292 research outputs found
The influence of the Lande -factor in the classical general relativistic description of atomic and subatomic systems
We study the electromagnetic and gravitational fields of the proton and
electron in terms of the Einstenian gravity via the introduction of an
arbitrary Lande -factor in the Kerr-Newman solution. We show that at length
scales of the order of the reduced Compton wavelength, corrections from
different values of the -factor are not negligible and discuss the presence
of general relativistic effects in highly ionized heavy atoms. On the other
hand, since at the Compton-wavelength scale the gravitational field becomes
spin dominated rather than mass dominated, we also point out the necessity of
including angular momentum as a source of corrections to Newtonian gravity in
the quantum description of gravity at this scale.Comment: 11 pages, 2 figure
Chaotic dynamics around astrophysical objects with nonisotropic stresses
The existence of chaotic behavior for the geodesics of the test particles
orbiting compact objects is a subject of much current research. Some years ago,
Gu\'eron and Letelier [Phys. Rev. E \textbf{66}, 046611 (2002)] reported the
existence of chaotic behavior for the geodesics of the test particles orbiting
compact objects like black holes induced by specific values of the quadrupolar
deformation of the source using as models the Erez--Rosen solution and the Kerr
black hole deformed by an internal multipole term. In this work, we are
interesting in the study of the dynamic behavior of geodesics around
astrophysical objects with intrinsic quadrupolar deformation or nonisotropic
stresses, which induces nonvanishing quadrupolar deformation for the
nonrotating limit. For our purpose, we use the Tomimatsu-Sato spacetime [Phys.
Rev. Lett. \textbf{29} 1344 (1972)] and its arbitrary deformed generalization
obtained as the particular vacuum case of the five parametric solution of Manko
et al [Phys. Rev. D 62, 044048 (2000)], characterizing the geodesic dynamics
throughout the Poincar\'e sections method. In contrast to the results by
Gu\'eron and Letelier we find chaotic motion for oblate deformations instead of
prolate deformations. It opens the possibility that the particles forming the
accretion disk around a large variety of different astrophysical bodies
(nonprolate, e.g., neutron stars) could exhibit chaotic dynamics. We also
conjecture that the existence of an arbitrary deformation parameter is
necessary for the existence of chaotic dynamics.Comment: 7 pages, 5 figure
Equatorial symmetry/antisymmetry of stationary axisymmetric electrovac spacetimes
Two theorems are proved concerning how stationary axisymmetric electrovac
spacetimes that are equatorially symmetric or equatorially antisymmetric can be
characterized correctly in terms of the Ernst potentials \E and or in
terms of axis-data.Comment: 8 page
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Introducción: La leptospirosis es una enfermedad zoonótica causada por Leptospira interrogans y es transmitida por contacto directo con secreciones animales o agua contaminada. Veterinarios y estudiantes de medicina veterinaria son población en riesgo de adquirir la infección.Objetivo: Determinar la seroprevalencia de infección por Leptospira interrogans entre estudiantes de una facultad de medicina veterinaria en Bogotá, Colombia.Métodos: Se procesaron 445 sueros por ELISA, de los cuales 42 muestras se analizaron mediante microaglutinación (MAT).Resultados: La seroprevalencia a Leptospira por ELISA IgM fue del 7,9 % (35de 445). De ellos 34 sueros fueron positivos por MAT al menos para un serovar.Conclusión: Este estudio confirma la utilidad del diagnóstico serológico en individuos con riesgo ocupacional para adquirir la leptospirosis y resalta la importancia del uso de barreras de protección para todas las poblaciones que tienen contacto regular con animales, incluidos los estudiantes de medicina veterinaria.Introduction: Leptospirosis is a zoonotic disease caused by Leptospira interrogans and is transmitted by direct contact with animal secretions or contaminated water. Veterinary and veterinary students are population at risk of infection.Objective: To determine the seroprevalence of Leptospira interrogans infection among students in a School of Veterinary Medicine in Bogotá, Colombia. Methods: We processed 445 sera by ELISA test; then we analyzed 42 samples by microagglutination (MAT).Results: Leptospira seroprevalence by ELISA IgM was 7.9% (35 of 445). 34 sera were positive by MAT at least for one serovar.Conclusion: This study confirms the usefulness of serological diagnosis in individuals with occupational risk for Leptospirosis and stand out the importance of using protective barriers by all populations who have regular animal contact including veterinary students
Realistic Exact Solution for the Exterior Field of a Rotating Neutron Star
A new six-parametric, axisymmetric and asymptotically flat exact solution of
Einstein-Maxwell field equations having reflection symmetry is presented. It
has arbitrary physical parameters of mass, angular momentum, mass--quadrupole
moment, current octupole moment, electric charge and magnetic dipole, so it can
represent the exterior field of a rotating, deformed, magnetized and charged
object; some properties of the closed-form analytic solution such as its
multipolar structure, electromagnetic fields and singularities are also
presented. In the vacuum case, this analytic solution is matched to some
numerical interior solutions representing neutron stars, calculated by Berti &
Stergioulas (Mon. Not. Roy. Astron. Soc. 350, 1416 (2004)), imposing that the
multipole moments be the same. As an independent test of accuracy of the
solution to describe exterior fields of neutron stars, we present an extensive
comparison of the radii of innermost stable circular orbits (ISCOs) obtained
from Berti & Stergioulas numerical solutions, Kerr solution (Phys. Rev. Lett.
11, 237 (1963)), Hartle & Thorne solution (Ap. J. 153, 807, (1968)), an
analytic series expansion derived by Shibata & Sasaki (Phys. Rev. D. 58 104011
(1998)) and, our exact solution. We found that radii of ISCOs from our solution
fits better than others with realistic numerical interior solutions.Comment: 13 pages, 13 figures, LaTeX documen
Sequencing of Vellozia Spp. genomes to understand drought tolerance and phosphorus acquisition in angiosperms.
PE1164. PAG 2019
ASIC-based tachometer without mechanical transducer for induction machines
A classical method for angular position and speed estimation in adjustable speed drives uses an incremental shaft encoder and an electronic circuit. This paper presents SLESS, a tachometer without mechanical transducer implemented on an ASIC using sensorless speed estimation technique. The ASIC is intended to serve as part of an integrated solution developed for fuzzy speed regulation and vector control of induction motors
A Sensitivity Analysis for Quality Measures of Quantitative Association Rules
There exist several fitness function proposals based on a combination
of weighted objectives to optimize the discovery of association
rules. Nevertheless, some differences in the measures used to assess the
quality of association rules could be obtained according to the values of
such weights. Therefore, in such proposals it is very important the user’s
decision in order to specify the weights or coefficients of the optimized objectives.
Thus, this work presents an analysis on the sensitivity of several
quality measures when the weights included in the fitness function of the
existing QARGA algorithm are modified. Finally, a comparative analysis
of the results obtained according to the weights setup is provided.MICYT TIN2011-28956-C02-00Junta de Andalucía P11-TIC-752
La pérdida de fitness de Acinetobacter baumannii resistente a colistina está asociada con una menor capacidad para crecer en condiciones deficientes en hierro.
Motivación: En un estudio anterior demostramos que las cepas de Acinetobacter baumannii que adquieren resistencia a colistina gracias a mutaciones en el sistema PmrAB presentan reducción in vivo del fitness y disminución de la virulencia1. El objetivo del presente estudio es caracterizar el papel del hierro libre en el fitness in vitro de estas cepas. Métodos: Se utilizaron las cepas de A. baumannii ATTCC 19606 (CMI colistina = 0,5 mg/L) y RC64, su derivado colistina-resistente obtenido mediante crecimiento en presencia de colistina (CMI colistina = 64 mg/L)2. Se realizaron curvas de crecimiento durante 24 horas en Mueller Hinton Broth (MHB) y suero humano (SH). Posteriormente, se determinó el crecimiento en Mueller Hinton Agar (MHA) con o sin el quelante de hierro 2,2'-bipiridil (Bip) mediante el cultivo en gotas de concentraciones decrecientes de las cepas (de 8 a 3 Log10 UFC/mL). Además, se determinó la CMI de Bip para ambas cepas, así como la concentración de hierro necesaria para permitir el crecimiento en SH. Por último, se caracterizó el crecimiento de ambas cepas en SH suplementado con Fe2+. Resultados: Ambas cepas presentaron un crecimiento similar al ser cultivadas en MHB; sin embargo, en SH la cepa RC64 mostró un crecimiento reducido. Adicionalmente, RC64 presentó un menor crecimiento en comparación con ATCC 19606 en placas de MHA suplementadas con Bip; sin embargo, cuando se crecieron en MHA sin Bip el crecimiento fue similar. La CMI de Bip en MHB fue de 64 mg/L para la cepa ATCC 19606 y 32 mg/L para RC64. Cuando se suplementó el SH con Fe2+, ATCC 19606 creció sin necesidad de dicho suplemento, mientras que RC64 requirió la adición de 0,5 mg/L de Fe2+. La cepa RC64 presentó una mayor tasa de crecimiento en SH suplementado con Fe2+ en comparación con su crecimiento en SH no suplementado. Conclusiones: La pérdida de fitness y virulencia en Acinetobacter baumannii asociada a la resistencia a colistina adquirida por mutaciones en el sistema PmrAB podría estar relacionada con una menor capacidad para crecer en condiciones pobres en hierro libre
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