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) |
Cell-based
| Quantity | Units | Notes |
| Length | dimensionless | Nondimensionalised by typical cell diameter (approx 10-5 m) |
| Time | hours |
Mechanics
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.