Thermal analysis of the LLR optical telescope tube assembly based in Hartebeesthoek Radio Astronomy Observatory

The Hartebeesthoek Radio Astronomy Observatory of South Africa is currently developing a lunar laser ranger (LLR) system based on a one metre aperture telescope in collaboration with National Aeronautics and Space Administration and the Observatoire de la Côte d’Azur. This LLR will be an addition to a limited list of operating LLR stations globally and it is expected to achieve sub-centimetre range precision to the Moon. Key to this expectation including the overall telescope operational performance is thermal analysis of the telescope structure, based on the thermal properties of component materials and their interaction with the environment through conventional heat transfer mechanisms. This paper presents transient thermal simulation results of the telescope’s optical tube and one metre primary mirror in terms of thermal variations and consequent structural deformations. The results indicate that on a non-windy, cloud-free and winter day, the temperature gradients on the structure could be within 1 °C with respect to the temporal ambient air temperatures at the site when these are between 9 and 23 °C. Furthermore, these gradients were coupled with thermally-induced total deformations that vary between 2.9 and 40.7 μm of the assembled telescope components. In overall, these findings suggest that both the tube and especially the mirror may respond very slowly to ambient temperatures; however, correcting for structural thermal variations is imperative in maximizing the pointing accuracy of the telescope thereby increasing the chance being on-target with the retroreflectors located on the Moon surface.P. L. Tsela hereby acknowledges research support in part by the National Research Foundation of South Africa for the grant, Unique Grant No. 93952.http://link.springer.com/journal/403282017-09-30hb2016Geography, Geoinformatics and Meteorolog

Strong plasmonic fluorescence enhancement of individual plant light-harvesting complexes

Plasmonic coupling of metallic nanoparticles and adjacent pigments can dramatically increase the brightness of the pigments due to the enhanced local electric field. Here, we demonstrate that the fluorescence brightness of a single plant light-harvesting complex (LHCII) can be significantly enhanced when coupled to single gold nanorods (AuNRs). The AuNRs utilized in this study were prepared via chemical reactions, and the hybrid system was constructed using a simple and economical spin-assisted layer-by-layer technique. Enhancement of fluorescence brightness of up to 240-fold was observed, accompanied by a 109-fold decrease in the average (amplitude-weighted) fluorescence lifetime from approximately 3.5 ns down to 32 ps, corresponding to an excitation enhancement of 63-fold and emission enhancement of up to 3.8-fold. This large enhancement is due to the strong spectral overlap of the longitudinal localized surface plasmon resonance of the utilized AuNRs and the absorption or emission bands of LHCII. This study provides an inexpensive strategy to explore the fluorescence dynamics of weakly emitting photosynthetic light-harvesting complexes at the single molecule level.Comment: 23 pages, 6 figures, 2 supplementary figures, and supplementary equation

Characterisation of penA and tetM resistance genes of Neisseria gonorrhoeae isolated in southern Africa - epidemiological monitoring and resistance development

Objective. To investigate penA and tetM resistance gene variation of Neisseria gonorrhoeae in order to define gene types for epidemiological monitoring and resistance development. Design. Isolates of N. gonorrhoeae which were susceptible and resistant to penicillin and/or tetracycline were selected. Strains comprised South African isolates (22 from Bloemfontein, 13 from Transvaal, 20 from the Cape) and 15 Botswana and 4 Namibia isolates. The penA genes (2 kb) of all strains and tetM genes (765 bp) of 11 high-level tetracycline-resistant strains were amplified and restricted with Hpall. Results and conclusions. Twelve different Hpall fingerprint patterns were obtained from the 74 isolates analysed for penicillin-binding protein (PBP) 2 gene (penA) alterations. Focusing on the transpeptidase domain, 25 isolates (3 whole gene patterns, minimal inhibitory concentrations (MICs) ~ 0,03 - 0,125 ug/ml) had restriction sites equivalent to those previously described for a susceptible strain. Of the remaining 9 PBP 2 'gene groups, 25 strains fell into a designated group E. Penicillin/ penicillin + clavulanic acid MICs determined on these group E isolates gave a range of 0,125 - 2,0 ug/ml, although MICs against 4 strains were ~ 0,03 ug/ml. MICs of penicillin/penicillin + c1avulanic acid for the 24 isolates that contained altered PBP 2 transpeptidase gene regions not designated group E were only ~ 0,03 - 0,125 ug/ml. The lack of a Hpall restriction site at nucleotide 1934 in the PBP 2 gene of group E strains was indicative of a small terminal region of N. cinerea DNA. This gene block, which was found in all the southern African areas studied, appears to predispose isolates to increased penicillin resistance. The 25,2 MDa conjugative plasmid carrying the tetM resistance determinant was readily demonstrated in 11 Botswana Namibia isolates exhibiting high-level resistance to tetracycline (MICs > 16 ug/ml). The tetM gene was shown to be of the American type

Enterococcal endocarditis - a case treated with teicoplanin and amoxycillin

The study aimed to determine the antibacterial therapy effective in the cure of endocarditis caused by Enterococcus faecalis resistant to clinically achievable levels of vancomycin. Isolation of the causative enterococcus had been achieved by direct inoculation of the resected valve into the culture medium in theatre. The patient was known to have had an aortic valve defect since childhood and had recently undergone splenectomy following trauma. Blood cultures were negative prior to valve replacement. A perivalvular abscess was noted at operation. In vitro minimal bactericidal results and serum activity were the basis of the postoperative choice of drugs. The minimal bactericidal level of teicoplanin was 250 µg/ml and that of amoxycillin 64 µg/ml. Neither is achievable with the advocated dosage. A combination of these two cell-wall-active agents successfully eliminated the infection. Acting at two different sites in the synthesis of the bacterial cell wall, teicoplanin and amoxycillin were found to be bactericidal in vitro at the trough levels of the antibiotics in the serum. The patient recovered fully

Additions to the marine decapod (Crustacea: Decapoda) fauna of South Africa

This report adds five previously unreported species to the decapod crustacean fauna of South Africa, as well as removing one species previously listed in error. It also documents locality (and/or reference specimen) data for 12 other species, most of which had been depicted in regional field guides, but without reporting when and where they had been collected. Almost all the species added were already known from adjacent African countries and their ranges are here extended into South Africa. Although some of these records are based on photographs, rather than collected specimens, it is argued that such records should be accepted as adequate evidence for inclusion of at least visually-distinctive crustacean species into the regional fauna

Favourable outcomes for the first 10 years of kidney and pancreas transplantation at Wits Donald Gordon Medical Centre, Johannesburg, South Africa

Background. It is important for centres participating in transplantation in South Africa (SA) to audit their outcomes. Wits Donald Gordon Medical Centre (WDGMC), Johannesburg, SA, opened a transplant unit in 2004. The first 10 years of kidney and pancreas transplantation were reviewed to determine outcomes in respect of recipient and graft survival.Methods. A retrospective review was conducted of all kidney-alone and simultaneous kidney-pancreas (SKP) transplants performed at WDGMC from 1 January 2004 to 31 December 2013, with follow-up to 31 December 2014 to ensure at least 1 year of survival data. Information was accessed using the transplant registers and clinical records in the transplant clinic at WDGMC. The Kaplan-Meier method was used to estimate 1-, 5- and 10-year recipient and graft survival rates for primary (first graft) kidney-alone and SKP transplants.Results. The overall 10-year recipient and graft survival rates were 80.4% and 66.8%, respectively, for kidney-alone transplantation. In the kidney-alone group, children tended towards better recipient and graft survival compared with adults, but this was not statistically significant. In adults, recipient survival was significantly better for living than deceased donor type. Recipient and graft survival were significantly lower in black Africans than in the white (largest proportion in the sample) reference group. For SKP transplants, the 10-year recipient survival rate was 84.7%, while kidney and pancreas graft survival rates were 73.1% and 43.2%, respectively.Conclusion. Outcomes of the first 10 years of kidney and pancreas transplantation at WDGMC compare favourably with local and international survival data

Productivity and abundance of Sclerocarya birrea subsp. caffra in and around rural settlements and protected areas of the Bushbuckridge lowveld, South Africa

Sclerocarya birrea (A. Rich.) Hochst, subsp. caffra (Sond.) Kokwaro is a common species throughout the semi-arid savannas of southern Africa, and is sought after by rural communities. It is frequently maintained in homesteads and fields in an agroforestry situation. It has also been identified by a number of international and national institutes as a key species for domestication and commercialisation. Yet, the sustainability of the resource and local user knowledge and practices have not been considered. This study reports on the abundance and productivity of S. birrea in four rural villages and neighbouring protected areas in the Bushbuckridge lowveld of the Limpopo Province, South Africa, where its common name is marula. The density of marula stems was measured in homestead plots, arable fields and the surrounding communal rangelands of each village. Fruit production was assessed by regular counting of fruit fall from marked trees of known size. Within the villages, fruit production was monitored via local community groups. Additional monitoring of fruiting was conducted on marked trees within local protected areas. The proportion of households planting or nurturing marula trees was determined through interviews with a stratified random sample of households. The density of marula trees was significantly higher in protected areas than the neighbouring communal lands, fields or homesteads. However, the majority of trees in protected areas were small, while those in homesteads were large and mature. Density of adult fruit-bearing female trees, was similar between the protected areas and homesteads, but less in fields and communal lands. S. birrea trees were maintained in 79 % of homesteads and 58 % of fields. Mean fruit yield per tree was significantly higher from village trees (less than 17 000 fruits) than protected area trees (more than 3 500 fruits), even after accounting for differences in tree size. The fresh mass of individual fruits was also greater on village trees than on trees in protected areas. Both these characteristics suggest some degree of historical selection of the trees in the homesteads and fields. There was a positive relationship between tree size and number of fruits produced

The ‘Galilean Style in Science’ and the Inconsistency of Linguistic Theorising

Chomsky’s principle of epistemological tolerance says that in theoretical linguistics contradictions between the data and the hypotheses may be temporarily tolerated in order to protect the explanatory power of the theory. The paper raises the following problem: What kinds of contradictions may be tolerated between the data and the hypotheses in theoretical linguistics? First a model of paraconsistent logic is introduced which differentiates between week and strong contradiction. As a second step, a case study is carried out which exemplifies that the principle of epistemological tolerance may be interpreted as the tolerance of week contradiction. The third step of the argumentation focuses on another case study which exemplifies that the principle of epistemological tolerance must not be interpreted as the tolerance of strong contradiction. The reason for the latter insight is the unreliability and the uncertainty of introspective data. From this finding the author draws the conclusion that it is the integration of different data types that may lead to the improvement of current theoretical linguistics and that the integration of different data types requires a novel methodology which, for the time being, is not available

The ‘Galilean Style in Science’ and the Inconsistency of Linguistic Theorising

Chomsky’s principle of epistemological tolerance says that in theoretical linguistics contradictions between the data and the hypotheses may be temporarily tolerated in order to protect the explanatory power of the theory. The paper raises the following problem: What kinds of contradictions may be tolerated between the data and the hypotheses in theoretical linguistics? First a model of paraconsistent logic is introduced which differentiates between week and strong contradiction. As a second step, a case study is carried out which exemplifies that the principle of epistemological tolerance may be interpreted as the tolerance of week contradiction. The third step of the argumentation focuses on another case study which exemplifies that the principle of epistemological tolerance must not be interpreted as the tolerance of strong contradiction. The reason for the latter insight is the unreliability and the uncertainty of introspective data. From this finding the author draws the conclusion that it is the integration of different data types that may lead to the improvement of current theoretical linguistics and that the integration of different data types requires a novel methodology which, for the time being, is not available