Ab initio simulation of paramagnetic NMR spectra: the 31P NMR in oxovanadium phosphates

A theoretical analysis of the temperature-dependent (31)P NMR signals for the ambient pressure vanadyl pyrophosphate AP-(VO)(2)P(2)O(7) and the oxovanadium hemihydrate hydrogenophosphate VO(HPO(4)).0.5H(2)O phases is reported. The ab initio calculation of the magnetic exchange parameters and the hyperfine constants gives access to an original ab initio simulation of NMR spectra. Such a strategy allows one to clarify the crystallographic nature of the different experimentally studied phases. For the vanadyl pyrophosphate ambient pressure structure, our simulations strongly support the presence of a monoclinic phase. Based on this assumption, hyperfine constants are extracted from the fit of the experimental data. These values are directly compared to the ab initio ones.     

On the nature of the charge-transfer transient in photocatalysis by the decatungstate anion

The decatungstate anion [W₁₀O₃₂]⁴⁻ is an efficient catalyst in the photooxidation of alkanes. Laser flash photolysis studies suggested that after photoexcitation the decatungstate anion relaxes to an intermediate with an electronic distribution similar to that of the singly reduced cluster. Using vibronic theory of mixed-valence compounds, we study possible electronic distributions of decatungstate with one excess electron in the LUMO. Under some conditions this electron can be delocalized over a part of equatorial tungsten centres. In some cases this delocalized electronic distribution can coexist with the electron localization at one tungsten site. The intermediate form in the photocatalytic reaction could be assigned to the partly delocalized state which can be attained from an initially localized photoexcited state.     

Spiral waves in rotating twisted elastic pipes

The problem of propagation of bending waves in rotating pipes prestressed by longitudinal force and torque is stated and solved. Such waves are shown to be spiral ones. It is established that four waves exist for every wavelength, two of which are right-handed spirals and the other two are left-handed. These waves propagate with different velocities in different directions __________ Translated from Prikladnaya Mekhanika, Vol. 44, No. 3, pp. 125–134, March 2008.     

ALADIN热曲线的微正则系综分析

用微正则瞬时多碎裂统计模型分析了ALADIN热曲线.结果表明落在ALADIN热曲线温度平台(温度扭曲)附近的弹剩余核(热核)的理论代表点,并不落在相应弹剩余核热曲线的温度平台(扭曲)范围内,从而对ALADIN热曲线是否可作为核液气相变的证据提出质疑.     

Formation of catalytically active layers on the surface of polymetallic alloys

A new method for the synthesis of catalysts on polymetallic supports via the formation of intermetallic (aluminide) layer on the support surface followed by leaching and stabilization of the layer has been proposed. The intermetallic layer structure and distribution of elements in the layer were studied by scanning electron microscope considering a nickel chromium stainless-steel grid as an example. The morphology and elemental composition of the active phase on the catalyst surface were studied. The complex structure of this phase was found to consist of two types of entities with different composition located on the continuous highly porous substrate. The catalyst sample was tested in deep oxidation of CO and propane and demonstrated high activity. The developed method can be used to obtain new high-performance polymetallic catalysts.     

相对论性核与乳胶(Ag)碰撞中灰粒子的系统研究 *

用描写相对论性核 核碰撞的LUCIAE模型和相应的事件产生器系统地研究了 1 4.6 ,6 0和 2 0 0AGeV的O核、2 0 0AGeV的Si和S核以及 1 1 .6AGeV的Au核与乳胶 (Ag)碰撞中灰粒子产生的平均多重数、多重数分布以及角分布 3个物理量同入射能量、射弹质量及碰撞中心度间的关系 ,还研究了再散射在灰粒子产生机制中的作用 .LUCIAE的这些研究结果与相应的EMU0 1乳胶实验结果都相一致 .