61 research outputs found
Superscaling analysis of the Coulomb Sum Rule in quasielastic electron-nucleus scattering
The Coulomb sum rule for inclusive quasielastic electron scattering in
C, Ca and Fe is analyzed based on scaling and superscaling
properties. Results obtained in the relativistic impulse approximation with
various descriptions of the final state interactions are shown. A comparison
with experimental data measured at Bates and Saclay is provided. The
theoretical description based on strong scalar and vector terms present in the
relativistic mean field, which has been shown to reproduce the experimental
asymmetric superscaling function, leads to results that are in fair agreement
with Bates data while it sizeably overestimates Saclay data. We find that the
Coulomb sum rule for a momentum transfer saturates to a
value close to 0.9, being very similar for the three nuclear systems
considered. This is in accordance with Bates data, which indicates that these
show no significative quenching in the longitudinal response.Comment: 22 pages, 6 figures. To be published in Phys. Lett.
Relativistic pionic effects in quasielastic electron scattering
The impact of relativistic pionic correlations and meson-exchange currents on
the response functions for electromagnetic quasielastic electron scattering
from nuclei is studied in detail. Results in first-order perturbation theory
are obtained for one-particle emission electronuclear reactions within the
context of the relativistic Fermi gas model. Improving upon previous analyses
where non-relativistic reductions of the currents were performed, here a fully
relativistic analysis in which both forces and currents are treated
consistently is presented. Lorentz covariance is shown to play a crucial role
in enforcing the gauge invariance of the theory. Effects stemming uniquely from
relativity in the pionic correlations are identified and, in particular, a
comprehensive study of the self-energy contributions and of the currents
associated with the pion is presented. First- and second-kind scaling for high
momentum transfer is investigated.Comment: 43 pages, 21 figure
Inelastic neutrino and antineutrino scattering on nuclei and ``strangeness'' of the nucleon
Possibilities to extract information on the strange form factors of the
nucleon from neutrino (antineutrino) inelastic scattering on nuclei, in an
energy range from 200 MeV to 1 GeV and more, are investigated in detail. All
calculations are performed within two relativistic independent particle models
(Fermi gas and shell model); the final state interactions of the ejected
nucleon are taken into account through relativistic optical model potentials.
We have shown that the values of the cross sections significantly depend on the
nuclear model (especially in the lower energy range). However the NC/CC
neutrino-antineutrino asymmetry in a medium--high energy range shows a rather
small dependence on the model and allows to disentangle different values of the
parameters that characterize the strange form factors. We have calculated also
the ratio of the cross sections for inelastic NC scattering of neutrinos on
nuclei, with the emission of a proton and of a neutron. Our calculations show
that this ratio depends rather weakly on the nuclear model and confirm previous
conclusions on the rather strong dependence of this ratio upon the axial
strange form factors.Comment: RevTeX file, 35 pages including 12 figure
A precise measurement of the magnetic field in the corona of the black hole binary V404 Cygni
Observations of binary stars containing an accreting black hole or neutron star often show x-ray emission extending to high energies (>10 kilo–electron volts), which is ascribed to an accretion disk corona of energetic particles akin to those seen in the solar corona. Despite their ubiquity, the physical conditions in accretion disk coronae remain poorly constrained. Using simultaneous infrared, optical, x-ray, and radio observations of the Galactic black hole system V404 Cygni, showing a rapid synchrotron cooling event in its 2015 outburst, we present a precise 461 ± 12 gauss magnetic field measurement in the corona. This measurement is substantially lower than previous estimates for such systems, providing constraints on physical models of accretion physics in black hole and neutron star binary systems.
This article has a correction. Please see: http://science.sciencemag.org/content/360/6386/eaat927
Delineating the molecular and phenotypic spectrum of the SETD1B-related syndrome
Purpose: Pathogenic variants in SETD1B have been associated with a syndromic neurodevelopmental disorder including intellectual disability, language delay, and seizures. To date, clinical features have been described for 11 patients with (likely) pathogenic SETD1B sequence variants. This study aims to further delineate the spectrum of the SETD1B-related syndrome based on characterizing an expanded patient cohort.
Methods: We perform an in-depth clinical characterization of a cohort of 36 unpublished individuals with SETD1B sequence variants, describing their molecular and phenotypic spectrum. Selected variants were functionally tested using in vitro and genome-wide methylation assays.
Results: Our data present evidence for a loss-of-function mechanism of SETD1B variants, resulting in a core clinical phenotype of global developmental delay, language delay including regression, intellectual disability, autism and other behavioral issues, and variable epilepsy phenotypes. Developmental delay appeared to precede seizure onset, suggesting SETD1B dysfunction impacts physiological neurodevelopment even in the absence of epileptic activity. Males are significantly overrepresented and more severely affected, and we speculate that sex-linked traits could affect susceptibility to penetrance and the clinical spectrum of SETD1B variants.
Conclusion: Insights from this extensive cohort will facilitate the counseling regarding the molecular and phenotypic landscape of newly diagnosed patients with the SETD1B-related syndrome
An evaluation of the reliability and sensitivity of the London Chest Activity of Daily Living Scale (LCADL)
AbstractWe have previously reported the validity of a new assessment tool; the London Chest Activity of Daily Living Scale (LCADL). This work investigates the reliability and responsiveness of that measure. Reliability was assessed in 19 patients with stable severe chronic obstructive pulmonary disease (COPD); median age (range) 66 (55–79) years, FEV1 mean (SD) 0.91 (0.29) l, by test–retest 4 weeks apart. Responsiveness was assessed in 59 patients; median age (range) 66 (38–84) years, FEV1 mean (SD) 0.87 (0.30) l, who had undergone at least 6 weeks of pulmonary rehabilitation. Test–retest scores of the LCADL showed a strong relationship with one another, Intraclass correlation coefficient Icc=0.93 95%CI (0.82–0.97) demonstrating evidence of good reliability. With the exception of the Domestic component, all domains of the LCADL showed a statistically significant reduction in dyspnoea during ADLs after pulmonary rehabilitation. There was a statistically significant improvement in the total LCADL score (mean difference (95% CI) −5.91 (from −9.23 to −2.60) after rehabilitation. These data support the use of the LCADL as an outcome measure in COPD which is valid, reliable and responsive to change
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