The chemical senses of taste and smell are the two least well understood of our senses. Recent advances in our understanding of the genetic and molecular mechanisms have led to increasing interest in olfaction and gustation. Amongst the practical applications of fragrances and flavours are commercial consumer products. The primary source for inspiration for these is nature and the work discussed in this thesis addresses methods for isolating selected aroma and taste molecules from natural sources, for use as new ingredients in food and fragrance applications. The methods are designed to deal with the challenges of isolating and identifying species present at very low concentrations (as low as parts per trillion), of unstable nature and with the desire to target specific functional groups. Carbonyl and thiol compounds have been selected for trapping due to their interesting fragrance and flavour characteristics respectively. A portable reactive trap has been designed, built, and tested to isolate aldehyde (or ketone) compounds from the headspace of living plants. The trap uses the derivatising reagent, 0-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride coated on to a solid sorbent, Tenax TA'-"'. Reagents with immobilised reactive groups capable of selective reacting with thiol compounds have been investigated and the proof of principle has been illustrated for three different methods. The nature identical status of the cooling compound, L-monomenthyl succinate, has been demonstrated by using highly sensitive and selective analytical techniques to identify this compound in the berries and leaves of plant Lycium barbarum. A preparative liquid chromatography system was used to simplify plant extracts which were subsequently analysed using nano liquid chromatography-electrospray ionisation-tandem mass spectrometry (nLC-ESI-MS/MS). This system could be applied to the analysis of other natural source extracts.

The results from EPR studies of CVD diamond which was intentionally silicon doped with isotopes in natural abundance or isotopically enriched are reported. The observation of hyperfine satellites arising due to the presence of 29Si has provided definitive evidence for the involvement of silicon in two EPR centres in diamond which were previously suspected to involve silicon: KUL1 and KUL3. KUL1 is unambiguously identified as the neutral silicon split vacancy defect (V-Si-V)0, whilst KUL3 is shown to be (V-Si-V)0 decorated with a hydrogen atom. Data have also revealed that (V-Si-V)0 is preferentially oriented in samples grown on {110} substrates. The negative nitrogen-vacancy centre (NV‑) has been investigated. Published parameters for the nitrogen hyperfine interaction produce an unsatisfactory fit to the experimental spectra and hence these parameters are redetermined. Optically-excited EPR has been used to estimate the degree of spin polarisation of the NV-ground state and the increase in signal intensity with illumination has permitted the interaction between the unpaired electron and neighbouring 13C atoms to be studied. Two sets of 13C hyperfine satellites have been identified, which account for ~100% of the unpaired electron probability density. Despite the predictions that the neutral charge state of NV should have an S = ½ ground state, this charge state has not previously been detected by EPR. Optically excited EPR measurements reveal a trigonal nitrogen containing defect in diamond with an excited state populated via optical excitation. Analysis of the spin-Hamiltonian parameters and the wavelength dependence of the optical excitation leads to assignment of this state to the 4A2 excited state of NV0.

Defects in single crystal diamond grown by chemical vapour deposition (SC-CVD) have been studied using electron paramagnetic resonance (EPR) and optical techniques. Annealing studies in the temperature range of 900 - 1600°C have been performed and the changes in EPR and Fourier transform infrared (FTIR) spectra for nitrogen doped SC-CVD have been documented. It has been possible to model the annealing behaviour of several hydrogen related defects and the associated kinetics and annealing parameters have been determined. Previously unreported optical absorption lines have been detected in the as-grown and annealed nitrogen doped samples. FTIR spectroscopy has been performed in conjunction with an applied uniaxial-stress to investigate hydrogen related absorption features in diamond. Several absorption lines have shown to shift and split under the application of uniaxial-stress and the symmetry and stress-splitting parameters for these defects have been determined. Models for the defects responsible are proposed. The mid-infrared absorption line at 3123 cm-1 is suggested to originate from a C-H stretch mode at the paramagnetic negative nitrogen-vacancy-hydrogen complex. For a 3123 cm-1 absorption line with a Lorentz linewidth of 3.8(2) cm-1, 1 cm-1 of absorption at 3123 cm-1 corresponds to 25(10) ppm of NVH- centres. A previously unreported paramagnetic defect has been detected and is given the label WAR1. It has an S = 1 ground state and a pseudo-C3v symmetry; the g and D spin Hamiltonian parameters have been determined and suggest that the defect is vacancy related.

Radioactive radon gas, after being released from rocks, soils and building structures, can pose a significant health threat to the building occupants. This is of particular concern in tight HVAC (Heating, Ventilating and Air-Conditioning) serviced buildings where there is re-circulating air with limited fresh air intake. A thorough survey was initiated at the Hong Kong University of Science and Technology (HKUST) in 1996 and results indicate a radon average concentration of 107 Bq/m3, which is approximately 50% of the World Health Organisation's (WHO) recommended standard (200 Bq/m3). About 10% of the measurements were in excess of this WHO limit, while 46% of the samples also showed average peak radon concentrations (264 Bq/m3) in excess of this WHO limit. To overcome these elevated indoor radon concentrations, their characteristics at HKUST was studied. Radon level was found to increase linearly as a function of the length of the HVAC shut off period, and decrease exponentially upon system resumption. Radon level predictive models were developed after a series of room chamber experiments with modification factors defined to account for the indoor sinks in an effort to enhance the accuracy and applicability of the models. Following a campus-wide energy audit, two energy efficient radon management approaches were derived from the predictive models and were subsequently integrated into the existing HKUST operations. The first was defined as an Active Radon Control Approach (ARCA), where HVAC operation schedules were modified to yield an energy saving potential of around HK$2.7 Million a year. ARCA is optimised to reduce the radon dose to the HKUST occupants following the radiation protection principle of "As Low as Reasonably Achievable (ALARA)", and with considerations of economical and operational constraints. The other was a Passive Radon Control Approach (PRCA) using Polyurethane-based (P-u) paint to cover building material surfaces to reduce the radon emission.

The sponsoring company for this Engineering Doctorate is a manufacturer of passive fire protection materials with about 80 employees. Its primary products are specialist coatings that provide protection from the heat of a fire. Since it is essentially a chemical blending company its core technical skills have been in the chemical formulation of these products. The company employed the Research Engineer (R. E.) to help find new applications for its materials and widen its product range. It identified that domestic Liquid Petroleum Gas cylinders are potentially dangerous because they may explode when exposed to the heat of a fire. It determined to develop an enclosure to protect them from fire for 30 minutes using its fire resistant coatings. This project was conceived as a simple diversification, transferring existing company technology to a new market area. However, LPG cylinders are very sensitive to fire and require highly effective insulation from heat to make them safe. To meet the company specification, the R. E. developed a new composite fire insulation eight times as effective as the original solution, by combining one of the company's products with other materials. The effectiveness of the insulation and the enclosure design were proven by completely engulfing it in flame from a burning pool of aviation fuel. A series of these tests showed that the R. E.'s design reliably keeps LPG cylinders cool and safe for more than 30 minutes. This experimental work was assessed by the Loss Prevention Council who have based a new fire test standard on it. During the development process it became apparent that the capabilities required to manufacture an engineered product are quite different from those needed for the creation of new coatings and materials. This new product required a revolutionary advance in the company's approach to design, test methods and production technology. The R. E. has developed a new method of fire testing to provide heat flow data for use in computer models. This is now used to reduce the number of prototypes needed for testing and so compress development time. In order to manufacture the new product the R. E. has had to develop new ways of processing the company's materials. These new moulding techniques have delivered substantial improvements in finish and reduction in material wastage. The capability of the company to produce complex shapes from materials that are difficult to process has been greatly enhanced. Although the Gas Safe product itself has not yet achieved commercial success, the Engineering Doctorate programme has made a positive contribution to the company. In the last two years a number of interesting new projects have been undertaken that would have been impossible without the new engineering approach and production techniques. These are now beginning to show a return and several new products based on this work are under development.

Reported in this thesis are the results of a combined theoretical and experimental study into improvements to the solid adsorption refrigeration or heat pumping cycle using the ammonia-activated charcoal pair. The three areas which have been examined are the cycle thermodynamics, the porosity characteristics of ammonia-charcoal pairs and the heat transfer through an ammonia granular charcoal packed bed. It was found through the use of advanced thermodynamic cycles utilizing multiple beds that the coefficient of performance of a refrigerator could be increased by sv 250% and the coefficient of amplification of a heat pump could be increased by co 110%. The coefficients of performance and amplification may also be increased to a lesser degree by judicious choice of the charcoal porosity characteristics. A survey of charcoal porosity characteristics revealed that the useful energy per cycle could be doubled by the correct choice of charcoal. The thermal conductivity of an ammonia granular charcoal bed was measured using a novel piece of apparatus. From the results it was decided for all practical purposes that the bed conductivity may be considered constant and equal to 0.165 W/m K. The power output of the cycle was found from modelling the dynamic desorption of a reactor using a one-dimensional finite difference model set in radial coordinates. The cycle simulations revealed that ideally the reactor should be constructed from solid charcoal shapes manufactured in such a way as to incorporate paths of enhanced conductance and be integral with the containing vessel wall.

Silicon carbide (SiC), with its wide bandgap, high thermal conductivity and natural oxide is a substrate that has given rise to a new generation of power devices than can operate at high temperature, high power and high frequency, though the material is not without its problems. SiC "heterojunction devices" are layers of germanium (Ge) or silicon (Si) that are deposited via molecular beam epitaxy (MBE) or wafer bonded onto the SiC surface. These narrow bandgap thin films can provide a high mobility channel region overcoming SiC's crippling channel mobility, which is most often made worse by a high density of interface states. Concentrating predominantly on Ge/SiC heterojunctions, this thesis characterises the physical and electrical nature of these structures, investigating the rectifying properties of the heterojunction interface and the ability of these layers to support a depletion region. A physical analysis of the layers revealed that the Ge formed in an unexpectedly uniform fashion, given the large lattice mismatch involved. At a deposition temperature of 500oC the Ge initially clumped into wide, shallow islands before merging, forming at best a 300 nm polycrystalline layer with a surface roughness of only 6 nm. This was in contrast to MBE deposited Si/SiC layers that formed tall islands that at 1 μm thick, still had not merged. After being formed into Ge/SiC heterojunction diodes they were electrically characterised. The layers displayed near ideal (η = 1:05) turn-on characteristics, low turn-on voltage (approximately 0.3 V less than Ni/SiC SBDs), reasonable on-resistance (12 m­Ωcm2) and minimal leakage current. The devices were shown to suffer severe Fermi level pinning that defined the way the materials' bands aligned. This occurred as a result of an inhomogeneous interface that also caused fluctuations in the size of the Schottky barrier height across the interface. New characterisation techniques relating to these phenomena were applied to a heterojunction for the first time. MBE formed Ge/SiC layers and wafer bonded Si/SiC layers were formed into MOS capacitors through the deposition of the high-K dielectric hafnium oxide (HfO2). The increased conduction band offset between oxide and narrow bandgap semiconductor suppressed leakage problems often seen in HfO2/SiC structures. Capacitance-voltage results showed that they could both support a depletion region, though the best results came from the MBE Ge/SiC diodes. Current-voltage results showed that the more uniform Si/SiC devices could block 3.5 MV/cm.

The wide-scale usage of VOCs in industrial processes requires monitoring the concentrations of these vapours to keep a safe operating environment. Most combustible hydrocarbons can be ignited as a gas-air mixture in the range of 0.5% to 15% by volume. This has led to the development of several portable air quality monitoring instruments. However, the high costs and lack of durability of these instruments has remained an issue to be addressed. This PhD thesis reports on the development and characterization of a novel low cost smart gas sensor technology adaptable for use in a portable instrument. The smart gas sensor devices have been developed to target four different VOCs in air. The smart gas sensor device combines a smart ASIC (SRL 194 designed at SRL, Warwick University) fabricated in standard 0.7 μm CMOS technology and two alkyl-dithiol based self-assembled gold nanoparticle chemoresistive sensors (fabricated at Sony Deutschland GmbH) in a ratiometric array to offer a robust system which can address the common mode variations found in polymer based gas sensor systems. The ratiometric ASIC sensor array architecture allows for the reduction of the baseline value’s dependence on environmental variations and the elimination of baseline drift due to long term application of DC voltage. Three ratiometric array arrangements - mono-type uni-variate with only one chemosensor per device, mono-type bi-variate with two chemosensors of the same film material per device and duo-type with a polar and a non-polar chemosensor per device and their variations were characterized in an automated FIA test station against exposure to methanol, ethanol, propan-1-ol, and toluene at 30°C and 0-5% rh. It was determined that the devices’ response output to VOC analytes was entirely dependent on the variation of the resistance ratio of the chemoresistive sensors in the ratiometric sensor array. The effects of variations of the temperature and rh on the smart sensor output were calibrated. The mono-type devices gave a high magnitude response to the vapours whereas the duo-type arrangement offered a high degree of discrimination between the test analytes with little post-processing steps. Three different alkyl-dithiol chemoresistive sensor films on gold electrodes were successfully used as the VOC vapour sensitive elements in each arrangement. The effects of using a silicone sealant gel as a partitioning layer were characterized and it was observed that at vapour concentrations less than 3000 ppm the silicone encapsulated chemosensor devices reported a larger response to the VOC analytes as compared to those without the silicone. The test devices reported promising response repeatability and reproducibility with excellent return to baseline properties, a negligible hysteresis and an error margin of under 10%. Ideal operating temperature was determined to be 40°C at which rh variations were found to be minimal. The test devices were found to be robust with little variation in the quality of the device output over the course of 18 months. The novel research demonstrated that it is possible to get high level of diversification between analytes from a low cost and robust gas sensor system for monitoring VOCs. The work carried out here has opened the opportunity to develop highly integrated programmable hand-held gas sensor and e-nose systems for environmental monitoring use in health and safety applications.

Ultraendurance mountain bike racing is a relatively new sport and has received scant research attention. The practical difficulty of field-testing during competition has played a role in this dearth of knowledge. The purpose of this thesis was to investigate the physiology and bioenergetics of cross-country marathon (XCM) and 24 hour team relay (24XCT) mountain bike racing. Study One analysed the physiological characteristics of XCM competitors and compared them to data from studies in the literature for Olympic-distance cross-country (XCO) mountain bike competitors. The XCM participants had lower mean peak aerobic capacity (58.4 ± 6.3 mL•kg-1•min-1), greater body mass (72.8 ± 6.7 kg) and estimated percentage body fat (10.4 ± 2.4%) compared to values reported for XCO competitors in the literature. Stature (1.77 ± 6.0 m) and normalised peak power output (5.5 ± 0.7 W•kg-1) were comparable. These data suggest that specific physiological characteristics of XCM competitors differ from those of XCO competitors. Study Two quantified and described the exercise intensity during a XCM race by monitoring heart rate responses. The mean heart rate (150 ± 10 beats•min-1) for the duration of the race equated to 82 percent of maximum heart rate and did not differ significantly throughout the race (p = 0.33). The data indicated that the XCM race was of a high aerobic intensity. Prior to the competition the relationship between heart rate and O2peak for each participant was established during an incremental laboratory test. Energy expenditure was estimated by assigning 20.2 kJ to each litre of oxygen consumed. The mean rate of energy expenditure during the race was estimated to be 59.9 kJ•min-1. Furthermore, no anthropometric or physiological measures were correlated to race speed, indicating that other factors contribute to race performance. The third study was a laboratory-based investigation to determine whether physiological factors relevant to 24XCT racing change with time of day. On separate days participants cycled on an ergometer for 20 min at 82 percent of maximum heart rate at 06:00, 12:00, 18:00, and 00:00 h. Significant differences (p < 0.05) were observed for several physiological responses (heart rate, oxygen uptake, salivary cortisol concentrations and intra-aural temperature) but not for performance variables (power output and self-selected cadence). It was concluded that the laboratory protocol lacked ecological validity and that it was necessary to test within a race using authentic 24XCT competitors. In order to measure in-race performance, Study Four examined the agreement between a bottom-bracket ambulatory ergometer (Ergomo®Pro) and the criterion SRM power meter in a field-based setting. Analysis of absolute limits of agreement found that the Ergomo®Pro had a systematic bias (± random error) of 4.9 W (± 6.12). Based on tolerances recommended in the literature the unit was considered fit for purpose for measuring power output during 24XCT racing. Study Five was a multiple case-study design that examined the physiological and performance parameters of a team during a 24XCT race. It was reported that mean work-shift speed (18.3 ± 2.6 km•h-1), power output (219 ± 50.9 W) and cadence (64.1 ± 9.3 rpm) were variable between participants and between work-shifts. A commonality amongst the participants was an increase in speed during the final work-shift compared to the penultimate one. A decline in work-shift heart rate was observed throughout the race. For the majority of participants an increase in gross efficiency (1.7 ± 1.4 %) was reported from the penultimate to the final work-shift. It was concluded that pacing strategies were employed and that the improved efficiency was caused, in part, by an increased familiarity with the course during the race. Study Six examined the nutritional practices and energy expenditure of the same team during the same 24XCT race. Energy expenditure during the work-shifts was estimated in accordance with Study Two. Resting energy expenditure during the recovery periods was estimated using the Harris and Benedict formula (1919). Food and fluid consumption were determined via food diaries and hydration status was assessed by measuring the refractive index of urine. Energy consumption (17.3 ± 2.2 MJ) was considerably less than energy expenditure (30.4 ± 6.1 MJ) with the former accounting for only 57 percent of the latter. The energy cost during the work-shifts was estimated to be 74.5 kJ•min-1. Mean fluid intake (6.3 ± 0.9 L) for the 24 h was sufficient to maintain hydration status. Based on these studies an integrated model of the factors that influence ultraendurance mountain bike performance was developed. The domains that influence race speed are physiological factors, technical and tactical factors, and nutritional strategies. The sub domain that influences these is environmental factors. Collectively this information is of practical importance to sport scientists, coaches and athletes involved with designing nutritional and tactical preparation strategies and training programmes for this sport.

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