Location: A review of cardiac cellular electrophysiology models @ 797bc599b7ec / models / 1975_mcallister / 1975_mcallister_noble_tsien.xml

Author:
David Nickerson <david.nickerson@gmail.com>
Date:
2021-09-15 23:15:11+12:00
Desc:
update jupyter notebook with FK model results
Permanent Source URI:
https://staging.physiomeproject.org/workspace/a1/rawfile/797bc599b7ec66eef984e817d4ce138aabd116a6/models/1975_mcallister/1975_mcallister_noble_tsien.xml

<?xml version="1.0" encoding="iso-8859-1"?>


<!-- FILE : MNT_purkinje_fibre_model_1975.xml

CREATED : September 2001

LAST MODIFIED : 5th April 2003

AUTHOR : Catherine Lloyd
         Department of Engineering Science
         The University of Auckland
         
MODEL STATUS : This model conforms to the CellML 1.0 Specification released on
10th August 2001, and the CellML Metadata 1.0 Specification released on 16 
January 2002.

DESCRIPTION : This file contains a CellML description of cardiac action
potentials in purkinje fibres, based on the McAllister-Noble-Tsien model, 1975. 

CHANGES: 
  19/10/2001 - CML - Removed document type definition as this is declared as  
                     optional according to the W3C recommendation.  
  24/10/2001 - CML - Made changes to some of the metadata, bringing them up to
                     date with the most recent working draft (26th September) of
                     the Metadata specification. 
  10/12/2001 - CML - Changed equations after checking with the mathml validator.
  03/01/2002 - CML - Altered parent-child relationships as x1 and x2 were made
                     to be gates of the plateau potassium currents.
  20/01/2002 - AAC - Updated metadata to conform to the 16/01/2002 CellML
                     Metadata Specification.
  28/02/2002 - CML - Corrected units.
  19/07/2002 - CML - Added more metadata.
  05/04/2003 - AAC - Changed the model name so the model loads in the database 
                     easier.
-->

<model
    name="mcallister_noble_tsien_model_1975"
    cmeta:id="MNT_purkinje_fibre_model_1975"
    xmlns="http://www.cellml.org/cellml/1.0#"
    xmlns:cellml="http://www.cellml.org/cellml/1.0#"
    xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
  <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#"
      xmlns:bqs="http://www.cellml.org/bqs/1.0#"
      xmlns:dc="http://purl.org/dc/elements/1.1/"
      xmlns:dcterms="http://purl.org/dc/terms/"
      xmlns:vCard="http://www.w3.org/2001/vcard-rdf/3.0#">
    <!--
      The following RDF block contains metadata that applies to this document
      as a whole, as indicated by the empty about attribute on the 
      <rdf:Description> element.
    -->
    <rdf:Description rdf:about="">
      <!--
        The Model Builder Metadata.  The Dublin Core "creator" element is used  
        to indicate the person who translated the model into CellML.
      -->
      <dc:creator rdf:parseType="Resource">
        <vCard:N rdf:parseType="Resource">
          <vCard:Family>Lloyd</vCard:Family>
          <vCard:Given>Catherine</vCard:Given>
          <vCard:Other>May</vCard:Other>
        </vCard:N>
        <vCard:EMAIL rdf:parseType="Resource">
          <rdf:value>c.lloyd@auckland.ac.nz</rdf:value>
          <rdf:type rdf:resource="http://imc.org/vCard/3.0#internet" />
        </vCard:EMAIL>
        <vCard:ORG rdf:parseType="Resource">
          <vCard:Orgname>The University of Auckland</vCard:Orgname>
          <vCard:Orgunit>The Bioengineering Research Group</vCard:Orgunit>
        </vCard:ORG>
      </dc:creator>
      
      <!--
        The Creation Date metadata. This is the date on which the model
        was translated into CellML.
      -->
      <dcterms:created rdf:parseType="Resource">
        <dcterms:W3CDTF>2001-09-27</dcterms:W3CDTF>
      </dcterms:created>
      
      <!--
        The Modification History metadata. This lists the changes that have been
        made to the document, who made the changes, and when they were made.
      -->
      <cmeta:modification rdf:parseType="Resource">
        <rdf:value>
          Changed some units and added a stimulus current.
        </rdf:value>
        <cmeta:modifier rdf:parseType="Resource">
          <vCard:N rdf:parseType="Resource">
            <vCard:Family>Nickerson</vCard:Family>
            <vCard:Given>David</vCard:Given>
            <vCard:Other>P</vCard:Other>
          </vCard:N>
        </cmeta:modifier>
        <dcterms:modified rdf:parseType="Resource"> 
          <dcterms:W3CDTF>2003-10-13</dcterms:W3CDTF>
        </dcterms:modified>
      </cmeta:modification>
      <cmeta:modification rdf:parseType="Resource">
        <rdf:value>
          Changed the model name so the model loads in the database easier.
        </rdf:value>
        <cmeta:modifier rdf:parseType="Resource">
          <vCard:N rdf:parseType="Resource">
            <vCard:Family>Cuellar</vCard:Family>
            <vCard:Given>Autumn</vCard:Given>
            <vCard:Other>A</vCard:Other>
          </vCard:N>
        </cmeta:modifier>
        <dcterms:modified rdf:parseType="Resource"> 
          <dcterms:W3CDTF>2003-04-05</dcterms:W3CDTF>
        </dcterms:modified>
      </cmeta:modification>
      <cmeta:modification rdf:parseType="Resource">
        <rdf:value>
          Added more metadata.
        </rdf:value>
        <cmeta:modifier rdf:parseType="Resource">
          <vCard:N rdf:parseType="Resource">
            <vCard:Family>Lloyd</vCard:Family>
            <vCard:Given>Catherine</vCard:Given>
            <vCard:Other>May</vCard:Other>
          </vCard:N>
        </cmeta:modifier>
        <dcterms:modified rdf:parseType="Resource"> 
          <dcterms:W3CDTF>2002-07-19</dcterms:W3CDTF>
        </dcterms:modified>
      </cmeta:modification>
      <cmeta:modification rdf:parseType="Resource">
        <rdf:value>
          Corrected units
        </rdf:value>
        <cmeta:modifier rdf:parseType="Resource">
          <vCard:N rdf:parseType="Resource">
            <vCard:Family>Lloyd</vCard:Family>
            <vCard:Given>Catherine</vCard:Given>
            <vCard:Other>May</vCard:Other>
          </vCard:N>
        </cmeta:modifier>
        <dcterms:modified rdf:parseType="Resource">
          <dcterms:W3CDTF>2002-02-28</dcterms:W3CDTF>
        </dcterms:modified>
      </cmeta:modification>
      <cmeta:modification rdf:parseType="Resource">
        <rdf:value>
          Updated metadata to conform to the 16/01/2002 CellML Metadata 1.0 
          Specification.
        </rdf:value>
        <cmeta:modifier rdf:parseType="Resource">
          <vCard:N rdf:parseType="Resource">
            <vCard:Family>Cuellar</vCard:Family>
            <vCard:Given>Autumn</vCard:Given>
            <vCard:Other>A.</vCard:Other>
          </vCard:N>
        </cmeta:modifier>
        <dcterms:modified rdf:parseType="Resource">
          <dcterms:W3CDTF>2002-01-20</dcterms:W3CDTF>
        </dcterms:modified>
      </cmeta:modification>
      <cmeta:modification rdf:parseType="Resource">
        <rdf:value>
          Altered parent-child relationships as x1 and x2 were made to be gates 
          of the plateau potassium currents.
        </rdf:value>
        <cmeta:modifier rdf:parseType="Resource">
          <vCard:N rdf:parseType="Resource">
            <vCard:Family>Lloyd</vCard:Family>
            <vCard:Given>Catherine</vCard:Given>
            <vCard:Other>May</vCard:Other>
          </vCard:N>
        </cmeta:modifier>
        <dcterms:modified rdf:parseType="Resource">
          <dcterms:W3CDTF>2002-01-03</dcterms:W3CDTF>
        </dcterms:modified>
      </cmeta:modification>
      <cmeta:modification rdf:parseType="Resource">
        <rdf:value>
          Changed equations after checking with the mathml validator.
        </rdf:value>
        <cmeta:modifier rdf:parseType="Resource">
          <vCard:N rdf:parseType="Resource">
            <vCard:Family>Lloyd</vCard:Family>
            <vCard:Given>Catherine</vCard:Given>
            <vCard:Other>May</vCard:Other>
          </vCard:N>
        </cmeta:modifier>
        <dcterms:modified rdf:parseType="Resource">
          <dcterms:W3CDTF>2001-12-10</dcterms:W3CDTF>
        </dcterms:modified>
      </cmeta:modification>
      <cmeta:modification rdf:parseType="Resource">
        <rdf:value>
          Made changes to some of the metadata, bringing them up to date with 
          the most recent working draft (26th September) of the Metadata 
          Specification.
        </rdf:value>
        <cmeta:modifier rdf:parseType="Resource">
          <vCard:N rdf:parseType="Resource">
            <vCard:Family>Lloyd</vCard:Family>
            <vCard:Given>Catherine</vCard:Given>
            <vCard:Other>May</vCard:Other>
          </vCard:N>
        </cmeta:modifier>
        <dcterms:modified rdf:parseType="Resource">
          <dcterms:W3CDTF>2001-10-24</dcterms:W3CDTF>
        </dcterms:modified>
      </cmeta:modification>
      <cmeta:modification rdf:parseType="Resource">
        <rdf:value>
          Removed document type definition as this is declared as optional 
          according to the W3C recommendation.
        </rdf:value>
        <cmeta:modifier rdf:parseType="Resource">
          <vCard:N rdf:parseType="Resource">
            <vCard:Family>Lloyd</vCard:Family>
            <vCard:Given>Catherine</vCard:Given>
            <vCard:Other>May</vCard:Other>
          </vCard:N>
        </cmeta:modifier>
        <dcterms:modified rdf:parseType="Resource">
          <dcterms:W3CDTF>2001-10-19</dcterms:W3CDTF>
        </dcterms:modified>
      </cmeta:modification>

      <!-- The Publisher metadata. -->
      <dc:publisher>
        The University of Auckland, Bioengineering Research Group
      </dc:publisher>
    </rdf:Description>
    
    <!--
      The following metadata refers to the model itself, as indicated by the
      reference to the ID "MNT_purkinje_fibre_model_1975", which is             
      declared on the <model> element.
    -->
    <rdf:Description rdf:about="#MNT_purkinje_fibre_model_1975">
      <!-- A human readable name for the model. -->
      <dc:title>
        The McAllister-Noble-Tsien Model of Cardiac Action Potentials in 
        Purkinje fibres, 1975
      </dc:title>
      
      <!-- A comment regarding the model. -->
      <cmeta:comment rdf:parseType="Resource">
        <rdf:value>
          This is the CellML description of McAllister, Noble and Tsien's       
          mathematical model of cardiac action potentials of Purkinje fibres.   
          It describes transmembrane ionic currents in terms of Hodgkin-Huxley             type equations.  It is a significant development of the Noble (1962)  
          model as more currents are added based on new experimental data.   
        </rdf:value>
        <!-- The creator of the comment. -->
        <dc:creator rdf:parseType="Resource">
          <vCard:FN>Catherine Lloyd</vCard:FN>
        </dc:creator>
      </cmeta:comment>
      
      <cmeta:bio_entity>Purkinje Fibre</cmeta:bio_entity>
      
      <!-- 
        The CellML Metadata Specification recommends that bibliographic metadata
        is used to provide information about the original model reference.  The 
        "identifier" attribute on the "BibliographicReference" class provides an
        elegant way to identify a cited reference using a database identifier            such as Pubmed.  All associated data such as author, journal title,     
        date, etc can be looked up on the database.
      -->
      <bqs:reference rdf:parseType="Resource">
        <bqs:Pubmed_id>1185607</bqs:Pubmed_id>
        <bqs:JournalArticle rdf:parseType="Resource">
          <dc:creator>
            <rdf:Seq>
              <rdf:li rdf:parseType="Resource">
                <bqs:Person rdf:parseType="Resource">
                  <vCard:N rdf:parseType="Resource">
                    <vCard:Family>McAllister</vCard:Family>
                    <vCard:Given>R</vCard:Given>
                    <vCard:Other>E</vCard:Other>
                  </vCard:N>
                </bqs:Person>
              </rdf:li>
              <rdf:li rdf:parseType="Resource">
                <bqs:Person rdf:parseType="Resource">
                  <vCard:N rdf:parseType="Resource">
                    <vCard:Family>Noble</vCard:Family>
                    <vCard:Given>Denis</vCard:Given>
                  </vCard:N>
                </bqs:Person>
              </rdf:li>
              <rdf:li rdf:parseType="Resource">
                <bqs:Person rdf:parseType="Resource">
                  <vCard:N rdf:parseType="Resource">
                    <vCard:Family>Tsien</vCard:Family>
                    <vCard:Given>R</vCard:Given>
                    <vCard:Other>W</vCard:Other>
                  </vCard:N>
                </bqs:Person>
              </rdf:li>
            </rdf:Seq>
          </dc:creator>
          <dc:title>
            Reconstruction of the electrical activity of cardiac purkinje fibres
          </dc:title>
          <dcterms:issued rdf:parseType="Resource">
            <dcterms:W3CDTF>1975-09</dcterms:W3CDTF>
          </dcterms:issued>
          <bqs:Journal rdf:parseType="Resource">
            <dc:title>Journal of Physiology</dc:title>
          </bqs:Journal>
          <bqs:volume>251</bqs:volume>
          <bqs:first_page>1</bqs:first_page>
          <bqs:last_page>59</bqs:last_page>
        </bqs:JournalArticle>
      </bqs:reference>
    </rdf:Description>
  </rdf:RDF>
  
  <!--
    Below, are defined some additional units for association with variables and
    constants within the model. The identifiers are fairly self-explanatory.
  -->
  <units name="ms">
    <unit prefix="milli" units="second" />
  </units>
  
  <units name="per_ms">
    <unit prefix="milli" units="second" exponent="-1" />
  </units>

  <units name="mV">
    <unit prefix="milli" units="volt" />
  </units>

  <units name="per_mV">
    <unit prefix="milli" units="volt" exponent="-1" />
  </units>
  
  <units name="per_mV_ms">
    <unit units="mV" exponent="-1" />
    <unit units="ms" exponent="-1" />
  </units>
  
  <units name="mS_per_mm2">
    <unit prefix="milli" units="siemens" />
    <unit prefix="milli" units="metre" exponent="-2" />
  </units>

  <units name="uF_per_mm2">
    <unit prefix="micro" units="farad" />
    <unit prefix="milli" units="metre" exponent="-2" />
  </units>

  <units name="uA_per_mm2">
    <unit prefix="micro" units="ampere" />
    <unit prefix="milli" units="metre" exponent="-2" />
  </units>
  
  <units name="concentration_units">
    <unit prefix="nano" units="mole" />
    <unit prefix="milli" units="metre" exponent="-3" />
  </units>
  
  <component name="interface" cmeta:id="interface">
    <variable name="time" public_interface="in" private_interface="out" units="ms" />
    <variable name="I_stim" public_interface="in" private_interface="out" units="uA_per_mm2"/>
  </component>

  <!--
    The "membrane" component is really the `root' node of our model.
    It defines the action potential variable "V" among other things.
  -->
  <component name="membrane" cmeta:id="membrane">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#membrane">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The main component of the model, containing the definition of the
            model's action potential.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- These variables are defined here and used in other components. -->
    <variable cmeta:id="Vm" name="V" initial_value="-80.0" public_interface="out" units="mV" />
    
    <!-- These variables are defined here and only used internally. -->
    <variable name="C" initial_value="0.1" units="uF_per_mm2" />
    
    <!-- These variables are imported from other components. -->
    <variable name="time" public_interface="in" units="ms" />
    <variable name="i_Na" public_interface="in" units="uA_per_mm2" />
    <variable name="i_si" public_interface="in" units="uA_per_mm2" />
    <variable name="i_K2" public_interface="in" units="uA_per_mm2" />
    <variable name="i_x1" public_interface="in" units="uA_per_mm2" />
    <variable name="i_x2" public_interface="in" units="uA_per_mm2" />
    <variable name="i_qr" public_interface="in" units="uA_per_mm2" />
    <variable name="i_K1" public_interface="in" units="uA_per_mm2" />
    <variable name="i_Na_b" public_interface="in" units="uA_per_mm2" />
    <variable name="i_Cl_b" public_interface="in" units="uA_per_mm2" />
    <variable name="I_stim" public_interface="in" units="uA_per_mm2" />
    
    <!--
      The membrane voltage (V) is calculated as an ordinary
      differential equation in terms of the currents.
    -->
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#membrane_voltage_diff_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The kinetics of the transmembrane potential, defined as the sum of
            the trans-sarcolemmal currents and an applied stimulus current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="membrane_voltage_diff_eq">
      <apply id="membrane_voltage_diff_eq"><eq />
        <apply><diff />
          <bvar><ci> time </ci></bvar>
          <ci> V </ci>
        </apply>
        <apply><divide />
          <apply><minus />
            <ci>I_stim</ci>
            <apply><plus />
              <ci> i_Na </ci>
              <ci> i_si </ci>
              <ci> i_K2 </ci>
              <ci> i_x1 </ci>
              <ci> i_x2 </ci>
              <ci> i_qr </ci>
              <ci> i_K1 </ci>
              <ci> i_Na_b </ci>
              <ci> i_Cl_b </ci>
            </apply>
          </apply>
          <ci> C </ci>
        </apply>
      </apply>
    </math>
  </component>
  
  <!--  
    The "fast_sodium_current" component contains the differential equations     
    governing the influx of sodium ions through the cell surface membrane       
    into the cell. 
  -->
  <component name="fast_sodium_current" cmeta:id="fast_sodium_current">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#fast_sodium_current">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The fast sodium current, primarily responsible for the upstroke of
            the action potential.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- These variables are defined here and used in other components. -->
    <variable name="i_Na" public_interface="out" units="uA_per_mm2" />
    <variable
        name="E_Na" public_interface="out"
        initial_value="40.0" units="mV" />

    <!-- This variable is defined here and only used internally. -->
    <variable name="g_Na" initial_value="1.5" units="mS_per_mm2" />
    
    <!-- 
      Time is imported from the "interface", and membrane potential is        
      imported from the "membrane" component.  These variables are used in the  
      "sodium_current" parent component, which also acts as an interface,       
      passing the variables to its encapsulated gate components. 
    -->
    <variable
        name="time" public_interface="in"
        private_interface="out" units="ms" />
    <variable
        name="V" public_interface="in"
        private_interface="out" units="mV" />
    
    <!-- These variables are imported from encapsulated components. -->
    <variable name="m" private_interface="in" units="dimensionless" />
    <variable name="h" private_interface="in" units="dimensionless" />
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#i_Na_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            Calculation of the fast sodium current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="i_Na_calculation_eq">
      <apply id="i_Na_calculation"><eq />
        <ci> i_Na </ci>
        <apply><times />
          <ci> g_Na </ci>
          <apply><power />
            <ci> m </ci>
            <cn cellml:units="dimensionless"> 3.0 </cn>
          </apply>
          <ci> h </ci>
          <apply><minus />
            <ci> V </ci>
            <ci> E_Na </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <!--
    The "fast_sodium_current_m_gate" is the activation m gate encapsulated      
    inside the "fast sodium current" component. 
  -->
  <component name="fast_sodium_current_m_gate"
    cmeta:id="fast_sodium_current_m_gate">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#fast_sodium_current_m_gate">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The voltage-dependent activation gate for the fast sodium channel -
            the m gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable name="m" initial_value="0.019" public_interface="out" units="dimensionless" />
        
    <!-- These variables are defined here and only used internally. -->
    <variable name="alpha_m" units="per_ms" />
    <variable name="beta_m" units="per_ms" />

    <!-- 
      These variables are imported from the "interface" and the "membrane" via
      the "fast_sodium_current" component.
    -->
    <variable name="V" public_interface="in" units="mV" />
    <variable name="time" public_interface="in" units="ms" />
   
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#alpha_m_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The opening rate of the m gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="alpha_m_calculation_eq">
      <apply id="alpha_m_calculation"><eq />
        <ci> alpha_m </ci>
        <apply><divide />
          <apply><plus />
            <ci> V </ci>
            <cn cellml:units="mV"> 47.0 </cn>
          </apply>
          <apply><minus />
            <cn cellml:units="dimensionless"> 1.0 </cn>
            <apply><exp />
              <apply><minus />
                <apply><divide />
                  <apply><plus />
                    <ci> V </ci>
                    <cn cellml:units="mV"> 47.0 </cn>
                  </apply>
                  <cn cellml:units="mV"> 10.0 </cn>
                </apply>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#beta_m_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The closing rate of the m gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="beta_m_calculation_eq">
      <apply id="beta_m_calculation"><eq />
        <ci> beta_m </ci>
        <apply><times />
          <cn cellml:units="per_ms"> 40.0 </cn>
          <apply><exp />
            <apply><minus />
              <apply><divide />
                <apply><plus />
                  <ci> V </ci>
                  <cn cellml:units="mV"> 72.0 </cn>
                </apply>
                <cn cellml:units="mV"> 17.86 </cn>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#dm_dt_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The kinetics of the m gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="dm_dt_eq">
      <apply id="dm_dt"><eq />
        <apply><diff />
          <bvar><ci> time </ci></bvar>
          <ci> m </ci>
        </apply>
        <apply><minus />
          <apply><times />
            <ci> alpha_m </ci>
            <apply><minus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <ci> m </ci>
            </apply>
          </apply>
          <apply><times />
            <ci> beta_m </ci>
            <ci> m </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <!--
    The "fast_sodium_current_h_gate" component is the inactivation h gate       
    encapsulated in the "fast sodium current" component.
  -->
  <component name="fast_sodium_current_h_gate"
    cmeta:id="fast_sodium_current_h_gate">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#fast_sodium_current_h_gate">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The voltage-dependent inactivation gate for the fast sodium channel
            - the h gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable
        name="h" initial_value="0.863" public_interface="out"
        units="dimensionless" />
        
    <!-- These variables are defined here and only used internally. -->
    <variable name="alpha_h" units="per_ms" />
    <variable name="beta_h" units="per_ms" />

    <!-- 
      These variables are imported from the "interface" and the "membrane" via
      the "fast_sodium_current" component.  
    -->
    <variable name="V" public_interface="in" units="mV" />
    <variable name="time" public_interface="in" units="ms" />
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#alpha_h_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The opening rate of the h gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="alpha_h_calculation_eq">
      <apply id="alpha_h_calculation"><eq />
        <ci> alpha_h </ci>
        <apply><times />
          <cn cellml:units="per_ms"> 0.0085 </cn>
          <apply><exp />
            <apply><minus />
              <apply><divide />
                <apply><plus />
                  <ci> V </ci>
                  <cn cellml:units="mV"> 71.0 </cn>
                </apply>
                <cn cellml:units="mV"> 5.435 </cn>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#beta_h_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The closing rate of the h gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="beta_h_calculation_eq">
      <apply id="beta_h_calculation"><eq />
        <ci> beta_h </ci>
        <apply><divide />
        <cn cellml:units="per_ms"> 2.5 </cn>
          <apply><plus />
            <apply><exp />
              <apply><minus />
                <apply><divide />
                  <apply><plus />
                    <ci> V </ci>
                    <cn cellml:units="mV"> 10.0 </cn>
                  </apply>
                  <cn cellml:units="mV"> 12.2 </cn>
                </apply>
              </apply>
            </apply>
            <cn cellml:units="dimensionless"> 1.0 </cn>
          </apply>
        </apply>
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#dh_dt_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The kinetics of the h gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="dh_dt_eq">
      <apply id="dh_dt"><eq />
        <apply><diff />
          <bvar><ci> time </ci></bvar>
          <ci> h </ci>
        </apply>
        <apply><minus />
          <apply><times />
            <ci> alpha_h </ci>
            <apply><minus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <ci> h </ci>
            </apply>
          </apply>
          <apply><times />
            <ci> beta_h </ci>
            <ci> h </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <component name="secondary_inward_current" 
    cmeta:id="secondary_inward_current">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#secondary_inward_current">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The secondary (or sometimes slow) inward current activates much more
            slowly than the sodium current and it is responsible for holding up
            the plateau after the initial activation and for controlling the
            duration of the action potential. At the time of this model, it was
            assumed that the flux of both Na and Ca ions through the cell
            membrane was responsible for this current. This channel has an
            activation gate d and an inactivation gate f. It was observed in
            earlier experiments that a portion of this current would not
            completely inactivate. This is represented by the second term in
            the secondary current equation which has an activation variable d1,
            but no deactivation variable.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable name="i_si" public_interface="out" units="uA_per_mm2" />
 
    <!-- These variables are defined here and only used internally. -->
    <variable name="g_si" initial_value="0.008" units="mS_per_mm2" />
    <variable name="g_si_" initial_value="0.0004" units="mS_per_mm2" />
    <variable name="E_si" initial_value="70.0" units="mV" />
    
    <!-- 
      Time is imported from the "interface", and membrane potential is        
      imported from the "membrane" component.  These variables are used in the  
      "secondary_inward_current" parent component, which also acts as an        
      interface, passing the variables to its encapsulated gate component.
    -->
    <variable
        name="time" public_interface="in"
        private_interface="out" units="ms" />
    <variable
        name="V" public_interface="in"
        private_interface="out" units="mV" />
    
    <!-- These variables are imported from encapsulated components. -->
    <variable name="d" private_interface="in" units="dimensionless" />
    <variable name="f" private_interface="in" units="dimensionless" />
    <variable name="d1" private_interface="in" units="dimensionless" />
             
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#i_si_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            Calculation of the second inward current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="i_si_calculation_eq">
      <apply id="i_si_calculation"><eq />
        <ci> i_si </ci>
        <apply><plus />
          <apply><times />
            <ci> g_si </ci>
            <ci> d </ci>
            <ci> f </ci>
            <apply><minus />
              <ci> V </ci>
              <ci> E_si </ci>
            </apply>
          </apply>
          <apply><times />
            <ci> g_si_ </ci>
            <ci> d1 </ci>
            <apply><minus />
              <ci> V </ci>
              <ci> E_si </ci>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <!--
    The "secondary_inward_current_d_gate" component is the d gate encapsulated  
    in the "secondary inward current" component.
  -->
  <component name="secondary_inward_current_d_gate"
    cmeta:id="secondary_inward_current_d_gate">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#secondary_inward_current_d_gate">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The voltage-dependent activation gate for the secondary inward
            current - the d gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable
        name="d" initial_value="0.002" public_interface="out"
        units="dimensionless" /> 

    <!-- These variables are defined here and only used internally. -->
    <variable name="alpha_d" units="per_ms" />
    <variable name="beta_d" units="per_ms" />
    
    <!-- 
      These variables are imported from the "interface" and the "membrane" via
      the "slow_inward_current" component.  
    -->
    <variable name="V" public_interface="in" units="mV" />
    <variable name="time" public_interface="in" units="ms" />

    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#alpha_d_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The opening rate of the d gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="alpha_d_calculation_eq">
      <apply id="alpha_d_calculation"><eq />
        <ci> alpha_d </ci>
        <apply><divide />
          <apply><plus />
            <ci> V </ci>
            <cn cellml:units="mV"> 40.0 </cn>
          </apply>
          <apply><times />
            <cn cellml:units="mV"> 500.0 </cn>
            <apply><minus />
              <cn cellml:units="ms"> 1.0 </cn>
              <apply><exp />
                <apply><minus />
                  <apply><divide />
                    <apply><plus />
                      <ci> V </ci>
                      <cn cellml:units="mV"> 40.0 </cn>
                    </apply>
                    <cn cellml:units="mV"> 10.0 </cn>
                  </apply>
                </apply>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#beta_d_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The closing rate of the d gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="beta_d_calculation_eq">
      <apply id="beta_d_calculation"><eq />
        <ci> beta_d </ci>
        <apply><times />
          <cn cellml:units="per_ms"> 0.02 </cn>
          <apply><exp />
            <apply><minus />
              <apply><divide />
                <apply><plus />
                  <ci> V </ci>
                  <cn cellml:units="mV"> 40.0 </cn>
                </apply>
                <cn cellml:units="mV"> 11.26 </cn>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#dd_dt_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The kinetics of the d gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="dd_dt_eq">
      <apply id="dd_dt"><eq />
        <apply><diff />
          <bvar><ci> time </ci></bvar>
          <ci> d </ci>
        </apply>
        <apply><minus />
          <apply><times />
            <ci> alpha_d </ci>
            <apply><minus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <ci> d </ci>
            </apply>
          </apply>
          <apply><times />
            <ci> beta_d </ci>
            <ci> d </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <!--
    The "secondary_inward_current_f_gate" component is the f gate encapsulated  
    in the "secondary inward current" component.
  -->
  <component name="secondary_inward_current_f_gate"
    cmeta:id="secondary_inward_current_f_gate">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#secondary_inward_current_f_gate">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The voltage-dependent inactivation gate for the secondary inward
            current - the f gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable
        name="f" public_interface="out"
        initial_value="0.794" units="dimensionless" /> 

    <!-- These variables are defined here and only used internally. -->
    <variable name="alpha_f" units="per_ms" />
    <variable name="beta_f" units="per_ms" />
    
    <!-- These variables are imported from parent and sibling components. -->
    <variable name="V" public_interface="in" units="mV" />
    <variable name="time" public_interface="in" units="ms" />
     
     
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#alpha_f_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The opening rate of the f gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="alpha_f_calculation_eq">
      <apply id="alpha_f_calculation"><eq />
        <ci> alpha_f </ci>
        <apply><times />
          <cn cellml:units="per_ms"> 0.000987 </cn>
          <apply><exp />
            <apply><minus />
              <apply><divide />
                <apply><plus />
                  <ci> V </ci>
                  <cn cellml:units="mV"> 60.0 </cn>
                </apply>
                <cn cellml:units="mV"> 25.0 </cn>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
        
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#beta_f_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The closing rate of the f gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="beta_f_calculation_eq">
      <apply id="beta_f_calculation"><eq />
        <ci> beta_f </ci>
        <apply><divide />
          <cn cellml:units="per_ms"> 0.02 </cn>
          <apply><plus />
            <apply><exp />
              <apply><minus />
                <apply><divide />
                  <apply><plus />
                    <ci> V </ci>
                    <cn cellml:units="mV"> 26.0 </cn>
                  </apply>
                  <cn cellml:units="mV"> 11.5 </cn>
                </apply>
              </apply>
            </apply>
            <cn cellml:units="dimensionless"> 1.0 </cn>
          </apply>
        </apply>
      </apply>
    </math>
        
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#df_dt_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The kinetics of the f gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="df_dt_eq">
      <apply id="df_dt"><eq />
        <apply><diff />
          <bvar><ci> time </ci></bvar>
          <ci> f </ci>
        </apply>
        <apply><minus />
          <apply><times />
            <ci> alpha_f </ci>
            <apply><minus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <ci> f </ci>
            </apply>
          </apply>
          <apply><times />
            <ci> beta_f </ci>
            <ci> f </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
    
  <!--
    The "secondary_inward_current_d1_gate" component is the d1 gate encapsulated
    in the "secondary inward current" component.
  -->
  <component name="secondary_inward_current_d1_gate"
    cmeta:id="secondary_inward_current_d1_gate">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#secondary_inward_current_d1_gate">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The activation variable for the slow component of the secondard
            inward current - the d1 gate (corresponds to the d&apos; variable in
            the MNT paper.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable
        name="d1" public_interface="out"
        units="dimensionless" /> 

    <!-- These variables are imported from other components. -->
    <variable name="V" public_interface="in" units="mV" />
    <variable name="time" public_interface="in" units="ms" />
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#d1_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            Calculation of the activation variable d1.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="d1_calculation_eq">
      <apply id="d1_calculation"><eq />
        <ci> d1 </ci>
        <apply><divide />
          <cn cellml:units="dimensionless"> 1.0 </cn>
          <apply><plus />
            <cn cellml:units="dimensionless"> 1.0 </cn>
            <apply><exp />
              <apply><minus />
                <apply><divide />
                  <apply><plus />
                    <ci> V </ci>
                    <cn cellml:units="mV"> 40.0 </cn>
                  </apply>
                  <cn cellml:units="mV"> 6.667 </cn>
                </apply>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <!--
    The pacemaker potassium current describes an outward flux of potassium ions 
    in terms of a single gate variable, s.
  -->
  <component name="pacemaker_potassium_current"
    cmeta:id="pacemaker_potassium_current">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#pacemaker_potassium_current">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            A potassium current activated over the "pace-maker" range of
            potentials. Provides the pacemaker function of the model.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- These variables are defined here and used in other components. -->
    <variable name="i_K2" public_interface="out" units="uA_per_mm2" />
    <variable name="I_K2" public_interface="out" units="uA_per_mm2" />
    
    <!-- This variable is defined here and only used internally. -->
    <variable name="E_K" initial_value="-110.0" units="mV" />
    
    <!-- These variables are imported from parent and sibling components. -->
    <variable
        name="time" public_interface="in"
        private_interface="out" units="ms" />
    <variable
        name="V" public_interface="in"
        private_interface="out" units="mV" />
    
    <!-- These variables are imported from encapsulated components. -->
    <variable name="s" private_interface="in" units="dimensionless" />
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#i_K2_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            Calculation of the pacemaker current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="i_K2_calculation_eq">
      <apply id="i_K2_calculation"><eq />
        <ci> i_K2 </ci>
        <apply><times />
          <ci> I_K2 </ci>
          <ci> s </ci>
        </apply>
      </apply>
    </math>
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#I_K2_max_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The maximal pacemaker current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="I_K2_max_calculation_eq">
      <apply id="I_K2_calculation"><eq />
        <ci> I_K2 </ci>
        <apply><times />
          <cn cellml:units="uA_per_mm2"> 0.028 </cn>
          <apply><divide />
            <apply><minus />
              <apply><exp />
                <apply><divide />
                  <apply><minus />
                    <ci> V </ci>
                    <ci> E_K </ci>
                  </apply>
                  <cn cellml:units="mV"> 25.0 </cn>
                </apply>
              </apply>
              <cn cellml:units="dimensionless"> 1.0 </cn>
            </apply>
            <apply><plus />
              <apply><exp />
                <apply><divide />
                  <apply><plus />
                    <ci> V </ci>
                    <cn cellml:units="mV"> 60.0 </cn>
                  </apply>
                  <cn cellml:units="mV"> 12.5 </cn>
                </apply>
              </apply>
              <apply><exp />
                <apply><divide />
                  <apply><plus />
                    <ci> V </ci>
                    <cn cellml:units="mV"> 60.0 </cn>
                  </apply>
                  <cn cellml:units="mV"> 25.0 </cn>
                </apply>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <!--
    The s gate component is encapsulated within the pacemaker potassium current.
  -->
  <component name="pacemaker_potassium_current_s_gate"
    cmeta:id="pacemaker_potassium_current_s_gate">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#pacemaker_potassium_current_s_gate">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The voltage-dependent gating variable for the pacemaker current -
            the s gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable name="s" initial_value="0.763" public_interface="out" units="dimensionless" />

    <!-- These variables are defined here and only used internally. -->
    <variable name="alpha_s" units="per_ms" />
    <variable name="beta_s" units="per_ms" />
    <variable name="E_s" initial_value="-52.0" units="mV" />
    
    <!-- These variables are imported from parent and sibling components. -->
    <variable name="V" public_interface="in" units="mV" />
    <variable name="time" public_interface="in" units="ms" />
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#alpha_s_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The opening rate of the s gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="alpha_s_calculation_eq">
      <apply id="alpha_s_calculation"><eq />
        <ci> alpha_s </ci>
        <apply><divide />
          <apply><times />
            <cn cellml:units="per_ms"> 0.001 </cn>
            <apply><minus />
              <ci> V </ci>
              <ci> E_s </ci>
            </apply>
          </apply>
          <apply><minus />
            <cn cellml:units="dimensionless"> 1.0 </cn>
            <apply><exp />
              <apply><minus />
                <apply><divide />
                  <apply><minus />
                    <ci> V </ci>
                    <ci> E_s </ci>
                  </apply>
                  <cn cellml:units="mV"> 5.0 </cn>
                </apply>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>

    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#beta_s_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The closing rate of the s gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="beta_s_calculation_eq">
      <apply id="beta_s_calculation"><eq />
        <ci> beta_s </ci>
        <apply><times />
          <cn cellml:units="per_ms"> 0.00005 </cn>
          <apply><exp />
            <apply><minus />
              <apply><divide />
                <apply><minus />
                  <ci> V </ci>
                  <ci> E_s </ci>
                </apply>
                <cn cellml:units="mV"> 15.0 </cn>
              </apply>
            </apply>
          </apply>
        </apply>    
      </apply>
    </math>

    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#ds_dt_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The kinetics of the s gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="ds_dt_eq">
      <apply id="ds_dt"><eq />
        <apply><diff />
          <bvar><ci> time </ci></bvar>
          <ci> s </ci>
        </apply>
        <apply><minus />
          <apply><times />
            <ci> alpha_s </ci>
            <apply><minus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <ci> s </ci>
            </apply>
          </apply>
          <apply><times />
            <ci> beta_s </ci>
            <ci> s </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component> 
  
  <!--
    The equations for the plateau potassium currents (x1 and x2) are based on   
    experiments performed by Noble and Tsien (1969) which showed that additional
    potassium currents were activated in the plateau range of potentials.  They 
    appear to play an essential role in membrane repolarisation.
  -->
  <component name="plateau_potassium_current1"
    cmeta:id="plateau_potassium_current1">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#plateau_potassium_current1">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The equations for the plateau potassium currents (x1 and x2) are
            based on experiments performed by Noble and Tsien (1969) which
            showed that additional potassium currents were activated in the
            plateau range of potentials. They appear to play an essential role
            in membrane repolarisation.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable name="i_x1" public_interface="out" units="uA_per_mm2" />
    
    <!--  This variable is defined here and only used internally. -->
    <variable name="I_x1" units="uA_per_mm2" />
    
    <!-- These variables are imported from parent and sibling components. -->
    <variable
        name="time" public_interface="in"
        private_interface="out" units="ms" />
    <variable
        name="V" public_interface="in"
        private_interface="out" units="mV" />
    
    <!-- This variable is imported from an encapsulated component. -->
    <variable name="x1" private_interface="in" units="dimensionless" />
        
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#i_x1_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            Calculation of the first plateau potassium current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="i_x1_calculation_eq">
      <apply id="i_x1_calculation"><eq />
        <ci> i_x1 </ci>
        <apply><times />
          <ci> x1 </ci>
          <ci> I_x1 </ci>
        </apply>
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#I_x1_max_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            Calculation of the maximal first plateau potassium current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="I_x1_max_calculation_eq">
      <apply id="I_x1_calculation"><eq />
        <ci> I_x1 </ci>
        <apply><times />
          <cn cellml:units="uA_per_mm2"> 0.012 </cn>
          <apply><divide />
            <apply><minus />
              <apply><exp />
                <apply><divide />
                  <apply><plus />
                    <ci> V </ci>
                    <cn cellml:units="mV"> 95.0 </cn>
                  </apply>
                  <cn cellml:units="mV"> 25.0 </cn>                      
                </apply>
              </apply>
              <cn cellml:units="dimensionless"> 1.0 </cn>
            </apply>
            <apply><exp />
              <apply><divide />
                <apply><plus />
                  <ci> V </ci>
                  <cn cellml:units="mV"> 45.0 </cn>
                </apply>
                <cn cellml:units="mV"> 25.0 </cn>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
      
  <!--
    The x1 gate component is encapsulated within the plateau potassium current 
    1.
  -->
  <component name="plateau_potassium_current1_x1_gate"
    cmeta:id="plateau_potassium_current1_x1_gate">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#plateau_potassium_current1_x1_gate">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The voltage-dependent gating variable for the first plateau
            potassium current - the x1 gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable name="x1" initial_value="0.051" public_interface="out" units="dimensionless" />

    <!-- These variables are defined here and only used internally. -->
    <variable name="alpha_x1" units="per_ms" />
    <variable name="beta_x1" units="per_ms" />
    
    <!-- These variables are imported from parent and sibling components. -->
    <variable name="V" public_interface="in" units="mV" />
    <variable name="time" public_interface="in" units="ms" />
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#alpha_x1_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The opening rate of the x1 gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="alpha_x1_calculation_eq">
      <apply id="alpha_x1_calculation"><eq />
        <ci> alpha_x1 </ci>
        <apply><times />
          <cn cellml:units="per_ms"> 5e-4 </cn>
          <apply><divide />
            <apply><exp />
              <apply><divide />
                <apply><plus />
                  <ci> V </ci>
                  <cn cellml:units="mV"> 50.0 </cn>
                </apply>
                <cn cellml:units="mV"> 12.1 </cn>                        
              </apply>
            </apply>
            <apply><plus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <apply><exp />
                <apply><divide />
                  <apply><plus />
                    <ci> V </ci>
                    <cn cellml:units="mV"> 50.0 </cn>
                  </apply>
                  <cn cellml:units="mV"> 17.5 </cn>
                </apply>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#beta_x1_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The closing rate of the x1 gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="beta_x1_calculation_eq">
      <apply id="beta_x1_calculation"><eq />
        <ci> beta_x1 </ci>
        <apply><times />
          <cn cellml:units="per_ms"> 0.0013 </cn>
          <apply><divide />
            <apply><exp />
              <apply><minus />
                <apply><divide />
                  <apply><plus />
                    <ci> V </ci>
                    <cn cellml:units="mV"> 20.0 </cn>
                  </apply>
                  <cn cellml:units="mV"> 16.67 </cn>                     
                </apply>
              </apply>
            </apply>
            <apply><plus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <apply><exp />
                <apply><minus />
                  <apply><divide />
                    <apply><plus />
                      <ci> V </ci>
                      <cn cellml:units="mV"> 20.0 </cn>
                    </apply>
                    <cn cellml:units="mV"> 20.0 </cn>
                  </apply>
                </apply>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#dx1_dt_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The kinetics of the x1 gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="dx1_dt_eq">
      <apply id="dx1_dt"><eq />
        <apply><diff />
          <bvar><ci> time </ci></bvar>
          <ci> x1 </ci>
        </apply>
        <apply><minus />
          <apply><times />
            <ci> alpha_x1 </ci>
            <apply><minus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <ci> x1 </ci>
            </apply>
          </apply>
          <apply><times />
            <ci> beta_x1 </ci>
            <ci> x1 </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <component name="plateau_potassium_current2"
    cmeta:id="plateau_potassium_current2">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#plateau_potassium_current2">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The second of the plateau potassium currents.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable name="i_x2" public_interface="out" units="uA_per_mm2" />
    
    <!--  This variable is defined here and only used internally. -->
    <variable name="I_x2" units="uA_per_mm2" />
    
    <!-- These variables are imported from parent and sibling components. -->
    <variable
        name="time" public_interface="in"
        private_interface="out" units="ms" />
    <variable
        name="V" public_interface="in"
        private_interface="out" units="mV" />
        
    <!-- This variable is imported from an encapsulated component. -->
    <variable name="x2" private_interface="in" units="dimensionless" />
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#i_x2_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            Calculation of the second plateau potassium current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="i_x2_calculation_eq">
      <apply id="i_x2_calculation"><eq />
        <ci> i_x2 </ci>
        <apply><times />
          <ci> x2 </ci>
          <ci> I_x2 </ci>
        </apply>
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#I_x2_max_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The linear maximal second plateau potassium current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="I_x2_max_calculation_eq">
      <apply id="I_x2_calculation"><eq />
        <ci> I_x2 </ci>
        <apply><plus />
          <cn cellml:units="uA_per_mm2"> 0.25 </cn>
          <apply><times />
            <cn cellml:units="mS_per_mm2"> 0.00385 </cn>
            <ci> V </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <!--
    The x2 gate component is encapsulated within the plateau potassium current 
    2.
  -->
  <component name="plateau_potassium_current2_x2_gate"
    cmeta:id="plateau_potassium_current2_x2_gate">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#plateau_potassium_current2_x2_gate">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The gating variable for the second plateau potassium current - the
            x2 gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable name="x2" initial_value="0.006" public_interface="out" units="dimensionless" />

    <!-- These variables are defined here and only used internally. -->
    <variable name="alpha_x2" units="per_ms" />
    <variable name="beta_x2" units="per_ms" />
    
    <!-- These variables are imported from parent and sibling components. -->
    <variable name="V" public_interface="in" units="mV" />
    <variable name="time" public_interface="in" units="ms" />
     
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#alpha_x2_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The opening rate for the x2 gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="alpha_x2_calculation_eq">
      <apply id="alpha_x2_calculation"><eq />
        <ci> alpha_x2 </ci>
        <apply><times />
          <cn cellml:units="per_ms"> 0.000127 </cn>
          <apply><divide />
            <cn cellml:units="dimensionless"> 1.0 </cn>
            <apply><plus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <apply><exp />
                <apply><minus />
                  <apply><divide />
                    <apply><plus />
                      <ci> V </ci>
                      <cn cellml:units="mV"> 19.0 </cn>
                    </apply>
                    <cn cellml:units="mV"> 5.0 </cn>                     
                  </apply>
                </apply>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#beta_x2_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The closing rate for the x2 gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="beta_x2_calculation_eq">
      <apply id="beta_x2_calculation"><eq />
        <ci> beta_x2 </ci>
        <apply><times />
          <cn cellml:units="per_ms"> 0.0003 </cn>
          <apply><divide />
            <apply><exp />
              <apply><minus />
                <apply><divide />
                  <apply><plus />
                    <ci> V </ci>
                    <cn cellml:units="mV"> 20.0 </cn>
                  </apply>
                  <cn cellml:units="mV"> 16.67 </cn>                     
                </apply>
              </apply>
            </apply>
            <apply><plus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <apply><exp />
                <apply><minus />
                  <apply><divide />
                    <apply><plus />
                      <ci> V </ci>
                      <cn cellml:units="mV"> 20.0 </cn>
                    </apply>
                    <cn cellml:units="mV"> 25.0 </cn>
                  </apply>
                </apply>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#dx2_dt_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The kinetics of the x2 gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="dx2_dt_eq">
      <apply id="dx2_dt"><eq />
        <apply><diff />
          <bvar><ci> time </ci></bvar>
          <ci> x2 </ci>
        </apply>
        <apply><minus />
          <apply><times />
            <ci> alpha_x2 </ci>
            <apply><minus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <ci> x2 </ci>
            </apply>
          </apply>
          <apply><times />
            <ci> beta_x2 </ci>
            <ci> x2 </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <component name="transient_chloride_current"
    cmeta:id="transient_chloride_current">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#transient_chloride_current">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The transient chloride current (i_qr) is responsible for the rapid
             repolarisation from the peak of the depolarisation spike of the
             action potential, to the start of the plateau. The current has 2
             gating variables, q and r.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- These variables are defined here and used in other components. -->
    <variable name="i_qr" public_interface="out" units="uA_per_mm2" />
    <variable
        name="E_Cl" public_interface="out"
        initial_value="-70.0" units="mV" />
 
    <!-- This variable is defined here and only used internally. -->
    <variable name="g_qr" initial_value="0.05" units="mS_per_mm2" />
    
    <!-- These variables are imported from parent and sibling components. -->
    <variable
        name="time" public_interface="in"
        private_interface="out" units="ms" />
    <variable
        name="V" public_interface="in"
        private_interface="out" units="mV" />
    
    <!-- These variables are imported from encapsulated components. -->
    <variable name="q" private_interface="in" units="dimensionless" />
    <variable name="r" private_interface="in" units="dimensionless" />
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#i_qr_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            Calculation of the transient chloride current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="i_qr_calculation_eq">
      <apply id="i_qr_calculation"><eq />
        <ci> i_qr </ci>
        <apply><times />
          <ci> g_qr </ci>
          <ci> q </ci>
          <ci> r </ci>
          <apply><minus />
            <ci> V </ci>
            <ci> E_Cl </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <!--  The encapsulated q gate. -->
  <component name="transient_chloride_current_q_gate"
    cmeta:id="transient_chloride_current_q_gate">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#transient_chloride_current_q_gate">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The voltage-dependent activation gate for the transient chloride
            channel - the q gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable
        name="q" initial_value="0.0" public_interface="out"
        units="dimensionless" />

    <!-- These variables are defined here and only used internally. -->
    <variable name="alpha_q" units="per_ms" />
    <variable name="beta_q" units="per_ms" />
    
    <!-- These variables are imported from parent and sibling components. -->
    <variable name="V" public_interface="in" units="mV" />
    <variable name="time" public_interface="in" units="ms" />

    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#alpha_q_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The opening rate for the q gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="alpha_q_calculation_eq">
      <apply id="alpha_q_calculation"><eq />
        <ci> alpha_q </ci>
        <apply><times />
          <cn cellml:units="per_mV_ms"> 0.008 </cn>
          <apply><divide />
            <ci> V </ci>
            <apply><minus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <apply><exp />
                <apply><minus />
                  <apply><divide />
                    <ci> V </ci>
                    <cn cellml:units="mV"> 10.0 </cn>
                  </apply>
                </apply>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#beta_q_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The closing rate for the q gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="beta_q_calculation_eq">
      <apply id="beta_q_calculation"><eq />
        <ci> beta_q </ci>
        <apply><times />
          <cn cellml:units="per_ms"> 0.08 </cn>
          <apply><exp />
            <apply><minus />
              <apply><divide />
                <ci> V </ci>
                <cn cellml:units="mV"> 11.26 </cn>
              </apply>
            </apply>
          </apply>
        </apply>       
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#dq_dt_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The kinetics of the q gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="dq_dt_eq">
      <apply id="dq_dt"><eq />
        <apply><diff />
          <bvar><ci> time </ci></bvar>
          <ci> q </ci>
        </apply>
        <apply><minus />
          <apply><times />
            <ci> alpha_q </ci>
            <apply><minus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <ci> q </ci>
            </apply>
          </apply>
          <apply><times />
            <ci> beta_q </ci>
            <ci> q </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  
  <!--  The encapsualted r gate. -->
  <component name="transient_chloride_current_r_gate"
    cmeta:id="transient_chloride_current_r_gate">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#transient_chloride_current_r_gate">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The voltage-dependent inactivation gate for the transient chloride
            current - the r gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable
        name="r" initial_value="0.126" public_interface="out"
        units="dimensionless" />

    <!-- These variables are defined here and only used internally. -->
    <variable name="alpha_r" units="per_ms" />
    <variable name="beta_r" units="per_ms" />
    
    <!-- These variables are imported from parent and sibling components. -->
    <variable name="V" public_interface="in" units="mV" />
    <variable name="time" public_interface="in" units="ms" />

    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#alpha_r_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The opening rate for the r gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="alpha_r_calculation_eq">
      <apply id="alpha_r_calculation"><eq />
        <ci> alpha_r </ci>
        <apply><times />
          <cn cellml:units="per_ms"> 0.00018 </cn>
          <apply><exp />
            <apply><minus />
              <apply><divide />
                <apply><plus/>
                  <ci> V </ci>
                  <cn cellml:units="mV">80</cn>
                </apply>
                <cn cellml:units="mV"> 25.0 </cn>
              </apply>
            </apply>
          </apply>
        </apply>       
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#beta_r_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The closing rate for the r gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="beta_r_calculation_eq">
      <apply id="beta_r_calculation"><eq />
        <ci> beta_r </ci>
        <apply><divide />
          <cn cellml:units="per_ms"> 0.02 </cn>
          <apply><plus />
            <apply><exp />
              <apply><minus />
                <apply><divide />
                  <apply><plus />
                    <ci> V </ci>
                    <cn cellml:units="mV"> 26 </cn>
                  </apply>
                  <cn cellml:units="mV"> 11.5 </cn>
                </apply>
              </apply>
            </apply>
            <cn cellml:units="dimensionless"> 1.0 </cn>
          </apply>
        </apply>
      </apply>
    </math>
      
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#dr_dt_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The kinetics of the r gate.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="dr_dt_eq">
      <apply id="dr_dt"><eq />
        <apply><diff />
          <bvar><ci> time </ci></bvar>
          <ci> r </ci>
        </apply>
        <apply><minus />
          <apply><times />
            <ci> alpha_r </ci>
            <apply><minus />
              <cn cellml:units="dimensionless"> 1.0 </cn>
              <ci> r </ci>
            </apply>
          </apply>
          <apply><times />
            <ci> beta_r </ci>
            <ci> r </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <!--
    The outward time-independent (or background) ionic current is carried       
    predominately by potassium ions and is represented by i_K1.
  --> 
  <component name="time_independent_outward_current"
    cmeta:id="time_independent_outward_current">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#time_independent_outward_current">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The time-independent (background) current carried by potassium ions.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!-- This variable is defined here and used in other components. -->
    <variable name="i_K1" public_interface="out" units="uA_per_mm2" />
    
    <!-- This variable is defined here and only used internally. -->
    <variable name="E_K1" initial_value="-30.0" units="mV" />
    
    <!-- These variables are imported from other components. -->
    <variable name="time" public_interface="in" units="ms" />
    <variable name="V" public_interface="in" units="mV" />
    <variable name="I_K2" public_interface="in" units="uA_per_mm2" />
        
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#i_K1_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            Calculation of the time-independent potassium current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="i_K1_calculation_eq">
      <apply id="i_K1_calculation"><eq />
        <ci> i_K1 </ci>
        <apply><plus />
          <apply><divide />
            <ci> I_K2 </ci>
            <cn cellml:units="dimensionless"> 2.8 </cn>
          </apply>
          <apply><times />
            <cn cellml:units="uA_per_mm2"> 0.002 </cn>
            <apply><divide />
              <apply><minus />
                <ci> V </ci>
                <ci> E_K1 </ci>
              </apply>
              <apply><minus />
                <cn cellml:units="dimensionless"> 1.0 </cn>
                <apply><exp />
                  <apply><minus />
                    <apply><divide />
                      <apply><minus />
                        <ci> V </ci>
                        <ci> E_K1 </ci>
                      </apply>
                      <cn cellml:units="mV"> 25.0 </cn>
                    </apply>
                  </apply>
                </apply>
              </apply>
            </apply>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  <!-- 
    The "sodium_background_current" is a time-independent diffusion of Na ions  
    down their electrochemical gradient, through the cell surface membrane into 
    the cytosol.
  -->
  <component name="sodium_background_current"
    cmeta:id="sodium_background_current">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#sodium_background_current">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The sodium background current is a time-independent diffusion of Na
            ions down their electrochemical gradient, through the cell surface
            membrane into the cytosol.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!--  This variable is defined here and used in other components. -->
    <variable name="i_Na_b" public_interface="out" units="uA_per_mm2" />
    
    <!-- This variable is defined here and only used internally. -->
    <variable name="g_Nab" initial_value="0.00105" units="mS_per_mm2" />
    
    <!-- 
        Time and membrane potential are imported from the "interface" and the
        "membrane" components.  The reversal potential is imported from the     
        "fast_sodium_current" component. 
    -->
    <variable name="time" public_interface="in" units="ms" />
    <variable name="V" public_interface="in" units="mV" />
    <variable name="E_Na" public_interface="in" units="mV" /> 
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#i_Na_b_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            Calculation of the sodium background current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="i_Na_b_calculation_eq">
      <apply id="i_Na_b_calculation"><eq />
        <ci> i_Na_b </ci>
        <apply><times />
          <ci> g_Nab </ci>
          <apply><minus />
            <ci> V </ci>
            <ci> E_Na </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  
  
  <!-- 
    The "chloride_background_current" contributes to maintaining the plateau and
    helps to determine the action potential duration.
  -->
  <component name="chloride_background_current"
    cmeta:id="chloride_background_current">
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#chloride_background_current">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            The chloride background current contributes to maintaining the
            plateau and helps to determine the action potential duration.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>

    <!--  This variable is defined here and used in other components. -->
    <variable name="i_Cl_b" public_interface="out" units="uA_per_mm2" />
    
    <!-- These variables are defined here and only used internally. -->
    <variable name="g_Clb" initial_value="0.0001" units="mS_per_mm2" />
    
    <!-- 
        Time and memebrane potential are imported from the "interface" and the
        "membrane" components.  The reversal potential is imported from the     
        "transient_chloride_current" component. 
    -->
    <variable name="time" public_interface="in" units="ms" />
    <variable name="V" public_interface="in" units="mV" />
    <variable name="E_Cl" public_interface="in" units="mV" /> 
    
    <rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:cmeta="http://www.cellml.org/metadata/1.0#">
      <rdf:Description rdf:about="#i_Cl_b_calculation_eq">
        <cmeta:comment rdf:parseType="Resource">
          <rdf:value>
            Calculation of the background chloride current.
          </rdf:value>
        </cmeta:comment>
      </rdf:Description>
    </rdf:RDF>
    <math xmlns="http://www.w3.org/1998/Math/MathML"
      cmeta:id="i_Cl_b_calculation_eq">
      <apply id="i_Cl_b_calculation"><eq />
        <ci> i_Cl_b </ci>
        <apply><times />
          <ci> g_Clb </ci>
          <apply><minus />
            <ci> V </ci>
            <ci> E_Cl </ci>
          </apply>
        </apply>
      </apply>
    </math>
  </component>
  


  <!--
    The following <group> element specifies how the components representing
    activation and inactivation gates are encapsulated inside their parent      
    currents.  
  -->
  <group>
    <relationship_ref relationship="encapsulation" />
    <component_ref component="interface">
      <component_ref component="membrane"/>
      <component_ref component="fast_sodium_current">
        <component_ref component="fast_sodium_current_m_gate" />
        <component_ref component="fast_sodium_current_h_gate" />
      </component_ref>
      <component_ref component="secondary_inward_current">
        <component_ref component="secondary_inward_current_d_gate" />
        <component_ref component="secondary_inward_current_f_gate" />
        <component_ref component="secondary_inward_current_d1_gate" />
      </component_ref>
      <component_ref component="pacemaker_potassium_current">
        <component_ref component="pacemaker_potassium_current_s_gate" />
      </component_ref>
      <component_ref component="transient_chloride_current">
        <component_ref component="transient_chloride_current_q_gate" />
        <component_ref component="transient_chloride_current_r_gate" />           
      </component_ref>
      <component_ref component="plateau_potassium_current1">
        <component_ref component="plateau_potassium_current1_x1_gate" />
      </component_ref>
      <component_ref component="plateau_potassium_current2">
        <component_ref component="plateau_potassium_current2_x2_gate" />
      </component_ref>
      <component_ref component="time_independent_outward_current" />
      <component_ref component="sodium_background_current" />
      <component_ref component="chloride_background_current" />
    </component_ref>
  </group>
  
  
  <!--
    "time" is passed from the "interface" component into the
    "membrane" and current components.
  -->
  <connection>
    <map_components
        component_1="membrane" component_2="interface" />
    <map_variables variable_1="time" variable_2="time" />
    <map_variables variable_1="I_stim" variable_2="I_stim" />
  </connection>

  <connection>
    <map_components
        component_1="fast_sodium_current" component_2="interface" />
    <map_variables variable_1="time" variable_2="time" />
  </connection>

  <connection>
    <map_components
        component_1="secondary_inward_current" component_2="interface" />
    <map_variables variable_1="time" variable_2="time" />
  </connection>

  <connection>
    <map_components
        component_1="pacemaker_potassium_current" component_2="interface" />
    <map_variables variable_1="time" variable_2="time" />
  </connection>
  
  <connection>
    <map_components
        component_1="plateau_potassium_current1" component_2="interface" />
    <map_variables variable_1="time" variable_2="time" />
  </connection>
  
  <connection>
    <map_components
        component_1="plateau_potassium_current2" component_2="interface" />
    <map_variables variable_1="time" variable_2="time" />
  </connection>
  
  <connection>
    <map_components
        component_1="transient_chloride_current" component_2="interface" />
    <map_variables variable_1="time" variable_2="time" />
  </connection>
   
  <connection>
    <map_components
        component_1="time_independent_outward_current" component_2="interface" />
    <map_variables variable_1="time" variable_2="time" />
  </connection>
  
  <connection>
    <map_components
        component_1="sodium_background_current" component_2="interface" />
    <map_variables variable_1="time" variable_2="time" />
  </connection>
  
  <connection>
    <map_components
        component_1="chloride_background_current" component_2="interface" />
    <map_variables variable_1="time" variable_2="time" />
  </connection>
  
  <!--
    Several variables are passed between the "membrane" and its sub-components.
  -->
  
  <connection>
    <map_components
        component_1="membrane" component_2="fast_sodium_current" />
    <map_variables variable_1="V" variable_2="V" />
    <map_variables variable_1="i_Na" variable_2="i_Na" />
  </connection>

  <connection>
    <map_components
        component_1="secondary_inward_current" component_2="membrane" />
    <map_variables variable_1="V" variable_2="V" />
    <map_variables variable_1="i_si" variable_2="i_si" />
  </connection>

  <connection>
    <map_components
        component_1="pacemaker_potassium_current" component_2="membrane" />
    <map_variables variable_1="V" variable_2="V" />
    <map_variables variable_1="i_K2" variable_2="i_K2" />
  </connection>
  
  <connection>
    <map_components
        component_1="plateau_potassium_current1" component_2="membrane" />
    <map_variables variable_1="V" variable_2="V" />
    <map_variables variable_1="i_x1" variable_2="i_x1" />
  </connection>
  
  <connection>
    <map_components
        component_1="plateau_potassium_current2" component_2="membrane" />
    <map_variables variable_1="V" variable_2="V" />
    <map_variables variable_1="i_x2" variable_2="i_x2" />
  </connection>
  
  <connection>
    <map_components
        component_1="transient_chloride_current" component_2="membrane" />
    <map_variables variable_1="V" variable_2="V" />
    <map_variables variable_1="i_qr" variable_2="i_qr" />
  </connection>
   
  <connection>
    <map_components
        component_1="time_independent_outward_current" component_2="membrane" />
    <map_variables variable_1="V" variable_2="V" />
    <map_variables variable_1="i_K1" variable_2="i_K1" />
  </connection>
  
  <connection>
    <map_components
        component_1="sodium_background_current" component_2="membrane" />
    <map_variables variable_1="V" variable_2="V" />
    <map_variables variable_1="i_Na_b" variable_2="i_Na_b" />
  </connection>
  
  <connection>
    <map_components
        component_1="chloride_background_current" component_2="membrane" />
    <map_variables variable_1="V" variable_2="V" />
    <map_variables variable_1="i_Cl_b" variable_2="i_Cl_b" />
  </connection>
  
  <!-- A few variables are passed between the other components. -->
  <connection>
    <map_components
        component_1="sodium_background_current" component_2="fast_sodium_current" />
    <map_variables variable_1="E_Na" variable_2="E_Na" />
  </connection>
  
  <connection>
    <map_components
        component_1="time_independent_outward_current" component_2="pacemaker_potassium_current" />
    <map_variables variable_1="I_K2" variable_2="I_K2" />
  </connection>
  
  <connection>
    <map_components
        component_1="transient_chloride_current" component_2="chloride_background_current" />
    <map_variables variable_1="E_Cl" variable_2="E_Cl" />
  </connection>
  
  <!--
    Several variables are passed between parent components and their            
    encapsulated gates.
  -->
  <connection>
    <map_components
        component_1="fast_sodium_current" component_2="fast_sodium_current_m_gate" />
    <map_variables variable_1="m" variable_2="m" />
    <map_variables variable_1="time" variable_2="time" />
    <map_variables variable_1="V" variable_2="V" />
  </connection>
  
  <connection>
    <map_components
        component_1="fast_sodium_current" component_2="fast_sodium_current_h_gate" />
    <map_variables variable_1="h" variable_2="h" />
    <map_variables variable_1="time" variable_2="time" />
    <map_variables variable_1="V" variable_2="V" />
  </connection>

  <connection>
    <map_components
        component_1="secondary_inward_current" component_2="secondary_inward_current_d_gate" />
    <map_variables variable_1="d" variable_2="d" />
    <map_variables variable_1="time" variable_2="time" />
    <map_variables variable_1="V" variable_2="V" />
  </connection>
  
  <connection>
    <map_components
        component_1="secondary_inward_current" component_2="secondary_inward_current_f_gate" />
    <map_variables variable_1="f" variable_2="f" />
    <map_variables variable_1="time" variable_2="time" />
    <map_variables variable_1="V" variable_2="V" />
  </connection>
  
  <connection>
    <map_components
        component_1="secondary_inward_current" component_2="secondary_inward_current_d1_gate" />
    <map_variables variable_1="d1" variable_2="d1" />
    <map_variables variable_1="time" variable_2="time" />
    <map_variables variable_1="V" variable_2="V" />
  </connection>
  
  <connection>
    <map_components
        component_1="pacemaker_potassium_current" component_2="pacemaker_potassium_current_s_gate" />
    <map_variables variable_1="s" variable_2="s" />
    <map_variables variable_1="time" variable_2="time" />
    <map_variables variable_1="V" variable_2="V" />
  </connection>
  
  <connection>
    <map_components
        component_1="transient_chloride_current" component_2="transient_chloride_current_q_gate" />
    <map_variables variable_1="q" variable_2="q" />
    <map_variables variable_1="time" variable_2="time" />
    <map_variables variable_1="V" variable_2="V" />
  </connection>
  
  <connection>
    <map_components
        component_1="transient_chloride_current" component_2="transient_chloride_current_r_gate" />
    <map_variables variable_1="r" variable_2="r" />
    <map_variables variable_1="time" variable_2="time" />
    <map_variables variable_1="V" variable_2="V" />
  </connection>
  
  <connection>
    <map_components
        component_1="plateau_potassium_current1" component_2="plateau_potassium_current1_x1_gate" />
    <map_variables variable_1="x1" variable_2="x1" />
    <map_variables variable_1="time" variable_2="time" />
    <map_variables variable_1="V" variable_2="V" />
  </connection>
  
  <connection>
    <map_components
        component_1="plateau_potassium_current2" component_2="plateau_potassium_current2_x2_gate" />
    <map_variables variable_1="x2" variable_2="x2" />
    <map_variables variable_1="time" variable_2="time" />
    <map_variables variable_1="V" variable_2="V" />
  </connection>

</model>