• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 12
  • 8
  • 6
  • 3
  • Tagged with
  • 35
  • 8
  • 7
  • 6
  • 6
  • 5
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Refinamento sequencial e paramétrico pelo método de Rietveld: aplicação na caracterização de fármacos e excipientes / Sequential and parametric refinement by the Rietveld method: application in the characterization of drugs and excipients

Tita, Diego Luiz [UNESP] 20 April 2018 (has links)
Submitted by Diego Luiz Tita (diego.tita@gmail.com) on 2018-05-11T17:51:31Z No. of bitstreams: 1 DR_TITA_DL_FINAL_A.pdf: 8672085 bytes, checksum: af81639f689b5a5fc78999ae952240a8 (MD5) / Approved for entry into archive by Ana Carolina Gonçalves Bet null (abet@iq.unesp.br) on 2018-05-15T12:53:22Z (GMT) No. of bitstreams: 1 tita_dl_dr_araiq_int.pdf: 8328482 bytes, checksum: be0fe77b0059e1880c4d517105e2c2f6 (MD5) / Made available in DSpace on 2018-05-15T12:53:22Z (GMT). No. of bitstreams: 1 tita_dl_dr_araiq_int.pdf: 8328482 bytes, checksum: be0fe77b0059e1880c4d517105e2c2f6 (MD5) Previous issue date: 2018-04-20 / O refinamento de estruturas cristalinas pelo método de Rietveld (MR) consiste em ajustar um modelo estrutural a uma medida de difração. Essa é uma ferramenta eficiente para identificação e quantificação de estruturas polimórficas presentes em fármacos e excipientes. Uma forma avançada do método é o refinamento sequencial por Rietveld (RSR) que visa, a partir de um conjunto de difratogramas de uma mesma amostra, estudar o comportamento do material em função de uma variável externa (e.g. temperatura, pressão, tempo ou ambiente químico). No presente trabalho, com o objetivo de estudar as transições polimórficas e as expansões/contrações dos parâmetros de cela unitária (PCU) dos insumos farmacêuticos: espironolactona (SPR), lactose monoidratada (LACMH) e lactose anidra (LACA), empregou-se o RSR em medidas obtidas em diferentes temperaturas. O RSR foi eficiente para que os PCU fossem refinados até temperaturas próximas ao ponto de fusão dos materiais. Após o RSR, a partir da análise matemática dos PCU obtidos, foram propostas funções que regem a tendência desses parâmetros quando submetidos à variação de temperatura. Com essas funções modelaram-se os PCU em uma outra modalidade de refinamento, o refinamento paramétrico por Rietveld (RPR), assim, os PCU seguem a modelagem imposta pelas equações obtidas via RSR. O RPR mostrou-se mais eficiente nas análises, o que evitou perda de fases ou problemas de ajustes, resultando assim em informações mais precisas do sistema. Embora o RSR e RPR serem métodos sofisticados para a caracterização dos materiais, a preparação das rotinas de programação dos refinamentos não é trivial, assim, nesse trabalho desenvolveu-se uma planilha (i.e. planilha SP-DLT) que facilita o emprego dos métodos. A planilha mostrou-se eficiente e rápida para programar todas as rotinas de refinamentos apresentadas nesse trabalho. Com os estudos dos insumos farmacêuticos observou-se que na amostra SPR a forma I, com o aumento da temperatura, se converte para forma II. A alfalactose monoidratada sofre desidratação e se converte para alfalactose, na amostra LACMH, e para betalactose, na amostra LACA. E, ainda com aumento de temperatura, a betalactose não sofre mudança de fase polimórfica. Assim, entende-se que o meio pode causar influência na rota de transição polimórfica. / The crystal structural refinement by the Rietveld method (MR) consists of fitting a structural model to a diffraction measure. This is an efficient tool for identification and quantification of polymorphic structures present in drugs and excipients. An advanced way to use this method is the Sequential Rietveld Refinement (RSR), which aims, from a set of data of the same sample, to study the behavior of the material as a function of an external variable (e.g. temperature, pressure, time or chemical environment). In the present work, with the objective of studying the polymorphic transitions and the expansions / contractions of the unit cell parameters (PCU) of the pharmaceutical ingredients: spironolactone (SPR), lactose monohydrate (LACMH) and anhydrous lactose (LACA), the RSR in measurements obtained at different temperatures. The RSR was efficient so that the PCU were refined to temperatures close to the melting point of the materials. After the RSR, from the mathematical analysis of the obtained PCU, functions were proposed that govern the trend of these parameters when submitted to the temperature variation. With these functions the PCU were modeled in another modality of refinement, the Parametric Rietveld Refinement (RPR), thus, the PCU follow the modeling imposed by the equations obtained via RSR. The RPR was more efficient in the analyzes, which avoided loss of phases or problems of adjustments, resulting in more accurate information of the system. Although RSR and RPR are sophisticated methods for characterization of materials, preparation of refinement programming routines is not trivial, so a spreadsheet (i.e. SP-DLT spreadsheet) has been developed in this paper to facilitate the use of methods. The worksheet proved to be efficient and quick to program all the refinement routines presented in this paper. With the studies of the pharmaceutical inputs it was observed that in the SPR sample, the form I, with the increase in temperature, converts to form II. Alfalactose monohydrate undergoes dehydration and converts to alfalactose in the LACMH sample and to betalactose in the LACA sample. And, even with temperature increase, the betalactose does not undergo polymorphic phase change. Thus, it is understood that the medium may cause influence on the polymorphic transition route.
32

Estudo do equil?brio l?quido-vapor do sistema ?gua+etanol+l?quido i?nico visando a separa??o do ?lcool anidro

Maciel, J?ssica Caroline da Silva Linhares 21 September 2012 (has links)
Made available in DSpace on 2014-12-17T15:01:30Z (GMT). No. of bitstreams: 1 JessicaCSLM_DISSERT.pdf: 2011571 bytes, checksum: 8e087d35d6e4c83d4f7eda24cd8d3e57 (MD5) Previous issue date: 2012-09-21 / Anhydrous ethanol is used in chemical, pharmaceutical and fuel industries. However, current processes for obtaining it involve high cost, high energy demand and use of toxic and pollutant solvents. This problem occurs due to the formation of an azeotropic mixture of ethanol + water, which does not allow the complete separation by conventional methods such as simple distillation. As an alternative to currently used processes, this study proposes the use of ionic liquids as solvents in extractive distillation. These are organic salts which are liquids at low temperatures (under 373,15 K). They exhibit characteristics such as low volatility (almost zero/ low vapor ), thermal stability and low corrosiveness, which make them interesting for applications such as catalysts and as entrainers. In this work, experimental data for the vapor pressure of pure ethanol and water in the pressure range of 20 to 101 kPa were obtained as well as for vapor-liquid equilibrium (VLE) of the system ethanol + water at atmospheric pressure; and equilibrium data of ethanol + water + 2-HDEAA (2- hydroxydiethanolamine acetate) at strategic points in the diagram. The device used for these experiments was the Fischer ebulliometer, together with density measurements to determine phase compositions. The experimental data were consistent with literature data and presented thermodynamic consistency, thus the methodology was properly validated. The results were favorable, with the increase of ethanol concentration in the vapor phase, but the increase was not shown to be pronounced. The predictive model COSMO-SAC (COnductor-like Screening MOdels Segment Activity Coefficient) proposed by Lin & Sandler (2002) was studied for calculations to predict vapor-liquid equilibrium of systems ethanol + water + ionic liquids at atmospheric pressure. This is an alternative for predicting phase equilibrium, especially for substances of recent interest, such as ionic liquids. This is so because no experimental data nor any parameters of functional groups (as in the UNIFAC method) are needed / O etanol anidro tem ampla aplica??o em ind?strias qu?mica, farmac?utica e de combust?veis. No entanto, os processos atuais para a sua obten??o envolvem custo elevado, alta demanda de energia e a utiliza??o de solventes t?xicos e poluentes. Esse problema ocorre devido ? forma??o de aze?tropo na mistura etanol + ?gua, n?o permitindo a separa??o completa por m?todos convencionais tais como destila??o simples. Como uma alternativa aos processos atualmente utilizados, este estudo prop?e a utiliza??o de l?quidos i?nicos como agentes na destila??o extrativa. Trata-se de sais org?nicos l?quidos a baixas temperaturas (abaixo de 373,15 K). Suas caracter?sticas, tais como baixa volatilidade (press?o de vapor muito baixa), estabilidade t?rmica e baixa corrosividade os tornam interessantes para aplica??es como catalisadores e solventes. Neste trabalho, dados experimentais de press?o de vapor de etanol e ?gua puros na faixa de press?o de 20 a 101 kPa, assim como dados de equil?brio l?quido-vapor(ELV) do sistema etanol + ?gua a press?o atmosf?rica, e dados de equil?brio do sistema etanol + ?gua + 2-HDEAA (acetato de 2-hidrodietanolamina) foram obtidos em pontos estrat?gicos do diagrama. O dispositivo usado para esses experimentos foi o ebuliometro de Fischer, juntamente com medidas de densidade para determinar a composi??o das fases. Os dados obtidos apresentaram coer?ncia com dados da literatura e consist?ncia termodin?mica, desta forma, a metodologia foi devidamente validada. Os resultados foram favor?veis, com o aumento da concentra??o de etanol na fase vapor, por?m o aumento n?o demonstrou ser elevado. O modelo preditivo COSMO-SAC (COnductor-like Screening MOdels Segment Activity Coefficient), desenvolvido por Lin e Sandler (2002), foi aplicado para os c?lculos de predi??o de Equil?brio L?quido-Vapor do sistema etanol + ?gua com l?quido i?nico a press?o atmosf?rica. Essa ? uma alternativa para a previs?o do equil?brio de fases, especialmente para subst?ncias de interesse recente, tais como l?quidos i?nicos, uma vez que nem dados experimentais, nem par?metros de grupos funcionais (como no m?todo UNIFAC) s?o necess?rios
33

Refinamento sequencial e paramétrico pelo método de Rietveld : aplicação na caracterização de fármacos e excipientes /

Tita, Diego Luiz. January 2018 (has links)
Orientador: Carlos de Oliveira Paiva Santos / Coorientadora: Selma Gutierrez Antonio / Banca: Marlus Chorilli / Banca: Vinícius Danilo Nonato Bezzon / Banca: Flavio Machado de Souza Carvalho / Banca: Alexandre Urbano / Resumo: O refinamento de estruturas cristalinas pelo método de Rietveld (MR) consiste em ajustar um modelo estrutural a uma medida de difração. Essa é uma ferramenta eficiente para identificação e quantificação de estruturas polimórficas presentes em fármacos e excipientes. Uma forma avançada do método é o refinamento sequencial por Rietveld (RSR) que visa, a partir de um conjunto de difratogramas de uma mesma amostra, estudar o comportamento do material em função de uma variável externa (e.g. temperatura, pressão, tempo ou ambiente químico). No presente trabalho, com o objetivo de estudar as transições polimórficas e as expansões/contrações dos parâmetros de cela unitária (PCU) dos insumos farmacêuticos: espironolactona (SPR), lactose monoidratada (LACMH) e lactose anidra (LACA), empregou-se o RSR em medidas obtidas em diferentes temperaturas. O RSR foi eficiente para que os PCU fossem refinados até temperaturas próximas ao ponto de fusão dos materiais. Após o RSR, a partir da análise matemática dos PCU obtidos, foram propostas funções que regem a tendência desses parâmetros quando submetidos à variação de temperatura. Com essas funções modelaram-se os PCU em uma outra modalidade de refinamento, o refinamento paramétrico por Rietveld (RPR), assim, os PCU seguem a modelagem imposta pelas equações obtidas via RSR. O RPR mostrou-se mais eficiente nas análises, o que evitou perda de fases ou problemas de ajustes, resultando assim em informações mais precisas do sistema. Embora o RSR e R... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The crystal structural refinement by the Rietveld method (MR) consists of fitting a structural model to a diffraction measure. This is an efficient tool for identification and quantification of polymorphic structures present in drugs and excipients. An advanced way to use this method is the Sequential Rietveld Refinement (RSR), which aims, from a set of data of the same sample, to study the behavior of the material as a function of an external variable (e.g. temperature, pressure, time or chemical environment). In the present work, with the objective of studying the polymorphic transitions and the expansions / contractions of the unit cell parameters (PCU) of the pharmaceutical ingredients: spironolactone (SPR), lactose monohydrate (LACMH) and anhydrous lactose (LACA), the RSR in measurements obtained at different temperatures. The RSR was efficient so that the PCU were refined to temperatures close to the melting point of the materials. After the RSR, from the mathematical analysis of the obtained PCU, functions were proposed that govern the trend of these parameters when submitted to the temperature variation. With these functions the PCU were modeled in another modality of refinement, the Parametric Rietveld Refinement (RPR), thus, the PCU follow the modeling imposed by the equations obtained via RSR. The RPR was more efficient in the analyzes, which avoided loss of phases or problems of adjustments, resulting in more accurate information of the system. Although RSR and RP... (Complete abstract click electronic access below) / Doutor
34

Chimie organométallique de surface sur hétéropolyacides anhydres de type Keggin : application en catalyse / Surface organometallic chemistry on anhydrous Keggin-type heteropolyacids : application in catalysis

Grinenval, Éva 28 October 2009 (has links)
L’objectif de ce travail de thèse était la préparation et la caractérisation des hétéropolyanions anhydres sur supports oxydes par la stratégie de chimie organométallique de surface. Les acides anhydres H3PMo12O40 et H3PW12O40 ont été préparés sur silice partiellement déshydroxylée. Cette réaction conduit à une interaction ionique par protonation des silanols de surface. La réactivité de ces hétéropolyacides anhydres en présence d’alkylsilanes a été étudiée en milieu homogène et a conduit à la formation d’espèces silylées cationiques [Et2MeSi+]3[HPA3-] et au dégagement d’hydrogène. Cette réactivité a ensuite été appliquée en milieu hétérogène en fonctionnalisant la surface de la silice par des groupements [(≡SiO)SiMe2H] et a conduit à la formation d’une espèce de surface polyoxometalate liée de manière covalente au support. L’introduction de fonction chloroalkylsilane à la surface de la silice [(≡SiO)SiMeCl2] et [(≡SiO)2SiMeCl] a également permis de former des liaisons covalentes Si Support-O-M HPA. Par ailleurs, Par ailleurs, l’activation du méthane a été observée sur tous les solides HPA/SiO2 à travers le dégagement de CO2, H2O, H2. L’activation C-H a lieu sur ces systèmes même à basse température et les données obtenues suggèrent la formation d’une espèce méthoxy de surface par réaction des protons acides avec le méthane / The aim of this work was the preparation and characterization of anhydrous heteropolyanions on oxide supports using surface organometallic chemistry approach. Anhydrous H3PMo12O40 and H3PW12O40 were prepared on partially dehydroxylated silica. This reaction led to an ionic interaction by protonation of surface silanols. The reactivity of these heteropoly compounds with alkylsilanes was studied in homogeneous conditions and led to the formation of cationic silicon species [Et2MeSi+]3[HPA3-] and release of hydrogen. This reactivity was then applied in heterogeneous conditions by introduction of silane groups [(≡SiO)SiMe2H] at the silica surface and led to the formation of a surface polyoxometalate species covalently bonded to the support. The introduction of chloroalkylsilane groups [(≡SiO)SiMeCl2] and [(≡SiO)2SiMeCl] has also enabled the formation of covalent bonds Si Support-O-M HPA. In addition, methane activation was observed on all HPA/SiO2 solids through the releases of CO2, H2O, H2. The C-H activation takes place on these systems even at low temperature and obtained data suggest the formation of a methoxy surface species by reaction of stronf acidic protons with methane
35

Metal catalysed alkylation of carbonyl compounds with formaldehyde

Lorusso, Patrizia January 2015 (has links)
Formaldehyde is a chemical used widely in the manufacture of building materials. A remarkable example is represented by the Lucite two-step Alpha technology for the large scale production of methyl methacrylate (MMA), the essential building block of all acrylic-based products. Esters and ketones are important intermediates in the manufacture of acrylate esters therefore α-hydroxymethylenation of carbonyl compounds using formaldehyde as a one carbon alkylating agent and subsequent dehydration to the corresponding methylenated derivatives has been explored in the current work. We report a novel catalytic approach for the synthesis of methyl methacrylate (MMA) via one-pot α-methylenation of methyl propanoate (a chemical intermediate of the ALPHA process) with formaldehyde, generated in situ by Ru-catalysed dehydrogenation of methanol. Elucidation of the mechanism involved in the catalytic dehydrogenation of methanol along with the collateral alcohol decarbonylation reaction was gained through a combined experimental and DFT study. The development of an alternative process where anhydrous formaldehyde is produced in situ would provide a simplification over the current second step of the ALPHA technology where the formaldehyde is initially produced as formalin, subsequently dehydrated to afford anhydrous formaldehyde in order to ensure high selectivity to MMA. As an alternative approach, ketones, in particular 3-pentanone and 2-butanone, were targeted as potential substrates in order to overcome some of the problems related to competing reactions that occur at the ester group. Hydroxymethylenation, followed by dehydration and Baeyer-Villager oxidation, possibly catalysed by enzymes to reverse the normal selectivity, leads to the formation of acrylate esters. The catalytic reaction is enabled by a gold carbene hydroxide complex in such a way that the substrate undergoes C-H activation and the nascent metal alkyl acts as a nucleophile towards the electrophilic formaldehyde, supplied in the form of alcoform* (solution of paraformaldehyde in methanol).

Page generated in 0.1196 seconds