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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The growth of Salmonella typhimurium, Staphylococcus aureus, and Bacillus cereus in bakery products as related to the food distribution system

Guy, Vicki H. 01 May 1981 (has links)
Current retail food distribution practices, microbial quality of bakery products, and the potential for growth of food borne pathogens (Staphylococcus aureus, Salmonella typhimurium, and Bacillus cereus) were examined using pumpkin pie as a model. The pumpkin pies, as obtained from the retail outlets, showed contamination with food pathogens. The aerobic plate counts reached high numbers (up to 10⁹/g) when stored at 25°C for the specified shelf life as indicated by pull dates. S. aureus was isolated from one sample and B. cereus from two samples of pumpkin pie. Baking conditions were sufficient to destroy IS. aureus and Salmonella typhimurium but not spores of B. cereus. The presence of S. aureus indicated post-processing contamination. When inoculated with S. aureus, Salmonella typhimurium and B. cereus, pumpkin pie supported the growth of all these organisms when stored at 25°C. When stored at severe abuse conditions (35°C), pumpkin pie supported the growth of S. aureus and Salmonella typhimurium but not B. cereus. Refrigeration at 4°C controlled the growth of the pathogens studied. The addition of 0.25% potassium sorbate to the pie filling inhibited the growth of Salmonella typhimurium and B. cereus but not S. aureus at 25°C. The findings of this study indicated a lack of knowledge regarding safe food handling practices among bakers. Current distribution practices indicated that pumpkin pies were often displayed at room temperature from two to five days. If contaminated, the product could become a public health hazard. / Graduation date: 1981
2

Effect of repeated puncture on the particulate matter contamination of multi-dose vials as assessed by the industrial model B Coulter Counter

Edirimanasinghe, Sylvester Mariadason, January 1968 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
3

A Comparison of Microbial Contamination in Commercial Intravenous Fluids Packaged in Glass and Flexible Plastic Containers

Guynn, James Bruce 01 January 1973 (has links)
An original study was undertaken in the pharmacy and at the nursing unit simulating conditions of actual use to determine contamination rates for intravenous fluids in glass bottles and flexible plastic bags.
4

On-site system effluent source tracking using geochemical and microbial tracers in a coastal catchment

Geary, Phillip M, University of Western Sydney, College of Science, Technology and Environment, School of Science, Food and Horticulture January 2004 (has links)
The principal aims of this thesis were to examine whether there were hydraulic links between individual on-site wastewater systems in sandy soils at Salt Ash and the Tilgerry Creek estuary near Port Stephens, New South Wales, and whether the chemical and microbiological contaminants from on-site systems could reach surface and groundwaters, and possibly lead to impacts on estuarine oyster growing waters. The research outcomes are contained within the thesis and in four refereed papers presented at conferences, and which have been subsequently published, or are in press. Copies of each of these papers are contained within the thesis Appendices. The presence of faecal contamination from domestic systems in the estuary, and surface drains in particular, has been confirmed by work contained in this thesis. The potential level of risk to human health from the consumption of contaminated oysters is, however, regarded as very low, although an assessment of health risk using established microbial assessment models has not been undertaken / Doctor of Philosophy (PhD)
5

Laser induced desorption time of flight mass spectrometer analysis of adsorbed surface contaminants on vacuum ultraviolet lithography optic materials

Surpaneni, Yamini. Allen, Susan D. January 2003 (has links)
Thesis (M.S.)--Florida State University, 2003. / Advisor: Dr. Susan Davis Allen, Florida State University, College of Engineering, Dept. of Electrical and Computer Engineering. Title and description from dissertation home page (viewed Apr. 12, 2004). Includes bibliographical references.
6

Using the Dusty Gas Model to investigate reaction-induced multicomponent gas and solute transport in the vadose zone

Molins Rafa, Sergi 05 1900 (has links)
Biogeochemical reactions and vadose zone transport, in particular gas phasetransport, are inherently coupled processes. To explore feedback mechanisms between these processes in a quantitative manner, multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions. Multicomponent gas diffusion is described based on the Dusty Gas Model, which provides the most generally applicable description for gas diffusion.Gas advection is described by Darcy's Law, which in the current formulation, is directly substituted into the transport equations. The model is used to investigate the interactions between geochemical reactions and transport processes with an emphasis to quantify reaction-induced gas migration in the vadose zone. Simulations of pyrite oxidation in mine tailings, gas attenuation in partially saturated landfill soil covers, and methane production and oxidation in aquifers contaminated by organic compounds demonstrate how biogeochemical reactions drive diffusive and advective transport of reactive and non-reactive gases. Pyrite oxidation in mine tailings causes a pressure reduction in the reaction zone and drives advective gas flow into the sediment column, enhancing the oxidation process. Release of carbondioxide by carbonate mineral dissolution partly offsets pressure reduction, and illustrates the role of water-rock interaction on gas transport. Microbially mediated methane oxidation in landfill covers reduces the existing upward pressure gradient, there by decreasing the contribution of advective methane emissions to the atmosphere and enhancing the net flux of atmospheric oxygen into the soil column. At an oil spill site, both generation of CH⁴ in the methanogenic zone and oxidation of CH⁴ in the methanotrophic zone contribute to drive advective and diffusive fluxes. The model confirmed that non-reactive gases tend to accumulate in zones of gas consumption and become depleted in zones of gas production. In most cases, the model was able to quantify existing conceptual models, but also proved useful to identify data gaps, sensitivity, and inconsistencies in conceptual models. The formulation of the model is general and can be applied to other vadose zone systems in which reaction-induced gas transport is of importance.
7

Using the Dusty Gas Model to investigate reaction-induced multicomponent gas and solute transport in the vadose zone

Molins Rafa, Sergi 05 1900 (has links)
Biogeochemical reactions and vadose zone transport, in particular gas phasetransport, are inherently coupled processes. To explore feedback mechanisms between these processes in a quantitative manner, multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions. Multicomponent gas diffusion is described based on the Dusty Gas Model, which provides the most generally applicable description for gas diffusion.Gas advection is described by Darcy's Law, which in the current formulation, is directly substituted into the transport equations. The model is used to investigate the interactions between geochemical reactions and transport processes with an emphasis to quantify reaction-induced gas migration in the vadose zone. Simulations of pyrite oxidation in mine tailings, gas attenuation in partially saturated landfill soil covers, and methane production and oxidation in aquifers contaminated by organic compounds demonstrate how biogeochemical reactions drive diffusive and advective transport of reactive and non-reactive gases. Pyrite oxidation in mine tailings causes a pressure reduction in the reaction zone and drives advective gas flow into the sediment column, enhancing the oxidation process. Release of carbondioxide by carbonate mineral dissolution partly offsets pressure reduction, and illustrates the role of water-rock interaction on gas transport. Microbially mediated methane oxidation in landfill covers reduces the existing upward pressure gradient, there by decreasing the contribution of advective methane emissions to the atmosphere and enhancing the net flux of atmospheric oxygen into the soil column. At an oil spill site, both generation of CH⁴ in the methanogenic zone and oxidation of CH⁴ in the methanotrophic zone contribute to drive advective and diffusive fluxes. The model confirmed that non-reactive gases tend to accumulate in zones of gas consumption and become depleted in zones of gas production. In most cases, the model was able to quantify existing conceptual models, but also proved useful to identify data gaps, sensitivity, and inconsistencies in conceptual models. The formulation of the model is general and can be applied to other vadose zone systems in which reaction-induced gas transport is of importance.
8

Effect of Solid Contamination on Stability of Model Oil-Water Emulsions

Khademi, Sima Unknown Date
No description available.
9

Field Trial of Residual LNAPL Recovery Using CO2-Supersaturated Water Injection in the Borden Aquifer

Nelson, Leif Carl January 2007 (has links)
The ability of supersaturated water injection (SWI) to recover non-aqueous phase liquids (NAPLs) was studied at the field scale as part of an ongoing program to evaluate its applicability to groundwater remediation. SWI uses Gas inFusionTM technology to efficiently dissolve gases into liquids at elevated pressures. SWI has been shown to both volatilize and mobilize residual NAPL ganglia (Li, 2004). During SWI pressurized water containing high concentrations of CO2 is injected into the subsurface below the zone of contamination. Once the injected water is in the aquifer the pressure drops substantially and the concentration of CO2 is no longer in equilibrium with the water and as a result CO2 bubbles nucleate. These bubbles then migrate upwards through the contaminated zone towards the water table. As they move they come into contact with residual NAPL ganglia and they either volatilize this NAPL, resulting in a bubble comprised of CO2 and gaseous NAPL, or mobilize this NAPL, resulting in a film of NAPL surrounding the bubble. In either case the bubbles continue to rise until they reach the water table at which point they are removed by a dual phase extraction system. In this work, a known amount of NAPL was emplaced below the water table at residual concentrations to represent a residual source of weathered gasoline. The source was created in a hydraulically isolated cell in an unconfined sand aquifer at CFB Borden, Ontario. After the source was emplaced SWI was used to remove as much of the contaminant mass as possible in 22.25 days of operation over three months. The goal of this project was to determine if SWI was capable of removing residual NAPL at a field site. It was successful in removing volatile NAPL but not non-volatile NAPL. 64% of the volatile compounds were removed but contaminant mass was still being removed when the system was shut down so with continued operation more mass would have been removed. There is no way of knowing how much more would have been removed had the project continued. These results indicate that continued development of the technology is warranted.
10

Soil and plant contents of lead and other trace elements with special reference to the influences of parent rock and pollution

Ginnever, Rhoda C. January 1985 (has links)
No description available.

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