A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfillment of the requirements for the degree of Master of Science. March 28, 2013 / The search for solutions to the important differential equations arising in extended surface heat transfer continues unabated. Extended surfaces, in the form of longitudinal fins are considered. First we consider the steady state problem and then the transient heat transfer models. Here, thermal conductivity and heat transfer coefficient are assumed to be functions of temperature. Thermal conductivity is considered to be given by the power law in one case and by the linear function of temperature in the other; whereas heat transfer coefficient is only given by the power law. Explicit analytical expressions for the temperature profile, fin efficiency and heat flux for steady state problems are derived using the one-dimensional Differential Transform Method (1D DTM). The obtained results from 1D DTM are compared with the exact solutions to verify the accuracy of the proposed method. The results reveal that the 1D DTM can achieve suitable results in predicting the solutions of these problems. The effects of some physical parameters such as the thermo-geometric fin parameter and thermal conductivity gradient, on temperature distribution are illustrated and explained. Also, we apply the two-dimensional Differential Transform Method (2D DTM) to models describing transient heat transfer in longitudinal fins. Furthermore, conservation laws for transient heat conduction equations are derived using the direct method and the multiplier method, and finally we find Lie point symmetries associated with the conserved vectors.

Thesis advisor: Alfredo Urzua / Thesis advisor: John Ebel / Nine empirical equations that estimate saturated hydraulic conductivity as a func- tion of grain size in well-graded sands with gravels having large uniformity coecients (U > 50) are evaluated by comparing their accuracy when predicting observed conduc- tivities in constant head permeability tests. According to the ndings of this thesis, in decreasing order of accuracy these equations are: USBR (Vukovic and Soro, 1992; USBR, 1978), Hazen (Hazen, 1892), Slichter (Slichter, 1898), Kozeny-Carman (Carrier, 2003), Fair and Hatch (Fair and Hatch, 1933), Terzaghi (Vukovic and Soro, 1992), Beyer (Beyer, 1966), Kruger (Vukovic and Soro, 1992), and Zunker (Zunker, 1932). These re- sults are based on multiple constant head permeability tests on two samples of granular material corresponding to well-graded sands with gravels. Using the USBR equation sat- urated hydraulic conductivities for a statistical population of 874 samples of well-graded sands with gravels forming 29 loads from a heap leaching mine in northern Chile are calculated. Results indicate that, using the USBR equation, on average the hydraulic conductivity of the leaching heaps has a two standard deviation range between 0.18 and 0.15 cm/s. Permeability tests on the actual material used in the heaps provided by the mine shows that the results presented in this thesis are consistent with actual observa- tions and represent saturated conductivities in heaps up to 3 m high under a pressures of up to 62 Kpa. In future work hydraulic conductivities can be combined with water retention curves, discharge rates, irrigation rates, porosities, and consolidation so as to evaluate the relationship between copper yields and the hydraulic conductivities of the heap. / Thesis (MS) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

Significant improvements in power conversion efficiency (>10%) of emerging thin-film photovoltaics have been achieved in the last 5 years. High efficiencies would not be possible without the development of new selective interfacial layers. However, a complete understanding of how interfacial layers function to improve the selectivity of charge extracting contacts in thin-film photovoltaics is still being sought. The goal of this work is to contribute to the understanding of the operation of selective interfacial layers based on the study of ionically functionalized fullerenes. Just as other ionically functionalized materials have shown promise as electron-selective interfacial layers in organic photovoltaics and mixed organic-inorganic halide perovskites, Chapter II demonstrates the utility of ionically functionalized fullerenes. High performing solar cells necessitate the use of conductive interfacial layers; anomalously high conductivity in ionically functionalized materials, which have been used as interfacial layers, has been ascribed to self-doping. This work demonstrates that less than 1% of an ionically functionalized fullerene is reduced in its highly conductive pristine state and is concurrent with the presence of distinct chemical species. These studies describe how the chemical origin of the high conductivity of ionically functionalized fullerenes does not require the invocation of direct anion reduction or significant chemical transformations such as Hofmann-like elimination reactions occurring to a stoichiometric degree. This work also addresses the question of how the selectivity of a charge extracting contact is improved by the presence of an interfacial layer. The quantification of energy barrier reduction, which is often discussed in terms of work function modification or energy-level alignment, is demonstrated using metal|semiconductor junctions modified with an ionically functionalized fullerene. The barrier height of high work function electrodes was reduced significantly, by as much as 0.45 V, and was correlated to thin (2–5 nm) portions of the film rather than fullerene aggregates. The studies that comprise this work form a coherent model for understanding the key factors that have resulted in the continued use of ionically functionalized interfacial layers, their high conductivity, and energy barrier modification of the charge extracting electrodes. This dissertation contains coauthored, previously published, and unpublished work. / 10000-01-01

"A numerical description of the extraordinary optoconductance (EOC) effect is presented using two separate models. Extraordinary optoconductance is part of a general class of EXX geometric effects involving the external perturbation of the properties of a 2D electron gas in a macroscopic semiconductor or metal-semiconductor hybrid structure. The addition of metallic inclusions, has been shown to increase the sensitivity of devices relying on EXX effects. Following the discovery of the first EXX effect, extraordinary magneto-resistance (EMR), an optical equivalent was suggested. Unlike EMR, where the external perturbation is an applied magnetic field, EOC results from the modification of the local charge density in the semiconductor by a focused laser. The first model assumes Gaussian charge densities for the photo-generated electron-hole pairs while the second model directly solves the semiconductor drift-diffusion equations using the finite element method (FEM). Results from both models are shown to agree with experimental EOC data, both as a function of the laser spot position and temperature. The FEM model has the ability to describe EOC in more complex geometries making it useful in designing EOC devices geared for particular applications. "

Thesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Chemical Engineering. / Bibliography: leaves 63-65. / M.S.

The last two decades have seen huge improvements in measuring the conductance of single molecules, especially with the establishment of the scanning tunneling microscope break-junction (STM-BJ) method. The availability of such a robust and reliable measurement technique allows for the study of more exotic molecules with built-in functionality. In this thesis, we employ creative chemical design to manipulate transport in a single molecule junction by tuning the conducting frontier orbitals. We investigate three classes of materials – thiophene dioxides, mixed-valence bis(triarylamines), and benzotriazinyl-based Blatter radicals. Within each system, we probe changes in conducting behavior or interfacial interactions that arise from modifying the molecular structure. First, we demonstrate that a family of thiophene pentamers, which typically conduct through their highest occupied molecular orbital (HOMO), can be induced to conduct through their lowest unoccupied molecular orbital (LUMO) instead. This is akin to switching between from hole to electron transport. The switching was achieved using chemical modifications that drastically lower the LUMO level toward the Fermi energy of gold: oxidation at the sulfur position to form thiophene dioxides combined with installing electron-withdrawing groups at the 3- and 4-positions of the thiophene moiety. The ability to tune HOMO versus LUMO transport is potentially useful for assembling molecular circuits with n- and p-type components. Next, we found that oxidation of bis(triarylamine) molecular wires into their mixed-valence state shifts their conducting orbitals close to the Fermi energy of gold, making these wires highly conducting. We measured the length dependent transport of three bis(triarylamine) molecules. In their neutral state, the conductance of these compounds decreases with increasing length, which is observed for many different systems. However, when they are chemically oxidized, the mixed-valence molecular wires show an increase in conductance with increasing length. Such wires that maintain good electrical transport over long distances are valuable for building efficient molecular devices. We then investigated the interaction of half-filled orbitals in organic radicals with gold substrates to explore the potential of these compounds for spintronic and magnetic applications. We found that a Blatter radical functionalized with gold-binding thiomethyl groups displays different charge transfer behavior depending on the environment. Under ultra-high vacuum, X-ray spectroscopy shows that the radical molecules in contact with the gold substrate gain a charge from gold and their singly unoccupied molecular orbitals get filled. Contrastingly, in solution-based single molecule measurements, the radical loses the electron from its singly occupied molecular orbital instead, and only the conductance of the oxidized species is detected. We further probed the nature of charge transfer between the Blatter radical and gold in ultra-high vacuum by comparing spectroscopic measurements from three different derivatives. The derivative that was functionalized with two thiomethyl groups in order for it to be measured in the STM-BJ was the only molecule to undergo charge transfer in ultra-high vacuum. Two other Blatter derivatives that had only one and no thiomethyl groups did not show the same charge transfer; these retained their radical character even when in contact with the gold substrate. Therefore, the results indicate that only one of the thiomethyl groups mediates charge transfer between radical and substrate. The body of work presented herein shows that chemical modifications to old and new systems can be used to modulate transport in junctions via the intrinsic character of the molecules rather than external engineering factors. Thiophene dioxides are a relatively nascent class of materials that already show versatility as molecular conductors, while organic mixed-valence and radical systems have been heavily researched in other fields but less so in molecular electronics. This thesis therefore seeks to encourage further research that takes advantage of the unique electronic structure of these materials systems to discover new transport phenomena.

Les matériaux de protection incendie sont largement utilisés pour assurer la sécurité des usagers des infrastructures. Les normes de protection incendie évoluant régulièrement, les matériaux doivent être de plus en plus performants. Ceux-ci sont généralement des mortiers constitués d’oxydes réfractaires et isolants. L’objectif de ce travail est de mettre au point un composite coupe-feu 4 h applicable par projection mais également de déterminer ses propriétés thermiques et mécaniques.Dans une première partie, cette étude reprend les différentes étapes de l’élaboration d’un matériau de protection incendie, après la présentation de la démarche qui a guidé l’élaboration de nos matériaux, nous nous sommes intéressés plus particulièrement à la composition chimique de la matrice ainsi que celle du ciment. Leurs propriétés thermiques et mécaniques ont été passées en revue.Les matières premières nécessaires à l’élaboration d’un mortier ont ensuite été sélectionnées. L’évolution, respectivement de la conductivité thermique, de la diffusivité, de la porosité, de la chaleur spécifique et des propriétés mécaniques des mortiers choisis en fonction de la nature et de la quantité de charges incorporées à la matrice a été étudiée. Une description des divers modèles analytiques et numériques permettant la représentation de la conductivité thermique et du module d’Young des matériaux a permis de développer un modèle capable de prédire le comportement thermique et mécanique des composites en fonction de la nature et de quantité de charges ajoutées.Dans une seconde partie, la cinétique de la réaction d’hydratation du plâtre afin de maîtriser les temps de prise et pour faciliter la production des projetés dans la chaîne industrielle a été étudiée. L’influence sur la cinétique d’hydratation, de la composition chimique du plâtre, de sa granulométrie et de l’ajout d’adjuvants couramment utilisés dans l’industrie plâtrière, a également été traitée.10A l’issue de cette étude, deux formulations de composites projetables ont été mises au point. / Fire protection materials are widely used to ensure the safety of users of the infrastructure. Standards of fire protection regularly operating, the materials must be more efficient. These are generally composed of refractory mortar and insulating oxides. The objective of this work is to develop a firewall composite 4 h applied by projecting but also to determine the thermal and mechanical properties.In the first part, this study describes the various stages of the development of a fire protection material, after the presentation of the approach that has guided the development of our materials, we are interested especially in the chemical composition of the matrix and that of the cement. Their thermal and mechanical properties have been reviewed.The raw materials for the preparation of mortar were selected. The evolution respectively of thermal conductivity, diffusivity, porosity, specific heat and the mechanical properties of mortars chosen according to the nature and amount of the fillers incorporated in the matrix has been studied. A description of the various analytical and numerical models for the representation of the thermal conductivity and Young's modulus of the materials led to the development of a model able to predict the thermal and mechanical behavior of composites based on the nature and amount of charges added.In a second part, the kinetics of the hydration reaction of gypsum to control setting time and to facilitate the production of the composite in the industrial chain was studied. The influence on the kinetics of hydration, of the chemical composition of the gypsum, particle size distribution and the addition of adjuvant commonly used in the plaster industry, has also been treated.At the end of this study, two formulations of composites applied by projection were developed.

Doctor of Philosophy(PhD) / The present study deals with the synthesis, characterization, determination of anticancer activity of three mononuclear trans-planaraminepalladium(II) complexes code named TH5, TH6 and TH7 and three trinuclear complexes code named TH1, TH8 and TH14. The activity of the compounds against human cancer cell lines: A2780, A2780cisR and A2780ZD0473R, cell uptake, DNA-binding and nature of interaction with pBR322 plasmid DNA have been determined. Whereas cisplatin binds with DNA forming mainly intrastrand GG adduct that causes local bending of a DNA strand, TH5, TH6, TH7, TH1 and TH8 bind with DNA forming mainly interstrand GG adducts that causes more of a global change in DNA conformation. Although TH5, TH6 and TH7 each have two substituted pyridine ligands in a trans-geometry (3-hydroxypyridine in TH5, 2-hydroxypyridine in TH6 and 4-hydroxypyridine in TH7), the compounds differ in their activity against ovarian cancer cell lines, indicating that non-covalent interactions involving the hydroxyl group may be playing a significant role in activity of the compounds. Among trinuclear complexes TH1 is found to be significantly more active than cisplatin. It is actually twice as active as cisplatin against the parent cell line A2780, thirteen times as active as cisplatin against the cisplatin-resistant cell line A2780cisR and 11.5 times as active as cisplatin against the cell line A2780ZD0473R. Whereas the resistance factor for cisplatin as applied to the cell lines A2780 and A2780cisR cell lines is 12.9 that for TH1 is 1.98. The results suggest that TH1 has been able to significantly overcome resistance operating in A2780cisR cell line. The compound is soluble in water so that it may be taken orally. Provided it has favourable toxicity profile, TH1 has the potential to be developed into a highly active anticancer drug with a wider spectrum of activity than cisplatin. Although platinum drugs use a shot-gun approach to kill cancerous cells, widespread use in the clinic and increasing volume of their sale indicate that even in the genomic age, there is still need for shot-gun drugs in the clinic.

One of the most critical parameters in the success of a hydraulic fracturing treatment is to have sufficiently high fracture conductivity. Unbroken polymers can cause permeability impairment in the proppant pack and/or in the matrix along the fracture face. The objectives of this research project were to design and set up an experimental apparatus for dynamic fracture conductivity testing and to create a fracture conductivity test workflow standard. This entirely new dynamic fracture conductivity measurement will be used to perform extensive experiments to study fracturing fluid cleanup characteristics and investigate damage resulting from unbroken polymer gel in the proppant pack. The dynamic fracture conductivity experiment comprises two parts: pumping fracturing fluid into the cell and measuring proppant pack conductivity. I carefully designed the hydraulic fracturing laboratory to provide appropriate scaling of the field conditions experimentally. The specifications for each apparatus were carefully considered with flexibility for further studies and the capability of each apparatus was defined. I generated comprehensive experimental procedures for each experiment stage. By following the procedure, the experiment can run smoothly. Most of dry runs and experiments performed with sandstone were successful.

Isolation of terrestrially-observed magnetic signals by restoring their diffusive loss due to subsurface electrical conductivity sufficiently correlates these signals with those derived from the Alfven ionospheric electron movement of refraction variation. Temporary magnetic observatories were established on a conductive sedimentary basin (with a sampling interval of 5 s) and on a resistive large igneous intrusion (with a sampling interval of 10 s). Conventional modeling techniques estimate and remove the effects of the magnetometer, geomagnetic diurnal changes, whorls (solar quiet current vortices), and some bays from the acquired signals. Conventional one-dimensional skin depth modeling estimates the diffusive attenuation. The residual magnetic signal and the diffusive filter (as applied to the topography) become quantities in the linear system estimation of the geoelectric subsurface. Angular frequency domain least squares solution of the equations yields an isolated magnetic anomaly spectrum. Interpretive refinement, by selection of the zero or near zero curvature onset of either the spectrum's real or imaginary component, critically prepares the signal solution for correlation to a pseudomagnetic anomaly signal. This is an independently-derived sequence of anomalous values derived from Global Positioning System (GPS) refracted ranges. Detailed application of the Biot-Savart law provides independent anomaly signals to which the magnetic anomalies correlations show great correlation improvement by the isolation. These correlation improvements are from 2% to 83% and 9% to 91% for the sedimentary basin and from 2% to 96% and 24% to 78% for the igneous intrusion.