Checking whether a software change alters previously established behavior. A reference output must first be justified rather than merely copied from old software.

Generating cases and checking general properties such as conservation, symmetry or bounds rather than only selected input-output pairs.

Testing relations between outputs for related inputs when an exact reference answer is unavailable. The expected relation must be valid for the scientific problem.

Continuous integration is a software engineering practice in which collaborators frequently combine small changes into a shared main line, conventionally at least daily, and check each integration through an automated software build and software testing. Fast feedback makes incompatible assumptions visible while the changes are still small. A server that tests isolated development branches contributes automation; frequent integration into the shared main line is the defining collaboration practice.^[ref]

For example, one developer changes a parser to return a new data structure, while another changes code that consumes the result. Each component can pass its own isolated unit tests while their combination fails. Integration testing of the shared revision exercises that interface and exposes the mismatch. The build result should identify the tested source revision so that a failure can be reproduced.

A hydroxyl-directed reduction of a β-hydroxy ketone with an acetoxyborohydride reagent, favouring an anti-1,3-diol through intramolecular hydride delivery.

Persistent differentiation of social roles through interactions between an individual’s behaviour and the responses of its partners. Such differentiation need not be genetically fixed.

The braincase is the part of the skull enclosing and protecting the brain. Openings transmit nerves and vessels while the surrounding skeletal walls provide support. Comparative reconstructions distinguish this neural enclosure from the jaws and more external skull-roof components.

The eye socket, distinct from a temporal fenestra behind it.

The roof of the mouth and its supporting anatomy. In avian comparisons, contacts among the vomer, palatine bone, pterygoid bone and braincase are important for cranial kinesis.

Movement between parts of the skull beyond ordinary lower-jaw rotation. joint surfaces, soft tissues, muscles and constraints elsewhere in the skull jointly determine realized movement.

A skull-base projection that contacts the palatal apparatus. Its size and articulation contribute to constraints on cranial kinesis.

A localized epithelial primordium of a feather. Its molecular identity and underlying dermal aggregation can be coupled through mechanical and chemical signals.

The epidermis is the outer stratified epithelial layer of the skin. Basal cell production and progressive differentiation maintain the outer barrier, including the stratum corneum. Production, upward movement and shedding must balance for stable tissue thickness.

Consolidation of a powder under simultaneous heating and applied pressure. Phase formation, density and connected porosity must be checked separately.

An RNA-imaging method using combinatorial codes with error-detection or correction properties. Redundant measurements help distinguish a true molecular identity from an imperfect sequence of observed signals.^[ref]

Identification of many nucleic acid targets through repeated rounds of fluorescent hybridization and imaging. Matching signals across rounds connects temporal coding with spatially retained molecular identities.

Measure the force and extension of an individual molecular tether under controlled displacement or load. A calibrated cantilever or optical trap converts deflection to force. Synthetic polymer stretching provides a nonbiological application; the observed curve also contains instrument and attachment compliance, and its loading-rate dependence can distinguish equilibrium elasticity from activated events.

A polymer with a repeating Si–O backbone and organic substituents at silicon. Its backbone is flexible but lacks a partly occupied electronic conduction band.

The rectangular function has value one on $|t|<1/2$ and zero on $|t|>1/2$. Endpoint values are convention-dependent and do not affect its ordinary integrals or Fourier transform. Shifts, amplitude changes and time rescaling produce a rectangular pulse of arbitrary height, center and duration. With $\hat{f}(k)=\int f(t)e^{-ikt}dt$, for $a>0$ the width-$2a$ pulse $f(t)=1_{|t|<a}$ has Fourier transform $2\sin (ak)/k$, with value $2a$ at zero by a limit. Its convolution with itself is a rescaled triangular function, $(2a-|t|)$ on $|t|<2a$ and zero outside, because the convolution measures the overlap length of two intervals.