Wind tunnel model and method

The design and development of a wind tunnel model equipped with pressure measuring devices are discussed. The pressure measuring orifices are integrally constructed in the wind tunnel model and do not contribute to distortions of the aerodynamic surface. The construction of a typical model is described and a drawing of the device is included

Cerenkov's Effect and Neutrino Oscillations in Loop Quantum Gravity

Bounds on the scale parameter {\cal L} arising in loop quantum gravity theory are derived in the framework of Cerenkov's effect and neutrino oscillations. Assuming that {\cal L} is an universal constant, we infer {\cal L}> 10^{-18}eV^{-1}, a bound compatible with ones inferred in different physical context.Comment: 6 pages, no figures, in print on MPL

Exploring the role of voluntary disease schemes on UK farmer bio-security behaviours: Findings from the Norfolk-Suffolk Bovine Viral Diarrhoea control scheme

The article describes the influence of a disease control scheme (the Norfolk-Suffolk Bovine Viral Diarrhoea Disease (BVD) Eradication scheme) on farmers' bio-security attitudes and behaviours. In 2010, a survey of 100 cattle farmers (53 scheme members vs. 47 out of scheme farmers) was undertaken among cattle farmers residing in Norfolk and Suffolk counties in the UK. A cross-sectional independent measures design was employed. The main analytical tool was content analysis. The following variables at the farmer-level were explored: the specific BVD control measures adopted, livestock disease priorities, motivation for scheme membership, wider knowledge acquisition, biosecurity behaviours employed and training course attendance. The findings suggest that participation in the BVD scheme improved farmers' perception of the scheme benefits and participation in training courses. However, no association was found between the taking part in the BVD scheme and livestock disease priorities or motivation for scheme participation, or knowledge about BVD bio-security measures employed. Equally importantly, scheme membership did appear to influence the importance accorded specific bio-security measures. Yet such ranking did not appear to reflect the actual behaviours undertaken. As such, disease control efforts alone while necessary, are insufficient. Rather, to enhance farmer bio-security behaviours significant effort must be made to address underlying attitudes to the specific disease threat involved

Manipulating Bose-Einstein condensed atoms in toroidal traps

We consider Bose-Einstein condensed atoms confined in a toroidal trap. We demonstrate that under conditions of one-dimensional behavior, the density distribution of the atoms may be exponentially localized/delocalized, even for very small variations in the trapping potential along the torus. This observation allows one to control the atom density externally via slight modifications of the trapping potential. For similar reasons, small irregularities of the trap may also have a very pronounced effect on the density of the cloud.Comment: 4 pages, RevTex, 2 figure

Measuring gravitational lens time delays using low-resolution radio monitoring observations

Obtaining lensing time delay measurements requires long-term monitoring campaigns with a high enough resolution (< 1 arcsec) to separate the multiple images. In the radio, a limited number of high-resolution interferometer arrays make these observations difficult to schedule. To overcome this problem, we propose a technique for measuring gravitational time delays which relies on monitoring the total flux density with low-resolution but high-sensitivity radio telescopes to follow the variation of the brighter image. This is then used to trigger high-resolution observations in optimal numbers which then reveal the variation in the fainter image. We present simulations to assess the efficiency of this method together with a pilot project observing radio lens systems with the Westerbork Synthesis Radio Telescope (WSRT) to trigger Very Large Array (VLA) observations. This new method is promising for measuring time delays because it uses relatively small amounts of time on high-resolution telescopes. This will be important because instruments that have high sensitivity but limited resolution, together with an optimum usage of followup high-resolution observations from appropriate radio telescopes may in the future be useful for gravitational lensing time delay measurements by means of this new method.Comment: 10 pages, 7 figures, accepted by MNRA

Self-assembled ErAs islands in GaAs for optical-heterodyne THz generation

We report photomixer devices fabricated on a material consisting of self-assembled ErAs islands in GaAs, which is grown by molecular beam epitaxy. The devices perform comparably and provide an alternative to those made from low-temperature-grown GaAs. The photomixer's frequency response demonstrates that the material is a photoconductor with subpicosecond response time, in agreement with time-resolved differential reflectance measurements. The material also provides the other needed properties such as high photocarrier mobility and high breakdown field, which exceeds 2×10^5 V/cm. The maximum output power before device failure at frequencies of 1 THz was of order 0.1 µW. This material has the potential to allow engineering of key photomixer properties such as the response time and dark resistance

Legacy data and cosmological constraints from the angular-size/redshift relation for ultra-compact radio sources

We have re-examined an ancient VLBI survey of ultra-comact radio sources at 2.29 GHz, which gave fringe amplitudes for 917 such objects with total flux density >0.5 Jy approximately. A number of cosmological investigations based upon this survey have been published in recent years. We have updated the sample with respect to both redshift and radio information, and now have full data for 613 objects, significantly larger than the number (337) used in earlier investigations. The corresponding angular-size/redshift diagram gives Omega_m=0.25+0.04/-0.03, Omega_\Lambda=0.97+0.09/-0.13 and K=0.22+0.07/-0.10. In combination with supernova data, and a simple-minded approach to CMB data based upon the angular size of the acoustic horizon, our best figures are Omega_m=0.298+0.025/-0.024, Omega_\Lambda=0.702+0.035/-0.036 and K= 0.000+0.021/-0.019. We have examined simple models of dynamical vacuum energy; the first, based upon a scalar potential V(phi)=omega_C^2 phi^2/2, gives w(0)=-1.00+0.06/-0.00, (dw/dz)_0=+0.00/-0.08; in this case conditions at z=0 require particular attention, to preclude behaviour in which phi becomes singular as z -->infinity. For fixed w limits are w=-1.20+0.15/-0.14. The above error bars are 68% confidence limits.Comment: 24 pages, 9 figure

Massive spheroids can form in single minor mergers

Accepted for publication in MNRAS, 12 pages, 6 figuresUnderstanding how rotationally supported discs transform into dispersion-dominated spheroids is central to our comprehension of galaxy evolution. Morphological transformation is largely merger-driven. While major mergers can efficiently create spheroids, recent work has highlighted the significant role of other processes, like minor mergers, in driving morphological change. Given their rich merger histories, spheroids typically exhibit large fractions of ‘ex situ’ stellar mass, i.e. mass that is accreted, via mergers, from external objects. This is particularly true for the most massive galaxies, whose stellar masses typically cannot be attained without a large number of mergers. Here, we explore an unusual population of extremely massive (M ∗ > 10 11M) spheroids, in the Horizon-AGN simulation, which exhibit anomalously low ex situ mass fractions, indicating that they form without recourse to significant merging. These systems form in a single minor-merger event (with typical merger mass ratios of 0.11–0.33), with a specific orbital configuration, where the satellite orbit is virtually co-planar with the disc of the massive galaxy. The merger triggers a catastrophic change in morphology, over only a few hundred Myr, coupled with strong in situ star formation. While this channel produces a minority (∼5 per cent) of such galaxies, our study demonstrates that the formation of at least some of the most massive spheroids need not involve major mergers – or any significant merging at all – contrary to what is classically believed.Peer reviewedFinal Accepted Versio