Exercise and Polycystic Ovary Syndrome.

Polycystic ovary syndrome (PCOS) is a complex endocrinopathy affecting both the metabolism and reproductive system of women of reproductive age. Prevalence ranges from 6.1-19.9% depending on the criteria used to give a diagnosis. PCOS accounts for approximately 80% of women with anovulatory infer-tility, and causes disruption at various stages of the reproductive axis. Evidence suggests lifestyle modification should be the first line of therapy for women with PCOS. Several studies have examined the impact of exercise interventions on reproductive function, with results indicating improvements in menstrual and/or ovulation frequency following exercise. Enhanced insulin sensitivity underpins the mechanisms of how exercise restores reproductive function. Women with PCOS typically have a cluster of metabolic abnormalities that are risk factors for CVD. There is irrefutable evidence that exercise mitigates CVD risk factors in women with PCOS. The mechanism by which exercise improves many CVD risk factors is again associated with improved insulin sensitivity and decreased hyperinsulinemia. In addition to cardiometabolic and reproductive complications, PCOS has been associated with an increased prevalence of mental health disorders. Exercise improves psychological well-being in women with PCOS, dependent on certain physiological factors. An optimal dose-response relationship to exercise in PCOS may not be feasible because of the highly individualised characteristics of the disorder. Guidelines for PCOS suggest at least 150 min of physical activity per week. Evidence confirms that this should form the basis of any clinician or healthcare professional prescription

A Simple Technique to Estimate the Flammability Index of Moroccan Forest Fuels

A formula to estimate forest fuel flammability index (FI) is proposed, integrating three species flammability parameters: time to ignition, time of combustion, and flame height. Thirty-one (31) Moroccan tree and shrub species were tested within a wide range of fuel moisture contents. Six species flammability classes were identified. An ANOVA of the FI-values was performed and analyzed using four different sample sizes of 12, 24, 36, and 50 flammability tests. Fuel humidity content is inversely correlated to the FI-value, and the linear model appears to be the most adequate equation that may predict the hypothetical threshold-point of humidity of extinction. Most of the Moroccan forest fuels studied are classified as moderately flammable to flammable species based on their average humidity content, calculated for the summer period from July to September

On the modelling of instability and flatness defects of sheets: application to rolling process

International audienceRolling of thin sheets generally induces flatness defects due to the small thickness of the sheet and to the thermo-elastic deformation of rolls, whose profile in the roll-bite does not generally match perfectly the strip thickness profile. This leads to heterogeneous plastic deformations throughout the strip width and then to out of mid-plane displacements that relax compressive residual stresses [1]. The most important flatness defects are “edge-waves” and “center-waves” buckles. During the rolling process, the buckling waves are usually suppressed by global traction. Thus, in some cases, the sheet may appear more or less flat, or even perfectly flat on the rolling line. Nevertheless we can still talk about flatness defects, insofar as there may be residual stresses in the sheet. This is why the post-bite stress profile is called “latent flatness defects”. Few works are available in the literature dealing with instability phenomena observed in rolling process. Among them we can cite [2-4].In the present work, we develop a numerical technique to compute flatness defects of thin sheet during the rolling process. To this end, we propose a coupling technique based on Arlequin method [6] which allows us to couple a three dimensional finite element model with a shell element well adapted to large displacements, large rotations and to instability phenomena [5]. To solve the resulting non linear problem, asymptotic numerical method is used. It is a numerical tool based on high order predictor algorithm which allows to compute instability responses with high accuracy [7]. Results of this algorithm are compared successfully with experimental data.REFERENCES[1] A. Hacquin, P. Montmitonnet, P. Guillerault, A steady state thermo-elastoviscoplastic finite element model of rolling with coupled thermo-elastic roll deformation, Journal of materials processing technology. 60 (1996) 109–116. [2] F. D. Fischer, F. G. Rammerstorfer, N. Friedl, W. Wieser, Buckling phenomena related to rolling and levelling of sheet metal, International journal of mechanical sciences 42 (10) (2000) 1887–1910.[3] S. Abdelkhalek, H. Zahrouni, M. Potier-Ferry, N. Legrand, P. Monmitonnet, P. Buessler, Coupled and uncoupled approaches for thin cold strip buckling prediction, International journal of material forming. 2 (2009) 833-836. [4] R. Nakhoul, P. Montmitonnet, M. Potier-Ferry, Multi-scale method for modeling thin sheet buckling under residual stresses in the context of strip rolling, International journal of solids and structures 66 (2015) 62–76.[5] H. Zahrouni, B. Cochelin, M. Potier-Ferry, Computing finite rotations of shells by an asymptotic-numerical method, Computer methods in applied mechanics and engineering. 175 (1999) 71–85. [6] H. Ben Dhia, Multiscale mechanical problems: the Arlequin method, Comptes Rendus de l’Académie des Sciences,Serie IIb,Paris, (1998) 899-904 [7] K. Kpogan, H. Zahrouni, M. Potier-Ferry, H. Ben Dhia. Buckling of rolled thin sheets under residual stresses by ANM and Arlequin method. International Journal of Material Forming. Vol. 10 (3), pages: 389-404, 201

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Experimental and numerical multi-scale approach for Sheet-Molding-Compound composites fatigue prediction based on fiber-matrix interface cyclic damage

In this paper, a multi-scale approach is proposed to predict the stiffness reduction of a Sheet-Molding-Compound (SMC) composite submitted to low cycle fatigue (until 2.105 cycles). Strain-controlled tensile fatigue tests (R = 0.1) are carried out at various strain ranges. Damage is investigated at both macroscopic and microscopic scales through the evolutions of Young's modulus and SEM observations, after interrupted fatigue tests at different lifetime periods. The results show that the fatigue degradation of the composite is mainly controlled by fiber-matrix interface debonding. A quantitative analysis allows determining the threshold and kinetics of the fiber-matrix interface damage during cyclic loading as a function of the orientation of fibers. Moreover, a fiber-matrix interface damage criterion, taking into account the local cyclic normal and shear stresses at the interface, is introduced in the Mori and Tanaka approach in order to predict the loss of stiffness. The parameters of this local criterion are identified by reverse engineering on the basis of the experimental results described above. Finally, the predicted loss of stiffness is very consistent with the experimental result