Understanding crack versus cavitation in pressure-sensitive adhesives: the role of kinetics

We perform traction experiments on viscous liquids highly confined between parallel plates, a geometry known as the probe-tack test in the adhesion community. Direct observation during the experiment coupled to force measurement shows the existence of several mechanisms for releasing the stress. Bubble nucleation and instantaneous growth had been observed in a previous work. Upon increasing further the traction velocity or the viscosity, the bubble growth is progressively delayed. At high velocities, cracks at the interface between the plate and the liquid appear before the bubbles have grown to their full size. Bubbles and cracks are thus observed concomitantly. At even higher velocities, cracks develop fully so early that the bubbles are not even visible. We present a theoretical model that describes these regimes, using a Maxwell fluid as a model for the actual fluid, a highly viscous silicon oil. We present the resulting phase diagramme for the different force peak regimes. The predictions are compatible with the data. Our results show that in addition to cavitation, interfacial cracks are encountered in a probe-tack traction test with viscoelastic, \emph{liquid} materials and not solely with viscoelastic solids like adhesives.Comment: 44 page

Complications en périnatalité chez les femmes enceintes atteintes de schizophrénie

Les données issues de la littérature nous montrent que le lien entre schizophrénie et complications en périnatalité peut se faire via de multiples facteurs : addictions, comorbidités, dé favorisation sociale, traitements médicamenteux … Dans cette étude populationnelle sur les bases de données d’hospitalisation en France entre 2015 et 2019, nous avons donc étudié l’association entre schizophrénie chez la mère, et complications pendant la grossesse, à l’accouchement et chez le nouveau-né, en appariant sur ces facteurs potentiellement vecteurs de confusion. Sur une population d’analyse appariée de 2875 accouchements de mères schizophrènes et 11 439 accouchements contrôles (population initiale d’étude de 3 667 461 accouchements uniques), nous avons retrouvé une augmentation du risque de complication pendant la grossesse et chez le nouveau-né dans le groupe schizophrène. En particulier, les femmes issues de ce groupe étaient plus à risque de diabète gestationnel, hypertension gravidique, thrombose, infection génito-urinaire, mort fœtale, menace d’accouchement prématuré, et accouchement par césarienne, et leurs nouveaux nés étaient de plus faible âge gestationnel et poids de naissance.Malgré un nombre de sujets important et un appariement sur de nombreux facteurs, les résultats de cette étude sont à interpréter avec prudence, du fait de l’imprécision des données due au manque d’exhaustivité et de précision du codage, ainsi que l’impossibilité de prendre en compte les traitements médicamenteux reçus par les patientes pendant la grossesse

Aureto e Aurasso (zéphirs et aquilons) : les beaux jours de la navigation de plaisance à Marseille : 1846-1914 / par Alphonse Cyprien Fabre,...

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Cavitation-induced force transition in confined viscous liquids under traction

We perform traction experiments on simple liquids highly confined between parallel plates. At small separation rates, we observe a simple response corresponding to a convergent Poiseuille flow. Dramatic changes in the force response occur at high separation rates, with the appearance of a force plateau followed by an abrupt drop. By direct observation in the course of the experiment, we show that cavitation accounts for these features which are reminiscent of the utmost complex behavior of adhesive films under traction. Surprisingly enough, this is observed here in purely viscous fluids

Texture Parameters Measured by UHF-MRI and CT Scan Provide Information on Bone Quality in Addition to BMD: A Biomechanical Ex Vivo Study

The current definition of osteoporosis includes alteration of bone quality. The assessment of bone quality is improved by the development of new texture analysis softwares. Our objectives were to assess if proximal femoral trabecular bone texture measured in Ultra high field (UHF) 7 Tesla MRI and CT scan were related to biomechanical parameters, and if the combination of texture parameters and areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry provided a better prediction of femoral failure than aBMD alone. The aBMD of 16 proximal femur ends from eight cadavers were investigated. Nineteen textural parameters were computed in three regions or volumes of interest for each specimen on UHF MRI and CT scan. Then, the corresponding failure load and failure stress were calculated thanks to mechanical compression test. aBMD was not correlated to failure load (R-2 = 0.206) and stress (R-2 = 0.153). The failure load was significantly correlated with ten parameters in the greater trochanter using UHF MRI, and with one parameter in the neck and the greater trochanter using CT scan. Eight parameters in the greater trochanter using UHF MRI combined with aBMD improved the failure load prediction, and seven parameters improved the failure stress prediction. Our results suggest that textural parameters provide additional information on the fracture risk of the proximal femur when aBMD is not contributive

Texture Parameters Measured by UHF-MRI and CT Scan Provide Information on Bone Quality in Addition to BMD: A Biomechanical Ex Vivo Study

The current definition of osteoporosis includes alteration of bone quality. The assessment of bone quality is improved by the development of new texture analysis softwares. Our objectives were to assess if proximal femoral trabecular bone texture measured in Ultra high field (UHF) 7 Tesla MRI and CT scan were related to biomechanical parameters, and if the combination of texture parameters and areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry provided a better prediction of femoral failure than aBMD alone. The aBMD of 16 proximal femur ends from eight cadavers were investigated. Nineteen textural parameters were computed in three regions or volumes of interest for each specimen on UHF MRI and CT scan. Then, the corresponding failure load and failure stress were calculated thanks to mechanical compression test. aBMD was not correlated to failure load (R-2 = 0.206) and stress (R-2 = 0.153). The failure load was significantly correlated with ten parameters in the greater trochanter using UHF MRI, and with one parameter in the neck and the greater trochanter using CT scan. Eight parameters in the greater trochanter using UHF MRI combined with aBMD improved the failure load prediction, and seven parameters improved the failure stress prediction. Our results suggest that textural parameters provide additional information on the fracture risk of the proximal femur when aBMD is not contributive

Prognostic value of forward flow indices in primary mitral regurgitation due to mitral valve prolapse

Degenerative mitral regurgitation (DMR) due to mitral valve prolapse (MVP) is a common valve disease associated with significant morbidity and mortality. Timing for surgery is debated for asymptomatic patients without Class I indication, prompting the search for novel parameters of early left ventricular (LV) systolic dysfunction. Aims To evaluate the prognostic impact of preoperative forward flow indices on the occurrence of post-operative LV systolic dysfunction. Methods We retrospectively included all consecutive patients with severe DMR due to MVP who underwent mitral valve repair between 2014 and 2019. LVOT TVI , forward stroke volume index, and forward LVEF were assessed as potential risk factors for LVEF <50% at 6 months post-operatively. Results A total of 198 patients were included: 154 patients (78%) were asymptomatic, and 46 patients (23%) had hypertension. The mean preoperative LVEF was 69 ± 9%. 35 patients (18%) had LVEF ≤ 60%, and 61 patients (31%) had LVESD ≥40 mm. The mean post-operative LVEF was 59 ± 9%, and 21 patients (11%) had post-operative LVEF<50%. Based on multivariable analysis, LVOT TVI was the strongest independent predictor of post-operative LV dysfunction after adjustment for age, sex, symptoms, LVEF, LV end systolic diameter, atrial fibrillation and left atrial volume index (0.75 [0.62–0.91], p < 0.01). The best sensitivity (81%) and specificity (63%) was obtained with LVOTTVI ≤15 cm based on ROC curve analysis. Conclusion LVOT TVI represents an independent marker of myocardial performance impairment in the presence of severe DMR. LVOT TVI could be an earlier marker than traditional echo parameters and aids in the optimization of the timing of surgery