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151.
152.
Fabrizio Cocco Stefano Andreucci Daniele Sechi Giulia Cossu Antonio Funedda 《地学学报》2019,31(5):485-493
The Corsica‐Sardinia block is a lithospheric fragment whose recent role in the geodynamics of the central‐Western Mediterranean basin is still enigmatic. The most recent regional structure in Sardinia is the Plio‐Pleistocene Campidano Basin, which is considered in a ‘post‐rift’ stage since the Middle Pleistocene. New structural and stratigraphic geological surveys along with luminescence ages provide evidence to support an ongoing tectonic activity since the Marine Isotopic Stage 7 (MIS7; ca. 220 ka) on the Sinis peninsula, the structural high that bounds the north‐western side of the Campidano Basin. In particular, this paper reveals for the first time the presence of N–S striking normal faults system offsetting late Pleistocene aeolianites (130 ± 12 ka; 82 ± 9 ka). 相似文献
153.
Wang Liang Zhang Xue Lei Qinghua Panayides Stelios Tinti Stefano 《Acta Geotechnica》2022,17(12):5639-5653
Acta Geotechnica - Soil flow is involved in many earth surface processes such as debris flows and landslides. It is a very challenging task to model this large deformational phenomenon because of... 相似文献
154.
155.
Pettine M Casentini B Fazi S Giovanardi F Pagnotta R 《Marine pollution bulletin》2007,54(9):1413-1426
The trophic status classification of coastal waters at the European scale requires the availability of harmonised indicators and procedures. The composite trophic status index (TRIX) provides useful metrics for the assessment of the trophic status of coastal waters. It was originally developed for Italian coastal waters and then applied in many European seas (Adriatic, Tyrrhenian, Baltic, Black and Northern seas). The TRIX index does not fulfil the classification procedure suggested by the WFD for two reasons: (a) it is based on an absolute trophic scale without any normalization to type-specific reference conditions; (b) it makes an ex ante aggregation of biological (Chl-a) and physico-chemical (oxygen, nutrients) quality elements, instead of an ex post integration of separate evaluations of biological and subsequent chemical quality elements. A revisitation of the TRIX index in the light of the European Water Framework Directive (WFD, 2000/60/EC) and new TRIX derived tools are presented in this paper. A number of Italian coastal sites were grouped into different types based on a thorough analysis of their hydro-morphological conditions, and type-specific reference sites were selected. Unscaled TRIX values (UNTRIX) for reference and impacted sites have been calculated and two alternative UNTRIX-based classification procedures are discussed. The proposed procedures, to be validated on a broader scale, provide users with simple tools that give an integrated view of nutrient enrichment and its effects on algal biomass (Chl-a) and on oxygen levels. This trophic evaluation along with phytoplankton indicator species and algal blooms contribute to the comprehensive assessment of phytoplankton, one of the biological quality elements in coastal waters. 相似文献
156.
Covelli S Piani R Acquavita A Predonzani S Faganeli J 《Marine pollution bulletin》2007,55(10-12):436-450
The role of suspended particulate matter (SPM) as an important carrier of mercury (Hg) dispersed into the Gulf of Trieste and in the adjacent Grado lagoon (Northern Adriatic Sea) was studied during a high Isonzo River inflow and the resulting river plume formation. Despite the fact that extreme flood events are rare during the year, they account for most of the PHg influx (37-112 ngL(-1)) into the Gulf of Trieste. When the river plume is diverted to the SW under the influence of an E-NE wind, the tidal flux acts as a "transport belt" carrying the PHg, mostly inorganic, into the Grado lagoon. A preliminary estimation indicates that the amount of PHg entrapped in the lagoon basin following a tidal semi-cycle accounts for 1.4 kg/12h, which corresponds to about 49% of the total Hg carried by the tidal flow. These findings should be considered in future remediation strategies in the lagoon environment. 相似文献
157.
Virender K. Sharma Frank J. Millero Concetta De Stefano Pasquale Crea 《Marine Chemistry》2007,106(3-4):463-470
The dissociation constants (pK1 and pK2) for methionine have been measured in artificial seawater as a function of salinity (S = 5 to 35) and temperature (5 to 45 °C). The seawater pK2 values were lower than the values in NaCl at the same ionic strength while the pK1 values in seawater were lower only at S = 35. In an attempt to understand these differences, we have made measurements of the constants in Na–Mg–Cl solutions at 25 °C. The measured values have been used to determine the formation of Mg2+ complexes and Pitzer interaction parameters for Mg2+ with methionine. The seawater model with the interaction parameters accounts for the differences between the value of pK1 and pK2 between NaCl and seawater. This study demonstrates that it is important to consider all of the ionic interactions in natural waters when examining the dissociation of organic acids. 相似文献
158.
Observations of Comet 9P/Tempel 1 around the Deep Impact event by the OSIRIS cameras onboard Rosetta
Horst Uwe Keller Sonia Fornasier Stubbe F. Hviid Jörg Knollenberg Miriam Rengel Gabriele Cremonese Detlef Koschny Ekkehard Kührt Holger Sierks Cesare Barbieri Hans Rickman Michael F. A'Hearn Maria-Antonella Barucci Vania da Deppo Björn J.R. Davidsson Stefano Debei Fritz Gliem José J. Lopez Moreno Giampiero Naletto Angel Sanz Andrés 《Icarus》2007,187(1):87-103
The OSIRIS cameras on the Rosetta spacecraft observed Comet 9P/Tempel 1 from 5 days before to 10 days after it was hit by the Deep Impact projectile. The Narrow Angle Camera (NAC) monitored the cometary dust in 5 different filters. The Wide Angle Camera (WAC) observed through filters sensitive to emissions from OH, CN, Na, and OI together with the associated continuum. Before and after the impact the comet showed regular variations in intensity. The period of the brightness changes is consistent with the rotation period of Tempel 1. The overall brightness of Tempel 1 decreased by about 10% during the OSIRIS observations. The analysis of the impact ejecta shows that no new permanent coma structures were created by the impact. Most of the material moved with . Much of it left the comet in the form of icy grains which sublimated and fragmented within the first hour after the impact. The light curve of the comet after the impact and the amount of material leaving the comet ( of water ice and a presumably larger amount of dust) suggest that the impact ejecta were quickly accelerated by collisions with gas molecules. Therefore, the motion of the bulk of the ejecta cannot be described by ballistic trajectories, and the validity of determinations of the density and tensile strength of the nucleus of Tempel 1 with models using ballistic ejection of particles is uncertain. 相似文献
159.
Thermal inertia determines the temperature distribution over the surface of an asteroid and therefore governs the magnitude the Yarkovsky effect. The latter causes gradual drifting of the orbits of km-sized asteroids and plays an important role in the delivery of near-Earth asteroids (NEAs) from the main belt and in the dynamical spreading of asteroid families. At present, very little is known about the thermal inertia of asteroids in the km size range. Here we show that the average thermal inertia of a sample of NEAs in the km-size range is . Furthermore, we identify a trend of increasing thermal inertia with decreasing asteroid diameter, D. This indicates that the dependence of the drift rate of the orbital semimajor axis on the size of asteroids due to the Yarkovsky effect is a more complex function than the generally adopted D−1 dependence, and that the size distribution of objects injected by Yarkovsky-driven orbital mobility into the NEA source regions is less skewed to smaller sizes than generally assumed. We discuss how this fact may help to explain the small difference in the slope of the size distribution of km-sized NEAs and main-belt asteroids. 相似文献
160.
Chiara Elmi Maria Franca Brigatti Luca Pasquali Monica Montecchi Angela Laurora Daniele Malferrari Stefano Nannarone 《Physics and Chemistry of Minerals》2010,37(8):561-569
Microprobe analysis, single crystal X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, and X-ray absorption spectroscopy were applied on Fe-rich osumilite from the volcanic massif of Mt. Arci, Sardinia, Italy. Osumilite belongs to the space group P6/mcc with unit cell parameters a = 10.1550(6), c = 14.306(1) Å and chemical formula (K0.729)C (Na0.029)B (Si10.498 Al1.502)T1 (Al2.706 Fe 0.294 2+ )T2 (Mg0.735 Mn0.091 Fe 1.184 2+ )AO30. Structure refinement converged at R = 0.0201. Unit cell parameter a is related to octahedral edge length as well as to Fe2+ content, unlike the c parameter which does not seem to be affected by chemical composition. The determination of the amount of each element on the mineral surface, obtained through X-ray photoelectron spectroscopy high-resolution spectra in the region of the Si2p, Al2p, Mg1s and Fe2p core levels, suggests that Fe presents Fe2+ oxidation state and octahedral coordination. Two peaks at 103.1 and 100.6 eV can be related to Si4+ and Si1+ components, respectively, both in tetrahedral coordination. The binding energy of Al2p, at 74.5 eV, indicates that Al is mostly present in the distorted T2 site, whereas the Mg peak at 1,305.2 eV suggests that this cation is located at the octahedral site. X-ray absorption at the Fe L2,3-edges confirms that iron is present in the mineral structure, prevalently in the divalent state and at the A octahedral site. 相似文献