Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 99 for “"polymorph"”.
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Polymorph Selection with Morphology Control Using Solvents and Additives
Sulphathiazole is a highly polymorphic model system exhibiting at least five polymorphic forms: I, II, III, IV, and V. Polymorph stability is known to be susceptible to solvent environment, and it is established that 1-propanol stabilizes the most metastable form I. This study examines the effect …
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Molecular insights on the solvent effect of methanol additive in glycine polymorph selection
… crystallization, the effect of solvent on polymorph selection has gained tremendous interest in recent years. In this thesis, molecular simulation techniques are used to gain insight into the solvent effect on glycine crystallization in water-methanol mixtures. We report the validation of …
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Crystallography of Pharmaceuticals: Ways to improve efficiency and assessing the fragment-based approach for enhanced polymorph discrimination
… our ability to distinguish between different polymorphs of a chemical. In this portion of the thesis, we studied three organics: sulfanilamide, theophylline, and cocaine.
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Diversity of compressional mechanisms among SiO2 polymorphs : case of coesite and cristobalite
… its simple chemical composition by numerous polymorphs. More than 30 stable or metastable phases of silica are known, most of which occur at ambient to moderate pressures (<9 GPa). Understanding polymorphism and densification mechanisms in silica is not only important from a geomaterial point …
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Diversity of compressional mechanisms among SiO<sub>2</sub> polymorphs : case of coesite and cristobalite.
… its simple chemical composition by numerous polymorphs. More than 30 stable or metastable phases of silica are known, most of which occur at ambient to moderate pressures (<9 GPa). Understanding polymorphism and densification mechanisms in silica is not only important from a geomaterial point …
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Aspects of transformation behaviour in olivines, pyroxenes and titanomagnetites
… to its high-density, garnet-structure polymorph, majorite, and olivine has been transformed to its high-density, spinel polymorph. The majorite, which occurs with both equant and dendritic habit, is associated with a glassy phase, from which it crystallized, and with a microcrystalline …
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Control of polymorphism in continuous crystallization
… the systematic understanding of the control of polymorphism in continuous crystallization. Variations in the polymorphism of the active pharmaceutical ingredient can undermine the bioavailability and the downstream processability of the drug substance. Thus, precise control of the drug …
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Investigation of batch and continuous crystallisation processes using non-invasive Raman and acoustic emission spectrometries
… point, monitor crystal growth and identify the polymorphs formed. Non-invasive broadband acoustic emission (AE) spectrometry was also investigated as a means to monitor the crystallisation profile (by integrating the AE intensity over specific frequency ranges) and changes in particle size (by …
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A computational investigation of nucleation processes in organic crystals
… The first portion of the thesis examines polymorphism, or the ability of a material to pack in different crystal lattices whilst retaining the same chemical composition. Transformation to a more stable polymorph can readily occur in the solid state, which has broad implications in …
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Antisolvent crystallisation in oscillatory baffled platforms
… on product outcomes. Metastable form II polymorph of anthranilic acid was consistently produced in a continuous unseeded antisolvent crystallisation from an ethanol and water solvent system.;The incorporation of process analytical technology (PAT) allowed for monitoring of various process …
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Crystal engineering approaches to solid-state pharmaceutical systems
… reports a novel, relatively simple technique for polymorph screening of compounds that are thermally stable, wherein homopolymer surface interactions direct the polymorph of a drug recrystallising from the supercooled melt. The study carried out demonstrates the ability to selectively crystallise …
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Effect of Bacterial Strain on MICP and its Application for the Erosion Control of Fine Sands
… in vitro experiments it was found that CaCO3 polymorph selection can be controlled through selection of ureolytic strain with appropriate precipitation kinetics, and that metastable polymorph stabilisation is dependent on the kinetics of the mobile water contained within the crystal structure. …
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Crystal structure prediction. A molecular modellling study of the solid state behaviour of small organic compounds.
… seek possible crystal packing arrangements (or polymorphs) a compound may adopt. Based on the chemical diagrams, this thesis investigates polymorphism of several small organic compounds. Plausible crystal packings of those compounds are generated, and their lattice energies are minimised using …
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The effect of calcium and magnesium on carbonate mineral precipitation during reactive transport in a model subsurface pore structure
… reflected brightfield microscopy and mineral polymorphs were determined using Raman spectroscopy. Although Mg was present, only calcium carbonate (CaCO3) polymorphs were observed. The presence of Mg affected both the rate of precipitation and the prevalence of different CaCO3 morphologies. The …
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Physicochemical and tableting properties of crystallised and spray-dried phenylbutazone containing polymeric additives. Effect of polymeric additives (hydroxypropyl methylcellulose and a polyoxyethylene-polyoxypropylene glycol) on the crystalline structure, physicochemical properties and tableting behaviour of crystallised and spray-dried phenylbutazone powders
… soluble drug, phenylbutazone, in alternative polymorphic form and containing low levels of two hydrophilic polymers - hydroxypropyl methylcellulose (H. P. M. C. ) and the surfactant poloxamer 188 - prepared by both conventional crystallisation and spray drying are reported. As an integral nart …
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Environmental controls on the skeletal mineralogy of marine calcifiers
… carbonate (CaCO3). The two principle CaCO3 polymorphs used by marine calcifiers are aragonite and calcite. In the abiotic precipitation of CaCO3, the Mg/Ca ratio and the temperature are established controls of polymorph formation, but the importance of other factors, for example salinity, …
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Synthesis and characterization of novel fluoride and oxide cathodes for rechargeable batteries
… cathode materials: the dirutile and rutile polymorphs of LiMnF4, and layered lithium-excess . . . Dirutile LiMnF4 was identified from high-throughput computation as a promising conversion cathode. The dirutile polymorph was synthesized through a new low temperature route, and the rutile …
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Crystallization Kinetics and Phase Behavior of Molecular Solutions
… supersaturation on crystallization kinetics and polymorph selectivity; and (ii) to develop a generalized phase diagram from first principles and verify its applicability to a wide range of molecular solutions. This thesis investigates how the rate of supersaturation affects macroscopic phase …
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The molecular genetics of Type 2 diabetes
… markers, restriction fragment length polymorph isms (RFLPs), mutation screening, separation of PCR products and direct sequencing of them. <br></br><br></br> Chapter 3 investigates the role of the glucokinase gene in five pedigrees with maturity onset diabetes of the young (MOOY). …
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A novel view on the early stage of crystallization
… only calcite (the thermodynamically stable polymorph) is finally obtained, while with decreasing binding strength in clusters, vaterite (the thermodynamically least stable polymorph) and presumably aragonite (the thermodynamically intermediate stable polymorph) are obtained additionally. …
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