Erosion of an older deposit and incorporation of its fossil material into a younger one. It can create a misleading apparent last occurrence.

Mixing remains produced at different times in one sampled assemblage. It can occur locally without long-distance transport, blurring short ecological events.

Postmortem loss and alteration of tissues. Replicated observations show that loss can be anatomically selective, so a decayed specimen may look systematically less derived.^[ref]

Preservation retaining anatomical information normally lost, especially soft tissues. Such deposits reveal otherwise hidden diversity but still select particular environments and tissue types.

Physical and chemical alteration after burial, potentially modifying fossil tissues and isotopic compositions.

Processes affecting remains before final burial, including decay, disarticulation, transport and surface modification. These mechanisms can continue or recur during reworking.

Transformation and loss of biological tissues after death through autolysis, microbial activity and associated processes. Decay rates differ among anatomical characters.

Separation of connected skeletal elements as supporting tissues fail or external forces act. An articulated skeleton need not have been buried instantly.

Movement of remains by currents, waves, gravity or organisms. Sorting depends on size, density, shape and articulation rather than solely on taxon abundance.

Erosion and redeposition of previously buried remains into a younger deposit, potentially confusing environmental and chronological interpretation.

Preservation retaining anatomical information normally removed by decay or burial alteration. It reflects particular preservational pathways, not an unbiased sample of all life.

Processes through which biological remains or traces enter the fossil record. Complete replacement by new minerals is only one possible pathway.

Fragmentation of molecular ions induced through electron transfer, useful for preserving and localizing some labile modifications in protein analysis.

Electron capture dissociation fragments multiply charged positive ions after they capture low-energy electrons. In peptide analysis, it can produce backbone cleavages while retaining some modifications that are readily lost by other fragmentation pathways.

Its behavior depends on charge state, structure, and competing relaxation processes. It is a gas-phase ion method in mass spectrometry, distinct from capturing an electron in a neutral solution-phase redox reaction.

A coreceptor associated with recognition of peptide–MHC-class-I complexes by cytotoxic T cells. It contributes to binding and signalling without replacing T-cell-receptor specificity.

A T-cell costimulatory receptor. Its interaction with B7 ligands on activated antigen-presenting cells contributes to naive-cell priming.

A coreceptor usually associated with recognition of peptide–MHC-class-II complexes. CD4 T-cell biological populations coordinate and regulate immune responses in addition to other context-dependent activities.

If a wanted response changes sign on reversing a controlled setting while an offset remains unchanged, the difference of the reversed readings isolates the response. For $V_{\pm }=\pm RI+V_0$, the estimator $(V_{+}-V_{-})/(2I)$ cancels $V_0$. The method requires offset stability between readings. It does not cancel a common current-scale calibration error, and it does not remove even-in-current Joule heating. A useful reversal test specifies which physical effects change sign, then tests the remaining effects independently.

If a controlled reversal changes the desired signal's sign while leaving an additive offset unchanged, readings $y_{+}=S+b$ and $y_{-}=-S+b$ separate them by half-difference and half-sum. Offset drift, gain changes, hysteresis or a background that also reverses violate the simple cancellation. Interleaving polarities and independent blank measurements test those assumptions; signal reversal does not cancel an arbitrary systematic error.