Thesis (Ph. D.)--University of Wisconsin, 1952. / Typescript (carbon copy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 44).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 364-384.

Thesis (M.S.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 95-103).

M.Sc. (Chemistry) / Catalyst deactivation is a process that plays an important role in many catalytic processes. The forming of coke is in this respect the most common cause for deactivation. The research that has been done here has tried to give some insight into the mechanism of cokeforming with the help of Fourier Transform Infrared Spectroscopy (F)'IR). For this purpose a cobalt catalyst on an alumina carrier was used. The influence of the reaction time, the carbon monoxide to hydrogen ratio and the temperature on the rate and amount of coke formed was determined. A cell was developed that could be heated up to 500°C and could simultaneously be used in FTIR-spectroscopy in situ research. This enabled the determination of spectra at certain time intervals. In this way the development of the characteristic bands could be followed. Two other methods were used to support the transmission spectra : Diffuse Reflectance Spectroscopy and the burning of the coke from the catalyst. The latter was done to determine the amount of coke that had formed on the catalyst surface during the run. The amount of coke decreased with an increase of the hydrogen to carbonmonoxide ratio in the feed. Temperature also had a marked influence on coke formation: It decreased at higher temperatures. As expected the amount of coke increased with reaction time. In general the coke contained only a small hydrogen content. In conclusion it may be mentioned that the results obtained can contribute to the characterization of coke formed on Fischer-Tropsch catalysts.

Bibliography : pages 244-253. / The objective of this study was to determine the effect that the type of catalyst and reaction would have on the rate of deactivation, properties of coke and transport properties of the catalyst. HY and HM were chosen because of their different pore structures and acid site distributions. Hexane cracking at 1 atmosphere and high pressure propene oligomerisation provided two different reaction types. The transport properties of the catalysts were compared by measuring adsorption and diffusion using the GC technique with ancillary information obtained from ammonia TPD, mercury porosimetry and BET surface area measurements. It was confirmed that a knowledge of the crystallite size distribution was necessary to predict the adsorption and diffusion of light hydrocarbons in HY and HM. The adsorption constants and heats of sorption were found to,be much greater in HM than in HY, in agreement with the presence of a greater number of strong acid sites detected in HM by ammonia TPD. The diffusivities of the Tight hydrocarbons were too large to measure in HY. In HM only methane diffusion was too fast to measure. Diffusivities decreased and adsorption constant increased with increasing molecular size. HY had greater activity and slower deactivation than HM towards hexane cracking. The reaction as well as coking took place in the micro-pores. The graphitic coke content of HY was much greater than in HM. The introduction of the macro-pore adsorption term was necessary to predict diffusion in coked samples, emphasizing the severity of the diffusional resistance. While hydrocarbon diffusivities decreased after cracking, adsorption constants were found to increase in the presence of graphitic coke in J-IY. In HM the deactivation took place primarily by pore blockage, with strong acid sites being preferentially removed. Both diffusivities and adsorption constants decreased in the presence of coke in HM. In HY and HM deactivated by oligomerisation, macro-pore adsorption had to be taken into account, again emphasizing the severe diffusional resistance. Reaction as well as graphitic coke occurred predominantly in the micro-pores in HY. High boiling point hydrocarbons were able to migrate into the mesopores where they closed the mouths of the micro-pores in HY. Strongly adsorbed high boiling point hydrocarbons which deactivated the catalyst presented far less diffusional resistance in HY than the equivalent mass of graphitic coke. These high boiling point hydrocarbons also markedly lowered the adsorption constants. Graphitic coke was responsible for the modification of the catalyst selectivity. Temperature runaway in HY caused severe coking and hence deactivation. The inactivity of HM below 200°C was caused by strong adsorption and high diffusional resistance of reactant and product. Pore blockage was the dominant deactivation mechanism in HM, while in HY it was partial pore blockage by graphitic coke and pore mouth closure by high boiling point hydrocarbons. It was possible to restore the activity of HY for oligomerisation by flushing the high boiling point hydrocarbons in flowing nitrogen.

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No description available.

Thesis (MSc) Stllenbosch University, 2001. / ENGLISH ABSTRACT: A prospective study was conducted in 1999 to establish the incidence and nature of acute poisonings in the Cape Town / Western Cape region. This study was based on an analysis of Poison Centre queries and acute poisoning admissions to Tygerberg Hospital over a period of 1 year (1999). Summary of findings for Hospital admissions (1010 cases): Acute poisonings were more common in adults (83%) than in children (17%) and drug overdose was by far the most common clinical entity in adult Hospital admissions (89% of cases). Most overdoses in adults were intentional (97%). Seventy five percent of these cases were female, predominantly in the 20-40 year age group. The incidence of non-drug chemical exposures in adults was relatively low (11%). In children, on the other hand, there was much less of a discrepancy between drug and non-drug chemical exposures (41% and 59% respectively). Paracetamol was the drug most commonly used in overdose in both adults and children. In adults ethanol featured in 17% of cases. Ingestion of paraffin and related volatile hydrocarbons were the most important cause of acute poisoning in children. Acute poisoning admissions due to drugs of abuse, excluding ethanol, were minimal in both age groups (1%). Toxic exposures to non-drug chemicals in the agricultural and industrial settings were low (3%). The number of exposures to biological toxins was also minimal (2%). Summary of findings for Poison Centre inqueries (3744 consultations): In 1999 the Tygerberg Poison Information Centre received 3744 calls, of which 2690 were related to acute human exposures to poisonous substances. The remainder of the calls (1054) was either about drug therapy, or general non-patient related toxicological matters. There were more calls regarding poisoning in adults (61%) than in children (39%). Most of the paediatric poisonings were accidental (97%), whereas in adults 55% were deliberate and 45% accidental. Forty four percent of the children and 52% of adults were female. In children, inqueries about exposures to potentially harmful non-drug household chemical products comprised 56% of poison calls, while drug overdose was 28% and exposures to biological toxins 16%. In adults 44% of inqueries were with regard to household products, 40% about drugs and 16% biological toxins. A comparison of Hospital admissions versus Poison Centre consultations: In order to make a valid comparison between Hospital admissions and Poison Centre consultations, acute poisoning cases originating from the same area were compared. Eight hundred and thirty four (90%) of patients admitted to Tygerberg Hospital and 592 (25%) of Poison Centre consultations originated from the same region, the Tygerberg catchment area. Several differences were noted when comparing poisoning cases reported to the Poison Centre and Hospital admissions. Six hundred and eighty eight (83%) adults and 145 (17%) children were admitted to Hospital in contrast to Poison Centre inqueries, where 322 (54%) were adults and 270 (46%) children. In adults, 99% of Hospital admissions versus 59% of Poison Centre consultations were regarded as self-inflicted. Ninety three percent of adults admitted to Hospital were drug overdoses, whereas only 48% of adult Poison Centre consultations involved ingestion of medicines. In adult overdoses with paracetamol and other analgesics, tricyclic antidepressants, antiepileptics, theophylline and ethanol were significantly higher in Hospital admissions than in Poison Centre consultations. In contrast, exposures to pesticides e.g. pyrethroids, misuse of recreational drugs e.g. cannabis and biological toxin exposures e.g. spider bites, were significantly higher in Poison Centre consultations than in Hospital admissions. In children, poisoning exposures to volatile hydrocarbons, especially paraffin, were significantly higher in Hospital admissions compared to Poison Centre enqueries. As is evident from the disparity in the results above, inqueries to the Tygerberg Poison Information Centre cannot be regarded as a reflection of the true incidence of acute poisonings in the community. Poison Information Centre statistics are distorted because of two factors: 1. Under-reporting to the Poison Information Centre. Healthcare providers are familiar with how to manage drugs commonly used in overdose (e.g. paracetamol) and certain household non-drug chemicals (e.g. paraffin), and often do not consult the Poison Centre for poison cases involving these substances. The number of inqueries received by the Poison Information Centre regarding these substances is, therefore, an under representation of actual incidence. 2. Over-reporting to the Poison Information Centre. The Tygerberg Poison Information Centre is well known for its expertise in biological toxins (e.g. spider and snake bites, scorpion stings, plant and mushroom ingestions, and marine toxins). Therefore, the number of inqueries received by the Centre with regard to these exposures is far higher than actual incidence of exposures. It is clear from this study that one cannot use data derived from a poison centre alone as an indicator of true incidence of poisoning in the community. A more accurate estimate of incidence of acute poisoning could be obtained by including data from hospital admissions, as well as those from primary health care facilities. Another prominent finding in this study was the high incidence of self-inflicted drug overdose in adult females, with paracetamol being the drug of choice. Poison prevention should therefore not be limited to children. Adult prevention programs need urgent attention. / AFRIKAANSE OPSOMMING: ‘n Prospektiewe studie om die insidensie en aard van akute vergigtigings in die Wes-Kaap vas te stel, is gedurende 1999 in Tygerberg Hospitaal uitgevoer. Die studie is gebaseer op ‘n analise van oproepe wat deur die Tygerbergse Vergifinligtingsentrum ontvang is en pasiente wat gedurende dieselfde tydperk met ‘n diagnose van akute vergiftiging by die Hospitaal toegelaat is. Qpsomming van Hospitaal toelatinqs (1010 qevalle): Toelatings van akute vergiftigings was meer algemeen by volwassenes (83%) as by kinders (17%). Die meeste hospitaal toelatings (83%) by volwassenes is a.g.v. geneesmiddeloordoseing. By 97% van volwassenes was gifstowwe doelbewus ingeneem, met vroue in die meerderheid (75%). Die insidensie van vergiftigings met nie-geneesmiddel verwante gifstowwe by volwassenes was laag (11%). By kinders was daar egter ‘n meer eweredige verspreiding tussen geneesmiddel (41%) en nie-geneesmiddel verwante (59%) gifstowwe. By beide volwassenes en kinders, was parasetamol die middel wat by die meeste oordoserings betrokke was. Alkohol was by 17% van vergiftigings by volwassenes betrokke. Paraffien en verwante vlugtige substanse was die belangrikste gifstowwe betrokke by akute vergiftigings by kinders. Akute vergiftigings as gevolg van die gebruik van dwelmmiddels was laag in alle ouderdomsgroepe (1%). Vergiftigings in die landbou en industriele sektore was laag (3%). Dit was ook die geval ten opsigte van blootstelling aan biologiese toksienes (2%). Opsomminq van Tyqerberq Verqifinliqtinqsentrum konsultasies (3744 qevalle): Gedurende 1999 het die Tygerberg Vergifinligtingsentrum 3744 oproepe ontvang waarvan 2690 as gevolg van akute vergiftigings was. Die ander 1054 oproepe het gehandel oor geneesmiddel terapie of algemene, nie-pasient verwante navrae. Daar is aangetoon dat oproepe ten opsigte van akute vergiftigings by volwassenes meer algemeen was as by kinders (61% en 39% respektiewelik). By kinders was die meeste vergiftigings per ongeluk (97%), terwyl by volwassenes die meeste doelbewus (55%) was. By kinders was 44% van die vroulike geslag teenoor 52% by volwassenes. By kinders was nie-geneesmiddel gifstowwe by 56% van akute vergiftigings betrokke en geneesmiddels by 44%. By volwassenes was dit 60% en 40%, respektiewelik. ‘n Verqelvkinq ten opsigte van Hospitaal toelatinqs en Verqifsentrum konsultasies: Om ‘n geldige vergelyking tussen Hospitaal toelatings en Vergifinligtingsentrum konsultasies te maak is gevalle van akute vergiftigings afkomstig uit dieselfde geografiese gebied.vergelyk. Toelatings tot Tygerberg Hospitaal 834 (90%) en 592 (25%) oproepe wat deur die Tygerbergse Vergifsentrum ontvang is, kom uit dieselfde opvangsgebied, naamlik die Tygerbergse substruktuur. Verskeie verskille tussen die twee instansies ten opsigte van die tipe vergiftigings is aangetoon. Volwassenes 688 (83%) en 145 (17%) kinders is met ‘n diagnose van akute vergiftiging by Tygerberg Hospitaal toegelaat in teenstelling met die Inligtingsentrum konsultasies waar 322 (54%) volwassenes en 270 (46%) kinders by betrokke was. By volwassenes was 99% van die toelatings die gevolg van doelbewuste vergiftiging (paraselfmoord), terwyl dit 59% van die Inligtingsentrum se navrae was. Drie en negentig persent van die volwassenes was in die Hospital toegelaat met geneesmiddel oordosering. Heelwat minder geneesmiddel oordosering (48%) was deur die Inligtingsentrum hanteer. Parasetamol en ander analgetika, trisikliese antidepressante, anti-epilepsie middels, alkohol en teofillien oordoserings by volwassenes was beduidend hoer by Hospitaal toelatings as by Vergifsentrum konsultasies. Akute vergiftiging deur paraffien en verwante vlugtige substanse by kinders was beduidend hoer by Hospitaal toelatings as wat gevind is by Inligtingsentrum navrae. Navrae ten opsigte van pestisied vergiftiging, gebruik van dwelmmiddels en blootstelling aan biologiese toksiene was beduidend hoer as by Hospitaal toelatings. Hierdie duidelike kontrasterende data dui daarop dat die tipe navrae wat deur die Tygerberg Vergifinligtingsentrum hanteer word nie noodwendig ‘n weerspieeling van die ware insidensie van akute vergiftiging in die gemeenskap is nie. Daar is 2 hoofredes hiervoor. 1. Onderrapportering by die Inligtingsentrum. Gesondheidverskaffers (dokters, verpleegsters, aptekers ens.) is vertroud met die behandeling van sekere algemene vergiftigings soos byvoorbeeld parasetamol oordosering en paraffien inname. Hulle ag dit derhalwe onnodig om die Sentrum hieroor te konsulteer. Dit lei dus tot onderrapportering. 2. Oorrapportering by die Inligtingsentrum. Die Tygerbergse Vergifinligtingsentrum is bekend vir sy vakkundigheid ten opsigte van blootstelling aan biologiese toksiene (spinnekopbyte, slangbyte, skerpioensteke, plante-en sampioen vergiftigings, ens). Dit is om hierdie rede dat vergiftigings deur biologiese agense, geraporteer aan die Sentrum, ‘n hoer syfer verteenwoordig as wat die werklike insidensie ten opsigte van die vergiftigings is. Hierdie studie toon dat vergifinligtingsentrum data nie noodwendig ‘n indikator van die ware insidensie van akute vergiftigings in die gemeenskap is nie. Dit is dus belangrik dat hospitaaltoelatingsdata asook data van primere gesondheidsklinieke ingesluit word om sodoende ‘n beter beeld te verkry van die ware insidensie van akute vergiftigings. ‘n Opmerklike bevinding tydens die studie was die hoe insidensie van doelbewuste geneesmiddel oordosering by volwasse vroue, met veral parasetamol as die middel van keuse. Programme wat fokus op die voorkoming van akute vergiftigings in volwassenes het dringende aandag nodig.

Thesis (M.S.)--University of Michigan, 1986.

During the last ten years, several patients have presented to the Renal Unit of Groote Schuur Hospital with acute renal failure following the use of traditional (N'anga or Gqirha) medication. The history together with abnormal liver-function tests and renal failure was thought to be suggestive of a toxic aetiology. The specific toxin however remained unknown, until during the admission of one patient, a relative brought in the medication, analysis of which revealed a high concentration of potassium dichromate. Subsequently elevated levels of chromium were demonstrated by atomic absorption spectrometry in the blood and urine of this patient. Following this case there have been six further cases of acute renal failure resulting from use of dichromate containing traditional remedies. These remedies were obtained from a variety of sources including street-hawkers, herbal chemists, and traditional healers. Clinical and laboratory data relating to these seven patients will be presented.