3,221 research outputs found
Probing viscoelastic properties of a thin polymer film sheared between a beads layer and quartz crystal resonator
We report measurements of viscoelastic properties of thin polymer films of
10-100 nm at the MHz range. These thin films are confined between a quartz
crystal resonator and a millimetric bead layer, producing an increase of both
resonance frequency and dissipation of the quartz resonator. The shear modulus
and dynamic viscosity of thin films extracted from these measurements are
consistent with the bulk values of the polymer. This modified quartz resonator
provides an easily realizable and effective tool for probing the rheological
properties of thin films at ambient environment.Comment: submitted to ap
A converse comparison theorem for backward stochastic differential equations with jumps
This paper establishes a converse comparison theorem for real-valued
decoupled forward backward stochastic differential equations with jumps.Comment: The former version contains an error in the proof of the main
theorem. This version presents a similar result, but for a more restricted
class of equations, so that the error is now fixe
Does rotation of B stars depend on metallicity? preliminary results from GIRAFFE spectra
We show the vsini distribution of main sequence B stars in sites of various
metallicities, in the absolute magnitude range -3.34 < Mv < -2.17. These
include Galactic stars in the field measured by Abt et al. (2002), members of
the h & chi Per open clusters measured by North et al. (2004), and five fields
in the SMC and LMC measured at ESO Paranal with the FLAMES-GIRAFFE
spectrograph, within the Geneva-Lausanne guaranteed time. Following the
suggestion by Maeder et al. (1999), we do find a higher rate of rapid rotators
in the Magellanic Clouds than in the Galaxy, but the vsini distribution is the
same in the LMC and in the SMC in spite of their very different metallicities.Comment: 2 pages, 1 figure, poster presented at the ESO/Arcetri Workshop on
"Chemical abundances and mixing in stars in the Milky Way and its
satellites", 13-17 Sept. 200
Phase Space Formulation of Filtering. Insight into the Wave-Particle Duality
A phase space formulation of the filtering process upon an incident quantum
state is developed. This formulation can explain the results of both quantum
interference and delayed-choice experiments without making use of the
controversial wave-particle duality. Quantum particles are seen as localized
and indivisible concentrations of energy and/or mass, their probability
amplitude in phase space being described by the Wigner distribution function.
The wave or particle nature appears in experiments in which the interference
term of the Wigner distribution function is present or absent, respectively,
the filtering devices that modify the quantum wavefunction throughout the
set-up, from its generation to its final detection, being responsible for the
modification of the Wigner distribution function.Comment: 32 pages, 12 figure
New distance and depth estimates from observations of eclipsing binaries in the SMC
A sample of 33 eclipsing binaries observed in a field of the SMC with
FLAMES@VLT is presented. The radial velocity curves obtained, together with
existing OGLE light curves, allowed the determination of all stellar and
orbital parameters of these binary systems. The mean distance modulus of the
observed part of the SMC is 19.05, based on the 26 most reliable systems.
Assuming an average error of 0.1 mag on the distance modulus to an individual
system, and a gaussian distribution of the distance moduli, we obtain a 2-sigma
depth of 0.36 mag or 10.6 kpc. Some results on the kinematics of the binary
stars and of the H II gas are also given.Comment: 6 pages, 4 figures, Proc. IAU Symp. No 256, The Magellanic System:
Stars, Gas and Galaxies, eds. Jacco Th. van Loon & Joana M. Oliveir
Prospectives
Tiré de: Prospectives, vol. 15, no 3, oct. 1979.Titre de l'écran-titre (visionné le 24 janv. 2013
A multiwavelength investigation of the massive eclipsing binary Cyg OB2 #5
The properties of the early-type binary Cyg OB2 #5 have been debated for many
years and spectroscopic and photometric investigations yielded conflicting
results. We have attempted to constrain the physical properties of the binary
by collecting new optical and X-ray observations. We find that the orbital
period of the system slowly changes though we are unable to discriminate
between several possible explanations of this trend. The best fit solution of
the continuum light curve reveals a contact configuration with the secondary
star being significantly brighter and hotter on its leading side facing the
primary. The mean temperature of the secondary star turns out to be only
slightly lower than that of the primary, whilst the bolometric luminosity ratio
is found to be 3.1. The solution of the light curve yields a distance of 925
+/- 25 pc much lower than the usually assumed distance of the Cyg OB2
association. Whilst we confirm the existence of episodes of higher X-ray
fluxes, the data reveal no phase-locked modulation with the 6.6 day period of
the eclipsing binary nor any clear relation between the X-ray flux and the 6.7
yr radio cycle. The bright region of the secondary star is probably heated by
energy transfer in a common envelope in this contact binary system as well as
by the collision with the primary's wind. The existence of a common photosphere
probably also explains the odd mass-luminosity relation of the stars in this
system. Most of the X-ray, non-thermal radio, and possibly gamma-ray emission
of Cyg OB2 #5 is likely to arise from the interaction of the combined wind of
the eclipsing binary with at least one additional star of this multiple system
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