463 research outputs found
Guillain-Barré syndrome as an atypical manifestation of an esophageal carcinoma
Guillain-Barré syndrome (GBS) is an acute demyelinating polyradiculoneuropathy normally associated with a preceding infection, but sometimes it can be linked to a subjacent malignancy. We report an unusual case of GBS occurring as the first clinical manifestation of an esophageal adenocarcinoma in a 65-year-old patient. A GBS neuropathy of undetermined origin may be associated with an underlying tumor and esophageal cancer has to be considered in the differential diagnosi
Colloidal behavior of aqueous montmorillonite suspensions in the presence of non-ionic polymer
In this paper we characterized at first, the rheological behavior of the bentonite suspensions and the aqueous solutions of polyethylene oxide (PEO), then we were investigated the influence of this polymer in a water-based drilling fluid model (6% of bentonite suspension). The objective is to exhibit how the non ionic polymer with molecular weight 6×103 g/mol. of varying concentration mass (0.7%, 1%, 2% et 3%) significantly alter the rheological properties (yield stress, viscosity, loss and elastic modulus) of the bentonite suspensions. The rheological measurements made in simple shear and in dynamic on the mixture (water-bentonite-PEO), showed rheological properties of bentonite suspensions both in the presence and absence of non-ionic polymer. The PEO presents an affinity for the bentonite particles slowing down their kinetic aggregation. The analysis by X-rays diffraction also allowed understanding the structure of this mixture. It had revealed the intercalation between of the clay platelets on one hand, and the links bridges assured by the chains of polymer between bentonite particles beyond a critical concentration in PEO on the other hand. The Herschel- Bulkley rheological model is used for the correlation of our experimental result
Numerical Simulation of the Mechanical Response of the Tunnels in the Saturated Soils by Plaxis
The forecast of settlement and movements caused by tunneling represents a significant challenge of technology. The evaluation of these movements is indeed of primary importance in order to prevent them. The methods of calculation making it possible to evaluate displacements and deformations in the ground due to tunneling give only one approximation of the true amplitudes of the movements in the ground. It is one of the assets of the Finite Element Method (FEM) which makes it possible a priori to treat configurations more complex and closer to reality. Our objective in this study is to calculate numerically the various movements caused by the construction of a shallow tunnel using a shield using PLAXIS 2D, the behavior of the ground is described by a perfectly plastic elastic model based on the criterion of Mohr-Coulomb. A comparison between the various methods: empirical, analytical and numerical in terms of settlement on the surface was carried out. The validation of these results was made by using results drawn from literature. We have also carried out a parametric study in order to analyze the influence of various geometrical and geotechnical parameters on the behavior of grounds due to tunneling. Lastly, we have treated the same example by supposing the existence of structures near the tunnel in order to see the influence of the presence of other structures on the profile of the settlements caused by tunneling. Results of our work agreed with those in literature
Numerical Approach of the Littoral Instability of Chalk Cliffs: Case of Grandes Dalles (The Large Flagstones)
The various situations representing coastal cliffs of Haute Normandy are tested on numerical models. The parameters taken into account are: the lithology of chalks and the presence or absence of fractures. It is a question of specifying the mechanical characteristics of chalk and the inside of the fractures. The chalk cliff of 80m height, with a vertical cliff face, is modeled in distinct elements in UDEC code. We consider initially the cliff with two layers, in dry and then in saturated state. Then, the cliff is taken with two layers; the chalk of Seaford constitutes the upper layer and the chalk of Lewes constitutes the lower layer, by introducing a fracture with a strong slope passing in the foot of the cliff and another time a fracture parallel with the cliff face
Inventory and world geographical distribution of the olive tree (Olea europaea L.) diseases caused by viruses, bacteria and phytoplasma
The objective of this work is to prepare an Inventory about the viral and bacterial diseases of the olive tree (Olea europaea L.) and to study their Geographical distribution in the world. Fifteen viruses were considered as pathogens on the olive tree, these viruses were reported in 22 countries in five continents showing different symptoms on different olive tree varieties. All viruses were reported in Italy, some of these viruses were found only in the Eurepean continent, such as Olive vein yellows associated virus (OVYaV), Olive yellow mottling and decline associated virus (OYMDaV), Olive mild mosaic virus (OMMV) and Olive semilatent virus (OSLV). Two bacteria were reported as pathogen on the olive tree; Pseudomonas savastanoi. pv. savastanoi responsible bacteria of thr olive knot; a serious disease of olive (Olea europaea L.) in the Mediterranean region. This bacteria was detected in 22 countries in five continents, the majority of these countries exist in the Mediterranean Basin. Another bacteria was Xylella fastidiosa responsible of the quick decline syndrome of olive (OQDS), was deteted in Europe in four countries (Italy, Spain, Portugal and Slovenia) and in America in three countries (USA, Argentina and Brazil). Phtoplasmas was reported in 5 countries in three continents (Europe, Asia and Australia)
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