When a body is exposed to a cold environment, the livid colour of livor mortis changes to cherry red. This colour change is due to an increase in the concentration of oxygenated haemoglobin. The chronological course and the extent of haemoglobin re-oxygenation associated with the exposure to low ambient temperatures have not been understood so far. The relations between refrigeration time under a constant ambient temperature (5 degrees C), skin temperature, body mass index (BMI), spectral reflectance curve and O2-Hb concentration in livor mortis were systematically investigated in 84 bodies brought to the Institute of Legal Medicine of the Freiburg University Hospital shortly after death. In the first measurements performed shortly after death, the reflectance curves of the livores of all bodies showed a broad minimum at 555 nm. After a refrigeration time of 44.9 +/- 17.9 h, the spectrum changed to the typical picture of O2-rich blood with 2 minima at 541 and 576 nm and a maximum at 560 nm in between. This qualitative change of the reflectance spectra was observed for a skin temperature of 10.3 +/- 2.7 degrees C. With the help of a physical skin model it was possible to calculate that due to the post-mortem exposure to cold the O2-Hb concentration in the livores rose from 0-1% to a value of up to 89.3%. The change in the reflectance curve was discernible from an oxygen saturation of 25 +/- 13.8%.

Raman scattering of pure NH3 in the stretching fundamental region around 3300 cm-1 was investigated at 21, 75, 200, and 225 °C to a maximum pressure of 2000 bars. The spectra obtained as the density was varied continuously between gaseous and liquidlike states at supercritical temperature (Tc = 132.5 °C) enabled a definite assignment of the four vibrations v\, p3, 2¡qA, and 2¡qE. The degree of Fermi resonance between and 2i/4a is determined from the density dependence of the Raman intensity of both vibrations. Quantitative determinations of the molar Raman scattering intensity indicate a maximum scattering intensity of the symmetric stretching vibration at a moderately high density of 0.40 ± 0.05 g/cm3. This result is compared to previously reported infrared data on pure NH3 where the v\ absorption intensity changes strongly with density. This was explained by assuming a variation of the NH3 molecular configuration as a function of density with a minimum in pyramidal height at about 0.40 g/cm3 density.

Our current research in the framework of an interdisciplinary project focuses on modelling the dynamics of the hemoglobin reoxygenation process in post-mortem human skin by reflectance spectrometry. The observations of reoxygenation of hemoglobin in livores after postmortem exposure to a cold environment relate the reoxygenation to the commonly known phenomenon that the color impression of livores changes from livid to pink under low ambient temperatures. We analyze the spectra with respect to a physical model describing the optical properties of human skin, discuss the dynamics of the reoxygenation, and propose a phenomenological model for reoxygenation. For additional characterization of the reflectance spectra, the curvature of the local minimum and maximum in the investigated spectral range is considered. There is a strong correlation between the curvature of specra at a wavelength of 560 nm and the concentration of O2-Hb. The analysis is carried out via C programs, as well as MySQL database queries in Java EE, JDBC, Matlab, and Python.