4,729 research outputs found

    Probing the extreme realm of AGN feedback in the massive galaxy cluster, RX J1532.9+3021

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    We present a detailed Chandra, XMM-Newton, VLA and HST analysis of one of the strongest cool core clusters known, RX J1532.9+3021 (z=0.3613). Using new, deep 90 ks Chandra observations, we confirm the presence of a western X-ray cavity or bubble, and report on a newly discovered eastern X-ray cavity. The total mechanical power associated with these AGN-driven outflows is (22+/-9)*10^44 erg/s, and is sufficient to offset the cooling, indicating that AGN feedback still provides a viable solution to the cooling flow problem even in the strongest cool core clusters. Based on the distribution of the optical filaments, as well as a jet-like structure seen in the 325 MHz VLA radio map, we suggest that the cluster harbours older outflows along the north to south direction. The jet of the central AGN is therefore either precessing or sloshing-induced motions have caused the outflows to change directions. There are also hints of an X-ray depression to the north aligned with the 325 MHz jet-like structure, which might represent the highest redshift ghost cavity discovered to date. We further find evidence of a cold front (r=65kpc) that coincides with the outermost edge of the western X-ray cavity and the edge of the radio mini-halo. The common location of the cold front with the edge of the radio mini-halo supports the idea that the latter originates from electrons being reaccelerated due to sloshing induced turbulence. Alternatively, its coexistence with the edge of the X-ray cavity may be due to cool gas being dragged out by the outburst. We confirm that the central AGN is highly sub-Eddington and conclude that a >10^10M_Sun or a rapidly spinning black hole is favoured to explain both the radiative-inefficiency of the AGN and the powerful X-ray cavities.Comment: Accepted for publication to ApJ (minor corrections), 16 pages, 16 figures, 5 tables. Full resolution at http://www.stanford.edu/~juliehl/M1532

    Influence of retardation effects on 2D magnetoplasmon spectrum

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    Within dissipationless limit the magnetic field dependence of magnetoplasmon spectrum for unbounded 2DEG system found to intersect the cyclotron resonance line, and, then approaches the frequency given by light dispersion relation. Recent experiments done for macroscopic disc-shape 2DEG systems confirm theory expectations.Comment: 2 pages,2 figure

    Microwave saturation of the Rydberg states of electrons on helium

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    We present measurements of the resonant microwave excitation of the Rydberg energy levels of surface state electrons on superfluid helium. The temperature dependent linewidth agrees well with theoretical predictions and is very small below 300 mK. Absorption saturation and power broadening were observed as the fraction of electrons in the first excited state was increased to 0.49, close to the thermal excitation limit of 0.5. The Rabi frequency was determined as a function of microwave power. The high values of the ratio of the Rabi frequency to linewidth confirm this system as an excellent candidate for creating qubits.Comment: 4 pages, 4 figure

    The development of life-cycle and risk assessment methodology using data from AWE Aldermaston

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    The research described in this thesis further develops Life-Cycle Assessment (LCA) methodology to include radiological releases to air, water and as waste. A new methodology has been developed to characterise radioactive aspects based on known effects to man and behaviour in the environment. Equivalency factors have been developed for nine radioisotopes (24'Am, 137Cs56 0Co, 239Pu52 41Pu53 HI 234U, 235U and 238U). A new LCA valuation method is developed for weighting environmental impacts in an Environmental Management System (EMS). A detailed LCA inventory of environmental burdens has been compiled from data from AWE Aldermaston and used as a case study to develop and demonstrate the methodologies developed in this work. As part of the research, the links between environmental aspects and impacts has been investigated using LCA, based on the high hazard facilities at AWE Aldermaston, which is a major industrial site. The case study also includes the contribution from vehicle use in the impact assessment. The results of this work have clearly identified which facilities and hence which processes are causing the most damaging environmental impact. New risk assessment methods are developed to quantify environmental accidents, that include revised consequence definitions that can be applied without the need for modelling and thus offer an economical alternative to existing methods. A new six-step screening methodology is presented to identify potential major accidents to the environment (MATTE) and to comply with the COMAH Regulations 1999. A method to prioritise MATTE scenarios has also been developed. The research has revealed that the current approach to significance assessment does not provide enough sophistication for sites as complex as AWE Aldermaston. The impacts of most concern are environmental irradiation, the generation of all categories of waste and global warming. The impacts associated with radioactive discharges (to air, water and as waste) are given the highest weighting largely reflecting the concern of the major stakeholder groups (local community, regulatory bodies and pressure groups). The methods proposed can be readily applied to any nuclear or chemical site.EThOS - Electronic Theses Online ServiceAEA Technology plcAWE plcUKAEAGBUnited Kingdo

    Particle-Number Reprojection in the Shell Model Monte Carlo Method: Application to Nuclear Level Densities

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    We introduce a particle-number reprojection method in the shell model Monte Carlo that enables the calculation of observables for a series of nuclei using a Monte Carlo sampling for a single nucleus. The method is used to calculate nuclear level densities in the complete (pf+g9/2)(pf+g_{9/2})-shell using a good-sign Hamiltonian. Level densities of odd-A and odd-odd nuclei are reliably extracted despite an additional sign problem. Both the mass and the TzT_z dependence of the experimental level densities are well described without any adjustable parameters. The single-particle level density parameter is found to vary smoothly with mass. The odd-even staggering observed in the calculated backshift parameter follows the experimental data more closely than do empirical formulae.Comment: 14 pages, 4 eps figures included, RevTe

    The effect of pressure on statics, dynamics and stability of multielectron bubbles

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    The effect of pressure and negative pressure on the modes of oscillation of a multi-electron bubble in liquid helium is calculated. Already at low pressures of the order of 10-100 mbar, these effects are found to significantly modify the frequencies of oscillation of the bubble. Stabilization of the bubble is shown to occur in the presence of a small negative pressure, which expands the bubble radius. Above a threshold negative pressure, the bubble is unstable.Comment: 4 pages, 2 figures, accepted for publication in Physical Review Letter

    Aid conditionalities, international Good Manufacturing Practice standards and local production rights: a case study of local production in Nepal

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    © 2015 Brhlikova et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http:// creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.This work was supported by the Economic and Social Research Council and the Department for International Development [RES-167-25-0110] through the collaborative research project Tracing Pharmaceuticals in South Asia (2006 – 2009). In addition to the authors of this paper, the project team included: Soumita Basu, Gitanjali Priti Bhatia, Erin Court, Abhijit Das, Stefan Ecks, Patricia Jeffery, Roger Jeffery, Rachel Manners, and Liz Richardson. Martin Chautari (Kathmandu) and the Centre for Health and Social Justice (New Delhi) provided resources drawn upon in writing this paper but are not responsible for the views expressed, nor are ESRC or DFID. Ethical review was provided by the School of Social and Political Science at the University of Edinburgh, and ethical approval in Nepal for the study granted by the Nepal Health Research Council (NHRC)

    Evaluation of the Productivity of a Single Subcutaneous Injection of LongRange in Stocker Calves Compared With a Positive (Dectomax) and a Negative (Saline) Control

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    Subclinical parasitism is commonly observed in stocker cattle. Treatment of internal parasites helps to improve weight gains, feed conversion, and immune status and decreases morbidity and mortality of beef cattle (Hawkins, 1993). Some of the most concerning classes of internal parasites include Cooperia, Haemonchus, and Ostertagia. Commonly used anthelmintics come in the form of pour-ons, oral drenches, and subcutaneous injections. A majority of these drugs are designed to be administered in a single dose and provide defense against stomach worms for approximately 14 to 42 days, but the typical grazing season lasts for approximately 120 days. For grazing cattle to have season-long protection from parasites, they may require a second dose of anthelmintic treatment, which would require cattle to be gathered and processed through a chute in the middle of the grazing season. LongRange (Merial, Duluth, GA) is the first single-dose extended release anthelmintic that provides approximately 100 to 150 days of protection. This is accomplished by combining two forms of the active ingredient: one that is released into the blood immediately after injection and a second that consists of a slow-release polymer that releases the active ingredient gradually throughout the grazing period. The objective of this study was to measure body weight productivity, fecal egg counts, and fly repellent capabilities of LongRange when administered once subcutaneously at 1.0 mg/kg body weight as a long-acting solution compared with a commercially available injectable (Dectomax; Zoetis, Florham Park, NJ) and saline in stocker cattle

    Exchange Frequencies in the 2d Wigner crystal

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    Using Path Integral Monte Carlo we have calculated exchange frequencies as electrons undergo ring exchanges in a ``clean'' 2d Wigner crystal as a function of density. The results show agreement with WKB calculations at very low density, but show a more rapid increase with density near melting. Remarkably, the exchange Hamiltonian closely resembles the measured exchanges in 2d He. Using the resulting multi-spin exchange model we find the spin Hamiltonian for r_s \leq 175 \pm 10 is a frustrated antiferromagnetic; its likely ground state is a spin liquid. For lower density the ground state will be ferromagnetic
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