An action performed or a feeling experienced in response to a situation or event
his reaction had bewildered her
The cycle of reactions (the Calvin cycle) that occurs in the second phase of photosynthesis and does not require the presence of light. It involves the fixation of carbon dioxide and its reduction to carbohydrate and the dissociation of water, using chemical energy stored in ATP
A coiled tube in which a reaction takes place.
A jet engine used to provide intermittent thrust for changing or correcting the velocity of a spacecraft; also in extended use.
A zone of one mineral enclosing another and formed by the reaction of the core with its surroundings.
(In a film or video recording) a portrayal of a person’s response to an event or to a statement made by another
The length of time taken for a person or system to respond to a given stimulus or event
(In behavioural typology) a physical or personality type which is expected to react in specific ways to a stimulus.
A type of wood with modified anatomical and biochemical features found in leaning stems and in the lower (in gymnosperms) or upper (in angiosperms) sides of branches.
(In a word association test) a word given by a subject in response to a stimulus word.
An irritation or inflammation of the skin caused by an adverse response to a substance that has been inhaled, ingested, touched, or purposefully applied or injected for a skin test.
The physiological response to stress in many vertebrates, mediated largely by hormones.
= aldol condensation.
A chemical reaction or other process in which the products themselves promote or spread the reaction, which under certain conditions may accelerate dramatically
The reaction of an antibody with an antigen other than the one that gave rise to it
Acute exacerbation of leprosy, occurring during certain treatments for the condition, and typically characterized by fever, redness and swelling of skin lesions, and often acute neuritis, occurring especially during leprosy treatment; an instance of this.
The reaction of something, especially the iris of the eye, to different intensities of light
The characteristic reaction of Millon's reagent with phenolic compounds, in which a white precipitate is produced that becomes pink or reddish on heating (described by Millon for a phenolic protein in Compte Rendu Hebd. de l'Acad. des Sci. (1849) 28 40).
A chemical or physical change which involves the transfer of material between phases, or the appearance or disappearance of a phase.
An addition reaction between an alkene and an aldehyde in the presence of an acid catalyst, yielding a 1,3-diol, an allyl alcohol, or a 1,3-dioxan, depending on the particular reactants and conditions used.
The response of the pupil to light, especially as a test of neurological function.
Chemistry. Of, relating to, or involving a rapid chemical reaction.
The site at which physical or chemical reaction occurs; (Biochemistry) the complex of protein and light-harvesting pigments at which the light reactions occur during photosynthesis.
A fictitious propulsion system for a spacecraft, powered by or involving some kind of reaction.
Any engine in which motive power is derived from the reaction exerted by a jet of escaping fluid (usually a gas).
A force equal and opposite to a force giving rise to it; compare sense 2b.
An assessment of an audience's reaction to a programme.
= reaction engine.
= reaction chamber.
A waterwheel impelled by the action of escaping water.
A reaction in which oxidation of one reactant is coupled with reduction of another.
An immediate, non-rational, conditioned response to a stimulus or a symbol.
A reaction in which one molecule combines with another to form a larger molecule with no other products
A process that involves rearrangement of the molecular or ionic structure of a substance, as opposed to a change in physical form or a nuclear reaction
A change in the identity or characteristics of an atomic nucleus that results when it is bombarded with an energetic particle, as in fission, fusion, or radioactive decay
= Pasteur effect. Now historical.
Any of a number of reactions discovered by Perkin, especially that in which, typically, an arylacrylic acid is formed by the condensation of an aromatic aldehyde with the anhydride of an aliphatic acid, in the presence of the sodium salt of the latter.
A modification of the Feulgen reaction for detecting plasmalogens and aldehydes in tissue.
A vessel in which a chemical reaction occurs, especially in an industrial process.
The tendency of a repressed wish or feeling to be expressed at a conscious level in a contrasting form
= reaction engine.
The sequence of actions which together constitute a reaction; specifically the steps (as bond breakage or formation, electron transfer, etc.) involved in a chemical reaction.
A mixture in which a reaction occurs; a mixture of reactants.
An established pattern of reacting to something; specifically a fixed or unchanging behavioural or neurological reaction.
A process constituting or involving a reaction, especially a chemical reaction.
A turbine in which the working fluid accelerates or expands and undergoes a drop in pressure in passing across or through the rotor, which is thereby propelled in the opposite direction to the flow.
A disorder found in troubled adolescents who perceive running away to be a solution to difficulties in the home, at school, etc.
A reaction in which a carbylamine is formed from an amine, employed in the carbylamine test; the test itself.
The reaction of antibody and antigen to form a visible precipitate; an instance of this.