Regions of surface water and groundwater exchange are major sites for the transfer and transformation of solutes and nutrients between stream and subsurface environments. Conventional stream and groundwater exchange investigations are limited by methodologies that require intensive field investigations and/or the set-up of expensive infrastructure. These difficulties are exacerbated where hydraulic gradients are very low and stream discharge highly variable. This thesis uses a suite of environmental tracers (Cl-, Rn-222, H-2 & O-18, Sr-87/Sr-86) to characterise the extent of stream and groundwater exchange between a sand bed stream and adjacent alluvial aquifer in a subtropical catchment (the Wollombi Brook) of eastern Australia. The aims were to identify sources and relative contributions of different sources of groundwater to stream discharge and specifically to improve the methodology of using Rn-222 to obtain quantitative estimate of groundwater fluxes. The sensitivity of the Rn-222 technique for identifying groundwater discharge based on the Rn-222 concentration in stream water was improved via an iterative numerical approach to account for Rn-222 loss from stream water via turbulent gas exchange and radioactive decay. Optimal distances between stream sampling points for defining the magnitude of groundwater discharge to stream flow based on Rn-222 concentrations in stream water is a function of average stream velocity and water depth. The maximum allowable distance between sampling points for determining the magnitude of groundwater discharge to the Wollombi Brook was 2 km. This work showed that groundwater discharged to all reaches of the Wollombi Brook during baseflow and flood recession conditions. Alluvial groundwater contributed less than 30% of water to stream flow in the mid Wollombi Brook catchment. Dilution of steady-state Rn-222 concentrations measured in transects from the stream to the alluvial sediments showed that significant surface water and groundwater exchange occurs even when gradients between surface water and groundwater are low. Lateral stream water influx to the adjacent alluvial aquifer was more extensive in the lowland areas of the Wollombi Catchment during low flow than flood recession conditions. Extensive stream water influx to the adjacent alluvial aquifer occurs contrary to the net direction of surface water and groundwater flux (as indicated by hydraulic gradients toward the stream channel). The rate of stream and groundwater exchange within the adjacent alluvial aquifer appears to be greatest during baseflow conditions. Fresh alluvial groundwater appeared to provide a buffer against higher salinity regional groundwater discharge to the alluvial aquifer in some reaches of the Wollombi Brook catchment. Pumping of the alluvial aquifer and diversions of surface water may jeopardise the water quality and volume of the alluvial aquifer and induce water flow from the regional aquifer toward the stream, potentially salinising the fresh alluvial aquifer and subsequently the stream. The change in the Cl- concentration and the variation in slope of the deuterium � oxygen-18 line between consecutive stream sampling points could be used to differentiate between regional and alluvial groundwater discharge to stream flow. Incorporating this information with three-component end-member mixing using [Sr2+] and Sr-87/Sr-86 showed that stream and alluvial groundwater exchange within the stream channel was highest in the lowland floodplains during low flow conditions. The least stream and alluvial groundwater exchange occurred in the low streambed gradient mid reaches of the Wollombi Brook regardless of stream stage. The greatest difference in the degree of stream and alluvial groundwater exchange between high and low stream stages occurred in the lowland floodplains of the Wollombi Brook.

Reliability based life cycle cost analysis is becoming an important consideration for decision-making in relation to bridge design, maintenance and rehabilitation. An optimal solution should ensure reliability during service life while minimizing the life cycle cost. Risk of failure is an important component in whole of life cycle cost for both new and existing structures. Research work presented here aimed to develop a methodology for evaluation of the risk of failure of reinforced concrete bridges to assist in decision making on rehabilitation. Methodology proposed here combines fault tree analysis and probabilistic time-dependent reliability analysis to achieve qualitative and quantitative assessment of the risk of failure. Various uncertainties are considered including the degradation of resistance due to initiation of a particular distress mechanism, increasing load effects, changes in resistance as a result of rehabilitation, environmental variables, material properties and model errors. It was shown that the proposed methodology has the ability to provide users two alternative approaches for qualitative or quantitative assessment of the risk of failure depending on availability of detailed data. This work will assist the managers of bridge infrastructures in making decisions in relation to optimization of rehabilitation options for aging bridges.

Clinical studies reported side effects of muscular spasms and muscle stiffness following the administration of clofibrate, a drug once used to treat hyperlipidaemia in patients. Experiments with clofibrate and its analogues in animal models showed it produced these myotonic symptoms in muscle by reducing the chloride conductance of the muscle membrane. The effects of 2-(4-chlorophenoxy)propionic acid, an analogue of clofibric acid, was assessed on the rat ClC-1 channel (rClC-1). Racemic 2-(4-chlorophenoxy)propionic acid shifted the voltage dependence of rClC-1 activation to more depolarising potentials, a mechanism accounting for myotonic symptoms previously reported. Experiments with resolved enantiomers revealed that the effects recorded were due exclusively to S-(–) 2-(4- chlorophenoxy)propionic acid. The R-(+) enantiomer was ineffective at the concentrations tested. Further experiments with the compound at differing Cl- concentrations in the extracellular solution suggested that S-(–) 2-(4-chlorophenoxy)propionic acid altered the gating of ClC-1 by decreasing the affinity of the binding site where Cl- normally acts to ‘gate’ the channel. Similarities in the effects reported for most dominant mutations in the CLCN1 gene that lead to myotonia congenita and 2-(4-chlorophenoxy)propionic acid prompted experiments that introduced these point mutations in the human ClC-1 (hClC-1) gene to compare their mode of action to that of the drug. These mutations, F307S and A313T, predominantly altered the slow, or common, gate of the channel. Conversely, the effect of 2-(4-chlorophenoxy)propionic acid was predominantly on the fast gating process of hClC-1. A macroscopically similar effect therefore, can be produced by two different modes of action. Results suggested that both drug and mutations exert their action by affecting the transition of the channel from its closed to open state subsequent to Cl- binding. Investigation of the interaction between rClC-1 gating and a further 25 compounds structurally related to clofibric acid identified a number of compounds effective at shifting the open probability of fast gating to depolarising potentials. Fewer were identified that influence slow gating. Some compounds affected both gating processes, however, none were identified which influenced slow gating alone. Ability to displace the voltage dependent activation of the fast gate appeared to depend largely on the lipophilicity of the molecules tested, indicating the importance of hydrophobic interactions between drug and channel protein. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1474724 / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2009

Some ill. mounted. Bibliography: leaves 106-118.

Dans les bassins versants reposant sur un socle géologique peu perméable et peu profond, les nappes superficielles de versant jouent un rôle prépondérant non seulement dans la genèse des débits mais également dans le transfert des solutés. Ces nappes, caractérisées par de fortes variations saisonnières des niveaux piézométriques, se développent dans un matériau aquifère constitué principalement de roche altérée et de matériaux non consolidés dont les propriétés hydrodynamiques restent peu étudiées. La connaissance du fonctionnement hydrologique et hydrochimique de ces systèmes, des processus qui déterminent les voies de transfert des solutés et leur temps de résidence dans le milieu, est essentielle en particulier dans un contexte où la recherche est de plus en plus sollicitée pour évaluer les effets de changements de pratiques agricoles sur les pollutions diffuses. Le travail présenté ici vise à comprendre les processus de transfert de solutés et de dénitrification dans les aquifères superficiels à partir de l'étude d'un aquifère d'un bassin versant élémentaire expérimental de l'ouest de la France, appartenant à l'ORE AgrHys. L'analyse repose sur les données acquises sur un dispositif instrumental original permettant un suivi spatial et temporel du niveau de la nappe et de sa composition chimique sur un versant. Les propriétés hydrodynamiques du matériau aquifère ont été étudiées au laboratoire et in situ, ce qui a permis de calibrer un modèle hydrologique à base physique et en 2D (développé avec le code Hydrus 2D) simulant de manière satisfaisante la dynamique saisonnière des niveaux piézométriques dans le versant. Les relations mises en évidence entre le cycle hydrologique et les variations intra-annuelles de la composition chimique, nous permettent de proposer un modèle conceptuel synthétisant les mécanismes mis en jeu dans le transfert d'un soluté conservatif dans la nappe. Une étude de la variabilité spatiale et temporelle de la composition isotopique de l'azote et de l'oxygène du nitrate n'a pas révélé la présence d'une dénitrification apparente dans l'aquifère. Enfin, un modèle de transport des solutés basé sur le modèle hydrologique calibré précédemment a permis de tester les hypothèses émises à partir des données expérimentales. La principale conclusion de ce travail est que les nappes superficielles de versant présentent une variabilité spatiale et temporelle importante, qui résulte de processus de mélange à partir de compartiments dont la contribution varie saisonnièrement. En période hivernale, la recharge rapide des nappes par des écoulements préférentiels joue un rôle important dans les variations de composition chimique de la partie supérieure de la nappe, ce que la plupart des modèles actuels ne permettent pas de prendre en compte.

<p>SiC is an attractive material since it has remarkable properties. For several years efforts have been put primarily in electronic applications. High power and high frequency devices can be fabricated on SiC due to its wide band gap, high breakdown field and high thermal conductivity. SiC devices can be used in harsh environment since its operation temperature is significantly high (about 1200 ). SiC bulk growth has been improved by seeded physical vapour transport (PVT) during last decades. However, the quality and doping concentration of SiC bulk are not good enough to be used as an active layer for devices. SiC epilayer growth by chemical vapour deposition (CVD) was established in the last three decades. Only about 5 µm/h growth rate is achieved by CVD with a standard process. Long deposition time is required to grow ≥100µm thick epilayer for high voltage devices. The main problem in standard CVD is the formation of silicon (Si) droplets due to supersaturation of Si-species on the growth surface or in the gas-phase, which is detrimental for devices performance. To solve the problem of Si-droplets, chloride-based CVD was introduced. Chlorinated species can dissolve the silicon aggregates through the formation of strong bonds to silicon species compared to Si-Si bonds. Typical chlorinated precursors are hydrogen chloride (HCl) and methyltrichlorosilane (MTS). In this thesis study, HCl was mainly used as chlorinated precursors. Distinct chlorinated precursors result in different chemical reactions which affect the epilayer growth appreciably. The Cl/Si ratio, which is the ratio of the amount of chlorinated precursors to silicon precursors, is a very critical growth parameter for morphology, growth rate and background doping concentration. The C/Si ratio and Si/H₂ ratio also affect the epilayer growth appreciably. Besides, growth temperature, growth pressure and temperature ramp up condition are other important growth parameters. In the CVD reaction chamber, the temperature profile and gas species distribution are not uniform along the whole susceptor length, which leads to different thickness of epilayer, morphology and doping concentration at different area of the reaction chamber. The polarity and off-angle of substrates can bring about complete different grown epilayers. Epitaxial defects are mainly replicated from the substrate. Therefore, the quality of substrates is very important as well. Deep energy levels can be introduced by adding transition metal such as vanadium (V), chromium (Cr) or tungsten (W). There are some limits which are needed to be overcome for a complete development of SiC. 4” SiC wafers are commercially available on the market, larger diameter would be very useful for the industrial development of SiC. High growth rate and good quality with controlled uniformity are desired for electronic applications. In this thesis, the influences of growth parameters such as C/Si and Cl/Si ratios, comparison between different precursors, growth condition in different areas of reaction chamber and effects of substrate polarity are discussed. Intentional incorporation of tungsten atoms is investigated by deep-level transient spectroscopy measurement and thermodynamic analysis.</p>

<p>The hypothetical assumption that chloride is conservative in the soil has been debated for the last decade. The results of the recent years of study in chlorine biogeochemistry show that chloride is non-conservative but rather participates in complex biogeochemical reactions in the soil. These interactions in nature inform the development of simplified hydrochemical model of chloride dynamics in the soil that is driven on soil routine component of HBV hydrological model. This novel attempt affords the opportunity to explore chlorine biogeochemistry further by evaluating the biological processes such as microbial biomass that predominate chlorine cycles in the same order of magnitude as earlier studied abiotic factors. Data from soil lysimeter experiment with different inputs treatments were used in the calibration and validation of both the hydrological and biogeochemical model. The results show that (1) model efficiency reduces with decreasing water residence and with increasing soil organic matter. (2) Longer water residence time (low water input), high chloride and high nitrogen input loads relatively enhance maximum biomass accumulation in a shorter time span. (3) Chloride retention time reduces with increasing chloride loads under short water residence. (4) Microbial biomass growth rate is highest under high chloride input treatments. (5) Biomass death rates shows reducing trend under short water residence (High water input). Further researches are therefore suggested for possible model expansion and to make the results of this model plausible under field conditions.</p>

Laboratory and modeling studies were performed with a mixed-anaerobic-culture obtained from the Evanite site in Corvallis, Oregon. The culture completely transforms trichloroethene (TCE) to cis-dichloroethene (c-DCE), vinyl chloride (VC), and finally to ethene. Acetylene inhibition studies were used to examine the culture's microbial activities. Kinetic studies determined the half-saturated constant (K[subscript s]), the maximum utilization rate (k[subscript max]X), and inhibition constants (K[subscript I]). The kinetic constants were used to model the results of inhibition studies using competitive and uncompetitive inhibition models. Acetylene was found to function as a reversible inhibitor and was used to probe the activities of reductive dechlorination. Various acetylene concentrations were used to differentiate microbial processes, including methanogenesis, acetogenesis, and halorespiration. Acetylene concentrations of 48, 192, and 12 ��M, respectively, were required to achieve 90% inhibition in the rates of methanogenesis, TCE and VC transformation. H���-dependent acetate production was not inhibited by acetylene. K[subscript s] values for TCE and VC were 12 ��M and 63 ��M, respectively. Model fitting of acetylene inhibition constants (K[subscript IC]) for TCE and VC transformations yielded the same value (0.4 ��M) for a competitive inhibition model. However, for uncompetitive inhibition the estimated K[subscript IU] for TCE to c-DCE, TCE to 1,1-DCE and VC to ethene were 13.3, 14.1 and 2.2 ��M, respectively. Competitive and uncompetitive inhibition models simulated experimental data equally well for results obtained at high TCE and VC concentrations. The models were further verified to fit transient data of acetylene inhibition at lower TCE and VC concentrations, and competitive inhibition resulted in a better fit to the experimental data. 1-chloro-1-fluoroethene (1,1-CFE) was found to track the rate of VC transformation well, since VC and 1,1-CFE had similar maximum transformation rates and K[subscript s] values. A competitive inhibition model with the measured K[subscript s] values, 63 and 87 ��M. was used to predict the rates of VC and 1,1-CFE transformation, respectively. The similar rates and results of acetylene and compound inhibition studies indicated VC and 1,1-CFE were transformed by the same enzyme. 1,1-CFE transformation by three different cultures, clearly demonstrate that 1,1-CFE was an excellent surrogate to track rates of VC transformation. / Graduation date: 2004

The currently accepted method for assessing the resistance of concrete to penetration of chloride ions is ASTM C1202, commonly known as the “Rapid Chloride Permeability (RCP) Test.” The test is time-consuming, laborious, has rather high variability, and, is to a degree, user sensitive, making it problematic for inclusion in a performance-based specification. A potential alternative to the RCP test is the “Surface Resistivity (SR) Test”, a method which is dramatically easier, faster, and has less variability than the RCP test. The research reported herein was directed toward determining a correlation between RCP and SR test measurements for Tennessee bridge deck concrete, based on cylinders collected from concrete bridge decks being constructed across the state, and evaluating the appropriateness of the SR test as an alternative to the RCP test for inclusion in a performance-based specification. Results of the testing showed a clear correlation between the two methods and identified potential limits for possible inclusion in a performance-based specification.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 132-142.