13,102 research outputs found
A Tractable Product Channel Model for Line-of-Sight Scenarios
We present a general and tractable fading model for line-of-sight (LOS)
scenarios, which is based on the product of two independent and non-identically
distributed - shadowed random variables. Simple closed-form
expressions for the probability density function, cumulative distribution
function and moment-generating function are derived, which are as tractable as
the corresponding expressions derived from a product of Nakagami- random
variables. This model simplifies the challenging characterization of LOS
product channels, as well as combinations of LOS channels with non-LOS ones. We
leverage these results to analyze performance measures of interest in the
contexts of wireless powered and backscatter communications, where both forward
and reverse links are inherently of LOS nature, as well as in device-to-device
communications subject to composite fading. In these contexts, the model shows
a higher flexibility when fitting field measurements with respect to
conventional approaches based on product distributions with deterministic LOS,
together with a more complete physical interpretation of the underlying
propagation characteristics.Comment: This work has been submitted to the IEEE for possible publication.
Copyright may be transferred without notice, after which this version may no
longer be accessibl
Determination of the light exposure on the photodiodes of a new instrumented baffle for the Virgo input mode cleaner end-mirror
As part of the upgrade program of the Advanced Virgo interferometer, the
installation of new instrumented baffles surrounding the main test masses is
foreseen. As a demonstrator, and to validate the technology, the existing
baffle in the area of the input mode cleaner end-mirror will be first replaced
by a baffle equipped with photodiodes. This paper presents detailed simulations
of the light distribution on the input mode cleaner baffle, with the aim to
determine the light exposure of the photodiodes under different scenarios of
the interferometer operation.Comment: 9 pages and 8 figure
Relativistic quantum mechanics of a Dirac oscillator
The Dirac oscillator is an exactly soluble model recently introduced in the
context of many particle models in relativistic quantum mechanics. The model
has been also considered as an interaction term for modelling quark confinement
in quantum chromodynamics. These considerations should be enough for
demonstrating that the Dirac oscillator can be an excellent example in
relativistic quantum mechanics. In this paper we offer a solution to the
problem and discuss some of its properties. We also discuss a physical picture
for the Dirac oscillator's non-standard interaction, showing how it arises on
describing the behaviour of a neutral particle carrying an anomalous magnetic
moment and moving inside an uniformly charged sphere.Comment: 19 pages, 1 figur
Rings and spirals in barred galaxies. I Building blocks
In this paper we present building blocks which can explain the formation and
properties both of spirals and of inner and outer rings in barred galaxies. We
first briefly summarise the main results of the full theoretical description we
have given elsewhere, presenting them in a more physical way, aimed to an
understanding without the requirement of extended knowledge of dynamical
systems or of orbital structure. We introduce in this manner the notion of
manifolds, which can be thought of as tubes guiding the orbits. The dynamics of
these manifolds can govern the properties of spirals and of inner and outer
rings in barred galaxies. We find that the bar strength affects how unstable
the L1 and L2 Lagrangian points are, the motion within the 5A5A5Amanifold tubes
and the time necessary for particles in a manifold to make a complete turn
around the galactic centre. We also show that the strength of the bar, or, to
be more precise, of the non-axisymmetric forcing at and somewhat beyond the
corotation region, determines the resulting morphology. Thus, less strong bars
give rise to R1 rings or pseudorings, while stronger bars drive R2, R1R2 and
spiral morphologies. We examine the morphology as a function of the main
parameters of the bar and present descriptive two dimensional plots to that
avail. We also derive how the manifold morphologies and properties are modified
if the L1 and L2 Lagrangian points become stable. Finally, we discuss how
dissipation affects the manifold properties and compare the manifolds in
gas-like and in stellar cases. Comparison with observations, as well as clear
predictions to be tested by observations will be given in an accompanying
paper.Comment: Typos corrected to match the version in press in MNRA
Emotional Capital in Family Businesses: Decisions from Human Resource Management Perspective
Nowadays, family businesses (FBs) have become a distinctive organizational model, not only for preserving the values of their founders in times of technological, political and economical changes but also for fostering a different kind of organization surrounded by emotional ties. This is particularly interesting to the human resource management (HRM) area, because managers must take decisions aimed at achieving economic and financial goals, which often affect the emotional stability of family members. Regarding this issue, the term emotional capital (EC) appears as a set of assets based on the emotions that the organization has developed over time with their employees. This chapter examines, from the HRM perspective, how human resource choices can be affected in order to preserve a positive EC for organizations. Due to the social implications emotions have in HRM, the chapter also links corporate social responsibility (CSR) as an important management strategy, focused on meeting employees and social concerns, as a way to strengthen the emotional bonds in companies. The literature review and institutional reports pointed the characteristics of FB in Spain, describing how companies could design human resource policies and practices aimed at keeping EC. Finally, the configurational approach of HRM is used to explain the design of the best possible human resource practices adapted to a particular context like FB
Reliability and validity of the Colombian version of the Revised Sociosexual Orientation Inventory
Sociosexuality refers to an individual’s disposition to have casual sex without establishing affective bonds and has been widely studied worldwide using the Revised Sociosexual Orientation Inventory (SOI-R; Penke & Asendorpf, 2008). Despite its many validations in different cultural contexts, no psychometric analyses of this instrument have been conducted in Spanish-speaking Latin American countries. To address this gap in the literature, we examined the psychometric properties of the SOI-R in Colombia. In a cross-sectional study with a large sample of participants (N = 812; 64% women), we conducted exploratory and confirmatory factor analyses to identify different factor structures and determine which had the best fit for our sample and examined the reliability of the scale. Results showed that a three-factor structure, with sociosexual behaviors, attitudes, and desire as first-order factors, and global sociosexuality as a second-order factor, had the best fit indexes. Each factor presented good reliability indexes. Replicating already established gender differences, we also found that men scored higher on each factor when compared to women. These findings show that the SOI-R is a reliable and valid instrument to assess sociosexuality in countries where sociosexuality research is underrepresented.info:eu-repo/semantics/publishedVersio
Ischemic Stroke and Epilepsy in a Patient with Tourette´s Syndrome: Association with the Antiphospholipid Syndrome and Good Response to Levetiracetam
The role played by different humoral factors, including antiphospholipid antibodies, in the pathogenesis of Tourette syndrome (TS) is still presently unclear. We present a patient with chronic and severe TS who, at the age of 16 years, presented an ischemic stroke in the left posterior cerebral artery and/or postero-inferior temporal branch of the left medial cerebral artery. A complete study was negative with the exception of a positive lupus anticoagulant. The stroke was related with the primary antiphospholipid syndrome (APS). The stroke manifested visual abnormalities and thereafter by secondary generalized complex partial seizures. The epileptic syndrome was initially difficult to control but responded dramatically to levetiracetam. With this therapy, the manifestations of TS, especially the tics, improved. We conclude that some TS cases may present APS. In addition, levetiracetam may be useful in the management of TS. Further investigations should pursue both these facts
Damselflies (Coenagrionidae) have been avoiding leaf veins during oviposition for at least 52 million years
Plant-insect interactions can provide extremely valuable information for reconstructing the oviposition behavior. We have studied about 1350 endophytic egg traces of coenagrionid damselflies (Odonata: Zygoptera) from the Eocene, identifying triangular or drop-shaped scars associated with them. This study aims to determine the origin of these scars. Our behavioral study of about 1,800 endophytic eggs from recent coenagrionids indicates that these scars were caused by ovipositor incisions, but without egg insertion. The scar correlates (χ2-test) with leaf veins in both fossil and extant species. We infer that a female would detect the proximity of a leaf vein and avoid egg-laying, generating a scar that also fossilizes. For the first time, a scar produced by the ovipositor has been identified, indicating the existence of undesirable areas for oviposition. Accordingly, we recognize that Coenagrionidae damselflies (narrow-winged damselflies or pond damselflies) have been avoiding leaf veins for at least 52 million years.Fil: Romero LebrĂłn, MarĂa Eugenia. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico CĂłrdoba. Instituto Multidisciplinar de BiologĂa Vegetal (P). Grupo Vinculado Centro de Relevamiento y EvaluaciĂłn de Recursos AgrĂcolas y Naturales; ArgentinaFil: Fernández GarcĂa, Marcos. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de NivologĂa, GlaciologĂa y Ciencias Ambientales; Argentina. Universidad Nacional de CĂłrdoba. Facultad de Ciencias Exactas, FĂsicas y Naturales; ArgentinaFil: Matushkina, Natalia. Taras Shevchenko National University Of Kyiv; UcraniaFil: Delclos Martinez, Xavier. Universidad de Barcelona; EspañaFil: Gleiser, Raquel M.. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico CĂłrdoba. Instituto Multidisciplinar de BiologĂa Vegetal (P). Grupo Vinculado Centro de Relevamiento y EvaluaciĂłn de Recursos AgrĂcolas y Naturales; Argentin
E. coli
Escherichia coli meningitis is a frequent pathology in children younger than 3 years old, but is an uncommon disease in adults. E. coli infection is the main cause of intrahospital bacteremia as a consequence of the employment of different medical procedures. Our patient, male, 69 years old, presented with fever, progressive difficulty in breathing, and shivers 24 h after transrectal prostate biopsy, with an absence of any other symptoms. He received prophylactic treatment with ciprofloxacin and later empirical treatment with ampicillin and tobramicin. After that, the patient presented with fever, headache, behavioral changes, somnolence, disorientation, a fluctuating level of conscience, cutaneous widespread pallor, and acute urinary retention. On physical exploration, we observed generalized hypoventilation, Glasgow 10, stiffness of the neck, inconclusive Kernig; the remaining neurological exploration was normal. Systematic of blood: leukocytes = 8,510/mm3 (94.5% polymorphonuclear), platelet = 87,000/mm3, pH = 7.51, pCO2 = 28.8 mmHg, pO2 = 61 mmHg, O2 saturation = 93.8%, and remaining values were normal. Chest X- ray, cranial CT scan, urine cultures were normal. Blood culture: E. coli. CSF: glucose <0.4 g/l, total proteins = 3.05 g/l, PMN = 7 cells. Microscopic examination of the CSF: Gram-negative bacilli; CSF's culture: abundant E. coli. The case of acute meningitis by multiresistant E. coli after transrectal prostate biopsy presented demonstrates that antibiotic prevention with ciprofloxacin is not absolutely risk free. Besides the use of antibiotic prevention for multiresistant microorganisms, the urologist and other physicians involved in the procedure must not forget that the rate of major complications of transrectal prostate biopsy is 1%, especially when it is performed in patients who will not benefit from that biopsy
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