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Search Results: 1 - 10 of 1728 matches for " Chibbaro Salvatore "
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Oblique Corpectomy to Manage Cervical Myeloradiculopathy
Chibbaro Salvatore,Makiese Orphee,Bresson Damien,Reiss Alisha,Poczos Pavel,George Bernard
Neurology Research International , 2011, DOI: 10.1155/2011/734232
Abstract: Background. The authors describe a lateral approach to the cervical spine for the management of spondylotic myeloradiculopathy. The rationale for this approach and surgical technique are discussed, as well as the advantages, disadvantages, complications, and pitfalls based on the author's experience over the last two decades. Methods. Spondylotic myelo-radiculopathy may be treated via a lateral approach to the cervical spine when there is predominant anterior compression associated with either spine straightening or kyphosis, but without vertebral instability. Results. By using a lateral approach, the lateral aspect of the cervical spine and the vertebral artery are easily reached and visualized. Furthermore, the lateral part of the affected intervertebral disc(s), uncovertebral joint(s), vertebral body(ies), and posterior longitudinal ligament can be removed as needed to decompress nerve root(s) and/or the spinal cord. Conclusion. Multilevel cervical oblique corpectomy and/or lateral foraminotomy allow wide decompression of nervous structures, while maintaining optimal stability and physiological motion of the cervical spine. 1. Introduction Cervical spondylotic myelopathy (CSM) and cervical spondylotic radiculopathy (CSR) are classically approached by anterior single or multiple disc space decompression [1, 2], multilevel corpectomy [3], laminectomy [4–10], or laminoplasty [11–18]. More recently, techniques using lateral multiple oblique corpectomy (MOC) and/or foraminotomy [19–28] have been used with increasing frequency. In general, when three or more levels are affected, the preferred techniques remain either an anterior multilevel corpectomy or a posterior route such as laminectomy, open door laminoplasty, and posterior foraminotomy. However, the best management of such pathology (especially if 3 or more levels are involved) remains controversial. The authors consider the cervical spine lateral approach a valid and safe option to treat such pathologies as it provides very good clinical results and maintains long-term spinal stability. The goal of this paper is to further and critically present the idea and rationale of the cervical spine lateral approach with its advantages, disadvantages, complications, and pitfalls in a critical review of their last 2 decades experience. 2. Technique Indication Predominant anterior compression associated with either straightening or kyphosis of the cervical spine in the absence of instability is the general indication for the proposed technique. In cases of both anterior and posterior compression, the posterior
Capillary filling with pseudo-potential binary Lattice-Boltzmann model
S. Chibbaro
Physics , 2008, DOI: 10.1140/epje/i2008-10369-4
Abstract: We present a systematic study of capillary filling for a binary fluid by using a mesoscopic lattice Boltzmann model for immiscible fluids describing a diffusive interface moving at a given contact angle with respect to the walls. The phenomenological way to impose a given contact angle is analysed. Particular attention is given to the case of complete wetting, that is contact angle equal to zero. Numerical results yield quantitative agreement with the theoretical Washburn law, provided that the correct ratio of the dynamic viscosities between the two fluids is used. Finally, the presence of precursor films is experienced and it is shown that these films advance in time with a square-root law but with a different prefactor with respect to the bulk interface.
Fluctuations of entropy production in turbulent thermal convection
Francesco Zonta,Sergio Chibbaro
Physics , 2015,
Abstract: We report on a numerical experiment performed to analyze fluctuations of the entropy production in turbulent thermal convection, a physical configuration that represents here a prototypical case of an out-of-equilibrium dissipative system. We estimate the entropy production from instantaneous measurements of the local temperature and velocity fields sampled along the trajectory of a large number of point-wise Lagrangian tracers. The entropy production is characterized by large fluctuations and becomes often negative. This represents a sort of "finite-time" violation of the second principle of thermodynamics, since the direction of the energy flux is opposite to that prescribed by the external gradient. We clearly show that the fluctuations of entropy production observed in the present system verify the fluctuation relation (FR), even though the system is time-irreversible.
Elastic wave-turbulence and intermittency
Sergio Chibbaro,Christophe Josserand
Physics , 2015,
Abstract: Weak Wave Turbulence is a powerful theory to predict statistical observables of diverse relevant physical phenomena, such as ocean waves, magnetohydrodynamics and nonlinear optics. The theory is based upon an asymptotic closure permitted in the limit of small nonlinearity. Here, we explore the possible deviations from this mean-field framework, in terms of anomalous scaling, focusing on the case of elastic plates. We establish the picture of the possible behaviors at varying the extent of nonlinearity, and we show that the mean-field theory is appropriate when all excited scales remain dominated by linear dynamics. The other picture is non-trivial and our results suggest that, when large scales contain much energy, the cascade sustains extreme events at small scales and the system displays intermittency.
Revisiting a Celebrated Bakerian Lecture  [PDF]
Salvatore Ganci
Optics and Photonics Journal (OPJ) , 2019, DOI: 10.4236/opj.2019.94005
Abstract: This paper revisits the optical contributions of Thomas Young to the theory of diffraction and, in particular, some experiments presented in his celebrated “Bakerian Lecture” of 1803. The major input to re-analyze some of Young’s experiments came by a recent paper appeared on an instructional and pedagogical journal. Diffraction experiments of Thomas Young are here revisited with particular reference to the coherence requirements of the white light source to see and measure diffraction fringes by pins, and in general to consider the difficulties in working in a “camera obscura”. If at the beginning of the nineteenth century, the experiments of Optics in a darkroom were considered “simple”, however they needed rooms about 7 meters long, completely darkened out, with a window mostly exposed to south, a darkened window and a small hole practiced on a dark sheet applied to a hole in the window shutter. Often a heliostat should be placed outside and a mirror inside the room to direct the cone of sunlight. Thomas Young worked only with a mirror interior to the darkened room in order to have a cone of light horizontally directed and moving the mirror at each observation. Today, these requirements are not easy to implement. However, only a single measure by Thomas Young will be repeated under his own conditions with a “reduced darkroom” using internally blackened cardboard tubes.
A note on the consistency of Hybrid Eulerian/Lagrangian approach to multiphase flows
Sergio Chibbaro,Jean-Pierre Minier
Physics , 2009, DOI: 10.1016/j.ijmultiphaseflow.2010.10.010
Abstract: The aim of the present paper is to introduce and to discuss inconsistencies errors that may arise when Eulerian and Lagrangian models are coupled for the simulations of turbulent poly-dispersed two-phase flows. In these hydrid models, two turbulence models are in fact implicitely used at the same time and it is essential to check that they are consistent, in spite of their apparent different formulations. This issue appears in particular in the case of very-small particles, or tracer-limit particles, and it is shown that coupling inconsistent turbulence models (Eulerian and Lagrangian) can result in non-physical results, notably for second-order fluid velocity moments. This problem is illustrated by some computations for fluid particles in a turbulent channel flow using several coupling strategies.
Mesoscopic lattice Boltzmann modeling of flowing soft systems
Roberto Benzi,Sergio Chibbaro,Sauro Succi
Physics , 2008, DOI: 10.1103/PhysRevLett.102.026002
Abstract: A mesoscopic multi-component lattice Boltzmann model with short-range repulsion between different species and short/mid-ranged attractive/repulsive interactions between like-molecules is introduced. The interplay between these composite interactions gives rise to a rich configurational dynamics of the density field, exhibiting many features of disordered liquid dispersions (micro-emulsions) and soft-glassy materials, such as long-time relaxation due to caging effects, anomalous enhanced viscosity, ageing effects under moderate shear and flow above a critical shear rate.
PDF model based on Langevin equation for polydispersed two-phase flows applied to a bluff-body gas-solid flow,
J. P. Minier,E. Peirano,S. Chibbaro
Physics , 2010, DOI: 10.1063/1.1718972
Abstract: The aim of the paper is to discuss the main characteristics of a complete theoretical and numerical model for turbulent polydispersed two-phase flows, pointing out some specific issues. The theoretical details of the model have already been presented [Minier and Peirano, Physics Reports, Vol. 352/1-3, 2001 ]. Consequently, the present work is mainly focused on complementary aspects, that are often overlooked and that require particular attention. In particular, the following points are analysed : the necessity to add an extra term in the equation for the velocity of the fluid seen in the case of twoway coupling, the theoretical and numerical evaluations of particle averages and the fulfilment of the particle mass-continuity constraint. The theoretical model is developed within the PDF formalism. The important-physical choice of the state vector variables is first discussed and the model is then expressed as a stochastic differential equation (SDE) written in continuous time (Langevin equations) for the velocity of the fluid seen. The interests and limitations of Langevin equations, compared to the single-phase case, are reviewed. From the numerical point of view, the model corresponds to an hybrid Eulerian/Lagrangian approach where the fluid and particle phases are simulated by different methods. Important aspects of the Monte Carlo particle/mesh numerical method are emphasised. Finally, the complete model is validated and its performance is assessed by simulating a bluff-body case with an important recirculation zone and in which two-way coupling is noticeable.
The FDF or LES/PDF method for turbulent two-phase flows
Sergio Chibbaro,jean-Pierre Minier
Physics , 2011, DOI: 10.1088/1742-6596/318/4/042049
Abstract: In this paper, a new formalism for the filtered density function (FDF) approach is developed for the treatment of turbulent polydispersed two-phase flows in LES simulations. Contrary to the FDF used for turbulent reactive single-phase flows, the present formalislm is based on Lagrangian quantities and, in particular, on the Lagrangian filtered mass density function (LFMDF) as the central concept. This framework allows modeling and simulation of particle flows for LES to be set in a rigorous context and various links with other approaches to be made. In particular, the relation between LES for particle simulations of single-phase flows and Smoothed Particle Hydrodynamics (SPH) is put forward. Then, the discussion and derivation of possible subgrid stochastic models used for Lagrangian models in two-phase flows can set in a clear probabilistic equivalence with the corresponding LFMDF.
Langevin PDF simulation of particle deposition in a turbulent pipe flow
Sergio Chibbaro,Jean-Pierre Minier
Physics , 2008, DOI: 10.1016/j.jaerosci.2008.03.002
Abstract: The paper deals with the description of particle deposition on walls from a turbulent flow over a large range of particle diameter, using a Langevin PDF model. The first aim of the work is to test how the present Langevin model is able to describe this phenomenon and to outline the physical as- pects which play a major role in particle deposition. The general features and characteristics of the present stochastic model are first recalled. Then, results obtained with the standard form of the model are presented along with an analysis which has been carried out to check the sensitivity of the predictions on different mean fluid quantities. These results show that the physical repre- sentation of the near-wall physics has to be improved and that, in particular, one possible route is to introduce specific features related to the near-wall coherent structures. In the following, we propose a simple phenomenological model that introduces some of the effects due to the presence of turbulent coherent structures on particles in a thin layer close to the wall. The results obtained with this phenomenological model are in good agreement with experimental evidence and this suggests to pursue in that direction, towards the development of more general and rigorous stochastic models that provide a link between a geometrical description of turbulent flow and a statistical one.
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