Hydrogen, being the simplest and most abundant element in the Universe, is of fundamental importance to condensed matter sciences. Through advances in high pressure experimental technique, hydrogen (and its isotope deuterium) has been contained and studied using in situ optical spectroscopy to 315 (275 GPa) at 300 K, pressure and temperature conditions previously thought to be inaccessible. At 200 GPa, hydrogen undergoes a phase transformation, attributed to phase III, previously observed only at low temperatures. This is succeeded at 220 GPa by a reversible transformation to a new phase, IV, characterized by the simultaneous appearance of the second vibrational fundamental mode, new low-frequency phonon excitations, and a dramatic softening and broadening of the first vibrational fundamental mode. To impose constraints on the P-T phase diagram, the temperature stability of phase IV is investigated through a series of low temperature experiments, where the phase IV-III transformation is observed. Analysis of the Raman spectra suggests that phase IV is a mixture of graphene-like layers, consisting of elongated H2 dimers experiencing large pairing fluctuations, and unbound H2 molecules. Isotopic comparisons reveal spectral differences between the phase IV-III transition of hydrogen and deuterium, which strongly indicates the presence of proton tunnelling in phase IV. Optical transmission spectra of phase IV reveals an overall increase of absorption and a closing band gap reaching 1.8 eV at 315 GPa. No differences between the isotopes were observed in absorption studies, resulting in identical values for the band gap. Extrapolation of the band gap yields 375 GPa as the minimum transition pressure to a metallic state of hydrogen (deuterium).

The purpose of this investigation was to study the effects of decreased barometric pressure on the transcapillary movement of molecules by monitoring the macromolecular capillary permeability with lymph derived primarily from the hepatic and gastrointestinal regions of the dog.

The problem of this study is to clarify and evaluate the effect of group influence upon decisions made by elementary school children.

Information on the density of hydrocarbons at high pressures and temperatures is of great importance in many fields, such as the study of ultra-deep reservoirs up to ~240 MPa and 250°C. However, density data at such high pressures and temperatures are often not available in the literature. In this study, experimental densities are reported for n-pentane, n-octane, 2,2,4-trimethylpentane, cyclooctane, n-decane, and toluene to ~280 MPa and ~250°C. These experimental densities are in good agreement with available literature data, although the literature data for many of these fluids do not extend to the pressures and temperatures utilized in this study.

Zr-2.5 Nb pressure tubes in CANDU reactors are susceptible to delayed hydride cracking (DHC), which is a sub-critical cracking process requiring hydrogen diffusion to a stress concentrator, precipitation, growth and fracture of hydrides. Service-induced and manufacturing flaws are present in some pressure tubes and these flaws may act as crack initiators. An engineering approach has been developed to assess the susceptibility of flaws to DHC. In this methodology, DHC is separated into the initiation and growth stages, and in terms of initiation, flaws are classified as blunt, sharp or crack-like. The experiments performed in this thesis are related to crack-like flaws, which are assessed in terms of the threshold stress intensity factor, K1H, below which DHC cannot occur. There is a large scatter in the overall KIH data base and a lower bound value is conservatively used for flaw assessment. Systematic studies on un irradiated Zr-2.5 Nb pressure tube material have shown that KIH increases with decreasing hydrogen in solution, increasing deviation from the radial-axial plane of the tube, and increasing temperature, while thermal cycling has no significant effect on K1H. Therefore, it may be justifiable to use higher KIH values for assessing flaws with known orientation, hydrogen concentration at the flaw location and operating thermal history. If crack initiation is postulated, as part of a defence-in-depth approach, crack growth is assessed under two scenarios. (1) When the hydrogen concentration is sufficient for cracking to continue under sustained hot conditions, a leak-before-break assessment is performed. DHC velocity is required to determine the time for a crack to grow to the critical crack length for unstable fracture. This thesis shows that crack velocities at different temperatures depend strongly on the thermal history, which affects the hydrogen concentration in solution. Crack velocity increases with increasing hydrogen in solution. In addition, hydrogen supersaturation is required for cracking to occur at the reactor operating temperatures of 2S0-31O°C. (2) When the hydrogen concentration is insufficient for cracking to occur at normal operating temperatures, cracking can only occur during reactor cool-down when hydrides can precipitate as a result of the lowering of temperature. The amount of postulated crack growth per cool-down cycle depends on the crack initiation temperature during cooling. This thesis shows that the crack initiation temperature decreases with increasing cooling rate, and by applying a load-reduction of 20% prior to cooling. Cracking during cooling can be suppressed altogether by allowing the crack tip stress to relax by creep, followed by a load reduction of 15-20%. Recommendations are made regarding reactor loading and thermal history which can reduce the propensity for DHC. From the observations on hydride morphologies and fracture surface features of the DHC cracks under different test conditions, evidence is presented which supports the hydride/stress interaction diffusion model. The observations also demonstrate the inadequacies of the critical length criterion for fracture of a hydrided region.

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It has generally been assumed that porosity reduction during mechanical compaction of a sediment is controlled by the increase in vertical effective stress. But the theory of mechanical compaction shows that it is the mean effective stress which controls porosity reduction. According to published data, horizontal stresses increase with overpressure, as well as with depth, so mean stress and vertical stress profiles are poorly correlated in overpressured sections. In this study, a new methodology was developed whereby mudrock pore pressures were estimated principally by comparison of void ratios calculated from wireline log response with hydrostatic mean effective stress (the mean effective stress assuming the pore pressure is hydrostatic). These pressure estimates in the low permeability units were compared to the direct measurements in the aquifer units and an interpretation is made as to the origin of the excess pressure. The results of analysis of seven wells from SE Asia are presented including one study where seismic velocity analysis and basin modelling were performed to assess the pore pressure. The main conclusions of the study are: The proposed new methodology for estimating shale pore pressure from void ratio and mean effective stress analysis appears to be more consistent with the data and represents an improvement on previous methodologies using porosity and vertical effective stress or depth. Analysis of the mudrocks in this study indicates that the shales often appear to have significantly higher pressures than the adjacent aquifer units. The results of using mean (as opposed to vertical) effective stress analysis indicates that the pressure profiles in the wells studied, the profiles disequilibrium compaction can account for all or nearly all of the encountered overpressures. Evidence has been found for significant overpressure generated by fluid expansion in one of the seven wells studied.« Further work to refine the Breckels and Van Eekelen (1982) relationship between overpressure and horizontal stress is proposed to improve the accuracy of the methodology used in this study.

M.Phil. (Optometry) / The primary aim of this research was to investigate whether the Icare® rebound tonometer may be used in place of the Goldmann tonometer to obtain accurate and reliable intraocular pressure measurements on a sample of the general population seeking eye care, in a South African context. Due to the portability of the Icare®, lack of dependency on other instrumentation and power source, together with the ease of use with minimal training, and without the use of topical anaesthetic favourable results of the instrument may lead to its widespread use. This could aid in earlier diagnosis of glaucoma where intraocular pressure remains the only modifiable risk factor. In the South African context, where a high prevalence of undiagnosed primary open angle glaucoma has been found, access and accuracy of intraocular pressure measurement could save and extend functional vision in this country. Patients presenting at the Department of Optometry for routine eye examinations were selected utilizing convenience sampling. The right and left eyes of 113 patients were assessed using both the Icare® TA01i and the Goldman applanation tonometer by independent examiners for each method, all readings of intraocular pressure with the Goldman being taken by the same experienced examiner. The age of the patients ranged from 20 to 89 years with a mean age 50.29 ±20.97 years. Using the Oculus Pachycam® when it became available, central corneal thickness was obtained on 71 patients (142 eyes). Analysis of data using descriptive statistics from SPSS (Statistical Programs for the Social Sciences) was performed in addition to the Bland-Altman method of comparative analysis for sets of data of corrected and uncorrected measurements between the instruments...

Thesis advisor: Alan Kafka / The stability of open-pit mine walls and other geotechnical infrastructure is a function of geometry, material properties and groundwater conditions (pore pressure distribution). A portion of failures are attributed to the effect of pore water pressures within the mine wall slopes. The objective of this research was to investigate the interaction between the increments/decrements of stresses that occur during the lithostatic unloading/excavation of the pit and the increments/decrements of pore water pressures. This interaction can be described by the theory of linear poroelasticity, which incorporates the coupling between changes in fluid pressure and changes in stress in porous media. The results of this thesis are displayed in the form of contour charts and graphs. / Thesis (MS) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

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