Cluster cross-sections for strong lensing: analytic and numerical lens models     

Massimo Meneghetti  Matthias Bartelmann  Lauro Moscardini † 《Monthly notices of the Royal Astronomical Society》2003,340(1):105-114

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Generating interface waves using a freely falling, instrumentedsource     

Stoll  R.D. Bautista  E.O. Akal  T. 《Oceanic Engineering, IEEE Journal of》1996,21(4):452-457

In recent years, interface waves such as the Scholte wave have become important tools in the study of the geoacoustic properties of near-bottom seafloor sediments. Traditionally, these waves have been generated by explosive or pneumatic sources deployed at or near the seafloor and monitored by ocean-bottom seismographs or geophone arrays. While these sources generate the requisite interface waves, they also produce higher frequency compressional waves in the water and sediment that tend to contaminate the surface wave and make inversion of the data difficult in the near field. In this paper, a new source consisting of a freely falling projectile instrumented with an accelerometer is described. When the projectile impacts the bottom, the exact time history of the vertical force applied to the sediment is known and therefore may be convolved with the transfer function of a sediment geoacoustic model to produce accurate synthetic seismograms. Moreover, the vertical force applied to the seafloor is very efficient in generating surface wave motion while producing very little compressional wave energy so that the near-field signals are much more easily analyzed. An example of the use of the new source is presented including inversion of the received signals to obtain shear-wave velocity and attenuation as a function of depth in the near bottom sediments at a shallow-water site  相似文献   

Feeding Habits of Ocinebrina edwardsi (Mollusca: Prosobranchia) a Common Mussel Drill of the Italian Coasts     

P. Tongiorgi    P. Nardi    L. Galleni    M. Nigro  U. Salghetti 《Marine Ecology》1981,2(2):169-180

Abstract. The shell-boring gastropod Ocinebrina edwardsi (PAYR.) lives associated with Mytilus galloprovincialis LMK on which it preys. Predation is preferentially directed towards small (< 15 mm long) mussels. The predation rate (number of mussels eaten per gastropod per day) for medium sized mussels (16–25 mm long) during a year ranges from 0.03 to 0.11. The predation rate is directly influenced by the sea-water temperature. Predation follows a seasonal cycle reaching a maximum in July and a minimum in January. O. edwardsi drills selectively the median anterior region of the mussel valve, close to the dorsal edge.  相似文献   

Climate proxies from Sr/Ca of coccolith calcite: calibrations from continuous culture of Emiliania huxleyi     

Heather M Stoll  Yair RosenthalPaul Falkowski 《Geochimica et cosmochimica acta》2002,66(6):927-936

Continuous culture of the coccolithophorid Emiliania huxleyi reveals that coccolith Sr/Ca ratios depend on temperature and growth rate. At a constant temperature of 18°C, coccolith Sr/Ca ratios increased nearly 15% as growth rate increased from 0.1 to 1.5 divisions per day and calcification rate increased from 1.5 to 50 pg calcite per cell per day. When temperature increased from 7 to 26°C, Sr/Ca ratios increased by more than 25% (i.e., 1%/1°C), although the range in growth and calcification rates was the same as for experiments at constant temperature. The temperature dependence of Sr/Ca ratios in coccoliths is consistent with that observed in planktonic foraminifera and abiogenic calcites, suggesting that it is controlled by thermodynamic processes. However, the positive correlation of coccolith Sr/Ca with temperature contrasts with field studies in the equatorial Pacific, where Sr/Ca ratios are highest at the locus of maximum upwelling and productivity despite depressed temperatures. This paradox may reflect different calcification rate effects between E. huxleyi and the other species dominating assemblages in the equatorial Pacific sediments, which may be resolved by new techniques for separation of monospecific coccolith samples from sediments. Models of crystal growth indicate that kinetic effects on Sr partitioning in calcite due to surface enrichment could explain the Sr/Ca variations observed in constant temperature experiments but not the larger amplitude calcification rate effects observed in equatorial Pacific sediments. Despite the dual influence of temperature and growth rate on coccolith Sr/Ca, coccolith Sr/Ca correlates with “b,” the slope of the dependence of carbon isotope fractionation in biomarkers (ε_p) on CO₂(aq) at a range of growth rates and temperatures. Consequently, using coccolith Sr/Ca in combination with alkenone ε_p may improve paleo-CO₂ determinations.  相似文献   

Cacti–shrub interactions in the coastal desert of northern Sinaloa, Mexico     

Alvaro Reyes-Olivas  Edmundo García-Moya  Lauro Lpez&#x;Mata 《Journal of Arid Environments》2002,52(4):431

Spatial patterns and replacement in ten cacti were studied on an island of the coastal desert of Sinaloa, México. Four platyopuntias had 74–92% of their individuals beneath shrub canopies, whereas three globose cacti, one columnar cactus and two cylindropuntias had similar or higher percentages of individuals in open spaces. This study advances the idea that open-space colonization is enhanced by less harsh physical and biotic conditions in coastal deserts, and by certain morphological and physiological adaptations of cacti. The absence of nurse-shrub replacement is understood as a result of induced co-existence by physical damage from cyclones in the coastal zone.  相似文献   

Evolution of sand waves in the Messina Strait, Italy   总被引：1，自引：0，他引：1  

V. C. Santoro  E. Amore  L. Cavallaro  M. De Lauro 《Ocean Dynamics》2004,54(3-4):392-398

In the present paper the morphodynamics of sand waves in the Messina Strait, Italy, is analysed by comparing data gathered during two different surveys carried out in 1991 and 2001, respectively. In particular, a morphometric analysis on the most recent data and a qualitative analysis of the differences between bottom bedform patterns, are carried out. At locations characterised by greater depths, only minor changes to the planimetric configuration of the field, i.e. crest orientation (which is seen to be orthogonal to the direction of net gross sand transport) and wave length are observed, while differences in wave length and crest direction are more evident in more shallow areas. On the other hand, wave height has significantly increased in the whole field. A possible explanation of such a change, based on the previsions of a theory which relates sand-wave growth and migration to the main components of the tidal ellipse, is provided.Responsible Editor: Jens Kappenberg  相似文献   

Convolutive independent component analysis for processing massive datasets: a case study at Campi Flegrei (Italy)     

Capuano  P.  De Lauro  E.  De Martino  S.  Falanga  M.  Petrosino  S. 《Natural Hazards》2016,86(2):417-429

A novel procedure is proposed to analyse continuous seismic signal on hourly scales to have a prompt discrimination among the different sources. Specifically, this approach is applied to a massive dataset recorded at Campi Flegrei caldera during the year 2006 when a swarm of volcano-tectonic earthquakes occurred. The convolutive independent component analysis is adopted to obtain a clear separation among meteo-marine microseism, anthropogenic noise, hydrothermal tremor in the absence of volcano-tectonic activity, whereas in non-stationary conditions a contribution connected to the corner frequency of the earthquakes emerges. A coarse-grained variable to be monitored continuously is introduced, i.e. the frequency associated with the maximum amplitude of the power spectral density of the deconvolutive independent components. That parameter is sensitive to the variation in the frequency bands of interest (e.g. that corresponding to the corner frequencies of volcano-tectonic events) and can be used as marker of the insurgence of seismic activity.

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The last deglaciation in the Picos de Europa National Park (Cantabrian Mountains,northern Spain)     

Ana Moreno  Blas L. Valero‐Garcés  Montserrat Jiménez‐Sánchez  María José Domínguez‐Cuesta  M. Pilar Mata  Ana Navas  Penélope González‐Sampériz  Heather Stoll  Pedro Farias  Mario Morellón  J. Pablo Corella  Mayte Rico 《第四纪科学杂志》2010,25(7):1076-1091

A sedimentological and geochemical study of the Lago Enol sequence (Cantabrian Mountains, northern Spain), together with detailed geomorphological mapping, provides a first record of glacier evolution and climate change over the last 40 ka in the Picos de Europa National Park. The Enol glacier retreated from its maximum extent prior to 40 ka BP as demonstrated by the onset of proglacial lacustrine sedimentation in two glaciated depressions: the Comella hollow to the north (before 40 ka BP) and the Lago Enol (before 38 ka BP). These results support previous evidence that the maximum extent of southern European glaciers occurred earlier than in northern Europe. Alternation of homogeneous and laminated proglacial sediments during the glacier retreat illustrate a dynamic glacial evolution during the Marine Isotope Stage (MIS) 3 (40–26 ka BP). A slight warming is detected at 26 ka ago with the change from proglacial sediments (in a lake located in contact to the glacier) to glaciolacustrine sedimentation (in a non‐contact or distal lake). Finally, the onset of organic‐rich sediments took place at 18 ka ago. This last transition occurred in two phases, similarly to the North Atlantic Last Termination, suggesting a link between North Atlantic Deep Water formation oscillations and palaeohydrological variability in the Cantabrian Mountains. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Electrochemical modelling of self-potential anomalies     

J. Stoll  J. Bigalke  E. W. Grabner 《Surveys in Geophysics》1995,16(1):107-120

An electrochemical model is proposed, which considers the redox conditions and the electrode kinetics at the mineral surface. Advanced modelling of self-potential (SP) anomalies over ore deposits takes into account the course of the redox potential distribution with depth and the oxidation-reduction processes acting at the mineral-electrolyte interface. The application of this model to a SP anomaly in the vicinity of the German Continental Deep Drilling Program (KTB) can explain the surface and borehole data and gives an estimation of the prevailing thermodynamical conditions in the ground.Exclusively, this paper deals with SP anomalies, which are associated with high conductive graphitic layers. It can be concluded that SP-anomalies give an important hint to electronical conducting structures in the earth's crust.  相似文献   

Quantifying the relative impact of hydrological and hydraulic modelling parameterizations on uncertainty of inundation maps     

A. Annis  F. Nardi  E. Volpi  A. Fiori 《水文科学杂志》2020,65(4):507-523

ABSTRACT

Flood risk management strongly relies on inundation models for river basin zoning in flood-prone and risk-free areas. Floodplain zoning is significantly affected by the diverse and concurrent uncertainties that characterize the modelling chain used for producing inundation maps. In order to quantify the relative impact of the uncertainties linked to a lumped hydrological (rainfall–runoff) model and a FLO-2D hydraulic model, a Monte Carlo procedure is proposed in this work. The hydrological uncertainty is associated with the design rainfall estimation method, while the hydraulic model uncertainty is associated with roughness parameterization. This uncertainty analysis is tested on the case study of the Marta coastal catchment in Italy, by comparing the different frequency, extent and depth of inundation simulations associated with varying rainfall forcing and/or hydraulic model roughness realizations. The results suggest a significant predominance of the hydrological uncertainty with respect to the hydraulic one on the overall uncertainty associated with the simulated inundation maps.  相似文献