15,681 research outputs found

    Bioassays with terrestrial and aquatic species as monitoring tools of hydrocarbon degradation

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    In this study chemical analyses and ecotoxicity tests were applied for the assessment of a heavily hydrocarbon-contaminated soil prior and after the application of a remediation procedure that consisted in the stimulation of soil autochthonous populations of hydrocarbon degraders in static-ventilated biopiles. Terrestrial bioassays were applied in mixtures of test soils and artificial control soil and studied the survival and reproduction of Eisenia fetida and the avoidance response of E. fetida and Folsomia candida. Effects on aquatic organisms were studied by means of acute tests with Vibrio fischeri, Raphidocelis subcapitata, and Daphnia magna performed on aqueous elutriates from test soils. The bioremediation procedure led to a significant reduction in the concentration of hydrocarbons (from 34264 to 3074 mg kg-1, i.e., 91 % decrease) and toxicity although bioassays were not able to report a percentage decrease of toxicity as high as the percentage reduction. Sublethal tests proved the most sensitive terrestrial bioassays and avoidance tests with earthworms and springtails showed potential as monitoring tools of hydrocarbon remediation due to their high sensitivity and short duration. The concentrations of hydrocarbons in water extracts from test soils were 130 and 100 µg L-1 before and after remediation, respectively. Similarly to terrestrial tests, most aquatic bioassays detected a significant reduction in toxicity, which was almost negligible at the end of the treatment. D. magna survival was the most affected by soil elutriates although toxicity to the crustacean was associated to the salinity of the samples rather than to the concentration of hydrocarbons. Ecotoxicity tests with aqueous soil elutriates proved less relevant in the assessment of hydrocarbon-contaminated soils due to the low hydrosolubility of hydrocarbons and the influence of the physicochemical parameters of the aquatic mediumPostprint (author's final draft

    Protoplanetary disk lifetimes vs stellar mass and possible implications for giant planet populations

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    We study the dependence of protoplanetary disk evolution on stellar mass using a large sample of young stellar objects in nearby young star-forming regions. We update the protoplanetary disk fractions presented in our recent work (paper I of this series) derived for 22 nearby (< 500 pc) associations between 1 and 100 Myr. We use a subsample of 1 428 spectroscopically confirmed members to study the impact of stellar mass on protoplanetary disk evolution. We divide this sample into two stellar mass bins (2 M_{\odot} boundary) and two age bins (3 Myr boundary), and use infrared excesses over the photospheric emission to classify objects in three groups: protoplanetary disks, evolved disks, and diskless. The homogeneous analysis and bias corrections allow for a statistically significant inter-comparison of the obtained results. We find robust statistical evidence of disk evolution dependence with stellar mass. Our results, combined with previous studies on disk evolution, confirm that protoplanetary disks evolve faster and/or earlier around high-mass (> 2 M_{\odot}) stars. We also find a roughly constant level of evolved disks throughout the whole age and stellar mass spectra. We conclude that protoplanetary disk evolution depends on stellar mass. Such a dependence could have important implications for gas giant planet formation and migration, and could contribute to explaining the apparent paucity of hot Jupiters around high-mass stars.Comment: Accepted for publication in A&A. 13 pages, 8 figures, 5 table

    Chemical abundances of late-type pre-main sequence stars in the σ\sigma-Orionis cluster

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    The young σ\sigma-Orionis cluster is an important location for understanding the formation and evolution of stars, brown dwarfs, and planetary-mass objects. Its metallicity, although being a fundamental parameter, has not been well determined yet. We present the first determination of the metallicity of nine young late-type stars in σ\sigma-Orionis. Using the optical and near-infrared broadband photometry available in the literature we derive the effective temperatures for these nine cluster stars, which lie in the interval 4300--6500 K (1--3 \Msuno). These parameters are employed to compute a grid of synthetic spectra based on the code MOOG and Kurucz model atmospheres. We employ a χ2\chi^2-minimization procedure to derive the stellar surface gravity and atmospheric abundances of Al, Ca, Si, Fe, Ni and Li, using multi-object optical spectroscopy taken with WYFFOS+AF2 at at the William Herschel Telescope (λ/δλ7500\lambda/\delta\lambda\sim7500). The average metallicity of the σ\sigma-Orionis cluster is [Fe/H] =0.02±0.09±0.13 = -0.02\pm0.09\pm0.13 (random and systematic errors). The abundances of the other elements, except lithium, seem to be consistent with solar values. Lithium abundances are in agreement with the "cosmic" 7^7Li abundance, except for two stars which show a logϵ(Li)\log \epsilon(\mathrm{Li}) in the range 3.6--3.7 (although almost consistent within the error bars). There are also other two stars with logϵ(Li)2.75\log \epsilon(\mathrm{Li})\sim 2.75. We derived an average radial velocity of the σ\sigma-Orionis cluster of 28±428\pm4km/s. The σ\sigma-Orionis metallicity is roughly solar.Comment: Accepted for publication in Astronomy and Astrophysic

    Tracking Advanced Planetary Systems (TAPAS) with HARPS-N. III. HD 5583 and BD+15 2375 - two cool giants with warm companions

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    Evolved stars are crucial pieces to understand the dependency of the planet formation mechanism on the stellar mass and to explore deeper the mechanism involved in star-planet interactions. Over the past ten years, we have monitored about 1000 evolved stars for radial velocity variations in search for low-mass companions under the Penn State - Torun Centre for Astronomy Planet Search program with the Hobby-Eberly Telescope. Selected prospective candidates that required higher RV precision measurements have been followed with HARPS-N at the 3.6 m Telescopio Nazionale Galileo under the TAPAS project. We aim to detect planetary systems around evolved stars to be able to build sound statistics on the frequency and intrinsic nature of these systems, and to deliver in-depth studies of selected planetary systems with evidence of star-planet interaction processes. For HD 5583 we obtained 14 epochs of precise RV measurements collected over 2313 days with the Hobby-Eberly Telescope (HET), and 22 epochs of ultra-precise HARPS-N data collected over 976 days. For BD+15 2375 we collected 24 epochs of HET data over 3286 days and 25 epochs of HARPS-S data over 902 days. We report the discovery of two planetary mass objects orbiting two evolved Red Giant stars: HD~5583 has a m sin i = 5.78 MJ_{J} companion at 0.529~AU in a nearly circular orbit (e=0.076), the closest companion to a giant star detected with the RV technique, and BD+15~2735 that with a m sin i= 1.06 MJ_{J} holds the record of the lightest planet found so far orbiting an evolved star (in a circular e=0.001, 0.576~AU orbit). These are the third and fourth planets found within the TAPAS project, a HARPS-N monitoring of evolved planetary systems identified with the Hobby-Eberly Telescope.Comment: 9 pages, 6 figures. Accepted by Astronomy and Astrophysic

    The Rothschild House business network in Spain as an example of entrepreneurial decision-taking and management structure.

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    In the period between 1835 and 1931 the Rothschild House established one of the most complex and influential business networks in Spanish economic history. This network controlled a wide range of activities, including financial services for the Spanish Government and the Bank of Spain, as well as the management of industrial, mining and railway firms. Instances of these firms are Rio Tinto Co., Société Minière et Metallurgique Peñarroya, MZA railway company and Deutsch & Cie, which was the main oil refining firm in Spain at the end of the 19th century.Spain 1835-1931, Rothschild, networks, Weisweiller, Bauer, foreign investments in Spain, railways, mining and refining companies, international raw material market, Public Finances, entrepreneurial function, agency problems, rent-seeking.

    Government Strategies to Attract R&D-intensive FDI

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    The final publication is available at Springer via 10.1007 / s10961-008-9091-1La competición entre países y regiones por atraer las actividades de I+D de las empresas multinacionales ha aumentado sustancialmente durante los últimos años, pero no hay suficientes estudios sobre las estrategias utilizadas por los gobiernos en esta competición. Este artículo propone una taxonomía de los principales instrumentos políticos para estimular la IED intensiva en I+D y presenta los resultados de un estudio de caso comparativo de dos países europeos: España e Irlanda. La principal conclusión es que una promoción eficiente de la IED intensiva en I+D requiere una mayor coordinación entre las políticas de innovación y las políticas de atracción de la IED, que tradicionalmente han funcionado de forma independiente. Otra recomendación que emana de este estudio es que las agencias de promoción de inversiones que deseen priorizar la IED intensiva en I+D deberían reconfigurar la gama de servicios que prestan para pasar a centrarse en los servicios postinversión (o “after-care”), ya que la IED-intensiva en I+D tiende a ocurrir a través de un proceso evolutivo y no tanto a través de inversiones “greenfield”.Competition among countries and regions to attract the R&D activities of multinational enterprises has increased substantially during the last years, but the strategies used by governments in this competition remain largely unexplored. This paper proposes a taxonomy of the main policy instruments available to stimulate inward R&D-intensive FDI and presents the results of a comparative case-study of two European countries: Spain and Ireland. The main conclusion is that an efficient promotion of R&D-intensive FDI calls for a closer coordination between innovation policy and inward investment promotion, which are two policy areas that have traditionally operated rather independently from each other. In addition, inward investment agencies targeting R&D-intensive FDI are advised to reconfigure the scope of services they provide by placing more emphasis on after-care, since R&D-intensive FDI tends to be evolutionary rather than greenfield

    Government strategies to attract R&D-Intensive FDI

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    Competition among countries and regions to attract the R&D activities of multinational enterprises has increased substantially during the last years, but the strategies used by governments in this competition remain largely unexplored. This paper proposes a taxonomy of the main policy instruments available to stimulate inward R&D-intensive FDI and presents the results of a comparative case-study of two European countries: Spain and Ireland. The main conclusion is that an efficient promotion of R&D-intensive FDI calls for a closer coordination between innovation policy and inward investment promotion, which are two policy areas that have traditionally operated rather independently from each other. In addition, inward investment agencies targeting R&D-intensive FDI are advised to reconfigure the scope of services they provide by placing more emphasis on after-care, since R&D-intensive FDI tends to be evolutionary rather than greenfield

    Indoor Air Quality Assessment: Comparison of Ventilation Scenarios for Retrofitting Classrooms in a Hot Climate

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    Current energy e ciency policies in buildings foster the promotion of energy retrofitting of the existing stock. In southern Spain, the most extensive public sector is that of educational buildings, which is especially subject to significant internal loads due to high occupancy. A large fraction of the energy retrofit strategies conducted to date have focused on energy aspects and indoor thermal comfort, repeatedly disregarding indoor air quality criteria. This research assesses indoor air quality in a school located in the Mediterranean area, with the objective of promoting di erent ventilation scenarios, based on occupancy patterns and carbon dioxide levels monitored on site. Results show that manual ventilation cannot guarantee minimum indoor quality levels following current standards. A constant ventilation based on CO2 levels allows 15% more thermal comfort hours a year to be reached, compared to CO2-based optimized demand-controlled ventilation. Nevertheless, the latter ensures 35% annual energy savings, compared to a constant CO2-based ventilation, and 37% more annual energy savings over that of a constant ventilation rate of outdoor air per person

    Energy-water-environment nexus underpinning future desalination sustainability

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    Energy-water-environment nexus is very important to attain COP21 goal, maintaining environment temperature increase below 2 °C, but unfortunately two third share of CO2 emission has already been used and the remaining will be exhausted by 2050. A number of technological developments in power and desalination sectors improved their efficiencies to save energy and carbon emission but still they are operating at 35% and 10% of their thermodynamic limits. Research in desalination processes contributing to fuel World population for their improved living standard and to reduce specific energy consumption and to protect environment. Recently developed highly efficient nature-inspired membranes (aquaporin & graphene) and trend in thermally driven cycle's hybridization could potentially lower then energy requirement for water purification. This paper presents a state of art review on energy, water and environment interconnection and future energy efficient desalination possibilities to save energy and protect environment

    Optical Characterization of a New Young Stellar Population in the Serpens Molecular Cloud

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    We report on the results of an optical spectroscopic survey designed to confirm the youth and determine the spectral types among a sample of young stellar object (YSO) candidates in the Serpens Molecular Cloud. We observed 150 infrared excess objects, previously discovered by the Spitzer Legacy Program "From Molecular Cores to Planet-Forming Disks" (c2d), bright enough for subsequent Spitzer/IRS spectroscopy. We obtained 78 optical spectra of sufficient S/N for analysis. Extinctions, effective temperatures and luminosities are estimated for this sample, and used to construct H-R diagrams for the population. We identified 20 background giants contaminating the sample, based on their relatively high extinction, position in the H-R diagram, the lack of Halpha emission and relatively low infrared excess. Such strong background contamination (25%) is consistent with the location of Serpens being close to the Galactic plane (5degrees Galactic latitude). The remaining 58 stars (75%) were all confirmed to be young, mostly K and M-type stars that are presumed to belong to the cloud. Individual ages and masses for the YSOs are inferred based on theoretical evolutionary models. The models indicate a spread in stellar ages from 1 to 15 Myr, peaking at 2 - 6 Myr, and a mass distribution of 0.2 to 1.2 Msun with median value around 0.8 Msun. Strong H emission lines (EW[Halpha] > 3 A) have been detected in more than half of the sample (35 stars). The mass accretion rates as derived from the H line widths span a broad distribution over 4 orders of magnitude with median accretion rate of 10^-8 Msun/yr. Our analysis shows that the majority of the infrared excess objects detected in Serpens are actively accreting, young T-Tauri stars.Comment: ApJ in pres
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