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Inorganic and metal-organic framework materials possessing accessible and permanent pores are receiving tremendous attention. Among them, zeolites are the most famous class due to their wide applications on petrochemistry and gas separation. Besides zeolites, the other oxide framework materials are also intensively investigated because of their diverse structures and compositions. Metal-organic frameworks are built from metal clusters and organic linkers. By rational designing the reagent, the network with desired topology and functionality can be synthesized. For all of the framework materials mentioned above, to explore novel framework structures is important for improving properties and discovering new applications. This thesis includes the synthesis of zeolites and structure characterization for various types of inorganic framework materials. The zeolite synthesis conditions was exploited. With the optimized condition, the zeolite ITQ-33 was synthesized as single crystals. From the single crystal X-ray diffraction data, the disorder in the structure is discovered and explained. Following the topic of disorder and twinning, we proposed a novel method of solving structure of pseudo-merohedric twinning crystal by using an example of a metal-organic complex crystal. Then we also showed methods for solving structures of high complexity and nano-crystal by using mainly powder X-ray diffraction and transmission electron microscopy. Four examples were shown in chapter 4 including open-framework germanates and metal-organic frameworks. / <p>At the time of the doctoral defence the following paper was unpublished and a status as follows: Paper  4: Manuscript</p>

A series of investigations were conducted in order to evaluate the effect of MOS supplementation in finfish aquaculture. Fish with great potential in aquaculture industry were tested with regards to effect of dietary MOS supplementation on intestinal histology and microbiology as well as overall animal health and production. Two levels of MOS supplementation were applied 0.2% and 0.4%. Experimental fish were Atlantic salmon (Salmon salar), rainbow trout (Oncorhynchys mykiss), sole (Solea senegalensis) and gilthead sea bream (Sparus aurata). The results from the sea bream studies revealed that MOS supplementation may have a beneficial effect on growth performance of fish greater than 100 g. Additionally, there is a systemic improvement of the intestinal histology for all species investigated, especially when using 0.4% of MOS supplementation level. Both light and electron microscopy revealed increased intestinal surface and improved intestinal integrity of MOS fed fish. MOS alters the intestinal microbiota, in the case of gilthead sea bream modulation was evident even when fish were fed 0.2% dietary MOS for as little as 2 weeks. Blood immune parameters were also affected by the MOS inclusion and total leukocytes counts were increased and leukocytes relative abundance was also changed. MOS induced intestinal microbial modulation was more evident in fish are reared in outdoor conditions. Feed utilization and digestibility were improved with the addition of 0.4% MOS supplementation in the Atlantic salmon. The sole experiment revealed that MOS could reduce fish mortalities induced by pasteurelliosis. These investigations, suggest a potential role for application of MOS in aquaculture. Future research should be conducted in order to evaluate other parameters that MOS may influence and ascertain optimum dosage for each fish species and developmental stage.

Transport imaging is a SEM-based technique used to directly image the motion and recombination of charge in luminescent semiconductors, allowing for the extraction of transport parameters critical to device operation. In this thesis, transport imaging for 1D structures was initiated with work on sample preparation, modeling and initial characterization. One dimensional structures are being integrated into forefront electronics due to their inherent advantages in size, packing density and power consumption. In this work the one dimensional equation for steady state minority carrier recombination distribution solved for the Gaussian source is derived and results from numerical simulations are presented. The diameter of the SEM beam is determined experimentally allowing for accurate simulation parameters. Intensity and drift measurements on four batches of top-down wire structure samples, fabricated on a AlGaAs/GaAs/AlGaAs double heterostructure using a FIB, are presented. Significant decreases in luminescence in FIB exposed regions are reported. Spatial luminescence from single bottom-up GaN and ZnO nanowires deposited by metal initiated metal-organic CVD on Au and SiO2 substrates is imaged. CL spectra for GaN and ZnO, with peak intensities at 3.27 and 3.29 eV, are characterized. Finally, several suggestions for further research are offered including transport imaging on contacted bottom-up nanowires and a potential application of transport imaging to FIB damage characterization.

Astrocytes are the most abundant non-neuronal cells in vertebrate brains. Although Drosophila melanogaster has fewer astrocytic cells relative to neuronal and other glial cell populations, they, like vertebrate astrocytes, are located in synaptic regions, organized into exclusive, minimally-overlapping domains, and play developmental roles in synaptogenesis. But, do Drosophila astrocytes have parallel roles in the regulation of synaptic signaling? Preliminary electron microscopic (EM) data indicates that astrocytic processes are located at a greater distance, on average, from Drosophila synapses than they are from vertebrate synapses, thus raising questions about their capacity to alter synaptic signals. Do astrocytic cells and processes occupy stereotyped synaptic regions across repeating segmental structures and across individuals? In the studies presented here, we have addressed these questions directly in the ventral nerve cord (VNC) of the third-instar larva. We collected the first whole-cell patch-clamp recordings from Drosophila astrocytes. These indicate that intrinsic membrane properties, such as low membrane resistance, high capacitance, a hyperpolarized resting potential relative to neurons, a passive current-voltage relationship, coupling to other astrocytic cells, and an absence of voltage-gated currents, are shared between astrocytes of highly divergent species. Next, we optogenetically activated of a group of glutamatergic pre-motor neurons and showed that astrocytes respond with a glutamate transporter current that is mediated by Eaat1, and that acute, pharmacological and chronic, genetic blockades of this transporter have subsequent effects on the decay of post-synaptic motor neuron currents. Then, we used three-dimensional EM to locate the pre-motor glutamatergic neurons that were activated in the physiological study and measured the distance from each presynaptic site to the nearest astrocytic process. We found that these distances vary 100-fold even along a single neurite and that these structures are rarely in direct contact, but that no synapse is positioned greater than one micron from an astrocytic process. Thus, it is in this anatomical configuration that the regulation of post-synaptic currents by Eaat1 occurs. Finally, we generated a library of single, fluorescently-labeled astrocytes that were co-labeled with fiduciary landmarks, and used this library to compare the placement of astrocyte cell bodies and arbors across VNC segments and individuals. We found substantial variation in the gross shape, size, and territory covered by astrocytes, and conclude that their neuropil domains are not reliably stereotyped. Given the consistent placement of neuronal connectome elements, this indicates that signals of a specific synapse are not regulated by a designated astrocyte. Together, these findings reveal new functional parallels between Drosophila and vertebrate astrocytes. These findings argue for the relevance and applicability of mechanistic discovery in Drosophila astrocytes, and set the stage for further inquiry into the genetic determinants of astrocyte morphology and physiology.

The focus of this thesis was to gather and analyze micromorphological and petrographic data on soils at the archaeological site of Dmanisi in order to better understand the extent to which the deposition and alteration of the sediments has affected the preservation of artifacts and faunal remains. A major goal of this research was to test hypothesis related to why bone material is discovered in some strata and not in others. This research focuses on the application of micromorphology (supplemented with other methods) to the soils through the use of petrographic analysis of thin sections and scanning electron microscopy. These techniques complement previous field analyses by providing a quantitative assessment of individual strata through point counting and chemical mapping. The results of this research support the hypothesis that the sediments are predominantly mafic ashes, while showing that there is very little soil development in the strata. This suggests quick episodic burial in a relatively dry climate, confirming the hypothesis for a short time sequence in the strata. Additionally, differential weathering probably did not play a significant role in the differential abundance of bone remains among the strata at Dmanisi.

Magnetic resonance imaging (MRI) methods thought to assess myelin and axon integrity are improving the understanding of white matter diseases like multiple sclerosis (MS). This thesis improved the understanding of how microstructural tissue changes caused by various pathologies influence MRI metrics by developing and applying MRI methods in a longitudinal study using the cuprizone mouse model of MS. In vivo and ex vivo MRI measurments (T1 and T2 relaxometry, diffusion tensor imaging, and quantitative magnetization transfer imaging) were correlated with tissue measurements taken from electron microscopy images of control and cuprizone fed mice at weeks 2 and 3 of cuprizone feeding. Significant Spearman correlations included mean diffusivity vs. myelinated axon fraction (ρ=0.84), ex vivo T2 vs. myelinated axon fraction (ρ=0.68), and normalized T2-weighted signal vs. myelinated axon fraction (ρ =-0.80). Multiparametric MRI studies show promise in bridging the gap between damage detected in images and clinical status associated with MS. / May 2016

A dissertation submitted to the University of the Witwatersrand in fulfilment of the requirements for the degree of Master of Science in Engineering (Metallurgy & Materials) 2016 / The surfaces of AISI 316L stainless steel plate were laser alloyed with ruthenium powder as well as a mixture of ruthenium and nickel powders using a Nd:YAG laser set at fixed operating parameters. The microstructure, elemental composition, and corrosion characteristics of the alloyed zone were analysed using optical and scanning electron microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and corrosion potential measurements. EDS analysis of the alloyed specimen showed that through the laser surface alloying, 2 mm surface layers with 12.5wt % Ru and 5.2wt% Ru were produced on an AISI 316L stainless steel. Similar microstructures which were dendritic and columnar grains, typical of weld beads under non-equilibrium cooling conditions were observed for all samples. Hardness profile measurements showed a significant increase from 160 HV for the substrate to a maximum of 247 HV for the alloyed layer. Using an Autolab potentiostat, the corrosion behaviour and resistance of the laser alloyed layers, substrate AISI 316L, and Hastelloy© C-276 were evaluated and compared in sulphuric acid solution of different concentration and temperatures. The Hastelloy© C-276, followed by the 12.5wt% Ru presented the most noble corrosion potential (Ecorr) and the lowest corrosion current density (icorr). However, in 60wt% H2SO4 and 40oC, the 5.22 wt% Ru alloys exhibited slightly better anticorrosive properties than 12.5wt% Ru. The observed corrosion potential, Ecorr, for untreated AISI 316L stainless steel sample in 40wt% sulphuric acid solution at 40oC was -277 mV. The 5.22 wt% Ru and 12.5wt% Ru alloyed stainless steel samples presented -240 mV, and 61 mV respectively in the same solution. Besides showing comparable performance to 5.2wt%Ru sample within specific short potential ranges, Hastelloy© C-276 was generally superior in all solutions. In addition it was found that the stability of the passive layer was improved with additions of Ru. Based on the developed costing equation the cost of 5 mm AISI 316L stainless steel plate with surface area (A = 1 m2) surface alloyed with 5.2wt% Ru to a depth of 2 mm using Nd: YAG laser is estimated at R15 989, and it is less than the cost of a Hastelloy© C-276 plate of similar size which is estimated at R19 900. As the material thickness increases, the cost benefit of laser surface treatment increases and vice versa. Reduction of the Ru additions to levels below 5.2wt% would improve cost competition without detracting from performance. / MT2017