Tuberculosis, caused by the intracellular pathogen Mycobacterium tuberculosis, is one of the most prevalent infectious diseases in our world today. In order to survive within the host the bacteria need to sense and respond to changes in the environment; however, signal transduction in this bacterium is poorly understood. PknB is a serine/threonine kinase essential for the in vitro survival of M. tuberculosis and therefore a potential drug target against the bacteria. It is the goal of the current study to elucidate downstream substrates of PknB. We have found that PknB shares in vitro substrates with another serine/threonine kinase, PknH, implying the potential complexity of the signaling pathways in the bacteria. We have also provided the first description of the coupling between serine/threonine kinases PknB and PknH with a two-component system response regulator DevR, and further proposed Ser/Thr phosphorylation as the negative regulator of DevR transcription activator activity based on LC-MS/MS analysis. Finally, we have identified a previously unknown phosphoprotein glyceraldehyde 3-phosphate dehydrogenase encoded by the ORF Rv1436, which demonstrates autophosphorylation activity and which phosphorylation is independent of PknB. Overall, the current study has contributed to advance our understanding of the signal transduction pathways and phosphoproteome in Mycobacterium tuberculosis. / Medicine, Faculty of / Medicine, Department of / Experimental Medicine, Division of / Graduate

This thesis describes the development of high performing low-cost and low-power ammonia sensors on plastic substrates using solution processing techniques. As a part of the Marie Curie Initial Training Networks, FlexSmell project aimed at the realisation of such sensors as elements of a sensing system on flexible tags for wireless compatible applications. Ammonia was selected as the target analyte due to its importance in many application fields including food industry, air and water quality monitoring. Polyaniline, a conjugated polymer, was used as the sensing layer for chemiresistive detection of ammonia because of its well-known gas sensing properties. Two distinctive strategies were adapted to tackle doped polyaniline’s lack of solution processablity. Firstly, dopant engineering was utilised to prepare doped polyaniline formulations in aprotic solvents such as n-methyl-2-pyrrolidone. Hybrid composites were then prepared by simply mixing the polyaniline solutions and carbon nanoparticles. Sensors made by spin coating the polyaniline hybrid composites on plastic substrates operating at ~80 °C showed sensitivities more than 6 times higher than that of a commercial metal oxide sensor when exposed to sub-ppm concentrations of ammonia in air. The incompatibility of the multifunctional dopants used in this method with printed electronics, as well as the high boiling point and toxicity of the solvent led to the second approach. A two-step vapour-phase deposition polymerisation method was exploited to in-situ polymerise different polymeric acid-doped polyaniline thin films on plastic substrates. Polyaniline sensors doped with poly(4-styrenesulphonic acid), demonstrated sensitive response to sub-ppm concentrations of ammonia vapour under both dry and humid conditions. These sensors showed enhanced recovery and repeatability when operated at elevated temperatures. Moreover, room temperature ammonia sensors were realised using Nafion as the dopant. Finally, ammonia sensors were made on small (~1 mm^2) printed polymeric micro-hotplates using a vapour-phase deposited polyaniline sensing layer in order to allow reliable operation at ~95 °C with power consumptions as low as 35 mW. Such low-cost, low-power, sensitive and selective ammonia chemiresistors may be incorporated in smart RFID tags for food, air and water quality monitoring.

Oleaginous yeasts posses the ability to accumulate increased amount of lipids under appropriate conditions. These microbial lipids vary in the composition of fatty acids which results in their wide application in the biotechnological industry. This master thesis focuses on the lipid production and fatty acids composition from waste substrates by the yeasts Metschnikowia depending on various cultivation conditions. The influence of temperature, the ratio of carbon and nitrogen in medium, and the concentration of different carbon sources was studied. The cheap and easy available waste substrates as glycerol and animal fat were used for the cultivation. The production characteristics of the yeasts were monitored by various technique including gas chromatography, Raman spectroscopy and fluorescence microscopy FLIM. Moreover, the partial optimalization of the pulse field gel electrophoresis was applied in order to characterize the karyotype of the yeasts Metschnikowia. All the studied strains were able to use the waste substrates and at the same time to produce lipids. The amount of lipids and mainly their compositions vary depending on the yeast strain and on the culture conditions. Nevertheless, the ability of the yeasts to produce significant amount of unsaturated fatty acids by manipulation of culture conditions was proved. The maximum lipid yield was achieved by M. pulcherrima 149 on glycerol medium and by M. andauensis 129 on medium containing waste animal fat.

No description available.

Hexagonal molybdenum nitride (δ-MoN) is one of the hardest superconductors, and its superconducting properties depend on the crystalline structure and the substrate of use. Herein, a versatile growth method has been utilized to grow single-crystalline (SC) δ-MoN thin films on any arbitrary substrate of interest. SC δ-MoN films have been achieved on amorphous substrates via the transfer of MoS2 precursors followed by chemical phase conversion. The transferred SC δ-MoN film on an amorphous SiO2/Si substrate exhibits superconductivity at Tc = 4.75 with an upper critical field Hc2(0) = 8.24 K. The effect of the transfer process was assessed by directly growing SC δ-MoN on an Al2O3 substrate, which showed enhanced superconductivity properties due to the nonuniformity in film thickness that the transfer process induces. The crystalline structure effect on superconductivity was studied by directly growing amorphous δ-MoN film on an amorphous SiO2/Si substrate. The amorphous film showed degraded superconducting behavior and confirmed that disorders in the crystal structure suppress superconductivity. The upper critical fields of the non-transferred δ-MoN films exceeded their Pauli paramagnetic limits, which could give rise to the existence of the Ising pairing effect, but further studies are needed to confirm this behavior.

The excessive accumulation of salt in the root zone of plants is a problem which is widespread in area, increasing in magnitude, and limiting in its effect upon productivity. Accumulation of salt in the rhizosphere has an effect upon moisture availability for plant use, the nutritional balance of the essential elements, and causes a reduction in plant growth with toxicity often resulting. When plants grow on substrates high in salt, the salt content of the plant also increases. This uptake of salt often results in changes in the morphology of the plant. Accumulation of salt within the plant cells interferes with the protoplasmic activity.

Gas source molecular beam epitaxy (GSMBE) has been used to grow InGaAs/lnP epitaxial layers in selected areas defined by SiO2-masked InP substrates, with the goal of obtaining controlled in-plane variations in the bandgap of the InGaAs wells. The ability to alter the bandgap of the semiconductor spatially over the surface in one growth procedure is desirable for integrating laser, waveguide and detector devices. To form the masked substrates, stripes (ranging in width from 2 pm to 50 pm) were opened up in SiO2 by standard photolithography. The crystal growths were carried out at various substrate temperatures (ranging from 460 °C to 510 °C) and arsenic fluxes (V/lll ratios ranging from 1.2 to 3.4). The properties of the epitaxial layers were investigated by using such analytical techniques as photoluminescence, electroluminescence and transmission electron microscopy (TEM). Photoluminescence measurements performed on waveguide stripes of decreasing width reveal an increasing red-shift of the e1-hh1 transition in InGaAs wells. The maximum red-shift occurred when growing at a high substrate temperature and a low arsenic flux. For example, a decrease in slit width from 50 pm to 10 pm resulted in a 25 meV shift of the photoluminescence peak. From cross-sectional TEM measurements, the wavelength shift observed can be attributed primarily to an increase in thickness of the InGaAs well, due to incorporation of additional indium and gallium migrating from the material on the masked regions. The interfaces in the centre of the stripe region are defect free; however, stacking faults and thickness variations are evident 1-2 pm from the edges. These results are confirmed by scanning photoluminescence, in which the maximum intensity occurs at the centre of the stripe and decreases to zero at the edges. Mapping of the peak wavelength across the stripe reveals a diffusion profile, with the edges being additionally red shifted by 10 nm. Reactive ion etching of the edge and the polycrystalline material results in a much improved spectral photoluminescence scan, in both increased intensity of the bandgap peak and elimination of lower energy peaks assumed to be correlated with edge effects. Finally, a stripe contact light emitting device, with a single 50 A quantum well InGaAs/lnP structure, was fabricated and electrically pumped. The device exhibited spectral peak wavelength shifts between narrow stripes (10 pm) and wide stripes (50 pm) of 22 nm, similar to the value observed by photoluminescence studies. / Thesis / Master of Engineering (ME)

The fire debris analyst is often faced with the complex problem of identifying ignitable liquid residues in the presence of products produced from pyrolysis and incomplete combustion of common building and furnishing materials. The purpose of this research is to investigate a modified destructive distillation methodology provided by the Florida Bureau of Forensic Fire and Explosive Analysis to produce interfering product chromatographic patterns similar to those observed in fire debris case work. The volatile products generated during heating of substrate materials are extracted from the fire debris by passive headspace adsorption and subsequently analyzed by GC-MS. Low density polyethylene (LDPE) is utilized to optimize the modified destructive distillation method to produce the interfering products commonly seen in fire debris. The substrates examined in this research include flooring and construction materials along with a variety of materials commonly analyzed by fire debris analysts. These substrates are also burned in the presence of a variety of ignitable liquids. Comparisons of ignitable liquids, pyrolysis products, and products from pyrolysis in the presence of an ignitable liquid are performed by comparing the summed ion spectra from the GC-MS data. Pearson correlation was used to determine if substrates could be discriminated from one another. A pyrolysis products database and GC-MS database software based on comparison of summed ion spectra are shown to be useful tools for the evaluation of fire debris.

The direct effects of a Virginia trout farm on benthic macroinvertebrates were examined using multiple approaches. Static laboratory tests with the amphipod, Hyallela azteca, were conducted with exposures to water taken from a spring, effluent above a sedimentation basin, and effluent below a sedimentation basin. On-site mesocosms were constructed to expose previously colonized artificial substrates to the same treatments as the laboratory tests. Flat-headed mayflies were also collected from a nearby stream and transported to the mesocosms for a 10 day exposure. There was no significant difference between treatments in the laboratory tests after 20 days, but after 28 days the control was significantly lower than the above sedimentation basin treatment in one test. In the multispecies field tests, a clear decrease in total invertebrate abundance and EPT abundance was seen in the effluent treatments compared to the spring water treatments, with a slight improvement in survival in the treatment below the sedimentation basin. However, only total invertebrate abundance after 21 days produced statistically significant differences. A significant difference was detected between the effluent and the spring treatments in the flat-headed mayfly field test. We suggest that the effects seen in this study do not explain the lack of taxa richness in the receiving stream. The main cause of mortality from trout effluents appears to be solids accumulating upon the organisms, and sedimentation basins should be effective best management practices for protecting macroinvertebrates. / Master of Science

<p> Highly orientated BaTi1-xNbx03 thin films, spanning the entire range of x, have been successfully deposited on (001) MgAl20 4 substrates by the pulsed laser deposition (PLD) method. The structure of the films is characterized with a range of techniques. It is found that increasing x gives rise to a Ti4+ to Ti3+ transformation in the oxidation state accompanied by increased conductivity with a semiconductormetal transition near x = 0.2. Temperature dependent magnetic measurements show an anomalous rise in the spin moment. In order to further reduce the lattice mismatch and keep the conductivity at the same time, a partial strontium-for-barium substitution, (Ba1-ySry)Ti0.5Nb0.5O3 withy = 0, 0.4, 0.5 and 0.6, were used. Such a substitution provides a means for independently tuning the lattice parameter and conductivity over a significant range of compositions. The y = 0.6 composition show a sharp interface with flawless epitaxy and good quality films. We attribute the improvements in the film quality to a decrease in the lattice misfit strain made possible through the superior lattice match to the substrate obtained through strontium substitution. Electronic structure calculations were carried out by the 1st principle method using the WIEN2k program in order to understand the electronic structure of these compounds. Based on the assumed ordered structures, the Fermi level of BaTi1-xNbxO3 gradually moved to the lower energies as x increase, while the valence bands were not significantly altered with the Nb ions substitutions. The fraction of each Ti4+ and Ti3+ component in BaTi1-xNbxO3 samples was extracted by the linear profile fitting of the corresponding Ti-L2,3 edge obtained by the electron energy loss spectra. The fitting results indicate a high fraction of Ti3+ is present than excepted as Nb content increase, which could arise from the loss of oxygen stoichiometry. The electron energy loss spectra of the 0-K edge is analyzed by comparison to the partial density of states calculation. The evolutions of 0-K edge features are explained in terms of the decrease of the Ti 3d band contribution and the increase of the Nb 4d band contribution as the Nb content increase.</p> / Thesis / Doctor of Philosophy (PhD)