In this paper, we explain the multifractal and thermodynamical properties o
f deterministic fractal spectra, and compare the most relevant behaviors wi
th those obtained for some natural spectra with multifractal properties. In
particular, we compare the heat capacity, C(T), derived from Cantor-set-ty
pe spectra with the ones obtained From several atomic spectra. We find that
, although many of the properties of deterministic fractals, previously rep
orted, are also reproduced in natural fractals (oscillations of C(T) in log
scale), new features appear in the natural case: the mean value of C(T) is
not always related to the multifractal properties, and the oscillations ar
e present in cases for which they disappear in deterministic fractals. (C)
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