Unsteady stagnation-point heat transfer during passage of a concentrated vortex

The unsteady boundary layer due to a single rectilinear vortex filament approaching a 2-D stagnation point is investigated. Assuming the vortex remains far from the surface, incompressible potential flow theory is used to determine the time dependent inviscid flow field. The unsteady boundary layer equations are solved by an alternating-direction-implicit finite-difference method. Two mechanisms which cause fluctuations in heat transfer are the unsteady velocity field in the boundary layer and secondly, the unsteady total temperature at the edge of the boundary layer. The relative importance of these mechanisms is dependent upon the total temperature fluctuations relative to the imposed temperature difference. As a vortex approaches a stagnation point it may be forced to one side of the stagnation line or the other, depending on its initial position. Results are presented for both of these cases

Increased heat transfer to elliptical leading edges due to spanwise variations in the freestream momentum: Numerical and experimental results

A study of the effect of spanwise variation in momentum on leading edge heat transfer is discussed. Numerical and experimental results are presented for both a circular leading edge and a 3:1 elliptical leading edge. Reynolds numbers in the range of 10,000 to 240,000 based on leading edge diameter are investigated. The surface of the body is held at a constant uniform temperature. Numerical and experimental results with and without spanwise variations are presented. Direct comparison of the two-dimensional results, that is, with no spanwise variations, to the analytical results of Frossling is very good. The numerical calculation, which uses the PARC3D code, solves the three-dimensional Navier-Stokes equations, assuming steady laminar flow on the leading edge region. Experimentally, increases in the spanwise-averaged heat transfer coefficient as high as 50 percent above the two-dimensional value were observed. Numerically, the heat transfer coefficient was seen to increase by as much as 25 percent. In general, under the same flow conditions, the circular leading edge produced a higher heat transfer rate than the elliptical leading edge. As a percentage of the respective two-dimensional values, the circular and elliptical leading edges showed similar sensitivity to span wise variations in momentum. By equating the root mean square of the amplitude of the spanwise variation in momentum to the turbulence intensity, a qualitative comparison between the present work and turbulent results was possible. It is shown that increases in leading edge heat transfer due to spanwise variations in freestream momentum are comparable to those due to freestream turbulence

Increased heat transfer to a cylindrical leading edge due to spanwise variations in the freestream velocity

The present study numerically demonstrates how small spanwise variations in velocity upstream of a body can cause relatively large increases in the spanwise-averaged heat transfer to the leading edge. Vorticity introduced by spanwise variations, first decays as it drifts downstream, then amplifies in the stagnation region as a result of vortex stretching. This amplification can cause a periodic array of 3 D structures, similar to horseshoe vortices, to form. The numerical results indicate that, for the given wavelength, there is an amplitude threshold below which a structure does not form. A one-dimensional analysis, to predict the decay of vorticity in the absence of the body, in conjunction with the full numerical results indicated that the threshold is more accurately stated as minimum level of vorticity required in the leading edge region for a structure to form. It is possible, using the one-dimensional analysis, to compute an optimum wavelength in terms of the maximum vorticity reaching the leading edge region for given amplitude. A discussion is presented which relates experimentally observed trends to the trends of the present phenomena

The cosmic evolution of radio-AGN feedback to z=1

This paper presents the first measurement of the radio luminosity function of 'jet-mode' (radiatively-inefficient) radio-AGN out to z=1, in order to investigate the cosmic evolution of radio-AGN feedback. Eight radio source samples are combined to produce a catalogue of 211 radio-loud AGN with 0.5<z<1.0, which are spectroscopically classified into jet-mode and radiative-mode (radiatively-efficient) AGN classes. Comparing with large samples of local radio-AGN from the Sloan Digital Sky Survey, the cosmic evolution of the radio luminosity function of each radio-AGN class is independently derived. Radiative-mode radio-AGN show an order of magnitude increase in space density out to z~1 at all luminosities, consistent with these AGN being fuelled by cold gas. In contrast, the space density of jet-mode radio-AGN decreases with increasing redshift at low radio luminosities (L_1.4 < 1e24 W/Hz) but increases at higher radio luminosities. Simple models are developed to explain the observed evolution. In the best-fitting models, the characteristic space density of jet-mode AGN declines with redshift in accordance with the declining space density of massive quiescent galaxies, which fuel them via cooling of gas in their hot haloes. A time delay of 1.5-2 Gyr may be present between the quenching of star formation and the onset of jet-mode radio-AGN activity. The behaviour at higher radio luminosities can be explained either by an increasing characteristic luminosity of jet-mode radio-AGN activity with redshift (roughly as (1+z) cubed) or if the jet-mode radio-AGN population also includes some contribution of cold-gas-fuelled sources seen at a time when their accretion rate was low. Higher redshifts measurements would distinguish between these possibilities.Comment: Accepted for publication in MNRA

A re-examination of the growth of the gummy shark (Mustelus antarcticus) from Queensland, Australia

The gummy shark (Mustelus antarcticus) is endemic to Australia and is the target of commercial fisheries in southern Australia. However, the Queensland population is subjected to low levels of fishing mortality. The present study re-analysed a limited length-at-age dataset collected from central Queensland to estimate growth parameters in a Bayesian framework, with informative priors for size-at-birth and maximum size. Growth parameters were estimated using a multi-model approach. This study showed that M. antarcticus caught in Queensland exhibits slow growth compared with conspecifics in southern Australia, and females grow slower and larger than do males. The combined length-at-age data for males and females was best described by the von Bertalanffy growth function and the growth parameters were L∞ = 1852 mm (total length, TL), L0 = 261 mm TL and k = 0.044 year−1 for males and females combined. The ‘BayesGrowth’ R package offers a simple method to minimise bias in the estimation of growth parameters from a limited length-at-age dataset in a Bayesian framework

A re-examination of the growth of the gummy shark (Mustelus antarcticus) from Queensland, Australia

The gummy shark (Mustelus antarcticus) is endemic to Australia and is the target of commercial fisheries in southern Australia. However, the Queensland population is subjected to low levels of fishing mortality. The present study re-analysed a limited length-at-age dataset collected from central Queensland to estimate growth parameters in a Bayesian framework, with informative priors for size-at-birth and maximum size. Growth parameters were estimated using a multi-model approach. This study showed that M. antarcticus caught in Queensland exhibits slow growth compared with conspecifics in southern Australia, and females grow slower and larger than do males. The combined length-at-age data for males and females was best described by the von Bertalanffy growth function and the growth parameters were L∞ = 1852 mm (total length, TL), L0 = 261 mm TL and k = 0.044 year−1 for males and females combined. The ‘BayesGrowth’ R package offers a simple method to minimise bias in the estimation of growth parameters from a limited length-at-age dataset in a Bayesian framework

Reaching older people with PA delivered in football clubs: the reach, adoption and implementation characteristics of the Extra Time Programme.

Background Older adults (OA) represent a core priority group for physical activity and Public Health policy. As a result, significant interest is placed on how to optimise adherence to interventions promoting these approaches. Extra Time (ET) is an example of a national programme of physical activity interventions delivered in professional football clubs for OA aged 55+ years. This paper aims to examine the outcomes from ET, and unpick the processes by which these outcomes were achieved. Methods This paper represents a secondary analysis of data collected during the evaluation of ET. From the 985 OA reached by ET, n=486 adopted the programme and completed post-intervention surveys (typically 12 weeks). We also draw on interview data with 18 ET participants, and 7 staff who delivered the programme. Data were subject to thematic analysis to generate overarching and sub themes. Results Of the 486 participants, the majority 95%, (n= 462) were White British and 59.7% (n=290) were female. Most adopters (65.4%/n=318) had not participated in previous interventions in the host clubs. Social interaction was the most frequently reported benefit of participation (77.2%, n=375). While the reach of the club badge was important in letting people know about the programme, further work enhanced adoption and satisfaction. These factors included (i) listening to participants, (ii) delivering a flexible age-appropriate programme of diverse physical and social activities, (iii) offering activities which satisfy energy drives and needs for learning and (iv) extensive opportunities for social engagement. Conclusions Findings emerging from this study indicate that physical activity and health interventions delivered through professional football clubs can be effective for engaging OA

Effect of soy in men with type 2 diabetes mellitus and subclinical hypogonadism: a randomised controlled study

Context: Isoflavones found in soy products have a chemical structure similar to estrogen, leading to concerns of an adverse estrogenic effect in men, particularly in those with type 2 diabetes mellitus (T2DM) who have low testosterone levels due to hypogonadism. Objective: The primary outcome was change in total testosterone levels. The secondary outcomes were the changes in glycaemia and cardiovascular risk markers. Design: Randomised double blind parallel study. Setting: Secondary care setting in UK. Participants: 200 men with T2DM with a total testosterone level≤12nmol/L Intervention: 15g soy protein with 66mg of isoflavones (SPI) or 15g soy protein alone without isoflavones (SP) daily as snack bars for three months. Results: There was no change in either total testosterone or in absolute free testosterone levels with either SPI or SP. There was an increase in TSH and reduction in fT4 (p&lt;0.01) after SPI supplementation. Glycaemic control improved with a significant reduction in HbA1c (-4.19(7.29)mmol/mol,p&lt;0.01) and HOMA-IR after SPI. Cardiovascular risk improved with a reduction in triglycerides, CRP and diastolic BP (p&lt;0.05) with SPI versus SP supplementation. There was 6% improvement in 10-year coronary heart disease risk after three months of SPI supplementation. Endothelial function improved with both SPI and SP supplementation (p&lt;0.01) with an increased reactive hyperemia index that was greater for the SPI group (p&lt;0.05). Conclusions: Testosterone levels were unchanged and there was a significant improvement in glycaemia and cardiovascular risk markers with SPI compared to SP alone over three months. There was significant increase in TSH and a reduction in fT4

New assays for carbamyl phosphate synthetase applicable in the presence of exogenous carbamyl phosphate.

New assays for carbamyl phosphate synthetase applicable in the presence of exogenous carbamyl phosphate