EURD: The Mission and the Stellar Absolute Fluxes of B-Type Stars     

Carmen Morales  Joaquín Trapero  José F. Gómez  Verónica Orozco  Alvaro Gimenez  Stuart Bowyer  Jerry Edelstein  Eric Korpela  Michael Lampton  Jeff Cobb 《Astrophysics and Space Science》2001,276(1):141-150

We present here stellar spectra of B stars obtained with the EURD spectrograph, one of the three instruments on board MINISAT-01. EURD is a spectrograph specially designed to detect diffuse radiation in thewavelength range between 350 and 1100 Å with 5 Å spectral resolution. EURD main scientific targets are: the spectrum of interstellar medium,atmospheric airglow, decaying neutrinos, Moon and early type stars.  相似文献   

Star-Forming Galaxies in Dense Environments     

José M. VÍlchez  Jorge Iglesias-P´ramo 《Astrophysics and Space Science》2002,281(1-2):343-346

We report on preliminary results from an ongoing study of star-forming galaxies in the Virgo Cluster with the aim of understanding the role played by the environment on their evolution. First, the chemical evolution of nine spiral galaxies located in the inner parts of the cluster has been studied using chemical abundances recomputed for a sample of HII regions. Second, long-slit optical spectroscopy has been obtained for 22 blue dwarf galaxies selected across the Virgo central field. This sample is a subset of a larger list of dwarf galaxies for which deep Hα imaging has been collected. Chemical abundances have been derived for the sample using either a direct estimation of the electron temperature or empirical calibrations. Abundance results correlate with blue and near infrared magnitude, total HI mass and color. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

An Analytical Model of Galaxy Formation     

Eduard Salvador-Solé  Alberto Manrique  Andreu Raig  Gullermo González-Casado  José María Solanes  Gustavo A. Bruzual 《Astrophysics and Space Science》2001,276(2-4):1065-1071

We present an analytical model of galaxy formation and evolution. After giving a rapid overview of the strategy employed and the main ingredients included in the model, we focus on describing the main differences between this model and other similar ones available. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Molecular Line Emission from Accretion Disks Around YSOs     

Itziar de Gregorio-Monsalvo  José F. Gómez  Paola D'Alessio 《Astrophysics and Space Science》2004,292(1-4):445-450

In this work, we model the expected molecular emission from protoplanetary disks, modifying different physical parameters, such as dust grain size, mass accretion rate, viscosity, and disk radius, to obtain observational signatures in these sources. Having in mind possible future observations, we study correlations between physical parameters and observational characteristics. Our aim is to determine the kind of observations that will allow us to extract information about the physical parameters of disks. We also present prospects for molecular line observations of protoplanetary disks, using millimeter and submillimeter interferometers (e.g., SMA or ALMA), based on our results.  相似文献   

Estimation of tree water stress from stem and soil water monitoring with time‐domain reflectometry in two small forested basins in Spain     

Virginia Hernández‐Santana  José Martínez‐Fernández  Carlos Morán 《水文研究》2008,22(14):2493-2501

Soil‐tree water relationships were studied using time domain reflectometry (TDR) in two small forested basins in Spain. The stem water content of two Mediterranean Quercus species (Quercus pyrenaica and Quercus rotundifolia) was measured using previously constructed species‐specific equations. To monitor soil moisture, a TDR station network was used in both cases. Sixteen Q. pyrenaica and six Q. rotundifolia individuals were selected to install two TDR probes in their trunks (at 20 and 120 cm above the ground) to monitor stem water content. Stem and soil water contents were measured fortnightly. The stem water content of both species showed a similar temporal trend for the period studied. A spring maximum (0·654 cm³ cm^?3 for Q. pyrenaica and 0·568 cm³ cm^?3 for Q. rotundifolia) was found to be associated with high transpiration and no soil moisture deficit, and a late‐summer minimum (0·520 cm³ cm^?3 for Q. pyrenaica and 0·426 cm³ cm^?3 for Q. rotundifolia) was associated with the end of the dry season. This drop in stem water content occurs when the available water in the soil decreases. This seasonal difference presumably reflects water withdrawn from stem storage to support the transpirational demands of the tree. Since plant water stress results in reduced stem water content and since this drop can be measured by TDR, it may be concluded that this technology offers a suitable tool for detecting plant water stress. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

First record of the pacific fanfishpteraclis aesticola (jordan and snyder, 1901) in the tropical eastern pacific     

José De La Cruz Agüero  Víctor Manuel Cota Gómez 《Ocean Science Journal》2008,43(3):161-164

One specimen ofPteraclis aesticola was collected off San José del Cabo, Baja California Sur, México (22°54′N, 109°45′W), in March 2007. Present record is the first reported occurrence of the species in the Tropical Eastern Pacific biogeographic region (Gulf of California to southern Ecuadorian waters). Its large fan-like anal and dorsal fins and its counts of fin rays and vertebrae can distinguish the Pacific fanfish from the other species in the genus. This fish may have not yet been recorded in the region because its presence has been overlooked in the past because of rarity and lack of commercial value.  相似文献   

The Global Structure of the Colliding Bubble Braneworld Universe     

José J. Blanco-Pillado  Martin Bucher 《Astrophysics and Space Science》2003,283(4):525-530

The one-brane Randall-Sundrum model offers an example of a model with an `infinite' extra dimension in which ordinary gravity is recovered at large distances and the usual (3+1)-dimensional cosmology at late cosmic times. This is possible because the `bulk' has the geometry of anti de Sitter space, the curvature length ℓ of which delineates the (3+1)-dimensional behavior at large distances from the (4+1)-dimensional behavior at short distances. This spacetime, however, possesses a past Cauchy horizon on which initial data must be specified in a natural and convincing way. A more complete story is required that singles out some set of initial conditions to resolve the `bulk' smoothness and horizon problems. One such complete story is offered by the colliding bubble braneworld universe, where bubbles filled with AdS ⁵ nucleate from dS ⁵ or M ⁵ through quantum tunnelling. A pair of such colliding bubbles forms a Randall-Sundrum-like universe in the future of the collision. Because of the symmetry of bubbles produced through quantum tunnelling, the resulting universe is spatially homogeneous and isotropic at leading order, and the perturbations at the next order are completely well defined and calculable. In this contribution we discuss the possible global structure of such a spacetime. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Chemical and geological control of spring water in Eastern Guaniguanico mountain range, Pinar del Rìo, Cuba     

Juan Reynerio Fagundo-Castillo  Joel José Carrillo-Rivera  Iñaki Antigüedad-Auzmendi  Patricia González-Hernández  Roberto Peláez-Díaz  Rebeca Hernández-Díaz  Dámaso Cáceres-Govea  José Ramón Hernández-Santana  Margaret Suárez-Muñoz  Clara Melián-Rodríguez  Mónica Rodríguez-Piña 《Environmental Geology》2008,55(2):247-267

Flows of different hierarchy, which travel through limestone, schist, sandstone and ultra-basic rocks, with ages from the Paleocene to the Jurassic, at Sierra del Rosario, Pinar del Río, Cuba, were characterized. The waters were sampled from 1984 until 2004 and the data were statistically processed by means of chemical equilibrium and physico-chemical models, under a flow system view of interpretation. Results demonstrate that the physico-chemical properties of the water are controlled by water–rock interaction resulting from residence time since rainwater infiltrate and the path it follows to the discharge zone and the type of aquifer material the different groundwater flows are in contact with. Geochemical indices allow the definition of the different types of flow (local, intermediate, regional) to be characterized, permitting a further definition of the different flow systems and rock type involved, as well as its use for water supply and medical use. The main geochemical processes which control the chemical composition acquisitions mode are: congruent dissolution of calcite, dolomite, and halite; incongruent dissolution of plagioclase and microcline minerals; pyrite oxidation, sulphate reduction, and silica dissolution at the surface or silica precipitation at deep saturation and circulation zones.  相似文献   

Predicting monthly precipitation along coastal Ecuador: ENSO and transfer function models     

de Guenni  Lelys B.  García  Mariangel  Muñoz  Ángel G.  Santos  José L.  Cedeño  Alexandra  Perugachi  Carlos  Castillo  José 《Theoretical and Applied Climatology》2017,129(3-4):1059-1073

Theoretical and Applied Climatology - It is well known that El Niño-Southern Oscillation (ENSO) modifies precipitation patterns in several parts of the world. One of the most impacted areas is...  相似文献   

Tectonic evolution of an intraplate basin: the Lower Tagus Cenozoic Basin,Portugal          下载免费PDF全文

João Carvalho  Carlos Pinto  Ruben Dias  Taha Rabeh  Luis Torres  José Borges  Ricardo Torres  Henrique Duarte 《Basin Research》2017,29(5):636-657

This article focuses on the reinterpretation of well, seismic reflection, magnetic, gravimetric, surface wave and geological surface data, together with the acquisition of seismic noise data to study the Lower Tagus Cenozoic Basin tectono‐sedimentary evolution. For the first time, the structure of the base of the basin in its distal and intermediate sectors is unravelled, which was previously only known in the areas covered by seismic reflection data (distal and small part of intermediate sectors). A complex geometry was found, with three subbasins delimited by NNE‐SSW faults and separated by WNW‐ESE to NW‐SE oriented horsts. In the area covered by seismic reflection data, four horizons were studied: top of the Upper Miocene, Lower to Middle Miocene top, the top of the Palaeogene and the base of Cenozoic. Seismic data show that the major filling of the basin occurred during Upper Miocene. The fault pattern affecting Neogene and Palaeogene units derived here points to that of a polyphasic basin. In the Palaeogene, the Vila Franca de Xira (VFX) and a NNE‐SSW trending previously unknown structure (ABC fault zone) probably acted as the major strike‐slip fault zones of the releasing bend of a pull‐apart basin, which produced a WNW‐ESE to NW‐SE fault system with transtensional kinematic. During the Neogene, as the stress regime rotated anticlockwise to the present NW‐SE to WNW‐ESE orientation, the VFX and Azambuja fault zones acted as the major transpressive fault zones and Mesozoic rocks overthrusted Miocene sediments. The reactivation of WNW‐ESE to NW‐SE fault systems with a dextral strike‐slip component generated a series of horsts and grabens and the partitioning of the basin into several subbasins. Therefore, we propose a polyphasic model for the area, with the formation of an early pull‐apart basin during the Palaeogene caused by an Iberia–Eurasia plates collision that later evolved into an incipient foreland basin along the Neogene due to a NW‐SE to WNE‐ESE oriented Iberia–Nubia convergence. This convergence is producing uplift in the area since the Quaternary except for the Tagus estuary subbasin around the VFX fault, where subsidence is observed. This may be due to the locking or the development of a larger component of strike‐slip movement of the NNE‐SSW to N‐S thrust fault system with the exception of the VFX fault, which is more favourably oriented to the maximum compressive stress.  相似文献