Dynamic photoelastic analysis by optical heterodyne polarimetry

This paper describes the mapping of the spatiotemporal principal stress distribution evolved with time in an epoxy photoelastic sample. In the optical heterodyne polarimeter exploited, the signal beam of light transmitted by the sample under continuously loaded condition is photomixed with the local oscillator beam of light made up of orthogonal linearly polarized two-frequency components. Every pixel of a MOS video camera used generates a beat photocurrent that possesses the two orthogonal field components of the elliptically polarized signal beam. The spatiotemporal principal stress distributions can be uniquely determined simultaneously and independently from these two orthogonal field components, and are successfully mapped in a time-sequential form. The spatial and temporal resolutions in the maps are 0.18 mm and 2.9 ms, respectively.     

Structure in the emission from pyrene evaporated films

Emission spectra and decay times of fluorescence of pyrene thin films prepared by evaporation onto substrates at liquid nitrogen temperature were measured. Structure in the emission from films warmed slowly up to higher temperature is found to the higher energy side of the excimer emission band. The decay time is about 410 ns at temperatures between 110 K and 210 K. But the emission from the film warmed up to a temperature above 210 K shows only the excimer emission. These results are discussed in relation to an amorphous structure in the pyrene evaporated thin film.     

Radial breathing modes of single-walled carbon nanotubes in resonance Raman spectra at high temperature and their chiral index assignment

Radial breathing modes (RBMs) in resonance Raman spectra from single-walled carbon nanotubes (SWCNTs) on a SiO₂/Si (0 0 1) substrate are studied between 25 and 720 °C. A change in the relative intensity of each RBM peak with temperature is observed, which originates from the temperature dependence of the resonance condition of nanotubes. For 25 °C, each RBM peak is reasonably assigned on the basis of data in the literature [J. Maultzsch, H. Telg, S. Reich, F. Hennrich, C. Thomsen, Phys. Rev. B 72 (2005) 205438]. By taking into account the temperature-dependent behavior of the relative intensity of the RBM peaks, each RBM peak is successfully assigned even for 720 °C. It is found that most of the observed RBM peaks for a laser excitation energy of E_exc = 1.96 eV are from chiral SWCNTs. These results make it possible to discuss further details of the chirality-dependent growth behavior observed for in situ Raman spectroscopy.     

Palladium-Catalyzed Decarboxylative Alkynylation of α-Acyloxyketones by C(sp3)−O Bond Cleavage

Palladium-catalyzed decarboxylative alkynylation of α-acyloxyketones triggered by C(sp³)−O bond cleavage is disclosed. The decarboxylation strategy featuring a neutral reaction condition enabled an unprecedent catalytic alkynylation of a ketone enolate. The reaction was applied to a variety of substrates, giving desired products in good yields. We successfully obtained X-ray crystallography of a new palladium–enolate intermediate that was synthesized by a reaction of [Pd(cod)(CH₂TMS)₂] with XPhos and α-acyloxyketone at room temperature, indicating facile C(sp³)−O bond disconnection.     

Synthesis of (Z)-β-(Carbonylamino)alkenylindium through Regioselective anti-Carboindation of Ynamides and Its Transformation to Multisubstituted Enamides

The regioselective anti-carboindation of ynamides by using InBr₃ and silylated nucleophiles was developed to synthesize (Z)-β-(carbonylamino)alkenylindiums. The X-ray crystallographic analysis of an alkenylindium suggested that the reaction proceeded in an anti-addition fashion. In contrast to reported syn-carbometalations of ynamides by using organometallics, a cooperation of InBr₃ and silylated nucleophiles to ynamides achieved an anti-addition, which was supported by DFT calculations. The scope of substrates included various ynamides and silylated nucleophiles, such as silyl ketene acetals and silyl ketene imines. The transformation of synthesized alkenylindiums by iodination, radical coupling, and Pd-catalyzed cross-coupling successfully afforded trisubstituted enamines with high regio- and stereoselectivities.     

Energy method in the partial Fourier space and application to stability problems in the half space

The energy method in the Fourier space is useful in deriving the decay estimates for problems in the whole space Rn. In this paper, we study half space problems in and develop the energy method in the partial Fourier space obtained by taking the Fourier transform with respect to the tangential variable x^′∈Rn−1. For the variable x₁∈R₊ in the normal direction, we use L² space or weighted L² space. We apply this energy method to the half space problem for damped wave equations with a nonlinear convection term and prove the asymptotic stability of planar stationary waves by showing a sharp convergence rate for t→∞. The result obtained in this paper is a refinement of the previous one in Ueda et al. (2008) [13].     

Stability of stationary solutions for the non-isentropic Euler-Maxwell system in the whole space

In this paper we discuss the asymptotic stability of stationary solutions for the non-isentropic Euler-Maxwell system in R³. It is known in the authors’ previous works [17, 18, 19] that the Euler-Maxwell system verifies the decay property of the regularity-loss type. In this paper we first prove the existence and uniqueness of a small stationary solution. Then we show that the non-stationary problemhas a global solution in a neighborhood of the stationary solution under smallness condition on the initial perturbation. Moreover, we show the asymptotic convergence of the solution toward the stationary solution as time tends to infinity. The crucial point of the proof is to derive a priori estimates by using the energy method.     

Birefringent side-hole fiber for use in strain sensor

Novel birefringent single-mode fibers are fabricated with a vacant hole on either side of the central elliptical core, referred to as side-hole fiber, and their intrinsic and tension-induced modal birefringences are measured to know their characteristic properties for the purpose of making a strain sensor. Five sampled side-hole fibers are prepared for measurements. The sensitivity of the strain sensor is primarily determined by two parameters, tension-induced and intrinsic modal birefringences. Tension-induced modal birefringence is controllable by optimal arrangement of the size and location of the side-holes in the cross-section of the fiber. A sensitivity diagram for designating and fabricating side-hole fibers is presented.