Synthèse dynamique d'un mouvement gymnique aérien

Une technique de simulation numérique de gestes aériens est présentée. La méthode développée repose sur la formulation d'un problème d'optimisation dynamique transformé en un problème d'optimisation paramétrique en vue de sa résolution. Elle ne nécessite aucune donnée définie au cours du temps. Le critère à minimiser porte sur les efforts moteurs articulaires. Les contraintes caractéristiques du mouvement sont traitées par pénalisation, ce qui permet de les satisfaire avec précision. La méthode proposée est appliquée à la synthèse d'un salto arrière. Les résultas obtenus montrent que des sauts parfaitement carpés ou groupés apparaissent spontanément selon le potentiel de rotation du mouvement

Comparison of total ankle replacement and ankle arthrodesis in patients with haemophilia using gait analysis : two case reports

BACKGROUND: Severe hemophilia is an inherited, lifelong bleeding disorder characterized by spontaneous bleeding, which results in painful joint deformities. Currently two surgical treatments are available to treat haemophilia-related ankle joint destruction: ankle arthrodesis and total ankle replacement. The aim of the present study was to compare these two surgical procedures in haemophiliac subjects. CASE PRESENTATION: Kinematic and dynamic parameters were quantified using a three-dimensional gait-analysis system in two similar clinical cases. In Caucasian case 1, ankle arthrodesis was chosen because of a kinematic ankle flexion defect and lack of dynamic power regeneration. The defect in energy absorption was compensated for by the contralateral side. Total ankle replacement in Caucasian case 2 allowed sparing the ipsilateral knee (maximum 0.27 preoperatively vs. 0.71 W/kg postoperatively) and hip joints powers (maximum 0.43 preoperatively vs. 1.25 W/kg postoperatively) because of the small ankle dorsiflexion motion. CONCLUSIONS: Total ankle replacement is recommended for haemophiliac patients who present with a preserved ankle range of motion

Estimation of muscle activation during different walking speeds with two mathematical approaches compared to surface EMG

Background Muscle force estimation could improve clinical gait analysis by enhancing insight into causes of impairments and informing targeted treatments. However, it is not currently standard practice to use muscle force models to augment clinical gait analysis, partly, because robust validations of estimated muscle activations, underpinning force modelling processes, against recorded electromyography (EMG) are lacking. Research Question Therefore, in order to facilitate future clinical use, this study sought to validate estimated lower limb muscle activation using two mathematical models (static optimisation SO, computed muscle control CMC) against recorded muscle activations of ten healthy participants. Methods Participants walked at five speeds. Visual agreement in activation onset and offset as well as linear correlation (r) and mean absolute error (MAE) between models and EMG were evaluated. Results MAE between measured and recorded activations were variable across speeds (SO vs EMG 15–68%, CMC vs EMG 13–69%). Slower speeds resulted in smaller deviations (mean MAE < 30%) than faster speeds. Correlation was high (r > 0.5) for only 11/40 (CMC) and 6/40 (SO) conditions (muscles X speeds) compared to EMG. Significance Modelling approaches do not yet show sufficient consistency of agreement between estimated and recorded muscle activation to support recommending immediate clinical adoption of muscle force modelling. This may be because assumptions underlying muscle activation estimations (e.g. muscles’ anatomy and maximum voluntary contraction) are not yet sufficiently individualizable. Future research needs to find timely and cost efficient ways to scale musculoskeletal models for better individualisation to facilitate future clinical implementation

Validity and reliability of 3D marker based scapular motion analysis : a systematic review

Methods based on cutaneous markers are the most popular for the recording of three dimensional scapular motion analysis. Numerous methods have been evaluated, each showing different levels of accuracy and reliability. The aim of this review was to report the metrological properties of 3D scapular kinematic measurements using cutaneous markers and to make recommendations based on metrological evidence. A database search was conducted using relevant keywords and inclusion/exclusion criteria in 5 databases. 19 articles were included and assessed using a quality score. Concurrent validity and reliability were analyzed for each method. Six different methods are reported in the literature, each based on different marker locations and post collection computations. The acromion marker cluster (AMC) method coupled with a calibration of the scapula with the arm at rest is the most studied method. Below 90–100° of humeral elevation, this method is accurate to about 5° during arm flexion and 7° during arm abduction compared to palpation (average of the 3 scapular rotation errors). Good to excellent within-session reliability and moderate to excellent between-session reliability have been reported. The AMC method can be improved using different or multiple calibrations. Other methods using different marker locations or more markers on the scapula blade have been described but are less accurate than AMC methods. Based on current metrological evidence we would recommend (1) the use of an AMC located at the junction of the scapular spine and the acromion, (2) the use of a single calibration at rest if the task does not reach 90° of humeral elevation, (3) the use of a second calibration (at 90° or 120° of humeral elevation), or multiple calibrations above 90° of humeral elevation

Muscle activation during gait in children with Duchenne muscular dystrophy

The aim of this prospective study was to investigate changes in muscle activity during gait in children with Duchenne muscular Dystrophy (DMD). Dynamic surface electromyography recordings (EMGs) of 16 children with DMD and pathological gait were compared with those of 15 control children. The activity of the rectus femoris (RF), vastus lateralis (VL), medial hamstrings (HS), tibialis anterior (TA) and gastrocnemius soleus (GAS) muscles was recorded and analysed quantitatively and qualitatively. The overall muscle activity in the children with DMD was significantly different from that of the control group. Percentage activation amplitudes of RF, HS and TA were greater throughout the gait cycle in the children with DMD and the timing of GAS activity differed from the control children. Significantly greater muscle coactivation was found in the children with DMD. There were no significant differences between sides. Since the motor command is normal in DMD, the hyper-activity and co-contractions likely compensate for gait instability and muscle weakness, however may have negative consequences on the muscles and may increase the energy cost of gait. Simple rehabilitative strategies such as targeted physical therapies may improve stability and thus the pattern of muscle activity

BCL-2 Inhibitor ABT-737 effectively targets leukemia-initiating cells with differential regulation of relevant genes leading to extended survival in a NRAS/BCL-2 mouse model of high risk-myelodysplastic syndrome

During transformation, myelodysplastic syndromes (MDS) are characterized by reducing apoptosis of bone marrow (BM) precursors. Mouse models of high risk (HR)-MDS and acute myelogenous leukemia (AML) post-MDS using mutant NRAS and overexpression of human BCL-2, known to be poor prognostic indicators of the human diseases, were created. We have reported the efficacy of the BCL-2 inhibitor, ABT-737, on the AML post-MDS model; here, we report that this BCL-2 inhibitor also significantly extended survival of the HR-MDS mouse model, with reductions of BM blasts and lineage negative/Sca1+/KIT+ (LSK) cells. Secondary transplants showed increased survival in treated compared to untreated mice. Unlike the AML model, BCL-2 expression and RAS activity decreased following treatment and the RAS:BCL-2 complex remained in the plasma membrane. Exon-specific gene expression profiling (GEP) of HR-MDS mice showed 1952 differentially regulated genes upon treatment, including genes important for the regulation of stem cells, differentiation, proliferation, oxidative phosphorylation, mitochondrial function, and apoptosis; relevant in human disease. Spliceosome genes, found to be abnormal in MDS patients and downregulated in our HR-MDS model, such as Rsrc1 and Wbp4, were upregulated by the treatment, as were genes involved in epigenetic regulation, such as DNMT3A and B, upregulated upon disease progression and downregulated upon treatment

Les théologies de la mort de Dieu

Depuis quelques années, des théologiens protestants ont consacré leurs efforts au difficile problème de la rencontre du christianisme et d'une culture moderne séculariste. Certains ont adopté une position radicale : élaborer un christianisme athée, centré exclusivement sur l'homme Jésus de Nazareth, sans référence à Dieu. L'A. analyse la pensée de trois de ces théologiens de la mort de Dieu : W. Hamilton, T. Altizer, P. van Buren.Leboeuf Fabien. Les théologies de la mort de Dieu. In: Revue des Sciences Religieuses, tome 41, fascicule 2, 1967. pp. 129-149

Modélisation des interactions instationnaires rotor-stator en turbomachine multi-étages

L'écoulement au sein des turbomachines multi-étages est assujetti à des phénomènes instationnaires de natures aléatoires et déterministes. On distingue en effet d'une part la turbulence, représentative du comportement stochastique du fluide, et d'autre part les interactions instationnaires entre les roues aubées, provoquées par la rotation de la machine. Ces interactions impliquent les sillages des aubages, les ondes de choc, et influent sur le blocage aérodynamique ou encore les transferts thermiques. Les interactions entre les rotors et les stators sont caractérisées par des échelles de temps allant de la période de rotation de la machine à plusieurs fois la plus haute fréquence de passage des aubages. Les échelles de longueur sont également diverses, variant de la circonférence de la machine à la fraction de la corde d'une aube. Toutes ces échelles de longueur et de temps s'ajoutent à celles de la turbulence. La simulation numérique des écoulements en turbomachine nécessite donc de poser plusieurs hypothèses de simplification. Pour la turbulence, les modèles de turbulence satisfaisant l'hypothèse de BOUSSINESQ sont largement employés dans l'industrie, alors que les interactions instationnaires sont souvent négligées. John. J. ADAMCZYK (réf [85-ADA]) a créé le "Système d'Equations du Canal Moyenne" (SECM) permettant de modéliser les interactions instationnaires déterministes dans le cadre d'écoulements stationnaires. Les instationnarités sont prises en compte par l'intermédiaire de corrélations déterministes à modéliser. Des modèles pour les corrélations déterministes ont été développés par ADAMCZYK et al. (réf [86-ADA] et [89-ADA]), RHIE et al. (réf [89-ADA]), HALL (réf [97-HA2]), KIRTLEY (réf [99-KIR]) et BUSBY et al. (réf [99-BUS]). Ce travail de thèse a d'abord consisté en l'analyse du SECM et des modèles de fermeture de la littérature qui lui sont associés. Un modèle, représentatif de la majorité de ces derniers, a été implanté dans un code de calcul multi-étages stationnaire industriel (CANARI-COMET développé par l'ONERA, SNECMA-Moteurs, et TURBOMECA). Pour valider celui-ci, une simulation instationnaire d'un étage de turbine transsonique (VEGA2 de l'ONERA) est analysée. Cette analyse porte tout d'abord sur les phénomènes instationnaires présents dans l'écoulement. Des instationnarités provoquant des mélanges radiaux aux répercutions stationnaires importantes sont identifiées. La moyenne temporelle de la simulation instationnaire et le résultat obtenu avec le modèle de CANARI-COMET sont ensuite comparés. Il en ressort que le modèle présente d'importantes déficiences. Une analyse complète des corrélations déterministes est réalisée à partir du résultat instationnaire et permet de confirmer la précédente conclusion. Il est établi que les défauts du modèle implanté dans CANARI-COMET sont liés à une hypothèse de base commune avec la plupart des modèles. Ceci ouvre des perspectives et des axes de recherche pour la modélisation des corrélations déterministes destinées à fermer le SECM. Ce dernier est étudié d'un point de vue de l'analyse des résultats qui en découlent. Il est montré que la procédure de moyenne ne permet pas de respecter un certain nombre de principes de la thermodynamique et que ceci doit être pris en compte.LYON-Ecole Centrale (690812301) / SudocSudocFranceF