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排序方式: 共有172条查询结果,搜索用时 15 毫秒
81.
Walter Finsinger Daniele Colombaroli Jacques‐Louis De Beaulieu Verushka Valsecchi Boris Vannière Elisa Vescovi Emmanuel Chapron André F. Lotter Michel Magny Willy Tinner 《第四纪科学杂志》2010,25(8):1239-1247
Despite the high potential of pollen records for climate reconstruction, pollen–climate relationships may be biased due to past and present human activities on the landscape. We use (i) transfer functions based on modern pollen–climate relationships to infer seasonal temperature and summer precipitation for the period 11 500–4500 cal. a BP and (ii) lake‐level change records based on different sedimentary proxies in multiple cores that are mainly indicative for summer hydrology at Lago dell'Accesa (central Italy). Quantitative reconstructions indicate lowest summer precipitation during two phases (8500–7700 cal. a BP and after 6000 cal. a BP) and a gradual winter temperature increase from 11 500 to ca. 8000 cal. a BP. Lowest summer precipitation was reconstructed during these phases characterised by vegetation shifts from open forests dominated by summergreen oaks (Quercus) to forests dominated by evergreen oaks (Quercus ilex), which are at present most abundant where summer drought is stronger. Similarly, the lake‐level record indicates two long‐lasting low summer precipitation phases (8800–7700 and 6400–4400 cal. a BP) that were interrupted by short‐term high summer precipitation events. Based on the broad agreement between the pollen‐inferred summer precipitation and the low‐frequency lake‐level changes, we suggest that the duration of the high summer precipitation events may have been too short to maintain drought‐sensitive trees, which may have been affected by high mortality rates when summer dry conditions returned. Although past and modern pollen–climate relationships may very likely have been affected by human activities since the Neolithic (i.e. when exploitation of the landscape started), we reject the hypothesis of a significant anthropogenic bias in the pollen‐based climate reconstruction. In addition, we suggest that pollen‐based and lake‐level reconstructions may have different inherent abilities of capturing high‐ and low‐frequency precipitation signals. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
82.
Ana I. Gómez de Castro Javier Lopez-Santiago Paola Sestito Victor Rodrigo Gudiel Fatima López Martínez Elisa de Castro Manuel Cornide Javier Yañez Gestoso 《Astrophysics and Space Science》2011,335(1):97-103
The Gould Belt is the local superassociation of star formation. The age of the Belt is some few 107 yr, henceforth, its population is dominated by luminous young OB associations and low mass pre-main sequence stars. Attempts
to unveil the low mass population have been run making use of the ROSAT all-sky survey. The all sky ultraviolet survey run
by the GALaxy Evolution eXplorer (GALEX) maps several regions in the Belt. In this contribution, we present the preliminary
analysis of the UV stellar population towards the Taurus region, one of the nearest and best studied regions of star formation. 相似文献
83.
Elisa Maria Alessi Gerard Gómez Josep J. Masdemont 《Celestial Mechanics and Dynamical Astronomy》2010,107(1-2):187-207
It is known that most of the craters on the surface of the Moon were created by the collision of minor bodies of the Solar System. Main Belt Asteroids, which can approach the terrestrial planets as a consequence of different types of resonance, are actually the main responsible for this phenomenon. Our aim is to investigate the impact distributions on the lunar surface that low-energy dynamics can provide. As a first approximation, we exploit the hyberbolic invariant manifolds associated with the central invariant manifold around the equilibrium point L 2 of the Earth–Moon system within the framework of the Circular Restricted Three-Body Problem. Taking transit trajectories at several energy levels, we look for orbits intersecting the surface of the Moon and we attempt to define a relationship between longitude and latitude of arrival and lunar craters density. Then, we add the gravitational effect of the Sun by considering the Bicircular Restricted Four-Body Problem. In the former case, as main outcome, we observe a more relevant bombardment at the apex of the lunar surface, and a percentage of impact which is almost constant and whose value depends on the assumed Earth–Moon distance dEM. In the latter, it seems that the Earth–Moon and Earth–Moon–Sun relative distances and the initial phase of the Sun θ 0 play a crucial role on the impact distribution. The leading side focusing becomes more and more evident as dEM decreases and there seems to exist values of θ 0 more favorable to produce impacts with the Moon. Moreover, the presence of the Sun makes some trajectories to collide with the Earth. The corresponding quantity floats between 1 and 5 percent. As further exploration, we assume an uniform density of impact on the lunar surface, looking for the regions in the Earth–Moon neighbourhood these colliding trajectories have to come from. It turns out that low-energy ejecta originated from high-energy impacts are also responsible of the phenomenon we are considering. 相似文献
84.
Domenico Miriello Marco Malagodi Silvestro Antonio Ruffolo Mauro Francesco La Russa Gino Mirocle Crisci Antonino Pezzino Rita Galluccio Donatella Barca Elisa Marasco 《Environmental Earth Sciences》2010,60(4):829-836
The monumental tomb of Jefferson Page, an officer in the American Navy, was built in 1899 and is located in the Non-Catholic
Cemetery of Rome (Italy). This study presents complementary diagnostic studies characterizing the stone of the tomb and the
weathering and decay phenomena it has undergone. The monument is made of a single type of whitish marble, variously veined
and often covered with black patinas. Petrographic, isotopic and LA-ICP-MS analyses attribute the marble to the Carrara district.
SEM/EDS and microbiological analyses indicate that the black patinas are due to cyanobacterial autotrophic and fungin heterotrophic
colonization. Fourier-transform infrared spectroscopy revealed the presence of organic material on some portions of the tomb,
due to undocumented restoration carried out with a mixture of marble powder and a polyester resin. 相似文献
85.
Elisa Rojo-Nieto Carmen Garrido-Pérez Giorgio Anfuso-Melfi Francisco Lopez-Aguayo Diego Sales-Marquez Jose Antonio Perales-Vargas-Machuca 《Estuaries and Coasts》2011,34(6):1129-1139
This paper reports a study of the occurrence and levels of polycyclic aromatic hydrocarbons (PAHs) in a bay characterised
by a chronic persistent impact. A total of 55 sediment samples were taken at different depths up to 111 m in two sampling
campaigns. Chemical analyses were carried out by gas chromatography-mass spectroscopy. The results indicate that: (1) significant
spatial variations exist, (2) levels of PAHs are related more strongly to the spatial distribution of sediments than to mineralogy/granulometry,
(3) the sediments are slightly-to-moderately contaminated by PAHs, and (4) these PAHs derive from pyrolytic and petrogenic
sources. Through use of an innovative data classification system (proposed according to depth and spatial location of sampling
points), and using factorial and cluster techniques, five zones have been differentiated depending on the contamination level
and source. 相似文献
86.
Elisa Cenci Matteo PizzolonNicole Chimento Carlotta Mazzoldi 《Estuarine, Coastal and Shelf Science》2011
Deployed for diverse purposes, artificial substrata can, theoretically, act as fish attractors or as fish producers. We tested these hypotheses by comparing fish assemblages on two artificial hard substrata, the Ca’ Roman and Sottomarina jetties, before (1994 and 2003) and after (2005 and 2006) the deployment of a new breakwater in the area. Our results support the fish production hypothesis. A remarkable increase in richness and abundance of sedentary species was observed on the extant substrata with the presence of the new barrier. More mobile species showed less definite trends. The net result has been a total increase in abundance and richness in the area. While fish assemblage showed important temporal variation in composition before deployment (Ca’ Roman, comparison between 1994 and 2003), clear trends of increasing abundance were concurrent with the presence of the new barrier. This increase in abundance, particularly of sedentary species, may be attributed to enhanced connectivity and/or an improvement in larval retention due to the changes in water circulation connected with the new breakwater, or to an increase in juveniles and/or adults promoted by changes in environmental conditions. Indeed, changes in benthic cover were recorded, with an increase of uncovered rock and the appearance of previously unrecorded algae after breakwater deployment. 相似文献
87.
Elisa Villa Heather Stoll Pedro Farias Luna Adrados R. Lawrence Edwards Hai Cheng 《Quaternary Research》2013,79(1):1-5
Cemented calcareous breccias appear in the Picos de Europa (Cantabrian Mountains, Spain) resting on glacially abraded surfaces and covered by moraines. U/Th dating of the calcite coating the clasts was successful in two samples, the oldest one indicating that the breccias accumulated during or prior to Marine Isotope Stage (MIS) 11, and the youngest indicating later cementation during MIS 8. The former introduces a limit for the age of the glaciation preceding the breccias, which cannot correspond to an event younger than MIS 12. This is the oldest absolute age so far obtained for intercalated glacial/interglacial deposits of the Iberian Peninsula. 相似文献
88.
The 2012 Northern Italy Earthquakes: modelling human behaviour 总被引:1,自引:1,他引:0
Gabriele Prati Elisa Saccinto Luca Pietrantoni Carles Pérez-Testor 《Natural Hazards》2013,69(1):99-113
The aim of this study was to investigate human behaviour during the 2012 Northern Italy Earthquakes. Furthermore, the current study used Kuligowski and Mileti’s (Fire Saf J 44:487–496, 2009) extended model and the Social Attachment Model as a framework to explain the behavioural responses. The study included 1839 participants who were affected by the earthquake occurred in the Emilia-Romagna region (Italy) on 20 May 2012. The most frequent behavioural responses during the earthquake were moving to another room of the house, escaping from home, and waiting in bed. According to Kuligowski and Mileti’s (Fire Saf J 44:487–496, 2009) extended model, perceived risk was associated with evacuation, and emergency preparedness was related to more efficient and effective responses during the earthquake. In line with the Social Attachment Model, affiliation behaviours were more frequent than flight behaviours, while, contrary to predictions, the social context did not influence emotional responses, evacuation behaviour, and search for protection. 相似文献
89.
Autoregressive modeling is used to estimate the spectrum of aliased data. A region of spectral support is determined by identifying the location of peaks in the estimated spatial spectrum of the data. This information is used to pose a Fourier reconstruction problem that inverts for a few dominant wavenumbers that are required to model the data. Synthetic and real data examples are used to illustrate the method. In particular, we show that the proposed method can accurately reconstruct aliased data and data with gaps. 相似文献
90.
The Italian strong motion network 总被引:2,自引:2,他引:0
Antonella Gorini Mario Nicoletti Paolo Marsan Riccardo Bianconi Rita De Nardis Luisa Filippi Sandro Marcucci Franco Palma Elisa Zambonelli 《Bulletin of Earthquake Engineering》2010,8(5):1075-1090
The Italian Strong Motion Network is a permanent monitoring system run by the Italian national emergency management department
(Dipartimento della Protezione Civile, DPC). The network is known as RAN (Rete Accelerometrica Nazionale). An extensive project
for updating and improving the technology of RAN instruments as well as the number of recording points was performed in the
last 10 years. A wide site selection survey was carried out from eastern Sicily along the Italian peninsula, covering high
seismic risk areas. The recording station density and the choice of high-quality digital strong motion instruments ensure
reliability of the RAN network in the long-term. At the end of 2008, the free field sites selection and instruments installation,
planned in the project, were quite completed. In planning and drawing the new RAN, special attention has been devoted to the
robustness of the transmission systems, and to the distribution of new stations in order to ensure plenty of data during a
seismic emergency. We spent special care both in the estimation of the RAN site responses and in the diffusion of the strong
motion data. In order to better identify damaged earthquake areas, improved ground motion parameters need to be set. Such
parameters will also assist future progress for engineering seismic design techniques as well as disaster mitigation. 相似文献