Browsing by Author "Maldonado, J."

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    DOES THE PRESENCE OF PLANETS AFFECT THE FREQUENCY AND PROPERTIES OF EXTRASOLAR KUIPER BELTS? RESULTS FROM THE HERSCHEL DEBRIS AND DUNES SURVEYS
    (2015) Moro-Martin, A.; Marshall, J. P.; Kennedy, G.; Sibthorpe, B.; Matthews, B. C.; Eiroa, C.; Wyatt, M. C.; Lestrade, J. -F.; Maldonado, J.; Rodriguez, D.; Greaves, J. S.; Montesinos, B.; Mora, A.; Booth, M.; Duchene, G.; Wilner, D.; Horner, J.
    The study of the planet-debris disk connection can shed light on the formation and evolution of planetary systems. and may help "predict" the presence of planets around stars with certain disk characteristics. In preliminary analyses of subsamples of the Herschel DEBRIS and DUNES surveys, Wyatt et al. and Marshall et al. identified a tentative correlation between debris and the presence of low-mass planets. Here we use the cleanest possible sample out of these Herschel surveys to assess the presence of such a correlation, discarding stars without known ages, with ages <1 Gyr, and with binary companions <100 AU. to rule out possible correlations due to effects other than planet presence. In our resulting subsample of 204 FGK stars, we do not find evidence that debris disks are more common or more dusty around stars harboring high-mass or low-mass planets compared to a control sample without identified planets. There is no evidence either that the characteristic dust temperature of the debris disks around planet-bearing stars is any different from that in debris disks without identified planets, nor that debris disks are more or less common (or more or less dusty) around stars harboring multiple planets compared to single-planet systems. Diverse dynamical histories may account for the lack of correlations. The data show a correlation between the presence of high-mass planets and stellar metallicity, but no correlation between the presence of low-mass planets or debris and stellar metallicity. Comparing the observed cumulative distribution of fractional luminosity to those expected from a Gaussian distribution in logarithmic scale, we find that a distribution centered on the solar system's value fits the data well, while one centered at 10 times this value can be rejected. This is of interest in the context of future terrestrial planet detection and characterization because it indicates that there are good prospects for finding a large number of debris disk systems (i.e., with evidence of harboring planetesimals, the building blocks of planets) with exozodiacal emission low enough to be appropriate targets for an ATLAST-type mission to search for biosignatures.
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    Effect of the marine environment on reinforced concrete durability in lberoamerican countries: DURACON project/CYTED
    (2007) de Rincon, O. Troconis; Sanchez, M.; Millano, V.; Fernandez, R.; de Partidas, E. A.; Andrade, C.; Martinez, I.; Castellote, M.; Barboza, M.; Irassar, F.; Montenegro, J. C.; Vera, R.; Carvajal, A. M.; de Gutierrez, R. M.; Maldonado, J.; Guerrero, C.; Saborio-Leiva, E.; Villalobos, A. C.; Tres-Calvo, G.; Torres-Acosta, A.; Perez-Quiroz, J.; Martinez-Madrid, M.; Almeraya-Calderon, F.; Castro-Borges, P.; Moreno, E. I.; Perez-Lopez, T.; Salta, M.; de Melo, A. P.; Rodriguez, G.; Pedron, Miguel; Derregibus, M.
    This work presents some of the results from the project: "Effect of the environment on reinforcement durability" (DURACON) in its first two-years period, which investigates the influence of urban and marine meteorochemical parameters on the performance of reinforced concrete structures. The results presented in this investigation are from 21 marine test sites only (no urban environments are included), distributed among I I countries (Argentina, Bolivia, Brazil, Chile, Colombia, Costa Rica, Mexico, Spain, Uruguay, Portugal and Venezuela). The environment was evaluated using ISO Standard 9223 and the concrete was characterized by measuring compressive strength, elastic modulus, total and effective porosity, chloride permeability according to ASTM standards, as well as the effective porosity and resistance to water absorption using the Fagerlund method. To that effect, concrete specimens (with and without reinforcement) were prepared for electrochemical and physical/mechanical/chemical tests using the existing materials in each participating country, following strict procedures which enabled the preparation of similar concrete samples. Two water/cement (w/c) ratios (0.45 and 0.65) were selected, where the concrete with 0.45 w/c ratio had to have a minimum cement content of 400 kg/m(3) and the one with 0.65 w/c ratio a compressive strength of 210 kg/cm(2). Type I Portland cement, siliceous sand, and crushed rock as coarse aggregates (13-mm maximum nominal size) were used. After a one-year exposure, the results of the corrosion potentiality and probability analysis of the reinforcement in the different test stations showed that, for marine atmospheres, the most aggressive environment to induce steel corrosion was at Portugal's Cabo Raso station, and the least aggressive one was at Chile's Valparaiso station. These results are comparable with the ones found using electrochemical measurements, after a two-year exposure. (C) 2007 Elsevier Ltd. All rights reserved.
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    First characterization of the gut microbiome associated with Mytilus chilensis collected at a mussel farm and from a natural environment in Chile
    (2022) Santibanez, P.; Romalde, J.; Maldonado, J.; Fuentes, D.; Figueroa, J.
    The gut microbiome of Mytilus chilensis was analyzed using a next-generation sequencing (NGS) approach using as target the V6-V8 16S rDNA gene regions. The resident gut bacterial communities were analyzed in individuals collected from two locations, both free-living in natural conditions (Wild Type group, WT) and those found in intensive commercial cultures at a Mussel Farm (MF group) off the Chilean coast. A total of 1.2 M of nonchimeric sequences were detected, belonging to 30 phyla, including Fusobacteria, Proteobacteria, Bacteroides, Tenericutes, and 404 genera taxa. The major fraction of the sequences detected corresponded to Vibrionaceae and Fusobacteriaceae families for MF and WT groups, respectively. The gut microbiome of M. chilensis showed a wide diversity of microorganisms; however, differences were observed depending on the origin of samples, where gut samples from the mussel farm showed a lower number of genera when compared to gut tissue samples collected from the wild type individuals. The dominant bacterial are Vibrio, Psychrilyobacter, Mycoplasma, and Psychromonas, that were present with different relative abundancies among the samples analyzed. This next generation sequencing technique, applied for the first time in Chilean mussel (M. chilensis), showed that the gut is a useful tissue for the study of bacterial communities in this bivalve mollusk. The results obtained in this work provided insights into the composition of the microbiota of M. chilensis, unravelling the great bacterial diversity and the effect of habitat on the bacterial community structure.
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    Genetic structure based on EST–SSR: a putative tool for fruit color selection in Japanese plum (Prunus salicina L.) breeding programs
    (2016) Gonzalez, M.; Salazar, E.; Castillo, J.; Morales, P.; Mura, I.; Maldonado, J.; Silva M., Hugo; Carrasco Gálvez, Basilio Alejandro