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91.
92.
CM Thaker S Rayaprol Krushna Mavani DS Rana MS Sahasrabudhe SI Patil DG Kuberkar 《Pramana》2002,58(5-6):1035-1039
The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO3 perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good
example of these properties is (La1−2x
Pr
x
Ca
x
)MnO3 (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T
c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using
X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for
understanding the structural, transport and magnetic properties are discussed in detail. 相似文献
93.
P. A. Büger und A. Reis 《Fresenius' Journal of Analytical Chemistry》1968,235(2):181-182
Ohne Zusammenfassung 相似文献
94.
Andresa JS Reis RM Gonzalez EP Santos LS Eberlin MN de Paula Nascente PA Tanimoto ST Machado SA Rodrigues-Filho UP 《Journal of colloid and interface science》2005,286(1):303-309
The present paper describes the one-pot procedure for the formation of self-assembled thin films of two silanes on the model oxidized silicon wafer, SiO2/Si. SiO2/Si is a model system for other surfaces, such as glass, quartz, aerosol, and silica gel. MALDI-TOF MS with and without a matrix, XPS, and AFM have confirmed the formation of self-assembled thin films of both 3-imidazolylpropyltrimethoxysilane (3-IPTS) and 4-(N-propyltriethoxysilane-imino)pyridine (4-PTSIP) on the SiO2/Si surface after 30 min. Longer adsorption times lead to the deposition of nonreacted 3-IPTS precursors and the formation of agglomerates on the 3-IPTS monolayer. The formation of 4-PTSIP self-assembled layers on SiO2/Si is also demonstrated. The present results for the flat SiO2/Si surface can lead to a better understanding of the formation of a stationary phase for affinity chromatography as well as transition-metal-supported catalysts on silica and their relationship with surface roughness and ordering. The 3-IPTS and 4-PTSIP modified SiO2/Si wafers can also be envisaged as possible built-on-silicon thin-layer chromatography (TLC) extraction devices for metal determination or N-heterocycle analytes, such as histidine and histamine, with "on-spot" MALDI-TOF MS detection. 相似文献
95.
We consider one typical two-parameter family of quadratic systems of 2 × 2 conservation laws, and study the geometry of the
behaviour of the possible solutions of the Riemann problem near an umbilic point, following the geometric approach presented
by Isaacson, Marchesin, Palmeira, Plohr, in A global formalism for nonlinear waves in conservation laws, Commun. Math. Phys. (1992). The corresponding phase portraits for the rarefaction curves, shock curves and composite curves
are discussed.
Financial support from FCT and Calouste Gulbenkian Foundation. 相似文献
96.
We discuss the analysis of linear constant coefficient differential algebraic equations
on infinite dimensional Hilbert spaces. We give solution concepts and discuss solvability criteria which are mainly based
on Laplace transform. Furthermore, we investigate the decoupling of these systems motivated by the Kronecker normal form for
the finite dimensional case. Applications are given by the analysis of mixed systems of ordinary differential, partial differential
and differential algebraic equations. 相似文献
97.
98.
Relatively f-disjunctive languages 总被引:2,自引:0,他引:2
Communicated by Boris M. Schein 相似文献
99.
In flow injection analysis, several plugs can be injected simultaneously into the same carrier system, in order to achieve overlapped zones. The potentialities of such sequential injections are studied in model systems with spectrophotometric detection; the procedure is shown to give better precision than the use of concentration gradients. The method is used with atomic absorption spectrometry to allow the determination of a wide range of manganese contents in rocks, and to facilitate the use of standard additions for the determination of copper in ethanol. 相似文献
100.
Trigo M Chen J Vishwanath VH Sheu YM Graber T Henning R Reis DA 《物理学评论B辑:凝聚态物质与材料物理学》2010,82(23):235205-235209
We use picosecond x-ray diffuse scattering to image the nonequilibrium vibrations in the lattice following ultrafast laser excitation. We present images of nonequilibrium phonons in InP and InSb throughout the Brillouin zone which remain out of equilibrium up to nanoseconds. The results are analyzed using a Born model that helps identify the phonon branches contributing to the observed features in the time-resolved diffuse scattering. In InP this analysis shows a delayed increase in the transverse-acoustic (TA) phonon population along high-symmetry directions accompanied by a decrease in the longitudinal-acoustic phonons. In InSb the increase in TA phonon population is less directional. 相似文献