Cytotaxonomic studies in Themeda triandra. I. Chromosome numbers and microsporogenesis

Metaphase I pairing associations and chiasmata, as well as anaphase I laggard and chromatid bridge data were collected from 53 collections of Themeda triandra Forsk. The distribution pattern of the diploids, tetraploids, pentaploids and hexaploids confirms that which was found by previous authors. Diploids occurred mainly in the eastern and southern coastal areas, hexaploids on the highveld and tetraploids in between, but with some overlap. The meiosis analysis suggests that the majority of the polyploids are segmental allopolyploids and that different homeologous genomes occur in this polyploid complex. It is likely that a certain amount of karyotype differentiation must have occurred between different diploid populations of this species

Indications of Short Periodicity in the FeXIV 503.3nm Emission Line at the 2008 Solar Eclipse

Observations at the 1 August 2008 total solar eclipse in western China were obtained through a narrow band interference filter centered on the 530.3 nm FeXIV emission line at a cadence of 30 frames/second. A simplified analysis indicates that in a position near the base of a coronal streamer a short period intensity periodicity is found. The analysis and results are presented

Indications of Short Periodicity in the FeXIV 503.3nm Emission Line at the 2008 Solar

Observations at the 1 August 2008 total solar eclipse in western China were obtained through a narrow band interference filter centered on the 530.3 nm FeXIV emission line at a cadence of 30 frames/second. A simplified analysis indicates that in a position near the base of a coronal streamer a short period intensity periodicity is found. The analysis and results are presented

A cytogenetic study of a hexaploid Themeda triandra Forssk. population

Twenty-four Themeda triandra plants, collected from a population on a 20-m2 plot in eastern Pretoria (Transvaal), were studied cytogenetically. All the plants were hexaploid (2n=6x=60). From the meiotic chromosome associations it is concluded that the collected plants can be divided into two apomictic clones, of which the smaller one probably arose by sexual segregation from the larger one. The data support the fact that the hexaploids are near obligate apomicts

Cytotaxonomic studies in Themeda triandra Forsk. Part II. Aneuploidy in a diploid population

Meiosis was studied in 24 plants from a diploid Themeda triandra Forsk. population. This population was found to include a high proportion of aneuploids (33,3%). Amongst these were trisomics (12,5%), tetrasomics (16,67%) and one possible hexasomic. The effect of the aneuploidy on meiosis is described and the possible causes of such a high proportion of aneuploids in a diploid population is discussed

Electromagnetic radio frequency heating in the pulsed electric current sintering (PECS) process

Pulsed electric current sintering offers rapid sintering of many materials compared with hot press sintering. Earlier studies had demonstrated that neither sparks nor plasma formation occur in a typical apparatus such as Dr. Sinter™. Hitchcock et al. showed that electromagnetic radio frequency (rf) emission occurred during the pulsing current and suggested this emission was a relevant augmentation to the hot press sintering in addition to the current flow in the specimen. In this report the importance of rf emission in the sintering process is demonstrated and opportunities to further exploit this approach to improve the sintering process are suggested

Atherosclerotic lesions in the thoracic aorta: A South African anatomical and histological mortuary study

Background. Worldwide, the prevalence of cardiovascular diseases such as atherosclerosis is on the increase. Younger people may be especially vulnerable owing to their exposure to risk factors such as drug abuse and HIV. Methods. The thoracic aortas of 149 South Africans under the age of 50 years were collected at the Salt River Mortuary, Cape Town, and examined macroscopically and microscopically for evidence of anomalies. The sample comprised predominantly males, and included black, coloured and white individuals. Results. A significantly higher level of macroscopic pathology was found in coloured males, although overall prevalence of pathology in this sample was lower than expected. A positive association was also found between body mass index and vascular pathology in the black and coloured population groups. Microscopic anomalies were common and present at high levels, irrespective of age and racial grouping. Conclusions. The widespread prevalence of microscopic anomalies in all groups suggests that these are normal variations that result from haemodynamic forces. The higher prevalence of atherosclerotic lesions in coloured males, however, probably results from specific genetic conditions such as hypercholesterolaemia or lifestyle factors such as diet or tik abuse. The findings suggest that coloured individuals may be at increased risk of developing cardiovascular disease