Rotational dynamics and internal structure of Titan     

Bruce G. Bills  Francis Nimmo 《Icarus》2011,214(1):351-355

Estimates of the moments of inertia of Titan, as separately deduced from its gravitational field and spin pole orientation, are quite different. This discrepancy can be resolved if Titan is either not precessing as a rigid body (e.g. if the shell is decoupled from the interior by an ocean), or if the spin pole is not fully damped (e.g. due to atmospheric excitation). By the end of the Cassini mission, continued monitoring of the changing spin pole orientation, by Cassini radar observations, will determine which effect dominates.  相似文献   

Causes of the Intraseasonal SST Variability in the Tropical Indian Ocean          下载免费PDF全文

Tim Li  Francis Tam  Xiouhua Fu  周天军  朱伟军 《大气和海洋科学快报》2008,1(1):18-23

Satellite observations reveal a much stronger intraseasonal sea surface temperature (SST) variability in the southern Indian Ocean along 5-10oS in boreal winter than in boreal summer. The cause of this seasonal dependence is studied using a 2?-layer ocean model forced by ERA-40 reanalysis products during 1987-2001. The simulated winter-summer asymmetry of the SST variability is consistent with the observed. A mixed-layer heat budget is analyzed. Mean surface westerlies along the ITCZ (5-10oS) in December-January-February (DJF) leads to an increased (decreased) evaporation in the westerly (easterly) phase of the intraseasonal oscillation (ISO), during which convection is also enhanced (suppressed). Thus the anomalous shortwave radiation, latent heat flux and entrainment effects are all in phase and produce strong SST signals. During June-July-August (JJA), mean easterlies prevail south of the equator. Anomalies of the shortwave radiation tend to be out of phase to those of the latent heat flux and ocean entrainment. This mutual cancellation leads to a weak SST response in boreal summer. The resultant SST tendency is further diminished by a deeper mixed layer in JJA compared to that in DJF. The strong intraseasonal SST response in boreal winter may exert a delayed feedback to the subsequent opposite phase of ISO, implying a two-way air-sea interaction scenario on the intraseasonal timescale. Citation: Li, T., F. Tam, X. Fu, et al., 2008: Causes of the intraseasonal SST variability in the tropical Indian ocean, Atmos. Oceanic Sci. Lett., 1, 18-23  相似文献   

Calculation of the local standard of rest from 20 574 local stars in the New Hipparcos Reduction with known radial velocities     

Charles Francis  Erik Anderson 《New Astronomy》2009,14(7):615-629

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The hypocentral resolution of microearthquake surveys carried out at sea     

Jeremy Duschenes  R. C. Lilwall  T. J. G. Francis 《Geophysical Journal International》1983,72(2):435-451

Summary. The ability to locate the hypocentres of earthquakes occurring along ridge crests and fracture zones accurately is a prerequisite to solving several problems associated with seafloor tectonics and oceanic crustal formation. Such resolution has rarely been achieved in the past, often because the seismic networks deployed were inadequate for the task. We demonstrate that sea surface receivers are not useful in such studies, and that the minimum acceptable size for a seafloor network is five receivers, of which at least one must be capable of detecting shear waves unambiguously.  相似文献   

A threshold for sequentially self-propagating star formation     

A.P. Whitworth  N. Francis 《Monthly notices of the Royal Astronomical Society》2002,329(3):641-646

When a stellar wind bubble expands into an homogeneous medium, there are two possible outcomes. This is due to the fact that the self-gravity of the swept-up shell acts in two orthogonal directions: tangentially , to promote fragmentation of the shell, and radially , to decelerate expansion of the shell. The outcome depends on whether self-gravity works faster in the tangential or the radial direction.
If the wind power ℒ_o is large and the effective isothermal sound speed a _o in the swept-up gas is small – approximately         – tangential self-gravity works faster. A thin dense shell is swept up and fragments while it is still expanding supersonically. This is the scenario often invoked to explain sequentially self-propagating star formation.
However, if ℒ_o is small and/or a _o is large, radial self-gravity works faster. Expansion of the bubble stalls before the shell can fragment. The expansion speed ceases to be supersonic, the outer shock dissipates, and the shell is neither thin nor dense. Under this circumstance, the shell is unlikely to fragment and star formation will not propagate sequentially.
These conclusions are probably not altered significantly when the medium into which the wind blows is inhomogeneous, provided that the mean density on opposite sides of the bubble does not differ by many orders of magnitude.  相似文献   

The Melting Relations of Iron, and Temperatures in the Earth's Core     

Francis Birch 《Geophysical Journal International》1972,29(4):373-387

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Les « Sables fauves », témoins de mouvements tectoniques dans le bassin d'Aquitaine au Miocène moyenThe ‘Sables fauves’, showing tectonic deformations in the Aquitaine Basin during Middle Miocene     

Philippe Gardère  Jacques Rey  Francis Duranthon 《Comptes Rendus Geoscience》2002,334(13):987-994

New data about the ‘Sables fauves’ clearly show two different kinds of organisations: stratigraphic superposition of Langhian and Serravallian units to the south and embankment of Serravallian sediments in Langhian deposits to the north. The result consists in two different palaeogeographic schemes. The Langhian Sea is widely extended, forming the ‘Lectoure Gulf’, whereas the Serravallian Sea is much more reduced, with valleys fillings to the north and a little gulf to the south. This involves a tectonic activity along a structure which orientation is N120°E (‘flexure de la Douze’) and a relative rising of the northern part, of about 30 m. To cite this article: P. Gardère et al., C. R. Geoscience 334 (2002) 987–994.  相似文献   

Effects of loads in the upper crust on estimates of the elastic thickness of the lithosphere   总被引：1，自引：0，他引：1  

Roger J. Banks  Susan C. Francis  Roger G. Hipkin 《Geophysical Journal International》2001,145(1):291-299

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Dysaerobic conditions during Heinrich events 4 and 5: Evidence from phosphorus distribution in a North Atlantic deep-sea core     

Federica Tamburini  Sylvain HuonPhilipp Steinmann  Francis E GroussetThierry Adatte  Karl B Fllmi 《Geochimica et cosmochimica acta》2002,66(23):4069-4083

Reactive phosphorus undergoes diagenetic transformation once transferred into marine sediments. The degree of regeneration and redistribution of phosphorus depends on early diagenetic and environmental conditions, which may be linked to larger scale phenomena, such as bottom water circulation, water column ventilation, and organic carbon flux. Phosphorus phases of the <50-μm-sized fraction of deep-sea sediments from core SU 90-09 (North Atlantic, 43°31′N, 30°24′W, 3375 m below sea level) have been analyzed using a sequential extraction technique (SEDEX method) to reconstruct phosphorus geochemistry during Heinrich events 4 and 5. Comparison with Holocene samples from the same site indicates that postdeposition diagenetic transformation has not affected phosphorus distribution in the deep part of the sediments. Total and reactive phosphorus average 0.40 ± 0.04 mg/g and 0.30 ± 0.05 mg/g, respectively, and are comparable to values found in analog deep-sea environments in the North Atlantic. Detrital phosphorus, the phase linked to igneous- and metamorphic-derived material, sharply increases during Heinrich events and covaries with the ice-rafted debris record, whereas authigenic and Fe-bound phosphorus phases, both influenced by redox conditions, decrease or even disappear. These findings suggest that during the deposition of Heinrich layers (HLs), environmental parameters hampered the precipitation of these phases. Large freshwater discharges in relation to iceberg surges may have provoked a temporary stratification of the water column. Accordingly, dysaerobic conditions in the sediments may have fostered the loss of dissolved phosphorus from the sediments to the water column, in a direct and rapid response to the changed conditions. Decreasing trends in organic matter elemental ratios (total organic carbon/organic phosphorus) and Rock-Eval oxygen index values, along with the presence of partly authigenic dolomite and ankerite within HLs, also support this assumption.  相似文献   

Scale-Compensation Stereoscope     

E. C. Francis 《The Photogrammetric Record》1965,5(26):137-138

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