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Wassell, D. F. "Mechanism and structure in ionic liquids." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403156.
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Nyberg, Erik. "Lubrication mechanism of hydrocarbon-mimicking ionic liquids." Licentiate thesis, Luleå tekniska universitet, Maskinelement, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65505.
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Lubrication is critical in order to achieve high efficiency and reliability of machine elements such as gears, bearings, and other moving mechanical assemblies (MMA). In space applications, tribological properties of lubricants are quickly growing more important. Traditional space systems such as satellites imply MMA such as gyroscopes, antenna pointing mechanisms, and solar array drives. These MMA operate in high vacuum (<10-5 Pa) under lightly loaded conditions. Modern space missions on the other hand, such as remotely operated vehicles used for in-situ Mars exploration relies on different types of MMA. In these robotic systems, electromechanical actuators are being used extensively to provide controlled motion. Gears and bearings in these actuators operate in an atmosphere mainly consisting of CO2 at ~10+3 Pa under heavily loaded contact conditions. In these conditions, the tribosystem is likely to operate in the boundary lubricated regime, with consequent risk of high friction and wear. High molecular weight fluids have significant heritage in space because of their low vapor pressure. They are currently employed as lubricants in a wide range of space applications, as they meet high demands on resistance to vacuum outgassing. Unfortunately, the large molecules are susceptible to degradation under heavy load. Ionic liquids (ILs) on the other hand, are synthetic fluids that consist entirely of ion pairs with opposing charge. The resulting ion bonds enable inherently low vapor pressure of the fluid without the need for a high molecular weight. For this reason ILs have been advocated as potential lubricants for space applications, but so far compatibility issues have hampered their use as lubricants. Countless IL variations are possible, and solutions are thus likely to exist. Constituent ions can be designed individually and combined in various configurations. However, the fundamental understanding of the lubricating mechanism of ionic liquids is still incomplete, and consequently the optimum molecular structure for IL lubricants remain unknown. In this thesis, a stepwise approach to molecular design of IL lubricants is described, and the resulting hydrocarbon-mimicking ionic liquids are evaluated in tribological experiments. In this thesis, the experiments focus on tribological performance, using steel-steel tribopairs in air environment under boundary lubrication (Paper I). Boundary film formation under a range of contact pressures and temperatures, is analyzed after tribotesting by optical profilometry, scanning electron microscopy (SEM), and energy dispersive X- iii ray spectroscopy (EDS) in Paper II. The analysis reveal formation of a highly effective boundary film based on silicate, that can be further enhanced by amine additives. This thesis demonstrates the feasibility of improving tribological performance of ionic liquids by molecular design.Projekt: Rymdforskarskolan 2015
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Patterson, Adele. "Retention properties of porous graphite." Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342124.
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Brandell, Daniel. "Understanding Ionic Conductivity in Crystalline Polymer Electrolytes." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5734.
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Huang, Yan. "Micro- and Nanogel Formation through the Ionic Crosslinking of Polyelectrolytes." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1417781855.
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Mendonça, Carlos Miguel Nóbrega. "Interactions between ionic liquids and cell membrane models." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13836.
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Mestrado em Biotecnologia MolecularThis work proposes the study of the interactions, at a molecular level, between diverse ionic liquids (ILs) and the membrane cells, by applying membrane cell models, namely Langmuir-Blodgett technique. We intend to establish a better understanding about the role of the interactions of ILs with membrane cells, in specific, the imidazolium and choliniumcholinium families. Hence, we propose the evaluation of the effect of the concentration as well as of the alkyl chain lengths of imidazolium ILs, on the lipid monolayers organization and stability and compare it with the behaviour of choliniumcholinium ILs. Summing up, this work is expected to provide an insight into the molecular mechanism contributing to the IL toxic activity that should help in the design of less toxic ILs.
Este trabalho propõe o estudo das interações, ao nível molecular, entre diversos líquidos iónicos (ILs) e membranas celulares mediante a aplicação de modelos de membrana celular segundo a técnica de Langmuir Blodgett. Pretendemos estabelecer uma melhor compreensão sobre o papel fundamental das interações de ILs com as membranas celulares, em particular os ILs da família imidazólio e colina. Assim, propõe-se a avaliação do efeito da concentração, bem como dos comprimentos da cadeia alquílica de ILs da família imidazólio, na organização e estabilidade de monocamadas lipídicas e a comparação com o comportamento de líquidos iónicos da família das Colinas. Em suma, este trabalho pretende fornecer uma visão sobre os factores moleculares que contribuem para a toxicidade dos ILs, que possam ajudar no desenvolvimento de ILs menos tóxicos.
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Marrocchelli, Dario. "Studying the conduction mechanism of stabilised zirconias by means of molecular dynamics simulations." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4631.
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Stabilised zirconias have a remarkable variety of technological and commercial applications, e.g., thermal barrier coatings, gas sensors, solid oxide fuel cells, ceramic knives and even fashion jewelry. This amazing versatility seems to originate from the creation of atomic defects (oxide ion vacancies) in the zirconia crystal. Indeed, these vacancies, and their interactions with other vacancies or cations, dramatically affect the structural, thermal, mechanical and electrical properties of zirconia. This thesis is concerned with the study of the role of the vacancy interactions on the conducting properties of these materials. This study was performed by using realistic, first-principles based molecular dynamics simulations. The first system studied in this thesis is Zr0:5 0:5xY0:5+0:25xNb0:25xO7. This has a fixed number of vacancies across the series but its conductivity changes by almost two orders of magnitude as a function of x. For this reason, Zr0:5 0:5xY0:5+0:25xNb0:25xO7 represents an ideal test-bed for the role of the cation species on the defect interactions and therefore on the ionic conductivity of these materials. Realistic inter-atomic potentials for Zr0:5 0:5xY0:5+0:25xNb0:25xO7 were developed on a purely first-principles basis. The observed trends of decreasing conductivity and increasing disorder with increasing Nb5+ content were successfully reproduced. These trends were traced to the influences of the cation charges and relative sizes and their effect on vacancy ordering by carrying out additional calculations in which, for instance, the charges of the cations were equalised. The effects of cation ordering were considered as well and their influence on the conductivity understood. The second part of this thesis deals with Sc2O3–doped (ScSZ) and Y2O3–doped (YSZ) zirconias. These systems are of great academic and technological interest as they find use in solid oxide fuel cells. Inter-atomic potentials were parametrised and used to predict the structural and conducting properties of these materials, which were found to agree very well with the experimental evidence. The simulations were then used to study the role of the vacancy interactions on the conducting properties of these materials. Two factors were found to influence the ionic conductivity in these materials: cation-vacancy and vacancy-vacancy interactions. The former is responsible for the difference in conductivity observed between YSZ and ScSZ. Vacancies, in fact, prefer to bind to the smaller Zr4+ ions in YSZ whereas there is not a strong preference in the case of ScSZ, since the cations have similar sizes in this case. This effect is observed at temperatures as high as T = 1500 K. Finally, it was found that vacancies tend to order so that they can minimise their mutual interaction and that this ordering tendency is what ultimately is responsible for the observed anomalous decrease of the ionic conductivity with increasing dopant concentration. The consequences of such a behaviour are discussed.
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Zhang, Yu. "Reaction and growth mechanism of metal nanostructures formed at the electrochemically polarizable interfaces between ionic liquids and water." Kyoto University, 2020. http://hdl.handle.net/2433/253295.
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Sebastián, Paula. "Surface Influence on the First Stages of Metal Electrodeposition in Ionic Liquids." Doctoral thesis, Universidad de Alicante, 2018. http://hdl.handle.net/10045/79870.
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Esta tesis es un estudio profundo de las propiedades interfaciales Metal|líquido iónico (LI), y como estas influyen en las primeras etapas de formación de electrodepósito metálico. Dos líquidos iónicos, de dos familias diferentes, se han escogido para el análisis: un Room Temperature Ionic Liquid (RTIL): [Emmim][Tf2N]; y un Deep Eutectic Solvent (DES): 1ChCl:2urea. Para estudiar la influencia superficial en los distintos procesos, se empleó monocristales de platino (Pt(111)) y de oro Au(hkl), principalmente. El análisis inicial de las propiedades interfaciales M(hkl)|LI se realizó utilizando, entre otras técnicas, la técnica de salto de temperatura con láser pulsante, técnica que además permitió estimar el valor de potencial de carga (valor característico de la interfase metal|electrolito) en cada caso. Una vez caracterizados electroquímicamente estos sistemas, ambos LIs se utilizaron para estudiar el depósito metálico en distintas superficies tanto orientadas como poliorientadas. En concreto, se investigó el depósito de Ag y Cu en DES y sobre carbono vítreo, obteniendo que el DES influenciaba el mecanismo de nucleación y crecimiento y permitía modular el tamaño de grano. Se analizó la formación de ad-capas UPD de Cu en Au(hkl) y en DES, observándose dependencia del proceso con la orientación del sustrato y el tipo de electrolito. Finalmente, se evaluó la aplicabilidad de estos dos solventes para modificar un sustrato orientado de platino (Pt(111)) con Ni, y la sensibilidad superficial del proceso, para ello combinando técnicas clásicas como voltametría cíclica y cronoamperometría con técnicas ex-situ como SEM y AFM (para recubrimientos de baja cobertura). El presente trabajo doctoral muestra el potencial de estos solventes para modificar una superficie con distinto metales y de forma sencilla, a través de la técnica formación de depósito electroquímico, abriendo la posibilidad de utilizar estos novedosos solventes para el diseño de nuevos materiales.
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Sun, Zhenchao. "Morphological Property Variation and Ionic Transfer Behaviors of Solid Reactants in Fe-based and CaO-based Chemical Looping Processes." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343072329.
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Nguyen, Thi Khanh Ly. "New generation of epoxy networks based on ionic liquids : From structuration to final properties." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI118/document.
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Les liquides ioniques (LIs), possédant d’excellentes propriétés intrinsèques et offrant une infinité de combinaisons possibles ouvrent de nouvelles perspectives dans le domaine des polymères, en particulier dans celui des réseaux époxyde. Ce travail de thèse présente la préparation, la caractérisation et la modification de réseaux époxy / liquides ioniques. Dans un premier temps, ce travail est dédié à étudier l'influence des LIs comme comonomères de prépolymère époxyde. Ainsi, la réactivité des LIs vers la DGEBA et leur rôle en tant qu’amorceurs et/ou durcisseurs de systèmes époxyde ont été étudiés. Ensuite, l’effet de la nature chimique des LIs sur les propriétés de réseaux époxy / LIs, y compris les propriétés thermomécaniques, la stabilité thermique, les propriétés de surface et les comportements mécaniques, a été démontré. En outre, le mécanisme de la réaction entre les prépolymères époxy et LIs a été révélé à l'aide de différentes méthodes (IRTF et RMN). Dans la deuxième partie, les agents modifiants (thermoplastiques et des particules cœur-coquille) ont été incorporés dans des réseaux époxy / LI en vue d'améliorer leurs performances mécaniques. Dans la dernière section, la combinaison des LIs et des réseaux époxyde biosourcés a été étudiée en tant que substituts partiels ou complets aux systèmes époxyde issus du pétrole afin de développer des matériaux à faible empreinte environnementale. Ainsi, l’utilisation des liquides ioniques a eu des effets bénéfiques sur la morphologie mais également sur les propriétés des réseaux. La relation entre la nature chimique des LIs, la morphologie et les propriétés obtenues a été soulignéeHaving excellent intrinsic properties with an infinity cation/anion combination, ionic liquids (ILs) have become very attractive in the field of polymer science, especially in the epoxy networks. Thus, this research work presents the preparation, characterization and modification of epoxy/IL networks. The first part of this work is dedicated to study the effect of ILs as comonomers in the formation of epoxy networks. The reactivity of ILs towards epoxy prepolymer and their role either as initiators or as curing agents in the formation of epoxy/IL networks was investigated. Then, the effect of the chemical nature of ILs on the final properties of epoxy/IL networks was demonstrated including thermomechanical properties, thermal stability, surface properties and mechanical behaviors. In addition, the mechanism of curing reaction between epoxy prepolymer and ILs was revealed using different methods (FTIR and NMR). In the second part, modifiers (thermoplastics and core-shell particles) were incorporated into epoxy/IL networks in order to improve their mechanical performances. In the last section, the combination of ILs and bio-based epoxy networks was studied as partial or complete substitutions for petroleum based epoxy systems aiming for “green materials” coatings applications. Thus, the unique properties of ionic liquids led to remarkable changes in morphology and properties of epoxy systems. The relation between the chemical nature of ILs, the morphology and the properties of obtained epoxy networks was highlighted
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Larkman, Philip M. "The electrophysiology of adult rat facial motoneurones in a novel in vitro brainstem slice : ionic mechanism and pharmacological characterisation of serotonin (5-hydroxytryptamine)-evoked depolarization." Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/29214.
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This study describes intracellular recordings from adult rat cranial motoneurones constituting the Facial Motor Nucleus of the brainstem, using a novel in vitro slice. Facial motoneurones (FMn's) were identified histologically using retrograde labelling with HRP and by antidromic invasion. Antidromically evoked action potentials were overshooting, with initial segment and somato-dendritic components and were often followed by depolarizing potentials. Directly-evoked overshooting action potentials were followed by a fast after hyperpolarization, a brief delayed depolarization and a longer lasting apamin sensitive ahp which was annulled near the predicted equilibrium potential for K+ ions. Intracellular Cs+ led to a widening of the spike and a reduction in the amplitude of the ahp. Depolarizing current pulses of longer duration showed a depolarizing pre-potential to precede spike generation. Passive membrane properties were investigated using longer duration current pulses and showed the response to be ohmic over a narrow voltage range around rest. The time constant for membrane charging (T) ranged from 1.5 to 4msec. Larger hyperpolarizing current pulses evoked voltage responses with a time dependent sg characteristic of inward 'anomalous' rectification which reached steady state within the pulse. A rebound depolarizing potential occurred subsequent to the current pulse. Voltage clamp studies showed this sag to be the result of a slowly developing inward current. Intracellular recordings in vi;ro from a variety of central ncuronal types have shown both inhibition and excitation to be modulatory consequences of serotonin receptor activation. lontophoretic application of 5-HT in vivo on rat facial motoneurones has been shown to evoke a depolarization associated with increased input resistance (Rm). This study has confirmed and further investigated the mechanism and pharmacology of this action in vitro. Supcrfusion of 5-HT evokes a slow depolarization associated with increased Rm, and a lengthening of T through a direct action on the post-synaptic membrane. Manual clamping of the membrane potential at the peak of the 5-HT response back dependent rectification. Estimated reversal potentials from peak current-voltage plots under these conditions were more negative than the predicted K^ equilibrium potential. Increasing the extracellular K+ concentration, [K+]0, shifted the reversal potential to more positive values in a manner predicted by the Ncrnst equation for a K+ conductance. Nor-adrenaline (NA) evoked a similar depolarization associated with increased Rm. However, lower NA concentrations were needed for equivalent size depolarizations and the change in input resistance was usually greater. The estimated reversal potential for the NA effect was more positive than for 5-HT and when manually clamped agreed well with the predicted value. Increased [K+]0 changed the reversal potential to a more positive level. Voltage clamp studies show both 5-HT and NA to evoke a slow inward current associated with a decrease in conductance which was greater for NA. 8-OH-DPAT and dipropyl-5-CT, 5-HTjx selective agonists and 2-CH3-5-HT a 5-HTs agonist were unable to mimic or antagonise 5-HT evoked responses. Methysergide selectively antagonized the 5-HT response leaving the NA response unaffected. LY-53857 also antagonised the 5-HT response while kctanserin was unable to fully abolish 5-HT depolarization even after prolonged exposure. Spiperone, methiothepin and ICS 205-930 were all ineffective antagonists.
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Nahra, Maguy. "Dépôts électrochimiques de tantale à partir d'une électrolyte liquide ionique : étude physico-chimique de l'électrolyte et analyse des étapes du dépôt." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI073/document.
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Le tantale est un métal à utilisation stratégique notamment dansle domaine de l'électronique et des implants biomédicaux,domaines qui requièrent la réalisation de dépôts de tantale encouches minces. L’objectif de cette thèse est de déposer par voieélectrochimique et à température ambiante du tantale métalliqueà partir d'un sel de tantale solubilisé dans un électrolyte liquideionique qui possède à la fois les propriétés d’un solvant et d’unélectrolyte. Ils ont une fenêtre électrochimique large qui les rendprometteurs pour l’électrodéposition des matériaux réfractairescomme le tantale. Nous avons établis au cours de cette thèse denouvelles connaissances sur les propriétés physico-chimiques etde transport de l’électrolyte formé du sel de tantale TaF5 et duliquide ionique [BMPyr][TFSI]. Ces études corrélées à desanalyses électrochimiques et des analyses de la morphologie etde la composition élémentaire du dépôt ont conduit à proposerun mécanisme de réduction du sel de tantale pentavalent entantale métallique. Du tantale métallique sous une formeamorphe existe dans les couches profondes du dépôtaccompagné de résidus du liquide ionique enfermé dans lespores des couches déposéesTantalum is a metal of strategic uses such as in the field ofelectronics and biomedical implants. These fields require thedeposition of thin metallic tantalum films on different substrates.The aim of this thesis is to perform tantalum electrodepositionfrom tantalum salt at room temperature using room temperatureionic liquids as electrolytes. Tantalum electrodeposition isimpossible in aqueous solutions; therefore ionic liquids are thebest choice for this application because of their largeelectrochemical window. Room temperature ionic liquidsaccomplish both the roles of a solvent and an electrolyte. Theirperspectives are encouraging for the electrodeposition ofrefractory metals as tantalum. We have established in this thesisnew knowledge about the physicochemical and transportproperties of the electrolyte formed by tantalum salt TaF5 andthe room temperature ionic liquid [BMPyr][TFSI]. These studiescorrelated with electrochemical analysis, morphology andelemental composition analysis of the layers deposited served usin the understanding of the reduction mechanism of tantalumsalt into its metallic form. An amorphous metallic form oftantalum exists in deeper layers of the deposit in addition toresidues of the ionic liquid trapped in the pores of the layers
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Mackenzie, Margaret A. "Mechanisms of ionic conduction in glass." Thesis, University of Aberdeen, 1987. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU499561.
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The effect on conductivity of progressively substituting foreign alkali for host alkali in a series of lithium aluminoborate glasses has been studied. The shape of the conductivity isotherm in the dilute foreign alkali region was found to be the same for both Na+ and K+ dopants. Assuming a 'regular interstitialcy model' for ionic conduction conductivity data for a variety of glasses were subjected to isothermal analysis, allowing concentrations of mobile species and mobilities to be calculated. Conductivity changes were found to be largely attributable to changes in mobility, the concentration term remaining remarkably constant. The a.c. behaviour of aluminoborate glasses has also been studied and modulus spectra fitted using the Kohlrausch-Williams-Watts function for various beta-values. Decreasing the total alkali content and substituting foreign alkali for host alkali was observed to cause some narrowing of the modulus, mixed-alkali glasses behaving much as though only 'host' cations were present. 'Microscopic' activation energies (E_a) have been calculated from beta-values (Ea=beta Ead.c.). These are found to follow the trend in experimentally observed activation energies indicating that the mixed alkali effect occurs as the result of decreases in both long- and short-range ionic mobilities. A cluster-bypass model has been proposed in an attempt to reconcile the above results. The model assumes that the mobile species are to be found in a tissue material surrounding the clusters. A brief examination of the site preferences of spectroscopic probe ions (T1+ and Pb2+) in mixed cation glasses by u.v. spectroscopy indicated a dependence of the frequency of the absorption band on the reagents used in glass preparation. This result is thought to point towards some structural effects persisting in the melt which in turn may be important with respect to cluster formation in the glass.
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Zhou, Yuan, and 周嫄. "Ionic mechanisms of chloroform-induced cardiac arrhythmias." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43085325.
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Zhou, Yuan. "Ionic mechanisms of chloroform-induced cardiac arrhythmias." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43085325.
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Guzel, Refika Mine. "Studies of ionic mechanisms associated with human cancers." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9812.
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The general aim of this thesis was to undertake a series of inter-related studies with a view to improving our understanding of the role of ion channel expression and its regulation in cancer cells with strong metastatic potential. The emphasis was on neonatal Nav1.5 (nNav1.5) subtype of voltage-gated sodium channel (VGSC). Chapter 1 (General Introduction) gives an account of the relevant literature and states the main aims of the studies. Chapter 2 details the Materials and Methods, ranging from quantitative molecular biology to in vitro assays of metastatic cell behaviour. Chapter 3 presents experiments on regulation of VGSCs by insulin and insulin-like growth factor1 (IGF1) in strongly metastatic human breast cancer (BCa) MDA-MB- 231 cells. The central strategy was to treat insulin and IGF1 as an integrated signalling system (”IIS”) and suppress it using pharmacological inhibitors and RNAi. Inhibiting IIS signalling suppressed metastatic cell behaviours (MCBs) and decreased nNav1.5 expression and activity. Chapter 4 describes studies on mRNA expression of a variety of cancer-associated ion channels (CAICs) in peripheral blood of normal human subjects with a view to laying the foundations for subsequent patient-based studies. The following 8 CAICs were studied: nNav1.5, VGSC-β1, VGSC-β1b, Kv1.3, Kv10.1, Kv11.1, KCa3.1 and TRPM8. Several differences were noted between healthy cases and cancer patients. In particular, nNav1.5 and Kv1.3 mRNA expressions were up- and down-regulated, respectively. Chapter 5 shows that the anti-diabetic drug Metformin suppressed Matrigel invasion and nNav1.5 mRNA expression in MDA-MB-231 cells. Chapter 6 involves studies on the strongly metastatic human colorectal cancer (CRCa) SW-620 cells, which were found to express nNav1.5 mRNA and protein. Silencing nNav1.5 expression had a significant inhibitory effect on Matrigel invasion. The thesis ends with a General Discussion and Conclusion chapter, integrating the findings in the context of the field at large and pointing to future directions.
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Brunel, Frédéric. "Synthèse, conception et élaboration de nouveaux systèmes dérivés de liquides ioniques antibactériens à base de phosphonium." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4087.
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Un récent rapport de l’OMS met en garde les autorités de santé sur l’émergence de résistances chez les bactéries et le développement de souches bactériennes multi-résistantes aux traitements antibiotiques actuels. La progression de ces phénomènes est dû à différents facteurs. L’environnement hospitalier concentre un usage important de traitements antibiotiques et représente ainsi un terreau favorable au développement de résistances chez les bactéries. Le staphylocoque doré, ainsi que sa souche résistante (SARM), s’avèrent problématiques et entraînent un grand nombre de maladies nosocomiales. Dans ce contexte, il est primordial de mettre au point de nouveaux agents antibactériens permettant de lutter contre ces bactéries. Les liquides ioniques (sels à point de fusion bas) démontrent d’importantes propriétés antibactériennes. Néanmoins les mécanismes de cet effet bactéricide n’ont pas encore été établis. Ainsi nous nous proposons, dans un premier temps, de synthétiser des liquides ioniques di-cationiques afin d’étudier les différents facteurs structuraux qui régissent leur activité antibactérienne. Dans un second temps, nous concevrons des liquides ioniques à base de phosphoniums fonctionnalisés avec une sonde fluorescente. En exploitant les propriétés spectroscopiques, nous tenterons d’observer leurs interactions avec les cellules bactériennes. Enfin, nous nous proposons d'utiliser les phosphoniums comme agents de fonctionnalisation de surface dans le but de mettre au point des surfaces aux qualités bactéricides intrinsèques. Pour ce faire nous utiliserons différentes méthodes comme la conception de monocouches auto-assemblées ou l’électropolymérisationA recent WHO report warns the health authorities about the emergence of new bacterial resistances and the development of multi-resistant strains against current antibiotics treatments. The growth of those resistances is due to several factors. The hospital environment concentrates a significant use of antibiotics and disinfectant representing a favorable ground for bacterial resistance development. Among them the Staphylococcus aureus and its methicillin resistant strain (MRSA) represent a crucial issue in care environments and is a major cause of hospital acquired infections. In this context, it is essential to develop new antibacterial agents to fight against these bacteria. Ionic liquid are low melting point salts, they show significant antibacterial properties. However, the fact that the mechanisms of action of their bactericidal effect have not been established yet constitutes a major obstacle to their development as bactericidal agents. Thus, we propose to synthetize ammonium- and phosphonium-based di-cationic ionic liquids in order to study the different structural factors that govern their antibacterial activity. Then we will develop phosphonium based ionic liquids functionalized with a fluorescent probe. By taking advantage of their spectroscopic properties we will try to observe their interactions with bacterial cells. Finally, we propose to use the phosphonium salts as surface functionalization agents in order to design surfaces with intrinsic antibacterial properties. To do so, we will use innovative methods such as conception of self-assembled monolayers or electropolymerization technics
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Liang, Huamin. "Ionic mechanisms underlying pacemaker activity in the murine embryonic heart /." Köln, 2009. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000264348.
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Obrocea, Gabriela Valeria. "Ionic mechanisms of anoxia, potential role for gamma-aminobutyric acid." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0027/NQ36789.pdf.
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Obrocea, Gabriela Valeria. "Ionic mechanisms of anoxia : potential role for y-aminobutyric acid." Thesis, University of Ottawa (Canada), 1998. http://hdl.handle.net/10393/4348.
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When ionic changes induced by GABA (5 mM) were compared to those evoked by O2 replacement by N2 for 5 min, anoxic responses were found to be very similar in direction of change and time-course. In stratum pyramidale (SP) there were increases in [K+] o and [Cl--]o and a decrease in [Na +]o, and in stratum radiatum (SR) an increase in [K +]o and decreases in [Cl--]o and [Na+]o. Changes in SR were greater than those in SP, except for D [K+]o evoked by GABA. To estimate changes in the extracellular space (ECS), variations in [TMA+] o were recorded during GABA and N2 exposures. Volume decreases were observed with both GABA and anoxia and significantly less in SP than in SR: 5.3 +/- 0.03% and 6.2 +/- 0.8%, respectively with N2 and 4.6 +/- 0.2% and 4.8 +/- 0.3% with GABA. The ECS reduction was insufficient to account for the ionic changes observed. The GABAA receptor antagonist, BMI (bicuculline methioidide) (100 m M) reversibly attenuated all ion changes evoked by GABA and N 2. In SP BMI depressed increases in [K+]o and [CI--]o with GABA by 90%, and with N 2 by 50--60%. In SR the D [K+]o evoked by GABA was blocked, and that with anoxia was attenuated by 70%; decreases in [Cl--] o were depressed by more than 50%, and [Na+]o changes in SP and SR were decreased by 20--30%. The GABAB agonist, baclofen (10° -- 3 x 10 3 m M) evoked dose-dependent increases in [K+]o in SP and SR, with EC50 = 40 and 39 m M, respectively. The sigmoid concentration-response curves and sensitivity of responses to the GABAB antagonists, indicate a receptor-mediated increase in D [K+]o, due to an increase in gK. The similar EC50 values at the soma and dendrites suggests that their GABAB receptors are identical. The higher affinity of GABA B cf. GABAA receptors supports the possibility that an early component of anoxic-evoked K+ accumulation may be due to activation of both GABAA and GABAB receptors. The observation that [K+]o increase with N2 can be enhanced by GABAB antagonism may reflect a protectant action of GABA B receptors by decrease of glutamate release from terminals and postsynaptic hyperpolarization. (Abstract shortened by UMI.)
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Geiger, Philipp [Verfasser]. "Straining Mechanisms in Mixed Ionic/Electronic Conductive Perovskite Ceramics / Philipp Geiger." München : Verlag Dr. Hut, 2019. http://d-nb.info/1200754956/34.
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Geiger, Philipp Torben [Verfasser]. "Straining Mechanisms in Mixed Ionic/Electronic Conductive Perovskite Ceramics / Philipp Geiger." München : Verlag Dr. Hut, 2019. http://d-nb.info/1200754956/34.
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Rizaner, Nahit. "Studies of ionic mechanisms in model cell lines of prostate cancer." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/8992.
Full textAbstract:
Metastasis is the major problem in clinical management of cancer, including prostate cancer (PCa). Biochemical conditions in tumour microenvironment (especially O2 and Ca2+ levels) are important for modulating metastatic cell behaviours (MCBs). Ionic mechanisms, in particular voltage-gated sodium channel (VGSC) and intracellular Ca2+ activities, were shown previously to be involved in MCBs in PCa. This PhD tested the hypotheses (1) that MCBs would be sensitive to hypoxia and be inhibited by VGSC blockers including those selective for the persistent current and (2) that VGSC activity would control intracellular Ca2+ signalling. Experiments were carried on a variety of model cell lines in a comparative approach: strongly metastatic Mat-LyLu and weakly metastatic AT-2 rat PCa cells, and analogous human PCa cell lines (PC-3M and LnCaP, respectively). Experiments on Mat-LyLu cells showed that hypoxia (2 % O2, 24 h) increased mRNA expression of Nav1.7, the predominant VGSC α-subunit expressed in PCa; however, both plasma membrane and intracellular VGSC protein levels were reduced. There was no change in cellular proliferation, Matrigel invasion or lateral motility, whilst transverse migration increased significantly. Treatment (24 h) with the VGSC blockers ranolazine, riluzole, lidocaine and procaine (micromolar concentrations) decreased Nav1.7 mRNA and total VGSC protein levels, and suppressed Matrigel invasion in both normoxia (~21 % O2) and hypoxia. PC-3M (but not LNCaP or Mat-LyLu) cells showed spontaneous, transient elevations of intracellular Ca2+ (“Ca2+ oscillations”). Ionic substitution and pharmacological experiments suggested that Ca2+ influx and release from intracellular stores both contributed to the oscillations. Importantly, acute treatment with tetrodotoxin and ranolazine decreased the oscillation amplitude and frequency. Thus, both hypotheses were confirmed, i.e. (1) that hypoxia increases PCa (Mat-LyLu) cell migration and VGSC expression and (2) that intracellular Ca2+ oscillations are downstream to VGSC activity. Overall, the thesis concludes that VGSC blockers could serve clinically as anti-metastatic agents.
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Swaminathan, Narasimhan. "Stress-defect transport interactions in ionic solids." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/28273.
Full textAbstract:
Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Qu, Jianmin; Committee Member: Kohl,Paul A.; Committee Member: Liu, Meilin; Committee Member: McDowell, David L.; Committee Member: Zhu, Ting.
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Cavanagh, Robert. "An investigation into mechanisms of non-ionic surfactant effect on epithelial cells." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/50916/.
Full textAbstract:
Amphipathic, non-ionic surfactants are widely used in pharmaceutical and food industries to enhance product features; as pharmaceutical excipients they achieve increased cell membrane permeability and consequently can improve the oral absorption of drugs across the intestinal epithelial barrier. The use of non-ionic surfactants has grown rapidly, and is predicted to increase, however, the mechanism(s) surrounding the induction of surfactant toxicity is not well established and, consequently, the potential risks of surfactant exposure are not well understood. This work studies the concentration- and time-dependent succession of events that occur during and following exposure of an intestinal epithelial cell model to a ‘typical’ non-ionic surfactant – Solutol HS15. The resulted gathered demonstrate that prior to a significant increase in membrane permeability to a model drug (FITC-dextran 4kDa), non-ionic surfactant, at concentrations above its critical micellar concentration (CMC), produced almost immediate redox and mitochondrial effects manifested as an increased NADH pool, increased ROS levels, and hyperpolarisation of the mitochondrial membrane potential. Apoptosis was triggered early in this initial phase, and relied on mitochondrial hyperpolarisation as a crucial step leading to subsequent depolarisation and caspase-3/7 activation. Inhibition of mitochondrial hyperpolarisation prolonged cell survival, delayed the onset of metabolic reduction by the mitochondrial, and inhibited caspase activation. The apoptotic cell death pathway appears to be triggered prior to the emergence of substantial membrane damage by the surfactant: loss of plasma membrane integrity, nuclear membrane permeabilisation, and perturbations in calcium homeostasis - indicators of a necrotic process. It is proposed that the rapid cellular response is triggered via rapid surfactant-induced increases in plasma membrane fluidity; a phenomenon akin to the membrane-regulated stress response following membrane fluidisation by heat shock, and consequently cell death events. Furthermore, work performed on differentiated Caco-2 monolayers, alongside culture models replicating the basement membrane and paracrine signalling, demonstrate surfactant toxicity is reduced. Toxicity in vivo is therefore predicted to be less than measured on the standard model.
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CABOVSKA, BAIBA. "INVESTIGATIONS OF SEPARATION MECHANISMS IN CAPILLARY ELECTROPHORESIS AND HIGH PERFORMANCE LIQUID CHROMATOGRAPHY." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1064411271.
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Croning, Micahel Daivd Richardson. "An investigation of the mechanisms mediating disturbances in brain ionic homeostasis during oxygen deprivation." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389194.
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Markmann, Andreas. "Theoretical study of photoinduced reactions in ionic crystals mechanisms, energy dissipation and coherence effects." Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415331.
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Stanger, Jonathan Jeffrey. "Charge Transfer Mechanisms in Electrospinning." Thesis, University of Canterbury. Physics and Astronomy, 2008. http://hdl.handle.net/10092/1667.
Full textAbstract:
Electrospinning is a method of producing nano structured material from a polymer solution or melt using high strength electric fields. It is a process that has yet to find extensive industrial application yet shows promise if obstacles such as low rate of production overcome perhaps by more complete theoretical modelling. This work examines the effects of adding an ionic salt to a solution of poly(vinyl alcohol) in water. The direct effect was an increase the charge density and electric current. It was found that an increase in charge density decreases the mass deposition rate and forms a thinner initial jet. When the sign of the charge on the polymer solution was changed from positive to negative the charge density increased and the initial jet diameter and mass deposition rate also decreased. It was proposed that a smaller radius of curvature is formed by the Taylor cone at higher charge densities resulting in a smaller “virtual orifice”. The extent of the bending instability was explored and it was found that adding ionic salt results in a decrease in the bending instability resulting in thicker fibres. Changing the sign of the charge on the polymer solution from positive to negative resulted in an increase in the bending instability and resulted in thinner fibres. The charge transfer mechanisms used in different electrospinning models are explored and some assumptions not explicitly stated are discussed. From this discussion a generalized equation describing the charge transport mechanisms is proposed.
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Swiderski, Konrad. "Quantitative investigation of reaction kinetics and mechanisms in ionic liquids using laser flash photolysis technique." Thesis, University of the West of Scotland, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544371.
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Stanford, Ian Martin. "Studies on synaptic and ionic mechanisms involved in the regulation of excitability in central neurones." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385452.
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Falconer, Stuart W. P. "Mechanisms underlying two different FMRF amide induced ionic currents in identified neurones of Helix aspersa." Thesis, University of St Andrews, 1992. http://hdl.handle.net/10023/14745.
Full textAbstract:
Application of the molluscan neuropeptide FMRFamide to two identified neurones in the cerebral ganglia of Helix aspersa induces quite different effects. In the Cl neurone, FMRFamide produces a slow hyperpolarizing current carried by K+ while with the C2 neurone it causes a fast depolarizing current carried by Na+. Possible mechanisms underlying the slow K+ response were examined and the fast response was characterized using voltage clamp techniques. Some patch clamp experiments were also used for the slow response. The slow response was shown to depend on a G protein, which was sensitive to inhibition by pertussis toxin, indicating that it was mediated by a Gi or Go protein. Second messengers such as cyclic AMP, cyclic GMP, IP3, arachidonic acid and Ca2+ along with the activation of protein kinase C were all found not to be directly involved in producing the FMRFamide response. These negative results with the second messengers gave rise to the view that the FMRFamide receptors and K+ ion channels may be linked directly through the activation of G proteins. 5-HT, probably acting through raised cyclic AMP levels, reduced the amplitude of the FMRFamide response which suggests that the channel opened by FMRFamide may be an "S" K+ type channel. Activation of protein kinase C by phorbol ester also reduced the FMRFamide response. A role for protein phosphorylation was indicated by the use of okadaic acid which inhibits protein phosphatases 1 and 2A. Its application reduced the amplitude of the FMRFamide response which suggested that increased protein phosphorylation levels lead to smaller responses. Thus, it seemed possible that protein phosphorylation levels controlled by cyclic AMP, protein kinase C activation and protein phosphatases 1 and 2A might modulate the activity of the receptor/ G protein/ ion channel complex. Alternatively, FMRFamide may operate through the activation of protein phosphatase(s) which reduce protein phosphorylation levels. Patch clamp studies in cell attached mode on the Cl neurone failed to reveal any channel openings induced by FMRFamide. This result also tends to rule out the direct involvement of a second messenger. The fast depolarizing FMRFamide response of the C2 neurone, which is due to the opening of a ligand gated channel, was found to be carried by Na+ and not Ca2+. Amiloride produced a reversible block of the current. Tetrodotoxin and lignocaine had no effect on the FMRFamide response while raised cyclic AMP levels potentiated the response. In the presence of okadaic acid and increased levels of cyclic AMP, the FMRFamide response is potentiated. This potentiation was not maintained in the presence of okadaic acid alone. The raised protein phosphorylation levels therefore did not cause potentiation, which suggested that cyclic AMP may have a direct effect on the receptor/channel complex.
34
Hu, Zhonghan. "Transport properties, optical response and slow dynamics of ionic liquids." Diss., University of Iowa, 2007. http://ir.uiowa.edu/etd/160.
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Одинцова, Олександра Павлівна. "Безпігментні одношарові склоемалеві покриття для побутової техніки." Thesis, НТУ "ХПІ", 2017. http://repository.kpi.kharkov.ua/handle/KhPI-Press/33516.
Full textAbstract:
Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) за спеціальністю 05.17.11 "Технологія тугоплавких неметалічних матеріалів". – Національний технічний університет "Харківський політехнічний інститут", Харків, 2017.
Дисертацію присвячено розробці безпігментних одношарових хімічно та термічно стійких темнозабарвлених склоемалевих покриттів для захисту побутової техніки, зокрема кухонних газових та електричних плит, що отримуються за технологією POESTA. Синтезовано основи отримання покриттів вказаного типу, згідно із якими розробляється скломатриця із заданими фізико-хімічними властивостями, на основі якої отримується склоемалева фрита шляхом введення в оптимізований склад скла комплексного активатору зчеплення, одночасно виконуючий роль активного забарвлюючого комплексу, який поєднує задані міцнісні характеристики безпігментних одношарових темнозабарвлених склоемалевих покриттів. Встановлено межі значень структурних факторів, які забезпечують міцну структуру кремнекисневого каркасу скла в системі R₂O (Na₂O+K₂O+Li₂O) – RO (CaO+BaO+SrO+MgO) – TiO₂ – ZrO₂ – B₂O₃ – SiO₂ і заданий рівень її структурнозалежних експлуатаційних властивостей за рахунок встановлених співвідношень склоутворювачів і модифікаторів. Розроблено склад і співвідношення комплексного активатора зчеплення із урахуванням його впливу на характеристики міцності системи "склоемаль – сталь", корозійну здатність склорозплаву та експлуатаційні властивості покриттів, який одночасно виконує роль активного забарвлюючого комплексу. Обрано іонний механізм забарвлення та встановлено колірні координати в ККС XYZ, RGB, L*a*b. Проведено промислові та лабораторно-промислові випробування на підприємствах та розроблено практичні рекомендації щодо використання результатів.The dissertation on competion of a scientific degree of the candidate of engineering science on a speciality 05.17.11 "Technology of refractory nonmetallic materials". – National Technical University "Kharkiv Polytechnical Institute", Kharkiv, 2017. The dissertation is devoted to the development of pigments free direct chemically and thermally resistant dark-colored glass-enamel coatings for the protection of household appliances, in particular kitchen gas and electric plates, obtained by the technology POESTA. The bases of obtaining the coatings of this type are synthesized, according to which the glass matrix is developed with the given physicochemical properties, on the basis of which glassmelee frit is obtained by introducing into the optimized composition of the MS complex agglomer activator, simultaneously performing the role of the active coloring complex which combines the specified strength characteristics of pigments free direct glass-enamel coatings with their dark coloring. The boundaries of the values of structural factors, which provide a solid structure of the silica-oxygen glass frame in the system R₂O (Na₂O+K₂O+Li₂O) – RO (CaO+BaO+SrO+MgO) – TiO₂ – ZrO₂ – B₂O₃ – SiO₂ and the specified level of its structurally dependent performance properties due to the established ratios of glass modifiers and modifiers. The composition and ratio of the complex coupler activator have been developed taking into account its influence on the strength characteristics of the glass-enamel-steel system, the corrosion capacity of the glass-fiber alloy and the operational properties of the coatings at the firing temperatures of 800 to 830 °C. Selected the ionic mechanism of color, which was realized by the components of the filling station, and the color coordinates are established in the XYZ, RGB, L*a*b, according to RAL. Industrial and laboratory-industrial tests were carried and practical recommendations for the use of development results are developed.
36
Gasser, Robert N. A. "Microelectrode study of the mechanisms of ionic and electrical changes during simulated ischaemia in isolated cardiac muscle." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670316.
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Boulfelfel, Salah Eddine. "Atomic Scale Investigation of Pressure Induced Phase Transitions in the solid State." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-25283.
Full textAbstract:
In this work, atomic scale investigation of pressure-induced transformations in the solid state have been carried out. A series of compounds including GaN, ZnO, CaF2, and AgI, in addition
to elemental phosphorus have been studied. The corresponding transition mechanisms have been
elucidated with a clear description of atomic displacements and intermediate structures involved
therein.
In the first group of compounds, the long standing debate on the transition path of the
wurtzite(WZ)-to-rocksalt(RS) transition in semiconductors, GaN and ZnO was resolved using geometrical
modeling combined with molecular dynamics (MD) simulations conducted in the frame
of transition path sampling (TPS) method. In GaN, a two-step mechanism through a metastable
intermediate phase with a tetragonal structure iT has been revealed from simulations. In ZnO,
the tetragonal intermediate structure was kinetically less stable, although still part of the real
transition mechanism. It appeared at the interface between WZ and RS as consequence of a layers
shearing. The transition regime in ZnO was characterized by a competition between iT structure
and another hexagonal intermediate with hexagonal symmetry iH. Although possible, the latter
is not functional for the transition.
In both cases, GaN and ZnO, two points of agreement with experiments have been revealed.
The tilting of structures after transition, and the phonon mode softening associated with atomic
displacements leading to the tetragonal structure iT
In the second group of compounds, the investigation of transitions in superionic conductors,
CaF2 and AgI, demonstrated a different and particular behavior of atomic motion under pressure.
The solid-solid reconstruction of CaF2 structure was shown to be initiated and precedented by high
disorder of the anionic sublattice. The percolation of fluoride ions through voids in the fluorite
structure created a thin interface of liquid like state. The sparce regions caused by the departure
of anions facilitates the cation sublattice reconstruction.
In AgI, ion diffusion during the wurtzite/zincnlende(ZB)$rocksalt transition was more pronounced
due to the extended stacking disorder WZ/ZB. The Ag+ ions profited not only from the
structure of the interface but used the combination of interstitial voids offered by both phases,
WZ and ZB, to achieve long diffusion paths and cause the cation sublattice to melt. Clearly, a
proper account for such phenomena cannot be provided by geometry-designed mechanisms based
on symmetry arguments.
In phosphorus, the question of how the stereochemically active lone pairs are reorganized during
the orthorhombic (PI) to trigonal (PV) structural transition was answered by means of simulations.
Computation was performed at different levels theory.
First, the mechanism of the transition was obtained from TPS MD simulations. MD runs
were performed within density functional tight binding method (DFTB). The analysis of atomic
displacements along the real transformation path indicated a fast bond switching mechanism.
In a second step, the nature of the interplay between orbitals of phosphorus during the bond
switching was investigated. A simultaneous deformation of lone pair and P−P bond showed
a mutual switching of roles during the transformation. This interplay caused a low dimensional
polymerization of phosphorus under pressure. The corresponding structure formed as zigzag linear
chain of fourfold coordinated phosphorus atoms (· · ·(P(P2))n · · ·) at the interface between PI and
PV phases.
A further result of this work was the development of a simulation strategy to incorporate
defects and chemical doping to structural transformations. On top of the transition path sampling
iterations, a Monte Carlo like procedure is added to stepwise substitute atoms in the transforming
system. Introducing a chemically different dopant to a pure system represents a perturbation to
the energy landscape where the walk between different phases is performed. Therefore, any change
in the transition regime reflects the kinetic preference of a given structural motif at times of phase
formation.
This method was applied to the elucidation of WZ-RS transition mechanism in the series of
semiconducting compounds AlN, GaN, and InN. Simulations showed that In atoms adopt the
same transformation mechanism as in GaN and favor it, while Al atoms demonstrated a significant
reluctance to the path going through tetragonal intermediate iT. The difference between transition
regime in mixed systems InxGa1−xN and AlxGa1−xN is in agreement with experiments on high pressure
behavior of AlN, GaN, and InN. While transitions in GaN and InN are reversible down
to ambient conditions, AlN is stable.
The work presented in this thesis constitutes the seed of new perspectives in the understanding
of pressure-induced phase transformations in the solid state, where the physics and the chemistry
are brought together by means of computer simulations.
38
Одинцова, Олександра Павлівна. "Безпігментні одношарові склоемалеві покриття для побутової техніки." Thesis, НТУ "ХПІ", 2017. http://repository.kpi.kharkov.ua/handle/KhPI-Press/33515.
Full textAbstract:
Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) за спеціальністю 05.17.11 "Технологія тугоплавких неметалічних матеріалів". – Національний технічний університет "Харківський політехнічний інститут", Харків, 2017.
Дисертацію присвячено розробці безпігментних одношарових хімічно та термічно стійких темнозабарвлених склоемалевих покриттів для захисту побутової техніки, зокрема кухонних газових та електричних плит, що отримуються за технологією POESTA. Синтезовано основи отримання покриттів вказаного типу, згідно із якими розробляється скломатриця із заданими фізико-хімічними властивостями, на основі якої отримується склоемалева фрита шляхом введення в оптимізований склад скла комплексного активатору зчеплення, одночасно виконуючий роль активного забарвлюючого комплексу, який поєднує задані міцнісні характеристики безпігментних одношарових темнозабарвлених склоемалевих покриттів. Встановлено межі значень структурних факторів, які забезпечують міцну структуру кремнекисневого каркасу скла в системі R₂O (Na₂O+K₂O+Li₂O) – RO (CaO+BaO+SrO+MgO) – TiO₂ – ZrO₂ – B₂O₃ – SiO₂ і заданий рівень її структурнозалежних експлуатаційних властивостей за рахунок встановлених співвідношень склоутворювачів і модифікаторів. Розроблено склад і співвідношення комплексного активатора зчеплення із урахуванням його впливу на характеристики міцності системи "склоемаль – сталь", корозійну здатність склорозплаву та експлуатаційні властивості покриттів, який одночасно виконує роль активного забарвлюючого комплексу. Обрано іонний механізм забарвлення та встановлено колірні координати в ККС XYZ, RGB, L*a*b. Проведено промислові та лабораторно-промислові випробування на підприємствах та розроблено практичні рекомендації щодо використання результатів.The dissertation on competion of a scientific degree of the candidate of engineering science on a speciality 05.17.11 "Technology of refractory nonmetallic materials". – National Technical University "Kharkiv Polytechnical Institute", Kharkiv, 2017. The dissertation is devoted to the development of pigments free direct chemically and thermally resistant dark-colored glass-enamel coatings for the protection of household appliances, in particular kitchen gas and electric plates, obtained by the technology POESTA. The bases of obtaining the coatings of this type are synthesized, according to which the glass matrix is developed with the given physicochemical properties, on the basis of which glassmelee frit is obtained by introducing into the optimized composition of the MS complex agglomer activator, simultaneously performing the role of the active coloring complex which combines the specified strength characteristics of pigments free direct glass-enamel coatings with their dark coloring. The boundaries of the values of structural factors, which provide a solid structure of the silica-oxygen glass frame in the system R₂O (Na₂O+K₂O+Li₂O) – RO (CaO+BaO+SrO+MgO) – TiO₂ – ZrO₂ – B₂O₃ – SiO₂ and the specified level of its structurally dependent performance properties due to the established ratios of glass modifiers and modifiers. The composition and ratio of the complex coupler activator have been developed taking into account its influence on the strength characteristics of the glass-enamel-steel system, the corrosion capacity of the glass-fiber alloy and the operational properties of the coatings at the firing temperatures of 800 to 830 °C. Selected the ionic mechanism of color, which was realized by the components of the filling station, and the color coordinates are established in the XYZ, RGB, L*a*b, according to RAL. Industrial and laboratory-industrial tests were carried and practical recommendations for the use of development results are developed.
39
Leoni, Stefano. "Theoretical and Experimental Investigations on Solid State Reactions: Phase Transition Mechanisms, Ionic Conduction, Domain Formation and Interface Reactivity." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-79219.
Full textAbstract:
In the practice of solid state chemistry, structural phase transitions are fairly common events. Nonetheless, their understanding, in terms of both: A rationalization of the observed changes in symmetry pattern and; An understanding of the mechanisms allowing for a particular transformation, are outstanding problems. The thermodynamic classification of phase transitions distinguishes between first and second order transitions, on the basis of the discontinuous behavior of quantities related to first or second derivatives of the free energy, respectively. Small atomic displacements are typically associated with second order phase transitions, and latent heat changes amount to a few calories per gram only. Additionally, the symmetries of the phases surrounding the transition are typically in the relation of a group and a subgroup. Reconstructive phase transitions, on the contrary, involve breaking of (large) parts of the bond scaffolding of the initial structure, and exhibit drastic changes at the transition point, with large latent heat and hysteresis effects. The corresponding atomic displacements can be in the order of the lattice parameters, and no group-subgroup is found, between the symmetry of the phases. These type of transitions have generally a strong first-order character.
Landau theory accounts for continuous, second-order phase transitions. As a phenomenological theory, it does not establish the existence of a phase transition, which remains an experimental fact. It only bridges microscopic characteristics, like space-group symmetries and structural changes, or phonon softening effects, with measurable macroscopic quantities. Therein, distortions are carried by an order parameter, which fully specifies the form of the analytical variational free energy. The latter is continuous and derivable with respect to temperature, pressure and atomic displacement, at the transition point.
First order, non-continuous phase transitions are still within the scope of Landau theory in the mentioned special case of the existence of a group-to-(isotropic) subgroup relationship. In the majority of cases, however, and for the most interesting phase transitions (for basic and applied research), such a relationship is missing, making the choice of an order parameter less straightforward. Most of the allotropic transformations of the elements, many intermetallic systems, and numerous insulating systems belongs to this class. This class also includes most interesting and fundamental electronic effects, like metallization in perovskites or spinel oxides for example.
This very simple fact of a missing symmetry condition has helped reinforcing the opinion of first-order phase transitions being a world apart, and possibly contributed to discouraging a firm theory to develop, able to account for their transformation mechanisms and the change of physical properties across phase transition. The thermodynamic distinction between first and second order phase transitions is too narrow, as, in case of first order phase transitions, it embraces both weakly discontinuous transition and reconstructive ones, where bonds are being strongly modified. Especially, a mean to qualify the distance between two structures (geometric, with respect to symmetry, a.s.o.), is missing. Clearly, a group-subgroup relationship may, and typically does imply shortest shifting distances, as a tiny atomic displacement can already do for a symmetry lowering. Naively, missing such a relation means no constraints, and apparently no means to conclude at a connection of two structures in general, let alone a full mechanistic analysis.
First order phase transitions proceed by nucleation and subsequent growth of the new phase from the initial one. Different from (second-order) continuous phase transitions, they do imply coexistence of the transforming motifs. The discontinuity in some order parameter between the two phases is driven by lowering of the free energy as the new phase forms. However, close to the transition, the original phase remains metastable, and a fluctuation is needed to cause the formation of the new phase to set in. Such a process responds to thermal changes, and depending on the height of the nucleation barrier, its rate may be slower or faster. In the former case, large deviations from equilibrium may be required to achieve transformation to the stable phase, which means that large hysteresis effects will be observed in the course of transformation.
The intent of this work consists in giving a face to the intermediate configurations appearing in first order phase transitions, in solid-solid reconstructive processes. Apart of a mechanistic elucidation, consisting in answering the question “Which atomic displacements bring structural motif A into structural motif B ?”, another purpose of this work is a rather pedagogical one, that is, showing that first-order phase transitions can be understood in detail, not only in principle but in fact. The core of the examples illustrated in this work is concerned with phase transformations where pressure represents the thermodynamic controlling parameter. Pressure is extensively used in chemical synthesis, as a mean to achieve novel properties, optical or mechanical just to mention a few. Additionally, reports on novel high-pressure polymorphs are regularly appearing. In this sense, pressure is a relevant parameter for approaching fundamental questions in solid state chemistry.
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Dé, Emmanuelle. "Etude fonctionnelle de la protéine membranaire OprF de Pseudomonas fluorescens et son implication dans la variation de résistance aux antibiotiques en fonction de la température de croissance bactérienne." Rouen, 1996. http://www.theses.fr/1996ROUES006.
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La bactérie psychrotrophe Pseudomonas fluorescens MF0 est plus sensible à la mezlocilline (β-lactamine) à basse température de culture (8°C) qu'à la température optimum de croissance (28°C). Cette modification de la résistance bactérienne serait due à une modulation de la pénétration de l'antibiotique à travers la membrane externe en fonction de la température de culture, via des protéines canaux appelées porines. Après avoir montré que la composition protéique des membranes externes ne présentait aucune différence significative pour des bactéries issues de cultures à 8°C et 28°C, un changement de la structure et de la fonction de la porine majoritaire de la membrane externe a été envisagé pour expliquer ce phénomène. La protéine majoritaire de 32 kDa de P. Fluorescens MF0 a donc été extraite et purifiée à partir de cultures à différentes températures afin de la reconstituer dans les bicouches lipidiques planes. Les résultats montrent que la diminution de la température de croissance bactérienne entraîne une diminution des valeurs de conductances unitaires de cette protéine (250 pS dans NaCl 1 M pour des cultures à 28°C et 80 pS pour des cultures à 8°C). Ce travail a été étendu à une autre bactérie psychrotrophe P. Fluorescens OE 28. 3 isolée du sol et a conduit aux mêmes résultats après reconstitution de la protéine majoritaire OprF extraite de cultures à 8°C et 28°C. La comparaison des porines OprF de P. Fluorescens MF0 et OE 28. 3 (séquences N-terminales, amplification PCR du gène OprF, réactions immunologiques) montrent : 1) une forte homologie de séquence (94% d'identité) pour ces protéines 2) qu'elles sont exprimées à partir d'un seul gène OprF en fonction de la température de culture. Des modifications de structure (ex : interactions avec le LPS) de cette protéine sont envisagées pour expliquer la variation de la taille du canal en fonction de la température de croissance bactérienne.
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Brikner, Natalya Anna. "On the identification and mitigation of life-limiting mechanisms of ionic liquid ion sources envisaged for propulsion of microspacecraft." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97350.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 185-193).
Life-limiting processes affecting ionic liquid ion sources (ILIS) are investigated in this research, motivated by the development of ILIS for propulsion of microspacecraft and other industrial applications. Micropropulsion in particular has received considerable interest in recent years due to the increasing utility of and demand for small satellites and the services they provide. A passively-fed, porous ILIS system which includes the ion thruster head, propellant supply system, and power electronics has been proposed by researchers in the Space Propulsion Laboratory at the Massachusetts Institute of Technology to address the gap in micropropulsion and provides the primary impetus for the work presented in this thesis. Spacecraft mission durations can reach up to 15 years with ongoing propulsion requirements and in ground-based applications, minimal servicing to replace the ion source is desirable. Thus, any embodiment of ILIS would benefit from operational lifetimes in excess of 1000 h. To date, successful long-duration operation of porous ILIS beyond tens of hours has not been achieved, precluded primarily by two critical challenges: electrochemistry and electrical discharges. Electrochemistry-chemical reactions between the source emitter and the ionic liquid-has been shown to be capable of fully deteriorating the source in fewer than 100 h. Electrical discharges, on the other hand, can cause source failure within a matter of seconds and are also challenging to predict and avoid. ILIS as a subcomponent of a larger spacecraft system exposed to the environment of space must also overcome challenges such as radiation and threats of micrometeorite impact. This research aims to investigate, quantify, and mitigate the primary life-limiting mechanisms of ILIS to support their successful long-life operation. A description of the onset of electrochemistry is applied to ILIS, and it is shown that existing methods for preventing electrochemistry would present a challenge to the drive electronics, requiring alternation of the polarity applied to the devices at kilohertz frequency. The relevance of an alternative contact method is revealedthe distal contact, which is shown to be effective at avoiding electrochemistry at the critical emission site. By contrast, a metal emitter with the traditional, direct electrical contact was electrochemically etched as it operated for a similar time and conditions, showing severe degradation. The distal technique has been implemented in the current version of the MIT propulsion system and more in-depth studies are ongoing to aid in distal electrode material selection and design. The source of another severe life-limiting mechanism was unknown prior to this work, but was known to be capable of causing device failure within seconds through electrical shorting, material ablation, polycondensation of the ionic liquid, and so on. Experiments performed as part of this effort revealed that electrical discharges were transpiring under certain conditions and inducing these source failures. An analytical framework for predicting the steady-state discharge is outlined for ILIS, though the process is likely complicated by the electrohydrodynamic interactions during porous ILIS operations. Given this difficulty, an experimental study was undertaken to preliminarily explore the operational and design conditions that support discharges so that they may be avoided in practical implementations and to guide future modeling efforts. Gas contamination and flooding of the substrate or unrestricted flow from the porous substrate are identified as the likely factors leading to this failure mechanism. Qualitative descriptions of those processes are provided along with suggestions for techniques for preventing them. The work concludes with a summary of other life-limiting mechanisms such as grid erosion and micrometeorite impact. Suggestions for future work related to electrochemistry include optimizing the distal electrode material properties, and understanding gas evolution there. For electrical discharges, an experimental study that resolves the challenges of the setup presented could provide more detail to the actual processes by helping to identify the ionized species. It is the hope of the author that the work discussed here and the work to come on mitigating these processes will contribute to the successful embodiment of ILIS as an appealing option for micropropulsion and for ground-based applications.
by Natalya Anna Brikner.
Ph. D.
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Huffaker, Ray Bringhurst. "Tachycardia-induced early afterdepolarizations ionic mechanisms and effects on wave propagation in 1, 2, and 3D tissue (computer simulation study) /." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1621830931&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Lé, Tao. "Fundamental insights into dynamic ionic exchange in vertically-oriented nanostructured materials via fast electrogravimetric methods. Applications to energy storage mechanisms." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS202.
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Une meilleure compréhension des mécanismes d’échanges ioniques au sein de matériaux d’électrode de supercondensateurs peut être obtenue en couplant les méthodes de caractérisation électrochimique avec des mesures de microbalance à quartz. Parmi les matériaux d’électrodes en cours de développement, une grande amélioration des performances ont été obtenues avec des nanostructures verticales, cependant la technique de microbalance à quartz électrochimique n’a pas encore été employée sur ce type d’électrodes. L’objectif de cette thèse est d’appliquer les méthodes de caractérisation par microbalance à quartz électrochimique à des électrodes de supercondensateurs nanostructurées verticalement. Les nanostructures étudiées au cours de cette thèse sont les nanofils de silicium, les nanofils de PEDOT, les nanofils hybrides silicium/PEDOT ainsi que les voiles de graphène orientés verticalement (VOGNs). La croissance de ces nanostructures a été obtenue directement sur la surface de la microbalance en minimisant les effets sur la qualité de cette dernière. L’effet de l’amortissement de la résonance par ces nanostructures a été étudié dans différents types d’électrolytes. Les échanges ioniques dynamiques ayant lieu au sein d’électrodes à base de VOGNs et de nanofils de PEDOT ont pu être dévoilés. Ces premières avancées dans l’application des mesures électrogravimétriques à des nanostructures verticales ont montré l’étendue des possibilités pour la caractérisation de supercondensateurs à électrodes nanostructurées. Les limites de ces techniques dues aux amortissements hydrodynamiques ont également été montrées pour les architectures plus épaissesA better understanding of the ionic exchange mechanisms within supercapacitor electrode materials can be obtained by coupling classical electrochemical techniques with microbalance measurements. Using vertically-oriented nanostructures, supercapacitor devices can be greatly enhanced, however microbalance measurements had not yet been performed with such electrodes. The aim of this Ph.D. thesis is to perform electrochemical quartz crystal microbalance measurements on vertically-oriented nanostructured electrodes for supercapacitors. The nanostructured materials studied throughout this work are silicon nanowires, PEDOT nanowires, hybrid PEDOT-silicon nanowires and vertically-oriented graphene nanosheets (VOGNs). The growth of these nanostructures was obtained directly on the surface of a microbalance while minimizing the effects on it’s quality. The effect of resonance damping with the nanostructures was studied in various electrolytes. The ionic exchange dynamics in VOGN and PEDOT nanowires have been unveiled. These first microbalance results on vertically-oriented nanostructures pave the way to characterizing other nanostructured electrodes for supercapacitors
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Himeno, Yukiko. "Ionic mechanisms underlying the positive chronotropy induced by β1-adrenergic stimulation in guinea-pig sinoatrial node cells : a simulation study." Kyoto University, 2008. http://hdl.handle.net/2433/135850.
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Du, Plooy Jeanette Noel. "Comparing platelet function and ultrastructure in smoking and thrombo-embolic ischemic stroke." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/33160.
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Stroke is serious neurological disease and is a major cause of death as well as disability throughout the globe. Stroke has a complex pathophysiology that involves inflammatory pathways, excitotoxicity mechanisms, oxidative damage, apoptosis, ionic imbalances, angiogenesis and neuroprotection.
85% of strokes are ischemic and occurs when a cerebral vessel, or any vessel supplying the brain, narrows or loses pressure resulting in subsequent brain ischemia and infarction downstream to the site of obstruction depriving tissues of vital oxygen and nutrients. This may be caused by either atherosclerotic thrombi or distant emboli defined as a mass of clotted blood or other material.
It is estimated that over a billion people currently smoke cigarettes or use other tobacco products, seeing as smoking is a major risk factor for stroke this is of major concern. Platelets are hematopoietic cells produced by bone marrow megakaryocytes. Platelets play a role in the development of ischemic stroke primarily by means of their participation in the formation of thromboemboli, the presence of abnormal platelet function may predispose patients to a pro-thrombotic, pro-inflammatory state. The reorganization of the cytoskeleton in platelets is an important factor in the complex mechanisms found in thrombosis and haemostasis. The platelet membrane contains a large number of receptors which specifically bind agonists that stimulate the physiological platelet response. Oxidative stress is one of the mechanisms involved in the neuronal damage of stroke. Oxidative stress is a state of imbalance between free radical production, in particular, reactive oxygen species (ROS), and the ability of the organism to neutralize them, leading to progressive oxidative damage. Smoking is known to result in the generation of various free radicals.
Flow cytometric analysis of the platelets of thrombo-embolic ischemic stroke patients and smokers revealed that the membranes of the two groups were altered in some form as well as an increased activation in both groups when compared to healthy individuals. Superoxide levels in the platelets were higher in smokers when compared to stroke patients, while hydrogen peroxide levels were elevated in the platelets of both groups. Superoxide was elevated in the whole blood samples of both groups. The production and subsequent reactions of reactive oxygen species appear to be influential in stroke and smoking and may likely be a crucial factor in the development of a pro-thrombotic, pro-inflammatory state which may prove to be a hallmark in the pathophysiology of stroke and smoking.
Confocal microscopy and Scanning electron microscopy showed that platelets of stroke patients and smokers appear to be more activated and more prone to form tight clots. Furthermore an increased amount of superoxide is present in the platelets of stroke patients and smokers, specifically in the centre of clots. This may be an indication that once platelets have aggregated and started to fuse together, the mitochondria are expelled from the platelets and “trapped” within the clot. Atomic force microscopy also indicated both the stroke patients and smoker‟s platelets appear to be in a more activated state than the control group. Here it is apparent that some form of cytoskeletal rearrangement takes place to a more severe extent in the stroke group than in the smokers. Necrosis may be present in the platelets of stroke patients while neither apoptosis nor necrosis can be identified in the platelets of smokers however some form of membrane alteration is likely present.
All the techniques used showed an increase in platelet activation in stroke patients and smokers, necrotic platelets may be present in the stroke patients while the platelet membrane of smokers seems to be altered. ROS is present and alters the platelet function of smokers and stroke patients in some way. It appears as if thrombo-embolic ischemic stroke patients and smokers‟ platelets have similar trends in activation but the processes involved to achieve this differ as there are structural differences present. These differences may prove a useful tool to further understand the pathophysiology behind thrombo-embolic ischemic stroke as well as to discover new therapeutic pathways.Dissertation (MSc)--University of Pretoria, 2013.
gm2014
Physiology
Unrestricted
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Rumple, Amber C. "Sustainable chemistry solutions for industrial challenges: mechanisms of PVC degradation and stabilization; reversible ionic liquids for CO₂ capture; efficient Suzuki coupling of basic, nitrogen containing substrates." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53474.
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The thermal degradation of polyvinyl chloride (PVC) is a significant processing challenge which can lead to deleterious mechanical and optical properties in a wide range of products. Synergetic studies on PVC model compounds and blends of bulk PVC provide unique insights into the thermal degradation and stabilization pathways in the presence of common additives. Model PVC compounds were selected to replicate specific defects (e.g., allylic, vicinal and tertiary) and tacticity (i.e., utilizing stereochemistry to investigate tacticity) commonly found in PVC. Model studies were conducted neat (solvent-free) with metal carboxylates. Experimental results highlight that the allylic and tertiary defects are more reactive than pristine PVC and isotactic sites are more reactive than their syndiotactic counterparts. Zinc stearate was found to act not in the role of substituent, but as a Lewis acid by facilitating dehydrochlorination of labile chlorides. This prevents the accumulation of hydrogen chloride and autocatalytic chain unzipping. In contrast, calcium stearate delayed the formation of zinc chloride, a much stronger Lewis acid than zinc stearate, through an ion exchange process to form calcium chloride. Thermal weight loss studies using blends of bulk PVC proved critical in transferring mechanistic insights into the context of a polymeric matrix.
Post-combustion carbon capture has traditionally involved the use of aqueous alkanol amine solutions. The regeneration of such systems, however, can be costly and energy intensive. We have developed an alternative system utilizing silylated alkylamines to reversibly capture CO2 under near ambient conditions. The silyl amines developed capture CO2 through chemical reaction to form reversible ionic liquids (RevIL). RevILs utilize no added water and are tunable by molecular design allowing us to influence industrially relevant carbon capture properties such as viscosity, temperature of reversal, and enthalpy of regeneration, while maximizing overall CO2 capture capacity. We demonstrate a strong structure-property relationship among the silyl amines where minor structural modifications lead to significant changes in the bulk properties of the RevIL.
Amine containing substrates are important building blocks for a variety of biological and pharmaceutical compounds. However, application of the otherwise versatile Suzuki reaction to these substrates has proved challenging due to either ligation of the amine to the palladium or to electronic effects slowing the oxidative addition step. Conventional methods to overcome these challenges involve protection-deprotection strategies or the use of designer ligands to facilitate reaction. We have shown that application of CO2 pressure and adjusting the water content of the reaction system facilitate the Suzuki coupling of 4-amino-2-halopyridines in high yield with the simple Pd(TPP)2Cl2 catalyst. The protocol was expanded to 2-halopyridines. The results of these investigations will be discussed.
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Leoni, Stefano [Verfasser], Gotthard [Akademischer Betreuer] Seifert, Michael [Akademischer Betreuer] O'Keeffe, and Yuri [Akademischer Betreuer] Grin. "Theoretical and Experimental Investigations on Solid State Reactions: Phase Transition Mechanisms, Ionic Conduction, Domain Formation and Interface Reactivity / Stefano Leoni. Gutachter: Gotthard Seifert ; Michael O'Keeffe ; Yuri Grin." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://d-nb.info/1067729623/34.
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Bodin, Charlotte. "Etude des dynamiques d’électrolytes à base de liquides ioniques redox pour une application en supercondensateur." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS145.
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Les électrolytes sont au cœur des batteries et des supercondensateurs et leur rôle premier est de conduire les ions, et même si leurs spécifications sont en fait plus complexes : stabilité chimique, grande tension de cellule, conductivité élevée. Cependant, selon la conception des molécules qui composent le cation et/ou l'anion, leur fonction pourrait s'étendre. Les liquides ioniques se prêtent particulièrement bien à cette fonctionnalisation de par leurs propriétés intéressantes en tant qu’électrolyte et leur facilité de synthèse. Dans le domaine des supercondensateurs, la densité d'énergie est une limite technologique. Pour y répondre, une stratégie innovante est l’ajout de molécules redox à l'électrolyte pour participer au stockage de charge. Malgré la promesse d'augmenter les densités énergétiques (ou capacités apparentes), l’utilisation d’électrolyte redox fait face à deux limites clairement identifiées : (1) la diffusion des molécules redox diminuent l'efficacité coulombique et (2) l'autodécharge est importante. L'une de ces possibilités est l'utilisation de liquides ioniques biredox (2 couples oxydo-réducteur). Ce travail de thèse s’est concentré sur l’étude des dynamiques d’électrolytes à base de liquides ioniques redox pour une application en supercondensateur. L’effet du confinement des électrolytes redox dans la porosité des électrodes de carbone a été plus particulièrement étudié. Cela a permis de mettre en avant des interactions différentes, entre diffusion et adsorption, entre les liquides ioniques redox et les électrodes. S’il ne répond pas à toute nos questions, le formalisme utilisé pour comprendre ces dynamiques électrochimiques différentes a permis d’allier théorie et expérimentation pour aller toujours plus loin dans la compréhension des interactions des liquides ioniques redox comme électrolyte pour le stockage de l’énergieElectrolytes are at the heart of batteries and supercapacitors and their primary role is to conduct ions, and even if their specifications are actually more complex: chemical stability, high cell voltage, high conductivity. However, depending on the design of the molecules that compose the cation and/or anion, their function could be expanded. Ionic liquids are particularly suitable for this functionalization because of their interesting properties as an electrolyte and their ease of synthesis.In the field of supercapacitors, energy density is a technological limitation. To address this, an innovative strategy is the addition of redox molecules to the electrolyte to participate in charge storage. Despite the promise to increase energy densities (or apparent capacities), the use of redox electrolyte faces two clearly identified limitations: (1) the diffusion of redox molecules decreases the coulombic efficiency and (2) the self-discharge is important. One of these possibilities is the use of biredox ionic liquids (2 oxidation-reducing pairs). This thesis work focused on the study of electrolyte dynamics based on redox ionic liquids for supercapacitor application. The effect of the confinement of redox electrolytes in the porosity of carbon electrodes has been studied. Thanks to this, the different interactions as diffusion and adsorption between redox ionic liquids and electrodes are described. The formalism used to understand these different electrochemical dynamics allow us to combine theory and experimentation to go ever further in understanding the interactions of redox ionic liquids as an electrolyte for energy storage
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Elbagerma, Mohamed A. "Analytical method development for structural studies of pharmaceutical and related materials in solution and solid state : an investigation of the solid forms and mechanisms of formation of cocrystal systems using vibrational spectroscopic and X-ray diffraction techniques." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/4467.
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Analysis of the molecular speciation of organic compounds in solution is essential for the understanding of ionic complexation. The Raman spectroscopic technique was chosen for this purpose because it allows the identification of compounds in different states and it can give information about the molecular geometry from the analysis of the vibrational spectra. In this research the ionisation steps of relevant pharmaceutical material have been studied by means of potentiometry coupled with Raman spectroscopy; the protonation and deprotonation behaviour of the molecules were studied in different pH regions. The abundance of the different species in the Raman spectra of aqueous salicylic acid, paracetamol, citric acid and salicylaldoxime have been identified, characterised and confirmed by numerical treatment of the observed spectral data using a multiwavelength curve-fitting program. The non-destructive nature of the Raman spectroscopic technique and the success of the application of the multiwavelength curve-fitting program demonstrated in this work have offered a new dimension for the rapid identification and characterisation of pharmaceuticals in solution and have indicated the direction of further research. The work also covers the formation of novel cocrystal systems with pharmaceutically relevant materials. The existence of new cocrystals of salicylic acid-nicotinic acid, DLphenylalanine , 6-hydroxynicotinic acid, and 3,4-dihydroxybenzoic acid with oxalic acid have been identified from stoichiometric mixtures using combined techniques of Raman spectroscopy (dispersive and transmission TRS), X-ray powder diffraction and thermal analysis. Raman spectroscopy has been used to demonstrate a number of important aspects regarding the nature of the molecular interactions in the cocrystal. Cocrystals of salicylic acid - benzamide, citric acid-paracetamol and citric acid -benzamide have been identified with similar analytical approaches and structurally characterised in detail with single crystal X-ray diffraction. From these studies the high selectivity and direct micro sampling of Raman spectroscopy make it possible to identify spectral contributions from each chemical constituent by a peak wavenumber comparison of single-component spectra (API and guest individually) and the two- component sample material (API/guest), thus allowing a direct assessment of cocrystal formation to be made. Correlation of information from Raman spectra have been made to the X-ray diffraction and thermal analysis results. Transmission Raman Spectroscopy has been applied to the study cocrystals for the first time. Identification of new phases of analysis of the low wavenumber Raman bands is demonstrated to be a key advantage of the TRS technique.
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Pearce, Gordon M. "Synthesis, adsorption and catalysis of large pore metal phosphonates." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/823.
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The synthesis and properties of metal phosphonates prepared using piperazine-based bisphosphonic acids have been investigated. The ligands N,N’-piperazinebis(methylenephosphonic acid) (H₄L), and the 2-methyl (H₄L-Me) and 2,5-dimethyl (H₄L 2,5-diMe) derivatives have been prepared using a modified Mannich reaction. Hydrothermal reaction of gels prepared from metal (II) acetates and the bisphosphonic acids results in the synthesis of four structures: STA-12, Ni VSB-5, Co H₂L.H₂O and Mg H₂L. STA-12, synthesised by reaction of Mn, Fe, Co or Ni acetate with H₄L or H₄L-Me, has been investigated further. STA-12 crystallises in the space group R⁻₃, and Ni STA-12 is the most crystalline version. Its structure was solved from synchrotron data (a = b = 27.8342(1) Å, c = 6.2421(3) Å, α = β = 90°, γ = 120°), and it has large 10 Å hexagonal shaped pores. Helical chains of Ni octahedra are coordinated by the ligands, resulting in phosphonate tetrahedra pointing towards the pore space. Water is present, both coordinated to the Ni²⁺ cations and physically adsorbed in the pores. Mixed metal structures based on Ni STA-12, where some Ni is replaced in the gel by another divalent metal (Mg, Mn, Fe or Co) can also be synthesised. Dehydration of STA-12 results in two types of behaviour, depending on the metal present. Rhombohedral symmetry is retained on dehydration of Mn and Fe STA-12, the a cell parameter decreasing compared to the as-prepared structures by 2.42 Å and 1.64 Å respectively. Structure solution of dehydrated Mn STA-12 indicates changes in the torsion angles of the piperazine ring bring the inorganic chains closer together. Fe and Mn STA-12 do not adsorb N₂, which is thought to be due to the formation of an amorphous surface layer. Dehydration of Ni and Co STA-12 causes crystallographic distortion. Three phases were isolated for Ni STA-12: removal of physically adsorbed water results in retention of rhombohedral symmetry, while dehydration at 323 K removes some coordinated water forming a triclinic structure. A fully dehydrated structure (dehydrated at 423 K) was solved from synchrotron data (a = 6.03475(5) Å, b = 14.9156(2) Å, c = 16.1572(7) Å, α = 112.5721(7)°, β = 95.7025(11)°, γ = 96.4950(11)°). The dehydration mechanism, followed by UV-vis and Infra-red spectroscopy, involves removal of water from the Ni²⁺ cations and full coordination of two out of three of the phosphonate tetrahedra forming three crystallographically distinct Ni and P atoms. No structural distortion takes place on dehydration of Ni and Co STA-12 prepared using the methylated bisphosphonate, and the solids give a higher N₂ uptake as a result. Dehydrated Ni and Co STA-12 were tested for adsorption performance for fuel related gases and probe molecules. Investigations were undertaken at low temperature with H₂, CO and CO₂, and ambient temperature with CO₂, CH₄, CH₃CN, CH₃OH and large hydrocarbons. Due to the presence of lower crystallinity, Co STA-12 has an inferior adsorption performance to Ni STA-12, although it has similar adsorption enthalpies for CO₂ at ambient temperature (-30 to -35 kJ mol⁻¹). Ni STA-12 adsorbs similar amounts of CO₂ and N₂ at low temperature, indicating the adsorption mechanisms are similar. Also, it adsorbs 10 × more CO₂ than CH₄ at low pressure, meaning it could be used for separation applications. Ni STA-12 adsorbs 2 mmol g⁻¹ H₂ with an enthalpy of -7.5 kJ mol⁻¹, the uptake being due to adsorption on only one-third of the Ni²⁺ cations. The uptake for CO is 6 mmol g⁻¹, with adsorption enthalpies ranging from -24 to -14 kJ mol⁻¹. This uptake is due to adsorption on all the Ni²⁺, meaning the adsorption enthalpies are high enough to allow the structure to relax. This is also observed for adsorption of CH₃CN and CH₃OH, where there is a return to rhombohedral symmetry after uptake. The adsorption sites in dehydrated Ni and Co STA-12 were investigated via Infra-red spectroscopic analysis of adsorbed probe molecules (H₂, CO, CO₂, CH₃CN and CH₃OH). The results indicate the adsorption sites at both low and ambient temperature are the metal cations and the P=O groups. The metal cation sites are also characterised as Lewis acids with reasonable strength. STA-12 was shown to have acidic activity for the liquid phase selective oxidations of 1-hexene and cyclohexene, although there is evidence active sites are coordinated by products and/or solvents during the reaction. STA-12 also demonstrates basic activity for the Knoevenagel condensation of ethyl cyanoacetate and benzaldehyde. Modification of STA-12 by adsorption of diamine molecules causes a slight increase in the basicity, and the highest conversions are where water and diamine molecules are both present.