The large-scale use of artificial light throughout the night has occurred in the last 100 years and continues to increase globally. Artificial light impacts many animal and plant taxa. The effects of artificial light on bats is species specific. The Namib Desert in Namibia is still relatively dark but subject to the same drivers of increasing development and urbanization that have increased the spread of artificial light globally. This study investigated the effects of the introduction of ultraviolet, yellow and white artificial light on the activity of bats in a rural environment with minimal development in the Namib Desert. Four sites, 100 m apart, had one light and one bat detector each. The fourth light was a dark control. Each site was sampled four times by each light type. Bat activity was recorded by the bat detectors. Eight bat species were recorded during the experiment. Activity increased for open air and clutter-edge foraging species analysed. Broadband white light caused the highest increases in activity followed by yellow light when compared with the dark control site. Ultraviolet light caused the lowest increases in activity contrary to expectations. / Mengwaga ye 100 ya go feta go bile le koketšego ye kgolo ya tšhomišo ya seetša sa maitirelo bošego ka moka. Setlwaedi se se ata kudu lefaseng ka moka go feta pele, gomme se ama diphoofolo tše ntši le mehuta ya dimela. Leganata la Namib go la Namibia gabotse le sa ntše le swiswetše, eupša le ka fase ga dikgontšhi tša go oketša tlhabollo le toropofatšo tšeo di hlotšego koketšego tšhomišong ya seetša sa maitirelo lefaseng ka bophara. Dikhuetšo tša seetša sa maitirelo go memankgagane di fapana go ya ka mohuta. Nyakišišo ye e nyakišišitše dikhuetšo tša tsebagatšo ya seetša sa maitirelo sa go phadima, serolwane le se sešweu go modiro wa memankgagane ka tikologong ya nagaselegae ya go ba le tlhabollo ye nyane ka Leganateng la Namib. Seetša se setee le tithekethara e tee ya mankgagane di hlomilwe go le lengwe le le lengwe la mafelo a mane, a go arogantšhwa ka 100 m. Seetša sa bone se be se le taolo ya leswiswi. Lefelo le lengwe le le lengwe le dirilwe mohlala makga a mane ka mohuta wo mongwe le wo mongwe wa seetša. Modiro wa mankgagane e rekotilwe ka ditithekethara tša mankgagane. Mehuta ya mankgagane ye seswai e rekotilwe nakong ya eksperimente. Modiro wa mehuta ya sebakabakeng le ya go sela thobekgeng ye e sekasekilwego e oketšegile. Seetša se sešweu sa porotepente se hlotše dikoketšego tša modiro, sa latelwa ke seetša se se serolwane, ge se bapetšwa le lefelo la taolo ya leswiswi. Go fapana le ditetelo, seetša sa go phadima se hlotše dikoketšego tša fasefase modirong. / School of Environmental Sciences / M. Sc. (Nature Conservation)

In the area of forensic chemistry, improved or new analysis methods are continually being investigated. One common and powerful technique used in forensic chemistry is wall-coated open-tubular column (WCOT) gas chromatography with electron ionization single quadrupole mass spectrometry (GC-MS). Improvements to and effectiveness of alternatives to this instrumental platform were explored in an array of parallel inquiries. The areas studied included the column for the chromatographic separation, the universal detection method employed, and the fragmentation method used to enhance molecular identification. <br><br>Superfine-micropacked capillary (SFµPC) columns may provide an alternative to commercial packed GC columns and WCOT GC columns that combines the benefits of the larger sample capacity of packed columns and the benefits of the excellent separation capabilities and mass spectrometry (MS) flow rate compatibility of WCOT columns. SFµPC columns suffer from high inlet pressure requirements and prior reported work has required specialized instrumentation for their use. Fabrication of and chromatography with SFµPC GC columns was successfully achieved with typical GC-MS instrumentation and within the flow rate limit of a MS. Additionally, the use of higher viscosity carrier gasses was demonstrated to reduce the required inlet pressure for SFµPC GC columns.<br><br>Recently, a new vacuum ultraviolet spectrometer (VUV) universal detector has been commercialized for GC. The ability of VUV detectors to acquire absorbance spectra from 125 nm to 430 nm poses a potential alternative to MS. As such, GC-VUV provides an exciting potential alternative approach to achieving excellent quantitative and qualitative analysis across a wide range of analytes. The performance of VUV and MS detectors for forensic analysis in terms of quantitative and qualitative analysis was compared. Analysis of alkylbenzenes in ignitable liquids was explored, which can be important evidence from suspected arson fires and are difficult to differentiate with MS. The VUV detector was found to have superior specificity and comparable sensitivity to the MS detector in scan mode.<br><br>Addition of thermolysis (Th) as an orthogonal fragmentation pathway provides the opportunity to increase the differences between MS fragmentation patterns. Fragmentation has been widely established to aid in identification of molecules with MS by providing characteristic fragments at characteristic relative abundances. However, molecules with very similar structures do not result in sizable spectral differences in all cases with typical MS fragmentation techniques. A series of Th units were fabricated and integrated into GC-Th-MS instruments. Th-MS was conducted with the thermally labile nitrate esters across a range of instrumentation and thermal conditions.<br>

No description available.

Uranus is one of the least explored planets in our solar system. Event though the Uranian Ly-α emission has been a subject of study for decades, there is not a consensus on the sources contribution to the total signal. This thesis aims to analyse the contribution from scattering of the solar flux to the Uranian Ly-α dayglow by solving the radiative transfer equation in a parameter study for the atmosphere. The sources are solar Ly-α resonant scattering and Rayleigh scattering by atomic and molecular hydrogen respectively. The radiative transfer equation is solved using the Feautrier Method Program, a program written by Randall G. Gladstone. The program was adjusted to the Uranian atmosphere and modelled with different variations in parameters, including the atmospheric temperature and particle density of Ly-α scatterers and absorbers. A parameter study is performed to investigate the dependency on the Ly-α signal on these parameters. The results showed a significant Ly-α limb brightening with a maximum intensity located around 400 km outside one planetary radius as seen from the disk center. The contributions to the Ly-α dayglow from Rayleigh scattering by H2 was calculated to be 160 R whereas the contribution from resonant scattering by H was 550 R. One feature that prevents direct comparison to observed data with this thesis is that some sources that contributes to Uranus Ly-α signal are omitted in the simulations. / Uranus är en av solsystemets minst utforskade planeter. Även om dess Ly-α-strålning har undersökt, råder ännu inte konsensus kring de olika källornas bidrag till den totala Ly-α signalen. Genom att lösa ekvationen för strålningstransport i en parameterstudie ämnar examensarbetet att studera bidraget från solens två källor till Uranus Ly-α- signal. De två källorna är resonant- och Rayleigh strålningsspridning från atomärt och molekulärt väte. Ekvationen för strålningstransport beräknas av ett program som heter Feautrier Method Program, skapat av Randall G. Gladstone. Programmet har justeras till Uranus atmosfär för att kunna beräkna strålningstransport för olika atmosfärersmodeller i en parameterstudie. Parameterna som ändras är temperaturen, partikeldensiteten hos spridare och absorberare i atmosfären. Från resultaten kan parameterstudien svara på beroendet av de olika källorna till Ly-α-signalen från Uranus. Resultaten visar en tydlig ökning av ljusintensitet vid Uranus kanter med maximum runt 400 km utanför planetens radie, sett från planetens mitt. Bidraget till Ly-α-signalen från Rayleigh stålningsspridning beräknades till 160 R och från resonant strålningsspridning till 550 R. En egenskap som hindrar direkt jämförelse med resultaten från detta examensarbete och observerad data är att alla bidragande källor till Uranus Ly-α signal inte simulerats.

Cholera is a water-borne disease that continues to ravage resource poor communities around the world especially those in developing countries. The disease is caused by Vibrio cholerae microorganisms whose natural habitat is the aquatic ecosystem. It is believed that this microorganism prior to becoming the primary cause of cholera acquired virulence factors expressed by two separate genetic elements. These genetic elements are known as VPIФ and CTXФ were acquired in that order for known physiological reasons. However only V. cholerae in possession of the CTX genetic element are capable of causing cholera disease. At present only two serotypes are known to have the ability to cause cholera and these are V. cholerae serotypes O1 and O139. SODIS (Solar disinfection) is an extremely low cost refined technology that can be used for the disinfection of water especially in areas where there is a considerable amount of sunshine. Although this technology is a composite of various factors the underlying principle is the use of solar ultraviolet radiation (SUVR). The preliminary target of SUVR is the cytoplasmic membrane and this was confirmed by flow cytometric analysis. The consequences of leaky cytoplasmic membrane include cellular death to the microorganism as well as an increase in cholera toxin secretion. The main objective of this study was to investigate the effect of solar ultraviolet radiation on the growth of V. cholerae and on the secretion of cholera toxin and to provide supporting information for the use of SODIS in South Africa while observing the possible role that climate may play in the onset of cholera disease. The initial part of the study evaluated the culturability, biomass increase and cholera toxin secretion in both a nutrient poor and a nutrient rich media by two toxigenic and one non toxigenic strain of V. cholerae. A series of pH and temperature combinations were used to achieve this objective. The result revealed that the microorganisms survived in both media. An increase in biomass was observed for all the bacteria grown in the nutrient rich media whereas in the poor nutrient media the bacteria remained culturable but no increase in biomass was observed. Interestingly lower temperatures seemed to provide more optimal growth conditions while high temperature on most occasions favoured cholera toxin secretion, in both media.The second part of the study required the exposure of the microorganisms to SUVR. A SODIS approach was used with a few modifications. The V. cholerae strains were exposed to solar radiation during all the seasons of the year. Evaluation of the viability, the increase in biomass and the detection of cholera toxin secretion was determined after each exposure to solar radiation. The results seem to suggest that the effect of SUVR depended on the season of the year, the nature of the media, strain, solar conditions and in the duration of solar exposure, in no particular order. The secretion of cholera toxin was mainly dependent on the media used, the season of the year and on the serotype of the strain. This study represents the first report on the evaluation of SUVR for the disinfection of water under South African conditions (Pretoria area) during all seasons of the year with variations in solar radiation levels and temperature. Furthermore what actually happened to V. cholerae during solar exposure in terms of cell morphology, cell viability and secretion of cholera toxin is also reported and this can give an insight of the possible role that SUVR may play in the onset of cholera. The main recommendation emanating from this study is the sensitisation of communities worldwide about the capacity that, SUVR carries to lighten the burden of communicable water borne diseases especially, in resource limited areas through the implementation of SODIS. / Life and Consumer Sciences / M. Sc. (Life Science)

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / The science payload for NASA's Extreme Ultraviolet Explorer (EUVE) satellite is controlled from the EUVE Science Operations Center (ESOC) at the Center for EUV Astrophysics (CEA), University of California, Berkeley (UCB). The ESOC is in the process of a transition from a single staffed shift to an autonomous, zero-shift, "lights out" science payload operations scenario (a.k.a., 1:0). The purpose of the 1:0 transition is to automate all of the remaining routine, daily, controller telemetry monitoring and associated "shift" work. Building on the ESOC's recent success moving from three-shift to one-shift operations (completed in Feb 1995), the 1:0 transition will further reduce payload operations costs and will be a "proof of concept" for future missions; it is also in line with NASA's goals of "cheaper, faster, better" operations and with its desire to out-source missions like EUVE to academe and industry. This paper describes the 1:0 transition for the EUVE science payload: the purpose, goals, and benefits; the relevant science payload instrument health and safety considerations; the requirements for, and implementation of, the multi-phased approach; a cost/benefit analysis; and the various lessons learned along the way.

Purpose: To model the time evolution of active caspase-3 protein expression in a healthy lens, and in a lens exposed to UVR-300 nm (UVR-B). To develop an automated method to classify the fluorescent signal of biomarkers in the lens epithelial cells. Methods: Six-week old Sprague-Dawley rats were used. Firstly, expression of active caspase-3 was studied in the lens epithelium of healthy rats. Secondly, rats were unilaterally exposed in vivo to 1 kJ/m2 UVR-B for 15 minutes. At 0.5, 8, 16, and 24 hours after the UVR-B exposure, the exposed and the contralateral non-exposed lenses were removed. Immunohistochemistry was done on three mid-sagittal sections from each lens. The florescent labelling for active caspase-3 in each lens section was counted three times. The time evolution of active caspase-3 expression in response to UVR-B exposure was modelled as a function of cell position in the lens epithelium. An automated objective method was developed to quantify the lens epithelial cells and to classify the fluorescent signal of active caspase-3. Active caspase-3 was selected as a model signal. Results: Active caspase-3 was abundant in the anterior pole of the normal lenses. Spatial distribution of active caspase-3 labelling in the lens epithelium was fitted to a logistic model. The probability of active caspase-3 expression was higher in the UVR-B exposed lenses (95% CI = 0.12 ± 0.01). There was no difference in the expression of active caspase-3 between the 0.5 and the 24 hours groups or between the 8 and the 16 hours groups. A difference was noted, when comparing the 0.5 and 24 hours groups with the 8 and 16 hours groups (Test statistic 7.01, F1;36;0.95= 4.11). Exposure to UVR-B has an impact on the average probability of labelling for active caspase-3 as a function of cell position. The probability of labelling as a function of cell number also varied as a function of time after UVR-B exposure. The automated method counted the lens epithelial cells and estimated the proportion of active caspase-3 labelling in the lens epithelium. Conclusions: Active caspase-3 is present in the healthy lens epithelial cells. Active caspase-3 exhibits higher expression at the anterior pole of the lens and the expression decreases towards the periphery. After UVR-B exposure, the expression of active caspase-3 in the lens epithelium increases with a peak of expression occurring around 16 hours after exposure. The average probability of labelling in the lens epithelium is dependent on both the UVR-B exposure and the time period elapsed after the exposure. The automated method enables objective and fast quantification of lens epithelial cells and the expression of fluorescent signal in the lens cells.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / This thesis begins with the description of the preparation of thirteen dithioesters (of the form Z- (C=S)-S-R) which were characterized via Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR) and ultraviolet spectroscopy (UV). The dithioesters were then used as reversible addition-fragmentation chain transfer (RAFT) mediating agents in the bulk polymerization of styrene, in order to observe differences in the kinetic behaviour of the polymerizations and, as a result, the efficiencies of the dithioesters in mediating the polymerizations.

Ce travail est consacré au développement par voie sol-gel de fluorures ALnF4 (A=Li, Na et Ln= Y, Gd) et de composites SiO2/LiGdF4 activés par les ions Eu3+. Le passage par un état sol a permis d'élaborer des poudres et des films de ces matériaux luminescents. L'emploi de précurseurs moléculaires induit une répartition homogène des ions dopants dans les matrices évitant la formation d'agrégats. Plusieurs techniques expérimentales (DRX, IR et Raman, EXAFS, RMN, RPE, MEB et MET) ont été utilisées pour caractériser les propriétés structurales et morphologiques. Elles ont permis de définir les paramètres de synthèse et les traitements thermiques appropriés à l'obtention de phases pures. Les propriétés optiques des poudres ont été étudiées après excitation dans l'UV pour souligner l'efficacité du procédé sol-gel à produire des matériaux optiques de qualité et sous excitation VUV afin d'évaluer leurs capacités à être utilisés comme luminophores quantiques

This study presents the first attempt to combine the fields of ultraviolet (UV) photobiology, plant cell wall biochemistry, aerobic methane production and reactive oxygen species (ROS) mechanisms to investigate the effect of UV radiation on vegetation foliage. Following reports of a 17% increase in decomposition rates in oak (Quercus robur) due to increased UV, which were later ascribed to changes in cell wall carbohydrate extractability, this study investigated the effects of decreased UV levels on ash (Fraxinus excelsior), a fast-growing deciduous tree species. A field experiment was set up in Surrey, UK, with ash seedlings growing under polytunnels made of plastics chosen for the selective transmission of either all UV wavelengths, UV-A only, or no UV. In a subsequent field decomposition experiment on end-of-season leaves, a significant increase of 10% in decomposition rate was found after one year due to removal of UV-B. However, no significant changes in cell wall composition were found, and a sequential extraction of carbohydrate with different extractants suggested no effects of the UV treatments on cell wall structure. Meanwhile, the first observations of aerobic production of methane from vegetation were reported. Pectin, a key cell wall polysaccharide, was identified as a putative source of methane, but no mechanism was suggested for this production. This study therefore tested the effect of UV irradiation on methane emissions from pectin. A linear response of methane emissions against UV irradiation was found. UV-irradiation of de-esterified pectin produced no methane, demonstrating esters (probably methyl esters) to be the source of the observed methane. Addition of ROS-scavengers significantly decreased emissions from pectin, while addition of ROS without UV produced large quantities of methane. Therefore, this study proposes that UV light is generating ROS which are then attacking methyl esters to create methane. The study also demonstrates that this mechanism has the potential to generate several types of methyl halides. These findings may have implications for the global methane budget. In an attempt to demonstrate ROS generation in vivo by UV irradiation, radio-labelling techniques were developed to detect the presence of oxo groups, a product of carbohydrate attack by ROS. Using NaB3H4, the polysaccharides of ash leaflets from the field experiment were radio-labelled, but did not show any significant decrease in oxo groups due to UV treatments. However, UV-irradiation of lettuce leaves showed a significant increase in radio-labelling, suggesting increased UV irradiation caused an increase in the production of ROS. The study shows that the use of this radio-labelling technique has the potential to detect changes in ROS production due to changes in UV levels and could be used to demonstrate a link between ROS levels and methane emissions.