Teses / dissertações sobre o tema "Cristallographie – Effets des hautes pressions"
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Kadri, Adel. "Aspects physico-chimiques des effets de la pression sur la cristallogenèse des protéines". Université Louis Pasteur (Strasbourg) (1971-2008), 2004. http://www.theses.fr/2004STR13024.
Texto completo da fonteSyamala, Vishnu Vijayakumar. "Molecular organization in solid-state using sigma-hole interactions : Exploring the effect of crystalline environment". Electronic Thesis or Diss., Université de Lorraine, 2022. https://docnum.univ-lorraine.fr/ulprive/DDOC_T_2022_0214_VIJAYAKUMAR_SYAMALA.pdf.
Texto completo da fonteUnderstanding the fundamentals of the formation and stabilization of non-covalent interactions is of paramount importance in the field of crystal engineering. In this direction, this thesis reports the crystallographic investigation of a sub-class of non-covalent interactions known as sigma-hole interactions. sigma-hole interactions are defined as those involving electrophilic sites (also called sigma-holes) associated to a covalently bonded atom belonging to either p-block (groups 13-18) or d-block (groups 8,11 and 12) of the periodic table, and nucleophilic sites coming from either the same or a different molecule. Depending upon the group of the atom on which the sigma-hole is present, the interaction can be further classified into various sub-classes. Out of these, we have focused on the cases of halogen bond (HaB) and chalcogen bond (ChB) interactions. As compared to the well-established case of hydrogen bonds (HB), the rationale behind the formation and stabilization of HaB and ChB are still less explored. This thesis is aimed exactly in such a direction, to provide a deeper insight into the characteristics of HaB and ChB interactions, mainly by understanding how the electron density is distributed among the interacting pair of atoms and how it eventually influences the molecular organization in solid-state. Two main stream topics of crystallography are covered during the course of this thesis: (i) high-pressure X-ray diffraction studies and (ii) charge density analysis. Structural and electronic investigations are carried out based on the data derived from single-crystal X-ray diffraction (SCXRD) experiments performed either at ambient or extreme conditions. The so-obtained crystal structures were used to derive the electron density distribution in the periodic phases. The electron distributions of the molecular systems extracted from their crystalline environments were used to calculate the electrostatic potential in molecular surfaces and to carry out the topological analyses of the electron density and its laplacian function within the framework of the Quantum Theory of Atoms in Molecules (QTAIM) methodology. The effect of crystalline environments in tuning the properties of sigma-hole interactions is also explored in detail. The information gathered from such analyses is not only helpful to better understand the molecules in hands, but also to design new molecular patterns with the aim to control the structure-properties relationship in molecular crystals
Djomani-Siawa, Doriane. "Hétérostructures allotropiques de semiconducteurs IV dans des nanofils : nouvelles opportunités more-than-Moore". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS074/document.
Texto completo da fonteWe have demonstrated an original way to induce a phase transformation in Si and Ge nanowires under external shear-stress. The transformation results in an unprecedented heterostructure with quasiperiodic embedded Ge-2H nanodomains distributed all along the nanowire. My thesisproject aims at understanding the mechanisms of this phase transformation and at characterizing the physical properties of the heterostructures 2H/3C in Si and Ge nanowires.We have carried out systematic structural analysis in Si- and Ge-2H/3C nanowires to evidence the key parameters of this phase transformation.The phase transformation occurs in shear bands localized along the (2-5-5) direction.The heterostructured nanowires are defined by a specific orientation relationship between the 3C and the 2H bands (both in Si and Ge nanowires)given by(1-10)3C//(-2110)2H and (110)3C//(0001)2H with the 2H bands lying mainly on (115)3C planes.The preliminary studies showed that shear-stress and the thermal budget above a threshold temperature of 350°C in Ge and 500°C in Si are mandatory for this transformation. These conditions meet the common criteria of a martensitic phase transformation. We have identified two key intrinsic parameters:the temperature and the nanowires crystallographic axis.In Si nanowires, we found that the formation of the shear bands i.e. the 2H nanodomains is related to the component of the shear-stress along the glide direction of the 3C/2H interface plane.Based on these results,the transformation could be consistent with a stress relief mechanism through the formation of (5-5-2)(1-15)3C shear bands.We have performed spatially resolved Raman measurements on single Si and Ge heterostructured nanowires to characterize their optical phonon modes.In Ge,we have detected 2 Raman bands at 288 cm⁻ ᴵ and 301 cm⁻ ᴵ attributed to the E2g and E1g + A1g + F2g modes.In Si, we have observed 3 Raman bands at 498, 515 and 520 cm⁻ ᴵ that are associated respectively to the E2g, A1g and F2g modes.Those values agree well with the literature.Moreover, we have performed Fourier Transform Infrared spectroscopy on transformed Ge nanowires to measure the optical band gap of the 2H phase.We have obtained a direct band gap of 0,58 eV attributed to the 2H phase and an indirect bandgap of 0,72 eV that might stem from the 3C phase. Those results are the first experimental data of the Ge-2H band gap.The values align well with the simulations that predict a narrow direct band gap for this structure.The 2H structure can also be achieved in bulk Si and Ge after unloading of the BC8 phase in a diamond anvil cell.The BC8 phase is unstable and convertsinto the 2H phase at room temperature in Ge or by thermal annealing in Si.In order to compare the bulk properties of the 2H phase, we have performedin-situ Raman and X-ray diffraction experiments in bulk samples by studyingvarious unloading pathways. In particular, unloading at room temperature ledto the formation of the ST12 phase or a mixture of the BC8 and ST12 phasesdepending on the unloading rate.The formation of the 2H phase is thuscomplex given its dependency on the unloading conditions and the hydrostaticconditions within the cell that are difficult to garanty. Our studies also reveala size effect. After unloading of Ge-3C nanowires, the nanostructures revertback to the 3C phase with an amorphous component detected.In addition, we have carried out in-situ band gap measurements in bulk Ge and Ge nanowires as a function of pressure.After unloading, we havemeasured optical gap values that are related to the band structure of theGe-ST12 allotrope with a direct bandgap of 0,53 eV and an indirect bandgapof 0,73 eV.Those results are consistent with the experimental values reported.The experiments on Ge nanowires showed an hysteresis behavior with theinitial value of the band gap measured after unloading.Those results clearly evidenced novel relaxation mechanisms at the nanoscale that need to be investigated
Guerrero, François. "Etude des effets des hautes pressions sur le debit carotidien". Aix-Marseille 2, 1993. http://www.theses.fr/1993AIX20660.
Texto completo da fonteMarie, Philippe. "Conception et développement d'un nouveau procédé d'émulsification par haute pression". Dijon, 2003. http://www.theses.fr/2003DIJOS054.
Texto completo da fonteNabhan, Mohamad Ammar. "Protéolyse et redistribution des protéines entre différentes fractions azotées après traitement du lait par hautes pressions". Vandoeuvre-les-Nancy, INPL, 2004. http://www.theses.fr/2004INPL054N.
Texto completo da fonteThe thermal treatments induce frequently undesirable modifications in foods that could be avoided by the use of minimum treatment strategies. Among these treatments, high pressures are already commercialized by the alimentary industry. Pressure/temperature combination induced denaturation of beta-lactogiobulin and the formation of aggregates composed principally of beta-lactogiobulin, kappa-casein and of aipha-lactaibumin and of alphas1-casein at a lesser extent. The treatment reduce plasmin activity and induce an irreversible unfolding of alpha-lactaibumin at pH 7. 0 and a significant quantity was recovered in proteose-peptones fraction. To ensure the stability of natural microflora of milk during 21 days, milk must be treated at least 400 MPa and at comparatively extreme temperature. To eliminate completely the studied pathogen bacteria and ensure no surviving during 21 days, a treatment of at least 500 MPa and 55°C for 5 min minimum is necessary. Our results show that pressurized milks present an odor, a taste, a color and a texture different of pasteurized milk. Although different, the jury do not mark preference to any milk tested
Douzals, Jean-Paul. "Effets des hautes pressions isostatiques sur les modifications physico-chimiques de l'amidon". Dijon, 1999. http://www.theses.fr/1999DIJO5004.
Texto completo da fonteCanelon, Carlos Eduardo. "Cinétique de floculation des asphaltènes dans les mélanges n-heptane-toluène et étude de leur stabilité dans le brut en présence de CO2 à haute pression et haute température". Pau, 2006. http://www.theses.fr/2006PAUU3004.
Texto completo da fonteThe first part of this thesis focuses on an experimental study of the kinetic of asphaltenes flocculation of theVenezuelan crude oils Furrial and Hamaca. The influence of the ratio resins-asphaltenes and n-heptane-toluene, on the flocculation constant rate analyzed. The experimental results are interpreted and modelled by an osmotic micro-model allowing to illustrate the stabilizing effect of the absorption of resins on asphaltene colloids. In the second part, an original device with high sensitivity and precision is presented. It allows measurements of structural modifications occurring in opaque paraffinic and of asphaltenic crudes at high pressure and temperature (0. 1 to 70 MPa and 273 - 473 K). Experimental results of the effects of CO2 injection into two Venezuelan crude oils (Furrial et Jusepin) are also reported
En la primera parte de esta memoria hemos abordado el estudio de la cinética de floculación de asfaltenos de crudos venezolanos Furrial y Hamaca. Analizamos la influencia de la relación entre la concentración de resinas-asfaltenos y la n-heptano-tolueno, sobre la constante de velocidad de floculación. Los resultados experimentales son interpretados y discutidos en términos de un micro-modelo osmótico que permite ilustrar el efecto estabilizador de la adsorción de resinas sobre la periferia coloidal de los asfaltenos. En la segunda parte, se presenta un dispositivo experimental original con una alta sensibilidad que permite mediciones de las modificaciones estructurales de medios opacos parafinicos y de asfaltenos, en condiciones de alta presión y temperatura (0,1 a 70 MPa y 273 a 473 K). Igualmente, se muestran los resultados experimentales obtenidos del efecto de inyección de CO2 para dos crudos venezolanos (Furrial y Jusepin)
Risso, Jean-Jacques. "Recherches concernant les effets neurochimiques des hautes pressions d'hélium chez le mammifère de laboratoire : contribution à l'étude des mécanismes du syndrôme nerveux des hautes pressions". Lyon 1, 1987. http://www.theses.fr/1987LYO10014.
Texto completo da fonteRisso, Jean-Jacques. "Recherches concernant les effets neurochimiques des hautes pressions d'hélium chez le mammifère de laboratoire contribution à l'étude des mécanismes du syndrome nerveux des hautes pressions /". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37609397k.
Texto completo da fonteCognigni, Andrea. "Méthodes expérimentales pour l'étude par BioXAS de métalloprotéines en variant le potentiel et la pression : application à l’étude de la superoxyde dismutase". Paris 11, 2005. http://www.theses.fr/2005PA112376.
Texto completo da fonteMoussa, Marwen. "Compréhension des mécanismes de l'inactivation cellulaire par les hautes pressions hydrostatiques et les basses températures". Dijon, 2009. http://www.theses.fr/2009DIJOS004.
Texto completo da fonteThe aim of this work was to understand the effects of high hydrostatic pressure (HHP) and low temperature on different cell models: bacteria, yeast, leukemia cells, spheroplasts, lipid vesicles. The viability of cells subjected to cold stress was first assessed, through long-term supercooling experiments (up to 71 days), versus freeze-thawing stress. Results showed that cells could be inactivated by the only action of sub-zero temperature, that is, without any water crystallization. The effects of HHP at room temperature were then studied as a function of cell hydration. We highlighted the crucial role of water in determining cellular damage under pressure. The combined effects of HHP and low temperature on cells were studied. Results showed a synergistic interaction between cold and HHP in their effects on microbial inactivation at pressures in the range of 100 to 300 MPa with an aw of 0. 992. However, at pressures greater than 300 MPa, this trend was reversed, and cold counteracted the inactivation effect of pressure. When the amount of water in the cell suspension was increased, the synergistic effect was enhanced. Conversely, when the aw was decreased by the addition of solute to the cell suspension, the baroprotective effect of subzero temperature increased sharply. These results support the argument that water compression is involved in the mechanisms of HHP inactivation of cells. From a thermodynamic point of view, the mechanical energy transferred to the cell during the pressure treatment can be characterized by the change in volume of the system, which depends on the water quantity in the cytoplasm. The consequences of cell volume compression at the cellular level were characterized through the assessment of metabolic activity, the study of cell membrane structure and integrity and the visualization of cell shape and ultrastructure
Thomas, Sébastien. "Modélisation numérique du comportement thermo-aéro-dynamique des garnitures d'étanchéité pour gaz réels hautes pressions". Phd thesis, Université de Poitiers, 2006. http://tel.archives-ouvertes.fr/tel-00135573.
Texto completo da fonteL'étude bibliographique révèle que peu de travaux sur les garnitures pour gaz à hautes pressions ont été réalisés. Les caractéristiques d'un écoulement à haute pression sont examinées et les points-clefs du modèle sont définis : gaz réels, effets d'inertie, effets thermiques, écoulement bloqué. A hautes pressions, le comportement du gaz diffère de celui d'un gaz parfait, un modèle de gaz réel est donc développé. L'équation de Reynolds pour un fluide compressible est modifiée afin de prendre en compte les effets d'inertie. Les effets thermiques dans l'écoulement sont également introduits dans le modèle. L'écoulement bloqué à la sortie du film fluide est résolu grâce à une méthode originale. Les déformations des solides et le couplage thermique sont pris en compte par la méthode des coefficients d'influence. La méthode des éléments finis est utilisée pour la discrétisation des équations et un algorithme itératif permet la détermination des champs de pression et de température. La comparaison avec une solution analytique et des données expérimentales permet de valider le modèle. L'influence du modèle du gaz est présentée. L'étude paramétrique menée avec le modèle numérique permet d'étudier l'influence des effets d'inertie sur l'écoulement par rapport au cas purement visqueux. Finalement, le couplage fluide-solides est étudié. Cette analyse montre que les déformations des faces influencent notablement le comportement des garnitures.
Tobé, Sylvia. "Etude des contraintes physico-chimiques des modèles cellulaires primitifs : catalyse ARN sous hautes pressions et réplication génétique en compartiment lipidique". Paris 6, 2010. http://www.theses.fr/2010PA066537.
Texto completo da fonteDaniel, Isabelle. "Aluminosilicates à haute pression et haute température : amorphes, verres, liquides et cristaux : étude par spectroscopie Raman". Lyon 1, 1995. http://www.theses.fr/1995LYO10279.
Texto completo da fonteFerlat, Guillaume. "Contributions expérimentale et numérique à l'étude de l'ordre local de liquides à haute température et sous haute pression". Lyon 1, 2002. http://www.theses.fr/2002LYO10248.
Texto completo da fonteMichoud, Grégoire. "Etude des effets des hautes pressions hydrostatiques sur Pyrococcus yayanosii, un piézophile extrême par une approche multi -"omics"". Thesis, Brest, 2014. http://www.theses.fr/2014BRES0078/document.
Texto completo da fonteNo
Bezaeva, Natalia Sergeyevna. "Effets de la pression, des chocs et des irradiations sur les propriétés magnétiques des roches terrestres et extraterrestres". Aix-Marseille 3, 2008. http://www.theses.fr/2008AIX30035.
Texto completo da fonteThis work contributes to the understanding of the effects associated with impacts (shocks) and radiations, two major events taking place in our Solar System, on remanent magnetization and intrinsic magnetic properties (magnetic susceptibility, coercivity of remanence B[CR,], hysteresis parameters) of extraterrestrial materials and their terrestrial analogues. We carried out experimental investigations of the effect of hydrostatic pressure up to 1. 2 GPa as well as effects of radiations by protons, argon ions and heavy ions on the magnetic properties of natural and synthetic samples - carriers of the most common magnetic mineralogies in terrestrial and extraterrestrial rocks (iron metal and nickel iron metal, titanium rich and titanium free magnetite, hematite, pyrrhotite, goethite and greigite). We also investigated the effect of shock waves on basalt and macroscopic samples of Saratov meteorites
Barthelemy-Requin, Magali. "Etude neurochimique in vivo de l'action des hautes pressions d'hélium, de l'azote et du pentobarbital sur la voie dopaminergique nigro-striée chez le rat : comparaison avec l'étude directe d'un récepteur spécifique par microdialyse". Lyon 1, 1995. http://www.theses.fr/1995LYO10077.
Texto completo da fonteJi, Hui. "Mécanique et physique de l’indentation du verre". Rennes 1, 2007. http://www.theses.fr/2007REN1S154.
Texto completo da fonteIn order to characterize the mechanical behaviour of glass using small size specimens, we develop methods based on the use of indentation, in particular the Vickers indentation which is by far the most common. Such tests cause high hydrostatic stresses in the glass in the area of application of the load. The glass lieing characterized by a relatively low atomic packing density compared with crystals for example, the induced pressure, which is typically of several GPa, cause densification of glass. Thus, in a first step, we studied the behaviour of glasses of different compositions at high pressure (up to 25 GPa) and we then studied the indentation behaviour by using these results. The work was focused on four types of glass – a soda-lime-silica window glass, a silica glass (SiO2), a chalcogenide glass (GeSe4) and a bulk metallic glass (Zr55Cu30Al10Ni5) – as well as a synthetic clay (plasticine), which proved to be an excellent model material for studying the rheology of glass at the macroscopic scale. All these results helped to propose a mechanism of deformation of the glass by indentation, with two separate processes (densification and shear-thinning viscous flow), whose contributions are highly dependent on the composition, through Poisson’s ratio
Cohé, Cécile. "Caractérisation de l'effet de la pression et de l'ajout de CO2 sur les flammes laminaires et turbulentes de prémélange pauvre méthane-air". Orléans, 2007. http://www.theses.fr/2007ORLE2010.
Texto completo da fonteYahiaoui, Mustapha. "Durcissement superficiel d’aciers inoxydables austénitiques par jet d’azote cryogénique à hautes pressions". Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0373.
Texto completo da fonteThis work focuses on the study of an original surface treatment technique that uses supercritical cryogenic nitrogen jet. This process was initially designed for environmentally friendly surface cleaning, where indeed such gas recycles in the air after operation. In the present work, this technique is implemented for surface hardening use without damage of the surface to be treated. Two types of operation cases are studied: static jet tool impingement, cinematic using jet tool scanning on the top surface. In fact, these two static and cinematic treatment cases can be used in industrial operations. In the first stage, the treatment was performed under static conditions in order to map the domains of use of the process. Variation of the experimental parameters (standoff distance and dwell time - treatment time-) made possible to define several uses of the nitrogen jet. In particular the hardening without any damage of the surface of the material to be treated such as AISI 316L stainless steel. Thus, the influence of the standoff distance and the dwell time on the evolution of surface microstructure and damage and hardening was studied. To quantify the effects of nitrogen jet on the microstructure, SEM (Scaning Electrons Microscope) observations and micro hardness measurements were carried out on the treated surfaces. As a result, for different conditions of treatment, the relationship between hardness and martensite rate during surface transformation process, is shown and plotted. Secondly, we focus on hardening without surface damage. The treatments were essentially carried out on both AISI 316L and AISI 304L metastable stainless steels. The influence of both torch velocity and jet static pressure on the variation of microstructure, martensite fractions and hardening level, was also studied and discussed. Thanks to both SEM/EBSD analysis and micro hardness measurements, the relationship between martensite rate and increase of hardness, is highlighted. It is also established that the treatment using several passes allows to increase the surface micro hardness without damage. Finally, it is found that, for some particular working parameters, the nitrogen jet process can also be used for surface hardening without martensitic transformation
Loukachenko, Natalia. "Mise au point de surfaces résistant à des sollicitations de roulement – glissement sous des pressions de contact élevées de 2,5GPa et jusqu'à 300°C : applications aux engrenages et aux transmissions par courroies". Vandoeuvre-les-Nancy, INPL, 2006. http://docnum.univ-lorraine.fr/public/INPL/2006_LOUKACHENKO_N.pdf.
Texto completo da fonteCar designers are seeking ways to improve the performance of power transmission mechanical parts which subjected to severe conditions. Attention should be drawn in particular to contact pressure and operating temperature. Our object was to seek a dual material – surface treatment resistant to contact fatigue phenomena under pressures of 2. 5GPa up to 300°C. Thermochemical treatments by carbon and nitrogen diffusion and hardening mechanisms associated with these treatments improve the surface properties of steels. Three approaches are considered in order to reach the objectives : 1) Hardening by chromium nitrides precipitation during nitriding (at 520°C) of chromium alloyed 32CrMoV13 industrial steel. It is a satisfactory solution to achieve the objectives; however, it requires a long thermochemical treatment; 2) Hardening by martensite transformation after carbo-nitriding with a high nitrogen concentration allowing nitrides precipitation during tempering at 300°C of slightly alloyed 27MnCr5 and 27CrMo4 steels. This type of treatment does not reach the objectives: carbo-nitriding layers evolve quickly with temperature increasing until 300°C; 3) Hardening by martensite transformation after carburizing of silicon alloyed 15NiMoCr10 steel. Silicon slows down martensite decomposition before 300°C. Results of microindentation at 300°C show that elastic characteristics of carburizing and tempered 15NiMoCr10 steel layer are reduced. The remaining values do not guarantee a sufficient endurance of steel carburised surface up to 300°C without it first being subjected to mechanical tests in real operating conditions. This steel and thermochemical treatment associated have however potential characteristics which justify these tests
Angelloz, Christophe. "Cristallisation sous pression du polypropylène isotactique en phase γ : étude cinétique, morphologique et mécanique". Lyon 1, 1999. http://www.theses.fr/1999LYO10083.
Texto completo da fonteCamelin, Christian. "Oxydation du silicium monocristallin sous haute pression d'oxygène sec". Bordeaux 1, 1985. http://www.theses.fr/1985BOR10583.
Texto completo da fonteLachaux, Thierry. "Etude des effets de la haute pression sur la structure et la dynamique des flammes turbulentes de prémélange pauvre de méthane-air". Orléans, 2004. http://www.theses.fr/2004ORLE2016.
Texto completo da fonteCoppari, Federica. "Transitions de phase induites par la pression dans des matériaux amorphes : germanium et alliages silicium-germanium". Paris 6, 2010. http://www.theses.fr/2010PA066392.
Texto completo da fonteModugno, Chloé. "Effets d'un traitement combinant hautes pressions et biopréservation sur l'inactivation et la reprise de croissance des spores de Bacillus et Clostridium". Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCK072/document.
Texto completo da fonteBacterial endospores are one of the most resistant life form on earth. Their capacity to survive to decontamination processes and their potential pathogenicity represent a real problem for the food industry. Currently, the only way to prevent their development in foods is the application of thermal treatments or the use of preservatives. However, these two methods have negative impacts on the nutritional properties of foods and on the consumers’ health. High hydrostatic pressure (HP) is a non-thermal process widely used for commercial pasteurization of foods. However, this process has a very low effect on spores and has therefore to be combined with other decontamination processes to enhance its effectiveness. The objective of this work was to evaluate the potential of the use of biopreservation as an additional hurdle for the inactivation of thermoresistant and pathogenic foodborne spores by HP. Biopreservation is a gentle decontamination process involving protective culture or the antimicrobial agents they produce, like nisin. Thanks to global investigation methods such as microspectroscopy, infrared spectroscopy or circular dichroism, this study showed that HP treatment could affect the antimicrobial properties of nisin. By affecting the secondary structures of this protein, HP can induce a drastic drop in its antimicrobial activity. However when added in the recovery medium of HP-treated spores, nisin can induce their synergistic inactivation (> 7log). This HP-sensitization of spore to nisin is due to the induction of the very first steps of the germination process, usually not detected by the current methods of germination analysis. These results bring knew knowledges about the underlying mechanisms of spores germination under HP and gives new perspectives for the combined used of HP and nisin at the industrial scale
Langrand, Christopher. "Étude expérimentale et in situ du mécanisme de transformation perovskite / post-perovskite et de sa cinétique dans le manteau terrestre". Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10157/document.
Texto completo da fonteThe radial seismic structure of the earth is marked by a sharp transition about 200 km above the core-mantle boundary. This defines the top of the region called the D'' layer. Moreover, at these P/T conditions, Bridgmanite (Pv), the main lower mantle mineral, transforms into its high-pressure phase, (Mg,Fe)SiO3 post-perovskite (pPv). This phase transition has received considerable interest due to its thermodynamic properties, the induced textures and microstructures that seem to explain many of the seismic anomalies of the D'' layer. However, its thermodynamic properties and transformation mechanisms are not very well known. The main purpose of this thesis was to investigate the Pv/pPv phase transition and its kinetics. To do so, we used a novel method, called Multigrain Crystallography, to characterize in-situ hundreds of crystals in a polycrystalline material. The reliability of the method for experiments under extreme conditions is tested in the first part of this manuscript. I then focus on the Pv/pPv phase transition mechanism on a structural analog of composition NaCoF3. I determine that the Pv to pPv transformation is martensitic and that the reverse transformation is reconstructive. Their impacts on the D'' layer microstructure are also discussed. Finally, I explore the kinetics of the (Mg0,86,Fe0,14)SiO3 Pv to pPv transition by time-series experiments. Moreover, based on our data, I present two possible kinetic models that include the effect of pressure, temperature, and grain size. These models have important implications to constrain the dynamics and kinetics of the Bridgmanite to pPv transition at the D'' layer P/T conditions
Mauricio, Iglesias Miguel. "Impact of high pressure thermal treatments on food/packaging interactions". Montpellier 2, 2009. http://www.theses.fr/2009MON20225.
Texto completo da fonteThe control of food/packaging interactions is essential to ensure the safety and quality of packed products. In particular, in the framework of the European Project Novel Q (IP6, Novel Processing Methods for the Production and Distribution of High Quality and Safe Foods), the effect of high pressure thermal (HP/T) treatments on food/packaging interactions was assessed in a variety of cases. Migration and scalping were studied for linear low density polyethylene (LLDPE), polylactide (PLA) and a wheat gluten/montmorillonite (WG/MMT) nanocomposite novel biodegradable and nanocomposite materials in food simulating liquids (FSL). Food/packaging interactions were studied after two HP/T treatments intended to perform a pasteurization (800 MPa, 5 min, 40°C) and a sterilization (800 MPa, 5 min, 115°C) treatment, as well as subsequent storage for 10 days. Specific migration of an additive (Uvitex OB) was assessed for LLDPE and PLA, whereas additional tests were carried out for WG/MMT, i. E. Overall migration, protein migration and nanoparticles migration. HP/T treatments did not significantly modify the migration or scalping in the conditions studied except for the release of nanoparticles from WG. Interestingly, the increase in the melting point of LLDPE during HP/T made possible to sterilize it. To date the most frequently used methods in migration assessment are based in time consuming methods based on destruction and quantification. To avoid them, modeling has been recently approved as a method for migration assessment. However, the parameters needed, i. E. Diffusivity (D) and the partition coefficient (K) are seldom available. The use of FTIR and Raman spectroscopy to assess migration behavior and, more importantly, to determine the diffusivity of an additive in LLDPE was successfully carried out allowing a complete characterization of mass transfer
Trégon, Bernard. "Evaluation et caractérisation d'une technologie d'assemblage MCM-L pour environnement haute pression forte température (120 MPa, 175°C)". Bordeaux 1, 2002. http://www.theses.fr/2002BOR12580.
Texto completo da fonteThe first part of this study is an analysis of electronics needs for severe environmental conditions, that is pressure/temperature combined stress, and so the different potentials applications domains, The second part establish a liste of degradation modes of assembly materials implied in prototypes manufacture. These protoypes are intend to word under 120Mpa of pressure and 175°C of température. Analytic modelisation of each degradation modes are listed; Then we designed and realised an environmental test bench to study our prototypes. The third part is a theoretical behavioural study of components parts under pressure/temperature combined stress. This study has been completed through an experimental analysis. Finally, the fourth part is an experimental analysis of complete prototypes manufactured for our study. This analysis deals about sturdiness of the electronic funcion, so as about the different assembly options degradations of each protoypes. This analysis has been completed with a simulation study using finite elements method
Cornet, Antoine. "Approche multi-échelle des verres d’oxyde : évolution structurale sous hautes pressions et processus de relaxation en température". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1206/document.
Texto completo da fonteThe oxide glasses form a class of materials with many fundamental and industrial interesting properties. Among these particularities we find the capability of such glasses to densify. Indeed, after a compression at pressures up to around ten gigapascal, a typical oxide glass presents an increase in density and several structural changes compared to the non-compressed glass. This observation led to the birth of the polyamophism theory in the decades 1990 and 2000. In the same way that a chemical compound can exist in different crystalline structure, it has been proposed that different amorphous structure exist, and that transitions between these amorphous states are possible.During this work, we tried to evidence the structural changes associated to the possible polyamorphism in oxide glasses. To do so, we followed two different approaches. In the old fashioned way, we probed in-situ the structure of different glasses during the compression, and we determined the dependence of the processes to the temperature (GeO2 glass) and to the polymerization degree (sodo-silicate glasses). In a second time, we compressed several similar glasses to perform permanent densification. Then we relaxed these densified glasses at high temperature, and we monitored in-situ the glassy structure during the transformation.This new approach allowed us to evidence the existence of an activated state during the relaxation of densified glasses to their pristine non-densified state. This transitory state is characterized by an increase of the inhomogeneity of the structure at all length scales, and seems to confirm the polyamorphism theory in oxide glasses
Noël, Marilyne. "Influence de la température et des hautes pressions hydrostatiques sur l'activité et la stabilité d'enzymes en présence ou non d'additifs". Toulouse, INSA, 2001. http://www.theses.fr/2001ISAT0018.
Texto completo da fonteThe thermal (40-60ʿC) or hyperbaric (300-500MPa) stability of the lipase of Rhizomucor miehei was studied. The kinetics of inactivation obtained allowed the kinetic and thermodynamic parameters related to the irreversible deactivation of this lipase to be determined. The use of a model led to the validation of these parameters. This study was supplemented by observations in fluorescence spectrophotometry which confirmed the existence of two different mechanisms at the molecular level, during the deactivation of the enzyme by these two agents. The combination of the effects of temperature and pressure made it possible to highlight a protective effect of the moderate pressures (0,1-350 MPa) against the thermal deactivation of lipase, and a synergistic action of the pressure and the low temperatures. Additives (salts and polyhydric alcohol's), allowed the half-life of lipase to be increased during hyperbaric (25 times) or thermal (500 times) processing in a spectacular way. A classification of polyhydric alcohol's according to their protective effect could be carried out. This classification was correlated by differential scanning microcalorimetry experiments. The comparison of the results obtained by these two approaches shown that enzyme activity and conformational stability is not dependent. A study of the combined effects of the temperature, pressure and polyhydric alcohol's, showed that the polyhydric alcohol's are protective agents and their efficiency depends on the total number of hydroxyls groups brought in the medium, as well as of the denaturing process intensity inflicted with protein
Abraini, Jacques Henri. "Réactions anxieuses et perturbations comportementales lors de confinements de longue durée en chambre hyperbare sous hautes pressions de mélanges respiratoires hydrogènes". Nice, 1995. http://www.theses.fr/1995NICE2014.
Texto completo da fonteLife conditions during deep diving include long term confinement at pressure environment (pressure increases of 1 bar; i. E the value of atmospheric pressure, every 10 meters depth). During the present study, we used the Cattell anxiety scale questionnaire to determine whether such conditions of occupational diving could induce anxious reactions related to confinement or pressure. Our results show that only few subjects, with psychological characteritics such as an anxious guilt or an incapacity to cope with frustration, developed anxious reactions else where, anxious reactions appear in relations ship with other factors such as time of confinement, pressure, psychosocial events or diving operations
Monkam, Kakmeni Pierre. "Contribution à l'étude de l'influence de la pression sur l'hydrodynamique et le transfert de matière dans les colonnes garnies". Lyon 1, 2001. http://www.theses.fr/2001LYO10052.
Texto completo da fonteRambert, Gaëlle. "Modélisation des couplages thermo-diffuso-mécaniques dans les matériaux polymères : application numérique à la décompression explosive". Poitiers, 2002. http://www.theses.fr/2002POIT2327.
Texto completo da fonteA fully coupled thermo-diffuso-mechanical model was developed in the framework of generalized standard media in order to describe polymer structures that are subjected to an explosive decompression under high temperature and high gas pressure. One considered a polymer-gas mixture defined by constant characteristic magnitudes. With the small perturbations and isotropy assumptions, the model was applied to elastic, viscoelastic and elasto-plastic behaviours. The thermo-diffuso-elasticity numerical implementation led to a qualitative study of coupling effects and to the introduction of the simplest elastic model defined by the dilation coefficients and the coefficient corresponding to the heat production due to the gas diffusion. This numerical tool should make easier the experiments analysis and the material characterization. .
Lamcharfi, Taj-dine. "Etudes structurales sous contraintes : effets de pression sur les propriétés du conducteur (TMTSF)2 PF6 : Présentation d'une chambre de Weissenberg opérant de 300 à 10 Kelvin". Bordeaux 1, 1986. http://www.theses.fr/1986BOR10549.
Texto completo da fonteGimenez-Fouque, Nelly. "Vieillissement hydrolytique de mousses syntactiques époxyde-amine / verre pour l'isolation thermique sous hautes pression : mécanismes de dégradation et simulation de la prise en eau". Lyon, INSA, 2005. http://theses.insa-lyon.fr/publication/2005ISAL0087/these.pdf.
Texto completo da fonteThe syntactic foams studied are made of hollow glass microspheres (diameter 46 µm) and of an epoxy/amine thermoset (DGEBA-MCDEA, Tg 174°C). Morphologies of the initial materials (3 volumic fractions of microspheres and 2 types of glass) were checked by thermogravimetric analysis (TGA) and 3D-Xray tomography. Different conditions of ageing were studied (20°C, 60°C, 100°C, 120°C, in deionized and artificial sea water, with and without pressure, up to 300 bar). The behavior of the foams was analysed through gravimetry, impedancemetry, TGA, differential calorimetry (DSC), thermal conductivity, uniaxial compression and 3D-Xray tomography. These complementary techniques have then led to the proposal of a simulation on the water absorption, taking in account the degradation of the foam
Bouibes, Amine. "Exploration de matériaux avancés pour des applications en génie civil". Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10112/document.
Texto completo da fonteThe civil engineering progress would not been possible without new materials development. In fact, new materials with efficient properties allowed the construction of modern structures, taller building, longer bridges,…etc. Furthermore, it is essential for the progress continuity of this field in the future. Especially, in the smart construction approach we will need new materials with the very efficient properties. The study of the properties of materials at the molecular level, allow a better understanding of how those materials will function and react on a macro level. It is through such studies that we are able to understand their behaviors under a large number of conditions. In this thesis, we focus our efforts on three types of materials. The first one is zinc carbonate. The second one is Lime, which is widely used in building and public works ; and the last one is zinc oxide, which is an important material for steel construction. The purpose here is to investigate in details the three different materials at various pressures and variable compositions by means of the universal structure prediction method based on ab initio tool. For smithsonite, a number of mechanical properties were evaluated. We mainly show that this system is harder and more rigid than the other carbonates. Besides, the investigation of its electronic properties reveals that the energy band-gap is close enough to some semiconductors. Moreover, two high-pressure phase transitions have been found: the first one at 87 GPa and second one at 121 GPa. Below 87 GPa, ZnCO3 is found to be the most stable structure with R-3c space group (calcite structure); and between 78 GPa and 121 GPa, ZnCO3 has another structure (magnesite phase II) with C2/m space group. Above 121 GPa, we show that new structure with P212121 space group becomes more stable. In addition, by means of variable composition ab initio evolutionary algorithm, we show surprisingly new stable compounds from Ca-O. At ambient pressure CaO2 is predicted as a thermodynamically stable system. This new compound goes from C2/c to I4/mcm space group structure at 18.5GPa. Under increasing pressure, further compounds become stable such as CaO3 which stabilize in P-421m space group structure above 65 GPa. Finally, our studies on ZnO show that ZnO2 becomes thermodynamically stable at pressure above 120 GPa. A phase transition is obtained at 10 GPa for ZnO, which is stable in B4 wurtzite structure at ambient conditions up to 10GPa. Above 10 GPa, ZnO becomes more stable in B1 structure. These results strongly support our predictions since they agree perfectly with available experiment and previous theoretical studies
Dasriaux, Marion. "Evolutions microstructurales du PEEK au-dessus de sa température de transition vitreuse lors de maintiens sous pression et température". Phd thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2012. https://theses.hal.science/docs/00/78/60/16/PDF/Manuscrit_Dasriaux_Marion.pdf.
Texto completo da fonteAt least one fraction of the amorphous phase of semi-crystalline polymers, confined by the crystalline lamellae, is in out-of-equilibrium state, so that "physical aging" or "secondary crystallization" features can be observed (e. G. , by calorimetry) even above the glass transition temperature. This issue has already been addressed in the literature in several semi-crystalline polymers at atmospheric pressure. But despite the well-known influence of pressure on molecular mobility, the pressure-sensitivity of these microstructure rearrangements has never been tackled. This study focuses on amorphous evolution occurring in highly pressurized Poly-Ether-Ether-Ketone (PEEK), in comparison with atmospheric pressure. The phenomenon is tracked by Differential Scanning Calorimetry (DSC). A significant influence of pressure is evidenced, pressure confining rearrangements within spatially limited domains. The stability and co-existence of reorganization processes upon successive annealings is also investigated. Finally, relationships between constrained and free amorphous phase rearrangements are discussed. The free fraction of the amorphous phase results relaxed after annealing at atmospheric pressure and stabilized into a denser state after high pressure annealing. All these results allow to discuss the phenomena involved in the microstructural evolution of PEEK: a "physical aging" or "secondary crystallization"
Kraych, Antoine. "Modélisation à l’échelle atomique du rôle des dislocations dans la déformation de la bridgmanite". Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10091/document.
Texto completo da fonteHeat transfer through the mantle is carried by convection, which involves plastic flow of the mantle constituents. In this study, we model the mobility of dislocations, and their role in the plastic deformation of bridgmanite, the most abundant constituent of the lower mantle. The dislocation structures at the atomic scale control their mobility, and hence their influence on the material’s deformation. We determine the structure of dislocations at pressure relevant for the lower mantle, by modeling these defects at the atomic scale with molecular static calculations. The thermally-activated mechanism of dislocation glide in bridgmanite, the kink-pair nucleation, is assessed by coupling a continuous model to the fundamental properties of dislocations. These results allow to estimate the glide velocity of dislocations, as a function of pressure and temperature. The model is able to reproduce the yield stress measured in laboratory deformation experiments. The model is also able to estimate the stress level needed to deform bridgmanite by dislocation glide at mantle conditions, and allows us to discuss their role in the deformation of the Earth’s lower mantle
Balon, Norbert. "Interaction des neurotransmissions GABAérgique et dopaminergique dans le système nigrostrié chez le rat soumis à la respiration de mélanges gazeux sous pression". Aix-Marseille 2, 2002. http://www.theses.fr/2002AIX20680.
Texto completo da fonteKriem, Badreddine. "Rôle des récepteurs à la sérotonine sur l'augmentation de la libération de dopamine et de l'activité locomotrice et motrice chez le rat soumis aux hautes pressions : approches voltamétriques et comportementales". Aix-Marseille 3, 1995. http://www.theses.fr/1995AIX30060.
Texto completo da fonteHalter, Fabien. "Caractérisation des effets de l'ajout d'hydrogène et de la haute pression dans les flammes turbulentes de prémélange méthane/air". Phd thesis, Université d'Orléans, 2005. http://tel.archives-ouvertes.fr/tel-00591421.
Texto completo da fonteGicquel, Solène. "Contribution à la modélisation du comportement mécanique du verre : études des relations entre densification et indentation". Rennes 1, 2009. http://www.theses.fr/2009REN1S031.
Texto completo da fonteThis work aims at improving the modelisation of mechanical behaviour of silica and silicate glasses during indentation. First we focused on measurement of permanent deformation observed in hydrostatic compression and indentation test, which is a change in volume called densification. Using an elastic model, both in analytical models of contact and in finite element simulation, we estimated such volume. In a second time, we proposed a constitutive model in order to evaluate the respective role of different type of deformation : shear stress and densification. These models were implemented to a finite element software (Cast3M). We also included in our models the pressure dependance of elastic properties, observed during compressive test, in order to improve the description of the comportment in indentation
Dasriaux, Marion. "Evolutions microstructurales du PEEK au-dessus de sa température de transition vitreuse lors de maintiens sous pression et température". Phd thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2012. http://tel.archives-ouvertes.fr/tel-00786016.
Texto completo da fonteFagni, Laurent. "Effets de hautes pressions d'hélium sur l'excitabilité cellulaire et la transmission synoptique dans le système nerveux central du Mammifère : électrophysiologie et neuropharmacologie de systèmes spinaux et hippocampiques in vivo et in vitro". Aix-Marseille 1, 1987. http://www.theses.fr/1987AIX11098.
Texto completo da fonteFagni, Laurent. "Effets de hautes pressions d'hélium sur l'excitabilité cellulaire et la transmission synaptique dans le système nerveux central du mammifère électrophysiologie et neuropharmacologie de systèmes spinaux et hippocampiques in vivo et in vitro /". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37604890b.
Texto completo da fonteBenazzouz, Brahim Khalil. "Étude par dynamique moléculaire des propriétés mécaniques et thermodynamiques de l’argile de type kaolinite". Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10010/document.
Texto completo da fonteKaolinite is one of the most abundant clays minerals on the earth surface. It covers wide applications in engineering. However, a real lack of studies both experimental and theoretical exists for this clay. This thesis aims to shed light on fundamental properties of kaolinite, especially its structural, mechanical and thermodynamics properties, which are still unknown. To this end we have employed molecular dynamics method based on classical potential. Good agreement was found between the obtained X-ray diffraction and the experimental one. After this step we have determined the mechanical properties of this clay. In order to predict the behaviour of kaolinite under geological constraints, we have considered theeffect of hydrostatic pressure on the clay. The variation of different mechanical quantities reveals the existence of structural phase transition for a pressure of 20 GPa. This result opens the way for conceiving, from kaolinite, other kind of clays with different properties. The new clay system, initially issued from kaolinite, could be then used for further applications.The second objective of this thesis is the study of thermodynamics properties of kaolinite under atmospheric pressure, by means of molecular dynamics calculation based on a recently developed force field. Among our main results, the calculation of superheating point, which is found at 1572 K. The transition from solid to liquid structure has also been observed from the density profiles and radial distribution functions. Finally, we have combined both pressure and temperature effects for the study of kaolinite. A relation has been proposed to describe solid-liquid phase and to determine the superheating point between 0.1MPa and 20 GPa. Besides, the double effect pressure-temperature allowed us to establish a phase diagram for kaolinite which can give a precise idea on the behaviour of this clay in some specific range of temperature and pressure
Mahendran, Srinivasan. "Modélisation numérique des propriétés de coeurs de dislocations dans l’Olivine (Mg2SiO4)". Thesis, Lille 1, 2018. http://www.theses.fr/2018LIL1R014/document.
Texto completo da fonteIt is widely accepted that the dissipation of heat from the core to the surface of the Earth through a thermally insulating mantle is only possible by convection process. Mantle convection is responsible for a large number of geological activities that occur on the surface of the Earth such as plate tectonic, volcanism, etc. It involves plastic deformation of mantle minerals. In Earth’s interior, the outer most layer beneath the thin crust is the upper mantle. One of the most common mineral found in the upper mantle is the olivine (Mg,Fe)2SiO4. Knowledge of the deformation mechanisms of olivine is important for the understanding of flow and seismic anisotropy in the upper mantle. The experimental studies on the plastic deformation of olivine highlighting the importance of dislocations of Burgers vector [100] and [001]. In this work, we report a numerical modelling at the atomic scale of dislocation core structures and slip system properties in forsterite, at pressures relevant to the upper mantle condition. Computations are performed using the THB1 empirical potential and molecular statics. The energy landscapes associated with the dislocation mobility are computed with the help of nudge elastic band calculations. Therefore, with this work, we were able to predict the different possible dislocation core structures and some of their intrinsic properties. In particular, we show that at ambient pressure [100](010) and [001]{110} correspond to the primary slip systems of forsterite. Moreover, we propose an explanation for the “pencil glide” mechanism based on the occurrence of several dislocation core configurations for the screw dislocation of [100] Burgers vector