Stability control of nonlinear micromechanical resonators under simultaneous primary and superharmonic resonances

Fast effects of a slow excitation on the main resonance of a nonlinear micromechanical resonator are analytically and experimentally investigated. We show, in particular, how the bifurcation topology of an undesirable unstable behavior is modified when the resonator is simultaneously actuated at its primary and superharmonic resonances. A stabilization mechanism is proposed and demonstrated by increasing the superharmonic excitation

Non linear dynamics of Mathieu resonators for resonant gyroscope applications

A complete model describing the non linear dynamics of Mathieu resonators is presented in order to study the stability of resonant MEM gyroscopes

Effects of candesartan cilexetil on carotid remodeling in hypertensive diabetic patients: the MITEC study

In hypertension and diabetes, early structural changes of the arterial wall precede or support atherosclerosis. There is evidence that some antihypertensive drugs exert an antiathero-sclerotic effect. Over 36 months, we investigated the effect of candesartan cilexetil (CC) on the common carotid intima-media thickness (IMT) vs amlodipine besylate (AML) in patients with type 2 diabetes and mild to moderate essential hypertension. After a 4-week wash-out period, 209 patients were randomized to either CC 8 mg or AML 5 mg once daily for a minimum of 1 month, after which, if BP was not normalized, the dosage was doubled, followed by the addition of hydrochlorothiazide 12.5 mg if necessary. No significant differences were observed between the two groups for change in IMT at M12 (−0.001 vs −0.027 mm/year for CC and AML respectively, p = 0.425), at M24 (−0.033 vs −0.019 mm per year respectively, p = 0.442), and at the last visit (−0.016 vs −0.039 mm per year respectively, p = 0.549). Within the group, comparisons did not show a significant difference in changes in IMT from baseline to the three visits. At the last visit, IMT regression was observed in 52.2% of patients receiving CC and in 51.3% of those receiving AML (p = 0.908). The augmentation in carotid lumen diameter from baseline was statistically greater in the AML group at the last visit (p = 0.034). BP variations during the study were similar in the two groups. The results of this study show that CC and AML treatments may alter identically the natural progression of carotid IMT in hypertensive type 2 diabetic patients

Parametric analysis of the nonlinear behavior of rotating structures

An efficient frequency-domain method is presented for the rapid parametric analysis of stability changes in nonlinear rotating systems which are modeled by three-dimensional finite elements. This method provides directly the stability boundary with respect to parameters such as the system nonlinearity or excitation level. Firstly, the response curve is calculated by combining Harmonic Balance Method and continuation. Then stability of equilibrium solutions is determined thanks to Lyapunov exponents. The singular points where a stability change often arises are detected with the sign change of the Jacobian determinant and then located through a penalty method that increases the solving equation system by a completing constraint. Tracking these points, which provides an efficient way to analyze parametrically the nonlinear behavior of a system, can be fulfilled, once again, by the continuation technique

A New Method for Non-Invasive Estimation of Human Muscle Fiber Type Composition

Background: It has been established that excellence in sports with short and long exercise duration requires a high proportion of fast-twitch (FT) or type-II fibers and slow-twitch (ST) or type-I fibers, respectively. Until today, the muscle biopsy method is still accepted as gold standard to measure muscle fiber type composition. Because of its invasive nature and high sampling variance, it would be useful to develop a non-invasive alternative.status: publishe

Pyruvate dehydrogenase fuels a critical citrate pool that is essential for Th17 cell effector functions

peer reviewedPyruvate dehydrogenase (PDH) is the central enzyme connecting glycolysis and the tricarboxylic acid (TCA) cycle. The importance of PDH function in T helper 17 (Th17) cells still remains to be studied. Here, we show that PDH is essential for the generation of a glucose-derived citrate pool needed for Th17 cell proliferation, survival, and effector function. In vivo, mice harboring a T cell-specific deletion of PDH are less susceptible to developing experimental autoimmune encephalomyelitis. Mechanistically, the absence of PDH in Th17 cells increases glutaminolysis, glycolysis, and lipid uptake in a mammalian target of rapamycin (mTOR)-dependent manner. However, cellular citrate remains critically low in mutant Th17 cells, which interferes with oxidative phosphorylation (OXPHOS), lipid synthesis, and histone acetylation, crucial for transcription of Th17 signature genes. Increasing cellular citrate in PDH-deficient Th17 cells restores their metabolism and function, identifying a metabolic feedback loop within the central carbon metabolism that may offer possibilities for therapeutically targeting Th17 cell-driven autoimmunity

Left main renal artery entrapment by diaphragmatic crura: spiral CT angiography

Entrapment of renal artery by the diaphragmatic crus is a rare cause of renal artery stenosis. Spiral computed tomography angiography provides a definitive diagnosis and shows the precise relationship of the artery to the diaphragmatic crus. The authors present a case of hypertension developing in a young 20-year-old female due to entrapment of the left renal artery by the diaphragmatic crus. This condition should be considered in young hypertensive patients with renal artery stenosis without cardiovascular risk factors

Doppler ultrasound in the measurement of pulse wave velocity: agreement with the Complior method

Aortic stiffness is an independent predictor factor for cardiovascular risk. Different methods for determining pulse wave velocity (PWV) are used, among which the most common are mechanical methods such as SphygmoCor or Complior, which require specific devices and are limited by technical difficulty in obtaining measurements. Doppler guided by 2D ultrasound is a good alternative to these methods. We studied 40 patients (29 male, aged 21 to 82 years) comparing the Complior method with Doppler. Agreement of both devices was high (R = 0.91, 0.84-0.95, 95% CI). The reproducibility analysis revealed no intra-nor interobserver differences. Based on these results, we conclude that Doppler ultrasound is a reliable and reproducible alternative to other established methods for the measurement of aortic PWV

Coupling dynamics of a geared multibody system supported by Elastohydrodynamic lubricated cylindrical joints

A comprehensive computational methodology to study the coupling dynamics of a geared multibody system supported by ElastoHydroDynamic (EHD) lubricated cylindrical joints is proposed throughout this work. The geared multibody system is described by using the Absolute-Coordinate-Based (ACB) method that combines the Natural Coordinate Formulation (NCF) describing rigid bodies and the Absolute Nodal Coordinate Formulation (ANCF) characterizing the flexible bodies. Based on the finite-short bearing approach, the EHD lubrication condition for the cylindrical joints supporting the geared system is considered here. The lubrication forces developed at the cylindrical joints are obtained by solving the Reynolds’ equation via the finite difference method. For the evaluation of the normal contact forces of gear pair along the Line Of Action (LOA), the time-varying mesh stiffness, mesh damping and Static Transmission Error (STE) are utilized. The time-varying mesh stiffness is calculated by using the Chaari’s methodology. The forces of sliding friction along the Off-Line-Of-Action (OLOA) are computed by using the Coulomb friction models with a time-varying coefficient of friction under the EHD lubrication condition of gear teeth. Finally, two numerical examples of application are presented to demonstrate and validate the proposed methodology.National Natural Science Foundations of China under Grant 11290151, 11221202 and 11002022, Beijing Higher Education Young Elite Teacher Project under Grant YETP1201