Geochemistry and petrogenesis of sodic and potassic mafic alkaline rocks in the Deccan Volcanic Province, Mumbai Area (India)     

L. Melluso  S. F. Sethna  M. D’Antonio  P. Javeri  L. Bennio 《Mineralogy and Petrology》2002,74(2-4):323-342

Summary Major element, trace element, Sr- and Nd-isotopes and mineral chemical data are reported for alkaline rocks (lamprophyres, tephrites, melanephelinites, nephelinites and nepheline syenites) cross-cutting the Deccan Trap lava flows south (Murud-Janjira area) and north of Mumbai (Bassein). These rocks range from sodic to potassic and have a large span in MgO (12–2 wt%). The lamprophyres have high content of incompatible elements (e.g., TiO₂ > 3.8 wt%, Nb > 130 ppm, Zr > 380 ppm, Ba > 1200 ppm), and relatively high initial (at 65 Ma) ¹⁴³Nd/¹⁴⁴Nd (0.5128) and low ⁸⁷Sr/⁸⁶Sr (0.7038–0.7042). They are likely to be small-degree melts (2–3%) of volatile- and incompatible element-enriched mantle sources, similar to other alkaline rocks in the northern Deccan, though slightly more potassium-rich. The nepheline-rich rocks have highly porphyritic textures (up to 57% phenocrysts of diopside ± olivine), and anomalously low contents of incompatible elements (e.g., TiO₂ < 1.3 wt%, Nb < 24 ppm, Zr < 100 ppm) indicating that they could not represent liquid compositions. Moreover, their very low initial ¹⁴³Nd/¹⁴⁴Nd ratios (0.5116–0.5120), at ⁸⁷Sr/⁸⁶Sr = 0.7045–0.7049, are unusual in the rocks related to the Deccan Traps and identify a new end-member in this province, that could be identified as “Lewisian-type” lower crust and/or enriched mantle. The melting episode that generated these alkaline rocks likely occurred close to the base of the ca. 100 km-thick Indian lithosphere, very shortly after the main eruption of the Deccan tholeiites. Received January 14, 2000; revised version accepted September 28, 2001  相似文献   

The extended structure of the Phoenix dwarf galaxy     

Sebastian L. Hidalgo  Antonio Aparicio  David MartÍnez-Delgado 《Astrophysics and Space Science》2003,284(2):595-598

The surface brightness profile in the V band of the Phoenix dwarf galaxy shows two stellar components: an inner one, which contains all the young stars of the galaxy, and an outer one predominantly populated by red stars. Deep color-magnitude diagrams (CMDs), based on Hubble Space Telescope (HST) observations and reaching the oldest turn-offs, are used to analyze the inner and outer stellar components. Results show that, together with an old stellar population, the outer field contains also an intermediate-age population. These results are compatible with a scenario in which star forming regions are shrinking with time (the shrinking scenario). It seems more difficult to support a halo-disk scenario, which would require extended structures populated only by really old stars. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

The Science Operations Centre of MINISAT-01     

Antonio Talavera  Jesús García  Carlos Quintana  Eduardo Fernandes 《Astrophysics and Space Science》2001,276(1):89-96

The Scientific Operations Centre (C.O.C.) takes care of all aspects of theMinisat-01 Mission related to the payload and its scientific instruments. Operations planning, preparation of commands, monitoring of the scientific instruments and data processing and distribution are the daily tasks carried out at the COC. We review these tasks along the operational life of Minisat-01 and we present a summary of the science operations andsome statistics on the usage of the satellite.  相似文献   

Magnetic Environments of Young Stellar Objects     

Antonio Chrysostomou  Rachel Curran  David Aitken  Tim Jenness  Chris Davis 《Astrophysics and Space Science》2003,287(1-4):161-164

We report on early results of magnetic field measurements towards a sample of young stellar objects. The results show a variety of field configurations, some of which can be explained by conventional models, while others cannot. We find that the field in some cases is curved over large scales and influenced by the gas kinematics in the local environment. This implies that, at these scales at least, the magnetic field plays a passive rôle in the star formation process.  相似文献   

Status of the Connection between Unidentified Egret Sources and Supernova Remnants: The Case of Cta 1     

Diego F. Torres  Thomas M. Dame  Gustavo E. Romero 《Astrophysics and Space Science》2005,297(1-4):393-398

In this paper we briefly comment on the observational status of the possible physical association between unidentified EGRET sources and supernova remnants (SNRs) in our Galaxy. We draw upon recent results presented in the review by Torres et al. (2003), concerning molecular gas in the vicinity of all 19 SNRs found to be positionally coincident with EGRET sources at low Galactic latitudes. In addition, we present new results regarding the supernova remnant CTA 1. Our findings disfavor the possibility of a physical connection with the nearby (in projection) EGRET source. There remains possible, however, that the compact object produced in the supernova explosion be related with the observed γ-ray flux.  相似文献   

The Magnetic Environments of Young Stellar Objects     

Antonio Chrysostomou  Rachel Curran  David Aitken 《Astrophysics and Space Science》2004,292(1-4):509-515

We report on early results of submillimetre polarimetric measurements towards a sample of young stellar objects. The results allow us to infer the magnetic field structure and show a variety of configurations, providing evidence for axial, helical and pinched (i.e. ‘hourglass’) magnetic field configurations. We find that in some cases the field is curved over large scales, implying that it is influenced by the gas kinematics in the local environment, and that at these scales at least, the magnetic field plays a passive rôle in the star formation process.  相似文献   

IN-FLIGHT PERFORMANCE OF THE VIRGO LUMINOSITY OSCILLATIONS IMAGER ABOARD SOHO     

Appourchaux  Thierry  Andersen  Bo N.  Fröhlich  Claus  Jiménez  Antonio  Telljohann  Udo  Wehrli  Christoph 《Solar physics》1997,170(1):27-41

The Luminosity Oscillations Imager (LOI) is a part of the VIRGO instrument aboard the Solar and Heliospheric Observatory (SOHO). The scientific objective of the LOI experiment is to identify and characterize pressure and internal gravity oscillations of the Sun by observing the radiance variations. The LOI is a low-resolution imager with 12 pixels, for the measurement of the radiance distribution over the solar disk at 500 nm. The low resolution capability of the instrument allows the identification of individual azimuthal orders for l = 0 to 7, without suffering the mixing that affects integrated solar disk instruments. The performance, calibrations and instrumental effects of the LOI are described together with the procedures for extracting the solar p modes.  相似文献   

Periodic Orbits Around Geostationary Positions     

Martín Lara  Antonio Elipe 《Celestial Mechanics and Dynamical Astronomy》2002,82(3):285-299

We generate families of planar periodic orbits emanating from the geostationary points, both stable and unstable. We show that, even for the unstable points, it is possible to have stable periodic orbits.This revised version was published online in October 2005 with corrections to the Cover Date.  相似文献   

Variations in cereal crop phenology in Spain over the last twenty-six years (1986–2012)     

Jose Oteros  Herminia García-Mozo  Roser Botey  Antonio Mestre  Carmen Galán 《Climatic change》2015,132(4):545-558

Over recent years, the Iberian Peninsula has witnessed an increase both in temperature and in rainfall intensity, especially in the Mediterranean climate area. Plant phenology is modulated by climate, and closely governed by water availability and air temperature. Over the period 1986–2012, the effects of climate change on phenology were analyzed in five crops at 26 sites growing in Spain (southern Europe): oats, wheat, rye, barley and maize. The phenophases studied were: sowing date, emergence, flag leaf sheath swollen, flowering, seed ripening and harvest. Trends in phenological response over time were detected using linear regression. Trends in air temperature and rainfall over the period prior to each phenophase were also charted. Correlations between phenological features, biogeographical area and weather trends were examined using a Generalized Lineal Mixed Model approach. A generalized advance in most winter-cereal phenophases was observed, mainly during the spring. Trend patterns differed between species and phenophases. The most noticeable advance in spring phenology was recorded for wheat and oats, the “Flag leaf sheath swollen” and “Flowering date” phenophases being brought forward by around 3 days/year and 1 day/year, respectively. Temperature changes during the period prior to phenophase onset were identified as the cause of these phenological trends. Climate changes are clearly prompting variations in cereal crop phenology; their consequences could be even more marked if climate change persists into the next century. Changes in phenology could in turn impact crop yield; fortunately, human intervention in crop systems is likely to minimize the negative impact.  相似文献   

The influence of environmental variability of a coastal lagoon ecosystem on genetic diversity and structure of white seabream [Diplodus sargus (Linnaeus 1758)] populations          下载免费PDF全文

Raquel Hernández‐García  Irene Muñoz  Antonio López‐Capel  Concepción Marcos  Ángel Pérez‐Ruzafa 《Marine Ecology》2015,36(4):1144-1154

As coastal lagoons serve as nursery areas for some marine and estuarine fish, selective pressures of these brackish or hypersaline lagoons may influence the genetic structure of species and populations. We examined spatial and temporal genetic patterns at eight microsatellite loci in white seabream [Diplodus sargus (Linnaeus 1758)] recruits from the Mar Menor (Southeast Spain) and compared these loci with those in coastal populations from the open sea, observing a high degree of genetic diversity and spatio‐temporal genetic stability. However, the results suggest the presence of subpopulations or genetic substructures in the Mar Menor D. sargus population that could be interpreted as a homogeneous mixture of individuals from three differentiated subpopulations in the Mediterranean and evidence of the Wahlund effect. It also suggests that D. sargus adults return to their original spawning habitat, thus conserving the genetic differences among the respective populations over time. Overall, this study demonstrates the importance of the Mar Menor coastal lagoon as a nursery area for the conservation of genetic diversity of D. sargus populations.  相似文献