Non-typhoidal Salmonella enterica serovars continue to be the leading cause of foodborne illnesses in United States. Chlorine, chlorine related, and quaternary compounds are generally used for disinfecting carcasses and equipment in processing industries. The current study was aimed at understanding the inactivation kinetics of four Salmonella serovars to chlorine, chlorine dioxide and cetylpyridinium chloride (CPC). The transcriptomic responses to oxidative stress was investigated in stationary and log phase cells of S. Typhimurium. The study was also aimed at understanding the effect of the chemicals on the expression of virulence genes associated with the Salmonella Pathogenecity Island 1 (SPI1). The possible induction of the viable but nonculturable (VBNC) state in Salmonella due to CPC was also investigated. The inactivation parameters for each serovar and the chemical were estimated based on the Hom's model, ln (N/N0) = -k C^n T^m and it appeared that while disinfectant contact time was significant, biocide concentration in the overall disinfection was insignificant. This was true especially for chlorine and CPC with subtle differences observed between the serovars. The inactivation efficacy was, however, dependent on both concentration and the exposure time for chlorine dioxide. The highest degree of inactivation was obtained with chlorine followed by chlorine dioxide and CPC. Transcriptomic responses of S. Typhimurium revealed significant downregulation of several metabolic processes such as tricarboxylic acid cycle, oxidative phosphorylation, and amino acid biosynthesis in both log and stationary phase cells. Several stress related genes such as usp, rpoS and ompR were upregulated in the stationary phase cells. Majority of the virulence genes associated with the SPI1 were found to be downregulated for all the treatments. While treatment with chlorine and CPC caused downregulation of all the virulence genes, treatment with chlorine dioxide caused significant upregulation of few (hilC, invC, sipA and sipB) genes associated with the SPI1. Finally, the induction of VBNC state was not concluded as a result of treatment with CPC. However, significant percentage of cells (45 percent) with intact membrane was established based on the BacLight assayTM.

Thesis (M.S.P.H.)--University of Michigan, 1940.

Thesis (M.S.P.H.)--University of Michigan, 1940.

No description available.

Eighty years of chlorine atomic weight measurements revealed no variation of the stable isotope ratio, 37C1/ 35C1 (with precision up to 1.0%.) in natural materials. This result is not surprising because chlorine occurs in relatively few compounds, has a strong affinity for the liquid phase, occurs mostly in the -1 oxidation state and organisms don't discriminate between chlorine isotopes. Chlorine isotopes have been found to fractionate in the laboratory during kinetic reactions, equilibrium between phases and diffusion. This dissertation examined chlorine isotope composition of chloride from sea water halite, hydrothermal water samples and ground-water samples where chloride was likely moving by diffusion. The measurement method was mass spectrometry of methyl chloride gas prepared by quantitative precipitation of AgC1 from solution, and reaction of the AgC1 with methyl iodide. The precision of the technique is 0.24%. Results from sea water indicate that isotope ratios in sea water do not vary beyond measured uncertainty, thus sea water became the designated standard called SMOC (Standard mean ocean chloride). Many of the samples measured in this study vary significantly, though most are within 1.0%, of SMOC. All halite and hydrothermal samples are heavier than SMOC. Halite results may indicate isotope effects durina precipitation or time dependent variations of sea water. Hydrothermal samples may indicate source differences and/or fractionation mechanisms. Milk River aquifer samples indicate that chloride in the same aquifer may vary due to dual filtration or differina sources. Samples from a Canadian glacial clay show a total chloride variation of 2.4%,, linearly distributed with depth. chloride in the clay is known to be diffusing against ground-water movement. The isotope distribution can be approximated with a counter-current column equation. Samples from Texas and Louisiana contain an isotope range of about 1.8%, linearly distributed with depths from 6,000 to 14,000 feet. The distribution can be approximated with a simple diffusion equation. As a tracing tool, chlorine isotope measurements showed that halite AO kilometers from the ocean in south Africa probably did not precipitate from sea water mist, and that oil field brines adiacent to the Weeks Island salt dome (Louisiana) probably did not receive substantial quantities dome chloride.

Ground water in excess of one million years old may now be accurately age dated by using the radionuclide Chlorine 36 (36Cl), which has a half-life of 3.01 x 105 years. To maintain a high degree of accuracy in the resultant age it is necessary to take into account the buildup of 36Cl, which is due to thermal neutron activation of 35Cl to 36Cl. The purpose of this research is to determine the thermal neutron flux in various geochemical subsurface environments by conducting field measurements of thermal neutron production rates at discrete locations. These data are then compared with the theoretical thermal neutron flux calculated for each location. The field measurements were conducted from the surface to a maximum depth of 44 meters in a copper, silver and zinc mine. The measured thermal neutron flux was found to be larger than the theoretical thermal neutron flux by a factor of from three to six when below 17 meters depth.

Digitized by Kansas Correctional Industries

No description available.

No description available.

No description available.