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351.
N. R. Serebryanaya G. A. Dubitskii V. D. Blank B. N. Mavrin L. A. Chernozatonskii E. A. Skryleva E. V. Skokan V. V. Aksenenkov 《Polymer Science Series A》2009,51(10):1049-1059
Powder X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and molecular dynamics have been employed
to investigate structural transformations in hexagonal and cubic modifications of fullerite C60 after the action of high pressure (4 GPa) within the temperature range 20–1450°C. It has been found that fullerene molecules
polymerize to afford polymer structures only in the case of face-centered cubic samples. Under the effect of high pressure
and temperature, fullerite C60 with a hexagonal close-packed structure is initially transformed into the cubic modification and, then, forms polymerized
structures, which, during an increase in the treatment temperature, become less stable and ordered than the same polymerized
structures obtained directly from cubic fullerite C60. X-ray photoelectron spectroscopy measurements suggest deformation of the cages of fullerene molecules in the polymerized
structures. 相似文献
352.
The iron (Fe) proteins of molybdenum (Mo)-, vanadium (V)-, and iron (Fe)-only nitrogenases are encoded by nifH, vnfH, and anfH, respectively. While the nifH-encoded Fe protein has been extensively studied over recent years, information regarding the properties of the vnfH- and anfH-encoded Fe proteins has remained scarce. Here, we present a combined biochemical, electron paramagnetic resonance (EPR) and X-ray absorption spectroscopy (XAS) analysis of the [Fe(4)S(4)] clusters of NifH, VnfH, and AnfH of Azotobacter vinelandii . Our data show that all three Fe proteins contain [Fe(4)S(4)] clusters of very similar spectroscopic and geometric structural properties, although NifH differs more from VnfH and AnfH with regard to the electronic structure. These observations have an interesting impact on the theory of the plausible sequence of evolution of nitrogenase Fe proteins. More importantly, the results presented herein provide a platform for future investigations of the differential activities of the three Fe proteins in nitrogenase biosynthesis and catalysis. 相似文献
353.
[Structure: see text] The reduction of aryl diazonium salts in the presence of nonactivated olefins provides rapid entry to carbodiazenylation products. The regioselective functionalization of double bonds is achieved in a one-pot process starting from aniline derivatives. Carboamination of olefins is possible via a two-step carbodiazenylation-hydrogenation sequence in which one aniline equivalent is recovered. 相似文献
354.
The continuous spectrum of analytical toroidally rotating magnetically confined plasma equilibria is investigated analytically and numerically. In the presence of purely toroidal flow, the ideal magnetohydrodynamic equations leave the freedom to specify which thermodynamic quantity is constant on the magnetic surfaces. Introducing a general parametrization of this quantity, analytical equilibrium solutions are derived that still posses this freedom. These equilibria and their spectral properties are shown to be ideally suited for testing numerical equilibrium and stability codes including toroidal rotation. Analytical expressions are derived for the low-frequency continuous Alfvén spectrum. These expressions still allow one to choose which quantity is constant on the magnetic surfaces of the equilibrium, thereby generalizing previous results. The centrifugal convective effect is shown to modify the lowest Alfvén continuum branch to a buoyancy frequency, or Brunt–Väisälä frequency. A comparison with numerical results for the case that the specific entropy, the temperature, or the density is constant on the magnetic surfaces yields excellent agreement, showing the usefulness of the derived expressions for the validation of numerical codes. 相似文献
355.
G. Canchel B. Blank M. Chartier F. Delalee P. Dendooven C. Dossat J. Giovinazzo J. Huikari A. S. Lalleman M. J. Lopez Jiménez V. Madec J. L. Pedroza H. Penttilä J. C. Thomas 《The European Physical Journal A - Hadrons and Nuclei》2005,23(3):409-415
In an experiment performed at the Accelerator Laboratory of the University of Jyväskylä, the -decay half-life of 62Ga has been studied with high precision using the IGISOL technique. A half-life of T1/2 = 116.09(17) ms was measured. Using - coincidences, the intensity of the 954 keV transition and an upper limit of the -decay feeding of the 0+2 state have been extracted. The present experimental results are compared to previous measurements and their impact on our understanding of the weak interaction is discussed. 相似文献
356.
Refraction and ultra‐small‐angle scattering of X‐rays in a single‐crystal diamond compound refractive lens 下载免费PDF全文
S. Gasilov A. Mittone T. dos Santos Rolo S. Polyakov S. Zholudev S. Terentyev V. Blank A. Bravin T. Baumbach 《Journal of synchrotron radiation》2017,24(6):1137-1145
In this work a double‐crystal setup is employed to study compound refractive lenses made of single‐crystal diamond. The point spread function of the lens is calculated taking into account the lens transmission, the wavefront aberrations, and the ultra‐small‐angle broadening of the X‐ray beam. It is shown that, similarly to the wavefront aberrations, the ultra‐small‐angle scattering effects can significantly reduce the intensity gain and increase the focal spot size. The suggested approach can be particularly useful for the characterization of refractive X‐ray lenses composed of many tens of unit lenses. 相似文献
357.
358.
Thermolysis of di-(4-chlorobenzoyl)-peroxide was carried out in the probe of an NMR. spectrometer. The dependence of product distribution and chemically induced dynamic nuclear polarization (CIDNP.) patterns on the concentrations of radical trapping agents gives evidence that the CIDNP. effects are caused by singlet-triplet transitions, dependent on nuclear spin, in transient benzoyloxy/phenyl radical pairs and by the selective formation of radical products from singlet state pairs. 相似文献
359.
The oxidation of phenetidine with sodium vanadate is proposed for determining phenothiazine derivatives by the kinetic method. The reaction rate was studied depending on the solution acidity and reagent concentrations, and the optimum determination conditions were selected. The analytical range was 3–100 ng/mL for six phenothiazine alkyl derivatives (aminazine, diprazine, promazine, meterazine, tisercine, and triphtazine). The detection limits (3 to 10 ng/mL) depend on the substituent in the phenothiazine molecule. The relative standard deviations were from 3 to 20%. 相似文献
360.