Stress-Corrosion Cracking of Brass

the mechanism of stress-corrosion cracking of brass has been sought for many years. Investigators have proposed many mechanisms, but each of these mechanisms has always had several drawbacks. This paper presents an account of experimental work done in the laboratory on this subject and compares it to the work of previous investigations. It evaluates the mechanisms presented by investigators and shows the failures of these mechanisms. A theory of Nitrogen Embrittlement is presented and an evaluation of this theory with experimental work follows

Assessment of an audit-feedback instrument for oral health care facilities in South Africa

Published ArticleThe assessment of an audit-feedback instrument (AFI) for infection prevention and control was conducted on a population of South African oral health care facilities, mainly to test its workability in the varied facility configurations. A purposive selection strategy was followed, selecting 50 South African oral health care facilities. Results from 49 completed AFIs revealed demographic details and information on infection prevention and control practices for the 11 AFI focus areas: Administrative controls; personnel protection controls; environmental- and work controls; surface contamination management; equipment maintenance; air- and waterline management; personal protective equipment usage; personal- and hand hygiene practices; sterilisation practices; sharps handling and waste management. None of the participating facilities demonstrated 100% compliance. Notably, administrative controls and air- and waterline management scored the lowest mean values; 31% and 36% respectively, while personal- and hand hygiene practices and waste management performed the best, at respectively 75% and 63%. The general lack of compliance with infection prevention and control precautions in the participating oral health care facilities clearly poses a safety hazard to patients and oral health care workers. These findings demonstrate the urgent need for a monitoring system, such as the AFI, to be instituted in South African oral health care facilities

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

Liability for Student Suicide in the Wake of Eisel

In the wake of Eisel, few commentaries have been written about the legal significance of student suicide. Although providing broad practical advice and limited case law analysis, the professional literature lacks a comprehensive and systematic analysis of Eisel\u27s common-law and constitutional tort effects. To fill this gap and address this question in terms of common law and constitutional liability, this Article is organized as follows. Part II provides a brief overview of the common law regarding liability for another\u27s suicide and shows that courts have generally disfavored this cause of action. Section III examines the Eisel decision in detail. Part III(A) traces the post-Eisel decisions that took the same common-law path to possible liability. Part III(B) analyzes why public educators do not need to be overly concerned with common-law liability for student suicides. Part IV examines the post-Eisel decisions that proceeded down the alternate path of an alleged constitutional tort. Part V examines the Armijo v. Wagon Mound Public School decision and demonstrates that the court established the possibility of § 1983 liability on the part of school officials in the wake of student suicide. Part V.A examines the pre- and post-Armijo cases addressing student suicide. Part V.B analyzes the unlikely probability of success under a § 1983 claim against school officials. Part VI provides a brief conclusion that educators have little to fear with regard to liability for a student\u27s suicide

Short communication Dairy farm borehole water quality in the greater Mangaung region of the Free State Province, South Africa

Published ArticleMost dairy farm effluent is discharged onto pastures and land by irrigation and poses a risk of enriching groundwater including borehole drinking water. Nitrate, coliforms and Escherichia coli (E. coli), in particular, may cause disease in humans and animals drinking contaminated water. The aim of this study was to obtain an understanding of the status of borehole drinking water quality, including physical, chemical and microbiological properties, on 75 dairy farms in the greater Mangaung region of the Free State, South Africa. Borehole drinking water samples were collected during autumn and spring of 2009 and the physical, chemical and microbiological parameters analysed and compared to the required standards prescribed by the South Africa National Standards (SANS) 241 of 2006. Most farms were compliant; however for combined nitrate and nitrite N, 37 of the farms exceeded the prescribed limit. Similarly, for total coliforms, 45 and for E. coli, 22 of the farms exceeded the acceptable limits. Nine of the farm boreholes were contaminated by N and E. coli. On one farm all of the bacteriological parameters and four of the chemical parameters exceeded the prescribed limits, and on two other farms four and five of the chemical parameters were exceeded. Further studies on water and waste management on dairy farms in the Manguang region of the Free State are suggested

Rigid and concave, 2,4-cis-substituted azetidine derivatives: A platform for asymmetric catalysis.

A series of single enantiomer, 2,4-cis-disubstituted amino azetidines were synthesised and used as ligands for copper-catalysed Henry reactions of aldehydes with nitromethane. Optimisation of ligand substituents and the reaction conditions was conducted. The enantiomeric excess of the formed products was highest when alkyl aldehydes were employed in the reaction (>99% e.e.). The absolute stereochemistry of one representative azetidine derivative salt was determined by analysis of the Flack parameter of an XRD single crystal structure. The origin of selectivity in catalysis was investigated computationally, revealing the importance of the amino-substituent in determining the stereochemical outcome. A racemic platinum complex of a cis-disubstituted azetidine is examined by XRD single crystal structure analysis with reference to its steric parameters, and analogies to the computationally determined copper complex catalyst are drawn. A preliminary example of the use of a cis-disubstituted azetidine scaffold in thiourea H-bonding catalyst is noted in the supporting information

Evaluation of induced polyploidy in Acacia mearnsii through stomatal counts and guard cell measurements

The black wattle, Acacia mearnsii, an important commercially grown tree in South Africa, is considered one of the top alien invader species within indigenous vegetation because of its abundant seed production and dispersal. One of the aims at the Institute for Commercial Forestry Research (ICFR) is to restrict the spread of wattle outside plantation boundaries. Current consideration has been given to polyploids, which could be semi-sterile or even sterile due to irregular meiosis that results in infertile gametes. Autotetraploids were produced by the scarification of seeds and treatment with different colchicine concentrations (0%, 0.01%, 0.03%, 0.05%, 0.07% and 0.1%) for various times (6h, 12h, 24h and 48h), rinsed and germinated in the dark at 25°C to induce chromosome doubling. Tetraploidy was successfully induced by applying 0.01% colchicine to chipped seeds for a period of 6h. This result was validated through percentage germination (90%), average seedling growth rate (16mm), seedling height (20mm) and percentage seedling survival (61%). Chromosome doubling was confirmed by stomatal guard cell length (39.9 ± 0.4 (SE) mm) and stomatal frequency measurements (12.0 ± 0.5 (SE))

Enhanced Production of Geothermal Heat through the Reaming of Underground Wells in the Production Zone [abstract]

Only abstract of poster available.Track I: Power GenerationIn order to extract heat from the high temperature rocks that lie relatively close to the surface in different parts of the world, wells must first be drilled down into those rocks. Once the wells are established then either natural fissures or artificially induced fractures are generated to create an underground network of channels in the hot rock. Either existing steam in the rock, or injected water is then pumped through this network as a way of extracting the heat, turning it into steam, and bringing it to the surface. At the surface the steam, depending on temperature, can be used to drive generators, and/or to provide district heating. The rocks through which the wells must be drilled are generally igneous, and thus of a high strength, tough and very hot, and conventional methods of drilling are difficult and slow. The use of high-pressure fluid jets to drill the wells has been shown to be faster than conventional drilling, and since the jets cut away from the bit, there are not the wear problems that are associated with conventional drilling tools. Further the jets have the potential to be re-oriented in the production zone to ream out the well from a radius of 4.5 inches to some 36 inches. This increases the productivity of individual wells, and reduces the number that may need to be drilled. Abrasive can also be introduced into the water-jet stream as it is pumped down the borehole, and it is also possible to create a cutting jet that can notch the walls of the borehole so that, under controlled pressurization, cracks can be grown out in preferred directions, and the process of heat extraction simplified