This work presents findings from experiments carried out using the neutron Laue method in tandem with laboratory source X-ray diffraction to characterise a series of organic molecular complexes which exhibit interesting, and potentially “tunable”, temperature dependent charge transfer effects, such as proton migration and proton disorder within hydrogen bonded networks. These subtle processes are studied by variable temperature neutron diffraction studies, allowing the positional and anisotropic displacement parameters of the hydrogen atoms to be refined accurately and their evolution with temperature followed. The hydrogen atom behaviour is found to be influenced by the local environment, including weak intermolecular interactions in the vicinity of the hydrogen bond under study. Complexes of urea and methyl substituted ureas with small organic acids are presented, which show robust and reproducible structural motifs. In favourable circumstances, these contain short, strong hydrogen bonds (SSHBs) within which the proton may undergo temperature dependent migration. By synthesising a number of complexes containing SSHBs, potential routes to the design of proton migration complexes are found, which utilise crystal engineering principles and pKa matching. Variable temperature studies conducted on these complexes also show unusual thermal expansion properties and phase transitions in urea-acid complexes which do not display proton migration. Systems containing hydrogen bonded dimers of 3,5-dinitrobenzoic acid are also studied, and shown to contain temperature proton disorder within moderate strength hydrogen bonds linking the dimers. The presence and potential onset temperature of any disorder is found to be influenced by interactions around the acid dimers and potential routes to controlling proton disorder are discussed. Complexes of the proton sponge, 1,8-bis(dimethylamino)napthalene (DMAN), with organic acids are also presented, in which the structures have been determined using neutron diffraction. DMAN readily accepts a proton from the acid co-molecules used in forming the complexes, forming a strong intramolecular SSHB within the protonated DMAN. Strong intermolecular hydrogen bonds are also induced between the acid molecules in many cases. The neutron studies presented here investigate the effect of weak interactions on the behaviour of hydrogen atoms located within these SSHBs, and also indicate over what distance such interactions significantly affect the hydrogen atom behaviour.

The aluminum industry is in need of high-speed in-situ elemental identification technology for molten metals. wTe Corporation of Bedford, MA was granted funds to research this technology for aluminum through the Advanced Technology Program (ATP) of the National Institute of Standards and Technology (NIST). As a secondary metal scrap processor, wTe Corporation is interested in increasing the value of scrap and better identification technology is one way of doing this. With better identification technology, foundries and smelters will be more confident in the melt chemistry and more apt to use secondary aluminum which decreases the energy required for processing by approximately 85%. wTe Corporation is exploring two avenues for in-situ molten metal identification: Laser Induced Breakdown Spectroscopy (LIBS) and X-Ray Fluorescence (XRF). The objectives of this work were to contribute to developing XRF technology for in-situ identification of molten metal by establishing a method of data instrumentation and analysis for XRF to determine aluminum melt composition, investigate the major alloying elements in the Al380 alloy series and determine the relationship between intensity and concentration, and to determine the effect of temperature on XRF Spectra. The XRF instrumentation development and the technical challenges associated with high temperature measurements are presented. The relationship between intensity and concentration is presented for three alloys within the 380 alloy series, and lastly it is observed that there are significant differences between liquid and solid spectra and that a calibration curve for liquid data is necessary. Several hypotheses are given as to why this difference between liquid and solid state spectra may occur.

Perovskite photovoltaics is one of the fastest growing opto-electronic technologies with device efficiencies currently exceeding 23%. The opportunity to deposit these abundant materials with large area solution processing techniques could make perovskites viable for low-cost production. However, since perovskite materials are prone to degradation, their lifetime needs to be improved to that of silicon solar cells before these devices can be commercialized. Moreover, unlike most semiconductors, trap densities in polycrystalline perovskite films in high-performing devices have been determined to be relatively large, suggesting a remarkable defect tolerance in perovskite films that needs to be understood in the context of the nature of the trap states and any residual non- radiative losses. These non-radiative losses are observed as photoluminescence heterogeneity within perovskite films, even for high-performing perovskite systems. In this work, we explore the degradation kinetics of perovskite devices under stress conditions and find that further stability improvements should focus on the mitigation of trap generation during ageing. Furthermore, we fabricate perovskite solar cells with a novel back-contact structure, in which electron- and hole-selective electrodes are co-positioned on the back side of the cell and spaced by 100 μm. By utilising grazing-incidence X-ray diffraction, we show that even in the earliest stages of conversion of precursors to perovskite we achieve remarkably high open-circuit voltages, suggesting that the defect tolerance of perovskites appears at an early stage in the conversion process. Moreover, we employ scanning X-ray diffraction with nanofocused beam and obtain detailed information, revealing overlapping grains located at different depths within perovskite films. We find that the critical grain size is the longer-range structural super-grains rather than the grains viewed with conventional microscopy techniques. These findings further highlight the presence of structural defects in perovskite materials and provide important insights towards improving the optoelectronic behaviour of these materials.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Bibliography: leaves 29-30. / by Rupert LaWendell Seals. / M.S.

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Rett syndrome (RTT) is an X-linked neurological disorder primarily caused by mutations in the MECP2 gene. The majority of RTT mutations disrupt the interaction of MeCP2 with DNA or TBL1X/TBL1XR1, which forms the scaffold of NCoR/SMRT co-repressor complex. Patients with RTT show no signs of neuronal death, although they have abnormal neuronal morphology, indicating that it is a neurodevelopmental rather than a neurodegenerative disease. It has been shown that reactivation of silenced MeCP2 in mice rescues the RTT phenotype, which implies that the disease is treatable. The RTT mutations in MeCP2 cluster to two regions - the methyl-CpG-binding domain (MBD) and NCoR/SMRT Interaction Domain (NID). While the interaction between MBD and DNA has been biochemically and structurally characterised, there are no structural data about the interaction between MeCP2 NID and TBL1XR1. The aim of this work was to understand how mutations in the NID cause RTT by characterising the interaction between MeCP2 and TBL1XR1. I have solved the structure of MeCP2 NID bound to TBL1XR1 WD40 domain. I show that a small region of the MeCP2 NID makes extensive contacts with TBL1XR1, and that these contacts are mediated primarily by MeCP2 residues known to be mutated in RTT. I also measured the affinities between TBL1XR1 and MeCP2-derived peptides using fluorescence anisotropy and surface plasmon resonance assays. I determined the affinity between MeCP2 NID peptide and TBL1XR1 to be around 10- 20 μM, and show that mutations in either MeCP2 or TBL1XR1 can abolish this interaction. Taken together, these data strongly suggest that the abolition of the interaction between MeCP2 NID and TBL1XR1 WD40 domain is sufficient to cause RTT. This knowledge can help with the rational design of small drug-like molecules that might be able to mediate the interaction between mutated MeCP2 and TBL1XR1, potentially helping to treat the disease.

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Medicine in Diagnostic Radiology Johannesburg, 2014 / INTRODUCTION South Africa presents a complex scenario with regard to patients consenting for medical procedures, because of the differing profiles of the population and the health care workers who perform the consenting procedures. AIM To evaluate consenting practice for CT scanning, within the South African tertiary referral setting and to determine if there are any associations between patient demographic profile and the level of understanding with the adequacy of consent. METHOD A prospective survey regarding consenting practices for CT scanning was performed in a form of an interview questionnaire in patients presenting to Chris Hani Baragwanath Academic and Charlotte Maxeke Johannesburg Academic hospitals. Determination of any associations between patient age, racial group, language and education was made with the level of understanding and adequacy of consent. RESULTS The survey was conducted on 117 patients; 86 from Charlotte Maxeke Johannesburg Academic Hospital and 31 from Chris Hani Baragwanath Academic Hospital. We found no significant association between gender and age category (p=0.11), racial group (p=0.17), education (p=0.26), home language (p=0.21) or residential area type (p=0.70). vi There was a significant, weak, association between age category and education (p=0.043; Cramer’s V=0.29). There was a significant, moderate association between the understanding of the language of consent and the home language of the patients (p=0.0013; phi coefficient=0.43). There was also some association between education and age. Just over 50% of patients felt that they had been given enough information and had had an opportunity to ask questions and only 33% had been offered an alternative to the CT scan. There was a significant difference in the mean adequacy of consent score with regards to racial group (p<0.0001), home language (p=0.0073), residential area type (p<0.0001) and level of education (p<0.0001). CONCLUSION Language differences between patients and personnel performing the consent procedure proved to be a major barrier in offering adequate consenting for CT Scans.

Thesis(M. Med (Anaesthesiology)--University of Limpopo(Medunsa Campus), 2010. / The purpose of this study was to interrogate the clinical relevance and cost effectiveness of the routine preoperative chest X-rays at DGMH. It was conducted as a descriptive cross-sectional prospective study of radiographic films in the Radiology department. A review of patients’ files and chest X-rays performed during a 6-month period from January to June 2008. Data from 100 patients’ files were included in the analysis. The age of patients ranged from 45 to 84years, the median age was 57years. The majority of patients younger than 50years were female, while the majority of male patients were over 50years. From a total of 100 patients only 8%(8 patients) were deemed unfit and consequently postponed or cancelled for further investigation and optimization. The cost for performing one routine chest X-ray was estimated to be R393 manpower, time and film inclusive, the total costs for the 100 patients included in this study being R39300. This study has provided some evidence that the routine preoperative chest X-rays can help in uncovering some abnormalities that were not apparent on clinical examination, it has pointed out that the impact of these uncovered abnormalities is very minimal on the planned surgery and that the costs associated with doing routine pre-operative chest X-rays can be substantial.

The beginning of X-ray astronomy is based on two accidental discoveries made in 1962. A single point source, Scorpio X-1 and remarkable discovery of the diffuse background radiation, three years before the microwave background was discovered. Over the past four decades, X-ray astronomy has matured into a major branch of astronomy, contributing to our understanding of the physical processes operating in many different types of sources, from stars to high redshift quasars. In 1990, the launch of the ROSAT satellite offered to unique opportunity to investigate the radio properties of X-ray emitters. A sample of faint X-ray emitters from a deep pointed observation is used in this thesis to investigate the prediction that sub-mJy radio source are a major contributor to the X-ray background. Another sample of 695 bright X-ray emitters were selected from ROSAT All Sky Survey for optical follow-up as a European Southern Observatory key project. The radio follow-up of the sample was undertaken for this thesis. The aim is to construct a catalogue of radio emitting X-ray (REX) sources to study their quantitative statistical properties and to select out a sample of BL-Lac objects for further study. Based on previous surveys approximately 19% or 130 of the X-ray sources should be directly associated with a radio emitter, of which 90% will be positionally coincident with the most plausible optical candidate for an X-ray source. This increases the efficiency of the optical identification program by about 15 percent. / Doctor of Philosophy (PhD)

Thesis (Ph.D.)--Montana State University--Bozeman, 2006. / Typescript. Chairperson, Graduate Committee: C. Martin Lawrence. Includes bibliographical references (leaves 146-159).