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Rocha, Stella Alonso. "Calculo do equilibrio de fases solido-liquido em misturas binarias por meio de tecnicas de minimização e analise de convexidade." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266226.
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Orientador: Reginaldo GuirardelloDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Esse trabalho é de caráter teórico e computacional e tem como objetivo o estudo e aplicação de técnicas de otimização para cálculo do equilíbrio sólido-líquido de misturas graxas binárias de origem natural, utilizando dois métodos: um problema de Programação Não-linear, implementado no software GAMS e o outro, uma análise de equações fazendo uso das condições de Kuhn-Tucker. O cálculo do equilíbrio de fases baseia-se na minimização da energia livre de Gibbs do sistema. Para a representação termodinâmica das misturas são utilizados modelos termodinâmicos capazes de representar as fases líquida e sólida. As misturas estudadas são compostas por ácidos graxos e triglicerídeos, as quais foram divididas conforme as características dos compostos utilizados: ácidos graxos saturados, insaturados e triglicerídeos, com diferentes combinações de compostos. A modelagem das fases foi desenvolvida gradativamente, inicialmente consideraram-se as fases ideais, posteriormente a fase líquida foi modelada pela equação de Margules 2-sufixos, com a fase sólida permanacendo ideal, e por fim a fase sólida foi descrita pela equação de SLAUGHTER & DOHERTY e a líquida continou a ser modelada por Margules 2-sufixos. Os modelos desenvolvidos nesse trabalho são classificados como modelos de programação não-linear convexa, o que garante a busca pelo mínimo global. Assim, quando aplicados à linguagem de programação GAMS, utilizando o solver CONOPT, ou quando utilizando as equações encontradas analiticamente, através de microcomputadores, os resultados obtidos garantem que a mínima energia livre de Gibbs foi encontrada e que a mistura está em equilíbrio. Os resultados encontrados foram comparados com os dados medidos por ROLEMBERG (2002), pela técnica DSC, apresentando uma satisfatória proximidade entre eles
Abstract: This work has a theorical and computational character which objective is the study and aplication of optimization technique for the solid-liquid equilibria calculation of binary fat mixtures with natural origin. Two methods was used: One Nonlienar Program problem,an algorithm using the software GAMS and the other, analysis of equations that use the Kuhn-Tucker constrains applied in softwares which can execute conventionals calculation, like Microsoft Excel. The calculation of phasee equilibria is based on the minimization of Gibbs free energy of the sistem. The termodynamic representation of mixtures use models which can represent liquid and solid phases. The mixtures are composed for fat acids and triglycerides which are divided on three characteristics: saturated fatty acids, unsatureted fatty acids and trigycerides with differents combination among themselves. The phases¿ modeling was developed starting for phases on ideal state. In the second step, the solid phase was considered ideal and the liquid phase was modeled using the Margules Model. At the end, it was used the Slaughter & Doherty equation to modeling the solid phase and the Margules Model continued to be used for the liquid phase. The models developed in this work are nonliner programming and convex equations, these characteristics are the proof that the optimal point found is the global optimum. So using the methods propoused in this work, the results, certainly are the minim Gibbs free energy and the compound are in equilibrium. The results founded were compared with experimental data for ROLEMBERG (2002), that were obtained with DSC technique, with satisfactory proximity among them
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
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Sommacal, Silvano, and silvano sommacal@anu edu au. "Computational petrology: Subsolidus equilibria in the upper mantle." The Australian National University. Research School of Earth Sciences, 2004. http://thesis.anu.edu.au./public/adt-ANU20050415.151025.
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Processes that take place in the Earths mantle are not accessible to direct observation. Natural samples of mantle material that have been transported to the surface as xenoliths provide useful information on phase relations and compositions of phases at the pressure and temperature conditions of each rock fragment. In the past, considerable effort has been devoted by petrologists to investigate upper mantle processes experimentally. Results of high temperatures, high pressure experiments have provided insight into lower crust-upper mantle phase relations as a function of temperature, pressure and composition. However, the attainment of equilibrium in these experiments, especially in complex systems, may be very difficult to test rigorously. Furthermore, experimental results may also require extrapolation to different pressures, temperatures or bulk compositions. More recently, thermodynamic modeling has proved to be a very powerful approach to this problem, allowing the deciphering the physicochemical conditions at which mantle processes occur. On the other hand, a comprehensive thermodynamic model to investigate lower crust-upper mantle phase assemblages in complex systems does not exist. ¶
In this study, a new thermodynamic model to describe phase equilibria between silicate and/or oxide crystalline phases has been derived. For every solution phase the molar Gibbs free energy is given by the sum of contributions from the energy of the end-members, ideal mixing on sites, and excess site mixing terms. It is here argued that the end-member term of the Gibbs free energy for complex solid solution phases (e.g. pyroxene, spinel) has not previously been treated in the most appropriate manner. As an example, the correct expression of this term for a pyroxene solution in a general (Na-Ca-Mg-Fe2+-Al-Cr-Fe3+-Si-Ti) system is presented and the principle underlying its formulation for any complex solution phase is elucidated.¶
Based on the thermodynamic model an algorithm to compute lower crust-upper mantle phase equilibria for subsolidus mineral assemblages as a function of composition, temperature and pressure has been developed. Included in the algorithm is a new way to represent the total Gibbs free energy for any multi-phase complex system. At any given temperature and pressure a closed multi-phase system is at its equilibrium condition when the chemical composition of the phases present in the system and the number of moles of each are such that the Gibbs free energy of the system reaches its minimum value. From a mathematical point of view, the determination of equilibrium phase assemblages can, in short, be defined as a constrained minimization problem. To solve the Gibbs free energy minimization problem a Feasible Iterate Sequential Quadratic Programming method (FSQP) is employed. The systems Gibbs free energy is minimized under several different linear and non-linear constraints. The algorithm, coded as a highly flexible FORTRAN computer program (named Gib), has been set up, at the moment, to perform equilibrium calculations in NaO-CaO-MgO-FeO-Al2O3-Cr2O3-Fe2O3- SiO2-TiO2 systems. However, the program is designed in a way that any other oxide component could be easily added.¶
To accurately forward model phase equilibria compositions using Gib, a precise estimation of the thermodynamic data for mineral end-members and of the solution parameters that will be adopted in the computation is needed. As a result, the value of these parameters had to be derived/refined for every solution phase in the investigated systems. A computer program (called GibInv) has been set up, and its implementation is here described in detail, that allows the simultaneous refinement of any of the end-member and mixing parameters. Derivation of internally consistent thermodynamic data is obtained by making use of the Bayesian technique. The program, after being successfully tested in a synthetic case, is initially applied to pyroxene assemblages in the system CaO-MgO-FeO-Al2O3-SiO2 (i.e. CMFAS) and in its constituent subsystems. Preliminary results are presented.¶
The new thermodynamic model is then applied to assemblages of Ca-Mg-Fe olivines and to assemblages of coexisting pyroxenes (orthopyroxene, low Ca- and high Ca clinopyroxene; two or three depending on T-P-bulk composition conditions), in CMFAS system and subsystems. Olivine and pyroxene solid solution and end-member parameters are refined, in part using GibInv and in part on a trial and error basis, and, when necessary, new parameters are derived. Olivine/pyroxene phase relations within such systems and their subsystems are calculated over a wide range of temperatures and pressures and compare very favorably with experimental constraints.
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Amon, Lynn. "Methods for calculating the free energy of atomic clusters /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/8595.
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Yong, May Yee. "A free energy minimization approach to protein folding and structure prediction." Thesis, University of Essex, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437815.
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Morozov, Alexandre V. "Free energy functions in protein structural stability and folding kinetics /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/9690.
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Ermantraut, Andreas [Verfasser], Ingo [Akademischer Betreuer] Krossing, and Thorsten [Akademischer Betreuer] Koslowski. "The experimental determination of the Gibbs free energy of transfer of single Ions without sxtra‐thermodynamic assumptions." Freiburg : Universität, 2018. http://d-nb.info/1165503239/34.
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Ridl, Kent Stephen. "Free Energy Minimization and Multicomponent, Multi-Phase Lattice Boltzmann Simulations of Van Der Waals Fluid Mixtures." Thesis, North Dakota State University, 2018. https://hdl.handle.net/10365/28732.
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In this thesis, we develop a general framework for the lattice Boltzmann method to simulate multiphase systems with an arbitrary number of components. Theoretical expectations are easily visualized for binary mixtures, so we focus on characterizing the performance of the method by numerically minimizing the free energy of a binary van der Waals mixture to generate phase diagrams. Our phase diagrams contain very intriguing features that are not well-known in today’s physics community but were understood by van der Waals and his colleagues at the turn of the 20th century. Phase diagrams and lattice Boltzmann simulation results are presented in a density-density plane, which best matches with LB simulations performed at constant volume and temperature. We also demonstrate that the algorithm provides thermodynamically consistent results for mixtures with larger numbers of components and high density ratios. All of the theoretical phase diagrams are recovered well by our lattice Boltzmann method.
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Bronneberg, Rob Anna Hubertus [Verfasser]. "MOQUAC, a New expression for the excess Gibbs free energy based on molecular orientations / Rob Anna Hubertus Bronneberg." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1027607713/34.
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Mao, Xin. "Computational exploration of high efficient catalysts for clean energy conversion." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/227951/1/Xin_Mao_Thesis.pdf.
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This thesis was a computational study of designing novel catalysts for three main circles involved in electrocatalysis. The method was based on density functional theory to design a series of clean, cheap, and efficient catalysts for water circle, carbon circle, and nitrogen circle reactions. The outcomes of this thesis are expected to provide some theoretical guidance for the global energy shortage and environmental challenges.
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Stepanian, S. G., A. Yu Ivanov, and L. Adamowicz. "Effect of low-temperature argon matrices on the IR spectra and structure of flexible N-acetylglycine molecules." AMER INST PHYSICS, 2016. http://hdl.handle.net/10150/622884.
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A study of how the matrix environment impacts the structure and IR spectra of N-acetylglycine conformers. The conformational composition of this compound is determined according to an analysis of the FTIR spectra of N-acetylglycine isolated in low temperature argon matrices. Bands of three N-acetylglycine conformers are identified based on the spectra: one major and two minor. The structure of all observed conformers is stabilized by different intramolecular hydrogen bonds. The Gibbs free energies of the conformers were calculated (CCSD(T)/CBS method), and these energy values were used to calculate conformer population at a temperature of 360 K, of which 85.3% belonged to the main conformer, and 9.6% and 5.1% to the minor conformers. We also determined the size and shape of the cavities that form when the N-acetylglycine conformers are embedded in the argon crystal during matrix deposition. It is established that the most energetically favorable cavity for the planar main conformer is the cavity that forms when 7 argon atoms are replaced. At the same time, bulky minor conformers were embedded into cavities that correspond to 8 removed argon atoms. We calculated the complexation energy between argon clusters and conformers, and the deformation energy of the argon crystal and the N-acetylglycine conformers. The matrix-induced shifts to the conformer oscillation frequency are calculated. Published by AIP Publishing.
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Borghi, Daniela de Freitas 1983. "Aplicação de métodos de otimização no cálculo de equilíbrio de misturas de biodiesel com utilização de metodologias rigorosas para estimativa de propriedades termodinâmicas." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266048.
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Orientadores: Reginaldo Guirardello, Charlles Rubber de Almeida AbreuTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: Atualmente, a produção de biodiesel tem sido objeto de estudo em diversos países devido à previsão de exaustão das fontes petrolíferas e também às suas características, já que este combustível possui vantagens ambientais em relação à emissão de gases poluentes. Trata-se de uma fonte de energia renovável e as matérias-primas para a sua produção são abundantes no Brasil. O biodiesel é produzido através da transesterificação de gordura animal ou óleo vegetal. Porém, os reagentes (óleo e etanol/metanol) e os produtos (éster metílico/etílico de ácidos graxos e glicerol) são parcialmente solúveis durante o processo. Assim, o conhecimento do equilíbrio de fases das misturas envolvidas em sua produção é um fator importante na otimização das condições da reação e da separação final dos produtos. Dentro deste contexto, o presente trabalho teve como objetivo realizar cálculos de equilíbrio de misturas de compostos envolvidos nos processos de produção de biodiesel, utilizando técnicas de otimização global. A modelagem matemática requer o conhecimento de propriedades termoquímicas de todas as espécies envolvidas e do equilíbrio de fases do sistema. Tais informações foram obtidas a partir do uso de uma metodologia utilizando o software Gaussian 03 e o método COSMO-SAC. E o equilíbrio de fases foi realizado através da minimização da energia de Gibbs do sistema. Foram obtidos perfis sigma a serem utilizados no método COSMO-SAC através do software MOPAC. Eles foram comparados com os perfis sigma de um banco de dados do grupo Virginia Tech (VT-2005) e percebeu-se que, apesar de apresentarem diferenças, qualitativamente eles possuem muitas semelhanças. Foi verificada a eficiência do modelo COSMO-SAC em predizer os coeficientes de atividade de uma mistura binária de metanol e glicerol e observou-se que os desvios médios absolutos entre os valores experimentais e os calculados estão acima de 27%, o que é um desvio muito alto. Além disso, utilizou-se a metodologia da minimização da energia de Gibbs para a realização do cálculo de equilíbrio de fases de misturas binárias contendo água, metanol e glicerol, com o auxílio da ferramenta computacional GAMS. Os desvios médios absolutos obtidos variaram de 1,55 a 7,96%, dependendo da mistura. Portanto, este modelo ainda precisa de refinamentos para se tornar uma ferramenta confiável
Abstract: Biodiesel production has been studied in several countries due to the forecast of petroleum sources depletion and to its characteristics, since this fuel has environmental advantages due to lower pollutant gas emissions. It is a renewable source of energy and raw materials for its production are abundant in Brazil. Biodiesel is produced by transesterification of vegetable oils or animal fat. However, reagents (oil and ethanol/methanol) and products (fatty acids ethyl/methyl ester and glycerol) are partially soluble in the process. Therefore, knowledge of the phase equilibrium mixtures involved in its production is an important factor in optimizing the reaction conditions and separation of the final products. In this context, this work aims to perform equilibrium calculations of mixtures of compounds involved in the biodiesel production process using global optimization techniques. Mathematical modeling requires the knowledge of thermochemical properties of all the species involved and the phase equilibrium of the system. Such information was obtained with a methodology using the Gaussian 03 software and COSMO-SAC method. The phase equilibrium was achieved by minimizing the Gibbs energy of the system. Sigma profiles to be used in COSMO-SAC method were obtained using the MOPAC software. It was compared with the sigma profiles from Virginia Tech group database (VT-2005) and it was realized that, despite having differences, qualitatively it is similar. The efficiency of COSMO-SAC model to predict the activity coefficients of a binary mixture of methanol and glycerol was verified and it was found that the average absolute deviation between experimental and calculated values are above 27%, a very high value. In addition, a methodology of Gibbs energy minimization we used to perform the calculation of the phase equilibrium of binary mixtures containing water, methanol and glycerol, with the GAMS software. The mean absolute deviations obtained ranged from 1.55 to 7.96% depending on the mixure. Therefore, this model still needs refinements to become a reliable tool
Doutorado
Engenharia Química
Doutora em Engenharia Quimica
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Negus, Charles H. "An Interactive Chemical Equilibrium Solver for the Personal Computer." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36826.
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The Virginia Tech Equilibrium Chemistry (VTEC) code is a keyboard interactive, user friendly, chemical equilibrium solver for use on a personal computer. The code is particularly suitable for a teaching / learning environment. For a set of reactants at a defined thermodynamic state given by a user, the program will select all species in the JANAF thermochemical database which could exist in the products. The program will then calculate equilibrium composition, flame temperature, and other thermodynamic properties for many common cases. Examples in this thesis show VTEC's ability to predict chemical equilibrium compositions and flame temperature for selected reactions, and demonstrate how VTEC can substitute for and aid in the design of lab experiments, and identify trends in parametric studies.
The 1976 NASA Lewis Chemical Equilibrium Code (CEC76) from which VTEC has been adapted uses Lagrangian multipliers to minimize free energy. CEC76 was written for mainframe computer use. Later versions of CEC76, adapted for personal computer use are available for a fee and have a very minimal user interface.Master of Science
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Jesus, Lorena Brancaglião de. "Aplicação de simulated annealing para o calculo de equilibrio de fases de misturas complexas." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266792.
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Orientadores: Reginaldo Guirardello, Lucio Cardozo-FilhoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: O conhecimento do equilíbrio de fases é de grande importância no projeto e análise de uma grande variedade de processos químicos, incluindo reatores e unidades de separação. É o caso, por exemplo, da indústria de produção de óleos vegetais e de produção de ácido cítrico. Geralmente, sistemas de interesse da indústria alimentícia são formados por muitos componentes. A determinação e o cálculo das propriedades termodinâmicas e do equilíbrio de fases, nesses casos, são bastante complicados. Devido à natureza não-convexa e não-linear de modelos termodinâmicos, necessários para descrever o problema do equilíbrio de fases, há um grande interesse na aplicação de técnicas de otimização para descrever o comportamento do equilíbrio. Problemas de otimização global, técnicas rápidas, seguras e robustas que têm certo grau de confiança para achar a solução global não foram ainda completamente desenvolvidos. Por isso, estudos desses métodos têm sido foco na simulação e otimização na engenharia química. Este trabalho tem como objetivo o estudo e aplicação de um método de busca estocástica para otimização global no cálculo do equilíbrio de fases de misturas complexas de sistemas de interesse da industria alimentícia. O método de busca estocástica utilizado é o algoritmo ¿simulated annealing¿ (SA) devido à sua principal vantagem em poder evitar mínimos locais (teoricamente) e de ser de fácil aplicação. A determinação do equilíbrio de fases é feita pela minimização da energia livre de Gibbs do sistema. Para a representação termodinâmica de misturas complexas de interesse da indústria alimentícia foram empregados os modelos NRTL (Non-Random-Two-Liquid) e UNIQUAC (UNIversal QUAsi-Chemical). Os dados experimentais utilizados como estudo de caso foram obtidos na literatura e foram caracterizados por meio de pseudo-componentes, uma vez que são formados por muitas substâncias diferentes. Os resultados obtidos para os casos estudados demonstraram que a aplicação da técnica de SA para minimização global da energia livre de Gibbs permite, juntamente com os modelos NRTL e UNIQUAC, a representação confiável dos dados experimentais em tempos muito bons de execução. Além disso, a técnica de SA mostrou-se robusta levando a resultados de mínimo global independentemente da estimativa inicial, mesmo para casos fortemente não-lineares e não-convexos
Abstract: In many industrial processes, during the phase of refining and separation, products form very complex mixtures. It is the case, for example, of the vegetal oil and citric acid industries. As these mixtures are formed by many components, determination and calculation of thermodynamic properties and phase equilibrium are very complicated. In this way, the use of the most rigorous methods able to calculate the phase equilibrium and to analyse the stability of phases of these mixtures becomes necessary. In this work, the determination of phase equilibrium is done by minimization of the Gibbs free energy of the system. The NRTL (Non-Random-Two-Liquid) and UNIQUAC (UNIversal QUAsi-Chemical) models were used for the thermodynamic representation of the complex mixtures, which were characterized by means of pseudo-components. Under conditions of constant temperature and pressure, the necessary and sufficient condition for a multiphase and multicomponent system to reach the equilibrium is that the Gibbs free energy is a global minimum. Based on this principle, equilibrium problems can be formulated and solved as otimization problems. The objective function for these problems is generaly highly nonlinear and usually nonconvex, and methods of global optimization are generally necessary for its minimization. The technique of global optimization studied and applied in this work is a method of random search named Simulated Annealing (SA), whose main advantages are the ability to avoid local minimum and the ease of application. The results obtained for the studied cases have demonstrated that the application of the technique of SA for global minimization of the Gibbs free energy, together with the models NRTL and UNIQUAC, allows a reliable representation of the experimental data in very short execution times. Moreover, the SA technique was robust, leading to the global minima independently of the initial estimate even for highly nonlinear and nonconvex cases
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
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Freitas, Antonio Carlos Daltro de 1986. "Análise termodinâmica da transformação de biomassa em combustíveis utilizando técnicas de otimização global." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266028.
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Orientador: Reginaldo GuirardelloTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: Há um crescente interesse por fontes alternativas de energia limpa, segura e renovável, e por tecnologias de transformação destas fontes em combustíveis. Dentre esses processos, a reação de gaseificação utilizando água supercrítica (SCWG), visando a produção de hidrogênio e a reação de síntese de Fischer-Tropsch (FT) visando a produção de combustíveis líquidos, vêm ocupando papel de destaque. Nesse contexto, essa tese teve como objetivo realizar a análise termodinâmica das reações envolvidas na transformação de biomassa em combustíveis, utilizando para isso, técnicas de otimização global. Foram aplicadas as metodologias de minimização da energia de Gibbs para sistemas com pressão e temperatura constantes e de maximização da entropia para sistemas com pressão e entalpia constantes. Os problemas foram formulados na forma de programações lineares e não lineares, e as metodologias propostas foram implementadas e resolvidas no software GAMS. Primeiramente foi realizada a análise termodinâmica da transformação de diferentes fontes renováveis de energia, tais como etanol, glicerol, glicose, celulose, lignina, bagaço de cana de açúcar e biomassa microalgal, em hidrogênio ou gás de síntese por meio da reação de SCWG. Posteriormente o uso do gás de síntese produzido, foi termodinamicamente avaliado visando a produção de combustíveis líquidos, por meio da reação de síntese de Fischer-Tropsch. Com esse trabalho, contribuímos com uma maior elucidação das condições reacionais mais favoráveis para cada um dos processos analisados, estudando ainda estratégias para se obter uma maior conversão dos reagentes e aumentar a produtividade dos compostos de interesse, além de verificar o comportamento energético dos sistemas associados
Abstract: There is a growing interest in alternative sources of clean, safe and renewable energy, and in technologies for processing these sources into fuels. Among these processes, the supercritical water gasification (SCWG) reaction, for hydrogen production, and the Fischer-Tropsch (FT) synthesis reaction, for liquid fuels production, have occupied a prominent role. In this context, this thesis performed the thermodynamic analysis of reactions involved in the transformation of biomass into fuels, using for it, global optimization techniques. Methodologies are applied to minimize Gibbs energy, in systems with constant pressure and temperature, and maximize the entropy, in systems with constant pressure and enthalpy. The problems are formulated in the form of linear and nonlinear programming, and the proposed methodologies are implemented and solved in the software GAMS. The thermodynamic analysis of the transformation of different sources such as ethanol, glycerol, glucose, cellulose, lignin, sugarcane bagasse and microalgal biomass in hydrogen or syngas, through the SCWG reaction are performed first. Later, the use of syngas produced are thermodynamically evaluated for the production of liquid fuels by the Fischer-Tropsch synthesis reaction. With this work we contribute to a further elucidation of the more favorable reaction conditions for each of the cases examined, also considering strategies to increase the conversion of reactants and the productivity of the desired products, as well as the realization of the energy characterization of the processe
Doutorado
Engenharia Química
Doutor em Engenharia Química
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Nohra, Michael. "Molecular Dynamics Study of Novel Cryoprotectants and of CO2 Capture by sI Clathrate Hydrates." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23084.
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The first project in this work used classical molecular dynamics to study the ice recrystallization inhibition potential of a series of carbohydrates and alcochols, using the hydration index, partial molar volumes and isothermal compressibilities as parameters for measuring their cryogenic efficacy. Unfortunately, after 8 months of testing, this work demonstrates that the accuracy and precision of the density extracted from simulations is not sufficient in providing accurate partial molar volumes. As a result, this work clearly demonstrates that current classical molecular dynamics technology cannot probe the volumetric properties of interest with sufficient accuracy to aid in the research and development of novel cryoprotectants.The second project in this work used molecular dynamics simulations to evaluate the Gibbs free energy change of substituting CO2 in sI clathrate hydrates by N2,CH4, SO2 and H2S flue gas impurities under conditions proposed for CO2 capture (273 K, 10 bar). Our results demonstrate that CO2 substitutions by N2 in the small sI cages were thermodynamically favored. This substitution is problematic in terms of efficient CO2 capture, since the small cages make up 25% of the sI clathrate cages, therefore a significant amount of energy could be spent on removing N2 from the flue gas rather than CO2. The thermodynamics of CO2 substitution by CH4, SO2 and H2S in sI clathrate hydrates was also examined. The substitution of CO2 by these gases in both the small and large cages were determined to be favorable. This suggests that these gases may also disrupt the CO2 capture by sI clathrate hydrates if they are present in large concentrations in the combustion flue stream. Similar substitution thermodynamics at 200 K and 10 bar were also studied. With one exception, we found that the substitution free energies do not significantly change and do not alter the sign of thermodynamics. Thus, using a lower capture temperature does not significantly change the substitution free energies and their implications for CO2 capture by sI clathrate hydrates.
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Bechtel, Tom B. "Electrochemical partitioning of actinides and rare earths in molten salt and cadmium solvents : activity coefficients and equilibrium simulation /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841263.
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Manjunath, Vishal Jain. "Effect Of Interfacial Top Electrode Layer On The Performance Of Niobium Oxide Based Resistive Random Access Memory." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552657250617694.
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Freitas, Antonio Carlos Daltro de 1986. "Análise termodinâmica de processos de reforma do metano e da síntese Fischer-Tropsch." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266746.
Full textAbstract:
Orientador: Reginaldo GuirardelloDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: As reações de reforma de hidrocarbonetos leves, especialmente o gás natural, são reações químicas de elevada importância e representam etapas chave para a produção em larga escala de hidrogênio, para uso em reações de hidrogenação ou em células a combustível, ou de gás de síntese para aplicação na produção de amônia, metanol ou ainda para a síntese de Fischer-Tropsch (FT). A síntese de Fischer-Tropsch e o principal processo de conversao de hidrocarbonetos leves, como o metano, em hidrocarbonetos maiores, de maior valor agregado, assim a determinação das condições termodinamicamente favoráveis para a operação deste tipo de processos se torna cada vez mais necessária. Dentro desse contexto, as reações de reforma a vapor, reforma oxidativa, reforma autotérmica, reforma seca, reforma seca autotérmica e reforma seca combinada com reforma a vapor foram termodinamicamente avaliadas com o objetivo de determinar as melhores condições de reação para a produção de gás de síntese e de hidrogênio. Posteriormente, o gás de síntese produzido foi utilizado para a produção de metanol, etanol e hidrocarbonetos lineares, sendo avaliadas as melhores estratégias para a produção de cada um desses compostos. Para isso foram utilizadas as metodologias de minimização da energia de Gibbs a pressão e temperatura constantes e de maximização da entropia a pressão e entalpia constantes. Ambos os casos foram formulados como problemas de otimização na forma de programação não-linear, e resolvidas com o solver CONOPT2 do software GAMS 23.1'MARCA REGISTRADA'. A partir dos resultados obtidos com a aplicação da metodologia de minimização da energia de Gibbs, verificou-se que todos os processos de reforma avaliados se mostraram favoráveis para a produção de hidrogênio e/ou de gás de síntese do ponto de vista termodinâmico. Tendo a reação de reforma a vapor se destacado para a produção de hidrogênio devido a elevada razao molar H2/CO obtida no produto. A reação de oxidação parcial mostrou bons resultados para a produção de gás de síntese, devido a razão molar H2/CO próxima de 2 no produto. A comparação com dados experimentais permitiu verificar que a metodologia de minimização da energia de Gibbs apresentou boa capacidade de predição e pela comparação com dados simulados obtidos na literatura, pode-se verificar que a metodologia utilizada pelo presente trabalho esta de acordo com os dados publicados. Os resultados obtidos com a aplicação da metodologia de maximização da entropia pode-se verificar que as reações de reforma oxidativa, reforma autotérmica e reforma seca autotérmica, apresentaram comportamento autotérmico, tanto para o uso de O2 como para o uso de ar como agente oxidante. O ar mostrou capacidade de diminuir a elevação da temperatura final do sistema, sendo seu uso promissor para evitar pontos quentes no reator. A comparação com dados de perfil térmico de reatores, para as reações de reforma oxidativa e reforma autotérmica, únicas obtidas na literatura, demonstraram a boa capacidade de predição da metodologia de maximização da entropia para determinação das temperaturas de equilíbrio das reações. As analises realizadas pela aplicação da metodologia de minimização da energia de Gibbs para as reações de síntese de metanol, etanol e hidrocarbonetos lineares, demonstraram a viabilidade da produção desses compostos. Todas reações de síntese avaliadas apresentaram grande dependência da influencia do catalisador (efeito cinético) para promover a produção dos produtos de interesse. Aplicando-se a metodologia de maximização da entropia foi possível determinar que todas as reações de síntese apresentaram comportamento exotérmico. As metodologias empregadas, bem como o solver CONOPT2 aplicado no software GAMS® 23.1 se mostraram rápidos e eficazes para a solução dos problemas propostos, com baixos tempos computacionais para todos os casos analisados
Abstract: The reactions of reforming of light hydrocarbons, especially natural gas, are chemical reactions of great importance and represent key steps for large scale production of hydrogen for use in hydrogenation reactions or fuel cells, or synthesis gas production, for application in the ammonia or methanol production, or to Fischer-Tropsch (FT) synthesis. The Fischer- Tropsch synthesis is the main process of converting light hydrocarbons such as methane, in hydrocarbons of higher value added. The determination of the thermodynamically favorable conditions for the operation for this type of process is required. Within this context, the reactions of steam reforming, oxidative reforming, autothermal reforming, dry reforming, dry autothermal reforming and dry reforming combined with steam reforming were thermodynamically evaluated to determine the best reaction conditions for the production of synthesis gas and hydrogen. For this, we used the methods of Gibbs energy minimization, at constant pressure and temperature, and the Entropy maximization, at constant pressure and enthalpy. Both cases were formulated as optimization problems in the form of non-linear programming and solved with the software GAMS 2.5® with the solver CONOPT2. The results obtained by the method of minimization of Gibbs energy, for all the reform processes evaluated, proved able to produce hydrogen and syngas. Since the reaction of steam reforming showed greater ability to hydrogen production, due to high H2/CO molar ratio obtained in the product. The partial oxidation reaction showed good results for the syngas production, due to H2/CO molar ratio close to 2 in the product. The comparison with experimental data has shown that the Gibbs energy minimization method showed good predictive ability. By comparison with simulated data from the literature we can see that the methodology of minimization of Gibbs energy, used in this work is in agreement with data obtained in the literature for the same methodology. The results obtained using the methodology of entropy maximization allowed us to verify that the reactions of partial oxidation, autothermal reforming and dry autothermal reforming had autothermal behavior, both for the use of O2 as for the use of air as oxidizing agent. The air has shown ability to reduce the final temperature rise of the system, and its use has proved interesting to avoid hot spots in the reactor. A comparison with data from the reactor's thermal profile, for the reactions of partial oxidation and autothermal reforming, only found in the literature, showed good predictive ability of the methodology of entropy maximization to determine the final temperature of the reaction. The analysis realized using the methodology of Gibbs energy minimization for the synthesis reactions of methanol, ethanol and linear hydrocarbons, demonstrated the feasibility of producing these compounds. All synthesis reactions evaluated were greatly dependent on the influence of the catalyst (kinetic effect) to promote the production of products of interest. Trough the entropy maximization method was determined that all synthesis reactions analyzed presents exothermic behavior, but in the reaction conditions evaluated here, these systems can be considered safe. The methodologies used and applied in the software GAMS ® 23.1, and solved with the solver CONOPT2 proved to be fast and effective for solving the proposed problems with low computational time in all cases analyzed
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
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Souza, Joviana Sartori de. "Análise global da estabilidade termodinâmica de misturas: um estudo com o método do conjunto gerador." Universidade do Estado do Rio de Janeiro, 2010. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=3068.
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O cálculo do equilíbrio de fases é um problema de grande importância em
processos da engenharia, como, por exemplo, na separação por destilação, em processos
de extração e simulação da recuperação terciária de petróleo, entre outros. Mas para
resolvê-lo é aconselhável que se estude a priori a estabilidade termodinâmica do
sistema, a qual consiste em determinar se uma dada mistura se apresenta em uma ou
mais fases. Tal problema pode ser abordado como um problema de otimização,
conhecido como a minimização da função distância do plano tangente à energia livre de
Gibbs molar, onde modelos termodinâmicos, de natureza não convexa e não linear, são
utilizados para descrevê-lo. Esse fato tem motivado um grande interesse em técnicas de
otimização robustas e eficientes para a resolução de problemas relacionados com a
termodinâmica do equilíbrio de fases. Como tem sido ressaltado na literatura, para
proporcionar uma completa predição do equilíbrio de fases, faz-se necessário não
apenas a determinação do minimizador global da função objetivo do teste de
estabilidade, mas também a obtenção de todos os seus pontos estacionários. Assim, o
desenvolvimento de metodologias para essa tarefa desafiadora tem se tornado uma nova
área de pesquisa da otimização global aplicada à termodinâmica do equilíbrio, com
interesses comuns na engenharia química e na engenharia do petróleo. O foco do
presente trabalho é uma nova metodologia para resolver o problema do teste de
estabilidade. Para isso, usa-se o chamado método do conjunto gerador para realizar
buscas do tipo local em uma rede de pontos previamente gerada por buscas globais
efetuadas com uma metaheurística populacional, no caso o método do enxame de
partículas.Para se obter mais de um ponto estacionário, minimizam-se funções de mérito
polarizadas, cujos pólos são os pontos previamente encontrados. A metodologia
proposta foi testada na análise de quatorze misturas polares previamente consideradas
na literatura. Os resultados mostraram que o método proposto é robusto e eficiente a
ponto de encontrar, além do minimizador global, todos os pontos estacionários
apontados previamente na literatura, sendo também capaz de detectar, em duas misturas
ternárias estudadas, pontos estacionários não obtidos pelo chamado método de análise
intervalar, uma técnica confiável e muito difundida na literatura. A análise do teste de
estabilidade pela simples utilização do método do enxame de partículas associado à
técnica de polarização mencionada acima, para a obtenção de mais de um ponto
estacionário (sem a busca local feita pelo método do conjunto gerador em uma dada
rede de pontos), constitui outra metodologia para a resolução do problema de interesse.
Essa utilização é uma novidade secundária deste trabalho. Tal metodologia simplificada
exibiu também uma grande robustez, sendo capaz de encontrar todos os pontos
estacionários pesquisados. No entanto, quando comparada com a abordagem mais geral
proposta aqui, observou-se que tal simplificação pode, em alguns casos onde a função
de mérito apresenta uma geometria mais complexa, consumir um tempo de máquina
relativamente grande, dessa forma é menos eficiente.The phase equilibrium calculation is an important problem in engineering processes, for example, in the separation by distillation, in extraction processes, and simulation of the tertiary petroleum recovery, among others applications. But, before this calculation is advisable a phase stability analysis, which will determine if a given mixture presents one or more phases. Such stability analysis can be approached as an optimization problem, called the minimization of the tangent plane distance function to molar Gibbs free energy, where thermodynamic models, with a non-convex and also non-linear nature, are used to describe this problem. Such fact has been motivating a large interest in robust and efficient techniques for optimization of problems related with the phase equilibrium thermodynamics. As has been highlighted in the literature, in order to provide a complete prediction of the phase equilibrium, the determination of the global minimizer of the objective function related with the stability test is not enough. Is also necessary the obtaining of all its stationary points. Thus, the development of methodologies for this challenging task became a new research area of global optimization applied to the phase equilibrium thermodynamics, with common interests in chemical and petroleum engineering. The focus of the present work is a new methodology to solve the stability test problem. For such, here it is used the called Generating Set Search method, which accomplishes local searches in points of a net previously generated by an evolutionary methaheuristic, the Particle Swarm algorithm. To obtain more than one stationary point, polarized merit functions are minimized, where the poles of such merit functions are the points previously found. The methodology proposal was tested in the analysis of fourteen polar mixtures, previously considered in the literature. The results showed that the proposed method is robust and efficient, being capable to find all stationary points previously indicated in the literature, besides the global minimizers. For two ternary mixtures, it was noticed that this method detected some stationary points not obtained before by the interval analysis method, a reliable technique very diffused in the literature. The stability analysis using only the Particle Swarm algorithm together with the polarization technique (without the local search done by the Generating Set Search method) constitutes other methodology for the resolution of the problem considered here. That use is a secondary novelty of this work. This simplified methodology exhibited also a significant robustness, being capable to find all the stationary points. However, when compared with the more general approach proposed here, in some cases, where the merit function presents a more complex geometry, it was observed that such simplification can consume a relatively large computational time. Therefore, the simplified methodology is less efficient.
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Trindade, Júnior Valter Nunes. "Aplicação do método da minimização da energia de Gibbs no cálculo de equilíbrio químico e de fases em sistemas eletrolíticos." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266821.
Full textAbstract:
Orientadores: Reginaldo Guirardello, Edson Antonio da SilvaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-19T12:35:11Z (GMT). No. of bitstreams: 1 TrindadeJunior_ValterNunes_M.pdf: 1919393 bytes, checksum: 3d6999675b8995d4420ac44773a78c43 (MD5) Previous issue date: 2011
Resumo: Em diversas aplicações industriais são utilizadas misturas contendo diferentes solutos, muitas vezes estes são solutos não voláteis, como por exemplo, os eletrólitos. O equilíbrio químico e de fases ocorrem nas diversas operações unitárias contidas nessas aplicações. As próprias etapas de produção, bem como as etapas de separação e purificação, são fundamentais para a qualidade dos produtos. Com isso, o cálculo do comportamento do equilíbrio de sais em solventes é de grande importância para o projeto e a otimização desses equipamentos. Desta forma, o objetivo principal deste trabalho foi o desenvolvimento de uma metodologia confiável e robusta para o cálculo do equilíbrio químico e de fases combinado, em soluções eletrolíticas. O estudo do comportamento do equilíbrio foi feito com a variação da pressão e/ou a temperatura nos sistemas estudados. Este trabalho propôs uma modelagem considerando uma fase vapor, n fases liquidas e uma fase sólida, por meio da metodologia de minimização da energia de Gibbs. A fase vapor foi considerada ideal e a fase solida foi considerada como sólido puro. Para representação da não idealidade da fase líquida foi utilizado o modelo NRTL eletrolítico, esta formulação matemática resulta em um problema que deve ser tratado como um problema de otimização não-linear. Os resultados obtidos foram comparados com dados experimentais extraídos da literatura em sistemas contendo um sal em solução com um solvente ou misturas de solventes no equilíbrio sólido-líquido e no equilíbrio líquido-vapor. A vantagem desta abordagem é não ter que estabelecer previamente quais fases se formarão, o processo de minimização da energia de Gibbs estabelece o número de fases formadas nos sistema automaticamente. Para a resolução do problema de otimização foi utilizado o software GAMS® (General Algebraic Modeling Systems), versão 23.2.1, com o solver CONOPT que utiliza o algoritmo do Gradiente Generalizado Reduzido
Abstract: In several industrial applications are used mixtures containing different solutes, often these solutes are non-volatile, such as electrolytes. The phase and chemical equilibrium in these processes occur in the various unit operations. The stages of production, as well as the separation and purification steps are critical to product quality. Thus, the calculation of the behavior of the equilibrium of salts in solvents is of great importance for the design and optimization of this type of equipment. The main objective of this work was to develop a methodology for calculation of the combined phase and chemical equilibrium in electrolytic solutions. In this study, the behavior of the equilibrium was done by varying the pressure and the temperature in the systems studied. In the model were made the following considerations: a vapor phase, n liquid phase and a solid phase, using the methodology of minimizing the Gibbs energy. The vapor phase was considered ideal and phase solida was considered as pure solid. To represent the nonideality of the liquid phase we used the electrolyte NRTL model (e-NRTL), in this way, the problem should be treated as a nonlinear optimization problem. The results were compared with literature data with solutions containing an electrolyte in solvent or solvents mixtures for Solid-Liquid and vapor-Liquid equilibrium. The modeling was written as a nonlinear programming. The advantage of this program is not having to know in advance what phases will be formed, the process of minimization of Gibbs energy determines the phases automatically. The program was solved in GAMS® software (General Algebraic Modeling System), version 23.2.1, with CONOPT solver that uses the Generalized Reduced Gradient algorithm
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
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Rocha, Stella Alonso. "Cálculo do equilíbrio sólido-líquido e ajuste de parâmetros para modelos temodinâmicos em misturas binárias e ternárias de ácidos graxos, seus ésteres e triacilgliceróis." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266894.
Full textAbstract:
Orientador: Reginaldo GuirardelloTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-19T03:13:19Z (GMT). No. of bitstreams: 1 Rocha_StellaAlonso_D.pdf: 2102940 bytes, checksum: d1db5bc412c8ae0218252291126c501e (MD5) Previous issue date: 2011
Resumo: O trabalho desenvolvido é de caráter teórico e computacional e tem como objetivo o estudo e aplicação de técnicas de otimização juntamente com análise de convexidade para cálculo do equilíbrio sólido-líquido, utilizando um problema de Programação Não-linear, implementado no software GAMS em conjunto com o software Microsoft Excel, aplicado a misturas graxas binárias e ternárias, de origem natural, compostas por ácidos graxos, triacilgliceróis, ésteres de etila e metila, baseando-se na minimização da energia de Gibbs do sistema. A modelagem das fases foi desenvolvida com dois modelos termodinâmicos, em que a fase sólida foi descrita por uma modificação da equação de Slaughter e Doherty e a líquida, modelada por Margules 2-sufixos. Assim esse trabalho trata da utilização de novas aplicações para a fase líquida, com o Modelo de Margules - 2 sufixos, que passa e ser usado e desenvolvido de dois modos: o primeiro, nomeado Margules Assimétrico, em que os parâmetros de interação de Margules são diferentes, e o outro, chamado Margules Simétrico, neste, os parâmetros são considerados equivalentes; e ainda com aplicação do Modelo de Wilson. Para tal desenvolvimento, a proposta é utilizar dados experimentais de equilíbrio, disponíveis da literatura, em caráter comparativo; e fazer o próprio cálculo dos dados da curva de equilíbrio, com os respectivos ajustes dos parâmetros nos modelos utilizados. Os resultados obtidos são apresentados na forma de diagrama de fases e ajustes de parâmetros dos modelos envolvidos, calculados e comparados pela técnica de minimização dos quadrados dos erros, que por sua vez apresentam-se satisfatória proximidade dos dados experimentais. Os resultados ainda foram comparados entre si e puderam apresentar algumas características de comportamento, para algumas classes de compostos
Abstract: This work has theorical and computational character which objectives are the study and application of optimization technique with convexity analysis to calculate solid-liquid equilibrium. This problem was a non-linear program, that was implemented in software GAMS and software Microsoft Excel, which the case studies are binary and ternary mixtures of fatty acids, triglycerides, ethyl and methyl esters using the minimization of Gibbs energy free of the systems. The description of phases was done based in two thermodynamics models, the solid phase was characterized using a modified Slaughter and Doherty model and liquid phase with Margules 2 - suffixes. In this work the on liquid phase, the Margules model assume two forms: Margules Asymmetric, where the Margules parameters are different and Margules Symmetric, with equal Margules parameters, after was used Wilson Model too. Experimental data was used in comparative mode and new equilibrium dates was obtained and the parameters model also was discovery. The results are described in form of phase diagrams, where the equilibrium data and the parameters model was calculated based in the square errors, that are nearly of the experimental data. Comparing the results with each other, in some classes of compounds, there are some similar ways
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química
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Campestrini, Marco. "Étude thermodynamique des équilibres solide-liquide-vapeur : application à la cryogénie et aux unités de séparation de l’air." Thesis, Paris, ENMP, 2014. http://www.theses.fr/2014ENMP0035/document.
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Dans le cadre du procédé de séparation cryogénique des gaz de l'air (T< 100 K), impuretés telles que le CO2 et le N2O peuvent se solidifier au niveau de l'échangeur de chaleur placé entre les deux colonnes de distillation cryogénique.La formation du solide doit être évitée pour deux principales raisons:- au niveau opérationnel, le solide constitue une résistance supplémentaire aux transferts de chaleur et de matière, et augmente les chutes de pression dans les colonnes de distillation;- au niveau sécurité, la présence d'une phase solide peut également favoriser l'accumulation d'hydrocarbures légers qui forment avec l'oxygène liquide des mélanges potentiellement inflammables.Les conditions de formation thermodynamique de la phase solide doivent être parfaitement maitrisées dans le cadre de la distillation cryogénique. C'est pourquoi, il est indispensable de disposer d'une équation d'état adaptée qui permette de représenter les diagrammes de phases impliquant une phase solide dans les conditions opératoire du procédé.L'objectif principal de la thèse est de développer un modèle thermodynamique pour représenter les équilibres de phases solide – fluides. Ce travail nécessite de mettre au point des algorithmes de résolution des équilibres bi et triphasiques et de déterminer le meilleur jeu de paramètres du modèle en s'appuyant sur la disponibilité des données expérimentales dans les conditions cryogéniques.Le modèle permet d'améliorer la connaissance des équilibres et constitue un outil indispensable pour maîtriser les risques associés à la présence de phases solides pour le procédé de distillation cryogéniqueIn the framework of the cryogenic air separation, impurities such as CO2 and N2O may solidify at the reboiler-condenser placed between the two distillation columns.The formed solid could provide an additional strength to the heat and material transfers, and increase the pressure drops in the distillation columns.Furthermore, the presence of a solid phase can promote the accumulation of light hydrocarbons which may form flammable mixtures with liquid oxygen.Therefore, the presence of solid phases must be controlled see avoided within the cryogenic air distillation process.The main issue of this thesis is to develop a suitable model for representing solid phases and their equilibrium with the liquid and vapor phases at the operating conditions of the process, and to obtain full phase diagrams which would improve the knowledge of phase equilibria and the control of the risks associated to the presence of solid phases
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Soueid, Salwa. "Micromagnétismes des films minces." Thesis, Paris Est, 2015. http://www.theses.fr/2015PESC1037/document.
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Les matériaux ferromagnétiques possèdent la propriété de devenir magnétiques, c’est à dire de s'aimanter, lorsqu'ils sont en présence d'un champ magnétique et de conserver une partie de leur magnétisation lorsque le champ est supprimé. C’est pour cette raison, ces matériaux sont devenus d'usage dans de nombreuses applications industrielles. Le modèle mathématique du micromagnétisme a été introduit par W.F. Brown (voir [11]) pour d'écrire le comportement de l'aimantation dans les matériaux ferromagnétiques depuis les années 40.Pour étudier ce phénomène, on le transforme en un système l'étude de ces équations donnent les informations physiques attendus dans des espaces appropriés. Dans cette thèse on s’est intéressé à des structures minces de films ferromagnétiques. En pratique, une structure mince est un objet tridimensionnel ayant une ou deux directions prépondérantes comme par exemple une plaque, une barre ou un fil. Nous étudions le comportement de l'énergie quand l'épaisseur du film tend vers zéro. Dans le premier travail, nous généralisons un résultat dû à Gioia et James à des dimensions supérieures à 4. Plus précisément, on considère un domaine mince borné ferromagnétique dans R^n, le but est d'étudier les comportements asymptotiques de l'énergie libre du domaine mince ferromagnétique. Dans le deuxième travail, on s'intéresse à une approche dynamique de problème micromagnétisme . On étudie le comportement asymptotique des solutions des équations Landau Lifshitz dans un multi-structure mince ferromagnétique composée de deux films minces orthogonaux d'épaisseur respectif h^a et h^b. On distingue différents régimes: lorsque lim h^a_n/h^b_n in ]0;infty[. On identifie le problème limite et on montre que ce dernier est couplé par une condition de jonction sur l'axe vertical x2, pour tout x2 in] -1/2,1/2[.La troisième partie est liée à ce dernier travail, nous complétons l'étude précédente lorsque lim h^a_n/h^b_n = 0 et +infty (voir [2]). En suite dans la quatrième chapitre, on a étudié des phénomènes de micromagnétisme dans un multi-structure mince: il s'agit d'un ouvert connexe de R3 composé de deux parties ayant un angle etha in ]0; pi[, le but est d'étudier les comportements asymptotiques de l'énergie libre dans ce domaine lorsque l'épaisseur tend vers zéro. Il s'agit d'un problème non convexe et non local (…)The ferromagnetic materials possess the magnetic property of future, that is to magnetize, when they are in the presence of a magnetic field and to keep a part of their magnetizing when the field is deleted. It is for that reason, these materials became of use in numerous industrial applications (...)
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Klímová, Markéta. "Predikce sekundární struktury RNA sekvencí." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221332.
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RNA secondary structure is very important in many biological processes. Efficient structure prediction can give information for experimental investigations of these processes. Many available programs for secondary structure prediction exist. Some of them use single sequence, the others use more related sequences. Pseudoknots are still problematic for most methods. This work presents several methods and publicly available software and the implementation of minimum free energy method is described.
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Stephens, Timothy W. "Characterization of Ionic Liquid Solvents Using a Temperature Independent, Ion-Specific Abraham Parameter Model." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699933/.
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Experimental data for the logarithm of the gas-to-ionic liquid partition coefficient (log K) have been compiled from the published literature for over 40 ionic liquids over a wide temperature range. Temperature independent correlations based on the Gibbs free energy equation utilizing known Abraham solvation model parameters have been derived for the prediction of log K for 12 ionic liquids to within a standard deviation of 0.114 log units over a temperature range of over 60 K. Temperature independent log K correlations have also been derived from correlations of molar enthalpies of solvation and molar entropies of solvation, each within standard deviations of 4.044 kJ mol-1 and 5.338 J mol-1 K-1, respectively. In addition, molar enthalpies of solvation and molar entropies of solvation can be predicted from the Abraham coefficients in the temperature independent log K correlations to within similar standard deviations. Temperature independent, ion specific coefficients have been determined for 26 cations and 15 anions for the prediction of log K over a temperature range of at least 60 K to within a standard deviation of 0.159 log units.
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Popovic, Marko. "Application of the Entropy Concept to Thermodynamics and Life Sciences: Evolution Parallels Thermodynamics, Cellulose Hydrolysis Thermodynamics, and Ordered and Disordered Vacancies Thermodynamics." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6996.
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Entropy, first introduced in thermodynamics, is used in a wide range of fields. Chapter 1 discusses some important theoretical and practical aspects of entropy: what is entropy, is it subjective or objective, and how to properly apply it to living organisms. Chapter 2 presents applications of entropy to evolution. Chapter 3 shows how cellulosic biofuel production can be improved. Chapter 4 shows how lattice vacancies influence the thermodynamic properties of materials. To determine the nature of thermodynamic entropy, Chapters 1 and 2 describe the roots, the conceptual history of entropy, as well as its path of development and application. From the viewpoint of physics, thermal entropy is a measure of useless energy stored in a system resulting from thermal motion of particles. Thermal entropy is a non-negative objective property. The negentropy concept, while mathematically correct, is physically misleading. This dissertation hypothesizes that concepts from thermodynamics and statistical mechanics can be used to define statistical measurements, similar to thermodynamic entropy, to summarize the convergence of processes driven by random inputs subject to deterministic constraints. A primary example discussed here is evolution in biological systems. As discussed in this dissertation, the first and second laws of thermodynamics do not translate directly into parallel laws for the biome. But, the fundamental principles on which thermodynamic entropy is based are also true for information. Based on these principles, it is shown that adaptation and evolution are stochastically deterministic. Chapter 3 discusses the hydrolysis of cellulose to glucose, which is a key reaction in renewable energy from biomass and in mineralization of soil organic matter to CO2. Conditional thermodynamic parameters, ΔhydG', ΔhydH', and ΔhydS', and equilibrium glucose concentrations are reported for the reaction C6H10O5(cellulose) + H2O(l) ⇄ C6H12O6(aq) as functions of temperature from 0 to 100°C. Activity coefficients of aqueous glucose solution were determined as a function of temperature. The results suggest that producing cellulosic biofuels at higher temperatures will result in higher conversion. Chapter 4 presents the data and a theory relating the linear term in the low temperature heat capacity to lattice vacancy concentration. The theory gives a quantitative result for disordered vacancies, but overestimates the contribution from ordered vacancies because ordering leads to a decreased influence of vacancies on heat capacity.
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Berg, Emily Katherine. "Thermodynamics of λ-PCR Primer Design and Effective Ribosome Binding Sites." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/89900.
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Recombinant DNA technology has been commonly used in a number of fields to synthesize new products or generate products with a new pathway. Conventional cloning methods are expensive and require significant time and labor; λ-PCR, a new cloning method developed in the Senger lab, has a number of advantages compared to other cloning processes due to its employment of relatively inexpensive and widely available materials and time-efficiency. While the amount of lab work required for the cloning process is minimal, the importance of accurate primer design cannot be overstated. The target of this study was to create an effective procedure for λ-PCR primer design that ensures accurate cloning reactions. Additionally, synthetic ribosome binding sites (RBS) were included in the primer designs to test heterologous protein expression of the cyan fluorescent reporter with different RBS strengths. These RBS sequences were designed with an online tool, the RBS Calculator.
A chimeric primer design procedure for λ-PCR was developed and shown to effectively create primers used for accurate cloning with λ-PCR; this method was used to design primers for CFP cloning in addition to two enzymes cloned in the Senger lab. A total of five strains of BL21(DE3) with pET28a + CFP were constructed, each with the same cyan fluorescent protein (CFP) reporter but different RBS sequences located directly upstream of the start codon of the CFP gene. Expression of the protein was measured using both whole-cell and cell-free systems to determine which system yields higher protein concentrations. A number of other factors were tested to optimize conditions for high protein expression, including: induction time, IPTG concentration, temperature, and media (for the cell-free experiments only). Additionally, expression for each synthetic RBS sequence was investigated to determine an accurate method for predicting protein translation. NUPACK and the Salis Lab RBS Calculator were both used to evaluate the effects of these different synthetic RBS sequences. The results of the plate reader experiments with the 5 CFP strains revealed a number of factors to be statistically significant when predicting protein expression, including: IPTG concentration, induction time, and in the cell-free experiments, type of media. The whole-cell system consistently produced higher amounts of protein than the cell-free system. Lastly, contrasts between the CFP strains showed each strain's performance did not match the predictions from the RBS Calculator. Consequently, a new method for improving protein expression with synthetic RBS sequences was developed using relationships between Gibbs free energy of the RBS-rRNA complex and expression levels obtained through experimentation. Additionally, secondary structure present at the RBS in the mRNA transcript was modeled with strain expression since these structures cause deviations in the relationship between Gibbs free energy of the mRNA-rRNA complex and CFP expression.Master of Science
Recombinant DNA technology has been used to genetically enhance organisms to produce greater amounts of a product already made by the organism or to make an organism synthesize a new product. Genes are commonly modified in organisms using cloning practices which typically involves inserting a target gene into a plasmid and transforming the plasmid into the organism of interest. A new cloning process developed in the Senger lab, λ-PCR, improves the cloning process compared to other methods due to its use of relatively inexpensive materials and high efficiency. A primary goal of this study was to develop a procedure for λ-PCR primer design that allows for accurate use of the cloning method. Additionally, this study investigated the use of synthetic ribosome binding sites to control and improve expression of proteins cloned into an organism. Ribosome binding sites are sequences located upstream of the gene that increase the molecule’s affinity for the rRNA sequence on the ribosome, bind to the ribosome just upstream of the beginning of the gene, and initiate expression of the gene. Tools have been developed that create synthetic ribosome binding sites designed to produce specific amounts of protein. For example, the tools can increase or decrease expression of a gene depending on the application. These tools, the Salis Lab RBS Calculator and NUPACK, were used to design and evaluate the effects of the synthetic ribosome binding sites. Additionally, a new method was created to design synthetic ribosome binding sites since the methods used during the design process yielded inaccuracies. Each strain of E. coli contained the same gene, a cyan fluorescent protein (CFP), but had different RBS sequences located upstream of the gene. Expression of CFP was controlled via induction, meaning the addition of a particular molecule, IPTG in this system, triggered expression of CFP. Each of the CFP strains were tested with a variety of v conditions in order to find the conditions most suitable for protein expression; the variables tested include: induction time, IPTG (inducer) concentration, and temperature. Media was also tested for the cell-free systems, meaning the strains were grown overnight for 18 hours and lysed, a process where the cell membrane is broken in order to utilize the cell’s components for protein expression; the cell lysate was resuspended in new media for the experiments. ANOVA and multiple linear regression revealed IPTG concentration, induction time, and media to be significant factors impacting protein expression. This analysis also showed each CFP strain did not perform as the RBS Calculator predicted. Modeling each strain’s CFP expression using the RBS-rRNA binding strengths and secondary structures present in the RBS allowed for the creation of a new model for predicting and designing RBS sequences.
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Costa, Deyse Gomes da. "Estudo teórico de hidróxidos lamelares com potencial aplicação tecnológica e ambiental." Universidade Federal de Juiz de Fora (UFJF), 2011. https://repositorio.ufjf.br/jspui/handle/ufjf/4461.
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Os hidróxidos duplos lamelares (HDL) ou compostos tipo-hidrotalcita vêm sendo muito estudados devido a suas inúmeras aplicações. No campo da catálise, estes compostos podem atuar como catalisadores, suportes para catalisadores ou precursores de catalisadores. É sabido que a morfologia do suporte tem grande influência sobre a dispersão, a atividade e a seletividade apresentada pelo catalisador. Nestes caso, o conhecimento detalhado dos efeitos do suporte e dos sítios catalíticos exigem a compreensão da estrutura do HDL. Entretanto, por causa da desordem estrutural, muitas vezes inerente ao material, torna-se a determinação completa da estrutura, via difração de raios X, raramente possível. As bandas largas presentes na análise do IV, fazem a atribuição das mesmas ambígua. Devido à complexidade dos HDL e à dificuldade de se adquirir ou interpretar os resultados experimentais, foi proposto um modelo para simular as características estruturais dos compostos tipo-hidrotalcita com o politipo 3R1, usando condições periódicas de contorno e cálculos ab initio dentro da teoria do funcional da densidade (DFT). As informações estruturais da hidrotalcita, obtidas experimentalmente, foram usadas para verificar a validade do modelo teórico. Os resultados mostraram boas concordâncias com os padrões de raios X do pó experimentais. O espectro na região do infravermelho, a entalpia e energia livre de Gibbs, também foram calculadas. Os cálculos de frequências vibracionais mostraram que as moléculas de água intercaladas são altamente organizadas devido às fortes interações intermoleculares com outras moléculas de água, com ânions interlamelares e com as hidroxilas das lamelas. A presença destas interações é refletida na presença do estiramento O-H das moléculas de água deslocadas para baixas frequências. A perda da degenerescência dos modos vibracionais v3 e do v4 foi observada, indicando a redução da simetria do íon carbonato. As modificações termodinâmicas e estruturais resultantes da substituição do íon presente no HDL Zn-Al-Cl também formam analisadas. O íon Cl- do HDL precursor foi trocado por uma série de ânions como o F-, Br-, OH-, NO3-, ClO4-, CO32- e SO42-. Os resultados mostraram que a intercalação do HDL com diferentes íons, afeta o gap de energia e a basicidade da lamela tipo-brucita. A entalpia e a energia livre de Gibbs, a densidade de estados (DOS) e a densidade de estados projetada (PDOS) foram avaliadas para todos os HDL.
The layered double hydroxide (LDH) or hydrotalcite-like compounds have been widely studied due to many applications they have. In catalysis field these compounds can act as catalyst, catalyst support or precursor for supports and catalysts. It is well known that the support morphology has larger influence on the dispersion, activity and selectivity of catalysts. In this case, detailed knowledge about support effects and catalytic sites requires understanding the LDH structure. However, because of the inherent structural disorder, complete structure determination using X-ray diffraction is rarely possible. The IR analysis present broad bands, which makes their assignment ambiguous. Due to the complexity of the LDH and the difficult of acquiring experimental data, we proposed a model to simulate structural features of the hydrotalcite-like compounds with 3R1 polytypes using periodic boundary conditions and ab initio density functional theory (DFT) calculations. The structural information of hydrotalcite from experiments were used to verify the validity of theoretical model. Our results showed good agreements to the powder X-ray patterns. The infrared spectroscopy, enthalpy and Gibbs free energy, also was calculated. The IR calculations showed that intercalated water molecules are highly ordered due the strong intermolecular interactions with other water molecules, interlayer anions and layer hydroxyls. These interaction is reflected by the presence of downshift vibrational frequencies of OH-stretching of interlayer water. The loss of degeneracy of the v3 and v4 vibrational modes are observed, indicating the reduction of the carbonate anion symmetry. The thermodynamic and structural modifications derived from anion exchange on a LDH containing Zn-Al-Cl was also analyzed. The Cl- ion to the LDH precursor was exchanged for a series of anions as F-, Br-, OH-, NO3-, ClO4-, CO32- and SO42-. The resulted show that intercalation of LDH with different anions affect their gap energy and basicity of brucite-like layer. The enthalpy and Gibbs free energy, density of charge, density of state (DOS) and projected density of state (PDOS) were evaluated for all substituted materials.
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Tavares, Filho Sérgio Rodrigues. "Simulação de estrutura e cálculo de propriedades de Zn5(OH)8Cl2.H2O e Zn5(OH)8(NO3)2.2H2O utilizando métodos ab initio." Universidade Federal de Juiz de Fora (UFJF), 2013. https://repositorio.ufjf.br/jspui/handle/ufjf/5515.
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FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais
Muitos compostos lamelares, como os hidróxidos duplos lamelares e os hidroxissais lamelares, vem ganhando cada vez mais atenção devido às suas inúmeras aplicabilidades no ramo de catálise, troca iônica e precursores para óxidos. Os dois compostos estudados aqui possuem sítios octaédricos e tetraédricos de zinco, sendo classificados por Louër et al. como hidroxissais do tipo II. O hidroxicloreto de zinco (Zn5(OH)8Cl2.H2O) é romboédrico e possui ocorrência natural sendo designado como simonkolleite. Enquanto que o hidroxinitrato de zinco diidratado (Zn5(OH)8(NO3)2.2H2O) é monoclínico e não possui ocorrência natural. Seus nitratos não se encontram coordenados aos zincos tetraédricos, como é o caso do composto Zn5(OH)8Cl2.H2O. Ao invés disso, suas moléculas de água se encontram coordenadas nos tetraedros e, para balancear a carga positiva das lamelas, esses nitratos se encontram na região interlamelar. Esses dois hidroxissais e uma modificação do hidroxinitrato de zinco com moléculas de amônia coordenadas aos tetraedros (BENARD, 1995) foram estudados por simulação computacional. O pacote Quantum ESPRESSO, baseado na Teoria do Funcional da Densidade (DFT – Density Functional Theory) com funções de onda planas e condições periódicas de contorno foi utilizado para a condução dos cálculos. As moléculas de água foram retiradas das estruturas hidratadas otimizadas e essas foram reotimizadas. Todos os dados experimentais foram comparados com os dados retirados das estruturas simuladas e um bom acordo foi obtido. A estrutura simulada do composto desidratado de Zn5(OH)8(NO3)2.2H2O não correspondeu à estrutura obtida pelo processo de calcinação, como foi visto pela análise termodinâmica do processo de desidratação. Porém, pôde ser concluído que essa estrutura corresponde ao mínimo local, pela ausência de frequências imaginárias. Cálculos de pós-processamento puderam ser conduzidos para uma análise das interações existentes nos compostos e das espécies químicas presentes neles. Os cloretos e os nitratos de ambos os compostos se mostraram equivalentes quimicamente, como foi visto pelo cálculo de pDOS (projected Density of States). As hidroxilas das células unitárias puderam também ser classificadas em dois grupos a partir de suas semelhanças químicas. Pôde-se concluir também com esse trabalho que o modelo de diminuição da célula unitária (DEYSE, 2012) foi capaz de diminuir os custos computacionais e prever certas propriedades dos compostos estudados.
Many layered compounds, like the double hydroxides and the hydroxide salts, have been gaining attention lately due to their various applicabilities in catalysis, anionic exchange and oxide precursors. The studied compounds here have octahedral and tetrahedral sites, which have been classified as type-2 hydroxide salts by Louër et al. Zinc hydroxide chloride monohydrate (Zn5(OH)8Cl2.H2O) is rhombohedric and is found in the nature as a mineral so-called simonkolleite. Whereas zinc hydroxide nitrate dihydrate (Zn5(OH)8(NO3)2.2H2O) is monoclinic and does not have natural occurrence. Their nitrates are not coordinated to the tetrahedral zincs, whereas the chlorides of Zn5(OH)8Cl2.H2O are grafted to the tetrahedral zincs. Their water molecules are grafted to the tetrahedrons and, in order to balance the charges, the nitrates are located in the interlayer region. Those hydroxide salts and a modification of the zinc hydroxide nitrate with ammonia molecules grafted to the tetrahedros (BENARD, 1995) have been studied by computational simulation. The Quantum ESPRESSO package based in the Density Functional Theory (DFT) with waveplanes and periodic boundary conditions was used for the calculations. The water molecules were removed from the optimized hydrate structures and, later on, those were re-optmized. All the experimental data were compared with the ones obtained by simulated structures and a good agreement was shown. The simulated dehydrate structure of Zn5(OH)8(NO3)2.2H2O did not correspond to the structure obtained by calcination, as it was shown by the thermodynamical analysis of the calcination process. However, it was concluded that this structure corresponds to a local minimum due to the lack of imaginary frequencies. Post-processing calculations were conducted in order to analyze the compounds' interactions and the chemical species. The chlorides and nitrates of both compounds were chemically equivalents, as it was shown by the pDOS calculations (projected Density of States). The hydroxyls of the unit cells could be classified in two groups based on their chemical equivalence. It could also be concluded with this work that the unit cell reduction method (DEYSE, 2012) was able to reduce the computational costs and to predict certain properties of the studied compounds.
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Mpongwana, Ncumisa. "Metabolic network modelling of nitrification and denitrification under cyanogenic conditions." Thesis, Cape Peninsula University of Technology, 2019. http://hdl.handle.net/20.500.11838/2982.
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Thesis (PhD (Chemical Engineering))--Cape Peninsula University of Technology, 2019Simultaneous nitrification and aerobic denitrification (SNaD) is a preferred method for single stage total nitrogen (TN) removal, which was recently proposed to improve wastewater treatment plant design. However, SNaD processes are prone to inhibition by toxicant loading with free cyanide (CN-) possessing the highest inhibitory effect on such processes, rendering these processes ineffective. Despite the best efforts of regulators to limit toxicant disposal into municipal wastewater sewage systems (MWSSs), free cyanide (CN-) still enters MWSSs through various pathways; hence, it has been suggested that CN- resistant or tolerant microorganisms be utilized for processes such as SNaD. To mitigate toxicant loading, organisms in SNaD have been observed to adopt a multiphase growth strategy to sequentially degrade CN- during primary growth and subsequently degrade TN during the secondary growth phase. However, CN- degrading microorganisms are not widely used for SNaD in MWSSs due to the inadequate application of suitable microorganisms (Chromobacterium violaceum, Pseudomonas aeruginosa, Thiobacillus denitrificans, Rhodospirillum palustris, Klebsiella pneumoniae, and Alcaligenes faecalis) commonly used in single-stage SNaD. The use of CN- degrading or resistant microorganisms for SNaD is a cost-effective method compared to the use of other methods of CN- removal prior to TN removal, as they involve multi-stage systems (as currently observed in MWSSs). The use of CN- degrading microorganisms, particularly when used as a consortium, presents a promising and sustainable resolution to mitigate inhibitory effects of CN- in SNaD. However, SNaD is known to be completely inhibited by CN- thus it is imperative to also study some thermodynamic parameters of SNaD under high CN- conditions to see the feasibility of the process. The Gibbs free energy is significant to understand the feasibility of SNaD, it is also vital to study Gibbs free energy to determine whether or not the biological reaction is plausible. The relationship between the rate of nitrification and Gibbs free energy was also investigated. The attained results showed that up to 37.55 mg CN-/L did not have an effect on SNaD. The consortia degraded CN- and achieved SNaD, with degradation efficiency of 92.9 and 97.7% while the degradation rate of 0.0234 and 0.139 mg/L/hr for ammonium-nitrogen (NH4-N) and CN- respectively. Moreover, all the free Gibbs energy was describing the individual processes were found to be negative, with the lowest Gibbs free energy being -756.4 and -1830.9 Kcal/mol for nitritation and nitratation in the first 48 h of the biological, reaction respectively. Additionally, a linear relationship between the rate of NH4-N and nitrite-nitrogen (NO2-N) degradation with their respective Gibbs free energy was observed. Linear model was also used to predict the relationship between NH4-N, NO2-N degradation and Gibbs free energy. These results obtained showed a good correlation between the models and the experimental data with correlation efficiency being 0.94 and 0.93 for nitritation, and nitratation, respectively. From the results found it can be deduced that SNaD is plausible under high cyanide conditions when cyanide degrading or tolerant microorganisms are employed. This can be a sustainable solution to SNaD inhibition by CN- compounds during wastewater treatment. Furthermore, a single strain was purified from the consortium and identified as Acinetobacter courvalinii. This bacterial strain was found to be able to perform sequential CN- degradation, and SNaD; an ability associated with multiphase growth strategy of the microorganism when provided with multiple nitrogenous sources, i.e. CN- and TN. The effect of CN- on nitrification and aerobic denitrification including enzyme expression, activity and protein functionality of Acinetobacter courvalinii was investigated. It was found that CN- concentration of up to 5.8 mg CN-/L did not affect the growth of Acinetobacter courvalinii. In cultures whereby the A. courvalinii isolate was used, degradation rates of CN- and NH4-N were found to be 2.2 mg CN-/L/h and 0.40 mg NH4-N/L/h, respectively. Moreover, the effect of CN- on NH4-N, nitrate-nitrogen (NO3-N) and NO2-N oxidizing enzymes was investigated, with findings indicating CN- did not affect the expression and activity of ammonia monooxygenase (AMO), but affected the activity of nitrate reductase (NaR) and nitrite reductase (NiR). Nevertheless, a slow decrease in NO2-N was observed after the addition of CN- thus confirming the activity of NaR and the activation of the denitrification pathway by the CN-. Moreover, five models’ (Monod, Moser, Rate law, Haldane, and Andrew’s model) ability to predict SNaD under CN- conditions, indicated that only Rate law, Haldane and Andrew’s models, were suited to predict both SNaD and CN- degradation. Due to low degradation rates of NH4-N and CN-, optimization of SNaD was essential. Therefore, response surface methodology was used to optimize the SNaD under CN- conditions. The physiological parameters that were considered for optimization were temperature and pH; with the result showing that the optimum for pH and temperature was 6.5 and 36.5oC respectively, with NH4-N and CN- degradation efficiency of 50 and 80.2%, respectively. Furthermore, the degradation kinetics of NH4-N and CN- were also studied under the optimum conditions in batch culture reactors, and the results showed that up to 70.6% and 97.3% of NH4-N and CN- were simultaneously degraded with degradation rates of 0.66 and 0.41 mg/L/h, respectively. The predictive ability of RSM was further compared with cybernetic models, and cybernetic models were found to better predict SNaD under CN- conditions. These results exhibited a promising solution in the management of inhibition effected of CN- towards SNaD at an industrial scale.
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Vincent, Matthew Ryan. "Crystallization and Melting Studies of Poly(ε-caprolactone) and Poly(ethylene oxide) using Flash™ Differential Scanning Calorimetry and Preparation and Characterization of Poly(δ-valerolactone) Fractions." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/101668.
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The isothermal crystallization and melting temperatures of poly(ε-caprolactone) were correlated using fast differential scanning calorimetry. The melting kinetics was found to be independent of isothermal crystallization temperature and time. The conventional Hoffman-Weeks method could not be used to determine the equilibrium melting temperature because the observed melting temperatures were greater than the crystallization temperatures by a constant, so the Gibbs-Thomson method was used instead, yielding an equilibrium melting temperature of 103.4 ± 2.3°C. A modification was proposed to the non-linear Hoffman-Weeks equation that included a non-linear undercooling dependence for the kinetic fold surface free energy upon crystallization and permitted accurate modeling of the observed melting behavior.
The isothermal crystallization rates of four narrow molecular weight poly(ethylene oxide) fractions were characterized using fast differential scanning calorimetry for crystallization temperatures spanning 100°C range with the lower limit approaching the glass transition. A transition from homogeneous to heterogeneous primary nucleation was observed at −5°C. The kinetic analysis suggested that the crystal growth geometry depends strongly on temperature, where rod-like structures begin to appear near the glass transition temperature, highly branched solid sheaves grow throughout the homogeneous primary nucleation temperature range, and spherulites grow in the heterogenous primary nucleation range.
Poly(δ-valerolactone) was synthesized using microwave-assisted techniques. Narrow molecular weight fractions were obtained using successive precipitation fractionation. Preliminary isothermal crystallization studies suggest that conventional thermal analysis methods are not adequate to measure the melting temperatures accurately due to reorganization during heating.Doctor of Philosophy
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Mukhortava, Ann. "Downhill folders in slow motion:." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-229473.
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Die Proteinfaltung ist ein Prozess der molekularen Selbstorganisation, bei dem sich eine lineare Kette von Aminosäuren zu einer definierten, funktionellen dreidimensionalen Struktur zusammensetzt. Der Prozess der Faltung ist ein thermisch getriebener diffusiver Prozess durch eine Gibbs-Energie-Landschaft im Konformationsraum für die Struktur der minimalen Energie. Während dieses Prozesses zeigt die freie Enthalpie des Systems nicht immer eine monotone Abnahme; stattdessen führt eine suboptimale Kompensation der Enthalpie- und der Entropieänderung während jedes Faltungsschrittes zur Bildung von Freien-Enthalpie-Faltungsbarrieren. Diese Barrieren und damit verbundenen hochenergetischen Übergangszustände, die wichtige Informationen über Mechanismen der Proteinfaltung enthalten, sind jedoch kinetisch unzugänglich. Um den Prozess der Barrierebildung und die strukturellen Merkmale von Übergangszuständen aufzudecken, werden Proteine genutzt, die über barrierefreie Pfade falten – so genannte “downhill folder“. Aufgrund der geringen Faltungsbarrieren werden wichtige Interaktionen der Faltung zugänglich und erlauben Einblicke in die ratenbegrenzenden Faltungsvorgänge. In dieser Arbeit vergleichen wir die Faltungsdynamiken von drei verschiedenen Varianten eines Lambda-Repressor-Fragments, bestehend aus den Aminosäuren 6 bis 85: ein Zwei-Zustands-Falter λWT (Y22W) und zwei downhill-folder-artige Varianten, λYA (Y22W/Q33Y/ G46,48A) und λHA (Y22W/Q33H/G46,48A). Um auf die Kinetik und die strukturelle Dynamik zu greifen zu können, werden Einzelmolekülkraftspektroskopische Experimente mit optische Pinzetten mit Submillisekunden- und Nanometer-Auflösung verwendet. Ich fand, dass die niedrige denaturierende Kraft die Mikrosekunden Faltungskinetik von downhill foldern auf eine Millisekunden-Zeitskala verlangsamt, sodass das System für Einzelmolekülstudien gut zugänglich ist. Interessanterweise zeigten sich unter Krafteinwirkung die downhill-folder-artigen Varianten des Lambda-Repressors als kooperative Zwei-Zustands-Falter mit deutlich unterschiedlicher Faltungskinetik und Kraftabhängigkeit. Drei Varianten des Proteins zeigten ein hoch konformes Verhalten unter Last. Die modellfreie Rekonstruktion von Freien-Enthalpie-Landschaften ermöglichte es uns, die feinen Details der Transformation des Zwei-Zustands-Faltungspfad direkt in einen downhill-artigen Pfad aufzulösen. Die Auswirkungen von einzelnen Mutationen auf die Proteinstabilität, Bildung der Übergangszustände und die konformationelle Heterogenität der Faltungs- und Entfaltungszustände konnten beobachtet werden. Interessanterweise zeigen unsere Ergebnisse, dass sich die untersuchten Varianten trotz der ultraschnellen Faltungszeit im Bereich von 2 μs in einem kooperativen Prozess über verbleibende Energiebarrieren falten und entfalten, was darauf hindeutet, dass wesentlich schnellere Faltungsraten notwendig sind um ein downhill Limit vollständig zu erreichenProtein folding is a process of molecular self-assembly in which a linear chain of amino acids assembles into a defined, functional three-dimensional structure. The process of folding is a thermally driven diffusive search on a free-energy landscape in the conformational space for the minimal-energy structure. During that process, the free energy of the system does not always show a monotonic decrease; instead, sub-optimal compensation of enthalpy and entropy change during each folding step leads to formation of folding free-energy barriers. However, these barriers, and associated high-energy transition states, that contain key information about mechanisms of protein folding, are kinetically inaccessible. To reveal the barrier-formation process and structural characteristics of transition states, proteins are employed that fold via barrierless paths – so-called downhill folders. Due to the low folding barriers, the key folding interactions become accessible, yielding insights about the rate-limiting folding events. Here, I compared the folding dynamics of three different variants of a lambda repressor fragment, containing amino acids 6 to 85: a two-state folder λWT (Y22W) and two downhill-like folding variants, λYA (Y22W/Q33Y/G46,48A) and λHA (Y22W/Q33H/G46,48A). To access the kinetics and structural dynamics, single-molecule optical tweezers with submillisecond and nanometer resolution are used. I found that force perturbation slowed down the microsecond kinetics of downhill folders to a millisecond time-scale, making it accessible to single-molecule studies. Interestingly, under load, the downhill-like variants of lambda repressor appeared as cooperative two-state folders with significantly different folding kinetics and force dependence. The three protein variants displayed a highly compliant behaviour under load. Model-free reconstruction of free-energy landscapes allowed us to directly resolve the fine details of the transformation of the two-state folding path into a downhill-like path. The effect of single mutations on protein stability, transition state formation and conformational heterogeneity of folding and unfolding states was observed. Noteworthy, our results demonstrate, that despite the ultrafast folding time in a range of 2 µs, the studied variants fold and unfold in a cooperative process via residual barriers, suggesting that much faster folding rate constants are required to reach the full-downhill limit
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Moghaddam, Amir. "Dynamics of transformation and fragmentation of composite liquid nano-particles." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/31776/1/Amir_Moghaddam_Thesis.pdf.
Full textAbstract:
Recent research on particle size distributions and particle concentrations near a busy road cannot be explained by the conventional mechanisms for particle evolution of combustion aerosols. Specifically they appear to be inadequate to explain the experimental observations of particle transformation and the evolution of the total number concentration. This resulted in the development of a new mechanism based on their thermal fragmentation, for the evolution of combustion aerosol nano-particles. A complex and comprehensive pattern of evolution of combustion aerosols, involving particle fragmentation, was then proposed and justified. In that model it was suggested that thermal fragmentation occurs in aggregates of primary particles each of which contains a solid graphite/carbon core surrounded by volatile molecules bonded to the core by strong covalent bonds. Due to the presence of strong covalent bonds between the core and the volatile (frill) molecules, such primary composite particles can be regarded as solid, despite the presence of significant (possibly, dominant) volatile component. Fragmentation occurs when weak van der Waals forces between such primary particles are overcome by their thermal (Brownian) motion. In this work, the accepted concept of thermal fragmentation is advanced to determine whether fragmentation is likely in liquid composite nano-particles. It has been demonstrated that at least at some stages of evolution, combustion aerosols contain a large number of composite liquid particles containing presumably several components such as water, oil, volatile compounds, and minerals. It is possible that such composite liquid particles may also experience thermal fragmentation and thus contribute to, for example, the evolution of the total number concentration as a function of distance from the source. Therefore, the aim of this project is to examine theoretically the possibility of thermal fragmentation of composite liquid nano-particles consisting of immiscible liquid v components. The specific focus is on ternary systems which include two immiscible liquid droplets surrounded by another medium (e.g., air). The analysis shows that three different structures are possible, the complete encapsulation of one liquid by the other, partial encapsulation of the two liquids in a composite particle, and the two droplets separated from each other. The probability of thermal fragmentation of two coagulated liquid droplets is discussed and examined for different volumes of the immiscible fluids in a composite liquid particle and their surface and interfacial tensions through the determination of the Gibbs free energy difference between the coagulated and fragmented states, and comparison of this energy difference with the typical thermal energy kT. The analysis reveals that fragmentation was found to be much more likely for a partially encapsulated particle than a completely encapsulated particle. In particular, it was found that thermal fragmentation was much more likely when the volume ratio of the two liquid droplets that constitute the composite particle are very different. Conversely, when the two liquid droplets are of similar volumes, the probability of thermal fragmentation is small. It is also demonstrated that the Gibbs free energy difference between the coagulated and fragmented states is not the only important factor determining the probability of thermal fragmentation of composite liquid particles. The second essential factor is the actual structure of the composite particle. It is shown that the probability of thermal fragmentation is also strongly dependent on the distance that each of the liquid droplets should travel to reach the fragmented state. In particular, if this distance is larger than the mean free path for the considered droplets in the air, the probability of thermal fragmentation should be negligible. In particular, it follows form here that fragmentation of the composite particle in the state with complete encapsulation is highly unlikely because of the larger distance that the two droplets must travel in order to separate. The analysis of composite liquid particles with the interfacial parameters that are expected in combustion aerosols demonstrates that thermal fragmentation of these vi particles may occur, and this mechanism may play a role in the evolution of combustion aerosols. Conditions for thermal fragmentation to play a significant role (for aerosol particles other than those from motor vehicle exhaust) are determined and examined theoretically. Conditions for spontaneous transformation between the states of composite particles with complete and partial encapsulation are also examined, demonstrating the possibility of such transformation in combustion aerosols. Indeed it was shown that for some typical components found in aerosols that transformation could take place on time scales less than 20 s. The analysis showed that factors that influenced surface and interfacial tension played an important role in this transformation process. It is suggested that such transformation may, for example, result in a delayed evaporation of composite particles with significant water component, leading to observable effects in evolution of combustion aerosols (including possible local humidity maximums near a source, such as a busy road). The obtained results will be important for further development and understanding of aerosol physics and technologies, including combustion aerosols and their evolution near a source.
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Mirmasoudi, Sara. "High Temperature Transient Creep Analysis of Metals." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1452693927.
Full text
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Liu, Qi. "CIRCE a new software to predict the steady state equilibrium of chemical reactions." Thesis, Compiègne, 2018. http://www.theses.fr/2018COMP2455/document.
Full textAbstract:
L'objectif de cette thèse est de développer un nouveau code pour prédire l'équilibre final d'un processus chimique complexe impliquant beaucoup de produits, plusieurs phases et plusieurs processus chimiques. Des méthodes numériques ont été développées au cours des dernières décennies pour prédire les équilibres chimiques finaux en utilisant le principe de minimisation de l'enthalpie libre du système. La plupart des méthodes utilisent la méthode des « multiplicateurs de Lagrange » et résolvent les équations en employant une approximation du problème de Lagrange et en utilisant un algorithme de convergence pas à pas de type Newton-Raphson. Les équations mathématiques correspondantes restent cependant fortement non linéaires, de sorte que la résolution, notamment de systèmes multiphasiques, peut être très aléatoire. Une méthode alternative de recherche du minimum de l’énergie de Gibbs (MCGE) est développée dans ce travail, basée sur une technique de Monte-Carlo associée à une technique de Pivot de Gauss pour sélectionner des vecteurs composition satisfaisant la conservation des atomes. L'enthalpie libre est calculée pour chaque vecteur et le minimum est recherché de manière très simple. Cette méthode ne présente a priori pas de limite d’application (y compris pour las mélanges multiphasiques) et l’équation permettant de calculer l’énergie de Gibbs n’a pas à être discrétisée. Il est en outre montré que la précision des prédictions dépend assez significativement des valeurs thermodynamiques d’entrée telles l'énergie de formation des produits et les paramètres d'interaction moléculaire. La valeur absolue de ces paramètres n'a pas autant d’importance que la précision de leur évolution en fonction des paramètres du process (pression, température, ...). Ainsi, une méthode d'estimation cohérente est requise. Pour cela, la théorie de la « contribution de groupe » est utilisée (ceux de UNIFAC) et a été étendue en dehors du domaine d'interaction moléculaire traditionnel, par exemple pour prédire l'énergie de formation d’enthalpie libre, la chaleur spécifique... Enfin, l'influence du choix de la liste finale des produits est discutée. On montre que la prédictibilité dépend du choix initial de la liste de produits et notamment de son exhaustivité. Une technique basée sur le travail de Brignole et Gani est proposée pour engendrer automatiquement la liste des produits stable possibles. Ces techniques ont été programmées dans un nouveau code : CIRCE. Les travaux de Brignole et de Gani sont mis en œuvre sur la base de la composition atomique des réactifs pour prédire toutes les molécules « réalisables ». La théorie de la « contribution du groupe » est mise en œuvre pour le calcul des propriétés de paramètres thermodynamiques. La méthode MCGE est enfin utilisée pour trouver le minimum absolu de la fonction d'enthalpie libre. Le code semble plus polyvalent que les codes traditionnels (CEA, ASPEN, ...) mais il est plus coûteux en termes de temps de calcul. Il peut aussi être plus prédictif. Des exemples de génie des procédés illustrent l'étendue des applications potentielles en génie chimiqueThe objective of this work is to develop a new code to predict the final equilibrium of a complex chemical process with many species/reactions and several phases. Numerical methods were developed in the last decades to predict final chemical equilibria using the principle of minimizing the Gibbs free energy of the system. Most of them use the “Lagrange Multipliers” method and solve the resulting system of equations under the form of an approximate step by step convergence technique. Notwithstanding the potential complexity of the thermodynamic formulation of the “Gibbs problem,” the resulting mathematical formulation is always strongly non-linear so that solving multiphase systems may be very tricky and having the difficult to reach the absolute minimum. An alternative resolution method (MCGE) is developed in this work based on a Monte Carlo technique associated to a Gaussian elimination method to map the composition domain while satisfying the atom balance. The Gibbs energy is calculated at each point of the composition domain and the absolute minimum can be deduced very simply. In theory, the technique is not limited, the Gibbs function needs not be discretised and multiphase problem can be handled easily. It is further shown that the accuracy of the predictions depends to a significant extent on the “coherence” of the input thermodynamic data such the formation Gibbs energy of the species and molecular interaction parameters. The absolute value of such parameters does not matter as much as their evolution as function of the process parameters (pressure, temperature, …). So, a self-consistent estimation method is required. To achieve this, the group contribution theory is used (UNIFAC descriptors) and extended somewhat outside the traditional molecular interaction domain, for instance to predict the Gibbs energy of formation of the species, the specific heat capacity… Lastly the influence of the choice of the final list of products is discussed. It is shown that the relevancy of the prediction depends to a large extent on this initial choice. A first technique is proposed, based on Brignole and Gani‘s work, to avoid omitting species and another one to select, in this list, the products likely to appear given the process conditions. These techniques were programmed in a new code name CIRCE. Brignole and Gani-‘s method is implemented on the basis of the atomic composition of the reactants to predict all “realisable” molecules. The extended group contribution theory is implemented to calculate the thermodynamic parameters. The MCGE method is used to find the absolute minimum of the Gibbs energy function. The code seems to be more versatile than the traditional ones (CEA, ASPEN…) but more expensive in calculation costs. It can also be more predictive. Examples are shown illustrating the breadth of potential applications in chemical engineering
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Venkatraman, Ashwin. "Gibbs free energy minimization for flow in porous media." Thesis, 2014. http://hdl.handle.net/2152/24828.
Full textAbstract:
CO₂ injection in oil reservoirs provides the dual benefit of increasing oil recovery as well as sequestration. Compositional simulations using phase behavior calculations are used to model miscibility and estimate oil recovery. The injected CO₂, however, is known to react with brine. The precipitation and dissolution reactions, especially with carbonate rocks, can have undesirable consequences. The geochemical reactions can also change the mole numbers of components and impact the phase behavior of hydrocarbons. A Gibbs free energy framework that integrates phase equilibrium computations and geochemical reactions is presented in this dissertation. This framework uses the Gibbs free energy function to unify different phase descriptions - Equation of State (EOS) for hydrocarbon components and activity coefficient model for aqueous phase components. A Gibbs free energy minimization model was developed to obtain the equilibrium composition for a system with not just phase equilibrium (no reactions) but also phase and chemical equilibrium (with reactions). This model is adaptable to different reservoirs and can be incorporated in compositional simulators. The Gibbs free energy model is used for two batch calculation applications. In the first application, solubility models are developed for acid gases (CO₂ /H2 S) in water as well as brine at high pressures (0.1 - 80 MPa) and high temperatures (298-393 K). The solubility models are useful for formulating acid gas injection schemes to ensure continuous production from contaminated gas fields as well as for CO₂ sequestration. In the second application, the Gibbs free energy approach is used to predict the phase behavior of hydrocarbon mixtures - CO₂ -nC₁₄ H₃₀ and CH₄ -CO₂. The Gibbs free energy model is also used to predict the impact of geochemical reactions on the phase behavior of these two hydrocarbon mixtures. The Gibbs free energy model is integrated with flow using operator splitting to model an application of cation exchange reactions between aqueous phase and the solid surface. A 1-D numerical model to predict effluent concentration for a system with three cations using the Gibbs free energy minimization approach was observed to be faster than an equivalent stoichiometric approach. Analytical solutions were also developed for this system using the hyperbolic theory of conservation laws and are compared with experimental results available at laboratory and field scales.text
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Sommacal, Silvano. "Computational petrology: Subsolidus equilibria in the upper mantle." Phd thesis, 2004. http://hdl.handle.net/1885/48196.
Full textAbstract:
Processes that take place in the Earth’s mantle are not accessible to direct
observation. Natural samples of mantle material that have been transported to the surface as xenoliths provide useful information on phase relations and compositions of phases at the
pressure and temperature conditions of each rock fragment. In the past, considerable effort has been devoted by petrologists to investigate upper mantle processes experimentally.
Results of high temperatures, high pressure experiments have provided insight into lower
crust-upper mantle phase relations as a function of temperature, pressure and composition.
However, the attainment of equilibrium in these experiments, especially in complex
systems, may be very difficult to test rigorously. Furthermore, experimental results may
also require extrapolation to different pressures, temperatures or bulk compositions. More
recently, thermodynamic modeling has proved to be a very powerful approach to this
problem, allowing the deciphering the physicochemical conditions at which mantle
processes occur. On the other hand, a comprehensive thermodynamic model to investigate
lower crust-upper mantle phase assemblages in complex systems does not exist. ¶ In this study, a new thermodynamic model to describe phase equilibria between silicate and/or oxide crystalline phases has been derived. For every solution phase the molar Gibbs free energy is given by the sum of contributions from the energy of the end-members, ideal mixing on sites, and excess site mixing terms. It is here argued that the end-member term of the Gibbs free energy for complex solid solution phases (e.g. pyroxene, spinel) has not previously been treated in the most appropriate manner. As an example, the correct expression of this term for a pyroxene solution in a general (Na-Ca-Mg-Fe2+-Al-Cr-Fe3+-Si-Ti) system is presented and the principle underlying its formulation for any complex solution phase is elucidated. ¶ ...
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Alazmi, Meshari. "Towards Rational Design of Biosynthesis Pathways." Diss., 2018. http://hdl.handle.net/10754/629904.
Full textAbstract:
Recent advances in genome editing and metabolic engineering enabled a precise construction of de novo biosynthesis pathways for high-value natural products. One important design decision to make for the engineering of heterologous biosynthesis systems is concerned with which foreign metabolic genes to introduce into a given host organism. Although this decision must be made based on multifaceted factors, a major one is the suitability of pathways for the endogenous metabolism of a host organism, in part because the efficacy of heterologous biosynthesis is affected by competing endogenous pathways. To address this point, we developed an open-access web server called MRE (metabolic route explorer) that systematically searches for promising heterologous pathways by considering competing endogenous reactions in a given host organism. MRE utilizes reaction Gibbs free energy information. However, 25% of the reactions do not have accurate estimations or cannot be estimated. To address this issue, we developed a method called FC (fingerprint contribution) to provide a more accurate and complete estimation of the reaction free energy.
To rationally design a productive heterologous biosynthesis system, it is essential to consider the suitability of foreign reactions for the specific endogenous metabolic infrastructure of a host. For a given pair of starting and desired compounds in a given chassis organism, MRE ranks biosynthesis routes from the perspective of the integration of new reactions into the endogenous metabolic system. For each promising heterologous biosynthesis pathway, MRE suggests actual enzymes for foreign metabolic reactions and generates information on competing endogenous reactions for the consumption of metabolites. The URL of MRE is http://www.cbrc.kaust.edu.sa/mre/. Accurate and wide-ranging prediction of thermodynamic parameters for biochemical reactions can facilitate deeper insights into the workings and the design of metabolic systems. Here, we introduce a machine learning method, referred to as fingerprint contribution (FC), with chemical fingerprint-based features for the prediction of the Gibbs free energy of biochemical reactions. From a large pool of 2D fingerprint-based features, this method systematically selects a small number of relevant ones and uses them to construct a regularized linear model. FC is freely available for download at http://sfb.kaust.edu.sa/Pages/Software.aspx.
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Kinsley, Nichole Michelle. "Energetics of ligand binding to activate site of glutathione transferase M1-1." Thesis, 2006. http://hdl.handle.net/10539/1715.
Full textAbstract:
Student Number : 0002483R -
MSc dissertation -
School of Molecular and Cell Biology -
Faculty of ScienceIsothermal titration calorimetry was used to investigate the forces that drive ligand binding to the active site of rGST M1-1. In an attempt to gain insight into the recognition of non-substrate ligands by GSTs, this study also investigates interactions between rGST M1-1 and ANS, a non-substrate ligand. At 25 °C, complex formation between rGST M1-1 and GSH, GSO3 -, and S-hexylglutathione is characterised by a monophasic binding isotherm with Kd values of 38.5 mM, 2.1 mM and 0.2 mM, respectively. One molecule of each ligand is bound per monomer of rGST M1-1. Binding of these ligands is enthalpically favourable and entropically unfavourable with a resultant favourable Gibbs free energy, overall. The effects of temperature and buffer ionisation on the energetics of binding were studied. The enthalpic and entropic contributions for all three ligands exhibited temperature dependence over the temperature range investigated (5-30 °C). The Gibbs free energy showed negligible changes with increasing temperature due to enthalpy-entropy compensation. The temperature dependence of the binding enthalpy yielded heat capacity changes of – 2.69 kJ/mol/K and –3.68 kJ/mol/K at 25 °C for GSH and S-hexylglutathione binding and –1.86 kJ/mol/K overall for GSO3 -. The linear dependence of DH on temperature for GSO3 - binding to rGST M1-1 suggests the formation of a more constrained complex which limits the fluctuations in conformations of the mu-loop at the active site. The non-linear dependence of DH on temperature for GSH and Shexylglutathione binding to the enzyme suggests the formation of a complex that samples different bound conformations due to the mobility of the mu-loop even after ligand is bound. Calorimetric binding experiments in various buffer systems with different ionisation enthalpies suggest that the binding of GSH to rGST M1-1 is coupled to the deprotonation of the thiol of GSH while GSO3 - binding to rGST M1-1 is independent of the buffer ionisation. At 25 °C, the rGST M1-1#1;ANS association is represented by a monophasic binding isotherm with one molecule of ANS bound per monomer of rGST M1-1. The interaction is both enthalpically and entropically driven with a Kd value of 27.2 mM representing moderate affinity. The effect of temperature on the interaction was investigated over the temperature range of 5-30 °C. The linear dependence of the binding enthalpy on temperature indicates that no significant structural changes occur upon binding of ANS to the enzyme (DCp = -0.34 kJ/mol/K). The change in heat capacity associated with the interaction can be attributed to the burial of the polar sulphonate group of ANS and the exposure of the anilino and naphthyl rings to solvent as well as the possibility of weak electrostatic interactions between ANS and residues at the active site. The effect of ethacrynic acid, GSH, GSO3 - and S-hexylglutathione on the fluorescence of ANS was investigated in order to obtain some idea as to the location of the ANS binding site on rGST M1-1. ANS was displaced by GSO3 -, S-hexylglutathione and ethacrynic acid, while no displacement occurred upon binding of GSH to the active site of rGST M1-1. Displacement studies and molecular docking simulations indicate that ANS binds to the H-site of rGST M1-1 and the possibility of a second binding site for the molecule cannot be ruled out.
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Ouarouer, Yosra. "Determination of kinetic parameters using Rancimat analysis." Master's thesis, 2017. http://hdl.handle.net/10198/19765.
Full textAbstract:
The physicochemical quality parameters, the total phenols contents and the oxidative stabilities at 120 to 160 ºC of commercial extra-virgin olive oils were assessed, allowing to confirm the quality grade as well as to group them according to the total phenols contents as low (88±7 mg CAE/kg), medium (112±6 mg CAE/kg) and high (144±4 mg CAE/kg) phenols levels. The results pointed out that oils with higher total phenols contents were more thermally stable. Kinetic and thermodynamic parameters were determined using the activated complex/transition-state theory, showing that their values did not significantly differ for the two highest total phenols contents, suggesting a hypothetically threshold saturation of the beneficial effect. High total phenols content would imply a significant more negative temperature coefficient, higher temperature acceleration factor, greater activation energy and frequency factor, higher positive enthalpy of activation, lower negative entropy of activation and greater positive Gibbs free energy of activation. The results confirmed that the lipid oxidation was a non-spontaneous, endothermic and endergonic process with activated formed complexes structurally more ordered than the reactants. A negative deviation from the Arrhenius behavior was observed for all oils being the super-Arrhenius behavior more marked for oils with lower total phenols contents.Neste estudo foram avaliados os parâmetros de qualidade físico-químicos, os teores de fenóis totais e as estabilidades oxidativas na gama de 120 a 160 º C, de azeites comerciais virgem extra, permitindo confirmar a classificação de vrigem extra, bem como agrupá-los de acordo com teores totais de fenóis em baixo teor (88 ± 7 mg CAE/kg), médio teor (112 ± 6 mg CAE/kg) e elevado teor (144 ± 4 mg CAE/kg) de fenóis. Os resultados demonstraram que os azeites com maior teor de fenóis totais foram mais estáveis termicamente. Parâmetros cinéticos e termodinâmicos foram determinados com base na teoria do complexo/estado de transição ativado, mostrando que seus valores não diferiram significativamente para os azeites com maiores teores de fenóis totais. Azeites com um alto teor de fenóis totais possuiam um coeficiente de temperatura significativamente mais negativo, maior fator de aceleração de temperatura, maior energia de ativação e fator de freqüência, maior entalpia positiva de ativação, menor entropia negativa de ativação e maior energia livre de Gibbs. Os resultados confirmaram que a oxidação lipídica é um processo não-espontâneo, endotérmico e endérgico em que os complexos formados são estruturalmente mais ordenados do que os reagentes que lhes deram origem. Um desvio negativo ao comportamento de Arrhenius foi observado para todos os azeites estudados sendo o comportamento supra-Arrhenius mais notório para azeites com menor teor de fenóis totais.