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1
Andrews, G. P. "Physicochemical characterisations of novel pharmaceutical polymer gel networks". Thesis, Queen's University Belfast, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397846.
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Hadrane, Bachchar. "Vanadates de métaux de transition à feuillets kagomé : effets de la microstructure et des substitutions cationiques sur les propriétés structurales, vibrationnelles, optiques et magnétiques". Electronic Thesis or Diss., Nantes Université, 2024. http://www.theses.fr/2024NANU4029.
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Cette thèse explore les effets de la microstructure et des substitutions cationiques sur les propriétés structurales, vibrationnelles, optiques et magnétiques de matériaux vanadates à feuillets Kagomé de cobalt et de zinc, dont les structures cristallines sont similaires à celles de minéraux (karpenkoite, martyite et vesignieite). La structure cristalline du pyrovanadate microstructuré Co3V2O7(OH)2·nH2O, préparé via la voie hydrothermale est résolue. Ses propriétés physicochimiques et magnétiques sont étudiées et comparées à celles reportées dans la littérature. L’effet de la substitution des ions Co2+ haut-spin par des ions Zn2+ est analysé pour une nouvelle solution solide microstructurée (Co1-xZnx)3V2O7(OH)2·wH2O. Les essais de synthèse du matériau Co3V2O7(OH)2·nH2O nanostructuré par coprécipitation à pression ambiante conduisent à un nouveau pyrovanadate microstructuré de formulation approchée NH4Co2.5V2O7(OH)2·H2O. Par ailleurs, l’orthovanadate BaCo3(VO4)2(OH)2 microstructuré est obtenu en utilisant Co3V2O7(OH)2·nH2O comme précurseur et ses propriétés sont comparées à celles d’échantillons nanostructurés récemment obtenus. Une telle comparaison est également réalisée pour le nouvel orthovanadate isostructural BaZn3(VO4)2(OH)2, préparé sous formes micro- et nanocristallisée. L’effet de la substitution cationique Co/Zn est étudié pour une nouvelle solution solide microstructurée Ba(Co1-xZnx)3(VO4)2(OH)2 et pour des échantillons nanostructurés de compositions similaires. Ce travail ouvre des possibilités d’études d’autres solutions solides analogues, comme Ba(Co1-xNix)3(VO4)2(OH)2This thesis explores the effects of microstructure and cationic substitutions on the structural, vibrational, optical, and magnetic properties of cobalt or zinc Kagome layered vanadate materials, whose crystalline structures are similar to those of minerals (karpenkoite, martyite, and vesignieite). The crystalline structure of the microstructured pyrovanadate Co3V2O7(OH)2·nH2O , prepared by the hydrothermal route, was solved. Its physicochemical and magnetic properties were studied and compared with those reported in the literature. The effect of the substitution of Zn2+ ions for high-spin Co2+ ions is analysed for a new microstructured solid solution (Co1-xZnx)3V2O7(OH)2·wH2O. Synthesis attempts of the nanostructured Co3V2O7(OH)2·nH2O material led to a new microstructured pyrovanadate with an approximate formula NH4Co2.5V2O7(OH)2·H2O. In addition, the microstructured orthovanadate BaCo3(VO4)2(OH)2 is obtained using Co3V2O7(OH)2·nH2O as a precursor and its properties are compared with those of recently obtained nanostructured samples. Such a comparison is also carried out for the new isostructural orthovanadate BaZn3(VO4)2(OH)2, prepared in micro- and nanocrystallised forms. The effect of Co/Zn cationic substitution is studied for a new microstructured solid solution Ba(Co1-xZnx)3(VO4)2(OH)2 and for nanostructured samples of similar compositions. This work opens up the possibility of studying other analogous solid solutions, such as Ba(Co1-xNix)3(VO4)2(OH)2
3
Trainor, D. M. "Physicochemical characterisation of cystic fibrosis sputum". Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398172.
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Griffith, Vivienne Jean. "Physicochemical characterisation of cyclodextrin-drug complexes". Doctoral thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/25979.
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The cyclodextrins and their derivatives are finding increasing application in the pharmaceutical industry as carrier molecules for many drugs, as complexation can result in improved physical characteristics such as increased aqueous solubility and dissolution rates. The aim of this work was to prepare solid cyclodextrin complexes with selected drugs which have already been shown to interact with cyclodextrins in solution and ultimately to grow crystals of these inclusion complexes of sufficient quality for single crystal X-ray structure determination. The designated drugs included an antibacterial, sulfathiazole; three non-steroidal anti-inflammatory drugs (NSAIDs), (S)-naproxen and the sodium salts of diclofenac and meclofenamic acid; and (L)-menthol, a compound used in many pharmaceutical preparations. The chosen host molecules were ,β-cyclodextrin, γ-cyclodextrin, heptakis(2,6-di-O-methyl)-, β-cyclodextrin (DIMEB) and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB). The unit cell parameters of thirteen cyclodextrin-drug complexes and of TRIMEB monohydrate were determined by X-ray photography and the cry tal structures of six of these complexes and of TRIMEB monohydrate were solved. The water content of the complexes was established by thermogravimetric analysis and the host:guest stoichiometries of those complexes whose crystal structures were not solved were determined by UV spectrophotometry or, in one case, by a combination of NMR and thermogravimetric analysis. The complexes were also characterised by differential scanning calorimetry. Hot stage microscopy was a useful method for initial testing for the formation of inclusion complexes of the native cyclodextrins, since their behaviour on heating differs markedly from that of the relevant host alone. The events observed could be correlated with the thermal analyses of the complexes. Complexes which contained alkali metal cations appeared to retain water molecules of crystallisation to higher temperatures, on average, than those which did not. XRD patterns were calculated from the crystal structures which were solved and matched the experimental patterns of the prepared samples well. The calculated patterns serve as the best references for establishing the identity and purity of prepared complexes. Host-guest interactions included hydrogen bonding, van der Waals contacts and hydrophobic interactions. Guest molecules maintained similar conformations on the whole as those observed in other crystal structures containing these particular guests. Conformations of the hosts were akin to those found in known crystal structures, except in TRIMEB monohydrate, where the TRIMEB conformation was distorted to a remarkable extent even in comparison with the distorted conformations observed in its complexes. In addition, one of the methylglucose residues is present in the ¹C₄ inverted chair conformation which has not been observed before in the cyclodextrins or their complexes in the solid state. The invariable occurrence in the TRIMEB host of C(6Gn)-H···0(5Gn-1) hydrogen bonds noted in this study is partly responsible for the uniformity in the conformation of TRIMEB in its complexes. The packing arrangement found in the diclofenac sodium-β-CD complex is unique and is the first example of a β-CD complex crystallising in the hexagonal crystal system. The inclusion by β-CD of meclofenamate sodium (a structural isomer of diclofenac sodium) is similar to that of diclofenac sodium, but the packing arrangement is different and while unique for a complex of unsubstituted β-CD, resembles the packing arrangement found in most of the known TRIMEB complexes.
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Badruddin, Ahmad Fasihuddin. "Physicochemical characterisation and properties of sago starch". Thesis, University of Salford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265740.
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Pena, Marcos Miguel Gonzalez. "Comparative physicochemical characterisation of thermally modified wood". Thesis, Bangor University, 2007. https://research.bangor.ac.uk/portal/en/theses/comparative-physicochemical-characterisation-of-thermally-modified-wood(544e97d3-72ad-444e-9ebc-4a5076663cd9).html.
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Small matched samples of beech, Scots pine and Norway spruce woods were heattreated to twenty schedules, at temperatures of 190, 210, 230 and 245°C for heating periods of 0.3, 1, 4, 8 and 16 h. Following thermal modification, physical changes and chemical composition in thermally modified wood (TMW) were analysed and compared to the characteristics of untreated materials. Most of the analysis were carried out using the heat-induced weight loss values (WL, %) as the independ~nt variable to make the comparisons. Average treatment WL values ranged from 0.3 to 27.0, from 0.6 to 21.5, and from 1.0 to 26.7 for beech, pine, and spruce samples respectively. A major finding of this research was that each characteristic changed following the same profile in the three wood species for all properties studied. Save for hardness in beech, the magnitude and rate of change of each property was often found not to be significantly different between species when relative-to-control values in function ofthe WL were compared. The results show that the gravimetric and dimensional changes in the transverse plane are mainly due to chemical breakdown of wood hemicelluloses. On the other hand, the readiness ofTMW to dimensional changes and moisture uptake below the FSP was of a much lower concern than in raw wood. Similarly, several mechanical properties were found to be little affected by heat exposure at treatment levels likely to be achieved industrially. Among these were compression strengths parallel and perpendicular to the axis in the tangential direction, and the axial modulus of elasticity in bending (MOE). Other mechanical strength parameters (e.g. shear strength, hardness and the modulus of rupture in bending) were reduced at almost any given treatment schedule, but the rate of reduction was mild. It is contended that design practices could make up for the strength loss incurred by the treatment for these properties. On the other hand, parameters related to the energy required to produce failure and also impact strength were greatly diminished at low levels of modification. This may restrict the use of TMW where unpredictable sudden loads may occur. Properties at the limit of proportionality were found to be less reduced than the same property at maximum load. Mechanical properties more affected by heat were found to be those more intimately related to the chemical integrity of the wood material and/or the structural configuration of wood polymers in the cell wall substance, whilst compression strength and hardness were more related to wood density. MOE was proposed to be more dependent of cellulose, microfibril angle and wood density, all of these little altered by wood heating. Lastly, a description of the colour changes in the test samples was undertaken using image analysis and qualitatively by infrared spectroscopy. It was determined that colour changes in wood were caused mainly by changes in the lignin. The major input of this work to the state of the art is given by modelling the properties studied using various linear, non-linear and multivariate methods. Properties in TMW were estimated from gravimetric, colour and moisture-related parameters. Solid-state mid-infrared spectra data, treatment parameters and interrelationship between variables were also explored. It is concluded that all changes in small heated samples of wood are amenable to be estimated efficiently in multiple ways, using cost-effective indicators. Remarkably encouraging results for the prediction of physical properties were found for models using colour parameters or by the analysis of the infrared spectra data. Whilst descriptions of the heat-induced changes in wood exist, prediction studies are fairly scarce and not comprehensive. This part of the study is thus very timely, giving the current requirements of quality control and assurance of TMW at the industrial stage. The relevance of these fmdings to property prediction in larger wood members would depend on the property considered; safety factors will probably be needed for some forms ofwood strength in larger heated materials.
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Stone, Lisa Ann. "Physicochemical characterisation of disease associated abnormal prion proteins". Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1446127/.
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The central feature of prion disease is the conversion of normal host-encoded cellular prion protein, PrPc, to an abnormal isoform, PrP. PrP80 appears to be the principal, if not the sole, component of infectious prions. Prion strain diversity seems to be encoded within PrP itself through a combination of PrP conformation, glycosylation and possibly other, as yet, unidentified post-translational modifications. Efficient purification of PrP will facilitate detailed chemical characterisation and investigation of conformations or assembly states required for prion infectivity. Purification of denatured PrP has been achieved through enrichment from brain homogenate using selective precipitation followed by chemical and thermal denaturation and isolation by immunoafTinity chromatography. These methods have isolated PrP from rodent prion strains with a yield of 50 % and purity of > 90 % of total protein and for the first time permit isolation of full length denatured PrPSc facilitating comprehensive structural analysis. Purified denatured PrP is expected to have all the covalent post-translational modifications that may be required for prion infectivity. In attempts to reconstitute prion infectivity, denatured PrP was refolded under different solvent conditions and assessed for changes in solubility, resistance to proteolytic digestion and infectivity in bioassay. Although distinct changes in the physicochemical properties of PrP were observed, to-date no evidence for reconstitution of prion infectivity has been found. In the course of these studies, it was discovered that Cu2f ions inhibit proteinase K activity and a detailed kinetic description of this inhibition was obtained. The lack of prion infectivity seen in refolded preparations of denatured PrP suggests a requirement for other as yet unidentified co-factors. The identity of PrP interacting proteins was investigated during the purification of PrP under differential extraction conditions in which prion infectivity was observed using an in vitro assay. Proteinase K digestion gave a change in prion infectivity implying that a correlation with the removal of a protease sensitive component occurred. Continuation of these studies may facilitate the identification of co-factors required for specific prion infectivity.
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Ngilirabanga, Jean Baptiste. "A supramolecular derivatised study of BIS(Adamantan-1- Aminium) carbonate". University of the Western Cape, 2014. http://hdl.handle.net/11394/4188.
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Magister Pharmaceuticae - MPharmIn this study, new solid supramolecular derivatised forms of bis(adamantine-1-aminium) carbonate (ADTCO3) were prepared. ADTCO3 is a derivative of amantadine used for Parkinson’s disease and has antiviral properties against influenza-A, dengue fever and pharmacological activity towards Parkinson’s disease. The new forms prepared were polymorphic and co-crystal forms of ADTCO3. Polymorphism is a phenomenon where the ability of a substance to exist in two or more crystalline forms occurs when crystallised under different conditions and co-crystallization is the process of formation of multicomponent crystals of a drug substance. New solid forms often display different mechanical, physicochemical and thermal properties that can remarkably influence the bioavailability, hygroscopicity and stability of active pharmaceutical ingredients (APIs). For the formation of polymorphs of ADTCO3, techniques such as dry grinding, solvent-drop grinding, co-precipitation, sublimation and vapour diffusion were applied. For the development of co-crystals and/or complex formation, ADTCO3 was treated in combination with ten selected co-formers viz; benzoic acid, 4-hydroxybenzoic acid, cinnamic acid, 4-hydroxycinnamic acid, succinic acid, tartaric acid, salicylic acid, L-glutamic acid, citric acid monohydrate and L-glutaric acid using similar techniques as applied in the polymorphism study. The first four co-formers were selected for their potential biological activity and the latter six were selected for their generally regarded as safe (GRAS) status. All products were isolated and characterized using different analytical techniques to assess the thermal behaviour of the products by hot stage microscopy (HSM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). FTIR spectroscopy and proton-nuclear magnetic resonance (1HNMR) were used to identify and determine the purity of the parent compounds and the modified forms. X-ray powder diffraction was used to determine the formation of a new phase and single crystal X-ray diffraction was applied at the initial stages to identify ADTCO3 by its unit cell parameters. Furthermore, the Cambridge Structural Database (CSD) and other resources were used to generate information on the molecular structures of all elucidated parent compounds, their polymorphs and reported co-crystals. Four different polymorphic forms of ADTCO3 were identified (viz. ADTCO3 Forms I to IV) and sixteen co-crystals (viz. ADTCO3BA1 to ADTCO3BA5, ADTCO3HBA, ADTCO3CIN, ADTCO3HCIN, ADTCO3SUC, ADTCO3LTTA, ADTCO3SA, ADTCO3CA, ADTCO3GLA, ADTCO3GA) were synthesised. Of the sixteen co-crystals 5 were identified as ADTCO3BA “salt” co-crystal polymorphic forms and 2 as ADTCO3SUC co-crystal polymorphic forms. Two solvated “salt” co-crystal forms were also identified, namely; ADTCO3GLA and ADTCO3LTTA. ADTCO3GLA had a mass loss of 10.3% (n = 2.4) and ADTCO3LTTA had a mass loss of 5.25% (n = 0.86). Finally, the rest of the co-crystals ADTCO3HBA, ADTCO3CIN, ADTCO3HCIN, ADTCO3SA, ADTCO3CA and ADTCO3GA all crystallised as “salt” co-crystals.
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Fisk, Ian. "Physicochemical characterisation of sunflower seed oil bodies ex-vivo". Thesis, University of Nottingham, 2007. http://eprints.nottingham.ac.uk/13575/.
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Oilseeds store energy as triacylglycerides during periods of dormancy in preparation for germination and the early stages of development. The triacylglyceride is stored in discrete organelles termed oil bodies. Oil bodies are formed during the synthesis of neutral lipids within the bilayer of cellular endoplasmic reticulum (ER); as lipid is synthesised it forms droplets of oil that swell distending the ER membrane and at a critical diameter separate from the ER by vesiculation forming independent organelles. These organelles are structurally stabilised by a phospholipid monolayer originating from the ER and the addition of highly amphiphilic oleosin proteins. Oil bodies have been shown previously to be extremely stable organelles that can be easily extracted and purified from oilseeds; our aim was to develop an understanding of the physical and chemical properties of sunflower oil bodies ex-vivo prior to their subsequent use in commercial products. Several novel findings were elucidated through this work: oil body phytochemical composition, their physical and oxidative stability and their ability to store and deliver flavour compounds. It was hypothesised that tocopherol is tightly associated with sunflower oil bodies. This was tested by recovering oil bodies from sunflower seed and washing them to remove extraneous proteins and associated phenolic compounds. Tocopherol remained with washed oil bodies (392 mg tocopherol.kg-1 oil body oil) and this population of tocopherol represented 38% of the total seed tocopherol. It was hypothesised that this high tocopherol concentration and its intrinsic association to oil body structures would contribute to an increased level of oxidative stability. Sunflower seed lipids were significantly more resistant to thermally induced oxidation when stabilised in oil body suspensions compared to sunflower oil emulsions stabilised by a range of commercial emulsifiers (sodium dodecyl sulfate, polyoxyethylenesorbitan monolaurate (tween 20) and dodecyltrimethylammonium bromide). Oxidative stability was assessed through lipid hydroperoxide concentration and the concentration of headspace hexanal. Maximum lipid hydroperoxide concentration in surfactant stabilised emulsions after 8 days at 45oC ranged between 26 and 333 mmol lipid hydroperoxide.kg-1 oil whereas lipid hydroperoxide concentrations in oil body suspensions did not exceed 12 mmol lipid hydroperoxide.kg-1 oil. In addition there was no development in oxidative rancidity over the 8 day storage trial of oil bodies stored at 5oC. The composition of phospholipids in a range of oil body preparations was assessed; purified oil bodies contained principally phosphatidylcholine (91%) and a smaller fraction of phosphatidylethanolamine (9%). Less purified preparations contained other phospholipid species; the presence of which was explained by contamination with either non-intrinsic cellular phospholipids or phospholipase D that catalysed the breakdown of phospholipids to phosphatidic acid. Mechanisms and the extent of oil body physical stability were assessed using charge analysis and resistance of oil body preparations to changes in temperature and pH. Oil bodies are stabilised by a combination of steric hindrance and electrostatic repulsion provided by the surface proteins and phospholipids. Oil bodies had a zeta potential of -30mV at neutral pH and the surface charge was pH dependant with an apparent isoelectric point of between pH3 and pH6 was calculated from electrophoretic mobility, streaming potential and creaming stability measurements. Purified oil bodies were physically stable to thermal stresses up to 45oC for 2 days, although less purified preparations lost structural integrity at temperatures above 25oC. When assessed for their ability to delivery flavour molecules, oil bodies had comparable bulk phase properties to artificial emulsions stabilised by tween 20. Oil bodies did show a greater rate of flavour delivery during headspace dilution, when compared with the model artificial emulsions, suggesting commercial benefits may be gained through the incorporation of oil bodies into commercial emulsions. The key findings of this work are that oil bodies are extremely stable organelles that are resistant to thermal stress and physical processing. When lipid is stored within oil bodies it has greater resistance to the onset of lipid oxidation which may be explained by the intrinsic association of phospholipids, proteins and phytochemicals (vitamin E).
10
Wood, David. "Physicochemical characterisation of pluronic block copolymers in aqueous solutions". Thesis, King's College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441991.
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Odlyha, Marianne. "Characterisation of cultural materials by measurement of their physicochemical properties". Thesis, Birkbeck (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247062.
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Jasim, Dhifaf. "Graphene oxide derivatives for biomedical applications". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/graphene-oxide-derivatives-for-biomedical-applications(83c552dc-50f6-4771-95b4-d1aace0db493).html.
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Graphene-based materials (GBM) have recently generated great interest due to their unique two-dimensional (2D) carbon geometry, which confers exceptional physicochemical properties that hold great promise in many fields, including biomedicine. An understanding of how these novel 2D materials interact with the biological milieu is therefore fundamental for their development and use. Graphene oxide (GO) has been proven more biologically friendly than the highly hydrophobic pristine graphene. Therefore, the main aim of this study was to prepare well-characterised GO derivatives and test the hypothesis of their possible use for biomedical applications. GO was prepared reproducibly by a modified Hummers' method and further functionalised by using a radio-metal chelating agent, namely 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) to form GO-DOTA. The constructs were extensively studied using structural, optical and surface characterisation techniques. GO prepared from different forms of graphite demonstrated differences mainly in structure and production yields. However, all GO constructs were found biocompatible, with the mammalian cell cultures tested; furthermore, the biocompatibility of GO prepared as papers was retained when they were used as substrates for cell growth. Radiolabelling of GO-DOTA was further carried out to yield highly stable radio-labelled constructs, both in vitro and in vivo. These constructs were used for in vivo whole-body imaging and biodistribution studies in mice after intravenous administration. Extensive urinary excretion and accumulation mainly in the reticuloendothelial system (RES), including the spleen, liver and lungs, was the main fate of all the GO derivatives used in this thesis. The physicochemical characteristics were determined to play a central role for their preferential fate and accumulation. While the thicker sheets tended to accumulate mainly in the RES, the thinner ones were mostly excreted via the kidneys. Finally, it was crucial to perform safety investigations involving the structure and function of organs at high risk of injury (mainly the kidney and spleen). Our results revealed that no severe structural damage or histopathologic or functional abnormality of these vital organs. However, some preliminary inflammatory responses were detected that require further investigation. In summary, this study helped gain a better understanding of how thin 2D materials interact with biological barriers and the results indicate that these materials could be potential candidates for biological applications. Nevertheless, further investigations are necessary to confirm our findings.
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Örnskov, Eivor. "Physicochemical and Biopharmaceutical Characterisation of Small Drug Molecules by Capillary Electrophoresis". Doctoral thesis, Uppsala University, Analytical Chemistry, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4008.
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Capillary Electrophoresis (CE) was explored as a means for physicochemical and biopharmaceutical characterisation of small drug molecules. Special attention was paid to the characterisation of acid-base and lipophilic properties of drug compounds by analysing their migration behaviour in different CE systems. The thesis comprises an overview of the field together with separate studies on the different topics.
The utility of CE for the determination of pKa of labile drug compounds was investigated. A general methodology was developed comprising key steps such as the use of a stabilising sample diluent, electromigration injection, and analyte characterisation by UV-Vis spectroscopy. The methodology was successfully applied for two sets of drug compounds, labile at low and high pH, respectively.
CE was also evaluated for experimental modelling of passive intestinal membrane permeability by studying analyte migration in liposomal, microemulsion and micellar electrolytes. Good correlation is reported between CE migration and Caco-2 cell absorption estimates and for in vitro inhibition of thrombin. Interestingly, a slightly better correlation was obtained for liposomal electrolytes.
The utility of liposomes in CE was further extended by developing a novel procedure for immobilising liposomes inside fused silica capillaries. This approach enabled direct on-line coupling of liposome CE to high sensitivity mass spectrometry. The utility of liposome-coated capillaries is demonstrated for estimating drug passive intestinal membrane permeability. Its use in biopharmaceutical drug profiling is discussed.
Utilising advanced molecular descriptors, commonly applied to in silico prediction of passive intestinal membrane permeability, migration of analytes in micellar CE systems could be well predicted. The novel approach was based on hierarchical multivariate analytics and use of molecular descriptors for both analytes and micellar media surfactants. Demonstrated results propose that the CE format could be useful to validate how representative molecular descriptors are for describing molecular behaviour in complex liquid media, e.g. physiological systems.
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Douglas, Mary Joan Paula. "Physicochemical characterisation of bioactive biodegradable polymers prepared using hot melt extrusion". Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492148.
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This work set out to characterise the extent to which the model antibacterial drug Nalidixic Acid (NA) affected the biodegradable polymer Polycaprolactone in terms of its' mechanical, thermal, and morphological properties alongside any changes in topography and by creating a monolithic dispersion for drug release. Also considered were the additional effects that a Polyethylene Glycol pore former and copolymer Poly l-lactide had on the Polycaprolactone and the Nalidixic Acid release profile. Overall it appeared that the addition of the NA caused the mechanical modulus to improve, producing increased stiffhess and less ductility in the blends. However, this stiffening led to attenuated strength and elongation. In terms ofthe thermal properties, a nucleating effect due to NA was noted alongside a decrease in crystallisation kinetics which led to the changes in mechanical properties. It was found that the Nalidixic Acid and Poly l-lactide acted as a filler material within the Polycaprolactone matrix, increasing the viscosity of the blends, which would influence subsequent processing temperatures and shear rates. The opposite effect was observed with the use of the Polyethylene Glycol, whereby, due to its low molecular weight it acted as a lubricating agent, thus decreasing the viscosity. The variations in the mechanical, thermal and morphological properties of the blends were ascribed to the immiscibility of the Polycaprolactone with the other materials, each existing as separate phases within the blends. The Nalidixic Acid release profiles indicate that rapid device exhaustion times and higher extent ofdrug release was observed when the blends were prepared by twin screw extrusion (to increase dispersion) and crash cooled (to increase Nalidixic Acid solubility). Overall no detrimental effects were noted on the Polycaprolactone matrix when used as a drug delivery vehicle for Nalidixic Acid, with the bulk Polycaprolactone remaining relatively unchanged.
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Heinz, Andrea, e n/a. "Novel approaches for physicochemical characterisation and quantification of amorphous pharmaceutical compounds". University of Otago. School of Pharmacy, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080924.133134.
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The amorphous state is becoming increasingly important in the pharmaceutical setting. Formulation of poorly water soluble drugs in the amorphous form enhances physicochemical properties of the drug, such as solubility and dissolution rate, which in turn may lead to an increased bioavailability. However, despite these advantages, many properties of the amorphous state are not yet understood and amorphous materials pose a challenge for structural analysis since they lack three dimensional long range order. Hence, compared to crystalline materials often little structural information can be gained using standard characterisation techniques.
In this thesis, a range of analytical techniques and data analysis tools were used to characterise as well as quantify amorphous drugs and compare them to their crystalline counterparts. Apart from established characterisation techniques such as X-ray powder diffraction, microscopy, and differential scanning calorimetry, molecular-level characterisation was carried out using vibrational spectroscopies including infrared, near infrared, and Raman spectroscopy combined with multivariate analysis methods. To obtain deeper understanding of the structure of amorphous drugs and their corresponding crystalline forms novel approaches such as pair distribution function analysis of X-ray diffraction data and computational chemistry were employed.
Three model drugs namely indomethacin, saquinavir, and fenofibrate were investigated in the scope of this thesis. For indomethacin differences between amorphous forms of indomethacin prepared by ball milling, spray drying, as well as melting and subsequent cooling were analysed using infrared, near infrared, and Raman spectroscopy in combination with principal component analysis. While all spectroscopic techniques were able to differentiate between the differently prepared samples, Raman spectroscopy proved to be most sensitive to small differences in the solid state of different samples. Consistent with the study of indomethacin, Raman spectroscopy combined with principal component analysis was the most sensitive analytical technique to detect structural changes induced by milling or heating saquinavir. In addition, pair distribution function transforms of the X-ray powder diffraction data significantly contributed to the understanding of differences in short-range and long-range order between differently treated saquinavir samples.
A combination of vibrational spectroscopy, quantum mechanical calculations, and multivariate analysis proved suitable for physicochemical analysis of amorphous fenofibrate. The results of the study support the idea that non hydrogen bonded molecules such as fenofibrate are likely to exhibit random molecular orientations and conformations in the amorphous phase since the weak intermolecular interactions that occur between such molecules can easily be disrupted.
A study of ternary mixtures of crystalline and amorphous forms of indomethacin showed that Raman and near-infrared spectroscopy in conjunction with PLS regression are well suited for quantification of the different solid-state forms simultaneously. It was found that near-infrared spectroscopy can be used to more accurately quantify the mixtures compared to Raman spectroscopy when fluorescing components, such as amorphous indomethacin, are present. Nevertheless quantification with Raman spectroscopy was still possible.
Overall, the analytical methods used in this thesis were successfully employed for qualitative and quantitative analysis of amorphous drugs and their crystalline counterparts. It could be shown that it is beneficial to use a combination of different analytical techniques and data analysis tools since results are complementary and allow a more comprehensive description of the solid state.
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Correia, Paula Maria dos Reis. "Physicochemical, morphological, functional and structural characterisation of chestnut and acorn starch". Doctoral thesis, ISA/UTL, 2010. http://hdl.handle.net/10400.5/3707.
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Wallace, Rachel. "Physicochemical characterisation of zinc oxide nanoparticles for use in toxicity studies". Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/5899/.
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This thesis is focused on the detailed physicochemical characterisation of zinc oxide (ZnO) nanoparticles (NPs) intended for use in toxicological investigations. A characterisation protocol has been developed in order to determine detailed physicochemical characteristics of 5 ZnO NP samples, selected to investigate in in vitro toxicity assays. The characterisation protocol aims to establish the samples’ distribution of particle sizes, morphology, crystallinity, phase content, purity, surface composition, dispersion and solubility and as such includes the following techniques: inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD), BET gas adsorption, thermogravimetric analysis with evolved gas analysis by Fourier transform infra-red spectroscopy (TGA-EGA with FTIR), FTIR, X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance spectroscopy (NMR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), plunge freezing transmission electron microscopy (PF-TEM) and Zeta potential measurement. Initially 12 commercial samples were sourced and screened using TEM to obtain information on the average particle size. 3 of the commercial samples were then selected to carry forward to toxicity studies: EN-Z-1, EN-Z-2 and EN-Z-3. Synthesis of ZnO NPs was investigated in house by a flame spray pyrolysis and a polyol route; 2 synthesized samples were carried forward to the toxicity studies: EN-Z-4 and EN-Z-6. A coating was detected on the surface of EN-Z-1 (a colloidal suspension in water), identified as an aliphatic polyether (TGA-EGA, FTIR, XPS and NMR). Physically and chemically adsorbed H2O and CO2 was detected at the surface of the other 4 samples, which were all dry powders. A small amount hydrozincite was present in EN-Z-2 and EN-Z-3, identified by XRD, TGA-EGA, FTIR, XPS and NMR. Additionally, a small amount of diethylene glycol was identified on the surface of EN-Z-6, left over from synthesis. The dispersion and solubility of the samples in water, Dulbecco’s modified Eagle Medium (DMEM) and bovine serum albumin (BSA) was investigated by DLS, PF-TEM and ICP-MS the results of which are presented in Chapter 6. Most samples showed similar dissolution kinetics and equilibrium solubility with the exception of EN-Z-1 which showed slower dissolution, presumably due to the coating present on the NPs. Due to the equilibrium solubility of ZnO in DMEM, for concentrations of ZnO below 10 μg/ml, a significant amount is dissolved or re-precipitated as zinc carbonate. The agglomeration and solubility of ZnO NPs was found to increase when suspended in DMEM as compared to in water. The solubility of ZnO was found to increase with decreasing solution temperature (37 and 25 ºC). The addition of BSA was found to have a dispersing effect on ZnO NP suspensions. PF-TEM was investigated as an alternative technique to DLS for measuring size distributions of ZnO NPs in suspensions. It was determined that PF-TEM measurements give an accurate representation of the range of agglomerates in the suspension, however the sampling size is very low and data processing is time consuming and therefore the technique should be used as a complementary technique to DLS. The cytotoxicity and genotoxicity of ZnO NPs was assessed using the MTT (thiazolyl blue tetrazolium bromide) and comet assay respectively. A lower toxicity was measured for ZnO NP powder samples as compared to the coated colloidal dispersion. The polymer coating enhances NP interaction with lipid membranes which may increase toxicity through increased cellular uptake followed by intracellular dissolution. Coated and uncoated ZnO NPs are taken up by A549 cells and were located in both the cytoplasm and the nucleus. In cells exposed to 100 μg/ml EN-Z-4 and EN-Z-6, smaller than primary particle size NPs were located in the cells, suspected to be zinc carbonate particles formed from dissolved zinc precipitating from solution in the extracellular or intracellular environment.
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He, Jing. "Physicochemical characterisation of organic materials of interest for astrobiology : Titan's aerosols analogues". Phd thesis, Ecole Centrale Paris, 2013. http://tel.archives-ouvertes.fr/tel-01000229.
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Since the achievement of the first results from the Cassini Huygens mission, Titan's aerosols present an astrobiological interest as their characterization enables to evaluate the prebiotic chemistry that occurred on the primitive Earth. To better understand the physical chemistry of the aerosols of Titan is important for scientists. The laboratory via analyzing the properties of tholins (analogues of Titan's aerosols) overcomes the difficulties for analyzing Titan's aerosols directly. In this thesis work, the research object is tholins produced by the PAMPRE experiment. Pyr-GC-MS analysis technique was used to characterize the composition and structure of tholins. The thermal stability and the properties change with the temperature have been realized by thermal degradation study. Finally, the evolution of organic aerosols after precipitation on the surface of Titan was also investigated through GC-MS analysis of tholins. The results obtained can be used to interpret data collected by observations of Titan from Earth or by the Cassini-Huygens probe, to better characterize the satellite and its evolution.
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Belhaja, Hanan. "Synthesis and Physicochemical Characterisation of Poly (?-caprolactone) Nanoparticles for Delivery of Propranolol". University of the Western Cape, 2017. http://hdl.handle.net/11394/6153.
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Magister Pharmaceuticae - MpharmCardiovascular diseases (CVDs) are a major cause of morbidity and mortality in both developed and developing countries; and account for around 30% of all deaths worldwide. Reports indicate that nanoparticle (NP) based drug systems are likely to meet the urgent demand for breakthrough innovation in CVDs therapy and diagnosis. NPs have the potential to improve pharmacokinetics and efficacy and reduce the toxicity of cardiovascular drugs. Propranolol is a non-selective beta blocker, and has long been used in the treatment of hypertension, angina and other CVDs. Propranolol has a short half-life (between 2-3 h) and exhibits toxicity, including bronchospasm, due to non-selective beta receptor stimulation. The aim of this study was to develop an NP drug delivery system for propranolol; studying the parameters around formulation of the NPs and their performance in-vitro.
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Hamill, Turlough Malachy. "Physicochemical and in vitro biological characterisation of novel hydrogel systems as urological biomaterials". Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527928.
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Du, Char My. "The application of physicochemical descriptors to the characterisation of liquid and solid phases". Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307650.
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Brown, Gavin Robert. "The physicochemical characterisation of cyclodextrin inclusion compounds with non-steroidal anti-inflammatory drugs". Thesis, University of Cape Town, 1997. http://hdl.handle.net/11427/23177.
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The cyclodextrins and their derivatives have been utilised as complexing agents for a wide range of pharmaceutical compounds, through their ability to include small molecular weight molecules inside an annular cavity formed by linked glucose residues of varying number. The non-steroidal anti-inflammatory drugs (NSAIDs), a group of agents that share a similar therapeutic effect in the management of inflammatory processes in the body, have been studied as guest molecules for inclusion in cyclodextrins, due to a number of potential advantages that are conferred by complexation, such as improved bioavailability, modified side-effect profiles and the control of drug release from novel formulations. This study has tested a number of commonly used NSAIDs belonging to certain structural groups, together with a number of cyclodextrins and their derivatives, and attempts have been made to prepare complexes in the solid state and characterise them using physicochemical methods. The cyclodextrins used were native seven' and eight-membered β- and y-cyclodextrin and two methylated derivatives of β-cyclodextrin, namely heptakis(2,6-di-0-methyl)-β-cyclodextrin and heptakis(2,3,6- tri-O-methyl)-β-cyclodextrin, abbreviated as DIMES and TRIMEB respectively. NSAIDs belonging to the salicylate, fenamate, profen, oxicam and indene structural groups were used. These included diflunisal, mefenamic acid, niflumic acid, tolfenamic acid, flufenamic acid, ibuprofen, ketoprofen, piroxicam, tenoxicam, indomethacin and sulindac.
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Bhatia, Radhika. "Characterisation of the combined effects of physicochemical parameters and toxicants on microbial cells". Thesis, University of Bedfordshire, 2005. http://hdl.handle.net/10547/622046.
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This thesis reports on the combined effects of toxicants and physicochemical factors on micro-organisms. The main objective of the project was to use multi-sensing systems such as mediated and non-mediated sensor systems, growth tests and physicochemical sensors to investigate novel stressor-toxicant-assay combinations. Screen-printed, disposable, developmental-phase, physicochemical sensor constructs (conductivity and dissolved oxygen) were validated under conditions compatible with microbial bioassays, to ascertain their potential role in toxicity testing. The conductivity sensor construct could be used to indirectly inform on the osmolality of the test samples, but the dissolved oxygen sensor construct was not found to give reproducible results. The results were thought to be compromised by in-house screen-printing using a complex carbon ink formulation for the working electrode. Escherichia coli and a consortium with ammonia oxidation capacity (CAOC) were used as the test species for the bioassays. The combined effects of four inorganic salts (NaCl, NaN03, KCl and KN03) and two toxicants (3,5-DCP and HgCh) on E. coli were investigated using the CellSense™ biosensor system, Clark oxygen electrode and microtitre plate growth assays. A variety of trends were observed with each salt-toxicantbioassay combination, emphasising a need for better understanding of the assay media and factors such as bioavailability, to interpret the toxicity data. The results also suggested the importance of using multiple bioassays with varied end points, for toxicity testing. The CAOC, which was isolated from the activated sludge, was tested for physicochemical stressor and toxicant effects using the mediated biosensors. The results were very different from those obtained with E. coli, indicating that each species reacts to toxicants and changes in physicochemical factors differently. Although the full potential of disposable, physicochemical sensors, at the point of toxicity testing was not achieved, the study did investigate previously uncharacterised, combined effects of salts and toxicants on microbial cells. It highlighted the need for development of hybrid systems and also offered a route towards integration of physicochemical and biological sensing systems for simultaneous monitoring of both environmental and biological elements.
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Margetson, D. N. "The Physicochemical and Rheological Characterisation of Drug-Polymer Systems Prepared by Hot-Melt Extrusion". Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517548.
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Bachelet, Marie. "Synthesis, physicochemical characterisation and biological evaluation of polymer-functionalised gold nanoparticles for cancer treatment". Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/58270.
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Most of the chemotherapeutics employed today are facing important limitations, including the inability to provide targeted therapy and intracellular drug degradation within the lysosomal compartments. These explain why the average survival rate, throughout all cancer types, is still as low as 50%. The aim of the present thesis is to develop multifunctional AuNPs for intracellular delivery. PEGylated AuNPs were prepared via grafting poly(ethylene glycol) onto the AuNP surface. The influence of the PEG chain length and grafting densities on the colloidal stability, the grafted polymer conformation, the stealth character and the interparticle interactions have been extensively investigated. Longer chain lengths favoured the stability of the colloids in aqueous solution and the preparation of long-range and ordered assemblies via “flexible” interparticle interactions whereas shorter chain lengths led to denser layers and “hard-to-contact” spheres. Highly stable biocompatible pH-responsive AuNPs were obtained through the grafting with the anionic poly(L-lysine isophthalamide) (PLP) conjugated with L-phenylalanine at 75 mol% (PP75). The polymer pH dependent coil-to-globule conformational change was retained between pH 5-6, tuned to the endosomal pH. The AuNPs@PP75 nanohybrids demonstrated a quick and highly reversible agglomeration-deagglomeration cycle. Doxorubicin was loaded at 0.6 wt% onto the nanohybrids without compromising the overall stability in biological media and was effectively delivered into drug-resistant human uterus sarcoma cell line. The synergistic effect of the chemotherapy with photothermal treatment increased the killing efficiency by 6 folds compared to the conventional free drug. The nanohybrids were finally entrapped into pH-responsive PLP hydrogels. The composite hydrogels retained a high pH-responsive swelling behaviour and demonstrated improved mechanical properties compared to the bare hydrogel. Controlled drug release ability and biocompatibility confirmed their suitability as potential cancer therapeutics via oral administration.
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Jourabchi, Seyed Amirmostafa. "Production and physicochemical characterisation of bio-oil from the pyrolysis of Jatropha curcus waste". Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/28825/.
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The increasing use of fossil fuels and the impending depletion of their reserves worldwide are driving alternative energy sources as one of the foremost consideration for research in energy, fuel, and power technology. Additionally, the increasing rate of harmful emissions especially carbon dioxide from the increased usage of fossil fuels have led to the need for more environmentally friendly replacement fuels. Presently, bio-oil originating from biomass has been proposed as an alternative fuel to fossil diesel. The aim of this research project is to optimally produce bio-oil in terms of quantity and quality from Jatropha curcas waste by using conventional and fast pyrolysis methods. Jatropha curcas shrub, which can be planted economically in tropical regions like Malaysia, is typically planted as a source of inedible oil for biodiesel production. The leftover pressed cake after oil extraction is an agricultural waste, which can be upgraded into fuel via pyrolysis. In this project, the pyrolysis parameters to achieve optimum quantity and quality of bio-oil from Jatropha curcas waste were determined. To achieve this, two fixed-bed pyrolysis rigs for conventional and fast pyrolysis processes were designed and fabricated, and a corresponding Design of Experiment was performed. By considering yield, calorific value, water content and acidity, the results from both methods were mathematically modelled after comparison and the optimum parameters for both methods were determined. The validated models of conventional and fast pyrolysis showed that optimum combined quantity and quality of bio-oil occur at reaction temperatures of 800 K and 747 K respectively but at the same nitrogen linear velocity of 0.0078 cm/s. At these optimum conditions, conventional and fast pyrolysis yield 50.08 wt% and 40.08 wt% of bio-oil with gross calorific values of 15.12 MJ/kg and 16.92 MJ/kg, water contents of 28.34 wt% and 28.02 wt%, and pH values of 6.77 and 7.01, respectively. The produced bio-oils from both rigs at their optimum points were dehydrated, and the physicochemical characteristics of the dehydrated bio-oils from both rigs were compared to standard specifications for burner biofuels. Based on ASTM D7554-10 standard for burner biofuel specifications, by reducing the sulphur contents, both dehydrated bio-oils can be used as burner fuel without any further processes. Finally, both 10% of optimised and dehydrated bio-oils emulsified in 90% diesel were tested and compared to EN590, the European standards for diesel used in commercial diesel engines and ASTM D6751-01, the standard biodiesel specifications. In addition to sulphur content, if the water content of both of these emulsified dehydrated bio-oils are removed, they can be commercially used as diesel fuel in diesel engines because their solid content, kinematic viscosity, ash content, flash point, cetane number and copper corrosion strip test results are within the range of EN590 standard.
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Velaga, Sitaram P. "Preparation of Pharmaceutical Powders using Supercritical Fluid Technology : Pharmaceutical Applications and Physicochemical Characterisation of Powders". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4006.
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Mapp, Lucy Kristina. "Novel multi-component systems of propyphenazone and lonidamine : characterisation, physicochemical properties and quantum crystallography studies". Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/418007/.
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This thesis reports novel multi-component systems of two APIs, PROPY and LON. Design and prediction strategies, tailored for each API, have been used to select appropriate co-former molecules used for subsequent screening and synthesis. Comprehensive characterisation of the products was followed by single crystal X-ray diffraction structural analysis and physicochemical property measurements. These include thermal properties, stability, dissolution and solubility which were characterised by DSC, TGA, PXRD and HPLC. A subset of PROPY systems were selected to probe the nature of the API···co-former interactions. The experimental electron density distribution, based on very high resolution single crystal diffraction, was modelled and a topological analysis undertaken using Bader’s Atoms in Molecules (AIM) approach. Atomic charges, intermolecular interactions and their energies have been subsequently derived and compared between systems. Complementary theoretical calculations using the PIXEL and Crystal Explorer interaction energy approaches were undertaken and used to investigate the intermolecular interactions beyond atom···atom contacts. These permitted the decomposition of the intermolecular interactions into their constituent energy components for a comprehensive analysis. This novel approach provided new insight into the driving forces behind the formation of the solid state. Furthermore, this quantum crystallography approach enabled an analysis of the effect of the co-former on structure and the range of influencing factors that determine the physicochemical properties of these multi-component systems.
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Wang, Qi. "Physico-chemical characterisation of water soluble non-starch polysaccharides". Thesis, King's College London (University of London), 1998. https://kclpure.kcl.ac.uk/portal/en/theses/physicochemical-characterisation-of-water-soluble-nonstarch-polysaccharides(0802c1fd-9a51-4f9f-b608-5b7343c605a2).html.
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This thesis is concerned with the development of physico-chemical techniques to characterise the properties of water soluble non-starch polysaccharides (s-NSP). The first part of this project was to characterise the structure and solution properties of s- NSP extracted from a plant, Detarium senegalense Gmelin. The extracted s-NSP was analysed by GLC and found to be similar in structure to tamarind xyloglucan. This was confirmed by comparing the oligosaccharides released on enzymatic digestion with those obtained from tamarind xyloglucan. Histochernical examination of detariurn seed showed the presence of xyloglucan in highly thickened cell walls. The intrinsic viscosity of detariurn gum was found to be high, indicating that the sample was of high molecular weight. The semi-dilute solution characteristics investigated by steady and dynamic shear rheometry, suggest that detarium gum is a well behaved linear polymer entanglement system. Static light scattering was also successfully applied to examine the molecular weight and architecture of the detarium xyloglucan macromolecules. The physiological behaviour of s-NSP when consumed is critically dependent on their physico-chemicapl roperties,i ncluding the rate and degreeo f hydration. In the second part of the project a method for determining the hydration rate of a powdered form of s- NSP was developed. A logarithmic model for describing the hydration kinetics of guar gum was also establishedT. his model was used to investigatet he effects of polymer concentration (C), molecular weight (M), and particle size on the hydration rate of guar gum. The results showed that there was a significant inverse relationship between hydration rate and M and mean particle size, respectively. The hydration rate increased with increasingC at a low concentrationr ange,b ut decreasedw hen C>1.2% (w/w). The pH in the lumen of the gastrointestinal tract of human is acidic, usually between 2.0 and 1.5 after a meal. The stability of guar gum in acidic conditions was investigated at temperatures 25,37 and 50'C. The results indicated that there was unlikely to be significant acidic degradation of guar gum in the human gastrointes final tract. The pH condition was also found to influence the hydration rate of guar gum. In general, the hydration rate was lower in an acid environment than it was in neutral conditions
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Stratigou, Evdokia. "Identification and characterisation of physicochemical processes controlling indoor concentrations of submicron aerosols and volatile organic compounds". Thesis, Ecole nationale supérieure Mines-Télécom Lille Douai, 2019. http://www.theses.fr/2019MTLD0007/document.
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Cette thèse développe les connaissances scientifiques sur l’origine et le comportement des polluants intérieurs en phases gazeuse et particulaire. Une description complète des processus physiques contrôlant les concentrations de polluants en air intérieur dans une pièce inoccupée et non meublée a été réalisée. En utilisant des paramètres bien quantifiés (taux de renouvellement d’air, facteur de pénétration et vitesse de dépôt), nous avons pu appliquer un modèle de bilan massique aux particules. Les résultats ont montré que, en l’absence significative de sources intérieures, une caractérisation fine des paramètres ci-dessus permettait de décrire de manière satisfaisante les concentrations intérieures en PM2.5 et PM10 à partir des données extérieures, tandis que les PM1 montrent une variabilité significativement plus marquée due aux transformations physicochimiques. Par la suite, les composés organiques volatils (COV) et la composition chimique des particules submicroniques ont été mesurés en temps réel lors d’une campagne intensive. Un enrichissement important des concentrations en COV a été observé lorsque l’air ambiant pénètre à l’intérieur du bâtiment, en particulier pour les COV oxygénés qui présentent une dépendance significative avec l’humidité relative, tandis que pour les particules les changements observés dépendent de leur composition chimique et de leur diamètre, montrant une diminution de 20% pour les PM1 à 86% pour les plus grosses particules (>5 μm). L’excès d’ammonium observé dans les deux environnements a permis de déconvoluer les nitrates organiques des inorganiques, ceux-ci présentant une dépendance plus forte avec la température, révélant une décomposition thermique plus importante en air intérieur. En résumé, l’environnement intérieur agit principalement comme une source d’émissions continues de COV, alors qu’une tendance inverse est observé pour les particules, du fait de transformations possibles pouvant se produire même dans les conditions les plus simples, sans occupant ni mobilierThis thesis improves the scientific knowledge on the origin, behavior and fate of gas and particle-phase pollutants indoors under unoccupied unfurnished conditions. A first campaign provided a complete description of the physical processes controlling the indoor concentrations. Using well quantified parameters (air exchange rate, penetration factor and deposition rate), a mass balance model provided insights for the particle budget closure. The results showed that when indoor sources are not significant, a careful characterization of the abovementioned parameters allows to estimate PM2.5 and PM10 in a satisfying manner from outdoor data. However the PM1 fraction shows a significantly higher variability due to physicochemical transformations. Subsequently, a second intensive campaign was performed to investigate volatile organic compounds (VOC) and PM1 chemical composition in real time. A strong increase in VOC concentrations was observed when outdoor air penetrates indoors, especially oxygenated VOC which exhibited a significant dependence on relative humidity, while the changes observed for particles once indoors depend on their chemical composition and diameter, showing a decrease from 20% for submicron particles up to, 86% for large ones (>5. µm). The investigation of ammonium neutralization revealed an excess of ammonium indoors and outdoors, which is attributed to organic- in addition to inorganic-bonded ammonium nitrate. The latter showed a stronger dependency on temperature gradient from outdoors to indoors, revealing stronger thermal decomposition once indoors. In summary, the indoor environment acts mainly as a continuous emission source of VOCs, while the opposite trend is observed the particles due to possible transformations that can occur even under the simplest conditions, with no occupants and no furnishing
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Stratigou, Evdokia. "Identification and characterisation of physicochemical processes controlling indoor concentrations of submicron aerosols and volatile organic compounds". Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Lille Douai, 2019. http://www.theses.fr/2019MTLD0007.
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Cette thèse développe les connaissances scientifiques sur l’origine et le comportement des polluants intérieurs en phases gazeuse et particulaire. Une description complète des processus physiques contrôlant les concentrations de polluants en air intérieur dans une pièce inoccupée et non meublée a été réalisée. En utilisant des paramètres bien quantifiés (taux de renouvellement d’air, facteur de pénétration et vitesse de dépôt), nous avons pu appliquer un modèle de bilan massique aux particules. Les résultats ont montré que, en l’absence significative de sources intérieures, une caractérisation fine des paramètres ci-dessus permettait de décrire de manière satisfaisante les concentrations intérieures en PM2.5 et PM10 à partir des données extérieures, tandis que les PM1 montrent une variabilité significativement plus marquée due aux transformations physicochimiques. Par la suite, les composés organiques volatils (COV) et la composition chimique des particules submicroniques ont été mesurés en temps réel lors d’une campagne intensive. Un enrichissement important des concentrations en COV a été observé lorsque l’air ambiant pénètre à l’intérieur du bâtiment, en particulier pour les COV oxygénés qui présentent une dépendance significative avec l’humidité relative, tandis que pour les particules les changements observés dépendent de leur composition chimique et de leur diamètre, montrant une diminution de 20% pour les PM1 à 86% pour les plus grosses particules (>5 μm). L’excès d’ammonium observé dans les deux environnements a permis de déconvoluer les nitrates organiques des inorganiques, ceux-ci présentant une dépendance plus forte avec la température, révélant une décomposition thermique plus importante en air intérieur. En résumé, l’environnement intérieur agit principalement comme une source d’émissions continues de COV, alors qu’une tendance inverse est observé pour les particules, du fait de transformations possibles pouvant se produire même dans les conditions les plus simples, sans occupant ni mobilierThis thesis improves the scientific knowledge on the origin, behavior and fate of gas and particle-phase pollutants indoors under unoccupied unfurnished conditions. A first campaign provided a complete description of the physical processes controlling the indoor concentrations. Using well quantified parameters (air exchange rate, penetration factor and deposition rate), a mass balance model provided insights for the particle budget closure. The results showed that when indoor sources are not significant, a careful characterization of the abovementioned parameters allows to estimate PM2.5 and PM10 in a satisfying manner from outdoor data. However the PM1 fraction shows a significantly higher variability due to physicochemical transformations. Subsequently, a second intensive campaign was performed to investigate volatile organic compounds (VOC) and PM1 chemical composition in real time. A strong increase in VOC concentrations was observed when outdoor air penetrates indoors, especially oxygenated VOC which exhibited a significant dependence on relative humidity, while the changes observed for particles once indoors depend on their chemical composition and diameter, showing a decrease from 20% for submicron particles up to, 86% for large ones (>5. µm). The investigation of ammonium neutralization revealed an excess of ammonium indoors and outdoors, which is attributed to organic- in addition to inorganic-bonded ammonium nitrate. The latter showed a stronger dependency on temperature gradient from outdoors to indoors, revealing stronger thermal decomposition once indoors. In summary, the indoor environment acts mainly as a continuous emission source of VOCs, while the opposite trend is observed the particles due to possible transformations that can occur even under the simplest conditions, with no occupants and no furnishing
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Mitra, Sabori. "Characterisation of physicochemical properties of different oat cultivars used in noodle processing: effects on quality and β-glucan". Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/562.
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Research characterised the physicochemical properties of different oat cultivars used in noodle processing and their effects on noodle quality and β-glucan content. The effect of oat cultivar, season and processing on noodle and β-glucan quality was investigated. This research provided an insight into the quality differences between oat cultivars, effect of season on oat cultivar quality and the oat cultivars most suitable for incorporation into oat-wheat noodles in terms of processing, sensory and nutritional properties.
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Homoud, Alyaa Munaji. "Characterisation of proteins in camel milk : the effect of heat treatment on physicochemical and functional properties related to yogurt". Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/3006.
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Camel milk plays a central role in the food supply of Eastern African and Middle Eastern countries (e.g. Kenya, Somalia, Saudi, and Ethiopia), home to the majority of the world’s camel population. Raw, and traditionally fermented camel milk has become increasingly commercialised and consumed in urban areas. This has led to an increased interest in the processing of camel milk for the urban market, with skimmed camel milk casein and whey powders soon to be commercialised, in a manner similar to the already widely available bovine dairy powders. However, little information is currently available concerning the effects of different processing methods (e.g. thermal treatment) on camel milk fractions. Currently there are no camel milk derived products, such as yoghurt or cheese, available in local Saudi supermarkets. Furthermore, the abundance of bioactive substances in camel milk have been reported to have useful effects; one of the most prominent is the anti-diabetic benefits revealed by in vivo studies. However, the presence of insulin in camel milk still remains to be proven. The aims of this thesis are twofold. The first area (Chapters 2, 3 and 4) describe the effect of heat treatment on camel milk components and their functional properties in an oil and water emulsion, and in yoghurt. In order to test these functional properties, camel skimmed milk, whey and casein were prepared and freeze dried. The key novel findings include: skimmed milk that had been heat treated and freeze dried showed significantly improved functionality for use in emulsions and yoghurts, whereas heat treated whey did showed no significantly enhanced functional properties. Furthermore, non-heated freeze dried casein significantly enhanced curd formation in yoghurt, and resulted in a smooth texture. Two fermented yoghurts were developed containing heat treated skimmed milk powder or casein with similar textural properties to bovine milk commercial yoghurt, that were acceptable in taste and texture, as determined by an independent study for sensory evaluation. The second area of this study (Chapter 5) concerned the characterisation of insulin in camel milk. As it was confirmed by previous studies that the presence of high concentration of insulin in camel milk comparing to bovine milk. Key findings were that no protein with a characteristic molecular weight similar to bovine or human insulin (5.8 KDa) could be detected using Western Blotting; however, a 62 KDa protein showed consistent immune reactivity. ELISA results showed high immune reactivity in camel whey. An in vivo assay showed biological insulin like activity in camel milk, but the validity of the assay still needs to be confirmed.
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Milly, Hussam. "The physico-chemical characterisation of bioactive glass air-abrasion on human enamel". Thesis, King's College London (University of London), 2014. http://kclpure.kcl.ac.uk/portal/en/theses/the-physicochemical-characterisation-of-bioactive-glass-airabrasion-on-human-enamel(93206812-6ff0-456b-8d10-4b9fc31a960a).html.
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Objectives: This research aimed to characterise the physico-chemical interaction of bioactive glass 45S5 (BAG) air-abrasion with human enamel including the controlled and selective removal of substrates and the remineralisation of enamel white spot lesions (WSLs). Materials and methods: The effect of six operating parameters on air-abrasion dynamic cutting efficiency/patterns was assessed using an enamel analogue material (MacorTM) and white light profilometry. Standardised resin composite restorations created within MacorTM blocks, were removed in simulated clinical conditions and scanned using triangulation laser profilometry to investigate the effect of operating parameters on the selective resin composite removal using BAG air-abrasion. The remineralisation of artificial enamel WSLs treated using BAG mixtures were evaluated using Raman micro-spectroscopy, microhardness and scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectrometry (EDX). The physical and optical changes in WSLs pre-conditioned using air-abrasion with BAG-polyacrylic acid (PAA-BAG) powder were detected using non-contact profilometry and optical coherence tomography (OCT). All comparisons were considered statistically significant if p < 0.05. Results: Significant differences in air-abrasion cutting efficiency / pattern were observed according to the tested parameters. BAG air-abrasion removed resin composite more selectively than conventional alumina air-abrasion and the effect of altering the unit’s operating parameters was significant. Enamel WSLs treated with BAG mixtures exhibited a significantly higher Knoop microhardness compared to the negative control. Raman micro-spectroscopy detected significantly higher phosphate content and the SEM images revealed mineral depositions on the surface of treated lesions. Pre-conditioning WSL surfaces with PAA-BAG air-abrasion increased WSL surface area. This pre-treatment increased Knoop microhardness and the mineral content of remineralised WSLs. Conclusions: The ultraconservative clinical applications of BAG air-abrasion can be improved by altering the operating parameters. BAG and PAA-BAG can remineralise enamel WSLs. Pre-conditioning the lesion surface with PAA-BAG air-abrasion modifies the lesion surface physically and consequently enhances remineralisation using BAG 45S5 therapy.
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Baumgart, Tobias. "Herstellung und physikochemische Charakterisierung von planaren gestützten Lipid-Modellmembran-Systemen Preparation and physicochemical characterisation of planar supported lipid model membrane systems /". [S.l.] : [s.n.], 2001. http://ArchiMeD.uni-mainz.de/pub/2001/0123/diss.pdf.
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Mohamed, Hatta Nur Syahirah. "Physicochemical Characterisation and Flocculation Analysis of a Novel Cationic Chitosan-Like Bioflocculant from Citrobacter Youngae GTC 01314 to Improve Sludge Dewatering". Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/84222.
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Bacterial strains from the genus Citrobacter are proven to be cultivated effectively in acetate medium
to produce chitosan-like bioflocculants with strong flocculation activity. Selected physicochemical
characteristics and flocculation behaviour of a novel bioflocculant from Citrobacter youngae GTC
01314 were studied in kaolin suspension, followed by evaluation of its dewatering performance in
activated sludge sample. The results confirmed the effectiveness of the bioflocculant in enhancing
sludge dewaterability which advocates its potential application in water and wastewater treatment.
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Gabet, Yann. "Étude et optimisation des interfaces fibre-matrice polymère de composites structuraux à base thermoplastique". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1244/document.
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Ces travaux de thèse portent sur l’étude et l’optimisation des propriétés interfaciales verre/PA 6-6 pour la conception de matériaux composites de structure. Une méthode visant à nettoyer et réactiver la surface du verre a dans un premier temps été développée. Elle permet de travailler avec des substrats de type fibres ou substrats modèles (plaques de verre) et d’obtenir des surfaces « contrôlées » avant l’application de nouveaux revêtements. La maîtrise de l’interface entre renfort et matrice nécessite l’optimisation de l’ensimage, dont les principaux constituants sont des agents filmogènes et des agents de couplage. Au cours de ce travail, nous avons donc étudié les propriétés thermiques, mécaniques et de surface des nouveaux revêtements appliqués sur les substrats de verre. Différents agents filmogènes, sélectionnés pour être compatibles avec les conditions de mise en oeuvre du PA 6-6, ainsi que deux agents de couplages usuels ont été étudiés. Par le choix d’une large gamme de familles d’agents filmogènes, nous avons montré que l’utilisation d’un agent filmogène de composition chimique proche de celle de la matrice permet d’atteindre de meilleures propriétés interfaciales. L’augmentation de la rugosité de surface du revêtement contribue également à cette amélioration. Le greffage des agents de couplage sur le verre s’est révélé bien plus efficace avec un traitement thermique à 150°C qu’à 110°C et un effet de synergie a pu être observé lors de leur association avec un agent filmogène. L’utilisation d’agents filmogènes à haute résistance thermique a permis d’obtenir des propriétés interfaciales très intéressantes, renforcées pour certains systèmes par l’ajout de nanoparticules. Enfin, afin d’accéder à une estimation de la ténacité de l’interface, un test de DCB en mode I a été adapté à notre problématique. Les résultats obtenus ont été complémentaires à ceux obtenus par les tests du plot et de la microgoutteThis work is devoted to the study and optimisation of glass/PA 6-6 interfacial properties for the conception of structural composite materials. A method to clean and reactivate glass surface was first developed. It allowed us to work with glass fibres and model substrates (glass plates), aiming to get controlled surfaces before the application of new coatings. Controlling the interface between the reinforcement and the matrix requires the optimisation of the sizing, which is mainly composed of film formers and coupling agents. This study consisted in the characterisation of thermal, mechanical and surface properties of the new coatings applied to the glass substrates. Different film former bases, selected for their compatibility with the processing conditions of PA 6-6, and two usual coupling agents were studied. This work allowed to identify different parameters that play a role in the improvement of interfacial properties. By working with a wide range of film formers, we could show that the use of a film former with close chemical composition from the matrix allows to reach better interfacial properties. Increasing the surface roughness of coatings also participates in this improvement. The grafting of coupling agents was more efficient after 150°C thermal treatment than 110°C, and a synergistic effect was obtained by their association to a film former. The use of film formers with high thermal resistance provided very interesting interfacial properties, also improved, for some, by the addition of silica nanoparticles. Finally, DCB mode I mechanical test was adapted to our system, allowing to estimate the fracture toughness of the glass/PA 6-6 interface which is a complementary result to the estimation of the adhesion force measured by pull-off and pull-out tests
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El, bakkali taheri Nadia. "Oxydase de l'acide 1-aminocyclopropane carboxylique : mode d'action et inactivation". Thesis, Aix-Marseille 3, 2011. http://www.theses.fr/2011AIX30042.
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L’oxydase de l’acide 1-AminoCyclopropane Carboxylique (ACC Oxydase, ACCO) catalyse la formation de l’éthylène, hormone essentielle à la vie des plantes. L’ACCO catalyse l’oxydation de l’ACC en éthylène en présence de dioxygène et de deux électrons (fournis in vitro par l’ascorbate). L'activité de l'enzyme requière également, pour des raisons encore incomprises, la présence de CO2 sous la forme d'ions bicarbonates. Il s’agit d’une enzyme qui contient un ion fer(II) dans un environnement non-hémique au site actif. Etant donné l’importance de l’éthylène chez les plantes, l’ACCO, ainsi que les autres enzymes impliquées dans sa biosynthèse, ont été très étudiées durant les vingt dernières années. Cependant, peu d’études ont porté sur le rôle de l’ion métallique et le mécanisme d’action ou sur les surprenants processus d’inactivation subis par l’enzyme. L’ACCO est en effet une enzyme connue pour son instabilité. Nous avons tout d’abord entrepris une caractérisation physicochimique et biochimique de l’enzyme. Le matériel protéique utilisé a tout d’abord été analysé une coupure entre les résidus Ala 290 et Gly 291 a été observée au cours de la purification de l'enzyme. Puis, grâce à l'utilisation de techniques spectroscopiques, nous avons cherché à obtenir plus d'informations sur la fixation des substrats/cofacteurs au site actif. Enfin l’étude des mutants et des complexes modèles de l’ACCO a été réalisée afin de mieux comprendre le mécanisme catalytique et de rechercher de nouvelles activités. Nous nous sommes aussi intéressés aux mécanismes d’inactivation de l’ACCO. En présence des effecteurs en excès, cette inactivation se traduit par une fragmentation et une modification de charge. Lorsque la concentration en fer est limitée, aucune modification physique de l’enzyme inactive n’est observée et l'enzyme garde un contenu global en aminoacide et une conformation tridimensionnelle intègres. Des processus oxydatifs se déroulant directement au site actif de l’enzyme sont susceptibles d’engendrer une telle perte d’activité par l'oxydation d'un nombre limité d'acides aminés. Des études en spectrométrie de masse ont été entreprises et sont toujours en cours afin d'identifier les modifications responsables de la perte d'activité de l'enzyme.Enfin nous avons recherché d’éventuelles partenaires protéiques qui pourraient conférer à l’ACCO une meilleure stabilité. Des études préliminaires ont été entreprises et des données de microscopie suggèrent que l'ACCO est localisée près des membranes de la vacuoleThe 1-AminoCyclopropane Carboxylic acid oxidase (ACC Oxidase, ACCO) catalyzes the last step of the biosynthesis of the plant hormone, ethylene. ACCO catalyzes the oxidation of ACC into ethylene in the presence of dioxygen and two electrons (provided in vitro by ascorbate). Carbon dioxide (or bicarbonate ions) are also required for optimum activity. ACCO is an non-heme iron(II) containing enzyme. Given the importance of ethylene in plants, studies on ACCO, as well as on the other enzymes involved in its biosynthesis, have attracted much attention in the past two decades. However, few studies focus on the role of the metal ion and on the catalytic mechanism or the intriguing inactivation processes. ACCO is indeed known for its instability. We first purified and characterised the enzyme. During the purification, a cleavage between residues Ala 290 and Gly 291 was observed. Then, using spectroscopic techniques, we intended to get more information on cofactor's binding in the active site. Finally studies of mutants and model complexes of ACCO were performed in order to get a better understanding of the catalytic mechanism and to look for new activities.We were also interested in the inactivation processes of ACCO. In the presence of an excess of effectors, this inactivation resulted in fragmentation and in pI modification. When the concentration of iron is limited, no modifications of the inactive enzyme were observed. The inactive enzyme maintained its amino acid content and three-dimensional conformation. The loss of activity is therefore likely to derive from oxidative processes directly at the active site. Mass spectrometry experiments were initiated and are still under progress. Finally we were interested in identifying possible protein partners of ACCO that could provide a better stability. Preliminary studies were thus initiated and from microscopy results, ACCO was found located close to the vacuole membrane
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Passicousset, Joël. "Descripteurs physico-chimiques de la biomasse lignocellulosique en hydrolyse enzymatique : vers une caractérisation in-situ". Thesis, Paris, Institut agronomique, vétérinaire et forestier de France, 2019. http://www.theses.fr/2019IAVF0004.
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Une des pistes envisagées pour réduire l’impact environnemental des activités humaines dans le secteur des transports est la production d’éthanol à partir de biomasse lignocellulosique. Parmi les différentes technologies envisagées pour ces substrats constitués majoritairement de cellulose, d’hémicelluloses, et de lignine, le procédé de conversion biochimique en éthanol représente une voie prometteuse, par la maturité relative de la filière, et la faisabilité immédiate de l’incorporation d’éthanol dans l’essence pour le parc automobile actuel. L’étape de prétraitement qui a pour but de rendre la cellulose plus accessible et plus digeste à l’étape d’hydrolyse enzymatique doit encore être optimisée afin de rendre économiquement viable ce procédé. Afin d’étudier les liens entre les conditions opératoires de prétraitement, les modifications physicochimiques apportées, et leurs effets sur la digestibilité des substrats, une palette d’échantillons avec une forte variabilité de paramètres physicochimiques était nécessaire. Ils ont été produits à partir d’une paille de blé prétraitée par cuisson acide et explosion vapeur avec une large gamme de paramètres opératoires. Une caractérisation multi-échelle et multi-technique a permis de connaître précisément les modifications physicochimiques opérées par le prétraitement. Ces résultats ont permis d’identifier les descripteurs pertinents permettant d’expliquer la réactivité d’un substrat en hydrolyse enzymatique. Un modèle empirique a ainsi pu être proposé pour traduire la réactivité de ces substrats prétraités en fonction des paramètres clés identifiés. Enfin, le suivi in situ au cours de l’hydrolyse enzymatique de la dégradation de la matrice et de l’adsorption des enzymes sur les tissus par microscopie à autofluorescence UV a permis de mieux appréhender les mécanismes d’hydrolyse de la biomasse prétraitée, dépendamment des conditions opératoires de prétraitementOne of the paths that are envisioned to reduce the environmental footprint of human’s activities in the field of the transportation is about ethanol production from lignocellulosic biomass. Amongst all the different processes that are projected to convert such substrates made of cellulose, hemicelluloses, and lignin, the bioconversion process into ethanol represents a promising option since it is quite mature, and ethanol is readily usable in the current gas-cars fleet. The pretreatment step that aims at making cellulose more accessible and more digestible to the enzymatic hydrolysis still needs improvements in order to make this process economically viable. To study the relations between operating conditions, physicochemical modifications, and their effects on substrates’ digestibility, a wide range of samples with a high variability of their physicochemical parameters was needed. Samples were produced from a wheat straw that was dilute-acid and steam exploded with a wide range of operating conditions. Multi-technique and multi-scale analyses led to a precise characterisation of the physicochemical effects provoked by the pretreatment. These results also allowed identifying key substrate parameters that are responsible for the substrate enzymatic digestibility. Based on the observations, an empirical model was proposed to express the substrate digestibility as a function of these critical parameters. Finally, in situ monitoring of tissue degradation and enzyme adsorption-desorption on plant tissues during saccharification was carried using UV-autofluorescence microscopy. Thanks tothese experiments, hydrolysis mechanisms on pretreated matrices are now better understood, and depend upon pretreatment operating conditions
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Chal, Bruno. "Vieillissement thermohygrique de silices nanostructurées, vers une compréhension des mécanismes". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI090.
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La réduction des émissions de gaz à effet de serre et de la consommation énergétique nécessite de promouvoir l’efficacité énergétique des bâtiments, premier secteur de dépense en France (40%). Les objectifs fixés par le récent plan climat prévoient de rénover thermiquement 500 000 logements par an pour réhabiliter l’ensemble du parc immobilier à l’horizon 2050. Les super-isolants thermiques (SIM), avec une conductivité thermique entre 4 et 20 mW.m-1.K-1, permettent une isolation efficace à moindre épaisseur, et offrent plus de liberté architecturale. Toutes les configurations superisolantes (Panneaux isolants sous vides (PIV), superisolants à pression atmosphérique (SIPA)) s’appuient sur des matériaux nanostructurés et majoritairement sur des silices, permettant de réduire drastiquement la conduction gazeuse (loi de Knudsen) et squelettique. Leurs caractéristiques structurelles et texturales (porosité > 92 %, nanopores, 200 m²/g plus petit Surface Spécifique plus petit 850 m²/g) mais aussi chimiques (différents groupes en surface : silanols SiOH, siloxanes SiOSi, hydrophobants SiR) pilotent leur efficacité thermique mais ouvrent aussi la voie à des évolutions en cas d’exposition à des conditions sévères couplées (Température et Humidité relative). La compréhension des phénomènes physico-chimiques mis en jeu dans leur vieillissement est donc nécessaire, c’est l’objet de cette thèse menée sur un ensemble de matériaux commerciaux (pulvérulents ou aerogels). L’approche originale proposée dans ces travaux couple des techniques locales, multi-échelles et globales (sorption de gaz, porosimétrie mercure, MET, tomographie aux électrons, SANS, FTIR, ATG…) et repose sur différentes conditions de vieillissement destinées à discriminer les mécanismes moteurs. L’emploi des diverses techniques a nécessité un travail d’adaptation préliminaire et des études paramétriques afin de répondre aux exigences et aux spécificités propres à la silice amorphe nanostructurée (porosité importante, sensibilité…). Cette démarche permet de démontrer que des modifications dans la chimie de surface (hydrolyse de siloxanes, condensation de silanols…) accompagnent des modifications de texture et de structure (réduction de la surface spécifique, décalage de la distribution de taille de pore…). Selon le type de silice ou d’aérogel étudié, la typologie et l’intensité de ces évolutions varient et des mécanismes plus spécifiques peuvent être mis en jeu. L’un des principaux mécanismes identifiés implique un déplacement de matière en surface, notamment rendu possible par la physisorption d’eau servant de media (dissolution/précipitation), et des forces capillaires. Ce travail de fond sur les mécanismes apporte une base de connaissance permettant de gagner en visibilité, donc en confiance, sur le devenir des superisolant et d’adapter leur formulation à leur utilisation. Les résultats acquis au cours de cette thèse pourront également implémenter des modélisations et des outils de simulationReducing greenhouse gas emissions and energy consumption imply to promote the energetic efficiency of buildings, first share of consumption in France (40%). The goals is to rehabilitate the entire building stock by 2050 with a 500 000 building thermal retrofitting rate per year.Superinsulation materials (SIM), with a thermal conductivity between 4 and 20 mW.m-1.K-1, offer the opportunity to suitably insulate with a low thickness, improving architectural flexibility. All superinsulation products (Vacuum Insulation Pannels (VIP), Superinsulation Materials at Atmospheric Pressure (SIAP)) are based on nanostructured materials and mainly on silica, which drastically lowers the skeletal and gaseous conductivities (Knudsen’s law). Their structural and textural properties (porosity > 92 %, nano-pores, 200 m²/g plus petit Specific Surface Area plus petit850 m²/g), as their chemical characteristics (different chemical groups at the surface), drive their thermal efficiency but also open the way for evolutions in case of exposition to harsh atmospheres (Temperature and Relative Humidity). Comprehension of physico-chemical phenomena taking part in ageing is thus compulsory to ensure efficient and durable materials at affordable price. This is the aim of this PhD thesis carried out a set of commercial products (divided silica or aerogels). The original approach proposed in this work combines local, multi-scale and global techniques (gaz sorption measurement, mercury porosimetry, TEM, electron tomography, SANS, FTIR, TGA…) and rests on several ageing conditions, which are intended to highlight driving mechanisms. Due to the specificities of nanostructured amorphous silica (high porosity, sensibility…), the use of these techniques preliminarily required adaptation work, which includes parametric studies. Ageing is tracked down to the nano particle and neck size within agglomerate and associated to usual engineering values. This approach allows to demonstrate that chemical modifications (siloxane bridges hydrolysis, silanol groups condensation…) come along with textural and structural modifications (reduction of the specific surface area, shifting of the pore size distribution…). According to the type of silica or aerogel analysed, the intensity and the evolution scenario differ, and more specific mechanisms can be involved. The main mechanism identified implies a displacement of matter through water layers adsorbed on the surface (physical adsorption of water, dissolution/precipitation). Capillary forces at the nano scale are evidenced by coupled techniques. Thermal measurements confirmed that thermal efficiency withstands ageing with adequate design This upstream work on mechanisms offers a knowledge base and allows gaining clarity, thus confidence, regarding superinsulation materials future. It also gives hints to adapt the synthesis according to the application. Results acquired during this thesis could also implement modelling and simulation tools
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Lopes, Maria Ascenção Ferreira da Silva. "Glass reinforced hydroxyapatite composites: structural, physicochemical characterisation and biological performance". Doctoral thesis, 1999. http://hdl.handle.net/10216/11338.
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Lopes, Maria Ascenção Ferreira da Silva. "Glass reinforced hydroxyapatite composites: structural, physicochemical characterisation and biological performance". Tese, 1999. http://hdl.handle.net/10216/11338.
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Paluch, Krzysztof J., L. Tajber, M. I. Amaro, O. I. Corrigan e A. M. Healy. "Impact of process variables on the micromeritic and physicochemical properties of spray-dried microparticles, part II: physicochemical characterisation of spray-dried materials". 2012. http://hdl.handle.net/10454/14361.
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YesObjectives In this work we investigated the residual organic solvent content and physicochemical properties of spray-dried chlorothiazide sodium (CTZNa) and potassium (CTZK) salts. Methods The powders were characterised by thermal, X-ray diffraction, infrared and dynamic vapour sorption (DVS) analyses. Solvent levels were investigated by Karl–Fischer titration and gas chromatography. Key findings Spray-drying from water, methanol (MeOH) and mixes of MeOH and butyl acetate (BA) resulted in amorphous microparticles. The glass transition temperatures of CTZNa and CTZK were ∼192 and ∼159°C, respectively. These materials retained their amorphous nature when stored at 25°C in dry conditions for at least 6 months with no chemical decomposition observed. DVS determined the critical relative humidity of recrystallisation of CTZNa and CTZK to be 57% RH and 58% RH, respectively. The inlet temperature dependant oxidation of MeOH to formaldehyde was observed; the formaldehyde was seen to deposit within the amorphous matrix of spray-dried product. Spray-drying in the open blowing mode coupled with secondary drying resulted in a three-fold reduction in residual BA (below pharmacopoeial permitted daily exposure limit) compared to spray-drying in the closed mode. Conclusions Experiments showed that recirculation of recovered drying gas increases the risk of deposition of residual solvents in the spray-dried product.
The Irish Research Council for Science and Engineering Technology (IRCSET), the Solid State Pharmaceutical Cluster (SSPC), supported by Science Foundation Ireland under grant number (07/SRC/B1158) and the Irish Drug Delivery Research Network, a Strategic Research Cluster grant (07/SRC/B1154) under the National Development Plan co-funded by EU Structural Funds and Science Foundation Ireland.
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Stranger, James W. "Characterisation of liquid electrolytes by determination of physicochemical and electrochemical properties using advanced nuclear magnetic resonance techniques". Thesis, 2015. http://hdl.handle.net/1959.7/uws:36608.
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Liquid electrolytes, commonly regarded as salts or salt solutions with a boiling point below 100 °C, are increasingly finding applications in numerous fields. The relationships between the structure and molecular dynamics of liquid electrolytes have yet to be fully understood despite considerable interest in the field. The aim of the research in this thesis was to explore and identify such relationships in order to provide a basis for future design of task-specific liquids electrolytes through manipulation of their structure.The first stage of this research was to validate the experimental methodology using a simple model system, i.e., crown ethers, and the understanding attained from this model system was applied to comprehensively study more complex systems, i.e., pure ionic liquids (ILs). Finally, ILs doped with lithium hexafluorophosphate (LiPF6) salt were investigated for their suitability as battery liquid electrolytes.
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Baumgart, Tobias [Verfasser]. "Herstellung und physikochemische Charakterisierung von planaren gestützten Lipid-Modellmembran-Systemen = Preparation and physicochemical characterisation of planar supported lipid model membrane systems / vorgelegt von Tobias Baumgart". 2001. http://d-nb.info/962994855/34.
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Schulze, Kai [Verfasser]. "Ni/Mg/Al catalysts derived from hydrotalcite-type precursors for the partial oxidation of propane : synthesis and characterisation of physicochemical and catalytic properties / von Kai Schulze". 2001. http://d-nb.info/981638511/34.
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Shafi, Shanjeeda. "Machine learning and mixture clustering methods for molecular drug discovery: prediction and characterisation of drugs and druggable targets". Thesis, 2021. http://hdl.handle.net/1959.13/1431097.
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Research Doctorate - Doctor of Philosophy (PhD)In the drug discovery process, approximately five to ten thousand compounds are initially screened but only 1% of these enter the preclinical testing stage that determines whether the compound is safe, efficacious, and feasible to use for a disease state. Owing to regulatory, toxicity, resistance and human health concerns, demand is increasing for refinement of and intensive use of molecular physicochemical properties via effective and robust mathematical methods for drug discovery. Chemoinformatics is now a well-recognised discipline focused on searching, identifying and extracting meaningful information from chemical sequences and structures of compounds. A candidate drug is usually a small molecule (~50 atoms) that acts by many different mechanisms of protein. Every year, several drugs are discarded from the market owing to poor pharmacodynamic and pharmacokinetic properties, which motivates this study that attempts to clarify the factors that facilitate compounds to be drug-like. The druglikeness of a molecule is characterised in part by its satisfying Lipinski’s rule-of-five (Ro5) regarding its molecular properties, such as mass and hydrophobicity, which play an important role in oral absorption, distribution, metabolism and excretion. A debate has existed for some time and now accelerated in the industry as to what constitutes a good ‘hit’. Increasing evidence suggests that relying completely on Lipinski’s Ro5 for potential drug synthesis may increase the likelihood of future drug failures. Retrospective analysis of failed drug discovery projects and incorporation of beyond Ro5 rules may provide useful information in innovating drugs for difficult targets. There is an urgent need to develop reliable computational methods for predicting drug-likeness of candidate molecules to identify those unlikely to survive the later stages of discovery and development. Visualisation and machine learning methods are two common approaches to uncover underlying patterns in the pharmacological property space, so called chemo-space, for drug design. Thus far, drug-likeness has been studied from several viewpoints, and in this thesis, we use proposed druggability rules (Hudson et al. 2012, 2014, 2017) to determine cut points for each molecular predictor based on non-Bayesian mixture model-based clustering with discriminant analysis, MC/DA (MclustDA R package). we also used decision tree for choosing cut-off ranges of molecular descriptors. To date, Hudson et al.’s (2014, 2017) results have established an improved scoring function, beyond the cut points of the Ro5. In this thesis, mixture-based modeling (Bayesian and two non-Bayesian) tools are applied via different ‘R’ packages (Rmixmod, depmixS4 and mixAK), to identify good and poor drug candidates using a combination of 9 and 10 molecular physicochemical and structural properties and scoring functions of violations (Hudson et al. 2014, 2017). The non-Bayesian Gaussian mixture method (GMM) is shown to be optimal at classifying true good and poor molecules correctly in terms of Ro5, oral_Ro5 drug-like (Divide into two parts: oral_Ro5 drug-like status1 and oral_Ro5 drug-like status2), eRo5 (extended rule of 5) and bRo5 (beyond rule of five) drugs classification, as suggested recently by Lipinski (2014, 2016) and Doak et al. (2014, 2016). In the thesis, the GMM approach, and the optimal 10 descriptors (whether continuous and categorical) set model (based on the following molecular parameters- MW, logP, logD, Hydrogen bond donors and acceptors, polar surface area, number of atoms and rings, Halogen), shows good predictive performance, with Matthews correlation coefficient (C) values in the range of 0.41–0.58, compared with other descriptors set models using Bayesian (mixAK) and non-Bayesian (HMM) methods in terms of computational time and higher sensitivity, specificity and C values. The GMM classification identified 1013 drug-like molecules of which 4 % were in bRo5 space and 266 non drug-like molecules of which 38% were in bRo5 space, supporting recent trends to more outside the Ro5 region. These mixture models are formed the basis to identify molecules and disease targets in the chemo-space using visualisation methods such as Principal component analysis (PCA), Factor analysis for mixed data (FAMD) and Correspondence analysis (CA). These three visualisation and data reductive methods successfully identify a group of molecules and specific disease targets with a prescribed range of ADME properties in different quadrants in the chemo space. This work also demonstrates that PCA, MCA and FAMD methods could be a powerful technique for exploring complex datasets in drug discovery study to identify outliers. It is shown that both lipophilicity measurement descriptors logP and logD have a significant influence on the facilitation of compounds and DC’s segregations. Two non-Bayesian mixture clustering approaches, the Gaussian mixture method (GMM via Rmixmod) and the Hidden Markov model (HMM via depmixS4) as applied in this thesis permit capture of the global properties of molecules with related targets. Based on these mixture approaches, this study is identified disease targets using the score function and molecular physicochemical properties of drugs-towards target. All mixture clustering models are identified 9 poor/non-druggable and 26 good/druggable targets with the anti-bacterial and adrenergic targets identified as the topmost poor and good druggable target respectively. Furthermore, three popular machine learning (ML) methods, such as (1) recursive partitioning, (2) naïve Bayesian and (3) support vector machine technique was also used to discriminate drug-like and non grug-like molecules based on molecular descriptors. Among these ML techniques, the SVM model is superior in terms of different rule-based drugs classifications and achieved a sensitivity range of 94% to 99% and specificity range of 84% to 100%, likewise exhibiting higher C values 0.68 to 0.99. The three-mixture based clustering with classification analyses results which use both LogD and logP are offering an excellent opportunity to consider these lipophilicity measurement descriptors (logP and logD) in conjunction with other descriptors to help predict permeability and solubility of active compounds in drug discovery. This study has the potential to significantly reduce the false classification of drugs and suggest an appropriate predictor set to help identify for new drug innovations.