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411.
Many alkali metal carboxylates when dissolved in poly(ethylene oxide) (PEO) oligomers, are phaseseparated by heating. These were revealed to be the crystals of the initially dissolved corresponding salts from the X-ray diffraction patterns. Some acetate salts achieve the lower limit of the lattice energy for phase separation of ordinary inorganic salts by heating in PEO oligomers. These carboxylate salts were therefore expected to show crystallization behavior in PEO oligomers by heating. The effects of cation size, alkyl chain length and molecular weight of PEO on the solubility are summarized. Negative temperature dependence of solubility of these acetate salts is seen in the PEO oligomers only when the salts have long alkyl chains. The salts containing larger cations needed a longer chain length of PEOs for crystallization by heating. These salts with longer alkyl chains showed positive temperautred dependence in lower molecular weight polyethers, but negative temperature dependence in solubility in PEO with molecular weights higher than 400. In PEO400, all the carboxylates with longer alkyl chains were phase separated by heating. 相似文献
412.
Copolymerization of methacrylic acid alkali metal salts (MAAM; M = Li, Na, K, Rb or Cs) and oligo(oxyethylene) methacrylate (MEO) was carried out in bulk or in poly(oligo(oxyethylene) methacrylate) (PMEO) at 60°C. The copolymers of MAAM and MEO which were obtained by bulk polymerization showed a cation conductivity of around 1 × 10?7 S/cm at room temperature. On the other hand, the copolymers obtained by radical polymerization in PMEO, showed a higher cation conductivity (10?6–10?5 S/cm). Furthermore, higher cation conductivity was observed for the copolymer systems containing alkali metal cations with a larger ion radius. This tendency was explained by the strength of the bond between alkali metal cation and ether oxygens. The degree of dissociation had little effect on this difference in the conductivity. The effective dissociation of methacrylic salts was enhanced in the copolymer compared to the homopolymer because of the suppression of the adjacent dissociative carboxylic acid groups. Arrhenius plots for ionic conductivity show the migration of ions along with the segmental motion of the polymer matrix. 相似文献
413.
Novel base-discriminating fluorescent (BDF) nucleoside, 8-fluorescence-labeled adenosine derivative (8PyA), was developed for the detection of thymine base on a target DNA. The BDF nucleoside was incorporated into oligodeoxynucleotides by post-synthetic modification. BDF probes containing 8PyA selectively emit fluorescence only when the base opposite BDF nucleoside is thymine and act as effective reporter probes for homogeneous SNP typing. 相似文献
414.
It was found that 2′-O-cyanoethyl group could be removed from 2′-O-cyanoethylated ribonucleoside derivatives by treatment with Bu4NF. This finding was successfully applied to the synthesis of oligoribonucleotides via their 2′-O-cyanoethylated derivatives as key intermediates where a cyanoethyl group was used as the 2′-hydroxyl protecting group. The rate of condensation using this protecting group in the presence of various activators was generally faster than that observed when a TBDMS group was used as the protecting group. 相似文献
415.
Kazuyuki Suzuki Kaori Nishizawa Takeshi Miki Kazumi Kato 《Journal of Sol-Gel Science and Technology》2007,42(3):251-256
(Y,Yb)MnO3 and HfO2 films were prepared using alkoxy-derived precursor solutions, and (Y,Yb)MnO3/HfO2/Si structures were fabricated. The thickness, surface uniformity and crystallinity of the HfO2 film affect the crystallization of Y0.5Yb0.5MnO3 films. The degree of c-axis orientation and crystallinity of the Y0.5Yb0.5MnO3 films were changed with preparation conditions of HfO2 films. It was difficult to obtain Y0.5Yb0.5MnO3 films with high crystallinity and high degree of c-axis orientation on the HfO2 films thinner than 10 nm. The degree of c-axis orientation and crystallinity of the Y0.5Yb0.5MnO3 films on HfO2 films were improved by using diluted HfO2 precursor solution in the case of 10 nm-thick HfO2 film. Following this, the capacitance-voltage (C-V) characteristics were improved. 相似文献
416.
Beryllium (ca. 10?2?10?4 M) is determined by adding excess of 1,2-phenylenediamine-N,N,N′, N′-tetraacetic acid (PhDTA, H4L) and back-titrating with copper(II); arsenazo-I serves as indicator. Formation constants of BeL and BeHL were determined by potentiometry: log KBeL=6.48±0.02 and log KHBeHL=3.48±0.03 (25°C, I=1 M in NaClO4). Expressions for the titration curve are given together with theoretical errors. 相似文献
417.
Ando K 《Journal of the American Chemical Society》2005,127(11):3964-3972
The alkylation of 4-methoxymethyl-gamma-butyrolactone enolate with methyl chloride was studied at the B3LYP/6-31+G* level. Conformer search of the free enolate gave 15 unique conformers within 5.39 kcal/mol. The transition structures for both anti- and syn-attacks of methyl chloride on these 15 conformers were located. In all cases, the anti-transition structures are more stable than the corresponding syn-ones. The alkylation of gamma-valerolactone was studied at the MP2, B3LYP, and HF levels of theory with the 6-31+G* basis set in the presence of Li+ and dimethyl ether molecules. Basis set effects were also examined by the comparison of the MP2 results with the 6-31+G*, 6-31+G**, and 6-311+G** basis sets in one case. This study shows that the main source of the anti-selectivity of 4-substituted gamma-butyrolactones is eclipsing strain in the syn-transition structures. 相似文献
418.
419.
Shigetomo Fukuhara Keisuke Sako Kazuomi Noda Kaori Nagao Koichi Miura Naoki Mochizuki 《Experimental & molecular medicine》2009,41(3):133-139
Angiopoietin-1 (Ang1) binds to and activates Tie2 receptor tyrosine kinase. Ang1-Tie2 signal has been proposed to exhibit two opposite roles in the controlling blood vessels. One is vascular stabilization and the other is vascular angiogenesis. There has been no answer to the question as to how Tie2 induces two opposite responses to the same ligand. Our group and Dr. Alitalo''s group have demonstrated that trans-associated Tie2 at cell-cell contacts and extracellular matrix (ECM)-anchored Tie2 play distinct roles in the endothelial cells. The complex formation depends on the presence or absence of cell-cell adhesion. Here, we review how Ang1-Tie2 signal regulates vascular maintenance and angiogenesis. We further point to the unanswered questions that must be clarified to extend our knowledge of vascular biology and to progress basic knowledge to the treatment of the diseases in which Ang1-Tie2-mediated signal is central. 相似文献
420.