ISO-LWS Observations of the NGC7129 Star Forming Region     

Elisabetta Tommasi  Dario Lorenzetti  Teresa Giannini  Brunella Nisini  Francesco Palla 《Astrophysics and Space Science》1998,261(1-4):187-190

We present far-infrared observations of the surroundings of the Herbig Be star LkHα234 in NGC7129, obtained with the Long Wavelength Spectrometer on board of the Infrared Space Observatory. [CII]158μm, [OI]63μm and [OI]146μm lines are detected everywhere in the mapped region and their intensity ratios are consistent with the model predictions of a photodissociation region. The spatial distribution of the emission features indicates the presence of a peak which does not coincide with the position of LkHα234, but is more likely associated with another nearby Herbig star, namely BD+65°1637; the far-ultraviolet field intensity and the density derived from our observations are fully consistent with this hypothesis. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Vertical migrations of the mangrove snail Cerithidea decollata (L.) (Potamididae) through a synodic month     

Marco Vannini  Cecilia Coffa  Elisabetta Lori  Sara Fratini 《Estuarine, Coastal and Shelf Science》2008,78(4):644-648

The vertical migration on mangrove trunks of the gastropod Cerithidea decollata was followed for 5 weeks, in a Kenyan mangrove. Most of the times, snails forage on the mud surface, during low tide, and climb back on trees well before the incoming tide. As soon as the sea retreats, the downward migration takes place and the snails spread again on the ground. The migratory behaviour of snails can vary widely, depending on the relative tide intensity, and different strategies can be exhibited. Individuals can spend several days on trees without migrating to the ground, around Spring Tides, or else, they might remain on the ground without bothering to migrate upwards, during Neap Tides, when the study area is not reached by the water. These irregular animal behaviours, relating to the complicated tide succession, can hardly be explained by the sole presence of an internal clock, and direct cues seem necessary to switch between different strategies, tuning the snails migratory behaviour to the actual local sea conditions.  相似文献   

The Canyon Diablo impact event: Projectile motion through the atmosphere     

Natalia ARTEMIEVA  Elisabetta PIERAZZO 《Meteoritics & planetary science》2009,44(1):25-42

Abstract— Meteor Crater is one of the first impact structures systematically studied on Earth. Its location in arid northern Arizona has been ideal for the preservation of the structure and the surviving meteoric material. The recovery of a large amount of meteoritic material in and around the crater has allowed a rough reconstruction of the impact event: an iron object 50 m in diameter impacted the Earth's surface after breaking up in the atmosphere. The details of the disruption, however, are still debated. The final crater morphology (deep, bowl‐shaped crater) rules out the formation of the crater by an open or dispersed swarm of fragments, in which the ratio of swarm radius to initial projectile radius C_d is larger than 3 (the final crater results from the sum of the craters formed by individual fragments). On the other hand, the lack of significant impact melt in the crater has been used to suggest that the impactor was slowed down to 12 km/s by the atmosphere, implying significant fragmentation and fragments' separation up to 4 initial radii. This paper focuses on the problem of entry and motion through the atmosphere for a possible Canyon Diablo impactor as a first but necessary step for constraining the initial conditions of the impact event which created Meteor Crater. After evaluating typical models used to investigate meteoroid disruption, such as the pancake and separated fragment models, we have carried out a series of hydrodynamic simulations using the 3D code SOVA to model the impactor flight through the atmosphere, both as a continuum object and a disrupted swarm. Our results indicate that the most probable pre‐atmospheric mass of the Meteor Crater projectile was in the range of 4.10⁸to 1.2.10⁹kg (equivalent to a sphere 46–66 m in diameter). During the entry process the projectile lost probably 30% to 70% of its mass, mainly because of mechanical ablation and gross fragmentation. Even in the case of a tight swarm of particles (C_d < 3), small fragments can separate from the crater‐forming swarm and land on the plains (tens of km away from the crater) as individual meteorites. Starting from an impactor pre‐atmospheric velocity of ?18 km/s, which represents an average value for Earth‐crossing asteroids, we find that after disruption, the most probable impact velocity at the Earth's surface for a tight swarm is around 15 km/s or higher. A highly dispersed swarm would result in a much stronger deceleration of the fragments but would produce a final crater much shallower than observed at Meteor Crater.  相似文献   

Large wood transport modelling by a coupled Eulerian–Lagrangian approach     

Persi  Elisabetta  Petaccia  Gabriella  Sibilla  Stefano 《Natural Hazards》2017,85(1):59-86

The fractal characteristics of the ultra-low-frequency (ULF) magnetic field variations recorded prior to the Tohoku earthquake (EQ) with M _W = 9 which happened on 11 March 2011 are studied in this article with the use of detrended fluctuation analysis and Higuchi fractal dimension algorithm. In the specific study, we use for our calculations only nighttime (LT = 3 a.m. ± 2 h) data because of their lowest contamination by industrial noise. A key aspect of our analysis is the investigation about any possible correlation of the ULF magnetic field variations or their calculated fractal characteristics with geomagnetic indices. Different preprocessing approaches are examined aiming at the minimization of any possible influences from global phenomena in the fractal analysis results, while in the same time retaining the scale-invariant character of ULF magnetic field variations after preprocessing. The obtained fractal analysis results imply locally driven change in the fractal characteristics of the ULF data prior to the Tohoku EQ, which is compatible with the change that has been reported prior to other large EQs.  相似文献   

Impact of event landslides on road networks: a statistical analysis of two Italian case studies     

Marco Donnini  Elisabetta Napolitano  Paola Salvati  Francesca Ardizzone  Francesco Bucci  Federica Fiorucci  Michele Santangelo  Mauro Cardinali  Fausto Guzzetti 《Landslides》2017,14(4):1521-1535

Despite abundant information on landslides, and on landslide hazard and risk, in Italy, little is known on the direct impact of event landslides on road networks and on the related economic costs. We investigated the physical and economic damage caused by two rainfall-induced landslide events in Central and Southern Italy, to obtain road restoration cost statistics. Using a GIS-based method, we exploited road maps and landslide event inventory maps to compute different metrics that quantify the impact of the landslide events on the natural landscape and on the road networks, by road type. The maps were used with cost data obtained from multiple sources, including local authorities, and specific legislation, to evaluate statistically the unit cost per metre of damaged road and the unit cost per square metre of damaging landslide, separately for main and secondary roads. The obtained unit costs showed large variations which we attribute to the different road types in the two study areas and to the different abundance of landslides. Our work confirms the long-standing conundrum of obtaining accurate landslide damage data and outlines the need for reliable, standardized methods to evaluate landslide damage and associated restoration costs that regional and local administrations can use rapidly in the aftermath of a landslide event. We conclude recommending that common standardized procedures to collect landslide cost data following each landslide event are established, in Italy and elsewhere. This will allow for more accurate and reliable evaluations of the economic costs of landslide events.  相似文献   

Contribution of tsunami data analysis to constrain the seismic source: the case of the 1693 eastern Sicily earthquake     

Stefano Tinti  Alberto Armigliato  Elisabetta Bortolucci 《Journal of Seismology》2001,5(1):41-61

The January 11, 1693 eastern Sicilyearthquake is comparable only with the December 28,1908 Messina Straits event in the Italian seismichistory as regards magnitude (M _L 7), level ofdestruction and number of victims. The shock generateda strong tsunami, which hit the entire eastern coastof Sicily and particularly the town of Augusta. Theproblem of which fault was responsible for theearthquake is still open. Several hypotheses have beenformulated in the literature on the basis of differentkinds of geological, macroseismic and tectonic data,but a general agreement has not been reached yet. Animportant contribution to the discussion may come fromthe analysis of the tsunami data. In two previouspapers (Piatanesi et al., 1996; Piatanesi and Tinti,1998), the hydro-dynamical study of the tsunami basedon finite-element (FE) numerical simulations wascarried out taking into consideration mostlytheoretical faults, i.e. faults selected for theirsignificance in tsunami generation irrespective of thecorresponding geological evidence. This paper has tobe considered the continuation of the mentioned works.We have studied new sources proposed in theliterature, consistent with macroseismic data and/orgeological observations, and simulated thecorresponding tsunamis. We also built a new FE gridintroducing significant improvements in the coastlinerepresentation, and developed and applied a newalgorithm in order to account for the effect of thesea-bottom topography on the tsunami initialcondition. Some of the examined faults are located inthe Scordia-Lentini (SL) graben region and interceptthe coastline, others are placed in correspondencewith the Hyblaean-Malta (HM) escarpment and runparallel or sub-parallel to the coast. The conclusionof our work is that none of these faults respectsfully the available observations on tsunami, and thatthe faults exhibiting the best fit are those placed inthe SL region. It is worth stressing that our resultsare important for the assessment of seismic andtsunami hazard/risk in eastern Sicily, keeping also inmind that the 1693 earthquake has been selected as thereference event for an earthquake-scenario study inCatania and in south-eastern Sicily, called `CataniaProject', funded by CNR/GNDT (Consiglio Nazionaledelle Ricerche/Gruppo Nazionale Difesa dai Terremoti).  相似文献   

Postcumulus processes in oceanic-type olivine-rich cumulates: the role of trapped melt crystallization versus melt/rock interaction     

G. Borghini  E. Rampone 《Contributions to Mineralogy and Petrology》2007,154(6):619-633

Combined microstructural and geochemical investigations on MORB-type primitive olivine-rich cumulates intruded in the Erro–Tobbio (ET) mantle peridotites (Voltri Massif, Ligurian Alps, Italy) revealed that significant chemical changes in minerals were caused by postcumulus crystallization. This is indicated by the occurrence of accessory interstitial minerals (Ti-pargasite, orthopyroxene and Fe–Ti oxides) and by systematic chemical zoning in intercumulus clinopyroxene, resulting in marked trace element (e.g. REE, Ti and Zr) enrichment at constant high Mg-numbers (0.88–0.91) and LREE depletion. Geochemical modelling shows that low trapped melt amounts (<5%) are sufficient to produce the observed trace element enrichments. Chemical zoning in large (mm-size) clinopyroxenes was dominantly caused by in situ fractional crystallization of trapped interstitial liquid rather then porous flow migration of externally derived evolved melts. Zr enrichment relative to REEs in vermicular clinopyroxene and pargasitic amphibole point to small-scale migration and interaction between residual evolved low melt fractions and the olivine cumulus matrix at final stage of crystallization. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Copper complexing capacity of phytoplanktonic cell exudates     

Alfredo Seritti  David Pellegrini  Elisabetta Morelli  Corrado Barghigiani  Romano Ferrara 《Marine Chemistry》1986,18(2-4)

Copper complexing capacity of cell exudates of Dunaliella salina in natural seawater culture medium was investigated in order to evaluate the influence of this organism on speciation of trace metals in seawater.Seawater samples were collected at 200 m and 2 miles off the coast and immediately filtered. Copper complexing capacity (CC_Cu) and stability constants (K′) of related cupric complexes were then measured. They were, respectively, 27.1 × 10⁻⁸ mol l⁻¹ and 0.56 × 10⁷ l mol⁻¹ for the samples collected at 200 m and 12.8 × 10⁻⁸ mol l⁻¹ and 6.10 × 10⁷ l mol⁻¹ for those collected 2 miles off the coast. A stock culture (20 ml, 10⁶ cells ml⁻¹) in log-phase was inoculated in 2 l of each sample of filtered natural seawater. The trend of cell influence was estimated on filtered culture medium by measuring CC_Cu and K′ after 1 h, 3 and 7 days. From the results it appears that CC_Cu increased with respect to time and this was related to the growth rate, indicating a certain relationship with cell metabolic activity.It can be concluded that a comparison between the culture referring to 200 m and 2 miles, respectively, shows that the former presents a CC_Cu two times higher than the latter while the K′ is ten times higher at 2 miles than that at 200 m.  相似文献   

The Role of a Macroalgal Covering Event on the Microphytobenthos Community in Intertidal Sediment (Marano Lagoon, Northern Adriatic Sea)   总被引：1，自引：0，他引：1  

Elisabetta Sdrigotti  Chiara Welker 《Marine Ecology》2002,23(S1):370-383

Abstract. This study examines the variation in microphytobenthos structure and functioning in an intertidal lagoon during a macroalgal covering event. Multivariate techniques, applied on the recorded data, highlighted a clear seasonal pattern except for the July sample. The sudden macroalgae ( Cladophora sp.) development, which occurred in that month, enabled us to identify the massive covering as a disturbance factor on the benthic ecosystem. This biotic anomaly affected benthic microalgal production and community respiration, shifting the ecosystem from a highly photoautotrophic to an heterotrophic condition as shown by the BTS Index. This trophic index is therefore a useful tool for identifying episodic stress events mainly in intertidal habitats.  相似文献   

Visible–near infrared spectral indices for mapping mineralogy and chemistry with OSIRIS‐REx     

Hannah H. Kaplan  Victoria E. Hamilton  Ellen S. Howell  F. Scott Anderson  M. Antonella Barrucci  John Brucato  Thomas H. Burbine  Beth E. Clark  Ed A. Cloutis  Harold C. Connolly  Elisabetta Dotto  Joshua P. Emery  Sonia Fornasier  Cateline Lantz  Lucy F. Lim  Frederic Merlin  Alice Praet  Dennis C. Reuter  Scott A. Sandford  Amy A. Simon  Driss Takir  Dante S. Lauretta 《Meteoritics & planetary science》2020,55(4):744-765

The primary objective of the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS‐REx) mission is to return to Earth a pristine sample of carbonaceous material from the primitive asteroid (101955) Bennu. To support compositional mapping of Bennu as part of sample site selection and characterization, we tested 95 spectral indices on visible to near infrared laboratory reflectance data from minerals and carbonaceous meteorites. Our aim was to determine which indices reliably identify spectral features of interest. Most spectral indices had high positive detection rates when applied to spectra of pure, single‐component materials. The meteorite spectra have fewer and weaker absorption features and, as a result, fewer detections with the spectral indices. Indices targeting absorptions at 0.7 and 2.7–3 μm, which are attributable to hydrated minerals, were most successful for the meteorites. Based on these results, we identified a set of 17 indices that are most likely to be useful at Bennu. These indices detect olivines, pyroxenes, carbonates, water/OH‐bearing minerals, serpentines, ferric minerals, and organics. Particle size and albedo are known to affect band depth but had a negligible impact on interpretive success with spectral indices. Preliminary analysis of the disk‐integrated Bennu spectrum with these indices is consistent with expectations given the observed absorption near 3 μm. Our study prioritizes spectral indices to be used for OSIRIS‐REx spectral analysis and mapping and informs the reliability of all index‐derived data products, including a science value map for sample site selection.  相似文献