Kerchoffs2003ContractionModel.cpp

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#include "Kerchoffs2003ContractionModel.hpp"
#include "Exception.hpp"
#include "TimeStepper.hpp"
#include <iostream>

const double Kerchoffs2003ContractionModel::a6 = 2.0; // 1/um
const double Kerchoffs2003ContractionModel::a7 = 1.5; // um
const double Kerchoffs2003ContractionModel::T0 = 180; // kPa
const double Kerchoffs2003ContractionModel::Ea = 20;  // 1/um
const double Kerchoffs2003ContractionModel::v0 = 0.0075; // um/ms
const double Kerchoffs2003ContractionModel::ls0 = 1.9; // um
const double Kerchoffs2003ContractionModel::ld = -0.4; // um
const double Kerchoffs2003ContractionModel::mActivationVoltage = 0.0;
const double Kerchoffs2003ContractionModel::mDeactivationVoltage = -70.0;

Kerchoffs2003ContractionModel::Kerchoffs2003ContractionModel()
    : AbstractOdeBasedContractionModel(1)
{
    mpSystemInfo = OdeSystemInformation<Kerchoffs2003ContractionModel>::Instance();

    mSarcomereLength = ls0;

    mStateVariables.push_back(mSarcomereLength-1.0/Ea); //steady state

    mIsActivated = false;
    mElectricallyUnactivated = true;
    mActivationTime = 0.0;
    mTime = 0.0;

    this->mParameters.resize(3);
    SetParameter("tr", 75.0); // ms
    SetParameter("td", 75.0); // ms
    SetParameter("b", 150.0); // ms/um
}


void Kerchoffs2003ContractionModel::EvaluateYDerivatives(double time,
                                                         const std::vector<double>& rY,
                                                         std::vector<double>& rDY)
{
    double lc = rY[0];
    rDY[0]=( Ea*(mSarcomereLength-lc) - 1 )*v0;
}


void Kerchoffs2003ContractionModel::SetInputParameters(ContractionModelInputParameters& rInputParameters)
{
    assert(rInputParameters.voltage != DOUBLE_UNSET);

    if (mIsActivated && (rInputParameters.voltage < mDeactivationVoltage))
    {
        // inactive (resting) - note don't set mIsActivated=false yet
        // as the cell may yet be producing force, and the code is such
        // that if mIsActivated=false, Ta=0
        mElectricallyUnactivated = true;
    }

    if (!mIsActivated && (rInputParameters.voltage > mActivationVoltage))
    {
        // activated
        mIsActivated = true;
        mActivationTime = mTime;
        mElectricallyUnactivated = false;
    }
}

void Kerchoffs2003ContractionModel::SetStretchAndStretchRate(double stretch, double stretchRate)
{
    mSarcomereLength = stretch*ls0;
}


double Kerchoffs2003ContractionModel::GetActiveTension(double lc)
{
    double f_iso = 0;
    if(lc > a7)
    {
        f_iso = T0 * pow(tanh(a6*(lc-a7)),2);
    }

    double f_twitch = 0;
    double b = this->GetParameter("b");
    double t_max = b*(mSarcomereLength - ld);
    if(mIsActivated)
    {
        double t_a = mTime - mActivationTime;

        if(t_a < t_max)
        {
            double tr = this->GetParameter("tr");
            double td = this->GetParameter("td");
            f_twitch = pow( tanh(t_a/tr)*tanh((t_max-t_a)/td), 2);
        }
        else if(mElectricallyUnactivated)
        {
            // t_a < t_ma => f_twitch=0 => Ta=0
            // In this case, if electrically unactivated as well,
            // set the state to be unactivated.
            mIsActivated = false;
        }
    }

    // expl is unstable for dt = 0.01, 0.001, impl is fine
    return (mSarcomereLength/ls0)*f_iso*f_twitch*(mSarcomereLength-lc)*Ea;
}


double Kerchoffs2003ContractionModel::GetActiveTension()
{
    return GetActiveTension(mStateVariables[0]);
}

double Kerchoffs2003ContractionModel::GetNextActiveTension()
{
    return GetActiveTension(mTemporaryStateVariables[0]);
}

template<>
void OdeSystemInformation<Kerchoffs2003ContractionModel>::Initialise()
{
    this->mVariableNames.push_back("lc");
    this->mVariableUnits.push_back("um");

    this->mParameterNames.push_back("tr");
    this->mParameterUnits.push_back("ms");
    this->mParameterNames.push_back("td");
    this->mParameterUnits.push_back("ms");
    this->mParameterNames.push_back("b");
    this->mParameterUnits.push_back("ms/um");

    this->mInitialised = true;
}