Hydraulic free-surface modelling with a novel validation approach

This work shows that a three-dimensional transient two-phase RANS CFD-VOF model can be used to predict the position of waves and hydraulic jumps within a complex hydraulic flow environment as measured during a series of full-scale experiments. A novel application of LIDAR is used to provide detailed measurements of the position of the water free-surface location during the physical experiments. The test environment is a recreational white-water course that provides a means to vary the flow rates of water and restrict the flow easily as required. Obstructions are added to the channel to create hydraulic jumps and other specific flow features. The influence of these obstructions on the flow has been analysed for size, velocity and position. The results of the study demonstrate that, although computationally intensive, the free-surface CFD approach can reliably predict a range of complex hydraulic flow features in medium/largescale open channel flow conditions. In order to reliably capture the full three-dimensional characteristics of the water free-surface a high resolution mesh (greater than 2.5 million cells) with time-steps in the order of milliseconds is necessary (Simulations presented here represent between 30 and 60 seconds of real-time)

Coupling Hydrodynamic and Biological Process Models for Wastewater Treatment

This thesis considers the problem of modelling bioreactors with complex mixing and biokinetic growth based on both soluble nutrients and photosynthesis. From the results of investigations performed on the different modelling methods for nutrient and photosynthesis dependent biomass growth a method of coupling the two biokinetic models was proposed. This new photosynthesis-nutrient (PN) model was then investigated, validated and determined capable of predicting growth characteristics dependent on both nutrient and photosynthetic processes. Additionally an investigation into the factors which may influence the results when using computational fluid dynamics (CFD) to model the flow field within a gas-lift bioreactor was performed. It was determined that one of the main factors which must be considered when modelling bioreactors with boundary layer flow separation is the choice of turbulence model. In the case presented here it was found that the transition SST turbulence model provided the best results with the k-w SST also performing well. Finally, a method of coupling the PN and CFD models was proposed and investigated. The photosynthesis-nutrient-hydrodynamic (PNH) model also incorporated a model for diffusion of light within the bioreactor to allow for investigations into the effects of light absorption and scattering within the bioreactor and how mixing affects the active biomass. Further investigation of this new PNH model determined that the coupling of the biokinetics and flow field provided some insight into the ability of a well-mixed bioreactor to counter low light penetration to an extent

Drugs and life-threatening ventricular arrhythmia risk: results from the DARE study cohort.

OBJECTIVES: To establish a unique sample of proarrhythmia cases, determine the characteristics of cases and estimate the contribution of individual drugs to the incidence of proarrhythmia within these cases. SETTING: Suspected proarrhythmia cases were referred by cardiologists across England between 2003 and 2011. Information on demography, symptoms, prior medical and drug histories and data from hospital notes were collected. PARTICIPANTS: Two expert cardiologists reviewed data for 293 referred cases: 130 were included. Inclusion criteria were new onset or exacerbation of pre-existing ventricular arrhythmias, QTc >500 ms, QTc >450 ms (men) or >470 ms (women) with cardiac syncope, all secondary to drug administration. Exclusion criteria were acute ischaemia and ischaemic polymorphic ventricular tachycardia at presentation, structural heart disease, consent withdrawn or deceased prior to study. Descriptive analysis of Caucasian cases (95% of included cases, n=124) and culpable drug exposures was performed. RESULTS: Of the 124 Caucasian cases, 95 (77%) were QTc interval prolongation-related; mean age was 62 years (SD 15), and 63% were female. Cardiovascular comorbidities included hypertension (53%) and patient-reported 'heart rhythm problems' (73%). Family history of sudden death (36%) and hypokalaemia at presentation (27%) were common. 165 culpable drug exposures were reported, including antiarrhythmics (42%), of which amiodarone and flecainide were the most common. Sotalol, a beta-blocking agent with antiarrhythmic activity, was also common (15%). 26% reported multiple drugs, of which 84% reported at least one cytochrome (CYP) P450 inhibitor. Potential pharmacodynamics interactions identified were mainly QT prolongation (59%). CONCLUSIONS: Antiarrhythmics, non-cardiac drugs and drug combinations were found to be culpable in a large cohort of 124 clinically validated proarrhythmia cases. Potential clinical factors that may warn the prescriber of potential proarrhythmia include older women, underlying cardiovascular comorbidity, family history of sudden death and hypokalaemia

Structural and functional characterisation of human sulfotransferases

The human aryl sulfotransferases HAST4 and HAST4v vary by only two amino acids but exhibit markedly different affinity towards the sulfonate acceptor p-nitrophenol and the sulfonate donor 3'-phosphoadenosine-5'-phosphosulfate (PAPS). To determine the importance of each of these amino acid differences, chimeric constructs were made of HAST4 and HAST4v. By attaching the last 120 amino acids of HAST-4v to HAST4 (changing Thr235 to Asn235) we have been able to produce a protein that has a K-m for PAPS similar to HAST4v. The reverse construct, HAST4v/4 produces a protein with a K-m for PAPS similar to HAST4. These data suggests that the COOH-terminal of sulfotransferases is involved in co-factor binding. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved

THREE DIMENSIONAL FREE-SURFACE MODELLING WITH A NOVEL VALIDATION APPROACH

We show that that a three-dimensional two-phase CFD-VOF model can reliably predict the position of waves and hydraulic jumps within the complex hydraulic flow environments of a recreational white-water course. The model is validated to predict the full transient behaviour of white-water ‘features’ that form such courses. A novel application of LIDAR provides high quality data for validation of the free-surface location. A RANS CFD model is implemented in this work which incorporates an explicit VOF model to predict the transient free surface behaviour of white-water phenomena. Experimental studies were undertaken in a recreational white-water course channel that provided a means to vary the flow rates of water and restrict the flow easily as required as well as in river with a controlled flow from a dam release. The addition of obstructions within the channels allowed analysis of the impact on the size, position, velocities associated with hydraulic jumps, waves and other key features necessary for white-water kayaking. The study includes an original application LIDAR which has successfully been used as a measurement tool allowing high quality free-surface data in a situation where other available options would be very difficult - either prohibitively expensive or would have had an impact on the flow being measured. LIDAR is not traditionally used to measure the surface of water as typically there is no return (reflection) from the water; however the broken water surface of white-water provides enough signal response to capture the detail of a stationary wave and other features. The results of the study establish that the free-surface CFD approaches can accurately predict the complex hydraulic behaviour in large-scale open channel flows. In order to reliably capture the full three- dimensional characteristics of the water free-surface using the VOF approach a structured, high resolution mesh with time-steps in order of milliseconds is necessary

Characterization of iodothyronine sulfatase activities in human and rat liver and placenta

In conditions associated with high serum iodothyronine sulfate concentrations, e.g. during fetal development, desulfation of these conjugates may be important in the regulation of thyroid hormone homeostasis. However, little is known about which sulfatases are involved in this process. Therefore, we investigated the hydrolysis of iodothyronine sulfates by homogenates of V79 cells expressing the human arylsulfatases A (ARSA), B (ARSB), or C (ARSC; steroid sulfatase), as well as tissue fractions of human and rat liver and placenta. We found that only the microsomal fraction from liver and placenta hydrolyzed iodothyronine sulfates. Among the recombinant enzymes only the endoplasmic reticulum-associated ARSC showed activity toward iodothyronine sulfates; the soluble lysosomal ARSA and ARSB were inactive. Recombinant ARSC as well as human placenta microsomes hydrolyzed iodothyronine sulfates with a substrate preference for 3,3'-diiodothyronine sulfate (3,3'-T(2)S) approximately T(3) sulfate (T(3)S) >> rT(3)S approximately T(4)S, whereas human and rat liver microsomes showed a preference for 3,3'-T(2)S > T(3)S >> rT(3)S approximately T(4)S. ARSC and the tissue microsomal sulfatases were all characterized by high apparent K(m) values (>50 microM) for 3,3'-T(2)S and T(3)S. Iodothyronine sulfatase activity determined using 3,3'-T(2)S as a substrate was much higher in human liver microsomes than in human placenta microsomes, although ARSC is expressed at higher levels in human placenta than in human liver. The ratio of estrone sulfate to T(2)S hydrolysis in human liver microsomes (0.2) differed largely from that in ARSC homogenate (80) and human placenta microsomes (150). These results suggest that ARSC accounts for the relatively low iodothyronine sulfatase activity of human placenta, and that additional arylsulfatase(s) contributes to the high iodothyronine sulfatase activity in human liver. Further research is needed to identify these iodothyronine sulfatases, and to study the physiological importance of the reversible sulfation of iodothyronines in thyroid hormone metabolism

Characterization of human iodothyronine sulfotransferases

Sulfation is an important pathway of thyroid hormone metabolism that facilitates the degradation of the hormone by the type I iodothyronine deiodinase, but little is known about which human sulfotransferase isoenzymes are involved. We have investigated the sulfation of the prohormone T4, the active hormone T3, and the metabolites rT3 and 3,3'-diiodothyronine (3,3'-T2) by human liver and kidney cytosol as well as by recombinant human SULT1A1 and SULT1A3, previously known as phenol-preferring and monoamine-preferring phenol sulfotransferase, respectively. In all cases, the substrate preference was 3,3'-T2 >> rT3 > T3 > T4. The apparent Km values of 3,3'-T2 and T3 [at 50 micromol/L 3'-phosphoadenosine-5'-phosphosulfate (PAPS)] were 1.02 and 54.9 micromol/L for liver cytosol, 0.64 and 27.8 micromol/L for kidney cytosol, 0.14 and 29.1 micromol/L for SULT1A1, and 33 and 112 micromol/L for SULT1A3, respectively. The apparent Km of PAPS (at 0.1 micromol/L 3,3'-T2) was 6.0 micromol/L for liver cytosol, 9.0 micromol/L for kidney cytosol, 0.65 micromol/L for SULT1A1, and 2.7 micromol/L for SULT1A3. The sulfation of 3,3'-T2 was inhibited by the other iodothyronines in a concentration-dependent manner. The inhibition profiles of the 3,3'-T2 sulfotransferase activities of liver and kidney cytosol obtained by addition of 10 micromol/L of the various analogs were better correlated with the inhibition profile of SULT1A1 than with that of SULT1A3. These results indicate similar substrate specificities for iodothyronine sulfation by native human liver and kidney sulfotransferases and recombinant SULT1A1 and SULT1A3. Of the latter, SULT1A1 clearly shows the highest affinity for both iodothyronines and PAPS, but it remains to be established whether it is the prominent isoenzyme for sulfation of thyroid hormone in human liver and kidney

A Longitudinal Study of Urinary Phthalate Excretion in 58 Full-Term and 67 Preterm Infants from Birth through 14 Months

Reproduced with permission from Environmental Health PerspectivesDanish Agency for Science, Technology and Innovation (09-067180) and by Kuopio University Hospital, EVO funding, Finlan