7,249 research outputs found
New limits on the EC and ECEC processes in Te
New limits on the double beta processes for Te have been obtained
using a 400 cm HPGe detector and a source consisting of natural Te0
powder. At a confidence level of 90% the limits are y for
the EC transition to the ground state, y for the ECEC transition to the first 2 excited
state of Sn (1171.26 keV) and y for
different ECEC() captures to the ground state of Sn.Comment: 9 pages, 4 figures; v2: minor change
Palatini's cousin: A New Variational Principle
A variational principle is suggested within Riemannnian geometry, in which an
auxiliary metric and the Levi Civita connection are varied independently. The
auxiliary metric plays the role of a Lagrange multiplier and introduces
non-minimal coupling of matter to the curvature scalar. The field equations are
2nd order PDEs and easier to handle than those following from the so-called
Palatini method. Moreover, in contrast to the latter method. no gradients of
the matter variables appear. In cosmological modeling, the physics resulting
from the new variational principle will differ from the modeling using the
Palatini method.Comment: 12 page
Roughening and preroughening in the six vertex model with an extended range of interaction
We study the phase diagram of the BCSOS model with an extended interaction
range using transfer matrix techniques, pertaining to the (100) surface of
single component fcc and bcc crystals. The model shows a 2x2 reconstructed
phase and a disordered flat phase. The deconstruction transition between these
phases merges with a Kosterlitz-Thouless line, showing an interplay of Ising
and Gaussian degrees of freedom. As in studies of the fully frustrated XY
model, exponents deviating from Ising are found. We conjecture that
tri-critical Ising behavior may be a possible explanation for the non-Ising
exponents found in those models.Comment: 25 pages in RevTeX 3.0, seven uuencoded postscript figures, REPLACED
because of submission error (figures were not included
Is surface melting a surface phase transition?
Monte Carlo or Molecular Dynamics calculations of surfaces of Lennard-Jones
systems often indicate, apart from a gradual disordering of the surface called
surface melting, the presence of a phase transition at the surface, but cannot
determine the nature of the transition. In the present paper, we provide for a
link between the continuous Lennard-Jones system and a lattice model. We apply
the method for the (001) surface of a Lennard-Jones fcc structure pertaining to
Argon. The corresponding lattice model is a Body Centered Solid on Solid model
with an extended range of interaction, showing in principle rough, flat and
disordered flat phases. We observe that entropy effects considerably lower the
strength of the effective couplings between the atoms. The Argon (001) face is
shown to exhibit a phase transition at T=70.5 +- 0.5 K, and we identify this
transition as roughening. The roughening temperature is in good correspondence
with experimental results for Argon.Comment: 17 pages REVTeX, 14 uuencoded postscript figures appende
Neutron monitors and muon detectors for solar modulation studies: 2. time series
The level of solar modulation at different times (related to the solar
activity) is a central question of solar and galactic cosmic-ray physics. In
the first paper of this series, we have established a correspondence between
the uncertainties on ground-based detectors count rates and the parameter
(modulation level in the force-field approximation) reconstructed from
these count rates. In this second paper, we detail a procedure to obtain a
reference time series from neutron monitor data. We show that we can
have an unbiased and accurate reconstruction (). We also discuss the potential of Bonner spheres spectrometers and muon
detectors to provide time series. Two by-products of this calculation
are updated values for the cosmic-ray database and a web interface to
retrieve and plot from the 50's to today
(\url{http://lpsc.in2p3.fr/crdb}).Comment: 15 pages, 5 figures, 2 tables. AdSR, in press. Web interface to get
modulation parameter phi(t): new tab in http://lpsc.in2p3.fr/crd
A magnetic liquid deformable mirror for high stroke and low order axially symmetrical aberrations
We present a new class of magnetically shaped deformable liquid mirrors made
of a magnetic liquid (ferrofluid). Deformable liquid mirrors offer advantages
with respect to deformable solid mirrors: large deformations, low costs and the
possibility of very large mirrors with added aberration control. They have some
disadvantages (e.g. slower response time). We made and tested a deformable
mirror, producing axially symmetrical wavefront aberrations by applying
electric currents to 5 concentric coils made of copper wire wound on aluminum
cylinders. Each of these coils generates a magnetic field which combines to
deform the surface of a ferrofluid to the desired shape. We have carried out
laboratory tests on a 5 cm diameter prototype mirror and demonstrated defocus
as well as Seidel and Zernike spherical aberrations having amplitudes up to 20
microns, which was the limiting measurable amplitude of our equipmentComment: To appear in Optics Expres
TIROS 1- Camera Attitude Data, Analysis of Location Errors, and Derivation of Correction for Calibration
Tiros i, camera attitude data, analysis of location errors, and derivation of correction for calibratio
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