A spliceosomal factor involved in substrate-specific 3′ splice-site recognition and progression through the second catalytic step. Interaction with Sex-lethal provides a mechanism of late splicing control.^[ref]

The dynamic RNA–protein machinery carrying out spliceosomal intron removal. Regulatory interference can occur during early assembly or later catalytic transitions.

Coordinated recognition of the boundaries of an exon, helping specify splice-site pairing. Disrupting communication can repress exon use without directly occupying one essential site.

A molecular species produced during a partially completed splicing reaction. Time-dependent accumulation can help distinguish an assembly defect from a later catalytic block.

Egg laying, including choice of timing and substrate. Plant choice by an adult can determine the conditions experienced by its offspring.

The CH free radical, whose ground electronic term is $X{}^2\Pi$.

The NH free radical, with triplet ground term $X{}^3{\Sigma }^{-}$. Two unpaired electrons occupy perpendicular approximately nonbonding orbitals in a simple valence model.

The hydroxyl radical is $\mathrm{HO}\cdot$, an oxygen-centered species with an unpaired electron. It differs from the hydroxide ion $\mathrm{O}{\mathrm{H}}^{-}$ despite containing the same two elements.

It reacts rapidly with many molecules through pathways such as hydrogen abstraction and addition to multiple bonds. Its atmospheric role follows from those kinetics: even a low abundance can strongly influence how long other reactive trace gases persist.

The hydroperoxyl radical is $\mathrm{H}{\mathrm{O}}_2\cdot$, a reactive hydrogen-oxygen species. It is related by proton transfer to the superoxide radical anion.

Its reactions help connect radical production, oxygen chemistry, and termination pathways in gases and solutions. Because its speciation depends on the medium, neutral hydroperoxyl and charged superoxide should not be treated as the same species under every condition.

A radical with an oxygen-centred peroxyl group, commonly formed when a carbon-centred radical adds molecular oxygen. Its reactions can recycle radicals, form an alkoxy radical, or produce a terminating organic nitrate branch, depending on the reaction partner and structure.

An alkoxy radical has the form $\mathrm{RO}\cdot$, with an unpaired electron associated with oxygen. It differs from the closed-shell alkoxide anion $\mathrm{R}{\mathrm{O}}^{-}$.

Hydrogen abstraction and carbon-carbon bond fragmentation are possible reaction pathways depending on the attached group and environment. Distinguishing radical character from negative charge is essential when interpreting how such an oxygen-centered species reacts.

A neutral nitrogen-oxide radical, distinct from the nitrate anion. It can add to unsaturated organic molecules and is important in some night-time oxidation pathways.

The radical $\mathrm{ClO}$ formed when a chlorine atom reacts with ozone. Its reaction partners and reservoirs depend on altitude and temperature; the chlorine monoxide dimer cycle is important under cold, activated polar conditions.

An oxygen-centred radical of form $\mathrm{RO}{\mathrm{O}}^{\bullet }$, often formed by rapid addition of dioxygen to a carbon-centred radical.

Radiation energetic enough to ionize matter. Its biological effects can include direct molecular damage and indirect chemical changes, with consequences depending on dose, timing and cellular context.

The monostatic radar cross section is $4\pi$ times the backward differential scattering cross-section. Equivalently, ${\sigma }_{\mathrm{back}}={\lim }_{r\to \infty }4\pi r^2{S}_{\mathrm{back}}/S_{\mathrm{inc}}$. It is a directional scattering measure with dimensions of area, not generally the geometric area or the total scattering cross-section. The definition may additionally specify the transmitted and received polarizations.

For a far-field free-space link with one reciprocal antenna transmitting and receiving at range $D$, the outward intensity is $P_{T}G/(4\pi D^2)$. The backward scattered intensity at the receiver is this times ${\sigma }_{\mathrm{back}}/(4\pi D^2)$. Multiplying by the matched antenna effective area $G{\lambda }^2/(4\pi )$ gives the displayed received power. Attenuation, misalignment and polarization mismatch require additional factors. The threshold for a root mean square voltage $V_m$ across a real matched load $R$ is $V_m^2/R$.

Quantum computation capable of approximating arbitrary finite quantum circuits using a specified universal quantum gate set, with an error tolerance and resource scaling.

In atomic units, the displayed integral is the direct electrostatic contribution between two normalized atomic orbitals $a,b$. It enters a two-electron energy expectation together with the exchange integral.

For two orthonormal spatial atomic orbitals, the normalized symmetric and antisymmetric two-particle factors have Coulomb energies $J_{ab}+K_{ab}$ and $J_{ab}-K_{ab}$. With common orbitals, the fermionic singlet state and triplet state therefore differ by $2K_{ab}$. This is an exchange interaction resulting from the state symmetry and the Coulomb operator, rather than a separate classical force.