Rare causes of scoliosis and spine deformity: experience and particular features

<p>Abstract</p> <p>Background</p> <p>Spine deformity can be idiopathic (more than 80% of cases), neuromuscular, congenital or neurofibromatosis-related. However, there are many disorders that may also be involved. We present our experience treating patients with scoliosis or other spine deformities related to rare clinical entities.</p> <p>Methods</p> <p>A retrospective study of the records of a school-screening study in North-West Greece was performed, covering a 10-year period (1992–2002). The records were searched for patients with deformities related to rare disorders. These patients were reviewed as regards to characteristics of underlying disorder and spine deformity, treatment and results, complications, intraoperative and anaesthesiologic difficulties particular to each case.</p> <p>Results</p> <p>In 13 cases, the spine deformity presented in relation to rare disorders. The underlying disorder was rare neurological disease in 2 cases (Rett syndrome, progressive hemidystonia), muscular disorders (facioscapulohumeral muscular dystrophy, arthrogryposis) in 2 patients, osteogenesis imperfecta in 2 cases, Marfan syndrome, osteopetrosis tarda, spondyloepiphyseal dysplasia congenita, cleidocranial dysplasia and Noonan syndrome in 1 case each. In 2 cases scoliosis was related to other congenital anomalies (phocomelia, blindness). Nine of these patients were surgically treated. Surgery was avoided in 3 patients.</p> <p>Conclusion</p> <p>This study illustrates the fact that different disorders are related with curves with different characteristics, different accompanying problems and possible complications. Investigation and understanding of the underlying pathology is an essential part of the clinical evaluation and preoperative work-up, as clinical experience at any specific center is limited.</p

Heterogeneous nucleation and growth of calcium carbonate on calcite and quartz

The precipitation of calcium carbonate as a binding salt for the consolidation of loose sand formations is a promising approach. The heterogeneous nucleation and growth of calcite were investigated in supersaturated solutions. The ionic activities in the solutions tested were selected so that they included both supersaturations in which crystal growth took place only following the introduction of seed particles and supersaturations in which precipitation occurred spontaneously past the lapse of induction times. In the latter case the supersaturation conditions were sufficiently low to allow the measurement of induction times preceding the onset of precipitation. The stability domain of the calcium carbonate system was established at pH 8.50, 25 °C, measuring the induction times in the range between 30 min and 2 h. The rates of precipitation following the destabilization of the solutions were measured from the pH and/or concentration–time profiles. The induction times were inversely proportional and rates proportional to the solution supersaturation as expected. The high-order dependence of the rates of precipitation on the solution supersaturation suggested a polynuclear growth mechanism. Fitting of the induction time–supersaturation data according to this model yielded a value of 64 mJ/m2 for the surface energy of the calcite nucleus. In the concentration domain corresponding to stable supersaturated solutions, seeded growth experiments at constant supersaturation showed a second-order dependence on the rates of crystal growth of calcite seed crystals. Inoculation of the stable supersaturated solutions with quartz seed crystals failed to induce nucleation. Raising supersaturation to reach the unstable domain showed interesting features: calcite seed crystals yielded crystal growth kinetics compatible with the polynuclear growth model, without any induction time. The presence of quartz seed crystals reduced the induction times and resulted in nucleation in the bulk solution. The kinetic data in the latter case were consistent with the polynuclear growth model and the surface energy for the newly forming embryo was calculated equal to 31.1 mJ/m2, because of the dominantly heterogeneous nature of the process

Characterization, Reconstruction and Transport Properties of Vosges Sandstones Caractérisation, reconstruction et propriétés de transport des grès des Vosges

A thorough study of Vosges sandstone samples is presented in this work. First, the geometry of these porous media is analyzed using serial thin sections. Then, random numerical samples are reconstructed according to the measured statistical geometrical parameters. Finally, the macroscopic transport properties are determined from the numerical solutions in the reconstructed samples of the local equations governing the corresponding transport phenomena and compared to available experimental data. Mercury intrusion in the simulated media is modelled and pore size distribution results are compared with those obtained from serial tomography. Dans cet article, nous présentons une étude approfondie d'échantillons de grès des Vosges. La géométrie de ces milieux est analysée en utilisant des coupes sériées. Puis des échantillons aléatoires sont reconstruits en accord avec les propriétés géométriques statistiques mesurées. Enfin, les propriétés macroscopiques de transport sont déduites des solutions numériques dans les échantillons reconstruits des équations locales qui régissent les transports correspondants, et elles sont comparées aux mesures disponibles. La pénétration de mercure dans les échantillons est modélisée et les résultats relatifs aux distributions de pores sont comparés à ceux obtenus sur les coupes sériées

Characterization, Reconstruction and Transport Properties of Vosges Sandstones

International audienceA thorough study of Vosges sandstone samples is presented in this work. First, the geometry of these porous media is analyzed using serial thin sections. Then, random numerical samples are reconstructed according to the measured statistical geometrical parameters. Finally, the macroscopic transport properties are determined from the numerical solutions in the reconstructed samples of the local equations governing the corresponding transport phenomena and compared to available experimental data. Mercury intrusion in the simulated media is modelled and pore size distribution results are compared with those obtained from serial tomography