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1
Crawford, R. J. "Interparticle forces in clay minerals." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291033.
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Hatharasinghe, Henegama Liyanage Mallika. "Studies of clay-polymer interactions." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368094.
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Kavanagh, Debbie M. "Chemical and physical characterization of clay bodies." Thesis, Aston University, 2001. http://publications.aston.ac.uk/9643/.
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Suitable methods for the assessment of the effect of freeze-thaw action upon ceramic tiles have been determined. The results obtained have been shown to be reproducible with some work in this area still warranted. The analysis of Whichford Potteries clays via a variety of analytical techniques has shown them to be a complex mix of both clay and non-clay minerals. 57Fe Mössbauer spectroscopy has highlighted the presence of both small and large particleα-Fe203, removable via acid washing. 19F MAS NMR has demonstrated that the raw Whichford Pottery clays examined have negligible fluorine content. This is unlikely to be detrimental to ceramic wares during the heating process. A unique technique was used for the identification of fluorine in solid-state systems. The exchange of various cations into Wyoming Bentonite clay by microwave methodology did not show the appearance of five co-ordinate aluminium when examined by 27Al MAS NMR. The appearance of Qo silicate was linked to an increase in the amount of tetrahedrally bound aluminium in the silicate framework. This is formed as a result of the heating process. The analysis of two Chinese clays and two Chinese clay raw materials has highlighted a possible link between the two. These have also been shown to be a mix of both clay and non-clay minerals. Layered double hydroxides formed by conventional and microwave methods exhibited interesting characteristics. The main differences between the samples examined were not found to be solely attributable to the differences between microwave and conventional methods but more attributable to different experimental conditions used.
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Rawson, Jolyon Oliver. "Physicochemical studies of clay polymer interactions." Thesis, Sheffield Hallam University, 1995. http://shura.shu.ac.uk/20267/.
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This thesis reports investigations into the colloid and solid state properties of clay/polymer complexes. The interactions between water soluble polymers and clay were investigated because of their importance to the oil industry which make use of clay/polymer interactions to control certain properties of drilling muds. [133]Cs and to a lesser extent [23]Na NMR have been evaluated as novel in situ probes to study the adsorption of polycations, and other cationic species, onto 25 gL[-1] suspensions of Westone-L. Westone-L is a low iron containing montmorillonite which was completely exchanged with either Cs[+] or Na[+] cations. The polycations FL15, FL16 and FL17, of general formula [(Me[2]NCH[2]CHOHCH[2)[n]][n+], and Magnafloc 1697, [(CH[2]CHCH[2]N(Me)[2]CH[2]CHCH[2])[n]][n+] have been shown to displace the exchangeable cation from the clay surface more effectively than other cationic species investigated such as Na[+], K[+], MeN[4+] and paraquat[2+]. This was shown through a decrease in linewidth and an increase in the [133]Cs or [23]Na NMR peak integral as cationic species were added to the clay. This information has been correlated with that obtained from particle size and zeta potential measurements in aqueous solution which suggest that the highly charged polycations investigated adsorb onto the surface of the clay via an 'electrostatic patch' mechanism. To complement these aqueous in situ techniques, several dry powder studies have been completed, including adsorption isotherms through Kjeldahl N analysis, variable temperature x-ray diffraction and thermogravimetric studies. These dry powder studies show conclusively that the exchangeable cation associated with the clay surface has a large bearing upon the amount and location of polymer adsorbed. The neutral polyglycol DCP101 is presently finding widespread use as a shale inhibitor in drilling muds. The mechanism by which this polymer interacts with clay has been investigated by recording the [133]Cs and [1]H NMR spectra of 25 gL[-1] suspensions of Cs[+] and Mn[2+] exchanged Westone-L treated with DCP101. These novel in situ investigations have shown that DCP101 does not displace the exchangeable cation associated with the clay. They have also shown that the water molecules in the hydration sphere of the Mn2+ cation associated with the clay surface are predominantly undisturbed by added DCP101. To complement these aqueous in situ investigations, several dry powder studies were carried out including adsorption isotherms through CHN analysis, variable temperature x-ray diffraction and thermogravimetric studies. These dry powder studies show that the exchangeable cation has a large bearing upon the quantity of polymer adsorbed. One further in situ NMR method has been evaluated with a view to investigating clay/polymer interactions. This method involved the addition of 10% D[2]O to a 40 gL[-1] suspension of clay which had been exchanged to the cation of interest. The resulting [2]H NMR spectrum showed a residual quadrupolar splitting, the magnitude of which depended upon several factors including clay concentration, state of aggregation of the clay platelets and the exchangeable cation associated with the clay. It was hoped that by monitoring the clay/D[2]O interactions via the [2]H residual quadrupolar splitting that information about clay/polymer systems in aqueous suspension would be forthcoming. The observed [2]H residual quadrupolar splitting was however found to be too sensitive to addition of polymer or ions to the clay suspension, resulting in its collapse to a singlet.
5
Bray, Helen Jane. "Kinetics of high-temperature transformations of clay minerals." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249204.
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Duan, Jinming. "Influence of dissolved silica on flocculation clay suspensions with hydrolysing metal salts." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264932.
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Collinson, S. J. M. "Structure and dynamics of the adsorbed phase." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354821.
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Chorom, Mostafa. "Behaviour of alkaline sodic soils and clays as influenced by pH and particle change." Title page, contents and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phc551.pdf.
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Copies of author's previously published articles inserted. Bibliography: leaves 173-196. The objective of this thesis is to investigate the factors affecting swelling and dispersion of alkaline sodic soils containing lime and the ways to manage these soils to improve their physical condition. Studies on pure clay systems are included to understand the fundamental process involved in swelling and dispersion of pure and soil clays.
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Rummey, Jacqueline Michelle. "EXAFS studies of polyoxometallates and chromium pillared clays." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305565.
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Martin, K. "The catalysis of organic reactions by clays and zeolites." Thesis, Aberystwyth University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381778.
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Rhodes, Cristopher Neil. "The characterisation of acid-treated montmorillonite clays as catalysts and as supports for lewis acid catalysts." Thesis, Leeds Beckett University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240205.
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Kravats, Andrea N. "Coarse grained molecular dynamics simulations of the coupling between the allosteric mechanism of the ClpY nanomachine and threading of a substrate protein." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384849649.
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Mandair, A. S. "Studies in clay chemistry." Thesis, Aston University, 1988. http://publications.aston.ac.uk/9717/.
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A study of clay chemistry has been approached with three aims: - to modify the conducting properties by intercalation of tetrathiafulvalene, - to study the electrochemistry of redox-active coordination compounds immobilised on clay coated electrodes, and - to study the role of clays as reagents in inorganic glass forming reactions using mainly solid-state magic-angle-spinning NMR. TTF was intercalated by smectites containing different interlayer and lattice cations. Evidence from ESR and 57Fe Mossbauer indicated charge-transfer from TTF to structural iron in natural montmorillonite, and to interlayer Cu2+ in Cu2+ exchanged laponite. No charge transfer was observed for laponite (Na+ form) itself. Ion exchange of TTF3(BF4)2 with laponite was found to proceed quantitatively. The intercalated species were believed to be (TTF)2+ dimers. Conductivity data showed an order of magnitude increase for the intercalated clays. The mechanism is thought to be ionic rather than CT as Na+ laponite showed a similar enhancement in conductivity. Mechanically robust colloidal clay films were prepared on platinum electrodes. After immersion in solutions containing redox active complexes [Co(bpy)3]3+ and [Cr(bpy)3]3+, the films became electroactive when a potential was applied. Cyclic voltammograms obtained for both complexes were found to be of the diffusion controlled type. For [Co(bpy)3]3+ immobilised on clay coated electrodes, a one-step oxidation and four-step reduction wave was observed corresponding to a one electron stepwise reversible reduction of Co(III), through Co(II), Co(I), Co(O) to Co(I) oxidation state. For [Cr(bpy)3]3+ the electrochemistry was complicated by the presence of additional waves corresponding to the dissociation of [Cr(bpy)3]3+ into the diaquo complex. ESR and diffuse reflectance data supported such a mechanism. 29Si, 27Al and 23Na MAS NMR spectroscopy, supported by powder XRD and FTIR, was used to probe the role of clays as reagents in glass forming reactions. 29Si MAS NMR was found to be a very sensitive technique for identifying the presence and relative abundance of crystalline and non-crystalline phases. In thermal reactions of laponite formation of new mineral phases such as forsterite, akermanite, sillimanite and diopside were detected. The relative abundance of each phase was dependent on thermal history, chemical nature and concentration of the modifier oxide present. In continuing work, the effect of selected oxides on the glass forming reactions of a model feldspar composition was investigated using solid state NMR alone. Addition of network modifying oxides generally produced less negative 29Si chemical shifts and larger linewidths corresponding to a wider distribution of Si-O-Si bond angles and lengths, and a dominant aluminosilicate phase with a less polymerised structure than the starting material. 29Si linewidths and 27Al chemical shifts were respectively correlated with cationic potential and Lewis acidity of the oxide cations. Anomalous Al(4) chemical shifts were thought to be due to precipitation of aluminate phases rather than a breakdown in Lowenstein's aluminium avoidance principle.
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Lao, Hongbai. "Novel microporous organo-clay materials and organo-clay polymeric composite membranes." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6830.
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A series of quaternarized ammonium mono and di-cations, quaternarized amino acid ester mono and di-cations, and quaternarized polyammonium cations were synthesized by methylation reaction. The synthesized quaternarized ammonium derivatives were incorporated into the interlamellar space of the smectites, montmorillonite (SWy-1) and hectorite (SHCa-1). The adsorption of these quaternarized ammonium cations by the smectites were studied by colorimetric and Na-electrode methods. Also the CEC values were determined from the adsorption isotherms and were found to be close to the CECs of the smectites. The intercalation of the quaternarized ammonium cations into the interlamellar space of the smectites were evaluated by X-ray powder diffraction technique and the changes of the interlayer spacings upon intercalation were measured. The adsorption and X-ray results indicated that the quaternarized ammonium cations adopt a parallel orientation arrangement in the interlamellar space of the smectites. Insight into the micropore structure of the prepared organo-smectites has been obtained with N$\sb2$ adsorption and desorption studies. The BET interlayer surface area, external surface area, micropore volume and mesopore volume were calculated from the N$\sb2$ adsorption and desorption isotherms. The total BET surface areas of the organo-smectites were in the range of 58-224 m$\sp2$/g, depending on the size of the intercalated cations. It has been implied that the incorporation of the quaternarized ammonium cations into the interlamellar space of the smectites results in a microporous material with a network of cavities whose height and volume are controlled by the size and the shape of the organic cation. The gas chromatographic properties of these organo-smectites have been determined with focus on the separation of air, CH$\sb4$ and CO$\sb2$ as well as the separation of C$\sb1$-C$\sb4$ and C$\sb5$-C$\sb8$ hydrocarbons. The organo-smectites have been proven to be a GC adsorbent for gas separations. The separation of methane and carbon dioxide was controlled by the interactions with the clay surface, not by the interaction with the substituents of the alkylammonium chain. The shapes of the microcavities played a role in the separation of gas mixtures. The CO$\sb2$ retention time has been found to increase with increasing the free surface area of the organo-smectite. Moreover, it has been shown that the retention time of C$\sb1$-C$\sb4$ hydrocarbons decreased with increasing the free volume of the organo-smectite. Furthermore, some microporous organo-smectite materials have been imbedded into the cross-linked polydimethylsiloxane (PDMS) polymers giving composite membranes. The composite membranes have been evaluated by the gas permeation experiments. The pure gas permeation results showed that the gas permeabilities decreased upon filling of the organo-smectites into the PDMS polymers. The pure gas permeability ratios of O$\sb2$/N$\sb2$ and CO$\sb2$/CH$\sb4$ were found to be controlled by both the organo-smectite content and the microporosity of the organo-smectites. The maximum pure gas permeability ratio for CO$\sb2$/CH$\sb4$ achieved was 8.7 as compared to 3.9 which was obtained for organo-smectite free PDMS membranes.
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Siddans, Bradley. "Epoxy/Clay Nanocomposites: Effect of Clay and Resin Chemistry on Cure and Properties." Queensland University of Technology, 2005. http://eprints.qut.edu.au/16024/.
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Polymer/clay nanocomposites consisting of an epoxy resin matrix filled with organoclays have been investigated. The main objective of this study was to determine which combination of components led to the greatest enhancement in properties of the epoxy resin. Exfoliation of the clay was desired, as exfoliated nanocomposites are known to exhibit great improvements in mechanical properties [1]. The epoxy resins studied were di-functional DGEBA and tetra-functional TGDDM. The epoxy resin was cured with three different hardeners, these included: the high functionality amine hardener, TETA, and two anhydride hardeners, accelerated MTHPA and pure HHPA. The three organoclays used, contained alkylammonium cations and were also compared to the unmodified clay. Morphology was investigated by XRD and TEM, and the flexural properties of the resulting nanocomposites were studied. The effect that the addition of an organoclay has on the cure of the epoxy resin was investigated using MDSC. Both the temperatures required to cure the resin with, and without, the clay, and any changes in the total heat flow that occurred were studied. The Tg++ of the cured nanocomposites was also measured using MDSC. The heat flow results indicated that the clays added to the epoxy resins act as a physical barrier, which prevents the resin from reaching full cure. In the higher functional resin, the addition of clay resulted in a significant decrease in the total heat flow, suggesting that a large amount of epoxy remains uncured, and, as a result, there should be a reduction in the amount of cross-linking. The lower cross-link density led to a significantly lower Tg and the mechanical properties were also poorer. The reactivity of the hardener towards the resin was found to have the greatest impact on the cured nanocomposite morphology. Intragallery polymerisation occurring at a faster rate than the extragallery polymerisation causes exfoliation. In order to achieve a balance that favours intragallery polymerisation, it was found that the curing reaction was required to be catalysed by the alkylammonium cation of the organoclay, and not catalysed by other means. The DGEBA cured with HHPA provided the largest layer expansion in the clay structure due to the alkylammonium cation catalysing the anhydride ring-opening reaction. The effect was not seen with TGDDM due to the tertiary amine in its structure. The accelerator within the MTHPA assisted extragallery polymerisation of the resin and the TETA cured readily without additional catalysis.
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Iqbal, Zafar. "Catalysis of organic reactions on clay." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254656.
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Omonmhenle, Selina Ilunakan. "Clay derived materials for environmental management." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5332/.
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Hydrotalcite-like compounds with Mg\(^2\)\(^+\)/Al\(^3\)\(^+\) and Zn\(^2\)\(^+\)/Al\(^3\)\(^+\) cations in the layer at different mole ratios with different anions in the galleries were synthesised in this study. The materials have been characterised by a range of techniques. The influence of layer cations, and interlayer anions, which in turn influences the crystallinity, can affect the properties of the hydrotalcites. Dodecylsulfate (DS) and dodecylbenzenesulfonate (DBS) anions were intercalated successfully into the galleries and characterisation studies by the same technique that were used for the parent hydrotalcites show that the hydrotalcites structure was maintained and the interlayer space expanded, suggesting that intercalation of other organic compounds may be possible. The intercalated dodecylsulfate and dodecylbenzenesulfonate anions arranged themselves in monolayer and bilayer configuration in the interlayer. These modified hydrotalcites have well-ordered layered structures, divalent/trivalent mole ratios that are close to those of the host precursors, and hydrophobic properties. SEM images show that the modification led to many of the particles being broken down into smaller pieces due to thermal pre-treatment and regeneration with organic anions, but overall morphology was maintained as the host. They show thermal transitions that are comparable to the host, exhibiting three decomposition steps but with increase in the temperature at which weight losses are completed. They show capacity to uptake phenol and 2-chlorophenol (2-CP) from aqueous solution with the compounds containing DBS anions showing higher sorption capacities for 2-CP than the corresponding DS-containing compounds. A pseudo second order reaction best described the sorption process.
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Morris, Jonathan David. "Physical and numerical modelling of grouted nails in clay." Thesis, University of Oxford, 1999. http://ora.ox.ac.uk/objects/uuid:530eeb78-5ead-4459-8733-3e6ae722c687.
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The research described in this thesis focussed on the bond resistance of grouted soil nails in clay. Physical modelling took the form of large scale element tests in the laboratory of drilled and grouted nails in a stiff clay. Nails were installed under different boundary stresses; testing was conducted at different constant rates of pull-out and also under sustained load conditions. Observed behaviour was compared with that predicted by measurements of interface shear resistance obtained in a conventional shear box. Numerical modelling was carried out in an attempt to improve understanding of the effects of installation processes on nail performance, and to investigate the trends in behaviour observed during laboratory tests. For this purpose, a one-dimensional finite element computer program was developed to include the effects of consolidation and the out-of-plane soil displacements associated with nail axial loading. The physical modelling showed that the loading rate has a significant effect on bond resistance. This has consequences for the interpretation of data from constant rate of displacement pull-out testing, the conventional method of verifying bond resistance in the field. It is suggested that this type of testing is inappropriate in low permeability soils, because capillary suctions develop which lead to increased bond resistance. Results from laboratory sustained load tests show that lower values of bond resistance are mobilised under the static load conditions more likely to exist in a real soil nailed structure. The numerical modelling confirms the behaviour observed during the laboratory tests, and shows that the mechanisms by which bond is mobilised are complex, depending critically on the dilation and consolidation characteristics of the soil. Nail installation procedures are modelled, and grout pressures are shown to strongly influence bond resistance. Interface tests show trends in behaviour similar to those observed during pull-out testing. However, difficulties exist in the qualitative use of interface test data to predict nail bond resistance.
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Latimer, Jennifer Michelle. "Physical and chemical weathering of illite in the presence of oxalate." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Thesis/Spring2010/j_latimer_042210.pdf.
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Thesis (M.S. in soil science)--Washington State University, May 2010.Title from PDF title page (viewed on July 8, 2010). "Department of Crop and Soil Sciences." Includes bibliographical references (p. 31-33).
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Ashcroft, R. C. "Organometallic precursors for pillared clay synthesis." Thesis, Aston University, 1993. http://publications.aston.ac.uk/9773/.
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The synthetic hectorite, laponite has been used within the paper industry to produce mildly conducting paper for use in electrographic printing. The aim of this research was to modify laponite in order to improve the electrical conductivity. In a continuation of a previous investigation involving organotin intercalation of laponite, the organotin precursor (p-CH3,OC6H4)4Sn was synthesised and characterised using Mass Spectroscopy, Infrared Spectroscopy and elemental analysis. Results of intercalation with this compound and a range of organobismuth and organoantimony compounds suggested that a halide content within the precursor was necessary for improvement in conductivity to be observed. Organometallic intercalation of a range of organotellurium compounds with laponite provided evidence that a hydrolysis reaction on the clay surface followed by the release of hydrochloric acid was an important first step if a reaction was to occur with the clay. Atomic Absorption Spectroscopy studies have shown that the acid protons underwent exchange with the interlayer sodium ions in the clay to varying degrees. Gas-liquid Chromatography and Infrared Spectroscopy revealed that the carbon-tellurium bond remained intact. Powder X-ray diffraction revealed that there had been no increase in the basal spacing. The a.c. conductivity of the modified clays in the form of pressed discs was studied over a frequency range of 12Hz - 100kHz using two electrode systems, silver paste and stainless steel. The a.c. conductivity consists of two components, ionic and reactive. The conductivity of laponite was increased by intercalation with organometallic compounds. The most impressive increase was gained using the organotellurium precursor (p-CH3OC6H4)2TeCl2. Conductivity investigations using the stainless steel electrode where measurements are made under pressure showed that in the case of laponite, where poor particle-particle contact exists at ambient pressure, there is a two order of magnitude increase in the measured a.c. conductivity. This significant increase was not seen in modified laponites where the particle-particle contact had already been improved upon. Investigations of the clay surface using Scanning Electron Microscopy suggested that the improvement in particle-particle contact is the largest factor in the determination of the conductivity. The other important factor is the nature and the concentration of the interlayer cations. A range of clays were synthesised in order to increase the concentration of sodium interlayer cations. A sol-gel method was employed to carry out these syntheses. A conductivity evaluation showed that increasing the concentration of the sodium cations within the clay led to an increase in the conductivity.
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Lee, Yat Sun. "Physical and numerical modelling of pipe-soil interaction in clay." Thesis, University of Sheffield, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.577564.
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To relieve the axial stress induce rature high-pressure pipelines in deepwater, current design methods leave the pipe unburied and allow the formation of the lateral buckles along the pipeline in a controlled manner. However, this approach requires a better understanding of the interaction between the seabed soil and the partially embedded pipeline under both vertical and lateral movements. Research has been carried out to examine the two soil-pipe interaction mechanisms, vertical pipe penetration and lateral pipe movement, involved in the installation and operation of an on-bottom offshore pipeline. The findings reported in this thesis improve the current knowledge of pipe-soil interaction in clay. A series of physical model tests was conducted to investigate the behaviour of pipe penetration and lateral pipe movement in clay. The experiments were carried out using short pipe sections in a I g model tank equipped with a transparent Perspex window in the front panel, from which high quality images were obtained for the measurement of the soil deformation in the tests using an image analysis technique. The computational limit analysis, Discontinuity Layout Optimisation (DLO), was adopted to back-analyse and compare with the experimental results. In addition, parametric studies were conducted using DLO to investigate the effects of the change in soil geometry and soil condition on the pipe resistances and soil flow mechanisms for the vertical pipe penetration and the lateral pipe sweep processes. Experimental results showed that pipe penetration, prior to the fully embedded flow-around failure mechanism at very deep penetrations, involves four distinct stages in development of the failure mechanism from 'soil heave' to 'local flow-around' at shallow and deep pipe embedments, respectively. Good agreement was observed between the experimental and numerical results. The results of the parametric studies suggested that the onset depth of the fully embedded flow-around failure mechanism is strongly dependent on the undrained strength profile and tensile strength of the soil. The lateral resistance of a partially embedded pipe under different loading conditions was measured at both small and large lateral displacements. Results showed that the lateral resistance is strongly affected by the change in soil geometry, soil heave induced by the initial penetration and formation of the active berm in front of the pipe during lateral movements. Based on the results from the numerical and experimental studies, design equations are proposed for the predictions of (i) the pipe penetration resistance at both shallow and deep embedments, and (ii) the lateral resistance of a partially embedded pipe under combined vertical and horizontal loads at both small and large lateral displacements.
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Gunduz, Erol Mehmet. "Playing With Clay| Knowledge Making Across Physical and Digital Materials." Thesis, Teachers College, Columbia University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10287813.
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Digital clay is a virtual material that exists currently in many 3D design software applications. Coupled with the rapid development of 3D printing technology, clay forms designed with a computer can now be externalized into the physical world as 3D prints or, vice versa, as digital scans. Recently, advanced tools have become available to artists and designers as affordable systems marketed to the professional consumer. As a response to these developments, my research examines the learning that occurs for eight artists who have been asked to play with physical and digital clay. This research employs a multiple case study methodology to understand the challenges of learning to work with digital clay and the supporting role of physical material engagement in this process. By interviewing participants and thematically analyzing their responses, I presented the subjective experience of the artists through portraiture showcasing the educational role play assumes when engaging across physical and digital media. Findings of the study suggest that engaging physical and digital materials calls upon a broad scope of cognitive processes including recollection and mental wanderings that contributed to reflection and discovery of novel ideas. Details from unstructured interviews were presented through narrative reporting as this research also strives to make sense of the participants' experience and situate the details of the study’s context.
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Saxe, Shoshanna Dawn. "Ground source heat storage and thermo-physical response of soft clay." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55158.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 137-141).
Ground source heat storage can condition buildings with reduced consumption of fossil fuels, an important issue in modem building design. However, seasonal heat storage can cause soil temperature fluctuations and possibly deformation of soft clays. This thesis evaluates the thermo-mechanical response of soft clays to seasonal heat storage and associated temperature fluctuations. A literature review reveals that, in normally consolidated to lightly overconsolidated clays, increases in soil temperature can lead to significant plastic strains and a reduction in soil strength. This behavior can be modeled through constitutive formulations that include thermal strain within the elasto-plastic framework of the well-known Modified Cam-Clay Model. The current research uses the MCC Picard (1994) model to study the ground response to a buried heat exchange pipe. The spacing of the pipe was found to govern the effectiveness of ground heat storage. With only one pipe in semi-infinite soil, heat transfer to the ground dissipates quickly and thermal-mechanical interaction is negligible; however, seasonal heat storage is not possible. Closely spaced heat pipes would permit effective seasonal heat storage, but could undergo significant thermally induced consolidation deformations.
by Shoshanna Dawn Saxe.
S.M.
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Lam, Sze Yue. "Ground movements due to excavation in clay : physical and analytical models." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/228701.
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In view of the recent catastrophes associated with deep excavations, there is an urgent need to provide vital guidelines on the design of the construction process. To develop a simple tool for predicting ground deformation around a deep excavation construction for preliminary design and decision-making purposes, small scale centrifuge models were made to observe the complicated mechanisms involved. A newly developed actuation system, with which the construction sequences ofpropping could be implemented, was developed, the new procedures were proven to give more realistic initial ground conditions before excavation with minimal development of pre-excavation bending moment and wall displacement. Incremental wall deformation profiles generally followed the O'Rourke cosine bulge equation and a new deformation mechanism was proposed with respect to wall toe fixity and excavation geometry. Validation of the conservation energy principle was carried out for the undrained excavation process. The total loss of potential energy was shown to be balanced by the total work done in shearing and the total elastic energy stored in structures with an error term of 30%. An improved mobilizable strength method (MSD) method using observed mechanistic deformation patterns was introduced to calculate the displacement profile of a multi-propped undrained excavation in soft clay. The incremental loss in potential energy associated with the formation of settlement toughs was balanced by the sum of incremental storage of elastic energy and the energy dissipation in shearing. A reasonable agreement was found between the prediction by the MSD method and the finite element results computed by an advanced MIT-E3 model for wall displacements, ground settlement, base heave and bending moment on fixed base walls. For cases of excavations supported by floating walls, the effect of embedded wall length, depth of the stiff layer, bending stiffness of wall and excavation geometry and over-consolidation ratio of soils were found to have a influence on the maximum wall deflection. In general, the predictions fell within 30% of the finite element computed results. A new chart Ψ versus normalized system stiffness was used to demonstrate that MSD could correctly capture the trend of wall displacements increasing with the ratio ofexcavation depth to depth of stiff layer, which could be controlled by increasing wall stiffness for very stiff wall system only. The incorporation of a simple parabolic curvequantifying small strain stiffness of soil was proven to be essential to good ground movement predictions. A new dimensionless group has been defined using the MSD concepts to analyze 110 cases of excavation. The new database can now be used to investigate the relationship between structural response ratio S and soil-structure stiffness ratio R where this is shown on log-log axes to capture the enormous range of wall stiffness between sheet-piles and thick diaphragm walls. Wall stiffness was found to have a negligible influence on the magnitude of the wall bulging displacements for deep excavation supported by fixed-based wall with stiffness ranging from sheet pile walls to ordinary reinforced concrete diaphragm walls, whereas excavations supported by floating walls were found to be influenced by wall stiffness due to the difference in deformation mechanisms.
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Stackhouse, Stephen. "Reactivity of the clay mineral montmorillonite : a first principles study." Thesis, Queen Mary, University of London, 2003. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1807.
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The recent development of clay-polymer nanocomposite materials has led to an increased interest in the structure and properties of clay minerals. In this thesis the reactivity of the clay mineral montmorillonite is explored by means of density functional theory based calculations. In particular three aspects are considered: catalytic properties, cation migration and dehydroxylation. The origin of the catalytic properties of the clay mineral is investigated in the context of the synthesis of clay-polymer nanocomposite materials, by in sttu, intercalative polymerisation. It is found that catalysis is most likely to occur at the clay mineral lattice-edge where exposed aluminium atoms act as Lewis acid sites. Migration of lithium cations into the clay mineral lattice is explored by means of first principles molecular dynamics. Comparison of calculated hvdrox-vl stretching frequencies, with those from experiment indicates that cations migrate to vacant octahedral sites, as oppose to the ditrigonal cavities. Dehydroxylation of the clay mineral is examined by consideration of a cis-vacant pyrophyllite structure. It is shown that dehydroxylation leads to formation of a tyan8-vacant structure, with aluminium in trigonal bipyramidal coordination and a highly distorted tetrahedral layer. Differences in the dehydroxylation behaviour of cm and tran8-vacant pyrophyllite are shown to be due to the fact that in the former adjacent hydroxyl groups bridge different pairs of aluminium atoms, while in the latter they are both bonded to the same pair. Overall density functional theory based calculations are shown to be a powerful tool for the studly of the structure and reactivity of clay minerals.
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Chow, John Kam Keung. "Sorption of radionuclides onto clay minerals and soils." Thesis, University of Salford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241543.
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Michael, Paul J. "Studies of clay minerals and their decomposition products." Thesis, Aston University, 1989. http://publications.aston.ac.uk/9813/.
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Mõssbauer spectroscopy and X-ray diffraction of five coals revealed the presence of pyrite, illite, kaolinite and Quartz, together with other minor phases. Analysis of the coal ashes indicated the formation of hematite and an Fe (3+) paramagnetic phase, the latter resulting from .the dehydroxylation of the clay minerals during ashing at 700 to 750 C. By using a combination of several physicochemical methods, different successive stages of dehydroxylation, structural consolidation, and recrystallisation of illite, montmorillonite and hectorite upon thermal treatment to 1300 C were investigated. Dehydroxylation of the clay minerals occurred between 450 and 750 C, the X-ray crysdallinity of illite and montmorillonite remaining until 800 C. Hectorite gradually recrystallises to enstatite at temperatures above 700°C. At 900 C the crystalline structure of all three clay minerals had totally collapsed. Solid state reactions occurred above 900 C producing such phases as spinel, hematite, enstatite, cristobalite and mullite. Illite and montmorillonite started to melt between 1200 and 1300°C, producing a silicate glass that contained Fe(3+) and Fe(2+) ions. Ortho-pnstatite, clino-enstatite and proto-enstatite were identified in the thermal products of hectorite, their relative proportions varying with temperature. Protoenstatite was stabilised with respect to metastable clinoenstatite upon cooling from 12000 C by the presence of exchanged transition metal cations. Solid state Nuclear Magnetic Resonance spectroscopy of thermally treated transition metal exchanged hectorite indicated the levels at which paramagnetic cations could be loaded on to the clay before spectral resolution is significantly diminished.
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Berti, Debora. "Clay mineralogy and its effect on physical properties in the Gulf of Mexico northwestern continental slope." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/1624.
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The clay mineral composition of sediments deposited in the last six oxygen isotope stages in the Gulf of Mexico continental slope was characterized. Smectite and illite were found to be the two major clay minerals of the clay fraction while kaolinite, chlorite and quartz were present in the clay fraction but in less proportions. Variations in clay mineral abundances, especially in the relative abundances of smectite and illite, were identified in relation to climate changes. Smectite was the most abundant mineral in sediments of the current (stage 1) and last interglacial maxima (stage 5) while illite dominates the clay min-eralogy of sediments from the last glacial maximum (stage 2). Relationships between clay mineralogy and physical properties were investigated as well. Significant positive correla-tions were found between Atterberg limits with the smectite content of the bulk sediment and with clay content. However, the relationship with smectite yielded a significantly higher correlation coefficient. Smectite and clay content also affect the natural water con-tent of sediments and its changes with depth.
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Villemure, Gilles. "Photochemical applications of the intercalation of organic cations in clay minerals." Thesis, University of Ottawa (Canada), 1987. http://hdl.handle.net/10393/21389.
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Mrayed, Sabri Mohamed Ali Chemical Sciences & Engineering Faculty of Engineering UNSW. "Molecular modelling applications in crystallization fouling and clay/polymer nanocomposites." Awarded by:University of New South Wales. Chemical Sciences & Engineering, 2007. http://handle.unsw.edu.au/1959.4/40682.
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The present work used ab initio density functional theory (DFT) to study two different physical phenomena crystallization fouling and clay-based polymer nanocomposites. In the first part, two foulant materials were studied including calcium carbonate, and calcium sulfate. The lattice energy and enthalpy of formations of each crystal system were predicted using DFT methods. The most stable forms of calcium carbonate foul ant, calcite and aragonite, were investigated. For calcium sulfate, both gypsum and anhydrite crystals were investigated. The thermodynamic solubility product of each crystal system, for both foul ants, was predicted from the lattice energy and enthalpy of formations. Comparison of the stability between the different crystal systems for the same foul ant material was carried out to elucidate the effect of crystal atomic configuration and space group on the stability of foulant materials. The effect of temperature on the formation and stability of foulant material was also carried out. The results obtained using DFT methods, for enthalpy of formation and thermodynamic solubility products, were comparable with the experimental data reported in the literature. In the second part, study has been made on the clay-based nylon 6 nanocomposite materials. The purpose was to understand the interfacial interactions between clay and polymer with and without surfactant component. Both sides of the clay were examined with nylon 6. In order to determine specifically the type of interfacial interaction between clay and nylon 6, the electron distribution around the whole system was predicted. The study was carried out at various isomorphic substitutions. The substitutions took place at both octahedral and tetrahedral layers of the clay. The strength between clay and nylon 6 was predicted by calculating the binding energy. The results obtained revealed that, the strength increases with the increase in the degree of isomorphic substitutions. The type of bond between nylon 6 and basal surface of the clay was found to be basically electrostatic interactions, and particularly hydrogen bonds. Whilst, the type of interactions between nylon 6 and clay edge surface was found to include covalent bonds as well as electrostatic interactions. The formation and breakage of covalent bonds between nylon 6 and clay means that, a chemical decomposition of the clay can happen when it is mixed with certain type of polymers. The presence of surfactant can decrease the interfacial interactions between clay and nylon 6.
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Ngabe, Barnabe. "Physical chemistry of sulphide self-heating." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123024.
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ABSTRACTA prerequisite step towards building a self-heating (SH) model for sulphide materials is the determination of physico-chemical parameters such as the specific heat capacity (Cp), and the energy of activation (Ea). The specific heat capacity of one copper and three nickel concentrates was determined over the temperature range 50 to 80oC in the presence of 6% moisture using the self-heating (SH) apparatus and confirmed by Drop Calorimetry. The Cp values from both techniques were comparable. The Cp values were similar for all concentrates increasing from 0.4 to 1.4 Jg-1K-1 as temperature increased from 50 to 80oC. From the Cp values, the enthalpy change (ΔH), the entropy change (ΔS) and the Gibbs free energy change (ΔG) for self-heating, were determined. The ΔG was negative, demonstrating that self-heating of the concentrates was spontaneous.Using the self-heating apparatus the, activation energy (Ea) was determined for the Ni-and Cu-concentrates and for pairs of sulphide minerals. The Ea ranged from 22 to 30 kJ.mol-1, implying a common reaction. Further support for a common reaction is the strong positive correlation between Ea and ln(QA/Cp) where Q (J.kg-1) is the heat of reaction causing self-heating and A the Arrhenius pre-exponential factor (s-1). Comparing to literature, the Ea values correspond to partial oxidation of hydrogen sulphide, supporting the contention that H2S may be an intermediate product in the self-heating of sulphide minerals. A positive relationship between Ea and the rest potential difference (ΔV) for the sulphide pairs and a negative relationship between Cp and ΔV were demonstrated which support a connection between self-heating and the galvanic effect.RESUMÉLa réalisation d'un modèle mathématique de l'auto-échauffement des concentrés sulfurés de nickel et de cuivre et des mélanges des minerais sulfurés, enjoint à la détermination des paramètres physico-chimiques tels que les capacités de chaleur spécifiques (Cp), et les énergies d'activation (Ea). Les capacités de chaleur spécifiques d'un concentré de cuivre et de trois concentrés de nickel contenant 6% d'humidité, ont été déterminées par utilisation d'un instrument de mesure de vitesse d'auto – échauffement et validées par la calorimétrie de chute dans l'intervalle de températures allant de 50 à 80oC. Les Cp (0.4 à 1.4 Jg-1K-1) obtenues sont similaires pour tous les échantillons. A partir des valeurs des Cp, les variations de l'enthalpie (ΔH), l'entropie (ΔS) et de l'énergie libre de Gibbs (ΔG) de l'auto échauffement ont été déterminées. La valeur négative de ΔG confirme le caractère spontané de l'auto échauffement des minerais sulfurés.Les énergies d'activation (Ea) pour l'auto-échauffement des concentrés de nickel et cuivre et des paires de minerais sulfurés étaient déterminées en faisant usage de l'appareil d'auto-échauffement. Les Ea ainsi obtenues oscillent entre 22 et 30 kJ.mol-1 : Ce qui est suggestif d'une rèaction chimique commune gouvernant l'auto-échauffement de ces matériaux. Ce fait est corroboré par la forte corrélation obtenue entre Ea et ln(QA/Cp) (Q (J.kg-1) est la chaleur de la rèaction chimique responsable de l'auto-échauffement et A (s-1) la constante d'Arrhenius).Ensuite celles-ci sont similaires à celle de l'oxydation partielle du H2S. Il se pourrait, ce faisant, que H2S soit un composé intermediaire lors de l'auto–échauffement des sulfures.Enfin, la corrélation positive entre Ea et la difference de potential (ΔV) dans les paires de minerais sulfurés et celle negative entre Cp et ΔV sont une preuve qu'il existe bel et bien une connection entre l'auto-échauffement et l'effet galvanique.
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Christy, R. K. "The physical chemistry of drug formulations." Thesis, University of Kent, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362185.
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Tudor, Jonathan Simon. "Synthesis and catalytic activity of organometallic-inorganic composite materials." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339188.
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Zysman-Colman, Eli. "The chemical and physical properties of polychalcogens." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84864.
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The optimized synthesis of acyclic dialkoxy disulfides and aromatic polysulfides is described and their physical properties probed. A theoretical survey of dialkoxy disulfides and thionosulfites was undertaken in order to determine the most efficacious method for accurately modeling these compounds. In particular, the origin of the high barrier to rotation in the dialkoxy disulfides was determined to be due to a generalized anomeric effect resulting from two lone pair donations of each sulfur atom into each of their respective sulfur-oxygen antibonding orbitals. The origin of the high rotational barrier was also verified experimentally, in particular with respect to solvent and substituent effects. Complimentary to this thermal process, the decomposition of dialkoxy disulfides was also investigated. It was determined that these compounds decompose under first order kinetics via an initial asymmetric S-O homolytic cleavage. Activation parameters for both of these processes were determined.Theoretical modeling on the relative ground state energies of dialkoxy disulfides is also described. It has been ascertained that the equilibrium position between the two isomers can be influenced by the ring size of the molecule; larger rings promote the dialkoxy disulfide isomer. These modeling studies were successfully corroborated experimentally. Of note is the synthesis of a new 8-membered ring dialkoxy disulfides as well as novel 7-membered ring thionosulfites. These compounds were also confirmed by single X-ray crystallography.
The kinetics of desulfurization of acyclic aromatic tri- and tetrasulfides is described. Tetrasulfides were found to transfer a sulfur atom to triphenylphosphine over ten times faster than their trisulfide analogues.
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Panagiotopoulos, Ioannis Polykarpos. "Clay influence on the threshold of movement and physical parameters of sand-mud deposits." Thesis, University of Southampton, 1996. https://eprints.soton.ac.uk/361139/.
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The erosion of mixed sediment deposits is described, under the action of unidirectional steady currents and (simulated) waves, separately, and in combination. The experiments were undertaken using a rectangular recirculating flume, incorporating an oscillating tray. The mixtures consisted of angular fine-grained quartz sands (D50=152.5 m and 215 m) combined with a very cohesive estuarine mud. Time-averaged erosion threshold current speeds, during the unidirectional and combined flow experiments, were measured. In addition, pore (water) pressure measurements, during the oscillatory and combined flow experiments, have been monitored. The results obtained under the action of currents show that there is an incremental increase, with clay content, in critical erosion shear stress. This increase is small for clay percentages lower than 11% (dry weight); it is larger for clay contents in excess of 11-14%. The quantity and cohesive nature of the clay fraction are suggested as the mechanisms to explain the bi-modal pattern of sediment erodibility. When the mixtures were subjected to different pre-threshold current speeds, together with various time-periods of flow, the critical erosion shear stress was higher than the original. In this process, current velocity is more important than flow duration. Data obtained under the influence of simulated wave action show that, for clay contents 11%, sediment erodibility is unaffected by the increasing clay concentrations. However, with clay contents in excess of 11-14%, a positive linear function may describe the variation in erosion threshold with clay content. Results obtained under the co-linear combined action of waves and currents demonstrate a significant and positive linear relation between erosion threshold and the cohesive additive. Furthermore, waves protect the sediment/water interface from the eroding competence of the steady currents. The resistance to erosion increases with a decrease in wave period (from 10 s to 6 s).
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Momot, Konstantin Igorevitch 1970. "Studies of nuclear magnetic relaxation processes in paramagnetic metalloporphyrin complexes." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282591.
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Temperature dependence of Nuclear Magnetic Resonance (NMR) chemical shifts and longitudinal and transverse relaxation times (T₁ and T₂) was studied for the pyrrole protons in a number of six-coordinate S = 1/2 iron(III) tetraphenylporphyrin (TPP) and tetramesitylporphyrin (TMP) complexes in the temperature range 190--310 K. In all complexes, temperature behavior of the chemical shifts and relaxation times is consistent with the presence of a low spin - high spin exchange caused by the dissociation of one axial ligand. In symmetric sterically hindered complexes, cyclic exchange induced by the synchronous rotation of axial ligands is also present. In all complexes, T₂s are considerably shorter than T₁s. Relaxation times in the TMP complexes are generally longer than corresponding values for the TPP complexes. Estimate of the electronic T₁ is given and mechanisms of nuclear relaxation are discussed. The rate of NOE buildup for a pair of pyrrole protons in [TMPFe(2-MeImH)₂]⁺ was measured; it is consistent with the Stokes rotational correlation time. A method is proposed to predict the detectability and optimum detection conditions of NOE between a pair of structurally rigid protons in similar complexes. Contrary to previous studies, no NOE is detected between pyrrole protons of two unsymmetrically substituted bis-N-methylimidazole Fe(III) TPP complexes. Two NMR approaches were utilized to measure the rate constant of axial ligand rotation in the TMP complex. Saturation transfer measurements yield overestimated rate constant. The measurement based on the temperature dependence of the T₂s(ΔH‡ = 48 ± 1 kJ/mol, ΔS‡ = -10 ± 6 J/K · mol) is consistent with previous studies. Modified MM2 potentials were also used to study the rotation of axial ligands in [TMPFe(1,2-Me₂Im)₂]⁺ and [TPPFe(1-MeIm)₂]⁺. Adiabatic potential energy surfaces (PES) for rotation of axial ligands were constructed for both complexes. Synchronous rotation of the axial ligands (ΔH‡ = 48 kJ/mol) is highly preferable in the TMP complex. For the TPP complex, the enthalpy barriers to synchronous and asynchronous rotation are 3.3 and 5.4 kJ/mol, respectively. The relationship between the orientation of axial ligands, distortion of metalloporphyrin core from planarity, and the bulkiness of axial ligands and porphyrin substituents is discussed.
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Jordan, Carly A. "Work Function Modification of Metal Electrodes via Printing of PEDOT:PSS and Carbon Nanotubes." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1440696711.
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Ji, Xiang Ji. "THE INFLUENCE OF ASSEMBLY PH AND CLAY INCLUSION ON THE ACTUATION OF POLYELECTROLYTE MULTILAYERS." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1468526322.
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Mashburn, Courtney Dyan. "Laboratory studies on the heterogeneous chemistry of clay minerals in the Earth's atmosphere." Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3239413.
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Grimes-Marchan, Thomas V. Cundari Thomas R. "Quantum perspectives on physical and inorganic chemistry." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-5172.
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Portal, Christophe. "Approaches to high throughput physical organic chemistry." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/2434.
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Over the past ten years, the development of High Throughput (HT) synthetic chemistry techniques has allowed the rapid preparation of libraries of hundreds to thousands of compounds. These tools are now extensively used for drug and material discovery programmes. The subsequent development of analytical capabilities to carry out qualitative and quantitative assessment of the compounds generated by HT synthesis as well as their HT screening has led to a dramatic broadening of the scope of HT techniques, ranging from image based analysis techniques to mass spectrometry (MS). Based on the latter, a range of solid phase and solution phase analytical constructs was developed to enable the qualitative and quantitative assessment of mixtures of small compounds, using positive electrospray MS as the sole analytical tool. A version of the construct allowed HT reactivity profiling to be carried out on a range of ten carboxylic acids, ten aldehydes and ten isonitriles in the Ugi 4-component condensation reaction. The effect of various parameters such as the concentration of the monomers on the reactivity was investigated. The elaboration of a HT Hammett parameter assessment method was made possible by the development of an electrophilic version of the construct. The value of the Hammett value was afforded by means of combinatorial Hammett plots and values were successfully evaluated in a HT mode for around thirty anilines with substituents in the meta and para position of the aromatic ring. Finally, analytical constructs were used in an attempt to evaluate enzyme reaction kinetics via the labelling of peptides and small drug fragment with coded constructs, to afford affinity determinations between the enzyme (protease) and peptidic or fragment based substrates.
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Slocum, Laura Elizabeth. "Evaluation of physical chemistry on-line modules." Virtual Press, 2001. http://liblink.bsu.edu/uhtbin/catkey/1221309.
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We have modeled in one-dimension two-dimensional (2-D) quantum wire structures: the notched electron stub tuner (NEST) and the double-notched electron stub tuner (D-NEST). The models consisted of square barriers representing the notches and square wells representing the stubs. We have calculated the transmission coefficient as a function of electron energy and/or device geometries to study electron transport through these quantum wire models. The transfer matrix method was used to calculate the transmission coefficient by utilizing a program written with Mathematica. The program and technique were verified using one-dimensional systems from the literature.We studied the principle of wave interference in the NEST model in the form of intersection points of several curves of the transmission coefficient versus barrier/well separation plotted with no offset. The creation of standing waves, in certain regions of the NEST model, by the interference of incident and reflected waves, gives rise to these intersection points. We have identified features in the conductance curves of the NEST and the transmission coefficient curves of the NEST model (the intersection points) that are very similar and may be explained by the same principle of wave interference.We have studied double-barrier resonant tunneling (DBRT) to assist in our study of the D-NEST model. The resonances in DBRT are attributed to the creation of standing waves between the two barriers for the tunneling and non-tunneling regimes. We attempted to prove the existence of these standing waves by studying the probability density in the D-NEST model. The well of the D-NEST model was scanned down the length of the double-barrier well region to investigate its effect on the transmission coefficient for this purpose. A small square barrier, used as a probe, was also used to study the probability density in the same way as the well was used. Initial scans of the probe above a simple square barrier gave us insight into the possibility of using it to scan for the probability density in the well region. The "over-the-barrier" resonances (attributed to standing waves) were studied in this case.We have developed knowledge of the transmission properties of these models that may aid in the understanding of the electron transport through the 2-D devices. We believe that to "fine tune" the conductance output of the D-NEST device, the second notch should be placed at a location that permits the creation of standing waves, for a specific electron energy value, between the two notches of the device. The "fine tuning" of the conductance output into a square-wave pattern could improve the devices performance as a potential switching mechanism.Department of Chemistry
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Frank, Robert A. "Physical chemistry of carbothermic reduction of alumina." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15150.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE
Vita.
Bibliography: leaves 177-180.
by Robert A. Frank.
M.S.
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Grimes-Marchan, Thomas V. "Quantum Perspectives on Physical and Inorganic Chemistry." Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc5172/.
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Applications of computational quantum chemistry are presented, including an analysis of the photophysics of cyclic trinuclear coinage metal pyrazolates, an investigation into a potential catalytic cycle utilizing transition metal scorpionates to activate arene C-H bonds, and a presentation of the benchmarking of a new composite model chemistry (the correlation consistent composite approach, ccCA) for the prediction of classical barrier heights. Modeling the pyrazolate photophysics indicates a significant geometric distortion upon excitation and the impact of both metal identity and substituents on the pyrazolates, pointing to ways in which these systems may be used to produce rationally-tuned phosphors. Similarly, thermodynamic and structural investigations into the catalyst system points to promising candidates for clean catalytic activation of arenes. The ccCA was found to reproduce classical reaction barriers with chemical accuracy, outperforming all DFT, ab initio, and composite methods benchmarked.
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Akinlotan, Oladapo Odunayo. "The sedimentology of the Ashdown formation and the Wadhurst Clay formation, southeast England." Thesis, University of Brighton, 2015. https://research.brighton.ac.uk/en/studentTheses/fbbe159f-ad9c-4def-87b5-dfeae8a9c567.
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Detailed sedimentological studies, using coastal and inland exposures, were carried out at formation and bed levels on the Ashdown and Wadhurst Clay formations (Late Berriasian-Valanginian) in the Weald, southeast England. Field descriptions of outcrops were conducted at seven sites and supplemented by borehole and 2D seismic data. Field samples were studied in detail using hand specimen analysis. The sandstones were described in hand specimen and via optical microscopy. Clay mineral and geochemical analyses on mudstones, shales, and ironstones were conducted using XRD, XRF, and SGR methods while SEM analyses were conducted on selected sandstones and ironstones. Porosity and permeability of selected sandstones were measured using pycnometry and gas permeametry respectively. The dominance of quartz arenites and kaolinite and the presence of thorium and Zr in the sediments suggest that they were sourced mainly from granitic and/or gneissic rocks. Materials from metamorphic sources appear to be secondary in abundance. The mineralogical and textural maturity of the sediments coupled with relatively short travel distance (~300km) suggests reworking from secondary or matured sources. The two formations received sediments from at least two sources. The clay mineral assemblage, sandstone composition, and gamma-ray data confirm that the main source of the sediments is the London Massif in the north and north east while sediments were also sourced from Armorica in the south based on the presence of detrital zircon. The palaeoclimatic conditions at the source area as revealed by the dominance of quartz arenites and kaolinite and the presence of thorium were warm and humid which led to intensive weathering. The mineralogy and geochemistry of the sediments suggest that they may have been directly or indirectly sourced from a stable craton. The lithology (sandstones, siltstones, mudstones, shales and ironstones); facies (channel and floodplain/overbank); sedimentary structures (channels, cross stratification, flaser bedding, ripples and planar laminations); sedimentary architecture (repeated cycles and vertically stacked multi-storey successions), and gamma ray data (more radioactive sandstone facies) confirm that the sediments within the two formations were deposited in predominantly fresh water environments although tidal and lagoonal conditions were clearly evident in the Ashdown Formation and Wadhurst Clay Formation respectively. The lithology and sedimentary facies show that deposition occurred in both braided and meandering river systems although meandering facies are more prominent in the lower Ashdown Formation. The presence of abundant load and slump structures and fresh green glauconite in the sandstones provide evidence that deposition was rapid while the water depth was shallow and not beyond 2 metres based on the widespread occurrence of colour mottling and frequent exposure of the sediments to the air. Early diagenesis was confirmed by the precipitation of sideritic ironstones while diagenetic alteration is minimal based on the clay mineral assemblage. Evidence from the shallow burial nature of sideritic ironstone, the proportion of illite-smectite and the nature of diagenesis confirm that the sediments have experienced shallow burial not beyond 2km. Enrichments in redox sensitive trace elements such as Mo, U, V and Co suggest anoxic conditions in the sediments. The highest levels of anoxia were in the lower sections of the formations. Palaeosalinity as indicated by sideritic ironstone indicates a pH between 6 and 10. Porosity ranges from 6.8% to 13. 2% with an average of 9.9% while permeability ranges from 0.4mD to 11.9mD with an average of 3.1mD. The main controls on porosity and permeability are grain sizes, grain shapes, and sorting and the porosity is mainly primary. The main control on sedimentation is the local tectonics at the source areas while palaeoclimatic conditions, sea level, river dynamics, and subsidence are secondary. The proximal part of the modern Niger Delta is proposed as an analogue for the palaeoenvironments of the Ashdown and Wadhurst Clay formations. More generally, the results presented in this thesis highlight the usefulness of integrating field, petrographic, mineralogical, and geochemical data, and the use of modern analogue to fully assess the depositional environments, stratigraphic variability, post depositional changes and controls on deposition within sedimentary basins.
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Gu, Yingying, and 顾莹莹. "Electrokinetic remediation of cadmium-contaminated natural clay of high buffer capacity." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46279015.
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Stewart, Laura. "Physical studies of diphytanylglycerol phospholipids." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5405.
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Anderson, Sandie Lanclyn. "Flocculation of clay suspensions using synthetic polymers." Ohio : Ohio University, 1986. http://www.ohiolink.edu/etd/view.cgi?ohiou1183126556.
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Jones, Ruth. "Chemistry of oxide superconductors." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304252.
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Cooper, Philip Andrew. "Surface chemistry of foams." Thesis, University of Hull, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335544.
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