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151.
Takakazu Kojima Takuzo Kurotu Ken-Ichi Masuda Yoshinobu Hosaka 《Journal of polymer science. Part A, Polymer chemistry》1985,23(2):343-349
The thermal decomposition of poly(sec-amyl methacrylate) is studied by simultaneous thermogravimetry–gas chromatography–mass spectrometry and by pyrolysis–gas chromatography. The TG curve has four distinct breaks and a plateau. Results of the identification of the evolved gas at the individual breaks by GC–MS techniques lead to the conclusion that these breaks correspond to the individual processes in the decomposition mechanism like that of poly(tert-butyl methacrylate): the first break, the depolymerization initiated at the unsaturated chain ends; the second break, the depolymerization initiated at the saturated chain ends; the third break, the ester decomposition; the plateau, the inhibition of decomposition by the formation of poly(methacrylic anhydride); the fourth break, the decomposition of poly(methacrylic anhydride). The extent of ester decomposition is related to the substituent constants based on Hammett equation. The ester decomposition product is separated into three pentene isomers by pyrolysis–gas chromatography: trans-2-pentene, cis-2-pentene, and 1-pentene. As raising decomposition temperature, the composition ratio of trans-2-pentene decreases and becomes constant above 620 K, and the composition ratios of cis-2-pentene and 1-pentene increase and also become constant above 620 K. These results are accounted for by mobility of atoms included in the substituent at forming a ring transition state. 相似文献
152.
Ken-Ichi Okamoto Akira Itaya Shigekazu Kusabayashi 《Journal of Polymer Science.Polymer Physics》1976,14(5):869-877
The photoconductivity of poly(N-acryloylcarbazole) (PACz), with the pendant carbazolyl group only a short distance from the skeletal chain of the polymer but separated from it by a carbonyl group, is investigated and compared with that of poly(N-vinylcarbazole) (PVCz). There is no significant difference between PACz and PVCz in the temperature, light intensity, and spectral dependences of the photocurrent. The photoconductivity of PACz, however, is much inferior to that of PVCz and even to that of poly(N-carbazolylethylvinylether), a representative vinyl polymer with pendant carbazolyl groups far from the skeletal chain. The poor photoconductivity of PACz is discussed in relation to the intensity of the electronic interaction between neighboring carbazolyl groups in the polymer chain and to singlet exciton migration. It is attributed mainly to an extremely low efficiency of extrinsic carrier generation via a singlet exciton, which is due to the poor electron-donating character and the extremely short lifetime of a singlet exciton in the presence of the carbonyl group. 相似文献
153.
154.
155.
Numerous peptide aptamers that recognize inorganic materials have been isolated using in vitro peptide evolution systems. However, it remains unknown how peptides interact with inorganic materials or how specific those interactions are. We, therefore, assessed the target specificities of the peptide aptamer TBP-1 (RKLPDAPGMHTW) by monitoring its ability to bind 10 different metals. We found that phages displaying TBP-1 bound to Ti, Si, and Ag surfaces but not to Au, Cr, Pt, Sn, Zn, Cu, or Fe. As previously seen with Ti, binding to Si and Ag was diminished by R1A, P4A, or D5A mutation, suggesting that the same molecular mechanism underlies TBP-1 binding to all three materials. We also observed that a synthetic TBP-1 peptide mediated mineralization of both silica and Ag. It, thus, appears that although the overall chemical characteristics of Ti, Si, and Ag surfaces are dissimilar, they share a common subnanometric structure that is recognized by TBP-1. 相似文献
156.
Effect of ultrasound sonication was examined on the electroplating of iridium in aqueous hexabromoiridate(III) solution. The electrodeposits were evaluated by observing the defects of the iridium deposits by means of voltammetry, in which the current-potential curves of the iridium deposits on copper were measured. Applying ultrasound sonication to the electroplating of iridium decreased the defects including the cracks in the deposit whenever the glycerol as the additives was contained or not in the electrolyte. 相似文献
157.
Ying Xu Hosho Katsura Takaaki Hirano Vladimir E. Korepin 《Journal of statistical physics》2008,133(2):347-377
We study a 1-dimensional AKLT spin chain, consisting of spins S in the bulk and S/2 at both ends. The unique ground state of this AKLT model is described by the Valence-Bond-Solid (VBS) state. We investigate
the density matrix of a contiguous block of bulk spins in this ground state. It is shown that the density matrix is a projector
onto a subspace of dimension
. This subspace is described by non-zero eigenvalues and corresponding eigenvectors of the density matrix. We prove that for
large block the von Neumann entropy coincides with Renyi entropy and is equal to
.
NSF Grant DMS-0503712. 相似文献
158.
Sakai K Koyata Y Shimada N Shibata K Hanamaki Y Itakura S Yagi T Hirano Y 《Optics letters》2008,33(5):431-433
We developed a new master-oscillator power-amplifier scheme consisting of a tapered semiconductor amplifier and a fiber-grating-stabilized laser diode for efficient green-light generation in a planar MgO:PPLN waveguide, and demonstrated cw green-light generation of 346 mW. 相似文献
159.
We have studied photoluminescence (PL) spectra of GaN crystals and InGaN ternary alloys at low temperatures as a function of the femtosecond laser excitation intensity. With an increase of the intensity, the broad PL due to electron–hole plasmas (EHP) appears below the biexciton PL in the GaN sample. On the other hand, the broad EHP PL appears above the localized exciton PL in the InGaN sample. The intensity dependence of PL properties of InGaN crystals is completely different from that of GaN crystals. The effect of alloy disorder on PL processes in ternary alloys is discussed. 相似文献
160.
Koichi Kajihara Taisuke Miura Hayato Kamioka Akira Aiba Motoko Uramoto Yukihiro Morimoto Masahiro Hirano Linards Skuja Hideo Hosono 《Journal of Non》2008,354(2-9):224-232
This article briefly summarizes the diffusion and reactions of interstitial oxygen species in amorphous SiO2 (a-SiO2). The most common form of interstitial oxygen species is oxygen molecule (O2), which is sensitively detectable via its characteristic infrared photoluminescence (PL) at 1272 nm. The PL observation of interstitial O2 provides key data to verify various processes related to interstitial oxygen species: the dominant role of interstitial O2 in long-range oxygen transport in a-SiO2; formation of the Frenkel defect pair (Si–Si bond and interstitial oxygen atom, O0) by dense electronic excitation; efficient photolysis of interstitial O2 into O0 with F2 laser light (λ = 157 nm, hν = 7.9 eV); and creation of interstitial ozone molecule via reaction of interstitial O2 with photogenerated O0. The efficient formation of interstitial O0 by F2 laser photolysis makes it possible to investigate the mobility, optical absorption, and chemical reactions of interstitial O0. The observed properties of O0 are consistent with the model that O0 takes the configuration of Si–O–O–Si bond. Interstitial O2 and O0 react with dangling bonds, oxygen vacancies, and chloride groups in a-SiO2. Reactions of interstitial O2 and O0 with mobile interstitial hydrogen species produce interstitial water molecules and hydroperoxy radicals. Interstitial hydroxyl radicals are formed by F2 laser photolysis of interstitial water molecules. 相似文献