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  2. Becquerel - Wikipedia

    en.wikipedia.org/wiki/Becquerel

    For example, 1 μs −1 would mean 10 6 disintegrations per second: (10 −6 s) −1 = 10 6 s −1, [4] whereas 1 μBq would mean 1 disintegration per 1 million seconds. Other names considered were hertz (Hz), a special name already in use for the reciprocal second (for periodic events of any kind), and fourier (Fr; after Joseph Fourier ). [ 4 ]

  3. Natural number - Wikipedia

    en.wikipedia.org/wiki/Natural_number

    It follows from the definition that each natural number is equal to the set of all natural numbers less than it. This definition, can be extended to the von Neumann definition of ordinals for defining all ordinal numbers , including the infinite ones: "each ordinal is the well-ordered set of all smaller ordinals."

  4. Natural logarithm of 2 - Wikipedia

    en.wikipedia.org/wiki/Natural_logarithm_of_2

    In a third layer, the logarithms of rational numbers r = ⁠ a / b ⁠ are computed with ln(r) = ln(a) − ln(b), and logarithms of roots via ln n √ c = ⁠ 1 / n ⁠ ln(c).. The logarithm of 2 is useful in the sense that the powers of 2 are rather densely distributed; finding powers 2 i close to powers b j of other numbers b is comparatively easy, and series representations of ln(b) are ...

  5. Specific strength - Wikipedia

    en.wikipedia.org/wiki/Specific_strength

    The first nanotube ropes (20 mm long) whose tensile strength was published (in 2000) had a strength of 3.6 GPa, still well below their theoretical limit. [41] The density is different depending on the manufacturing method, and the lowest value is 0.037 or 0.55 (solid). [37]

  6. Collatz conjecture - Wikipedia

    en.wikipedia.org/wiki/Collatz_conjecture

    Numbers from 1 to 9999 and their corresponding total stopping time Histogram of total stopping times for the numbers 1 to 10 8. Total stopping time is on the x axis, frequency on the y axis. Histogram of total stopping times for the numbers 1 to 10 9. Total stopping time is on the x axis, frequency on the y axis. Iteration time for inputs of 2 ...

  7. List of thermal conductivities - Wikipedia

    en.wikipedia.org/wiki/List_of_thermal_conductivities

    6.37 ⋅ 10 7 at 273.15 K; 5.71 ⋅ 10 7 at 300K; 4.15 ⋅ 10 7 at 400K. [41] International Annealed Copper Standard (IACS) pure =1.7×10 −8 Ω•m =58.82×10 6 Ω −1 •m −1. For main article, see: Copper in heat exchangers. The TPRC recommended values are for well annealed 99.999% pure copper with residual electrical resistivity of ρ 0 ...

  8. Isotopes of oxygen - Wikipedia

    en.wikipedia.org/wiki/Isotopes_of_oxygen

    There are three known stable isotopes of oxygen (8 O): 16 O, 17 O, and 18 O. Radioactive isotopes ranging from 11 O to 28 O have also been characterized, all short-lived. The longest-lived radioisotope is 15

  9. Age of the universe - Wikipedia

    en.wikipedia.org/wiki/Age_of_the_universe

    NASA's Wilkinson Microwave Anisotropy Probe (WMAP) project's nine-year data release in 2012 estimated the age of the universe to be (13.772 ± 0.059) × 10 9 years (13.772 billion years, with an uncertainty of plus or minus 59 million years).