419 research outputs found
El principio unidireccional en el "periplo" de Avieno y sus repercusiones en la crítica textual
Si la idea base del Periplo es rechazada, un examen del contenido del poema nos permite justificar la colocación original de los pasajes sostenida por los partidarios de la teoría tradicional desde Avienus que no describe los temas geográficos de acuerdo a normas unidireccionales sino en base a una técnica que puede ser designada como escenográfica.If the idea of the Periplus-basis is rejected, an examination of the contents of
the poem allows us to justify the original placing of those passages suspected by
the • supporters of the traditional theory, since Avienus does not describe the geographical
subjects according to the unidirectional rule, but based on a technique
that may be designated as «scenographic»
La plataforma submarina y la costa atlántica Argentina durante los últimos 22.000 años
La glaciaciones ocurridas en la región expusieron en diferente grado la actual plataforma continental Argentina (océano Atlántico sudoccidental). Este trabajo de divulgación científica da a conocer un modelo de evolución paleogeográfica de las costas de la Pampa y la Patagonia, y brinda la posibilidad de localizar temporalmente la formación de los principales rasgos costeros del extremo sur de América del sur. Se incluyen además otras lecturas sugeridas relacionadas al tema
Stability of the Scalar Potential and Symmetry Breaking in the Economical 3-3-1 Model
A detailed study of the criteria for stability of the scalar potential and
the proper electroweak symmetry breaking pattern in the economical 3-3-1 model,
is presented. For the analysis we use, and improve, a method previously
developed to study the scalar potential in the two-Higgs-doublet extension of
the standard model. A new theorem related to the stability of the potential is
stated. As a consequence of this study, the consistency of the economical 3-3-1
model emerges.Comment: to be published in EPJ C, 13 page
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Initial tests and operation of a 110 GHz, 1 MW gyrotron with evacuated waveguide system on the DIII-D tokamak
A gyrotron producing nominally 1 MW at 110 GHz has been installed at the DIII-D tokamak and operated in a program of initial tests with a windowless evacuated transmission line. The alignment and first test operation were performed in an air environment at atmospheric pressure. Under these conditions, the tube produced rf output in excess of 800 kW for pulse lengths greater than 10 msec and power near 500 kW for pulse lengths of about 100 msec into a free space dummy load. The gyrotron was operated into evacuated corrugated waveguide in the full power parameter regime for pulse lengths of up to 500 msec injecting greater than 0.5 MW into DIII-D for a preliminary series of experiments. Generated powers greater than 900 kW were achieved. A parasitic oscillation at various frequencies between 20 and 100 MHz, which was generated during the pulsing of the gyrotron electron beam, was suppressed somewhat by a capacitive filter attached to the gyrotron itself. Addition of a magnetic shield intended to alter the magnetic field geometry below the cathode eliminated internal tube sparks. Rework of the external power and interlock circuitry to improve the immunity to electromagnetic interference was also done in parallel so that the fast interlock circuitry could be used. The latest results of the test program, the design of the free space load and other test hardware, and the transmission line will be presented
Scalar Potential Without Cubic Term in 3-3-1 Models Without Exotic Electric Charges
A detailed study of the criteria for stability of the scalar potential, and
the proper electroweak symmetry breaking pattern in some 3-3-1 models without
exotic electric charges is presented. In this paper we concentrate in a scalar
sector with three Higgs scalar triplets, with a potential that does not include
the cubic term, due to the presence of a discrete symmetry. For the analysis we
use, and improve, a method previously developed to study the scalar potential
in the two-Higgs-doublet extension of the standard model. Our main result is to
show the consistency of those 3-3-1 models without exotic electric charges.Comment: 19 page
Texture zeros for the standard model Quark mass matrices
ABSTRACT: A way of counting free parameters in the quark mass matrices of the standard model, including the constraints coming from weak basis transformations, is presented; this allow to understand the exact physical meaning of the parallel and non-parallel texture zeros which appear in some “ans¨atz” of the 3 × 3 quark mass matrices, including the CP violation phenomena in the analysis, it is shown why the six texture zeros are ruled out. Finally, a five texture zeros “ans¨atze”which properly copes with all experimental constrains, including the angles of the unitary triangle, is presented
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
Data collected by the Pierre Auger Observatory through 31 August 2007 showed
evidence for anisotropy in the arrival directions of cosmic rays above the
Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron catalog). An updated
measurement of this fraction is reported here using the arrival directions of
cosmic rays recorded above the same energy threshold through 31 December 2009.
The number of arrival directions has increased from 27 to 69, allowing a more
precise measurement. The correlating fraction is , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . The enlarged set of arrival directions is
examined also in relation to other populations of nearby extragalactic objects:
galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in
hard X-rays by the Swift Burst Alert Telescope. A celestial region around the
position of the radiogalaxy Cen A has the largest excess of arrival directions
relative to isotropic expectations. The 2-point autocorrelation function is
shown for the enlarged set of arrival directions and compared to the isotropic
expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201
Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory
Atmospheric parameters, such as pressure (P), temperature (T) and density,
affect the development of extensive air showers initiated by energetic cosmic
rays. We have studied the impact of atmospheric variations on extensive air
showers by means of the surface detector of the Pierre Auger Observatory. The
rate of events shows a ~10% seasonal modulation and ~2% diurnal one. We find
that the observed behaviour is explained by a model including the effects
associated with the variations of pressure and density. The former affects the
longitudinal development of air showers while the latter influences the Moliere
radius and hence the lateral distribution of the shower particles. The model is
validated with full simulations of extensive air showers using atmospheric
profiles measured at the site of the Pierre Auger Observatory.Comment: 24 pages, 9 figures, accepted for publication in Astroparticle
Physic
The exposure of the hybrid detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a detector for ultra-high energy cosmic rays.
It consists of a surface array to measure secondary particles at ground level
and a fluorescence detector to measure the development of air showers in the
atmosphere above the array. The "hybrid" detection mode combines the
information from the two subsystems. We describe the determination of the
hybrid exposure for events observed by the fluorescence telescopes in
coincidence with at least one water-Cherenkov detector of the surface array. A
detailed knowledge of the time dependence of the detection operations is
crucial for an accurate evaluation of the exposure. We discuss the relevance of
monitoring data collected during operations, such as the status of the
fluorescence detector, background light and atmospheric conditions, that are
used in both simulation and reconstruction.Comment: Paper accepted by Astroparticle Physic
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