Thesis (Ph. D.)--Columbia University, 1941. / Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: p. 29.

Thesis (Ph. D.)--Columbia University, 1941. / Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: p. 29.

Bibliography: pages 83-90. / Beta alumina solid electrolyte material is conventionally synthesized by the high temperature solid state reaction of α-Al₂O₃ with soda and a stabilizer ion such as lithia or magnesia. This reaction requires a reconstructive transformation of the α-Al₂O₃ oxygen sublattice and results in a two-phase mixture of β and β"-Al₂O. In order to maximize the preferred β"-Al₂O₃ phase an additional peak heat treatment schedule is required. This work investigated the replacement of the α-Al ₂O₃ component of the reaction mixture with a range of synthetic aluminium hydroxide precursor materials. Four different aluminium hydroxide precursors were synthesized by the controlled hydrolysis of a common aluminium isopropoxide parent material. The oxygen sublattice of each aluminium hydroxide precursor was engineered by varying the alkoxide hydrolysis conditions. These precursors were used to synthesize beta alumina powders by the high temperature solid state reaction with soda and lithia, resulting in powders with a nominal composition of Li₀.₃₈Na₁.₆₅Al₁₀.₆₆O₁₇. The solid state reactions were monitored by differential thermal analysis and thermogravimetric analysis. The structural development of the reaction products with increasing temperature, was monitored by powder X-ray diffraction. A significant observation was the direct formation of single phase β"-Al₂O₃ at 1200 °C by the solid state reaction of soda and lithia with certain aluminium hydroxides. The work concludes with the proposal of a generalized mechanism relating the aluminium hydroxide precursor oxygen sublattice to the nature of the beta alumina reaction product.

The precipitation and crystallization of aluminum (oxy)hydroxides from chloride solutions by neutralization appears to be quite complex and depends on several parameters, namely, temperature, the OH/Al molar ratio, aging and solution composition. The precipitation of aluminum from AlC13 solutions was found to be complete at substoichiometric OH/Al ratios (typically ~ 2.7), and resulted in the production of an amorphous material that transformed to crystalline phases upon aging at OH/Al ≥3. The predominant phases precipitated from 0.5M AlCl3 solutions at 22, 60 and 95° C at an OH/Al ratio of 3 after 24 hours of aging were pseudoboehmite, bayerite and boehmite, respectively. Increasing the OH/Al ratio and aging time at both 22°C and 60°C promoted crystallization of bayerite over poorly crystalline boehmite. At 95°C, regardless of aging time or degree of neutralization, boehmite was consistently obtained. Increasing the AlCl3 concentration to 2.0M proved to suppress the crystallization of bayerite at 22°C and 60°C, and favoured the crystallization of pseudoboehmite instead. Between the bayerite and pseudoboehmite products, the former exhibited the best settling behaviour (30% settled slurry density after 1 week), while settling did not occur at all for the latter. / Precipitates produced from mixed AlCl3-NaCl solutions exhibited an increasing tendency to form pseudoboehmite over bayerite with increasing sodium chloride concentration. Upon neutralizing mixed AlCl3-MgCl 2 systems, the final solution pH decreased significantly with increasing magnesium chloride concentration. Furthermore, increasing concentrations of MgCl2 promoted the precipitation of poorly crystalline mixed magnesium-aluminum-hydroxide hydrates, identified as Mg6Al2(OH)18·4.5H 2O by XRD. Increases in temperature (up to 125°C), aging time (48 hours) and OH/Al ratio (3.45) were unsuccessful in improving the crystallinity or transformation of these precipitates.

Thesis (M.Eng.). / Written for the Dept. of Mining and Materials Engineering. Title from title page of PDF (viewed 2009/06/17). Includes bibliographical references.

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Immunity is known to be sexually dimorphic. This dimorphism may be attributed to the action of different hormones. Aluminum is a component of several vaccines and acts as an adjuvant of immunogenicity. The activation of the Nalp3 inflammasome plays a role in aluminum’s adjuvancy. Estrogen affects immune cells by regulating the expression of genes involved in immune-related mechanisms; such as the modulation of cytokine secretion. We hypothesized that estrogen modulates the aluminum-induced secretion of IL-1β and IL-18. Using an ex vivo mouse macrophage model this study examined: (i) the effects of estrogen on Nalp3 inflammasome genes expression and (ii) the estrogen receptor involved in the modulation of these genes. Our results indicate that estrogen up-regulates Nalp3 gene expression via ERα/β heterodimerization, and caspase-1 activity may be indirectly modulated due to the up-regulation of SPI-6 via ERβ.

Made available in DSpace on 2014-07-29T15:12:49Z (GMT). No. of bitstreams: 1 dissertacao fernando damasceno.pdf: 2320631 bytes, checksum: 27fcd42bbb835c6752f9bc475e38b816 (MD5) Previous issue date: 2009-05-26 / Aluminum hydroxides are efficient phosphate adsorbents. In this work it was investigated the adsorptions of phosphate in three different forms of aluminum hydroxide (amorphous, bayerite and pseudo-boehmite). The adsorption isotherms present the amount of phosphate adsorbed as a functions of the equilibrium concentration of orthophosphate ions aqueous solutions, in pH = 5. The products of adsorption were characterized by infrared spectroscopy, 27Al e 31P NMR spectroscopy, XRD analysis, and by zeta potential measurements of the aqueous dispersions. The adsorption isotherms of phosphate on aluminum hydroxide showed that when the hydroxides are treated with diluted phosphate solutions (< 2,0 mmolL-1) the three hydroxides adsorb similar amount of phosphate. When the hydroxides are treated with concentrated phosphate solutions (> 2,0 mmolL-1) bayerite and amorphous aluminum hydroxide incorporate much more phosphate than pseudo-boehmite. The IR and the NMR 27Al and 31P analysis of the adsorption products showed that when the adsorption is carried out in low concentrate phosphate solutions, the adsorbed species are surface aluminum phosphate complexes, while in samples treated with concentrated phosphate solution the products of adsorption are solid phases of aluminum phosphate. These results suggest that the incorporation of phosphate by the three aluminum hydroxides studied occur in two steps. In the first step the phosphate are adsorbed yielding surface complexes; in the second step the incorporation of phosphate occur via the process of aluminum dissolution and precipitation of an aluminum phosphate phase. The XRD analysis showed that the precipitate formed during the dissolution-precipitation process is amorphous and become crystalline after heated at 750 °C for 30 min. The slope of the zeta potential measurements of the aqueous suspensions of the adsorption products suggests that the concentration of the phosphate solution at which the transition of phosphate incorporation by adsorption changes to phosphate incorporation by dissolution-precipitation is similar for the three hydroxides (2 mmolL-1). The results showed that the incorporation of phosphate by precipitation-dissolution occur on the three hydroxides but with lower extension on pseudo-bohemite. This behavior might by related to the lower dissolution of pseudo-bohemite because it is more condensed than amorphous aluminum hydroxide and bayerite / Hidróxidos de alumínio são conhecidos como bons adsorventes de fosfato. Nesse trabalho investigou-se a eficiência na incorporação de fosfato de três diferentes tipos de hidróxido de alumínio (amorfo, bayerita e pseudo-boehmita). O estudo foi realizado obtendo-se as isotermas de adsorção de fosfato nos três hidróxidos. Determinou-se o potencial zeta dos produtos das adsorções e caracterizou-se os produtos por espectroscopia na região do infravermelho, espectroscopia de RMN (31P e 27Al) e difratometria de raios X. As curvas de adsorção mostram que em concentrações baixas de fosfato (< 2,0 mmolL-1) os três hidróxidos de alumínio incorporam quantidades semelhantes de fosfato, enquanto que em concentrações altas de fosfato (> 2,0 mmolL-1) o hidróxido de alumínio amorfo e a bayerita incorporam quantidades de fosfato superior à quantidade incorporada pela pseudo-boehmita. A caracterização dos produtos da adsorção por IV e RMN revelou que quando se emprega soluções diluídas de fosfato, os produtos de adsorção são complexos superficiais de ortofosfato com alumínio, o que é indicativo de que a incorporação de fosfato se dá por adsorção. Nas amostras tratadas com soluções de fosfato concentradas foi observada a presença de uma fase de fosfato de alumínio, o que sugere que nestas condições, a incorporação de fosfato ocorre principalmente pelo processo de dissolução do hidróxido de alumínio seguida de precipitação de uma fase de fosfato de alumínio. As análises por DRX dos produtos da adsorção em altas concentrações de fosfato revelaram que a fase formada durante o processo de dissolução-precipitação é amorfa e transforma-se em AlPO4 cristalino quando submetida a aquecimento a temperatura de 750 °C por 30 min. As medidas de potencial zeta dos produtos de adsorção indicam que nos três hidróxidos estudados o processo de incorporação de fosfato se dá pelos mesmos processos: inicialmente, por adsorção de fosfato e em seguida por dissolução do hidróxido e precipitação de fosfato de alumínio. Os resultados mostram que a incorporação de fosfato por dissolução-precipitação ocorre nos três hidróxidos, mas com maior extensão no hidróxido de alumínio amorfo e na bayerita e com menor extensão na pesudo-boehmita. Esse comportamento pode estar relacionado com o fato da pseudo-boehmita ser o hidróxido de alumínio mais condensado e consequentemente menos susceptível ao processo de dissolução

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The fate and mobility of boric acid in the environment is largely controlled by adsorption reactions with soil organic matter and soil minerals to form surface complexes (Marzadori et al., 1991; Su and Suarez, 1995; Yermiyahu et al., 1995; Peak et al., 2002). The effects of humic acid (HA) and dissolved CO2 on boric acid adsorption on amorphous (am)-Al(OH)3 were investigated as their influence on sorption is potentially important. Although a model system was used in the studies, the findings should be generally useful to better understand the mobility and bioavailability of boric acid in the soil ecosystems.<p>In this dissertation, boric acid adsorption on pure am-Al(OH)3 and 5% w/w HA coated am-Al(OH)3 were investigated both as a function of pH (4.5 11) and initial boric acid concentration (0 4.5 mmol L-1). Batch adsorption isotherm experiments were also conducted with samples exposed to atmospheric CO2 and anaerobic (N2) conditions to examine the effects of dissolved CO2 on boric acid adsorption. Both the pH envelope and the adsorption isotherm experiments showed that the HA coating on am-Al(OH)3 and the presence of dissolved CO2 decreased boric acid adsorption. <p>Raman spectroscopy and boron (B) K-edge X-ray Absorption Near Edge Structure (XANES) spectroscopy were used to investigate the coordination of boric acid adsorbed at mineral/water interfaces. The Raman spectroscopy was less successful than expected as there were difficulties in identifying B bands in the 5% w/w HA coated am-Al(OH)3 samples.<p>The B K-edge XANES spectroscopy yielded better results. The XANES spectra of boric acid adsorption samples showed that both trigonal BO3 and tetrahedral BO4 coordinated complexes are present on the pure and HA coated mineral surfaces. At pH 7.0 and 9.2, the adsorption of boric acid on am-Al(OH)3 is predominantly inner-sphere trigonal complexes; with minor amounts of inner-sphere tetrahedral complexes. Both macroscopic and spectroscopic experiments revealed that the combination of HA coating on am-Al(OH)3 and dissolved CO2 decreased boric acid adsorption compared to adsorption on pure am-Al(OH)3.<p>The discoveries in this dissertation contribute significantly in understanding the effects of HA and dissolved CO2 has on boric acid adsorption in the environment. Since B speciation and the stability of am-Al(OH)3 mineral and HA changes with pH, the bioavailability of B is expected to change as well with pH. The adsorption on boric acid on am-Al(OH)3 and/or HA coated am-Al(OH)3 is expected to decrease the amount of boric acid available to plants. Therefore the nutrient management regimen will have to be modified for soils that are high in natural organic matter, carbonate and/or aluminum hydroxyl species.