Дисертації з теми "Dissolution mechanisms"
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Qiu, Yang. "Dissolution mechanisms: theoretical and experimental investigations." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/1892.
Mercadé-Prieto, Ruben. "Dissolution mechanisms of protein gels in alkali." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613336.
Bluteau, Marie-Claude. "The incongruent dissolution of scorodite-solubilities, kinetics and mechanisms /." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82470.
Worley, William Gabriel. "Dissolution kinetics and mechanisms in quartz- and grainite-water systems." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28068.
Frogner, Paul. "Dissolution mechanisms of albite and hornblende and of calcite in sandstone." Doctoral thesis, Stockholms universitet, Institutionen för geologi och geokemi, 1998. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-117137.
Maldei, Michael. "Low-temperature dry scrubbing reaction kinetics and mechanisms limestone dissolution and solubility." Ohio : Ohio University, 1993. http://www.ohiolink.edu/etd/view.cgi?ohiou1175715332.
Jonker-Brash, Robina Ann. "Erosion of refractories : mechanisms for dissolution of graphite by iron-carbon melts." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297215.
Mandich, Nenad V. "Mechanisms of chromium deposition and dissolution under direct and pulse reverse plating conditions." Thesis, Aston University, 1996. http://publications.aston.ac.uk/15349/.
Lanzl, Caylyn Ashley. "Size-dependent reactivity of hematite nanoparticles: environmental implications of dissolution mechanisms and aggregation." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2557.
Franke, Mark Douglas. "An investigation of the kinetics and mechanisms in the dissolution of alumina in aqueous sulfuric acid." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/10921.
Tamani, Fahima. "Towards a better understanding of the drug release mechanisms in PLGA microparticles." Thesis, Lille 2, 2019. http://www.theses.fr/2019LIL2S048.
Poly (lactic-co-glycolic) acid (PLGA)-based microparticles represent an attractive choice to control drug release over periods ranging from a few days up to several months, while ensuring good biocompatibility and complete biodegradability. Different types of mass transport phenomena might be involved in the control of drug release from PLGA-microparticles, including for instance water diffusion, drug dissolution, drug diffusion, polymer degradation, autocatalysis and polymer swelling. The relative importance of these phenomena can strongly depend on the composition, size and preparation technique of the systems. However, generally ensembles of microparticles are studied, differing in size and behavior.In order to better understand the drug release mechanisms from PLGA microparticles, the behavior of single microparticles after exposure to the release medium was studied.On the one hand, the main objective of this work was to better understand the root causes for the (up to) 3 drug release phases observed with poly (lactic-co-glycolic acid) (PLGA) microparticles containing drug particles: The 1st release phase (“burst release”), 2nd release phase (with an “about constant release rate”) and 3rd release phase (which is again rapid and leads to complete drug exhaust). The behavior of single microparticles was monitored upon exposure to phosphate buffer pH 7.4, in particular with respect to their drug release and swelling behaviors. In this study, PLGA-based microparticles were prepared by simple emulsion solvent extraction/evaporation method. Diprophylline and caffeine were selected as a model drugs at 5% of drug loading. In all cases, the release medium was phosphate buffer pH 7.4. Particle size analysis, thermal analysis, morphology, swelling and polymer degradation were evaluated to better understand the observed phenomena. Importantly, each microparticle releases the drug “in its own way”, depending on the exact distribution of the tiny drug crystals within the system. During the burst release, drug crystals with direct surface access rapidly dissolve. During the 2nd release phase tiny drug crystals (often) located in surface near regions which undergo swelling, are released. During the 3rd release phase, the entire microparticle undergoes substantial swelling. This results in high quantities of water inside the system, which becomes “gel-like”. The drug crystals dissolve and dissolved drug molecules rather rapidly diffuse through the highly swollen polymer gel.On the other hand, the importance of the experimental conditions on the in vitro drug release measurements was evaluated. The key factors described in the literature such as size, and temperature that may alter the in vitro drug release profiles from PLGA microparticles were evaluated. PLGA-based microparticles were prepared by simple emulsion solvent extraction/evaporation method. Diprophylline was selected as a model drug at 5% of drug loading. The studies were carried out both from ensembles of microparticles (in vitro release kinetics, PLGA degradation kinetics, morphology of microparticles after exposure to the medium) and from single microparticles (in vitro release, swelling kinetics and wet mass). All studies were performed under different release conditions (37°C/80 rpm, 20°C/80 rpm, 4°C/0 rpm) in order to identify which mechanisms, control the release of diprophylline. The obtained results show that the experimental conditions can impact the release kinetics in a significant or negligible way. These differences are due to the complicity of the mechanisms involved in the release of drug from PLGA microparticles
Yang, Yang. "Removal Mechanisms of Protective Iron Carbonate Layer in Flowing Solutions." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1339731278.
Burns, Kathie Lee. "A Rotating Disk Study of the Mechanisms of Calcite Dissolution in the Presence of Environmentally Benign Polyaspartic Acid." NCSU, 2002. http://www.lib.ncsu.edu/theses/available/etd-09022002-161459/.
Hussain, Amjad. "A study of the mechanisms of milling-induced enhancement of solubility and dissolution rate of poorly soluble drugs." Thesis, De Montfort University, 2015. http://hdl.handle.net/2086/11106.
McIntosh, Monique Sandra. "Mechanisms and Factors Affecting Chromium Oxide Particle reduction in Iron-Chromium Honeycombs." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6934.
Panthi, Sadrish. "Exploring a Distinct Element Method Approach for Coupled Chemo-Mechanical Mechanisms in Geomaterials." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1388742157.
Oskarsson, Magnus. "Study on the Mechanisms for Corrosion and Hydriding of Zircaloy." Doctoral thesis, Stockholm : Tekniska högsk, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3045.
Heczko, Alexander [Verfasser], Thomas [Akademischer Betreuer] Kittsteiner, and Marion [Akademischer Betreuer] Ott. "On the (non-)existence of efficient partnership dissolution mechanisms and the performance of combinatorial auctions / Alexander Heczko ; Thomas Kittsteiner, Marion Ott." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1185984364/34.
Cagnon, Benjamin. "Etude fondamentale de la dissolution des silicates amorphes et cristallins : apport à la robustesse des modèles." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALU012.
The safety of high-level nuclear waste geological storage is a major scientific and technological challenges of our century. These wastes, inherited from nuclear fuels, are vitrified and stored on production sites (La Hague, Marcoule), waiting on the opening of a storage facility. Their chemical durability is the object of several studies to assess the impact of the release of radionuclides in the environment. Based on this background, this thesis relies on two axes.The first one focuses on the effect of structural disorder on the dissolution of silicates at 90°C, pH 1.5 and 3. Historically, two alteration mechanisms have been identified to explain silicate dissolution: the dissolution–reprecipitation mechanism, generally attributed to crystals, and the hydrolysis–recondensation mechanism, generally attributed to glasses. However, recent studies have shown the need to revisit this dichotomy. To address this point, the dissolution of an amorphous silicate, albite glass, and its crystalline equivalent, albite feldspar, in contact with a solution marked with 29Si was studied. Through the incorporation of this isotope into the altered layer, the contribution of the solution to the formation of the altered layer was quantified to discuss the significance of each mechanism. An antagonistic effect of Al was highlighted as a function of the amorphous and crystalline structure. Moreover, we suggested that the limitation of transport properties within the gel was the key phenomenon controlling the alteration throughout the experiment.The second axis concerns the dissolution of a model glass (International Simple Glass – ISG) in an environment rich in Ca and Si. One of the most likely scenarios for the geological storage site suggests that environmental fluids more or less concentrated in Si and Ca would come into contact with the glass. A 6-oxides glass simulating the nuclear glass was altered in a solution at 90°C, pH > 10. Literature shows that the presence of Ca can have antagonistic effects on the material's dissolution depending on the environment. Among these effects, calcium silicate hydrates (CSH) can precipitate and promote glass alteration.Through the evolution of the dissolution rate, two observations were made: i) the alteration rate is strongly correlated with the solution's saturation state with respect to amorphous silica and ii) the presence of secondary phases, especially CSH, has only a secondary effect on the short-term alteration rate (<20 days). For longer duration experiments, a resumption of glass alteration was observed between 19 days and 76 days, corresponding to a period of CSH growth. After this period, a competition between the formation of CSH and calcium carbonate limited the glass alteration. Finally, the effect of Ca and the transport properties of the gel formed during the first 20 days of alteration were studied in more detail. The addition of calcium to the solution reduces the alteration. Two main effects are discussed: the first consists of a catalytic effect on the recondensation of the gel, and the second on the formation of a (Si, Ca)-rich layer that passivates the gel. It was found that the gel diffusion coefficients based on the tracing experiment were systematically several orders of magnitude lower than those based on the total thickness of the gel. If this difference is partly explained by a variation in temperature, other hypotheses such as i) the evolution of the transport properties of the gel layer during the experiment, ii) a difference in diffusivity between the penetration and release of glass elements within this layer, or iii) a post-mortem restructuration of the gel, are discussed. In conclusion, this work brings several critical information to the understanding of the mechanistic continuum existing between the dissolution of crystalline and vitreous silicates, and of the glass dissolution in chemically relevant environments for long-term geological storage
Nicard, Cyril. "Mécanismes de corrosion d'aciers revêtus par AlSi(ZnMg)." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEC006.
The main objectives of the thesis are: - To correlate the microstructure of aluminum-based coatings developed on a hot dip galvanizing pilot with their electrochemical behavior - To identify the corrosion products that form during accelerated corrosion tests as a function of the composition and microstructure of the coatings - To demonstration formation mechanisms of corrosion products in relation to the microstructure of the coatings, the selective dissolution of the phases and the nature of the corrosive environment - To explain corrosion mechanisms of coatings for cold and hot application / Identification of the most robust and promising compositions for the targeted applications
Cordara, Théo. "Effet de la présence de produits de fission sur les mécanismes de dissolution de composés modèles à base de dioxyde d'uranium." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT176/document.
The dissolution of spent nuclear fuels, performed in concentrated nitric acid solution, is a complex process due to some chemical and microstructural heterogeneities. As instance, the presence of Fission Products (FP) in various phases constitutive of spent nuclear fuels can affect the chemical durability of the materials. In this context, three systems of interest representing fresh UO2 used as reference material, and UO2 doped with FP products dissolved in the fluorite structure (lanthanide elements) or incorporated as metallic precipitates (platinoids) were prepared by oxalic or hydroxide precipitation. Dense pellets with microstructure representative for spent nuclear fuel were prepared through sintering step at high temperature.The multiparametric study of the dissolution (macroscopic approach) was developed by varying independently several parameters. While incorporation of lanthanide elements induced a significant increase of the normalized dissolution rates, it remained lower compared to that observed for platinoids. Moreover, increase of nitric acid concentration or temperature led to the decrease of the chemical durability of the prepared materials. Additionally, significant modification of the preponderant mechanism of dissolution occurred for nitric acid concentration higher than 0.5 mol.L-1.For the three selected systems, the monitoring of the evolving solid/solution interface (microscopic approach) was performed operando by Environmental Scanning Electron Microscopy. Compared to pure UO2, the presence of FP (lanthanide elements or metallic platinoids) induced preferential dissolution of grain boundaries and triple junctions. Coupling the results obtained from micro- and macroscopic approaches led to complementary data of strong interest in order to improve the understanding of the role of FP during the dissolution of UO2
Cha, Minsu. "Mineral dissolution in sediments." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50144.
Felton, David Scott. "Theoretical dissolution coefficient for rock fractures." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/21505.
Booth, Jonathan. "The mechanism of solid-liquid interactions." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337524.
Joulié, Marion. "Mécanisme de dissolution de matériaux actifs d'électrodes de type LiNi1/3Mn1/3Co1/3O2 d'accumulateurs Li-ion en vue de leur recyclage." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2015. http://www.theses.fr/2015ENCM0011/document.
Basic hydrometallurgical routes represent an alternative to recover valuable metals such as nickel and cobalt from spent Li-ion batteries. The first step of hydrometallurgical process, lixiviation step is optimized by studying the behaviour of LiNi1/3Mn1/3Co1/3O2 (NMC) positive electrode active material, due to its good performances which make it an adequate candidate for the electric vehicles. First of all, the study of thermodynamic aspects allows predicting the behaviour of NMC material in various acidic media. Then, the kinetic approach leads to define the mechanism occurring during the leaching step and to outline the rate-limiting step of the dissolution. The reductive effect of mineral, organic and metallic reducing agents to promote leaching of NMC material is evaluated. The approach comparatively evaluates the reducing power impact of weak (sulfuric and hydrochloric acids), strong reducing agents (citric, oxalic and formic acids and hydrogen peroxide) and copper and aluminum from Li-ion batteries current collectors. This work points out the strong interest to advantageously use current collectors inherently present in the fraction treated by hydrometallurgy
Baum, Theo. "The physical chemistry of the anisotrophic dissolution mechanism of single crystal silicon." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364157.
Kittsteiner, Thomas. "Applications of mechanism- and auction-design to partnership dissolution and sequential sale." [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10605025.
Chan, Teng Ian. "Investigating the molecular dissolution mechanism of binary solid dispersions by molecular dynamics simulations." Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3690969.
Zhou, Peng. "An in situ kinetic investigation of the selective dissolution mechanism of Cu alloys." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066251/document.
The selective dissolution mechanisms of Cu alloys in tap water and perspiration solution were investigated. Atomic emission spectroelectrochemistry (AESEC) was used to obtain the elemental dissolution kinetics. The first part of the thesis focused on the dissolution mechanism of Cu. Most Cu(II) species are soluble and are released into tap water, leaving behind a Cu2O film on the surface. A kinetic analysis suggests that the dissolution mechanism involves simultaneous Cu dissolution and film formation. The second part investigated the dissolution behavior of Cu-42Zn and Cu-21Zn-3Si-P. A two-stage dissolution process of dezincification was proposed: a first stage of a rapid growth of the dezincified layer and a second stage where the growth of dezincified layer was much slower. The third part concentrated on the effect of Zn content on the dissolution of Cu-Zn alloys, by investigating the dissolution behavior of alloys with various Zn content (0-45 wt%). The two-stage dissolution mechanism was further clarified. For α phase: an initial stage in which Cu and Zn are oxidized congruently, but only Zn2+ was released into water, Cu forming a Cu2O film, and a second stage where Cu was released into water in the form of Cu2+. For β' phase, the second stage is the same to the initial stage. The increase of Zn content in the alloy results in a time extension of the initial stage and retard Cu2+ release. The final part focused on the effect of Sn on Cu release from Cu-Sn alloys. The enhanced effect of Sn on Cu release was identified. However, the increase of Sn content didn’t monotonically increase the Cu release efficacy of Cu-Sn alloys, which was due to the passivity of Sn
Hoskins, Alan Richard. "Mechanism of the dissolution of acrylonitrile based polymers in aqueous inorganic salt solutions." Thesis, University of Bradford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287107.
Cherezov, Ilia. "Modelling convective dissolution and reaction of carbon dioxide in saline aquifers." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/268170.
Pakarinen, Darius. "On the mechanism of H2O2 decomposition on UO2-surfaces." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-240564.
Geologiskt djupförvar av förbrukat kärnbränsle har undersökts som lösning i Sverige i över 40 år nu. Svensk kärnbränslehantering (SKB) driftsätter det geologiska djupförvaret och måste säkerställa att det förbrukade kärnbränslet hålls isolerat från omgivningen i tusentals år. Under denna tid måste förseglingen stå emot fysikalisk stress och korrosion. Det är därför viktigt för en säkerhetsanalys att undersöka de olika reaktioner som kommer ske. Om förseglingen bryts ned kommer kärnbränslet i kontakt med vattnet i berggrunden vilket leder till radiolys av vatten. Väteperoxid som skapas under radiolysen kan sedan oxidera den exponerade ytan av kärnbränslet, detta ökar upplösningen av radiotoxiska produkter. Väteperoxiden kan även katalytisk sönderdelas på kärnbränslets yta. Syftet med arbetet var att få fram selektiviteten för katalytisk sönderdelning av väteperoxid. Detta skulle uppnås analytiskt med kumarin som avskiljare för detektion av hydroxylradikaler som bildas när väteperoxid sönderdelas. Detta producerade det fluorescerande 7-hydroxykumarinet som med hög precision kunde mätas spektrofluorometriskt. Resultaten gav en ca 0,16% förhållande mellan •OH-produktion och väteperoxidkonsumtion. Likartade experiment gjordes med ZrO2 för jämförelse men resultaten var ofullständiga. Effekten av bikarbonat (en beståndsdel i grundvatten) undersöktes också. Genom addition av bikarbonat ökade experimentens reproducerbarhet och ökade även upplösningen av uran. Både uranet och bikarbonaten minskade den utgående fluorescerande signalen från 7-hydroxykumarinet.
Simonnet, Marie. "Dissolution de l’oxyde de thorium : cinétique et mécanisme." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112226/document.
Studies of new energy sources are necessary to meet the rising global demand. In the nuclear area, Th-U cycle has been reinvestigated to supplement or replace the currently used U-Pu cycle. This project though needs further improvement to be operated in an industrial plant, especially on the reprocessing process, which consists in fuel dissolution in nitric acid medium, followed by liquid-liquid extraction. Still, unlike uranium, thorium oxide does not dissolve in concentrated nitric acid. Small amounts of fluoride are required to achieve the dissolution. The dissolution is rather slow and HNO₃-HF mixture is very corrosive. The aim of this project is thus to find an efficient dissolution method which both decreases corrosion and improves dissolution rate. The synthetized thorium oxide powder has been dissolved in chosen conditions. Effects of solid parameters, dissolution method and dissolution medium have been studied. Results show a strong dependence on oxide crystallinity. No improvement on dissolution rate was observed with power ultrasounds, except for the temperature increase, which greatly enhances dissolution rate. No other complexing agents than fluoride allows total dissolution. Rising HNO₃ and HF concentrations increases dissolution rate until the amount of fluorides is so high that a precipitate forms at the surface. This study led to the proposal of a dissolution mechanism whose limiting step is the formation of an activated complex. Based on kinetics and equilibrium equations, initial dissolution rate was then written as a function of the different studied parameters. Experimental results were finally fitted by this relation to find kinetics and thermodynamics constants, proving the accuracy of the proposed mechanism
Raisch, Philipp Michael. "New techniques for studying the antisotropic dissolution mechanism of single crystal silicon in aqueous KOH." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368635.
Gaulard, Coralie. "Influence de l'environnement sur l'altération de la matrice UO2 du combustible irradié en situation de stockage." Thesis, Evry-Val d'Essonne, 2012. http://www.theses.fr/2011EVRY0019/document.
Within the framework of the geological disposal of spent nuclear fuel, research on the long term behavior of spent fuel is undertaken and in particular the study of mechanisms of UO2 oxidation and dissolution in water-saturated host rock. Under the law program on the sustainable management of radioactive materials and waste of June 28, 2006, France was chose as the reference solution the retreatment of spent fuel and disposal in deep geological repository of vitrified final waste. Nevertheless, studies on a direct disposal of spent fuel will continue for safety. The disposal concept provides for conditioning spent fuel in a steel container whose seal is guaranteed for a period specified in the order of 10,000 years. It is also reasonable to assume that the groundwater comes into contact with the fuel after the deterioration of container and lead to the UO2 matrix degradation and the release of radionuclides. The oxidation/dissolution of UO2 has been studied by means electrochemical methods coupled to XPS and ICP-MS measurements.A thermodynamic and bibliographic study of U(VI)/UO2(s) system allowed to show the effect of the physical and chemical conditions of the solution on the system, and to show the different mechanisms proposed to describe the oxidation and the dissolution of the uranium dioxide in different media (non-complexing, carbonate and clay). The study of the oxidation/dissolution of UO2 in acidic and non-complexing media (0.1 mol/L NaCF3SO3, pH = 3), where UO22+/UO2(s) predominates and the formation of precipitates is limited or even avoided, showed a mechanism with two electrochemical steps and a model characteristic of UO2 oxidation in acidic non-complexing media. Then, the study in neutral non-complexing media (0.05 mol/L NaCl, pH = 7.5) showed a mechanism with two electrochemical steps and one chemical step (EEC) in which both electrochemical steps are similar to those proposed in acidic media. Finally, a first approach of the UO2 oxidation/dissolution was carried out in carbonate media (0.05 mol/L NaCl + 2x10-3 mol/L NaHCO3, pH = 7.5) and in the presence of clay (MX80) in the solution. These studies have respectively shown the influence of carbonates and MX80 on the dissolution of uranium dioxide
Chen, Wei Jie. "Investigation of molecular dissolution mechanism of ketoprofen binary and ternary solid dispersions by molecular dynamics simulations." Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3690953.
Tôn-Thât, Laurent. "Interactions dissolution / plasticité dans les alliages cubiques à faces centrées - Fluage du cuivre mono et polycristallin assisté par la dissolution anodique." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2009. http://tel.archives-ouvertes.fr/tel-00628259.
Le, Moigne Nicolas. "Mécanismes de gonflement et de dissolution des fibres de cellulose." Phd thesis, École Nationale Supérieure des Mines de Paris, 2008. http://tel.archives-ouvertes.fr/tel-00353429.
Bi, Wu. "PEM fuel cell catalyst degradation mechanism and mathematical modeling." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/29756.
Committee Chair: Fuller, Thomas; Committee Co-Chair: Deng, Yulin; Committee Member: Gallivan, Martha; Committee Member: Kohl, Paul; Committee Member: Singh, Preet. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Bode, Corinna. "PLGA implants for ocular drug delivery." Thesis, Lille 2, 2019. http://www.theses.fr/2019LIL2S008.
Until today, the treatment of posterior eye diseases, such as age-related macular degeneration, diabetic retinopathy and uveitis, remains challenging. The eye with its different ocular barriers is well protected from external factors. Those barriers also reduce the bioavailability of drugs to the vitreous. After a topical administration, only a limited amount (0.001 – 0.0004 %) reaches the vitreous. This is caused by for example reflexive blinking, tear dilution and a low corneal permeability of the drug. After a systemic or oral administration, the blood-aqueous and the blood-retinal barrier hinder the drug from entering and only around 2 % of the administered drug is found in the vitreous. In order to reach therapeutic concentrations, a high dose has to be given which in turn increases the risk for systemic side effects. The most efficient way to treat posterior diseases remains the intravitreal injection. However, small lipophilic molecules like dexamethasone can easily diffuse through the retina and the blood-ocular barriers and, thus, have a limited half-life of just a few hours. Since many of the posterior diseases are chronic, a frequent intravitreal injection would be necessary. Every intravitreal injection bears the risks for retinal detachment, hemorrhage, and other side effects. Biodegradable implants for intravi-treal administration can prolong the drug release and in turn decrease the side effects. Poly(lac-tic-co-glycolic acid) (PLGA) is a widely used polymer that is biocompatible and biodegrada-ble. It can also sustain the drug release from a few days up to several months. In this study, in-situ forming implants (ISFI) and pre-formed implants prepared via hot melt extrusion were studied in depth. The aim of this work was (i) to study the impact of the volume of the release medium, polymer type and concentration as well as drug content of different ISFI, (ii) to eval-uate the drug release, swelling and degradation behavior of pre-formed implants prepared with different drug loadings and polymer types, (iii) to visualize the drug release and water uptake of ISFI and pre-formed implants using colored model drugs and (iv) to investigate the effect of varying amounts of different additives on key features of ISFI. This knowledge can help to manufacture implants with different release profiles. Our studies show that ISFI are rather ro-bust regarding different volumes of the vitreous humor that could be encountered in vivo. How-ever, the polymer molecular weight and polymer concentration have a strong influence on the morphology and swelling behavior of the implants. Consequently, the degradation and drug release are affected. For pre-formed implants the swelling “orchestrates” the drug release. In the beginning only limited amounts of water can diffuse into the implants. Thus, only insignif-icant amounts of the drug are dissolved and can be released. When the PLGA starts to degrade, the polymer becomes more hydrophilic and bigger amounts of water can penetrate. This poly-mer swelling facilitates drug dissolution and diffusion and initiates the drug release. The studies using colored model drugs corroborate the role of water penetration and drug dissolution for pre-formed implants. Concerning ISFI, it visualized the importance of the polymer concentra-tion on the resulting inner implant structure and consequently the water uptake and drug release. The swelling behavior and morphology of ISFI could also be significantly altered using differ-ent additives. The overall effect on the drug release was limited
Shin, Hosung. "Development of discontinuities in granular media." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29653.
Committee Chair: Santamarina, J. Carlos; Committee Member: Bachus, Robert C.; Committee Member: Burns, Susan E.; Committee Member: Cartwright, Joseph A.; Committee Member: Goldsztein, Guillermo; Committee Member: Mayne, Paul W. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Besseyrias, Alain. "Dissolution coulométrique de toles d'acier galvanisé allié : étude des mécanismes et amélioration de la technique d'analyse." Grenoble INPG, 1995. http://www.theses.fr/1995INPG0111.
Salgueiro, Azevedo Marcele. "Mécanismes de corrosion de l'acier revêtu d'alliage à base de ZnMgAl en tests accélérés et en environnement naturel." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066603/document.
Factors differing corrosion mechanisms of ZnMgAl coatings on steel in natural environments and in accelerated tests with NaCl solution were identified. A new electrolyte (RW) containing NH4+, HCO3-, Cl- and SO42- was developed, for which the accelerated tests respected the relative corrosion rates of different Zn-based coatings and the delayed formation of layered double hydroxides (LDH) known for field exposure. Considering dissolution-precipitation mechanism of corrosion, the role of ions present in RW electrolyte on the leaching kinetics and on the accumulation of insoluble products was studied. NH4+ and HCO3- were demonstrated to increase the anodic reactivity and cathodic Al dissolution. LDH formation was delayed by NH4+, HCO3- and SO42-. Higher anodic reactivity of ZnMgAl than zinc coating combined with better resistance in corrosion tests indicated the importance of cathodic reaction (oxygen reduction). Comparing oxygen reduction currents on fresh coatings and on the surface under patinas, clear barrier effect of basic zinc salts (BZS) and LDH was demonstrated. The barrier effect was lost under cathodic polarization on Zn coating due to the transformation BZS ->ZnO/Zn(OH)2 but was stable on ZnMgAl in the same conditions – the inhibiting effect of Mg2+ on the kinetics of this transformation was evidenced. A residual “skeleton” of unreacted Al contributed to the increased compactness of the corrosion products
Biganska, Olga. "Étude physico-chimique des solutions de cellulose dans la N-Méthylmorpholine-N-Oxyde." Phd thesis, École Nationale Supérieure des Mines de Paris, 2002. http://tel.archives-ouvertes.fr/tel-00443727.
Єрмоленко, Ірина Юріївна. "Удосконалення електрохімічного рециклінгу псевдосплавів вольфраму". Thesis, НТУ "ХПІ", 2012. http://repository.kpi.kharkov.ua/handle/KhPI-Press/22265.
Wang, Huijun. "A Study on the Reaction between MgO Based Refractories and Slag-Towards the Development of Carbon-free Lining Material." Doctoral thesis, KTH, Mikro-modellering, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214420.
QC 20170918
European RFCS LEANSTORY project
Fitouri, Raja. "Fonctionnalité de superdésintégrants en compression directe : influence de l'environnement physico-chimique dû à la formulation de comprimés orodispersibles." Thesis, Montpellier 1, 2013. http://www.theses.fr/2013MON10272.
This work is devoted to the study of environmental superdisintegrants naturally occurring chemically modified by different formulations in different dissolution media. This study aims to develop predictive methodologies and investigative tools to better understand the mechanism of disintegration to ensure the best possible development of finished orodispersible products with well defined properties. In a first step, we studied the influence of the environment on the disintegration of tablets formulated with superdisintegrants from an inert matrix using solvents of several chemical natures. In a second step we have made the picture a few examples of active substances also with different physico-chemical nature. The overall results of these examples have shown that the nature of the environmental community has a great influence on disintegration. To understand these results, rheological studies using the DLVO theory, the model of the double layer and the Einstein relation have been conducted on these polymers. The effect of viscosity has been instrumental in the study of mechanism approach
Berger, Pascal. "Etude du mecanisme de la dissolution par oxydoreduction chimique et electrochimique des bioxydes d'actinides (uo2, npo2, puo2, amo2) en milieu aqueux acide." Paris 6, 1988. http://www.theses.fr/1988PA066073.
Li, Ying. "Les huiles végétales comme solvants alternatifs pour l’éco-extraction des produits naturels." Thesis, Avignon, 2014. http://www.theses.fr/2014AVIG0254.
The green extraction has arisen as a new trend in the valorisation of natural resources. As the growing concern on thesafety, health and environment, vegetable oils as alternative solvents have drawn great interests in the green extractionof bioactive compounds from nature plants. Apart from lipophilic carotenoids in this work., compounds with more polarproperties have been initially studied.Firstly, the solubility of major volatile aroma compounds in various vegetable oils was originally investigated through atheoretical modelling of their Hansen solubility parameters, followed by real experimental extractions for verification.Multivariate statistical analyses assisted to classify the solvent power of these oil solvents so as to select the optimal oil.Secondly, the revisit of polar paradox theory inspired us to achieve direct extraction of phenolic compounds usingvegetable oils as solvents. The appropriate addition of surfactants could significantly increase the extraction efficiency.The small angle X-ray scatting helped to further study the effect of surfactants on the supramolecular structure of thevegetable oils. Lastly, the extraction of carotenoids was intensified with the integration of ultrasounds and sunflower oilas the substitute to organic solvents, in which the optimized procedure has been compared with the conventional organicsolvent extraction in terms of procedures, kinetics, yields and environmental impacts
Varloteaux, Clément. "Modélisation multi-échelles des mécanismes de transport réactif : impact sur les propriétés pétrophysiques des roches lors du stockage du CO2." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00809288.