Research potential and limitations of trace analyses of cremated remains

Human cremation is a common funeral practice all over the world and willpresumably become an even more popular choice for interment in thefuture. Mainly for purposes of identification, there is presently agrowing need to perform trace analyses such as DNA or stable isotopeanalyses on human remains after cremation in order to clarify pendingquestions in civil or criminal court cases. The aim of this study was toexperimentally test the potential and limitations of DNA and stableisotope analyses when conducted on cremated remains.For this purpose, tibiae from modern cattle were experimentally crematedby incinerating the bones in increments of 100 degrees C until a maximumof 1000 degrees C was reached. In addition, cremated human remains werecollected from a modern crematory. The samples were investigated todetermine level of DNA preservation and stable isotope values (C and Nin collagen, C and O in the structural carbonate, and Sr in apatite).Furthermore, we assessed the integrity of microstructural organization,appearance under UV-light, collagen content, as well as the mineral andcrystalline organization. This was conducted in order to provide ageneral background with which to explain observed changes in the traceanalyses data sets. The goal is to develop an efficacious screeningmethod for determining at which degree of burning bone still retains itsoriginal biological signals. We found that stable isotope analysis ofthe tested light elements in bone is only possible up to a heat exposureof 300 degrees C while the isotopic signal from strontium remainsunaltered even in bones exposed to very high temperatures. DNA-analysesseem theoretically possible up to a heat exposure of 600 degrees C butcan not be advised in every case because of the increased risk ofcontamination. While the macroscopic colour and UV-fluorescence ofcremated bone give hints to temperature exposure of the bone’s outersurface, its histological appearance can be used as a reliable indicatorfor the assessment of the overall degree of burning

Quantum chemical calculations of X-ray emission spectroscopy

The calculation of X-ray emission spectroscopy with equation of motion coupled cluster theory (EOM-CCSD), time dependent density functional theory (TDDFT) and resolution of the identity single excitation configuration interaction with second order perturbation theory (RI-CIS(D)) is studied. These methods can be applied to calculate X-ray emission transitions by using a reference determinant with a core-hole, and they provide a convenient approach to compute the X-ray emission spectroscopy of large systems since all of the required states can be obtained within a single calculation removing the need to perform a separate calculation for each state. For all of the methods, basis sets with the inclusion of additional basis functions to describe core orbitals are necessary, particularly when studying transitions involving the 1s or- bitals of heavier nuclei. EOM-CCSD predicts accurate transition energies when compared with experiment, however, its application to larger systems is restricted by its computational cost and difficulty in converging the CCSD equations for a core-hole reference determinant, which become increasing problematic as the size of the system studied increases. While RI-CIS(D) gives accurate transition energies for small molecules containing first row nuclei, its application to larger systems is limited by the CIS states providing a poor zeroth order reference for perturbation theory which leads to very large errors in the computed transition energies for some states. TDDFT with standard exchange-correlation functionals predicts transition energies that are much larger than experiment. Optimization of a hybrid and short-range cor- rected functional to predict the X-ray emission transitions results in much closer agreement with EOM-CCSD. The most accurate exchange-correlation functional identified is a modified B3LYP hybrid functional with 66% Hartree-Fock exchange, denoted B66LYP, which predicts X-ray emission spectra for a range of molecules including fluorobenzene, nitrobenzene, ace- tone, dimethyl sulfoxide and CF3Cl in good agreement with experiment

Software for the frontiers of quantum chemistry:An overview of developments in the Q-Chem 5 package

This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange–correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods include novel variants of both coupled-cluster and configuration-interaction approaches along with methods based on the algebraic diagrammatic construction and variational reduced density-matrix methods. Methods highlighted in Q-Chem 5 include a suite of tools for modeling core-level spectroscopy, methods for describing metastable resonances, methods for computing vibronic spectra, the nuclear–electronic orbital method, and several different energy decomposition analysis techniques. High-performance capabilities including multithreaded parallelism and support for calculations on graphics processing units are described. Q-Chem boasts a community of well over 100 active academic developers, and the continuing evolution of the software is supported by an “open teamware” model and an increasingly modular design