3,045 research outputs found
Algunas soluciones exactas para una ecuaciĂłn de Klein Gordon
In solving practical problems in science and engineering arises as a direct consequence differential equations that explains the dynamics of the phenomena. Finding exact solutions to this equations provides importan information about the behavior of physical systems. The Lie symmetry method allows tofind invariant solutions under certain groups of transformations for differential equations.This method not very well known and used is of great importance in the scientific community. By this approach it was possible to find several exactinvariant solutions for the Klein Gordon Equation uxx â utt = k(u). A particularcase, The Kolmogorov equation uxx â utt = k1u + k2un was considered.These equations appear in the study of relativistic and quantum physics. The general solutions found, could be used for future explorations on the study for other specific K(u) functions.Al resolver problemas prĂĄcticos en ciencia e ingenierĂa surge como consecuencia directa las ecuaciones diferenciales que explican la dinĂĄmica de los fenĂłmenos. Encontrar soluciones exactas a estas ecuaciones proporciona informaciĂłn importante sobre el comportamiento de los sistemas fĂsicos. El mĂ©todo de simetrĂa de Lie permite encontrar soluciones invariantes bajo ciertos grupos de transformaciones para ecuaciones diferenciales. Este mĂ©todo, poco conocido y utilizado, es de gran importancia en la comunidad cientĂfica. Mediante este enfoque, fue posible encontrar varias soluciones exactas invariables para la ecuaciĂłn de Klein Gordon uxx - utt = k (u). Un caso particular, se considerĂł la ecuaciĂłn de Kolmogorov uxx - utt = k1u + k2un. Estas ecuaciones aparecen en el estudio de la fĂsica relativista y cuĂĄntica. Las soluciones generales encontradas podrĂan utilizarse para futuras exploraciones en el estudio para otras funciones especĂficas de K (u)
Electronic plasma diffusion with radiation reaction force and time-dependent electric field
In this work the explicit solution of the electronic plasma diffusion with
radiation reaction force, under the action of an exponential decay external
electric field is given. The electron dynamics is described by a classical
generalized Langevin equation characterized by an Ornstein-Uhlenbeck-type
friction memory kernel, with an effective memory time which accounts for the
effective thermal interaction between the electron and its surroundings
(thermal collisions between electrons + radiation reaction force). The incident
electric field exerts an electric force on the electron, which in turn can
induce an additional damping to the braking radiation force, allowing a delay
in the electron characteristic time. This fact allows that the effective memory
time be finite and positive, and as a consequence, obtaining physically
admissible solutions of the stochastic Abraham-Lorentz-like equation. It is
shown that the diffusion process is quasi-Markovian which includes the
radiation effects.Comment: 16 pages, 8 figure
Variable broad lines and outflow in the weak blazar PBC J2333.9-2343
IndexaciĂłn: Scopus; Scielo.Funding text #1
1Instituto de FĂsica y AstronomĂa, Facultad de Ciencias, Universidad de ValparaĂso, Gran Bretaña 1111, Playa Ancha, ValparaĂso, Chile 2INAF â Istituto di Astrofisica e Planetologia Spaziali di Roma (IAPS-INAF), Via del Fosso del Cavaliere 100, I-00133 Roma, Italy 3INAF â Osservatorio Astronomico di Roma, via Frascati 33, I-00078 Monte Porzio Catone, Italy 4Excellence Cluster Universe, Technische UniversitĂ€t MĂŒnchen, Boltzmannstr. 2, D-85748, Garching, Germany 5European Southern Observatory, Karl-Schwarzschild-Str 2, D-85748 Garching b. MĂŒnchen, Germany 6Instituto Nacional de AstrofĂsica, Ăptica y ElectrĂłnica, Apartado Postal 51-216, 72000 Puebla, MĂ©xico 7Argelander Institute for Astronomy, University of Bonn, Auf dem HĂŒgel 71, D-53121 Bonn, Germany 8International Max Planck Research School of Astronomy and Astrophysics at the Universities of Bonn and Cologne, Auf dem HĂŒgel 69, D-53121 Bonn, Germany 9INAF â Osservatorio di Astrofisica e Scienza dello Spazio, via Gobetti 93/3, I-40129 Bo...View all
Funding text #2
We acknowledge the referee, M. Villar MartĂn, for her comments and suggestions that helped to improve the paper. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester, the NASA/IPAC extragalactic database (NED), the STARLIGHT code, and the IRAF software. Based upon observations carried out at the Observatorio AstronĂłmico Nacional on the Sierra San Pedro MĂĄrtir (OAN-SPM), Baja California, MĂ©xico. LHG and FP acknowledge the ASI/INAF agreement number 2013-023-R1, LHG partial support from FONDECYT through grant 3170527, MP from ESSTI under the MoST, and from MINECO through research projects AYA2013-42227-P and AYA2016-76682-C3-1-P (AEI/FEDER, UE), LHG and SC from the Spanish grant AYA2013-42227-P, VC by CONACyT research grant 280789, EFJA from the Collaborative Research Center 956, subproject A1, funded by DFG, and GV from the DFG Cluster of Excellence âOrigin and Structure of the Universeâ (www.universe-cluster.de).PBC J2333.9-2343 is a peculiar active nucleus with two giant radio lobes and a weak blazarlike nucleus at their centre. In this work we show new optical, ultraviolet (UV), and X-ray data taken from the San Pedro MĂĄrtir telescope, the New Technology Telescope, NTT/EFOSC2, and the Swift/XRT satellite. The source is highly variable at all frequencies, in particular the strongest variations are found in the broad Hα component with a flux increase of 61±4 per cent between 2009 and 2016, following the X-ray flux increase of 62±6 per cent between 2010 and 2016. We also detected a broad HÎČ component in 2016, making the optical classification change from type 1.9 to type 1.8 in 1 yr. We have also detected a broad component of the [OIII]λ5007 line, which is blue-shifted and of high velocity, suggesting an origin from a highly disturbed medium, possibly an outflow. The line flux variability and broad widths are indicative of a jet that is, at least in part, responsible for the ionization of the broad line region (BLR) and narrow line region (NLR). © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.https://academic.oup.com/mnras/article-abstract/478/4/4634/4999938?redirectedFrom=fulltex
Crossing the phantom divide in an interacting generalized Chaplygin gas
Unified generalized Chaplygin gas models assuming an interaction between dark
energy and dark matter fluids have been previously proposed. Following these
ideas, we consider a particular relation between dark densities, which allows
the possibility of a time varying equation of state for dark energy that
crosses the phantom divide at a recent epoch. Moreover, these densities decay
during all the evolution of the Universe, avoiding a Big Rip. We find also a
scaling solution, i.e. these densities are asymptotically proportional in the
future, which contributes to the solution of the coincidence problem.Comment: Improved version, 10 pages, 4 figures, References adde
Evaluation of the smooth muscle cell component and apoptosis in the varicose vein wall
This study was designed to evaluate the role of the smooth muscle cell and the apoptosis in the pathogenesis of the varicose vein. Segments of saphenous vein were obtained from healthy subjects and from those with varicose veins. The vein specimens were subdivided according to subject age (younger or older than 50 years) and according to the varicose vein source (distal or proximal). Morphological, ultrastructural, cell proliferation (anti-PCNA method) and cell death (TUNEL method) analysis were performed. The walls of healthy, control vein specimens acquired a more collagenous and papillomatous appearance with age. A slight increase in the number of TUNEL-positive cells was also observed in specimens from older subjects. The proportion of apoptotic cells was much greater in the varicose veins than in control specimens. Most cellular alterations were seen in proximal varicose segments obtained from young subjects. These specimens showed hypertrophic areas with a high degree of cellularity (both in the media and in the thickened intima). The highest proportion of apoptotic cells and collagenisation were also observed in these areas. The enhanced number of apoptotic cells in varicose veins observed mainly in proximal/young vein specimens could be responsible, at least in part, for the acceleration of the final fibrosclerotic process characteristic of the varicose vein wall
Holocene geochemical footprint from Semiarid alpine wetlands in southern Spain
Here we provide the geochemical dataset that our research group has collected after 10 years of investigation in the Sierra Nevada National Park in southern Spain. These data come from Holocene sedimentary records from four alpine sites (ranging from âŒ2500 to âŒ3000âmasl): two peatlands and two shallow lakes. Different kinds of organic and inorganic analyses have been conducted. The organic matter in the bulk sediment was characterised using elemental measurements and isotope-ratio mass spectrometry (EA-IRMS). Leaf waxes in the sediment were investigated by means of chromatography with flame-ionization detection and mass spectrometry (GC-FID, GC-MS). Major, minor and trace elements of the sediments were analysed with atomic absorption (AAS), inductively coupled plasma mass spectrometry (ICP-MS), as well as X-ray scanning fluorescence. These data can be reused by environmental researchers and soil and land managers of the Sierra Nevada National Park and similar regions to identify the effect of natural climate change, overprinted by human impact, as well as to project new management policies in similar protected areas.Universidad de Granada. Departamento de EstratigrafĂa y PaleontologĂaJunta de AndalucĂa: Grupos de investigaciĂłn RNM190 y RNM309Junta de AndalucĂa: Proyecto P11-RNM-7332España, Ministerio de EconomĂa y Competitividad: Proyecto CGL2013-47038-RRamĂłn y Cajal Fellowship: RYC-2015-18966Small Research Grant by the Carnegie Trust for the Universities of ScotlandMarie Curie Intra-European Fellowship of the 7th Framework Programme for Research,
Technological Development and Demonstration of the European Commission: NAOSIPUK. Grant Number: PIEF-GA-2012-62302
Guidelines for the definition of operational management units
The objective of fisheries management is the sustainable exploitation of the fish resources over the extent of their spatial distribution. Along with the Common
Fisheries Policy (CFP) objectives, the socio-economic viability of the fisheries exploiting the resource is also to be achieved. To reach these aims, managers need to
define the management units they are going to work with. For the purpose of GEPETO project, we define a management unit (MU) as the set of
fishing fleets exploiting a common pool of fish resources with strong spatial overlapping and sharing of habitats, which make them being typically fished together.
In other words, a MU is the set of fishing fleets exploiting a common fish community over their spatial distribution. MUs have to be defined by the fish community, by the
spatial range of distribution of the fish community, and by the set of fishing fleets sharing the exploitation of the fish communityL'objectif de gestion de la pĂȘche est l'exploitation durable des ressources halieutiques sur l'Ă©tendue de leur rĂ©partition spatiale. Avec la nouvelle
Politique Commune de la pĂȘche (PCP) l' objectif de la viabilitĂ© socio-Ă©conomique des pĂȘcheries exploitant la ressource doit Ă©galement ĂȘtre rĂ©alisĂ©. Pour l'atteindre, les gestionnaires doivent dĂ©finir des unitĂ©s de gestion. Les partenaires du projet GEPETO, dĂ©finissent une unitĂ© de gestion (MU) comme l'ensemble des
flottes de pĂȘche exploitant un pool commun de ressources halieutiques disponibles dans des habitats communs, ce qui les rend trĂšs imbriquĂ©es.
En d'autres termes, un MU est l'ensemble des flottes de pĂȘche exploitant une communautĂ© de poissons ordinaires sur leur rĂ©partition spatiale. La MU peu ĂȘtre dĂ©finie par la communautĂ© de poissons, par la gamme spatiale de la distribution de la communautĂ© de poissons, et par l'ensemble des flottes de pĂȘche qui partagent l'exploitation de la communautĂ© de poissons
Optical spectroscopy of 4U 1812-12: an ultra-compact X-ray binary seen through an H II region
The persistent, low-luminosity neutron star X-ray binary 4U 1812-12 is a
potential member of the scarce family of ultra-compact systems. We performed
deep photometric and spectroscopic optical observations with the 10.4 m Gran
Telescopio Canarias in order to investigate the chemical composition of the
accreted plasma, which is a proxy for the donor star class. We detect a faint
optical counterpart (g~25, r~23) that is located in the background of the
outskirts of the Sharpless 54 H II region, whose characteristic nebular lines
superimpose on the X-ray binary spectrum. Once this is corrected for, the
actual source spectrum lacks hydrogen spectral features. In particular, the
Halpha emission line is not detected, with an upper limit (3 sigma) on the
equivalent width of <1.3 A. Helium (He I) lines are neither observed, albeit
our constraints are not restrictive enough to properly test the presence of
this element. We also provide stringent upper limits on the presence of
emission lines from other elements, such as C and O, which are typically found
in ultra-compact systems with C-O white dwarfs donors. The absence of hydrogen
features, the persistent nature of the source at low luminosity, as well as the
low optical to X-ray flux ratio confirm 4U 1812-12 as a compelling
ultra-compact X-ray binary candidate, for which we tentatively propose a
He-rich donor based on the optical spectrum and the detection of short
thermonuclear X-ray bursts. In this framework, we discuss the possible orbital
period of the system according to disc instability and evolutionary models.Comment: Accepted for publication in A&
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