920 research outputs found

    Accurate Fundamental Stellar Parameters

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    We combine results from interferometry, asteroseismology and spectroscopic analyses to determine accurate fundamental parameters (mass, radius and effective temperature) of 10 bright solar-type stars covering the H-R diagram from spectral type F5 to K1. Using ``direct'' techniques that are only weakly model-dependent we determine the mass, radius and effective temperature. We demonstrate that model-dependent or ``indirect'' methods can be reliably used even for relatively faint single stars for which direct methods are not applicable. This is important for the characterization of the targets of the CoRoT and Kepler space missions.Comment: 2 pages. To appear in the proceedings of IAU Symp. 265: Chemical Abundances in the Universe: Connecting First Stars to Planet

    Gravitational scattering of stars and clusters and the heating of the Galactic disk

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    Could the velocity spread, increasing with time, in the Galactic disk be explained as a result of gravitational interactions of stars with giant molecular clouds (GMCs) and spiral arms? Do the old open clusters high above the Galactic plane provide clues to this question? We explore the effects on stellar orbits of scattering by inhomogeneities in the Galactic potential due to GMCs, spiral arms and the Galactic bar, and whether high-altitude clusters could have formed in orbits closer to the Galactic plane and later been scattered. Simulations of test-particle motions are performed in a realistic Galactic potential. The effects of the internal structure of GMCs are explored. The destruction of clusters in GMC collisions is treated in detail with N-body simulations of the clusters. The observed velocity dispersions of stars as a function of time are well reproduced. The GMC structure is found to be significant, but adequate models produce considerable scattering effects. The fraction of simulated massive old open clusters, scattered into orbits with |z| > 400 pc, is typically 0:5%, in agreement with the observed number of high-altitude clusters and consistent with the present formation rate of massive open clusters. The heating of the thin Galactic disk is well explained by gravitational scattering by GMCs and spiral arms, if the local correlation between the GMC mass and the corresponding voids in the gas is not very strong. Our results suggest that the high-altitude metal-rich clusters were formed in orbits close to the Galactic plane and later scattered to higher orbits. It is possible, though not very probable, that the Sun formed in such a cluster before scattering occurred.Comment: 19 pages, 15 figure

    Intranuclear cascade models lack dynamic flow

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    We study the recent claim that the intranuclear cascade model exhibits collective sidewards flow. 4000 intranuclear cascade simulations of the reaction Nb(400 MeV/nucleon)+Nb are performed employing bound and unbound versions of the Cugnon cascade. We show that instability of the target and projectile nuclei in the unbound cascade produces substantial spurious sidewards flow angles, for spectators as well as for participants. Once the nuclear binding is included, the peak of the flow angle distributions for the participants alone is reduced from 35° to 17°. The theoretical ‘‘data’’ are subjected to the experimental multiplicity and efficiency cuts of the plastic ball 4π electronic spectrometer system. The flow angular distributions obtained from the bound cascade—with spectators and participants subjected to the plastic ball filter—are forward peaked, in contrast to the plastic ball data. We discuss the uncertainties encountered with the application of the experimental efficiency and multiplicity filter. The influence of the Pauli principle on the flow is also discussed. The lack of flow effects in the cascade model clearly reflects the absence of the nuclear compression energy that can cause substantially larger collective sidewards motion—there is too little intrinsic pressure built up in the cascade model

    ENVIE Co-ordination action on indoor air quality and health effects; WP3 Final report – Characterisation of spaces and source

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    Human exposure to environmental pollutants occurs via various pathways. For many pollutants, especially the volatile ones, air exposure is the dominant pathway. Exposure via air occurs both outdoors and indoors, with diverse types of indoor spaces playing a role, e.g., home, workplace, and passenger cabins of means of transportation. In average people spend over 90% of their time indoors, that percentage being particularly high for some specific groups as new-born, elderly, disabled or sick people. The global exposure to air contaminants is therefore drastically determined by indoor conditions. It is now well established that indoor air pollution contributes significantly to the global burden of disease of the population. For a majority of indoor air contaminants, particularly in the presence of common indoor sources, however, indoor concentrations usually exceed outdoor concentrations, for some pollutants even with an indoor/outdoor ratio of 10 or 20. Emissions are identified, accordingly to the EnVIE approach and grouped into four categories: building materials and related sources, including dampness and moulds; ventilation, natural and mechanical, including, or not, heating, cooling and humidification/ dehumidification; consumer products, furnishing, cleaning and household products; and occupant activities. Emission of chemical substances from construction materials and products in buildings to the indoor air have been reported and reviewed for a wide range of substances, including those formed during secondary reactions, causing complaints of irritation and odour. During the last two decades there has been increasing advances in construction technology that have caused a much greater use of synthetic building materials. Whilst these improvements have led to more comfortable buildings, they also provide indoor environments with contaminants in higher concentrations than are found outside. Wood and cork are now frequently used as a building product for floor coverings, because the material is often regarded as “natural” and “healthy”. However, industrial products, even based on natural raw materials, may contain a number of artificial ingredients and the chemical emissions will strongly depend on the type of additives and the manufacturing process. Modern interior paints are usually based on a polymeric binder. In order to fulfil requirements on e.g., durability, paint contains various functional chemicals. Water-borne paints usually also contains small amounts of approved biocides. Polymeric binders with a very low content of residual monomers have been developed for paint. Besides the release of substances to the indoor air due to primary emission, damp building materials may give rise to volatile substances formed during secondary reactions. Semi-volatile organic compounds (SVOCs) are now receiving much more attention than heretofore. The HVAC (Heating, Ventilation and Air Conditioning) systems as providers, among others, of services of cleaning and dilution of pollutants in the indoor air are also recognized as potential pollution sources. Several studies have shown that the prevalence of SBS symptoms is often higher in air conditioned buildings than in buildings with natural ventilation. 8 The outdoor air introduced indoors through either ventilation systems or natural means is also an important and not always controllable source for the intake of some outdoor pollutants. Outdoor air used for ventilation may also be source of pollution containing particulate matter, particulates of biological origin (microorganisms, pollen, etc.) and various gases like NOx and O building structures which is a driving force for the airflows which will transport to indoors water vapour and gaseous or particulate contaminants. Volatile organic compounds are emitted from a wide variety of household and consumer products with emission rates that are strongly dependent on the type of application and are distributed over several orders of magnitude. A number of product classes are identified and information on ingredients and available data on emissions from individual products are presented. Human activities and the associated use of products encompass a wide range of indoor sources involving release of inorganic gases, particles and organic compounds as a consequence of the activity. For some releases such as with air fresheners the release is a necessary part of the activity to achieve the intended effect whereas for others, such as the release of combustion fumes from a gas appliance, the purpose of the action (in this case generation of heat) is different from the emission. Combustion processes are an important source of a range of air pollutants as carbon monoxide, nitrogen dioxide, sulphur dioxide, particulates and associated inorganic and organic chemicals, organic vapours e.g. formaldehyde, acetaldehyde, and benzene. Sources of these are present in both ambient and indoor environments. The concentrations present in the ambient air provide a baseline for the level of pollutant found indoors as this air enters indoors by processes of infiltration and ventilation. However, the concentration indoors will be modified by processes of sorption to surfaces and chemical reaction depending on the chemical and physical properties of the pollutant and internal surfaces. People themselves are a source of emissions of chemicals and gases, notably CO range of organic compounds that are referred to as body odours. The removal of such body odours is a prime objective of ventilation in order to achieve a satisfactory indoor environment. WP3 aims at to characterize spaces and sources in order to understand where and how to act to guarantee good IAQ. From the two strategies for good IAQ, source control and ventilation, the precautionary principle suggests that first priority shall be given to source control, avoiding, mitigating or simply managing sources of emissions. An overview of all policies on IAQ or related to IAQ, existing or in preparation, directly related to indoor air sources, but also covering outdoor air and industrial emissions, which could affect indirectly IAQ is made. Considering the presented it could be concluded that IAQ is yet poorly regulated at EU level, and in view of that some recommendations are made. The recommendations on policies have taken into account the existing related to IAQ policies such as new EU policies on chemicals (REACH; 2006/121/EC), consumer products (GPSD; 2001/95/EC), construction products (CPD; 89/106/EC) and energy performance of buildings (EPBD; 2002/91/EC) all refer to IAQ issues - suggesting that they could, and probably should, contribute to IAQ policy development and advocate an integrative and comprehensive policy approach centred

    (Di)lepton physics with ALICE

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    Physics perspectives with(di)lepton measurements with the ALICE detector at the LHC are reviewed. Special emphasis is placed on heavy flavor physics.Comment: 4 pages, 1 figure, 18th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions : Quark Matter 2005, Budapest, Hongrie, Ao\^{u}t 2005, submitted to Nuclear Physic

    System size and beam energy dependence of azimuthal anisotropy from PHENIX

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    We present azimuthal anisotropy measurements in Au+Au and Cu+Cu collisions at sNN\sqrt{s_{NN}} = 62.4 and 200 GeV. Comparison between reaction plane and cumulant v2v_2 measurements in Au+Au collisions at sNN\sqrt{s_{NN}} = 200 GeV show that non-flow contributions, originating mainly from jets, influence the extracted v2v_2 for pTp_T \gtrsim 3.5 GeV/c. Number of constituent quark (NCQ) scaling of v2v_2, when studied as a function of transverse kinetic energy KETKE_T, is seen to hold for Au+Au collisions at sNN\sqrt{s_{NN}} = 62.4 and 200 GeV and for Cu+Cu collisions at sNN\sqrt{s_{NN}} = 200 GeV for KETKE_{T} \lesssim 1 GeV/c. Differential hexadecupole flow v4v_4 seems to exhibit scaling with integral v2v_2 for centrality \le 40% as has been observed for differential v2v_2.Comment: 4 pages, 3 figures, Proceedings of the QM2008 Conference, Jaipur, India February 4-10 200

    Measurements of Cold Nuclear Matter Effects on J/psi in the PHENIX Experiment via Deuteron-Gold Collisions

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    A new calculation of R_{dAu} has been performed using the 2003 d+Au data and the higher-statistics 2005 p+p data. These nuclear modification factors are compared to calculations using nuclear-modified PDFs and a J/psi breakup cross section is extracted. These values are then used to project the cold nuclear matter effects in Au+Au collisions. Additionally, a more data-driven projection is performed.Comment: 4 pages, 6 figures, proceedings for Quark Matter 200

    Measurement of charm and bottom production in p+p collisions at s\sqrt{s} = 200 GeV at RHIC-PHENIX

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    RHIC-PHENIX has observed a large suppression pattern and azimuthal anisotropy of non-photonic electron at mid-rapidity (η<0.35\mid\eta\mid<0.35) in Au+Au collisions at sNN=200\sqrt{s_{NN}} = 200 GeV. To understand these results and the interaction of heavy quarks in the hot and dense medium, experimental determination of production ratio of charm over bottom is one of the most important topics, since the behavior of bottom may differ from charm in the medium. We measured the ratio of charm over bottom and total cross section of bottom via partial reconstruction of D0^0\toe+^+ K^- νe\nu_e decay in p+p collisions at s=200\sqrt{s} = 200 GeV. Total cross sections of charm and bottom were also measured via di-electron continuum in p+p collisions at s=200\sqrt{s} = 200 GeV.Comment: 4pages, 4figures,coferenc

    Measurements of heavy quark production via single leptons at PHENIX

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    The measurement of single leptons from the semi-leptonic decay of heavy-flavor hadrons has long been a means for studying heavy-quark production. PHENIX has measured single muons in pp collisions at forward rapidity and single electrons in both pp and AuAu collisions at mid-rapidity at sqrt(s_NN)=200 GeV. The most recent PHENIX single lepton results are presented in the context of state-of-the-art pQCD calculations. An updated azimuthal anisotropy, v2(pT), measurement for heavy-flavor single electrons in AuAu collisions is also presented.Comment: 4 pages, 4 figures, presented at the 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions, "Quark Matter 2008", Jaipur, India, February 4-10, 200
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