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Troe J.,University of Gttingen | Troe J.,Max Planck Institute for Biophysical Chemistry | Ushakov V.G.,RAS Institute of Problems of Chemical Physics
Journal of Chemical Physics | Year: 2011

Master equations for thermal unimolecular reactions and the reverse thermal recombination reactions are solved for a series of model reaction systems and evaluated with respect to broadening factors. It is shown that weak collision center broadening factors Fc en twc can approximately be related to the collision efficiencies c through a relation Fc en twc ≈ max { c 0.14, 0.64(0.03)}. In addition, it is investigated to what extent weak collision falloff curves in general can be expressed by the limiting low and high pressure rate coefficients together with central broadening factors F cent only. It is shown that there cannot be one best analytical expression for broadening factors F(x) as a function of the reduced pressure scale x k 0k ∞. Instead, modelled falloff curves of various reaction systems, for given k 0, k ∞, and F cent, fall into a band of about 10 width in F(x). A series of analytical expressions for F(x), from simple symmetric to more elaborate asymmetric broadening factors, are compared and shown to reproduce the band of modelled broadening factors with satisfactory accuracy. © 2011 American Institute of Physics. Source

Morawe C.,European Synchrotron Radiation Facility | Osterhoff M.,European Synchrotron Radiation Facility | Osterhoff M.,University of Gttingen
X-Ray Optics and Instrumentation | Year: 2010

This paper provides a comprehensive overview on the utilization of curved graded multilayer coatings as focusing elements for hard X-rays. It concentrates on the Kirkpatrick-Baez (KB) focusing setup that has been developed at 3rd generation synchrotron sources worldwide. The optical performance of these devices is evaluated applying analytical and numerical approaches. The essential role of the multilayer coating and its meridional d-spacing gradient are discussed as well as important technological issues. Experimental data and examples of operational KB focusing devices and applications complement the work. © 2010 Christian Morawe and Markus Osterhoff. Source

Misassignment between DNA samples and clinical or epidemiological data may compromise the results of genetic association studies. Genotyping in replicates or controlling for Hardy-Weinberg equilibrium cannot identify misassignments caused by sample mix-ups. DNA-based sex identification (sex typing) is currently the best strategy to identify mix-ups. Here we review the available methods and present validated protocols for sex typing. The protocols are based on single-nucleotide differences between the human amelogenin genes, AMELX and AMELY, and are optimized for real-time PCR (TaqMan®), primer-extension (SNaPshot™) and PCR-RFLP genotyping platforms. In addition, we review the limitations of the sex-typing strategy, including a limited ability to identify single sample mix-ups, the dependence of the power of this approach on the sex distribution in the study population, and rare genetic conditions. Alternative strategies for mix-up identification and possible consequences of mix-up identification are also discussed. © 2010 Future Medicine Ltd. Source

Botschwina P.,University of Gttingen | Oswald R.,University of Gttingen
Journal of Chemical Physics | Year: 2011

Explicitly correlated coupled cluster theory at the CCSD(T)-F12x (x a, b) level T. B. Adler, J. Chem. Phys. 127, 221106 (2007) has been employed in a study of the potential energy surfaces for the complexes H2C 3H+ · Ar and c-C3H3 + · Ar. For the former complex, a pronounced minimum with Cs symmetry was found (De ≈ 780 cm-1), well below the local "H-bound" minimum with C2v symmetry (D e ≈ 585 cm-1). The absorption at 3238 cm-1 found in the recent infrared photodissociation spectra A. M. Ricks, J. Chem. Phys. 132, 051101 (2010) is, thus, interpreted as an essentially free acetylenic CH stretching vibration of the propargyl cation. A global minimum of C s symmetry was also obtained for c-C3H3 + (De ≈ 580 cm-1), but the energy difference with respect to the local C2v minimum is only 54 cm-1. © 2011 American Institute of Physics. Source

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