Self-Modulation of Scattering Intensity from a Silica Sphere Coated with a Sol-Gel Film Doped with J-Aggregates

A micrometer-sized nonlinear optical resonator constituted of a silica microsphere coated with J-aggregates has been fabricated by the sol-gel process. We determined the scattering light spectrum and discuss the application of the observed effect for the realization of an optical switching element. Optical evaluation of the sphere has been performed in the attenuated-total-reflection (ATR) configuration. We excited a whispering gallery mode and measured the nonlinear ATR signal dependence on excitation intensity. The experimental result agrees very well with the simulation results obtained using the Mie theory and the finite-difference time-domain method taking into account optical Kerr nonlinearity. The permittivity of the film of J-aggregates was measured by ATR method at several wavelengths and the value at the desired wavelength was determined by extrapolation using the Lorentz function.     

Highly cation-deficient manganese perovskite, La1−xMn1−yO3 with x=y

Oxidative (δ>0) nonstoichiometry in the perovskite ‘LaMnO_3+δ’ has been known to be manifested not with O interstitials but rather with cation vacancies of equal amounts at the two cation sites, La and Mn, i.e. La_1−xMn_1−yO₃ with x=y. Here, we report the fabrication of samples with record-high cation-vacancy concentrations (x>0.12 or δ>0.4) by means of a variety of high-pressure oxygenation techniques. Linear (negative) dependence of the cell volume on x was observed within the whole x range investigated, down to 56.9 Å³ (per formula unit) for a sample oxygenated at 5 GPa and 1100 °C using Ag₂O₂ as an excess oxygen source. With increasing degree of cation deficiency in La_1−xMn_1−xO₃, the ferromagnetic transition temperature was found to follow a bell shape with respect to x exhibiting a maximum of ∼250 K about x≈0.1. For moderately oxygenated samples large magnetoresistance effect was evidenced.     

Gas permeability and permselectivity of polyimides with large aromatic rings

Polyimides with large aromatic rings were prepared from 3,6-diaminocarbazole (CDA), N-ethyl-3,6-diaminocarbazole (ECDA), 2,7-diaminofluorene (DAF), 2,7-diaminofluorenon (DAFO), and dimethyl-3,7-diaminodibenzothiophene-5,5-dioxide (DDBT) with 2-bis(2,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA). Their physical properties, including gas permeability and permselectivity, were investigated in comparison with those of the related polyimides from 1,3-phenylenediamine (mPD). Glass transition temperatures of the polyimides with large aromatic rings were much higher than those of the mPD-based polyimides as a result of increased rigidity of the former polymer chains. With changing diamine from mPD to the large aromatic diamines, charge transfer (CT) interaction between the moieties of acid anhydride and diamine seems to be enhanced, judging from the red shift of absorption edge of the polyimide films and the red shift of CT excitation band of the 6FDA-based polyimides in solution. Fraction of free space (V_F) was a little smaller for the polyimides with large aromatic rings except DDBT than for the mPD-based polyimides, probably because of enhancement in polymer chain-chain interactions as a result of the increased CT interaction. The DDBT-based polyimides had large V_F than the mPD-based polyimides because of the nonplanar structure of neighboring dibenzothiophene-5,5-dioxide and imide rings. For the 6FDA-based polyimides, permeability coefficients to H₂, O₂, N₂, CO₂, and CH₄ were in the order, DAFO < mPD ～ DAF < CDA < ECDA < DDBT. As for the membrane performance for H₂/CH₄, CO₂/CH₄, and O₂/N₂ systems, it is significant to change diamine from mPD to DDBT or CDA, but not to DAF or DAFO. The DDBT-based polyimides were excellent for H₂/CH₄ and CO₂/CH₄ separations. © 1995 John Wiley & Sons, Inc.     

Complements of Intersections in Constructive Mathematics

We examine, from a constructive perspective, the relation between the complements of S, T, and S ∩ T in X, where X is either a metric space or a normed linear space. The fundamental question addressed is: If x is distinct from each element of S ∩ T, if s ? S, and if t ? T, is x distinct from s or from t? Although the classical answer to this question is trivially affirmative, constructive answers involve Markov's principle and the completeness of metric spaces. Mathematics Subject Classification: 03F65, 46S30.     

Synthesis of trans-4-aminomethylcyclohexanecarbonyl-L- and -D-phenylalanine-4-carboxymethylanilide and examination of their inhibitory activity against plasma kallikrein.

Based on studies of structure-activity relationship, trans-4-aminomethylcyclohexanecarbonyl-L-phenylalanine-4-carbox ymethylanilide (Tra-Phe-APAA) was designed as a selective plasma kallikrein inhibitor and synthesized. Tra-Phe-APAA inhibited plasma kallikrein with a Ki value of 0.81 microM, while it inhibited glandular kallikrein, plasmin, urokinase, factor Xa and thrombin with Ki values of greater than 500, 390, 200, greater than 500, and greater than 500 microM, respectively. However, its stereoisomer, Tra-D-Phe-APPA did not exhibit any detectable inhibitory activity against the above enzymes.     

Quantum phase transitions of spin chiral nanotubes

Recently many interesting magnetic nanostructures have been fabricated and much attention is arising on the rich magnetic properties that originate in the quantum effects eminent in the nanoscale world. One of the peculiar aspects of the quantum effects is the spin excitation gap. In the spin-1/2 low-dimensional systems, the spin gap often appears when the lattice dimerization or the frustration in the spin–spin interaction are introduced. In the present study, we investigate the ground-state property of the spin-1/2 antiferromagnetic spin chiral nanotubes with the spatial modulation in the spin–spin interaction. The ground-state phase diagrams of them are determined by observing the behavior of the expectation value of the Lieb–Schultz–Mattis slow-twist operator calculated by the quantum Monte Carlo method with the continuous-time loop algorithm. We discuss the relation between the characteristic of the topology of the phase diagram and the chiral vector of the nanotubes.