In signal transduction, inositol trisphosphate usually means inositol 1,4,5-trisphosphate: a soluble intracellular second messenger. An extracellular ligand, its cell-surface receptor, IP3 and the released calcium ions are distinct components. IP3 binds an IP3 receptor on the endoplasmic reticulum, promoting stored ${\mathrm{Ca}}^{2+}$ release into the cytosol.^[ref]

The useful separation is spatial: an extracellular message can control an internal store without entering it. The existing intracellular-injection experiment under metabotropic receptor tests bypassing reception; the Pancreatic IP3 store fractionation experiment below tests which internal compartment supplies the released calcium. Neither question is answered merely by observing a downstream membrane electric current.

Online text: docs.scipy.org/doc/scipy-1.16.2/reference/generated/scipy.integrate.solve_ivp.html

Cited passages: solve_ivp, method parameter: explicit versus implicit methods and stiffness; solve_ivp, rtol and atol parameters: local error estimates, additive scaling and component-specific atol.

A cathetometer measures differences of vertical height using a sighting telescope mounted on a vertical measuring column. The telescope is aligned horizontally, sighted on a first feature, translated vertically and sighted on a second feature. Their scale readings determine the height difference without placing a ruler directly against either feature.

A manometer supplies a useful application: the two liquid surfaces can be sighted separately to determine the column-height difference used to infer pressure. The optical reference, column alignment, meniscus reading and scale measurement calibration all affect the result. Greater apparent magnification alone cannot correct a tilted reference or an incorrectly identified liquid surface.^[ref]

For a nonrelativistic spin-one-half electron of charge $-e$, with $e>0$, the Pauli Hamiltonian isThe wavefunction has two spin components and $B=\nabla \times A$. If $\pi =-i\hslash \nabla +eA$, then $[{\pi }_i,{\pi }_j]=-ie\hslash {ϵ}_{ijk}{B}_k$; the Pauli matrix multiplication law gives $(\sigma \cdot \pi {)}^2={\pi }^2+e\hslash \sigma \cdot B$, explaining the spin-coupling sign. Thus $i\hslash {\partial }_t\Psi =H_P\Psi$ extends the Schrödinger equation to include the electron's magnetic moment.