Dimethylether is a non-toxic liquefied gas, which is projected to become one of the fundamental chemical feedstock in the future. Dimethylether can be produced from syngas via a two-step (indirect) process that involves synthesis of methanol by hydrogenation of CO/CO2 over a copper based catalyst and subsequent dehydration of methanol to DME over an acidic catalyst. Alternatively, DME can be produced in an one-step (direct) process using a hybrid (bifunctional) catalyst system that permits both methanol synthesis and dehydration in a single process unit. In the present research work the production of DME has been studied by applying both the indirect and direct processes. Firstly, the methanol synthesis and methanol dehydration reactions involved in the indirect process have been studied separately. Afterwards, these two reactions have been combined in the direct DME production process by using a hybrid catalyst comprising a methanol synthesis and a methanol dehydration component. The methanol synthesis by CO2 hydrogenation has been investigated over commercial and home-made CuO/ZnO/Al2O3 catalysts with the aim to identify optimal experimental conditions (CO2:H2 ratio, flow rate, temperature) that could be then used in the direct conversion of CO2/H2 mixtures into methanol/DME. Obtained results reveal that the conversion of CO2 and the yields of reaction products (CH3OH and CO) increase when the concentration of H2 in the feed and the reaction contact time are increased. It was found that both Cu+/Cu0 species are important for the conversion of CO2/H2, although the presence of Cuo seems to be more important for selectivity/yield of methanol. The stability of the CuO/ZnO/Al2O3 catalyst has been also investigated. It was observed that the main reason for the deactivation of catalyst is the water produced via the methanol synthesis and reverse water gas shift reactions. However, the catalytic activity and products selectivity were recovered slowly to their original levels after applying a regeneration procedure, indicating that deactivation by water is reversible. The dehydration of methanol to dimethylether (DME) has been investigated over a range of catalysts including alumina, silica-alumina and zeolites with different physicochemical characteristics. The effects of temperature and the presence of water vapour in the feed on catalytic performance have been studied in detail. The reactivity of catalysts has been evaluated by determining the reaction rates per gram of catalyst per acid site (total: Brönsted+Lewis) and per Brönsted/Lewis mole ratio. In addition, the reaction mechanism has been investigated over a selected catalyst, with the use of transient-MS and in situ DRIFTS techniques. Results obtained for alumina catalysts show that the catalytic activity and selectivity are determined to a large extent by the textural properties, degree of crystallinity and total amount of acid sites of catalysts. In particular, the methanol conversion curve shifts toward lower reaction temperatures with an increase of specific surface area. However, the enhanced catalytic activity of high-SSA samples cannot be attributed solely to the higher amount of surface acid sites, implying that the reaction rate is determined to a large extent from other parameters, such as textural properties and degree of crystallinity. Results of mechanistic studies indicate that interaction of methanol with the Al2O3 surface results in the formation of two kinds of methoxy groups of different adsorption strength. Evidence is provided that DME evolution is associated with methoxy species that are weakly adsorbed on the Al2O3 surface, whereas more strongly held species decompose to yield surface formate and, eventually, CH4 and CO in the gas phase. Results obtained over zeolite catalysts show that catalytic performance depends on the topology of zeolites due to differences in micropore structure and Si/Al ratio as well as on the number, strength and nature of active acid sites. The activity of zeolite catalysts for the methanol dehydration to DME follows the order ZSM-5 > Ferrierite > Mordenite ~ Beta ~ USY > H-Y. The strong Brönsted acid sites of ZSM-5 zeolites with relatively high Si/Al ratio represent the most active sites in methanol dehydration to DME reaction. However, the overall reactivity of the ZSM-5 zeolites is also affected by the balance of the Brönsted to Lewis acid sites. The activity of Beta and USY zeolites is determined by both Lewis and Brönsted acid sites. The moderate/low reactivity of Ferrierite, Mordenite and H-Y zeolite are determined by the abundant Brönsted acid sites of relatively weak/moderate strength. The direct CO2 hydrogenation to methanol/DME has been investigated using admixed catalysts comprising a methanol synthesis (commercial copper based catalyst: CZA1) and a methanol dehydration component (different alumia/zeolite catalysts: γ-Al2O3, ZSM-5, W/γ-Al2O3, USY(6), Ferrierite(10)). It has been revealed that the conversion of CO2 is always lower than the corresponding equilibrium values predicted by thermodynamics, indicating operation in the kinetic regime. The nature of the methanol dehydration component of the admixed catalysts was found to be important for both CO2 conversion and methanol dehydration. In particular, DME selectivity/yield, depends strongly on the nature of acid sites (both Lewis and Brönsted) as well as the textural (meso/macro porosity) and topological properties of methanol dehydration component of the admixed catalysts. The yield of DME obtained at a temperature of 250oC decreases following the order CZA1/ZSM-5, CZA1/USY(6) > CZA1/Ferrierite(10) > CZA1/ W/γ-Al2O3 >> CZA1/γ-Al2O3. The long-term stability experiments conducted over selected bifunctional catalytic systems revealed that the catalysts deactivate with time-on-stream, mainly due to water produced via methanol synthesis, methanol dehydration and reverse water gas shift reactions. In case of the CZA1/ZSM-5 admixed catalyst the catalytic activity and products selectivity were almost recovered after regeneration indicating that deactivation by water is reversible. / --

Depuis quelques années, le domaine de l’extraction végétale est en pleine mutation, avec à la fois un intérêt croissant des consommateurs pour des ingrédients d’origine naturelle, combiné à des préoccupations environnementales. Il apparaît dès lors indispensable de remplacer les procédés actuels utilisant des solvants pétrochimiques nocifs par de nouveaux procédés d’extraction réduisant le besoin énergétique, la toxicité du solvant et la quantité de déchets tout en s’assurant du rendement et de la qualité de l’extrait obtenu. L’objectif de cette thèse a donc consisté à développer un nouveau procédé d’extraction mettant en œuvre des gaz liquéfiés comme solvants. Ce manuscrit présentera tout d’abord l’état de l’art sur les gaz liquéfiés existants et leur mise en œuvre pour l’extraction des produits naturels. A l’issue de cette présentation, 3 gaz liquéfiés ont été sélectionnés (n-butane, HFO-1234ze et le DME) comme solvants pour mener des essais au laboratoire, grâce à un prototype dont la conception est détaillée dans le chapitre II. Dans un second temps, les essais réalisés à l’aide de ces gaz liquéfiés pour l’extraction de composés lipophiles ont été décrits. L’approche expérimentale a été couplée à une approche prédictive par l’utilisation d’outils d’aide à la décision : les paramètres de solubilité de Hansen et le modèle COSMO-RS. La prédiction théorique ainsi que les essais expérimentaux ont confirmé l’intérêt des gaz liquéfiés pour la solubilisation et l’extraction de composés lipophiles d’intérêt biologique et à haute valeur ajoutée. Parallèlement l’étude des impacts du procédé sur l’environnement, la qualité, la réglementation et la sécurité ont montré que l’extraction par gaz liquéfié était un procédé facilement transposable à l’échelle industrielle. / In recent years, the industrial sector of vegetable extraction has been evolving due to the growing interest of consumers for natural food ingredients combined with growing environmental concerns. Therefore, it seems essential to replace existing processes using toxic petroleum bases solvents with greener extraction processes with lower energy consumption, less wastes but higher extract quality. The objective of this thesis has consisted in the research and development of a new extraction process using liquefied gases as liquid solvents. First, this manuscript will outline the state of the art on the liquefied gases and how they are used for extraction of natural products. After this survey, 3 liquefied gases (n-butane, HFO-1234ze and DME) have been selected for laboratory scale experiments performed using a dedicated extraction unit whose design is detailed in chapter II. Then, the tests performed with these 3 gases for extraction of lipophilic compounds from several plant materials has been described. The experimental approach has been combined with a predictive one using decision tools: Hansen Solubility Parameters and COSMO-RS model. This survey demonstrated that liquefied gases are interesting solvents for solubilization and extraction of lipophilic compounds of interest. In parallel, the impacts of the process on environment, safety regulation and quality showed that liquefied gas extraction could be easily transposed at industrial scale.

This dissertation develops a systematic targeting method based on the C-H-O ternary diagram for the conceptual design of gasification-based biorefineries. The approach is applied using dimethyl ether (DME) as case study. A stoichiometric equilibrium model is presented for calculation of the C-H-O chemical equilibria to evaluate and predict equilibrium syngas composition, operating temperature, type and amount of oxidant required in biomass gasification. Overall atomic species balances are developed and process targets are plotted on the C-H-O ternary diagram. Sustainability metrics are incorporated to provide useful insights into the efficiency of biorefinery process targets. It was found that syngas at 1200 and 1500 K is predominantly H2 and CO. Moreover, DME biorefineries have two main process targets, based on the indirect and direct synthesis routes. Gasification at 1200 K and 1 atm. using H2O/CO2 = 2.642 (w/w) and H2O/CH4 = 1.645 (w/w) achieved syngas composition targets for the direct and indirect methods respectively. Comparatively, the integrated biorefinery based on indirect route was more efficient, producing 1.903 ton of DME per ton of biomass feedstock. The process is 100% carbon-efficient and recycles 1.025 tons of H2O. / Civil and Chemical Engineering / M. Tech. (Chemical Engineering)

El trabajo presentado en esta Tesis está motivado por la necesidad de los motores de combustión interna alternativos de reducir el consumo de combustible y las emisiones de CO2 mientras se satisfacen las cada vez más restrictivas regulaciones de emisiones contaminantes. Por lo tanto, el objetivo principal de este estudio es optimizar un sistema de combustión de encendido por compresión controlado por mezcla para probar su potencial como motores de futura generación. Con esta meta se ha desarrollado un sistema automático que combina CFD con métodos de optimización avanzados para analizar y entender las configuraciones óptimas. Los resultados presentados en este trabajo se dividen en dos bloques principales. El primero corresponde a la optimización de un sistema de encendido por compresión convencional alimentado con diésel. El segundo se centra en un concepto de combustión avanzado donde se ha sustituido el fuel por Dimetil-eter. En ambos casos, el estudio no sólo halla una configuración óptima sino que también se describen las relaciones causa/efecto entre los parámetros más relevantes del sistema de combustión. El primer bloque aplica métodos de optimización no-evolutivos a un motor medium-duty alimentado por diésel tratando de minimizar consumo a la vez que se mantienen las emisiones contaminantes por debajo de los estándares de emisiones contaminantes impuestos. Una primera parte se centra en la optimización de la geometría de la cámara de combustión y el inyector. Seguidamente se extiende el estudio añadiendo los settings de renovación de la carga de y de inyección al estudio, ampliando el potencial de la optimización. El estudio demuestra el limitado potencial de mejora de consumo que tiene el motor de referencia al mantener los niveles de emisiones contaminantes. Esto demuestra la importancia de incluir parámetros de renovación de la carga e inyección al proceso de optimización. El segundo bloque aplica una metodología basada en algoritmos genéticos al diseño del sistema de combustión de un motor heavy-duty alimentado con Dimetileter. El estudio tiene dos objetivos, primero la optimización de un sistema de combustión convencional controlado por mezcla con el objetivo de lograr mejorar el consumo y reducir las emisiones contaminantes hasta niveles inferiores a los estándares US2010. Segundo la optimización de un sistema de combustión trabajando en condiciones estequiométricas acoplado con un catalizador de tres vías buscando reducir consumo y controlar las emisiones contaminantes por debajo de los estándares 2030. Ambas optimizaciones incluyen tanto la geometría como los parámetros más relevantes de renovación de la carga y de inyección. Los resultados presentan un sistema de combustión convencional óptimo con una notable mejora en rendimiento y un sistema de combustión estequiométrica que es capaz de ofrecer niveles de NOx menores al 1% de los niveles de referencia manteniendo niveles competitivos de rendimiento. Los resultados presentados en esta Tesis ofrecen una visión extendida de las ventajas y limitaciones de los motores MCCI y el camino a seguir para reducir las emisiones de futuros sistemas de combustión por debajo de los estándares establecidos. A su vez, este trabajo también demuestra el gran potencial que tiene el Dimetil-eter como combustible para futuras generaciones de motores. / The work presented in this Thesis was motivated by the needs of internal combustion engines (ICE) to decrease fuel consumption and CO2 emissions, while fulfilling the increasingly stringent pollutant emission regulations. Then, the main objective of this study is to optimize a mixing-controlled compression ignition (MCCI) combustion system to show its potential for future generation engines. For this purpose an automatic system based on CFD coupled with different optimization methods capable of optimizing a complete combustion system with a reasonable time cost was designed together with the methodology to analyze and understand the new optimum systems. The results presented in this work can be divided in two main blocks, firstly an optimization of a conventional diesel combustion system and then an optimization of a MCCI system using an alternative fuel with improved characteristics compared to diesel. Due to the methodologies used in this Thesis, not only the optimum combustion system configurations are described, but also the cause/effect relations between the most relevant inputs and outputs are identified and analyzed. The first optimization block applies non-evolutionary optimization methods in two sequential studies to optimize a medium-duty engine, minimizing the fuel consumption while fulfilling the emission limits in terms of NOx and soot. The first study targeted four optimization parameters related to the engine hardware including piston bowl geometry, injector nozzle configuration and mean swirl number. After the analysis of the results, the second study extended to six parameters, limiting the optimization of the engine hardware to the bowl geometry, but including the key air management and injection settings. The results confirmed the limited benefits, in terms of fuel consumption, with constant NOx emission achieved when optimizing the engine hardware, while keeping air management and injection settings. Thus, including air management and injection settings in the optimization is mandatory to significantly decrease the fuel consumption while keeping the emission limits. The second optimization block applies a genetic algorithm optimization methodology to the design of the combustion system of a heavy-duty Diesel engine fueled with dimethyl ether (DME). The study has two objectives, the optimization of a conventional mixing-controlled combustion system aiming to achieve US2010 targets and the optimization of a stoichiometric mixing-controlled combustion system coupled with a three way catalyst to further control NOx emissions and achieve US2030 emission standards. These optimizations include the key combustion system related hardware, bowl geometry and injection nozzle design as input factors, together with the most relevant air management and injection settings. The target of the optimizations is to improve net indicated efficiency while keeping NOx emissions, peak pressure and pressure rise rate under their corresponding target levels. Compared to the baseline engine fueled with DME, the results of the study provide an optimum conventional combustion system with a noticeable NIE improvement and an optimum stoichiometric combustion system that offers a limited NIE improvement keeping tailpipe NOx values below 1% of the original levels. The results presented in this Thesis provide an extended view of the advantages and limitations of MCCI engines and the optimization path required to achieve future emission standards with these engines. Additionally, this work showed how DME is a promising fuel for future generation engines since it is able to achieve future emission standards while maintaining diesel-like efficiency / El treball presentat en esta Tesi està motivat per la necessitat dels motors de combustió interna alternatius de reduir el consum de combustible i les emissions de CO2 mentres se satisfan les cada vegada mes restrictives regulacions d'emissions contaminants. Per tant, l'objectiu principal d'este estudi es optimitzar un sistema de combustió d'encesa per compressió controlat per mescla per a provar el seu potencial com a motors de futura generació. Amb esta meta s'ha desenrotllat un sistema automàtic que combina CFD amb mètodes d'optimització avançats per a analitzar i entendre les configuracions òptimes. Els resultats presentats en este treball es dividixen en dos blocs principals. El primer correspon a l'optimització d'un sistema d'encesa per compressió convencional alimentat amb dièsel. El segon se centra en un concepte de combustió avançat on s'ha substituït el fuel per Dimetil-eter. En ambdós casos, l'estudi no sols troba una configuració òptima sinó que també es descriuen les relacions causa/efecte entre els paràmetres més rellevants del sistema de combustió. El primer bloc aplica mètodes d'optimització no-evolutius a un motor mediumduty alimentat per dièsel tractant de minimitzar consum al mateix temps que es mantenen les emissions contaminants per davall dels estàndards d'emissions contaminants impostos. Una primera part se centra en l'optimització de la geometria de la cambra de combustió i l'injector. A continuació s'estén l'estudi afegint els settings de renovació de la càrrega de i d'injecció a l'estudi, ampliant el potencial de l'optimització. L'estudi demostra el limitat potencial de millora de consum que té el motor de referència al mantindre els nivells d'emissions contaminants. Açò demostra la importància d'incloure paràmetres de renovació de la càrrega i injecció al procés d'optimització. El segon bloc aplica una metodologia basada en algoritmes genètics al disseny del sistema de combustió d'un motor heavy-duty alimentat amb Dimetil-eter. L'estudi té dos objectius, primer l'optimització d'un sistema de combustió convencional controlat per mescla amb l'objectiu d'aconseguir millorar el consum i reduir les emissions contaminants fins nivells inferiors als estàndards US2010. Segon l'optimització d'un sistema de combustió treballant en condicions estequiomètriques acoblat amb un catalitzador de tres vies buscant reduir consum i controlar les emissions contaminants per davall dels estàndards 2030. Ambdós optimitzacions inclouen tant la geometria com els paràmetres més rellevants de renovació de la càrrega i d'injecció. Els resultats presenten un sistema de combustió convencional òptim amb una notable millora en rendiment i un sistema de combustió estequiomètrica que és capaç d'oferir nivells de NOx menors al 1% dels nivells de referència mantenint nivells competitius de rendiment. Els resultats presentats en esta Tesi oferixen una visió estesa dels avantatges i limitacions dels motors MCCI i el camï que s'ha de seguir per a reduir les emissions de futurs sistemes de combustió per davall dels estàndards establits. Al seu torn, este treball també demostra el gran potencial que té el Dimetil-eter com a combustible per a futures generacions de motors. / Hernández López, A. (2018). Optimization and analysis by CFD of mixing-controlled combustion concepts in compression ignition engines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/103826 / TESIS

Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Truck manufacturers are working to develop equipment using auxiliary power units to supply the trucks with electricity, which operate independently of the main engine. Fuel cell-based auxiliary power units could offer high efficiencies and low noise and vibrations. The hydrogen required for the fuel cell can be generated in an onboard fuel reformer. This thesis is devoted to hydrogen generation from dimethyl ether, DME, by autothermal reforming focusing on the application of fuel cell auxiliary power units. In the search for alternative fuels, DME has lately been identified as a promising diesel substitute. The first part of the thesis gives an introduction to the field of DME reforming with a literature survey of recent studies within the area. Included are also results from thermodynamic equilibrium calculations. In the following parts of the thesis, experimental studies on autothermal reforming of DME are presented. A reformer constructed to generate hydrogen to feed a 5 kWe polymer electrolyte fuel cell is evaluated with emphasis on trying to work close to a practically viable process, i.e. without external heating and using gas mixtures resembling real conditions. Additional experiments have been conducted to investigate the use of catalytic oxidation of dimethyl ether as a heat source during startup. The results of these studies are presented in Paper I. In the second experimental study of this thesis, which is presented in Paper II, Pd-based monolithic catalysts are evaluated at small scale for use in autothermal reforming of DME. A screening of various catalyst materials has been performed followed by a study of the influence on the product composition of varying operating parameters such as oxygen-to-DME ratio, steam-to-DME ratio, and temperature. / QC 20101115

No description available.

Controlled Auto Ignition (CAI) combustion is a new combustion principle in internal combustion engines which has in recent years attracted increased attention. In CAI combustion, which combines features of spark ignition (SI) and compression ignition (CI) principles, air/fuel mixture is premixed, as in SI combustion and auto-ignited by piston compression as in CI combustion. Ignition is provided in multiple points, and thus the charge gives a simultaneous energy release. This results in uniform and simultaneous auto-ignition and chemical reaction throughout the whole charge without flame propagation. CAI combustion is controlled by the chemical kinetics of air/fuel mixture with no influence of turbulence. The CAI engine offers benefits in comparison to spark ignited and compression ignited engines in higher efficiency due to elimination of throttling losses at part and idle loads. There is a possibility to use high compression ratios since it is not knock limited, and in significant lower NOx emission (≈90%) and particle matter emission (≈50%), due to much lower combustion temperature and elimination of fuel rich zones. However, there are several disadvantages of the CAI engine that limits its practical application, such as high level of hydrocarbon and carbon monoxide emissions, high peak pressures, high rates of heat release, reduced power per displacement and difficulties in starting and controlling the engine. Controlling the operation over a wide range of loads and speeds is probably the major difficulty facing CAI engines. Controlling is actually two-components as it consists of auto-ignition phasing and controlling the rates of heat release. As CAI combustion is controlled by chemical kinetics of air/fuel mixture, the auto-ignition timing and heat release rate are determined by the charge properties such as temperature, composition and pressure. Therefore, changes in engine operational parameters or in types of fuel, results in changing of the charge properties. Hence, the auto-ignition timing and the rate of heat release. The Thesis investigates a controlled auto-ignition (CAI) combustion in internal combustion engines suitable for transport applications. The CAI engine environment is simulated by using a single-zone, homogeneous reactor model with a time variable volume according to the slider-crank relationship. The model uses detailed chemical kinetics and distributed heat transfer losses according to Woschini's correlation [1]. The fundamentals of chemical kinetics, and their relationship with combustion related problems are presented. The phenomenology and principles of auto-ignition process itself and its characteristics in CAI combustion are explained. The simulation model for representing CAI engine environment is established and calibrated with respect to the experimental data. The influences of fuel composition on the auto-ignition timing and the rate of heat release in a CAI engine are investigated. The effects of engine parameters on CAI combustion in different engine concepts fuelled with various fuels are analysed. The effects of internal gas recirculation (IEGR) in controlling the auto-ignition timing and the heat release rate in a CAI engine fuelled with different fuels are investigated. The effects of variable valve timings strategy on gas exchange process in CAI engine fuelled with commercial gasoline (95RON) are analysed.

Piptadenia stipulacea belongs to the Fabaceae family,and is widely distributed in the caatinga. This species is commonly known in the Brazilian Northeast as jurema-branca , carcará and rasga-beiço , and is used in folk medicine in inflammation.In this study, we attempted to identify the possible antinociceptive and anti-inflammatory activities of the aqueous phase, the ethyl acetate phase and one flavonoid obtained from aerial parts of Piptadenia stipulacea. Aerial parts of Piptadenia stipulaceawere used and after fractionation, the flavonoid Galetin 3,6-dimethyl ether(FGAL) was obtained of the chloroformic phase of this plant. Experiments were conducted on Swiss mice using the acetic acid-induced writhing test, the hot plate test, the formalin test and zymosan A-induced peritonitis test. To characterize the mechanism(s) responsible for these antinociceptive and anti-inflammatory actions of FGAL, COX inhibitor screening assay kit and test of DPPH was used. The aqueous and ethyl acetate phases (100 mg/kg, p.o.); and the flavonoid FGAL (100 μmol/kg, p.o. or i.p.), reduced the nociception produced by acetic acid, by 49,9 ± 11,2, 54,6 ± 5,3, 39,0 ± 6,8 and64,8% ± 8,1, respectively. As FGAL have greater antinociceptive activity when administered intraperitoneally compared to oral route, we chose this route you follow up the study with FGAL. The ethyl acetate phase (100 mg/kg, p.o.) reduced nociception in the hot plate, indicating that this fraction exhibited central activity. The ethyl acetate phase (100 mg/kg, p.o.) reduced the formalin effects in both phases by 40,2± 10,3 and59,9% ± 6,5, respectively. Treatment with the aqueous phase (100 mg/kg, p.o.) and FGAL (100_mol/kg, i.p.) only protected the second phase by 78,5± 5,5 and 64,0% ± 8,0, respectively. In addition, it was observed in the zymosan A-induced peritonitis test that the aqueous phase, the ethyl acetate phase and FGAL exhibited anti-inflammatory activity, reducing significantly the number of recruit cells by 35,8 ± 4,9, 37,7 ± 6,2 and 31,3% ± 13,3, respectively. Moreover, FGAL at 0,2μM was able to inhibit COX-1 (79,5% ± 0,6) and COX-2 (56,0% ± 3,8), with an inhibition profile similar to indomethacin in the same concentration (93.0 ±2.6and79.0±1.5%, respectively), showinginhibitionofCOX-1 in greaterproportionthanCOX-2. Furthermore, indomethacin was more effective, both COX-1 andCOX-2 when compared to FGAL. In the test of DPPH, FGAL showed high radical scavenging activity. These results infer that the aqueous phase, the ethyl acetate phase and FGAL obtained from aerial parts of Piptadeniastipulacea are able to modulate the peripheral nociception and acute inflammatory response. TheflavonoidFGALinhibitCOX-1 andCOX-2, probably for its ability to scavenge free radicals, this being one of its mechanism of action in nociception and inflammation. Moreover, the results corroborate the popular use of Piptadenia stipulacea by their anti-inflammatory property. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Piptadenia stipulacea,pertence à família Fabaceae, é amplamente distribuída na caatinga. Esta espécie é conhecida no Nordeste brasileiro como jurema-branca, carcará e rasga-beiço, sendo utilizada na medicina popular para tratar inflamação. Neste trabalho, buscou-se investigar a atividade antinociceptiva e anti-inflamatória da fase aquosa, fase acetato de etila e de um flavonoide isolado das partes aéreas de Piptadenia stipulacea. As partes aéreas de Piptadenia stipulacea foram usadas para o fracionamento e, posteriormente o flavonóide galetina 3,6-dimetil éter(FGAL)foi obtido da fase clorofórmica da planta. Experimentos foram realizados em camundongos Swiss usando o modelo de contorções abdominais induzidas por ácido acético, ensaio da placa quente, teste de formalina e peritonite induzida por zymosan A. Para caracterizar o mecanismo de ação de FGAL responsável por sua ação antinociceptiva, o ensaio de inibição de cicloxigenase (COX) in vitro e a análise da atividade sequestrante radicalar através do método fotocolorimétrico de consumo de 2,2-difenil-1-picrihidrazila(DPPH) foram utilizados. As fases aquosa e acetato de etila(100 mg/kg, v.o.); e o flavonoide FGAL (100 μmol/kg, v.o. ou i.p.) reduziram a nocicepção produzida por ácido acético, na proporção de 49,9 ± 11,2, 54,6 ± 5,3, 39,0 ± 6,8 e 64,8% ± 8,1, respectivamente.Por FGAL apresentar maior atividade antinociceptiva ao ser administrado pela via intraperitoneal quando comparado com a via oral, escolheu-se essa via para dar sequência ao estudo com FGAL. Posteriormente, verificou-se também a inibição da nocicepção no ensaio de placa quente através do tratamento com a fase acetato de etila (v.o., 100 mg/kg), indicando que esta fase apresenta atividade central. A fase acetato de etila (v.o., 100 mg/kg) reduziu a nocicepção gerada pela aplicação de formalina em ambas as fases do teste, apresentando porcentagem de inibição de 40,2 ± 10,3e 59,9% ± 6,5, respectivamente. O tratamento com a fase aquosa (100 mg/kg, v.o.) e FGAL (100 μmol/kg, i.p.) apenas se mostraram ativos na segunda fase do teste de formalina na proporção de 72,6± 5,5 e 66,0% ± 8,0, respectivamente. Além disso, as fases aquosa (100 mg/kg, v.o.), acetato deetila (100 mg/kg, v.o.) e FGAL (100 μmol/kg, i.p.) tambémapresentaram efeito anti-inflamatório significante quando comparadas ao grupo controle, apresentando porcentagem de inibição de recrutamento celular na peritonite induzida por zymosan A de 35,8 ± 4,9, 37,7 ± 6,2 e 31,3% ± 13,3, respectivamente.FGAL, na concentração de 0,2 μM inibiu COX-1 (79,5% ± 0,6) e COX-2 (56,0% ± 3,8), com um perfil de inibição similar ao observado para indometacina na mesma concentração (93,0 ± 2,6 e 79,0% ± 1,5, respectivamente), apresentando inibição de COX-1 em maior proporção do que COX-2. Além disso, indometacina inibiu de forma mais eficaz, tanto COX-1 como COX-2 quando comparado a FGAL. No teste de2,2-difenil-1-picriidrazila(DPPH), FGAL, na concentração de 0,3 mM, mostrou alta atividade sequestrante radicalar. Estes resultados inferem que a fase aquosa, a fase acetato e FGAL obtidos das partes aéreas de Piptadenia stipulacea são capazes de modular a antinocicepção e a resposta inflamatória aguda.O flavonoide FGAL inibe COX-1 e COX-2, provavelmente por sua capacidade de sequestrar radicais livres, sendo este um dos seus mecanismos de ação na nocicepção e inflamação. Além disso, os resultados encontrados corroboram com o uso popular de Piptadenia stipulacea por suas propriedade anti-inflamatória.

The role of a protein-repelling coating is to limit the interaction between a device and its physiological environment. Plasma-polymerized-PEG (pp-PEG) surfaces are of great interest since they are known to avoid protein adsorption. and cell attachment. However, in all the studies previously published in the literature, the PEG coatings have been prepared using low pressure processes. <p>In this thesis, we synthesize biocompatible pp-PEG coatings using atmospheric pressure plasma. Two original methods are developed to obtain these pp-PEG films. 1. Atmospheric pressure plasma liquid deposition (APPLD) consists in the injection of the precursor, tetra(ethylene glycol)dimethylether (tetraglyme), by means of a liquid spray, directly in the post-discharge of an atmospheric argon plasma torch. 2. In atmospheric pressure plasma-enhanced chemical vapor deposition (APPECVD), tetraglyme vapors are brought in the post-discharge trough a heating sprinkler. The chemical composition, as well as the non-fouling properties of the APPLD and APPECVD films, are compared to those of PEG coatings synthesized by conventional low pressure plasma processes.<p>In the first part of the study, the effect of the power on the chemical composition of the films has been investigated by infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS) and secondary ions mass spectroscopy (SIMS). <p>The surface analysis reveals that for the APPECVD samples, the fragmentation of the precursor increases as the power of the treatment is increased. In other terms, the lower the plasma power is, the higher the “PEG character” of the resulting films is. Indeed, the C-O component (286.5 eV) of the XPS C 1s peak is decreasing while the hydrocarbon component (285 eV) is increasing as the power of the plasma is increased. The same conclusion can be drawn from the signature ToF-SIMS peaks (m/z = 45 (CH3&61485;O&61485;CH2+ and +CH2CH2&61485;OH), 59 (CH3&61485;O&61485;CH2&61485;CH2+), 103 (CH3&61485;(O&61485;CH2&61485;CH2)2+)) that are decreasing in the case of high power treatments. Accordingly, IRRAS measurements show that the C-O stretching band is decreasing for high power plasma deposition. This is in agreement with the observations made from the analysis of the LP PECVD coatings and from the literature.<p>The films deposited by the APPLD process do not show the same behavior. Indeed, whatever the power injected into the discharge is, we are able to achieve films with a relatively high PEG character (&61566;83 %).<p>The second part of this study is dedicated to the evaluation of the non-fouling properties of the coatings by exposing them to proteins (bovine serum albumin and human fibrinogen) and cells (mouse fibroblasts (L929 and MEF)) and controlling the adsorption with XPS (proteins) and SEM (cells).<p>For the APPECVD samples, a low plasma power (30 W) leads to an important reduction of protein adsorption and cell adhesion (over 85%). However, higher-powered treatments tend to reduce the non-fouling ability of the surfaces (around 50% of reduction for a 80 W deposition). <p>The same order of magnitude (over 90% reduction of the adsorption) is obtained for the APPLD surfaces, whatever is the power of the treatment. <p>Those results show an important difference between the two processes in terms of power of the plasma treatment, and a strong relationship between the surface chemistry and the adsorption behavior: the more the PEG character is preserved, the more protein-repellent and cell-repellent is the surface. / Le rôle d’une couche empêchant l’adsorption de protéines est de limiter les interactions entre un implant et le milieu physiologique auquel il est exposé. Les films de poly(éthylène glycol) polymérisés par plasma (pp-PEG) sont d’intérêt majeur car ils sont connus pour empêcher l’adsorption de protéines ainsi que l’attachement cellulaire. Cependant, dans toutes les études publiées précédemment, les couches de type PEG ont été réalisées sous vide.<p>Dans cette thèse de doctorat, nous synthétisons des couches de type pp-PEG biocompatibles par plasmas à pression atmosphérique. A cette fin, deux méthodes originales ont été développées. 1. La première méthode consiste en l’injection du précurseur, le tetra(éthylène glycol) diméthyl éther (tetraglyme), en phase liquide, en nébulisant ce dernier au moyen d’un spray, directement dans la post-décharge d’une torche à plasma atmosphérique fonctionnant à l’argon. En anglais, nous appelons ce procédé « Atmospheric pressure plasma liquid deposition (APPLD) ». 2. Dans la deuxième méthode, appelée en anglais « Atmospheric pressure plasma-enhanced chemical vapor deposition (APPECVD)», le tetraglyme est amené en phase vapeur dans la post-décharge, au moyen d’un diffuseur chauffant. La composition chimique des dépôts de type APPLD et APPECVD, ainsi que leurs propriétés d’anti-adsorption sont évaluées, et comparées aux dépôts pp-PEG obtenus par les méthodes à basse pression conventionnelles.<p>Dans la première partie de cette étude, nous nous focalisons sur la composition chimique des films déposés, et plus particulièrement sur l’influence de la puissance injectée dans le plasma sur cette composition chimique. A cette fin, nous avons fait appel à des techniques d’analyse telles que la spectroscopie de réflexion-absorption infrarouge (IRRAS), la spectroscopie des photoélectrons X (XPS) et la spectrométrie de masse des ions secondaires (SIMS). <p>Il en ressort que les films de type APPECVD perdent progressivement leur « caractère PEG » à mesure que la puissance de la décharge plasma est élevée. Cela serait dû à une plus grande fragmentation du précurseur dans la post-décharge d’un plasma plus énergétique. Cette tendance est cohérente avec ce que nous avons observé pour les dépôts à basse pression ainsi que dans la littérature.<p>Dans le cas des films de type APPLD, un tel comportement n’a pas été mis en évidence :quelle que soit la puissance dissipée dans le plasma, les films présentent un « caractère PEG » relativement élevé.<p>La deuxième partie de cette thèse est dédiée à l’évaluation des propriétés d’anti-adsorption des films synthétisés, en les exposant à des protéines (albumine de sérum bovin et fibrinogène humain) et des cellules (fibroblastes de souris, L929 et MEF). L’adsorption de protéines est contrôlée par XPS tandis que l’attachement cellulaire est contrôlé par imagerie SEM.<p>Pour les échantillons de type APPECVD, un dépôt à faible puissance (30 W) mène à une importante réduction de l’adsorption de protéines et de cellules (> 85%) tandis qu’à de plus hautes puissances (80 W), l’anti-adsorption est sensiblement diminuée (50% de réduction). Dans le cas des dépôts de type APPLD, quelle que soit la puissance du plasma, une forte diminution de l’adsorption de protéines et de cellules est observée (> 90 %).<p>Ces résultats montrent une différence majeure entre les deux procédés quant à l’influence de la puissance du plasma ainsi qu’une forte relation entre la composition chimique de la surface synthétisée et son pouvoir d’anti-adsorption :plus le « caractère PEG » du dépôt est conservé, plus la surface empêchera l’interaction avec les protéines et les cellules. <p><p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Autoignition characteristics of pre-vaporized iso-octane, primary reference fuels, gasolines, and dimethyl ether (DME) have been investigated experimentally in a coflow with elevated temperature of air. With the coflow air at relatively low initial temperatures below autoignition temperature Tauto, an external ignition source was required to stabilize the flame. Non-autoignited lifted flames had tribrachial edge structures and their liftoff heights correlated well with the jet velocity scaled by the stoichiometric laminar burning velocity, indicating the importance of the edge propagation speed on flame stabilization balanced with local flow velocity. At high initial temperatures over Tauto, the autoignited flames were stabilized without requiring an external ignition source. The autoignited lifted flames exhibited either tribrachial edge structures or Mild combustion behaviors depending on the level of fuel dilution. For the iso-octane and n-heptane fuels, two distinct transition behaviors were observed in the autoignition regime from a nozzle-attached flame to a lifted tribrachial-edge flame and then a sudden transition to lifted Mild combustion as the jet velocity increased at a certain fuel dilution level. The liftoff data of the autoignited flames with tribrachial edges were analyzed based on calculated ignition delay times for the pre-vaporized fuels. Analysis of the experimental data suggested that ignition delay time may be much less sensitive to initial temperature under atmospheric pressure conditions as compared with predictions. For the gasoline fuels for advanced combustion engines (FACEs), and primary reference fuels (PRFs), autoignited liftoff data were correlated with Research Octane Number and Cetane Number. For the DME fuel, planar laser-induced fluorescence (PLIF) of formaldehyde (CH2O) and CH* chemiluminescence were visualized qualitatively. In the autoignition regime for both tribrachial structure and mild combustion, formaldehyde were found mainly between the fuel nozzle and the lifted flame edge. On the other hand, they were formed just prior to the flame edge for the non-autoignited lifted flames. The effect of fuel pyrolysis and partial oxidation were found to be important in explaining autoignited liftoff heights, especially in the Mild combustion regime. Flame structures of autoignited flames were investigated numerically for syngas (CO/H2) and methane fuels. The simulations of syngas fuel accounting for the differential diffusion have been performed by adopting several kinetic mechanisms to test the models ability in predicting the flame behaviors observed previously. The results agreed well with the observed nozzle-attached flame characteristics in case of non-autoignited flames. For autoignited lifted flames in high temperature regime, a unique autoignition behavior can be predicted having HO2 and H2O2 radicals in a broad region between the nozzle and stabilized lifted flame edge. Autoignition characteristics of laminar nonpremixed methane jet flames in high- temperature coflow air were studied numerically. Several flame configurations were investigated by varying the initial temperature and fuel mole fraction. Characteristics of chemical kinetics structures for autoignited lifted flames were discussed based on the kinetic structures of homogeneous autoignition and flame propagation of premixed mixtures. Results showed that for autoignited lifted flame with tribrachial structure, a transition from autoignition to flame propagation modes occurs for reasonably stoichiometric mixtures. Characteristics of Mild combustion can be treated as an autoignited lean premixed lifted flame. Transition behavior from Mild combustion to a nozzle-attached flame was also investigated by increasing the fuel mole fraction.