1,414 research outputs found
Global attractors for Cahn-Hilliard equations with non constant mobility
We address, in a three-dimensional spatial setting, both the viscous and the
standard Cahn-Hilliard equation with a nonconstant mobility coefficient. As it
was shown in J.W. Barrett and J.W. Blowey, Math. Comp., 68 (1999), 487-517, one
cannot expect uniqueness of the solution to the related initial and boundary
value problems. Nevertheless, referring to J. Ball's theory of generalized
semiflows, we are able to prove existence of compact quasi-invariant global
attractors for the associated dynamical processes settled in the natural
"finite energy" space. A key point in the proof is a careful use of the energy
equality, combined with the derivation of a "local compactness" estimate for
systems with supercritical nonlinearities, which may have an independent
interest. Under growth restrictions on the configuration potential, we also
show existence of a compact global attractor for the semiflow generated by the
(weaker) solutions to the nonviscous equation characterized by a "finite
entropy" condition
Antenna-coupled TES bolometer arrays for CMB polarimetry
We describe the design and performance of polarization selective
antenna-coupled TES arrays that will be used in several upcoming Cosmic
Microwave Background (CMB) experiments: SPIDER, BICEP-2/SPUD. The fully
lithographic polarimeter arrays utilize planar phased-antennas for collimation
(F/4 beam) and microstrip filters for band definition (25% bandwidth). These
devices demonstrate high optical efficiency, excellent beam shapes, and
well-defined spectral bands. The dual-polarization antennas provide
well-matched beams and low cross polarization response, both important for
high-fidelity polarization measurements. These devices have so far been
developed for the 100 GHz and 150 GHz bands, two premier millimeter-wave
atmospheric windows for CMB observations. In the near future, the flexible
microstrip-coupled architecture can provide photon noise-limited detection for
the entire frequency range of the CMBPOL mission. This paper is a summary of
the progress we have made since the 2006 SPIE meeting in Orlando, FL
Antenna-coupled TES bolometer arrays for CMB polarimetry
We describe the design and performance of polarization selective
antenna-coupled TES arrays that will be used in several upcoming Cosmic
Microwave Background (CMB) experiments: SPIDER, BICEP-2/SPUD. The fully
lithographic polarimeter arrays utilize planar phased-antennas for collimation
(F/4 beam) and microstrip filters for band definition (25% bandwidth). These
devices demonstrate high optical efficiency, excellent beam shapes, and
well-defined spectral bands. The dual-polarization antennas provide
well-matched beams and low cross polarization response, both important for
high-fidelity polarization measurements. These devices have so far been
developed for the 100 GHz and 150 GHz bands, two premier millimeter-wave
atmospheric windows for CMB observations. In the near future, the flexible
microstrip-coupled architecture can provide photon noise-limited detection for
the entire frequency range of the CMBPOL mission. This paper is a summary of
the progress we have made since the 2006 SPIE meeting in Orlando, FL
Improvement of Postprandial Endothelial Function After a Single Dose of Exenatide in Individuals With Impaired Glucose Tolerance and Recent-Onset Type 2 Diabetes
Astrophysical factors:Zero energy vs. Most effective energy
Effective astrophysical factors for non-resonant astrophysical nuclear
reaction are invariably calculated with respect to a zero energy limit. In the
present work that limit is shown to be very disadvantageous compared to the
more natural effective energy limit. The latter is used in order to modify the
thermonuclear reaction rate formula so that it takes into account both plasma
and laboratory screening effects.Comment: 7 RevTex pages. Accepted for publication in Phys.Rev.
Atomic effects in astrophysical nuclear reactions
Two models are presented for the description of the electron screening
effects that appear in laboratory nuclear reactions at astrophysical energies.
The two-electron screening energy of the first model agrees very well with the
recent LUNA experimental result for the break-up reaction , which so far defies all available theoretical models.
Moreover, multi-electron effects that enhance laboratory reactions of the CNO
cycle and other advanced nuclear burning stages, are also studied by means of
the Thomas-Fermi model, deriving analytical formulae that establish a lower and
upper limit for the associated screening energy. The results of the second
model, which show a very satisfactory compatibility with the adiabatic
approximation ones, are expected to be particularly useful in future
experiments for a more accurate determination of the CNO astrophysical factors.Comment: 14 RevTex pages + 2 ps (revised) figures. Phys.Rev.C (in production
Screening enhancement factors for laboratory CNO and rp astrophysical reactions
Cross sections of laboratory CNO and rp astrophysical reactions are enhanced
due to the presence of the multi-electron cloud that surrounds the target
nuclei. As a result the relevant astrophysical factors are overestimated unless
corrected appropriately. This study gives both an estimate of the error
committed if screening effects are not taken into account and a rough profile
of the laboratory energy thresholds at which the screening effect appears. The
results indicate that, for most practical purposes, screening corrections to
past relevant experiments can be disregarded. Regarding future experiments,
however, screening corrections to the CNO reactions will certainly be of
importance as they are closely related to the solar neutrino fluxes and the rp
process. Moreover, according to the present results, screening effects will
have to be taken into account particularly by the current and future LUNA
experiments, where screened astrophysical factors will be enhanced to a
significant degree.Comment: 6 RevTex pages + 2 ps figures. (Revised version). Accepted for
publication in Journal of Physics
The Certification Matters: A Comparative Performance Analysis of Combat Application Tourniquets versus Non-Certified CAT Look-Alike Tourniquets
Anomaly Cancelation in Field Theory and F-theory on a Circle
We study the manifestation of local gauge anomalies of four- and
six-dimensional field theories in the lower-dimensional Kaluza-Klein theory
obtained after circle compactification. We identify a convenient set of
transformations acting on the whole tower of massless and massive states and
investigate their action on the low-energy effective theories in the Coulomb
branch. The maps employ higher-dimensional large gauge transformations and
precisely yield the anomaly cancelation conditions when acting on the one-loop
induced Chern-Simons terms in the three- and five-dimensional effective theory.
The arising symmetries are argued to play a key role in the study of the
M-theory to F-theory limit on Calabi-Yau manifolds. For example, using the fact
that all fully resolved F-theory geometries inducing multiple Abelian gauge
groups or non-Abelian groups admit a certain set of symmetries, we are able to
generally show the cancelation of pure Abelian or pure non-Abelian anomalies in
these models.Comment: 48 pages, 2 figures; v2: typos corrected, comments on circle fluxes
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