The Design, Development and Characterisation of a new Biosensor for In-vivo Neurochemical Monitoring of ᴅ-Serine

The desire to monitor important neurotransmitters in the in vivo environment, in real-time and in conscious subjects has been the driving force behind the continued development over the last 40 years of a range of biosensor devices. This is a none too difficult task considering the milieu of substances that are present in vivo, particularly in the brain where there also exists a wide range of electroactive species, and where foreign objects are treated as hostile and subject to severe biological strain. Nevertheless, the rewards for developing a selective and sensitive biosensor are worth the effort. Today they are used, have been used and will increasingly be used for extremely important medical processes, including developing an understanding of disease etiology, determination of key intercession points in these pathologies, preclinical and clinical testing of proposed new treatments, and earlier diagnosis of medical conditions. With this in mind this thesis focused on the development and characterisation of a ᴅ-serine biosensor based around the flavin enzyme ᴅ-amino acid oxidase. In the recent past ᴅ-serine has been elevated from an “unnatural” amino acid to be recognised as a very important neurotransmitter that could be responsible for the regulation of a large portion of glutamate signalling in the forebrain. It has been highly implicated in a number a severe and widely occurring neurodegenerative diseases, ranging from schizophrenia to amyotrophic lateral sclerosis. Initial groundwork and development of a biosensor was underway when this thesis began. Extensive investigation and characterisation of this sensor, conducted at the start of this thesis, found that the biosensor displayed satisfactory sensitivity and selectivity properties. However, for the purposes of this project, to develop a biosensor suitable for chronic in vivo monitoring of ᴅ-serine, it was deemed unfit. This was due to an uneconomical and difficult to reproduce production methodology. Thus, from a solid starting point, from which much useful information had been gleamed, an entirely new biosensor was designed with the underlining principal of reproducibility and economic viability added to the need for sensitivity and selectivity. The final design involved the use of the cross-linking agent glutaraldehyde in conjunction with methyl methacrylate to immobilise the ᴅ-amino acid oxidase on to the surface of the electrode. To achieve effective interference rejection the dual use of Nafion® followed by an electropolymerised layer of poly-o-phenylenediamine was utilised. The electrode surface was a 125 μm Pt/Ir wire that was 0.5 mm in length. The design achieved a sensitivity of 16.47 ± 0.18 μA.cm-2.mM-1. It was found that the response was oxygen independent up to 100 μM ᴅ-serine. The limit of detection was determined to be 0.425 ± 0.005 μM and the biosensor has a response time of 5.95 ± 0.75 s. In the in vivo environment it was demonstrated that the biosensor could detect both increases and decreases in the endogenous concentration of ᴅ-serine, particularly in response to typical and traditional N-methyl-ᴅ-aspartate receptor antagonists like MK-801. Our device will make it possible to monitor, in vivo in real-time and without interference, the concentration of, and changes that occur in ᴅ-serine in a conscious subject. This could have a major impact on medical processes, both normal and pathological, whereby the metabolism of ᴅ-serine is of interest, including the development and testing of potential new drugs

In-field solar drying of ventilated large hay packages

The purpose of this study was to test and develop a machine which would form, from the tractor seat, a ventilation tunnel in a high-density round bale having a moisture content above 35%. The ventilation tunnel would vent the interior of the bale and allow drying of the hay by natural air flow. High-moisture bales were pierced with either one tunnel or three tunnels. Bale dimensions were taken before and after piercing. The result of these measurements showed less than 5 cm (2 inch) change in any bale dimension as a result of the piercing operation. Hydraulic gauge pressure was recorded during the piercing operation to determine the force required to produce a tunnel. The mean force developed by a 20.3 cm (8 inch) cone in producing a center tunnel was 11528.94 Newtons (2591.81 pounds). The drying experiments consisted of comparing the effects of black plastic, chimneys and the number of tunnels on the drying rate of the high-moisture bales. An analysis of variance of the amount of moisture loss indicated no significant difference in any of the various treatments at the 90% confidence level

Simulation of ultrasonic lamb wave generation, propagation and detection for an air coupled robotic scanner

A computer simulator, to facilitate the design and assessment of a reconfigurable, air-coupled ultrasonic scanner is described and evaluated. The specific scanning system comprises a team of remote sensing agents, in the form of miniature robotic platforms that can reposition non-contact Lamb wave transducers over a plate type of structure, for the purpose of non-destructive evaluation (NDE). The overall objective is to implement reconfigurable array scanning, where transmission and reception are facilitated by different sensing agents which can be organised in a variety of pulse-echo and pitch-catch configurations, with guided waves used to generate data in the form of 2-D and 3-D images. The ability to reconfigure the scanner adaptively requires an understanding of the ultrasonic wave generation, its propagation and interaction with potential defects and boundaries. Transducer behaviour has been simulated using a linear systems approximation, with wave propagation in the structure modelled using the local interaction simulation approach (LISA). Integration of the linear systems and LISA approaches are validated for use in Lamb wave scanning by comparison with both analytic techniques and more computationally intensive commercial finite element/difference codes. Starting with fundamental dispersion data, the paper goes on to describe the simulation of wave propagation and the subsequent interaction with artificial defects and plate boundaries, before presenting a theoretical image obtained from a team of sensing agents based on the current generation of sensors and instrumentation

The migrations of East Coast Humpback whales (Megaptera novaeangliae)

Southern hemisphere hwnpback whales undertake annual migrations from summer Antarctic feeding grounds, to breeding grounds in coastal sub-tropical and tropical waters in winter. En route the whales utilise extreme coastal waters as migratory corridors. After severe depletion by commercial whaling between 1904 and 1963, the species is showing a recovery off the east coast of southern Africa. The close proximity of the migration to the coast allowed for a recovery - monitoring programme to be carried out through shore-based visual surveys from Cape Vidal, northern Natal. Surveys of the northward migration were undertaken each winter from 1988 to 1991, and a survey of the southward migration was undertaken in 1990. Daily observations were carried out from an approximately 60 m high vantage point on a headland, during which attempts were made to measure migration characteristics for each group observed, including distance offshore, speed and bearing (measured by theodolite) and group size ( estimated by observers and confirmed by interception of groups by ski-boat). Characteristics of the northward migration were unaffected by environmental parameters (sighting conditions, wind speed or direction, and time of day) or interactive parameters (other migration characteristics). Each year's northward migration was comprised of waves, and apart from the distance offshore, there was no difference in the migration characteristic of each wave. Significant differences were found in group size, distance offshore and speed of the northward migration between years. No differences were found between the mean group sizes or speeds of the northward and southward migrations in 1990, although the southward migration was found to be significantly further offshore than its northward counterpart. The measurement of migration characteristics has played an integral part in population estimation, and in the choice of optimum periods to monitor annual abundance. Results of the 1988 and 1989 surveys suggested that not all groups within view were sighted by observers. Independent-observer surveys were therefore carried out in both 1990 (22 days) and 1991 (51 days), to determine the proportion of the population within the survey area that was being missed by observers using a single mark-release model. Results were stratified into three distance intervals from the shore and three sighting - condition intervals; there were constant sighting probabilities from the south tower under different sighting conditions, while those from the north tower increased slightly as sighting conditions improved. Sighting probabilities of both towers were highest in the intermediate distance interval, and decreased in both the inshore and offshore regions. Daily densities (expressed as the number of groups crossing the midline in front of the towers), adjusted for groups missed with distance from the shore and under different sighting conditions, were multiplied by the mean group size of the survey year, and resulting daily densities of individuals were summed to provide totals of whales passing the towers during each survey. The abundance estimate of 1711, made during the northward migration of 1990, was considered the most reliable estimate of population size made, although no associated cv could be calculated. The estimate of 1777 made during the 1991 survey had an associated cv of O .12 calculated by bootstrapping of daily data. The time series of four years is too short to provide an estimate of the recovery rate of the population, but the numbers sighted show the population to have undergone considerable recovery since protection in October 1963.Thesis (PhD)--University of Pretoria, 1994.Zoology and EntomologyPhDUnrestricte

Enhancing the usability of rely-guarantee conditions for atomicity refinement

Formal methods are a useful tool for increasing the confidence in the correctness of computer programs with respect to their specifications. Formal methods allow designers to model specifications and these formal models can then be reasoned about in a rigourous way. Formal methods for sequential processes are well-understood, however formal methods for concurrent programs are more difficult, because of the interference which may arise when programs run concurrently. Rely-guarantee reasoning is a well-established formal method for modelling concurrent programs. Rely-guarantee conditions offer a tractable and compositional approach to reasoning about concurrent programs, by allowing designers to reason about the interference inherent in concurrent systems. While useful, there are certain weaknesses in rely-guarantee conditions. In particular, the requirement for rely-guarantee conditions to describe whole-state updates can make large specifications unwieldy. Similarly, it can be difficult to describe problems which exhibit distinct phases of execution. The main contribution of this thesis is to show ways in which these two weaknesses of rely-guarantee reasoning can be addressed. In turn, this enhances the usability of rely-guarantee conditions. Atomicity refinement is a potentially useful tool for simplifying the development of concurrent programs. The central idea is that designers can record (possibly unrealistic) atomicity assumptions about the eventual implementation of a program. This fiction of atomicity simplifies the design process by avoiding the difficult issue of interference. It is then necessary to identify ways in which this atomicity can be relaxed and concurrent execution introduced. This thesis also argues that the choice of data representation plays an important role in achieving atomicity refinement. In addition, this thesis presents an argument that rely-guarantee conditions and VDM offer a potentially fruitful approach to atomicity refinement. Specifically, rely-conditions can be used to represent assumptions about atomicity and the refinement rules of VDM allow different data representations to be introduced. To this end, a more usable approach to rely-guarantee reasoning would benefit the search for a usable form of atomicity refinement. All of these points are illustrated with a novel development of Simpson’s Four-Slot, a mechanism for asynchronous communication between processes.EThOS - Electronic Theses Online ServiceEPSRCGBUnited Kingdo

The 2006-2009 Puget Sound Land-Use/Land-Cover Change Map

Land cover change is associated with human development is one of the most important indirect stressors in the Salish Sea Ecosystem, and is a Vital Sings indicator for the Puget Sound Partnership. In January 2014, the Washington Department of Fish and Wildlife completed the first iteration of the Puget Sound land cover change map covering the 2006-2009 time period. The map was created from 1-m National Agriculture Imagery Program aerial imagery using a hybrid data mining-photo interpretation process developed for mapping change with high resolution imagery. The map depicts over 36,000 individual change events covering over 85,000 acres throughout the basin, and represents one of the largest area, highest-resolution change maps ever created. The process we employed includes reviewing every change location to remove commission error while omission error was assessed using a more traditional sampling approach applied to non-change areas. Additionally, at each location the initial land cover, change agent (development, forestry, natural, etc.), total change area, canopy reduction and increase in impervious and semipervious surface were quantified during the photo interpretation step. The median change event was smaller than one acre, which is too small to be reliably assessed using intermediate resolution remote sensing data like LandSat. The spatial precision of the map provides a robust base layer for intersection analyses with other data sets such as riparian buffers, urban and planned growth area boundaries, mapped wetlands, mapped ownership, land-use, parcels. From these intersections, change rates can be calculated by area of interest. Sound-wide results will be presented along with information on obtaining the data and examples of potential analyses

The Yellowstone Hotspot, Greater Yellowstone Ecosystem, and Human Geography

Active geologic processes associated with the Yellowstone hotspot are fundamental in shaping the landscapes of the greater Yellowstone ecosystem (GYE), a high volcanic plateau flanked by a crescent of still higher mountainous terrain. The processes associated with the Yellowstone hotspot are volcanism, faulting, and uplift and are observed in the geology at the surface. We attribute the driving forces responsible for the northeastward progression of these processes to a thermal plume rising through the Earth’s mantle into the base of the southwest-moving North American plate. This progression began 16 million years ago (Ma) near the Nevada-Oregon border and arrived at Yellowstone about 2 Ma. Before arrival of the hotspot, an older landscape existed, particularly mountains created during the Laramide orogeny about 70–50 Ma and volcanic terrain formed by Absaroka andesitic volcanism mostly between 50–45 Ma. These landscapes were more muted than the present, hotspot-modified landscape because the Laramide-age mountains had worn down and an erosion surface of low relief had developed on the Absaroka volcanic terrain. The Yellowstone Plateau was built by hotspot volcanism of rhyolitic lavas and caldera-forming rhyolite tuffs (ignimbrites). Streams eroding back into the edges of this plateau have created scenic waterfalls and canyons such as the Grand Canyon of the Yellowstone and Lewis Canyon. Rhyolite is poor in plant nutrients and forms sandy, well-drained soils that support the monotonous, fire-adapted lodgepole pine forests of the Yellowstone Plateau. Non-rhyolitic rocks surround this plateau and sustain more varied vegetation, including spruce, fir, and whitebark pine forests broken by grassy meadows. Heat from the hotspot rises upward and drives Yellowstone’s famed geysers, hot springs, and mudpots. These thermal waters are home to specialized, primitive ecosystems, rich in algae and bacteria. The rock alteration associated with hydrothermal systems creates the bright colors of Yellowstone’s Grand Canyon. Basin-and-range-style faulting has accompanied migration of the hotspot to Yellowstone and formed the linear mountains and valleys that occur north and south of the hotspot track, which is the present-day eastern Snake River Plain. High rates of basin-and-range faulting occurred adjacent to the migrating Yellowstone hotspot, creating distinctive landscapes within the GYE such as the Teton Range/Jackson Hole, with characteristic rugged, forested ranges and adjacent flat-floored grassy valleys. The difference in altitude between the mountains and valleys provides a topographic gradient in which vegetation maturation advances with altitude; animal-migration patterns also follow this trend. The valleys provide natural meadows, agricultural land, town sites, and corridors for roads. Uplift of the GYE by as much as 1 km (3,000 ft) during the last 5 million years has resulted in ongoing erosion of deep, steep-walled valleys. Many prominent ecological characteristics of Yellowstone derive from this hotspot-induced uplift, including the moderate- to high- altitude terrain and associated cool temperatures and deep snowfall. Modern and Pleistocene climate and associated vegetation patterns strongly relate to the topography created by the hotspot and its track along the eastern Snake River Plain. Winter air masses from the moist northern Pacific Ocean traverse the topographic low of the Snake River Plain to where orographic rise onto the Yellowstone Plateau and adjacent mountains produces deep snow. A winter precipitation shadow forms on the lee (eastern) sides of the GYE. During Pleistocene glacial times, this moisture conduit provided by the hotspot-track-produced ice-age glaciers that covered the core of the present GYE. These glaciers sculpted bedrock and produced glacial moraines that are both forested and unforested, sand and gravel of ice-marginal streams and outwash gravels that are commonly covered with sagebrush-grassland, and silty lake sediments that are commonly covered by lush grassland such as Hayden Valley. The effects of the Yellowstone hotspot also profoundly shaped the human history in the GYE. Uplift associated with the hotspot elevates the GYE to form the Continental Divide, and streams drain radially outward like spokes from a hub. Inhabitants of the GYE 12,000–10,000 years ago, as well as more recent inhabitants, followed the seasonal green-up of plants and migrating animals up into the mountain areas. During European immigration, people settled around Yellowstone in the lower parts of the drainages and established roads, irrigation systems, and cultural associations. The core Yellowstone highland is too harsh for agriculture and inhospitable to people in the winter. Beyond this core, urban and rural communities exist in valleys and are separated by upland areas. The partitioning inhibits any physical connection of communities, which in turn complicates pursuit of common interests across the whole GYE. Settlements thus geographically isolated evolved as diverse, independent communities

A GPU-Computing Approach to Solar Stokes Profile Inversion

We present a new computational approach to the inversion of solar photospheric Stokes polarization profiles, under the Milne-Eddington model, for vector magnetography. Our code, named GENESIS (GENEtic Stokes Inversion Strategy), employs multi-threaded parallel-processing techniques to harness the computing power of graphics processing units GPUs, along with algorithms designed to exploit the inherent parallelism of the Stokes inversion problem. Using a genetic algorithm (GA) engineered specifically for use with a GPU, we produce full-disc maps of the photospheric vector magnetic field from polarized spectral line observations recorded by the Synoptic Optical Long-term Investigations of the Sun (SOLIS) Vector Spectromagnetograph (VSM) instrument. We show the advantages of pairing a population-parallel genetic algorithm with data-parallel GPU-computing techniques, and present an overview of the Stokes inversion problem, including a description of our adaptation to the GPU-computing paradigm. Full-disc vector magnetograms derived by this method are shown, using SOLIS/VSM data observed on 2008 March 28 at 15:45 UT