Organometallic compounds derived from tin, boron, and zinc, have been used extensively in transition metal-catalysed cross-coupling, and continue to hold status as the go-to reagents to form new carbon-carbon bonds. Recently, organosilicon compounds have emerged as an attractive alternative to these established reagents, benefitting from low toxicity, low cost, and general ease of handling. While the fundamental reactivity of arylsilane reagents (Ar-SiR3) is well known, their role in transition metal-catalysed reactions is generally less well studied. This thesis comprises an investigation into the effect of ortho-substitution of these arylsilane reagents, and specifically, their application in gold-catalysed direct arylation. In Chapter 2, the transmetalation of these reagents to gold(III) is assessed using a combination of in situ reaction monitoring coupled with kinetic simulations. This allowed a scale of reactivity to be constructed for a range of structurally diverse arylsilanes, and uncovered that more sterically hindered arylsilanes actually exhibit accelerated rates of transmetalation. In Chapter 3, the reactivity of ortho-substituted arylsilanes in gold-catalysed arylation is addressed. The majority of arylsilanes tested in the previous chapter were found to be unable to undergo coupling, despite the viability of transmetalation having been demonstrated. Slight modification of the ortho-substituent, to incorporate a tethered ligand, was found to have a dramatic effect on reactivity, and allowed the coupling of a variety of substrates. The nature of the ligand, as well as the substitution of the tether was found to have a significant impact on the rate of coupling. Chapter 4 describes the way in which the reactivity of ortho-substituted arylsilanes might be exploited in a 'Catch and Release' protocol for catalyst recovery. This aims to combine the established benefits of homogeneous and heterogeneous catalysis to offer an alternative to current methods of catalyst recycling in industrial chemistry. A number of different 'Catch and Release' mechanisms were considered, and the validity of the concept was demonstrated in a monophasic system.

Thesis (M. Sc. (Chemistry)) --University of Limpopo, 2018 / The dissertation describes the use of 2-benzenesulfonyloxyquinoxaline as a good coupling partner for different amine substrates. The palladium-mediated cross- coupling of aryl electrophiles and amines has become a widely used method of constructing arylamine frameworks. The formation of carbon-nitrogen bonds was accomplished via palladium-catalysed Buchwald-Hartwig amination employing different amine substrates to yield substituted quinoxaline-2-amines compounds in good to moderate yields. Buchwald ligands (Xphos, tButylxphos and BrettPhos), were varied with different amine substrates in an attempt of improving the yields. Compounds 81a N-phenylquinoxalin-2-amine and 82b, N-benzylquinoxalin-2-amine were obtained with the yield over 70 % employing Xphos as the ligand. Significant attention has also been given to the application of cross coupling reaction protocols in substrates bearing electron withdrawing substituents. The presence of deactivating groups on the arylamine such as fluoro, nitro and iodo proved to be a challenge as only few compounds were synthesised in moderate yields. Compound 81b, N-(4-fluorophenyl)quinoxalin-2-amine which has electronegative atom attached, showed significant improvement when employing tButyl-Xphos ligand rather than XPhos since the yield improved from 10 % to 71 %. Furthermore, nucleophilic substitution on Buchwald-Hartwig coupled compounds by treating them with alkyl iodides was successful when using methyl and ethyl electrophiles on the N-H group of 81a 2-quinoxalineamine. The synthesised quinoxaline derivatives comprised 7 novel compounds. The in vitro analysis on anti-tubercular screening against H37RvMA strains of Mycobacterium tuberculosis was conducted on 9 compounds. The results revealed none of the compounds to have promising inhibition percentages against Mycobacterium tuberculosis when compared with rifampicin which was used as a positive control. Screening against malaria with chloroquine as the control also did not yield any active compounds.

Molecules with unusual steric crowding are always interesting in chemistry. They give the opportunity to explore the limits of stable molecular structures and the synthesis of unnatural products. They also provide points of calibration for modern computational methods. This dissertation describes the design, synthesis and characterization of two types of crowded complex aromatic compounds. The goal of the first project was to synthesize in-keto cyclophanes, that is, molecules with ketone oxygens pressed toward the centers of benzene rings. Several likely precursors were synthesized and fully characterized, but attempts to make the in-keto cyclophanes themselves were unsuccessful. The nonbonded interaction between the ketone oxygen and basal benzene ring may be so close in the target structures as to prevent the formation of an in-keto cyclophane. The second project describes the design, synthesis and characterization of several macrobicyclic, bis(triarylelement)-containing cyclophanes with various bridgehead heteroatoms. Computational studies accurately predicted that when the bridgehead substituents are small (lone pairs or protons), an in,in bridgehead stereochemistry is strongly favored, but larger bridgehead substituents favor the formation of in,out stereoisomers. The NMR spectra of several of these compounds show unusual through-space spin-spin coupling between atoms along the central axis. Most importantly, one of these compounds, an in,in-bis(hydrosilane), possesses a hydrogen-hydrogen nonbonded contact distance of approximately 1.56 Å, a new “world record” for such a contact in any crystallographically characterized compound. / 1 / Jie Zong

Renewable energy-hydrogen systems for remote area power supply (RAPS) constitute an early niche market for sustainable hydrogen energy. The primary objective of this research has been to investigate the possibility of direct coupling of a PV array to a proton exchange membrane (PEM) electrolyser by appropriate matching of the current-voltage characteristics of both the components. The degree to which optimal matching can be achieved by direct coupling has been studied both theoretically and experimentally. A procedure for matching the maximum power point output of a PV array with the PEM electrolyser load to maximise the energy transfer between them has been presented. The key element of the matching strategy proposed is to vary the series-parallel stacking of individual cells in both the PV array and the PEM electrolyser so that the characteristic current (I) -voltage (V) curves of both the components align as closely as possible. This procedure is applied to a case study of direct coupling a PV array comprising 75 W panels (BP275) to a PEM electrolyser bank assembled from 50 W PEM electrolyser stacks (h-tec StaXX7). It was estimated theoretically that the optimal PV-electrolyser combination would yield an energy transfer of over 94% of the theoretical maximum on annual basis. This combination also gave the lowest hydrogen production cost on a lifecycle basis. An experimental test of this theoretical result for direct coupling was conducted over a period of 728 hours, with an effective direct-coupling operational time of about 467 hours (omitting the hours of zero solar radiation). Close agreement between the theoretically predicted and actual energy transfer from the PV array to the electrolyser bank in this trial was found. The difference between theoretical and experimental hydrogen production was less then 1.2%. The overall solar-to-hydrogen energy conversion efficiency was found to be 7.8%. The electrolysers were characterised before and after the direct coupling experiment, and showed a small decline in Faraday efficiency and energy efficiency. But this decline was less than the uncertainties in the measured values, so that no firm conclusions about electrolyser degradation can be drawn at this stage. Another direct-coupling experiment, using a larger scale PV-electrolyser system, that is, a 2.4 kW PV array at RMIT connected to the 'Oreion Alpha 1' stand-alone 2 kW PEM electrolyser developed by the CSIRO Energy Technology, was also successfully conducted for a period of 1519 hours (with 941 hours of effective operational time of the electrolyser). Energy-efficient direct coupling of a PV array and electrolyser as examined in this thesis promises to improve the economic viability of solar-hydrogen systems for remote power supply since the costs of an electronic coupling system employing a maximum power point tracker (MPPT) and dc-to-dc converter (around US$ 700/ kW) are avoided.

Master of Engineering (Research) / The overall objective of this research was to realise the practical application of Hierarchical Asynchronous Parallel Evolutionary Algorithms for Multi-objective and Multidisciplinary Design Optimisation (MDO) of UAV Systems using high fidelity analysis tools. The research looked at the assumed aerodynamics and structures of two production UAV wings and attempted to optimise these wings in isolation to the rest of the vehicle. The project was sponsored by the Asian Office of the Air Force Office of Scientific Research under contract number AOARD-044078. The two vehicles wings which were optimised were based upon assumptions made on the Northrop Grumman Global Hawk (GH), a High Altitude Long Endurance (HALE) vehicle, and the General Atomics Altair (Altair), Medium Altitude Long Endurance (MALE) vehicle. The optimisations for both vehicles were performed at cruise altitude with MTOW minus 5% fuel and a 2.5g load case. The GH was assumed to use NASA LRN 1015 aerofoil at the root, crank and tip locations with five spars and ten ribs. The Altair was assumed to use the NACA4415 aerofoil at all three locations with two internal spars and ten ribs. Both models used a parabolic variation of spar, rib and wing skin thickness as a function of span, and in the case of the wing skin thickness, also chord. The work was carried out by integrating the current University of Sydney designed Evolutionary Optimiser (HAPMOEA) with Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) tools. The variable values computed by HAPMOEA were subjected to structural and aerodynamic analysis. The aerodynamic analysis computed the pressure loads using a Boeing developed Morino class panel method code named PANAIR. These aerodynamic results were coupled to a FEA code, MSC.Nastran® and the strain and displacement of the wings computed. The fitness of each wing was computed from the outputs of each program. In total, 48 design variables were defined to describe both the structural and aerodynamic properties of the wings subject to several constraints. These variables allowed for the alteration of the three aerofoil sections describing the root, crank and tip sections. They also described the internal structure of the wings allowing for variable flexibility within the wing box structure. These design variables were manipulated by the optimiser such that two fitness functions were minimised. The fitness functions were the overall mass of the simulated wing box structure and the inverse of the lift to drag ratio. Furthermore, six penalty functions were added to further penalise genetically inferior wings and force the optimiser to not pass on their genetic material. The results indicate that given the initial assumptions made on all the aerodynamic and structural properties of the HALE and MALE wings, a reduction in mass and drag is possible through the use of the HAPMOEA code. The code was terminated after 300 evaluations of each hierarchical level due to plateau effects. These evolutionary optimisation results could be further refined through a gradient based optimiser if required. Even though a reduced number of evaluations were performed, weight and drag reductions of between 10 and 20 percent were easy to achieve and indicate that the wings of both vehicles can be optimised.

The objective of this body of work was to produce a code system capable of processing boundary angular flux data from discrete ordinates calculations in 2D and 3D Cartesian and cylindrical geometries into cumulative probability density functions that can be used with a Monte Carlo radiation transport code to define neutron and photon initial positions, directions, and energies. In order to accomplish this goal, the DISCO (DetermInistic-Stochastic Coupling Operation) code was created to interface between the DORT and TORT deterministic radiation transport codes and the MCNP stochastic radiation transport code. DISCO introduces new methods to use the boundary angular flux data, along with information regarding the deterministic quadrature sets and spatial mesh structure, to create cumulative probability density functions that are passed to MCNP for sampling within the source.F90 subroutine that was also generated as part of this work. Operating in concert, DISCO and the MCNP source.F90 subroutine create a source term according to the discrete ordinates angular flux information. In order to validate the work described herein, 24 test cases were created to exercise the different geometries and execution modes available. The results of these test cases confirm that the methodology and corresponding implementation is appropriate and functioning correctly. Furthermore, this work incorporates several novel features such as compatibility with all 2D and 3D Cartesian and cylindrical geometries, an angular and spatial indexing scheme to reduce random sampling operations, a streamlining of process execution, and the ability for the resulting Monte Carlo code to operate in either serial and parallel mode.

The mechanism of carbon coupling reactions is traditionally represented in a very broad schematic. This thesis seeks to explore the mechanism of these reactions by focusing on Heck olefination. The Heck reaction has become a powerful tool in synthetic labs but the mechanism of this reaction has remained a topic of debate since the reaction's discovery. The catalytic cycle that has come to be accepted, while accurate in its own right, is not nearly as detailed as the complexity of the various stages of the Heck reaction suggest it should be. This study seeks to elucidate the nature of the oxidative addition of aryl halide to a palladium catalyst using a ligand that has been shown to have high activity in facilitating oxidative addition of aryl chlorides and bromides in other coupling reactions. This information is then compared to other studies in the field so that conclusions can be drawn about the oxidative addition. Also, selectivity studies seek to determine the nature of the migratory insertion of an olefin into the Pd-Ar bond. Again, comparison of results obtained in this study are compared to previous results so that a more definitive conclusion can be drawn about the oxidative addition.

We give a necessary and sufficient condition for the existence of an increasing coupling of N (N >= 2) synchronous dynamics on S-Zd (PCA). Increasing means the coupling preserves stochastic ordering. We first present our main construction theorem in the case where S is totally ordered; applications to attractive PCAs are given. When S is only partially ordered, we show on two examples that a coupling of more than two synchronous dynamics may not exist. We also prove an extension of our main result for a particular class of partially ordered spaces.

We analyze the notions of monotonicity and complete monotonicity for Markov Chains in continuous-time, taking values in a finite partially ordered set. Similarly to what happens in discrete-time, the two notions are not equivalent.<br> However, we show that there are partially ordered sets for which monotonicity and complete monotonicity coincide in continuous time but not in discrete-time. / Nous étudions les notions de monotonie et de monotonie complète pour les processus de Markov (ou chaînes de Markov à temps continu) prenant leurs valeurs dans un espace partiellement ordonné. Ces deux notions ne sont pas équivalentes, comme c'est le cas lorsque le temps est discret. Cependant, nous établissons que pour certains ensembles partiellement ordonnés, l'équivalence a lieu en temps continu bien que n'étant pas vraie en temps discret.

A faithful depiction of the tropical atmosphere requires three-dimensional sets of observations. Despite the increasing amount of observations presently available, these will hardly ever encompass the entire atmosphere and, in addition, observations have errors. Additional (background) information will always be required to complete the picture. Valuable added information comes from the physical laws governing the flow, usually mediated via a numerical weather prediction (NWP) model. These models are, however, never going to be error-free, why a reliable estimate of their errors poses a real challenge since the whole truth will never be within our grasp. The present thesis addresses the question of improving the analysis procedures for NWP in the tropics. Improvements are sought by addressing the following issues: - the efficiency of the internal model adjustment, - the potential of the reliable background-error information, as compared to observations, - the impact of a new, space-borne line-of-sight wind measurements, and - the usefulness of multivariate relationships for data assimilation in the tropics. Most NWP assimilation schemes are effectively univariate near the equator. In this thesis, a multivariate formulation of the variational data assimilation in the tropics has been developed. The proposed background-error model supports the mass-wind coupling based on convectively-coupled equatorial waves. The resulting assimilation model produces balanced analysis increments and hereby increases the efficiency of all types of observations. Idealized adjustment and multivariate analysis experiments highlight the importance of direct wind measurements in the tropics. In particular, the presented results confirm the superiority of wind observations compared to mass data, in spite of the exact multivariate relationships available from the background information. The internal model adjustment is also more efficient for wind observations than for mass data. In accordance with these findings, new satellite wind observations are expected to contribute towards the improvement of NWP and climate modeling in the tropics. Although incomplete, the new wind-field information has the potential to reduce uncertainties in the tropical dynamical fields, if used together with the existing satellite mass-field measurements. The results obtained by applying the new background-error representation to the tropical short-range forecast errors of a state-of-art NWP model suggest that achieving useful tropical multivariate relationships may be feasible within an operational NWP environment.