Multivariate discriminant analysis distinguishes metal- from non metal-related biomarker responses in the clam Chamaelea gallina     

Rodríguez-Ortega MJ  Rodríguez-Ariza A  Gómez-Ariza JL  Muñoz-Serrano A  López-Barea J 《Marine pollution bulletin》2009,58(1):64-327

Molecular biomarkers are among the most sensitive and earliest responses to pollutants. However, lack of detailed knowledge on variability of responses and their possible seasonal variation limit their use. In addition, the seasonality of biological processes modulates the response of organisms to pollutant stressors. Using multivariate statistics, we have studied the influence of environmental and biological factors on the response of a battery of molecular biomarkers in the clam Chamaelea gallina collected along the South-Spanish littoral. Multivariate discriminant analysis clearly distinguished biomarker response between clean and polluted areas, using heavy metals as indicator of pollution. Such differences disappeared when the dataset was normalised for metal content, thus indicating that pollution was the main significant cause of the changes observed between clean and polluted sites. In conclusion, this work shows that, when applying a complete biomarker panel, multivariate statistical tools can be used to discern pollutant- from non pollutant-related responses.  相似文献   

Underground Temperature Measurements as a Tool for Volcanic Activity Monitoring in the Island of Tenerife, Canary Islands     

A. Eff-Darwich  J. Coello  R. Viñas  V. Soler  M. C. Martin-Luis  I. Farrujia  M. L. Quesada  J. de la Nuez 《Pure and Applied Geophysics》2008,165(1):135-145

The spatial distribution of groundwater temperatures in the volcanic island of Tenerife, Canary Islands, has been inferred through measurements of water temperatures collected in the vast network of wells and subhorizontal tunnels, locally called “galleries,” which constitutes the main water supply of the island. The spatial coverage of the network of galleries allows us to reach from depth almost any geological feature of the island. The complex spatial distribution of temperatures in the interior of Tenerife is the result of the complex geological evolution of the island. Groundwater temperatures are greatly affected by groundwater flow and are considerably warmer in those galleries located in areas where water circulation is reduced due to the low permeability of materials and/or to the low infiltration rate of cooling meteoric water. In this sense, groundwater temperature should be characterized in quiescent conditions (background level), in order to facilitate monitoring changes in heat flow, such as those induced by ascending gases expected with an increase in volcanic activity.  相似文献   

Chemical characteristics of the crater lakes of Popocatetetl, El Chichon, and Nevado de Toluca volcanoes, Mexico     

M. A. Armienta  S. De la Cruz-Reyna  J. L. Macías 《Journal of Volcanology and Geothermal Research》2000,97(1-4)

Three crater lakes from Mexican volcanoes were sampled and analyzed at various dates to determine their chemical characteristics. Strong differences were observed in the chemistry among the three lakes: Nevado de Toluca, considered as dormant, El Chichón at a post-eruptive stage, and Popocatépetl at a pre-eruptive stage. Not surprisingly, no influence of volcanic activity was found at the Nevado de Toluca volcano, while the other volcanoes showed a correlation between the changing level of activity and the evolution of chemical trends. Low pHs (<3.0) were measured in the water from the active volcanoes, while a pH of 5.6 was measured at the Nevado de Toluca Sun lake. Changes with time were observed at Popocatépetl and El Chichón. Concentrations of volcanic-gas derived species like Cl⁻, SO₄²⁻ and F⁻ decreased irregularly at El Chichón from 1983 until 1997. Major cations concentrations also diminished at El Chichón. A 100% increase in the SO₄²⁻ content was measured at Popocatépetl between 1985 and 1994. An increase in the Mg/Cl ratio between 1992 (Mg/Cl=0.085) and 1994 (Mg/Cl=0.177) was observed at Popocatépetl, before the disappearance of the crater lake in 1994. It is concluded that chemical analysis of crater lakes may provide a useful additional tool for active-volcano monitoring.  相似文献   

Artificial neural networks for parameter estimation in geophysics   总被引：12，自引：0，他引：12  

Carlos Calderón-Macías  Mrinal K. Sen  & Paul L. Stoffa 《Geophysical Prospecting》2000,48(1):21-47

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Quiet-time periods observed by EPHIN/SOHO during the minimum of the 22nd solar cycle     

Gómez-Herrero  Raúl  RodrÍguez-FrÍas  M. Dolores  del Peral  Luis  Sequeiros  Juan  Müller-Mellin  Reinhold  Kunow  Horst  Sierks  Holger 《Solar physics》2000,194(2):405-413

An analysis of the hydrogen and helium isotopic composition from EPHIN data, during the quiet-time period from January 1 to June 1, 1996, is presented. An isotopic discrimination and background rejection have been applied and relationships between the abundances of ²H/¹H, ³He/⁴He, and ⁴He/¹H have been calculated. The energy spectra in the 4–50 MeV nucl^–1 range have been obtained and the contribution of the different spectral components have been analysed in this energy range. We conclude that the main contribution to the ⁴He spectrum is of anomalous origin, while the proton and ³He spectra have contributions mainly from particles of solar origin at low energies and from the galactic cosmic radiation modulated by the heliosphere at high energies. The deuterium spectrum is mainly of galactic origin.  相似文献   

Tectonics of an extinct ridge-transform intersection,Drake Passage (Antarctica)     

Maldonado  Andrés  Carlos Balanyá  Juan  Barnolas  Antonio  Galindo-Zaldívar  Jesús  Hernández  Javier  Jabaloy  Antonio  Livermore  Roy  Miguel Martínez-Martínez  José  Rodríguez-Fernández  José  Sanz de Galdeano  Carlos  Somoza  Luis  Suriñach  Emma  Viseras  César 《Marine Geophysical Researches》2000,21(1-2):43-68

New swath bathymetric, multichannel seismic and magnetic data reveal the complexity of the intersection between the extinct West Scotia Ridge (WSR) and the Shackleton Fracture Zone (SFZ), a first-order NW-SE trending high-relief ridge cutting across the Drake Passage. The SFZ is composed of shallow, ridge segments and depressions, largely parallel to the fracture zone with an `en echelon' pattern in plan view. These features are bounded by tectonic lineaments, interpreted as faults. The axial valley of the spreading center intersects the fracture zone in a complex area of deformation, where N120° E lineaments and E–W faults anastomose on both sides of the intersection. The fracture zone developed within an extensional regime, which facilitated the formation of oceanic transverse ridges parallel to the fracture zone and depressions attributed to pull-apart basins, bounded by normal and strike-slip faults.On the multichannel seismic (MCS) profiles, the igneous crust is well stratified, with numerous discontinuous high-amplitude reflectors and many irregular diffractions at the top, and a thicker layer below. The latter has sparse and weak reflectors, although it locally contains strong, dipping reflections. A bright, slightly undulating reflector observed below the spreading center axial valley at about 0.75 s (twt) depth in the igneous crust is interpreted as an indication of the relict axial magma chamber. Deep, high-amplitude subhorizontal and slightly dipping reflections are observed between 1.8 and 3.2 s (twt) below sea floor, but are preferentially located at about 2.8–3.0 s (twt) depth. Where these reflections are more continuous they may represent the Mohorovicic seismic discontinuity. More locally, short (2–3 km long), very high-amplitude reflections observed at 3.6 and 4.3 s (twt) depth below sea floor are attributed to an interlayered upper mantle transition zone. The MCS profiles also show a pattern of regularly spaced, steep-inclined reflectors, which cut across layers 2 and 3 of the oceanic crust. These reflectors are attributed to deformation under a transpressional regime that developed along the SFZ, shortly after spreading ceased at the WSR. Magnetic anomalies 5 to 5 E may be confidently identified on the flanks of the WSR. Our spreading model assumes slow rates (ca. 10–20 mm/yr), with slight asymmetries favoring the southeastern flank between 5C and 5, and the northwestern flank between 5 and extinction. The spreading rate asymmetry means that accretion was slower during formation of the steeper, shallower, southeastern flank than of the northwestern flank.  相似文献   

Environmental monitoring using acetylcholinesterase inhibition in vitro. A case study in two Mexican lagoons.     

G Rodríguez-Fuentes  G Gold-Bouchot 《Marine environmental research》2000,50(1-5):357-360

Cholinesterase inhibition is considered a specific biomarker of exposure and effect for organophosphorous pesticides. Its use for monitoring has been hindered, particularly in tropical countries where organophosphates are widely used for malaria and dengue control, because of the frequent lack of suitable controls. An in vitro technique is proposed as a biochemical method for monitoring pollutant mixtures in sediment toxicity tests. Brain homogenate from the fish Oreochromis niloticus is used as the enzyme source. Optimum incubation time, extraction solvent and effect of crude oil on acetylcholinesterase (AChE) are reported. The method described was used in sediments from two Mexican lagoons, located in an oil extraction area where pesticides are used in agriculture and vector control campaigns. AChE inhibitions from 3 to 21% were found in these lagoons, even in the presence of high concentrations of petroleum.  相似文献   

The Evolution of HII Regions     

J. Franco  S.E. Kurtz  G. GarcÍa-Segura  P. Hofner 《Astrophysics and Space Science》2000,272(1-3):169-179

Here we review some recent results on the observed properties of UCH IIregions, and on the new class of Super-ultra-compact H II regions, and describe the theoretical scheme for H II region expansion, from star-forming cloud cores to the more diffuse external medium. High-pressure cores can stop the expansion on relatively short time scales, of the order of 3× 10⁴ yr, and the resulting pressure equilibrium UCH II regions have small sizes and large ion densities. If the ionization front enters into the decreasing density gradient of the cloud core, the expansion is accelerated and the H II region“pops” out of the core and becomes a “blister”-like region. The properties of the outflows depend on the cloud density structure, and a variety of different shocks can be formed. Density inhomogeneities inside photoionized regions are smoothed out on short time scales, but new clumps are continuously created at the cool shell generated by the shock front. Instabilities in both the ionization and shock fronts cause the fragmentation of the shell, maintaining the presence of clumps during the whole evolution. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

A laser beacon for monitoring the mesospheric sodium layer at La Palma     

L. Michaille  A. D. Cañas  J. C. Dainty  J. Maxwell  T. Gregory  J. C. Quartel  F. C. Reavell  R. W. Wilson  N. J. Wooder 《Monthly notices of the Royal Astronomical Society》2000,318(1):139-144

We report the results of the first laser beacon experiment at the astronomical site of La Palma (Canary Islands). A continuous wave low‐power laser (a few hundred mW) system has been set up. The laser, tuned on the sodium D₂ line at 589 nm, is launched close to the zenith angle. The emission of the mesospheric sodium layer is observed from a telescope located 160 m away from the laser. The layer is therefore resolved in altitude and the different features of its dynamics are investigated.  相似文献   

Volcanic stratigraphy of the Quaternary La Garrotxa Volcanic Field (north‐east Iberian Peninsula)          下载免费PDF全文

XAVIER BOLÓS  LLORENÇ PLANAGUMÀ  JOAN MARTÍ 《第四纪科学杂志》2014,29(6):547-560

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