Principes biomécanique de la prothèse du genou

L’articulation du genou, la plus grosse articulation du corps humain, est une articulation mixte trochoïde-trochléenne. Le mouvement de flexion se compose d’une phase de roulement et d’une phase de glissement. Lorsque l’articulation est fléchie, des mouvements de rotation sont possibles, (ces mouvements sont automatique). Dans la rotation, le fémur et les ménisques se déplacent par rapport au tibia ; par contre, dans la flexion et l’extension, le fémur se déplace par rapport aux ménisques par des mouvements de glissement et de roulement. La détérioration de cette articulation amène à l’utilisation de la PTG, les matériaux utilisés sont le titane, polyéthylène, chrome-cobalt et l’oxinium, le plus performant est l’oxinium pour ses propriétés mécaniques trés élevés

Optimization of two dimensional chiral photonic crystal nanostructures

A chiral photonic crystal (CPC) in 2D is a structure that presents the variation of the dielectric permittivity and the chirality parameter along two directions of space. The objective of this paper is to simulate and study geometric effects on the characteristics of 2D chiral photonic crystal based on dielectric material using Comsol Multiphysics 5.0 environment. The properties of Chiral Photonic Crystal are discussed based on transmission coefficient (S21) and reflection coefficient (S11)

Modeling and Parameter Estimation of Radar Sea-Clutter with Trimodal Gamma Population, Journal of Telecommunications and Information Technology, 2022, nr 2

Real radar data often consist of a mixture of Gaussian and non-Gaussian clutter. Such a situation creates one or more inflexion points in the curve of the empirical cumulative distributed function (CDF). In order to obtain an accurate fit with sea reverberation data, we propose, in this paper, a trimodal gamma disturbance model and two parameter estimators. The non-linear least-squares (NLS) fit approach is used to avoid computational issues associated with the maximum likelihood estimator (MLE) and moments-based estimator for parameters of the mixture model. For this purpose, a combination of moment fit and complementary CDF (CCDF) NLS fit methods is proposed. The simplex minimization algorithm is used to simultaneously obtain all parameters of the model. In the case of a single gamma probability density function, a zlog(z) method is derived. Firstly, simulated life tests based on a gamma population with different shape parameter values are worked out. Then, numerical illustrations show that both MLE and zlog(z) methods produce closer results. The proposed trimodal gamma distribution with moments NLS fit and CCDF NLS fit estimators is validated to be in qualitative agreement with different cell resolutions of the available IPIX database

Testing for high frequency features in a noisy signal

Given nonstationary data, one generally wants to extract the trend from the noise by smoothing or filtering. However, it is often important to delineate a third intermediate category, that we call high frequency (HF) features: this is the case in our motivating example, which consists in experimental measurements of the time-dynamics of depolymerising protein fibrils average size. One may intuitively visualise HF features as the presence of fast, possibly nonstationary and transient oscillations, distinct from a slowly-varying trend envelope. The aim of this article is to propose an empirical definition of HF features and construct estimators and statistical tests for their presence accordingly, when the data consists of a noisy nonstationary 1-dimensional signal. We propose a parametric characterization in the Fourier domain of the HF features by defining a maximal amplitude and distance to low frequencies of significant energy. We introduce a data-driven procedure to estimate these parameters, and compute a p-value proxy based on a statistical test for the presence of HF features. The test is first conducted on simulated signals where the ratio amplitude of the HF features to the level of the noise is controlled. The test detects HF features even when the level of noise is five times larger than the amplitude of the oscillations. In a second part, the test is conducted on experimental data from Prion disease experiments and it confirms the presence of HF features in these signals with significant confidence

Isolement par chromatographie de partage centrifuge (CPC) des métabolites secondaires de l’extrait acétate d’éthyle des fleurs de Senecio giganteus Desf. (Asteraceae)

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Strategic Workforce Planning and sales force : a demographic approach to productivity

Sales force Return on Investment (ROI) valuation with marketing mix frameworks is nowadays common. Sizing discussions then generally follow based on market data and business assumptions. Yet, according to our knowledge, little has been done to embed sales force demographic data (age/experience, tenure, gender etc...) as well as dynamics (especially turnover) in order to investigate the impact of the salesforce characteristics on sales. This paper illustrates such an attempt. It shows that sales force ROI valuation can benefit from a correction on turnover and that optimizinga sales rep hiring policy can unleash additional ROI points. The results are yet heavily dependent in the data structure of the study and their generalization would have to be investigated

Senecipyrrolidine, an unusual pyrrolidine alkaloid isolated from Jacobaea gigantea (Desf.) Pelser (Asteraceae)

Alkaloids and phenolic compounds are among the most biologically active natural products from the Jacobaea/Senecio genera (Asteraceae). To isolate original natural products directly from Jacobaea gigantea crude polar extracts, centrifugal partition chromatography (CPC) was used. Previously, we reported the phytochemical study of J. gigantea (syn. Senecio giganteus) n-butanol extract using various classical chromatographical techniques combined with CPC. Herein major constituents from the J. gigantea crude ethyl acetate extract and further compounds from the n-butanol extract were purified in only one step using this technique. A new pyrrolidine alkaloid, named senecipyrrolidine was isolated along with thirteen known compounds – chiro-inositol, three phenolic acids, six flavonoids, two quinones and emiline, another pyrrolidine alkaloid – from crude n-butanol or ethyl acetate extracts. Pyrrolidine alkaloids were isolated for the first time in the Jacobaea/Senecio genera and were probably biogenetically related to the two isolated quinones derivatives jacaranone and 3a-hydroxy-3,3a,7,7a-tetrahydrobenzofuran-2,6-dione, isolated in this species

Fast counter current chromatography of n-butanolic fraction from Senecio giganteus (Asteraceae)

Phenolic derivatives such as quinones, acid-phenols and flavonoids were successfully isolated from a n-butanolic fraction of Senecio giganteus Desf. (Asteraceae) flowers, namely jacaranone (1), 3a-hydroxy-3,3a,7,7a-tetrahydrobenzofuran-2,6-dione (2), chlorogenic acid (3), hyperoside (4), quercetin 3-O-β-D-robinobioside (5), isorhamnetin-3-O-β-D-glucuronide (6), quercetin-3-O-β-D-glucuronide (7), and isorhamnetin-3-O-β-D-glucuronide-6″-methyl ester (8). These compounds were purified through either classical polyamide filtration followed by fractionation on Si gel, or through fast centrifugal partition chromatography (FCPC). Using FCPC, the major compounds could be readily isolated from the crude n-butanolic fraction. Compounds 1-8 were identified by means of spectroscopic and spectrometric analysis (UV, 1H, 13C and 2D NMR, and MS). This work described for the first time the phytochemical composition of this endemic Algerian plant