3,730 research outputs found
Asteroseismology of delta Scuti stars in open clusters: Praesepe
The present paper provides a general overview of the asteroseismic potential
of delta Scuti stars in clusters, in particular focusing on convection
diagnostics. We give a summarise of the last results obtained by the authors
for the Praesepe cluster of which five delta Scuti stars are analysed. In that
work, linear analysis is confronted with observations, using refined
descriptions for the effects of rotation on the determination of the global
stellar parameters and on the adiabatic oscillation frequency computations. A
single, complete, and coherent solution for all the selected stars is found,
which lead the authors to find important restrictions to the convection
description for a certain range of effective temperatures. Furthermore, the
method used allowed to give an estimate of the global parameters of the
selected stars and constrain the cluster.Comment: 6 pages, 1 figure. Accepted for publication in Communications in
Asteroseismolog
Even convexity, subdifferentiability, and Î-regularization in general topological vector spaces
In this paper we provide new results on even convexity and extend some others to the framework of general topological vector spaces. We first present a characterization of the even convexity of an extended real-valued function at a point. We then establish the links between even convexity and subdifferentiability and the Î-regularization of a given function. Consequently, we derive a sufficient condition for strong duality fulfillment in convex optimization problems.MICINN of Spain, Grant MTM2011-29064-C03-02
Multi-site observations of Delta Scuti stars 7 Aql and 8 Aql (a new Delta Scuti variable): The twelfth STEPHI campaign in 2003
We present an analysis of the pulsation behaviour of the Delta Scuti stars 7
Aql (HD 174532) and 8 Aql (HD 174589) -- a new variable star -- observed in the
framework of STEPHI XII campaign during 2003 June--July. 183 hours of high
precision photometry were acquired by using four-channel photometers at three
sites on three continents during 21 days. The light curves and amplitude
spectra were obtained following a classical scheme of multi-channel photometry.
Observations in different filters were also obtained and analyzed. Six and
three frequencies have been unambiguously detected above a 99% confidence level
in the range 0.090 mHz--0.300 mHz and 0.100 mHz-- 0.145 mHz in 7 Aql and 8 Aql
respectively. A comparison of observed and theoretical frequencies shows that 7
Aql and 8 Aql may oscillate with p modes of low radial orders, typical among
Delta Scuti stars. In terms of radial oscillations the range of 8 Aql goes from
n=1 to n=3 while for 7 Aql the range spans from n=4 to n=7. Non-radial
oscillations have to be present in both stars as well. The expected range of
excited modes according to a non adiabatic analysis goes from n=1 to n=6 in
both stars.Comment: 8 pages, 7 fugures, 5 tables, accepted for publication in
Astronomical Journa
Combining quantitative approaches to differentiate between backed products from discoidal and Levallois reduction sequences
Backed flakes (core edge flakes and pseudo-Levallois points) represent special products of Middle Paleolithic
centripetal flaking strategies. Their peculiarities are due to their roles as both a technological objective and in the
management of core convexities to retain its geometric properties during reduction. In Middle Paleolithic contexts, these backed implements are commonly produced during Levallois and discoidal reduction sequences.
Backed products from Levallois and discoidal reduction sequences often show common geometric and
morphological features that complicate their attribution to one of these methods. This study examines the
identification of experimentally produced discoidal and recurrent centripetal Levallois backed products
(including all stages of reduction) based on their morphological features. 3D geometric morphometrics are
employed to quantify morphological variability among the experimental sample. Dimensionality reduction
though principal component analysis is combined with 11 machine learning models for the identification of
knapping methods. A supported vector machine with polynomial kernel has been identified as the best model
(with a general accuracy of 0.76 and an area under the curve [AUC] of 0.8). This indicates that combining
geometric morphometrics, principal component analysis, and machine learning models succeeds in capturing the
morphological differences of backed products according to the knapping methodThis research has been
supported by the project SI1/PJI/2019-00488 funded by Comunidad
Autonoma de Madrid and Universidad Autonoma de Madrid. FR
research studies are also supported by the project ID2019-103987GBC33 funded by the Spanish Ministry of Science and Innovatio
The contribution of 2D and 3D geometric morphometrics to lithic taxonomies: Testing discrete categories of backed flakes from recurrent centripetal core reduction
Paleolithic lithic assemblages are usually dominated by fakes and display a high degree of morphological variability. When analyzing Paleolithic lithic assemblages, it is common to classify fakes into categories based on their morphological and technological features, which are linked to the position of the fake in the reduction sequence and how removals are organized in a given production method. For the analysis of Middle Paleolithic lithic assemblages, two categories of fakes are commonly identifed: coreâedge fakes and pseudo-Levallois points. A third type, coreâedge fakes with a limited back, is also commonly found in the archaeological literature, providing an alternative category whose defnition does not match the two previous types but shares many of their morphological and technological features. The present study addresses whether these three fakes constitute discrete categories based on their morphological and technological attributes. 2D and 3D geometric morphometrics are employed on an experimental set composed of the three categories of fakes to quantify morphological variation. Machine learning models and principal components biplots are used to test the discreteness of the categories. The results indicate that geometric morphometrics succeed in capturing the morphological and technological features that characterize each type of product. Pseudo-Levallois points have the highest discreteness of the three technological products, and while some degree of mixture exists between core edge fakes and core edge fakes with a limited back, they are also highly distinguishable. We conclude that the three categories are discrete and can be employed in technological lists of products for the analysis of lithic assemblages and that geometric morphometrics is useful for testing for the validity of categories. When testing these technological categories, we stress the need for well-defned and shared lithic analytical units to correctly identify and interpret the technical steps and decisions made by prehistoric knappers and to properly compare similarities and diferences between stone tool assemblages. These are key aspects for current research in which open datasets are becoming more and more common and used to build interpretative techno-cultural models on large geographical scales. Now more than ever, lithic specialists are aware of the need to overcome diferences in taxonomies between diferent school tradition
Local order and magnetic behavior of amorphous and nanocrystalline yttrium iron garnet produced by swift heavy ion irradiations
International audienceThin epitaxial films of gallium or scandium-doped and undoped yttrium iron garnet (Y3Fe5O12 or YIG) on nonmagnetic Gd3Ga5O12 substrates were irradiated with swift heavy ions (50âMeVâ32S, 50âMeVâ63Cu, and 235âMeVâ84Kr) in the electronic slowing down regime. The mean electronic stopping power in the films was always larger than the threshold for amorphous track formation in YIG which is around 4.5 MeV/ÎŒm in this low ion-velocity range. The local order and magnetic properties of the damaged films were then studied at room temperature by 57Fe conversion electron Mössbauer spectroscopy (CEMS) and x-ray absorption spectroscopy (XAS) at the iron K edge in the fluorescence mode. In the case of paramagnetic gallium or scandium-substituted films (YIG:Ga, YIG:Sc) irradiated with 32S or 63Cu ions, the CEMS data show that the tetrahedral Fe3+ sites are preferentially damaged, while the octahedral sites are conserved. This is confirmed by the decrease of the pre-edge peak in the XAS data of the ferrimagnetic undoped YIG films showing that the number of tetrahedral iron sites is decreased in the amorphous phase obtained with 84Kr ion irradiation, due to the formation of fivefold-coordinated pyramidal sites, as already found in a previous study on undoped YIG sinters amorphized by 3.5 GeV 132Xe ion irradiation. In the case of the nanophase induced by ion-beam recrystallization of the tracks with 32S or 63Cu irradiations, a further decrease of the pre-edge peak is found. This is interpreted by (i) an increase of the fivefold-coordinated pyramidal sites and/or (ii) a probable decomposition of the garnet into orthoferrite (YFeO3) and haematite (α-Fe2O3) under the high-pressure and high-temperature conditions in the thermal spike generated by the ions. The CEMS data of irradiated undoped YIG also show that both the amorphous and nanocrystalline phases have a paramagnetic behavior at room temperature. The nanophase magnetic behavior is analyzed on the basis of a superparamagnetic relaxation above the blocking temperature, whereas the amorphous phase behavior is ascribed to a speromagnetic state
The Iturin and Fengycin Families of Lipopeptides Are Key Factors in Antagonism of Bacillus subtilis Toward Podosphaera fusca
Podosphaera fusca is the main causal agent of cucurbit powdery mildew in Spain. Four Bacillus subtilis strains, UMAF6614, UMAF6619, UMAF6639, and UMAF8561, with proven ability to suppress the disease on melon in detached leaf and seedling assays, were subjected to further analyses to elucidate the mode of action involved in their biocontrol performance. Cell-free supernatants showed antifungal activities very close to those previously reported for vegetative cells. Identification of three lipopeptide antibiotics, surfactin, fengycin, and iturin A or bacillomycin, in butanolic extracts from cell-free culture filtrates of these B. subtilis strains pointed out that antibiosis could be a major factor involved in their biocontrol ability. The strong inhibitory effect of purified lipopeptide fractions corresponding to bacillomycin, fengycin, and iturin A on P. fusca conidia germination, as well as the in situ detection of these lipopeptides in bacterial-treated melon leaves, provided interesting evidence of their putative involvement in the antagonistic activity. Those results were definitively supported by site-directed mutagenesis analysis, targeted to suppress the biosynthesis of the different lipopeptides. Taken together, our data have allowed us to conclude that the iturin and fengycin families of lipopeptides have a major role in the antagonism of B. subtilis toward P. fusca.
The Iturin and Fengycin Families of Lipopeptides Are Key Factors in Antagonism of Bacillus subtilis Toward Podosphaera fusca
Podosphaera fusca is the main causal agent of cucurbit powdery mildew in Spain. Four Bacillus subtilis strains, UMAF6614, UMAF6619, UMAF6639, and UMAF8561, with proven ability to suppress the disease on melon in detached leaf and seedling assays, were subjected to further analyses to elucidate the mode of action involved in their biocontrol performance. Cell-free supernatants showed antifungal activities very close to those previously reported for vegetative cells. Identification of three lipopeptide antibiotics, surfactin, fengycin, and iturin A or bacillomycin, in butanolic extracts from cell-free culture filtrates of these B. subtilis strains pointed out that antibiosis could be a major factor involved in their biocontrol ability. The strong inhibitory effect of purified lipopeptide fractions corresponding to bacillomycin, fengycin, and iturin A on P. fusca conidia germination, as well as the in situ detection of these lipopeptides in bacterial-treated melon leaves, provided interesting evidence of their putative involvement in the antagonistic activity. Those results were definitively supported by site-directed mutagenesis analysis, targeted to suppress the biosynthesis of the different lipopeptides. Taken together, our data have allowed us to conclude that the iturin and fengycin families of lipopeptides have a major role in the antagonism of B. subtilis toward P. fusca.
Donald Trump y el cambio en EU: la voluntad de ser un espectĂĄculo admirado
Un retrato del empresario convertido en candidato y luego en presidente, que permite ver que la visiĂłn de Donald Trump de los Estados Unidos como un paĂs disminuido y debilitado en medio de paĂses que sĂłlo quieren aprovecharse de Ă©l, tiene mĂĄs de 20 años. El texto ayuda a perfilar la personalidad del presidente del paĂs mĂĄs poderoso del mundo y el modo en que se relaciona, en la bĂșsqueda siempre de sacar el mayor provecho con el menor costo.ITESO, A.C
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