Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

The development of new analytical techniques is one of the driving forces in the advancement of scientific understanding. The measurement of the properties of aerosol particles is an active area of research due to the impact aerosol has on atmospheric processes. Single particle size and composition are key properties that govern many atmospheric processes, but the measurement of these properties is challenging due to the large dynamic range of size and composition that exists in the environment. Mineral dust represents a significant fraction of the global aerosol mass loading and has a profound impact on the earth's radiative budget through the direct interaction with solar and terrestrial radiation, and by affecting microphysical properties of clouds. In addition, mineral dust is involved in the geochemical cycling of many compounds that are vital for the health and vitality of ecosystems. The importance of the chemical and crystallographic properties of a material, or mineral phase, has been highlighted recently. Measurements of the elemental composition of single particles is possible with off-line analysis of dust collected on filters , but mineral phase is usually obtained from X-ray diffraction of bulk samples. These techniques are labour intensive and the lack of ambient measurements is a limiting factor in the development of models that attempt to resolve the complexity of atmospheric processes. Time-of-flight mass spectrometry (TOF-MS) is well suited to on-line single particle composition measurements due its sensitivity and high temporal resolution. Single particle mass spectrometry (SPMS) is a class of TOF-MS technique that is able to identify mineral dust particles from their chemical signature in the mass spectrum. Analysis of refractory mineral dust by mass spectrometry requires laser desorption ionisation (LDI) by high energy pulsed lasers, a process that renders the composition measurement non-quantitative due to incomplete ionisation and matrix effects. Consequently, the identification of mineral phase is not possible because the reproducibility of the measurement is lower than the natural variation between common minerals. This thesis reports the development of a commercially available single particle mass spectrometer for the measurement of the physiochemical properties of mineral dust. The optical particle detection system is improved for the more efficient detection of single particles in the size range relevant to the ambient measurement of mineral dust aerosol, and a model is developed that will aid the further development of particle detection in SPMS. A novel method for the on-line differentiation of mineral phase in single particles is presented which exploits differences in ion arrival times at the TOF-MS detector of a silicate molecular ion species, that arise from the influence of mineral phase on the ion formation process during the LDI process. The efficacy of the technique is demonstrated with the differentiation of mineral phase in laboratory generated mineral dust from clay mineral standards. The deployment of the improved instrument to measure Saharan dust outflow resulted in the first ever on-line identification of the clay mineral fraction in ambient mineral dust.

Large quantities of asbestos are used in the building and repairing of ships. Much is used in easily recognisable form and some is incorporated into materials which bear little or no superficial resemblance to the crude fibre at all, but which may still give rise to highly dangerous dust when sawn or otherwise manipulated. The inhalation of this dust over a period of time gives rise to a very disabling and sometimes fatal form or pneumoconiosis known as asbestosis and it is the aim of this article to discuss the prevention of this disease in Dockyard workers .

This paper examines the American Dust Bowl to understand the political impacts of the catastrophe which devastated the American Plains during the 1930s. I use county-level panel analysis to analyze whether the Dust Bowl led to a change in voting patterns in more eroded counties compared to less eroded counties. I look to see whether, in the years following the Dust Bowl, there was shift in vote shares against the Democratic Party who were typically the incumbents during the period of the Dust Bowl. I use presidential, congressional, senatorial and gubernatorial election return for approximately the three decades following the Dust Bowl, i.e. between 1940 and 1968. My results show that the Dust Bowl is associated with a shift away from the Democratic Party for more affected counties. I find these effects to last for at least a decade (throughout the 1940s). I also look at the potential effects of the net migration and New Deal expenditure in the Plains. I find that less net migration may have been one of the reasons behind this change in voting behavior of counties and that New Deal expenditure could potentially have been a strong mitigative tool for the Democratic Party. / Graduate

No description available.

Airborne dust and methane are common problems in the underground coalmines. They pose health and safety risk to mining personnel, and a safety risk to mining equipment as well. In order to prevent these risks air borne dust and methane concentrations must be reduced to within the acceptable levels. In South Africa, the dust and methane concentration in coalmines should not exceed 2.0 mg/m³ and 0.5% per volume, respectively. Mine ventilation is one of the popular ways of controlling both dust and methane. Different ventilation systems have been designed since the history of underground coal mining. Unfortunately, none provides ultimate solution to the dust and methane problem, especially in the most critical areas of the underground coalmine, like blind-end of the heading and last through road. By changing airflow patterns and air velocity, it is possible to obtain an optimum ventilation design that can keep dust and methane within the acceptable levels. Since it is very difficult to conduct experiments in the underground coalmine due to harsh environmental conditions and tight production schedules, the designer made use of the Computational Fluid Dynamics (CFD) modelling technique. The models were then experimentally verified and validated using a scaled down model at University of Pretoria. After verification further numerical analysis was done to in order to device a method for determining optimum fan positions for different heading dimensions. This study proves that CFD can be used to model ventilation system of a scaled down coalmine model. Therefore chances that this might be true for the actual mine are very high but it needs to be investigated. If this is found to be true then CFD modelling will be a very useful tool in coalmine ventilation system research and development. / Dissertation (MSc)--University of Pretoria, 2011. / Mechanical and Aeronautical Engineering / unrestricted

An optical microscope coupled to a flow cell was used to investigate ice nucleation on five atmospherically relevant mineral dusts at temperatures ranging from 233 to 247 K. Kaolinite and muscovite particles were found to be efficient ice nuclei in the deposition mode, requiring relative humidities with respect to ice (RHi) below 112% in order to initiate ice crystal formation. Quartz and calcite particles, by contrast, were poor ice nuclei, requiring relative humidities close to water saturation before ice crystals would form. Montmorillonite particles were efficient ice nuclei at temperatures below 241 K, but poor ice nuclei at higher temperatures. In several cases, there was a lack of quantitative agreement between these data and previously published work. This can be explained by several factors including mineral source, particle size, observation time and surface area available for nucleation. Heterogeneous nucleation rates (Jhet) were calculated from the onset data. Jhet values ranged from 60 to 1100 cm-²s-¹ for the five minerals studied. These values were then used to calculate contact angles (θ) for each mineral according to classical nucleation theory. The contact angles measured for kaolinite and muscovite ranged from 6 to 12º; for quartz and calcite the contact angles were much higher, ranging from 25 to 27º. The contact angles measured for montmorillonite were less than 15º at temperatures below 241 K, and above 20º at higher temperatures. The reported Jhet and θ values may allow for a more direct comparison between laboratory studies and can be used when modeling ice cloud formation in the atmosphere. The roles of H₂SO₄ and (NH4)₂SO₄ coatings on the ice nucleating properties of kaolinite were also investigated. Onset data was collected for H₂SO₄ coated and (NH4)₂SO₄ coated kaolinite particles at temperatures ranging from 233 to 247 K. In contrast to uncoated kaolinite particles, which were effective ice nuclei, H₂SO₄ coated particles were found to be poor ice nuclei, requiring relative humidities close to water saturation before nucleating ice at all temperatures studied. (NH4)₂SO₄ coated particles were poor ice nuclei at 245 K, but effective ice nuclei at 236 K. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

An intervention to improve adoption of dust control technology is designed, implemented and evaluated using three theoretical frameworks: the Health Belief Model (HBM), Diffusion of Innovation, and the Technology Acceptance Model. A quasi-experimental design (pretest-posttest, with control group) was used to evaluate the effectiveness of the intervention. An integrated conceptual model, employing key constructs from these frameworks, was developed to predict and describe "adoption readiness". Adoption readiness combines the attitudes and perceptions about a technology with the capacity to implement the technology. The primary hypothesis was that the key construct scores of the three theoretical models would improve post-intervention, particularly, "adoption readiness". Workers in the drywall finishing industry have been found to be at risk of developing respiratory disease and disability. Studies have shown that drywall finish workers have been subject to overexposure to dust concentrations that contain respiratory heath hazardous particles including silica, talc, mica, and calcite. Prevention through Design (PtD) solutions, which are effective at reducing dust levels, do exist for these operations. Some of these PtD solutions include using vacuum sanders, wet sanding methods, pole sanding and using low dust joint compound in lieu of using personal protective equipment (PPE) as a primary form of exposure protection. Previous studies have determined barriers to adoption of current PtD solutions for dust exposure reduction. Usability, productivity, quality of finish and cost were all identified as barriers to adoption. An intervention directed at those involved in the drywall industry is needed to increase the usage of engineered dust control. This dissertation project developed, implemented, and evaluated three interventions to address the barriers to adoption through education and marketing strategies. Development of the interventions included strategies to improve industry usage of dust control technologies. The interventions targeted workers, small companies, and large companies involved in drywall finishing. / Ph. D.

Contaminated tomatoes have become a commonly implicated vehicle of Salmonella outbreaks. Exposure of tomatoes to pathogen could occur in the field. Blossom inoculation with Salmonella can result in contaminated fruit but natural routes of blossom contamination are not well known. Salmonellae have been known to survive in agricultural soil. Since dispersal of soil particulate by wind is a common phenomenon, the potential of airborne soil particulate as a vehicle of Salmonella contamination in tomato blossoms was examined. It was determined that Salmonella enterica serotype Anatum, Baildon, Braenderup, Montevideo, Newport, Javiana had similar survival patterns in both soil and water. At the end of 40 days, populations of Salmonella in soil dropped by 2.59 log CFU/g and 5.11 log CFU/g when enumerated on Tryptic Soy Agar Yeast Extract (TSAYE) and xylose lysine Tergitol 4 (XLT4) agar respectively. Salmonella populations in water reduced by 2.55 log CFU/ml (TSAYE, enumeration) and 2.94 log CFU/ml (XLT4, enumeration). Blossom to fruit formation takes 20-30 days in tomatoes hence the introduction or presence of the pathogen in agricultural soil and water could increase risk of blossom contamination. Also, it was determined that all Salmonella serotypes tested were capable of biofilm production on glass coverslips and quartz particles. Biofilm based attachment of Salmonella to sand might aid in its dispersal. To visualize transfer of pathogen from soil particulate to blossom in real-time, bioluminescent S. Baildon, S. Braenderup, S. Newport, S. Javiana and S. Anatum were created.Heat shock procedure was developed to improve electrotransformation efficiency in Salmonella. Transformed strains were compared for bioluminescence production and plasmid stability. S. Newport had the best bioluminescence properties but no difference was observed between strains for plasmid stability. Imaging of soil particulate - S. Newport mixture inoculated blossoms, indicated that the event led to pathogen transfer to blossom. It was also determined that S. Newport â soil particulate contaminated blossoms developed into fruits that were positive for S. Newport. S. Newport presence in blossom, fruit surface and internal tissue indicates that contaminated soil particulate could serve as a vehicle of tomato contamination. / Ph. D.