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861.
We report the effects of partial substitutions of the VIIIa elements: Fe (3d) and Ru (4d) in the intermetallic perovskite superconductor MgCNi3. In both the MgCNi3−xRux and MgCNi3−xFex systems, the superconducting critical temperature (TC) decreases monotonically as x is increased. TC decreases more slowly in the case of Ru, suggesting that the 3d electrons in Fe are magnetically pair breaking. This is supported by the normal state magnetic susceptibility measurements (χ), which shows that χ increases with Fe and decreases with Ru doping. No ferromagnetism is observed in either system. 相似文献
862.
H. Kuramochi J. Okabayashi F. Takano M. Mizuguchi T. Manago H. Akinaga 《Surface science》2004,550(1-3):192-198
Strong magnetic poles at characteristic rectangular defects have been observed using a magnetic force microscope on a MnAs(
1 0 0) thin film with the thickness of 30 nm. The MnAs thin film was epitaxially grown on a GaAs(0 0 1) substrate. The magnetic poles were in one-arranging direction, being independent of the magnetization direction of the film. The poles were pinned at the edges of the rectangular defects until just below the Curie temperature, and formed a stable magnetic-field loop on the MnAs surface. The stability of the magnetic pole pinning shows the distinctive feature of the magnetic domain structure on the surface with a strong anisotropy, which was built in the heterostructure of MnAs and GaAs. 相似文献
863.
S. S. Stavitskaya N. T. Kartel’ N. N. Tsyba M. F. Kovtun T. P. Petrenko 《Russian Journal of Applied Chemistry》2007,80(3):379-385
The mineral and chemical compositions, as well as some structure-sorption characteristics were determined for clay minerals selected for examination. The integrated coefficients of contamination of bottom sediments with each of the toxicant metals (Fe, Ni, Co, Cu, Zn, Pb, Mn) were calculated. The minerals examined presumably can be used in medicine as efficient application materials, cosmetic agents, and sorbents (enterosorbents). 相似文献
864.
R. A. Stukan T. V. Dudareva Yu. N. Kil’yanov A. V. Polyakova 《Russian Journal of Inorganic Chemistry》2006,51(1):1-4
A tetragonal 123 phase with the composition close to CeLa2 { Cu
2
2+
} [Mg2+]O8 (the braces indicate the Cu(2) positions; the brackets indicate the Cu(1) positions) with the parameters a = b = 0.3909(3) nm, c = 1.6591(8) nm was prepared at 860°C under an oxygen atmosphere with an elevated oxygen pressure. When the lanthanum-for-barium
substitution was incomplete, the resulting 123 phase had the composition close to CeLa1.7Ba0.3{ Cu
1.7
2+
} [Mg]O8 with the unit cell parameters a = b = 0.3868(3) nm, c = 1.6578(8) nm that contains Cu3+ in the Cu(2) positions. The partial substitution of barium for lanthanum (the melting point of barium oxide is almost 500°C
lower that of the lanthanum oxide) appreciably facilitated the synthesis: the 123 phase in this sample was more than 90%.
The existence of Cu3+ in the Cu(2) positions enhanced the electrical conductivity of the sample. 相似文献
865.
Synthetic routes to oxidation of cobalt atoms in cobalt trimethylacetate complexes containing coordinated pyrazole molecules have been considered. 相似文献
866.
Lemi Türker 《Journal of mathematical chemistry》1992,9(4):341-349
A novel method, based on the topology of the cardinal vertex, is described to find an upper bound for the largest eigenvalue of a graph. 相似文献
867.
Two-dimensional on-line particle imaging velocimetry 总被引:3,自引:0,他引:3
A high-performance algorithm is described for the on-line computation of two-dimensional velocity maps using particle displacement imaging. It relies on the computation of direct correlations in a multiple-scale spatial hierarchy. Layered rejection criteria based on correlation quality and conditional averaging techniques are employed to achieve the robustness required for continuous, unsupervised operation. Implementations are described using a UNIX-based workstation and a DOS-based personal computer with a real-time image processing/correlator subsystem. The cooperation of the algorithm with other real-time visualization techniques is demonstrated using the example of colour-coded streak integration.The authors wish to thank Dr. Philippe Georis of the Université Libre de Bruxelles (ULB) for making available to us video sequences of his Marangoni convection experiment. 相似文献
868.
A. B. Pierini G. L. Borosky M. T. Baumgartner 《International journal of quantum chemistry》1992,41(5):759-761
We here report an AM 1 study for the reaction of different types of radicals with the acetone enolate ion 1 and other ambident nucleophiles. The theoretical reactivity order determined is phenyl > methyl > tert-butyl ? bicyclo-[2.2.1]hept-1-yl. The activation energy for the coupling of aliphatic radicals is ascribed mainly to nonbonded interactions. Considering possible solvent effects, we propose the same order of reactivity in solution. The coupling reaction of phenyl radical with 1 is an exothermic process with nonactivation energy in the gas phase. Any energy barrier in solution is here ascribed to desolvation of the anion. The regiochemistry of the coupling of radicals with ambident nucleophiles such as 1 , phenoxide, or phenylamide anions is also explained on a theoretical basis. © 1992 John Wiley & Sons, Inc. 相似文献
869.
B. F. Araujo H. T. Matsuda T. A. Kuada J. A. Araujo 《Journal of Radioanalytical and Nuclear Chemistry》1992,166(1):75-83
In the actinide separation process using TBP as extractant, hydrolytic and radiolytic reactions cause a gradual decomposition of the extractant, resulting in the formation of degradation products which can affect process performance adversely. The TBP diluent has to be cleaned from these degradation products before it is reused. This paper deals with a procedure for solvent cleanup, using a fourstage continuous contactor for increasing the scrubbing efficiency. 相似文献
870.
Daniel T. Valentine 《国际流体数值方法杂志》1995,21(2):155-180
The disarrangement of a perturbed lattice of vortices was studied numerically. The basic state is an exponentially decaying, exact solution of the Navier-Stokes equations. Square arrays of vortices with even numbers of vortex cells along each side were perturbed and their evolution was investigated. Whether the energy in the perturbation grows somewhat before it decays or decays monotonically depends on the initial strength of the vortices of the basic state, the extent of lateral confinement and the structure of the perturbation. The critical condition for temporally local instability, i.e. the critical amplitude of the basic state that must be exceeded to allow energy transfer from the basic state to the perturbation, is discussed. In the strongly confined case of a square lattice of four vortices the appearance of enchancement of global rotation is the result of energy transfer from the basic state to a temporally local unstable mode. Energy is transferred from the basic state to larger-scaled structures (inverse cascade) only if the scales of the larger structures are inherently contained in the initial structure of the perturbation. The initial structure of the double array of vortices is not maintained except for a very special form of perturbation. The facts that large scales decay more slowly than small scales and that, when non-linearities are sufficiently strong, energy is transferred from one scale to another explain the differences in the disarrangement process for different initial strengths of the vortices of the basic state. The stronger vortices, i.e. the vortices perturbed in a manner that increases their strength, tend to dominate the weaker vortices. The pairing and subsequent merging (or capture) of vortices of like sense into larger-scale vortices are described in terms of peaks in the evolution of the square root of the palinstrophy divided by the enstrophy. 相似文献