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A ligand that reduces receptor activation by an agonist or endogenous signal under specified conditions. Behavioural selectivity cannot be inferred solely from an in-vitro affinity label.

An antifungal drug inhibits fungal growth or damages fungal cells. Different classes act on membrane sterols, cell-wall synthesis or cell division. The target helps explain both the range of susceptible organisms and limits of selectivity.^[ref]

The fluid-filled inner-ear structure whose graded mechanics and sensory cells transform sound-driven vibration into neural signals. Distributed frequency selectivity, active feedback and temporal coding contribute distinct information; a cochlear place response alone does not identify the physical source of a sound.

The glomerular filtration barrier comprises the specialized capillary endothelium, basement membrane and podocyte-associated filtration slits of the glomerulus. Their combined properties determine what enters the initial filtrate. Size selectivity is therefore a feature of a layered interface rather than one simple open sieve.

Researcher in membrane signaling. Yen and collaborators investigated how PIP2 stabilizes active GPCR states and changes coupling selectivity, connecting membrane lipids with receptor behavior.^[ref]

A neuron whose recorded activity has related selectivity during action execution and observation. This response property does not by itself identify the neuron’s necessary behavioural function or its developmental origin.

A nonsteroidal anti-inflammatory drug is a drug in the group including ibuprofen, naproxen and aspirin. These agents commonly reduce prostaglandin production through cyclooxygenase inhibition. Their shared pathway does not make their duration, selectivity or other effects identical.

Correlation-based learning among spatially arranged ON and OFF inputs, with synaptic competition and lateral interactions, can select elongated simple cell receptive fields. Neighbor interactions coordinate preferred orientations across cortex, while competition allows different orientations to persist. Selectivity within one cell and a spatial map across many cells are separate predictions, and neither follows from unbounded Hebbian learning alone.

A cochlear hair-cell class contributing mechanical feedback that increases weak-sound sensitivity and sharpens frequency selectivity. Its feedback-dependent effects are part of the cochlear amplifier.

A is the predicted major diastereomer. At the carbon adjacent to the ketone, take phenyl as the large group, vinyl as medium, and hydrogen as small. There is no adjacent heteroatom donor that would force a five-membered chelate. The appropriate first model is therefore the non-chelating Felkin-Anh model.

View along the carbonyl-carbon–stereocentre bond. Rotate to place the large alpha phenyl group approximately perpendicular to the carbonyl plane. Of the two resulting approaches opposite that large group, the favourable Bürgi-Dunitz trajectory passes nearer hydrogen rather than vinyl. Propyl transfer to the carbonyl and protonation of its oxygen give the configuration labelled A: in the printed projection the new OH projects forward and the propyl bond backward, while the original vinyl bond remains backward. Rotation used to construct a Newman projection must not be mistaken for inversion of the original stereocentre.

This is a relative-selectivity prediction, not a numerical product ratio. Simple attack on the face that happens to look less crowded in the initial flat drawing is unreliable because the relevant C–C single bond can rotate. B is the competing product from the less favourable approach beside vinyl. The model and its preference for the trajectory beside the small group are described in the institutional treatment.^[ref]

Aqueous base selectively converts the methyl ester to a carboxylate, and brief acidification gives the corresponding monoacid while retaining the tert-Butyl ester. At the methyl-ester end, a hydroxide lone pair attacks the acyl carbon and the carbonyl pi pair moves to oxygen. The tetrahedral intermediate collapses as the oxygen anion reforms C=O and the acyl C–OMe bond breaks to methoxide. proton transfer then gives the carboxylate and methanol. carboxylate formation makes the net saponification effectively irreversible under the basic conditions; protonation protonates that carboxylate.

The tert-Butyl ester reacts more slowly under these conditions because its bulky alkoxy group hinders acyl attack, and tert-butoxide is a stronger base and poorer leaving group than methoxide. The selectivity is kinetic, not an assertion that tert-butyl esters can never undergo base hydrolysis. The work-up should be sufficiently mild and brief to avoid the separate acid-labile pathway.

Anhydrous trifluoroacetic acid instead removes the tert-butyl group, leaving the methyl ester. protonation activates the ester; in a useful reactive protonation form the alkoxy oxygen bears the proton. The O–C(tert-butyl) bond then cleaves with its electron pair going to oxygen, producing the carboxylic acid and a tert-butyl-cation-like fragment. Loss of a methyl proton gives 2-methylpropene and regenerates the acid catalyst. Carbonyl-oxygen protonation and charge delocalization can precede cleavage; drawing alkoxy-oxygen protonation is a transparent way of tracking the bonds broken. The key distinction is alkyl–oxygen cleavage here versus acyl–oxygen cleavage in the base reaction. Methyl-cation formation is strongly unfavourable, and without water ordinary acid-catalysed methyl-ester hydrolysis is not available. No water is required to account for the tert-butyl deprotection or its alkene by-product.

Perforated patch recording obtains intracellular electrical access through pores in the patch under the patch pipette, with less open exchange of large cytoplasmic components than conventional whole-cell recording. Pore selectivity matters: retaining some components does not guarantee unchanged ion concentrations. Monitor patch-clamp series resistance as access develops and distinguish a perforated patch from accidental full rupture.

A product is a species formed by a chemical reaction. In a balanced reaction equation, products are conventionally written on the right, although a reversible reaction can produce the original reactants in its reverse direction.

A reaction mixture can contain a desired product, by-products, intermediates, and unreacted starting material. Chemical yield measures the amount of a specified product relative to a stated reference, whereas selectivity concerns preference among competing transformations or products. Identifying a product therefore requires both composition and its role in the reaction being described.

Two oriented linear filters in quadrature have responses $A\cos \phi$ and $A\sin \phi$ to a suitably matched narrowband grating. Their squared sum is $A^2$, independent of phase $\phi$, while orientation and spatial-frequency selectivity remain. A nonlinear output function or normalization can transform this energy into firing rate. Ideal quadrature gives an exact phase identity for the matched stimulus; finite approximate filter pairs need not have perfect invariance for arbitrary images.

Inferring a particular mental process from a neural response associated with it. The inference is weak when the same response occurs during many other processes; task contrasts, functional selectivity and intervention evidence can constrain alternatives.

A region around the meeting of temporal and parietal cortex. Tests of selectivity for theory of mind require nonmental controls matched for relevant alternatives such as language, attention and representational demands.

A neuron active preferentially at a particular part of a temporally extended task or interval. Temporal selectivity can coexist with selectivity for location, behavior and sequence identity; it is not a claim that the cell is an isolated clock.

A reagent-bearing strip used for selected chemical tests of urine. Its assay selectivity and reading conditions differ from those of historical wet-chemical tests.

Recognition that preserves object or face identity despite changes in viewpoint. The aim is tolerance together with selectivity: responding identically to every object would be invariant but useless for distinguishing identity. Tolerance may be partial and differ across processing stages.