No description available.

No description available.

The behaviour of natural convective buoyancy-driven flows within a hot-water store due to the forced passage of colder water through the heat-exchanger's pipe are reviewed in the light of recent advances in experimental throughout the literature. The exchanger designs, for natural unworkable for the engineer complication arises because the heat exchanger are sensitive to and numerical studies, reported empirical development of heat convection problems, are often with a specification. The heat transfer performance of the the initial boundary conditions of the problem, ranging from the initial charged temperature of the water in the insulated tank of a fixed dimensíon, to the physical properties of the heat-exchanger's pipe. It was concluded that an improvement in the heat transfer performance can be derived by determining the optium length and the orientation of the heat-exchanger's arrangement. Further benefits are derived by correlating the thermal convective behaviour, within the hot-water store, with the forced passage of colder water through the heat exchanger's pipe. A convective flow model, based upon the experimental results, is described to advance the heat exchanger design principles in the situation of transient natural convection. Assumptions employed in the experimental work confirm that realistic and reasonable results can be obtained from the thermal analysis of the vertical cylindrícal store in two-dimensions.

The thesis reports on an experimental and computational study of kinetic heating at hypersonic speeds. Of particular interest is the transition of the laminar boundary layer to a state of turbulent motion. The experiments are performed in a Mach 9 Gun tunnel with a 5° semi-angle cone geometry. Twelve hemispherically blunted nose radii are tested at three unit Reynolds numbers. Testing has indicated that as the nose is progressively blunted, the transition region moves downstream. Further amounts of bluntness enhance other instability mechanisms and transition events are witnessed in the near nose regions. There are clearly two transitional regimes, denoted the "small bluntness" and "transition reversal" regime, respectively. This study investigates the structure of the transitional boundary layer in both regimes using thin film heat transfer rate gauges and liquid crystal surface thermography. The heat transfer measurements indicate that the small bluntness transition regime is governed by the rapid formation, growth and merging of turbulent events. Transition occurs over hundreds of boundary layer lengths. The reversal regime transition process is characterised by the birth of turbulent events in the nose and near nose regions. The temporal formation rate of the events is governed by roughness. In a low roughness environment, transition occurs over many model lengths. Increasing the roughness level, increases the spot formation rate, and transition is witnessed immediately downstream of the spherical nose region. The role of roughness is further explored using boundary layer trips. The trip causes a laminar wake which rapidly undergoes transition and forms a turbulent wedge. Event circumferential spreading angles are found for a variety of trip geometries and locations. The heat transfer distribution in the wedge is mapped using the thin film gauges. Computational work is used to perform laminar flow field predictions. Of interest is the entropy layer caused by the presence of the bow shock, and its interaction with the boundary layer. Heat transfer predictions in the transitional region are also performed aided with the experimentally obtained intermittency information.

No description available.

An apparatus and technique based on Angstrom's method is developed for measuring the thermal diffusivity of fruits and vegetables. The reproducibility of the results is found to be satisfactory with typical standard deviations of less than 6&'37. A detailed error analysis reveals that the accuracy of the technique is 7.1&'37. However, on checking the system with materials of known thermal diffusivities there was found to be a systematic error of the order of a factor of 2. A number of possible reasons for this are discussed. A method is outlined for predicting the optimum heat treatment parameters for the control of the potato disease blackleg. Some field trials were conducted which allowed the theory to be tested. During the field trials a varietal susceptibility to heat treatment was detected. The last part of the thesis concentrates on developing a means of quantifying this. Two methods were developed, the first based on the principle of increased cellular membrane permeability of damaged tissue and the second on a change in the speed of sound in damaged tissue.

No description available.

No description available.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. 01 September 2014. / In this thesis I explore the evidence for whether gravity is an emergent phenomenon. I provide a review of black hole thermodynamics and demonstrate how it provides evidence that gravity is an emergent phe- nomenon. In addition I provide a review of Jacobson's calculation which shows how the Einstein eld equations can be interpreted as a thermo- dynamic equation of state. I then use Jacobson's work and the Seiberg- Witten map to derive a new gravitational equation of state which shows what gravity on a non-commutative manifold would look like.

PhD, Faculty of Science (Molecular and Cell Biology), University of the Witwatersrand, 2001. / Phenylalanine 51 (F51) in the human class alpha GST forms part of a hydrophobic lockand- key intersubunit motif at the dimer interface. Protein engineering techniques were used to replace the phenylalanine key with serine. The results indicated that the mutant protein is dimeric with a native-like core structure indicating that F51 at the dimer interface is not essential for dimerisation to occur. Replacing F51 with serine impacts on the catalytic and ligandin function suggesting that tertiary structural changes have occurred at/near the active and non-substrate ligand binding sites. The F51S mutant also displays an enhanced exposure of hydrophobic surface as well as ligandin function. The F51S mutant displays a diminished conformational stability when compared to the wildtype protein. The lock-and-key intersubunit motif, therefore, although not essential for dimerisation to occur does stabilise the quaternary structure at the dimer interface. A unique structural feature of the class alpha GSTs is the C-terminal helix (residues 207- 221). In this study, the role of F221 was assessed by deleting it from the C-terminal helix 9 of hGSTA1-1. The results showed that the deletion of F221 does not affect the secondary, tertiary and quaternary structure of the protein as observed using far-UV CD measurements, enzyme activity and conformational stability as probes, respectively. The wild-type protein binds ~ 1.7-fold more ANS than the F221del protein. Binding affinity studies indicated that although both proteins bind ANS with the same affinity, the wildtype protein binds ANS with a higher capacity than the F221del protein. ANS binding to the wild-type and F221del proteins in the presence of urea (0 - 5.5 M urea) indicated that F221 is required for stabilising helix 9 at the C-terminal of hGSTA1-1. Therefore, F221 is not required for catalysis nor does it impact on the conformational stability of the protein. F221 does, however, affect the ligandin function and is required for the stability of helix 9 at the C-terminus of hGSTA1-1. ITC was used to dissect the binding energetics of glutathione (GSH) and glutathione sulfonate (GSO3 -) to the wild-type and Y8F hGSTA1-1 proteins. The contribution of the tyrosyl hydroxyl group to the binding of GSH and GSO3 - indicated that the Y8F mutant binds GSH tighter than the wild-type protein and the wild-type protein, in turn, binds GSO3 - tighter than the Y8F mutant protein. The Y8F mutant displays a larger negative vi DCp than the wild-type protein when complexed with either GSH or GSO3 -. This indicates the burial of a larger solvent-exposed hydrophobic surface area for the Y8F mutant than the wild-type protein. The burial of a large solvent-exposed hydrophobic surface area is related to the immobilisation of helix 9 onto domain I in the presence of active site ligands. The observation that the Y8F mutant displays burial of larger solventexposed hydrophobic surface area suggests that the tyrosyl hydroxyl group controls the dynamics of helix 9 at the C-terminal of hGSTA1-1. The DDG values also suggest that the tyrosyl hydroxyl group stabilises the thiolate anion at the active site in the wild-type protein. The binding energetics of non-substrate ligands (ANS and BSP) to the wild-type human class alpha GSTA1-1 were evaluated. The stoichiometry of the interaction between the wild-type protein and ANS indicated that one molecule of ANS binds per protein monomer. The binding interactions between ANS and the wild-type protein are enthalpically favourable indicating the possibility of hydrogen bond formation. ANS binding to the wild-type protein also resulted in the reduction of non-polar surface area exposed to solvent. It is proposed that the ANS binding site is the region adjacent to domain I that becomes buried when helix 9 is immobilised. The binding of BSP to the wild-type protein involves a high and low affinity set of binding sites. The high affinity binding site binds one molecule of BSP per protein monomer whereas the low affinity site is capable of accommodating a minimum of ~ four BSP molecules. The binding energetics to the high affinity site is both enthalpically and entropically favourable with each term contributing favourably to the favourable Gibbs free energy of binding. Binding to the lower affinity site is not very favourable enthalpically and the major driving force behind the favourable Gibbs free energy of association is the entropic factor. This interaction, therefore, appears to be entropically driven.