267 research outputs found
Mechanistic and Kinetic Aspects of the Direct Electrochemical Oxidation of 4-t-Butyltoluene
The direct electrochemical oxidation of 4-t-butyltoluene at graphite electrodes in methanol, using NaClO4 as electrolyte, as been investigated in order to obtain an insight into the mechanism and kinetics of the anodic reactions taking place. It is shown that an increase in current density affects the product distribution, leading to a better yield of the target product 4-t-butylbenzaldehyde dimethyl acetal and a lower percentage of unknowns at the expense of an increase in electrical charge. It is suggested that oxidation takes place by two mechanisms : a direct one involving oxidation of the substrate at the electrode, and an indirect one where a pool of solvent radicals assists in the oxidation process. Further evidence is provided for reaction mechanisms in studies where the substrate loading is varied, and also where the ratio of substrate to solvent is varied ; when the concentration of the substrate is high, there is evidence of the formation of dimers and other unknowns. Under certain conditions, these anodic reactions can be regarded as parallel consecutive second order reactions. The role played by the solvent is confirmed by kinetic data.
South African Journal of Chemistry Vol.55 2002: 125-13
Leadless cardiac pacing in resource limited settings: A Groote Schuur hospital experience with the Micra leadless pacemaker
Background: Cardiac pacemakers improve survival and quality of life in patients with atrioventricular (AV) block. However, conventional pacemakers carry a small risk of both acute and chronic lead and pacemaker generator complications. Leadless pacemakers negate these risks by not having a pacing lead and a subcutaneous generator. We report our Groote Schuur Hospital experience with the Medtronic Micra transcatheter pacing system (TPS).Methods: We report a consecutive case series of patients that received the Micra leadless pacemaker. The Micra transcatheter pacemaker, a single chamber ventricular pacemaker, is inserted using a TPS via the femoral vein into the right ventricle. Implantation data were obtained, and medical records were reviewed for the 6 weeks and 1-year follow-up visits.Results: A total of 5 patients were implanted with a Micra leadless pacemaker from 11 March 2015 - 2 November 2016. Four patients were male and 1 female, with an average age of 64 years. Four patients received the pacemaker for a second- or third-degree AV block and 1 patient received the pacemaker for unexplained syncope and right bundle branch block. The Micra leadless pacemaker was successfully implanted in all patients with no acute implantationrelated complications. One-year follow-up was available for 4 patients with good pacing thresholds, sensitivity and impedance. One patient demised after 9 months post Micra implantation due to unrelated causes (acute myeloid leukaemia).Conclusion: The Micra leadless pacing system is safe and effective and shows good short-term results in a real-world, resource-limited setting. This form of pacing offers a viable option for patients who require pacing for AV block, especially in patients with vascular access problems or who are at high risk of lead or pacemaker generator complications
The contribution of energy efficiency towards the success of industrial organisations in South Africa
The original publication is available at http://sajie.journals.ac.zaENGLISH ABSTRACT: Internationally, governments and lobby groups increasingly put pressure on organisations to reduce their impact on the environment. To this end, various studies show the drivers, barriers, and contributions of energy efficiency towards a more sustainable environment, particularly through reduced greenhouse gas emissions and other by-products. In the study summarised in this paper, the factors that drive organisational success were compared with the effects that energy efficiency projects have on organisations. Methods, policies, and strategies on the application of energy efficiency were also studied. The findings are that, in general, most organisations have energy efficiency policies and strategies in place, and they include internal and external stakeholders in their energy efficiency efforts. These efforts also show a positive correlation with the factors that contribute to the perceived success of organisations in the South African industrial sector. These strategies must be maintained in the longer term, as energy efficiency will play a more important role in the future.AFRIKAANSE OPSOMMING: Organisasies, wêreldwyd, word toenemend onder druk geplaas deur regerings- en aksiegroepe om hul impak op die omgewing te verminder. Na aanleiding hiervan toon verskeie
studies die drywers, struikelblokke en bydraes van energie-doeltreffendheid na ʼn meer
volhoubare omgewing, veral ten opsigte van groenhuisgas-emissies en ander neweprodukte.
In hierdie studie is die faktore wat die sukses van organisasies dryf vergelyk met die effek
van die toepassing van energiedoeltreffendheidsprojekte op organisasies. Metodes, beleid
en strategieë in terme van die toepassing van energiedoeltreffendheid is ook bestudeer. Die
bevindinge is dat die meeste organisasies, oor die algemeen, beleid en strategieë in plek
het in terme van energiedoeltreffendheid; dié organisasies sluit interne en eksterne belanghebbendes
in waar hulle strewe na energiedoeltreffendheid. Hierdie aktiwiteite toon ʼn
positiewe korrelasie met die faktore wat waarde bydra ten opsigte van die oënskynlike
sukses van organisasies in die Suid-Afrikaanse industriële sektor. Dus moet hierdie
strategieë in plek gehou word in die langtermyn, aangesien energiedoeltreffendheid ʼn
belangriker rol sal speel in die toekoms
The use of ultraviolet radiation as a non-thermal treatment for the inactivation of alicyclobacillus acidoterrestris spores in water, wash water from a fruit processing plant and grape juice concentrate
Alicyclobacillus acidoterrestris is a non-pathogenic, spore-forming bacterium
that can survive the commercial pasteurisation processes commonly used
during fruit juice production. Surviving bacterial endospores germinate, grow
and cause spoilage of high acid food products. Fruit juices can be treated
using ultraviolet light (UV-C) with a wavelength of 254 nm, which has a
germicidal effect against micro-organisms. In this study, A. acidoterrestris was
inoculated into water, used wash water from a fruit processing plant and grape
juice concentrate. Ultraviolet dosage levels (J L−1) of 0, 61, 122, 183, 244, 305
and 367 J L−1 were applied using a novel UV-C turbulent flow system. The UV
treatment method was shown to reliably achieve in excess of a 4 log10
reduction (99.99%) per 0.5 kJ L-1 of UV-C dosage in all the liquids inoculated
with A. acidoterrestris. The applied novel UV technology could serve as an
alternative to thermal treatments of fruit juices for the inactivation of
Alicyclobacillus spores as well as in the treatment of contaminated wash water used in fruit processing.Department of HE and Training approved lis
Application of Gamma Irradiation Treatment on the Physicochemical and Microbiological Quality of an Artisanal Hard Cheese
The objective of this study was to evaluate the efficacy of gamma irradiation, applied to different cheese sample sizes (250g and 500 g), against Listeria monocytogenes, Escherichia coli, coliforms and aerobic colony counts. The effects on cheese physicochemical and odour properties and all costs involved for the treatment were quantified. The Cobalt-60 γ-irradiator was used at a maximum dose of 5.0 kGy. The values for cheese moisture (28.6%), ash (3.78%), pH (5.1), protein (29.6%), fat (30.7%), salt (1.95%) and water activity (0.92%) were within the acceptable ranges for hard cheese after gamma irradiation treatment. The colour (yellowness, redness, chroma and hue angle) and texture (cohesive-ness and springiness) values decreased (p < 0.05) with the treatment. Compounds such as safrole, acetylpyrazine, thiophene, 3,5-octadien-2-one and 1-Octen-3-one were present after the treatment, regardless of sample size. The gamma irradiation treatment resulted in 100%, 87.2%, 85.1% and 77.3% reduction in L. monocytogenes, coliforms, E. coli and aerobic colony counts, respectively. The study highlighted the efficacy of irradiation treatment and its affordability for resource-limited producers
Mathematical models and the fight against diseases in Africa
n this age of molecular biology, The healthcare industry, politicians and the community at large are trying to find ‘magic bullet’ drugs and vaccines to conquer disease. Although smallpox has been eradicated and polio may soon be a scourge of the past, many pathogens replicate rapidly and mutate prodigiously, enabling them to evolve ways to circumvent our immune systems, as well as our drugs and vaccines. To fight and win the war against new emerging infections such as HIV/AIDS, TB and now SARS (severe acute respiratory syndrome), it is important to understand the temporal and spatial dynamics of the pathogens in human and, in some cases, animal reservoirs or vector populations. It is also necessary to understand the complex web of socio-economic factors pertinent to controlling the spread of disease, so that feasible, affordable and, most importantly, effective public-health policies can be devised and implemented
The challenges of achieving high training coverage for IMCI: case studies from Kenya and Tanzania
Health worker training is a key component of the integrated management of childhood illness (IMCI). However, training coverage remains low in many countries. We conducted in-depth case studies in two East African countries to examine the factors underlying low training coverage 10 years after IMCI had been adopted as policy. A document review and in-depth semi-structured interviews with stakeholders at facility, district, regional/provincial and national levels in two districts in Kenya (Homa Bay and Malindi) and Tanzania (Bunda and Tarime) were carried out in 2007–08
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