1,240 research outputs found
The subdwarf B star SB 290 - A fast rotator on the extreme horizontal branch
Hot subdwarf B stars (sdBs) are evolved core helium-burning stars with very
thin hydrogen envelopes. In order to form an sdB, the progenitor has to lose
almost all of its hydrogen envelope right at the tip of the red giant branch.
In close binary systems, mass transfer to the companion provides the
extraordinary mass loss required for their formation. However, apparently
single sdBs exist as well and their formation is unclear since decades. The
merger of helium white dwarfs leading to an ignition of core helium-burning or
the merger of a helium core and a low mass star during the common envelope
phase have been proposed. Here we report the discovery of SB 290 as the first
apparently single fast rotating sdB star located on the extreme horizontal
branch indicating that those stars may form from mergers.Comment: 5 pages, 4 figures, A&A letters, accepte
Substructure of inner dynein arms, radial spokes, and the central pair/projection complex of cilia and flagella.
Examine the species and beam-energy dependence of particle spectra using Tsallis Statistics
Tsallis Statistics was used to investigate the non-Boltzmann distribution of
particle spectra and their dependence on particle species and beam energy in
the relativistic heavy-ion collisions at SPS and RHIC. Produced particles are
assumed to acquire radial flow and be of non-extensive statistics at
freeze-out. J/psi and the particles containing strangeness were examined
separately to study their radial flow and freeze-out. We found that the strange
hadrons approach equilibrium quickly from peripheral to central A+A collisions
and they tend to decouple earlier from the system than the light hadrons but
with the same final radial flow. These results provide an alternative picture
of freeze-outs: a thermalized system is produced at partonic phase; the
hadronic scattering at later stage is not enough to maintain the system in
equilibrium and does not increase the radial flow of the copiously produced
light hadrons. The J/psi in Pb+Pb collisions at SPS is consistent with early
decoupling and obtains little radial flow. The J/psi spectra at RHIC are also
inconsistent with the bulk flow profile.Comment: 12 pages, 4 figures, added several references and some clarifications
et
Politische Dimensionen von MilitĂ€rĂŒbungen und Manövern â ein Projektbericht
Die virtuellen Kriege und Operationen, die in MilitĂ€rĂŒbungen gespielt und geprobt werden, können entweder der Abschreckung dienen oder aber Angriffe vorbereiten bzw. zur Maskierung tatsĂ€chlicher Angriffe dienen. FĂŒr Beobachter ist es vielfach nicht offensichtlich, um welche Art von MilitĂ€rĂŒbung es sich handelt. Die Ergebnisse eines vierjĂ€hrigen internationalen Projektes zu politischen Dimensionen von MilitĂ€rĂŒbungen richten das Schlaglicht insbesondere auf MissverstĂ€ndnisse und deren ungewollte politische Auswirkungen, die im Extremfall unbeabsichtigt zum Krieg fĂŒhren können
Sub-stellar companions of intermediate-mass stars with CoRoT: CoRoTâ34b, CoRoTâ35b, and CoRoTâ36b
Theories of planet formation give contradicting results of how frequent close-in giant planets of intermediate mass stars (IMSs; 1.3â€Mââ€3.2Mââ ) are. Some theories predict a high rate of IMSs with close-in gas giants, while others predict a very low rate. Thus, determining the frequency of close-in giant planets of IMSs is an important test for theories of planet formation. We use the CoRoT survey to determine the absolute frequency of IMSs that harbour at least one close-in giant planet and compare it to that of solar-like stars. The CoRoT transit survey is ideal for this purpose, because of its completeness for gas-giant planets with orbital periods of less than 10 d and its large sample of main-sequence IMSs. We present a high precision radial velocity follow-up programme and conclude on 17 promising transit candidates of IMSs, observed with CoRoT. We report the detection of CoRoTâ34b, a brown dwarf close to the hydrogen burning limit, orbiting a 1.1âGyr A-type main-sequence star. We also confirm two inflated giant planets, CoRoTâ35b, part of a possible planetary system around a metal-poor star, and CoRoTâ36b on a misaligned orbit. We find that 0.12±0.10 per cent of IMSs between 1.3â€Mââ€1.6Mâ observed by CoRoT do harbour at least one close-in giant planet. This is significantly lower than the frequency (â 0.70±0.16 per centâ ) for solar-mass stars, as well as the frequency of IMSs harbouring long-period planets (â âŒ8 per centâ )
Future Experiments in Relativistic Heavy Ion Collisions
The measurements at RHIC have revealed a new state of matter, which needs to
be further characterized in order to better understand its implications for the
early evolution of the universe and QCD. I will show that, in the near future,
complementary key measurements can be performed at RHIC, LHC, and FAIR. I will
focus on results than can be obtained using identified particles, a probe which
has been the basis for this conference over the past three decades. The
sophisticated detectors, built and planned, for all three accelerator
facilities enable us to measure leptons, photons, muons as well as hadrons and
resonances of all flavors almost equally well, which makes these experiments
unprecedented precision tools for the comprehensive understanding of the
physics of the early universe.Comment: 10 pages, 4 figures, Proceedings for Summary Talk at SQM 2007,
Levoca, Slovakia, June 24-29, 200
Photoluminescent diamond nanoparticles for cell labeling: study of the uptake mechanism in mammalian cells
Diamond nanoparticles (nanodiamonds) have been recently proposed as new
labels for cellular imaging. For small nanodiamonds (size <40 nm) resonant
laser scattering and Raman scattering cross-sections are too small to allow
single nanoparticle observation. Nanodiamonds can however be rendered
photoluminescent with a perfect photostability at room temperature. Such a
remarkable property allows easier single-particle tracking over long
time-scales. In this work we use photoluminescent nanodiamonds of size <50 nm
for intracellular labeling and investigate the mechanism of their uptake by
living cells . By blocking selectively different uptake processes we show that
nanodiamonds enter cells mainly by endocytosis and converging data indicate
that it is clathrin mediated. We also examine nanodiamonds intracellular
localization in endocytic vesicles using immunofluorescence and transmission
electron microscopy. We find a high degree of colocalization between vesicles
and the biggest nanoparticles or aggregates, while the smallest particles
appear free in the cytosol. Our results pave the way for the use of
photoluminescent nanodiamonds in targeted intracellular labeling or biomolecule
deliver
III.7 Planets orbiting stars more massive than the Sun
This book is dedicated to all the people interested in the CoRoT mission and the beautiful data that were delivered during its six year duration. Either amateurs, professional, young or senior researchers, they will find treasures not only at the time of this publication but also in the future twenty or thirty years. It presents the data in their final version, explains how they have been obtained, how to handle them, describes the tools necessary to understand them, and where to find them. It also highlights the most striking first results obtained up to now. CoRoT has opened several unexpected directions of research and certainly new ones still to be discovered
Thermodynamic analysis of the Quantum Critical behavior of Ce-lattice compounds
A systematic analysis of low temperature magnetic phase diagrams of Ce
compounds is performed in order to recognize the thermodynamic conditions to be
fulfilled by those systems to reach a quantum critical regime and,
alternatively, to identify other kinds of low temperature behaviors. Based on
specific heat () and entropy () results, three different types of
phase diagrams are recognized: i) with the entropy involved into the ordered
phase () decreasing proportionally to the ordering temperature
(), ii) those showing a transference of degrees of freedom from the
ordered phase to a non-magnetic component, with their jump
() vanishing at finite temperature, and iii) those ending in a
critical point at finite temperature because their do not decrease
with producing an entropy accumulation at low temperature.
Only those systems belonging to the first case, i.e. with as
, can be regarded as candidates for quantum critical behavior.
Their magnetic phase boundaries deviate from the classical negative curvature
below \,K, denouncing frequent misleading extrapolations down to
T=0. Different characteristic concentrations are recognized and analyzed for
Ce-ligand alloyed systems. Particularly, a pre-critical region is identified,
where the nature of the magnetic transition undergoes significant
modifications, with its discontinuity strongly
affected by magnetic field and showing an increasing remnant entropy at . Physical constraints arising from the third law at are discussed
and recognized from experimental results
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