Thesis advisor: Dunwei Wang / Electrochemical CO2 reduction reaction (CRR) provides a solution to both the increasing global demand of energy by forming valuable chemical products for fuel production, and global warming by reducing the amount of CO2 in the environment. To efficiently reduce CO2, we sought to understand the reaction mechanism using a polycrystalline Au electrode and the super concentrated LiTFSI solution (WiS) as the electrolyte. By varying both the electrolytic potential and the concentration of WiS, we investigated the factors determining product selectivity and found that reaction kinetics and mass transport together direct the selectivity towards CO. We probed the rate limiting step (RLS) of CO2 reduction by observing the variation of product distribution with water availability in solution, and discovered that the RLS was likely to involve only a single electron transfer to form COO*–. Lastly, we proposed that in WiS, H2O were the dominant proton sources for both CO2 reduction and H2 evolution reactions. In 21m WiS, the competing hydrogen evolution reaction was kinetically inhibited, so CO production was favored with a selectivity of 90% at a potential as early as -0.4V vs RHE. This study demonstrated the great potential of WiS as a platform for studying multi-proton, multi-electron transfer reactions. / Thesis (BS) — Boston College, 2018. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Scholar of the College. / Discipline: Chemistry.

Providing sustainable supplies of water and energy is a critical global challenge. Polymer membranes dominate desalination and could be crucial to power generation applications, which include reverse osmosis (RO), nanofiltration (NF), forward osmosis (FO), pressure-retarded osmosis (PRO), electrodialysis (ED), membrane capacitive deionization (CDI), and reverse electrodialysis (RED). Improved membranes with tailored water and salt transport properties are required to extend and optimize these technologies. Water and salt transport structure/property relationships provide the fundamental framework for optimizing polymer materials for membrane applications. The water and salt transport and free volume properties of a series of sulfonated styrenic pentablock copolymers were characterized. The polymers' water uptake and water permeability increase with degree of sulfonation, and the block molecular weights could be used to tune water uptake, permeability, and selectivity properties. The presence of fixed charge groups, i.e., sulfonate groups, on the polymer backbone influence the material's salt transport properties. Specifically, the salt permeability increases strongly with increasing salt concentration, and this increase is a result of increases in both salt sorption and diffusivity with salt concentration. The data for the sulfonated polymers, including a sulfonated polysulfone random copolymer, are compared to those for an uncharged polymer to determine the influence of polymer charge on salt transport properties. The sulfonated styrenic pentablock copolymer permeability data are compared to literature data using the water permeability and water/salt selectivity tradeoff relationship. Fundamental transport property comparisons can be made using this relationship. The effect of osmotic de-swelling on the polymers and the transport properties of composite membranes made from sulfonated styrenic pentablock copolymers are also discussed. The sulfonated styrenic pentablock copolymers were exposed to multi-valent ions to determine their effect on the polymer's salt transport properties. Magnesium chloride permeability depends less on upstream salt concentration than sodium chloride permeability, presumably due to stronger association between the sulfonate groups and magnesium compared to sodium ions. Triethylaluminum was used to neutralize the polymer's sulfonic acid functionality and presumably cross-link the polymer. The mechanical, transport, and free volume properties of these aluminum neutralized polymers were studied. / text

O sistema estuarino Timonha / Ubatuba està localizado na divisa dos Estados do Cearà e PiauÃ, 500 km à noroeste de Fortaleza, nordeste do Brasil. A bacia hidrogrÃfica afluente ao sistema estuarino ocupa uma Ãrea de 2.165 km2. A porÃÃo norte està inserida em terrenos PaleozÃicos do Planalto da Ibiapaba, Embasamento Cristalino, FormaÃÃo Barreiras e depÃsitos QuatemÃrios enquanto que a porÃÃo sul està ~sentada sobre terrenos PrÃÂCambrianos com exumaÃÃes do GranitÃide Chaval. A procura por Ãreas para expansÃo da carcinicultura, crescimento urbano e desenvolvimento agroindustrial pode representar o comprometimento da saÃde desse ecossistema, considerado o maior do Estado do Cearà Estes impactos tendem a se incrementar com a construÃÃo e operaÃÃo do aÃude pÃblico ItaÃna, com capacidade de armazenamento de 77,5 milhÃes de m3, localizado 17 km à montante da Ãrea estuarina. A par destes problemas e considerando as hipÃteses de minimizÃÂlos ou elimina-Ios, este trabalho considerou os elementos estruturais, dinÃmicos e controladores do estado de evoluÃÃo atual do sistema estuarino, contribuindo com informaÃÃes Ãteis para o uso adequado e sustentÃvel da Ãrea. Os processos hidrodinÃmicos e sedimentolÃgicos estÃo subordinados, sobretudo, ao regime sazonal das precipitaÃÃes onde somam-se processos de assoreamento da foz pela deriva litorÃnea e oscilaÃÃo da marÃ. A construÃÃo do reservatÃrio implicou na reduÃÃo de 91% da descarga fluvial do rio Timonha apresentando atualmente, uma vazÃo de 5,6 X 108 m3 ao longo de um ano. A vazÃo regularizada nÃo à suficiente para promover os processos de mistura e diluiÃÃo de sais, contribuindo para inversÃo da salinidade no perÃodo e estiagem. No perÃodo chuvoso, a salinidade do rio Timonha aumenta progressivamente em direÃÃo ao mar com regimes oscilando do limnÃtico  0,5) ao euhalino (30,0 à 40,0). Na estiagem, o regime à tipicamente euhalino com fortes indÃcios de hipersalinizaÃÃo (> 40,0). No Ubatuba, o regime salino variou de polihalino (18,0 à 30,0) a euhalino entre os perÃodos de chuva e estiagem. Os estuÃrios sÃo do tipo 2a no perÃodo chuvoso e do tipo Ia no perÃodo de estiagem. O balanÃo de sal do rio Timonha no perÃodo de chuva foi de + 0,3 t enquanto que no perÃodo de estiagem foi 0,01. No Ubatuba o balanÃo referente ao perÃodo de chuva foi de - 0,1 t e na estiagem foi de - 0,2 1. A profundidade mÃdia do sistema à de 5m com mÃximas observadas no Ubatuba. O substrato à formado predominantemente por areias mÃdias e sedimentos bioclÃsticos. O total de sedimentos exportados para deriva litorÃnea, ao longo de um ano, foi de 250 t enquanto que a carga importada foi de 150 1. O volume do prisma de marà no Timonha foi de aproximadamente 3,6 x 107 m3 e no rio Ubatuba 4) x 107 m3. Considerando o modelo simplificado, o tempo de residÃncia do Timonha à de 1 dia no perÃodo de chuva e 5 dias no de estiagem No Ubatuba esse tempo à de 0,5 dia no perÃodo chuvoso e 2 dias na estiagem Considerando o tempo de residÃncia calculado para cada segmento dos canais estuarinos dos rios Timonha e Ubatuba observa-se que o modelo linear nÃo à o mais representativo para anÃlise da capacidade de diluiÃÃo do sistema. Com base no modelo segmentado, observa-se que, no Timonha, a Ãrea situada entre 3,7 km e 7,0 km de distÃncia do mar assume forte tendÃncia à retenÃÃo de Ãgua, com tempo de residÃncia equivalente à aproximadamente uma semana. Essa Ãrea parece ser a mais inadequada à recepÃÃo de descarga direta de efluentes. Em comparaÃÃo com outros estuÃrios tropicais, o sistema apresenta uma boa capacidade de diluiÃÃo e baixo tempo residÃncia. A ausÃncia de monitoramento para a correÃÃo das vazÃes liberadas pelo AÃude ItaÃna em perÃodos de estiagem prolongados e os processos de assoreamento da foz poderÃo representar os principais vetores de comprometimento da capacidade de suporte do estuÃrio.

Du fait de problèmes de santé publique, l’industrie agroalimentaire doit réduire la quantité de sel et de matière grasse dans les aliments, et donc dans les charcuteries. Lors de la fabrication des saucissons secs, une diminution combinée des taux de sel et de matière grasse animale peut se traduire par des problèmes de stabilité microbiologique, des défauts d’arôme et de texture dus à des modifications physicochimiques et biochimiques. Dans ce contexte, les objectifs de cette thèse étaient : (1) d’étudier l’impact d’une réduction directe des teneurs en sel et en matière grasse animale sur les évolutions physicochimiques et biochimiques au sein des produits, (2) d’identifier les composés aromatiques responsables de l’arôme du saucisson sec, ainsi que leurs origines, (3) de développer de nouvelles formulations de saucissons secs à teneurs réduites en sodium et en acides gras saturés, et (4) d’étudier les transferts d’eau et sel et de développer une isotherme de sorption spécifique pour le saucisson sec. L’étude de l’effet d’une réduction directe combinée a mis en évidence la difficulté de fabriquer des saucissons secs à teneurs réduites en sel et en matière grasse animale, sans modifier les évolutions physicochimiques et biochimiques. Une identification des composés volatils odorants de saucissons secs de haut de gamme a permis de montrer que l’aromatisation par l’ail et le poivre noir pouvait être un levier technologique permettant d’améliorer la qualité aromatique des saucissons secs allégés en sel et en matière grasse animale. L’impact de l’aromatisation et d’une substitution partielle combinée du sel par le chlorure de potassium et du gras de bardière de porc par l’huile de tournesol oléique sur les propriétés physicochimiques, les réactions biochimiques et les attributs sensoriels de saucissons secs, a été étudié. Cette étude a montré le rôle important de l’aromatisation qui agit en introduisant des molécules aromatiques qui rehaussent l’acceptabilité des produits par les consommateurs, en tant qu’exhausteur de la perception du goût salé et aussi, sur les processus fermentaires qui vont conditionner l’aspect et la texture finale du produit. La substitution partielle combinée est une solution efficace pour conserver au mieux la qualité organoleptique des saucissons, en permettant, d’une part, d’éviter les défauts texturaux et sensoriels liés aux modifications physicochimiques, protéolytiques et lipolytiques générés par une réduction directe combinée, et d’autre part, d’améliorer l’arôme du produit en rehaussant les niveaux d’oxydations lipidique et protéique. L’étude des transferts d’eau et de sel a mis en évidence une migration du sel vers le cœur du saucisson, et a permis de déterminer des valeurs de diffusivité apparente de l’eau en surface de ces produits. Il a été montré qu’une forte réduction en matière grasse réduisait la diffusivité de l’eau à la surface du saucisson. Une isotherme de sorption spécifique permettant de prédire l’aw en fonction des teneurs en eau, en lipides et en sel a été construite en adaptant un modèle de Ross établi pour la gélatine salée et grasse. / Because of public health problems, the food industry must lower sodium and animal fat contents in all food products, therefore in cured meat products. During dry-fermented sausage manufacture, a combined reduction both in salt and animal fat contents may induce microbial safety problems and textural and aroma defects due to physical-chemical and biochemical changes. On account of that, this work of thesis aims (1) to investigate the impact of a direct reduction on the salt and animal fat contents on the physical-chemical and biochemical evolutions in the products, (2) to identify the aromatic compounds responsible for the aroma of dry-fermented sausage, and their origins, (3) to develop new nutritionally-improved formulations of dry-fermented sausages with less sodium and saturated fatty acids, and (4) to study the impact of lipid and sodium chloride contents on water transfers in dry-fermented sausages and to build a specific sorption isotherm curve for dry sausages. The study of the effect of a combined direct reduction highlighted the difficulty of manufacturing sodium-reduced fat-reduced dry sausages, without affecting the physical-chemical and biochemical evolutions. Identification of odorous volatile compounds of high quality dry sausages showed that flavouring, especially garlic and black pepper, could be a good solution for improving the aromatic quality of salt-reduced fat-reduced dry-fermented sausages. The impact of flavouring and of a combined salt and animal fat replacement by potassium chloride and oleic sunflower oil, respectively, on physical-chemical properties, biochemical reactions and sensory attributes of dry-fermented sausages was then studied. This specific study showed the crucial role played by flavouring which introduces aromatic molecules that enhance the product acceptability by consumers, which acts as an enhancer of the saltiness perception and which improves the product appearance and texture by boosting the fermentation process. Consequently, the combined partial substitution is an efficient solution to preserve at best the organoleptic quality of the products, allowing, on one hand, avoiding the textural and sensory defects related to physical-chemical, proteolytic and lipolytic modifications induced by a combined direct reduction, and on the other hand, enhancing the product aroma by increasing the levels of lipid and protein oxidations. The study on water and salt transfers highlighted a salt diffusion towards the dry sausage core, and made it possible to determine values of apparent water diffusivity at the sausage surface. We demonstrated that a strong reduction in animal fat content significantly lowered the water diffusivity value at the product surface. A specific sorption isotherm curve based on a modified Ross model was built, allowing dry-fermented sausages water activity to be calculated as a function of water, fat and salt contents.