v1.5.3

Documentation: http://periodictable.readthedocs.org/en/v1.5.3

1.5.3 2020-11-04

Known issues:

• Incoherent scattering computed for contrast matched mixture in D2O_sld(),
  differs from the value that would be computed for a compound with the same
  isotope proportions and density computed in neutron_sld(). This may change
  in a future release.

Breaking changes:

• Fix calculation of contrast match points for biomolecules. The old
  formula used the density of H2O for the D2O sld calculation.
• Modify biomolecule support to use H[1] rather than T for labile hydrogen.
  This will result in less error when the labile formula is used in lieu
  of the natural formula or the contrast-matched formula, and make it more
  obvious from glancing at the formula that labile hydrogen is present.
• Modify fasta.Molecule attributes, dropping Hmass and Hsld. Hnatural
  has been moved to natural_formula. The formula with labile hydrogen is
  stored in labile_formula, as well as formula as before.

New:

• Add replace() method to formula to allow isotope substitution.
• Add nsf.D2O_match() and nsf.D2O_sld() functions.

Modified:

• Neutron wavelength now defaults to 1.798 A when wavelength and energy are
  both None in neutron_sld() and neutron_scattering() rather than
  throwing an assertion error.
• table can be passed to neutron sld calculators as the source of isotope
  information when parsing the chemical formula.
• Switch unit test framework from nose to pytest.
• Update docs.

See README.rst for complete history.