3,860 research outputs found
The formation of helium lines in the spectrum of COM J1740-5340
The He I 5876A absorption line recently discovered in the spectrum of the
companion to the millisecond pulsar PSR J1740-5340 is tentatively attributed to
electron impact excitations due to the irradiation of its atmosphere by
gamma-rays emitted by the pulsar's magnetosphere. Numerical calculations,
similar to those carried out previously for Type Ib SNe, indicate that a pulsar
beam with photon energies ~ 1 MeV gives rise to a 5876A line of the observed
strength if the beam's spin-down conversion efficiency approaches 1%. However,
a significant difficulty for the proposed mechanism is the strength of the
singlet line at 6678A. Compared to the corresponding triplets, singlet lines
are weak because of the loss of excitation when photons emitted in decays to
the ground state ionize hydrogen atoms, an effect absent in the hydrogen-free
atmospheres of Type Ib SNe.Comment: Accepted for publication in A&
On the design of amplify-and-forward MIMO-OFDM relay systems with QoS requirements specified as Schur-convex functions of the MSEs
In this paper, we focus on the design of linear and nonlinear architectures in amplify-and-forward multiple-input–multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) relay networks in which different types of services are supported. The goal is to jointly optimize the processing matrices to minimize the total power consumption while satisfying the quality-of-service (QoS) requirements of each service specified as Schur-convex functions of the mean square errors (MSEs) over all assigned subcarriers. It turns out that the optimal solution leads to the diagonalization of the source–relay–destination channel up to a unitary matrix, depending on the specific Schur-convex function
A Search for Pulsars in Quiescent Soft X-Ray Transients. I
We have carried out a deep search at 1.4 GHz for radio pulsed emission from
six soft X-ray transient sources observed during their X-ray quiescent phase.
The commonly accepted model for the formation of the millisecond radio pulsars
predicts the presence of a rapidly rotating, weakly magnetized neutron star in
the core of these systems. The sudden drop in accretion rate associated with
the end of an X-ray outburst causes the Alfv\`en surface to move outside the
light cylinder, allowing the pulsar emission process to operate. No pulsed
signal was detected from the sources in our sample. We discuss several
mechanisms that could hamper the detection and suggest that free-free
absorption from material ejected from the system by the pulsar radiation
pressure could explain our null result.Comment: accepted by Ap
Physiological toolkit to assess the health impacts on a Magellanic Penguin Spheniscus Magellanicus colony in a high-use touristic region of Patagonia, Argentina
We evaluated the health status of Magellanic Penguins Spheniscus magellanicus inhabiting a region on the Valdes Peninsula (Patagonia, Argentina) that is subject to extensive tourism. We compared individuals nesting along tour trails with others inhabiting non-touristic zones. Hematocrits, blood cell counts, glucose, cholesterol, total proteins, and heterophil/lymphocyte were considered as stress indices. Most parameters were not affected by tourism. Adults and chicks tested positive for bacterial pathogens in both the touristic and control areas. These data complemented a long-term database of systematic physiological monitoring on penguins and will be useful tools for future comparative analyses.Fil: D'Amico, Verónica L.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Bertellotti, Néstor Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentin
A scoring test on probabilistic seismic hazard estimates in Italy
"Probabilistic estimates of seismic hazard represent a basic element for seismic risk reduction strategies and they are a key element of seismic regulation. Thus, it is important to select the most effective estimates among the available ones. An empirical scoring strategy is described here and is applied to a number of time-independent hazard estimates available in Italy both at national and regional scale. The scoring test is based on the comparison of outcomes provided by available computational models at a number of accelero-metric sites where observations are available for 25 years. This comparison also allows identifying computational models that, providing outcomes that are in contrast with observations, should thus be discarded. The analysis shows that most of the hazard estimates proposed for Italy are not in contrast with observations and some computational models perform significantly better than others do. Furthermore, one can see that, at least locally, older estimates can perform better than the most recent ones. Finally, since the same computational model can perform differently depending on the region considered and on average return time of concern, no single model can be considered as the best-performing one. This implies that, moving along the hazard curve, the most suitable model should be selected by considering the specific problem of concern.
Quantum test of the equivalence principle for atoms in superpositions of internal energy eigenstates
The Einstein Equivalence Principle (EEP) has a central role in the
understanding of gravity and space-time. In its weak form, or Weak Equivalence
Principle (WEP), it directly implies equivalence between inertial and
gravitational mass. Verifying this principle in a regime where the relevant
properties of the test body must be described by quantum theory has profound
implications. Here we report on a novel WEP test for atoms. A Bragg atom
interferometer in a gravity gradiometer configuration compares the free fall of
rubidium atoms prepared in two hyperfine states and in their coherent
superposition. The use of the superposition state allows testing genuine
quantum aspects of EEP with no classical analogue, which have remained
completely unexplored so far. In addition, we measure the Eotvos ratio of atoms
in two hyperfine levels with relative uncertainty in the low ,
improving previous results by almost two orders of magnitude.Comment: Accepted for publication in Nature Communicatio
Hygienic and sanitary standards of housing in Europe: a comparative analysis of nine countries
In recent years, growing interest was devoted to housing conditions from both scientific community and public health, so they are now considered among the main environmental and social health determinants of health of the population. Aim of the study is to analyze and compare the current regulations regarding housing sanitary requirements in different Countries of the EU (Sweden, United Kingdom, Denmark, the Netherlands, France, Germany, Portugal, Spain) with the contents of the Italian Health Ministerial Decree 5th July 1975. From the websites of the official channels of the various countries the regulations have been downloaded. For the comparison, only the aspects of BCs concerning the scale of the building were examined; the comparison concerned all the requirements of the Health Ministerial Decree of 5.07.1975 and some other parameters (e.g. indoor chemical pollution, ionizing radiation, non-ionizing radiation) not provided for in the Ministerial Decree, treated in the other standards regulations, and relevant for the indoor well-being of the occupants. The authors observe a wide variability in the contents and in the formulation of the hygienic-sanitary requirements among the different Building Codes, above all as regards the dimensional data and some fundamental themes (e.g. heating systems, mechanical ventilation) whose treatment is often not it is updated with respect to the technological-scientific innovation consolidated over the past few years. A diverse approach among European Countries is also observed: from a market-oriented logic (e.g. UK), to a prescriptive one (Italy), to a functionality-oriented (the Netherlands). The comparative analysis we carried out made it possible to identify convergences and divergences in the standards analysed for the different European countries. As far as the Italian legislation on the usability of residential premises, finally, considering the health, social, environmental and economic trends, many standards contained in the MD 5th July 1975 should be reviewed and updated
C4BQ0: a genetic marker of familial HCV-related liver cirrhosis.
Source
Department of Medicine and Pneumology, V Cervello Hospital, Via Trabucco 180, 90146 Palermo, Italy. [email protected]
Abstract
BACKGROUND AND METHODS:
Host may have a role in the evolution of chronic HCV liver disease. We performed two cross-sectional prospective studies to evaluate the prevalence of cirrhosis in first degree relatives of patients with cirrhosis and the role of two major histocompatibility complex class III alleles BF and C4 versus HCV as risk factors for familial clustering.
FINDINGS:
Ninety-three (18.6%) of 500 patients with cirrhosis had at least one cirrhotic first degree relative as compared to 13 (2.6%) of 500 controls, (OR 7.38; CI 4.21-12.9). C4BQ0 was significantly more frequent in the 93 cirrhotic patients than in 93 cirrhotic controls without familiarity (Hardy-Weinberg equilibrium: chi2 5.76, P = 0.016) and in 20 families with versus 20 without aggregation of HCV related cirrhosis (29.2% versus 11.3%, P = 0.001); the association C4BQ0-HCV was found almost only in cirrhotic patients with a family history of liver cirrhosis.
CONCLUSIONS:
Our studies support the value of C4BQ0 as a risk indicator of familial HCV related cirrhosis
The Relationships between Cognitive Styles and Creativity: The Role of Field Dependence-Independence on Visual Creative Production
Previous studies explored the relationships between field dependent-independent cognitive
style (FDI) and creativity, providing misleading and unclear results. The present research explored
this problematic interplay through the lens of the Geneplore model, employing a product oriented
task: the Visual Creative Synthesis Task (VCST). The latter requires creating objects belonging
to pre-established categories, starting from triads of visual components and consists of two
steps: the preinventive phase and the inventive phase. Following the Amabile’s consensual assessment
technique, three independent judges evaluated preinventive structures in terms of originality
and synthesis whereas inventions were evaluated in terms of originality and appropriateness. The
Embedded Figure Test (EFT) was employed in order to measure the individual’s predisposition
toward the field dependence or the field independence. Sixty undergraduate college students (31
females) took part in the experiment. Results revealed that field independent individuals outperformed
field dependent ones in each of the four VCST scores, showing higher levels of creativity.
Results were discussed in light of the better predisposition of field independent individuals in mental
imagery, mental manipulation of abstract objects, as well as in using their knowledge during
complex tasks that require creativity. Future research directions were also discussed
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