Methyl bromide is a widely used soil disinfectant that, because of its ozone depleting properties, is being phased out in the EC by 2005.  Soil steaming is a well-established system of soil disinfestation and is increasingly seen as a viable option to methyl bromide replacement.  Traditional glasshouse steaming techniques create a number of problems because it involves treatment of soil with high-temperature (100-140°C) steam for up to eight hours or more.  This not only eliminates unwanted soil-borne pests and diseases, but also creates a ‘biological vacuum’, in which target pests and pathogens may quickly re-enter and luxuriate, perpetuating the need for regular disinfestation.   Soil steaming at lower temperatures, e.g. at 70°C, does not normally result in these unwanted side effects, because of the partial survival of the saprophytic microflora population. In this study agricultural soil samples, containing a range of important soil-borne pests and pathogens, were treated with steam in a specially designed laboratory steam-rig.  It was found that treatment at 60°C, for a duration of only 3 minutes plus eight minutes ‘resting’ (“low-temperature/short duration soil steaming”) was enough to 100% kill soil-borne fungal pathogens <i>Sclerotinia sclerotiorum, Sclerotium cepivorum, Verticillium dahlia</i>e and <i>Pythium ultimum;  </i>potato cyst nematodes <i>Globodera rostochiensis </i>and <i>Globodera pallida,</i> and weeds <i>Chenopodium album </i>and <i>Agropyron repens.</i> When low temperature/short duration soil steaming was compared with a chemical soil disinfectant, using the fumigant dazomet (Basamid) at a rate of 760 kg/ha, both disinfestation methods resulted in 100% elimination of the above pathogens, nematodes and weeds and caused IGR (Increased Growth Response) of lettuce plants. In a further study, using four different soil types at three different matric potentials, it was found that efficacy of low-temperature/short duration steaming is dependent on soil type and soil moisture content, and that treatment of soil in a moist state is more effective than treatment in a dry state, especially when treating fine-textured sand and loam soils. Soil samples containing survival structures of soil pests were also treated with ozone gas in a specially designed ozone treatment chamber, but this did not result in elimination of target organisms.

No abstract / Mini Dissertation (MPhil)--University of Pretoria, 2019. / Public Law / MPhil / Unrestricted

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Recurrent Airway Obstruction (RAO)-affected horses experience bronchoconstriction and airway inflammation in response to inhalation of irritants including hay molds. Steaming hay reduces fungal content, but the effect on the antigenic potential has not been investigated. We tested the hypothesis that RAO-affected horses develop less severe clinical disease when fed steamed versus non-steamed hay and this reduction coincides with decreased hay fungal content. Six RAO-affected horses in clinical remission were divided in two groups and fed steamed or non-steamed hay for 10 days using a two-way cross-over design. Hay was steamed using a commercial hay-steamer. Clinical assessment was performed daily. Full assessment, including airway endoscopy, tracheal mucous scores and maximal change in pleural pressure, was performed on days 1, 5, and 10. Bronchial fluid sampling and cytology were performed on days 1 and 10. Hay core samples were collected pre- and post-steaming and cultured to determine fungal and bacterial concentrations. Statistical analysis was based on data distribution and quantity and performed using SAS®. P-value <0.05 was significant. Steaming significantly decreased the number of bacterial and fungal colony-forming-units in hay. Horses fed non-steamed hay experienced a significant increase in clinical score and a trend towards airway neutrophilia, while parameters were unchanged in horses fed steamed hay. Only horses fed non-steamed hay experienced a significant increase in tracheal mucous score. Horses fed steamed hay gained significantly more weight compared to horses fed non-steamed hay, even though the amount of hay consumed not greater on a dry matter basis. These results indicate that steaming reduces the RAO-affected horse's response to hay which coincides with a reduction in viable fungal content of hay. / Master of Science

Orientador: Elias Taylor Durgante Severo / Banca: Mario Tomazello Filho / Banca: Edson Luiz Furtado / Resumo: A madeira de Eucalyptus grandis Hill ex Maiden submetida ao tratamento de vaporização apresenta maior qualidade na indústria de serrados e otimização durante o processo de secagem. O objetivo desta pesquisa foi verificar o efeito da vaporização em toras e em madeira serrada nas propriedades químicas e na resistência natural a fungo e cupins da madeira de Eucalyptus grandis. Para isso, foram empregados quatro tratamentos: material controle, madeira vaporizada em toras (vapor saturado, 20 horas à 90°C), madeira pré-vaporizada em tábuas (1 hora de aquecimento inicial seguida de 3 horas de vapor saturado a 90ºC) e material submetido às duas vaporizações, ou seja, tábuas pré-vaporizadas obtidas de toras vaporizadas. Para caracterização química foram utilizadas as normas TAPPI (1999); para determinar a resistência natural a fungo foram utilizados os procedimentos das normas ASTM D-1413 (1994) e ASTM D-2017 (1994) e, para cupim, a metodologia desenvolvida pelo Instituto de Pesquisas Tecnológicas (1980). Os resultados mostraram que: (1) a vaporização promoveu algumas modificações não estatisticamente significativas na composição química da madeira, como: acréscimos de até 5,07% do teor de solubilidade em NaOH 1%, decréscimos de até 21,80% no teor de solubilidade em água quente, acréscimos no teor de extrativos totais para madeira vaporizada em tora e aquela pré-vaporizada em tábuas na ordem de 4,80% e 9,50%, respectivamente, enquanto a madeira submetida à vaporização conjunta (vaporizada/pré-vaporizada) apresentou decréscimo de 7,10%; aumento de até 6,77% no teor de lignina Klason, e redução de até 4,75% no teor de hemiceluloses. Outras modificações, no entanto, foram significativas, como: redução de 3,10% no teor de holocelulose e de 5,06% no teor de celulose... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The steamed wood of Eucalyptus grandis Hill ex Maiden has a better quality to the sawn industry and optimizes the drying process The aim objective of this work was evaluate the effect of vaporization in logs and lumber on chemical properties and Eucalyptus grandis's natural resistance to dry wood termites (Cryptotermes brevis) and to the fungus Pycnoporus sanguineus. For this, four treatments were used: control material, steamed wood logs (saturated steam, 20 hours at 90 ° C), pre-steamed wood on tables (1 hour initial warm-up followed by 3 hours of saturated steam at 90 º C) and materials that were submitted to two sprays, i.e., pre-steamed boards obtained from vaporized logs. For the chemical characterization was used TAPPI (1999), to determine the natural resistance to fungus were used procedures of ASTM D-1413 (1994) and ASTM D-2017 (1994) standards and, for termites, the methodology developed by the Instituto de Pesquisas Tecnológicas (1980). Results showed that: (1) vaporization promoted no significant modifications in the chemical composition of wood, such as additions of 5.07% in the level of solubility in NaOH 1%, solubility decrease of 21.80% in the level of solubility in hot water, increases in the total extractive content for the log wood and pre-vaporized boards in the order of 4.80% and 9.50% respectively, while the vaporized wood/pre-vaporized on boards showed a decrease of 7.10%; increase of 6.77% in Klason lignin content and reduction of 4.75% in the content of hemicelluloses. Other modifications, however, were significant, as reduction of 3.10% in the holocellulose content and 5.06% in cellulose content, (2) there was also no significant effect on the susceptibility of wood when vaporized and exposed to the white-rot fungus, Pycnoporus sanguineus. The steamed wood... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-06-11T19:30:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-08-12Bitstream added on 2014-06-13T20:20:45Z : No. of bitstreams: 1 rocha_cd_me_botfca.pdf: 830969 bytes, checksum: 21c7d0889cf28e59388bd1c31c7c5072 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A madeira de Eucalyptus grandis Hill ex Maiden submetida ao tratamento de vaporização apresenta maior qualidade na indústria de serrados e otimização durante o processo de secagem. O objetivo desta pesquisa foi verificar o efeito da vaporização em toras e em madeira serrada nas propriedades químicas e na resistência natural a fungo e cupins da madeira de Eucalyptus grandis. Para isso, foram empregados quatro tratamentos: material controle, madeira vaporizada em toras (vapor saturado, 20 horas à 90°C), madeira pré-vaporizada em tábuas (1 hora de aquecimento inicial seguida de 3 horas de vapor saturado a 90ºC) e material submetido às duas vaporizações, ou seja, tábuas pré-vaporizadas obtidas de toras vaporizadas. Para caracterização química foram utilizadas as normas TAPPI (1999); para determinar a resistência natural a fungo foram utilizados os procedimentos das normas ASTM D-1413 (1994) e ASTM D-2017 (1994) e, para cupim, a metodologia desenvolvida pelo Instituto de Pesquisas Tecnológicas (1980). Os resultados mostraram que: (1) a vaporização promoveu algumas modificações não estatisticamente significativas na composição química da madeira, como: acréscimos de até 5,07% do teor de solubilidade em NaOH 1%, decréscimos de até 21,80% no teor de solubilidade em água quente, acréscimos no teor de extrativos totais para madeira vaporizada em tora e aquela pré-vaporizada em tábuas na ordem de 4,80% e 9,50%, respectivamente, enquanto a madeira submetida à vaporização conjunta (vaporizada/pré-vaporizada) apresentou decréscimo de 7,10%; aumento de até 6,77% no teor de lignina Klason, e redução de até 4,75% no teor de hemiceluloses. Outras modificações, no entanto, foram significativas, como: redução de 3,10% no teor de holocelulose e de 5,06% no teor de celulose... / The steamed wood of Eucalyptus grandis Hill ex Maiden has a better quality to the sawn industry and optimizes the drying process The aim objective of this work was evaluate the effect of vaporization in logs and lumber on chemical properties and Eucalyptus grandis´s natural resistance to dry wood termites (Cryptotermes brevis) and to the fungus Pycnoporus sanguineus. For this, four treatments were used: control material, steamed wood logs (saturated steam, 20 hours at 90 ° C), pre-steamed wood on tables (1 hour initial warm-up followed by 3 hours of saturated steam at 90 º C) and materials that were submitted to two sprays, i.e., pre-steamed boards obtained from vaporized logs. For the chemical characterization was used TAPPI (1999), to determine the natural resistance to fungus were used procedures of ASTM D-1413 (1994) and ASTM D-2017 (1994) standards and, for termites, the methodology developed by the Instituto de Pesquisas Tecnológicas (1980). Results showed that: (1) vaporization promoted no significant modifications in the chemical composition of wood, such as additions of 5.07% in the level of solubility in NaOH 1%, solubility decrease of 21.80% in the level of solubility in hot water, increases in the total extractive content for the log wood and pre-vaporized boards in the order of 4.80% and 9.50% respectively, while the vaporized wood/pre-vaporized on boards showed a decrease of 7.10%; increase of 6.77% in Klason lignin content and reduction of 4.75% in the content of hemicelluloses. Other modifications, however, were significant, as reduction of 3.10% in the holocellulose content and 5.06% in cellulose content, (2) there was also no significant effect on the susceptibility of wood when vaporized and exposed to the white-rot fungus, Pycnoporus sanguineus. The steamed wood... (Complete abstract click electronic access below)

Hydrocracking is one of the most essential catalytic processes in the oil industry for the conversion of heavy fractions of petroleum (light and heavy vacuum gas oil, demetallized oil) and renewable hydrocarbon feedstocks to high-quality fuels. Hydrocracking relies on a bifunctional catalytic process that combines catalytic cracking and hydrogenation steps. In principle, hydrocracking is aimed to convert heavy and ultraheavy oils with maximum fuel selectivity and minimum formation of light gases and polyaromatic compounds, from this high activity and selectivity of the catalyst, is achieved by finding a good balance between its acidic and hydrogenation properties. For this study, platinum catalyst impregnated on alumina was applied for hydrogenation reaction, whereas cracking function was accomplished by ultrastable Y (USY) zeolite. The central objective of the thesis was to study the fundamental effect of extra framework aluminum (EFAl) species forming with the hydrothermal treatment of USY on hydrocracking of selected model compound – n-hexadecane. Three commercial USY zeolites with different SiO2/Al2O3 ratios were steamed until they reached down to the conversion curve of the reference USY sample physically mixed with 1% Pt supported on alumina in a 1:10 ratio. XRD patterns showed that the crystalline faujasite structure was kept after steaming. In the physisorption of argon, slight changes were observed in surface area and pore volumes which were correlated to the structural collapse of the zeolite framework. Dealumination of the zeolite framework was verified by 27Al MAS NMR. FTIR spectroscopy of pyridine adsorption and TPD of ammonia were employed to investigate the acidity of the samples. From the results, it was found that the concentration of Brønsted acid sites was the main contributor to the activity-acidity relationship in n-hexadecane hydrocracking. To gain more insight into the relationship, samples were subjected to n-hexane cracking. Turnover frequency analysis supported the proposal about hydrocracking reaction and also revealed the chemical influence of EFAl on Brønsted acidity observed in catalytic cracking of hexane.

Weeds and soil-borne diseases can cause large yield losses in field-grown tomato (Solanum lycopersicum) production. Techniques have been developed to reduce soil-based problems. In this study, we evaluated the impacts of cover crops, soil steaming, and plastic mulch to reduce weed and disease pressure in field-grown tomatoes. Four cover crop treatments were grown in the fall and winter before spring planting. Soils were steamed to a target temperature of 71.1 °C for 0, 5, or 20 minutes. Plastic mulch was also used on half of the rows. Yield, weed densities, and disease incidence were recorded. Reduced flowering time and stringent flowering requirements may reduce the ability to conduct crosses in many plants. Many factors control flowering. Terminal Flowering Locus 1 (TFL1) inhibits flower development. In this study, we attempted to transiently downregulate TFL1 via virus-induced gene silencing (VIGS) in Antirrhinum, Penstemon, Petunia, Rosa, and Rudbeckia.

This research explored different catalytic cracking zeolite additives to improve propylene selectivity and minimize dry gas yield. A comprehensive study of the effect of zeolite structure, pore system and crystal size on maximizing propylene production in FCC unit and the effect of post synthetic modifications on the physicochemical properties and cracking activity of ZSM-5 was investigated using X-ray diffraction (XRD), pyridine adsorption fourier transform infra-red (FTIR), 27Al and 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) and the catalytic cracking using n-heptane, as a model compound for heavy naphtha. The catalytic performances of these additives were evaluated in a fixed-bed reactor unit using n-heptane as a model compound for naphtha at temperatures 450 - 500 oC and W/F 38 - 92 gcat.h/mol. A range of zeolites were tested with ZSM-5 showing the optimum results at high feed conversion. Further studies on ZSM-5 crystal size illustrated that nano ZSM-5 (300 nm) was superior compared to the regular ZSM-5 (2000 - 4000 nm) in achieved conversion level and propylene selectivity. These improvements were attributed to the shorter path lengths for the reactant reducing diffusion constraints significantly. Modifying nano ZSM-5 acidity using steaming, acid leaching and silanation showed significant improvement over nano ZSM-5 parent. Mild steaming of nano ZSM-5 improved both n-heptane conversion and propylene selectivity whilst severe steaming only improved propylene selectivity. This work attempted to address the often discussed catalytic activity enhancement from mild steaming and identified newly created moderate acid sites as the source of increased activity. Dealumination by acid leaching decreased the total aluminium content of nano ZSM-5 and changed the Brønsted/Lewis ratio. Increasing the B/L ratio, increased the conversion and propylene selectivity. In addition, this research focussed for the first time on the silanation of nano ZSM-5 and its effect on n-heptane cracking, in particular, propylene and dry gas selectivity. Silica was deposited on the external surface of nano ZSM-5 neutralising the acidic sites and as a result, dry gas yield was significantly decreased due to the elimination of non-selective cracking. However, the trade off with conversion was high.

This thesis focused on the modelling of a pulping process. The purpose was to see if an accurate model can be crated based on relatively simple premises and if the errors can be identified or analysed. To realise this, the authors conducted a literature study to identify the current state of the art regarding the chemical pulping process. In addition, flow charts and sample data from a case study were examined. Based on the literature review and case study, model assumptions were derived. The model is divided into sixteen components. Where mixing occurs, lumped conditions are assumed. The model has five validation points, four of which are temperatures and a mass flowrate. These are shown as deviations from the measured values. In conclusions, it was the model could produce stable results over a narrow time frame. More so if the transition period at the start of the simulation is overlooked. Several new model assumptions are presented with the purpose to increase accuracy e.g. account for the components ability to store mass.