1,938 research outputs found
Catálogo de meteoritos y tectitas de la colección del Museu de Geologia de Barcelona
The first part of this work is about the chronological evolution of the collection of meteorites from the Museu de Geologia de Barcelona (MGB), and the second part is a catallogue of the collection, distribuying the samples in four sections: Spanish meteorites, meteorites from other localities, tektites and pseudometeorites and material related to the meteorites.
Key words: Catallogue, Meteorite, Tektite, Pseudometeorite, Museu de Geologia de Barcelona, Spain.El presente trabajo refiere la evolución cronológica de la colección de meteoritos del Museu de Geologia de Barcelona (MGB), y cataloga los ejemplares de dicha colección, distribuyéndolos en cuatro apartados: Meteoritos españoles, meteoritos de otras localidades, tectitas y pseudometeoritos y material relacionado con los meteoritos.
Palabras clave: Catálogo, Meteorito, Tectita, Pseudometeorito, Museu de Geologia de Barcelona, España
Metabolic and functional consequences of cytosolic 5′-nucleotidase-IA overexpression in neonatal rat cardiomyocytes
Adenosine exerts a spectrum of energy-preserving actions on the heart negative chronotropic effects. The pathways leading to adenosine formation have remained controversial. In particular, although cytosolic 5′-nucleotidases can catalyze adenosine formation in cardiomyocytes, their contribution to the actions of adenosine has not been documented previously. We recently cloned two closely related AMP-preferring cytosolic 5′-nucleotidases (cN-IA and -IB); the A form predominates in the heart. In this study, we overexpressed pigeon cN-IA in neonatal rat cardiomyocytes using an adenovirus. cN-IA overexpression increased adenosine formation and release into the medium caused by simulated hypoxia and by isoproterenol in the absence and presence of inhibitors of adenosine metabolism. Adenosine release was not affected by an ecto-5′-nucleotidase inhibitor, α,β-methylene-ADP, but was affected by a nucleoside transporter, dipyridamole. The positive chronotropic effect of isoproterenol (130 ±3 vs. 100 ±4 beats/min) was inhibited (107 ±3 vs. 94 ±3 beats/min) in cells overexpressing cN-IA, and this was reversed by the addition of the adenosine receptor antagonist 8-(p-sulfophenyl)theophilline (120 ± 3 vs. 90 ± 4 beats/min). Our results demonstrate that overexpressed cN-IA can be sufficiently active in cardiomyocytes to generate physiologically effective concentrations of adenosine at its receptors.Fil: Sala-Newby, Graciela B.. University of Bristol; Reino UnidoFil: Freeman, Nicola V. E.. University of Bristol; Reino UnidoFil: Curto, Maria de Los Angeles. University of Bristol; Reino Unido. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Instituto de Investigaciones en IngenierÃa Genética y BiologÃa Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Newby, Andrew C.. University of Bristol; Reino Unid
Modeling stock markets' volatility using GARCH models with normal, Student's t and stable Paretian distributions
As GARCH models and stable Paretian distributions have been revisited in the recent past with the papers of Hansen and Lunde (J Appl Econom 20: 873–889, 2005) and Bidarkota and McCulloch (Quant Finance 4: 256–265, 2004), respectively, in this paper we discuss alternative conditional distributional models for the daily returns of the US, German and Portuguese main stock market indexes, considering ARMA-GARCH models driven by Normal, Student’s t and stable Paretian distributed innovations. We find that a GARCH model with stable Paretian innovations fits returns clearly better than the more popular Normal distribution and slightly better than the Student’s t distribution. However, the Student’s t outperforms the Normal and stable Paretian distributions when the out-of-sample density forecasts are considered.info:eu-repo/semantics/acceptedVersio
Determinantes da remuneração nas empresas portuguesas
A análise e explicação das determinantes das diversas formas de remuneração em Portugal são o principal objectivo deste trabalho. Apesar da existência de diversos estudos sobre remunerações, até agora não foram desenvolvidos estudos sobre quais as determinantes explicativas da realidade empresarial. Este estudo identifica o conjunto de caracterÃsticas das empresas e dos colaboradores que explicam o montante e a probabilidade de auferir remuneração variável e quais as determinantes da remuneração base, comparando-se os dois modelos através do «colaborador padrão». Os resultados mostram que a remuneração variável é mais utilizada nos nÃveis hierárquicos superiores, na área comercial, em empresas de menor dimensão, em filiais de empresas estrangeiras e para colaboradores com educação superior. Quanto à rendibilidade, os resultados revelam uma relação positiva com a probabilidade de existência de remuneração variável. No entanto, os montantes de remuneração variável são mais elevados nas empresas com menor rendibilidade
The HARPS search for southern extrasolar planets. XXIII. 8 planetary companions to low-activity solar-type stars
In this paper, we present our HARPS radial-velocity data for eight
low-activity solar-type stars belonging to the HARPS volume-limited sample:
HD6718, HD8535, HD28254, HD290327, HD43197, HD44219, HD148156, and HD156411.
Keplerian fits to these data reveal the presence of low-mass companions around
these targets. With minimum masses ranging from 0.58 to 2.54 MJup, these
companions are in the planetary mass domain. The orbital periods of these
planets range from slightly less than one to almost seven years. The eight
orbits presented in this paper exhibit a wide variety of eccentricities: from
0.08 to above 0.8.Comment: 8 pages, 2 figures, accepted for publication in A&
The HARPS search for southern extrasolar planets: XXXIII. New multi-planet systems in the HARPS volume limited sample: a super-Earth and a Neptune in the habitable zone
The vast diversity of planetary systems detected to date is defying our
capability of understanding their formation and evolution. Well-defined
volume-limited surveys are the best tool at our disposal to tackle the problem,
via the acquisition of robust statistics of the orbital elements. We are using
the HARPS spectrograph to conduct our survey of ~850 nearby solar-type stars,
and in the course of the past nine years we have monitored the radial velocity
of HD103774, HD109271, and BD-061339. In this work we present the detection of
five planets orbiting these stars, with m*sin(i) between 0.6 and 7 Neptune
masses, four of which are in two multiple systems, comprising one super-Earth
and one planet within the habitable zone of a late-type dwarf. Although for
strategic reasons we chose efficiency over precision in this survey, we have
the capability to detect planets down to the Neptune and super-Earth mass
range, as well as multiple systems, provided that enough data points are made
available.Comment: 7 pages, 14 figures, accepted for publication by A&A, 04-01-201
Superspace Geometrical Realization of the N-Extended Super Virasoro Algebra and its Dual
We derive properties of N-extended GR super Virasoro algebras. These include
adding central extensions, identification of all primary fields and the action
of the adjoint representation on its dual. The final result suggest
identification with the spectrum of fields in supergravity theories and
superstring/M-theory constructed from NSR N-extended supersymmetric Virasoro algebras.Comment: 17 pages Latex Typos in TeX file has been correcte
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