Voorlopige verslag oor die reaksie van dorre karooveld op beweiding gedurende spesifieke jaargetye: Boesmangrasveld

Uittreksel

Die plantegroeiveranderinge in 32 persele van boesmangrasveld wat vir vier jaar volgens bepaalde jaargetye bewei is, is volgens die wydgepasiëerdepuntmetode bepaal. Daar is bevind dat die effek van beweiding gedurende die somermaande November, Desember en Januarie was om die starabedekking van beide Stipagrostis ciliata en S. obtusa te onderdruk. Die effek van beweiding gedurende die winter, Mei, Junie en Julie daarenteen was om die bedekking van S. ciliata te vermeerder.     

The first isolations of Campylobacter mucosalis from pigs in South Africa

The first isolations of Campylobacter mucosalis in South Africa are described. Isolations were made from a 6-week-old weaner pig with necrotic enteritis and from 2 gingival swabs of suckling piglets from herds with histories of porcine intestinal adenomatosis. The isolates were serologically identified as being serotype A strains.     

The demonstration of the K-antigen of Campylobacter fetus venerealis using a microtitre agglutination test

Using specific antisera prepared against heat-treated and untreated cells in a microtitre system, 7 strains of Campylobacter fetus venerealis were examined for the presence of K-antigen. The technique was effective for distinguishing between strains and it was found that 4 out of 7 isolates contained microcapsules, therefore being potentially suitable for vaccine production.     

An accurate, sensitive and reproducible method for the colorimetric estimation of free fatty acids in plasma

A sensitive and reproducible method permitting the estimation of 0,030-3,000 mM free fatty acids (FFA) in plasma with a standard error of 0,006 5 was developed. The method is based on the extraction of phosphate-buffered plasma with a chloroform-heptane-methanol mixture, formation of the cobalt complex and on the subsequent determination of the metal with 1-nitroso-2-naphthol. The method was used to obtain normal values (mean 0,547 mM range 0,147-1,197 mM) for Merino wethers fed lucerne hay.     

Socioecological Determinants of Drought Impacts and Coping Strategies for Ranching Operations in the Great Plains

In Great Plains rangelands, drought is a recurring disturbance. Ranchers in this region expect to encounter drought but may not be adequately prepared for it. Efforts to encourage drought preparedness would benefit from a better understanding of the conditions under which managers make decisions to minimize the impacts of drought. We tested the direct and moderating roles of the drought hazard and the social-ecological context on drought impacts and response. This study was conducted with ranchers in western and central South Dakota and Nebraska following the drought that began in 2012. We surveyed ranchers regarding the effects of the drought and their responses and used multimodel analysis to explore the relationships among measures of drought preparedness, drought response, and drought impacts. Drought severity was the primary predictor of all impacts, but specific types of impacts were varied depending on the operation’s enterprise mix, resources, and management. The socioecological characteristics of the ranch system predicted drought response actions taken, by either providing the necessary resources and capacity to take action or creating sensitivity in the system that required action to be taken. We conclude with recommendations for learning from current drought experiences in order to better adapt to future drought events.     

Electronic confinement and coherence in patterned epitaxial graphene

Ultrathin epitaxial graphite was grown on single-crystal silicon carbide by vacuum graphitization. The material can be patterned using standard nanolithography methods. The transport properties, which are closely related to those of carbon nanotubes, are dominated by the single epitaxial graphene layer at the silicon carbide interface and reveal the Dirac nature of the charge carriers. Patterned structures show quantum confinement of electrons and phase coherence lengths beyond 1 micrometer at 4 kelvin, with mobilities exceeding 2.5 square meters per volt-second. All-graphene electronically coherent devices and device architectures are envisaged.