substrates

GPS TEC and ionosonde TEC over Grahamstown, South Africa: first comparisons

The Grahamstown, South Africa (33.3°S, 26.5°E) ionospheric field station operates a UMass Lowell digital pulse ionospheric sounder (Digisonde) and an Ashtech geodetic grade dual frequency GPS receiver. The GPS receiver is owned by Chief Directorate Surveys and Mapping (CDSM) in Cape Town, forms part of the national TrigNet network and was installed in February 2005. The sampling rates of the GPS receiver and Digisonde were set to 1 s and 15 min, respectively. Data from four continuous months, March–June 2005 inclusive, were considered in this initial investigation. Data available from the Grahamstown GPS receiver was limited, and, therefore, only these 4 months have been considered. Total Electron Content (TEC) values were determined from GPS measurements obtained from satellites passing near vertical (within an 80° elevation) to the station. TEC values were obtained from ionograms recorded at times within 5 min of the near vertical GPS measurement. The GPS derived TEC values are referred to as GTEC and the ionogram derived TEC values as ITEC. Comparisons of GTEC and ITEC values are presented in this paper. The differential clock biases of the GPS satellites and receivers are taken into account. The plasmaspheric contribution to the TEC can be inferred from the results, and confirm findings obtained by other groups. This paper describes the groundwork for a procedure that will allow the validation of GPS derived ionospheric information with ionosonde data. This work will be of interest to the International Reference Ionosphere (IRI) community since GPS receivers are becoming recognised as another source for ionospheric information