Changes in the development of the line radiative transfer code (LTR)

1.0 -> 1.1:

- restructuring of the field handling in the radiative transfer part,
  elimination of the emissivities -> 20% speed-up of the code
- Enabling compile-time and command line options giving the default
  values for the output file structure and setting overwrite mode
- Removal of a bug in the Sobolev part which could slow down the
  convergence in certain cases


1.1 -> 1.2:

- introduction of a first approximation for the treatment of turbulence
  and clumping in space or velocity space (effective optical depths)
  (Martin, Sanders & Hills 1984, MNRAS 208, 35)
- Addition of the turbulence correlation length as additional parameter
  in the set of physical input parameters
- Possibility to eliminate most of the annoying questions during the
  program execution by command line options or compiler directives


1.2 -> 1.21:

- removal of a severe bug in the central transfer code, addition of
  a second order term important for large velocity gradient regimes


1.21 -> 1.3:

- introduction of the treatment of a central HII region in the cloud
  core, addition of new physical parameters for the electron density 
  and temperature within the HII region
- new molecule added (SiO in the ground vibrational state)
- new collision rates for CS taken from Turner et al. 1992, ApJ 399,114,
  now all molecules except HCO+ can be treated at kinetic temperatures
  up to 300K
- improvement of the ray spacing in the final computation of the
  line profiles in case of large velocity gradients
- removal of a bug in the spatial intensity integration appearing at 
  density edges
- further exception handling added for very high intensities (e.g. 
  local masers)


1.3 -> 1.31

- removal of a bug in the transfer on the central ray which wasted
  computing time
- accuracy improvement for the routine computing the central optical 
  depth given as control output


1.31 -> 1.4:

- improvement of the accelerated lambda iteration, convergence speed
  up for large optical depths, "overshooting" prevented
- better extrapolation of the CO-ortho-H2 collision rates beyond 100K
  providing a smooth transition to the values for CO-para-H2
- addition of a two new observational parameters for a better map control
  (central offset and number of map points)
- increase of the size of all fields in frequency points