reactivityn.
/ˌriːakˈtɪvᵻti/, U.S. /ˌriækˈtɪvᵻdi/ 1. The state or power of being reactive; capacity or tendency to react or respond to a stimulus, sensitivity; the state or condition of exhibiting a physiological or pathological reaction; the degree of such a reaction.
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1832 N. Tucker tr. E. Swedenborg Apocalypse Revealed (new ed.) I. x. 514 If you take away man's activity or re-activity [L. activum aut reactivum], do you not also take away his capacity of reception, consequently all that belongs to him as man, and with it the act itself?
1850 Lancet 10 Aug. 164/2 By ‘reactivity’ I mean that function of a nervous centre by which it tends to excite the phenomena of muscular contraction.
1896 T. C. Allbutt et al. Syst. Med. I. 558 Our knowledge..of vital reactions and reactivity.
1934 Jrnl. Theol. Stud. 35 402 The author would establish that religion consists in simultaneous reactivity of the affective, conative and cognitive elements of mentality.
1949 Brit. Jrnl. Psychol. Dec. 86 When the individual's P.G.R. [= psychogalvanic reflex] scores are obtained for a given attitude they must be expressed for each person relative to his own general P.G.R. reactivity.
1965 Nature 4 Sept. 1052/1 Individual variations in reactivity, to trifluoperazine or to ‘Psilocybin’ seem to be mirrored in the size of the Weber ratio.
1991 Lancet 9 Mar. 595/2 Subjects were tested for atopy by immediate skin-test reactivity to various common allergens.
2006 Wellness Options 15 Aug. 44/3 Higher intakes of DHA plus EPA can favourably influence several risk factors for CVD and fatal heart attacks, including..reduction in blood platelet reactivity and other thrombogenic risk factors.
2.
a. Capacity or tendency to react chemically; the degree to which a substance is chemically reactive.
ΘΚΠ
the world > matter > chemistry > chemical reactions or processes > [noun] > reactivity
reactivity1888
the world > life > biology > biological processes > stimulation > [noun] > stimulability or irritability
irritability1755
excitability1788
vital contractility1830
reactivity1888
stimulability1975
1888 Nature 22 Mar. 503/1 The occurrence of colour..is more frequently than not concomitant with a high degree of reactivity.
1907 Chem. Abstr. 1 1395 Transformation of open chains to cyclic compounds enhances their reactivity.
1950 Sci. News 15 70 Consideration of the chemical reactivity of crystals will obviously be focussed primarily on the surfaces.
1981 P. Sykes Guidebk. to Mechanism in Org. Chem. (ed. 5) iv. 86 The effect of structure on relative reactivity may be seen particularly clearly when a halogen atom is located at the bridgehead of a bicyclic system.
2006 Science 28 Apr. 501/2 Components are classified based on size and structure (mono- to hexacyclic, compact or extended geometry), and the relative reactivities of each class are then compared under varying desulfurization conditions.
b. spec. The rate of reaction of a coke or coal with carbon dioxide or (in later use) oxygen, under specified conditions.
ΘΚΠ
the world > matter > chemistry > chemical reactions or processes > [noun] > reaction rate > of coke or coal
reactivity1926
society > occupation and work > materials > fuel > coal or types of coal > [noun] > reactivity
reactivity1926
1926 Rep. Fuel Res. Board 1925 (Dep. Sci. & Industr. Res.) 23 A method has been designed which gives an empirical figure for reactivity to carbon dioxide.
1930 Engineering 22 Aug. 251/4 A convenient distinction has been drawn between the combustibility of a coke, denoting the rate at which it burns in oxygen or air, and its reactivity, meaning the rate at which it reacts with carbon dioxide and produces the reducing atmosphere in which the metallic iron is extracted.
1947 G. W. Himus Elem. Fuel Technol. xv. 296 The ‘Reactivity Value’ of coke is defined by the Fuel Research Board as ‘the number of millilitres of carbon monoxide formed from 100 millilitres of carbon dioxide’ under certain definitely specified conditions.
1971 Materials & Technol. II. x. 601 Gas coke..has a lower reactivity than most coals and is not suitable for use on open fires.
1971 Materials & Technol. II. x. 604 The reactivity of coke with respect to oxygen is often measured by the Critical Air Blast (C.A.B.) method.
2005 Fuel Processing Technol. 87 9/2 The reactivity of a coke sample is therefore related to its total anisotropic content and the proportion of different structures.
3. Nuclear Physics. The extent to which a nuclear reactor, or part of one, deviates from a steady critical condition; a numerical measure of this.Originally in a broader sense.
ΘΚΠ
the world > matter > physics > atomic nucleus > nuclear fission > [noun] > minimum of fissile material > deviation from
reactivity1945
1945 H. D. Smyth Gen. Acct. Devel. Atomic Energy Mil. Purposes viii. 89 The reactivity of the pile was so far above expectations that it would have been beyond the capacity of the control rods to handle if the remainder of the heavy water had been added.
1947 Physical Rev. 72 17/1 The reactivity of a chain-reacting pile depends critically on the balance of neutron production, absorption, and leakage.
1960 Gloss. Atomic Terms (U.K.A.E.A.) 44 At any steady state of operation the reactivity is zero.
2006 Energy Conversion & Managem. 47 2772 The change of excess reactivity along burnup is theoretically zero, and shim rods will not be required for this reactor.
This entry has been updated (OED Third Edition, December 2008; most recently modified version published online March 2022).
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