1,292 research outputs found
1.65 micrometers (H-band) surface photometry of galaxies. III: observations of 558 galaxies with the TIRGO 1.5m telescope
We present near-infrared H-band (1.65 micron) surface photometry of 558
galaxies in the Coma Supercluster and in the Virgo cluster. This data set,
obtained with the Arcetri NICMOS3 camera ARNICA mounted on the Gornergrat
Infrared Telescope, is aimed at complementing, with observations of mostly
early-type objects, our NIR survey of spiral galaxies in these regions,
presented in previous papers of this series. Magnitudes at the optical radius,
total magnitudes, isophotal radii and light concentration indices are derived.
We confirm the existence of a positive correlation between the near-infrared
concentration index and the galaxy H-band luminosity. (Tables 1 and 2 are only
available in electronic form upon request to [email protected])Comment: 12 pages, 6 figures. Accepted for publication in A&A
Circumferential buckling of a hydrogel tube emptying upon dehydration
A cylindrical hydrogel tube, completely submerged in water, hydrates by swelling and filling its internal cavity. When it comes back into contact with air, it dehydrates: the tube thus expels the solvent through the walls, shrinking. This dehydration process causes a depression in the tube cavity, which can lead to circumferential buckling. Here we study the occurrence of such buckling using a continuous model that combines nonlinear elasticity with Flory-Rehner theory, to take into account both the large deformations and the active behaviour of the hydrogel. In quasi-static approximation, we use the incremental deformation formalism, extended to the chemo-mechanical equations, to determine the threshold value of the enclosed volume at which buckling is triggered. This critical value is found to depend on the shell thickness, chemical potential and constitutive features. The results obtained are in good agreement with the results of the finite element simulations of the complete dynamic problem
Oscillations of solar atmosphere neutrinos
The Sun is a source of high energy neutrinos (E > 10 GeV) produced by cosmic
ray interactions in the solar atmosphere. We study the impact of three-flavor
oscillations (in vacuum and in matter) on solar atmosphere neutrinos, and
calculate their observable fluxes at Earth, as well as their event rates in a
kilometer-scale detector in water or ice. We find that peculiar three-flavor
oscillation effects in matter, which can occur in the energy range probed by
solar atmosphere neutrinos, are significantly suppressed by averaging over the
production region and over the neutrino and antineutrino components. In
particular, we find that the relation between the neutrino fluxes at the Sun
and at the Earth can be approximately expressed in terms of phase-averaged
``vacuum'' oscillations, dominated by a single mixing parameter (the angle
theta_23).Comment: v2: 11 pages, 8 eps figures. Content added (Sec. III D and Fig. 6),
references updated. Matches the published versio
The TNG Near Infrared Camera Spectrometer
NICS (acronym for Near Infrared Camera Spectrometer) is the near-infrared
cooled camera-spectrometer that has been developed by the Arcetri Infrared
Group at the Arcetri Astrophysical Observatory, in collaboration with the
CAISMI-CNR for the TNG (the Italian National Telescope Galileo at La Palma,
Canary Islands, Spain).
As NICS is in its scientific commissioning phase, we report its observing
capabilities in the near-infrared bands at the TNG, along with the measured
performance and the limiting magnitudes. We also describe some technical
details of the project, such as cryogenics, mechanics, and the system which
executes data acquisition and control, along with the related software.Comment: 7 pages, 5 figures, compiled with A&A macros. A&A in pres
Unification of gravity, gauge fields, and Higgs bosons
We consider a diffeomorphism invariant theory of a gauge field valued in a
Lie algebra that breaks spontaneously to the direct sum of the spacetime
Lorentz algebra, a Yang-Mills algebra, and their complement. Beginning with a
fully gauge invariant action -- an extension of the Plebanski action for
general relativity -- we recover the action for gravity, Yang-Mills, and Higgs
fields. The low-energy coupling constants, obtained after symmetry breaking,
are all functions of the single parameter present in the initial action and the
vacuum expectation value of the Higgs.Comment: 12 pages, no figures. v2 minor correction
Probing non-standard decoherence effects with solar and KamLAND neutrinos
It has been speculated that quantum gravity might induce a "foamy" space-time
structure at small scales, randomly perturbing the propagation phases of
free-streaming particles (such as kaons, neutrons, or neutrinos). Particle
interferometry might then reveal non-standard decoherence effects, in addition
to standard ones (due to, e.g., finite source size and detector resolution.) In
this work we discuss the phenomenology of such non-standard effects in the
propagation of electron neutrinos in the Sun and in the long-baseline reactor
experiment KamLAND, which jointly provide us with the best available probes of
decoherence at neutrino energies E ~ few MeV. In the solar neutrino case, by
means of a perturbative approach, decoherence is shown to modify the standard
(adiabatic) propagation in matter through a calculable damping factor. By
assuming a power-law dependence of decoherence effects in the energy domain
(E^n with n = 0,+/-1,+/-2), theoretical predictions for two-family neutrino
mixing are compared with the data and discussed. We find that neither solar nor
KamLAND data show evidence in favor of non-standard decoherence effects, whose
characteristic parameter gamma_0 can thus be significantly constrained. In the
"Lorentz-invariant" case n=-1, we obtain the upper limit gamma_0<0.78 x 10^-26
GeV at 95% C.L. In the specific case n=-2, the constraints can also be
interpreted as bounds on possible matter density fluctuations in the Sun, which
we improve by a factor of ~ 2 with respect to previous analyses.Comment: Minor changes. Version accepted for publication in Phys. Rev.
Cu-exchanged 3D-printed geopolymer/ZSM-5 monolith for selective catalytic reduction of NOx
Cu-exchanged zeolites with MFI structure, such as ZSM-5, represent effective catalysts for SCR processes when the application requires a good thermal stability under a wide range of temperature as for the after-treatment of exhaust gas from diesel engine. The production of zeolite in a structured form, mandatorily required for mobile applications, is quite complex due to the poor adhesion of the material. In this paper 3D-printed geopolymers containing about 37 % ZSM-5 are proposed as potentially structured catalysts for SCR applications. The production of the monolith and the pre-treatment necessary to introduce copper as active exchanged cation are investigated. The effect of pre-treatments on the physical and morphological structure of both geopolymer and zeolite and on the nature of copper introduced in the subsequent step was studied using characterization techniques such as SEM, XRD, N2 physisorption and Temperature Programmed Reduction (TPR)
Day-night asymmetry of high and low energy solar neutrino events in Super-Kamiokande and in the Sudbury Neutrino Observatory
In the context of solar neutrino oscillations among active states, we briefly
discuss the current likelihood of Mikheyev-Smirnov-Wolfenstein (MSW) solutions
to the solar neutrino problem, which appear to be currently favored at large
mixing, where small Earth regeneration effects might still be observable in
Super-Kamiokande (SK) and in the Sudbury Neutrino Observatory (SNO). We point
out that, since such effects are larger at high (low) solar neutrino energies
for high (low) values of the mass square difference \delta m^2, it may be
useful to split the night-day rate asymmetry in two separate energy ranges. We
show that the difference \Delta of the night-day asymmetry at high and low
energy may help to discriminate the two large-mixing solutions at low and high
\delta m^2 through a sign test, both in SK and in SNO, provided that the
sensitivity to \Delta can reach the (sub)percent level.Comment: 6 pages (RevTeX) + 4 figures (PostScript). Final version, to appear
in Phys. Rev.
Geometric Effects and Computation in Spin Networks
When initially introduced, a Hamiltonian that realises perfect transfer of a
quantum state was found to be analogous to an x-rotation of a large spin. In
this paper we extend the analogy further to demonstrate geometric effects by
performing rotations on the spin. Such effects can be used to determine
properties of the chain, such as its length, in a robust manner. Alternatively,
they can form the basis of a spin network quantum computer. We demonstrate a
universal set of gates in such a system by both dynamical and geometrical
means
Where we are on : addendum to "Global neutrino data and recent reactor fluxes: status of three-flavour oscillation parameters"
In this addendum to arXiv:1103.0734 we consider the recent results from
long-baseline searches at the T2K and MINOS experiments and
investigate their implications for the mixing angle and the
leptonic Dirac CP phase . By combining the indication for a
non-zero value of coming from T2K data with global neutrino
oscillation data we obtain a significance for of about
with best fit points for normal
(inverted) neutrino mass ordering. These results depend somewhat on assumptions
concerning the analysis of reactor neutrino data.Comment: 5 pages, 2 figures and 1 tabl
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