I studied selenium contamination at Cibola National Wildlife Refuge (Cibola NWR) in the lower Colorado River Valley, California and Arizona. My objectives were to: (1) determine whether local irrigation practices resulted in exposure of fish to toxic levels of selenium; (2) assess the risks to humans of consuming fish from Cibola NWR; (3) assess whether diversity and abundance of fish were related to selenium concentrations or other water quality variables. Water, sediment, fish, crayfish, and aquatic plants were collected from sites which received irrigation return flows and sites which did not. Selenium was below toxic levels at sites receiving irrigation return flows. Selenium was at the toxicity threshhold for fish at two sites receiving water directly from the Colorado River. Concentrations of selenium in fillets of largemouth bass (Micropterus salmoides) from one lake exceeded levels that elicit consumption advisories in California. Most people would be unlikely to consume toxic amounts of fish, but an advisory should be posted to inform people about potential risks. Gill nets were used to determine species diversity and abundance. There were no strong correlations between selenium levels and indices of species richness and equitability. There was a consistent inverse relationship between selenium levels and catch-per-unit-effort for all species combined. This inverse relationship suggested that selenium may be one of a suite of factors limiting abundance of fish. Correlations between indices of species diversity and abundance and values of water quality variables generally were not significant. Temperature and salinity may have limited abundance of some species seasonally. Increases in selenium levels at sites that are already at the toxicity threshhold could impair reproduction of sensitive species. Population declines and concern about edibility of fish could impair the recreational fishery. Therefore, site-specific ways to reduce selenium accumulation should be studied and implemented. Site-specific limnological conditions may play a role in accumulation of selenium to toxic levels, but major sources of selenium appear to be upstream in the Colorado River basin rather than local agricultural practices. Therefore, selenium input to the Colorado River from sources throughout the basin should be monitored and reduced where possible.

A series of Pt(S₂N₂)(P(OR)[subscript n]R′[subscript(3-n)])₂ complexes were prepared and analysed using ³¹P NMR and IR spectroscopy, elemental analysis and X-ray crystallography. Similarly, a series of Pt(SeSN₂)(P(OR)[subscript n]R′[subscript(3-n)])₂ complexes were also prepared and analysed. The ¹J[subscript(Pt-P)] coupling constants and Pt-P bond lengths for these complexes are influenced by the oxygen content of their phosphorus ligands. The ³¹P NMR spectra for a series of [Pt(S3N)(P(OR)[subscript n]R′[subscript(3-n)])₂][BF₄] complexes are also reported. Planar [S₂N₂H]⁻ complexes were prepared and the X-ray crystal structure of [Pd(S₂N₂H)(bipy)][Cl] is reported. The X-ray structures of MX₂(P(OR)[subscript n]R′[subscript(3-n)])₂ are reported and compared with the previously reported analogues. The magnitude of the ¹J[subscript(Pt-P)] varies linearly with the Pt-P bond length (l[subscript(Pt-P)] = 2.421 – J/24255) for the 12 platinum-containing complexes. This correlation is compared to that of a larger series of complexes. A series of M(ndsdsd₂ (ndsdsd = bis[(nitrilo(diphenyl)-λ⁶-sulfanyl)](diphenyl)-λ⁶-sulfanediimide (Ph₂S(=N-(Ph₂)S≡N)₂)) complexes were prepared and characterised using elemental analysis and multinuclear NMR and IR spectroscopy where appropriate. The X-ray crystal structures of five examples are reported.

<p>Coal fired power plants generate approximately 45% of the electricity produced in the United States every year, and each year, over 100 million tons of coal ash are produced as a by-product of electricity generation. Coal ash is a solid waste made up principally of bottom ash, fly ash, and flue gas desulfurization materials. The chemical composition of coal ash varies depending on the feed coal source, combustion parameters, and the presence and type of air pollution control devices that remove contaminants from the flue gas into the solid waste stream. Although a significant portion of coal ash waste is recycled, the majority of coal ash is disposed in landfills and holding ponds. Coal ash impoundments have a long history of environmental degradation, which includes: contaminant leaching into groundwater, the discharge of contaminant-laden effluent into surface waters, and catastrophic impoundment failures and ash spills. Despite these known problems, coal ash is not considered a hazardous waste, and thus is not subject to stringent disposal requirements. The current coal ash management system is based on risk assessments of coal ash that do not include environmental parameters that have a profound impact on coal ash contaminant mobility, particularly for the toxic elements such as mercury, arsenic, and selenium. This dissertation research focused on the biogeochemical transformations of mercury, arsenic, and selenium associated with coal ash materials in an effort to: (1) define the key environmental parameters controlling mercury, arsenic, and selenium fate during disposal and ash spills; and (2) delineate the relationship between coal ash characteristics, environmental parameters, and leaching potential. </p><p> The impact of coal ash on mercury transformations in anaerobic systems was assessed using anaerobic sediment-ash microcosms to mimic an ash spill into a benthic aquatic system. Anaerobic sediments are the primary zones for the microbial conversion of inorganic mercury to methyl mercury (MeHg), a process that is mediated by anaerobic bacteria, particularly sulfate reducing bacteria (SRB). MeHg is a potent neurotoxin that biomagnifies up the aquatic food chain, presenting a human health risk-- especially to children and pregnant women. The results of the sediment-ash microcosm experiments indicated negligible net production of MeHg in microcosms with no ash and in microcosms amended with the low-sulfate/low-Hg ash. In contrast, microcosms amended with sulfate and mercury-rich ash showed increases in MeHg concentrations that were two to three times greater than control microcosms without ash. The enhancement MeHg production in the microcosms was likely due to large quantities of leachable sulfate that stimulated the activity of methylating bacteria. Overall, these results highlight the importance of considering both the geochemical conditions of the receiving environment and the chemical composition of the coal ash in assessing the MeHg potential of coal ash. </p><p> The hypothesis that sulfate-rich coal ash can change sediment microbial communities, enhancing MeHg production, was tested by analyzing coal ash impacts on the SRB community in the sediment-ash microcosms using Terminal Restriction Fragment Length Polymorphism (T-RFLP), Quantitative Polymerase Chain Reaction (q-PCR), and Reverse Transcription-qPCR (RT-qPCR). Coal ash did not appear to cause significant changes to the structure of the overall bacterial community, though results showed that it may have caused a decrease in the evenness for species distribution for both SRB and the overall microbial community. During the five-day incubation experiment, the coal ash had a temporary significant effect on SRB abundance during the first one to two days of the experiment and a more sustained effect on SRB activity. This stimulation of SRB population growth and activity also corresponded with increasing net MeHg production. Overall, results indicate that coal ash amendments do not cause large shifts in the overall microbial community or the SRB community, but results indicate that there are connections between SRB abundance/activity and MeHg production. More research is needed to determine how coal ash directly impacts Hg methylating microorganisms, which include diverse array of microorganisms outside of SRB.</p><p> The effect of aerobic and anaerobic conditions on arsenic and selenium leaching from coal ash in an ash spill scenario was also assessed using sediment-ash microcosms. The fate of arsenic and selenium associated with coal ash is of particular concern due to the leachability of these elements at neutral pH and their tendency to bioaccumulate in aquatic organisms. Both the redox speciation of arsenic and selenium, and the pH of the aquatic system, are known to influence leaching into the environment, yet current environmental risk assessments of coal ash focus on pH alone as the primary driving force for arsenic and selenium leaching from coal ash and do not take into account the effects of anaerobic conditions and microbial activity. In this research, total dissolved concentrations of arsenic and selenium, dissolved speciation of arsenic, and solid phase speciation of selenium were monitored to determine the biogeochemical transformations and leaching of arsenic and selenium under differing redox conditions. The results from the sediment-ash microcosm studies showed that redox potential was the major determinant of arsenic and selenium mobility in the microcosm systems with greater arsenic leaching occurring in anaerobic microcosms and greater selenium leaching occurring in aerobic microcosms. Furthermore, the experiments provided clues to how coal ash influences the geochemistry of the benthic environment and how these influences affect the speciation and longer term solubility of arsenic and selenium. </p><p> Finally, experiments were conducted to determine how differing CaO, SO3, and Fe2O3 concentrations in coal ash affect the release of arsenic and selenium from sediment-ash mixtures in a simulated ash spill environment. Aerobic and anaerobic sediment-ash microcosms were constructed to mimic an ash spill into a benthic aquatic system, and a variety of coal ash materials were tested as amendments, including seven fly ashes, one lime-treated fly ash sample, and two FGD samples. Results showed that, in most cases, the sediment in the microcosm buffered the system at neutral, which counteracted leaching impacts of differing CaO and SO3 concentrations in the microcosms. Regardless of ash material, leaching of selenium was greater under aerobic conditions and was correlated with the total selenium content of the microcosm. Maximum leaching of arsenic occurred in anaerobic microcosms for some ash materials and in aerobic microcosms for other materials, suggesting that ash material chemistry played a significant role in controlling arsenic mobility. In both aerobic and anaerobic microcosms, dissolved arsenic concentration was correlated with total arsenic content of the ash material and in anaerobic microcosms, dissolved arsenic concentrations also correlated with the total iron content of the ash material. Overall, the results of these experiments showed that arsenic and selenium release under environmentally relevant conditions cannot be predicted by the CaO and SO3 content of the ash material. Rather, the total arsenic, total selenium content, and total iron content of the ash material are good predictors of the worst case environmental leaching scenario.</p><p> These investigations illuminated two major conclusions: (1) microbial activity and differing redox conditions are key in determining the impact of coal ash on the environment and in determining the mobility of coal ash contaminants, and (2) coal ash characteristics, such as sulfate and iron content, can change the redox chemistry and microbial activity of the surrounding environment, further influencing the fate of ash contaminants. This work will be useful in designing a framework that accurately predicts the leaching potential of ash contaminants under environmentally relevant conditions. The results will also be helpful in developing treatment technologies for ash impoundment effluent, guiding decisions on ash pond closure and remediation, and in designing long-term monitoring plans and remediation strategies for ash-impacted sites.</p> / Dissertation

<p>Selenium (Se) is a micronutrient necessary for the function of a variety of important enzymes; Se also exhibits a narrow range in concentrations between essentiality and toxicity. Oviparous vertebrates such as birds and fish are especially sensitive to Se toxicity, which causes reproductive impairment and defects in embryo development. Selenium occurs naturally in the Earth's crust, but it can be mobilized by a variety of anthropogenic activities, including agricultural practices, coal burning, and mining. </p><p>Mountaintop removal/valley fill (MTR/VF) coal mining is a form of surface mining found throughout central Appalachia in the United States that involves blasting off the tops of mountains to access underlying coal seams. Spoil rock from the mountain is placed into adjacent valleys, forming valley fills, which bury stream headwaters and negatively impact surface water quality. This research focused on the biological impacts of Se leached from MTR/VF coal mining operations located around the Mud River, West Virginia. </p><p>In order to assess the status of Se in a lotic (flowing) system such as the Mud River, surface water, insects, and fish samples including creek chub (Semotilus atromaculatus) and green sunfish (Lepomis cyanellus) were collected from a mining impacted site as well as from a reference site not impacted by mining. Analysis of samples from the mined site showed increased conductivity and Se in the surface waters compared to the reference site in addition to increased concentrations of Se in insects and fish. Histological analysis of mined site fish gills showed a lack of normal parasites, suggesting parasite populations may be disrupted due to poor water quality. X-ray absorption near edge spectroscopy techniques were used to determine the speciation of Se in insect and creek chub samples. Insects contained approximately 40-50% inorganic Se (selenate and selenite) and 50-60% organic Se (Se-methionine and Se-cystine) while fish tissues contained lower proportions of inorganic Se than insects, instead having higher proportions of organic Se in the forms of methyl-Se-cysteine, Se-cystine, and Se-methionine. </p><p>Otoliths, calcified inner ear structures, were also collected from Mud River creek chubs and green sunfish and analyzed for Se content using laser ablation inductively couple mass spectrometry (LA-ICP-MS). Significant differences were found between the two species of fish, based on the concentrations of otolith Se. Green sunfish otoliths from all sites contained background or low concentrations of otolith Se (< 1 µg/g) that were not significantly different between mined and unmined sites. In contrast creek chub otoliths from the historically mined site contained much higher (&#8805; 5 µg/g, up to approximately 68 µg/g) concentrations of Se than for the same species in the unmined site or for the green sunfish. Otolith Se concentrations were related to muscle Se concentrations for creek chubs (R2 = 0.54, p = 0.0002 for the last 20% of the otolith Se versus muscle Se) while no relationship was observed for green sunfish. </p><p>Additional experiments using biofilms grown in the Mud River showed increased Se in mined site biofilms compared to the reference site. When we fed fathead minnows (Pimephales promelas) on these biofilms in the laboratory they accumulated higher concentrations of Se in liver and ovary tissues compared to fathead minnows fed on reference site biofilms. No differences in Se accumulation were found in muscle from either treatment group. Biofilms were also centrifuged and separated into filamentous green algae and the remaining diatom fraction. The majority of Se was found in the diatom fraction with only about 1/3rd of total biofilm Se concentration present in the filamentous green algae fraction </p><p>Finally, zebrafish (Danio rerio) embryos were exposed to aqueous Se in the form of selenate, selenite, and L-selenomethionine in an attempt to determine if oxidative stress plays a role in selenium embryo toxicity. Selenate and selenite exposure did not induce embryo deformities (lordosis and craniofacial malformation). L-selenomethionine, however, induced significantly higher deformity rates at 100 µg/L compared to controls. Antioxidant rescue of L-selenomethionime induced deformities was attempted in embryos using N-acetylcysteine (NAC). Pretreatment with NAC significantly reduced deformities in the zebrafish embryos secondarily treated with L-selenomethionine, suggesting that oxidative stress may play a role in Se toxicity. Selenite exposure also induced a 6.6-fold increase in glutathione-S-transferase pi class 2 gene expression, which is involved in xenobiotic transformation. No changes in gene expression were observed for selenate or L-selenomethionine-exposed embryos.</p><p>The findings in this dissertation contribute to the understanding of how Se bioaccumulates in a lotic system and is transferred through a simulated foodweb in addition to further exploring oxidative stress as a potential mechanism for Se-induced embryo toxicity. Future studies should continue to pursue the role of oxidative stress and other mechanisms in Se toxicity and the biotransformation of Se in aquatic ecosystems.</p> / Dissertation

This thesis is concerned with the synthesis and evaluation of various tellurium-based chain-breaking antioxidants. The purpose is to find novel regenerable compounds with improved radical-trapping capacity. In the first part of this work, we explore the possibilities to incorporate tellurium into tocopherols and aromatic amines. Overall, tocopherols carrying alkyltelluro groups are better radical-trapping agents than the corresponding sulfur- and selenium analogues. Among them, 7-octyltelluro δ-tocopherol showed a ca. 17-fold higher reactivity than recorded for α-tocopherol and much better regenerability. Even longer inhibition times were recorded for the corresponding bis(tocopheryl) tellurides. In the aromatic amine series, diphenyl amines carrying alkyltelluro groups were shown to function as efficient radical-quenchers capable of inhibiting peroxidation for 460 min in the presence of N-acetylcysteine. Thiol-consumption experiments suggested that the long inhibition times are due to efficient quenching of in-situ formed alkoxyl radicals in a solvent cage. In the second part of the thesis, we study how the antioxidant properties are affected by variations in the electron density at tellurium and the number of alkyltelluro substituents in the molecule. Evaluation of a series of aryltelluro phenols carrying electron donating and electron withdrawing groups in the para-position of the aryl moiety suggested that a high electron density at the heteroatom prolonged the inhibition time. Among alkyltelluro phenols, alkyltelluro resorcinols and bis(alkyltelluro) phenols, phenols carrying alkyltelluro groups in both ortho positions were superior when it comes to radical-trapping activity and regenerability.

Context: This thesis deals with the robustness testing of web applications on a different web browser using a Selenium WebDriver to automate the browser. To increase the efficiency of this automation testing, we are using a robustness method. Robustness method is a process of testing the behaviour of a system implementation under exceptional execution conditions to check if it still fulfils some robustness requirements. These robustness tests often apply random algorithms to select the actions to be executed on web applications. The search-based technique was used to automatically generate effective test cases, consisting of initial conditions and fault sequences. The success criteria in most cases: "if it does not crash or hang application, then it is robust". Problem: Software testing consumes a lot of time, labour-intensive to write test cases and expensive in a software development life cycle. There was always a need for software testing to decrease the testing time. Manual testing requires a lot of effort and hard work if we measure in terms of person per month [1]. To overcome this problem, we are using a search-based approach for robustness testing of web applications which can dramatically reduce the human effort, time and the costs related to testing. Objective: The purpose of this thesis is to develop an automated approach to carry out robustness testing of web applications focusing on revealing defects related to a sequence of events triggered by a web system. To do so, we will employ search-based techniques (e.g., NSGA-II algorithm [1]). The main focus is on Ericsson Digital BSS systems, with a special focus on robustness testing. The main purpose of this master thesis is to investigate how automated robustness testing can be done so that the effort of keeping the tests up to date is minimized when the functionality of the application changes. This kind of automation testing is well depended on the structure of the product being tested. In this thesis, the test object was structured in a way, which made the testing method simple for fault revelation and less time-consuming. Method: For this approach, a meta-heuristic search-based genetic algorithm is used to make efficiency for robustness testing of the web application. In order to evaluate the effectiveness of this proposed approach, the experimental procedure is adapted. For this, an experimental testbed is set up. The effectiveness of the proposed approach is measured by two objectives: Fault revelation, Test sequence length. The effectiveness is also measured by evaluating the feasible cost-effective output test cases. i Results:The results we collected from our approach shows that by reducing the test sequence length we can reduce the time consuming and by using the NSGA-2 algorithm we found as many faults as we can when we tested on web applications in Ericsson. Conclusion: The attempt of testing of web applications, was partly succeeded. This kind of robustness testing in our approach was strongly depended on the algorithm we are using. We can conclude that by using these two objectives, we can reduce the cost of testing and time consuming.

O objetivo deste estudo clínico randomizado duplo-cego foi avaliar o efeito da suplementação oral de zinco e selênio concomitante ao tratamento com rosuvastatina sobre os marcadores de estresse oxidativo e inflamação, bem como o status de zinco e selênio, em pacientes com aterosclerose, apresentando angina estável. A amostragem foi composta por adultos e idosos, 47 homens e 29 mulheres, com diagnóstico de aterosclerose coronariana por angiografia, atendidos no Serviço de Hemodinâmica do Natal Hospital Center - Natal / RN. O projeto foi aprovado pelos Comitês de Ética em Pesquisa da UFRN e da FCF-USP. A coleta de dados foi realizada no primeiro momento e após 4 meses do tratamento com rosuvastatina 10 mg, concomitante à suplementação com zinco (30mg/d) e selênio (150&#181;g/d), ou placebo, sendo avaliados os parâmetros antropométricos e dietéticos, zinco e selênio plasmáticos e eritrocitários, perfil lipídico, LDL minimamente oxidada, anticorpos anti-LDL(-), imunocomplexos Ac-LDL(-), GPx, SOD, IL-6 e PCR-as. Houve predominância do gênero masculino, idade média em torno de 60 anos, ex-fumantes, portadores de hipertensão arterial, alta freqüência do sobrepeso/obesidade e circunferência abdominal aumentada/muito aumentada. As dietas caracterizaram-se como hipocalórica, hiperprotéica, normoglicídica e hipolípídica, com baixo teor de fibra e altas prevalências de inadequação de ingestão de zinco e selênio. O status de zinco e selênio no plasma e eritrócitos não foi alterado significativamente nos grupos placebo e suplementado entre os dois momentos do estudo. A terapia com a rosuvastatina mostrou-se eficaz na redução das concentrações de colesterol total, LDL, colesterol não-HDL, triacilgliceróis e PCR-as, independente da suplementação com os minerais zinco e selênio. As concentrações de LDL(-), Ac anti-LDL(-), imunocomplexos, IL-6 e as atividades das enzimas SOD e GPx não foram modificadas em função das intervenções com rosuvastatina associadas ou não à suplementação. Conclui-se que o tratamento com rosuvastatina 10mg durante 4 meses não alterou o status de zinco e selênio considerando os biomarcadores avaliados. A suplementação de zinco e selênio não influenciou os biomarcadores de estresse oxidativo e inflamação. Estudos adicionais serão necessários para avaliação da necessidade de suplementação neste grupo de pacientes com aterosclerose, analisando-se outras doses, tempo de suplementação e biodisponibilidade da forma química dos minerais prescritos. / The aim of this randomized double-blind study was to evaluate the effect of oral zinc and selenium supplementation, concomitant with rosuvastatin treatment, on markers of oxidative stress and inflammation, as well as the status of zinc and selenium in adult patients with atherosclerosis and stable angina. The study included 47 men and 29 women, average age around 60 years, with coronary atherosclerosis diagnosed by angiography at the Hemodynamic Service at Natal Hospital Center - Natal / RN. The project was approved by the Ethics Committee of UFRN and FCF-USP. Data from patients were obtained at beggining and after four months of treatment with 10 mg rosuvastatin, concomitantly with zinc (30mg/d) and selenium (150&#181;g/d) supplementation or placebo. The anthropometric and dietary data, zinc and selenium concentrations in plasma and erythrocyte, lipid profile, electronegative LDL (LDL(-)), anti- electronegative LDL, Ac-LDL(-) immune complexes, GPx and SOD activities, IL-6 and hs-CRP were evaluated in all patients. Most patients were former smokers with arterial hypertension, high rate of overweight/obesity and increased waist circumference. The diets contained low-calorie, hyperproteic, normoglycidic, low-fat and fiber content and inadequate intake of zinc and selenium. The status of zinc and selenium in plasma and erythrocytes was not changed significantly in the supplemented and placebo groups between the two moments of the study. Rosuvastatin therapy was effective in reducing total cholesterol, LDL, non-HDL cholesterol, triglycerides and hs-CRP level, regardless of supplementation with the minerals zinc and selenium. The concentrations of LDL (-), anti- LDL (-), immune complexes, IL-6 and the activities of SOD and GPx were not modified by zinc and selenium supplementation associated with rosuvastatin. In conclusion, the treatment with 10 mg rosuvastatin for 4 months did not change either the status of zinc and selenium or the biomarkers evaluated in this study. Zinc and selenium supplementation did not affect oxidative stress and inflammation biomarkers. Additional studies are needed to evaluate the need for antioxidant minerals supplementation in patients with atherosclerosis, mainly to investigate other doses, duration of supplementation and bioavailability of the chemical form of the prescribed minerals.

A química do selênio é um assunto de crescente interesse devido a sua presença em diversos ambientes químicos, em particular, na atmosfera terrestre. A ausência de estudos sobre espécies relativamente simples contendo 2-4 átomos motivou este projeto, que se concentrou na investigação teórica rigorosa de uma serie de espécies moleculares: SeF, SeCl, SeBr, HSeF, HFSe, HSeCl, HClSe, HSeBr, HBrSe e de vários isômeros na superfície de energia potencial 1[H, S, Se, Cl]. Propriedades espectroscópicas de um conjunto de estados eletrônicos e o calor de formação das moléculas SeF, SeCl e SeBr foram determinados. Juntamente com os novos resultados desta investigação, sugerimos uma revisão e correção de alguns dados teóricos e experimentais da literatura. Aspectos energéticos, estruturais e espectroscópicos associados aos pontos estacionários nas superfícies de energia potencial singleto [H, Se, X], X = F, Cl e Br, e [H, S, Se, Cl] também foram caracterizados, assim como determinados os calores de formação dos isômeros mais estáveis. Barreiras energéticas para os vários processos de isomerização foram estimadas bem como o gasto energético envolvido nas diferentes possibilidades de dissociação dos isômeros mais estáveis. No caso dos sistemas triatômicos ainda estimamos as constantes de velocidade para as reações de isomerizações direta e reversa. Nesse contexto, esperamos que este trabalho possa servir como uma referência para estudos teóricos e experimentais futuros desses sistemas e/ou de outros de complexidade idêntica. / The chemistry of selenium is a subject of increasing interest due to its presence in many chemical enviroments, specially in the Earth\'s atmosphere. The lack of studies of relatively simple species containing 2-4 atoms has motivated this project which was focused on a rigorous theoretical investigation of a series of molecular especies: SeF, SeCl, SeBr, HSeF, HFSe, HSeCl, HClSe, HSeBr, HBrSe, and the isomers on the 1[H, S, Se, Cl] potential energy surface. Spectroscopic properties of a set of electronic states and the heat of formation of SeF, SeCl, and SeBr were determined. Along with the new results from this investigation, we showed that some theoretical and experimental data reported in the literature be revised and corrected. Energetic, structural, and spectroscopic aspects associated with the stationary points on the singlet potential energy surfaces [H, Se, X], X = F, Cl e Br, and [H, S, Se, Cl] were also characterized, and the heats of formation of the most stable isomers evaluated. Energetic barriers for the various processes of isomerization were estimated, as well as the energy involved in the dierent possibilities of dissociation of the most stable isomers. In the case of triatomic systems, we still estimated the rate constants for the direct and reverse reactions. In this context, we expect that this work should serve as reference in future theoretical and experimental studies on these systems and/or others of similar complexity

Fatores dietéticos como o selênio (Se) são apontados como importantes moduladores do risco de desenvolvimento do câncer de mama. Essa neoplasia pode apresentar sua origem no início do desenvolvimento e, assim, a alimentação materna poderia ter importantes repercussões na programação fetal da doença. A fim de verificar se diferentes concentração de selênio na dieta materna poderiam programar o risco da progênie feminina ao câncer de mama, ratas foram alimentadas com ração contendo 0,15 (CO), 1,0 (SUP) ou 0,05 (DEF) ppm de Se durante a gestação e sua progênie feminina iniciada com DMBA. A progênie do grupo SUP apresentou menor suscetibilidade à carcinogênese, indicado pelo menor número médio e multiplicidade de adenocarcinomas mamários (p< 0,05), enquanto a do grupo DEF apresentou maior suscetibilidade à carcinogênese, indicado pela maior incidência dos mesmos (p< 0,05). Mães do grupo DEF apresentaram menor concentração de Se no sangue (p< 0,05) e sua prole apresentou menor atividade da enzima GPx1 (p< 0,05). Além disso, observou-se na glândula mamária da progênie de 50 dias menor expressão (western blot e qPCR) de ER&#945;, Her-2, EGFR e Ras no grupo SUP em comparação aos grupos CO e DEF (p< 0,05). Analisou-se, ainda, o padrão de metilação global do DNA (HPLC-DAD), expressão das enzimas DNMT1, 3a e 3b (qPCR), o padrão global de modificações pós traducionais em histonas (western blot) e o padrão de metilação da região promotora do gene Er&#945; (modificação com bissulfito e pirossequenciamento) na glândula mamária da progênie de 50 dias. Não houve diferença no padrão de metilação global do DNA e expressão das enzimas DNMTs (p>0,05). Houve aumento na expressão de H4K16 acetilada nos grupos SUP e DEF (p< 0,05). Finalmente, em comparação a progênie do grupo DEF, a do grupo SUP apresentou região promotora de Er&#945; com aumento marginal (p=0,07) na metilação de dois dinucleotídeos CpG. Conclui-se que o consumo de diferentes concentrações de Se na dieta materna tem impacto sobre a suscetibilidade da progênie ao câncer de mama na vida adulta através da modulação da expressão de receptores e oncogenes relacionados ao desenvolvimeto dessa neoplasia, além da influência em processos epigenéticos. Tais resultados apontam para a existência de uma \"janela de programação\" no início do desenvolvimento sensível a ação do Se, resultando em diminuição do risco de câncer de mama quando suplementado na dieta materna e o inverso quando de sua deficiencia. / Based on epidemiological studies and animal models, the essential micronutrient selenium has been highlighted as a promising dietary factor associated to breast cancer risk reduction. Breast cancer may have its origin in early development and thus the maternal diet could have important implications in the fetal programming of the disease. In order to ascertain whether differences in selenium concentration in maternal diet could modulate the susceptibility of female offspring to breast cancer, a biological assay was conducted in which female rats were fed a diet with 0.15 (CO), 1.0 (SUP) or 0.05 (DEF) ppm of selenium during gestational period and the female offspring subjected to a mammary carcinogenesis model induced by DMBA. SUP group offspring presented decreased susceptibility to mammary carcinogenesis, as indicated by lower (p< 0,05) average number and multiplicity od adenocarcinomas, while the DEF group offspring had a greater susceptibility, as indicated by the increase (p< 0,05) in adenocarcinomas incidency. Mothers of the DEF group pesented lower (p< 0,05) Se blood concetrations and their offspring presented lower (p<0,05).GPx1 activity. In addition, there was a decrease (p< 0,05) in ER&#945;, Her-2, EGFR and Ras expression (western blot and qPCR) in the mammary gland of 7 weeks old female SUP group offspring when compared to CO and DEF groups offspring. DNA global methylation pattern (HPLC-DAD), DNMT1, 3a e 3b expression (qPCR), global pattern of post-translational modification in histones (western blot) and methylation status of Er&#945; promoter region (bisulfite modification and pyrosequencing) were also evaluated in the mammary gland of 7 weeks old offspring. There was no diffrence (p>0,05) in DNA global methylation pattern and DNMTs expression. There was an increase in acetilated H4K16 expression in groups SUP and DEF (p< 0,05). Lastly, when compared to DEF offspring, the SUP offspring presented a marginal increase in the methylation of two CpG dinucleotides in the Er&#945; promoter region. In conclusion, the consumption of different selenium concentration in maternal diet plays a role in the progeny\'s breast cancer susceptibility through the modulation of receptors and oncogenes expression, in addition to modifications in epigenetic patterns. These results indicate the presence of a \"programming window\" in the beggining of development susceptible to selenium effects, resulting in decreased breast cancer risk when supplemented and the opposite when deficient.

Estudos apontam que a região Amazônica apresenta concentrações significativas de selênio nos solos e que, por isso, a população não estaria susceptível à deficiência desse mineral. Em contrapartida, a região também apresenta dados de concentrações elevadas de mercúrio nos solos e rios, entretanto, a população não apresenta sinais clínicos evidentes de contaminação. Acredita-se que o selênio, um mineral antioxidante, possa ser um possível colaborador para a aparente tolerância ao mercúrio, pois uma das ações desse mineral é a de destoxificar o organismo contra metais tóxicos. Dependendo das concentrações no organismo, o mercúrio pode potencializar a geração das espécies reativas de oxigênio e, dessa forma, as defesas antioxidantes intrínsecas das células podem ser prejudicadas, resultando na condição conhecida por estresse oxidativo. A contaminação por mercúrio pode, ainda, comprometer a saúde tanto das mulheres quanto das crianças, pois esse metal, na forma de metilmercúrio, pode atravessar a barreira placentária e se concentrar, principalmente, no cérebro do feto. Aliado a isso, a presença de polimorfismos em certos genes podem alterar a expressão de enzimas antioxidantes como a glutationa peroxidase 1, que é dependente de selênio, assim como da glutationa S-transferase, que atua na destoxificação do mercúrio no organismo. Vários estudos apresentam dados de concentrações de mercúrio em ribeirinhos da Amazônia, no entanto, resultados referentes às concentrações de selênio, ao estresse oxidativo e a polimorfismos genéticos na população da área urbana são raros. Diante disso, este estudo objetivou avaliar o estado nutricional relativo ao selênio, concentrações de mercúrio e a possível relação desses parâmetros com o estresse oxidativo e os polimorfimos Pro198Leu (rs 1050450) no gene da glutationa peroxidase 1 e GSTM1 no gene da glutationa S-transferase em mulheres em idade fértil residentes em área de risco de exposição ao mercúrio, da cidade de Porto Velho (RO). As voluntárias foram avaliadas por meio de medidas antropométricas (peso, estatura e circunferência da cintura) e aplicou-se o registro alimentar para avaliação do consumo alimentar. Realizou-se uma coleta de sangue para análise de selênio, atividade da enzima glutationa peroxidase, marcadores de estresse oxidativo e polimorfismos genéticos. O selênio foi determinado por espectrometria de absorção atômica com geração de hidretos acoplados à cela de quartzo (HGQTAAS). Para análise de mercúrio, foi coletada uma amostra do cabelo das voluntárias, sendo sua concentração determinada pelo método de espectrometria de absorção atômica com geração de vapor frio (CV AAS). Para avaliar o estresse oxidativo foram determinadas: a concentração plasmática de Malondialdeído (MDA) e a Capacidade de Absorção de Radicais de Oxigênio (ORAC). Participaram do estudo 200 mulheres com idade entre 19 e 50 anos. A ingestão alimentar média de selênio foi de 49,3 ± 19,2 &#181;g/dia e a prevalência de ingestão inadequada foi de 40,9%. As concentrações médias do mineral no plasma e nos eritrócitos foram, respectivamente, 49,8 + 18,6 &#181;g/L e 75,4 + 29,9 &#181;g/L. A atividade média da glutationa peroxidase foi de 45,1+ 19,4 U/g Hb. A concentração média de mercúrio nos cabelos foi de 625 + 766 ng g-1. Ao avaliar a presença do SNP Pro198Leu, observou-se que 56,7% das participantes apresentaram genótipo selvagem, 36,8% heterozigotos e 6,8% homoizgotos para leucina. Quanto ao polimorfismo de deleção GSTM1, 42,5% das voluntárias apresentaram o genótipo nulo ou deletado, ou seja, relacionado a ausência de expressão da glutationa S-transferase. Esses resultados permitem concluir que a maioria das participantes apresentou estado nutricional deficiente em relação ao selênio. Apesar disso, tanto a atividade enzimática da glutationa peroxidase, como os biomarcadores do estresse oxidativo não sofreram interferência desta deficiência. O polimorfismo Pro198Leu, também não interferiu no status de selênio e no estresse oxidativo. Quanto à avaliação do polimorfismo GSTM1, o genótipo nulo ou deletado também não mostrou associação com as concentrações de mercúrio e o estresse oxidativo. / Studies have shown that the Amazon region has significant concentrations of selenium in soils and therefore, the population is not susceptible to deficiency of this mineral. However, the region also presents data from high levels of mercury in soils and rivers, however, the population has no obvious clinical signs of contamination. It is believed that selenium, an antioxidant mineral may be a possible contributor to the apparent tolerance because of its actions in the detoxification of the body from toxic metals. Depending on the concentrations in the body, mercury can increase the generation of reactive oxygen species and thus the intrinsic antioxidant defenses of cells can be damaged, resulting in the condition known as oxidative stress. The mercury contamination may also compromise the health of both women and children, since this metal in the form of methylmercury can cross the placental barrier and concentrate mainly in the fetal brain. In addition, the presence of genetic polymorphisms can alter the expression of antioxidant enzymes such as glutathione peroxidase 1, which is selenium dependent, as well as glutathione S-transferase, which can be responsible for the mercury detoxification in the body. Several studies have shown mercury levels of riverine people from Amazon, however, results regarding selenium concentrations, oxidative stress and polymorphisms in the urban population are area. Thus, this study aimed to evaluate selenium status, mercury levels and the possible relationship of these with oxidative stress and genetic polymorphisms Pro198Leu (rs 1050450) in glutathione peroxidase 1 gene and GSTM1 in the glutathione S-transferase gene in women living in mercury exposure risk area, from the city of Porto Velho (RO). The of the volunteers was assessed using anthropometric measurements (weight, height and waist circumference) and evaluation of food consumption, by the food record. Blood samples were collected for selenium analysis, glutathione peroxidase enzyme\'s activity, oxidative stress and genetic polymorphisms. Selenium was determined by hydride generation quartz tube atomic absorption spectroscopy (HGQT AAS). For mercury analysis, a hair sample of volunteers was collected, and its concentration was determined by atomic absorption spectrometry method with cold vapor (CV AAS). To evaluate oxidative stress plasma concentrations of malondialdehyde (MDA) and Oxygen Radical Absorbance Capacity (ORAC) were determined We enrolled 200 volunteers aged between 19 and 50. The average of selenium intake was 49,3 ± 19,2 &#181;g/day and the prevalence of inadequate intake was 40,9%. Mean selenium concentration on plasma and erythrocytes were respectively 49,8 + 18,6 &#181;g/L and 75,4 + 29,9 &#181;g/L. Glutathione peroxidase showed mean activity of 45,1 + 19,4 U/g Hb and mercury levels of 625 + 766 ng g-1. Evaluating the presence of the SNP Pro198Leu, it was observed that 56,7% of the were participants had wild type genotype, 36,8% heterozygous and 6,8% were homozygous for leucine. For the GSTM1 null deletion polymorphism, 42,5% of the volunteers had a null genotype, ie, do not express the enzyme glutathione S-transferase. These results indicate that the majority of participants had selenium deficiency in plasma and erythrocytes. Nevertheless, most of them had adequate activity of glutathione peroxidase. There was no association between selenium concentrations and the biomarkers used to assess oxidative stress. The Pro198Leu polymorphism did not interfere in selenium concentrations, as well as in the oxidative stress. The evaluation of GSTM1 polymorphism had no association with mercury levels and oxidative stress