3,864 research outputs found
Seismic waveform tomography of the central and eastern Mediterranean upper mantle
Abstract. We present a seismic waveform tomography of the upper mantle beneath the central and eastern Mediterranean down to the mantle transition zone. Our methodology incorporates in a consistent manner the information from body and multimode surface waves, source effects, frequency dependence, wavefront healing, anisotropy and attenuation. This allows us to jointly image multiple parameters of the crust and upper mantle. Based on the data from ∼ 17 000 unique source–receiver pairs, gathered from 80 earthquakes, we image radially anisotropic S velocity, P velocity and density. We use a multi-scale approach in which the longest periods (100–150 s) are inverted first, broadening to a period band of 28–150 s. Thanks to a strategy that combines long-period signals and a separation of body and surface wave signals, we are able to image down to the mantle transition zone in most of the model domain. Our model shows considerable detail in especially the northern part of the domain, where data coverage is very dense, and displays a number of clear and coherent high-velocity structures across the domain that can be linked to episodes of current and past subduction. These include the Hellenic subduction zone, the Cyprus subduction zone and high-velocity anomalies beneath the Italian peninsula and the Dinarides. This model is able to explain data from new events that were not included in the inversion.</jats:p
IGR J22517+2218=MG3 J225155+2217: a new gamma-ray lighthouse in the distant Universe
We report on the identification of a new soft gamma ray source, namely IGR
J22517+2218, detected with IBIS/INTEGRAL. The source, which has an observed
20-100 keV flux of ~4 x10^-11 erg cm-2 s-1, is spatially coincident with MG3
J225155+2217, a quasar at z=3.668. The Swift/XRT 0.5-10 keV continuum is flat
(Gamma=1.5) with evidence for a spectral curvature below 1-2 keV either due to
intrinsic absorption (NH=3 +/- 2 x 10^22 cm-2) or to a change in slope (Delta
Gamma= 0.5). X-ray observations indicate flux variability over a 6 days period
which is further supported by a flux mismatch between Swift and INTEGRAL
spectra. IGR J22517+2218 is radio loud and has a flat radio spectrum; optically
it is a broad line emitting quasar with the atypical property of hosting a
narrow line absorption system. The Source Spectral Energy Distribution is
unusual compared to blazars of similar type: either it has the synchrotron peak
in the X/gamma-ray band (i.e. much higher than generally observed) or the
Compton peak in the MeV range (i.e. lower than typically measured). IGR
J22517+2218=MG3 J225155+2217 is the second most distant blazar detected above
20 keV and a gamma-ray lighthouse shining from the edge of our Universe.Comment: 4 pages, 4 figures, Accepted for publication in Astrophysical Journal
Letter
Fokker-Planck equation with variable diffusion coefficient in the Stratonovich approach
We consider the Langevin equation with multiplicative noise term which
depends on time and space. The corresponding Fokker-Planck equation in
Stratonovich approach is investigated. Its formal solution is obtained for an
arbitrary multiplicative noise term given by , and the
behaviors of probability distributions, for some specific functions of %
, are analyzed. In particular, for , the physical
solutions for the probability distribution in the Ito, Stratonovich and
postpoint discretization approaches can be obtained and analyzed.Comment: 6 pages in LATEX cod
Phase-sensitive quantum effects in Andreev conductance of the SNS system of metals with macroscopic phase breaking length
The dissipative component of electron transport through the doubly connected
SNS Andreev interferometer indium (S)-aluminium (N)-indium (S) has been
studied. Within helium temperature range, the conductance of the individual
sections of the interferometer exhibits phase-sensitive oscillations of
quantum-interference nature. In the non-domain (normal) state of indium
narrowing adjacent to NS interface, the nonresonance oscillations have been
observed, with the period inversely proportional to the area of the
interferometer orifice. In the domain intermediate state of the narrowing, the
magneto-temperature resistive oscillations appeared, with the period determined
by the coherence length in the magnetic field equal to the critical one. The
oscillating component of resonance form has been observed in the conductance of
the macroscopic N-aluminium part of the system. The phase of the oscillations
appears to be shifted by compared to that of nonresonance oscillations.
We offer an explanation in terms of the contribution into Josephson current
from the coherent quasiparticles with energies of order of the Thouless energy.
The behavior of dissipative transport with temperature has been studied in a
clean normal metal in the vicinity of a single point NS contact.Comment: 9 pages, 7 figures, to be published in Low Temp. Phys., v. 29, No.
12, 200
Dilatation of the Great Arteries in an Infant with Marfan Syndrome and Ventricular Septal Defect
We describe an infant presenting with contractures of the fingers, a large ventricular septal defect (VSD), and severe pulmonary artery dilatation. He had clinical and echocardiographic features of both neonatal or infantile Marfan syndrome (MFS) and congenital contractural arachnodactyly. After surgical VSD closure, the aortic root developed progressive dilatation while the size of pulmonary artery returned to normal limits. Eventually the diagnosis of MFS was confirmed by DNA analysis
Donor states in modulation-doped Si/SiGe heterostructures
We present a unified approach for calculating the properties of shallow
donors inside or outside heterostructure quantum wells. The method allows us to
obtain not only the binding energies of all localized states of any symmetry,
but also the energy width of the resonant states which may appear when a
localized state becomes degenerate with the continuous quantum well subbands.
The approach is non-variational, and we are therefore also able to evaluate the
wave functions. This is used to calculate the optical absorption spectrum,
which is strongly non-isotropic due to the selection rules. The results
obtained from calculations for Si/SiGe quantum wells allow us to
present the general behavior of the impurity states, as the donor position is
varied from the center of the well to deep inside the barrier. The influence on
the donor ground state from both the central-cell effect and the strain arising
from the lattice mismatch is carefully considered.Comment: 17 pages, 10 figure
Patient-perceived hand function measured can predict treatment for Dupuytren's disease
BACKGROUND: Web based patient-reported outcome measures (PROMs) could aid surgeons to remotely assess the need for examination and subsequent treatment of Dupuytren's disease (DD) patients. We studied whether the Unité Rhumatologique des affections de la Main (URAM) and the Michigan Hand Questionnaire (MHQ) could predict DD treatment.METHODS: In this prospective cohort study, we compared MHQ and URAM scores of treated patients with untreated patients. For the treatment group, we selected a score closest to one year before treatment. For controls we randomly selected a score. Additionally, we tested the predictive value of a one-year change score between 15 months and 6 weeks before treatment. The primary outcome measure was DD treatment.The predictive value was determined using the Area Under the Curve (AUC). An AUC >0.70 was considered as good predictive ability, 0.70-0.50 as poor predictive ability and <0.50 as no predictive ability.RESULTS: We included 141 patients for the MHQ analysis and 145 patients for the URAM analysis. The AUC of the MHQ and URAM scores measured one year before treatment were 0.80 (95% CI 0.71-0.88) and 0.75 (95% CI 0.68-0.82), respectively. The one-year change score resulted in an AUC of <0.60 for both questionnaires.CONCLUSIONS: Our results show that both the MHQ and URAM score measured around one year before treatment can predict treatment for DD. If future studies show that telemonitoring of DD patients with PROMs is also cost-effective, web-based PROMs could optimise patient care and treatment effectiveness of DD.</p
The Diffuse Gamma-Ray Background from Supernovae
The Cosmic Gamma-ray Background (CGB) in the MeV region is believed to be due
to photons from radioactivity produced in SNe throughout the history of
galaxies in the universe. In particular, gamma-ray line emission from the decay
chain 56Ni-> 56Co->56Fe provides the dominant photon source. Although iron
synthesis occurs in all types of SNe, the contribution to the CGB is dominated
by SNIa events due to their higher photon escape probabilities. Estimates of
the star formation history in the universe suggest a rapid increase by a factor
\~ 10 from the present to a redshift z_p ~ 1.5, beyond which it either remains
constant or decreases slowly. We integrate the observed star formation history
to determine the CGB from the corresponding SN rate history. In addition to
gamma-rays from short-lived radioactivity in SNIa and SNII/Ibc we also
calculate the minor contributions from long-lived radioactivities (26Al, 44Ti,
60Co, and electron-positron pair annihilation). Although progenitor evolution
for SNIa is not yet fully understood, various arguments suggest delays of order
1-2 Gy between star formation and the production of SNIa's. The effect of this
delay on the CGB is discussed. We emphasize the value of gamma-ray observations
of the CGB in the MeV range as an independent tool for studies of the cosmic
star formation history. If the delay between star formation and SNIa activity
exceeds 1 Gy substantially, and/or the peak of the cosmic star formation rate
occurs at a redshift much larger than unity, the gamma-ray production of SNIa
would be insufficient to explain the observed CGB. Alternatively, the cosmic
star formation rate would have to be higher (by a factor 2-3) than commonly
assumed, which is in accord with several upward revisions reported in the
recent literature.Comment: Minor changes, 26 pages, 9 figures, Accepted by Ap
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