Experimental identification of Ca isotopic fractionations in higher plants     

Florian Cobert  Pascale Bourgeade  Pierre-Marie Badot  Peter Stille 《Geochimica et cosmochimica acta》2011,75(19):5467-5482

Hydroponic experiments have been performed in order to identify the co-occurring geochemical and biological processes affecting the Ca isotopic compositions within plants. To test the influence of the Ca concentration and pH of the nutritive solution on the Ca isotopic composition of the different plant organs, four experimental conditions were chosen combining two different Ca concentrations (5 and 60 ppm) and two pHs (4 and 6). The study was performed on rapid growing bean plants in order to have a complete growth cycle. Several organs (root, stem, leaf, reproductive) were sampled at two different growth stages (10 days and 6 weeks of culture) and prepared for Ca isotopic measurements.The results allow to identify three Ca isotopic fractionation levels. The first one takes place when Ca enters the lateral roots, during Ca adsorption on cation-exchange binding sites in the apoplasm. The second one takes place when Ca is bound to the polygalacturonic acids (pectins) of the middle lamella of the xylem cell wall. Finally, the last fractionation occurs in the reproductive organs, also caused by cation-exchange processes with pectins. However, the cell wall structures of these organs and/or number of available exchange sites seem to be different to those of the xylem wall. These three physico-chemical fractionation mechanisms allow to enrich the organs in the light ⁴⁰Ca isotope. The amplitude of the Ca isotopic fractionation within plant organs is highly dependent on the composition of the nutritive solution: low pH (4) and Ca concentrations (5 ppm) have no effect on the biomass increase of the plants but induce smaller fractionation amplitudes compared to those obtained from other experimental conditions. Thus, Ca isotopic signatures of bean plants are controlled by the external nutritive medium. This study highlights the potential of Ca isotopes to be applied in plant physiology (to identify Ca uptake, circulation and storage mechanisms within plants) and in biogeochemistry (to identify Ca recycling, Ca content and pH evolutions in soil solutions through time).  相似文献   

ENSIP: the El Niño simulation intercomparison project     

M. Latif  K. Sperber  J. Arblaster  P. Braconnot  D. Chen  A. Colman  U. Cubasch  C. Cooper  P. Delecluse  D. Dewitt  L. Fairhead  G. Flato  T. Hogan  M. Ji  M. Kimoto  A. Kitoh  T. Knutson  H. Le Treut  T. Li  S. Manabe  O. Marti  C. Mechoso  G. Meehl  S. Power  E. Roeckner  J. Sirven  L. Terray  A. Vintzileos  R. Voß  B. Wang  W. Washington  I. Yoshikawa  J. Yu  S. Zebiak 《Climate Dynamics》2001,18(3-4):255-276

An ensemble of twenty four coupled ocean-atmosphere models has been compared with respect to their performance in the tropical Pacific. The coupled models span a large portion of the parameter space and differ in many respects. The intercomparison includes TOGA (Tropical Ocean Global Atmosphere)-type models consisting of high-resolution tropical ocean models and coarse-resolution global atmosphere models, coarse-resolution global coupled models, and a few global coupled models with high resolution in the equatorial region in their ocean components. The performance of the annual mean state, the seasonal cycle and the interannual variability are investigated. The primary quantity analysed is sea surface temperature (SST). Additionally, the evolution of interannual heat content variations in the tropical Pacific and the relationship between the interannual SST variations in the equatorial Pacific to fluctuations in the strength of the Indian summer monsoon are investigated. The results can be summarised as follows: almost all models (even those employing flux corrections) still have problems in simulating the SST climatology, although some improvements are found relative to earlier intercomparison studies. Only a few of the coupled models simulate the El Niño/Southern Oscillation (ENSO) in terms of gross equatorial SST anomalies realistically. In particular, many models overestimate the variability in the western equatorial Pacific and underestimate the SST variability in the east. The evolution of interannual heat content variations is similar to that observed in almost all models. Finally, the majority of the models show a strong connection between ENSO and the strength of the Indian summer monsoon.  相似文献   

Gravitational deformation and inherited structural control on slope morphology in the subduction zone of north‐central Chile (ca. 29–33°S)          下载免费PDF全文

Juan Becerra  César Arriagada  Eduardo Contreras‐Reyes  Sebastián Bascuñan  Gregory P. De Pascale  Christian Reichert  Juan Díaz‐Naveas  Natalia Cornejo 《Basin Research》2017,29(6):798-815

Subduction zones provide direct insight into plate boundary deformation and by studying these areas we better understand tectonic processes and variability over time. We studied the structure of the offshore subduction zone system of the Pampean flat‐slab segment (ca. 29–33°S) of the Chilean margin using seismic and bathymetric constraints. Here, we related and analysed the structural styles of the offshore and onshore western fore‐arc. Overlying the acoustic top of the continental basement, two syn‐extensional seismic sequences were recognised and correlated with onshore geological units and the Valparaíso Forearc Basin seismic sequences: (SII) Pliocene‐Pleistocene and (SI) Miocene‐Pliocene (Late Cretaceous (?) to Miocene‐Pliocene) syn‐extensional sequences. These sequences are separated by an unconformity (i.e. Valparaíso Unconformity). Seismic reflection data reveal that the eastward dipping extensional system (EI) recognised at the upper slope can be extended to the middle slope and controlled the accumulation of the older seismic package (SI). The westward dipping extensional system (EII) is essentially restricted to the middle slope. Here, EII cuts the eastward dipping extensional system (EI), preferentially parallel to the inclination of the older sequences (SI), and controlled a series of middle slope basins which are filled by the Pliocene‐Pleistocene seismic sequence (SII). At the upper slope and in the western Coastal Cordillera, the SII sequence is controlled by eastward dipping faults (EII) which are the local reactivation of older extensional faults (EI). The tectonic boundary between the middle (eastern outermost forearc block) and upper continental slope (western coastal block) is a prominent system of trenchward dipping normal fault scarps (ca. 1 km offset) that resemble a major trenchward dipping extensional fault system. This prominent structural feature can be readily detected along the Chilean erosive margin as well as the two extensional sets (EI and EII). Evidence of slumping, thrusting, reactivated faults and mass transport deposits, were recognised in the slope domain and locally restricted to some eastern dipping faults. These features could be related to gravitational effects or slope deformation due to coseismic deformation. The regional inclination of the pre‐Pliocene sequences favoured the gravitational collapse of the outermost forearc block. We propose that the structural configuration of the study area is dominantly controlled by tectonic erosion as well as the uplift of the Coastal Cordillera, which is partially controlled by pre‐Pliocene architecture.  相似文献   

Reply to comment on Duplex at the lateral tip of a thrust fault: the “La Cagalière” example (NE Pyrenees,France) by B. Laumonier et al     

Dominique Frizon de Lamotte  Christine Souque  Pascale Leturmy  Philippe Robion 《Geodinamica Acta》2013,26(2):183-184

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Assessment and mapping of the intrinsic vulnerability to pollution: an example from Keritis River Basin (Northwestern crete, Greece)   总被引：1，自引：1，他引：0  

S. Parisi  S. Pascale  F. Sdao  P. Soupios 《Environmental Earth Sciences》2013,70(6):2659-2670

Due to the geological and hydrogeological characteristics, the carbonate aquifers are frequently vulnerable to natural and/or anthropogenic polluting sources. The aim of the present study is to evaluate the intrinsic vulnerability to pollution of the Keritis River Basin (northwestern Crete, Greece). The huge amount of the flowing groundwater represents a strategic water resource to be allocated to drinking water purpose and to agricultural activities, too. The studied groundwater are characterized by quality degradation processes represented by the anthropogenic and natural pollution such as olive oil farming, agriculture activities, industrial waste and salt water intrusion. For a better management and protection of the water resources, the assessment and mapping of groundwater vulnerability to pollution are very important. From this investigation, the Keritis Basin showed an intrinsic vulnerability degree from extremely high to very low. This study allows to define the strategies which will permit a proper safeguard criteria, against the pollution sources of the Keritis Basin groundwater resources.  相似文献   

Star formation histories of local group dwarf galaxies     

Chisato Ikuta  Nobuo Arimoto  Pascale Jablonka 《Astrophysics and Space Science》2003,284(2):589-594

We present the study of the star formation histories (SFHs) of a sample of Local Group dwarf galaxies (LGDGs), via the analysis and modelling, with the means of an evolutionary stellar population synthesis, of their colour-magnitude (CM) diagrams. It appears that important parameters to describe the SFHs are star formation rate (SFR) and duration of star formation. We find a possible correlation between the mass and the SFRs. The correlation might be the origin of the observed luminosity-metallicity relation in the LGDGs. A well-defined correlation between the durations of star formation and the distance from M31 or the Galaxy indicates that the current early-type dwarf galaxies should have been transformed from late-type by strong tidal force of the massive galaxies. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Chemical and dynamical evolution of spiral galaxies     

Sébastien Poirier  Pascale Jablonka  Jean-Michel Alimi 《Astrophysics and Space Science》2003,284(2):849-852

We investigate the consequences of the hypothesis of the secular evolution (growth of the bulge from disc material via a bar and temporal evolution of the Hubble sequence) on the chemical evolution of a galaxy. We present the first dynamical and chemical results of our 3D tree-SPH simulations. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

A laboratory model of splash‐form tektites     

Linda T. ELKINS‐TANTON  Pascale AUSSILLOUS  Jos BICO  David QUR  John W. M. BUSH 《Meteoritics & planetary science》2003,38(9):1331-1340

Abstract— Splash‐form tektites are generally acknowledged to have the form of bodies of revolution. However, no detailed fluid dynamical investigation of their form and stability has yet been undertaken. Here, we review the dynamics and stability of spinning, translating fluid drops with a view to making inferences concerning the dynamic history of tektites. We conclude that, unless the differential speed between the molten tektite and ambient is substantially less than the terminal velocity, molten tektites can exist as equilibrium bodies of revolution only up to sizes of 3 mm. Larger tektites are necessarily non‐equilibrium forms and so indicate the importance of cooling and solidification during flight. An examination of the shapes of rotating, translating drops indicates that rotating silicate drops in air will assume the shapes of bodies of rotation if their rotational speed is 1% or more of their translational speed. This requirement of only a very small rotational component explains why most splash‐form tektites correspond to bodies of revolution. A laboratory model that consists of rolling or tumbling molten metallic drops reproduces all of the known forms of splashform tektites, including spheres, oblate ellipsoids, dumbbells, teardrops, and tori. The laboratory also highlights important differences between rolling drops and tumbling drops in flight. For example, toroidal drops are much more stable in the former than in the latter situation.  相似文献   

A search for interstellar pyrimidine   总被引：1，自引：0，他引：1  

Yi-Jehng Kuan  Chi-Hung Yan  Steven B. Charnley  Zbigniew Kisiel  Pascale Ehrenfreund  Hui-Chun Huang 《Monthly notices of the Royal Astronomical Society》2003,345(2):650-656

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Influences of Natural and Anthropogenic Factors and Tidal Restoration on Terrestrial Arthropod Assemblages in West Coast North American Estuarine Wetlands     

Aaron T. David  Pascale A. L. Goertler  Stuart H. Munsch  Brittany R. Jones  Charles A. Simenstad  Jason D. Toft  Jeffery R. Cordell  Emily R. Howe  Ayesha Gray  Michael P. Hannam  William Matsubu  Erin E. Morgan 《Estuaries and Coasts》2016,39(5):1491-1504

Compared to benthic and water-column invertebrate assemblages, considerably less is known about terrestrial arthropods inhabiting estuarine wetlands despite their importance to tidal wetland biodiversity and productivity. We also need to know more about how human modification of estuaries, including efforts to restore estuarine wetlands, affects these assemblages. To address this knowledge gap, we assembled data from multiple studies on terrestrial arthropod assemblages from 87 intertidal wetland sites in 13 estuaries along the west coast of North America. Arthropods were sampled between 1998 and 2013 with fallout traps deployed in wetlands for 1 to 3 days at a time. We describe patterns in the abundance and taxonomic composition of terrestrial arthropods and evaluate the relative ability of natural and anthropogenic factors to explain variation in abundance and composition. Arthropod abundance was highly variable. Vegetation assemblage, precipitation, and temperature best explained variation in arthropod abundance, while river discharge, latitude, and developed and agricultural land cover surrounding sampling sites were less important. Arthropod abundance rapidly achieved levels of reference wetlands after the restoration of tidal influence to leveed wetlands, regardless of surrounding land cover. However, arthropod assemblage composition was affected by the amount of developed land cover as well as restoration age. These results suggest that restoration of tidal influence to leveed wetlands can rapidly restore some components of estuarine wetland ecosystems but that recovery of other components will take longer and may depend on the extent of anthropogenic modification in the surrounding landscape.  相似文献