<p>Hydrogen is abundant, uniformly distributed throughout the Earth's surface and its oxidation product (water) is environmentally benign. Owing to these features, it is considered as an ideal synthetic fuel for a new world energetic matrix (renewable, secure and environmentally friendly) that could allow a sustainable future development. However, for this prospect to become a reality, efficient ways to produce, transport and store hydrogen still need to be developed. In the present thesis, theoretical studies of a number of potential hydrogen storage materials have been performed using density functional theory. In NaAlH₄ doped with 3d transition metals (TM), the hypothesis of the formation of Ti-Al intermetallic alloy as the main catalytic mechanism for the hydrogen sorption reaction is supported. The gateway hypothesis for the catalysis mechanism in TM-doped MgH₂ is confirmed through the investigation of MgH₂ nano-clusters. Thermodynamics of Li-Mg-N-H systems are analyzed with good agreement between theory and experiments. Besides chemical hydrides, the metal-organic frameworks (MOFs) have also been investigated. Li-decorated MOF-5 is demonstrated to possess enhanced hydrogen gas uptake properties with a theoretically predicted storage capacity of 2 wt% at 300 K and low pressure.</p><p>The metal-hydrogen systems undergo many structural and electronic phase transitions induced by changes in pressure and/or temperature and/or H-concentration. It is important both from a fundamental and applied viewpoint to understand the underlying physics of these phenomena. Here, the pressure-induced structural phase transformations of NaBH₄ and ErH₃ were investigated. In the latter, an electronic transition is shown to accompany the structural modification. The electronic and optical properties of the low and high-pressure phases of crystalline MgH₂ were calculated. The temperature-induced order-disorder transition in Li₂NH is demonstrated to be triggered by Li sub-lattice melting. This result may contribute to a better understanding of the important solid-solid hydrogen storage reactions that involve this compound. </p>

Preservation of tissue structure, morphology and biomarkers is of utmost importance for pathological examination of biopsy specimens for diagnostic and therapeutic purposes. However current methods employed to evade tissue degradation and preserve biomarkers have several shortcomings that include irreproducibility, morphological artifacts and altered biomarker antigenicity. These artifacts may affect the analysis and subsequent diagnosis of the tissue pathology. This creates need for developing improved preservation methods that reproducibly maintain tissue morphology and biomarker antigenicity and are simple, rapid and inexpensive. Experiments conducted for testing the hypothesis that cryopreservation procedures yield high quality morphology and antigenicity showed that cryopreservation maintains tissue structure, morphology and antigenicity at equivalent or better levels compared to standard freezing techniques. In order to understand the mechanisms of osmotic transport in cellular systems upon exposure to multi-component solutions that are prevalent in virtification protocols, experimental studies were undertaken using microfluidics for single cell manipulation. The experimental data yielded permeability parameters in binary and ternary solutions for MC3T3-E1 murine osteoblasts for the first time. The hydraulic conductivity (L(p)) decreased with increasing concentrations but the solute permeability either increased or decreased with increasing solution concentration. The changes in hydraulic conductivity were consistent with previously published trends and conform to a functional relationship in the form of Arrhenius type relationship between L(p) and solution concentration. Further a theoretical model was developed from principles of linear irreversible thermodynamics to simulate multi--‐‑component mass transport across membrane. The model was successfully validated by comparison with experimental data for murine osteoblasts and showed good agreement between the numerical predictions and experimental observations. The modeling approach can be used to investigate the transport mechanisms, which show that in multicomponent osmotic transport response, the dynamics is dictated by slower moving solute.

No description available.

The measurement of vapour-liquid equilibrium data is extremely important as such data are crucial for the accurate design, simulation and optimization of the majority of separation processes, including distillation, extraction and absorption. This study involved the measurement of vapour-liquid equilibrium data, using a modified version of the static total pressure apparatus designed within the Thermodynamics Research Unit by J.D. Raal and commissioned by Motchelaho, (Motchelaho, 2006 and Raal et al., 2011). This apparatus provides a very simple and accurate means of obtaining P-x data using only isothermal total pressure and overall composition (z) measurements. Phase sampling is not required. Phase equilibrium measurement procedures using this type of apparatus are often tedious, protracted and repetitive. It is therefore useful and realizable in the rapidly advancing digital age, to incorporate computer-aided operation, to decrease the man hours required to perform such measurements. The central objective of this work was to develop and implement a control scheme, to fully automate the original static total pressure apparatus of Raal et al. (2011). The scheme incorporates several pressure feedback closed loops, to execute process step re-initialization, valve positioning and motion control in a stepwise fashion. High resolution stepper motors were used to engage the dispensers, as they provided a very accurate method of regulating the introduction of precise desired volumes of components into the cell. Once executed, the control scheme requires approximately two days to produce a single forty data points (P-x) isotherm, and minimizes human intervention to two to three hours. In addition to automation, the apparatus was modified to perform moderate pressure measurements up to 1.5 MPa. Vapour-liquid equilibrium test measurements were performed using both the manual and automated operating modes to validate the operability and reproducibility of the apparatus. The test systems measured include the water (1) + propan-1-ol (2) system at 313.15 K and the n-hexane (1) + butan- 2-ol system at 329.15 K. Phase equilibrium data of binary systems, containing the solvent morpholine-4-carbaldehyde (NFM) was then measured. The availability of vapour-liquid equilibrium data for binary systems containing NFM is limited in the literature. The new systems measured include: n-hexane (1) + NFM (2) at 343.15, 363.15 and 393.15 K, as well as n-heptane (1) + NFM (2) at 343.15, 363.15 and 393.15 K. The modified apparatus is quite efficient as combinations of the slightly volatile NFM with highly volatile alkane constituents were easily and accurately measured. The apparatus also allows for accurate vapour-liquid equilibrium measurements in the dilute composition regions. A standard uncertainty in the equilibrium pressure reading, within the 0 to 100 kPa range was calculated to be 0.106 kPa, and 1.06 kPa for the 100 to 1000 kPa pressure range. A standard uncertainty in the equilibrium temperature of 0.05 K was calculated. The isothermal data obtained were modelled using the combined (-) method described by Barker (1953). This involved the calculation of binary interaction parameters, by fitting the data to various thermodynamic models. The virial equation of state with the Hayden-O’Connell (1975) and modified Tsonopoulos (Long et al., 2004) second virial coefficient correlations were used in this work to account for vapour phase non-ideality. The Wilson (1964), NRTL (Renon and Prausnitz, 1968), Tsuboka-Katayama-Wilson (1975) and modified Universal Quasi-Chemical (Anderson and Prausnitz, 1978) activity coefficient models were used to account for the liquid phase non-ideality. A stability analysis was carried out on all the new systems measured to ensure that two-liquid phase formation did not occur in the measured temperature range. A model-free method based on the numerical integration of the coexistence equation was also used to determine the vapour phase compositions and activity coefficients from the measured P-z data. These results compare well with the results obtained by the model-dependent method. The infinite dilution activity coefficients for the systems under consideration were determined by the method of Maher and Smith (1979b), and by suitable extrapolation methods. Excess enthalpy and excess entropy data were calculated for the systems measured, using the Gibbs-Helmholtz equation in conjunction with the fundamental excess property relation. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

This thesis presents the thermodynamic and economic assessment of gas power cycles for 100 MW solar thermal power generation systems. A gas power cycle for solar power generation is a totally different technology from the current state of the art solar power generation systems. As a result, this thesis provides an assessment of the solar power generation systems with gas power cycles and provides guidance in the selection of design and operating parameters for gas power cycle based solar power generation system. The gas power cycle based power generation systems are assessed by means of thermodynamic and economic models developed and simulated using commercial thermodynamic analysis software. The gas cycle based power generation systems considered in this study are Cold Gas Turbine, High Temperature Solar Gas Turbine and Lorentz Cycle Gas Turbine. The system models are assessed for their thermodynamic performance using theory based turbo-machinery models with practical performance and loss data. In addition, extensive cost models have been developed for assessing the economic performance of the system models to determine their practical feasibility. The results from this study indicate that the most economical power generation system is the HTSGT system for a high peak cycle temperature utilizing the central receiver power tower solar collector system. The LCGT system also has a comparable performance at the same operating temperature. The CGT system assessed for operating with parabolic trough solar collector system at a lower peak cycle temperature had an inferior performance compared to the current state of the art technology for the power generation using parabolic troughs.

In the following thesis, I will conduct a thermodynamic analysis of the Taub-NUT spacetime in various dimensions, as well as show uses for Taub-NUT and other Hyper-Kahler spacetimes. <br /><br /> Thermodynamic analysis (by which I mean the calculation of the entropy and other thermodynamic quantities, and the analysis of these quantities) has in the past been done by use of background subtraction. The recent derivation of the (A)dS/CFT correspondences from String theory has allowed for easier and quicker analysis. I will use Taub-NUT space as a template to test these correspondences against the standard thermodynamic calculations (via the N&ouml;ether method), with (in the Taub-NUT-dS case especially) some very interesting results. <br /><br /> There is also interest in obtaining metrics in eleven dimensions that can be reduced down to ten dimensional string theory metrics. Taub-NUT and other Hyper-Kahler metrics already possess the form to easily facilitate the Kaluza-Klein reduction, and embedding such metrics into eleven dimensional metrics containing M2 or M5 branes produces metrics with interesting Dp-brane results.

Proliferating cell nuclear antigen (PCNA) is an essential protein in the cell. It is involved in transcription and many types of DNA repair and replication. Homologues of this protein are found in all orders of life. The high level of conservation and essential nature of PCNA infers that it may be a potential drug target for anti-caner drugs in humans and also a potential anti-parasitic target. X-ray structures of PCNA from Homo sapiens (Hs), Schizosaccharomyces pombe (Sp) and Leishmania major (Lm) are now available and can be used as a template for structure based drug design. In this work PCNA from these three species have been prepared in milligram quantities for biochemical and biophysical studies. The previously unknown structure of LmPCNA has been solved in an uncomplexed form and also complexed with a dodecapeptide to a resolution of 3.0Å. A comparison of PCNA structures and their peptide complexes for the three species identifies structural differences which may be relevant in analysing thermodynamic contributions of binding. All eukaryotic PCNA molecules exist as ring shaped trimers which form around DNA. In this work the oligomeric state of LmPCNA has been determined to be hexameric both in solution and in the crystal. It has also been hypothesised that HsPCNA is hexameric however these would seem to form hexamers in which the trimeric rings associate “back-to-back” while LmPCNA trimers would seem to associate “face-to-face”. The binding affinities for these three PCNAs have been determined with a selection of peptides derived from the Hs p21 protein. This work has shown, using a selection of different techniques including Surface Plasmon Resonance (SPR), Isothermal Titration Calorimetry (ITC) and Dynamic Scanning Fluorimetry (DSF); that HsPCNA and SpPCNA have similar affinities for a 12mer peptide (Kd of ~1μM) however LmPCNA shows significantly weaker interactions (Kd of ~10μM). This is most likely due to divergence in the sequence and structure of LmPCNA. A systematic investigation by SPR on the effect of peptide linker length on binding has been carried out using a series of synthesised peptides with different lengths of chemical spacer. The series of streptavidin immobilised peptides show that longer spacers are required for the recovery of the PCNA peptide binding affinity. The results presented in this work indicate that a linker length of at least 20Å is required for measurable protein binding activity. This interaction is improved with longer peptide spacers.

Approved for public release, distribution is unlimited / An analysis of in-situ aircraft observations collected in the parent cloud of a waterspout is presented. Previous waterspout studies were confined mainly to photometric and model simulated data, no in-situ observations were made internal to the parent cloud. On 27 June 2002 the Cooperative Institute for Remotely Piloted Aircraft Studies (CIRPAS) UV-18A Twin Otter aircraft collected observations in a cloud that had developed in a cloud line, located approximately 15km south of Key West, and that formed a waterspout. This study attempts to analyze the waterspout formation process using these data and through a series of scale interactions, from the synoptic scale down to the individual cloud scale. Based upon the analyzed data a hypothetical formation process is developed. The background synoptic scale flow is shown to establish the necessary ambient shear as a key factor in the waterspout formation. The orientation of mesoscale convergent boundaries and thermodynamic processes, internal to the cloud, proved to be an essential factor in developing the vertical motion patterns necessary for formation of an organized circulation in the shear region and to provide the tipping and stretching of the resultant vortex necessary to account for the waterspout formation. This is consistent with conclusions derived from previous studies. / Captain, United States Air Force

This study focuses on understanding the development of gap outflow and the air-sea interaction processes during the 26 February 2004 Tehuano event over the Gulf of Tehuantepec, Mexico. The Navy's Coupled Ocean Atmospheric Mesoscale Prediction System (COAMPS) was used to simulate the gap wind event and was compared to satellite, scatterometer, and coincident in situ aircraft and dropsondes measurements collected during the Gulf of Tehuantepec Experiment (GOTEX). Comparisons between model results and the observations suggest that COAMPS performed the best in simulating the outflow jet within 200 km offshore, although the simulated surface fluxes deviated significantly from the observations. This is the region where the dominant dynamical forcing arises from the coastal topography. Larger discrepancies were found in model result further away from the coast, especially to the south and southeast of the gulf where the air-sea exchange became increasingly important. Detailed inter-comparison between COAMPS and the aircraft measurements at 40 m also shows the strong spatial and temporal variations of boundary layer thermodynamics and turbulence, which require improved characterization of the sea surface temperature, upper air conditions, and initial conditions for COAMPS. The results also point to the needs for improved surface flux parameterization, particularly in high wind conditions.

Nuclear Magnetic Resonance (NMR) Spectroscopy is a crucial tool for determining the structures of biological molecules. This technique can also be used to extract thermodynamic parameters of these molecules, enhancing our understanding of their biological roles. DNA is analyzed through NMR Spectroscopy in order to identify the effect of sequence on expressivity. DNA predominantly resides in BI orientation, but a second conformation, BII, also exists. DNA can switch between BI and BII backbone conformations and the likelihood of this switching is dependent upon the energetic barrier between these two sub-states. The secondary structure of DNA, and thus its adoption of BI and BII conformation, is sequence-dependent. Therefore, the identity and neighboring base pairs of a segment of DNA have a large effect on the flexibility of the backbone. Methylation also affects backbone structure. The methyl group has been shown to promote either stabilization and/or destabilization on proximate bases. This thesis uses variable temperature NMR and Mathematica modeling to determine the backbone conformations, rate of inter-conversion between BI/BII conformations, and the energetic barrier of this fluctuation for each nucleotide step in DNA dodecamers containing the CRE binding sequence. This has been a long-term goal of the Hatcher-Skeers lab, and the data from this thesis would have been added to years of flanked CRE DNA information to reveal any patterns. In this experiment, 5’-TTTC-3’ CRE DNA dodecamers underwent NMR analyses to extract backbone flexibility parameters. Additionally, the effect of methylation was studied in scans with methylated cytosine in the central CRE sequence. The TRX scale was used to predict the BII character of these sequences. Due to technical errors, the experimental results were not able to accurately represent the specific dynamics of each backbone step. However, general trends were identified, such as adherence to and veracity of the TRX scale and the effect of methylation. It was found that the %BII of the native DNA closely resembled the TRX predictions, whilst the methylated sequence did not. The largest changes in activation energy due to methylation occurred in the central CRE sequence, suggesting methylation is a localized effect. The results reflected several trends from past CRE experiments, but the data cannot be explicitly analyzed due to the technical errors.