Relationship between Electrical Activity and Grain Boundary Structural Configuration in Polycrystalline Silicon

Temperature dependent electron beam induced current (EBIC) technique has been applied to investigate the electrical activities of grain boundaries (GBs) in polycrystalline silicon. The GB character, misorientation and orientation of GB plane, were analyzed using a FE-SEM/EBSP/OIM system prior to the EBIC measurements. The EBIC contrasts were found to depend on GB character; low GBs showed weak contrasts compared with general GBs at any temperatures, and also demonstrated to vary at GB irregularities such as boundary steps. These results indicate that electrical properties depend on the orientation of the GB plane as well as the misorientation. On the other hand, there existed less differences in temperature dependence of EBIC contrast irrespective of GB characters. The EBIC contrast decreased with increasing temperature, showed a minimum around 250 K, then increased again with further increasing temperature. The resulting temperature dependence of EBIC contrast probably comes from the combination of two types of recombination processes of carriers. One is related to a shallow level associated with an inherent GB structure, though the exact energy levels also would probably depend on GB structures, and the other to a deep level associated with impurities segregated at GBs, which acts as recombination center.     

Reactivity of amorphous aluminas prepared by the thermal decomposition of aluminum chloride and nitrate

The physicochemical properties and reactivity of amorphous aluminas, Al₂O₃(C1) and Al₂O₃(N), which were prepared by the thermal decomposition of AlCl₃ · 6 H₂O and Al(NO₃)₃ · 9 H₂O at 600°C for 2–300 h, were investigated by means of TG, DTA, X-ray diffraction, SEM and IR. The reactivity of Al₂O₃(Cl) for ZnAl₂O₄ formation was, in general, higher than that of Al₂O₃(N) and was influenced by the content of residual chlorine in Al₂O₃(Cl). The rate of ZnAl₂O₄ formation followed the Avrami—Erofeev equation in the ZnOAl₂O₃(Cl) system and the Jander equation ZnOAl₂O₃(N) system, respectively.     

Syntheses and fluorescence of RNA conjugates having pyrene-modified adenosine and nitrobenzene-modified uridine base pairs

We prepared RNA duplexes possessing 2′-O-(1-pyrenylmethyl)adenosine and 5-(4-nitrophenyl)uridine base pairs. In the duplexes, pyrene serves as a photo-excitable electron donor and 5-(4-nitrophenyl)uridine acts as an electron acceptor. The donor-acceptor-modified RNA duplexes showed very weak fluorescence originating from the pyrene monomer and excimer emissions, which occur due to electron transfer from the excited pyrene to the nitrobenzene acceptor.     

Biogenetic type synthesis of (±)-concinndiol and (±)-aplysin 20

Based on the biogenetical consideration, the titled natural products were synthesized via the common intermediate ($\text{7}$).     

Magnetic field dependence of 11B NMR in CeB6

The ¹¹B nuclear magnetic resonance in a dense Kondo system CeB₆ has been observed by the spin echo technique below 4.2 K at fixed frequencies of 2.5, 6.5, 13.33 and 18.00 MHz, which correspond to magnetic fields of 1.83, 4.76, 9.76 and 13.18 KOe for the free ¹¹B nucleus, respectively. The spectra in the phase II appeared to have two peaks in the magnetic field applied in the [111] direction, the spacing of which was found to be very small in zero external field and increased monotonically (up to 0.11 kOe at 2.6 K) with increasing field. On the other hand, the spectra in the phase III were complex. Especially, the spectra observed for [111] at 6.5 MHz were found to spread over 1.9 KOe and to have several peaks. From comparison between the experiments and the dipolar field calculation based on the recent neutron diffraction measurements, possible magnetic structures were examined for the phases II and III.     

Homogeneous two-component polycondensation without strict stoichiometric balance via the Tsuji-Trost reaction: remote control of two reaction sites by catalysis

Carothers and Flory established the fundamental principles of homogeneous two-component polycondensation reactions by which a variety of commonly used polymers such as polyesters and polyamides (nylons) are synthesized even now. One of the most critical factors to achieve a high degree of polymerization is a strict adherence of stoichiometric balance of the two components. An imbalanced ratio of the two starting materials leads to lower degree of polymerization and, consequently, polymers of poor quality. Here we report the details of a strategy, validated by appropriate experiments, which enables an efficient homogeneous two-component polycondensation via palladium-catalyzed allylic substitution (the Tsuji-Trost) reaction without strict stoichiometric balance.     

Synthesis of 8-aryl-3,5,7,3′,4′-penta-O-methylcyanidins from the corresponding quercetin derivatives by reduction with LiAlH4

Synthesis of 8-aryl-3,5,7,3′,4′-penta-O-methylcyanidins from the corresponding quercetin derivatives by reduction with LiAlH₄ is reported. Regioselective iodination at the 8-position of penta-O-methylquercetin followed by a Suzuki-Miyaura reaction gave the 8-arylated quercetin derivatives. By the reduction of 8-arylated quercetins using 4 equiv. of LiAlH₄ at room temperature for 30 min, the corresponding anthocyanidins were obtained with a good yield.