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81.
82.
Genuario Belmonte Gianmarco Ingrosso Marco Poto Gianluca Quarta Marisa D'Elia Raffaele Onorato & Lucio Calcagnile 《Marine Ecology》2009,30(3):376-382
Submarine caves at the Cape of Otranto (SE, Italy) host pseudostalactites. Only recently have they been recognised as originating mainly from the marine tube worm Protula tubularia (Serpulidae, Polychaeta). Their formation depends on the adaptability, life history and behaviour of that species in the cave habitat. The dating of calcareous tubes in the pseudostalactite core represents the first attempt to describe the formation of such bio-construction, and the gregarious behaviour of the species. Calcareous tubes along the core axis of three pseudostalactites removed from the cave lu Lampiùne (Otranto, South East Italy) have been dated using the 14 C method. Measures established ages from 2600 to 5000 years for the three structures. This extremely long period (when compared with the life span of each worm) suggests that each tube aggregation is the result of punctuated growth periods alternated with long standstill phases. At the end of a growth period, each tube aggregation was covered with a brownish concretion, completing the pseudostalactite. 相似文献
83.
The paper presents the results of a numerical analysis of the excavation of a tunnel in a non-cohesive soil. In situ test data recorded before and during the works are presented first. The constitutive law adopted and the procedure followed for modelling the injection phase is discussed next. It is shown that, in order to match the movements recorded within the soil mass, a rather complex procedure, allowing for either uniform diffusion of the mix or formation of mix lenses (‘claquage’), should be adopted. Calculated and observed data during the various phases of the excavation are then finally compared. 相似文献
84.
Mauro Di Vito Lucio Lirer Giuseppe Mastrolorenzo Giuseppe Rolandi 《Bulletin of Volcanology》1987,49(4):608-615
On 29 September 1538 a week-long eruption began in Campi Flegrei forming a new volcano, Monte Nuovo. From contemporary accounts of the eruption, it has been possible to reconstruct the main phases of activity. These phases may be correlated with different depositional units identified in the field. The eruption opened with a hydromagmatic phase, during which a large amount of external water (meteoric or sea water) was able to interact with the magma. The exhaustion of the water supply and decrease in volatile content initiated a change in the dynamic conditions of eruption, which became more purely magmatic in character and less explosive. 相似文献
85.
Abstract Models of differentially rotating compressible deep spherical shells are computed according to the method of Belvedere and Paternò (1977): the heat transport is entirely convective, small-scale motions are parametrized by a thermal diffusivity and a kinematic viscosity, and the limit of slow rotation and large viscosity is considered. In order to adapt the resulting differential rotation to the observed equatorial acceleration of the Sun, the heat transport must be more effective in the vicinity of the equator. In all models the latitude dependence of the transport coefficient induces meridional circulation in the form of a large cell, with rising material at high latitudes and sinking material near the equator. On top of this cell, one or two thin countercells develop in a minority of cases. Large pole-equator temperature differences and meridonal velocities at the surface are obtained when the Prandtl number is 1. But values of, say, 1/10 are sufficiently small to allow the models to be applied to the Sun. In general an angular velocity increasing with depth is found, and the surfaces of constant angular velocity are inclined towards greater depth and higher latitude. 相似文献