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541.
Ren Tschaggelar Besnik Kasumaj Maria Grazia Santangelo Jrg Forrer Patrik Leger Henry Dube Franois Diederich Jeffrey Harmer Rolf Schuhmann Ins García-Rubio Gunnar Jeschke 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,200(1):81-87
The construction and performance of a cryogenic 35 GHz pulse electron nuclear double resonance (ENDOR) probehead for large samples is presented. The resonator is based on a rectangular TE102 cavity in which the radio frequency (rf) B2-field is generated by a two turn saddle ENDOR coil crossing the resonator along the sample axis with minimal distance to the sample tube. An rf power efficiency factor is used to define the B2-field strength per square-root of the transmitted rf power over the frequency range 2–180 MHz. The distributions of the microwave B1- and E1-field, and the rf B2-field are investigated by electromagnetic field calculations. All dielectrics, the sample tube, and coupling elements are included in the calculations. The application range of the probehead and the advantages of using large sample sizes are demonstrated and discussed on a number of paramagnetic samples containing transition metal ions. 相似文献
542.
543.
Gmoser Rebecca Ferreira Jorge A. Taherzadeh Mohammad J. Lennartsson Patrik R. 《Applied biochemistry and biotechnology》2019,189(1):160-174
Applied Biochemistry and Biotechnology - A new post-treatment method of fungal biomass after fermentation is revealed. The post-treatment strategy was utilized to produce pigments as an additional... 相似文献
544.
H. Schut Galindo R. Escobar Z. I. Kolar A. van Veen G. Clet 《Radiation Physics and Chemistry》2000,58(5-6):715-718
Results of positron annihilation measurements on NaY pressed powders and deposited thin films using slow positron beam and conventional fast positron techniques are presented. In lifetime experiments using an external 22Na source an averaged long lifetime of 1.8 ns with a sum intensity of 27% was observed in pressed powders in the presence of air at room temperature (RT). In literature this lifetime is ascribed to positrons annihilating in water filled or β cages Habrowska, A.M., Popiel, E.S., 1987. Positron annihilation in zeolite 13X. J. Appl. Phys. 62, 2419. By means of isotopic exchange some of the Na was replaced by 22Na. These powders showed a long lifetime component of 7–8 ns with an intensity increasing from 1 to 12% when heated under normal atmosphere from RT to 200°C. No significant increase of the shorter (1.5 ns) lifetime was observed, while its intensity dropped from 13.4 to 6.6%. Both effects are ascribed to the loss of water from cages only. The beam experiments revealed a high fraction of 3-gamma annihilations in the pressed powder and thin film samples, indicating the annihilation of o-Ps and thereby the existence of large open volumes. 相似文献
545.
Site-specific 13C labeling offers a desirable means of eliminating unwanted relaxation pathways and coherent magnetization transfer in NMR relaxation experiments. Here we use [1-13C]-glucose as the sole carbon source in the growth media for protein overexpression in Escherichia coli. The approach results in specific incorporation of 13C at isolated positions in the side chains of aromatic amino acids, which greatly simplifies the measurements and interpretation of 13C relaxation rates in these spin systems. The method is well suited for characterization of chemical exchange by CPMG or spin-lock relaxation methods. We validated the method by acquiring 13C rotating-frame relaxation dispersion data on the E140Q mutant of the C-terminal domain of calmodulin, which reveal conformational exchange dynamics with a time constant of 71 mus for Y138. 相似文献
546.
Västilä P Wettergren J Adolfsson H 《Chemical communications (Cambridge, England)》2005,(32):4039-4041
The direct in situ formation of highly efficient ruthenium-catalysts for the asymmetric reduction of ketones was obtained by combining chiral ligand building blocks with a ruthenium precursor. 相似文献
547.
Novel simple and highly modular dipeptide-analogue ligands combined with [RuCl2(p-cymene)]2 were demonstrated to efficiently catalyze the reduction of ketones under hydrogen transfer conditions with enantioselectivities up to 96%. 相似文献
548.
Patrik Fazekas 《Zeitschrift für Physik B Condensed Matter》1982,45(3):215-221
The conditions for the appearance of a reentrant superconducting phase in granular materials are studied in mean field approximation applied to periodic models. We assume that the relevant low-lying excitation is the transfer of a Cooper pair from a grain to one of its neighbours, and neglect pair breaking. Both on-grain (U) and nearest neighbour (V) Coulomb interactions are taken into account, and the Coulomb problem is treated in Bethe-Peierls approximation. WhenV/U is not too large, reentrance is predicted ifV/U>(4+3z)?1/2 wherez is the coordination number. This result is different from a recent criterion suggested by ?imánek, which allows reentrance only in the immediate vicinities of certain discrete values ofV/U. For strong enoughV/U, the models treated here show a transition to an ionic-salt-like charge-ordered state. Reentrant superconductivity is shown to occur also on an ionic background. In actual systems, close-packing effects partially frustrate the ionic ordering and enhance the reentrant feature. 相似文献
549.
Paul Binger Patrik Müller Petra Philipps Barbara Gabor Richard Mynott Albert T. Herrmann Franz Langhauser Carl Krüger 《欧洲无机化学杂志》1992,125(10):2209-2212
Bis(trimethylphosphane)titanocene ( 1 ) reacts with 2-methylene-1,1-diphenylcyclopropane ( 2 ) to give red crystalline (η2-2-methylene-1,1-diphenylcyclopropane)(trimethylphosphane)titanocene ( 3 ). In solution complex 3 degrades smoothly to form the new Cp2Ti(PMe3) – C2 – Ti(PMe3)Cp2 complex 4 , the crystal structure of which has been elucidated by an X-ray analysis. 相似文献
550.
A statistical mechanics model for a faceted crystal is the 3D Ising model at zero temperature. It is assumed that in one octant all sites are occupied by atoms, the remaining ones being empty. Allowed atom configurations are such that they can be obtained from the filled octant through successive removals of atoms with breaking of precisely three bonds. If V denotes the number of atoms removed, then the grand canonical Boltzmann weight is q
V
, 0<q<1. As shown by Cerf and Kenyon, in the limit q1 a deterministic shape is attained, which has the three facets (100), (010), (001), and a rounded piece interpolating between them. We analyse the step statistics as q1. In the rounded piece it is given by a determinantal process based on the discrete sine-kernel. Exactly at the facet edge, the steps have more space to meander. Their statistics is again determinantal, but this time based on the Airy-kernel. In particular, the border step is well approximated by the Airy process, which has been obtained previously in the context of growth models. Our results are based on the asymptotic analysis for space-time inhomogeneous transfer matrices. 相似文献