<p> The presence of 0.10 moles/l. of glycine, glutamic acid, aspartic acid or leucine in a saturated bicarbonate solution will promote the formation of aragonitic calcium carbonate at 25.2°C. Magnesium ion, with or without an amino acid, also promotes the formation of aragonite. With increased amino acid concentration glutamic acid and alanine tend to promote the formation of more calcitic calcium carbonate, glycine and valine tend to promote the formation of more aragonitic calcium carbonate. Lysine and alanine show an increased tendency to form calcite at higher ionic strengths (.20) whereas glutamic acid shows the reverse. Some correlation with solubility and equilibrium constants for magnesium-amino acid complexes is indicated.</p> / Thesis / Candidate in Philosophy

A new paradigm for the formation of calcified skeletons suggests mineralization proceeds through amorphous calcium carbonate (ACC) precursors. The implications of this strategy in carbonate crystallization are widespread, particularly for understanding factors controlling impurity and isotopic signatures in calcium carbonates. The first chapter is a literature review of the biomineralization processes used by two important model organisms: the sea urchin larva and the foraminifera. Sea urchin larvae provide a thoroughly studied example of mineralization by an ACC pathway that is under biological control through regulation of protein chemistry and the local mineralization environment. A review of how foraminifera produce their test structures is also examined to explore the question of how organisms regulate the Mg content in proportion to the temperature their environments of formation. The second chapter demonstrates that acidic biomolecules regulate the composition of ACC for a suite of model carboxylated molecules. The physical basis for the systematic trend in Mg content is related to the ability of the affinity of the biomolecule for binding Ca versus Mg. The third chapter builds on these findings to explore the transformation of Mg-rich ACC precursors to calcites of exceptionally high Mg-contents that could not be produced by classical step-dominated growth processes. The data indicate that these materials are likely a result of a nucleation-dominated pathway. The final, fourth chapter develops Raman spectroscopy-based calibrations for determining Mg contents in ACC. The calibrations are based upon peak position or peak width of the carbonate υ₁ stretch. / Ph. D.

Recent advances in high-resolution analytical methods have brought about a paradigm shift in our understanding of how crystalline materials are formed. The scientific community now recognizes that many earth materials form by multiple pathways that involve metastable intermediates. Biogenic calcium carbonate minerals are now recognized to develop by aggregating molecules or clusters to form amorphous phases that later transform to one or more crystalline polymorphs. Amorphous calcium carbonate (ACC) is now recognized as a precursor to CaCO₃ biominerals in a wide variety of natural environments. Recent studies suggest an ACC pathway may imprint a different set of dependencies from those established for classical growth processes. Previous ACC studies provided important insights, but a quantitative understanding of controls on ACC composition when formed at near-physiological conditions is not established. The Mg content of ACC and calcite is of particular interest as a minor element that is frequently found in final crystalline products in calcified skeletons. This three-part dissertation investigated biological and well-characterized synthetic ACC using high-energy x-ray methods, Raman spectroscopy, and mechanical tests. The findings establish chemical and physical properties of ACC in the exoskeleton of crustaceans and show Mg and P levels are tuned in the mineral component to optimize exoskeleton function that could be sensitive to ecological or environmental conditions. Calcite and chitin crystallinity exhibit a similar body-part-specific pattern that correlates directly with the mechanical strength of the exoskeleton. Insights from this study suggest precise biological control of ACC chemistry in the to regulate exoskeleton properties. Laboratory measurements using quantitative methods and compositions that approximate the physiological conditions of crustaceans, demonstrate at least two types of ACC are formed by controlling Mg concentration and alkalinity. We also find temporal changes in the short-range ordering of ACC after precipitation that is dependent upon carbonate content. The findings from this study provide a quantitative basis for deciphering relationships between ACC structures, solution chemistry, and the final transformation products under biologically relevant conditions. / Ph. D. / With the development of new imaging methods for nano-scale materials, scientists across diverse disciplines have recognized that many earth materials can form complex shapes by the formation and aggregation of nanocrystals or structureless (amorphous) particles. Biological minerals, such as shells and skeletons, are well-documented to form CaCO₃ via both of these attachment pathways, particularly amorphous calcium carbonate (ACC). However, little is known about the ACC properties and the factors that determine the final composition of skeletal minerals. This three-part dissertation focuses on ACC and calcite in the exoskeletons of crustaceans to understand how animals form composite exoskeletons of calcium carbonate minerals. This knowledge is important because CaCO₃ minerals are the primary component of the shells and skeletons of many economically important marine species. These minerals are also prevalent in the geological record as roadmaps for the evolutionary record. Amorphous and crystalline forms of CaCO₃ are also used as inert 'filler' materials for pharmaceutical products. By designing a series of experiments to characterize ACC in exoskeletons from lobsters and crabs, one part of the dissertation shows relationships between chemical composition and physical behavior of the materials. Building on this biomineral information, a separate experimental study synthesizes ACC under near-physiological conditions to show how amorphous CaCO₃ forms under controlled conditions. The findings have far-reaching consequences for understanding the complex chemistry that underlies the formation of calcium carbonate as a component of shells and skeletons, and what physical properties are optimized by the composition of these materials.

No description available.

3 pp. / Originally published: 2002 / It is important to know how much calcium you need to consume each day as more than 2500 mg of calcium each day can be harmful. Calcium should be obtained from foods and beverages first, then from supplements if necessary. Taking more than 500 mg of calcium at one time should be avoided. If you choose to take a calcium supplement, calcium citrate or calcium carbonate should be chosen.

Master of Science / Department of Grain Science & Industry / Xiuzhi Susan Sun / Bio-based protein adhesives derived from renewable resources, especially soy protein are becoming more significant due to the concerns about environment and health related issues and the limit of petroleum recourses. However, the relatively poor water resistance of soy-based protein adhesives limits its wide applications. The goal of this study was to improve the water resistance performance of soy-based protein adhesives by chemical modification. The specific objectives are 1) to modify soy protein with calcium carbonate (CaCO[subscript]3) and sodium bisulfite (NaHSO[subscript]3) as the denaturing agents; 2) to investigate the effects of calcium carbonate (CaCO[subscript]3) concentrations, curing time and curing temperatures on adhesion performance of the modified soy-based protein adhesives. In this study, the co-effects of NaHSO[subscript]3 and CaCO[subscript]3 on adhesion properties of soy protein adhesives were investigated. NaHSO[subscript]3 was added to soy flour slurry at constant concentration 6g/L, while concentration of CaCO[subscript]3 was chosen in the range of 0 to 23g/L. Soy protein adhesives modified with 4g/L and 16g/L CaCO[subscript]3 were selected to characterize the adhesion performance on 3 ply yellow pine plywood using the Response Surface Method (RSM). The effects of curing temperature and curing time on the adhesion properties were also studied. The major findings are 1) 4g/L CaCO[subscript]3, 6g/L NaHSO[subscript]3 modified soy protein adhesives (MSPA) had better adhesion performance (both dry and wet) than 16g/L CaCO[subscript]3, 6g/L NaHSO[subscript]3 MSPA; 2) Higher temperature (170°C) resulted in higher wet shear adhesion strengths; 3) Longer hot press time had positive impact on wet adhesion shear strength; and 4) 4g/L CaCO[subscript]3, 6g/L NaHSO[subscript]3 MSPA showed better adhesion shear strength after 2 weeks storage than 16g/L CaCO[subscript]3, 6g/L NaHSO[subscript]3 MSPA. In general, 4g/L CaCO[subscript]3, 6g/L NaHSO[subscript]3 MSPA, under longer hot press time and higher temperature would lead to a better adhesion performance.

Muitos organismos vivos, tal como seus constituintes, são formados por sistemas químicos complexos que envolvem a interação entre compostos orgânicos e inorgânicos ligados química e/ou fisicamente. Nestes sistemas as matrizes orgânicas são geralmente compostas por macromoléculas como polissacarídeos e proteínas. Essas moléculas têm o papel de direcionar a nucleação e o crescimento da porção inorgânica. O uso de superfícies metálicas adequadas recobertas por este tipo de filme híbrido tem potencial aplicação em implantes de substituição óssea, no qual são requeridas superfícies quimicamente inertes, mas que ao mesmo tempo estimulem processos de calcificação. Nesta tese estudou-se o crescimento de CaCO3 sobre superfícies metálicas de alumínio e aço inox recobertas por matrizes orgânicas compostas por diferentes poliânions e pelo policátion quitosana, na forma de filmes montados camada-a-camada (do inglês LbL), na presença ou não de fosfolipídeos (filmes Langmuir-Blodgett), formando um meio confinado para o crescimento do mineral. Diferentes técnicas foram utilizadas: microscopia eletrônica, microscopia de força atômica, espectroscopias de reflexão nas regiões do Uv-vis, e do infravermelho, Raman, espalhamento e difração de raios-X. Estudou-se a influência de diferentes grupos carregados dos fosfolipídeos e dos poliânions, tal como sua conformação, no crescimento de CaCO3. O tipo de interação entre o poliânion e a quitosana leva ao crescimento de matrizes poliméricas com diferenças em suas espessuras e capacidade de retenção de líquido, modificando as condições de supersaturação local e influenciando no tipo de estrutura de CaCO3. Puderam ser identificados dois polimorfos formados sobre os filmes orgânicos de poli(ácido acrílico) e quitosana, sugerindo que existem dois diferentes sítios onde a nucleação pode ser iniciada: a partir da solução de CaCl2 aprisionada na matriz polimérica e o outro a partir dos íons cálcio ligados como contra-íons aos grupos negativamente carregados do poliânion. Na presença do pré-recobrimento LB, a natureza da cabeça polar do fosfolipídeo direciona o tipo de ligação e crescimento da matriz polimérica, que levam ao crescimento de partículas de CaCO3 com morfologia e tamanho variados, explicados em termos da presença de ambientes com diferenças de concentrações locais de Ca2+. Além disso, verificou-se que a rugosidade superficial dos suportes metálicos pode favorecer a formação do polimorfo de CaCO3 cineticamente mais estável, mostrando que o processo de cristalização sobre estes suportes é um processo governado por difusão. A hidrofilicidade dos suportes é aumentada pela presença da matriz orgânica e pela presença de CaCO3 sobre as matrizes. O crescimento de CaCO3 em meios confinados tridimensionais, formados por membranas de policarbonato modificadas com filme finos de polieletrólitos, também foi estudado. Este tipo de molde leva à formação de estruturas cilíndricas que seguem a morfologia dos poros da membrana. A presença de poli(ácido acrílico) leva a formação de estruturas cilíndricas ocas, enquanto que cilindros completamente preenchidos foram formados nos poros contendo quitosana na última camada. Estes resultados foram explicados com base em diferenças na etapa de nucleação: na presença de PAA a nucleação de CaCO3 deve iniciar-se a partir dos íons Ca2+ ligados ao poliânion que, por sua vez, está ligado diretamente às paredes do molde; já na presença que quitosana, com maior capacidade de retenção de liquido e sem interação específica com Ca2+ a nucleação e seqüente cristalização devem ocorrer por todo o poro da membrana. As estruturas formadas são em sua maioria monocristais de calcita hexagonal orientadas na direção cristalográfica <2 -2 1>. / Some living organisms as well as their constituents are formed by complex chemical systems which involves the interaction among organic and inorganic compounds bounded physically or chemically. In these systems the organic matrices are usually composed by macromolecules like polysaccharides and proteins. These molecules have an important hole in tailoring the nucleation and the sequent growth of the inorganic portion. Metallic surfaces coated with these hybrid films have potential application as implants for bone substitution for which the surfaces must be chemically inert but at the same time they should stimulate calcification processes. In this present thesis we studied the growth of CaCO3 over aluminium and stainless steal surfaces coated with layer-by-layer films composed by different polyanions and chitosan as polycation, in the presence or not of phospholipids (Langmuir-Blodgett films). These organic matrices formed a confined medium within which CaCO3 particles were growth. Different techniques were applied in order to understand these systems: electronic microscopy, atomic force microscopy, UV-Vis and infrared reflection spectroscopy, Raman, and X-ray scattering and diffraction. We studied the influence of the different charged groups of the phospholipids and the polyanion as well as their conformation on CaCO3 growth. The type of interaction between the polycation and the polyanions tailors the growth of the organic matrices, forming films with different thickness and different water retention abilities which change the local supersaturation conditions changing the structure of the CaCO3 formed. Two types of CaCO3 polymorphs were growth over poly(acrylic acid) (PAA) and chitosan films suggesting that there are two sites where the nucleation can be started: the CaCl2 solution retained in the gel-like organic films and the Ca2+ ions bounded to the negative groups of the polyanion. In the presence of the LB pre-coating, the nature of the phospholipid polar head tailors the binding and the growth of the polymeric matrices leading to the formation of CaCO3 particles with difference in their sizes and morphologies. This result was explained in basis of the differences in the Ca2+ local concentrations in each situation. Moreover, it was observed that the surface roughness of the supports can favour the formation of vaterite, the kinetically most stable CaCO3 polymorph, showing that the crystallization may be guided by diffusion processes. The hidrophilicity of the supports was improved by the presence of both organic and hybrid films. The growth of CaCO3 in tridimentional confined mediums was done using LbL modified polycarbonate membranes as template. This template leads to the formation of cylindrical CaCO3 particles following the morphology of the membrane pores. CaCO3 tube-like structures were formed in presence of PAA, while rod-like structures were formed in presence of chitosan in the top LbL layer. These results were explained on basis of the difference in the nucleation stages: in the presence of PAA the nucleation starts on the Ca2+ ions bounded to the polyanion that is linked to the walls of the template; in the presence of chitosan that presents higher water retention ability and has no specific interaction with Ca2+ ions, the nucleation and sequent crystallization should occur through the entire pore of the membrane. The electron diffraction patterns showed that the CaCO3 structures are single crystals of the calcite polymorph oriented in < 2 -2 1> crystallographic direction.

Orientador: Eduardo Hochuli Vieira / Banca: Idelmo Rangel Garcia Júnior / Banca: Walter Leal de Moura / Resumo: Proposição: Este estudo teve como objetivo avaliar, através de estudo microscópico por análises histológica, histométrica e imunoistoquímica, o comportamento ósseo frente à presença de cimento de fosfato-carbonato de cálcio em defeitos experimentais. Materiais e Método: Foram confeccionados defeitos não-críticos em tíbias de 30 ratos machos adultos (Rattus norvegicus albinus, Wistar), em dois grupos, Controle e Tratado. As lâminas foram obtidas nos períodos de 10, 20 e 30 dias pósoperatórios e as imagens teciduais foram analisadas qualitativa e quantitativamente. Resultados: Não houve diferença estatística na área de neoformação óssea entre os grupos controle e tratado (P=0,258) e entre a expressão de RANK-L e OPG (P=0,589). Observou-se também áreas mínimas de invasão de tecido conjuntivo e periósteo com presença tardia do cimento em áreas distintas do defeito. Conclusão: De acordo com a metodologia aplicada, foi possível concluir que o uso de cimento de fosfato-carbonato de cálcio não alterou significativamente o processo de regeneração ósseo em tíbias de rato. / Abstract: Proposition: This study had as objective evaluates, through histological, histometric and imuno-histochemical microscopic analysis, the bone behavior face to the presence of calcium phosphate-carbonate cement in experimental defects. Materials and Method: Non-critical defects were made in tibias of 30 adult male rats (Rattus norvegicus albinus, Wistar), in two groups, Control and Treated. The slices were obtained in the periods of 10, 20 and 30 postoperative days. The snapped images were quantitative and qualitative analyzed. Results: There was not statistics difference in the bone formation area (AO) between the groups control and treated (P=0,258) and between RANK-L and OPG expressions (P=0,589). It was also observed minimal areas of invasion of conjunctive tissue and periosteum with presence of the cement in areas different of the defect. Conclusion: In agreement with the applied methodology, it was possible to conclude that the use of calcium phosphate-carbonate cement didn't alter significantly the process of bone repair in rat tibias. / Mestre

abstract: Variations of 238U/235U in sedimentary carbonate rocks are being explored as a tool for reconstructing oceanic anoxia through time. However, the fidelity of this novel paleoredox proxy relies on characterization of uranium isotope geochemistry via laboratory experimental studies and field work in modern analog environmental settings. This dissertation systematically examines the fidelity of 238U/235U in sedimentary carbonate rocks as a paleoredox proxy focusing on the following issues: (1) U isotope fractionation during U incorporation into primary abiotic and biogenic calcium carbonates; (2) diagenetic effects on U isotope fractionation in modern shallow-water carbonate sediments; (3) the effects of anoxic depositional environments on 238U/235U in carbonate sediments. Variable and positive shifts of 238U/235U were observed during U uptake by primary abiotic and biotic calcium carbonates, carbonate diagenesis, and anoxic deposition of carbonates. Previous CaCO3 coprecipitation experiments demonstrated a small but measurable U isotope fractionation of ~0.10 ‰ during U(VI) incorporation into abiotic calcium carbonates, with 238U preferentially incorporated into the precipitates (Chen et al., 2016). The magnitude of U isotope fractionation depended on aqueous U speciation, which is controlled by water chemistry, including pH, ionic strength, carbonate, and Ca2+ and Mg2+ concentrations. Based on this speciation-dependent isotope fractionation model, the estimated U isotope fractionation in abiotic calcium carbonates induced by secular changes in seawater chemistry through the Phanerozoic was predicted to be 0.11–0.23 ‰. A smaller and variable U isotope fractionation (0–0.09 ‰) was observed in primary biogenic calcium carbonates, which fractionated U isotopes in the same direction as abiotic calcium carbonates. Early diagenesis of modern shallow-water carbonate sediments from the Bahamas shifted δ238U values to be 0.270.14 ‰ (1 SD) higher than contemporaneous seawater. Also, carbonate sediments deposited under anoxic conditions in a redox-stratified lake—Fayetteville Green Lake, New York, USA— exhibited elevated δ238U values by 0.160.12 ‰ (1 SD) relative to surface water carbonates with significant enrichments in U. The significant U isotope fractionation observed in these studies suggests the need to correct for the U isotopic offset between carbonate sediments and coeval seawater when using δ238U variations in ancient carbonate rocks to reconstruct changes in ocean anoxia. The U isotope fractionation in abiotic and biogenic primary carbonate precipitates, during carbonate diagenesis, and under anoxic depositional environments provide a preliminary guideline to calibrate 238U/235U in sedimentary carbonate rocks as a paleoredox proxy. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2018

Monitoring of Bear Lake was conducted in 1981 and 1982 to describe the current limnology and trophic state of the lake. The nutrientt loadings of various parameters were measured from April, 1981 through June, 1982. The rate of coprecipitation of phosphorus was determined for different initial phosphorus concentrations by use of non-algal assays. Algal bioassays with Selenastrum capricornutum were used to determine the reduction in potential algal biomass as a result of the coprecipitation of phosphorus. The lake exhibit-.ed chemical characteristics indicative of mesotrophy or eutrophy. Total phosphorus values averaged 11μg/1 for 1981 and 20 μg/1 for 1982. A hypolimnetic accumulation of phosphorus was also not:ed for the stratified periods. Addittionally, hypolimnetic oxygen deficit values were indicative of mesotrophy in 1981 and eutrophy in 1982. The chlorophyll concentrations were characteristic of oligotrophic conditions during both years however. Phosphorus was found to be limiting production approximately 85% of the year. The Bear River Contributed approximately 60% of the total phosphorus loading to the lake in 1981 and 50% in 1982. Overall, the total phophorus loading increased 195% between the dry year, 1981, and the wet year, 1982. Vollenweider's (1976) phosphorus loading model described the loading to Bear Lake as indicative of mesotrophic conditions in 1981 and eutrophic conditions in 1982. Calcium and magnesium concentrations fluctuated widely throughout the year. The Mg:Ca molar ratio varied from 1:1 in the spring to 3.5:1 in the fall. Total hardness values did not vary in response to the changing ionic concentrations and this was attributed to preferential replacement of precipitated calcium by the Bear River inflow. Non-algal assays quantified the removal of phosphorus by coprecipitation at increasing initial phosphorus by concentration. The rate of removal initial decreased substantially as phosphorus levels increased with a shift in reaction order from second order to first order noted at approximately 50 μg/1. Predictive models were derived from the initial assays and verified with data from a separate experiment which use filtered Bear Lake water. The models accurately predicted the amount of phosphorus removed by coprecipitation at all phosphorus levels. Algal bioassays in synthetic Bear Lake and soft-water media were used to evaluate the efficiency of the coprecipitation mechanism when in competition with algae for phosphorus. An average reduction in biomass of 40% was noted between the media at similar nutrient levels.