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1
Ogden, Sam. "High-Pressure Microfluidics." Doctoral thesis, Uppsala universitet, Mikrosystemteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-208915.
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In this thesis, some fundamentals and possible applications of high-pressure microfluidics have been explored. Furthermore, handling fluids at high pressures has been addressed, specifically by creating and characterizing strong microvalves and pumps. A variety of microstructuring techniques was used to realize these microfluidic devices, e.g., etching, lithography, and bonding. To be able to handle high pressures, the valves and pumps need to be strong. This necessitates a strong actuator material. In this thesis, the material of choice is paraffin wax. A new way of latching paraffin-actuated microvalves into either closed or open position has been developed, using the low thermal conductivity of paraffin to create large thermal gradients within a microactuator. This allows for long open and closed times without power consumption. In addition, three types of paraffin-actuated pumps are presented: A peristaltic high-pressure pump with integrated temperature control, a microdispensing pump with high repeatability, and a pump system with two pumps working with an offset to reduce flow irregularities. Furthermore, the fundamental behavior of paraffin as a microactuator material has been explored by finite element modeling. One possibility that arises with high-pressure microfluidics, is the utilization of supercritical fluids for different applications. The unique combination of material properties found in supercritical fluids yields them interesting applications in, e.g., extraction and cleaning. In an attempt to understand the microfluidic behavior of supercritical carbon dioxide, the two-phase flow, with liquid water as the second phase, in a microchannel has been studied and mapped with respect to both flow regime and droplet behavior at a bi-furcating outlet.
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Misner, Scottie. "High Blood Pressure." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2010. http://hdl.handle.net/10150/146443.
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Crescenzo, Domenico. "Pressure measurement in the high pressure fuel system." Thesis, KTH, Förbränningsmotorteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-267549.
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In order to meet the demanding legislations on diesel engines exhaust emissions, an always more accurate control over the amount of fuel injected in the cylinders is required. A comprehensive understanding of the main factors involved in the injection process, therefore, should be achieved. Such factors are the pressure in the common rail, the injection ontime and the temperature at the injector. The rail pressure, in particular, has been the focus of this project: Its accurate acquisition is crucial for the correct determination of the injection duration and, consequently, for an improved control over the amount of fuel injected. The rail pressure, however, is characterized by significant instabilities affecting the measurement. An experimental campaign has been conducted on a Scania D13 engine in order to characterize and understand the rail pressure signature during engine steady operations: The superposition of injections, pump strokes and water-hammer instabilities forms a complex pattern extensively discussed. An attempt to model the pressure fast transients has been made: While the frequency content of the phenomenon investigated is correctly interpreted, the results obtained in the time domain diverge significantly in amplitude and phase from the experimental data collected. Finally, the measurement strategy adopted today at Scania CV AB to acquire the rail pressure has been investigated and its accuracy assessed. On the basis of the knowledge achieved, a new adaptive measurement technique, capable of changing the estimation process accordingly to the engine operating condition detected, is proposed. The potentiality of an increased accuracy in controlling the amount of fuel injected is proved for engine steady operations. Further investigation regarding the method tolerance to engine transients, however, is required.
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Pogson, Mark. "High pressure vibrational spectroscopy." Thesis, University of Leicester, 1987. http://hdl.handle.net/2381/33858.
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The study of solids at high pressure and variable temperature enables development of accurate interatomic potential functions over wide ranges of interatomic distances. A review of the main models used in the determination of these potentials is given in Chapter one. A discussion of phonon frequency as a variable physical parameter reflecting the interatomic potential is given. A high pressure Raman study of inorganic salts of the types MSCN, (M = K,Rb,Cs & NH4+) and MNO2, (M = K,Na) has been completed. The studies have revealed two new phases in KNO2 and one new phase in NaNO2 at high pressure. The accurate phonon shift data have enabled the determination of the pure and biphasic stability regions of the phases of KNO2. A discussion of the B1, B2 relationship of univalent nitrites is also given. In the series of thiocyanates studied new phases have been found in all four materials. In both the potassium and rubidium salts two new phases have been detected, and in the ceasium salt one new phase has been detected, all at high pressure, from accurate phonon shift data. These transitions are discussed in terms of second-order mechanisms with space groups suggested for all phases, based on Landau's theory of second-order phase transitions. In the ammonium salt one new phase has been detected. This new phase transition has been interpreted as a second-order transition. The series of molecular crystals CH3HgX, (X = Cl,Br & I) has been studied at high pressure and at variable temperature. In Chapter five, their phase behaviour at high pressure is detailed along with the pressure dependencies of their phonon frequencies. In the chloride and the bromide two new phases have been detected. In the bromide one has been detected at high temperature and one at high pressure, the latter being interpreted as the stopping of the methyl rotation. In the chloride one phase has been found at both low temperature as well as high pressure, and the other only at high pressure, the latter again associated with the stopping of methyl rotation. The iodide displays two high pressure transitions. A Raman-active soft-mode has been observed in all three analogues, at both high pressure and variable temperature. For the chloride and bromide analogues there is a discussion of the nature of the soft-mode along with the mechanism associated with the I/II transition. The results of the X-ray crystal structure determination of CH3HgBr at ambient temperature and pressure are given.
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Summonte, Luca. "High pressure fog system." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5685/.
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Markkula, Mikael. "Synthesis, structure and properties of high pressure and ambient pressure ternary vanadium oxides." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8061.
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Transition metal oxides have been extensively studied during past decades. The purpose of this research was to synthesize new or little characterised transition metal oxides using high-pressure/high-temperature (HPHT) techniques. Various ternary vanadium oxides have been synthesised at ambient and high pressure conditions. All compounds have been studied by neutron and laboratory X-ray powder diffraction and magnetisation measurements. In some cases resistivity and synchrotron X-ray powder diffraction measurements were also carried out. The MnVO3 perovskite containing localized 3d5 Mn2+ and itinerant 3d1 V4+ states has been synthesised at 8 GPa and 1100°C. MnVO3 crystallises in Pnma space group (a = 5.2741(6) Å, b = 7.4100(11) Å, and c = 5.1184(8) Å at 300 K) and is metallic at temperatures of 2 – 300 K and at pressures of up to 67 kbar. Synchrotron X-ray powder diffraction study on the combined sample of several high pressure products showed slight variation in the stoichiometry of MnVO3. Incommensurate Mn spin order was discovered in the neutron powder diffraction measurements, which reveal a (0.29 0 0) magnetic vector below the 46 K spin ordering transition, and both helical and spin density wave orderings are consistent with the diffraction intensities. Electronic structure calculations show large exchange splittings of the Mn and V 3d bands, and (kx 0 0) crossings of the Fermi energy by spin up and down V 3d bands may give rise to Ruderman-Kittel-Kasuya-Yosida coupling of Mn moments, in addition to their superexchange interactions. The new compound CoVO4 has been discovered in a high pressure synthesis experiment. Magnetic susceptibility measurement, synchrotron X-ray and neutron powder diffraction studies were carried out. Refinements of the synchrotron X-ray and neutron data show CoVO4 to crystallise in space group Pbcn (a = 4.5012(2) Å, b = 5.5539(3) Å, and c = 4.8330(2) Å at 300 K (synchrotron X-ray data)). The magnetic susceptibility measurement reveals that Co3+ is most likely in a low spin state in CoVO4. Monoclinic brannerite type CoV2O6 was synthesised in ambient pressure. Neutron powder diffraction measurements were carried out and an antiferromagnetic order with an a x b x 2c supercell was observed below TN = 15 K. High spin Co2+ moments of magnitude 4.77(4) μB at 4 K lie in the ac plane and are ferromagnetically coupled within chains of edge-sharing CoO6 octahedra parallel to b axis. No structural transition is observed down to 4 K, but a magnetostriction accompanying antiferromagnetic order at TN = 15 K was discovered. A field-induced 1/3 magnetisation plateau and corresponding changes in the magnetic structure were studied by carrying out neutron powder diffraction measurements at 2 K in applied magnetic fields of 0, 2.5 and 5.0 T. Three collinear magnetic phases were observed as field increases; the above antiferromagnetic state with propagation vector (0 0 ½), a ferrimagnetic (¯⅓ 1 ⅓) phase, and a (0 0 0) ferromagnetic order. Co2+ moments of 4.4 - 5.0 μB have a large orbital component and are aligned close to the c-axis direction in all cases. Spin-lattice coupling leads to a magnetostriction and volume expansion as field increases. The ferrimagnetic phase accounts for the previously reported 1/3 magnetisation plateau, and demonstrates that monoclinic CoV2O6 behaves as an accidental triangular antiferromagnetic lattice in which further frustrated orders may be accessible. Orthorhombic columbite-type NiV2O6 and CoV2O6 compounds were synthesised at 6 GPa and 900°C. Metamagnetism and magnetic transitions were found in magnetic measurements. Powder neutron diffraction studies in zero and applied field were carried out. Both compounds were refined in space group Pbcn and the following lattice parameters were obtained at 300 K, CoV2O6: a = 13.4941(20) Å, b = 5.5736(9) Å, and c = 4.8082(8) Å and NiV2O6: a = 13.3725(17) Å, b = 5.5344(7) Å, and c = 4.8162(7) Å. Neutron powder diffraction studies in zero field did not reveal any magnetic peaks for either of the compounds but magnetic order emerges in applied fields between 1 and 4 T.
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Schick, Martin Christopher. "High pressure NMR of ubiquitin /." Zürich, 1998. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=12586.
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Jakob, Thomas. "High pressure surface plasmon spectroscopy." [S.l. : s.n.], 2002. http://ArchiMeD.uni-mainz.de/pub/2002/0084/diss.pdf.
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Fraioli, Patrick Augusto. "High pressure routes to biosphenols." Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333907.
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Hugh-Jones, Demelza Alice. "High pressure behaviour of pyroxenes." Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297171.
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Rushton, Guy James. "High-pressure turbine shroud leakage." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616194.
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Quesada, Cabrera R. "Molecular solids at high pressure." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/18772/.
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High pressure science has extended its applications beyond its classic domain of physics and geophysics. Diamond anvil cell techniques have been adapted to the study on chemical transformations at high pressure and pressure-modified reaction kinetics, contributing to a better understanding of reaction processes and new preparative strategies and opening unexplored chemical pathways for new materials. In this thesis, we aim to present examples of the contribution of the diamond anvil cell to high pressure science, as well as to explore potential applications for this revolutionary perturbation tool. We first introduce a study on sodium silicide (NaSi), a Zintl phase, a potential compound for polymerization at high pressure. This system is an interesting model that illustrates some of the common processes observed in high pressure research. The investigation on the behaviour of sodium orthonitrate (Na3NO4) at high pressure aimed to analyse possible routes towards the synthesis of as yet unknown orthocarbonates and maybe discover compounds with an ever higher coordination for nitrogen or a NO4-containing three-dimensional network. Recently synthesised polyoxometalate (POM) clusters have shown interesting thermochromic properties, which has been related to a redox reaction occurring within the metal-oxygen cage. At high temperature, it has been proposed that the SO3 heteroanion groups contained in the cluster transform to SO4 by the introduction of bridging oxygen from the cage. An oxygen rearrangement would reduce up to four metal atoms, inducing the colour change. We aimed to investigate here whether a similar electron localization process is possible upon compression of these systems. Finally, we develop pioneering high-pressure DAC experiments on amyloid fibrils, using synchrotron X-ray diffraction. Our approach allows us to estimate the Young’s modulus of these biological macromolecular materials and discuss their low compressibility for applications in nanotechnology.
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Du, Rand Marlie. "High pressure fluid phase equilibria." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51789.
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Thesis (MScEng)--University of Stellenbosch, 2000.ENGLISH ABSTRACT: Supercritical extraction is being investigated as a possible alternative to the processes currently used in the fractionation of paraffinic waxes. By removing the lighter carbon fractions from the wax, the wax hardness will be improved and its melting temperature range reduced, hence improving the performance of the wax product in certain applications. In order to evaluate and operate such an extraction process optimally, it is necessary to have a thermodynamic model that accurately represents the process system. There are, however, currently no predictive models available for these systems. In order to fit present models to the systems, accurate phase equilibrium data of the supercritical solvent - n-alkane systems are needed. Unfortunately, the amount of reliable published data on these systems in the required operating range is very limited. A view cell was designed and developed with which these high pressure equilibria could be studied. The binary phase equilibria of supercritical CO2 with n-CI2, n-CI6, n-C20, n-C24, n-C28 and n-C36 and of supercritical ethane with n-CI6, n-C24 and n-C28 were measured in the temperature range 313 - 367 K. It was found that the systems with these two solvents have very different types of phase behaviour. The n-alkane solubility is much higher in ethane, but supercritical CO2 will provide a much better degree of control over the selectivity achieved in an extraction process. Of the various equations of state investigated, it was found that the Patel Teja equation of state provided the best fit of the CO2 - n-alkane systems and that the Soave-Redlich- Kwong equation fitted the ethane - n-alkane systems the best. The interaction parameters of both these equations of state display a functional relationship with temperature and nalkane acentric factor, making it possible to determine parameter values for application at other operating temperatures and with other n-alkane systems. It was found that the current equations of state were not able to represent the phase equilibria accurately over the entire range of operating conditions. The poor performance of the equations of state can be attributed to inherent flaws in the existing equations of state.
AFRIKAANSE OPSOMMING: Superkritiese ekstraksie word tans ondersoek as 'n moontlike altematief vir die prosesse wat huidiglik gebruik word om paraffiese wasse te fraksioneer. Die Iigter koolstofwasse word verwyder om die washardheid te verhoog en die temperatuurgebied waaroor die was smelt te verklein. Dit verbeter dan die was se kwaliteit en werkverrigting. Modelle wat die superkritiese ekstraksie proses akkuraat kan voorstel word egter benodig om die ekstraksie proses te kan evalueer en optimaal te bedryf. Daar is tans geen modelle beskikbaar wat die proses direk kan voorstel nie. Akkurate fase-ewewigsdata word benodig om bestaande modelle aan te pas vir gebruik in hierdie sisteme. Daar is egter baie min betroubare faseewewigsdata vir die superkritiese oplosmiddel - n-alkaan sisteme beskikbaar in die literatuur. 'n Sig-sel, waarrnee hierdie hoe druk data gemeet kan word, is ontwerp en ontwikkel. Die volgende binere fase ewewigte is in die temperatuur gebied 313 - 367 K gemeet: superkritiese CO2 met n-CI2, n-CI6, n-C20, n-C24, n-C28 en n-C36, en superkritiese Etaan met n-CI6, n-C24 en n-C28. Daar is gevind dat hierdie twee superkritiese oplosmiddelsisteme verskillende tipes fase-ewewigsgedragte openbaar. Die n-alkane het 'n baie boer oplosbaarheid in Etaan, maar deur superkritiese C02 in 'n ekstraksie kolom te gebruik, sal tot beheer oor die selektiwiteit van die ekstraksieproses lei. Uit die verskillende toestandsvergelykings wat ondersoek is, is daar gevind dat die Patel- Teja vergelyking die CO2 sisteme die beste kon beskryf en dat die Soave-Redlich-Kwong vergelyking die beste vergelyking was om die Etaan sisteme mee te modelleer. Beide die toestandsvergelykings se interaksie parameters het 'n funksionele verband met temperatuur en die n-alkaan asentrise faktor getoon. Dit is dus moontlik om waardes vir die parameters vir sisteme by ander temperature en met ander n-alkaan tipes te bepaal. Daar was gevind dat die bestaande toestandsvergelykings nie die die fase-ewewigte oor die hele eksperimenele gebied akkuraat kon voorstel nie. Dit kan toegeskryf word aan foute wat inherent is aan die vergelykings.
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Brown, Philip. "High-pressure states of bismuth." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/269971.
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Bismuth is among the most studied of all elements, but its behaviour under pressure exhibits myriad unexpected puzzles even after many decades of research. Bismuth narrowly avoids being an insulator: a Peierls-type distortion almost completely gaps the electronic energy bands, producing a rhombohedral metal with a tiny overlap of conduction and valence bands. The resulting solitary free electron per 100,000 atoms can travel large distances in high-purity crystals, leading to a host of unusual properties. We show that the rhombohedral structure can be tuned with pressure, driving the carrier concentration to nearly zero. We compare our measurements to recent experimental advances implying the formation of novel electronic order driven by the pairing of low-density electrons and holes, and show evidence for a previously unseen phase at very low temperatures in the semiconducting state. We also present a method for calculating the carrier density and resistivity as a function of pressure, based on phenomenological band parameters and a simple charge-balance argument, and demonstrate that this approach can quite well describe most - but not all - of the observed behaviour of the resistivity. At higher pressures, bismuth undergoes a transition into a quasiperiodic host-guest structure. Here, two distinct crystal lattices coexist and interpenetrate, but the lattice parameters are incommensurate. This crystal thus lacks a single unit cell - an unexpected complexity for a simple element. The discovery of such unusual structures in elements is a new phenomenon and their physical properties are rather unexplored. We present experimental measurements of the resistivity and magnetic susceptibility in the incommensurate host-guest state. We argue that the experimental data (in particular, the shape of the normal-state electrical resistivity, and the high value of the low-temperature upper critical field) may be evidence for strong electron-phonon coupling. This strong coupling is consistent with theoretical predictions which suggest the presence of a low-energy phonon mode arising due to the vanishing energy cost of moving guest atoms through the host lattice.
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Xu, Juncheng. "High Temperature High Bandwidth Fiber Optic Pressure Sensors." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/25988.
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Pressure measurements are required in various industrial applications, including extremely harsh environments such as turbine engines, power plants and material-processing systems. Conventional sensors are often difficult to apply due to the high temperatures, highly corrosive agents or electromagnetic interference (EMI) noise that may be present in those environments. Fiber optic pressure sensors have been developed for years and proved themselves successfully in such harsh environments. Especially, diaphragm based fiber optic pressure sensors have been shown to possess advantages of high sensitivity, wide bandwidth, high operation temperature, immunity to EMI, lightweight and long life.
Static and dynamic pressure measurements at various locations of a gas turbine engine are highly desirable to improve its operation and reliability. However, the operating environment, in which temperatures may exceed 600 °C and pressures may reach 100 psi (690 kPa) with about 1 psi (6.9kPa) variation, is a great challenge to currently available sensors. To meet these requirements, a novel type of fiber optic engine pressure sensor has been developed. This pressure sensor functions as a diaphragm based extrinsic Fabry-Pérot interferometric sensor. One of the unique features of this sensor is the all silica structure, allowing a much higher operating temperature to be achieved with an extremely low temperature dependence. In addition, the flexible nature of the sensor design such as wide sensitivity selection, and passive or adaptive temperature compensation, makes the sensor suitable for a variety of applications
An automatically controlled CO2 laser-based sensor fabrication system was developed and implemented. Several novel bonding methods were proposed and investigated to improve the sensor mechanical ruggedness and reduce its temperature dependence.
An engine sensor testing system was designed and instrumented. The system generates known static and dynamic pressures in a temperature-controlled environment, which was used to calibrate the sensor.
Several sensor signal demodulation schemes were used for different testing purposes including a white-light interferometry system, a tunable laser based component test system (CTS), and a self-calibrated interferometric-intensity based (SCIIB) system. All of these sensor systems are immune to light source power fluctuations, which offer high reliability and stability.
The fiber optic pressure sensor was tested in a F-109 turbofan engine. The testing results prove the sensor performance and the packaging ruggedization. Preliminary laboratory and field test results have shown great potential to meet not only the needs for reliable and precise pressure measurement of turbine engines but also for any other pressure measurements especially requiring high bandwidth and high temperature capability.Ph. D.
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Giordano, Valentina. "High-pressure high-temperature phases of carbon dioxide." Paris 6, 2006. http://www.theses.fr/2006PA066529.
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Norrby, Niklas. "High pressure and high temperature behavior of TiAlN." Licentiate thesis, Linköpings universitet, Nanostrukturerade material, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-78830.
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This licentiate thesis mainly reports about the behavior of arc evaporated TiAlN at high pressures and high temperatures. The extreme conditions have been obtained in metal cutting, multi anvil presses or diamond anvil cells. Several characterization techniques have been used, including x-ray diffraction and transmission electron microscopy. Results obtained during metal cutting show that the coatings are subjected to a peak normal stress in the GPa region and temperatures around 900 °C. The samples after metal cutting are shown to have a stronger tendency towards the favorable spinodal decomposition compared to heat treatments at comparable temperatures. We have also shown an increased anisotropy of the spinodally decomposed domains which scales with Al composition and results in different microstructure evolutions. Furthermore, multi anvil press and diamond anvil cell at even higher pressures and temperatures (up to 23 GPa and 2200 °C) also show that the unwanted transformation of cubic AlN into hexagonal AlN is suppressed with an increased pressure and/or temperature.
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Zhu, Songming 1961. "Phase transition studies in food systems during high pressure processing and its applications to pressure shift freezing and high pressure thawing." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84862.
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High-pressure (HP) depresses the phase-transition point of water especially in the case of ice-I (down to -21°C at about 210 MPa). This phenomenon has several potential advantages in food processing applications, such as pressure shift freezing (PSF) and HP thawing. However, scientific knowledge available in this area is still relatively limited. The main objectives of this research were to investigate the phase-transition behavior of foods under pressure processing in the context of PSF and HP thawing techniques and to evaluate their impact on product quality.Distilled water and fresh pork muscle were tested by a HP differential scanning calorimeter (DSC) using isothermal pressure scan (P-scan) and isobaric temperature scan (T-scan). P-scan tests showed that the phase-transition temperature (T) of pork was a function of the weighted-average pressure (P¯1--2): T = -1.17 - 0.102P¯1--2 - 0.00019 P&d1;21-2 (R2 = 0.99) that was much lower than that of pure ice. The phase-change latent heat of pork was estimated by P-scan. T-scan indicated the phase-transition point at a constant pressure, but it showed less accurate than P-scan. The ratio (Rice, %) of ice crystals formed by rapid release of pressure (P) was evaluated using the HP DSC: Rice-water = 0.115P + 0.00013P2 (R2 = 0.96) for water, and Rice-pork = 0.084P + 0.00012P2 (R2 = 0.95) for pork muscle. In the developed method, the pressure-dependent thermal properties of test materials are not required.
A preliminary study on ice-crystal formation was carried out using small gelatin gel samples frozen by conventional air freezing (CAF), liquid immersion freezing (LIF) and PSF at different pressures. The ovoid structure left from ice crystals was evaluated for area, equivalent diameter, roundness and elongation. The diameter (mean +/- S.D.) was 145 +/- 66, 84 +/- 26, 91 +/- 30, 73 +/- 29, and 44 +/- 16 mum for the treatments of CAF, LIF and PSF at 100, 150 and 200 MPa, respectively. Roundness and elongation did not show a clear trend with different freezing tests. Similar experiments using small-size Atlantic salmon (Salmo salar) resulted in the diameter of 110 +/- 41, 17 +/- 8.4, 16 +/- 8.8, 8.2.5 and 5.0 +/- 2.1 mum for CAF, LIF and PSF at 100, 150 and 200 MPa, respectively. The roundness was 0.38 +/- 0.14, 0.55 +/- 0.21, 0.57 +/- 0.18, 0.63 +/- 0.14 and 0.71 +/- 0.14 for the above treatments, respectively. (Abstract shortened by UMI.)
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Wang, Xiao. "Development of novel high pressure instrumentation." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10525.
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The application of pressure to chemical substances can change their physical properties (optical, magnetic, and electrical) and it can also be used to alter some chemical reactions. The need for compatible pressure generating instruments is constantly growing in various high pressure (HP) researches. The work described in this thesis is focused on development, construction, testing of several high pressure cells of novel design. These designs were developed to meet the requirements of different research collaborations. The main objective of this project is to develop high pressure cells for magnetic studies in the magnetic properties measurement system known as MPMS, which is the most popular commercial magnetometer nowadays. Three high pressure cells were designed and tested for different type of magnetic measurements. The first design presented in this thesis is a cylinder type pressure cell which is specially designed to measure the magnetic susceptibility of the pressure-sensitive material under pressure. The cell is driven by compressed helium gas which allows the internal pressure to be adjusted with small increments (1 MPa) through the regulator of the external gas cylinder. The cell was made of non-magnetic beryllium copper alloy and designed to work up to 100 MPa at 400 K temperature. The design was verified with finite element analysis (FEA) simulation and its sample volume was optimised to provide large sample capacity which allows high quality data to be collected in the MPMS. Modified from the earlier turnbuckle magnetic diamond anvil cell (TM-DAC) reported in Konstantin V. Kamenev (KVK) group, the second high pressure cell presented in this thesis is an opposed diamond anvil pressure cell. The working mechanism of this cell is based on the turnbuckle principle. The cell was specifically developed for iHelium3 system which is a add-on cryostat of the MPMS. The cell was coded TM-3He-DAC to distinguish with the original TMDAC. The cell is 6 mm in diameter and 7 mm in length, which are smaller than the dimensions of the predecessor (TM-DAC). Copper titanium alloy was used in building the cell to further reduce the magnetic background from the cell. The cell is capable of achieving close to 5 GPa sample pressure in the loading test and the magnetic background is significantly lower than the TM-DAC. The development of this cell enables high pressure magnetic measurements to be performed at extreme low temperature (0.5 K) in the iHelium3 system. The third high pressure cell developed for the MPMS is also a turnbuckle diamond anvil cell, however, all the material used in the cell is non-metallic to enable high-pressure ac magnetic measurement to be performed. An advanced high strength polymer was assessed using finite element analysis and experimental testing. The performance and failure modes for the key components of the cell working in tension and in compression were evaluated and the ways for optimising the designs were established. The cell is coded PTM-DAC in this thesis and the composite gasket was also developed and tested for the PTM-DAC. The cell is approximately 14 mm long, 8.5 mm in diameter and was demonstrated to reach pressures of 5.6 GPa. Ac susceptibility data collected on Dy2O3 and U6Fe demonstrated the performance of the cell in magnetic property measurement and confirmed that there was no screening of the sample by the environment which typically accompanies used of conventional metallic high pressure cells in oscillating magnetic fields. Based on the experience of from the development of above two turnbuckle diamond anvil cell, a turnbuckle sapphire anvil cell (T-SAC) was developed in this project for high-pressure neutron scattering. Commercial spherical sapphire were used as anvil in the cell as they are much more cost effective if compared to the diamond anvil. The developed T-SAC can generate and maintain sample pressures above 6 GPa with a sample volume 6 X 10-² mm³ which is 6 times that of conventional diamond anvil cell (DAC). Failure analysis was performed on the sapphire anvil to gain a better understanding of the failure mechanism of the spherical sapphire anvil. The cell had been used in measuring the crystal structure of single crystal niobium at 1.6 GPa through small angle neutron scattering (SANS) technique. The cell is less than 16 mm in length and 14 mm in diameter, it is the smallest sapphire anvil cell to date. The miniature feature allow it can be fit into most cryostat of modern scientific instrument without difficulties. Lastly, two piston-cylinder type high pressure cells were developed for high-pressure chemistry studies. These cells were designed to pressurise large amount of liquid sample (particular for water-based sample) up to 800 MPa in a controllable manner. Each design is presented separately with stress analysis in FEA and a description of the working mechanism. Hoop strain at the external surface of the cell was measured and then the internal pressure was calculated through the Lam´e equation. After that, the load and attainable internal pressure was calibrated for the users. These cells have been used in the high-pressure study of salicylaldoximes process, bio-diesels decomposition and crystallization, material polymerisation and pharmaceutical experiments.
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Vanpeteghem, Carine B. "High-pressure high-temperature structural studies of binary semiconductors." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/11496.
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The last decade has seen a tremendous improvement in high-pressure diffraction techniques. Among other things, this has led to a completely new understanding of the structural systematics of the group IV, III-V and II-VI semiconductors. Many phases have been shown to have more complex, lower-symmetry, high-pressure structures than previously thought. One of the most surprising discoveries has been the non-existence of the diatomic b-tin structure, long believed to be one of the principal high-pressure phases of the III-V and II-VI systems. However, most of the work to date has been performed at room temperature and in fact, very little is yet known about the high-pressure phases of these systems above room temperature. The work presented in this thesis centres on the use of high temperature under pressure to investigate further the absence of the diatomic, site-ordered, b-tin or b-tin-like phases have been found but appear to be site-disordered. Additionally, the P-T phase diagrams of these systems are explored above room temperature. This work has required the development the existing high-pressure facilities on the SRS synchrotron source of Daresbury Laboratory to allow routine high-pressure high-temperature (hp/ht) experiments. These technical developments are described. High-temperature studies of GaSb under pressure reveal a new, previously unknown phase. A detailed study of the structural ordering in the hp/ht phases of GaSb is performed by combining two different experimental techniques. It is shown, by x-ray powder-diffraction, that all the hp and hp/ht phases of GaSb are site-disordered over about two unit cells or less. A complementary high-pressure EXAFS study demonstrates the absence of complete order over nearest-neighbour distances.
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Sphicas, Panagiotis. "High pressure and high temperature measurements on diesel sprays." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/18063.
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Environmental, financial and legal reasons demand the development of cleaner diesel engines. Atomization, evaporation and mixing phenomena observed during injection of Diesel fuel affect the produced emissions. To study these phenomena, under engine-like conditions (50bar, 1000K), a chemically preheated constant volume chamber was built. A system of sensors, driven in real-time by a FPGA (Field Programmable Gate Array) and controlled by a Real Time Controller, was built to monitor and control the operations. A modern common rail fuel injection system (Bosch CP3) was driven by a purpose-modified Hartridge 1100 test stand and controlled by the FPGA (Field Programmable Gate Array). Chemical heating is a technique used widely to simulate the ambient conditions of an industrial combustor in a constant volume vessel. A flammable mixture is ignited in an optically accessible vessel, attempting to produce a post-combustion high pressure and high temperature environment. The flammable mixture usually consists of Hydrogen and a Hydrocarbon. Hydrogen is added, to assist with the ignitability of the pre-ignition mixture and to simulate the water present in industrial combustors as a result of exhaust gas recirculation. To this direction, the mole ratio of Hydrogen to Hydrocarbon and the mixture molecular weight were introduced as independent variables for the first time in the literature of constant volume combustion. An initial computer model, assuming perfect combustion, was used for calculation of adiabatic temperature and pressure. A second computer model investigated the effect of chemical dissociation by solving for the minimization of Gibbs energy and was compared to the former one. To verify the calculations, a dual pressure transducer technique and a High-Speed Schlieren technique were used to validate the combustion conditions inside the vessel To further understand the atomization, evaporation and mixing phenomena in sprays, a Diesel spray was visualized using back-illumination and Schlieren High-Speed cinematography at high pressure and room temperature. To understand the evaporation behaviour of a spray and map the vapour fuel distribution, a tracer Laser Induced Fluorescence was applied on a Dodecane/Methyl-naphthalene spray under evaporating and non-evaporating conditions. To compare the experimental findings to the theoretical models in literature, the evaporation of a single droplet in post-combustion vessel gases was simulated using a purpose-programmed FORTRAN code. A supercritical phase change was suggested to explain the sudden phase change and large differences between the theoretical model and the experimental results.
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Almström, Linda, and Camilla Söderström. "Alternative materials for high-temperature and high-pressure valves." Thesis, Karlstads universitet, Fakulteten för teknik- och naturvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-7393.
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AB SOMAS Ventiler manufactures valves for different applications. A valve of type DN VSSL 400, PN 100, used in high-temperature and high-pressure applications was investigated in this thesis. This type of valve is coated with high cobalt alloys to achieve the tribological properties needed for this severe condition. However there is a request from AB Somas Ventiler to find another solution. This request is based on the fact that demands on higher temperatures, from customers, yields higher requirements on the material. It is also a price issue since cobalt is quite expensive. Materials investigated were high-nitrogen steel, Vanax 75, nickel-based superalloy Inconel 718 and hardened steels, EN 1.4903 and EN 1.4923 presently used as base material in the valve. Calculation of contact pressure that arises when the valve is closed was first approached by using finite element method (FEM). Several models were constructed to show the behavior of the valve during closing in terms of deformation. Hot wear tests, in which a specimen was pressed against a rotating cylinder, were performed to be able to compare the materials to the solution of today and among each other. Data extracted from the tests were compiled in the form of coefficients of friction. Profilometer examinations were used to reveal the volumes of worn and adhered material and together with scanning electron microscopy (SEM) the wear situation for each material couple could be assessed. Wear mechanisms detected in SEM were adhesive and abrasive and the results clearly showed that the steels were not a good solution because of severe adhesive wear due to the similarity of mating materials creating a more efficient bonding between the asperities. Vanax 75 showed much better performance but there was still an obvious difference between the steels and the superalloy in terms of both coefficient of friction and amount of wear. On this basis, Inconel 718 was selected as the most suitable material to replace the high cobalt alloys used in the valves today.AB Somas ventiler är ett företag som tillverkar ventiler för ett brett spann av applikationer. I det här examensarbetet har undersökningar genomförts på en ventil av modell DN VSSL 400, PN 100, som normalt används i applikationer för höga tryck och höga temperaturer. Ventilen beläggs i dagsläget med höghaltiga koboltlegeringar för att uppnå de tribologiska egenskaper som krävs i de påfrestande arbetsförhållanden som råder. AB Somas Ventiler har dock framfört en förfrågan om att hitta en alternativ lösning, en förfrågan som grundar sig i att kundernas ständiga önskemål på att ventilerna ska klara högre arbetstemperaturer också medför högre krav på ventilmaterialen. Det är även en prisfråga, då kobolt är en dyr legering att använda sig av. De material som inkluderades i undersökningen var det kvävelegerade stålet Vanax 75, nickelbaserade superlegeringen Inconel 718 samt de två stålen EN 1.4903 och EN 1.4923 i härdat tillstånd. De två sistnämnda används idag som basmaterial i ventilen. Genom att använda den finita element metoden (FEM) kunde en första beräkning göras av det kontakttryck som uppstår då ventilen stängs. Flera modeller konstruerades för att simulera ventilens deformation vid stängning. Där efter utfördes nötningstester i hög temperatur på de alternativa materialen, genom att låta en provbit pressas mot en roterande cylinder, för att sedan kunna göra en jämförelse mellan materialen och även med den nuvarande lösningen. Från nötningstesterna erhölls data som kunde användas för att ta fram friktionskoefficienter för de olika materialparen. Med hjälp av undersökningar med profilometer och svepelektronmikroskop (SEM) kunde värden på nötta och vidhäfta volymer erhållas tillsammans med information om nötningssituationer för ytorna mellan de olika materialparen. De nötningsmekanismer som påvisades med hjälp av SEM-undersökningen var adhesiv och abrasiv nötning, och resultaten visade tydligt att nötningen av stålen var omfattande, på grund av att lika material i kontakt med varandra skapar starkare band mellan ytorna, och att de därför inte var en intressant lösning. Det kvävelegerade Vanax 75 uppförde sig visserligen bättre men en tydlig skillnad mot superlegeringarna kunde dock fortfarande konstateras, sett till både friktionskoefficient och mängden slitage. Baserat på dessa resultat valdes Inconel 718 som det bäst lämpade materialet att ersätta de höghaltiga koboltlegeringarna som idag används i ventilen.
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Rowane, Aaron J. "High-Temperature, High-Pressure Viscosities and Densities of Toluene." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4188.
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High-temperature, high-pressure (HTHP) conditions are exemplified in ultra-deep petroleum reservoirs and can be exhibited within diesel engines. Accurate pure component hydrocarbon data is essential in understanding the overall behavior of petroleum and diesel fuel at these conditions. The present study focuses on the HTHP properties of toluene since this hydrocarbon is frequently used to increase the octane rating of gasoline and toluene occurs naturally in crude oil. In this thesis experimental densities and viscosity are presented to 535 K and 300 MPa extending the database of toluene viscosity data to higher temperature than previous studies. The data is correlated to a Tait-like equation and a Padѐ approximate in conjunction with a single mapping of the isotherms. Free-volume theory and a superposition of the viscosity in relation to the Leonnard-Jones repulsive force are both used to model the toluene viscosity data. It was found that the data are in good agreement with the available literature data.
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Munro, Keith Alistair. "High-pressure high-temperature behaviour of the lanthanide metals." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28881.
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The high-pressure behaviour of the lanthanide series of metals has been the subject of study since the work of Percy Bridgman in the 1940s. Differences in said behaviour between the different lanthanide metals are attributed to the increasing occupation of the 4f electron shell as Z increases. Upon compression, or as Z decreases, the trivalent lanthanides (La to Lu, excluding Eu and Yb) undergo a common phase transformation sequence through various close packed structures: hcp → Sm-type (the structure adopted by samarium at ambient conditions) → dhcp → fcc → distorted fcc (d-fcc). Upon further compression, the lanthanide metals experience a first order transition to a "volume collapsed" phase. Many studies have focused on the low-Z members of the series, since the various phase transitions occur at much lower pressure where it is comparatively easy to collect high quality data. By contrast, the other members of the series have received comparability little attention, and there are even fewer reports of the structural behaviour of the lanthanide metals at high pressure and high temperature. This thesis contains the results of angle-dispersive x-ray powder diffraction experiments at high pressure and high temperature of the various members of the lanthanide metals. Ce has been the subject of many previous studies, but a systematic x-ray diffraction study of the fcc/d-fcc phase boundary has never been attempted. Furthermore, the location in P-T space of the high temperature fcc/bct/d-fcc triple point has only been inferred, due to the lack of data on the fcc/bct phase boundary at high temperature. The high-pressure high-temperature phase diagram of Ce is presented and discussed. La is unique amongst the lanthanide metals due to its empty 4f shell at ambient conditions. Despite this, La undergoes the common lanthanide transformation sequence up to the d-fcc phase, after which it undergoes a re-entrant transition back to the fcc phase at 60 GPa. The diffraction peaks of d-fcc La are shown in this thesis to undergo changes in intensity upon compression, indicating a transformation to the oI 16 structure found in Pr. La is one of the few elements whose behaviour has been unknown above 100 GPa, and results of La's structural behaviour upon compression to 280 GPa are presented and discussed. At 76 GPa, La begins a transition from the fcc phase to a new phase with the bct structure. Finally, the d-fcc→fcc re-entrant phase transition has been determined at various temperatures, and the d-fcc stability region has been mapped out. Finally, x-ray diffraction experiments were performed on Gd up to 100 GPa and ~700 K, to determine the structure of the d-fcc phase and the "volume collapsed" phase. While d-fcc Gd does not undergo pressure-induced changes similar to its low Z brethren, the d-fcc Gd remains stable up to 41 GPa at 700 K, putting a constraint on the d-fcc stability region. The data collected on Gd's "volume collapsed" phase cannot be fitted to the currently accepted mC4 structure. This has implications for our understanding of the lanthanide series as a whole, since most of of the heavier members, and some of the lighter lanthanides, are reported to adopt the mC4 structure.
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Conley, Clark Alexander. "High-pressure GH₂/GO₂ combustion dynamics." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013840.
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Berg, Sven. "Ultra high-pressure compaction of powder." Doctoral thesis, Luleå tekniska universitet, Material- och solidmekanik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16908.
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Sintering at high-pressure improves the properties of the material, either through new sintering aids becoming available or through improving intergranular bonding. This gives the manufactured products potential advantages like faster cut rates, and more precise and cleaner production methods that add up to cost efficiency and competitive edge. The production of synthetic diamond products demands tooling that can achieve high pressures and deliver it with a high degree of certainty. The common denominator for almost all high-pressure systems is to use capsules where a powder material encloses the core material. Numerical analysis of manufacturing processes with working conditions that reach ultra high pressure (above 10 GPa) requires a constitutive model that can handle the specific behaviours of the powder from a low density to solid state. The work in this thesis deals with characterization and simulation of the material behaviour during high-pressure compaction in powder pressing. Some of the work was focused on investigating the material when used as compressible gasket in high-pressure systems. The aim was to increase the knowledge of the high-pressure pressing process. This includes a better understanding of how mean stress develops in the compact during pressing and an insight into the development material models concerning highpressure materials. Both experimental and numerical investigations were made to gain knowledge in these fields. The mechanical behaviour of a CaCO3 powder mix was investigated using the Brazilian disc test, uniaxial compression testing and closed die experiments. The aim of the experimental work was to provide a foundation for numerical simulation of CaCO3 powder compaction at higher pressures. Friction measurements of the powder were also conducted. From the experimental investigations, density dependent material parameters were found. An elasto-plastic Cap model was developed for ultra high-pressure powder pressing. To improve the material model, density dependent constitutive parameters were included. The model was implemented as a user-defined material subroutine in a nonlinear finite element program. The model was validated against pressure measurements using phase transitions of Bismuth. The measurements were conducted in a Bridgman anvil apparatus. The simulations showed that thin discs with small radial extrusion generate a plateau at a low-pressure level, while thick discs with large radial extrusion generate a pressure peak at a high-pressure level. The results showed that FE-results can be used to engineer pressure peaks needed to seal HPHT-systems. For compressible gaskets, it was found that diametral support increases the phase transformation load. Higher initial density of the powder compact and diametral support generate higher pressure per unit thickness. The results from the validation using pressure measurements showed that the simulation model was indeed capable of reproducing load–thickness curves and pressure profiles, up to 9 GPa, close to the experimental curves.Godkänd; 2011; 20111020 (bersve); DISPUTATION Ämnesområde: Hållfasthetslära/Solid Mechanics Opponent: Professor Javier Oliver, Dept of Strength of Materials and Structural Analysis, Technical University of Catalonia, Barcelona, Spain, Ordförande: Bitr professor Pär Jonsén, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Torsdag den 15 december 2011, kl 09.00 Plats: E246, Luleå tekniska universitet
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Manolis, Ionnis Georgios. "High pressure gas-liquid slug flow." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633654.
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Srichai, Somprasong. "High pressure separated two-phase flow." Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/8656.
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Neuendorf, Annette J., and n/a. "High Pressure Synthesis of Conducting Polymers." Griffith University. School of Science, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20040218.112214.
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An experimental investigation of the high pressure synthesis of water soluble, self doping conducting polymers is presented. 2- And 3-aminobenzenesulfonic acid and the respective sodium sulfonates have been polymerised. Optimal polymerisation conditions have been determined with respect to yield, conductivity and molecular weight. Reaction parameters such as oxidant, pressure, catalysts, reaction time and temperature and the use of additives were investigated. The minimum pressure required for polymerisation was 7 kbar. An increase in pressure had a negligible effect on polymer characteristics. The polymers were generated in aqueous, non-acidic media, to ensure they were selfdoping when characterised. Conductivities of between 10-6 Scm-1 and 10-3 Scm-1 were measured. The sulfonate salts reacted faster than the sulfonic acids and for both a longer reaction time resulted in higher yields and conductivities. These polymers were completely water soluble, of high molecular weight and able to be cast as thin films. The arylamines 5- and 8-aminonaphthalene-2-sulfonic acid and their respective sodium sulfonates were polymerised at elevated pressure. The naphthalene sulfonate salts polymerised at atmospheric pressure, but displayed a higher molecular weight when reacted under pressure. Generally the naphthalene monomers reacted similarly to the benzene monomers, although there were some differences. Conductivity and yield decreased with increased reaction times and the use of 0.1M equivalents of ferrous sulfate had an negligible effect on the polymers. The polynaphthalenes were highly water soluble, self doping and had conductivities in the order 10-5 to 10-3 Scm-1. A measurement of the activation volume for the polymerisation of 2-methoxyaniline and sodium 8-aminonaphthalene-2-sulfonate was performed. These were determined to be -44 ± 3 cm3mol-1 and -62 ± 10 cm3mol-1 respectively. These large negative values are consistent with rate limiting monomer oxidation.
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Penny, George B. S. "High-pressure synthesis of electronic materials." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4161.
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High-pressure techniques have become increasingly important in the synthesis of ceramic and metallic solids allowing the discovery of new materials with interesting properties. In this research dense solid oxides have been synthesised at high pressures, and structural investigations have been conducted using x-ray and neutron diffraction. The perovskite LaPdO3 has been synthesised at pressures of 6{10GPa. Neutron diffraction studies have been carried out from 7{260K to investigate any structural distortions, particularly related to the possibility of charge order at low temperatures. No reduction in symmetry associated with charge ordering has been observed; the material appears to remain metallic with only one unique Pd site down to 7K. LaPdO3 adopts the GdFeO3-type Pbnm structure. The PdO6 octahedra exhibit a tetragonal distortion throughout the temperature range with a shortening of the apical Pd{O bonds of 2:5% relative to the equatorial bonds. Attempts to prepare analogues of the perovskite containing smaller rare earths have resulted in multi-phase samples, and further RPdO3 perovskites remain inaccessible although there is evidence for a small amount of the perovskite phase in the products of synthesis attempts with neodymium. Three new oxypnictide superconductors, RFeAsO1 xFx (R = Tb, Dy and Ho) have been synthesised at 7{12GPa. The materials are isostructural with other recently discovered iron arsenide superconductors and have Tc's of 52:8 K, 48:5K and 36:2K respectively, demonstrating a downturn in Tc in the series for smaller R. Systematic studies on TbFeAsO0.9F0.1 and HoFeAsO0.9F0.1 show negative values of dTc=dV in contrast to those reported for early R containing materials. Low-temperature neutron diffraction measurements on both materials, and synchrotron studies on HoFeAsO0.9F0.1 reveal no tetragonal to orthorhombic transitions as observed in early R-containing materials with lower doping levels. Magnetic reflections are evident but they are shown to be from R2O3 and RAs impurities with TN's of 5:5K for Tb2O3, 6:5K for HoAs and 1:7K < TN < 4K for Ho2O3. The implications of these results for superconductivity in the iron arsenides are discussed.
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Scovell, Katherine A. "Continuous flow reactions at high pressure." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537684.
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Stevens, James G. "Reactions in high pressure carbon dioxide." Thesis, University of Nottingham, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546690.
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Cameron, Andrew Alexander. "High pressure slab waveguide CO2 lasers." Thesis, Heriot-Watt University, 1997. http://hdl.handle.net/10399/1223.
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Haselwimmer, Robert Kurt William. "The Millikelvin ultra-high pressure facility." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620919.
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Alireza, Patricia Lebre. "High pressure studies of calcium ruthenate." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619917.
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Fletcher, Patrick Alan. "High pressure vibrational and EXAFS spectroscopy." Thesis, University of Leicester, 1987. http://hdl.handle.net/2381/33673.
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Bovornratanaraks, Thiti. "High-pressure structural studies of strontium." Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/12447.
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Previous structural work has shown that strontium undergoes a sequence of phase transitions up to 46 GPa. The relatively complex structures of Sr-IV and Sr-V, stable above 35 GPa and 46 GPa respectively, could not be solved and doubts remained about the correct assignment of the Sr-III structure. It is only comparatively recently, however, that experimental techniques have been developed to allow the detailed structural characterisation of these phases. To resolve these remaining uncertainties, the author has carried out a re-examination of the high-pressure structures and transitions in strontium using angle-dispersive powder-diffraction techniques with the image-phase area detector on station 9.1 at the SRS Daresbury Laboratory. The experimental set up has been improved so that data of sufficient quality could be obtained to allow the structures of these high pressure phases to be both correctly identified and accurately refined. The previously reported structure of Sr-III was found to be wrongly identified as having an orthorhombic Imma symmetry (with a structure similar to that of Si-III) and this has now been correctly identified as having the archetypal b-tin (I41 /amd) structure. The higher pressure phase of Sr, Sr-IV, has also been solved and the structure solution showed that it has a very complex monoclinic structure. This is the first time that this complex monoclinic structure has been reported in an element. Finally, the crystal structure of Sr-V has also been closely studied in comparison with the recently reported Ba-IV structure - based on the similarity of the diffraction patterns observed. The Sr-V structure is indeed found to be essentially the same as that of Ba-IV and it also has an intra-phase structural transition similar to those observed in Ba-IV.
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Wilson, Craig W. "High-pressure studies of ammonia hydrates." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/8921.
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Ammonia and water are major components of many planetary bodies, from comets and icy moons such as Saturn's Titan to the interiors of the planets Neptune and Uranus. Under a range of high pressures and/or low temperatures known to occur in these planetary bodies, ammonia and water form a series of compounds known as ammonia hydrates. Ammonia and water form three stoichiometric compounds, ammonia hemihydrate, ammonia monohydrate and ammonia dihydrate, which have ammonia-to-water ratios of 2:1, 1:1 and 1:2 respectively. Therefore a good understanding of the three stable ammonia hydrates is required for modelling the interiors of these bodies. Additionally, the ammonia hydrates are the simplest systems to incorporate mixed (N-H O and O-H N) hydrogen bonds. Such bonds are important biochemically, and along with O-H O H-bonds, mixed H-bonds are responsible for the second-order structure of DNA, and they are also responsible for the proton transfer reactions in enzymic processes. The understanding of these bonds and processes rests on the knowledge of the relationship between bond strength and geometry, and the ammonia hydrates provide a rich range of geometries against which models of such mixed H-bonds can be tested. X-ray and neutron diffraction techniques have been used to investigate the behaviour of the ammonia-water complex and further the understanding of this system. This includes solving the structure of a phase which was previously thought to be an ammonia monohydrate phase, but has been shown here to be a mixture of an ammonia hemihydrate phase and Ice VII. In addition to this, x-ray and neutron diffraction experiments have been performed to explore how this phase behaves under changing pressure and temperature conditions, and what other implications that this has on the ammonia-water system. It has been found that ammonia hemihydrate can also form a structural phase observed to form in both ammonia monohydrate and ammonia dihydrate within the same pressure and temperature regime, which opens the possibility of a solid solution existing between all three stoichiometric ammonia hydrates.
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Davidson, Alistair J. "High-pressure studies of energetic materials." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/16976.
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Although high pressure has been used extensively to study a range of materials that include metals, minerals, and ices, a class of material that has received rather less attention is energetic materials (explosives, propellants). The work presented has used high-pressure techniques to investigate polymorphism in energetic materials. Novel-high pressure phases of RDX (cyclotrimethylenetrinitramine or cyclonite) and ammonium perchlorate are reported, which have both been structurally characterised using single-crystal X-ray and powder neutron diffraction. Of particular importance has been the successful determination of the structure of the elusive high-pressure –form of RDX. Equations of state for both polymorphs of both compounds have been determined. High-pressure measurements of HMX (cyclotetramethylenetetranitramine or octogen) revealed no phase transitions up to 8.46 GPa. An equation of state up to this pressure has been determined. Crystallisation of HMX from DMSO at 0.1 GPa gives a 1:2 HMX-DMSO solvate which has been structurally characterised by single-crystal X-ray diffraction. The high-pressure behaviour of TATP (triacetone triperoxide) has been explored. Hydroxylammonium perchlorate has been investigated using high-temperature single-crystal X-ray diffraction and powder neutron diffraction, and a high-temperature phase has been fully structurally characterised for the first time. High-pressure studies of hydroxylammonium perchlorate indicate the presence of two new polymorphs. High-pressure measurements have been conducted on ammonium nitrate up to 7.85 GPa, showing no phase transitions. An equation of state has been determined over this pressure range. Studies have also been undertaken on the simple molecular compound thiourea dioxide. Two new high-pressure phases have been identified and structurally characterised using both single-crystal X-ray and powder neutron diffraction.
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Goto, Atsushi. "Material migration during high pressure metamorphism." 京都大学 (Kyoto University), 1993. http://hdl.handle.net/2433/168941.
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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第5292号
理博第1466号
新制||理||813(附属図書館)
UT51-93-F49
京都大学大学院理学研究科地質学鉱物学専攻
(主査)教授 坂野 昇平, 教授 鎮西 清高, 教授 西村 進
学位規則第4条第1項該当
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Wilkinson, Victoria Ailsa. "High pressure photoluminescence of semiconductor structures." Thesis, University of Surrey, 1990. http://epubs.surrey.ac.uk/844514/.
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High pressure photoluminescence has been used to study semiconductor structures. The measurements have been made in a miniature cryogenic diamond anvil cell (DAC). The results reported cover a wide range of materials and many different aspects are discussed. This in part serves to demonstrate the versatility and importance of the technique. New developments in DAC technology are fully described, in particular the introduction of electrical feedthroughs and the importance of the gasket geometry. The technologically important material system GaAs/AlXGa1-X As has been studied under hydrostatic pressure. Band offsets and their pressure dependencies are determined with spectroscopic accuracy and show interesting deviations from the expected behaviour. The effect of substrate orientation on the band offsets has also been investigated. The binding energy of excitons in GaAs/AlAs super lattices in the vicinity of F-X (Type I to Type II) crossover is measured for the first time. The emerging new material systems containing strained layers have been studied, particularly In GaXAs1-X grown pseudomorphically on GaAs. In this system the pressure coefficients of the PL from strained quantum wells are found to have an unexpected dependence on the composition. Comparison with strained InAs/InP quantum wells suggests that this is in fact a strain effect rather than alloy. The band line-up in InXGa1-XAs/GaAs and InXGa1-XAs/AlyGa1-y As quantum well structures is determined from the crossing of P and X states. A preliminary study of the dilute magnetic semiconductor Cd1-XMnXTe is made. High pressure magnetic field measurements on this material are expected to yield information on the nature of the exchange interactions. To this end CdTe/CdMnTe super lattices have been characterised under hydrostatic pressure. Films of a-Si:H are studied under pressure. The intensity of the PL is found to be maintained upto ~90 kbar, in contrast with previous published data. The PL exhibits a small red shift of 1.9 meV/kbar which is compared with the pressure coefficients of the PL from other amorphous materials.
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Pieterse, Casper. "High pressure feedwater heaters replacement optimisation." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/61325.
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Widespread uncertainty exists regarding the ideal replacement time of installed feedwater heaters in coal fired power plants. Eskom consequently identified the need for this research project to find the optimal age at which to replace high pressure (HP) feedwater heaters. Previous work has failed to quantify the unique financial risk of tube failures, which varies for individual heaters. Using life cycle cost (LCC) methodology, a framework is developed for the optimisation of the HP feedwater heater replacement age in Eskom coal fired power plants and integrated into existing software used in the organization. This entails identifying the most significant cost factors involved in the lifecycle of HP heaters and determining how they evolve over time by conducting a case study. Minimum life cycle cost for an actual HP heater is calculated in the case study based on failure data and cost information supplied by the power plant. This optimisation of replacement time can realise significant savings in annualised LCC compared to current practice.Dissertation (MEng)--University of Pretoria, 2016.
Mechanical and Aeronautical Engineering
MEng
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Staneff, Geoff D. Asimow Paul David. "High-pressure synthesis of thermoelectric materials /." Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-05262005-004951.
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Neuendorf, Annette J. "High Pressure Synthesis of Conducting Polymers." Thesis, Griffith University, 2004. http://hdl.handle.net/10072/366536.
Full textAbstract:
An experimental investigation of the high pressure synthesis of water soluble, self doping conducting polymers is presented. 2- And 3-aminobenzenesulfonic acid and the respective sodium sulfonates have been polymerised. Optimal polymerisation conditions have been determined with respect to yield, conductivity and molecular weight. Reaction parameters such as oxidant, pressure, catalysts, reaction time and temperature and the use of additives were investigated. The minimum pressure required for polymerisation was 7 kbar. An increase in pressure had a negligible effect on polymer characteristics. The polymers were generated in aqueous, non-acidic media, to ensure they were selfdoping when characterised. Conductivities of between 10-6 Scm-1 and 10-3 Scm-1 were measured. The sulfonate salts reacted faster than the sulfonic acids and for both a longer reaction time resulted in higher yields and conductivities. These polymers were completely water soluble, of high molecular weight and able to be cast as thin films. The arylamines 5- and 8-aminonaphthalene-2-sulfonic acid and their respective sodium sulfonates were polymerised at elevated pressure. The naphthalene sulfonate salts polymerised at atmospheric pressure, but displayed a higher molecular weight when reacted under pressure. Generally the naphthalene monomers reacted similarly to the benzene monomers, although there were some differences. Conductivity and yield decreased with increased reaction times and the use of 0.1M equivalents of ferrous sulfate had an negligible effect on the polymers. The polynaphthalenes were highly water soluble, self doping and had conductivities in the order 10-5 to 10-3 Scm-1. A measurement of the activation volume for the polymerisation of 2-methoxyaniline and sodium 8-aminonaphthalene-2-sulfonate was performed. These were determined to be -44 ± 3 cm3mol-1 and -62 ± 10 cm3mol-1 respectively. These large negative values are consistent with rate limiting monomer oxidation.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Science
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Martin, Ffion A. "High pressure liquid moulding of composites." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/51888/.
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Automotive manufacturers are responding to increasingly stringent demands on fuel consumption by developing novel lightweight designs with new materials. Carbon fibre composites are seen to offer high specific properties – leading to low weight solutions, but their cost and manufacturing rate are currently unsuited to automotive high volume cost targets. This thesis presents a novel composites manufacturing process offering high production rates and low process costs. The process is termed ALCM, Advanced Liquid Compression Moulding and is a novel derivative of High Pressure Resin Transfer Moulding. In the two-stage ALCM process, features of both liquid moulding and compression moulding techniques are exploited. In the first stage the mould tool is held open by a small amount during the injection phase. This allows the fibre preform to expand into the mould cavity, increasing its permeability, thus reducing overall injection pressure requirements. In the second stage the tool is closed to finalise the resin infusion and form the finished component to the required geometry and fibre volume fraction. Two work packages are presented in this thesis: Objective 1 is to study a range of experimental parameters to characterise the ALCM process; Objective 2 is to simulate the ALCM manufacturing process using the Finite Element method. In Objective 1 a range of experiments explore the feasibility of the ACLM process to manufacture large structural components using carbon fibre NCF (non-crimp fabrics) with fast-curing epoxy resin. The experiments were performed on the newly-installed high pressure RTM injection equipment and large bed press at the National Composites Centre, UK. Characterisation of the ALCM process was undertaken using two mould tool geometries – a 1240x790mm rectangular flat plate tool and a top hat shape tool with the same planform area and 180mm depth. Generally, high quality mouldings were produced, with void content seen to be typically lower than 0.5%, and injection flow rate across the experimental range did not affect the void content. Flat plaque experiments were performed at resin injection flow rates between 35 and 85g/s and three different levels of tool opening during the first resin injection stage, leading to in-mould pressures of 100bar. Results from mouldings filled with between 18% and 100% of total resin volume demonstrated that, in the liquid moulding stage of ALCM whilst the mould tool is held open, the resin flow in the preform is in-plane. The in-plane flow through the preform follows Darcy’s law for flow through porous media, however it was seen that spaces around the preform inside the rigid mould tool were conduits for resin flow governed by Navier-Stokes flow. It was found that in the resin injection stage, after a minimum tool opening, the resin channels in the mould alleviate resin injection pressure to a greater affect than increasing permeability (through lower fibre volume fraction). In the flat panel mouldings, resin channels around the component perimeter determine the fill pattern. In the top hat shape mouldings, resin channels were present at corner bend radii and were seen to be advancing the flow front. Resin channels were found to be problematic through reducing the proportion of injected resin volume that remained in the preform. Injected resin volume determined by feedback from an in-mould pressure sensor, rather than prescribed volume of resin, demonstrated the process consistency across sixteen repeated flat panels. Preform/fibre wash was found to be a critical problem as a result of the high injection pressures. The effect varied from local wrinkle defects to complete wash out and was shown to be linked to the degree of preform stabilisation by binder or edge clamping and fibre tow wash to the fabric stitch and inlet configuration. Critically the extent of fibre wash was sensitive to small variations in preform geometry at the higher injection flow rates experimented. In Objective 2, the simulation methodology developed using the well-known University of Delaware, LIMS Liquid Injection Moulding Simulation software. The modelling methodology was successfully adapted to the ALCM process, employing a low FVF injection using a Finite Element Control Volume approach, followed by compression as each node becomes a resin injection gate. The simulation was used to predict fill pattern, mould pressure and press clamping force. Results from simulation models representing the flat and top hat shape panels correlated to experiments and found that the Darcy flow assumption is valid for predicting fill pattern provided that the preform remains fixed and resin channels are represented. Correct representation of changing resin viscosity is necessary to reliably calculate pressure and therefore press clamping force. A full-size vehicle floor was the technical demonstrator component. This large component, with surface area 3m2 was ultimately manufactured within a 5 minutes cure cycle. At the time of writing, this is believed to be the largest structural composite component manufactured at this production rate. It was found that the methodology developed in Objective 2 could be applied to give good correlation between simulation and experimental results for resin fill pattern and process pressure, with the additional requirement that resin outflow from the preform into the tool be characterised. The floor component is produced from three preforms. Fibre wash at the preform joint was observed at resin injection flow rates of 85g/s and above. An innovative design of Anchored Through-Thickness Reinforcement at the preform joint was incorporated and was seen to stabilise the preform joint, eliminating fibre wash The two part resin used in the process is a new formulation developed to have short cure time. At moulding temperatures between 1300C and 1100C the resin cure time was between 3 and 8 minutes. It was found that conventional rheometry characterisation techniques were not satisfactory for defining the resin viscosity in the initial reaction stages. The dielectric analysis technique was investigated for the first time in this application. Results found that this method is suitable for fast cure resin rheo-kinetics characterisation.
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Piccirilli, Federica. "High pressure studies of amyloid proteins." Doctoral thesis, Università degli studi di Trieste, 2012. http://hdl.handle.net/10077/7435.
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2010/2011In questa tesi viene presentato lo studio di due proteine amiloidi, l'insulina e l' -sinucleina , condotto attraverso l'utilizzo della spettroscopia infrarossa a trasformata di Fourier in alta pressione. Con il nome di brille amiloidi ci si riferisce ad aggregati proteici altamente ordinati che si vengono a depositare in diversi organi o tessuti durante lo sviluppo di molte importanti patologie, le amiloidosi. Tra queste, vista la crescente di usione nelle popolazioni occidentali, vale la pena citare il morbo di Parkinson, e il morbo di Alzheimer. Le conoscenze relative alla termodinamica degli aggregati amiloidi e alle cinetiche di aggregazione sono ancora limitate. Ci o che maggiormente complica la ricerca di strategie atte ad inibire la reazione e la sostanziale irreversibilit a del processo di aggregazione. Le brille amiloidi dimostrano infatti una sorprendente stabilit a termodinamica. L'introduzione di tecniche di alta pressione nello studio dei sistemi biologici ha negli ultimi anni evidenziato le potenzialit a e l'utilit a della bio sica delle alte pressioni in particolare nello studio degli stati conformazionali delle proteine . Attraverso una variazione di pressione, si possono infatti gestire le distanze intra- e inter-molecolari in modo controllato. Dal presente studio emerge che l'applicazione dell'alta pressione e in grado di indurre la rottura degli aggregati amiloidi con un'e cienza che dipende dallo stato di maturazione della brilla (nel caso dell'insulina) e dalla speci ca mutazione genetica (nel caso della sinucleina). E' stato inoltre individuata una sequenzialit a nel processo di dissociazione indotto, che sembra ri ettere la pre-esistente gerarchia di strutture della catena peptidica. Attraverso l'applicazione dell'alta pressione e stato dunque possibile stabilizzare stati intermedi di brillazione. Quest'ultimo rappresenta il punto di forza della bio sica in alta pressione, che permette di popolare e quindi caratterizzare stati energeticamente instabili a pressione ambiente, fornendo dunque nuove linee di ricerca da seguire per la comprensione delle amiloidosi.
In this thesis is presented the investigation of the infrared properties at high pressures of two amyloidogenic proteins: insulin and -synuclein. Amyloid brils are highly ordered protein aggregates occurring during the development of many serious diseases, like Alzheimer's and Parkinson's diseases. Despite a major e ort both from the biological and biophysical communities, very little is known about the thermodynamics of the aggregated protein state and the kinetic mechanisms of its formation. Fibrillation is an irreversible process and a key challenge is the development of therapeutical strategies able to inhibit or reverse the formation of amyloids. Hydrostatic pressure has proven to be a powerful tool for the study of biological systems. Contrary to temperature - whose e ects show both on volume and thermal energy simultaneously - pressure leads to a controlled change of inter- and intramolecular distances, and enables to determine the stability of a protein structure. From the present study, it comes out that high pressure is able to induce the disaggregation of brils with an e cacy which depends on the maturation stage (insulin) and on speci c point mutations (synuclein). Our results show how high pressure disaggregation occurs following a sequential mechanism that re ects the protein's structure hierarchy. Pressure allows to address intermediate states, which are probably occurring along the aggregation reaction pathway, thus providing a new clue to the understanding of amyloidosis.
XXIV Ciclo
1979
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Pace, Edward John. "High pressure studies of hydrogen-chalcogen systems." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33258.
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Binary element-hydride systems have become a pertinent topic for high pressure research, following the measurement of record high temperature superconductivity in the dense hydrogen-sulfur system. The experimental study followed predictions of superconductivity with high transition temperature (Tc) in (H2S)2H2 at high pressures, leading to the current consensus that the high Tc phase is H3S, produced from the decomposition and recombination of H2S at high pressures. However, conjecture over the behaviour of hydrogen sulfide upon compression, and experimental limitations, cast significant ambiguity over interpretations of the structure and mechanism of the superconducting phase. Nonetheless, theory also predicts high Tc superconductivity in the dense hydrogen selenide and telenide systems; both experimentally uncharted at high pressures prior to this study. This thesis explores and maps the phase diagrams of hydrogen-chalcogen (S, Se, Te) systems using a combination of high pressure Raman spectroscopy and x-ray diffraction techniques. Gaining a comprehensive understanding of the behaviour of these systems under pressure is crucial to the eventual elucidation of the true nature of high Tc superconductivity. Hydrogen sulfide (H2S) and hydrogen selenide (H2Se) are appreciably toxic. A simple in situ synthesis technique is reported for producing hydrogen-chalcogenides directly from their constituent elements within diamond anvil cells, circumventing the need to condense toxic gases. This technique is also utilised to provide excess hydrogen, in order to produce the hydrogen-rich cocrystals thought to be vital to the formation of the high Tc phase. The hydrogen-sulfur system is most thoroughly investigated, and first presented. High quality Raman spectroscopic data provides an experimental review of pure H2S. Studies of (H2S)2H2 evaluate the current known ambient temperature phases and reveal three novel low temperature phases. Phase II0 is identified on cooling of phase I to 173 K (10 GPa), via splitting of both the single S-H stretching mode and low-frequency H2 vibron; sharp stretching modes indicate a significant reduction in orientational disorder. Successive splitting of the low-frequency H2 vibrons indicates two additional phase changes at 29 GPa (phase III0) and 53 GPa (phase- IV0) respectively, at 80 K. Phase IV0 is associated with an overall increase in symmetry. Evidence is also presented for a tentative fourth novel low temperature phase at ~160 GPa (20 K) and for the formation of an exceptionally stable hydrogen-sulfur compound with potentially novel stoichiometry. The behaviour of the H2S and (H2S)2H2 mixed molecular system is also reported; demonstrating that the coexistence of (H2S)2H2 and H2S can influence the hydrogen-bonding within both systems at high pressures. The first high pressure studies of the hydrogen-selenium system at ambient temperature are reported. The high pressure phase sequence of H2Se (I { I0 - IV) is identified by Raman spectroscopy, mirroring that of H2S. The isothermal boundaries for phases I0 and IV are found at 7 and 12 GPa respectively, at 300 K. Phase IV may have higher symmetry than phase IV H2S. X-ray diffraction and Raman spectroscopy demonstrate that the H2Se:H2 mixtures form cocrystals of (H2Se)2H2 from 4.2 GPa, with tetragonal space group I4=mcm, analogous to (H2S)2H2. Both H2Se and (H2Se)2H2 are shown to decompose into their constituent elements above 24 GPa. Attempts to synthesise the elusive H2Te directly from hydrogen and tellurium are reported. No reaction occurs upon heating Te in H2 at 0.2 GPa to 573 K. No visible reaction occurs between H2 and the high-pressure phases of Te, upon laser-heating. No photoreaction occurs upon exposure of tellurium in hydrogen to intense laser light (532 nm) at 0.2 GPa and 300 K, but formation may be stabilised at lower temperatures.
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Kolbus, Lindsay Marie. "Structural variations of feldspars at high pressure and high temperature." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/77063.
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Feldspar minerals are framework aluminosilicates that comprise approximately 60 percent of the Earth's crust. The elastic and thermodynamic properties of this important mineral group are needed for the interpretation of seismic wave velocities, for understanding cation partioning patterns and for the determination of phase boundaries and reactions involving feldspars in the Earth's crust. Until recently, no systematic approach has been applied to describe the structural behavior of feldspars as a function of pressure, temperature and composition. In this thesis, high-pressure and high-temperature X-ray diffraction data were collected for feldspars over a range of compositions which has led to the development a structural model that allows one to predict the structural evolution of feldspars at depth in the Earth's crust. Specifically, the equations of state have been determined for two plagioclase feldspars (An20 and An78) with different states of Al/Si ordering using single-crystal X-ray diffraction. This study has shown that the introduction of Al,Si disorder into plagioclase structures at constant composition softens the structure by 4(1)% for An0, 2.5(9)% for An20 and is essentially zero for An78 compositions. The effect of pressure on the structure of an ordered An20 was also determined up to 9.15 GPa using single-crystal X-ray diffraction and it was found that the dominant compression mechanism involves tilting of the AlO4 and SiO4 tetrahedra. Similarly, high-temperature single-crystal X-ray diffraction data collected from an ordered An26 plagioclase and powder X-ray diffraction collected on a suite of Na-rich plagioclases that were refined using the Rietveld method indicate that the major structural response to increased temperature involves tilting of the tetrahedra. Building on ideas originally proposed by Dr. Helen Megaw, the changes in the conformation of the tetrahedral framework of feldspars can be described in terms of four distinct tilt systems of rigid tetrahedra. This model demonstrates that the fundamental reason for the observed anisotropy and volume change of feldspars lies in the topology of the tetrahedral framework with the greatest contribution attributed to tilt systems 2 and 3.Ph. D.
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Bloom, Scott Harris. "Superconducting and normal compounds : some high field/high pressure effects /." Thesis, Connect to Dissertations & Theses @ Tufts University, 1989.
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Thesis (Ph.D.)--Tufts University, 1989.Submitted to the Dept. of Physics. Includes bibliographical references (leaves 192-204). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Larsen, Håvard. "Behaviour of polymer muds under high pressure – high temperature conditions." Thesis, Norwegian University of Science and Technology, Department of Petroleum Engineering and Applied Geophysics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1534.
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A well is classified as a HPHT (High Pressure High Temperature) well if the static bottomhole temperatures are greater than 350 °C and when the formation pressures exceed 1800 kg/m3 ECD. Mud weights as high as 2400 kg/m3 may be required to maintain a proper well control. The temperature of the drilling fluid when circulating in the well may range from 0 °C to 150 °C and it is important that the drilling fluid maintain acceptable rheological properties within the whole range. The rheological properties of the mud will strongly depend on the temperature and the pressure variations. The problems regarding HPHT wells are mostly due to ECD and cuttings transport.
In order to control and measure the viscosity for deep HPHT wells we have conducted laboratory experiments that deal with aging at different temperatures on a polymer mud, as well as pressure and temperature effects on a field mud. We have also calculated the annular pressure using Landmark Wellplan software. To calibrate the instruments, i.e. the Physica HPHT viscometer and a Fann viscometer, we used ubelohde, known to give an exact value of the viscosity of a fluid. The calibration liquid was a 2-stroke motor oil with different amounts of Exxsol-D60 added.
The aging experiments were conducted in a mixture of water and HEC that were put in three different incubators at 20 °C, 60 °C and 90 °C for 1, 3, 8, 11, 15 and 20 days. The results showed that the viscosity decreased rapidly in the solutions that were aged at the highest temperatures and that most of the decrease took place during the first day of aging.
In the experiments on real (field) mud exposed to high pressures and temperatures the Physica viscometer was used. The results showed that the pressure effects were negligible compared to the temperature effects. During the measurements we experienced that the viscosity decreased as the temperature increased and that the decrease in the viscosity was more significant from 20 to 60 °C than from 60 to 90 °C.
Based on the results obtained in the laboratory and an evaluation of fluid implication on well pressure, we were able to draw the following main conclusions:
• Laboratory experiments are very educational. To learn that reality is not straight forward to measure was enlightening.
• The viscosity is very dependant on the temperature.
• The combined effect of pressure on the viscosity of a field mud is negligible.
• The annular pressure differences calculated in Landmark Wellplan did not show any significant differences for the different well temperatures.