First Results from ROTES: The ROtse Telescope Eclipsing-binary Survey     

I. Ribas  J. C. Morales  C. Allende Prieto  C. Jordi  D. H. Bradstreet  S. J. Sanders 《Astrophysics and Space Science》2006,304(1-4):231-233

Detached eclipsing binaries (EBs) provide a unique opportunity to carry out stringent tests on stellar evolution models. The value of EBs is enhanced by their membership in open clusters, but the number of known systems is still very scarce. We have started a systematic search for late-type EBs in the nearest open clusters with the fully robotic ROTSE3b telescope at McDonald Observatory in West Texas. On our first campaigns on the Hyades and Collinder 359, we have identified a number of previously unknown eclipsing binary candidates. Some of these stars have been selected for spectroscopic and photometric follow-up. Here we present details of the observing and reduction strategy as well as the first results of this ongoing survey.  相似文献   

Motion close to the Hopf Bifurcation Of the vertical family of periodic orbits of L4     

Mercè Ollé  Joan R. Pacha  Jordi Villanueva 《Celestial Mechanics and Dynamical Astronomy》2004,90(1-2):87-107

The paper deals with different kinds of invariant motions (periodic orbits, 2D and 3D invariant tori and invariant manifolds of periodic orbits) in order to analyze the Hamiltonian direct Hopf bifurcation that takes place close to the Lyapunov vertical family of periodic orbits of the triangular equilibrium point L₄ in the 3D restricted three-body problem (RTBP) for the mass parameter, μ greater than (and close to) μ_R (Routh’s mass parameter). Consequences of such bifurcation, concerning the confinement of the motion close to the hyperbolic orbits and the 3D nearby tori are also described.  相似文献   

Erratum: Chemical abundances determined from meteor spectra – II. Evidence for enlarged sodium abundances in meteoroids     

Josep M. Trigo-Rodríguez  Jordi Llorca  Juan Fabregat 《Monthly notices of the Royal Astronomical Society》2004,350(3):1152-1152

  相似文献   

The Spanish fireball network   总被引：1，自引：0，他引：1  

Josep M Trigo-Rodríguez  Jordi Llorca  A J Castro-Tirado  J L Ortiz  J A Docobo  J Fabregat 《Astronomy& Geophysics》2006,47(6):6.26-6.28

Josep M Trigo-Rodríguez, Jordi Llorca, Alberto J Castro-Tirado, José L Ortiz, José A Docobo and Juan Fabregat describe their interdisciplinary approach to minor bodies in the solar system.  相似文献   

Tailored data compression using stream partitioning and prediction: application to Gaia     

Jordi Portell  Enrique García-Berro  Xavier Luri  Alberto G. Villafranca 《Experimental Astronomy》2006,21(3):125-149

Gaia is the most ambitious space astrometry mission currently envisaged and it will be a technological challenge in all its aspects. Here we describe a proposal for the data compression system of Gaia, specifically designed for this mission but based on concepts that can be applied to other missions and systems as well. Realistic simulations have been performed with our Telemetry CODEC software, which performs a stream partitioning and pre-compression to the science data. In this way, standard compressors such as bzip2 or szip boost their performance and decrease their processing requirements when applied to such pre-processed data. These simulations have shown that a lossless compression factor of 3 can be achieved, whereas standard compression systems were unable to reach a factor of 2.   相似文献   

Global change revealed by palaeolimnological records from remote lakes: a review   总被引：1，自引：0，他引：1  

Jordi Catalan  Sergi Pla-Rabés  Alexander P. Wolfe  John P. Smol  Kathleen M. Rühland  N. John Anderson  Jiři Kopáček  Evžen Stuchlík  Roland Schmidt  Karin A. Koinig  Lluís Camarero  Roger J. Flower  Oliver Heiri  Christian Kamenik  Atte Korhola  Peter R. Leavitt  Roland Psenner  Ingemar Renberg 《Journal of Paleolimnology》2013,49(3):513-535

Over recent decades, palaeolimnological records from remote sites have provided convincing evidence for the onset and development of several facets of global environmental change. Remote lakes, defined here as those occurring in high latitude or high altitude regions, have the advantage of not being overprinted by local anthropogenic processes. As such, many of these sites record broad-scale environmental changes, frequently driven by regime shifts in the Earth system. Here, we review a selection of studies from North America and Europe and discuss their broader implications. The history of investigation has evolved synchronously with the scope and awareness of environmental problems. An initial focus on acid deposition switched to metal and other types of pollutants, then climate change and eventually to atmospheric deposition-fertilising effects. However, none of these topics is independent of the other, and all of them affect ecosystem function and biodiversity in profound ways. Currently, remote lake palaeolimnology is developing unique datasets for each region investigated that benchmark current trends with respect to past, purely natural variability in lake systems. Fostering conceptual and methodological bridges with other environmental disciplines will upturn contribution of remote lake palaeolimnology in solving existing and emerging questions in global change science and planetary stewardship.  相似文献   

Changes of the Macrobenthos Community with Non-native Mangrove Rehabilitation (Kandelia obovata) and Salt Marsh Invasion (Spartina alterniflora) in Ximen Island,Zhejiang, China     

Wang  Qiuxuan  Song  Li  Agusti  Susana  Duarte  Carlos  Christakos  George  Wu  Jiaping 《Ocean Science Journal》2021,56(4):395-405

Ocean Science Journal - Macrobenthos organisms are vital ecological components of intertidal wetlands. This work studied effects of non-native mangrove rehabilitation (Kandelia obovata) and salt...  相似文献   

Shallow water tidal currents in close proximity to the seafloor and boundary-induced turbulence   总被引：1，自引：0，他引：1  

Iossif Lozovatsky  Zhiyu Liu  Harindra Fernando  Jordi Armengol  Elena Roget 《Ocean Dynamics》2012,62(2):177-191

Velocity measurements with vertical resolution 0.02 m were conducted in the lowest 0.5 m of the water column using acoustic Doppler current profiler (ADCP) at a test site in the western part of the East China Sea. The friction velocity u _* and the turbulent kinetic energy dissipation rate ε _wl(ζ) profiles were calculated using log-layer fits; ζ is the height above the bottom. During a semidiurnal tidal cycle, u _* was found to vary in the range (1–7) × 10⁻³ m/s. The law-of-the-wall dissipation profiles ε _wl(ζ) were consistent with the dissipation profiles ε _mc(ζ) evaluated using independent microstructure measurements of small-scale shear, except in the presence of westward currents. It was hypothesized that an isolated bathymetric rise (25 m height at a 50-m seafloor) located to the east of the measurement site is responsible for the latter. Calculation of the depth integrated internal tide generating body force in the region showed that the flanks of the rise are hotspots of internal wave energy that may locally produce a significant turbulent zone while emitting tidal and shorter nonlinear internal waves. This distant topographic source of turbulence may enhance the microstructure-based dissipation levels ε _mc(ζ) in the bottom boundary layer (BBL) beyond the dissipation ε _wl(ζ) associated with purely locally generated turbulence by skin currents. Semi-empirical estimates for dissipation at a distance from the bathymetric rise agree well with the BBL values of ε _mc measured 15 km upslope.  相似文献   

How do early successional patterns in man-made wetlands differ between cold temperate and Mediterranean regions?     

Albert Ruhí  Jan Herrmann  Stéphanie Gascón  Jordi Sala  Dani Boix 《Limnologica》2012,42(4):328-339

The early stages of succession in newly created wetlands should be impacted by the region in which the wetland is located, since climate may have filtered the dominant biological strategies of the taxa leading this process and may condition their dynamics. We studied the early successional patterns of macroinvertebrates within man made ponds, located in cold temperate (Scandinavian Peninsula) and Mediterranean regions (Iberian Peninsula), during the first three years following their creation. We predicted (1) non random subsets of the regional species pool (deterministic assembly) guiding the successional process in cold temperate wetlands, and random (stochastic) assembly in the Mediterranean region; (2) higher successional rates in Mediterranean ponds than in the cold temperate ponds, with contrary episodes of highest and lowest change throughout the year; and (3) a significant difference in the composition of biological traits between regions, due to the dominance of traits adapted to hydrological variability in the Mediterranean region. Hypotheses on community structure (1) and the composition of dominant biological traits (3) were mostly supported – deterministic assembly mechanisms in the cold temperate ponds and stochastic assembly in the Mediterranean ponds; and a dominance of different biological traits between regions, explained by the need to overcome hydrological disturbances in the Mediterranean ponds. The dynamics of succession (2) were explained by climatic factors in the cold temperate region but not in the Mediterranean ponds. We suggest that the intrinsic hydrological variability of Mediterranean lentic systems may be a major factor driving community changes in man-made wetlands in this region. In order to generalize the observed patterns, we performed a meta-analysis of the temporal trends of taxonomic distinctness parameters of other successional studies across a latitudinal gradient in Europe, which supported the differences we had observed between latitudinal extremes.  相似文献   

March 1, 2005 Daylight Fireball Over Galicia (NW of Spain) and Minho (N. Portugal)     

José Angel Docobo  Josep Maria Trigo-Rodríguez  Jiri Borovicka  Vakhtang S. Tamazian  Vera Assis Fernandes  Jordi Llorca 《Earth, Moon, and Planets》2008,102(1-4):537-542

A daylight bolide was observed over Galicia (NW Spain) and Minho (N. Portugal) on March 1, 2005 at 15 h10 min ± 3 min UTC. We interviewed 23 eyewitnesses of the event in order to obtain the azimuth, altitude, and slope of the fireball’s trajectory. Reports suggest an atmospheric ending height below 20 km, indicating that meteorite survival was likely. From the reconstructed trajectory and the fireball’s duration, we obtained the approximate heliocentric orbits for the meteoroid. Assuming an entry velocity higher than 20 km s⁻¹ which is consistent with its estimated duration, the meteoroid originated in the asteroid belt.  相似文献