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排序方式: 共有911条查询结果,搜索用时 31 毫秒
1.
2.
Z. A. Samoilenko V. D. Okunev E. I. Pushenko T. A. D’yachenko A. Cherenkov P. Gierlowski S. J. Lewandowski A. Abal’oshev A. Klimov A. Szewczyk 《Technical Physics》2003,48(2):250-256
Crystallographic phase transitions in perovskite-like LaSrMnO metallic oxides are studied. The transitions are induced when
internal stresses generated during film synthesis (at temperatures between 450 and 730°C) vary (decrease or increase) upon
subsequent irradiation by a KrF laser emitting in the UV range. As the synthesis temperature T
s grows, the rhombohedral-to-orthorhombic phase transition occurs at 650–670°C. The resistivity is shown to be either temperature-independent,
ρ(T)=const, at T<T
crit, or varies and reaches a maximum, ρ(T)=ρmax, at the Curie temperature T
c. Optical transmission spectra taken at photon energies ℏω=0.5–2.5 eV exhibit both a high (0.8–0.9) and low (0.1–0.3) transmission
coefficient t, depending on the synthesis temperature. As follows from X-ray diffraction data, the laser irradiation causes a phase transition
only in LaSrMnO films grown at T
s<650°C. Phases of different size scales appear: the long-range-order orthorhombic matrix and mesoscopic-range-order rhombohedral
clusters are observed in the films grown at T
s=450–550°C and the rhombohedral matrix with orthorhombic clusters, in the films grown at T
s=550–650°C. 相似文献
3.
A new method for the solution of the damped Burgers' equation is described. The marker method relies on the definition of a convective field associated with the underlying partial differential equation; the information about the approximate solution is associated with the response of an ensemble of markers to this convective field. Some key aspects of the method, such as the selection of the shape function and the initial loading, are discussed in some details. The marker method is applicable to a general class of nonlinear dispersive partial differential equations. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006 相似文献
4.
5.
6.
Sticking probability for oxygen adsorption on thin iron films and readsorption on surface sites liberated due to incorporation of the adsorbate adatoms below the surface during thermal treatment has been studied by means of the Wagener flow method. Sticking probability for oxygen adsorption on oxidized thin iron films has also been measured for comparison.
, . .相似文献
7.
María Beatriz de la Calle Guntiñas Michiel Ceulemans Claudia Witte Ryszard Łobiński Freddy C. Adams 《Mikrochimica acta》1995,120(1-4):73-82
A method is presented for the selective determination of the volatile selenium species dimethylselenide and dimethyldiselenide, using a commercially available purge-and-trap injection system coupled to capillary gas chromatography-microwave induced plasma-atomic emission spectrometry. The efficiency of the purging step was evaluated and the parameters affecting the purge and trap processes were optimized. The method was applied to the determination of volatile selenium compounds in lake water. Relative detection limits of 2ng/l for dimethylselenide and dimethyldiselenide, corresponding to an absolute detection limit of 10 pg, were achieved. 相似文献
8.
9.
A. Hulanicki R. Lewandowski A. Lewenstam M. Chmurska H. Matuszak 《Mikrochimica acta》1985,87(3-4):253-264
Summary
The Study of Titration Conditions in the Aluminium and Beryllium-Fluoride Systems
The conditions for the titrimetric determination of aluminium and beryllium using fluoride as a titrant and a fluoride indicator electrode have been determined. 10g ml–1 Al and 3g ml–1 Be have been determined with precision better than 0.4%. The formation of slightly soluble sodium hexafluoroaluminate or tetrafluoroberyllate is primarily responsible for the end point breaks. The study of the reaction conditions (ethanol, sodium and acetate ions concentration) made the calculation of stepwise stability constants for aluminium- or beryllium-fluoride complexes, aluminium- or beryllium-acetate complexes as well as that of the solubility products of the corresponding sodium salts possible. 相似文献
10.
A new complex of bis-axially coordinated iron(II) phthalocyanine by 4-cyanopyridine (4-CNpy) has been obtained in crystalline form as an adduct with two 4-CNpy molecules. The [FePc(4-CNpy)2] · 2(4-CNpy) crystallises in the monoclinic system, space group P21/c with two molecules in the unit cell. The iron(II) coordinates four isoindole nitrogen atoms of the almost planar phthalocyaninato(2−) macroring and axially two nitrogen atoms of 4-CNpy molecules. The coordination polyhedron around the Fe(II) atom approximates to a tetragonal by-pyramid. Four equatorial Fe–N bonds are shorter (1.936(2) Å) than two axial Fe–N bonds (2.027(2) Å). The centrosymmetric FePc(4-CNpy)2 molecules form alternating sheets parallel to the bc crystallographic plane and solvated 4-CNpy molecules that are anti-parallel oriented by their polar cyano groups are located between the sheets of FePc(4-CNpy)2 molecules. Ligation of the intermediate-spin iron(II) phthalocyanine by 4-CNpy molecules leads to the low spin Fe(II) complex. The importance of the d(π) → π∗(Pc) back donation is manifested in the difference between the values of C–N isoindole and C–N azamethine bond lengths of the Pc macrocycle. The thermal analysis of the crystals of [FePc(4-CN)2] · 2(4-CNpy) shows two steps responsible for a loss of solvated (∼170 °C) and coordinated (∼235 °C) 4-CNpy molecules. 相似文献