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Prevenire e limitare il danno estetico: dall’incisione cutanea alla ricostruzione cranica.
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CATASTROPHIC FRAGMENTATION AND FORMATION OF FAMILIES: PRELIMINARY RESULTS FROM A NEW NUMERICAL MODEL
No full textPreliminary results of an improved version of the semiempirical model for catastrophic break up processes developed by Paolicchi et al., (1989) are presented. Among the several changes with respect to the old version, the most important seem to be related to the new treatment of gravitational effects, including self-compression and reaccumulation of fragments. In particular, the new model is able to analyze processes involving both cm-sized objects, like those studied by means of laboratory experiments, as well as much larger bodies, for which self- gravitational effects are dominant; moreover, in this latter case the model seems in principle adequate to describe with the same physics very different phenomena, like the formation of plausible asteroid families and the creation of single, rapidly spinning, objects. This fact, if confirmed by refined analyses, may be of high importance for our general understanding of asteroid collisional evolution
An Improved Semi-Empirical Model of Catastrophic Impact Processes I-Theory and Laboratory Experiments
No full textSeveral improvements to the semi-empirical approach to the physics of catastrophic breakup events (see P. Paolicchi, A. Cellino, P. Farinella, and V. Zappalà,Icarus77, 187–212, 1989) have been recently developed and are described in the present paper. The main new features of the model consist of the derivation of a set of realistic, non-overlapping fragments, as well as of a better treatment of the role played by gravitational effects. The main physical results obtained by means of the improved model in situations similar to those encountered in laboratory experiments are discussed, and compared with the experimental evidence and with the outcomes of hydrodynamical simulations, as well as with the analogous results found in the previous version of the model. The present model appears as being able to fit, also quantitatively, the experiments, and to enlight hidden interrelations among various observed properties, in spite of its simplified physics. The problems related to the possibility of deriving reliable fragment mass distributions are pointed out and extensively discussed. The systematic extension of the present model to the cases in which gravitational effects are dominating will be postponed to a forthcoming paper
Stereotactic Radiosurgery Maningiomas
No full textSchmidek and sweet operative neurosurgical techniques: indications, methods, and results
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