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81.
Highly oriented tungsten bronze K0.4(Pb0.6Ba0.4)0.8Nb2O6 ferroelectric thin films have been prepared from metal alkoxides and metal acetate by chemical process. The formation of solid solution with potassium was found to be very effective to form the tungsten bronze phase at lower temperatures compared with (Pb0.6Ba0.4)Nb2O6. The amount of potassium in the composition of Kx(Pb0.6Ba0.4)1 – x/2Nb2O6 [0 x 0.4] is also important to crystallize in the tungsten bronze phase. K0.4(Pb0.6Ba0.4)0.8Nb2O6 films with c-axis preferred orientation were successfully synthesized on MgO(1 0 0) and Pt(1 0 0)/MgO(1 0 0) substrates above 700°C. KPBN60 thin film on Pt(1 0 0)/MgO(1 0 0) showed a remnant polarization of 20 C/cm2 and a coercive field of 140 kV/cm at –150°C.  相似文献   
82.
Production of radiation defects in a widely used scintillation material BaF2 has been studied by means of a combination spectroscopy of synchrotron radiation (SR) and laser, in which defects produced by SR irradiation are sensitively detected by observing the luminescence stimulated by laser light. The photostimulated luminescence arises from the recombination of self-trapped holes (VK centers) with electrons released from trapped centers by laser light. The obtained result reveals that the production efficiency of radiation defects is drastically dependent on the excitation photon energy of valence or core excitons.  相似文献   
83.
The reaction of manganese acetate with octacyanotungastate in an aqueous solution of concentrated acetic acid gives two new three-dimensional cyano-bridged manganese(II)-tungstate(V) bimetallic assemblies, [Mn(II)(2)(H(2)O)(2)(CH(3)COO)][W(V)(CN)(8)].2H(2)O (1) (tetragonal space group I4/mcm, a = b = 11.9628(9) A, c = 13.367(2) A, and Z = 4) and Cs(I)(0.5)Mn(II)(2)[W(V)(CN)(8)](CH(3)CO(2))(1.5).H(2)O (2) (monoclinic space group C2/c, a = 16.274(2) A, b = 22.948(6) A, c = 13.196(1) A, beta = 128.040(6) degrees, and Z = 8). In complex 1, W(V)(CN)(8) adopts a square antiprismatic geometry, and each CN group coordinates to the Mn(II) ions forming W-Mn(4)-W-Mn(4)-...columnar linkages where four sites on the Mn(II) ion with octahedral geometry are occupied by CN groups. The columns are parallel and interlock, yielding a network structure. Complex 2 contains two different coordination geometries for W(V)(CN)(8), namely, square antiprismatic and dodecahedral. The columnar structures appear also in 2, where the Mn(II) ions in two different environments provide three and four coordinated sites to the CN groups. The columns are bridged by both dodecahedral W(V)(CN)(8) groups and acetates. Cs ions were intercalated in the lattice by the formation of short attractive contacts with the acetates. The field-cooled magnetization, ac susceptibility, and the field dependence of magnetization measurements show that both 1 and 2 are ferrimagnets with ordering temperatures 40 and 45 K, respectively. The investigation of the magnetostructural correlation shows that the ferrimagnetic ordering in 1 and 2 are attributed to the dominant antiferromagnetic exchange pathways d(z)2(W)-d(x')(y')(Mn) and d(x)2(-y)2(W) - d(x')(y')(Mn).  相似文献   
84.
We have calculated the characteristics of reflected near infrared light, which is incident on the skin surface, scattered in the skin tissue and detected, in the wavelength range from 1000 nm to 1900 nm. We have used a Monte Carlo method to calculate the propagation path, the average photon visit depth, the average photon path length, etc. for the cases of short source-detector distances, to which the isotropic scattering approximation cannot be applied. An experiment to validate the simulation results was also conducted using a liquid phantom.  相似文献   
85.
We present a review on recent study of the type I to type II transition in short-period superlattices (SLs) of GaAs/AlAs by means of cyclotron resonance (CR) in pulsed high magnetic fields. The behavior of CR varies depending on the thickness of the GaAs and AlAs layers. In CR of (GaAs)n/(AlAs)n, the resonance peak at the X minima was observed in the type II regime for n smaller than 14, whereas the resonance at the Γ point was observed for n>15. We estimated electron masses on X and Γ point in the SLs by using the empirical sp3 tight-binding method including second-nearest-neighbor interaction. These calculations have shown good agreement with the experimental results. Moreover, it was found that the angular dependence of the CR peak position does not obey the simple cosine dependence due to the subband mixing in high magnetic fields. From the angular dependence in the SLs, the longitudinal and transverses electron masses of AlAs at the X point were deduced to be mt=0.21m0 and ml=1.04m0, respectively.  相似文献   
86.
A new method is presented for the analysis of zero point energies of linear chains and their generalized analogues. The aspect of form and topological considerations play a fundamental role in the method.  相似文献   
87.
Synthesis of benzo[3,4]cyclohepta[1,2-e]pyrimido[1,2-c]pyrimidines, corresponding to the B,D-dihomo-11,13,15-triazasteroidal skeleton as a novel ring system is described. Their effects on reserpine-induced hypothermia in mice and inhibitory activity against collagen-induced platelet aggregation were also investigated.  相似文献   
88.
Asymmetric oxidation of 1,2-diols using N-bromosuccinimide (NBS) in the presence of copper(II) triflate and (R,R)-Ph-BOX has been exploited. This oxidation was applicable to asymmetric desymmetrization of meso-hydrobenzoin and kinetic resolution of dl-hydrobenzoin and racemic-cycloalkane-cis-1,2-diols to afford optically active α-ketoalcohols with good to high enantiomeric excess.  相似文献   
89.
By using the approach via the aspect of form and general topology, as well as basic notions of abstract algebra, a theoretical framework has been developed which elucidates the mechanism of the additivity relationships between structure and properties in molecules having many identical moieties. The main theorem, the Asymptotic Linearity Theorem (ALT), together with an auxiliary theorem, the a Independence Theorem, implies that the zero-point vibrational energy (or total pi-electron energy for the case of alternant hydrocarbons)E n of a linearly extended system B-A n -B having n repeating identical moieties has the asymptotic expansionE n = n + +o(1) as n , where is independent of the choice of the end moieties B and B. The theorem being formulated in a general context, the actual implication of the ALT is much broader than the above two applications would indicate.On leave from: Institute for Fundamental Chemistry, 34-4 Nishihiraki-cho, Takano, Sakyo-ku, Kyoto 606, Japan.  相似文献   
90.
The present Part VII of this series of articles is a direct extension of Part VI, where (1) fundamental methodology in the repeat space theory (RST) and (2) frontier electron theory of reactivity indices were theoretically linked. This part presents an estimate of the size of the regular index set, which was a central notion in Part VI, and two new theorems that are simpler and more powerful than the main theorem in Part VI. The main theorem in this part enables one to globally contextualize the Generalized Alpha Existence Theorem (a theorem essential in the RST and proved in Part V) and the μ Existence Theorem (derived from the main theorem in Part VI) into the star algebra structure of the generalized repeat space ??r(q, d). © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004  相似文献   
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