4,017 research outputs found

    The MICE luminosity monitor

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    The MICE experiment will provide the first measurement of ionisation cooling, a technique suitable for reducing the transverse emittance of a tertiary muon beam in a future neutrino factory accelerator facility. MICE is presently in the final stages of commissioning its beam line. The MICE luminosity monitor has proved an invaluable tool throughout this process, providing independent measurements of particle rate from the MICE target, normalisation for beam line detectors and verification of simulation codes

    Radiative Hydrodynamic Simulations of HD209458b: Temporal Variability

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    We present a new approach for simulating the atmospheric dynamics of the close-in giant planet HD209458b that allows for the decoupling of radiative and thermal energies, direct stellar heating of the interior, and the solution of the full 3D Navier Stokes equations. Simulations reveal two distinct temperature inversions (increasing temperature with decreasing pressure) at the sub-stellar point due to the combined effects of opacity and dynamical flow structure and exhibit instabilities leading to changing velocities and temperatures on the nightside for a range of viscosities. Imposed on the quasi-static background, temperature variations of up to 15% are seen near the terminators and the location of the coldest spot is seen to vary by more than 20 degrees, occasionally appearing west of the anti-solar point. Our new approach introduces four major improvements to our previous methods including simultaneously solving both the thermal energy and radiative equations in both the optical and infrared, incorporating updated opacities, including a more accurate treatment of stellar energy deposition that incorporates the opacity relevant for higher energy stellar photons, and the addition of explicit turbulent viscosity.Comment: Accepted for publication in Ap

    Atmospheric Dynamics of Short-period Extra Solar Gas Giant Planets I: Dependence of Night-Side Temperature on Opacity

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    More than two dozen short-period Jupiter-mass gas giant planets have been discovered around nearby solar-type stars in recent years, several of which undergo transits, making them ideal for the detection and characterization of their atmospheres. Here we adopt a three-dimensional radiative hydrodynamical numerical scheme to simulate atmospheric circulation on close-in gas giant planets. In contrast to the conventional GCM and shallow water algorithms, this method does not assume quasi hydrostatic equilibrium and it approximates radiation transfer from optically thin to thick regions with flux-limited diffusion. In the first paper of this series, we consider synchronously-spinning gas giants. We show that a full three-dimensional treatment, coupled with rotationally modified flows and an accurate treatment of radiation, yields a clear temperature transition at the terminator. Based on a series of numerical simulations with varying opacities, we show that the night-side temperature is a strong indicator of the opacity of the planetary atmosphere. Planetary atmospheres that maintain large, interstellar opacities will exhibit large day-night temperature differences, while planets with reduced atmospheric opacities due to extensive grain growth and sedimentation will exhibit much more uniform temperatures throughout their photosphere's. In addition to numerical results, we present a four-zone analytic approximation to explain this dependence.Comment: 35 Pages, 13 Figure

    Modelling the local and global cloud formation on HD 189733b

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    Context. Observations suggest that exoplanets such as HD 189733b form clouds in their atmospheres which have a strong feedback onto their thermodynamical and chemical structure, and overall appearance. Aims. Inspired by mineral cloud modelling efforts for Brown Dwarf atmospheres, we present the first spatially varying kinetic cloud model structures for HD 189733b. Methods. We apply a 2-model approach using results from a 3D global radiation-hydrodynamic simulation of the atmosphere as input for a detailed, kinetic cloud formation model. Sampling the 3D global atmosphere structure with 1D trajectories allows us to model the spatially varying cloud structure on HD 189733b. The resulting cloud properties enable the calculation of the scattering and absorption properties of the clouds. Results. We present local and global cloud structure and property maps for HD 189733b. The calculated cloud properties show variations in composition, size and number density of cloud particles which are strongest between the dayside and nightside. Cloud particles are mainly composed of a mix of materials with silicates being the main component. Cloud properties, and hence the local gas composition, change dramatically where temperature inversions occur locally. The cloud opacity is dominated by absorption in the upper atmosphere and scattering at higher pressures in the model. The calculated 8{\mu}m single scattering Albedo of the cloud particles are consistent with Spitzer bright regions. The cloud particles scattering properties suggest that they would sparkle/reflect a midnight blue colour at optical wavelengths.Comment: Accepted for publication (A&A) - 21/05/2015 (Low Resolution Maps

    Pore geometry as a control on rock strength

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    This study was funded via RJW's University of Leicester start-up fund, as part of AAB's PhD project. We thank Don Swanson and Mike Poland at HVO, Hawai'i, for their help and advice during fieldwork planning and sample collection in the Koa'e fault system, and the National Park Service for granting a research permit to collect rock samples. Sergio Vinciguerra is thanked for access to the Rock Mechanics and Physics lab at the British Geological Survey and Audrey Ougier-Simonin is thanked for her help preparing samples and advice during testing. We thank Mike Heap (EOST Strasbourg) and an anonymous reviewer for their detailed and careful comments that greatly improved the manuscript.Peer reviewedPostprin

    Critical velocity ionisation in substellar atmospheres

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    The observation of radio, X-ray and Hα emission from substellar objects indicates the presence of plasma regions and associated high-energy processes in their surrounding envelopes. This paper numerically simulates and characterises Critical Velocity Ionisation, a potential ionisation process, that can efficiently generate plasma as a result of neutral gas flows interacting with seed magnetized plasmas. By coupling a Gas-MHD interactions code (to simulate the ionisation mechanism) with a substellar global circulation model (to provide the required gas flows) we quantify the spatial extent of the resulting plasma regions, their degree of ionisation and their lifetime for a typical substellar atmosphere. It is found that the typical average ionisation fraction reached at equilibrium (where the ionisation and recombination rates are equal and opposite) ranges from 10-5 to 10-8, at pressures between 10-1 and 10-3 bar, with a trend of increasing ionisation fraction with decreasing atmospheric pressure. The ionisation fractions reached as a result of Critical Velocity Ionisation are sufficient to allow magnetic fields to couple to gas flows in the atmosphere

    The Use and Acceptance of the English Canon in the High School Classroom

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    The literary canon has been viewed in the high school ELA classroom for many generations. The works it contains are now somewhat dated and there are certain movements claiming it should be replaced with different types of modern literature. This paper seeks to address how the canon is viewed in the classroom, including what problems people associate with it, and what solutions to those problems are available. The literary canon is a staple in ELA education and will continue to be for some time to come. Keywords: ELA, Canon, Educatio

    Compassion Fatigue in Veterinary Practice

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    As a member of the Virbac Animal Health Advisory Council, I was given access to a qualitative and quantitative exploration on Compassionate Care in veterinary practice. The qualitative portion was a discussion entitled Veterinarian Focus Group on Compassionate Care & Related Issues, whereas the quantitative results were obtained during a Compassionate Care Online Survey conducted in April 2010. This data is the first of its kind in veterinary medicine. The forum results include discussions in current and past training, end-of-life care and hospice, euthanasia and post-euthanasia procedures, and compassion fatigue. The objectives of this forum included: assessing the level of current and past “training” given to the veterinarians in the forum group in managing staff and clients in end-of-life care, euthanasia and related issues; gathering insights on perspectives/definitions of “end-of-life” and “hospice” care for pets; exploring euthanasia and post-euthanasia protocols being used in the practices represented at the forum; identifying perceived issues surrounding the euthanasia procedure and any aftereffects among staff; and assessing awareness of the term and the existence of “compassion fatigue” within the profession. The survey objectives included: measuring the existence of “formalized” policies/practices in place to handle terminally ill patients and euthanasia both medically and emotionally with pet owners and staff; measuring the number of times a clinic typically faces these situations; measuring awareness of the term “compassion fatigue” and use of any coping tools or strategies for the veterinarian and clinic staff; and accessing the level of concern about compassion fatigue. Combined with the presenter’s years of research and experience in veterinary practice and animal care, and compassion fatigue in particular, this presentation will wrap in-the-trenches concepts around numbers to provide an enlightening glimpse at the inner workings of the emotional aspects of animal caregiving in veterinary medicine

    Effects on muscle tension and tracking task performance of simulated sonic booms with low and high intensity vibrational components

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    Effects of simulated sonic booms with high and low intensity vibrational components on tracking task performance and muscle tension in human subject

    Reliability of laboratory tests of VSTOL and other long duration noises

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    Paired-comparison and magnitude estimations of the subjective noisiness or unacceptability of noise from fixed wing jet aircraft and simulated noise of VSTOL aircraft were obtained from groups of subjects given different instructions. These results suggest that VSTOL noises can be evaluated in terms of their noisiness or unwantedness to people with reasonable accuracy by units of the physical measures designated as PNdBM, with or without tone corrections, and dBD sub 2. Also, that consideration should be given to the use of D sub 2 as an overall frequency weighting function for sound level meters instead of the presently available A weighting. Two new units of noise measurement, PLdB and dB(E), used for predicting subjective noisiness, were found to be less accurate than PNdBM or dBD sub 2 in this regard
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