Characterization of in‐plane structures of vapor deposited thin‐films of distyryl‐oligothiophenes by grazing incidence x‐ray diffractometry

The in‐plane structures of vapor deposited ultrathin films of distyryl‐oligothiophenes (DS‐2T) on SiO₂ substrate were characterized by grazing incidence x‐ray diffractometry (GIXD). Two polymorphs, low‐temperature and high‐temperature phases, were identified, and the two dimensional unit cell parameters were determined for each polymorph. The polymorphism depends on substrate temperature and film thickness. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermal ratcheting of solder-bonded elastic and elastoplastic layers

The cyclically growing deflection of solder-bonded elastic and elastoplastic layers subjected to cyclic thermal loading is studied. Finite element analysis of a Si/Sn–95Pb/OFHC-Cu layered structure is performed by taking into account the temperature-dependent viscoplastic behavior of Sn–95Pb as well as the uniaxial ratcheting behavior of OFHC-Cu. A temperature-dependent power law is employed for the viscoplasticity of Sn–95Pb, while a combined nonlinear kinematic and isotropic hardening model is assumed for the cyclic plasticity of OFHC-Cu. It is shown that the temperature-dependent viscoplasticity of Sn–95Pb and the uniaxial ratcheting of OFHC-Cu are the controlling factors for the cyclic growth of deflection of the layered structure under temperature cycling. It is also shown that cyclic hardening of OFHC-Cu plays an important role for the cyclic growth of deflection, and that elastic stress in the Si layer cyclically develops noticeably if the cyclic growth of deflection is significant.     

LPE Growth of Ga1 – xInxSb Multi-grading Layers

Electronegativity difference approach (ENDA) has been successfully employed to obtain good prediction of the In atomic fraction, energy bandgap and lattice constant of the Ga_{1 – x}In_xSb/Ga_{1 – y}In_ySb/GaSb system. Nearly lattice-matched GalnSb epilayers with In atomic fraction of 0.42 have been obtained by the liquid phase epitaxy. The cut-off wavelength was 2.2 μm at room temperature.     

Instability of Stimulated Brillouin Scattering in a Fiber Ring Resonator

We investigate theoretically the instability of transient stimulated Brillouin scattering (SBS) in a high- finesse fiber ring resonator consisting of a fiber ring and directional coupler. Unlike many reports to date, the linear phase detuning of the cavity is taken into account. It is found that SBS instabilities including the self-pulsing and chaotic behavior can occur even if the length of the fiber resonator is very short. SBS instabilities depend strongly on the linear phase detuning, the input power, and the coupling coefficient of the coupler.     

Integrated Optic Pressure Sensor Using Intermodal Interference between Two Mutual Orthogonal Guided-Modes

We theoretically and experimentally investigated fundamental characteristics of an integrated optic pressure sensor using intermodal interference between the lowest-order TM-like and TE-like modes. The sensor consists of a rectangular diaphragm and a straight single-mode waveguide along an edge of the diaphragm. Its operation is based on a difference of phase retardations produced in the two guided modes through the photoelastic effect. The sensor was fabricated by bonding two glass substrates together: a Corning 0211 glass 300 μMm thick to form a waveguide and a thick substrate with a 10 mm × 10 mm square hole to define the diaphragm. The fabricated sensor was successfully tested using a He-Ne laser at 633 nm. The halfwave pressure was measured to be 77 kPa which is almost double the theoretical estimate.     

Negative muon capture ratios for nitrogen oxide molecules

Journal of Radioanalytical and Nuclear Chemistry - Per-atom muon capture ratios are precisely determined from characteristic muonic X-ray measurements of three nitrogen oxide samples (NO, N2O, and...     

Mechanistic Insights into Rhenium-Catalyzed Regioselective C-Alkenylation of Phenols with Internal Alkynes

A (μ-aryloxo)rhenium complex was isolated and confirmed as a key precatalyst for rhenium-catalyzed ortho-alkenylation (C-alkenylation) of unprotected phenols with alkynes. The reaction exclusively provided ortho-alkenylphenols; the formation of para or multiply alkenylated phenols and hydrophenoxylation (O-alkenylation) products was not observed. Several mechanistic experiments excluded a classical Friedel–Crafts-type mechanism, leading to the proposed phenolic hydroxyl group assisted electrophilic alkenylation as the most plausible reaction mechanism. For this purpose, the use of rhenium, a metal between the early and late transition metals in the periodic table, was key for the activation of both the soft carbon–carbon triple bond of the alkyne and the hard oxygen atom of the phenol, at the same time. ortho-Selective alkenylation with allenes also provided the corresponding adducts with a substitution pattern different from that obtained by the addition reaction with alkynes.     

ANION–CATION VERSUS WEAK INTERMOLECULAR INTERACTIONS IN THE STRUCTURES OF Et4N+, Pr4N+, AND Bu4N+ CATION SALTS WITH THE [W(CN)6(bpy)]2– ANION

Journal of Structural Chemistry - Cyanide complexes are used as metalloligands to obtain multicore complexes with magnetic properties. Hexacyanides [W(CN)6(L)]1–/2–...