Comprehensive two-dimensional supercritical fluid and gas chromatography (SFCxGC)

A novel chromatographic method was devised that makes use of the superb group separation power of normal phase supercritical fluid chromatography (SFC) combined with a fast second separation by a resistively heated gas chromatograph (GC). The SFC was operated isothermally with stopped flow to provide the time required for the GC analysis. The GC analysis had a typical cycle time of 1 minute. During this time the GC column was independently heated at a rate of 450°C/min to 250°C and actively cooled down again to -50°C before the next GC injection takes place. This was achieved with an in-house designed, resistively heated, temperature programmable gas chromatograph. Various temperature measurement circuits were also evaluated. An interface was developed that allows transfer between the SFC and the GC in such a way that the entire eluent from the first separation is analysed by the second separator. Chromatographic resolution was not lost during the transfer process from the first to the second separation stages. The interface also allows for the exchange of the carrier gas used in the second gas chromatographic separation to provide for the maximum separation speed. In the first separation, a silica gel packed column and the novel application of a silica gel porous layer open tubular capillary column was used for SFC group separation. The SFCxGCftp was applied to petrochemical samples and essential oils and the results were compared to that obtained with a commercially available GCxGC system.Thesis (PhD)--University of Pretoria, 2003.Chemistryunrestricte

The non-payment of mortgage bonds in South Africa: The voice of defaulters

The aim of this article was to provide an understanding of the reasons for the non payment of mortgage bonds in the South African context. The article starts off with a brief history on housing finance under apartheid from 1948 to 1994. It then conceptualise current housing finance to the lower end of the market (mainly for black people) in South Africa. This is followed by a literature review of possible reasons that contribute to the non payment of mortgage bonds in the South African context and a brief overview of the methodology followed during the interviews with defaulters. In the fourth part of the paper, the results from the empirical survey are discussed. The results of the survey confirm previous research that financial reasons are a fundamental factor that influences the non payment of mortgage bonds. According to the respondents, other factors that influence non payment include educational problems, political interfer ence and peer pressure, and the reaction and efficiency of the banks. The recommendations of respondents on solving the problem of non payment in clude shorter loan periods, improvement of bank management, and mortgage bond education. Reward programmes are also mentioned as a possible solution to defaulting. The study concludes that long term affordability is one of the main reasons that contribute towards the non payment of mortgage bonds. An additional conclusion is that financial institutions need to rethink their management of mortgage loans to lower income households

The innerworkings of digital storytelling

Traditionally, storytelling was used for entertainment and the transfer of know-how. The advent of digital media gave rise to new possibilities for telling stories. When the context is, for example, to relay information about how to protect a person from COVID-19, it is referred to as serious storytelling. The main objective of this research was to establish what skills and attributes would be required for someone to autonomously “tell” a serious digital story in a resource constrained environment. A systematic literature review of peer reviewed articles resulted in a knowledge bank of articles. Atlas Ti was used to qualitatively analyse these articles. Even though a resource constrained environment may be a limiting factor for telling a digital story, this research has found that emotional support, digital inclusion, as well as assisting individuals with their devices, can pave the way to autonomous digital storytelling

Transport characteristics of Pd Schottky barrier diodes on epitaxial n-GaSb as determined from temperature dependent current-voltage measurements

Please read abstract in the article.SA Research Chairs Initiative of the Department of Science and Technology, National Research Foundation and the NMMU.http://www.elsevier.com/locate/tsfhb201

Diagnosis, monitoring and treatment of tuberous sclerosis complex: A South African consensus response to international guidelines

Tuberous sclerosis complex (TSC) is a genetic disorder with multi-system manifestations and a high burden of disease. In 2013, an international panel of TSC experts revised the guidelines for the diagnosis, surveillance and treatment of the disorder. In South Africa (SA), a local multidisciplinary group of healthcare professionals and TSC researchers reviewed the international guidelines to generate an SA consensus clinical update on the identification, diagnosis, treatment and lifelong monitoring of individuals who live with TSC. We strongly endorse dissemination and use of the international guidelines for the assessment, monitoring and treatment of TSC. In addition, we strongly support access to genetic testing and to mTOR (mammalian target of rapamycin) inhibitors to treat subependymal giant cell astrocytomas not amenable to surgery and renal angiomyolipomas larger than 3 cm, and as adjunctive treatment for refractory focal seizures. We await with interest results from mTOR inhibitor trials of skin and TSC-associated neuropsychiatric disorders (TAND). With regard to training, we recommend the inclusion of TSC in undergraduate and postgraduate medical and health sciences curricula, and the promotion of other continuing professional development events to raise awareness about TSC. We also support the development of a TSC user/carer/parent organisation to provide an informal support network for families across SA. We acknowledge that some progress has been made in recent years in SA, but much remains to be done. We hope that this SA onsensus clinical update based on the international guidelines will make a positive contribution to increase knowledge and improve clinical care for all patients who live with TSC in SA, and their families

Deep level transient spectroscopy (DLTS) study of defects introduced in antimony doped Ge by 2 MeV proton irradiation

Please read the abstract in the article.The South African National Research Foundation and Monash University, South Africa.http://www.elsevier.com/locate/physbnf201

dc-Hydrogen plasma induced defects in bulk n-Ge

Bulk antimony doped germanium (n-Ge) has been exposed to a dc-hydrogen plasma. Capacitance-voltage depth profiles revealed extensive near surface passivation of the shallow donors as evidenced by ˜ a 1.5 orders of magnitude reduction in the free carrier concentration up to depth of ˜ 3.2 µm. DLTS and Laplace-DLTS revealed a prominent electron trap 0.30 eV below the conduction (Ec-0.30 eV). The concentration of this trap increased with plasma exposure time. The depth profile for this defect suggested a uniform distribution up to 1.2 µm. Annealing studies show that this trap, attributed to a hydrogen-related complex, is stable up to 200 °C. Hole traps, or vacancy-antimony centers, common in this material after high energy particle irradiation, were not observed after plasma exposure, an indication that this process does not create Frenkel (V-I) pairs.The South African Research Chair’s Initiative of the Department of Science and Technology, National Research Foundation, as well as by the Nelson Mandela Metropolitan University (NMMU).http://www.elsevier.com/locate/phys

Field dependence of the E1' and M3' electron traps in inductively coupled Ar plasma treated n-Gallium Arsenide

Inductively coupled Ar plasma etching of n-type (Si doped) Gallium Arsenide (GaAs) introduces several electron traps, Ec – 0.04 eV (labelled E10), Ec – 0.19 eV, Ec – 0.31 eV, Ec – 0.53 eV, and Ec – 0.61 eV (behaving like the well documented M3 and labelled M30 in this study), of which the metastable defects Ec – 0.04eV (E10 ), and Ec – 0.07 eV are novel. Furthermore, E10 and M30 exhibit strong field enhanced carrier emission. Double-correlation deep level transient spectroscopy was used to investigate the field dependent emission behaviour of these two defects. It is shown that for both traps, the observed enhanced emission is due to phonon assisted tunnelling. The latter observation is contrary to the literature reports suggesting that enhanced carrier emission for M3 occurs via the Poole-Frenkel mechanism.http://jap.aip.org/nf201

Ar plasma induced deep levels in epitaxial n-GaAs

Ar plasma etching of n-type (Si doped) GaAs introduces several electron traps (Ec - 0.04 eV, Ec - 0.07 eV, Ec - 0.19 eV, Ec - 0.31 eV, Ec - 0.53 eV, and Ec - 0.61 eV). The trap, Ec - 0.04 eV, labelled E10 and having a trap signature similar to irradiation induced defect E1, appears to be metastable. Ec - 0.31 eV and Ec - 0.61 eV are metastable too and they are similar to the M3/M4 defect configuration present in hydrogen plasma exposed n-GaAs.South African National Research Foundationhttp://jap.aip.org/nf201