A physical model of Titan's clouds     

Owen B. Toon  R.P. Turco  James B. Pollack 《Icarus》1980,43(3):260-282

We have constructed a model of the physical processes controlling Titan's clouds. Our model produces clouds that qualitatively match the present observational constraints in a wide variety of model atmospheres, including those with low atmospheric pressures (25 mbar) and high atmospheric pressures. We find the following: (1) high atmospheric temperatures (160°K) are important so that there is a large scale height in the first few optical depths of cloud; (2) the aerosol mass production occurs at very low aerosol optical depth so that the cloud particles do not directly affect the photochemistry producing them; (3) the production rate of aerosol mass by chemical processes is probably greater than 3.5 × 10^?14 g cm^?2 sec^?1; (4) and the eddy diffusion coefficient is less than 5 × 10⁶ cm² sec^?1 except perhaps in the top optical depth of the cloud. Our model is not extremely sensitive to particle shape, but it is sensitive to particle density. Higher particle densities require larger aerosol mass production rates to produce satisfactory clouds. Particle densities of unity require a mass production rate on the order of 3.5 × 10^?13 g cm^?2 sec^?1. We also show that an increase in mass input causes a decrease in the mean particle size, as required by J. B. Pollack et al. (1980, Geophys. Res. Lett. 7, 829–832), to explain the observed correlation between the solar cycle and Titan's albedo; that coagulation need not be extremely inefficient in order to obtain realistic clouds as proposed by M. Podolak and E. Podolak (1980, Icarus43, 73–83); that coagulation could be inefficient due to photoelectric charging of the particles; and, that the lifetime of particles near the altitude of unit optical depth is a few months, as required to explain the temporal variability observed by S. T. Suess and G. W. Lockwood and D. P. Cruikshank and J. S. Morgan (1979, Bull. Amer. Astron. Soc.11, 564). Although Titan's aerosols are ottically thick in the vertical direction, the atmosphere is so extended that the horizontal visibility is greater than that found anywhere at Earth's surface.  相似文献   

A multiscale framework for the simulation of the anisotropic mechanical behavior of shale          下载免费PDF全文

Weixin Li  Roozbeh Rezakhani  Congrui Jin  Xinwei Zhou  Gianluca Cusatis 《国际地质力学数值与分析法杂志》2017,41(14):1494-1522

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Reply to comment on ‘Insights from the Mw 6.3 2009 L’Aquila earthquake (Central Apennines) – unveiling new seismogenic sources through their surface signatures: the adjacent San Pio Fault’     

Daniela Di Bucci  Paola Vannoli  Pierfrancesco Burrato  Umberto Fracassi  Gianluca Valensise 《地学学报》2011,23(6):421-423

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Chandra smells a RRAT     

Bryan M. Gaensler  Maura McLaughlin  Stephen Reynolds  Kazik Borkowski  Nanda Rea  Andrea Possenti  Gianluca Israel  Marta Burgay  Fernando Camilo  Shami Chatterjee  Michael Kramer  Andrew Lyne  Ingrid Stairs 《Astrophysics and Space Science》2007,308(1-4):95-99

“Rotating RAdio Transients” (RRATs) are a newly discovered astronomical phenomenon, characterised by occasional brief radio bursts, with average intervals between bursts ranging from minutes to hours. The burst spacings allow identification of periodicities, which fall in the range 0.4 to 7 seconds. The RRATs thus seem to be rotating neutron stars, albeit with properties very different from the rest of the population. We here present the serendipitous detection with the Chandra X-ray Observatory of a bright point-like X-ray source coincident with one of the RRATs. We discuss the temporal and spectral properties of this X-ray emission, consider counterparts in other wavebands, and interpret these results in the context of possible explanations for the RRAT population. B.M.G. acknowledges the support of NASA through LTSA grant NAG5-13023 and of an Alfred P. Sloan Fellowship.  相似文献   

The investigation of potential earthquake sources in peninsular Italy: A review     

Gianluca Valensise  Daniela Pantosti 《Journal of Seismology》2001,5(3):287-306

We summarise and discuss almost a century of progress inthe understanding of the main characteristics of large Italian earthquakes.Topics of discussion include (1) the distribution of the largest earthquakesin relation with Late Pleistocene and Holocene faulting, (2) the geologicaland tectonic setting of the 1908 Messina Straits, 1915 Fucino Plain and1980 Irpinia earthquakes, (3) some of the geodynamic motivations for thecharacteristics of Italian seismicity, and (4) the resulting implications for theassessment of seismic hazard. In a subsequent section of the paper we present a summaryof recent achievements in the understanding and characterization of Italianseismicity, with special emphasis on the assignment of large historicalearthquakes to specific sources identified through geological observationsand on the evaluation of average recurrence intervals for individualearthquake sources. The final section describes some of the efforts being madefor matching the newly acquired geological evidence with instrumental andhistorical observations of Italian seismicity and the hypotheses than can bederived for anticipating the locus of large earthquakes of the future.  相似文献   

Introduction à la géochimie: J.C. Allègre et G. Michard. Presses Universitaires de France,Paris, 1973, 220 pp., 79 figs., FF 32.—     

G.H. Turco 《Chemical Geology》1975,16(1):70-71

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Mythos and techne: An essay on the intercultural function of territory in sub-Saharan geography     

Angelo Turco 《GeoJournal》2004,60(4):329-337

Territorial symbolism in sub-Saharan Africa calls to mind multiple forms of knowledge. More particularly, territorial significance is fed both by magical and sacred beliefs and by knowledge based on empirical observation and concrete practices. These two types of knowledge differ widely as to their nature, the procedures by which they are formed, and the cultural values they embody. Nevertheless, semantic interaction between mythical knowledge and technical knowledge is remarkably rich. By blurring the distinction between mythos and techne, this semantic interaction seems to constitute an important cultural tool for building feelings of social security in that it reinforces and stabilizes socio-geographic patterns, and more especially those which regulate access to space and natural resources. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Plate kinematics of the Western Mediterranean region during the Oligocene and Early Miocene     

Antonio Schettino  Eugenio Turco 《Geophysical Journal International》2006,166(3):1398-1423

The tectonic history of the Western Mediterranean region during the Oligocene and Early Miocene is illustrated through a series of plate reconstructions, from chron C13n to chron C6n. The reconstructions are based on a new interpretation of published magnetic anomaly data and two-ships seismic data, and their integration with known geological constraints, in order to determine style and timing of the backarc extension processes in the Liguro-Provençal, Valencia and Algerian basins. In particular, a reinterpretation of the regional magnetic anomaly field allowed the calculation of the instantaneous Euler poles associated with the motion of 11 microplates relative to Eurasia and Iberia. Furthermore, a quantitative analysis of the acoustic basement morphology and the balancing of deep crustal profiles were used to estimate the closure and pre-rift rotation angles associated with the Euler poles of opening of the Ligurian, Provençal, Valencia and Algerian basins. This rigorous reconstruction of the geometry of the pre-rift continental margins of Iberia and Eurasia could furnish important insights into the study of Mediterranean tectonics for older times.  相似文献   

Observations of physical effects from tsunamis of December 30, 2002 at Stromboli volcano, southern Italy   总被引：1，自引：0，他引：1  

Stefano Tinti  Alessandra Maramai  Alberto Armigliato  Laura Graziani  Anna Manucci  Gianluca Pagnoni  Filippo Zaniboni 《Bulletin of Volcanology》2006,68(5):450-461

On December 30, 2002, following an intense period of activity of Stromboli volcano (south Tyrrhenian Sea, Italy), complex mass failures occurred on the northwest slope of the mountain which also involved the underwater portion of the volcanic edifice for a total volume of about 2–3×10⁷ m³. Two main landslides occurred within a time separation of 7 min, and both set tsunami waves in motion that hit the coasts of Stromboli causing injuries to three people and severe damage to buildings and structures. The tsunamis also caused damage on the island of Panarea, some 20 km to the SSE from the source. They were observed all over the Aeolian archipelago, at the island of Ustica to the west, along the northern Sicily coasts to the south as well as along the Tyrrhenian coasts of Calabria to the east and in Campania to the north. This paper presents field observations that were made in the days and weeks immediately following the events. The results of the quantitative investigations undertaken in the most affected places, namely along the coasts of Stromboli and on the island of Panarea, are reported in order to highlight the dynamics of the attacking waves and their impact on the physical environment, on the coastal structures and on the coastal residential zone. In Stromboli, the tsunami waves were most violent along the northern and northeastern coastal belt between Punta Frontone and the village of Scari, with maximum runup heights of about 11 m measured on the beach of Spiaggia Longa. Measured runups were observed to decay rapidly with distance from the source, typical of tsunami waves generated by limited-area sources such as landslides.  相似文献   

A Mössbauer and FTIR study of synthetic amphiboles along the magnesioriebeckite – ferri-clinoholmquistite join     

Giancarlo Della Ventura  Günther J. Redhammer  Gianluca Iezzi  Frank C. Hawthorne  Arnaud Papin  Jean-Louis Robert 《Physics and Chemistry of Minerals》2005,32(2):103-113

A series of amphiboles along the magnesioriebeckite—Na₂Mg₃Fe³⁺ ₂Si₈O₂₂(OH)₂– ferri-clinoholmquistite—Li₂Mg₃Fe³⁺ ₂Si₈O₂₂(OH)2 - join, defined by the ^BLi^B Na_–1 exchange vector, were hydrothermally synthesized at 700°C, 0.4 GPa, NNO + 1 redox conditions. Powder XRD and SEM-EDAX showed a very high (> 90%) amphibole yield for all samples. X-ray patterns were indexed in the C2/m space group; refined cell-parameters show a linear decrease of a and as a function of chemistry. IR spectra in the OH-stretching region show four main and rather sharp bands; these are assigned to Mg and Fe²⁺ at M(1,3), and indicate that the obtained amphiboles depart from the nominal octahedral composition (^M1,3Mg₃). The IR spectra also show that there is an increasing filling-up of the A-site for increasing Na in the system (increasing solid-solution toward, arfvedsonite). Mössbauer spectra show four well-defined quadrupole doublets which are assigned to Fe³⁺ at M2 and to Fe²⁺ at M1, M3 and M4, respectively. The Fe³⁺/Fe²⁺ content derived from fitted peak areas show variable Fe³⁺ concentration along the series. Mössbauer spectra also show a distinct alteration of ⁵⁷Fe hyperfine parameters with changing Na–Li at M4. The most evident variation is observed for the quadrupole splitting of Fe³⁺ at M2, which increases by 50% from ferri-clinoholmquistite to magnesio-riebeckite; this suggest that the M2 octahedron in ferri-clinoholmquistite is much closer to the ideal geometry than the M2 octahedron in magnesio-riebeckite. Mössbauer spectra show also a well-defined increase in the Fe²⁺ quadrupole splitting of the M1 and M3 octahedra, which is attributed to the Na–Li distribution at the B-sites.  相似文献