1,602 research outputs found
The spectroscopic orbits and the geometrical configuration of the symbiotic binary AR Pavonis
We analyze optical and near infrared spectra of intermediate and high
resolution of the eclipsing symbiotic system AR Pavonis. We have obtained the
radial velocity curves for the red and the hot component from the M-giant
absorption lines and from the wings of Halpha, H and He II4686 emission
profiles, respectively. From the orbital elements we have derived the masses,
Mgiant=2.5 and Mhot =1.0 solar masses, for the red giant and the hot component,
respectively. We also present and discuss radial velocity patterns in the blue
cF absorption spectrum as well as various emission lines. In particular, we
confirm that the blue absorption lines are associated with the hot component.
The radial velocity curve of the blue absorption system, however, does not
track the hot companion's orbital motion in a straightforward way, and its
departures from an expected circular orbit are particularly strong when the hot
component is active. We suggest that the cF-type absorption system is formed in
material streaming from the giant presumably in a region where the stream
encounters an accretion disk or an extended envelope around the hot component.
The broad emission wings originate from the inner accretion disk or the
envelope around the hot star.We also suggest that the central absorption in H
profiles is formed in a neutral portion of the cool giant's wind which is
strongly concentrated towards the orbital plane. The nebula in AR Pav seems to
be bounded by significant amount of neutral material in the orbital plane. The
forbidden emission lines are probably formed in low density ionized regions
extended in polar directions and/or the wind-wind interaction zone.Comment: 12 pages, 5 figures, accepted by A&
Structure of the 0110 de sapo Antiform in the Sanabria-Alcañices Atea (Zamora, Orense, NW Spain)
[Resumen] La antiforma del 0110 de sapo ha sido reinterpretada en el sector de Sanabria, mostrándose la existencia de una ventana tectónica en la que afloran cuatro unidades superpuestas, denominadas de arriba hacia abajo, unidades de Peña Trevinca (Cámbrico-Silúrico), Ribadelago (formación 0110 de sapo), Viana (Serie de
Porto «s.str.», Precámbrico-Cámbrico) y Villanueva (Cámbrico-OrdovĂcico). En el sector de Alcañices existe asimismo una unidad con sedimentos y rocas volcánicas de carácter oceánico y edad silĂşrico-devĂłnica a la que se superpone discordante una sucesiĂłn turbidĂtica de edad Tournaisiense (formaciĂłn San Vitero), denominada unidad de Aliste y considerada tambiĂ©n alĂłctona. Los datos que apoyan esta interpretaciĂłn son de tipo estructural, principalmente la existencia de niveles de milonitas y blastomilonitas entre las mismas, asĂ como las diferencias litolĂłgicas y de metamorfismo. Los criterios de cizalla parecen indicar que en este apilamiento existieron primero movimientos hacia el SW, quizás entre el OrdovĂcico y DevĂłnico inferior (fase 1, prehercĂnica), siguiendo despuĂ©s una deformaciĂłn intensa con desplazamiento tangencial y vergencia E, otra parecida pero menos intensa y, finalmente, una cuarta retrovergente que dio lugar a la antiforma del 0110 de sapo.[Abstract] The 0110 de sapo antiform has been reinterpreted in the Sanabria area and a tectonic window described allowing the appearance of four superposed units called,
from top to bottom, Peña Trevinca unit (Cambro-Silurian), Ribadelago unit (0110 de sapo), Viana unit (Porto Group s.sfr. Precambrian-Cambrian), and Villanueva unit (Cambro-Ordovician). In the Alcañices area , there is also a unit with sediments and volcanics of oceanic character of Siluro-Devonian age unconformably overlain by a turbiditic succession of Tournaisian age (San Vitero formation), which is called Aliste unit and considered also as allochthonous. Data supporting this interpretation are mainly structural, as the existence of extensive mylonites and blastomylonites at their contacts, as well as differences in lithology and metamorphism. Shear criteria seem to indicate that in this pile, there were first SW-directed movements, perhaps between Ordovician and Lower Devonian (prehercynian phase 1), followed then by 2 hercynian E-vergent folding phases, the first (phase 2) very strong, the second less marked (phase 3), and a retrovergent 4th phase which gave rise to the 0110 de sapo antiform
Description of Silvinichthys pedernalensis n. sp. (Teleostei, Siluriformes) from the Andean Cordillera of southern South America
DescripciĂłn de Silvinichthys pedernalensis sp. n. (Teleostei, Siluriformes) de la cordillera de los Andes en la parte meridional de SudamĂ©rica Se describe una nueva especie, Silvinichthys pedernalensis, en un arroyo andino de la provincia de San Juan, en Argentina, a partir del patrĂłn de coloraciĂłn y caracteres merĂsticos, morfomĂ©tricos y osteolĂłgicos. S. pedernalensis difiere notablemente de todos los demás miembros conocidos del gĂ©nero Silvinichthys debido a la combinaciĂłn de los siguientes rasgos: ausencia de cintura y aleta pĂ©lvica, hueso supraorbital ancho, 14–18 odontoides interoperculares, 6–8 odontoides operculares, 7 radios ramificados de la aleta pectoral, 11 radios de la aleta dorsal, 7 pterigiĂłforos de la aleta dorsal, 6 radios branquiĂłstegos, 14 radios dorsales procurrentes de la aleta caudal y 15 ventrales, 16 costillas, 39 vĂ©rtebras, pigmentaciĂłn marmĂłrea oscura de la cabeza y el cuerpo, altura de la cabeza (9,9–12,2% de la longitud estándar [LE]), ancho interorbital (28,3–36,1% de la longitud de la cabeza [LC]), longitud de la barbilla nasal (27,3–39,0% LE), longitud de la barbilla maxilar (39,5–61,7% LE), longitud de la barbilla submaxilar (24,7–41,9% LE), longitud del hocico (40,6–44,4% LC), altura del cuerpo (10,1–12,6% LE), ancho de la aleta anal (10,2–11,7% LE) y longitud del pedĂşnculo caudal (19,3–21,5% LE).DescripciĂłn de Silvinichthys pedernalensis sp. n. (Teleostei, Siluriformes) de la cordillera de los Andes en la parte meridional de SudamĂ©rica Se describe una nueva especie, Silvinichthys pedernalensis, en un arroyo andino de la provincia de San Juan, en Argentina, a partir del patrĂłn de coloraciĂłn y caracteres merĂsticos, morfomĂ©tricos y osteolĂłgicos. S. pedernalensis difiere notablemente de todos los demás miembros conocidos del gĂ©nero Silvinichthys debido a la combinaciĂłn de los siguientes rasgos: ausencia de cintura y aleta pĂ©lvica, hueso supraorbital ancho, 14–18 odontoides interoperculares, 6–8 odontoides operculares, 7 radios ramificados de la aleta pectoral, 11 radios de la aleta dorsal, 7 pterigiĂłforos de la aleta dorsal, 6 radios branquiĂłstegos, 14 radios dorsales procurrentes de la aleta caudal y 15 ventrales, 16 costillas, 39 vĂ©rtebras, pigmentaciĂłn marmĂłrea oscura de la cabeza y el cuerpo, altura de la cabeza (9,9–12,2% de la longitud estándar [LE]), ancho interorbital (28,3–36,1% de la longitud de la cabeza [LC]), longitud de la barbilla nasal (27,3–39,0% LE), longitud de la barbilla maxilar (39,5–61,7% LE), longitud de la barbilla submaxilar (24,7–41,9% LE), longitud del hocico (40,6–44,4% LC), altura del cuerpo (10,1–12,6% LE), ancho de la aleta anal (10,2–11,7% LE) y longitud del pedĂşnculo caudal (19,3–21,5% LE).Silvinichthys pedernalensis, a new species, is described from an Andean stream in Provincia San Juan, Argentina, based on its coloration pattern, and its meristic, morphometric and osteological characters. S. pedernalensis differs markedly from all other known members of the genus Silvinichthys as a result of the combination of the absence of pelvic girdle and fin, the wide supraorbital bone, the number of interopercle odontodes 14–18, the number of opercular odontodes 6–8, the branched pectoral–fin rays 7, the dorsal–fin rays 11, the number of dorsal pterygiophore 7, the branchiostegal rays 6, the dorsal procurrent caudal–fin rays 14 and ventral 15, the ribs 16, the vertebrae 39, the dark marmorated pigmentation on the body and head, the head depth 9.9–12.2% SL, the interorbital wide 28.3–36.1% HL, the nasal barbel length 27.3–39.0% SL, the maxillary barbel length 39.5–61.7% SL, the submaxillary barbel length 24.7–41.9% SL, the snout length 40.6–44.4% HL, the body depth 10.1–12.6% SL, the anal base fin 10.2–11.7% SL, and the caudal peduncle length 19.3–21.5% SL
Tachyon fields with effects of quantum matter in an Anti-de Sitter Universe
We consider an Anti-de Sitter universe filled by quantum conformal matter
with the contribution from the usual tachyon and a perfect fluid. The model
represents the combination of a trace-anomaly annihilated and a tachyon driven
Anti-de Sitter universe. The influence exerted by the quantum effects and by
the tachyon on the AdS space is studied. The radius corresponding to this
universe is calculated and the effect of the tachyon potential is discussed, in
particular, concerning to the possibility to get an accelerated scale factor
for the proposed model (implying an accelerated expansion of the AdS type of
universe). Fulfillment of the cosmological energy conditions in the model is
also investigatedComment: 14 Latex pages, no figure
Vanishing Cosmological Constant in Modified Gauss-Bonnet Gravity with Conformal Anomaly
We consider dark energy cosmology in a de Sitter universe filled with quantum
conformal matter. Our model represents a Gauss-Bonnet model of gravity with
contributions from quantum effects. To the General Relativity action an
arbitrary function of the GB invariant, f(G), is added, and taking into account
quantum effects from matter the cosmological constant is studied. For the
considered model the conditions for a vanishing cosmological constant are
considered. Creation of a de Sitter universe by quantum effects in a GB
modified gravity is discussed.Comment: 8 pages latex, 1 figure. To appear in Int. J. Mod. Phys.
Spin and Center of Mass in Axially Symmetric Einstein-Maxwell Spacetimes
We give a definition and derive the equations of motion for the center of
mass and angular momentum of an axially symmetric, isolated system that emits
gravitational and electromagnetic radiation. A central feature of this
formulation is the use of Newman-Unti cuts at null infinity that are generated
by worldlines of the spacetime. We analyze some consequences of the results and
comment on the generalization of this work to general asymptotically flat
spacetimes.Comment: 20 page
Comparison of engagement and emotional responses of older and younger adults interacting with 3D cultural heritage artefacts on personal devices
The availability of advanced software and less expensive hardware allows museums to preserve and share artefacts digitally. As a result, museums are frequently making their collections accessible online as interactive, 3D models. This could lead to the unique situation of viewing the digital artefact before the physical artefact. Experiencing artefacts digitally outside of the museum on personal devices may affect the user's ability to emotionally connect to the artefacts. This study examines how two target populations of young adults (18–21 years) and the elderly (65 years and older) responded to seeing cultural heritage artefacts in three different modalities: augmented reality on a tablet, 3D models on a laptop, and then physical artefacts. Specifically, the time spent, enjoyment, and emotional responses were analysed. Results revealed that regardless of age, the digital modalities were enjoyable and encouraged emotional responses. Seeing the physical artefacts after the digital ones did not lessen their enjoyment or emotions felt. These findings aim to provide an insight into the effectiveness of 3D artefacts viewed on personal devices and artefacts shown outside of the museum for encouraging emotional responses from older and younger people
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