Units used in Chaste

Cardiac Units

Note: F=Farad, S=Siemen=Amp/Volt, A=Ampere, u=micro (ie mu).

Quantity Units Notes
Length cm hence surface-area-to-volume ratio is cm-1 etc
Time ms
Voltage or intra- or extracellular potential mV
Capacitance per unit surface area uF cm-2 Cm, which we refer to as the capacitance, is actually a capacitance per unit area. The SI unit
of capicitance is the Farad ( = Coulombs/Volts) (C=Q/V)
Conductivities mS cm-1
(Stimulus) currents per unit volume uA cm-3 Applies to (intracellular) stimulus currents given to cells in mono/bidomain problems
(ie a stimulus current as a RHS source term in the bidomain equations. Note we don't allow
RHS extracellular stimuli)
Currents per unit area uA cm-2 Applies to all ionic currents (single-cell/mono/bidomain equations), intracellular stimuli
in single-cell problems or applied as Neumann boundary conditions, and extracellular
stimuli through electrodes (which are also Neumann boundary conditions)


Quantity Units Notes
Length dimensionless Nondimensionalised by typical cell diameter (approx 10-5 m)
Time hours


Material laws parameters, pressures, and active stresses (in cardiac electro-mechanics) are in kPa. For mechanics simulations the user is free to choose the units for all other quantities, but should do so consistently. For example, if gravity is applied, then [density * gravitational acceleration] should be equal kPa/[length] (here [] denotes "units of"), since the governing equations state that divergence of stress summed with density times gravitational acceleration is zero.

Last modified 6 years ago Last modified on Nov 30, 2014, 4:38:09 PM

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