Interplay of thermochemistry and Structural Chemistry, the journal (volume 17, 2006) and the discipline

Abstract  

In the current study we relate the contents of the journal of “Structural Chemistry” for the calendar year 2006 to thermochemistry. Each paper is briefly summarized and supplemented by a comment which explicitly interrelates the content of the study to chemical energetics.     

Supercontinuum and gas cell in a single microstructured fiber

We exploit both the high nonlinearity and the holey structure of microstructured fibers to combine a broad-band light source and a gas cell in a single microstructured fiber. A broadband supercontinuum is formed by launching nanosecond pulses from a compact, Q-switched Nd:YAG laser into a microstructured fiber filled with acetylene. This continuum is self-referenced to the acetylene lines in the 1500 nm region. The performance of different index-guiding narrow-core microstructured fibers as nonlinear and host media is evaluated. The concept offers many possibilities and can be applied to various gases absorbing at different wavelengths.     

Coherent vibrational energy transfer along a peptide helix

To measure the transport of vibrational energy along a peptide helix, Hamm and co-workers [J. Phys. Chem. B 112, 9091 (2008)] performed time-resolved vibrational experiments, which showed that the energy transport rate increases by at least a factor of 4, when a localized C=O mode of the peptide instead of an attached chromophore is excited. This finding raises the question if coherent excitonic energy transfer between the C=O modes may be of importance for the overall energy transport in peptides. With this idea in mind, nonequilibrium molecular dynamics simulations as well as quantum-classical calculations are performed, which qualitatively reproduce the experimental findings. Moreover, the latter model (an exciton Hamiltonian whose matrix elements depend on the instantaneous positions of the peptide and solvent atoms) indeed exhibits the signatures of coherent quantum energy transport, at least within the first few picoseconds and at low temperatures. The origin of the observed decoherence, the absence of vibrational self-trapping, and the possibility of quantum interference between various transport paths are discussed in some detail.     

Trends of Pesticides in Norwegian Streams and Rivers (1996-2000)

In Norway twelve streams and medium size rivers have been monitored for pesticides in a four to six years period. During these years the central authorities have accomplished efforts to minimize the risk for pesticides entering the water bodies. Trend analyses have been done on the years 1996-2000 to gain information on whether there have been reductions in the retrieval of the pesticides: (1) Frequency of pesticides detection; (2) Sum concentration of all individual pesticides in each sample; (3) Environmental risk by weighing the concentration of each pesticide against the environmental maximum residue limits (MRL). As a whole, developments in streams and rivers show both positive and negative trends regarding the different parameters studied. The tendency is that the different parameters show the same development within the stream. The situation in these streams has not changed much during this 5 years period, but there are indications towards a slight positive development. Trend analyses might therefore be useful together with careful interpretation.