Rearrangement of the main-chain and subsequent thermal degradation of polyphenylene-ether

Studies of the thermal rearrangement and degradation of polyphenylene-ether (PPE) have been carried out by TGA (thermo-gravimetric analysis), GC-MS (gas chromatography-mass spectroscopy) and ¹H-NMR. 2,6-Xylenol was a major scission product in the temperature range 420–700 °C, and 3,5-xylenol, as a scission product, decreased with increasing temperature. Four monomeric and eight dimeric scission products were observed at relatively high temperatures. The distribution of the scission products, which changed with increasing temperature, led to the suggestion that rearrangement of the PPE main-chain occurred to form diphenyl methylene groups, followed by thermal degradation.     

One-Handed Helical Polyacetylenes Bearing Axially-Chiral 2-Arylpyridyl-N-Oxide Units for Efficient Chromatographic Enantioseparation of Chiral Aromatic and Aliphatic Alcohols

A series of poly(biarylylacetylene)s (PBAs) bearing axially-chiral (S)-and (R)-pyridyl-N-oxide residues with a methoxy, propoxy, or acetyloxy substituent at the 3-position of the biaryl units was synthesized. All the PBAs formed a preferred-handed helix, while the helical sense preference was varied depending on the substituents despite the same twist-sense of the biaryl units. Among them, the propoxy-bound helical PBA showed an exceptionally high chiral recognition ability as a chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC) and efficiently resolved not only various chiral aromatic alcohols, but also a variety of chiral aliphatic alcohols; the latter still remains difficult to resolve by commercially-available CSPs in HPLC. Such practically-useful both handed helical PBA-based CSPs can be produced from the racemic PBA composed of fully racemic monomer units through deracemization of the biaryl units with a chiral alcohol.     

Oscillatory Reaction of a Pendant Drop in a Liquid–Air System under Microwave Irradiation

A Belousov–Zhabotinsky reaction in a pendant drop under microwave radiation was observed under nonstirring conditions. The period decreased as the irradiation power and time were increased because the droplet temperature increased. Moreover, the color change of the solution during the oscillatory reaction depended on the irradiation power and time although the droplet temperature returned to room temperature quickly. Irradiation at higher powers or longer times suspended the oscillatory reaction. However, for moderate irradiation powers or times, the oscillatory reaction stopped after irradiation because the concentration distribution of the reagents became homogeneous. After a time, the oscillatory reaction restarted because a concentration gradient developed again. Accordingly, the effect of the microwave irradiation history continued because the oscillatory reaction stopped even after the irradiation was stopped. This is because the rotation of the polar molecule caused by the irradiation produced a flat concentration distribution for the reagents through increased molecular diffusion.     

基于实验设计法的工程结构优化设计

基于实验设计法,提出了一种新的工程结构优化设计方法,这种方法将设计变量的水平值配列于正关表中,按正交表的参数组合条件进行结构解析,通过对设计变量对于目标函数值的方差分析和F检验,改变设计变量的水平值,进而通过迭代计算使设计变量趋地最优解,本文以杵架结构为计算例,验证了本方法的全局收敛性和优化精度,由于无需构建目标函数和约束函数以及微分计算,此方法具有简单而又适应广泛的优点。     

Future directions for higher-efficiency HIT solar cells using a Thin Silicon Wafer

To reduce the power generation cost of heterojunction with intrinsic thin layer (HIT) solar cells, it is necessary to use a thinner crystalline silicon wafer, as well as to improve the conversion efficiency. We have experimentally confirmed that V_OC of the HIT solar cell increases with decreasing the wafer thickness, and can reach a very high V_OC of 747 mV with a 58-μm-thick wafer owing to a sufficiently low surface recombination velocity. We also indicate the future directions for improving the efficiency. The uniformization of the texture size of the silicon surface and reduction of the carrier density in TCO film while maintaining an equal or lower conductivity are effective for improving the optical confinement.     

Control of luminescence and conductivity of delafossite-type CuYO2 by substitution of rare earth cation (Eu, Tb) and/or Ca cation for Y cation

Delafossite-type oxides of CuTb_yY_1−yO₂, CuEu_yY_1−yO₂, CuCa_xTb_yY_1−x−yO₂ and CuCa_xEu_yY_1−x−yO₂ have been prepared by solid state reactions. The lattice-parameter dependence on the composition implies substitution of the Tb³⁺, Eu³⁺ and Ca²⁺ cations for the Y³⁺ site. Noticeable sharp emission lines due to the f-f transitions (⁵D₄→⁷F_J, J=3-6) of Tb³⁺ or due to the f-f transitions (⁵D₀→⁷F_J, J=0-4) of Eu³⁺ are observed at room temperature. Electrical conductivities of CuCa_xTb_yY_1−x−yO₂ and CuCa_xEu_yY_1−x−yO₂ are larger than those of CuTb_yY_1−yO₂ and CuEu_yY_1−yO₂, indicating the increase of the hole concentration caused by the substitution of Ca²⁺ for the Y³⁺ site. These results indicate the controllability of the luminescence and conductivity in CuCa_xTb_yY_1−x−yO₂ and CuCa_xEu_yY_1−x−yO₂ delafossite-type oxides by simultaneous substitution of the rare earth Tb³⁺ or Eu³⁺ cation and the Ca²⁺ cation for the Y³⁺ site.     

Self-aldol condensation of unmodified aldehyde in supercritical carbon dioxide catalyzed by amine grafted on silica

Self-aldol condensation of an unmodified aldehyde has been effected by 3-N-methylaminopropylated silica as a catalyst in supercritical carbon dioxide, to give an α,β-unsaturated aldehyde (enal). Aldehydes having acid or base-sensitive substituents provided desired enals.