Development of a floating tidal energy system suitable for use in shallow water

A proposal is made for the use of a traditional streamwaterwheel suspended between two floating catamaranNPL series demi-hulls as means of generating electricalpower. Two prototype devices, of lengths 1.6m and 4.5m,have been developed, constructed and tested. It was foundthat the concept is sound although greater investment isrequired with regards to the materials and bothhydrodynamic and aerodynamic design of the waterwheelto ensure an economically viable system. The workpresented concentrates on practical aspects associated withdesign, construction and trial testing in Southampton waterof the 4.5m prototype. The relatively low cost, ease ofdeployment, and the fact that conventional boat mooringsystems are effective, combine to make this an attractivealternative energy solution for remote communities

Tidal turbines that survive?

Tidal turbines offer an exciting opportunity to exploit ocean current flows to generate sustainable energy. However, a key to their success is the ability to operate with minimal intervention in the ocean over extended periods (15-20 years). This talk explored the likely design and operational issues that will influence satisfactory performance associated with material corrosion and biofouling. The main difficulty is that turbine economic viability is capital driven so whole system, including operation and maintenance needs to be as cost-effective as possible. Although can use approaches developed from those applied for ship design and in the offshore industry there is a need to appreciate that cost-drivers are different. For instance a ‘Gold plated’ technology approach from oil and gas industry may not deliver cost-effective solutions

Selected Chemical Modifications of Red Oak and Hard Maple Flakes for Flakeboard Manufacturing

The feasibility of using low chemical concentrations, time, and pressure for modifying red oak and hard maple flakes was investigated. Red oak and hard maple flakes were pretreated with water, sodium hydroxide, and acetic acid for different times and pressures to determine weight loss. The chemically modified flakes were processed into flakeboards. Untreated aspen, red oak, and hard maple panels were used as controls. Compared to the hard maple controls, hard maple panels had a reduction in press closing time for all treatment levels. However, a reduction in press closing time for treated red oak compared to red oak controls was evident only for very high weight loss values. Weight loss for red oak and hard maple can be controlled, and it appeared that acetic acid treatments produced better properties for both species compared to sodium hydroxide or water treatments. Mechanical properties were reduced in hard maple for all treatments and in red oak for some treatments, particularly sodium hydroxide treatments. Bending strength values for acetic acid-treated red oak panels were not significantly different from red oak control values. Water and acetic acid treatments for red oak produced similar dimensional stability values compared to red oak controls. This indicated that weight loss can be controlled without detriment to the dimensional stability of the panels. Density, internal bond, thickness swell, water absorption, and linear expansion values for red oak control and acetic acid-treated red oak panels compared favorably with aspen control panels. Density, internal bond, thickness swell, water absorption, and linear expansion values for hard maple control and linear expansion values for water and acetic acid-treated hard maple panels also compared favorably with aspen control panels

Economic viability of alternative horizontal axis tidal turbine concepts: operation and maintenance simplicity is the key?

A recent dti funded study[1] examined the difference in power capture between a variety of concept horizontal axis tidal turbines (HATT). The aim of the work was to examine the trade-off between design complexity and expected economic cost over the lifetime of tidal turbine farm. Two types of mechanical complexity were examined. The first assumed that the device was free to yaw as the tidal current changes direction. In this case the difference in power capture came from the use of either an optimum uni-directional blade or for a fixed device a bi-directional blade design developed at the University of Southampton. The second complexity was whether the blades would have a controllable pitch. For the basis of the comparison it was assumed that the basic turbine would have a fixed diameter of 20m and be sited in 40m water depth with a spring mean maximum tidal current of 2.5m/s. The methodology adopted was to analyse the hydrodynamic performance and tidal cycle energy capture using a blade element momentum code. In order to make a best-case comparison a blade shape design optimisation was carried out for both the uni and bi-directional blades by searching of the order of 50,000 combinations of chord and twist distributions. A range of alternative blade rpm control strategies were examined to see how this would influence the energy capture. A detailed mechanical system representation was developed so that the reliability and availability of each turbine within the farm could be assessed with a stochastic Monte-Carlo simulation applied to examine variability. The result of the work based on the establishment of a systematic framework, using realistic assumptions was the extent to which the loss in energy conversion efficiency of the simpler concepts was counterbalanced by a reduction in capital and O&amp;M costs. It was concluded that such a simple system is technically feasible and is competitive on a life cycle cost basis and worthy of further consideration<br/

Coupled global-local modelling for dynamic submarine power cables

This is the author accepted manuscript. The final version is available from EWTEC via the link in this recordConventional power transmission cables have been designed to operate in conditions that differ considerably from those experienced by cables servicing floating offshore renewable energy (ORE) device. Cables attached to floating platforms are subject to greater levels of mechanical and electrical stress due to the motion of the platform in a highly energetic offshore environment and are termed dynamic cables. The combination of the different loads from waves, wind and currents, in shallower waters are complex and need to be assessed through a combination of coupled numerical models and experimental tests. Global analyses, assessing the overall motions of the floating platform, moorings and cables, are carried out to provide data to inform the cable design process. Such analyses are highly dependent on the input of local structural response coefficients which are available only through detailed local structural analysis numerically and/or experimentally. There is a strong need to gain a better understanding of the local structural assessment of cable cross-sections and the coupling of the data attained through the local assessments with the global modal. This work incorporates a coupled global-local numerical model of a dynamic subsea cable attached to a floating point-absorber buoy. The results indicate the sensitivity of the global analysis to the locally determined structural results, primarily bending stiffness and tensile stiffness. In the case of the South West Moorings Test Facility (SWMTF) buoy and the lightweight composite armoured cable, bending stiffness is a key governing parameter and axial stiffness is not a governing parameter. The paper will be of use to researchers and practitioners in the areas of cable designers, technology development and design certification.Engineering and Physical Sciences Research Counci

Metabolism and Effects on Endogenous Metabolism of Paracetamol (Acetaminophen) in a Porcine Model of Liver Failure

The metabolic fate, toxicity and effects on endogenous metabolism of paracetamol (acetaminophen, APAP) in 22 female Landrace cross large white pigs were evaluated in a model of acute liver failure (ALF). Anaesthetized pigs were initially dosed at 250 mg/kg via an oroduodenal tube with APAP serum concentrations maintained above 300 mg/L using maintenance doses of 0.5-4g/h until ALF. Studies were undertaken to determine both the metabolic fate of APAP and its effects on the endogenous metabolic phenotype of ALF in using 1H NMR spectroscopy. Increased concentrations of citrate combined with pre-ALF increases in circulating lactate, pyruvate and alanine in plasma suggest mitochondrial dysfunction and a switch in hepatic energy metabolism to glycolysis in response to APAP treatment. A specific liquid chromatography-tandem mass spectrometry assay was used to quantify APAP and metabolites. The major circulating and urinary metabolite of APAP was the phenolic glucuronide (APAP-G), followed by p-aminophenol glucuronide (PAP-G) formed from N-deacetylated APAP. The PAP produced by N-deacetylation was the likely cause of the methaemoglobinemia and kidney toxicity observed in this, and previous, studies in the pig. The phenolic sulfate of APAP, and the glutathione-derived metabolites of the drug were only found as minor components (with the cysteinyl conjugate detected but not the mercapturate). Given its low sulfation, combined with significant capacity for N-deacetylation the pig may represent a poor translational model for toxicology studies for compounds undergoing significant metabolism by sulfation, or which contain amide bonds which when hydrolysed to unmask an aniline lead to toxicity. However, the pig may provide a useful model where extensive amide hydrolysis is seen for drugs or environmental chemicals in humans, but not in e.g., the rat and dog which are the pre-clinical species normally employed for safety assessment

The analysis of acetaminophen (paracetamol) and seven metabolites in rat, pig and human plasma by U(H)PLC–MS

A U(H)PLC–MS/MS method is described for the analysis of acetaminophen and its sulphate, glucuronide, glutathione, cysteinyl and N-acetylcysteinyl metabolites in plasma using stable isotope-labeled internal standards. P-Aminophenol glucuronide and 3-methoxyacetaminophen were monitored and semi-quantified using external standards. The assay takes 7.5 min/sample, requires only 5 μl of plasma and involves minimal sample preparation. The method was validated for rat plasma and cross validated for human and pig plasma and mouse serum. LOQ in plasma for these analytes were 0.44 μg/ml (APAP-C), 0.58 μg/ml (APAP-SG), 0.84 μg/ml (APAP-NAC), 2.75 μg/ml (APAP-S), 3.00 μg/ml (APAP-G) and 16 μg/ml (APAP). Application of the method is illustrated by the analysis of plasma following oral administration of APAP to male Han Wistar rats

The analysis of acetaminophen (paracetamol) and seven metabolites in rat, pig and human plasma by U(H)PLC–MS

A U(H)PLC–MS/MS method is described for the analysis of acetaminophen and its sulphate, glucuronide, glutathione, cysteinyl and N-acetylcysteinyl metabolites in plasma using stable isotope-labeled internal standards. P-Aminophenol glucuronide and 3-methoxyacetaminophen were monitored and semi-quantified using external standards. The assay takes 7.5 min/sample, requires only 5 μl of plasma and involves minimal sample preparation. The method was validated for rat plasma and cross validated for human and pig plasma and mouse serum. LOQ in plasma for these analytes were 0.44 μg/ml (APAP-C), 0.58 μg/ml (APAP-SG), 0.84 μg/ml (APAP-NAC), 2.75 μg/ml (APAP-S), 3.00 μg/ml (APAP-G) and 16 μg/ml (APAP). Application of the method is illustrated by the analysis of plasma following oral administration of APAP to male Han Wistar rats

Charge Density Wave-Assisted Tunneling Between Hall Edge States

We study the intra-planar tunneling between quantum Hall samples separated by a quasi one-dimensional barrier, induced through the interaction of edge degrees of freedom with the charge density waves of a Hall crystal defined in a parallel layer. A field theory formulation is set up in terms of bosonic (2+1)-dimensional excitations coupled to (1+1)-dimensional fermions. Parity symmetry is broken at the quantum level by the confinement of soliton-antisoliton pairs near the tunneling region. The usual Peierls argument allows to estimate the critical temperature $T_c$, so that for $T > T_c$ mass corrections due to longitudinal density fluctuations disappear from the edge spectrum. We compute the gap dependence upon the random global phase of the pinned charge density wave, as well as the effects of a voltage bias applied across the tunneling junction.Comment: Additional references + 1 figure + more detailed discussions. To be published in Phys. Rev.

Parmodulins Inhibit Thrombus Formation Without Inducing Endothelial Injury Caused by Vorapaxar

Protease-activated receptor-1 (PAR1) couples the coagulation cascade to platelet activation during myocardial infarction and to endothelial inflammation during sepsis. This receptor demonstrates marked signaling bias. Its activation by thrombin stimulates prothrombotic and proinflammatory signaling, whereas its activation by activated protein C (APC) stimulates cytoprotective and antiinflammatory signaling. A challenge in developing PAR1-targeted therapies is to inhibit detrimental signaling while sparing beneficial pathways. We now characterize a novel class of structurally unrelated small-molecule PAR1 antagonists, termed parmodulins, and compare the activity of these compounds to previously characterized compounds that act at the PAR1 ligand–binding site. We find that parmodulins target the cytoplasmic face of PAR1 without modifying the ligand-binding site, blocking signaling through Gαq but not Gα13 in vitro and thrombus formation in vivo. In endothelium, parmodulins inhibit prothrombotic and proinflammatory signaling without blocking APC-mediated pathways or inducing endothelial injury. In contrast, orthosteric PAR1 antagonists such as vorapaxar inhibit all signaling downstream of PAR1. Furthermore, exposure of endothelial cells to nanomolar concentrations of vorapaxar induces endothelial cell barrier dysfunction and apoptosis. These studies demonstrate how functionally selective antagonism can be achieved by targeting the cytoplasmic face of a G-protein–coupled receptor to selectively block pathologic signaling while preserving cytoprotective pathways