Graphite epoxy composites are being used in aerospace industry and spacecraft applications for their light weight and high strength. As a matter of fact these materials also have some disadvantages like damage which is hazardous when used in cryogenic application. Composite materials IM7/977-2, IM7/5555 and IM7/5276-1 are of interest for the aerospace industry and this research concentrates on study of microcracking, delamination and other defects in the [0/90]s composite laminates of the above materials. These materials were uni-axially tested to pre-determined stress levels and the damages in the material were recorded in the form of microcrack density at different stress levels. In this research work the use of X-Ray Microtomography has proven to be an excellent tool to characterize the crack connectivity and damage information three dimensionally. Dye penetrant technique was also used in this work to enhance the visibility of the cracks.

MSc., Faculty of Science, University of the Witwatersrand, 2011 / This dissertation presents the results of a crystallographic investigation into nineteen novel n-aminopyridinium perhalometallates of the general formula (C5H7N2 +)2MX4 2- where n = 2, 3 or 4, M = Zn, Cd or Hg and X = Cl, Br or I. The aim was to identify positional effects of the cation hydrogen bonding donor groups on the structures and to possibly identify robust synthons. Overall structural trends were also studied. The hybrid crystals were synthesized using temperature controlled crystallization methods and were characterized using X- ray diffraction techniques. Eighteen of the nineteen hybrid crystals displayed isolated tetrahedral perhalometallate anions. The results were classified into six different classes of isostructural compounds. Eight of the nineteen hybrid structures (42%) contained water. The 42% include two 3-ammoniopyridinium structures and all cadmium and mercury containing 4-aminopyridinium structures. The effect of a change in metal and/ or halide on the structure was investigated, and the overall structural trends in each n-aminopyridinium family were identified. Four different synthons were observed in the 2-aminopyridinium series while one synthon was observed throughout the 4-aminopyridinium series. A common synthon was observed in both the 3-aminopyridinium and 3-ammoniopyridinium series.

M.Sc., Faculty of Science, University of the Witwatersrand, 2011 / The objective of the study was to investigate the preparation of glass beads for base metal analysis of mining samples prior to x-ray fluorescence analysis. The research method used included the investigation of different fluxes, oxidising, non-wetting agents, fusion temperature and time. The experiments were carried out using different fusion instruments: Electrofluxer and Katanax followed by both EDXRF and WDXRF analysis. The x-ray spectrometers were calibrated with standards prepared from pure oxides and the results compared to values determined by alternative techniques. Different statistical methods were used to validate the experiments including factorial designs. Not all the elements and oxides were recovered successfully, however, perfect glass beads were prepared. The two areas of concern were addressed successfully: firstly the loss of copper was overcome by using an alternative heating mechanism of the Katanax and sodium iodide as the non-wetting agent. Secondly, the sulphur was successfully oxidised and retained in the glass beads.

Student Number : 0011001D - PhD thesis - School of Chemistry - Faculty of Science / The subject of this thesis is the development of a potentially simple, general and economical synthetic protocol for the potent antimalarial alkaloid febrifugine (1) and its analogues. In Chapter 1, the interesting history of 1, which includes a description of several reported total syntheses of 1, is discussed. Natural products derived from 1, as well as promising synthetic derivatives that display good antimalarial activity, are also discussed. The structure-activity relationships determined to date for 1 and its derivatives are presented in order to substantiate the need for the development of new synthetic strategies towards derivatives of 1 and its 3″-unsubstituted analogue, (±)- deoxyfebrifugine (14). A brief overview of the general strategies used in the Organic Chemistry Group at the University of the Witwatersrand for the synthesis of alkaloids is given in Chapter 2. The Eschenmoser sulfide contraction reaction between a thiolactam and an α- bromocarbonyl compound results in the formation of a vinylogous amide (or “enaminone”) product, which can be further manipulated to produce commonly encountered alkaloidal molecular skeletons. The chosen approach to 1 is based on reaction between the pivotal bromide 3-(3-bromo-2-oxopropyl)quinazolin-4(3H)-one (105) and suitable 3-substituted piperidine-2-thiones. A series of model studies, described in Chapter 3, was performed in order to test the feasibility of the synthetic strategy. These studies resulted in a new preparation of the key bromide 105 and a new and efficient synthesis of (±)-deoxyfebrifugine (14). Enaminone analogues derived from five-, seven-, eight-, nine- and thirteen-membered thiolactams were also prepared for comparison. An interesting difference in the sensitivity of the five- and six-membered model cyclic vinylogous amides towards reducing agents was observed. Whereas three piperidine analogues of 14 could be prepared in high yields by the chemoselective hydrogenation of six-membered cyclic vinylogous amide precursors, the five-membered analogues either reacted nonselectively under various standard hydrogenation conditions, or resisted reduction entirely. An extension of the approach towards the synthesis of a 3″-amino analogue of febrifugine (1) from L-ornithine is discussed in Chapter 4. Several 3-aminated piperidin-2-ones and thiones were prepared, but the subsequent enaminones were stable and characterizable only when the piperidinylidene ring nitrogen was alkylated. However, chemoselective reduction of the enaminone C=C bond in 3-{(E)-3-[(3S)-3- (tert-butoxycarbonylamino)-1-(4-methoxybenzyl)piperidin-2-ylidene]-2-oxopropyl}- quinazolin-4(3H)-one (221), an interesting 3-acylamino dehydro analogue of 1, did not give the desired azafebrifugine, but instead yielded a 5,6,7,8-tetrahydro-1Hpyrido[ 3,2-c][1,2]oxazine derivative. Several approaches to febrifugine (1) itself based on the successful model studies are discussed in Chapter 5. Initially, stereoselective α-bromination and subsequent substitution by oxygen of piperidin-2-ones derived from the chiral auxiliary (S)- phenylglycinol was explored. Unexpected racemization occurred at the α-position of the lactam during this route. A second approach to 3-hydroxypiperidin-2-one from Larginine was also problematic. Finally, the utility of α-hydroxylation methodology (including Davis methodology) on N-substituted piperidin-2-ones was explored. This route yielded a range of 3-oxygenated lactams and thiolactams, many of which displayed optical activity. The crystal structures of several 3-substituted thiolactams were determined and compared. However, attempts to apply the sulfide contraction procedure to these precursors were unsuccessful. Some investigations designed to explore the structural differences between vinylogous amides derived from the quinazoline-containing bromide 105 and thiolactams of different ring sizes are discussed in Chapter 6. Single crystal X-ray diffraction and NMR spectral data are compared for this series of compounds, the results revealing that the enaminone group in the five-membered ring derivative 3- [(3Z)-2-oxo-3-(pyrrolidin-2-ylidene)propyl]quinazolin-4(3H)-one 155 possesses a significantly different electronic distribution to the other analogues in the series.

Thesis advisor: Stephen Wilson / The magnetic interaction in materials generally can be categorized into two extremes: localized and itinerant. This work will focus on the electronic and magnetic properties of two prototypical magnetic compounds, which fall into the opposite extremes, i:e:, the spin-orbit coupled Mott insulator Sr₂IrO₄ (Sr214) described by the localized Heisenberg model and the itinerant helical (nearly-ferromagnetic) metal MnSi pictured with band or Stoner magnetism. The single layered cuprate analogue Sr₂IrO₄ has attracted considerable attentions in recent years, due to its unusual electronic and magnetic properties and the potential to access superconducting states. The exotic jeff = 1/2 ground state for the Ir⁴⁺ (5d⁵) ions results from the delicate balance of competing/cooperating energy scales, such as the stronger spin-orbit coupling (SOC) in 5d materials as compared to 3d transition metal oxides (TMOs), crystal electric field (CEF) splitting and electron-electron correlations. Superconducting states are theoretically predicted to be achievable if sufficient carriers are introduced into this spin-orbit assisted compound, which later triggers tremendous experimental works toward the realization of superconductivity. Here in this work a combined study of various probes, such as transport, magnetization, X-ray and neutron scattering measurements, focusing on the electronic and magnetic properties, is presented in the perturbed spin-orbit coupled Mott (SOM) state. Specifically in electron doped (Sr₁₋ₓLaₓ)₂IrO₄, a detailed mapping of magnetism with respect to electron doping is presented, demonstrating the gradual transition from long range magnetic order in parent state, to intermediate short range order, and eventually into the incommensurate (IC) spin density wave (SDW) state with increasing electron doping. Our picture supports the conjecture that the quenched Mott phases in electron-doped Sr₂IrO₄ and hole doped La₂CuO₄ share common competing electronic phases. On the other hand, the prototypical itinerant metal MnSi is examined by inelastic neutron scattering (INS). Our experimental data directly demonstrate the collapse of linear spin wave theory for localized Heisenberg magnets in the large energy limit, although the low energy dispersion is still described by the ferromagnetic spin wave theory. Most importantly, our observations display the chimney-like dispersion spectrum up to the energy scale of at least 240 meV, which is more than one order of magnitude larger than the Heisenberg interaction energy scale. For the first time, solid characterizations of Stoner excitations in itinerant helimagnet (nearly ferromagnetic) have been demonstrated up to an exceedingly large energy scale. Our intriguing results will greatly promote further understanding and exploration of Stoner excitations in itinerant magnets. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2016. / In this PhD thesis, the synthesis, crystal chemistry and thermoresponsive behaviour of non-porous borophosphates [ABPO5 (A= Ca, Sr, Ba) and BPO4] and porous borophosphates [NH4Fe(III)[BP2O8(OH)] and MIxMIIz(H2O)2[BP2O8].zH2O (MI = Na, NH4 and MII = Mn, Co)] phases were investigated. Understanding the crystal structure dynamics as a function of temperature of the selected porous and non-porous borophosphates revealed the thermal stability of the studied compounds, while serving as a predictive measure of the effects of temperature on other materials properties and subsequent applications. The non-porous borophosphates were synthesized using the solid state method, whereas the porous borophosphates were synthesized using the hydrothermal method. The powder X-ray diffraction (PXRD) technique, along with the application of the Rietveld refinement method, was the principle characterisation technique employed for the non-destructive and non-invasive thermoresponsive characterisation of the studied borophosphate phases. This thesis consists of seven chapters, four of which are independent papers corresponding to four chapters. Chapter 1 reviews the relevant scientific literature, while chapter 2 describes the methods of characterisation used in this thesis. Concerning the highly thermally stable non-porous borophosphates, chapter 3 presents the thermal expansion behaviour of ABPO5 compounds, which have been determined from the sequential application of the Rietveld refinement method of variable temperature powder X-ray diffraction (VT-PXRD) data. For trigonal ABPO5 compounds, a near linear expansion of the unit cell axes was found for all structures as a function of temperature. The variation of the crystal structure with temperature of ABPO5 compounds was also established. With the general understanding that borophosphates display intriguing crystal structure architectures, chapter 4 describes the synthesis and characterisation of four metal borophosphate hydrates: NaMII(H2O)2[BP2O8](H2O); MII = Co (I), Mn (II) and (NH4)0.5MII1.25(H2O)2[BP2O8](H2O)0.5; MII = Co (III), Mn (IV). The structures refined at room temperature from PXRD data revealed that isostructural phases I and II have an ordered arrangement of water molecules in the voids, whereas isostructural phases III and IV have fractional and disordered distribution of water molecules in the voids. Scanning electron microscope (SEM), fourier transform infrared spectroscopy (FT-IR), variable temperature powder X-ray diffraction (VT-PXRD) and thermogravimetric analysis (TGA) for all compounds are also presented. Chapter 5 was an investigation into the synthesis, crystal structure and thermal properties of the porous iron borophosphate NH4Fe(III)[BP2O8(OH)]. Variable temperature PXRD and thermogravimetric analysis were used to investigate the compounds thermal stability and expansion behaviour. Thermal investigations indicated that the compound is stable up to 470 °C. Of great importance to the accurate and/or precise measurement of the crystal structures and lattice parameters of the phases investigated using powder diffraction was the correct application of the Rietveld refinement method to the measured diffraction data. Therefore, chapter 6 is an investigation into a number of different Rietveld refinement approaches, which were aimed at modelling the changes in the atomic coordinates of BPO4 as a function of temperature. Parametric Rietveld refinements and rigid body Rietveld refinements were among the refinement strategies employed. / LG2017

Thesis advisor: Evan R. Kantrowitz / For nearly 60 years the ATP activation and the CTP inhibition of Escherichia coli aspartate transcarbamoylase (ATCase) has been the textbook example of allosteric regulation. We present kinetic data and 5 X-ray structures determined in the absence and presence of a Mg2+ concentration within the physiological range. In the presence of 2 mM divalent cations (Mg2+, Ca2+, Zn2+) CTP does not significantly inhibit the enzyme while the allosteric activation by ATP is enhanced. The data suggest that the actual allosteric inhibitor in vivo of ATCase is the combination of CTP, UTP and a M2+ cation and the actual allosteric activator is ATP and M2+ or ATP, GTP and M2+. The structural data reveals that two NTPs can bind to each allosteric site with a Mg2+ ion acting as a bridge between the triphosphates. Thus the regulation of ATCase is far more complex than previously believed and calls many previous studies into question. The X-ray structures reveal the catalytic chains undergo essentially no alternations, however, several regions of the regulatory chains undergo significant structural changes. Most significant is that the N-terminal regions of the regulatory chains exist in different conformations in the allosterically activated and inhibited forms of the enzyme. Here, a new model of allosteric regulation is proposed. / Thesis (MS) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

by Chan Wing-yee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 93-95). / ACKNOWLEDGEMENT --- p.i / ABSTRACT --- p.ii / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- General Introduction --- p.1 / Chapter 1.2 --- "Clinical Significance of Fe, Cu and Zn" --- p.2 / Chapter 1.3 --- Alternative Methods of Analysis --- p.5 / Chapter 1.4 --- Principles of Energy Dispersive X-ray Fluorescence Spectrometry --- p.11 / Chapter 1.5 --- Research Plan --- p.20 / Chapter CHAPTER 2 --- EXPERIMENTAL --- p.22 / Chapter 2.1 --- Energy Dispersive X-ray Fluorescence Analysis --- p.22 / Chapter 2.1.1 --- Apparatus --- p.22 / Chapter 2.1.2 --- Reagents --- p.25 / Chapter 2.1.3 --- Procedure --- p.28 / Chapter 2.2 --- Atomic Absorption Spectrometric Analysis --- p.32 / Chapter 2.2.1 --- Apparatus --- p.32 / Chapter 2.2.2 --- Reagents --- p.32 / Chapter 2.2.3 --- Procedure --- p.34 / Chapter CHAPTER 3 --- RESULTS AND DISCUSSION --- p.38 / Chapter 3.1 --- Optimisation of Excitation Conditions --- p.38 / Chapter 3.1.1 --- Effect of Filter --- p.38 / Chapter 3.1.2 --- Effect of Tube Voltage --- p.43 / Chapter 3.1.3 --- Effect of Tube Current --- p.44 / Chapter 3.2 --- Optimisation of Preconcentration Procedure --- p.46 / Chapter 3.2.1 --- Effect of Sample Area and Collimator Size --- p.46 / Chapter 3.2.2 --- Effect of pH --- p.51 / Chapter 3.2.3 --- Effect of Ligand Concentration --- p.54 / Chapter 3.2.4 --- Effect of Mixing Time --- p.57 / Chapter 3.2.5 --- Effect of Standing Time --- p.59 / Chapter 3.2.6 --- Study of Sample Homogeneity --- p.61 / Chapter 3.3 --- Optimisation for Deproteination --- p.63 / Chapter 3.3.1 --- Effect of Different Protein Precipitants --- p.63 / Chapter 3.3.2 --- Effect of Trichloroacetic Acid Concentration --- p.65 / Chapter 3.3.3 --- Effect of Hydrochloric Acid Concentration --- p.67 / Chapter 3.3.4 --- Effect of Temperature --- p.69 / Chapter 3.3.5 --- Effect of Incubation Time --- p.71 / Chapter 3.4 --- Study of Blanks --- p.74 / Chapter 3.5 --- Construction of Calibration Curves --- p.77 / Chapter 3.6 --- Determination of Detection Limit and Sensitivity --- p.84 / Chapter 3.7 --- Accuracy and Reproducibility Tests --- p.86 / Chapter 3.8 --- Parallel Check --- p.89 / Chapter CHAPTER 4 --- CONCLUSION --- p.92 / REFERENCES --- p.93

by Ho Sing Yiu. / Thesis (M. Phil.)--Chinese University of Hong Kong, 1991. / Includes bibliographical references. / ACKNOWLEDGEMENT --- p.i / ABSTRACT --- p.ii / Chapter CHAPTER 1 --- GENERAL INTRODUCTION --- p.1 / Chapter PART I --- DERIVATIVE SPECT3ROPHOTOMETRIC METHOD FOR THE SIMULTANEOUS DETERMINATION OF COPPER AND NICKEL IN ALLOYS / Chapter CHAPTER 2 --- INTRODUCTION --- p.5 / Chapter CHAPTER 3 --- EXPERIMENTAL --- p.14 / Chapter CHAPTER 4 --- RESULTS AND DISCUSSION --- p.18 / Chapter PART II --- X-RAY FLUORESCENCE SPECTROMETRIC METHOD FOR THE SIMULTANEOUS DETERMINATION OF SEVEN METALS IN WATER SAMPLES / Chapter CHAPTER 5 --- INTRODUCTION --- p.43 / Chapter CHAPTER 6 --- EXPERIMENTAL --- p.58 / Chapter CHAPTER 7 --- RESULTS AND DISCUSSION --- p.65 / Chapter CHAPTER 8 --- CONCLUSION --- p.99 / REFERENCES --- p.101

by Ho, Chi-Kin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 62-64). / Chapter 1 --- Introduction / Chapter 2 --- Previous Work --- p.2-1 / Chapter 2.1 --- Thresholding --- p.2-1 / Chapter 2.2 --- Edge Detection --- p.2-2 / Chapter 2.3 --- Region Growing --- p.2-2 / Chapter 2.4 --- Radial Contour Model --- p.2-3 / Chapter 2.5 --- Regularized Region Contrast --- p.2-3 / Chapter 2.6 --- Deformable Model --- p.2-4 / Chapter 3 --- The ODD-Balloons Model --- p.3-1 / Chapter 3.1 --- Design Rationale --- p.3-1 / Chapter 3.2 --- Overview --- p.3-5 / Chapter 3.3 --- 2-D Deformations --- p.3-8 / Chapter 3.4 --- Orthogonal Cut and Volume Transfer --- p.3-11 / Chapter 3.5 --- Smoothing Operation --- p.3-17 / Chapter 3.6 --- Properties --- p.3-20 / Chapter 3.6.1 --- Conformation to 3-D Shape --- p.3-20 / Chapter 3.6.2 --- Noise Sensitivity --- p.3-20 / Chapter 3.6.3 --- Convergence and Efficiency --- p.3-22 / Chapter 3.6.4 --- Easy-to-Use --- p.3-23 / Chapter 3.7 --- Summary --- p.3-24 / Chapter 4 --- Experiment Results --- p.4-1 / Chapter 4.1 --- Synthetic Data Experiments --- p.4-1 / Chapter 4.2 --- Real Data Experiment --- p.4-3 / Chapter 4.3 --- Discussions --- p.4-6 / Chapter 5 --- Conclusion and Future Work --- p.5-1 / Chapter 5.1 --- Conclusion --- p.5-1 / Chapter 5.2 --- Recommended Future Work --- p.5-2 / Appendix A Discrete Implementation of 2-D Deformation --- p.A-1 / Appendix B Choosing Elasticity and Rigidity Coefficients of 2-D Deformation --- p.B-1 / Bibliography --- p.BIB-1