Occurrence and distribution of polycyclic aromatic hydrocarbons in surface sediments of San Diego Bay marinas     

Carlos Neira  Jennifer Cossaboon  Guillermo Mendoza  Eunha Hoh  Lisa A. Levin 《Marine pollution bulletin》2017,114(1):466-479

Polycyclic aromatic hydrocarbons (PAHs) have garnered much attention due to their bioaccumulation, carcinogenic properties, and persistence in the environment. Investigation of the spatial distribution, composition, and sources of PAHs in sediments of three recreational marinas in San Diego Bay, California revealed significant differences among marinas, with concentrations in one site exceeding 16,000 ng g^? 1. ‘Hotspots’ of PAH concentration suggest an association with stormwater outfalls draining into the basins. High-molecular weight PAHs (4–6 rings) were dominant (> 86%); the average percentage of potentially carcinogenic PAHs was high in all sites (61.4–70%) but ecotoxicological risks varied among marinas. Highly toxic benzo(a)pyrene (BaP) was the main contributor (> 90%) to the total toxic equivalent quantity (TEQ) in marinas. PAHs in San Diego Bay marina sediments appear to be derived largely from pyrogenic sources, potentially from combustion products that reach the basins by aerial deposition and stormwater drainage from nearby streets and parking lots.  相似文献   

Variations in the dynamic response of structures founded on piles induced by obliquely incident SV waves     

Cristina Medina  Guillermo M. Álamo  Juan J. Aznárez  Luis A. Padrón  Orlando Maeso 《地震工程与结构动力学》2019,48(7):772-791

Although the seismic actions generally consist of a combination of waves, which propagates with an angle of incidence not necessarily vertical, the common practice when analyzing the dynamic behavior of pile groups is based on the assumption of vertically incident wave fields. The aim of this paper is to analyze how the angle of incidence of SV waves affects the dynamic response of pile foundations and piled structures. A three-dimensional boundary element-finite element coupling formulation is used to compute impedances and kinematic interaction factors corresponding to several configurations of vertical pile groups embedded in an isotropic homogeneous linear viscoelastic half-space. These results, which are provided in ready-to-use dimensionless graphs, are used to determine the effective dynamic properties of an equivalent single-degree-of-freedom oscillator that reproduces, within the range where the peak response occurs, the response of slender and nonslender superstructures through a procedure based on a substructuring model. Results are expressed in terms of effective flexible-base period and damping as well as maximum shear force at the base of the structure. The relevance and main trends observed in the influence of the wavefront angle of incidence on the dynamic behavior of the superstructure are inferred from the presented results. It is found that effective damping is significantly affected by the variations of the wave angle of incidence. Furthermore, it comes out that the vertical incidence is not always the worst-case scenario.  相似文献   

Pressure and density gradients in H II Regions     

José Franco  Stan E. Kurtz  José A. GarcÍa-Barreto  Guillermo GarcÍa-Segura  Eduardo de la Fuente  Peter Hofner  Alejandro Esquivel 《Astrophysics and Space Science》2001,277(1):71-74

Here we discuss the effects of large ambient pressures and decreasing density gradients on the observed properties of dusty UC hii regions. Dust absorption can effectively reduce the size of the photo ionized region, and density gradients can modify the spectral index of the emission. The effects of the density gradients seem to be present in both galactic and extragalactic HII regions.  相似文献   

Characterization of Intensity Variations Along Fe XIV Coronal Loops – A Case Study     

Costa  Andrea  Stenborg  Guillermo 《Solar physics》2004,222(2):229-245

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Dynamical Behavior of Asteroids Near Resonance: the 4:1 gap and the 7:2 Group     

Miquel Grau  Guillermo González-Casado 《Celestial Mechanics and Dynamical Astronomy》1998,72(3):169-186

A comparative study of the evolution of the Sun–Jupiter–Asteroid system near the 4:1 and 7:2 resonances is performed by means of two techniques that proceed differently from the Hamiltonian corresponding to the planar restricted elliptic three-body problem. One technique is based on the classical Schubart averaging while the other is based on a mapping method in which the perturbing part of the Hamiltonian is expanded and the resulting terms are ordered according to a weight function that depends on the powers of eccentricities and the coefficients of the terms. For the mapping method the effect of Saturn on the asteroidal evolution is introduced and the degree of chaos is estimated by means of the Lyapunov time. Both methods are shown to lead to similar results and can be considered a suitable tool for describing the evolution of asteroids in the Kirkwood gap and the group corresponding to the 4:1 and 7:2 Jovian resonances, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Radial Velocity Measurements with FXCOR     

José J. Rodes  Guillermo Bernabeu  Juan Fabregat 《Astrophysics and Space Science》1998,263(1-4):259-262

We present measured radial velocities of two peculiar early B type stars, to check their membership to the open cluster NGC 663. The radial velocities have been obtained with the cross correlation technique, using as a template stars from the list of Liu et al. (1989). We have obtained accuracies around 3-4 km/s in our radial velocity measurements. From our results we conclude that both stars are probably non members of the cluster. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

On the fate of processed matter in dwarf galaxies     

Sergey A. Silich  & Guillermo Tenorio-Tagle 《Monthly notices of the Royal Astronomical Society》1998,299(1):249-266

Two-dimensional calculations of the evolution of remnants generated by the strong mechanical energy deposited by stellar clusters in dwarf galaxies ( M  ∼ 10⁹–10¹⁰ M⊙) are presented. The evolution is followed for times longer than both the blowout time and the presumed span of energy injection generated by a coeval massive stellar cluster. The remnants are shown to end up wrapping around the central region of the host galaxy, while growing to kiloparsec-scale dimensions. Properties of the remnants such as luminosity, size, swept-up mass and expansion speed are given as functions of time for all calculated cases.   The final fate of the swept-up galactic gas and of the matter processed by the central starburst is shown to be highly dependent on the properties of the low-density galactic halo. Superbubbles powered by star clusters, with properties similar to those inferred from the observations, slow down in the presence of an extended halo to expansion speeds smaller than the host galaxy escape velocity. Values of the critical luminosity required for the superbubbles to reach the edge of the galaxies with a speed comparable to the escape speed are derived analytically and numerically. The critical luminosities are larger than those in the detected sources, and thus the superbubbles in amorphous dwarf galaxies must have already undergone blowout and are presently evolving into an extended low-density halo. This will inhibit the loss of the swept-up and processed matter from the galaxy.  相似文献   

Conodont geothermometry of the lower Paleozoic from the Precordillera (Cuyania terrane), northwestern Argentina     

Gustavo G. Voldman  Guillermo L. Albanesi  Víctor A. Ramos 《Journal of South American Earth Sciences》2010,29(2):278-288

The thermal history of the Precordillera terrane of northwestern Argentina has been constrained by the conodont colour alteration index (CAI) in combination with previously published paleothermal data (e.g., illite crystallinity and clay mineral assemblages). The pattern of paleotemperatures displays an increase in paleotemperatures to the west and south of the basin. This configuration shows a gradual and continuous transition from diagenesis to low-grade metamorphism, which is apparently not controlled by any of the morpho-structural subdivisions of the Precordillera (i.e., Western, Central, or Eastern). According to our results, the lower Paleozoic sedimentary burial played a secondary role in the heating of the Precordillera. Instead, the predominant component was loading by thrust sheets, which reflects the effects of the Devonian collision of Chilenia, particularly, in the Western Precordillera. Conversely, our paleothermometric data from the easternmost exposures of the Precordillera do not evidence anomalies referable to any of the accretionary events that contributed to the early Paleozoic building of the southern proto-Andean margin of Gondwana. Instead, the expected thermally altered conodonts from the Cuyania accretion are represented by metamorphosed conodont elements transported to the deeper settings of the west. The CAI data also suggest that overburden depth varied from ca. 3.6 km in the shelf region of the Eastern Precordillera to ca. 12 km in the slope to rise deposits of the Western Precordillera, thus providing constrains for the palinspastic restoration across the orogen. On the other hand, the smooth increase of peak paleotemperatures to the south of the Precordillera is associated with the exposure of deeper crustal levels at that sector, probably related to larger shortening due to stronger collisional effects, or alternatively, a weaker mechanical response of its elastic lithosphere.  相似文献   

A proposal for boundary delimitation for integrated coastal zone management initiatives     

Pau Balaguer  Rafael Sard  Maurici Ruiz  Amy Diedrich  Guillermo Vizoso  Joaquin Tintor 《Ocean & Coastal Management》2008,51(12):806-814

ICZM relies heavily on the definition of major multidisciplinary characteristics/elements of the coastal area of interest. Usually, only terrestrial boundaries are considered, which tend to respond to a specific sectoral problem and can be determined by administrative limits. In this study, we propose a method for establishing a decision-making tool to inform boundary delimitation for ICZM initiatives that is proactive and widely applicable as opposed to reactive and problem specific. This method integrates environmental, economic and societal characteristics of the marine and terrestrial boundaries of the coastal zone, starting at the boundary of the jurisdictional zone of influence (shoreline units), increasing in detail through the definition of their influential areas from jurisdictional, environmental or socio-economic perspectives (functional areas) and, within them, specifying the finest scale at which relevant indicator data may be obtained (analysis units).  相似文献   

Upper‐crustal extension during oblique collision: the Temsamane extensional detachment (eastern Rif,Morocco)     

Guillermo Booth‐Rea  Antonio Jabaloy‐Sánchez  Ali Azdimousa  Lahcen Asebriy  Mercedes Vázquez Vílchez  José Miguel Martínez‐Martínez 《地学学报》2012,24(6):505-512

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