MODELLING OF GEAR CHANGING BEHAVIOUR

This paper deals with the modelling of the gear changing behaviour. After presentation of the main synchronizer tasks, the state of the art is described. Reconsideration of the gear changing process allows better definition of synchronizer working phases. Based on this, a numerical simulation software of the synchronizer behaviour has been realized. Phenomena of angular velocity synchonization and second bump in gear changing force are modelled in details. Various mechanical behaviour influencing phenomena are taken into consideration with large number of input parameters. The software is validated with literature data. Then, it is used to investigate the effect of main parameters considered with gear changing process for a 5 speed manual car gearbox. Effects of gear changing force, synchronized inertia and initial angular velocity difference variations are shown. Visualization of parameter effects such as angle error of synchronizer cone and relative position of gear splines and sleeve splines help for better understanding of gearbox behaviour during gear changing

Assessment of Aging of the Human Skin by In Vivo Ultrasonic Imaging

The ultrasonic imaging technique that we have developed provides cross-sectional images of human skin in vivo with a resolution of about 80 μm axially (i.e., deep into the skin) and 250 μm lateral (parallel to the surface). In order to study aging skin, we obtained ultrasonic images from the mid-fore-arm (volar and dorsal sides) of 142 women. Ultrasonically, on the images, the dermis appears composed of two bands: a dark superficial one where the ultrasonic waves are propagated in a relatively homogeneous or non-echogenic medium, and a deeper one, which is lighter in color, suggesting a heterogeneous medium. Our results show that skin is thicker on the dorsal than on the volar forearm. In contrast to previously published results, skin thickness remains constant until the seventh decade of life, diminishing thereafter. The relative thicknesses of the two bands show marked variations with age: a progressive thickening of the dark band, from zero in infants to approximately 75% of total skin thickness in aged subjects, while the light band shows the inverse trend. Comparing the amplitude of the bands on the volar and dorsal forearm, the relative thickness of the dark band is larger on the dorsal (exposed) side and increases with age. These findings and the analysis of variously stained biopsies taken in some of our patients lead us to assign this dark band to a zone in the upper dermis where the collagen network is delicate, dense, and well organized. This is supported by some data in the literature. The thickness of this subepidermal non-echogenic band appears to be a far more sensitive marker of skin aging at the dermal level than is the measurement of skin thickness

La osmoregulación como factor potencial de la distribución diferencial de dos especies crípticas de góbido, Pomatoschistus microps y P. marmoratus, en las lagunas mediterráneas francesas

This study was aimed at the detection of potential differences in the osmoregulatory capacity of two cryptic species of gobies, Pomatoschistus microps (Krøyer, 1838) and P. marmoratus (Risso, 1810), that have different distributions in French Mediterranean lagoons characterised by different salinity regimes. Specimens of both species were experimentally exposed to different salinities, their salinity tolerance was evaluated and their blood osmolality was measured. Both species are strong osmoregulators over a wide range of salinities but P. microps showed higher performances of hyper-regulation at very low salinities (10 and 40 mosm/kg, i.e. freshwater 0.3 and 1.4) and of hypo-regulation at high salinities (1500 mosm/kg, 51). Only P. microps was able to tolerate freshwater exposure over 4 days. We conclude that the high osmoregulatory capacity found in P. microps is linked to its better survival at very low salinities and is a physiological requirement for living in areas such as the Mauguio lagoon where salinity is highly variable. In contrast, as osmoregulation of P. marmoratus is less efficient at extreme salinities, this species cannot colonise such environments and is restricted to habitats where salinity is more stable, such as the Thau lagoon.Este estudio tuvo por objeto la detección de diferencias potenciales en la capacidad osmorreguladora de dos especies crípticas de góbido, Pomatoschistus microps (Krøyer, 1838) y P. marmoratus (Risso, 1810), que presentan diferentes áreas de distribución en lagunas mediterráneas francesas caracterizadas por regímenes de salinidad distintos. Especímenes de ambas especies fueron expuestos experimentalmente a diferentes salinidades, evaluándose su tolerancia a la salinidad y midiéndose su osmolalidad sanguínea. Ambas especies tienen una amplia capacidad osmoreguladora en un amplio rango de salinidades. Sin embargo, en comparación con P. marmoratus, P. microps mostró mayores rendimientos hiper-regulatorios a salinidades muy bajas (10 y 40 mosm/kg, es decir agua dulce 0.3 y 1.4) e hipo-regulatorios a salinidades altas (1500 mosm/kg, 51). Sólo P. microps fue capaz de tolerar la exposición al agua dulce durante 4 días. Podemos concluir que la gran capacidad osmoreguladora encontrada en P. microps está ligada a su mayor supervivencia a salinidades muy bajas, siendo un requerimiento fisiológico para vivir en áreas tales como la laguna de Mauguio, donde la salinidad es muy variable. Por el contrario, puesto que la osmoregulación de P. marmoratus es menos eficiente en salinidades extremas, esta especie no puede colonizar tales ambientes y se ve restringida a hábitats donde la salinidad es más estable, como la laguna de Tha

SIV(SM)/HIV-2 Vpx proteins promote retroviral escape from a proteasome-dependent restriction pathway present in human dendritic cells

BACKGROUND: Vpx is a non-structural protein coded by members of the SIV(SM)/HIV-2 lineage that is believed to have originated by duplication of the common vpr gene present in primate lentiviruses. Vpx is incorporated into virion particles and is thus present during the early steps of viral infection, where it is thought to drive nuclear import of viral nucleoprotein complexes. We have previously shown that Vpx is required for SIV(MAC)-derived lentiviral vectors (LVs) infection of human monocyte-derived dendritic cells (DCs). However, since the requirement for Vpx is specific for DCs and not for other non-dividing cell types, this suggests that Vpx may play a role other than nuclear import. RESULTS: Here, we show that the function of Vpx in the infection of DCs is conserved exclusively within the SIV(SM)/HIV-2 lineage. At a molecular level, Vpx acts by promoting the accumulation of full length viral DNA. Furthermore, when supplied in target cells prior to infection, Vpx exerts a similar effect following infection of DCs with retroviruses as divergent as primate and feline lentiviruses and gammaretroviruses. Lastly, the effect of Vpx overlaps with that of the proteasome inhibitor MG132 in DCs. CONCLUSION: Overall, our results support the notion that Vpx modifies the intracellular milieu of target DCs to facilitate lentiviral infection. The data suggest that this is achieved by promoting viral escape from a proteasome-dependent pathway especially detrimental to viral infection in DCs

Systèmes de surveillance automatique en usinage : moyens et méthodes

Les exigences industrielles et économiques actuelles conduisent les entreprises manufacturières à surveiller, d’une manière fiable et précise, les conditions de réalisation et/ou de fabrication des produits et essentiellement celles liées à l’obtention des pièces par enlèvement de matière. Des systèmes de surveillance automatique d’usinage se révèlent indispensables au bon fonctionnement et à la sécurité du processus de fabrication. Ces derniers favorisent une meilleure qualité des pièces et une productivité optimale. Ce processus de surveillance (de monitoring) s’appuie sur le traitement d’un signal acquis en temps réel lors de la fabrication. Ce signal est basé sur des critères scientifiques qui garantissent une efficacité maximale des informations enregistrées. Dans ce contexte, la présente contribution se propose de présenter une revue des différents résultats issus des travaux expérimentaux portant sur ces systèmes de monitoring. Une première partie de cette communication aura pour objet la présentation des méthodes employées dans la surveillance automatique de la production par usinage des métaux. Plus spécifiquement, nous aborderons les différentes approches de diagnostic à la base des modèles développés par la communauté scientifique. Notre intérêt portera sur l’étude des diagnostics des systèmes industriels et sur les objectifs scientifiques et industriels traitant le système de surveillance afin de détecter précocement toute déviation de comportement de la machine ou de l’outil. Une deuxième partie de cette communication sera consacrée à la mise en situation d’un projet de recherche en cours. Ce projet que nous entreprenons vise la conception et la modélisation d’un système de diagnostic en temps réel de l’usure des outils de coupe en tournage. Ce système envisagé suite à un travail expérimental vise l’évaluation ainsi que la prévention de ces défaillances lors d’une opération de fabrication

1,3 Dioxolane versus tetrahydrofuran as promoters for CO 2 -hydrate formation: Thermodynamics properties, and kinetics in presence of sodium dodecyl sulfate

This paper makes a comparison between tetrahydrofuran (THF) and 1,3 dioxolane (DIOX) in terms of their respective performances as promoters for the formation of clathrate hydrates with CO2. The aim is to find products that can be substituted for THF, which is known to be harmful and difficult to handle. Drawing on a review of the chemical and physical properties of these two organic compounds, experiments were performed using high-pressure differential scanning calorimetry (DSC) and a batch reactor. Details of the thermodynamic equilibria of mixed THF+CO2 and DIOX+CO2 hydrates obtained with various additive concentrations are provided, along with hydrate kinetics data relating to the hydrate formation. The effect of the presence of an anionic surfactant, SDS (sodium dodecyl sulfate), on hydrate formation kinetics was also evaluated, showing that a combination of THF or DIOX and SDS is a very advantageous solution for accelerating hydrate formation. THF has been found to outperform DIOX as a hydrate promoter from both a thermodynamic, and a kinetic standpoint in presence of SDS. However, DIOX remains an interesting practical solution, due to the benefits offered as the least toxic and aggressive of these two organic compounds

Response surface methodology to optimise Accelerated Solvent Extraction of steviol glycosides from Stevia rebaudiana Bertoni leaves

Following the approval of steviol glycosides as a food additive in Europe in December 2011, large-scale stevia cultivation will have to be developed within the EU. Thus there is a need to increase the efficiency of stevia evaluation through germplasm enhancement and agronomic improvement programs. To address the need for faster and reproducible sample throughput, conditions for automated extraction of dried stevia leaves using Accelerated Solvent Extraction were optimised. A response surface methodology was used to investigate the influence of three factors: extraction temperature, static time and cycle number on the stevioside and rebaudioside A extraction yields. The model showed that all the factors had an individual influence on the yield. Optimum extraction conditions were set at 100°C, 4min and 1 cycle, which yielded 91.8%±3.4% of total extractable steviol glycosides analysed. An additional optimisation was achieved by reducing the grind size of the leaves giving a final yield of 100.8%±3.3%

Full field modeling of recrystallization and grain growth thanks to a level set approach: towards modeling by industry

International audienceMetal forming modeling can be predictive only if the strain rate, strain and temperature dependency of the flow behaviour are correctly described. The mechanical properties and behaviour of metallic materials mainly depends on the content and structure of dislocation network, this points out the need to incorporate microstructure concepts into the numerical models. The goal is to correctly describe the main physical mechanisms occurring in metals during thermomechanical processes i.e. work-hardening, recovery, grain boundary migration, nucleation and grain growth related to dynamic, static or metadynamic recrystallization. Macroscopic and homogenized models are widely used in the industry, mainly due to their low computational cost. If this mean field framework is quite convenient, it can be synonymous, for a given material, with a large amount of experiments with advanced laboratory devices. Moreover, the homogenization of the microstructure does not permit to capture some very local phenomena

Original Surgical Treatment and Long-term Follow-up for Chronic Inflammatory Demyelinating Polyradiculoneuropathy Causing a Compressive Cervical Myelopathy: Review of the Literature

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a chronic relapsing disease of unknown aetiology. The diagnosis of this disease is still very complicated. The treatment is medical but, in some cases, a surgical decompression might be required. In rare cases it develops a radicular hypertrophy that can cause a cervical myelopathy; this pathology should be put in differential diagnosis with neurofibromatosis 1 and Charcot-Marie-Tooth (CMT) syndromes. The cases of CIDP cervical myelopathy reported in the literature are rare and even more rarely a surgical decompression was described. Here we report a first and unique case of CIDP cervical myelopathy treated with an open-door laminoplasty technique with 10-year postoperative follow-up (FU). The surgical decompression revealed to be effective in stopping the progression of myelopathy without destabilizing the spine. The patient that before surgery presented a severe tetraparesis could return to walk and gain back his self-care autonomy. At 10-year FU he did not complain of neck pain and did not develop a cervical kyphosis. In case of cervical myelopathy caused by radicular hypertrophy, CIDP should be kept in mind in the differential diagnosis and an open-door laminoplasty is indicated to stop myelopathy progression