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  2. Dollar (reactivity) - Wikipedia

    en.wikipedia.org/wiki/Dollar_(reactivity)

    Reactivity in its most general sense would not be measured in dollars or cents. This is because k eff measures the total value of reactivity, a summation of the reactivity of both the prompt and delayed neutrons. However, reactivity in dollars is dependent on the delayed neutron fraction (β eff). [2] Reactivity in dollars = ⁠ ρ / β eff ⁠

  3. Periodic trends - Wikipedia

    en.wikipedia.org/wiki/Periodic_trends

    However, in group XIII (boron family), the electronegativity first decreases from boron to aluminium and then increases down the group. It is due to the fact that the atomic size increases as we move down the group, but at the same time the effective nuclear charge increases due to poor shielding of the inner d and f electrons.

  4. Nuclear reactor physics - Wikipedia

    en.wikipedia.org/wiki/Nuclear_reactor_physics

    Reactivity is an expression of the departure from criticality. δk = (k − 1)/k. When the reactor is critical, δk = 0. When the reactor is subcritical, δk < 0. When the reactor is supercritical, δk > 0. Reactivity is also represented by the lowercase Greek letter rho (ρ). Reactivity is commonly expressed in decimals or percentages or pcm ...

  5. Mathematical formulation of the Standard Model - Wikipedia

    en.wikipedia.org/wiki/Mathematical_formulation...

    This article describes the mathematics of the Standard Model of particle physics, a gauge quantum field theory containing the internal symmetries of the unitary product group SU(3) × SU(2) × U(1). The theory is commonly viewed as describing the fundamental set of particles – the leptons, quarks, gauge bosons and the Higgs boson.

  6. Glossary of physics - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_physics

    mathematical physics The application of mathematics to problems in physics and the development of mathematical methods suitable for such applications and for the formulation of physical theories. mathematics The abstract study of topics encompassing quantity, structure, space, change, and other properties. matrix

  7. Reactivity (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Reactivity_(chemistry)

    Both factors are actually distinct, and both commonly depend on temperature. For example, it is commonly asserted that the reactivity of alkali metals (Na, K, etc.) increases down the group in the periodic table, or that hydrogen's reactivity is evidenced by its reaction with oxygen. In fact, the rate of reaction of alkali metals (as evidenced ...

  8. 2-group - Wikipedia

    en.wikipedia.org/wiki/2-group

    Thus, both the first and second homotopy groups of a space are contained within its fundamental 2-group. As this 2-group also defines an action of π 1 (X,x) on π 2 (X,x) and an element of the cohomology group H 3 (π 1 (X,x), π 2 (X,x)), this is precisely the data needed to form the Postnikov tower of X if X is a pointed connected homotopy 2 ...

  9. Group 12 element - Wikipedia

    en.wikipedia.org/wiki/Group_12_element

    Group 12, by modern IUPAC numbering, [1] is a group of chemical elements in the periodic table. It includes zinc (Zn), cadmium (Cd), mercury (Hg), [ 2 ] [ 3 ] [ 4 ] and copernicium (Cn). [ 5 ] Formerly this group was named IIB (pronounced as "group two B", as the "II" is a Roman numeral ) by CAS and old IUPAC system.