2,560 research outputs found
Stratigraphic variations control deformation patterns in evaporite basins : Messinian examples, onshore and offshore Sicily (Italy)
Acknowledgements and Funding We are grateful to Ente Minerario Siciliano and Italkali for the provision of extensive subsurface data from Realmonte, Corvillo and Mandre areas. We thank F. Peel and an anonymous referee for comments. Seismic reflection data are available for inspection and interpretation at the Virtual Seismic Atlas (www. seismicatlas.org). R.M. acknowledges a MIUR Cofin-PRIN 2010â2011 grant.Peer reviewedPublisher PD
Distortion of the acoustic peaks in the CMBR due to a primordial magnetic field
In this paper we study the effect of a magnetic field on the fluctuation
spectrum of the cosmic microwave background. We find that upcoming measurements
might give interesting bounds on large scale magnetic fields in the early
Universe. If the effects are seen, it might be possible to establish the
presence of different fields in different patches of the sky. Absence of any
effect, will provide by one order of magnitude a better limit for a primordial
field, now given by nucleosynthesis.Comment: 10 pages, 2 .ps figures included, extra reference added and
typographical errors correcte
Ureteroscopic laser treatment of upper urinary tract neoplasms.
BACKGROUND: Endoscopic management of upper urinary tract transitional cell carcinoma has assumed an important role in diagnosis and treatment. The introduction of small diameter rigid and flexible ureteroscopes has permitted access to the upper tract. Biopsy techniques have been developed for accurate diagnosis, and the addition of lasers has given the urologists an excellent tool for treatment. METHODS: Medical literature available relative to the endoscopic laser treatment of upper tract neoplasms has been reviewed. RESULTS: Ureteroscopic treatment has been characterized by good success with high recurrence rates, both in the upper tract and in the bladder. Bladder recurrence rates are similar to those seen after surgical treatment of upper tract tumors. Surveillance has been ureteroscopic since the other diagnostic options are inadequate. The holmium and neodymium:YAG lasers are the devices most commonly used now for the endoscopic treatment of upper tract tumors. CONCLUSION: Ureteroscopic treatment of upper tract neoplasms usually with ablation and resection using the neodymium and holmium: YAG lasers is a current acceptable procedure. This should be considered as one of the options in tumor treatment
Extended Skyrme interaction (II): ground state of nuclei and of nuclear matter
We study the effect of time-odd components of the Skyrme energy density
functionals on the ground state of finite nuclei and in nuclear matter. The
spin-density dependent terms, which have been recently proposed as an extension
of the standard Skyrme interaction, are shown to change the total binding
energy of odd-nuclei by only few tenths of keV, while the time-odd components
of standard Skyrme interactions give an effect that is larger by one order of
magnitude. The HFB-17 mass formula based on a Skyrme parametrization is
adjusted including the new spin-density dependent terms. A comprehensive study
of binding energies in the whole mass table of 2149 nuclei gives a root mean
square (rms) deviation of 0.575 MeV between experimental data and the
calculated results, which is slightly better than the original HFB-17 mass
formula. From the analysis of the spin instabilities of nuclear matter,
restrictions on the parameters governing the spin-density dependent terms are
evaluated. We conclude that with the extended Skyrme interaction, the Landau
parameters and could be tuned with a large flexibility
without changing the ground-state properties in nuclei and in nuclear matter.Comment: 18 pages, 4 tables, 6 figure
Determining the effects of cattle grazing treatments on Yosemite toads (Anaxyrus [=Bufo] canorus) in montane meadows.
Amphibians are experiencing a precipitous global decline, and population stability on public lands with multiple uses is a key concern for managers. In the Sierra Nevada Mountains (California, USA), managers have specifically identified livestock grazing as an activity that may negatively affect Yosemite toads due to the potential overlap of grazing with toad habitat. Grazing exclusion from Yosemite toad breeding and rearing areas and/or entire meadows have been proposed as possible management actions to alleviate the possible impact of cattle on this species. The primary objective of this study was to determine if different fencing treatments affect Yosemite toad populations. We specifically examined the effect of three fencing treatments on Yosemite toad breeding pool occupancy, tadpoles, and young of the year (YOY). Our hypothesis was that over the course of treatment implementation (2006 through 2010), Yosemite toad breeding pool occupancy and early life stage densities would increase within two fencing treatments relative to actively grazed meadows due to beneficial changes to habitat quality in the absence of grazing. Our results did not support our hypothesis, and showed no benefit to Yosemite toad presence or early life stages in fenced or partially fenced meadows compared to standard USDA Forest Service grazing levels. We found substantial Yosemite toad variation by both meadow and year. This variation was influenced by meadow wetness, with water table depth significant in both the tadpole and YOY models
A Two-Threshold Model for Scaling Laws of Non-Interacting Snow Avalanches
The sizes of snow slab failure that trigger snow avalanches are power-law
distributed. Such a power-law probability distribution function has also been
proposed to characterize different landslide types. In order to understand this
scaling for gravity driven systems, we introduce a two-threshold 2-d cellular
automaton, in which failure occurs irreversibly. Taking snow slab avalanches as
a model system, we find that the sizes of the largest avalanches just
preceeding the lattice system breakdown are power law distributed. By tuning
the maximum value of the ratio of the two failure thresholds our model
reproduces the range of power law exponents observed for land-, rock- or snow
avalanches. We suggest this control parameter represents the material cohesion
anisotropy.Comment: accepted PR
Neutron Irradiation of Mg11B2 : From the Enhancement to the Suppression of Superconducting Properties
In this letter we present the effect of neutron irradiation up to fluences of
3.9 1019 n/cm2 on the superconducting properties of MgB2. In order to obtain a
disorder structure homogeneously distributed, the experiment was carried out on
bulk samples prepared with the 11B isotope. Up to fluences of 1018 n/cm2 the
critical temperature is slightly diminished (36 K) and the superconducting
properties are significantly improved; the upper critical field is increased
from 13.5 T to 20.3 T at 12 K and the irreversibility field is doubled at 5 K.
For larger neutron fluences the critical temperature is suppressed down to 12 K
and the superconducting properties come out strongly degraded.Comment: 13 pages, 4 figures. Submitted to Appl.Phys.Let
Cosmological Magnetogenesis driven by Radiation Pressure
The origin of large scale cosmological magnetic fields remains a mystery,
despite the continuous efforts devoted to that problem. We present a new model
of magnetic field generation, based on local charge separation provided by an
anisotropic and inhomogeneous radiation pressure. In the cosmological context,
the processes we explore take place at the epoch of the reionisation of the
Universe. Under simple assumptions, we obtain results (i) in terms of the order
of magnitude of the field generated at large scales and (ii) in terms of its
power spectrum. The amplitudes obtained (B ~ 8.10^(-6) micro-Gauss) are
considerably higher than those obtained in usual magnetogenesis models and
provide suitable seeds for amplification by adiabatic collapse and/or dynamo
during structure formation.Comment: 9 pages, 2 figure
Radiative Neutrino Decay in Media
In this letter we introduce a new method to determine the radiative neutrino
decay rate in the presence of a medium. Our approach is based on the
generalisation of the optical theorem at finite temperature and density.
Differently from previous works on this subject, our method allows to account
for dispersive and dissipative electromagnetic properties of the medium. Some
inconsistencies that are present in the literature are pointed-out and
corrected here. We shortly discuss the relevance of our results for neutrino
evolution in the early universe.Comment: 11 pages, 3 encapsulated figure
Mechanically reinforced MgB2 wires and tapes with high transport currents
Monofilamentary MgB2-wires with a 2- or 3-component sheath containing
mechanical reinforcing stainless steel (SS) were prepared and characterized. In
direct contact to the superconductor Nb, Ta or Fe was used. For a selection of
samples with a Fe and Fe/SS sheath, we investigated the transport critical
current behaviour in magnetic fields changing systematically the geometrical
shape from a round wire to a flat tape. A strong increase of the current
densities in flat tapes was observed and possible reasons for this are
discussed. Reinforcing the sheath in the outer layer with different amounts of
stainless steel leads to a systematic field dependent decrease of the transport
critical current density with increasing steel amount. This is an indication
for a pre-stress induced degradation of the critical currents in MgB2 wires and
first Ic-stress-strain experiments seem to confirm this observation and
interpretation.Comment: 12 pages, 5 figures. Submitted to Physica C (Proceedings of EUCAS
2001
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