Lithospheric thermal structure in the Baltic shield   总被引：1，自引：0，他引：1  

V. Pasquale  M. Verdoya  P. Chiozzi 《Geophysical Journal International》1991,106(3):611-620

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A statistical study of gamma-ray burst afterglows measured by the Swift Ultraviolet Optical Telescope     

S. R. Oates  M. J. Page  P. Schady  M. de Pasquale  T. S. Koch  A. A. Breeveld  P. J. Brown  M. M. Chester  S. T. Holland  E. A. Hoversten  N. P. M. Kuin  F. E. Marshall  P. W. A. Roming  M. Still  D. E. Vanden Berk  S. Zane  J. A. Nousek 《Monthly notices of the Royal Astronomical Society》2009,395(1):490-503

We present the first statistical analysis of 27 Ultraviolet Optical Telescope (UVOT) optical/ultraviolet light curves of gamma-ray burst (GRB) afterglows. We have found, through analysis of the light curves in the observer's frame, that a significant fraction rise in the first 500 s after the GRB trigger, all light curves decay after 500 s, typically as a power law with a relatively narrow distribution of decay indices, and the brightest optical afterglows tend to decay the quickest. We find that the rise could be either produced physically by the start of the forward shock, when the jet begins to plough into the external medium, or geometrically where an off-axis observer sees a rising light curve as an increasing amount of emission enters the observers line of sight, which occurs as the jet slows. We find that at 99.8 per cent confidence, there is a correlation, in the observed frame, between the apparent magnitude of the light curves at 400 s and the rate of decay after 500 s. However, in the rest frame, a Spearman rank test shows only a weak correlation of low statistical significance between luminosity and decay rate. A correlation should be expected if the afterglows were produced by off-axis jets, suggesting that the jet is viewed from within the half-opening angle θ or within a core of a uniform energy density  θ_c  . We also produced logarithmic luminosity distributions for three rest-frame epochs. We find no evidence for bimodality in any of the distributions. Finally, we compare our sample of UVOT light curves with the X-ray Telescope (XRT) light-curve canonical model. The range in decay indices seen in UVOT light curves at any epoch is most similar to the range in decay of the shallow decay segment of the XRT canonical model. However, in the XRT canonical model, there is no indication of the rising behaviour observed in the UVOT light curves.  相似文献   

Jet breaks at the end of the slow decline phase of Swift GRB light curves     

M. De Pasquale  P. Evans  S. Oates  M. Page  S. Zane  P. Schady  A. Breeveld  S. Holland  P. Kuin  M. Still  P. Roming  P. Ward 《Monthly notices of the Royal Astronomical Society》2009,392(1):153-169

The Swift mission has discovered an intriguing feature of gamma-ray burst (GRBs) afterglows, a phase of shallow decline of the flux in the X-ray and optical light curves. This behaviour is typically attributed to energy injection into the burst ejecta. At some point this phase ends, resulting in a break in the light curve, which is commonly interpreted as the cessation of the energy injection. In a few cases, however, while breaks in the X-ray light curve are observed, optical emission continues its slow flux decline. This behaviour suggests a more complex scenario. In this paper, we present a model that invokes a double component outflow, in which narrowly collimated ejecta are responsible for the X-ray emission while a broad outflow is responsible for the optical emission. The narrow component can produce a jet break in the X-ray light curve at relatively early times, while the optical emission does not break due to its lower degree of collimation. In our model both components are subject to energy injection for the whole duration of the follow-up observations. We apply this model to GRBs with chromatic breaks, and we show how it might change the interpretation of the GRBs canonical light curve. We also study our model from a theoretical point of view, investigating the possible configurations of frequencies and the values of GRB physical parameters allowed in our model.  相似文献   

Kinetic approaches to particle acceleration at cosmic ray modified shocks     

Elena Amato  Pasquale Blasi  Stefano Gabici 《Monthly notices of the Royal Astronomical Society》2008,385(4):1946-1958

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Dynamical friction in modified Newtonian dynamics     

Carlo Nipoti  Luca Ciotti  James Binney  Pasquale Londrillo 《Monthly notices of the Royal Astronomical Society》2008,386(4):2194-2198

We have tested a previous analytical estimate of the dynamical friction time-scale in modified Newtonian dynamics (MOND) with fully non-linear N -body simulations. The simulations confirm that the dynamical friction time-scale is significantly shorter in MOND than in equivalent Newtonian systems, i.e. systems with the same phase-space distribution of baryons and additional dark matter. An apparent conflict between this result and the long time-scales determined for bars to slow and mergers to be completed in previous N -body simulations of MOND systems is explained. The confirmation of the short dynamical-friction time-scale in MOND underlines the challenge that the Fornax dwarf spheroidal poses to the viability of MOND.  相似文献   

Forest structure of a maple old-growth stand: a case study on the Apennines mountains (Southern Italy)     

Pasquale A. Marziliano  Vittoria Coletta  Angelo Scuderi  Clemente Scalise  Giuliano Menguzzato  Fabio Lombardi 《山地科学学报》2017,14(7):1329-1340

In Europe, very small forest areas can be considered to be old-growth, and they are mainly located in Eastern Europe. The typical structures of old growth forests infrequently occur in Mediterranean mountainous environments, since they have been affected by human activities for centuries. This study focused on a remote and almost pure Italian maple stand located in southern Italy, which has not been managed for long time due to its inaccessibility. The effects of natural evolution on the forest stand were evaluated through the analysis of the spatial and chronological structure and the regeneration patterns, then estimating the amounts and quality of deadwood occurrence. Across the whole stand, all the trees with DBH (diameter at breast height) larger than 50 cm (LLT, large living trees) were measured (DBH and height) and age was also determined through a dendrochronological approach. The diameters observed ranged between 50 and 145 cm with ages of 120 to 250 years. The Latham index calculated for trees within the sample plot highlighted a multilayered canopy with a dominant layer of large living trees (age > 120 years). The size-class distribution of stems had a reverse-J shape, and basal area was 52 m² ha^-1. Deadwood was exclusively constituted by standing dead trees and CWD and its volume was on average 31 m³ ha^-1.Pure Italian maple forests are generally rare in Europe, and it was unexpected to find a forest stand characterized by a so complex structure with old growth attributes. The study of complex forest stand, even if small, could give precious information on the forest evolution, clarifying also diverse auto-ecological traits of tree species that usually are not common in our forests.  相似文献   

Urban Dispersion Modelling and Experiments in the Daytime and Nighttime Atmosphere   总被引：1，自引：0，他引：1  

Pasquale Franzese  Pablo Huq 《Boundary-Layer Meteorology》2011,139(3):395-409

An analytical model of atmospheric dispersion in urban areas in both daytime and nighttime conditions is presented. The model is based on a Gaussian formulation where the horizontal and vertical diffusion coefficients are determined according to analytical theories. The model is validated with dispersion measurements from field experiments conducted in Oklahoma City, Salt Lake City, St. Louis and London, U.K. The theory is in good agreement with the data for both daytime and nighttime conditions. The data support the conclusion that the magnitude of the nighttime stratification in the urban atmosphere is weak; however, its effects on dispersion are not negligible. The predicted existence of two distinct dispersion regimes, in the near and in the far field, is also confirmed by the data. The good collapse of the data suggests that urban dispersion is governed by the characteristic length scales of atmospheric boundary-layer turbulence, rather than urban canopy length scales that are more likely to affect dispersion only in the vicinity of the source.  相似文献   

Formation and stability of mixed Mg/Ca/phytate species in synthetic seawater media: Consequences on ligand speciation     

Pasquale Crea  Concetta De Stefano  Demetrio Milea  Silvio Sammartano   《Marine Chemistry》2008,112(3-4):142-148

The results of a potentiometric investigation (by ISE-H⁺, glass electrode) on the speciation of phytate ion (Phy¹²⁻) in an ionic medium simulating the major components (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻ and SO₄²⁻) of natural seawater, at different salinities and t = 25 °C, are reported. The work was particularly aimed at determining the possible formation of mixed Ca²⁺–Mg²⁺–phytate ion pairs, and to establish how including the formation of these mixed species would affect the speciation modeling in seawater media. After testing various speciation models, that considering the formation of the MgCaH₃Phy⁵⁻, MgCaH₄Phy⁴⁻, Mg₂CaH₃Phy³⁻ and Mg₂CaH₄Phy²⁻ species was accepted, and corresponding stability constants were determined at two salinities (S = 5, 10). A discussion is reported both on the choice of the experimental conditions and on the possibility to extend these results to those typical of real seawater. A detailed procedure is also described to demonstrate that the stability of these species is higher than that statistically predicted. As reported in literature, a parameter, namely log X, has been determined in order to quantify this extra stability for the formation of each mixed species at various salinities. For example, at S = 10, log X₁₁₃ = 2.67 and log X₁₁₄ = 1.37 for MgCaH₃Phy⁵⁻ and MgCaH₄Phy⁴⁻ (statistical value is log X_stat = 0.60), and log X₂₁₃ = 6.11 and log X₂₁₄ = 2.15 for Mg₂CaH₃Phy³⁻ and Mg₂CaH₄Phy²⁻ (log X_stat = 1.43), respectively. Results obtained also showed that the formation of these species may occur even in conditions of low salinity (i.e. low concentration of alkaline earth cations) and low pH (i.e., more protonated ligand).  相似文献   

New records of cold‐water coral sites and fish fauna characterization of a potential network existing in the Mediterranean Sea          下载免费PDF全文

Gianfranco D'Onghia  Crescenza Calculli  Francesca Capezzuto  Roberto Carlucci  Angela Carluccio  Porzia Maiorano  Alessio Pollice  Pasquale Ricci  Letizia Sion  Angelo Tursi 《Marine Ecology》2016,37(6):1398-1422

New cold‐water coral (CWC) sites were recorded along the Apulian margin (Central Mediterranean). The species composition and depth distribution of CWCs were updated. A distribution of the CWC sites coincident with the course of the dense‐water masses that flow between the Southern Adriatic and Northern Ionian was confirmed. The faunal assemblages of five of these CWC sites were investigated and compared using experimental longlines during the spring–summer and autumn–winter seasons, between 2010 and 2014. Differences in ecological variables amongst the sites in each season were evaluated by means of a set of univariate and multivariate methods (analysis of variance, permutational multivariate analysis of variance, non‐metric multidimensional scaling). Although some differences were detected in relation to the different depths examined during spring–summer, the CWC sites showed similar features in terms of species richness and diversity as well as in the abundance of the same fish species (Galeus melastomus, Conger conger, Helicolenus dactylopterus, Merluccius merluccius, Phycis blennoides and Pagellus bogaraveo) most probably because of the distribution of adult specimens in structurally complex and heterogeneous habitats, which act as a potential ‘refuge network’ with respect to commercial fishing. The presence of maturing and mature individuals as well as post‐reproductive females indicates that these CWC sites also act as spawning areas, representing a potential ‘renewal network’ for the fish populations. The term ‘network’ used here refers to several similar subsystems (CWC sites) that play the same ecological role in a wider system (Apulian margin). These CWC communities need coherent conservation measures and management strategies according to the Ecosystem Approach to Fisheries.  相似文献   

Rainfall erosivity in Italy: a national scale spatio-temporal assessment   总被引：2，自引：0，他引：2  

Pasquale Borrelli  Nazzareno Diodato  Panos Panagos 《International Journal of Digital Earth》2016,9(9):835-850

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