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Alpha Method

The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform

Antoine Nordez – 1st expert on this subject based on the ideXlab platform

  • Muscle and tendon stiffness assessment using the Alpha Method and ultrafast ultrasound
    European Journal of Applied Physiology, 2015
    Co-Authors: Hugo Hauraix, Alexandre Fouré, Sylvain Dorel, Christophe Cornu, Antoine Nordez

    Abstract:

    Purpose The Alpha Method enables the dissociation of the passive (i.e., tendinous tissues) and active (i.e., fascicles) part of muscle–tendon stiffness. It is based on two main assumptions (i.e., a constant tendon stiffness and a muscle stiffness proportional to the torque produced), which have not been approved in vivo. The purpose of this study was to validate these two assumptions using ultrafast ultrasound, and to compare fascicle and tendon stiffness as determined by both Methods. Methods Ten healthy males performed a fast-stretch experiment on the ankle plantar flexors. The mathematical model of the Alpha Method allowed to estimate the stiffness of muscle and tendinous tissues on the basis of the assumptions associated to the behaviors of muscle fascicles and tendinous tissues. Muscle and tendon stiffness of the gastrocnemius medialis were also calculated from ultrafast ultrasound measurements. Results Muscle stiffness measured by the ultrasound Method increased from 217 ± 83 to 720 ± 265 N/mm with an increasing level of force (from 30 to 90 % MVC). Tendinous stiffness measured by the ultrasound Method remained constant across the force level ( P  

  • Muscle and tendon stiffness assessment using the Alpha Method and ultrafast ultrasound
    European Journal of Applied Physiology, 2015
    Co-Authors: Hugo Hauraix, Alexandre Fouré, Sylvain Dorel, Christophe Cornu, Antoine Nordez

    Abstract:

    Purpose
    The Alpha Method enables the dissociation of the passive (i.e., tendinous tissues) and active (i.e., fascicles) part of muscle–tendon stiffness. It is based on two main assumptions (i.e., a constant tendon stiffness and a muscle stiffness proportional to the torque produced), which have not been approved in vivo. The purpose of this study was to validate these two assumptions using ultrafast ultrasound, and to compare fascicle and tendon stiffness as determined by both Methods.

  • In vivo assessment of both active and passive parts of the plantarflexors series elastic component stiffness using the Alpha Method: a reliability study.
    International Journal of Sports Medicine, 2009
    Co-Authors: Alexandre Fouré, Antoine Nordez, Christophe Cornu

    Abstract:

    : The aim of this study was to investigate the reliability of an in vivo adaptation of the short range stiffness experiment associated with the application of a mathematical model to determine the stiffness of both torque dependent and independent components of the plantarflexors series elastic component. Fourteen subjects participated in this study. The experimental protocol consisted of quickly moving the ankle joint in dorsiflexion during constant voluntary isometric plantarflexion at 7 submaximal torque levels. Relationships between joint stiffness and torque were established and the stiffness of both torque dependent and independent components were determined using the Alpha Method. The day-to-day reliability was assessed for joint stiffness and stiffness of both torque dependent and independent components (ICC higher than 0.88 and CVs lower than 6.0%). This Method could then be used to better understand adaptive subjacent mechanisms to assess the effects of training protocols, and the rehabilitation of neuromuscular pathologies or traumatisms.

Hugo Hauraix – 2nd expert on this subject based on the ideXlab platform

  • Muscle and tendon stiffness assessment using the Alpha Method and ultrafast ultrasound
    European Journal of Applied Physiology, 2015
    Co-Authors: Hugo Hauraix, Alexandre Fouré, Sylvain Dorel, Christophe Cornu, Antoine Nordez

    Abstract:

    Purpose The Alpha Method enables the dissociation of the passive (i.e., tendinous tissues) and active (i.e., fascicles) part of muscle–tendon stiffness. It is based on two main assumptions (i.e., a constant tendon stiffness and a muscle stiffness proportional to the torque produced), which have not been approved in vivo. The purpose of this study was to validate these two assumptions using ultrafast ultrasound, and to compare fascicle and tendon stiffness as determined by both Methods. Methods Ten healthy males performed a fast-stretch experiment on the ankle plantar flexors. The mathematical model of the Alpha Method allowed to estimate the stiffness of muscle and tendinous tissues on the basis of the assumptions associated to the behaviors of muscle fascicles and tendinous tissues. Muscle and tendon stiffness of the gastrocnemius medialis were also calculated from ultrafast ultrasound measurements. Results Muscle stiffness measured by the ultrasound Method increased from 217 ± 83 to 720 ± 265 N/mm with an increasing level of force (from 30 to 90 % MVC). Tendinous stiffness measured by the ultrasound Method remained constant across the force level ( P  

  • Muscle and tendon stiffness assessment using the Alpha Method and ultrafast ultrasound
    European Journal of Applied Physiology, 2015
    Co-Authors: Hugo Hauraix, Alexandre Fouré, Sylvain Dorel, Christophe Cornu, Antoine Nordez

    Abstract:

    Purpose
    The Alpha Method enables the dissociation of the passive (i.e., tendinous tissues) and active (i.e., fascicles) part of muscle–tendon stiffness. It is based on two main assumptions (i.e., a constant tendon stiffness and a muscle stiffness proportional to the torque produced), which have not been approved in vivo. The purpose of this study was to validate these two assumptions using ultrafast ultrasound, and to compare fascicle and tendon stiffness as determined by both Methods.

Mehmet Unal – 3rd expert on this subject based on the ideXlab platform

  • An efficient analysis for absorption and gain coefficients in “Single Step-Index Waveguide”s by using the Alpha Method
    Pamukkale University Journal of Engineering Sciences, 2010
    Co-Authors: Mehmet Unal

    Abstract:

    I n this study, some design parameters such as normalized frequency and especially normalized propagation constant have been obtained, depending on some parameters which are functions of energy eigenvalues of the carriers such as electrons and holes confined in a single step-index waveguide laser (SSIWGL) or single stepindex waveguide (SSIWG). Some optical expressions about the optical power and probability quantities for the active region and cladding layers of the SSIWG or SSIWGL have been investigated. Investigations have been undertaken in terms of these parameters and also individually the optical even and odd electric field waves with the lowest-modes were theoretically computed. Especially absorption coefficients and loss coefficients addition to some important quantities of the single step-index waveguide lasers for the even and odd electric field waves are evaluated.

  • The analysis of a semiconductor single asymmetric and symmetric step-index laser for even and odd fields by Alpha Method
    Turkish Journal of Electrical Engineering and Computer Sciences, 2010
    Co-Authors: Mustafa Temiz, Mehmet Unal

    Abstract:

    In this work, semiconductor step-index single waveguide has been analyzed by Alpha Method. A requested quantity of wave guide can be obtained in terms of normalized propagation constant, which is represented by Alpha belonging to active region. Based on this Method, structural properties of the material containing any requested quantity of the waveguide is theoretically calculated, when the width of the active region, the refractive indices of the regions and the wavelength are given. In the TE mode some important parameters, such as the propagation constants for regions of the semiconductor step-index single waveguide, the wave numbers, the effective index of refraction of the active region, the dielectric constant, the phase constant, the absorption coefficients, and the confinement factors of the regions, stray ratios of the field probabilities to the cladding regions from the active region, arised power per unit length and effective mass of electron in the active region, h , z coordinate variables for energy eigenvalues for charged carriers in the orthogonal coordinate system z -h , have been estimated, calculated theoretically and validities of found formulas have been tested, numerically. Since the effective refractive index belonging to the active region is constant, the quantities such as the phase constant, the phase velocity, the dielectric constant, the parameters h , z , the field amplitudes, the power raised per unit length, and effective mass of the electron being constant have been observed. In this novel study, some design parameters such as the normalized frequency and a specially normalized propagation constant have been obtained, depending on some parameters which are functions of energy eigenvalues of the carriers such as electrons and holes confined in a semiconductor single asymmetric and symmetric step-index wave guide (SCSAaSSIWG) for even and odd fields. Some optical expressions about the optical power and probability quantities for the active region and cladding layers of the SCSAaSSIWG have been investigated in terms of these parameters.

  • The investigation of electric and magnetic fields on TE mode of single laser diode Zn0.72Cd0.28Se-ZnSe
    2010 IEEE 18th Signal Processing and Communications Applications Conference, 2010
    Co-Authors: Mehmet Unal, Yusuf Hacisalihoglu

    Abstract:

    In this work, being explored the refractive index profile of laser diode Zn0.72Cd0.28Se-ZnSe, the important structural and design parameters such as normalized frequency, normalized propagation constant, propagation constants for the laser diode, confinement factor are obtained by Alpha Method and the variations of electromagnetic fields in the regions of semiconductor single step-index laser are investigated.