12,280 research outputs found
Normal state magnetotransport properties of -FeSe superconductors
We present -FeSe magnetotransport data, and describe them
theoretically. Using a simplified microscopic model with two correlated
effective orbitals, we determined the normal state electrical conductivity and
Hall coefficient, using Kubo formalism. With model parameters relevant for
Fe-chalcogenides, we describe the observed effect of the structural transition
on the ab-plane electrical resistivity, as well as on the magnetoresistance.
Temperature-dependent Hall coefficient data were measured at 16 Tesla, and
their theoretical description improves upon inclusion of moderate electron
correlations. We confirm the effect of the structural transition on the
electronic structure, finding deformation-induced band splittings comparable to
those reported in angle-resolved photoemission.Comment: 6 pages, 5 figure
Impact of communicative and informative strategies on influenza vaccination adherence and absenteeism from work of health care professionals working at the university hospital of palermo, Italy: A quasi-experimental field trial on twelve influenza seasons
Every year, about 20% of health care workers (HCWs) acquire influenza, continuing to work and encouraging virus spreading. Influenza vaccination coverage rates and absenteeism from work among HCWs of the University Hospital (UH) of Palermo were analyzed before and after the implementation of several initiatives in order to increase HCWs’ awareness about influenza vaccination. Vaccines administration within hospital units, dedicated web pages on social media and on the UH of Palermo institutional web site, and mandatory compilation of a dissent form for those HCWs who refused vaccination were carried out during the last four influenza seasons. After the introduction of these strategies, influenza vaccination coverage went up from 5.2% (2014/2015 season) to 37.2% (2018/2019 season) (p<0.001), and mean age of vaccinated HCWs significantly decreased from 48.1 years (95% CI: 45.7–50.5) to 35.9 years (95% CI: 35.0–36.8). A reduction of working days lost due to acute sickness among HCWs of the UH of Palermo was observed. Fear of adverse reactions and not considering themselves as a high-risk group for contracting influenza were the main reasons reported by HCWs that refused vaccination. Strategies undertaken at the UH of Palermo allowed a significant increase in vaccination adherence and a significant reduction of absenteeism from work
Algebraic Characterization of Vector Supersymmetry in Topological Field Theories
An algebraic cohomological characterization of a class of linearly broken
Ward identities is provided. The examples of the topological vector
supersymmetry and of the Landau ghost equation are discussed in detail. The
existence of such a linearly broken Ward identities turns out to be related to
BRST exact antifield dependent cocycles with negative ghost number.Comment: 30 pages, latex2e file, subm. to Journ. of Math. Phy
The Lithium Depletion Boundary and the Age of the Young Open Cluster IC~2391
We have obtained new photometry and intermediate resolution ( \AA\ ) spectra of 19 of these objects
(14.9 17.5) in order to confirm cluster membership. We
identify 15 of our targets as likely cluster members based on their
photometry, spectral types, radial velocity, and H emission strengths.
Higher S/N spectra were obtained for 8 of these probable cluster members in
order to measure the strength of the lithium 6708 \AA\ doublet and thus obtain
an estimate of the cluster's age. One of these 8 stars has a definite lithium
detection and two other (fainter) stars have possible lithium detections. A
color-magnitude diagram for our program objects shows that the lithium
depletion boundary in IC~2391 is at =16.2. Using recent theoretical model
predictions, we derive an age for IC~2391 of 535 Myr. While this is
considerably older than the age most commonly attributed for this cluster
(35 Myr) this result for IC~2391 is comparable those recently derived for
the Pleiades and Alpha Persei clusters and can be explained by new models for
high mass stars that incorporate a modest amount of convective core
overshooting.Comment: ApJ Letters, acccepte
A Robust Filter for the BeppoSAX Gamma Ray Burst Monitor Triggers
The BeppoSAX Gamma Ray Burst Monitor (GRBM) is triggered any time a
statistically significant counting excess is simultaneously revealed by at
least two of its four independent detectors. Several spurious effects,
including highly ionizing particles crossing two detectors, are recorded as
onboard triggers. In fact, a large number of false triggers is detected, in the
order of 10/day. A software code, based on an heuristic algorithm, was written
to discriminate between real and false triggers. We present the results of the
analysis on an homogeneous sample of GRBM triggers, thus providing an estimate
of the efficiency of the GRB detection system consisting of the GRBM and the
software.Comment: Proc. 5th Huntsville GRB Symposiu
El estado inicial durante el acondicionamiento del acero para la electrodeposición de Zinc en medio ácido
En el presente trabajo se estudia el acondicionamiento de electrodos de acero para la electrodeposición de zinc a partir de soluciones de ZnCl2 + NH4Cl. El control del “estado inicial”, determinado por el potencial de acondicionamiento, Ei, y la densidad de corriente inicial anódica, ja,i, son de fundamental importancia para el proceso de electrodeposición. Los valores del potencial a circuito abierto, ECA, son afectados por los iones presentes tanto para soluciones de base de NH4Cl y de (NH4)2SO4, como para soluciones de electrodeposición. La comparación de las cronoamperometrías en el potencial inicial, Ei, muestra que este debe ser levemente más positivo que el ECA. Se encuentra que si se parte siempre de un valor de ja,i ≤ 100 (μAcm-2) estacionario y con el electrodo pulido siempre en iguales condiciones, se aseguran las condiciones de reproducibilidad experimental en las diferentes técnicas de electrodeposición.Fil:Mahmud, Z. Instituto Nacional de Tecnología Industrial (INTI). Procesos SuperficialesFil:Gordillo, G. Universidad de Buenos Aires (UBA). Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química FísicaFil:Ventura D'Alkaine, C. Universidade Federal de São Carlos (UFSCar
The early evolution of Globular Clusters: the case of NGC 2808
Enhancement and spread of helium among globular cluster stars have been
recently suggested as a way to explain the horizontal branch blue tails, in
those clusters which show a primordial spread in the abundances of CNO and
other elements involved in advanced CNO burning (D'Antona et al. 2002). In this
paper we examine the implications of the hypothesis that, in many globular
clusters, stars were born in two separate events: an initial burst (first
generation), which gives origin to probably all high and intermediate mass
stars and to a fraction of the cluster stars observed today, and a second,
prolonged star formation phase (second generation) in which stars form directly
from the ejecta of the intermediate mass stars of the first generation. In
particular, we consider in detail the morphology of the horizontal branch in
NGC 2808 and argue that it unveils the early cluster evolution, from the birth
of the first star generation to the end of the second phase of star formation.
This framework provides a feasible interpretation for the still unexplained
dichotomy of NGC 2808 horizontal branch, attributing the lack of stars in the
RR Lyr region to the gap in the helium content between the red clump, whose
stars are considered to belong to the first stellar generation and have
primordial helium, and the blue side of the horizontal branch, whose minimum
helium content reflects the helium abundance in the smallest mass
(~4Msun)contributing to the second stellar generation. This scenario provides
constraints on the required Initial Mass Function, in a way that a great deal
of remnant neutron stars and stellar mass black holes might have been produced.Comment: 23 pages, 7 figures, in press on The Astrophysical Journa
CNO enrichment by rotating AGB stars in globular clusters
AGB stars have long been held responsible for the important star-to-star
variations in light elements observed in Galactic globular clusters. We analyse
the main impacts of a first generation of rotating intermediate-mass stars on
the chemical properties of second-generation globular cluster stars. The
rotating models were computed without magnetic fields and without the effects
of internal gravity waves. They account for the transports by meridional
currents and turbulence. We computed the evolution of both standard and
rotating stellar models with initial masses between 2.5 and 8 Msun within the
metallicity range covered by Galactic globular clusters. During central
He-burning, rotational mixing transports fresh CO-rich material from the core
towards the hydrogen-burning shell, leading to the production of primary 14N.
In stars more massive than M > 4 Msun, the convective envelope reaches this
reservoir during the second dredge-up episode, resulting in a large increase in
the total C+N+O content at the stellar surface and in the stellar wind. The
corresponding pollution depends on the initial metallicity. At low- and
intermediate-metallicity, it is at odds with the constancy of C+N+O observed
among globular cluster low-mass stars. With the given input physics, our models
suggest that massive rotating AGB stars have not shaped the abundance patterns
observed in low- and intermediate-metallicity globular clusters. Our
non-rotating models, on the other hands, do not predict surface C+N+O
enhancements, hence are in a better position as sources of the chemical
anomalies in globular clusters showing the constancy of the C+N+O. However at
the moment, there is no reason to think that intermediate mass stars were not
rotating.Comment: Accepted in Astronomy and Astrophysics, 7 pages, 3 figure
Lymphocyte Subsets and Inflammatory Cytokines of Monoclonal Gammopathy of Undetermined Significance and Multiple Myeloma
Almost all multiple myeloma (MM) cases have been demonstrated to be linked to earlier monoclonal gammopathy of undetermined significance (MGUS). Nevertheless, there are no identified characteristics in the diagnosis of MGUS that have been helpful in differentiating subjects whose cancer may progress to a malignant situation. Regarding malignancy, the role of lymphocyte subsets and cytokines at the beginning of neoplastic diseases is now incontestable. In this review, we have concentrated our attention on the equilibrium between the diverse lymphocyte subsets and the cytokine system and summarized the current state of knowledge, providing an overview of the condition of the entire system in MGUS and MM. In an age where the therapy of neoplastic monoclonal gammopathies largely relies on drugs capable of acting on the immune system (immunomodulants, immunological checkpoint inhibitors, CAR-T), detailed knowledge of the the differences existing in benign and neoplastic forms of gammopathy is the main foundation for the adequate and optimal use of new drugs
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