Wavelength-tunable excited-state absorption and optical limiting effects in the Q band region based on silicon phthalocyanine oligomers

Optical limiting effects of silicon phthalocyanine (SiPc) oligomers have been examined in the Q band region in order to demonstrate a novel concept for controlling the wavelength of optical limiting effects.     

The equations for modular function fields of principal congruence subgroups of prime level

We determine the equation with integral coefficients of the modular, function fields with respect to the principal congruence subgroup ofSL ₂ (ℤ) of prime level.     

Thermal and photochemical reactions of a stable thiobenzaldehyde, 2,4,6-tri-t-butylthiobenzaldehyde

Thermal and photochemical reactions of the title compound gave benzothiolane $\text{2}$ in high yield; the reaction with free radicals also afforded $\text{2}$ along with some other products.     

Chemoselective Oxidation of Secondary Hydroxy Functions Catalyzed by [PMo12O40]3-[C5H5N+(CH2)15 CH3]3

Abstract

The epoxidation of allylic alcohols with H₂O₂ catalyzed by a new Mo-species, [PMo₁₂O₄₀]^3?[C₅H₅N⁺(CH₂)₁₅CH₃]₃ (MPCP), prepared from 12-molybdatophosphoric acid (H₃PMo₁₂O₄₀) and cetylpyridinium chloride [C₅H₅N⁺(CH₂)₁₅CH₃ · Cl^?], has recently rep0rted.) The high regioselectivity for the epoxidation by this MPCP-H₂O₂ system was comparable to that of Sharpless method using t-BuOOH as oxidant.     

Computation of transition to turbulence in the compression stage of a reciprocating engine

The transition to turbulent flow in the compression stage of a reciprocating engine is studied by obtaining the finite-difference numerical solutions to the governing Navier-Stokes equations without using explicit turbulence models. A computational method is developed under the assumption that the flow is in a low-subsonic regime with strong compression. The numerical method is a simple extension of the well known MAC method. Computations were performed for three different chamber geometries at the engine speed of 1400 rpm. The results of the computations clearly demonstrate the transient process in which large tumbling vortices break down into smaller ones near the end of the compression process. The transition process is also caught experimentally by using Mach-Zehnder interferometry.     

Improvement of boundary conditions for non-planar boundaries represented by polygons with an initial particle arrangement technique

The boundary conditions represented by polygons in moving particle semi-implicit (MPS) method (Koshizuka and Oka, Nuclear Science and Engineering, 1996 Koshizuka, S., and Y. Oka. 1996. “Moving-Particle Semi-Implicit Method for Fragmentation of Incompressible Fluid.” Nuclear Science and Engineering 123: 421–434.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) have been widely used in the industry simulations since it can simply simulate complex geometry with high efficiency. However, the inaccurate particle number density near non-planar wall boundaries dramatically affects the accuracy of simulations. In this paper, we propose an initial boundary particle arrangement technique coupled with the wall weight function method (Zhang et al. Transaction of JSCES, 2015 Zhang, T.G., S. Koshizuka, K. Shibata, K. Murotani, and E. Ishii. 2015. “Improved Wall Weight Function With Polygon Boundary in Moving Particle Semi-Implicit Method.” Transaction of JSCES. No. 20150012. [Google Scholar]) to improve the particle number density near slopes and curved surfaces with boundary conditions represented by polygons in three dimensions. Two uniform grids are utilized in the proposed technique. The grid points in the first uniform grid are used to construct boundary particles, and the second uniform grid stores the same information as in the work by Zhang et al. The wall weight functions of the grid points in the second uniform grid are calculated by newly constructed boundary particles. The wall weight functions of the fluid particles are interpolated from the values stored on the grid points in the second uniform grid. Because boundary particles are located on the polygons, complex geometries can be accurately represented. The proposed method can dramatically improve the particle number density and maintain the high efficiency. The performance of the previously proposed wall weight function (Zhang et al.) with the boundary particle arrangement technique is verified in comparison with the wall weight function without boundary particle arrangement by investigating two example geometries. The simulations of a water tank with a wedge and a complex geometry show the general applicability of the boundary particle arrangement technique to complex geometries and demonstrate its improvement of the wall weight function near the slopes and curved surfaces.     

High‐resolution solid‐state NMR study of the domain structure and molecular motion in drawn films of a vinylidene fluoride and trifluoroethylene copolymer with 73 mol % vinylidene fluoride

The heterogeneous higher order structure and molecular motion in a single crystalline film of a vinylidene fluoride (VDF) and trifluoroethylene (TrFE) copolymer with 73 mol % VDF was investigated with the ¹H–¹³C cross‐polarization/magic‐angle spinning NMR technique. A transient oscillation was observed in plots of the ¹³C peak intensity versus the contact time for the CH₂, CHF, and CF₂ groups. On the basis of the extended cross‐relaxation theory of spin diffusion, we determined that the oscillation behavior was caused by the TrFE‐rich segments in the chain and that the crystal consisted of VDF‐rich and TrFE‐rich domains. The former had TrFE‐rich segments in VDF and TrFE fractions of 0.24 and 0.27, respectively, and the latter had VDF‐rich segments in a VDF fraction of 0.49. The spin–lattice relaxation time T_1ρH in the rotating frame for each group was minimal in the three temperature regions of β, α_b, and α_c (↑) on heating and in the two temperature regions of α_1D and α_c (↓) on cooling. The α_c (↑) and α_c (↓) processes depended on the first‐order ferroelectric phase‐transition regions on heating and cooling, respectively. The motional modes for the other processes were confirmed by the T_1ρH minimum behavior of the VDF and TrFE groups in the TrFE‐rich domain and the VDF‐rich segments in the VDF‐rich domain. The β and α_b processes were attributed to the flip–flop motion of the TrFE‐rich segments and the competitive motion of the TrFE‐ and VDF‐rich segments in the ferroelectric phase, respectively. The α_1D process was due to the one‐dimensional diffusion motion of the conformational defects along the chain in the paraelectric phase, accompanied by the trans and gauche transformation of the VDF conformers of ttg⁺tg^? and g⁺tg^?tt. The effect of the competitive motion of the TrFE‐rich segment on the thermal stability of the VDF‐rich segment in the chain near the Curie temperature was examined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1026–1037, 2002     

Determination of diltiazem hydrochloride enantiomers in dog plasma using chiral stationary-phase liquid chromatography

The separation and determination of d- and l-diltiazem hydrochloride in dog plasma by a two-column high-performance liquid chromatographic technique are described. Diltiazem hydrochloride and its metabolites were extracted from dog plasma and analyzed on a conventional column (Nucleosil 5C18) with a volatile buffer system. The column effluent of diltiazem hydrochloride was collected and evaporated. The enantiomeric ratio of the collected diltiazem was determined using a chiral column (Chiralcel OC). The method was accurate and sensitive.