M.A. / Two species of multimammate mouse, Mastomys coucha and M. natalensis are common, and widely distributed in southern Africa, occurring sympatrically in some areas, and allopatrically in others. The limits of their distribution are only provisional so far. As they share a high degree of morphological similarity, they are, as yet, impossible to identify with certainty in the field. Each species of multimammate mouse carries important diseases: with M. coucha being a carrier for the bacterium causing plague, and M. natalensis carrying the virus causing Lassa fever. In many areas, multimammate mice, being highly adaptable and ecological generalists, have become co-habitants with humans. This fact, coupled to the medical significance of both species, lends importance to being able to identify each species where it occurs, especially in areas where they occur sympatrically. Thus, a total of 40 specimens of M. natalensis were trapped from Richards Bay and La Lucia ridge in KwaZulu-Natal, and 43 specimens of M. coucha from Montgomery Park in Johannesburg and from the shores of the Vaal Dam in the Free State with the aim of comparing these two species via gel electrophoresis. These specimens were from allopatric populations from the centres of their provisional distributions. It was expected that there would be genetic differences between the two sibling species. Blood, liver, and muscle samples were taken, either in the field from dead specimens caught in snap-traps, or back in the laboratory from live-trapped specimens. Fifteen proteins or enzymes provided interpretable results at a total of 39 loci. Nineteen of these were polymorphic

In this work I investigate the expulsion of carriers from nanostructures using the double-barrier quantum well (DBQW) as an example and discuss manifestations of this effect in the spectrum of the DBQW in absence of bias, and in the tunneling current in presence of bias. Assuming equality of the Fermi energy in all regions of the considered system, I compute the relative density of carriers localized in the DBQW and conclude that a fraction of carriers is expelled from this nanostructure.

No description available.

Bats and birds are known to be the reservoirs of a number of zoonotic diseases. The capacity of flight and the diversity of these animals may make them special in maintaining and disseminating diverse viruses leading to instances of emerging zoonoses. In particular bats are increasingly recognized to be reservoirs of a wide range of viruses, including Nipah, Ebola and severe acute respiratory syndrome (SARS) coronaviruses. In most instances these viruses appear to establish long-term persistence in bats. In this thesis I report the identification of novel astroviruses from different insectivorous species of apparently healthy bats sampled in Hong Kong and in 11 provinces of Mainland China with high positive rates. Astroviruses are important causes of diarrhea in many animal species, including humans. This study revealed a remarkably high genetic diversity of bat astroviruses, which form novel distinct phylogenetic groups in the genus Mamastrovirus. Evidence for varying degrees of host restriction for bats astroviruses has been found. The finding of diverse astroviruses in Miniopterus bats captured within a single cave habitat in Hong Kong illustrates a very unusual virus host relationship between astroviruses and these bats. Surveillance of astroviruses in rodents, the only mammal with species numbers surpassing that of bats, has revealed a novel astrovirus in only 1.6 % of the faecal samples of urban brown rat (Rattus norvegicus) in Hong Kong in marked contrast with the prevalence and diversity of astroviruses in bats. Rat astrovirus was phylogenetically related to human astroviruses MLB1 which was detected from clinical samples from diarrhoeal patients in Hong Kong in this study. The unusually high positive rates of astroviruses in bats have been again highlighted. Avastroviruses were detected in 7.1% of the aquatic wild bird samples. Avastrovirus have also been detected in doves in Hong Kong, pond herons and a less whistling duck in Cambodia. A phylogenetic analysis of these novel astroviruses together with other previously known astroviruses revealed that avastrovirus can be divided into 3 monophyletic groups. On the other hand, avian coronaviruses was detected in 12.5% of the aquatic wild bird samples. Phylogenetic analysis of these avian coronaviruses has led us to suggest taxonomic separation of these viruses into two groups as gammacoronaviruses and deltacoronaviruses. Frequent interspecies transmissions of gammacoronaviruses between duck species were demonstrated. Analysis of the avian viral sequences and host mitochondrial DNA sequences suggested that some coronaviruses may have coevolved with birds from the same order. With the discoveries of coronaviruses and astroviruses in mammalian and birds, we now have a better understanding on the diversity and ecology of these two virus families in wildlife. These findings provide new insights into the ecology and evolution of these viruses in nature and have revealed possible inter-species transmissions of these viruses. The role of bats as a reservoir of viruses with potential to pose zoonotic threats to human health was also reinforced. Studies of the virus ecology in wildlife as demonstrated in this thesis will help formulating better strategies for controlling emerging diseases in the future. / published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

Call number: LD2668 .T4 1961 D64

Call number: LD2668 .T4 1964 S15 / Master of Science

The Solute Carrier (SLC) superfamily is the largest group of membrane-bound transporters, currently with 456 transporters in 52 families. Much remains unknown about the tissue distribution and function of many of these transporters. The aim of this thesis was to characterize select SLCs with emphasis on tissue distribution, cellular localization, and function.       In paper I, we studied the leucine transporter B0AT2 (Slc6a15). Localization of B0AT2 and Slc6a15 in mouse brain was determined using in situ hybridization (ISH) and immunohistochemistry (IHC), localizing it to neurons, epithelial cells, and astrocytes. Furthermore, we observed a lower reduction of food intake in Slc6a15 knockout mice (KO) upon intraperitoneal injections with leucine, suggesting B0AT2 is involved in mediating the anorexigenic effects of leucine.     In paper II, we studied the postnatal, forebrain-specific deletion of Slcz1, belonging to the SLC18 family, in conditional KO mice (cKO). We observed a decreased response to diazepam and a higher neuronal activity in cortex and hippocampus of cKO mice, as well as an impairment in short-term recognition memory. Intracellular expression was found in neurons but not astrocytes with IHC, indicating SLCZ1 is implicated in neuronal regulation of locomotion and memory.    In paper III, we performed the first detailed histological analysis of PAT4, a transporter belonging to the SLC36 family, involved in the activation of mTOR complex 1 on lysosomes. We found abundant Slc36a4 mRNA and PAT4 expression in mouse brain, using ISH and IHC. We used IHC to localize PAT4 to both inhibitory and excitatory neurons and epithelial cells. We also found both intracellular- and plasmalemmal expression and partial colocalization of PAT4 with lysosomal markers.    Lastly, in paper IV, we provided the first tissue mapping of orphan transporter MCT14 (SLC16A14). Using qPCR, we detected moderate to high Slc16a14 mRNA in the central nervous system and kidney. We found widespread Slc16a14 and MCT14 in mouse brain using ISH and IHC. We also found MCT14 to have intracellular and plasmalemmal expression in mainly excitatory but also inhibitory neurons, as well as epithelial cells. We found MCT14 to be most closely related to MCT8, MCT2 and MCT9, suggesting a similar role for this transporter.

The solubilities of three poorly water soluble drugs, phenytoin, diazepam and benzocaine, were measured in various cosolvent-water mixtures. The data were generally described by the relationship: log (S(m)/S(w)) = Σf₁σ₁ where S(m) is the solubility of the drug in the cosolvent-water mixture, S(w) is the solubility of the drug in water, f₁ is the volume fraction of cosolventi and σ₁ is the slope of the log(S(m)/S(w)) vs. f₁ plot. In most cases, some positive or negative deviation from the log-linear solubility equation is observed. The deviation is similar for all three drugs in many of the cosolvent-water mixtures. This suggests that the deviation is primarily due to interactions between the solvent components. However, it could not be predicted from any of the physical properties of the solvent mixtures. Changes in the solute crystal structure could not be identified as a source of nonideality. The deviations from the log-linear solubility equation may involve such factors as changes in solvent structure, hydrophobic hydration, density changes and hydrogen bonding differences between solute and cosolvent. The slopes, σ₁, of the solubilization plots were related to various indexes of solvent polarity including dielectric constant, solubility parameter, partition coefficient, surface tension and interfacial tension. The best correlations were obtained with measures of solvent cohesive forces such as interfacial tension and solubility parameter. In general, the solubilities in mixtures of aprotic cosolvents and water are higher than predicted by any of the polarity indexes. The slopes are thus related to the hydrogen bonding ability of the cosolvent as expressed by the density of proton donor and acceptor groups of the neat cosolvent. The slopes of the solubilization plots can be predicted from linear relationships with polarity indexes of the cosolvent. Therefore it is possible to estimate the slope, σ, in any cosolvent-water mixture from the solubilities in two solvents for a given drug. Furthermore, the solubility in any cosolvent water mixture can be estimated by combining the log-linear solubility equation with the estimated slopes.

We have developed metrics of the performance and operational impacts of METOC support to strike operations conducted on operational aircraft carriers (CVs). Our goal was to assess that support and make recommendations on improving it. We adapted an existing automated real time METOC metrics system, which was developed for land based training missions, for use on CVs by developing a new data collection form, new metrics, and new collection, analysis, and reporting architecture for the remote entering of sensitive mission data without compromise. The weather support element of a CV, the OA division, does not provide strike mission planning support, but does provide situational awareness to pilots. Our system allows that situational awareness to be measured and assessed using metrics that quantify the performance of the forecasts, the relationship of the forecasts to the mitigating actions taken by pilots due to adverse weather conditions, and the effects of individual weather phenomena on the execution of strike missions. A key element of the data collection, analysis, and reporting system developed in this study is the collection of METOC related data from pilots during their intelligence debriefings. This system is readily adaptable for the assessment of METOC support to other warfare areas.

We explore the effects of surface plasmon hybridization in graphene nanostructures and silver nanoparticles as applied to novel plasmonic phenomena. The analysis is based on the theory of surface plasmon hybridization under the boundary charges method. This method, which is based in the electrostatic approximation, has been largely used to predict the resonant frequencies in strongly coupled nanoparticle clusters. Here, we extend this formalism to analyze novel plasmonic phenomena such as the blueshift of modes in graphene plasmonics, near-field radiation, thermal transport and plasmon-induced hot carrier generation in silver nanoparticles. Furthermore, we develop analytical solutions for graphene nanodisks and metallic spheres that allow for fast and accurate modeling. The analytic models provide the basis to derive a large number of results, including prediction of hybrid eigenmodes and bandstructures, far-field response, and near-field response under thermally induced fluctuations. We predict that the strong near-filed coupling in graphene nanodisk stacks can induce a blueshift in the resonant frequencies up to the near-infrared part of the spectrum. We find that the strong near-filed coupling between disks can also lead to large values of radiative thermal conductance when thermally induced fluctuations are included. In this regard, an enhancement over the blackbody limit of up to two and four orders of magnitude was observed for co-planar and co-axial disk configurations. The strong coupling between coplanar disks was also explored for the development of plasmonic waveguides by considering long co-planar disk arrays. It was observed that the array posseses great potential for plasmonic waveguiding, with a strong degree of confinement for disks smaller than 200 nm. Thermal activation of the guided modes showed a thermal conductivity of up to 4.5 W/m K and thermal diffusivity of up to 1:4 x 10-3 m2/s. The large values of thermal diffusivity suggest the potential of graphene disk waveguides for thermotronic interconnects. The plasmon-induced hot carrier generation in silver nanosphere dimers was also studied. The modeling considered analytical solution for metallic nanospheres, from which the electrostatic potential of each sphere was obtained. Using these results, the hot carrier generation was explored under the basis of the Fermi golden rule. The results show a large number of hot carriers at the low frequency modes. This values exceed the number of generated hot carriers on a single sphere. The energy distribution of photogenerated electrons and holes showed a large energy gap that can be explored in photocatalysis and photovoltaic energy conversion.