An investigation into coal damage during blasting.

A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilrMnt of the requirements for the degreel of Doctor of Philosophy.This thesis has investigated ways of exerting control over coal breaking during blasting. Its ultimate objective has been to optimise the use of explosive energy in blasting so as to ensure reduced production of coal fines in the comminution process. The investigations reported were conducted on laboratory models at a scale of a controllable energy to enable the development of a theoretical background for the thesis, However, the bulk of the work was undertaken insitu in surface and underground coal operations. The research was conducted in three phases. The first phase dealt with the approach to modelling the primary crushing mechanism which generates the coal fines during the blasting operation. A laboratory apparatus to simulate blast-generated dynamic loading was devised. Dynamic coal crushing test conducted on a set of over 150 samples of coal showed an exponential relationship; between the comminution energy and the subsequent coal damage. A comminution index (Com ) characterising the ability of coal to generate fines was derived. The second phase of the research concerned the field investigations. This had the following double aim: validating the hypothesis of the influence of the dynamic loading of the shock waves and that of the inherent discontinuities imbedded in coal on fines generation; and quantifying the problem of fines in the blasting techniques currently used in the local mining industry. Three sites were used, namely Kleinkopje of AMCOAL, Greenside of Goldfields and ATC, Tavistock of JCI. The investigations undertaken at Kleinkopje (surface mining operation) involved the determination of discontinuities by logging inherent fractures appearing on 75 diamond drilled cores of coal and the monitoring of 76 blasts conducted on the sites sampled for discontinuities. These investigations indicated a good correlation between the fines observed in blasted piles and the fracture frequency of the pre" existing fractures per metre of coal. The work undertaken in underground collieries (Greenside and Tavistock) demonstrated the enormity of the fines' problem in the local mining operations. Approximately a third of the coal broken underground was observed, in 30 blasts sampled and analysed, to fall into the category of fragments of under 6 mm termed 'coal fines', Which generate low income. The third phase of the research dealt with the optimisation of coal breaking during blasting. A series of 100 trial blasts was undertaken with the aim of searching for a blasting technique that enables the generation of fewer coal fines. A number of options were investigated. Trial blasts carried out were evaluated and their results are discussed in this thesis. The results of the fieldwork undertaken confirmed that fines generation is site speolflc, However, the decoupling technique used with high VOD explosive products may be successfully employed to reduced coal fines generation in strong coals (few inherent fractures).Andrew Chakane 201

Coronary Artery Bypass Grafting (CABG) versus Percutaneous Coronary Intervention (PCI) in treatment of left main coronary artery disease

BackgroundCoronary artery bypass graft surgery (CABG) has been widely used for left main coronary artery disease (LMCAD). Percutaneous coronary intervention (PCI) has become an option for this condition.AimsTo summarize the current evidence that compare between CABG vs. PCI in regards to ‎cardiac death, stroke, and myocardial infarction.‎Methods We searched randomized trials of treatment of LMCAD with PubMed, Google Scholar, and EBSCO.Results Five randomized studies were retrieved, which compared the efficacy between CABG vs. PCI in treatment of LMCAD.ConclusionPCI may be reasonable management of patients with LM stenosis involving distal bifurcation or with coexisting multivessel disease

Women\u27s response to reproductive trauma secondary to contraceptive iatrogenesis: A phenomenological approach to the Dalkon Shield case

This study describes the meaning of the experience of being injured by a birth control method called the Dalkon Shield intrauterine device (IUD). Women whose reproductive organs were irrevocably damaged by the Dalkon Shield are the subjects of this study. In the interest of the feminist perspective which includes the women\u27s health movement, this study focuses on the women\u27s reality of their experience with a defective contraceptive, namely the Dalkon Shield. In addition to the collection of demographic information about the informants and information related to the events preceding the selection of the Dalkon Shield as a contraceptive method, the women\u27s anticipated expectations with the IUD prior to insertion, and impact upon their general health, psyche, marriage, and relationship with others is investigated. A triangulation of qualitative data sources from three different groups of women derived at different times and means is combined with the qualitative phenomenological method. The existential-phenomenological tradition offers the best methodological support for investigation of the human meaning of a lived experience. In-depth interviews were transcribed and analyzed using the three phase approach of: (1) discovery; (2) coding the data; and (3) discounting of findings as developed by Taylor and Bogdan (1984). The HyperQual Version 4 for Macintosh Computer was used to tag and stack data chunks. Some major significant findings were: (1) women injured by the Dalkon Shield experienced mild to severe psychosocial and physical trauma. (2) There is more than one outcome of a negative experience with the Dalkon Shield. (3) There is more than one style of coping with the ramifications of a negative experience with the Dalkon Shield. Forty percent of the women interviewed had patterns consistent with mild to moderate post-traumatic stress disorder. (4) Ranges of emotion evolve over time. (5) The negative Dalkon Shield experience can be conceptualized as a phenomenon of six phases which begins with a predisposing belief system of: blind faith ; physical trauma ; the perception of doctors\u27 privileged knowledge ; violation ; fury ; and persistent remorse . Implications for health care providers, educators, biomedical researchers, and society are discussed

Women\u27s response to reproductive trauma secondary to contraceptive iatrogenesis: A phenomenological approach to the Dalkon Shield case

This study describes the meaning of the experience of being injured by a birth control method called the Dalkon Shield intrauterine device (IUD). Women whose reproductive organs were irrevocably damaged by the Dalkon Shield are the subjects of this study. In the interest of the feminist perspective which includes the women\u27s health movement, this study focuses on the women\u27s reality of their experience with a defective contraceptive, namely the Dalkon Shield. In addition to the collection of demographic information about the informants and information related to the events preceding the selection of the Dalkon Shield as a contraceptive method, the women\u27s anticipated expectations with the IUD prior to insertion, and impact upon their general health, psyche, marriage, and relationship with others is investigated. A triangulation of qualitative data sources from three different groups of women derived at different times and means is combined with the qualitative phenomenological method. The existential-phenomenological tradition offers the best methodological support for investigation of the human meaning of a lived experience. In-depth interviews were transcribed and analyzed using the three phase approach of: (1) discovery; (2) coding the data; and (3) discounting of findings as developed by Taylor and Bogdan (1984). The HyperQual Version 4 for Macintosh Computer was used to tag and stack data chunks. Some major significant findings were: (1) women injured by the Dalkon Shield experienced mild to severe psychosocial and physical trauma. (2) There is more than one outcome of a negative experience with the Dalkon Shield. (3) There is more than one style of coping with the ramifications of a negative experience with the Dalkon Shield. Forty percent of the women interviewed had patterns consistent with mild to moderate post-traumatic stress disorder. (4) Ranges of emotion evolve over time. (5) The negative Dalkon Shield experience can be conceptualized as a phenomenon of six phases which begins with a predisposing belief system of: blind faith ; physical trauma ; the perception of doctors\u27 privileged knowledge ; violation ; fury ; and persistent remorse . Implications for health care providers, educators, biomedical researchers, and society are discussed

Voces del subalterno femenino en dos novelas hondureñas : Blanca Olmedo (Principios del siglo XX) y los días y los muertos (principios del siglo XXI)

Tesis (MSc. en Lengua y Literatura Hispánica)-Universidad Nacional Autónoma de Nicaragua, LeónUNAN-Leó

Does an opportunistic predator preferentially attack non-vigilant prey?

The dilution effect as an antipredation behaviour is the main theoretical reason for grouping in animals and states that all individuals in a group have an equal risk of being predated if equally spaced from each other and the predator. Stalking predators, however, increase their chance of attack success by preferentially targeting nonvigilant individuals, potentially making relative vigilance rates in a group relatively important in determining predation compared with the dilution effect. Many predators, however, attack opportunistically without stalking, when targeting of nonvigilant individuals may be less likely, so that the dilution effect will then be a relatively more important antipredation reason for grouping. We tested whether an opportunistically hunting predator, the sparrowhawk, Accipiter nisus, preferentially attacked vigilant or feeding prey models presented in pairs. We found that sparrowhawks attacked vigilant and feeding mounts at similar frequencies. Our results suggest that individuals should prioritize maximizing group size or individual vigilance dependent on the type of predator from which they are at risk. When the most likely predator is a stalker, individuals should aim to have the highest vigilance levels in a group, and there may be relatively little selective advantage to being in the largest group. In contrast, if the most likely predator is an opportunist, then individuals should simply aim to be in the largest group and can also spend more time foraging without compromising predation risk. For most natural systems this will mean a trade-off between the two strategies dependent on the frequency of attack of each predator type. (C) 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.</p