A eficiência do fosfato natural (FN) pode ser melhorada se aplicado junto com uma fonte de elevada solubilidade em água. O presente trabalho constou de quatro experimentos realizados em casa-de-vegetação do Laboratório de Fertilidade do Solo do CENA/USP, nos quais cultivaram-se plantas de milho (Zea mays L.) e de soja [Glycine max (L.) Merr.] em amostras de um Latossolo Vermelho Amarelo distrófico utilizando-se o método da diluição isotópica de 32P para: a) verificar se o efeito de uma fonte de P de elevada solubilidade em água no aumento da disponibilidade do P do FN é fisiológico (disponibilidade inicial de P) ou químico (acidificação), b) avaliar o efeito das doses e das proporções das misturas de superfosfato triplo com fosfatos naturais, e c) comparar a eficiência do fosfato natural de Patos de Minas com o de Gafsa aplicados com o SFT. As fontes de P usadas foram o superfosfato triplo (SFT) como fonte padrão e fosfatos naturais (FNs) de Patos de Minas e de Gafsa. A aplicação de uma fonte de P solúvel em água juntamente com fosfato natural melhorou o aproveitamento do fósforo do FN tanto pelo milho como pela soja, embora esse efeito seja pequeno para o fosfato natural de Patos. Para o milho, a simples presença de P na forma solúvel em água na fase inicial de desenvolvimento não melhorou o aproveitamento do P da fonte natural, provavelmente por causa do menor período de tempo de desenvolvimento das plantas em relação à soja, no qual efeito foi significativo. A compactação do FN de Gafsa com SFT aumentou o aproveitamento do P do FN para o milho comparado à aplicação deste localizado no solo e na soja esse efeito foi maior obtendo aproveitamento superior ao do FN de Gafsa misturado ao solo. Assim, a maior utilização do P do FN pela soja ocorreu tanto pelo efeito químico quanto fisiológico. A aplicação localizada do SFT proporcionou resultado melhor do que quando este fertilizante foi misturado ao solo, ocorrendo o contrário para o fosfato natural. As doses de fósforo aplicadas com as misturas de superfosfato triplo com os FNs não afetaram o aproveitamento do P do fosfato natural pelo milho e pela soja, enquanto que o aumento do SFT nas proporções das misturas aumentaram significativamente o aproveitamento do P dos fosfatos naturais. Ao contrário do FN de Patos, o aproveitamento de P do FN de Gafsa quando misturado na proporção 80 SFT: 20 FN, na soja, foi tão eficiente quanto o SFT aplicado sozinho. / The efficiency of phosphate rock (PR) can be improved applying it together with watersoluble P fertilizer. Four experiments were carried out in the greenhouse of the Soil Fertility Laboratory, CENA/USP (Centro de Energia Nuclear na Agricultura - Universidade de São Paulo), with maize (Zea mays L.) and soybean [Glycine max (L.) Merr.] grown in a dystrophic Typic Haplustox using 32P dilution technique to: a) verify if the increasing effect of water-soluble P source on PR phosphorus availability is physiological (initial higher P availability) or chemical (acidification), b) evaluate the effect of rate and proportion of triple superphosphate (TSP) mixed with PR, and c) compare the efficiency of Patos de Minas with of Gafsa PR applied with TSP. The P sources utilized were the TSP as standard P source and Patos de Minas and Gafsa PR. The application of a water-soluble P source improved the PR phosphorus utilization efficiency by maize and soybean, although this effect was small for the Patos PR. For maize, the simple presence of P in water-soluble form at initial stage of plant growth did not increase the PR phosphorus utilization, probably due to the short growing period in relation to soybean, in which the effect was significant. The compaction of Gafsa PR with TSP increased the absorption of PR P by maize plants. Compared to its localized application in the soil this effect was bigger in soybean plants, obtaining better efficiency than the Gafsa PR mixed in the soil. Therefore, the increased PR P utilization by soybean plants occurred by both chemical and physiological effect. The localized application of TSP promoted better results than when this fertilizer was mixed in the soil, unlike with PR. The increasing rate of P applied in mixed form (TSP and PR) did not affect the PR P utilization by the crops, while the increasing proportion of TSP in the mixture increased the absorption of PR P. The Gafsa PR, when mixed with TSP in proportion 80 TSP: 20 PR, was as efficient as the TSP applied sole.

The doctoral thesis is focused on the study, research and development of refractories with phosphate bonding. Primary motivation is preparation of phosphate-based binders that can be applied for non-shaped insulating material fabricated by “in situ” foaming. The phosphate binders based on Al2O3-H3PO4 system are one of the most common in refractory technology. The amphoteric nature of the aluminium and its oxides require the setting of Al2O3-H3PO4 binders under the higher temperatures. Application of higher temperatures is necessary to obtain the minimal manipulation strength of as-prepared green bodies. The main goal of the work is preparation of ytrium phosphate-based binders via different preparation techniques. Yttrium based binders would allow phosphate refractory preparation by standard way, i.e via reaction between binder and reactive aggregate, without structural disintegration of foamed material even before getting manipulation strength or the final firing procedure. Yttrium is more basic than aluminium and therefore more reactive in Y2O3-H3PO4 system.. Yttrium oxide is highly refractory material and sintered yttrium monophosphate has excellent properties from the thermal and corrosive stability point of view. This fact should compensate higher price of this material. Experimental part of this work studies the possibilities of binders preparation in Y2O3-H3PO4 system. The mixtures were designed to prepare binding phase Y(H2PO4)3. Products of these reactions were characterized in phase and chemical point of view. In order to study and describe setting and hardening processes of phosphate binders, the products were “in situ” analyzed by the thermal analyses and high-temperature diffraction analysis up to the 1300 °C. High temperature products were then characterized by means of phase and chemical composition and morphology.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Calcium phosphate-filled restorative materials were developed to provide calcium (Ca) and phosphate (PO4) ions, which have been proposed to enhance remineralization of demineralized tooth structure. Recently, tricalcium phosphate (TCP)-filled restorative materials were introduced as an alternative to amorphous calcium phosphate. The TCP filler has a more crystalline structure than ACP and is therefore potentially stronger. The aim of the present study was to examine TCP-filled restorative resins at different concentration levels at different time intervals to characterize the concentrations of Ca and PO4 ions released, and to measure the water sorption (WS) of these resins. An in vitro study was conducted by formulating resin composite using TCP as the filler mixed with EBPADMA, HmDMA, and HEMA as the resin matrix. One-hundred- sixty samples were prepared, 40 samples of each filler concentration (30 percent, 40 percent, 50 percent, and 60 percent) by weight. From each filler concentration, 5 samples of each of the 8 time points (time intervals of 4 h, 8 h, 12 h, 24 h, 3 d, 7 d, 14 d, and 21 d) were immersed in 100-ml deionized water. Calcium and PO4 ions were measured using atomic absorption spectroscopy and light spectroscopy, respectively. Water sorption (WS) was measured according to ISO 4049 specification and then the WS and the diffusion coefficient were calculated. The significance level was set at p = 0.001. The results indicated that Ca and PO4 ion release increased with increasing filler level at a rate faster than being linear. In addition, WS results were very high and failed to meet the ISO 4049 specification requirement. Diffusion coefficient results were also high. One-way ANOVA test for only 21-day data revealed that there is a statistically significant difference in filler level percent, and two-way ANOVA testing revealed that there is a statistically significant interaction between time and filler level percent on the Ca, PO4 released and WS. It can be concluded that the concentrations of Ca and PO4 released and WS were affected by composition of the monomers, filler level and type, dispersion, and the absence of coupling agent. Although this TCP-filled restorative material may release Ca and PO4, it cannot serve as a restorative material due to high WS values. Further study is needed to improve the material and evaluate its ability in promoting remineralization of the tooth structure in order for it to serve its purpose.

La présence de phosphore dans les eaux comporte des risques pour la faune aquatique et la santé humaine. Ainsi, ce projet de recherche aborde cette problématique sur le traitement des eaux usées. En effet, il s’intègre dans La Stratégie pancanadienne sur la gestion des effluents d'eaux usées municipales du Conseil canadien des ministres de l’Environnement. Cette stratégie vise la diminution de la toxicité des rejets d’eaux usées, ce qui englobe les rejets de phosphore dans certains cas. Afin de remédier à ce problème, plusieurs techniques ont été développées, dont l’adsorption qui présente de nombreux avantages et peut être réalisée avec plusieurs types de matériaux, dont les biomatériaux. Cette étude est orientée vers la recherche de nouveaux matériaux adsorbant à base de biopolymère, à savoir le chitosane. Ce projet vise le traitement du phosphate par adsorption à l’aide d’hydrogel de chitosane microsphérique (HCM) pour déterminer l’efficacité de ce dernier. Les HCM ont été préparés par une méthode séquentielle consistant en la pulvérisation d’une solution de chitosane solubilisée suivi d’un processus de gélification. La caractérisation des HCM ont été fait par la distribution de taille et le potentiel zêta. Des essais en cuvée ont été effectués avec des microbilles de chitosane afin de déterminer la cinétique d’adsorption de ce processus. L’équilibre d’adsorption a été atteint en 30 minutes et le modèle représentant le mieux le phénomène cinétique d’adsorption est de pseudo-deuxième ordre. Dans ce processus d’élimination du phosphate, plusieurs facteurs influencent l’efficacité du traitement, dont la concentration initiale des anions phosphates, la concentration en adsorbant, le pH et la température de la solution. L’analyse du coefficient de distribution du phosphate sur les HCM démontre que l’adsorption est plus efficace dans des solutions peu concentrées (dont la concentration initiale est inférieure à 50 ppm de phosphate) et que le pH favorisant l’adsorption était de l’ordre de 6.5. Selon le modèle de Boyd, le taux d'adsorption est contrôlé par la diffusion dans la couche limite. Langmuir, Freundlich et Dubinin-Radushkhevic (D-R) ont été appliqués comme modèles d’adsorption pour décrire les isothermes et les résultats ont démontré une corrélation significative avec le modèle de Freundlich (R[indice supérieur 2] = 0,975). Les valeurs moyennes d'énergie libre obtenues avec le modèle D-R dévoilent que la sorption était de nature physique. Les variations d’énergie libre de Gibbs (ΔG) et d’enthalpie (ΔH) ont démontré le caractère spontané et exothermique de la réaction. Tandis que la valeur négative de ΔS indique une diminution de la variation l'entropie.

published_or_final_version / abstract / Biochemistry / Master / Master of Philosophy

No description available.

Il existe un intérêt croissant pour le développement de levures S. cerevisiae œnologiques à rendement abaissé de conversion des sucres en alcool. Nous proposons ici une approche originale basée sur la réorientation du flux carboné vers la voie des pentoses phosphate (VPP). Dans un premier temps, nous avons montré que le flux à travers la VPP est limité par le niveau de réoxydation du NADPH et par la capacité de la voie elle même. Nous avons ensuite mis en évidence le rôle crucial du facteur de transcription Stb5 dans le maintien d'un flux basal à travers la VPP. La surexpression de STB5, couplée à l'introduction d'un système de réoxydation du NADPH, est une stratégie intéressante pour amplifier le flux à travers la VPP. En parallèle, une stratégie d'évolution dirigée basée sur l'adaptation des souches sur gluconate, un hexose mal assimilé et incorporé au niveau de la VPP, a été développée. Des souches évoluées présentant une meilleure assimilation du gluconate ont été obtenues après 70, 180 et 240 générations. En fermentation, ces souches produisent la même quantité d'éthanol que la souche parentale mais présentent des phénotypes complètement nouveaux, en particulier des performances fermentaires accrues, de faibles besoins en azote, une production d'acétate réduite et une forte production de composés aromatiques. L'analyse 13C-flux et transcriptomique d'une souche évoluée ECA5 révèle une amplification de la VPP d'un facteur 1.5 par rapport à la souche parentale EC1118, en lien avec la surexpression de GND1 et TKL1. L'expression de nombreux gènes du métabolisme azoté et de la voie Ehrlich, de l'homéostasie des protons et de la glycolyse est augmentée chez ECA5, alors que les gènes de stress et de la respiration sont globalement réprimés, de façon cohérente avec les phénotypes observés. Outre le développement de nouvelles souches d'intérêt œnologique, ce travail apporte un éclairage nouveau sur le fonctionnement de la VPP et sur ses liens avec le métabolisme central et secondaire / There is an ever-growing interest in the development of S. cerevisiae wine yeast strains with reduced ethanol yield. We proposed a novel approach based on rerouting the carbon flux towards the pentose phosphate (PP) pathway. First, we showed that the flux through the PP pathway is limited both by the absence of a mechanism for reoxidation of NADPH and by the intrinsic capacity of the pathway. We also showed that the transcription factor Stb5 plays a key role in maintaining a basal flux through the PP pathway to meet the requirements for NADPH and biosynthetic precursors. Over-expression of STB5 is a potentially useful strategy for increasing the flux through the PP pathway, provided that an alternative system of reoxidation of NADPH is expressed. In parallel, we investigated an evolutionary engineering strategy based on long-term batch culture on gluconate, a substrate poorly assimilated by S. cerevisiae cells and metabolized by the PP pathway. We selected strains that had evolved a greater gluconate consumption capacity after 70, 180 and 240 generations. During wine fermentation, these evolved strains produced similar amounts of ethanol as the parental strain but displayed completely novel phenotypes, including higher fermentation rates, lower nitrogen requirements, lower levels of acetate production, and enhanced production of aroma compounds. 13C flux analysis and transcripomic analysis of one of these strains, ECA5, showed a greater flux through the PP pathway consistent with the observed increased expression of GND1 and TKL1. The expression of genes associated with nitrogen metabolism, the Ehrlich pathway, proton homeostasis and glycolysis was stronger than in the parental strain, whereas genes involved in stress response and respiration were down-regulated, in agreement with the phenotypes of ECA5. In addition to providing strains with considerable potential for wine making, this work sheds new light on the operation of PP pathway and its links with central and secondary metabolism

The Proterozoic period saw some of the most fundamental revolutions in the biological and geological world. During this period, life diversified and set the stage for the radiation of multicellular life, altering the face of the planet in the process. The fossil record of this time is not yet fully understood, and a revisitation of a historically reported fossil deposit in the 1 Ga Torridon rocks of northwest Scotland shows that they host the fossils of the earliest non-marine eukaryotes, as well as a full and diverse fossil assemblage preserved in sedimentary phosphates and shales. Fine scale sedimentology of the fluvio-lacustrine rocks of the Torridon Group reveals them to be laid down in a laterally variable basin with distinctly different palaeoenvironments. The resident biota is seen to be similarly variable between lithofacies. New criteria for classifying taphonomic effects are presented, and used to characterise assemblages from different palaeoenvironments, with broader applications beyond this study. The Torridon rocks are also host to macrostructures on the surfaces and soles of beds, and these are interpreted as of likely biological origin, with their variability mapped between different lithofacies. High-resolution studies of both the preserved biota and the mineralogy of the preserving medium reveal in detail not only the fine scale structure of the fossil organisms, but also the reasons for their exceptional preservation. Phosphate is analysed in detail to explain its enigmatic occurrence in Proterozoic lakes. To place the Torridon deposits in context, both older and younger rocks were examined in comparison, from the 2 Ga Gunflint Formation of Ontario, Canada, and the Precambrian-Cambrian successions of eastern Newfoundland respectively. New finds of phosphate in these rocks help to reveal biochemical interactions and evolution on the early Earth, with implications for further understanding life on our own planet and elsewhere.

Calcium phosphate spheres as biomaterials have been attracting attention in recent years. Calcium phosphate occurs naturally in bone, and a hollow structure could be advantageous for drug loading and release. The combination of a calcium phosphate chemistry and a spherical-hollow structure could be an optimal strategy for specific biomaterial applications, e.g., certain dental and drug-delivery applications. The focus of this thesis is on the synthesis, formation mechanism and applications of hollow, spherical calcium phosphate particles. First, the thesis describes two methods for the synthesis of calcium phosphate (CaP) spherical particles. The first method involves synthesis of hollow calcium phosphate spherical particles via a supersaturated buffer solution based on a previous study. It was utilised to prepare spheres for applications in drug delivery and dentistry. The second method was developed to explain the mechanism of formation of hollow calcium phosphate spheres. It aimed at revealing the particular function of magnesium in the formation of spherical particles. With the use of this modified method, it could be concluded that the only ions active in the formation of CaP spherical particles are calcium ions, phosphate ions and magnesium ions. Compared with the thermodynamics of micellisation, a new model, called three ions virtual micelle effect, was developed to explain the mechanism of the Mg function. Following this mechanism, a series of spherical particles of other compositions were explored. These spherical particles included strontium phosphate, barium phosphate, calcium fluoride, strontium fluoride and barium fluoride. In this thesis, CaP spheres were studied for the controlled delivery of active ingredients and as active agent for tooth remineralisation. The first investigated application was to control the release of vancomycin from Poly(methyl methacrylate) (PMMA) cement via strontium-doped CaP spheres (SCPS). The results showed that incorporation of CaP spheres into PMMA could enhance antibiotic release while maintaining the mechanical strength. The second application was to control hydrogen peroxide (HP) release from two bleaching gel, in which CP-loaded CaP spheres were the active ingredient. One gel with low HP concentration was developed as an at-home bleaching gel, and one with high HP concentration was developed as an in-office bleaching gel. The results showed that CaP spheres would give a controlled release of peroxide and thus have a potential to increase the efficacy of the bleaching. The third application was to investigate the potential for an anti-sensitivity effect of the spheres, as active agents in toothpaste. We studied the tooth tubules occlusion and the remineralisation effect of CaP spheres. After 7 days of application, the open dentin tubules and surface were fully covered by a newly formed apatite layer, demonstrating the remineralisation potential of the spheres.