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171.
Linda Schmidtobreick Claus Tappert Alessandro Ederoclite Ivo Saviane Elena Mason 《Astrophysics and Space Science》2006,304(1-4):303-305
We report preliminary results of an observing run at the 1--m telescope at CTIO during which we followed RR Pic over several nights in February 2005. The resulting light curves show no sign of an eclipse. Apart from the 3.48 h period, which is usually interpreted as the orbital one, we find an additional period at P=3.78 h, which we interpret as the superhump period of the system.We furthermore present high–resolution Doppler maps in Hα, Hβ and He II, which we derived from observations at the NTT, La Silla in February 2004. They show strong variations in the emission distribution from one day to the next. While Hα and Hβ emission clearly show the accretion disc with some additional isolated sources, the He II emission is confined to an elongated region at low velocities. 相似文献
172.
Luigi Folco Massimo D'Orazio Alessandro Burroni 《Meteoritics & planetary science》2006,41(8):1183-1198
Abstract— The Frontier Mountain (FRO) 93001 meteorite is a 4.86 g fragment of an unshocked, medium‐ to coarse‐grained rock from the acapulcoite‐lodranite (AL) parent body. It consists of anhedral orthoenstatite (Fs13.3 ± 0.4Wo3.1 ± 0.2), augite (Fs6.1 ± 0.7Wo42.3 ± 0.9; Cr2O3 = 1.54 ± 0.03), and oligoclase (Ab80.5 ± 3.3Or3.1 ± 0.6) up to >1 cm in size enclosing polycrystalline aggregates of fine‐grained olivine (average grain size: 460 ± 210 μm) showing granoblastic textures, often associated with Fe,Ni metal, troilite, chromite (cr# = 0.91 ± 0.03; fe# = 0.62 ± 0.04), schreibersite, and phosphates. Such aggregates appear to have been corroded by a melt. They are interpreted as lodranitic xenoliths. After the igneous (the term “igneous” is used here strictly to describe rocks or minerals that solidified from molten material) lithology intruding an acapulcoite host in Lewis Cliff (LEW) 86220, FRO 93001 is the second‐known silicate‐rich melt from the AL parent asteroid. Despite some similarities, the silicate igneous component of FRO 93001 (i.e., the pyroxene‐plagioclase mineral assemblage) differs in being coarser‐grained and containing abundant enstatite. Melting‐crystallization modeling suggests that FRO 93001 formed through high‐degree partial melting (≥35 wt%; namely, ≥15 wt% silicate melting and ?20 wt% metal melting) of an acapulcoitic source rock, or its chondritic precursor, at temperatures ≥1200 °C, under reducing conditions. The resulting magnesium‐rich silicate melt then underwent equilibrium crystallization; prior to complete crystallization at ?1040 °C, it incorporated lodranitic xenoliths. FRO 93001 is the highest‐temperature melt from the AL parent‐body so far available in laboratory. The fact that FRO 93001 could form by partial melting and crystallization under equilibrium conditions, coupled with the lack of quench‐textures and evidence for shock deformation in the xenoliths, suggests that FRO 93001 is a magmatic rock produced by endogenic heating rather than impact melting. 相似文献
173.
F. Parello P. Allard W. DAlessandro C. Federico P. Jean-Baptiste O. Catani 《Earth and Planetary Science Letters》2000,180(3-4):325-339
Chemical and isotopic ratio (He, C, H and O) analysis of hydrothermal manifestations on Pantelleria island, the southernmost active volcano in Italy, provides us with the first data upon mantle degassing through the Sicily Channel rift zone, south of the African–European collision plate boundary. We find that Pantelleria fluids contain a CO2–He-rich gas component of mantle magmatic derivation which, at shallow depth, variably interacts with a main thermal (100°C) aquifer of mixed marine–meteoric water. The measured 3He/4He ratios and δ13C of both the free gases (4.5–7.3 Ra and −5.8 to −4.2‰, respectively) and dissolved helium and carbon in waters (1.0–6.3 Ra and −7.1 to −0.9‰), together with their covariation with the He/CO2 ratio, constrain a 3He/4He ratio of 7.3±0.1 Ra and a δ13C of ca. −4‰ for the magmatic end-member. These latter are best preserved in fluids emanating inside the active caldera of Pantelleria, in agreement with a higher heat flow across this structure and other indications of an underlying crustal magma reservoir. Outside the caldera, the magmatic component is more affected by air dilution and, at a few sites, by mixing with either organic carbon and/or radiogenic 4He leached from the U–Th-rich trachytic host rocks of the aquifer. Pantelleria magmatic end-member is richer in 3He and has a lower (closer to MORB) δ13C than all fluids yet analyzed in volcanic regions of Italy and southern Europe, including Mt. Etna in Sicily (6.9±0.2 Ra, δ13C=−3±1‰). This observation is consistent with a south to north increasing imprint of subducted crustal material in the products of Italian volcanoes, whose He and C (but also O and Sr) isotopic ratios gradually evolve towards crustal values northward of the African–Eurasian plate collision boundary. Our results for Pantelleria extend this regional isotopic pattern further south and suggest the presence of a slightly most pristine or ‘less contaminated’, 3He-richer mantle source beneath the Sicily Channel rift zone. The lower than MORB 3He/4He ratio but higher than MORB CO2/3He ratio of Pantelleria volatile end-member are compatible with petro-geochemical evidence that this mantle source includes an upwelling HIMU–EM1-type asthenospheric plume component whose origin, according to recent seismic data, may be in the lower mantle. 相似文献
174.
Giuseppe Cello Giovanni Deiana Luca Ferelli Leonardo Marchegiani Laura Maschio Stefano Mazzoli Alessandro Michetti Leonello Serva Emanuele Tondi Tiziano Vittori 《Journal of Seismology》2000,4(4):357-364
On September 26, 1997, at 00.33 h(GMT), a Mw 5.7 earthquake occurred in the axial zone of theUmbria-Marche Apennines of central Italy, in the Colfiorito basin area. At09.40 h (GMT), a Mw 6.0 earthquake again struck the area withinthe Colfiorito basin, a major intramontane basin filled with Quaternarycontinental deposits. The two main shocks, and the associated aftershockswere within a roughly NNW-SSE trending zone of largest damage (Imax10), in which ground deformation has been observed. Along this trend,Cello et al. (1997a) had mapped a few capable faults, showingtranstensional to pure extensional kinematics. Field inspection of themapped faults, carried out after the main shocks, revealed that some ofthem were locally reactivated (for lengths of several hundreds metres andsurface slip in the range of 2–8 cm) during the September 26, 1997earthquakes. 相似文献
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179.
Andrea De Montis Simone Caschili Alessandro Chessa 《Journal of Geographical Systems》2011,13(1):49-65
The aim of this paper is to study the dynamics of the commuting system of two insular regions of Italy, Sardinia and Sicily,
inspected as complex networks. The authors refer to a 20-year time period and take into account three census data sets about
the work and study-driven inter-municipal origin-destination movements of residential inhabitants in 1981, 1991 and 2001.
Since it is likely that the number of municipalities (in this case, the vertices of the system) does not display sharp variations,
the authors direct the study to the variation of the properties emerging through both a topological and a weighted network
representation of commuting in the time periods indicated. 相似文献
180.
In this note we observe that a problem of linear approach to Granger causality testing between CO2 and global temperature is that such tests can have low power. The probability to reject the null hypothesis of non-causality when it is false is low. Regarding non-linear Granger causality, based on multi-layer feed-forward neural network, the analysis provides evidence of significant unidirectional Granger causality from CO2 to global temperature. 相似文献