As fundamental components of chalk stream ecosystems, aquatic macrophytes are intrinsically linked to flow regime and physicochemical stability. Assessment of the River Itchen, Hampshire, a classic lowland chalk stream faced with ecosystem degradation, indicates the significance of the discharge regime for controlling both water quality and the spatiotemporal distribution of macrophyte assemblages. Experimental studies using outdoor artificial stream mesocosms signify their effectiveness for macrophyte growth studies and in identifying causality attributed to environmental stressors. In such experiments, the keystone chalk stream macrophyte Ranunculus pseudofluitans was identified as having preferences to moderate water velocities, with morphological and physiological trait responses causing distinct morphotypes depending on development in optimal or sub-optimal conditions. Furthermore, when subjected to flow, nutrient and periphytic competitive stressors, main trait responses were categorised as developmental, functional and confounded, respectively, with most traits linked to healthy development associated with flow. In addition, significant filamentous algal growth under low-nutrient conditions, but removal in increased velocities, highlights the importance of flow as a control mechanism. Examination of ontogenetic effects suggest trait variation with age, and overall developmental stage linked to a combination of environmental and plant age effects. This study demonstrates the necessity for good, consistent flow regimes in chalk streams, which enhances macrophyte community diversity, promoting development of keystone taxa, which in turn encourage beneficial heterogeneous flow patterns.

Nanoscale silver particles represent a new generation of cost-effective antibacterial technologies. Due to the increased manufacturing and use of silver nanoparticles (Ag NPs) in consumer goods their release and accumulation into the environment is highly likely but their fate, behaviour and toxicity to organisms is still very much unknown. The present study has investigated the effect that different environmental conditions have on the behaviour and fate of Ag NPs in waters by determining aggregation state, stability and solubility. This work has also determined their interaction and uptake to laboratory grown planktonic and biofilm bacteria, as well as to natural marine biofilms using analytical, electron microscopy and molecular tools. The outcomes of this work describe the effects that environmental factors such as pH, ionic strength and presence of humic substances (HS) have on the stability, behaviour and ultimately fate of Ag NPs in water, with direct implications on bioavailability of NPs to organisms. Higher pH values as well as the presence of organic of matter in the media increased stability and with this the residence time of the particles in suspension. On the other hand, pH values of 6 and also absence of organic matter increased the precipitation of NPs in suspension. Planktonic Pseudomonas fluorescens was highly susceptible to Ag NPs when grown and exposed at pH 9 only. However, toxicity was also mitigated when natural organic matter (HS) was present. Due to the low solubility of the Ag NPs in the media a NP-mediated toxic mechanism is suggested as the mode of toxicity of Ag NPs to planktonic P. fluorescens cells. Environmental parameters were also crucial for the uptake and interaction of Ag NPs to 3-d old Pseudomonas putida biofilms. Ag NPs were uptaken by the cells under all conditions, and decreased biofilm biovolume per surface area when HS were not present. With HS, Ag NPs did not significantly affect biomass; however uptake of Ag NPs doubled under this condition. Ag NPs in suspension had an effect on a natural marine biofilm community. A dosedependent decrease on biomass was recorded, but more importantly Ag NPs stopped biofilm succession and development and/or settling of new taxa on the resident biofilm community. Critical characterisation of Ag NP behaviour under different conditions is crucial for determining which organisms are more likely to interact with Ag NPs in different environmental compartments, and assess the possibility of longer term exposures. This work provides relevant information on the fate and toxicological effects of a short term exposure of Ag NPs to bacterial cells in an aqueous environment, with possible implications on their bioaccumulation and food web transfer.

Producing reliable estimates of changes in precipitation at local- and regional-scales remains an important challenge in climate change science. Statistical downscaling methods are often utilised to bridge the gap between the coarse resolution of General Circulation Models (GCMs) and the higher-resolutions at which information is required by the majority of end users. However, the skill of GCM precipitation, particularly in simulating temporal variability, is not fully understood and statistical downscaling typically adopts a ‘Perfect-Prog’ (short for perfect prognosis) approach in which the derivation of high-resolution precipitation projections is based on real world statistical relationships between large-scale atmospheric ‘predictors’ and local-scale precipitation. Here, a ‘nudged’ simulation of the ECHAM5 GCM is conducted in which the large-scale climatic state is forced towards historical observations of large-scale circulation and temperature for the period 1958-2001. By comparing simulated and observed precipitation it is possible to, for the first time, quantify GCM skill in simulating temporal variability of precipitation. Correlation between simulated and observed monthly mean precipitation is shown to be as strong as 0.8-0.9 in many parts of Europe, North America and Australia. A nudged simulation permits the development of an alternative approach to statistical downscaling, known as Model Output Statistics (MOS), to correct precipitation as simulated by ECHAM5. It is also shown that MOS correction offers greater skill than Perfect-Prog methods when estimating local-scale monthly mean precipitation. The strongest-performing MOS models are applied to ECHAM5 climate change simulations and are shown to produce high-resolution precipitation projections that support those of RCM simulations. The potential for extending the MOS approach to daily precipitation is also assessed, with recommendations made for further research and application.

An ecological and chemical analysis of eight Welsh streams impacted by mine drainage is used to discern the effects of water and sediment related variables and elucidate the most important variables in the impact of mine pollution on freshwater macroinvertebrate communities. The implications of this are to be considered for improving mine water remediation techniques and work towards the achievement of the environmental objectives set by the EU Water Framework Directive (WFD). Streams impacted by coal and metal mine drainage present a clear ecological impact in response to water and sediment related variables, demonstrating that both sediment and water are key aspects in mine drainage pollution of freshwater ecosystems. However, the WFD does not include metal concentration guidelines for sediments, neither has the UK set mandatory standards for them, and sediments are not currently being routinely monitored or remediated in the UK. To achieve the environmental objectives set by the WFD, the Coal Authority and the Environment Agency are constructing several engineered wetlands in the UK to treat mine drainage. One of these constructed engineered wetlands was seen to successfully remediate mine water removing trace metals and suspended solids and increasing pH and dissolved oxygen. However, the remediation scheme seemed to fail to improve the electrolyte status of the water and stream sediment quality. As a result, the benthic community in the receiving stream appeared to have a poor recovery.

Climate change is projected to increase the frequency and severity of extreme events, adding to the plethora of existing pressures that streams and rivers already face. Compound events such as drought may comprise numerous stressors that occur in concert to elicit ecological change. However the causal mechanisms of such impacts remain unknown, and research attempting to disentangle impacts of compound events, or link effects across levels of ecological organisation, remains in its infancy. This research investigates impacts of key drought stressors –sedimentation, dewatering and warming – across multiple ecological, hierarchical levels. At the individual level, macroinvertebrates displayed differential thermal sensitivity to warming which may explain idiosyncratic ecological responses reported elsewhere, whilst sedimentation intensified predator-prey interactions. Mesocosms were effective tools for studying drought stressors independently and in combination at the community and functional level. Dewatering main effects reduced the density of a common taxon and functional feeding group biomass, whilst all three stressors sometimes interacted together in complex ways. Stressors also had quantifiable effects at the whole-system level, e.g. stream metabolism. This study provides initial findings pertaining to drought impact causative mechanisms across multiple levels of ecological complexity, highlighting the importance of an experimental approach to predict future effects of compound events.

During the early Palaeogene warm interval megathermal climatic regimes expanded beyond their current tropical limits. The early Palaeogene sporomorph (pollen and spore) record of the US Gulf Coastal Plain (GCP) documents an extra-tropical vegetation type that developed under these megathermal climatic conditions. It is therefore suitable to address hypotheses concerning the importance of tropical climates in controlling low latitude spatial and temporal diversity patterns. Here, I construct a new sporomorph dataset comprising 151 samples, 41831 counted specimens and 214 sporomorph morphotypes. Fifty-nine of these morphotypes were not found in the published literature and are newly described. I demonstrate that previous studies of the GCP sporomorph record that have relied on biostratigraphic datasets have underestimated the true species richness of this region. Compositional heterogeneity was important for maintaining regional species richness on the GCP. The rate and scale dependency of spatial turnover in Holocene tropical and extra-tropical sporomorphs records precluded associating the GCP vegetation more closely with any particular modern biome, however. Finally, I show that warming extra-tropical regions to megathermal levels did not stimulate increased speciation there, which does not support a direct control of temperature on speciation rate in the low latitudes.

The effect of Ni and Ni(Pt) alloy with ~5 and 10 at. % Pt on the agglomeration and Ge out-diffusion in Nickel germanosilicide formed on Si₀.₇₅Ge₀.₂₅(100) has been studied. A remarkable improvement in the agglomeration behavior with increasing Pt atomic percentage is observed by sheet resistance measurements and scanning electron microscopy (SEM). In addition, x-ray diffraction (XRD) shows that only NiSiGe or Ni(Pt)SiGe phase exists from 400 to 800°C. However, Ge out-diffusion from the monogermanosilicide grains is obvious at 600°C and 700°C for Ni/SiGe and Ni(Pt)(Pt at.%~10%)/SiGe, respectively, evident by XRD and micro-Raman spectroscopy. The improved melting temperature of Ni(Pt)SiGe solution compared to that of NiSiGe is the likely reason of seeing better surface morphology and suppressing Ge out-diffusion of the germanosilicide grains observed. / Singapore-MIT Alliance (SMA)

In our thesis, we develop a modified fabrication method based on Ge condensation mechanism to fabricate SGOI (SiGe-on-insulator) Wafer. The advantages of this technique are as follows; (1) Low fabrication temperature. (2) Smooth SiGe/SiO2 interface without using CMP and good crystal quality. (3) Better gate dielectric layer quality by dry oxidation. In our experiment, we use silicon wafer rather than the SOI wafer to avoid cost because of the high price of the SOI wafer. First, a 700Å Si0.85Ge0.15 layer was grown on a thin SOI layer. The Ge atoms were rejected from the oxidized layer and pushed into the remaining SiGe layer by using dry oxidation at 925¢J. Since it has been confirmed that the total amount of the Ge atom in the SGOI layer is conserved, the Ge fraction can be varied from 15% to 35%. During the fabrication procedure, we use semiconductor measurement instruments like AFM /SEM /Raman spectroscopy to verify the SiGe layer quality and built complete parameters database. Then we make two different structure Si/SiGe heterojunction MOS capacitors on this wafer to verify the necessity of the Si cap layer to SGOI substrate. According to the experiment results, we can find the device with Si cap layer has better performences than the one without Si cap about 10% ~ 20% in electric characteristics. Based on the experiment results, it is proved that a high quality SGOI wafer on the SOI wafer can be fabricated.

Taphonomy `the study of processes of preservation and how they affect information in the fossil record' (Behrensmeyer and Kidwell, 1985) is an important geological discipline. This study, by incorporating experiments on carbonate transplanted to shallow water with benthic sampling, explored the relationship between the calcimass of living and dead (sub-fossil) constituents of a deep water brachiopod-bivalve community in the Firth of Lorn (site 1. of Curry, 1982). The community, which occurs on a gently sloping sea floor at depths between 160 and 200m, was investigated by dredging, grab sampling, coring and video transects. Biomass and calcimass of the community were determined indirectly from regressions of shell length against weight on animals collected from 10 grab samples. The large endobyssate bivalve M. modiolus, which forms large stable clumps modifies the sediment by introducing `secondary hardbottom' (sensu Surlyk, 1972) into an otherwise soft sediment. The valves of living M. modiolus serve as substrate for a diverse epifauna, the most distinctive member of which is the articulate brachiopod Terebratulina retusa. The standing calcimass (2370.5 g/m2/yr) and carbonate production (excluding polychaetes, bryozoans and barnacles) of the community is very high (330 g/m2/yr) which in the absence of carbonate destruction would result in a rate of autochthonous carbonate accumulation in excess of 1 mm/yr. M. modiolus contributes 93.5% of the standing calcimass, but accounts for only 37.8% of estimated production (mainly due to a lifespan estimated at 40 years). Three other species, the ophiuroid Ophiothrix fragilis, the bivalve Astarte sulcata and the articulate brachiopod Terebratulina retusa together contribute an additional 58.5% of carbonate production. Length-frequency histograms of 0-year class T. retusa from seasonal samples suggest that growth rate is initially slow (an increase in length from 0.212 mm to 0.539 mm over the first 260 days). Similar rates have been published from laboratory studies (Rickwood, 1977; Stricker and Read, 1985) but growth rate is well below that estimated from conventional length-frequency histograms (eg. Curry, 1982) or field studies (Thayer, 1977; Doherty, 1979). Autecological implications of a strongly sigmoidal growth curve were investigated by examining substrate related mortality. Larval T. retusa appear non-selective in their choice of substrate and although virtually all adult T. retusa are attached to mature M. modiolus, 35 alternative substrates were recorded. Patterns of substrate utilization suggest that from a length of approximately 2 mm to maturity there is an increase in the proportion of T. retusa attached to the surface of M. modiolus, indicating that alternative substrates (eg. hydroid thecae, ascidian tests and calcareous worm tubes) are more liable to fail as the Terebratulina mature. At lengths below 2 mm the surface of M. modiolus appears to be sub-optimal, the proportion of Terebratulina utilizing this substrate falling from approximately 80% of settlement to 40% at lengths of between 1.7 & 2.8 mm. It is postulated that grazing pressures, believed to be restricted to this substrate (Akpan, 1981) may account for this inflection at lengths of approximately 2.3 mm grazers being unable to disloge brachiopods above this critical size. Estimates of carbonate production were compared with the composition of biogenic carbonate from > 4 mm, > 2 mm, and > 1 mm sediment fractions of grab and box core samples. Ophiothrix fragilis and Amphiura chaijei which together were estimated to contribute 31.6% of total carbonate production accounted for only 0.5% of autochthonous carbonate in these fractions. Even accounting for the concentration of ophiuroid debris in the finer fractions, the absence of ophiuroid debris is remarkable. Excluding ophiuroid debris and the two most minor autochthonous carbonate contributors, reveals an apparent trend in the remaining autochthonous carbonate towards selective preservation bias of smaller items. These trends were not seen in field experiments of relative rates of abrasion and laboratory studies of relative dissolution rates of the major carbonate components. Furthermore, estimated rates of destruction by abrasion were very low and S.E.M. examination of grains recovered from the death assemblage did not show evidence of dissolution. This size related bias may therefore provide evidence of the consequence of selective bioerosion of non-agitated grains first proposed by Boekschoten (1968). Terebratulina retusa is an outlier to this trend, being less common than estimates of production and preservation would predict, corresponding with the semi-quantitative evidence for under-representation of articulate brachiopods in death assemblages from the Algerian shelf (Caulet, 1967) and Canadian sub-littoral (Nobel et al. 1976). T. retusa shells recovered from the sediment were extremely friable. Initially this was thought to be a localized dissolution phenomenon, however S.E.M. preparations subsequently demonstrated that the observed strength loss was a consequence of a skeletal architecture which is common to the majority of articulate brachiopods. The rate of `softening' was determined experimentally and proved to be remarkably rapid (93% strength loss 200 days after death, as measured by point loading; Collins, 1986). The friable carbonate liberates large numbers of distinctive calcite fibres into the sediment which should be recognizable as microfossils. Similar observations of structurally weakened brachiopod carbonate have subsequently been reported from the Norwegian coast, the Mediterranean, western USA and New Zealand. The reduced strength of brachiopod shells will increase the potential for mechanical and bio-mechanical fragmentation and therefore under-representation. It is probable that the magnitude of `softening' is inversely related to size and is liable to bias against smaller shells (Collins, 1986). A significant deviation from the expected 1:1 ratio of pedicle to brachial valves of T. retusa (bv/pv = 1.6) was similar to the figure for Terebratulina septentrionalis from a shallow subtidal rocky coastline on the east coast of Canada (bv/pv = 1.5: Noble & Logan 1981). The preferential preservation of brachial valves of T. retusa compares with a strongly biased preservation of pedicle valves for Macandrevia cranium from the Scottish shelf and Gryphus vitreus from Corsica. It is suggested that biased valve ratios of these four Recent examples are the consequence of selective destruction, selective transport need not be invoked. Transport was also investigated experimentally, by laying a representative sample of shells on a moderately exposed sediment surface, at a depth of 9 m. Positions were recorded in a series of photographic mosaics and final recovery included suction sampling to a depth of approximately 30 cm. The large Modiolus valves moved the greatest distances, an unusual result thought to be due to reworking of larger items by crabs with a biologically bound and bioturbated sediment and entrapping the smaller shells and valves. It is suggested that the significance of current-mediated transport has been overstated, due to over concentration on the swash zone and flume tank and the failure to recognize the potential for biologically mediated transport and sediment binding.

The management of large scale strategic urban combined drainage systems is becoming increasingly dependent upon weather radar systems which can provide quantitative precipitation information to improve the overall efficiency of a system's operational performance. Thus, there has been an increasing requirement for a more detailed knowledge of the radar rainfall data accuracy and the development of a mathematical rainfall-runoff model that can be used to analyse and control a system in real-time. Within this context, several important factors including signal attenuation, temporal and spatial data resolutions and rainfall quantisation schemes that determine the accuracy of radar rainfall estimates were examined in this thesis. In order to facilitate real-time flow simulation and forecast, a Conceptually Parametrised Transfer Function (CPTF) model has been developed based on Dynamic Linear Reservoir theory. The model is structurally simple and operationally reliable. It can be easily identified and robustly updated following a pulse response-to-CPTF procedure in which Genetic Algorithms play a key role. Using the model, the accuracy of areal rainfall estimates obtained by the Hameldon Hill radar has been assessed, firstly by comparing the radar rainfall estimates with `ground truth', and then by comparing the simulated hydrographs with the actual flow observations. Finally, a case study was conducted using radar rainfall data to highlight the potential benefit of real-time control for the strategic urban drainage system in the Fylde Coast. The major achievements documented in this thesis are: 1) A rule for determination of an appropriate input data resolution for hydrological models; 2) A general probability density function for describing the sampled radar rainfall intensities; 3) An efficient quantising law (ß-Law) and an associated adaptive rainfall quantisation scheme; 4) Three general conceptual pulse-response functions developed based on Dynamic Linear Reservoir theory; 5) CPTF model; and 6) A case study on the potential benefit of real-time control in the Fylde urban drainage system.