Die plek van navorsing oor kosmiese strale in die fisika*

Reeds sedert die vroeë veertiger jare word navorsing in die departement Fisika op die gebied van kosmiese strale ge­ doen. In hierdie voordrag sal gepoog word om aan te toon wat kosmiese strale is en wat die plek daarvan in ’n fisikadepartement is. Vanselfsprekend sal dit onmoontlik wees om in die bestek van een lesing die terrein volledig te verken. Die orde van behandeling is soos volg: .Die ontdekking van kosmiese strale. Die samestelling en energieverdeling van die primêre strale. Die wisselwerking tussen kosmiese strale en die atmos- feer. Groot buie van kosmiese strale.Die variasie van die intensiteit van kosmiese strale met plek en tyd van waarneming. Herkoms van kosmiese strale

Ophiostoma gemellus and Sporothrix variecibatus from mites infesting Protea infructescences in South Africa

Ophiostoma (Ophiostomatales) represents a large genus of fungi mainly known from associations with bark beetles (Curculionidae: Scolytinae) infesting conifers in the northern hemisphere. Few southern hemisphere native species are known, and the five species that consistently occur in the infructescences of Protea spp. in South Africa are ecologically unusual. Little is known about the vectors of Ophiostoma spp. from Protea infructescences, however recent studies have considered the possible role of insects and mites in the distribution of these exceptional fungi. In this study we describe a new species of Ophiostoma and a new Sporothrix spp. with affinities to Ophiostoma, both initially isolated from mites associated with Protea spp. They are described as Ophiostoma gemellus sp. nov. and Sporothrix variecibatus sp. nov. based on their morphology and comparisons of DNA sequence data of the 28S ribosomal, ß-tubulin and internal transcribed spacer (ITS1, 5.8S, ITS2) regions. DNA sequences of S. variecibatus were identical to those of a Sporothrix isolate obtained from Eucalyptus leaf litter in the same area in which S. variecibatus occurs in Protea infructescences. Results of this study add evidence to the view that mites are the vectors of Ophiostoma spp. that colonize Protea infructescences. They also show that DNA sequence comparisons are likely to reveal additional cryptic species of Ophiostoma in this unusual niche

Change-making in a (post)apartheid city: An auto-ethnographical essay

We reflect on living and doing ministry in a (post)apartheid South African city, negotiating ongoing demographic and sociopolitical transitions and discerning appropriate faith responses. We speak about the inevitability of these transitions, but then suggest that a view of theology and ministry as change-making is not inevitable but a vocation and art to be acknowledged, embraced and fostered. We argue for an epistemology from below or within, drawing from Parker Palmer’s notion of knowing as loving – in community – and reflecting on his idea that ‘to know’ is ‘to be known’. In stressing the importance of reading the city, we show how reading the city means to be read by the city too. It is in the journeys of ongoing self-awareness, and personal confrontation, change and conversion – in relation to issues of gender, race, location and class – that transformational urban imaginaries can be birthed. Finally, we reflect on urban change-making as a process of personal, communal, institutional and systemic transformation, happening on many different levels at the same time, through creating conditions and spaces for change to occur. It is an ongoing call for deepening our journeys in response to the overwhelming groans, of humanity and creation alike, for Gods’ urban shalom

Nitric oxide turnover in permeable river sediment

We measured nitric oxide (NO) microprofiles in relation to oxygen (O-2) and all major dissolved N-species (ammonium, nitrate, nitrite, and nitrous oxide [N2O]) in a permeable, freshwater sediment (River Weser, Germany). NO reaches peak concentrations of 0.13 mu mol L-1 in the oxic zone and is consumed in the oxic-anoxic transition zone. Apparently, NO is produced by ammonia oxidizers under oxic conditions and consumed by denitrification under microoxic conditions. Experimental percolation of sediment cores with aerated surface water resulted in an initial rate of NO production that was 12 times higher than the net NO production rate in steady state. This initial NO production rate is in the same range as the net ammonia oxidation rate, indicating that NO is transiently the main product of ammonia oxidizers. Stable isotope labeling experiments with the N-15-labeled chemical NO donor S-nitroso-N-acetylpenicillamine (SNAP) (1) confirmed denitrification as the main NO consumption pathway, with N2O as its major product, (2) showed that denitrification combines one free NO molecule with one NO molecule formed from nitrite to produce N2O, and (3) suggested that NO inhibits N2O reduction

Metabolic changes in the lungs after ischaemia

CITATION: Engelbrecht, F. M., Edwards, I. J. & De Beer, D. P. 1980. Metabolic changes in the lungs after ischaemia. South African Medical Journal, 58:409-413.The original publication is available at http://www.samj.org.zaThe effects of variable periods of ischaemia on the isolated lungs of rats and rabbits, stored for up to 6 hours at 4°C, 21°C and 37°C under standardized conditions, were investigated in vitro in terms of oxygen consumption, the rate of 1-14C-leucine incorporation into soluble proteins, and 1-14C-palmitate incorporation into total phospholipids and lipid fractions. The endogenous oxygen uptake of rat lung slices in an air phase, from tissues stored at 4°C and 21°C under ischaemic conditions for 6 hours and at 37°C for 4 hours, was significantly different from the control values. The oxygen uptake of lungs from animals anaesthetized with pentobarbitone prior to exsanguination and stored for only 2 hours at 37°C differed significantly from control values. Judged by the rate of incorporation of radiolabelled leucine into soluble proteins and that of palmitate into total lipids and phospholipids of lungs after storage for increasing periods at 4°C and 37°C, significant differences were already found after 1 1/2 hours. From this observation it would appear that these parameters are very sensitive indicators for assessing irreversible lung damage due to ischaemia.Publisher’s versio

Photosynthesis-controlled calcification in a hypersaline microbial mat

We investigated the hypothesis that sulfate reduction rather than oxygenic photosynthesis promotes calcification in a hypersaline microbial mat by increasing the ion concentration product: ICP 5 [Ca2+] X [CO32-]. Pore‐water 3 calcium concentration profiles directly measured with microsensors show that calcium concentration in the photic zone decreased in illuminated mats and increased slightly in dark mats. High pH values in the photic zone of illuminated mats resulted in higher carbonate concentrations (2.25 mmol L-1) than in dark mats (0.75 mmol L-1), although the dissolved inorganic carbon (DIC) pore‐water concentration in the former was much lower (5.9 mmol L-1) than in the latter (9.9 mmol L-1). The pH‐induced rise in carbonate concentration in the light was the main factor influencing the ICP, while changes in Ca-1 concentration played a subsidiary role. Sulfate reduction did not result in a net pH increase in these mats, as rates in the photic zone were comparable between illuminated and dark mats (4 and 5 nmol cm-2 h-1, respectively), and pH increased in illuminated mats but not in dark mats. Calcium carbonate precipitation in the photic zone of these hypersaline mats is primarily controlled by photosynthesisinduced pH and carbonate concentration increases. However, heterotrophic bacteria, including sulfate reducers, play an important complementary role in calcification because they maintain high concentrations of DIC in the mat pore water

‘Between life and death’ : on land, silence and liberation in the capital city

This article reflects on the unfinished task of liberation – as expressed in issues of land – and drawing from the work of Franz Fanon and the Durban-based social movement Abahlali baseMjondolo. It locates its reflections in four specific sites of struggle in the City of Tshwane, and against the backdrop of the mission statement of the Faculty of Theology at the University of Pretoria, as well as the Capital Cities Research Project based in the same university. Reflecting on the ‘living death’ of millions of landless people on the one hand, and the privatisation of liberation on the other, it argues that a liberating praxis of engagement remains a necessity in order to break the violent silences that perpetuate exclusion.This article was initially a presentation to the Symposium Social Cohesion 2013, directed by Prof. Dr Johann-Albrecht Meylahn, Department of Practical Theology, Faculty of Theology, University of Pretoria, Pretoria, South Africa.http://www.hts.org.zaam201