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  2. Time constant - Wikipedia

    en.wikipedia.org/wiki/Time_constant

    In an increasing system, the time constant is the time for the system's step response to reach 1 − 1 / e ≈ 63.2% of its final (asymptotic) value (say from a step increase). In radioactive decay the time constant is related to the decay constant ( λ ), and it represents both the mean lifetime of a decaying system (such as an atom) before it ...

  3. Entropy as an arrow of time - Wikipedia

    en.wikipedia.org/wiki/Entropy_as_an_arrow_of_time

    Here, as common experience demonstrates, when a hot body T 1, such as a furnace, is put into physical contact, such as being connected via a body of fluid (working body), with a cold body T 2, such as a stream of cold water, energy will invariably flow from hot to cold in the form of heat Q, and given time the system will reach equilibrium.

  4. Nuclear drip line - Wikipedia

    en.wikipedia.org/wiki/Nuclear_drip_line

    Thus, alpha decay can be considered either a form of particle decay or, less frequently, as a special case of nuclear fission. The timescale for the nuclear strong force is much faster than that of the nuclear weak force or the electromagnetic force , so the lifetime of nuclei past the drip lines are typically on the order of nanoseconds or less.

  5. Secular equilibrium - Wikipedia

    en.wikipedia.org/wiki/Secular_equilibrium

    Secular equilibrium can occur in a radioactive decay chain only if the half-life of the daughter radionuclide B is much shorter than the half-life of the parent radionuclide A. In such a case, the decay rate of A and hence the production rate of B is approximately constant, because the half-life of A is very long compared to the time scales ...

  6. Entropy and life - Wikipedia

    en.wikipedia.org/wiki/Entropy_and_life

    The second law can be conceptually stated [22] as follows: Matter and energy have the tendency to reach a state of uniformity or internal and external equilibrium, a state of maximum disorder (entropy). Real non-equilibrium processes always produce entropy, causing increased disorder in the universe, while idealized reversible processes produce ...

  7. Valley of stability - Wikipedia

    en.wikipedia.org/wiki/Valley_of_stability

    Heavy nuclides are susceptible to α decay, and these nuclear reactions have the generic form, A Z X → A-4 Z-2 X′ + 4 2 He. As in β decay, the decay product X′ has greater binding energy and it is closer to the middle of the valley of stability. The α particle carries away two neutrons and two protons, leaving a lighter nuclide. Since ...

  8. Water fluoridation ‘less effective’ than in the past – study

    www.aol.com/water-fluoridation-less-effective...

    [1/2] The #Gvt has announced plans to extend the current water fluoridation scheme in the North East to reach an extra 1.6m people.. Water fluoridation is the single most effective #PublicHealth ...

  9. Deborah number - Wikipedia

    en.wikipedia.org/wiki/Deborah_number

    The Deborah number (De) is a dimensionless number, often used in rheology to characterize the fluidity of materials under specific flow conditions. It quantifies the observation that given enough time even a solid-like material might flow, or a fluid-like material can act solid when it is deformed rapidly enough.