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No description available.

Elemental proxy models for temperature and seawater chemistry begin by assuming compositional signatures reflect environmental conditions of formation. The Mg/Ca ratio in marine cements and calcified skeletal structures is a widely used proxy for reconstructing past earth environments. Many studies have positively correlated Mg content in biogenic carbonates with temperature, but it is difficult to differentiate the effect of temperature from other environmental factors. Supersaturation, precipitation rate, salinity, pH, and ion concentration have also been proposed as drivers of Mg/Ca. Furthermore, it is difficult to distinguish environmental signatures from the “vital effect,” or the influences superimposed by the growth needs and metabolic activities of the organism. To construct viable paleoenvironmental proxies from biomineral compositions, we must resolve the effects of environmental conditions from the vital effects of the organism by first understanding the underlying thermodynamic and kinetic mechanisms for incorporating minor and trace elements. Using in situ Atomic Force Microscopy, controlled solution chemistries, and different ion microprobe techniques, this dissertation investigates the kinetics and thermodynamics of calcite growth to establish an inorganic baseline for uptake of Mg. I use this information to quantify the enhancement in Mg/Ca due to the presence of hydrophilic 27-mer peptides, demonstrating a possible origin of vital effects. Likewise I measure the effect of ionic strength on signatures and find that growth rate and background electrolyte proved more important than salinity in determining Mg contents. The findings contribute to the ongoing discussion regarding the relative importance of unique seawater parameters in determining Mg/Ca in calcite. Mg contents are significantly enhanced by biomolecules relative to the amounts attributed to temperature differences, while Mg content is less influenced by salinity variation than by changing supersaturation or driving force. In addition to sorting out the relative importance of environmental factors, our results begin to address the interplay of these different parameters in concert, and at different scales. At sites of calcification, the local biochemistry within an organism may shift in response to more saline waters. At a geological scale, interpreting past temperatures and particularly those of the Last Glacial Maximum depends on our ability to sort out and account for this interplay of salinity and temperature on Mg/Ca. Processes underlying inorganic and biogenic carbonate mineralization and interpretations of their formation environments are better understood by examining the influence of environmental parameters and biomolecular chemistry on kinetics and thermodynamics of calcite growth and stability. / Ph. D.

Carbonic anhydrase (CA) from acetate-grown Methanosarcina thermophila strain TM-1 was purified> 10,OOO-fold (22% recovery) to apparent homogeneity and a specific activity of 4,900 units mg⁻¹.The gene encoding this CA was isolated fronl a partial genomic library on a 12-kb fragment and sequenced. Comparison of the deduced anlino acid sequence with the N-terminaI sequence of the purified protein shows that the gene encodes an additional 34 N-terminal residues with properties characteristic of signal peptides in secretory proteins. The deduced amino acid sequence has no significant identity to any known CAs, but has, among others, 35% sequence identity to the first 197 deduced N-terminal amino acids of a proposed CO₂-concentrating-mechanism protein from <i>Synechococcus</i> sp. strain PCC7942. / Ph. D.

The Ca-ATPase is an integral membrane enzyme which translocates two calcium ions from the cytoplasm of the cell to the sarcoplasmic reticulum lumen utilizing ATP breakdown as its energy source, in order to promote muscle relaxation. The focus of this research is the cardiac isoform of the Ca-ATPase which undergoes allosteric regulation by the phosphoprotein phospholamban (PLN). The Ca-ATPase is thought to be a target for nitrative stress and is affected by several chronic diseases of the heart. In the heart, age-based nitration of the Ca-ATPase inhibits Ca²⁺ transport activity but the physical mechanism by which nitration inhibits Ca-ATPase activity is not understood. Conversely, nitroxyl (HNO), a new candidate for drug therapy for congestive heart failure (CHF), improves overall cardiovascular function by increasing Ca-ATPase activity in the heart. However, the physical mechanism for this activation is unknown. Therefore, we have used enzyme kinetics, fluorescence spectroscopy, and EPR spectroscopy studies to determine the effects of ONOO⁻ and HNO on the Ca-ATPase and the physical regulation of the Ca-ATPase by PLN. Treatment of Ca-ATPase with a nitrating agent, ONOO⁻, inhibited Ca-ATPase activity, and the [ONOO⁻]-dependent inhibition of the Ca-ATPase was more effective in the presence of PLN. ONOO⁻ did not affect the [Ca²]-dependence of Ca-ATPase activity either in the presence or absence of PLN. ONOO⁻ had no effect on Ca-ATPase rotational mobility or oligomeric interactions, as affected by PLN, but ONOO⁻ decreased the amplitude of the Ca²⁺-dependent E2 to E1•Ca2 conformational change, both in the absence and presence of PLN. Treatment with HNO had no affect on the [Ca²⁺]-dependence of Ca-ATPase activity in the absence of PLN; however in the presence of PLN, the [Ca²⁺]-dependent activity was shifted to lower Ca²⁺ levels and corresponded to the uncoupling of PLN from the Ca-ATPase. HNO decreased Ca-ATPase rotational mobility and increased the Ca-ATPase Ca²⁺-dependent conformational transition, consistent with uncoupling PLN from the Ca-ATPase. Taken together, these results suggest that ONOO⁻ inactivates a fraction of enzyme units to lower overall enzyme activity, whereas HNO uncouples PLN from the Ca-ATPase with increases in Ca-ATPase conformational flexibility and Ca-ATPase activity. / Ph. D.

Although scholars have often acknowledged the spirituality in the writings of Clement of Alexandria (cir. 150-215 AD), a thorough study of the Platonic category θεωρία as it appears in this second century Father has never been undertaken. Most studies on Christian spirituality either ignore Clement's role altogether, or rush past him with little comment in favor of the great Origen (cir. 185-255 AD). Stromateis, Clement's most enigmatic work, contains over 75 occurrences of θεωρία. A close examination of these texts reveals that his use of the term is somewhat different from two of his greatest philosophical and spiritual mentors, Plato and Philo. Clement uses this term (usually translated "contemplation") to refer to a spiritual experience which occurs in space and time, as well as an ethereal one and one which occurs in the mind. A possible explanation for this difference lies with Clement's claim in the opening chapter of the work: he is the recipient of an oral tradition which has never been recorded, but which he plans to include in the Stromateis. This thesis demonstrates: 1) that Clement is the first Christian writer to adapt this philosophical category into Christian spirituality; 2) the primary purpose of Stromateis is to present the third stage in a spiritual pathway - to reveal θεωρία as the spiritual "meat" for the advanced believer; and 3) to present God and His contact with the Christian as immediate. In a radical move, going against the philosophical setting of the day, Clement presents this Platonic category as a means for the Christian to experience an immanent God.

Esta pesquisa é basicamente desenvolvida em duas partes: (i) um capítulo introdutório, discutindo os principais problemas que envolvem a obra, além de algumas informações que julgamos relevantes acerca de alguns personagens que figuram no livro II; e (ii) a tradução do livro II das Helênicas. Em ambas as duas partes inserimos notas de rodapé de natureza histórica, linguística e/ou literária que contribuem para o esclarecimento de aspectos relevantes do texto. Na primeira parte desta pesquisa, fazemos um breve resumo das Helênicas, com ênfase no livro II. Com base na leitura da bibliografia crítica, comentamos brevemente algumas das principais questões em torno da obra: (i) a questão da composição; (ii) a suposição de que a primeira parte das Helênicas seja uma continuidade da História da Guerra do Peloponeso de Tucídides; (iii) nexos com seus predecessores: Heródoto e Tucídides; (iv) o caráter didático de cunho moral das Helênicas e, finalmente, (v) a repercussão e receptividade das Helênicas na Antiguidade e nos estudos mais recentes. Para a tradução e o estudo do texto grego, utilizamos a edição de E. C. Marchant (Oxford Classical Texts, 2008) / This research is basically divided in two parts: (i) an introductory chapter, discussing the main issues concerning the work, and providing additionally some biographical details about the main characters of Book II; and (ii) the translation into Portuguese of Book II of Xenophon\'s Hellenica. The study is enriched by footnotes with historical, linguistic and/or literary informations in order to clarify relevant aspects of the text. In the introductory chapter, we present a brief summary of Xenophon\'s Hellenica emphasizing the content of Book II. Based on the recent literature on Xenophon, we comment briefly some important issues concerning the work as a whole, such as (i) the problem of its composition and arrangement; (ii) the assumption that the first part of the Hellenica consists in a continuation of Thucydides\' History of the Peloponnesian War; (iii) Xenophon\'s relationship with his predecessors: Herodotus and Thucydides; (iv) the ethical and didactical purpose of the Hellenica, and finally (v) the reception of the Hellenica in Antiquity and in the modern and contemporary literature on Xenophon. For the translation and the study of the Greek text we have used EC Marchant\'s edition (Oxford Classical Texts, 2008)

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Esta pesquisa é basicamente desenvolvida em duas partes: (i) um capítulo introdutório, discutindo os principais problemas que envolvem a obra, além de algumas informações que julgamos relevantes acerca de alguns personagens que figuram no livro II; e (ii) a tradução do livro II das Helênicas. Em ambas as duas partes inserimos notas de rodapé de natureza histórica, linguística e/ou literária que contribuem para o esclarecimento de aspectos relevantes do texto. Na primeira parte desta pesquisa, fazemos um breve resumo das Helênicas, com ênfase no livro II. Com base na leitura da bibliografia crítica, comentamos brevemente algumas das principais questões em torno da obra: (i) a questão da composição; (ii) a suposição de que a primeira parte das Helênicas seja uma continuidade da História da Guerra do Peloponeso de Tucídides; (iii) nexos com seus predecessores: Heródoto e Tucídides; (iv) o caráter didático de cunho moral das Helênicas e, finalmente, (v) a repercussão e receptividade das Helênicas na Antiguidade e nos estudos mais recentes. Para a tradução e o estudo do texto grego, utilizamos a edição de E. C. Marchant (Oxford Classical Texts, 2008) / This research is basically divided in two parts: (i) an introductory chapter, discussing the main issues concerning the work, and providing additionally some biographical details about the main characters of Book II; and (ii) the translation into Portuguese of Book II of Xenophon\'s Hellenica. The study is enriched by footnotes with historical, linguistic and/or literary informations in order to clarify relevant aspects of the text. In the introductory chapter, we present a brief summary of Xenophon\'s Hellenica emphasizing the content of Book II. Based on the recent literature on Xenophon, we comment briefly some important issues concerning the work as a whole, such as (i) the problem of its composition and arrangement; (ii) the assumption that the first part of the Hellenica consists in a continuation of Thucydides\' History of the Peloponnesian War; (iii) Xenophon\'s relationship with his predecessors: Herodotus and Thucydides; (iv) the ethical and didactical purpose of the Hellenica, and finally (v) the reception of the Hellenica in Antiquity and in the modern and contemporary literature on Xenophon. For the translation and the study of the Greek text we have used EC Marchant\'s edition (Oxford Classical Texts, 2008)