Detection of discontinuities in scattered data approximation

A Detection Algorithm for the localisation of unknown fault lines of a surface from scattered data is given. The method is based on a local approximation scheme using thin plate splines, and we show that this yields approximation of second order accuracy instead of first order as in the global case. Furthermore, the Detection Algorithm works with triangulation methods, and we show their utility for the approximation of the fault lines. The output of our method provides polygonal curves which can be used for the purpose of constrained surface approximation. This revised version was published online in June 2006 with corrections to the Cover Date.     

A rapid and precise method for determination of D/H ratios of plant methoxyl groups

Stable hydrogen isotope ratio measurements of specific plant components are increasingly used in numerous fields of research, including sample origin verification and climate research. A recently suggested method with considerable potential in this context is the D/H isotope ratio (δ²H value) analysis of plant matter methoxyl groups. The method entails ether or ester cleavage with hydriodic acid (HI) to form the gaseous compound methyl iodide (CH₃I) and measurement of the δ²H value of this gas. Here we describe a method for the rapid and precise δ²H analysis of plant matter methoxyl groups using gas chromatography/pyrolysis/isotope ratio mass spectrometry (GC/P/IRMS). The conditions for sample preparation were investigated for isotope discrimination effects, the GC conditions were optimized, the reproducibility of the measurement of standards was studied, and the precision of the method was defined. The reproducibility of δ²H values determined for a CH₃I standard on 20 consecutive measurements was found to be 2‰. The method was also tested on four methoxyl‐rich plant components: vanillin, lignin, wood and pectin. The analytical precision obtained, when expressed as the average standard deviation for these compounds, was better than 1.6‰. The described method is rapid, allowing preparation and analysis of a sample within 1 h, and produces accurate and reproducible isotopic measurements. Copyright © 2008 John Wiley & Sons, Ltd.     

Photolysis and gas phase pyrolysis of 1,2,3-benzoselenadiazole - matrix-isolation of benzoselenirene

Based on comparative studies on 1,2,3-benzothiadiazole benzoselenirene is identified as an intermediate in the low temperature photolysis and gas phase pyrolysis of 1,2,3-benzoselenadiazole by IR spectroscopy.