Energy potential of a tidal fence deployed near a coastal headland

Enhanced tidal streams close to coastal headlands appear to present ideal locations for the deployment of tidal energy devices. In this paper, the power potential of tidal streams near an idealized coastal headland with a sloping seabed is investigated using a near-field approximation to represent a tidal fence, i.e. a row of tidal devices, in a two-dimensional depth-averaged numerical model. Simulations indicate that the power extracted by the tidal fence is limited because the flow will bypass the fence, predominantly on the ocean side, as the thrust applied by the devices increases. For the dynamic conditions, fence placements and headland aspect ratios considered, the maximum power extracted at the fence is not related in any obvious way to the local undisturbed kinetic flux or the natural rate of energy dissipation due to bed friction (although both of these have been used in the past to predict the amount of power that may be extracted). The available power (equal to the extracted power net of vertical mixing losses in the immediate wake of devices) is optimized for devices with large area and small centre-to-centre spacing within the fence. The influence of energy extraction on the natural flow field is assessed relative to changes in the M2 component of elevation and velocity, and residual bed shear stress and tidal dispersion

Modelling tidal energy extraction in a depth-averaged coastal domain

An extension of actuator disc theory is used to describe the properties of a tidal energy device, or row of tidal energy devices, within a depth-averaged numerical model. This approach allows a direct link to be made between an actual tidal device and its equivalent momentum sink in a depth-averaged domain. Extended actuator disc theory also leads to a measure of efficiency for an energy device in a tidal stream of finite Froude number, where efficiency is defined as the ratio of power extracted by one or more tidal devices to the total power removed from the tidal stream. To demonstrate the use of actuator disc theory in a depth-averaged model, tidal flow in a simple channel is approximated using the shallow water equations and the results are compared with the published analytical solutions. © 2010 © The Institution of Engineering and Technology

Strength Degradation of Sapphire Fibers During Pressure Casting of a Sapphire-Reinforced Ni-Base Superalloy

Transient-liquid-phase (TLP) bonding was used to fabricate a Haynes 230 Ni-base superalloy/sapphire fiber composite for high-temperature applications. Boron was used as a melting-point depressant for the Ni, to aid superalloy infiltration of the fibers. Preliminary study of the composite indicated an incomplete TLP bonding cycle. Therefore, microstructural and microchemical analyses were carried out to determine the TLP bonding mechanism. It was found that the TLP process did not occur under local thermodynamic equilibrium conditions at the solid/liquid interfaces, contrary to the primary assumption of conventional models, so a modified model for TLP bonding is proposed. The main differences between the proposed and the conventional models are: (a) the concentration of the melting-point depressant increases with time during isothermal solidification, (b) extensive boride segregation at grain boundaries and boride precipitation occurs within grains adjacent to the interlayer in the initial composite assembly, (c) because of the relatively high boron concentration in the interlayer, the TLP bonding cycle was incomplete, resulting in residual-liquid borides. To achieve ideal TLP bonding, four modifications are recommended: (i) use less boron, (ii) use finer sapphire fibers, (iii) create smaller initial grain sizes in the matrix and (iv) increase the homogenization time

Optical and infrared photometry of the blazar PKS0537-441

We present a large collection of photometric data on the Blazar PKS 0537-441 in the VRIJHK bands taken in 2004-2009. At least three flare-like episodes with months duration, and >3 mag amplitude are apparent. The spectral energy distribution is consistent with a power law, and no indication of a thermal component is found. We searched for short time scale variability, and an interesting event was identified in the J band, with a duration of ~25 minutes.Comment: 10 pages, 3 figures, in press in ApJ

Glueball matrix elements on anisotropic lattices

We describe a lattice calculation of the matrix elements relevant for glueball production in $J / \psi$ radiative decays. The techniques for such a calculation on anisotropic lattices with an improved action are outlined. We present preliminary results showing the efficacy of the computational method.Comment: 3 pages (LaTeX), 3 figures (PostScript), Presented at Lattice '9

Relationship of Body Composition Variables and Performance Outcomes in Male Professional Soccer Players

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Relationship between nutritional status and treatment-related neutropenia in children with nephroblastoma

Background: Assessment of nutritional status of paediatric oncology patients is crucial, as it may influence treatment and clinical outcomes. Concurrent malnutrition and cancer in children may lead to reduced chemotherapy delivery due to impaired tolerance and increased toxicity. Aim: This study aimed to determine the relationship between nutritional status and the prevalence, frequency and duration of treatment-related neutropenia in a cohort of South African children with nephroblastoma. Methods: Seventy-seven children between the ages of 1 and 12 years diagnosed with nephroblastoma at Inkosi Albert Luthuli Central Hospital (IALCH), Durban, between 2004 and 2012, were studied prospectively. Nutritional status was assessed using weight, height, mid-upper arm circumference (MUAC), triceps skinfold thickness (TSFT) and serum albumin. The administration of filgastrim (Neupogen®) was used as a surrogate for neutropenia and the frequency and duration of its use was recorded. Results: There was a significant relationship between the prevalence of treatment-induced neutropenia and malnutrition defined by MUAC. The mean frequency and duration of neutropenia was significantly higher in those classified as malnourished using MUAC. There was a positive correlation between frequency and duration of neutropenia. Conclusions: Malnutrition was prevalent among children with nephroblastoma. The prevalence of treatment-induced neutropenia was higher in those with poor nutritional status, identified by MUAC. Poor nutritional status according to MUAC was also linked to an increased frequency and duration of neutropenia. It is important to include MUAC in the nutritional assessment of children with nephroblastoma

Socioeconomic inequalities in outcome of pregnancy and neonatal mortality associated with congenital anomalies: population based study

Objectives To investigate socioeconomic inequalities in outcome of pregnancy and neonatal mortality associated with congenital anomalies