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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.
111

Propriétés physico-chimiques et fonctionnelles des gommes hydrocolloïdes des écorces de Triumfetta cordifolia et Bridelia thermifolia

Saidou, Clement 19 November 2012 (has links) (PDF)
Triumfetta cordifolia et Bridelia thermifolia sont deux arbustes de la région tropicale d'Afrique dont les gommes extraites des écorces fraîches ou séchées sont confinées aux utilisations traditionnelles, notamment dans la cuisine (propriétés d'épaississement et d'aromatisation des sauces, d'amélioration de la texture des pâtisseries) et dans le procédé de décantation des bières traditionnelles de sorgho (bili-bili). Dans le but d'identifier la nature des gommes responsables de ces propriétés et d'évaluer leur potentiel de valorisation, la composition chimique (protéines, polysaccharides, fibres et minéraux) des écorces a été déterminée. Les gommes ont été extraites, caractérisées sur le plan chimique (composition en monosaccharides et en minéraux) et physique (comportement rhéologiques des extraits, poids moléculaire, viscosité intrinsèque et rayon de giration) et l'effet combiné des facteurs du milieu (température, pH, et concentration saline (NaCl, KCl, CaCl2 et MgCl2)) influençant la viscosité a été analysé selon un plan composite centré. Enfin, un essai d'application de ces gommes dans la préparation des beignets de maïs et de sorgho a été réalisé. Les résultats des analyses chimiques montrent une prédominance des polysaccharides dans les écorces (52 et 55% respectivement pour B. thermifolia et T. cordifolia) et dans les extraits (76 et 80% respectivement pour B. thermifolia et T. cordifolia), avec des teneurs 5 à 8 fois supérieures à celles des protéines. Ce qui permet de considérer que ces polysaccharides sont responsables des propriétés physiques d'épaississement exprimées par les extraits. Ces propriétés ne sont aucunement modifiées par le séchage des écorces. Les polysaccharides des extraits sont constitués principalement de rhamnose (24,51%), de galactose (15,23%), d'acides glucuronique (25,51%) et galacturonique (20,23%). La présence significative d'acides uroniques justifie la persistance des minéraux dans les extraits purifiés. Les masses moléculaires moyennes des polysaccharides sont de 6,14 x106 et 3,58 x106Da respectivement pour T. cordifolia et B. thermifolia. Sur le plan physique, leurs viscosités intrinsèques et leur rayon de giration sont relativement élevés (18,33dl/g et 269,6nm pour T. cordifolia; 17,98dl/g et 217,8nm pour B. thermifolia). La cinétique de séchage des écorces de T. cordifolia et B. thermifolia se déroule en deux périodes cinétiques représentées par deux constantes de séchage k1 et k2 qui augmentent avec la température de séchage. La viscosité des extraits diminue pour des températures de séchage des écorces au-délà de 70°C. Cette baisse de viscosité des extraits serait plus le résultat d'un changement de conformation des polysaccharides que de leur dégradation. L'étude du comportement rhéologique de ces polysaccharides traduit un comportement rhéofluidifiant, viscoélastique, peu thixotrope et avec des contraintes seuil d'écoulement comprises entre 0,2 et 5Pa et entre 0,5 et 1Pa respectivement pour T. cordifolia et B. thermifolia à des concentrations comprises entre 0,52 et 0,82g/l. La température et les cations monovalents (K+ et Na+) ont un effet dépresseur sur la viscosité des gommes tandis que les pHs faiblement acide et alcalin et les cations divalents (Ca2+ et Mg2+) l'augmentent. L'effet combiné de ces facteurs sur la viscosité des gommes se décrit de façon satisfaisante par un modèle de second degré. L'analyse des interactions entre les facteurs de variation (définit dans le modèle) met en évidence, pour chaque facteur, une plage de valeurs pour lesquelles il contribue à l'obtention d'une zone de viscosités optimales et offre sur le plan pratique une gamme de choix des niveaux de variables en fonction du niveau de viscosité voulue. L'incorporation d'extraits de T. cordifolia (3,5 g/l) et B. thermifolia (11 g/l) dans la farine de maïs ou de sorgho, contribue de façon significative à l'amélioration du gonflemen
112

The use of diatoms to indicate water quality in wetlands : A South African perspective / by Malebo D. Matlala

Matlala, Malebo Desnet January 2010 (has links)
In a semi-arid country like South Africa, the availability and quality of water has always played an important part in determining not only where people can live, but also their quality of life. The supply of water is also becoming a restriction to the socio-economic development of the country, in terms of both the quality and quantity of what is available. Thus different monitoring techniques should be put in place to help inform the process of conserving this precious commodity and to improve the quality of what is already available. Water quality monitoring has traditionally been by the means of physico-chemical analysis; this has more recently been augmented with the use of biomonitoring techniques. However, since the biota commonly used to indicate aquatic conditions are not always present in wetlands; this study tested the use of diatoms as bio-indicators in wetlands. Diatom samples were collected from thirteen wetlands in the Western Cape Province, and cells from these communities were enumerated and diatom ?based indices were calculated using version 3.1 of OMNIDIA. These indices were useful for indicating water quality conditions when compared to the measured physico-chemical parameters. In addition, most diatom species found were common to those found in riverine environments, making the transfer of ecological optima possible. The objective of the study was to provide a preliminary diatom-based index for wetlands, however, given the relatively small study area and the strong bias towards coastal wetlands it was deemed inadvisable to construct such an index, instead several indices are recommended for interim use until further research that more comprehensively covers wetlands in South Africa has been conducted. It is thus the recommendation of this study that more data is collected for comparison to other wetlands and that in the interim, indices such as SPI be applied for routine biomonitoring of these environments. / Thesis (M.Sc. (Botany))--North-West University, Potchefstroom Campus, 2010.
113

The use of diatoms to indicate water quality in wetlands : A South African perspective / by Malebo D. Matlala

Matlala, Malebo Desnet January 2010 (has links)
In a semi-arid country like South Africa, the availability and quality of water has always played an important part in determining not only where people can live, but also their quality of life. The supply of water is also becoming a restriction to the socio-economic development of the country, in terms of both the quality and quantity of what is available. Thus different monitoring techniques should be put in place to help inform the process of conserving this precious commodity and to improve the quality of what is already available. Water quality monitoring has traditionally been by the means of physico-chemical analysis; this has more recently been augmented with the use of biomonitoring techniques. However, since the biota commonly used to indicate aquatic conditions are not always present in wetlands; this study tested the use of diatoms as bio-indicators in wetlands. Diatom samples were collected from thirteen wetlands in the Western Cape Province, and cells from these communities were enumerated and diatom ?based indices were calculated using version 3.1 of OMNIDIA. These indices were useful for indicating water quality conditions when compared to the measured physico-chemical parameters. In addition, most diatom species found were common to those found in riverine environments, making the transfer of ecological optima possible. The objective of the study was to provide a preliminary diatom-based index for wetlands, however, given the relatively small study area and the strong bias towards coastal wetlands it was deemed inadvisable to construct such an index, instead several indices are recommended for interim use until further research that more comprehensively covers wetlands in South Africa has been conducted. It is thus the recommendation of this study that more data is collected for comparison to other wetlands and that in the interim, indices such as SPI be applied for routine biomonitoring of these environments. / Thesis (M.Sc. (Botany))--North-West University, Potchefstroom Campus, 2010.
114

Qualidade da água utilizada para consumo em escolas no município de São Carlos-SP

Scuracchio, Paola Andressa [UNESP] 15 December 2010 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:23:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-15Bitstream added on 2014-06-13T19:09:24Z : No. of bitstreams: 1 scuracchio_pa_me_arafcf.pdf: 218891 bytes, checksum: c8aae0d323ca8f97bd9a60baa02de3d6 (MD5) / Universidade Estadual Paulista (UNESP) / Sabe-se da importância de se tratar a água destinada ao consumo humano, pois, é capaz de veicular grande quantidade de contaminantes físico-químicos e/ou biológicos, cujo consumo tem sido associado a diversos problemas de saúde. Assim, é necessário saber se a qualidade da água destinada ao consumo humano, responde as exigências da legislação. O objetivo desta pesquisa foi avaliar a qualidade da água que abastece as escolas e creches municipais da cidade de São Carlos – SP. Foram coletadas 186 amostras de água, em três pontos distintos: rede, reservatório e filtro. Para análise de coliformes totais e coliformes fecais/E. coli utilizou-se a técnica de substratos cromogênicos/Colilert; para contagem de bactérias heterotróficas foi utilizada a técnica de cultivo em profundidade; para determinação do pH adotou-se leitura direta no pHâmetro; para determinação de flúor foi utilizado o método SPANDS; para determinação de cloro utilizou-se o método DPD; para determinação de turbidez foi utilizado o método nefelométrico e para determinação da cor o método colorimétrico. Para coliformes fecais/E.coli apenas uma amostra do filtro apresentou positividade. Para coliformes totais, sete amostras (22,5%) da rede, seis (19,3%) do reservatório e seis (19,3%) do filtro apresentaram contaminação na primeira colheita e sete (22,5%) amostras da rede, três (9,6%) do reservatório e sete (22,5%) do filtro na segunda coleta. Para bactérias heterotróficas uma amostra da rede, uma do reservatório e 13 (41,9%) do filtro apresentaram contagens acima de 500UFC/ml na primeira coleta e três (9,6%) amostras da rede e do reservatório e 14 (45,1%) do filtro na segunda coleta. Para pH, cinco amostras (16,1%) da rede e uma do filtro não atenderam ao padrão exigido pela legislação na primeira coleta e sete amostras (22,6%) da rede na segunda coleta... / Today, we know the importance of treating water for human consumption, therefore, is capable of conveying large amounts of physical and chemical contaminants and / or biological agents, whose consumption has been associated with several health problems. Thus, it is necessary to know if the quality of water intended for human consumption, answers the requirements of the law. The aim of this study was to evaluate the quality of water supply schools and day care centers of São Carlos - SP. We collected 186 samples of water, on three points: network, tank and filter. For analysis of total coliform and fecal coliform / E. coli we used the technique of chromogenic substrates / Colilert; for heterotrophic bacterial count technique was used to grow in depth, to determine pH reading was adopted in direct pHâmetro; for determination of fluoride, the method SPANDS; to determine chlorine used the DPD method, for determination of turbidity nephelometric method was used to determine the color and colorimetric method. For fecal coliform / E.coli only one sample was positive filter. For total coliforms, seven samples (22.5%) of the network, six (19.3%) of the tank and six (19.3%) of the filter was contaminated in the first harvest and seven (22.5%) samples of the network three (9.6%) of the reservoir and seven (22.5%) of the filter in the second collection. Heterotrophic bacteria from a sample network, a tank and 13 (41.9%) of the filter had counts above 500UFC/ml the first harvest and three (9.6%) samples of the network and the reservoir and 14 (45, 1%) of the filter in the second harvest. For pH, five samples (16.1%) of the network and a filter did not meet the standard required by legislation in the first harvest and seven samples (22.6%) of the net in the second harvest. For fluoride 27 (87.0%) of the network, 24 (77.4%) of the reservoir and 25 (80.6%) were outside of the filter pattern in the first... (Complete abstract click electronic access below)
115

Qualidade da água de múltiplos usos na microrregião de Itapecuru-Mirim-MA

Alves, Lúcia Maria Coêlho [UNESP] 07 June 2010 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:32:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-06-07Bitstream added on 2014-06-13T19:03:31Z : No. of bitstreams: 1 alves_lmc_dr_jabo.pdf: 5616819 bytes, checksum: 4a53256d90bbcf403f575125bc5a14c7 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A água é um recurso natural indispensável à vida, é essencial à promoção social, à produção de alimentos e ao desenvolvimento econômico. Com o objetivo de se avaliar a qualidade microbiológica e físico-química de águas subterrâneas e superficiais na microrregião de Itapecuru-Mirim-MA foram colhidas 172 amostras de água, sendo 86 no período chuvoso (março a maio) e 86 amostras no período de estiagem (agosto a outubro). Destas, 39 amostras eram águas consumidas em residências rurais procedentes de poços artesianos, poços rasos, fontes naturais e Rede Publica de Abastecimento, 05 eram de uso doméstico, 08 de lavagem dos tetos das vacas; 02 de uso em laticínios, 01 de uso em matadouro, 01 de fábrica de polpas de frutas, 18 de bebedouros dos animais, 09 águas de uso em piscicultura e 03 de irrigação de hortaliças. Foram analisados parâmetros microbiológicos e físico-químicos e aplicado um questionário fechado contendo perguntas objetivas para se avaliar o nível de conhecimento das pessoas quanto à qualidade da água usada ou consumida e mapeado geograficamente os pontos de colheitas. Os resultados das análises microbiológicas e físico-químicas identificaram 52 (66,66 %) amostras de água de consumo humano em desacordo com os padrões microbiológicos e 23 (29,48%) em desacordo com os parâmetros físico-químicos, nove (90%) amostras de água de uso doméstico não atenderam aos padrões microbiológicos, enquanto seis (60%) não o foram para os padrões físico-químicos, para água de lavagem dos tetos evidenciaramse 13 (81,25%) e 10 (62,50%) amostras, respectivamente, fora dos padrões microbiológicos e físico-químicos vigentes. Não foi constatada contaminação microbiológica nem físico-química para água de uso em laticínio e em fábrica de polpa de frutas. Referente à água de uso em matadouro, uma (50%) amostra não atendeu aos padrões... / Water is a natural resource essential for life, it is essential to social promotion, food production and economic development. In order to evaluate the microbiological and physical chemistry quality of groundwater and surface water in the municipality of Itapecuru-Mirim-MA were collected 172 water samples, including 86 in the rainy season (March-May) and 86 samples in the dry weather period (August- October). From these total, 39 samples were water consumed in rural residences coming from shallow water wells, artesian water wells, natural sources and public water supply, 05 were domestic water, 08 from teat washings of cows; 02 for use in dairy products, 01 from the slaughterhouse, 01 from a factory fruit pulps, 18 from animal drinking fountains, 09 water samples used for pisciculture and 03 from vegetables irrigation. They were all analyzed for the microbiological and physical-chemical parameters. A close questionnaire with objective questions was also applied to evaluate the awareness level of people about the water quality used or consumed and the crops points were geographically mapped. The microbiological and physical-chemical results identified 52 (66,66%) water samples for human consumption in discordance with the microbiological standards and 23 (29,48%) in discord to the physical-chemical parameters, nine (90%) water samples for domestic use did not attend to the microbiological standards, while six (60%) were not for the physical-chemical parameters. The teat washing water results showed that 13 (81,25%) and 10 (62,50%) samples, respectively, were out of the microbiological and physical-chemical actual patterns. It was not detected microbiological contamination of water used in the dairy and in the fruit pulp factory. Referring to the water used in the slaughterhouse, one (50%) sample did not attend to the microbiological patterns, but all samples attended to the physical-chemical...(Complete abstract click electronic access below)
116

Polymères associatifs par interaction covalente réversible diol-acide boronique / Associative polymers based on the diol-boronic acid reversible covalent interaction

Fournier, Rémi 28 October 2016 (has links)
Ce travail de thèse porte sur la synthèse et l'étude physico-chimique de polymères associatifs hydrosolubles à associations complémentaires. Utilisant la chimie covalente réversible, ce système met en jeu l'association d'un poly(diol) et d'un poly(acrylamide) partiellement hydrolysé portant des fonctions d'acide boronique. Ces dernières sont introduites par une technique de greffage qui a été optimisée et finement caractérisée. Le mélange des deux polymères permet d'obtenir des solutions visqueuses et des gels dynamiques et ceci pour de faibles concentrations. La possibilité de viscosifier des formulations en-dessous de la concentration de gélification constitue un résultat marquant qui distingue ce système de nombreux polymères à association hydrophobe. Dans le régime de gel, les propriétés rhéologiques linéaires sont analysées en relation avec l'étude de la force des interactions moléculaires qui ont été mesurées par la RMN du bore et une technique de fluorescence. La rhéologie non-linéaire apporte des informations essentielles sur la relation entre le cisaillement et la structure du réseau réversible formé. L'utilisation d'un système de visualisation de l'échantillon sous écoulement permet l'observation d'effets locaux fortement non-linéaires. L'influence des différents paramètres, comme le pH et la température, sur les propriétés dynamiques des solutions peut être rationalisée et modélisée en termes de lois d'échelles. L'originalité de ce concept de système associatif par associations complémentaires est mise en perspective au travers d'une revue de la littérature rationalisant le lien entre architecture et rhéologie des polymères associatifs hydrosolubles. / This thesis deals with the synthesis and the physical chemistry study of water-soluble complementary associative polymers. Based on reversible covalent chemistry, this system brings into play the association of a poly(diol) and of a partially hydrolyzed poly(acrylamide) bearing boronic acid moieties. The latter are introduced by a grafting technique which has been optimized and finely characterized. The mixing of these two polymers allows obtaining viscous solutions and visco-elastic gels at relatively low polymer concentrations. The possibility to make formulations viscous below the gel point represents a remarkable result, which differentiates this system to numerous associative polymers based on hydrophobic interactions. In the gel regime, the linear rheological properties are analyzed with regard to the strength of molecular interactions which have been measured by boron NMR and a fluorescence technique. Non-linear rheology brings essential information about the relationship between shearing and the structure of the formed reversible network. The use of a visualization setup of samples under flow enables the observation of very non-linear local effects such as wall slip and shear-banding. The influence of various parameters, as pH and temperature, on the dynamical properties of solutions and gels can be rationalized and modeled in terms of scaling laws. The originality of this concept of associative system with complementary associations is put into perspective through a literature review on the relationship between architecture and molecular interactions on one hand, and rheological properties of associative polymers on the other hand.
117

Compréhension et modélisation des mécanismes de flottation appliqués au désencrage de papier récupéré / Understanding and modelling of the mechanisms of flotation applied to the de-inking of recovered papers

Allix, Jérémy 20 January 2011 (has links)
La flottation est la principale étape du processus de recyclage,ayant pour but l’élimination de l’encrede la pâte. Pour une moyenne de seulement 2% d’encre présent dans la pâte, le rendement estd’environ 80 %. Les pertes sont ainsi principalement composées de fibres, charges minérales etéléments fins. Le procédé de flottation est le seul processus permettant une séparation sélective desparticules d’encre de la pâte à papier, lors du recyclage des papiers récupérés. Ce processus estappliqué par toutes les usines européennes de désencrage et, bien qu'il soit reconnu comme étant leplus sélectif, il génère des pertes solides qui restent encore trop important (15 à 20% de pertes) parrapport au 2% en poids de l'encre appliquée en général sur imprimé. Ainsi, la sélectivité de la flottationa besoin d'être améliorée. Cette amélioration permettrait à la fois d'augmenter le rendement duprocédé de désencrage ainsi que de réduire les volumes de boues produites au cours de désencrageet donc de simplifier tous les problèmes liés à la valorisation de ces boues. Les travaux retranscritsdans ce mémoire ont, dans un premier temps, pour but d'améliorer la connaissance fondamentale desphénomènes se produisant au cours de flottation, en particulier pour obtenir une meilleureconnaissance i) sur les mécanismes de transport des différentes particules (encres, fibres decellulose, éléments fins et charges minérales) au cours de la flottation, en présence de différentstensio-actifs utilisés, ii) des rôles des la chimie utilisée ainsi que leur propre utilisation lors de laflottaison. Dans un deuxième temps, la modélisation des mécanismes de transport dans la pâte etdans la mousse, en tenant compte de paramètres mécaniques (débit de pâte, d’air, turbulence, laconception des cellules…) et physico – chimiques, pour ainsi finalement développer une simulation duprocédé de flottation permettant d'évaluer l'incidence de la chimie utilisée ainsi que des paramètresmécaniques des cellules. Cette simulation permettra par la suite d’améliorer à la fois l’efficacité descellules existantes mais aussi des lignes de désencrages. / Flotation is the main step of de-inking to remove the ink from the pulp. Whereas the target is toremove 2% of ink from the pulp, there is a loss of 20% of total matters (fibers, fillers and ashes). Theflotation process is the only process allowing to more or less selectively separate the particles frominks during recycling of recovered papers. This process is applied by all the European deinking millsand, although being recognized as being the most selective, it generates solid losses which remainstill too important (15 to 20% of losses) compared to the 2% of ink in weight applied to printed papers.Thus, the selectivity of flotation requires to be improved. Such improvement would at the same timeallow to increase the deinking process yield but also to reduce in parallel the volumes of sludgegenerated during de-inking and thus to simplify all the problems connected with the valorisation ofthese sludges. On the one hand, the objectives of this study are to improve fundamental knowledge ofthe phenomena occurring during flotation, in particular to obtain a better knowledge i) on mechanismsof transport of the various particles (ink, fibres and fines cellulose, mineral loads) during flotation in thepresence of various surface-active components from de-inking, ii) of the role of surface-activesubstances and their elimination during flotation. On the other hand, modelling of the mechanisms oftransport in the pulp and in the froth, taking into account mechanical parameters (air ratio, turbulence,design of the cells) and physico – chemical parameters has been highlighted to finally develop asimulation of the flotation process allowing to evaluate the incidence of the design of the cells,simulation which should then make it possible to improve the effectiveness of the existing cells.
118

Association des copolymères à séquences (1->4)-a-L-guluronane en présence d’ions calcium / Ca2+-driven association of polymers featuring (1->4)-a-L-guluronan sequences

Wolnik, Anna 05 February 2014 (has links)
Les alginates forment des gels transparents en solution aqueuse en présence de certains ions divalents. Cette propriété est principalement attribuée à la formation de zones de jonction impliquant les séquences (1->4)-a-L-guluronane de chaînes adjacentes. Des oligomères d'alginates ont été utilisés comme briques élémentaires pour la synthèse de polymères biohybrides contenant des chaines pendantes oligo-(1->4)-a-L-guluronane. La rhéologie et la diffusion de la lumière ont permis d'étudier leur gélification ionotropique. De plus, une image atomistique des associations entre chaines latérales a été donnée grâce à la modélisation moléculaire et la microscopie de force atomique. Les polymères biohybrides portant des résidus pendant (1->4)-a-L-guluronane forment des gels en présence de Ca2+. L'addition de blocs guluronane ou mannuronane au gel préformé fait diminuer sa force avec quasiment la même efficacité. L'étude par dynamique moléculaire de séquences (1->4)-a-L-guluronan totalement chargées en présence d'ions Ca2+ suggère qu'environ 8 unités de répétition sont suffisantes pour former spontanément des zones de jonction. De plus, l'analyse conformationnelle de duplexes de chaines (1->4)-a-L-guluronane ayant 12 unités de répétition révèle une grande variété de conformations accessibles, ce qui est consistant avec la difficulté d'obtention de cristaux de Ca2+-guluronate de dimension suffisante pour les études cristallographiques. Les forces d'adhésion entre des homo-oligomères d'alginates en présence de Ca2+ mesuré par spectroscopie de force atomique montrent que la force d'interaction croit selon l'ordre suivant: M-M < M-G or G-M < G-G. Un résultat important est que les blocs mannuronanes, en complexe avec le calcium, peuvent être impliqués dans des associations homotypiques et hétérotypiques. Ce résultat est consistant avec la détection d'agrégats d'oligomères de mannuronanes observés en diffusion de la lumière pendant l'addition de CaCl2. Les blocs M contribuent donc également à la formation du gel mais la force associée est plus faible que celle des blocs G. / Alginates form transparent hydrogels in aqueous solution upon addition of some divalent cations. This property is mostly due to the formation of junction zones involving (1->4)-a-L-guluronan sequences on adjacent polymer chains. Oligomers of alginates were used as molecular bricks for the synthesis of biohybrid polymers featuring (1->4)-a-L-guluronan sequences as side chains. Rheology and Light Scattering have been applied to investigate their ionotropic gelation. In addition, an atomistic picture of the Ca2+-driven side chain associations was also provided thanks to Molecular Modeling and Atomic Force Spectroscopy. Biohybrid polymers carrying (1->4)-a-L-guluronan residues formed soft and transparent hydrogels in the presence of Ca2+. The addition of either guluronan, or mannuronan blocks to the pre-formed gel reduced its strength almost with the same efficiency. A molecular dynamics investigation of fully charged (1->4)-a-L-guluronan sequences in the presence of a neutralizing amount of Ca2+ ions suggested that about 8 repeating units may be sufficient to the spontaneous formation of junction zones. Furthermore, conformational analysis of (1->4)-a-L-guluronan chain having 12 repeating units in duplexes revealed a wide variety of accessible conformations, a feature consistent with the general difficulty in obtaining crystals of Ca2+-guluronate with suitable lateral dimensions for crystallographic studies. The adhesion forces between homo-alginate oligomers in the presence of Ca2+ measured by Atomic Force Spectroscopy showed that the strength of interactions increased in the following order: M-M < M-G or G-M < G-G. One of the most significant findings to emerge from this study is that mannuronan blocks complexed via calcium ions can be involved in both homotypic and heterotypic associations. This result is consistent with the detection of aggregates observed for mannuronan oligomers by Light Scattering during the addition of CaCl2. Thus, M-blocks also contribute to the gel formation but their strength seemed to be however weaker than G-blocks.
119

Qualidade da água utilizada para consumo em escolas no município de São Carlos-SP /

Scuracchio, Paola Andressa. January 2010 (has links)
Orientador: Adalberto Farache Filho / Banca: João Bosco Faria / Banca: Clovis Wesley de Oliveira Souza / Resumo: Sabe-se da importância de se tratar a água destinada ao consumo humano, pois, é capaz de veicular grande quantidade de contaminantes físico-químicos e/ou biológicos, cujo consumo tem sido associado a diversos problemas de saúde. Assim, é necessário saber se a qualidade da água destinada ao consumo humano, responde as exigências da legislação. O objetivo desta pesquisa foi avaliar a qualidade da água que abastece as escolas e creches municipais da cidade de São Carlos - SP. Foram coletadas 186 amostras de água, em três pontos distintos: rede, reservatório e filtro. Para análise de coliformes totais e coliformes fecais/E. coli utilizou-se a técnica de substratos cromogênicos/Colilert; para contagem de bactérias heterotróficas foi utilizada a técnica de cultivo em profundidade; para determinação do pH adotou-se leitura direta no pHâmetro; para determinação de flúor foi utilizado o método SPANDS; para determinação de cloro utilizou-se o método DPD; para determinação de turbidez foi utilizado o método nefelométrico e para determinação da cor o método colorimétrico. Para coliformes fecais/E.coli apenas uma amostra do filtro apresentou positividade. Para coliformes totais, sete amostras (22,5%) da rede, seis (19,3%) do reservatório e seis (19,3%) do filtro apresentaram contaminação na primeira colheita e sete (22,5%) amostras da rede, três (9,6%) do reservatório e sete (22,5%) do filtro na segunda coleta. Para bactérias heterotróficas uma amostra da rede, uma do reservatório e 13 (41,9%) do filtro apresentaram contagens acima de 500UFC/ml na primeira coleta e três (9,6%) amostras da rede e do reservatório e 14 (45,1%) do filtro na segunda coleta. Para pH, cinco amostras (16,1%) da rede e uma do filtro não atenderam ao padrão exigido pela legislação na primeira coleta e sete amostras (22,6%) da rede na segunda coleta... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Today, we know the importance of treating water for human consumption, therefore, is capable of conveying large amounts of physical and chemical contaminants and / or biological agents, whose consumption has been associated with several health problems. Thus, it is necessary to know if the quality of water intended for human consumption, answers the requirements of the law. The aim of this study was to evaluate the quality of water supply schools and day care centers of São Carlos - SP. We collected 186 samples of water, on three points: network, tank and filter. For analysis of total coliform and fecal coliform / E. coli we used the technique of chromogenic substrates / Colilert; for heterotrophic bacterial count technique was used to grow in depth, to determine pH reading was adopted in direct pHâmetro; for determination of fluoride, the method SPANDS; to determine chlorine used the DPD method, for determination of turbidity nephelometric method was used to determine the color and colorimetric method. For fecal coliform / E.coli only one sample was positive filter. For total coliforms, seven samples (22.5%) of the network, six (19.3%) of the tank and six (19.3%) of the filter was contaminated in the first harvest and seven (22.5%) samples of the network three (9.6%) of the reservoir and seven (22.5%) of the filter in the second collection. Heterotrophic bacteria from a sample network, a tank and 13 (41.9%) of the filter had counts above 500UFC/ml the first harvest and three (9.6%) samples of the network and the reservoir and 14 (45, 1%) of the filter in the second harvest. For pH, five samples (16.1%) of the network and a filter did not meet the standard required by legislation in the first harvest and seven samples (22.6%) of the net in the second harvest. For fluoride 27 (87.0%) of the network, 24 (77.4%) of the reservoir and 25 (80.6%) were outside of the filter pattern in the first... (Complete abstract click electronic access below) / Mestre
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Produção e propriedades de álcoois graxos etoxilados com distribuição estreita de oligômeros / Production and properties of ethoxylated fatty alcohols with a narrow oligomer distribution

Carmen Sílvia Bentivoglio Ruiz 12 November 1997 (has links)
No presente trabalho, realizado conjuntamente na Universidade e na Indústria, foi feita a investigação dos catalisadores isopropóxido de alumínio e Aliso B na reação de etoxilação de álcool laurílico, com o objetivo de obter produtos com distribuição estreita de oligômeros. Os experimentos foram realizados em escala piloto e foram investigadas a influência da temperatura, da concentração de catalisador e da relação molar entre ácido (promotor) e catalisador no processo. Todos os estudos tiveram caráter comparativo, tomando como base a reação e os produtos gerados a partir do uso de hidróxido de potássio que é o catalisador mais amplamente empregado para esse tipo de preparação industrial. Primeiramente foi estudada a forma de carregamento do reator, determinando e otimizando seu modo de operação. A partir desses dados, avaliou-se a influência da temperatura na taxa de consumo de óxido de etileno, na distribuição de oligômeros do produto e na formação de glicol como subproduto. Também foi avaliada a influência da concentração de catalisador e relação molar promotor:catalisador na taxa de consumo de óxido de etileno e formação de glicoI. As avaliaçãoes foram feitas para as reações de etoxilação gerando produtos com grau de etoxilação 2, 3, 4 e 6 mols de óxido de etileno. Através dos resultados foram estabelecidas as melhores condições de processo, considerando as limitações de processo dos reatores industriais para gerar o produto desejado. / In the present work, developed in an association between University and Industry, different catalysts were evaluated, such as aluminum isopropoxide and Aliso B, for ethoxylation of laurilic alcohol, aiming to obtain narrowly distributed oligomers. The experiments were carried out in a pilot plant and the influence of temperature, catalyst concentration and molar relationship between acid (promoter of the reaction) and catalyst were evaluated. All the evaluations made were comparative, using for comparison the reaction and the products generated when potassium hydroxide is used as catalyst, which is commonly the case in industry. Initially we studied the charging of the reactional vessel in order to determine and optimize operational procedures. Then, we evaluated the influence of temperature on the ethylene oxide consumption rate, the oligomer distribution and the generation of glycol as a byproduct. We also evaluated the influence of catalyst concentration and molar relation of promoter : catalyst on the ethylene oxide consumption rate and on the generation of glycol. The evaluations were made for the ethoxylation reactions generating products with ethoxylation grades of 2, 3, 4 and 6 moles of ethylene oxide. Through the results, we have optimized processing conditions, considering the process limitations of industrial vessels for the generation of the desired product.

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