920 research outputs found
Accurate Fundamental Stellar Parameters
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
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
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
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
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
We present azimuthal anisotropy measurements in Au+Au and Cu+Cu collisions at
= 62.4 and 200 GeV. Comparison between reaction plane and
cumulant measurements in Au+Au collisions at = 200 GeV
show that non-flow contributions, originating mainly from jets, influence the
extracted for 3.5 GeV/c. Number of constituent quark
(NCQ) scaling of , when studied as a function of transverse kinetic energy
, is seen to hold for Au+Au collisions at = 62.4 and 200
GeV and for Cu+Cu collisions at = 200 GeV for
1 GeV/c. Differential hexadecupole flow seems to exhibit
scaling with integral for centrality 40% as has been observed for
differential .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
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 = 200 GeV at RHIC-PHENIX
RHIC-PHENIX has observed a large suppression pattern and azimuthal anisotropy
of non-photonic electron at mid-rapidity () in Au+Au
collisions at 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 De K decay in p+p
collisions at GeV. Total cross sections of charm and bottom
were also measured via di-electron continuum in p+p collisions at GeV.Comment: 4pages, 4figures,coferenc
Measurements of heavy quark production via single leptons at PHENIX
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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