2,560 research outputs found

    Stratigraphic variations control deformation patterns in evaporite basins : Messinian examples, onshore and offshore Sicily (Italy)

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    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 2010–2011 grant.Peer reviewedPublisher PD

    Distortion of the acoustic peaks in the CMBR due to a primordial magnetic field

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    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.

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    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

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    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 G0G_0 and G0â€ČG_0^\prime 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.

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    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

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    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

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    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

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    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

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    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

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    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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