14,005 research outputs found
Loop quantum effect and the fate of tachyon field collapse
We study the fate of gravitational collapse of a tachyon field matter. In
presence of an inverse square potential a black hole forms. Loop quantum
corrections lead to the avoidance of classical singularities, which is followed
by an outward flux of energy.Comment: Contribution to the conference of Loops'11, Madri
Recurrent Coronal Jets Induced by Repetitively Accumulated Electric Currents
Three extreme-ultraviolet (EUV) jets recurred in about one hour on 2010
September 17 in the following magnetic polarity of active region 11106. The EUV
jets were observed by the Atmospheric Imaging Assembly (AIA) on board the Solar
Dynamics Observatory (SDO). The Helioseismic and Magnetic Imager (HMI) on board
SDO measured the vector magnetic field, from which we derive the magnetic flux
evolution, the photospheric velocity field, and the vertical electric current
evolution. The magnetic configuration before the jets is derived by the
nonlinear force-free field (NLFFF) extrapolation.
We derive that the jets are above a pair of parasitic magnetic bipoles which
are continuously driven by photospheric diverging flows. The interaction drove
the build up of electric currents that we indeed observed as elongated patterns
at the photospheric level. For the first time, the high temporal cadence of HMI
allows to follow the evolution of such small currents. In the jet region, we
found that the integrated absolute current peaks repetitively in phase with the
171 A flux evolution. The current build up and its decay are both fast, about
10 minutes each, and the current maximum precedes the 171 A by also about 10
minutes. Then, HMI temporal cadence is marginally fast enough to detect such
changes.
The photospheric current pattern of the jets is found associated to the
quasi-separatrix layers deduced from the magnetic extrapolation. From previous
theoretical results, the observed diverging flows are expected to build
continuously such currents. We conclude that magnetic reconnection occurs
periodically, in the current layer created between the emerging bipoles and the
large scale active region field. It induced the observed recurrent coronal jets
and the decrease of the vertical electric current magnitude.Comment: 10 pages, 7 figures, accepted for publication in A&
Sobre la autonomía constitucional del Servicio Electoral y el control judicial del Tribunal Calificador de Elecciones
Este comentario analiza el alcance de la sentencia del Tribunal Calificador de Elecciones sobre el recurso de queja interpuesto por el pacto electoral “Nueva Mayoría” en contra de la resolución de la Directora (s) del SERVEL ante la negativa de esta de inscribir dicho pacto para las elecciones primarias de Alcalde 2016. La sentencia además de concluir que el Servicio Electoral actuó erradamente al requerir la comparecencia personal de todos los presidentes y secretarios de los partidos políticos, se pronunció sobre la procedencia del recurso de queja ante las actuaciones de dicho Servicio y la sujeción del mismo, como parte de la Administración, al control judicial. El comentario también analiza la forma en que el Tribunal Calificador de Elecciones apreció la prueba en el caso
Bayesian optimization for the inverse scattering problem in quantum reaction dynamics
We propose a machine-learning approach based on Bayesian optimization to
build global potential energy surfaces (PES) for reactive molecular systems
using feedback from quantum scattering calculations. The method is designed to
correct for the uncertainties of quantum chemistry calculations and yield
potentials that reproduce accurately the reaction probabilities in a wide range
of energies. These surfaces are obtained automatically and do not require
manual fitting of the {\it ab initio} energies with analytical functions. The
PES are built from a small number of {\it ab initio} points by an iterative
process that incrementally samples the most relevant parts of the configuration
space. Using the dynamical results of previous authors as targets, we show that
such feedback loops produce accurate global PES with 30 {\it ab initio}
energies for the three-dimensional H + H H + H reaction
and 290 {\it ab initio} energies for the six-dimensional OH + H
HO + H reaction. These surfaces are obtained from 360
scattering calculations for H and 600 scattering calculations for OH.
We also introduce a method that quickly converges to an accurate PES without
the {\it a priori} knowledge of the dynamical results. By construction, our
method illustrates the lowest number of potential energy points (i.e. the
minimum information) required for the non-parametric construction of global PES
for quantum reactive scattering calculations.Comment: 9 pages, 8 figure
Constant of Motion for several one-dimensional systems and outlining the problem associated with getting their Hamiltonians
The constants of motion of the following systems are deduced: a relativistic
particle with linear dissipation, a no-relativistic particle with a time
explicitly depending force, a no-relativistic particle with a constant force
and time depending mass, and a relativistic particle under a conservative force
with position depending mass. The problem of getting the Hamiltonian for these
systems is determined by getting the velocity as an explicit function of
position and generalized linear momentum, and this problem can be solved a
first approximation for the first above system.Comment: 15 pages, Te
INFORME SOBRE CONSERVACIÓN DE UN MURO DE FORO ROMANO DE TARRAGONA. COMISIÓN CENTRAL DE MONUMENTOS
TiO2 sintetizado por el método de precursor polimerico (Pechini): estructura de la resina intermedia
En este trabajo se ha utilizado el método de precursor polimérico (método de Pechini) para sintetizar dióxido de titanio,
proceso que ha permitido tener un mayor control sobre la pureza del óxido y el tipo de fase que ha presentado el material
obtenido, fase anatasa en el presente caso. Durante el proceso de síntesis se ha obtenido una resina que se ha caracterizado
utilizando la espectroscopia de Resonancia Magnética Nuclear (RMN) y la espectroscopia infrarroja con transformada de
Fourier (FTIR) para determinar su estructura y con base en ella se ha propuesto un modelo para la conformación de la
misma. Posteriormente esta resina se ha sometido a un tratamiento térmico para obtener los polvos cerámicos que se han
caracterizado empleando diferentes técnicas, principalmente, difracción de rayos X (DRX) y microscopia electrónica (MET
y MEB). Los resultados indican que se puede obtener TiO2 fase anatasa a los 450ºC con un tamaño de partícula <100nm.Peer reviewe
Cuadro sinóptico del nuevo sistema métrico-decimal de pesas y medidas y arreglo de monedas, establecido el primero por la Ley 19 de Julio de 1849 y el segundo por el Decreto-Ley de 19 de Octubre de 1868
Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-201
Twisting solar coronal jet launched at the boundary of an active region
A broad jet was observed in a weak magnetic field area at the edge of active
region NOAA 11106. The peculiar shape and magnetic environment of the broad jet
raised the question of whether it was created by the same physical processes of
previously studied jets with reconnection occurring high in the corona. We
carried out a multi-wavelength analysis using the EUV images from the
Atmospheric Imaging Assembly (AIA) and magnetic fields from the Helioseismic
and Magnetic Imager (HMI) both on-board the SDO satellite. The jet consisted of
many different threads that expanded in around 10 minutes to about 100 Mm in
length, with the bright features in later threads moving faster than in the
early ones, reaching a maximum speed of about 200 km s^{-1}. Time-slice
analysis revealed a striped pattern of dark and bright strands propagating
along the jet, along with apparent damped oscillations across the jet. This is
suggestive of a (un)twisting motion in the jet, possibly an Alfven wave. A
topological analysis of an extrapolated field was performed. Bald patches in
field lines, low-altitude flux ropes, diverging flow patterns, and a null point
were identified at the basis of the jet. Unlike classical lambda or
Eiffel-tower shaped jets that appear to be caused by reconnection in current
sheets containing null points, reconnection in regions containing bald patches
seems to be crucial in triggering the present jet. There is no observational
evidence that the flux ropes detected in the topological analysis were actually
being ejected themselves, as occurs in the violent phase of blowout jets;
instead, the jet itself may have gained the twist of the flux rope(s) through
reconnection. This event may represent a class of jets different from the
classical quiescent or blowout jets, but to reach that conclusion, more
observational and theoretical work is necessary.Comment: 12 pages, 9 figures, accepted for publication in A&
Las Ciudades españolas y su arquitectura municipal al finalizar la edad media : discurso leido el dia 20 de mayo de 1917
Copia digital : Diputación de Málaga. Biblioteca Canovas del Castillo, 201
- …