In this thesis we demonstrate the algorithmic usefulness of the so-called Mal'cev correspondence for computations with infinite polycyclic groups. This correspondence between Q-powered nilpotent groups and rational nilpotent Lie algebras was discovered by Anatoly Mal'cev in 1951. We show how the Mal'cev correspondence can be realized on a computer. We explore two possibilities for this purpose and compare them: the first one uses matrix embeddings and the second the Baker-Campbell-Hausdorff formula. Then, we describe a new collection algorithm for polycyclically presented groups, which we call Mal'cev collection. Algorithms for collection lie at the heart of most methods dealing with polycyclically presented groups. The current state of the art is "collection from the left" as recently studied by Gebhardt, Leedham-Green/Soicher and Vaughan-Lee. Mal'cev collection is in some cases dramatically faster than collection from the left, while using less memory. Further, we explore how the Mal'cev correspondence can be used to describe symbolically the collection process in polycyclically presented groups. In particular, we describe an algorithm that computes the collection functions for splittable polycyclic groups. This algorithm is based on work by du Sautoy. We apply it to the computation of pro-p-completions of polycyclic groups. Finally we describe a practical algorithm for testing polycyclicity of finitely generated rational matrix groups. Previously, not only did no such method exist but it was not clear whether this question was decidable at all. Most of the methods described in this thesis are implemented in the computer algebra system GAP and publicly available as part of the GAP packages Guarana and Polenta. Reports on the implementation including runtimes for some examples are given at the appropriate places.

Chronically contaminated killifish from Newark Bay (NB) NJ, and New Bedford Harbor (NBH) MA, have developed resistance to halogenated aromatic hydrocarbons that bind to and activate the aryl hydrocarbon receptor (AHR). To study the mechanisms of resistance, adult killifish were exposed to halogenated and non-halogenated AHR ligands and enzymatic and toxicological endpoints were measured in adult and embryonic fish. The chlorinated and non-chlorinated AHR ligands 3,34,4-tetrachlorobiphenyl (PCB77) and benzo-a-pyrene (B[a]P) induced cytochrome P450 1A (CYP1A) in reference site, but not in NB killifish. Expression of CYP3A (not part of the AHR gene battery) was inducible only in Flax Pond killifish. Basal expression of the phase II enzyme glutathione-s-transferase (GST) was higher in NB killifish. These results suggest that NB killifish are resistant to CYP1A induction by chlorinated and non-chlorinated AHR ligands. Higher basal GST activity observed in NB killifish could be protective against toxicity caused by contaminants found in this site. Activation of AHR and induction of CYP1A, by AHR ligands has been associated with the toxic effects caused by these chemicals. To determine the association between resistance to CYP1A induction and the toxicity caused by AHR ligands, CYP1A activity, developmental deformities and reactive oxygen species (ROS) production were measured in reference site and contaminated (NB and NBH) killifish embryos exposed to AHR ligands. 3,34,45-pentachlorobiphenyl (PCB126) and 3-methylcholantherene (3-MC) induced CYP1A, and ROS production in reference site embryos. NB and NBH embryos were resistant to PCB126 induction of CYP1A, but responded to 3-MC. Killifish embryos from NB and NBH were resistant to PCB126 induced deformities. PCB126 and 3-MC did not increase ROS production in NB or NBH killifish embryos. Alpha-naphthoflavone (ANF) (an AHR/CYP1A inhibitor) blocked PCB126 mediated deformities and CYP1A induction in reference site embryos, but increased ROS production. The P450 inhibitor, piperonyl butoxide (PBO) was able to block PCB126 mediated induction of CYP1A activity and ROS production. These results suggest that PCB126 induced deformities are dependent on activation of AHR and CYP1A induction. In chronically contaminated killifish populations, loss of sensitivity to coplanar PCBs and PAHs could be through reduced expression of AHR, or altered DNA sequence or methylation status of the CYP1A gene promoter. Hepatic AHR expression, measured by photoaffinity labeling, was lower in NB killifish than reference site animals, suggesting that NB killifish express less AHR protein. DNA sequence analysis did not reveal considerable differences between contaminated and reference site populations, however additional DNA fragments were observed in some promoters but not in others. The methylation of the CYP1A promoters was studied using methylation sensitive restriction enzymes and no differences were detected between reference site and NB killifish. Treatment with the DNA methyltransferase inhibitor AzaC did not restore CYP1A induction by PCB126 in NB killifish. These studies suggest that resistance to activation of AHR and induction of xenobiotic activating enzymes (CYP1A and CYP3A) in combination with increased expression of conjugating enzymes (GST) protects chronically contaminated killifish against these chemicals.

Dimethylbenz (a) anthracene (EMBA), a carcinogen that requires metabolic activation to produce active metabolites capable of binding to DNA, has been studied in the trout and other fish. Polycyclic aromatic hydrocarbons (PAH) are of importance as they are ubiquitous in the environment and their carcinogenic effects in fish from contaminated waters are an important indication of the pollution risks to man. Since such pollution risk assessment presents the involvement of multiple agents, the study of the modulation of PAH-DNA binding produced by other agents is important. In this study the effect, of dietary pretreatment at 500 ppm, 100 ppm and 2000 ppn, using BNF, Aroclor 1254, or indole-3-carbinol (I3C) respectively on DMBA-DNA binding was examined. To study the effect of age on sensitivity to DMBA-DNA binding, adult trout and fry were used in two separate studies. The fish were fed treatment diet for at least two weeks. Fry were then injected with [³H] DMBA, at 22.4 μCi/3.9 x 10⁻² μmole/fish and adult trout at 284 μCi/1.58 μmole/fish. Liver DNA was isolated, purified and binding of radioactivity to DNA was examined and computed as the covalent binding index (CBI). Mean CBI for control dietary group vising adult trout was 1000 fold lower than for fry. Statistical analysis of covalent binding index for the treatment groups revealed that a statistically significant (p < 0.05) inhibition in DNA-DMBA binding response in adult trout and fry was produced fcy the DNF dietary treatment only. Diethylnitrosamine (DENA), a potent hepatocarcinogen in several animal species belongs also to the class of compounds that require metabolic activation. Dietary treatment and continuous exposure of trout to the carcinogen in water, have produced hepatocellular carcinctnas. The water exposure also produced a dose related DNA ethylation of the O⁶ position of guanine, believed to be the promutagenic adduct produced after DENA exposure. This study examines two other routes of exposure to DENA, in vitro hepatocyte incubations and i.p. injection. Adult trout and fry were injected with [³H] DENA. Adult fish received 3.3, 16.5, and 33 mg/kg DENA, and fry received 10, 50 and 100 mg/kg. Hepatocyte incubation was performed with doses up to 220 μM [³H] DENA, or 1 mM unlabelled DENA. DNA from fish livers and from hepatocyte pellets was isolated, purified and examined for radioactive binding of the DENA metabolites or in the case of the unlabelled DENA, was analyzed for O⁶ and N7 adduct using an HPIC technique with fluorescence detection. O⁶-EtG adduct after DENA exposure, in DNA of hepatocytes obtained from trout pretreated with beta-naphthoflavone (BNF, a known inducer of cytodhrcme P-450 dependent enzyme activities involved in the activation of xenobiotics) was below the limits of detection of the HPDC-fluorescenoe detection procedure used. To examine further if the lack of DNA binding and absence of the O⁶-EtG adduct was due to rapid repair, the persistence of O⁶-EtG after exposure to 40 nM ethylnitrosourea (ENU, a direct ethylating agent) was studied in hepatocytes at 2, 4, and 5 hours after treatment. The activity of the alkyltransferase protein involved in the repair of alkylguanines also was determined using liver extracts from adult rainbow trout. The studies did not reveal a significantly high rate of repair. It is concluded that i.p. injection and in vitro hepatocyte incubations are not a good method for studying the kinetics of activation and DNA binding of DENA in the rainbow trout. The i.p. route may lead to substantial loss of the dose of the carcinogen administered and hepatocyte incubations are limited by the toxic effects of increasing carcinogen concentration. The reasons mentioned above, coupled with low levels of metabolism of nitrosamines in trout results in the inability to detect and study the appearance, persistence and repair of the O⁶-EtG adduct. / Graduation date: 1989

The persistance of industrially derived polycyclic aromatic hydrocarbons in the subsurface may be significantly affected by the metabolism of soil bacteria. This study was conducted to determine the ability of indigenous soil bacteria to decrease the concentration of four polycyclic aromatic hydrocarbons (naphthalene, fluorene, anthracene, and pyrene) and to utilize the compounds as a substrate for growth. Soil cores from petroleum contaminated and non-contaminated sites contained 10⁵ - 10⁷ viable microorganisms per gram dry weight of soil. Gram negative rod-shaped bacteria predominated. Decreases in the concentration of the four polycyclic aromatic hydrocarbons were observed during incubation with bacterial isolates in aqueous suspension by the use of high performance liquid chromatography. Corresponding increases in bacterial numbers indicated utilization of the compounds as a carbon source. Soil samples from the contaminated sites contained greater numbers of bacteria utilizing anthracene and pyrene than soil samples from non-contaminated sites. Degradation rates of the four polycyclic aromatic hydrocarbons were related to the compound, its concentration, and the bacterium. Biodegradation of pyrene was positively correlated with the presence of oxygen. Pyrene was biodegraded by an Acinetobacter sp. under aerobic conditions but not under anaerobic or microaerophilic conditions. Studies with radiolabeled ¹⁴C-anthracene demonstrated utilization of the labeled carbon as a source of carbon by viable bacterial cells in aqueous suspension. Incorporation of ¹⁴C into cellular biomass however was not observed during incubation of ¹⁴C-anthracene in soil.

No description available.

The environmental fate of polycyclic aromatic hydrocarbons (PAH) is a significant issue, raising interest in bioremediation. However, the physio-chemical characteristics of PAHs and the physical, chemical, and biological properties of soils can drastically influence in the degradation. Moreover, PAHs are toxic and carcinogenic for humans and their rapid degradation is of great importance. The process of degradation of pollutants can be enhanced by manipulating abiotic factors. The effect of soil pH on degradation of PAHs with a view to manipulating soil pH to enhance the bioremediation of PAH’s was studied. The degradation rate of key model PAHs (Phenanthrene, Anthracene, Fluoranthene, and Pyrene) was monitored in J Arthur Brower’s topsoil modified to a range of pH between pH 4.0 and pH 9.0 at half pH intervals. Photo-catalytic oxidation of PAHs in the presence of a catalyst (TiO2) under UV light at two different wavelengths was studied. The degradation of PAHs during photo-catalytic oxidation was carried out at varying soil pH, whilst the degradation rate of each individual PAH was monitored using HPLC. It was observed that pH 6.5 was most suitable for the photo-degradation of all the PAHs, whilst in general acidic soil had greater photo-degradation rates than alkaline soil pH. Photo-degradation of PAHs at 375 nm exhibited greater degradation rates compared to 254 nm. Phenanthrene at both the wavelengths had greater degradation rate and pyrene has lower degradation rate of the four PAHs. Pure microbial cultures were isolated from road-side soil by shaken enrichment culture and characterized for their ability to grow on PAHs. Bacterial PAH degraders, isolated via enrichment were identified biochemically and by molecular techniques using PCR amplification and sequencing of 16S rDNA. Sequences were analyzed using BLAST (NCBI) and their percentage identity to known bacterial rDNA sequences in the GeneBank database (NCBI) was compared. The 6 bacterial strains were identified as Pseudomonas putida, Achromobacter xylosoxidans, Microbacterium sp., Alpha proteobacterium, Brevundimonas sp., Bradyrhizobium sp. Similarly, fungal PAH degraders were identified microscopically and with molecular techniques using PCR amplification and sequencing of 18S rDNA and identified as Aspergillus niger and Penicillium freii. Biodegradation of four PAHs with two and four aromatic rings were studied in soil with inoculation of the six identified bacteria and two identified fungi over a range of pH. It was observed that pH 7.5 was most suitable for the degradation of all the PAHs maintained in the dark. A degradation of 50% was observed in soil pH 7.5 within first three days which was a seventh of the time taken at pH 5.0 and pH 6.5 (21 days). Greater fungal populations were found at acidic soil pH and alkaline soil pH, in comparison with neutral pH 7.0. Pencillium sp. was found to be more prevalent at acidic pH whilst Aspergillus sp. was found to be more prevalent at pH 7.5-8.0. Bacterial populations were greater at pH 7.5 which was highly correlated with soil ATP levels. It was therefore evident that the greatest rates of degradation were associated with the greatest bacterial population. Soil enzyme activities in general were also greatest at pH 7.5. The converse effect of pH was found with fastest rate of photo-catalytic degradation at the optimal conditions were observed at acidic condition in soil pH 6.5 whilst, the results obtained during biodegradation at the optimal conditions exhibits fastest rate of degradation at alkaline conditions particularly at pH 7.5. Thus, manipulation of soil pH to 7.5 has significant potential to dramatically increase the degradation rate of PAHs.

Detection, identification and separation of polycyclic aromatic compounds in environmental samples are of extreme importance since many of these compounds are well known for their potential carcinogenic and/or mutagenic activities. Selective quenching of molecular fluorescence can be utilized effectively to analyze mixtures containing different polycyclic aromatic hydrocarbons. Molecularly organized assemblies are used widely in detection and separation of these compounds mainly because of less toxicity and enhanced solubilization capabilities associated with these media. Feasibility of using nitromethane and the alkylpyridinium cation as selective fluorescence quenching agents for discriminating between alternant versus nonalternant polycyclic aromatic hydrocarbons (PAHs) is critically examined in several molecularly organized micellar solvent media. Fluorescence quenching is used to probe the structural features in mixed micelles containing the various combinations of anionic, cationic, nonionic and zwitterionic surfactants. Experimental results provide valuable information regarding molecular interactions between the dissimilar surfactants.

The objective of this study was to explore intramolecular ketene cycloadditions with the anticipated results of developing new synthetic methodology for the synthesis of polycyclic compounds difficult to obtain by other procedures. (o-Alkenylphenoxy)ketenes were initially selected for this study because these ketenes provided a favorable proximity for the intramolecular [2+2] cycloaddition reactions. The difunctional precursors, (o-alkenylphenoxy)- acetic acids, were readily prepared from o-alkenylphenols and ∝-halocarboxylic acids and were converted to the corresponding acid chlorides by reaction with oxalyl chloride. The acid chlorides were dehydrochlorinated to the corresponding (o-alkenylphenoxy)ketenes by treatment with triethylamine. The ketenes undergo a facile intramolecular [2+2] cycloaddition to give polycyclic eye 1obutanones. The (o-vinylphenoxy)ketenes are clearly more reactive than the (o-allylphenoxy)ketenes and provide much better yields of the cycloaddition products because of electronic effects in the transition state in the cycloaddition process. The intramolecular [2+2] cycloadditions of keteniminium salts were included in this study as a more electrophilic alternative to ketenes that will react with less nucleophilic carbon-carbon double bonds. However, the use of keteniminium salts instead of ketenes in Intramolecular cycloadditions does have some limitations. The synthesis of benzofurans via the intramolecular [2+2] cycloadditions of (o-acylphenoxy)ketenes was accomplished. The initially formed ß-lactone cycloaddition products spontaneously underwent decarboxylation to the benzofurans. The aromaticity of the benzofurans is apparently a very strong driving force for the cycloaddition. During the course of this study, two new synthetic methods were discovered which in many instances represent a significant Improvement over existing methods. The Wittig Reactions of ketoacids without protecting the carboxyl groups provide a reliable source of the precursor unsaturated acids needed for intramolecular ketene-olefin cycloadditions. Also, the one-pot preparation of intramolecular ketene cycloaddition products from the carboxylic acid via the tosylate represents a new synthetic method. This procedure eliminates the acid halide preparation, isolation and purification step, thereby significantly simplifying the synthesis.

Appendices data can be found at: A: http://dx.doi.org/10.15142/T35P49 B: http://dx.doi.org/10.15142/T3201B C: http://dx.doi.org/10.15142/T3X59V D: http://dx.doi.org/10.15142/T3SG6K F: http://dx.doi.org/10.15142/T3NP4N

Le Bassin d’Arcachon est une lagune très riche écologiquement et suscite un attrait touristique et ostréicole important. Cette pression anthropique a soulevé ces dernières années des questions sociétales quant à sa qualité environnementale. Ainsi, ancrés dans des projets soutenus par les acteurs locaux (Région Aquitaine, Syndicat Intercommunal du Bassin d’Arcachon, Conseil général de la Gironde), ces travaux de thèse ont permis de dresser un bilan de la qualité de ce système et de ses bassins versants relativement à l’introduction des hydrocarbures aromatiques polycycliques (substances prioritaires selon la directive cadre sur l’eau, UE, 2000). Ces polluants organiques sont présents dans les différents compartiments environnementaux suivis (sédiments, colonne d’eau) de la lagune, en concentrations élevées pour quelques sites et pouvant induire des effets toxiques chez le biota aquatique. Ils sont généralement présents dans les eaux et sédiments des tributaires à un niveau bruit de fond, mais des concentrations importantes ont été observées pour un ruisseau, ainsi que lors d’un évènement de tempête. Ils sont principalement issus des processus de combustion incomplète de matières organiques (gaz d’échappement, chauffage, feux de forêt) ; des apports terrigènes et diagénétiques de pérylène ont également pu être mis en évidence. Les transferts des HAP vers le biota benthique (huître), et leur bioaccumulation sont effectifs malgré des capacités de dépuration importante relativement à d’autres classes de composés organiques hydrophobes. Comme alerté par le réseau national d’observation coordonné par IFREMER, les teneurs dans les organismes augmentent depuis une dizaine d’année, et s’approchent aujourd’hui de la valeur guide AFSSA pour la consommation humaine. Outre l’aspect de qualité environnementale, ces résultats peuvent apporter des informations quant aux problématiques nationales actuelles de surveillance chimique des productions conchylicoles (DGAL, 2008 ; AFSSA, 2008). / Abstract