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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.

Influence of a mixture of two polychlorinated biphenyls (PCB 47/77) on pro-inflammatory cytokines (IL-6, TNF-[alpha]) and associative behavior in young Sprague-Dawley rats

Asbrock, Christina Marie. January 2006 (has links)
Thesis (M.S.)--Bowling Green State University, 2006. / Document formatted into pages; contains xviii, 92 p. : ill. Includes bibliographical references.

A characterization of the effects of polychlorinated biphenyl mixtures on the expression of peptidylglycine [alpha]-amidating monooxygenase in neuroendocrine cells

Frederick, Karen S. January 2006 (has links)
Thesis (M.S.)--Bowling Green State University, 2006. / Document formatted into pages; contains ix, 85 p. : ill. Includes bibliographical references.

Bacterial challenge in Lumbricus terrestris a terrestrial invertebrate immunotoxicity model /

McDonald, Jennifer C. Venables, Barney J., January 2007 (has links)
Thesis (M.S.)--University of North Texas, May, 2007. / Title from title page display. Includes bibliographical references.

Genotoxicity of 4-monochlorobiphenyl in the lung of transgenic male 344 Fisher rats

Maddox, Catherine Michael. January 2007 (has links)
Thesis (M.S.)--University of Iowa, 2007. / Supervisor: Gabriele Ludewig. Includes bibliographical references (leaves 56-61).

Analysis and remediation of dioxins and selected polychlorinated biphenyls from the environment using hollow fibre microporous membrane liquid-liquid extraction and molecularly imprinted polymers

27 January 2014 (has links)
M.Tech. (Chemistry) / Please refer to full text to view abstract

2,5,2',5'-Tetrachlorobiphenyl and 3,4,3',4'-tetrachlorobiphenyl as inducers of hepatic microsomal enzymes in rhesus monkeys

Nielsen-Smith, Kathryn Anne 06 1900 (has links) (PDF)
M.S. / Bio-organic Chemistry / Single doses of tetrachlorobiphenyls, shown to be free of any chlorinated dibenzodioxins or dibenzofurans to a level of 1 ppm, were given to rhesus monkeys (Macaca mulatta) and the hepatic microsomal enzyme response measured periodically for 32 days. Liver biopsies, obtained by a closed needle technique, provided the tissue samples. Aryl hydrocarbon hydroxylase (measured as benzo[a]pyrene hydroxylase), aminopyrine - N - demethylase and cytochrome P-450 were measured on each sample. Animals treated with 25 mg/kg body weight of 2,5,2' ,5'- tetrachlorobiphenyl showed a marked increase in the demethylase activity, which peaked at 1 to 2 days after treatment, and had no effect on the x hydroxylase activity or the position of the absorption maximum of the CO difference spectrum of cytochrome P-450. This is phenobarbital like inductive behavior. The animals treated with 1 mg/kg body weight of 3, 4, 3’, 4’-tetrachlorobiphenyl showed a 3-methylcholanthrene type inductive profile. The hydroxylase activity was significantly increased and peaked at 2 days after treatment. The demethylase activity was not changed. The position of the cytochrome P-450 difference spectrum absorption maximum was shifted to 448 nm. The control animals received just the acetone / corn oil vehicle and showed no changes in any of the biochemical activities measured in the course of this experiment. This data supports the structure activity relationships, established in rats, for chlorobiphenyls as inducers of hepatic microsomal enzyme activity in rhesus monkeys.

The effects of prenatal PCBs on female reproduction: development, behavior, and gene expression

Steinberg, Rebecca Meg, 1977- 28 August 2008 (has links)
Polychlorinated biphenyls (PCBs) are a class of bioactive chemical once used in industrial applications, but which now contaminate the world environment. PCBs are lipophilic with few natural degadatory mechanisms, and thus they accumulate in human and animal tissues, and are passed to subsequent generations via transfer between mother and offspring. Research has shown that PCBs can interfere with brain and sexual organ development, and adult sexual behaviors and reproduction. However, previous studies produced contradictory results based on the dose and method of administration, species, and the age at exposure. The research detailed in this thesis elucidates the effects of prenatal exposure to low levels of a commercial mixture of PCBs, Aroclor (A) 1221, on female reproductive function. The studies undertaken in this dissertation focus on three areas relevant to understanding long-term effects of PCBs on reproductive physiology in female rats: (1) developmental effects in two generations, (2) sexual behaviors in the first generation, and (3) gene expression in the first generation. In the first research section of this dissertation, the sexual and somatic development of PCB-exposed animals is investigated in first (F1) and second (F2) generation females. Dose-dependent effects are observed in both generations, and a greater number of endpoints are significantly affected in the F2, including circulating hormone levels and uterine and ovarian weight. The second research section of the dissertation explores whether sexual behaviors in the first generation of exposed animals are altered by A1221, using a paced mating paradigm designed to elucidate female-typical behaviors. Several salient behaviors are affected by PCB exposure, including likelihood to mate, mating trial pacing, and stress-related vocalizations. The third research chapter discusses the results of a genomewide microarray assay performed on the preoptic area of the brain. The preoptic area is a neuroendocrine control center implicated in regulation of reproductive physiology and behavior. Taken together, these results suggest that A1221 has long lasting and trans-generational effects on the development and behavior of exposed females, accompanied by altered gene expression in a neuroendocrine region of the brain. These findings have implications for female reproductive health and reproductive success in wildlife and humans.

Dechlorination of 3, 3’, 4, 4’ – tetrachlorobiphenyl (PCB77) in water, by nickel/iron nanoparticles immobilized on L-lysine/PAA/PVDF membrane

03 November 2014 (has links)
M.Sc. (Chemistry) / Zero-valent nanoscale metal, especially iron nanoparticles have attracted significant attention with regards to remediation of organochlorinated compounds in drinking water. For a more rapid and complete dechlorination, a second and usually electronegative element is often added, resulting in the formationof bimetallic nanoparticles. However, in the absence of surfactants,the bimetallic nanoparticles easily aggregate into large particles (if they are not anchored on solid supports) with wide size distributions, thus losing their reactivity. This work reports an in-situ synthesis method of bimetallic nanoparticles immobilized on L-lysine functionalized microfiltration membranes by chemical reduction of metal ions chelated by amine and hydroxyl functional groups of L-lysine on the composite. The immobilization of the nanoparticles on membranes offers many advantages: reduction of particle loss, prevention of particle agglomeration and application under convective flow. The objective of this research wasto produce catalytic filtration membranes for dechlorination of organic compound, PCB-77. This was achieved first by (i) the modification of commercial PVDF to introduce functional groups that render the membrane more hydrophilic and have the ability to capture metal ions through chelation, and secondly (ii) the controlled introduction of catalytic nanoparticles onto the composite membrane surface, anchored through chelation to the surface functional groups. This approach was selected with aview to produce uniform surface distribution of monodispersed bimetallic nanoparticles that are resistant to leaching during the reduction reactions. The modification of the PVDF membrane was achieved by firstly performing an in situ polymerization of acrylic acid followed by covalently bonded L-lysine to the polymerized acrylic acid chains using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC). The Fe ions were introduced to the composite by L-lysine chelation and subsequently reduced to Fe0 with NaBH4, and finally deposition of Ni2+ which later were also reduced to Ni0 with NaBH4. The Fe/Ni bimetallic NPs system was chosen based on its proven ability for the total dechlorination of chlorinated organic compounds. Systematic characterization of the composite was performed using ATR-FTIR, FESEM, EDS, HRTEM, XRD, AFM and Contact Angle measurements. A relatively uniform distribution of Fe/Ni nanoparticles was found in L-lysine/PAA/PVDF membrane. The diameter of Fe/Ni nanoparticles was predominantly within the range 20-30 nm. Furthermore, the mechanism of the catalytic dechlorination of the model compound, PCB 77, was investigated by careful analysis of the reaction products. It is generally known that zero-valent iron undergoes corrosion to provide hydrogen atoms and electrons for the reductive catalytic hydrodechlorination reaction. The second metal in the bimetallic system on the other hand, acts as...

Analysis of polychlorinated biphenyls in transformer oils

Phillips, Lyndal, University of Western Sydney, College of Science, Technology and Environment, School of Science, Food and Horticulture January 2002 (has links)
Polychlorinated Biphenyls (PCBs) were seen as a significant engineering advance when first commercially produced in 1929. They were used as insulators and cooling fluids in electrical transformers and capacitors. There are 209 PCB congenors that are chemically and thermally stable with low inflammability and reactivity. However,they are also highly toxic, suspected carcinogens and bioaccumulate in the food chain. Due to these characteristics they are listed by the United Nations as one of the sixteen worlds persistent organic pollutants POPs). By international agreement, undertaken by the UN, the production of PCBs has been banned and gradually their use will be phased out. Several tests and procedures are discussed in some detail in this research. / Master of Science (Hons)

Reductive, dechlorination of sediment-sorbed polychlorinated biphenyls by vitamin B������(subscript s)

Trobaugh, Darin James 01 July 1998 (has links)
The reductive dechlorination of chlorobiphenyls in sediment by titanium(III) citrate-reduced vitamin Bus was studied in batch reactors. Long term ampoule studies demonstrated reductive dechlorination of sediment-sorbed 2,3,4,5,6-pentachlorobiphenyl (2,3,4,5,6-PeCB) to tetra-, tri-, di-, and monochlorobiphenyl products. Over 50% chlorine removal was observed over 160 days. The results of the ampoule experiment were compared to previous experiments with aqueous PCBs, and both systems appeared to follow the same pathway. Theoretical product distributions based on free energies of formation were compared to product distributions for the ampoule experiments, and both aqueous and sediment-sorbed PCB reductive dechlorination followed the thermodynamically favored pathway. Although chlorines were removed from all positions, reductive dechlorination was generally preferred at the ortho position. / Graduation date: 1999

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