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491.
Makoto Nishiki Wataru Oi Kazuaki Ito 《Journal of inclusion phenomena and macrocyclic chemistry》2008,61(1-2):61-69
The anion binding properties of the indolylmethanes (1) were investigated by 1H-NMR spectroscopy in CDCl3. Tris(3-methylindol-2-yl)methane (1a) selectively bound a chloride anion the over other tested anions (Br?, I?, HSO 4 ? , and NO 3 ? ). In contrast, analogous compounds, phenyl bis(3-methylindol-2-yl)methane (1b), 2-hydroxyphenyl bis(3-methylindol-2-yl)methane (1c), tri(indol-3-yl)methane (1d), and phenyl di(indol-2-yl)methane (1e), showed a low anion binding ability and selectivity. These results indicate that the number and a position of the binding sites (indole NH protons) of the indolylmethanes are important factors for the formation of the complex with an anion. The high binding ability and selectivity of 1a toward a chloride anion is attributed to the proper size of the binding pocket for a chloride anion and the formation of multiple hydrogen bonds between the three indole NH protons and a chloride anion. The anion affinity of 1a was significantly affected by the cation component of quaternary ammonium salts, indicating that it is ion pair binding and not solely anion binding. 相似文献
492.
Tetsu Ito Wataru Shichi Yoshie Nishioka Masao Ichida Hideki Gotoh Hidehiko Kamada Hiroaki Ando 《Journal of luminescence》2008,128(5-6):865-867
The dependence of electron spin g-factor on magnetic field has been investigated in GaAs/AlGaAs quantum wells. We have estimated the electron g-factor from spin precession frequency in time-resolved photoluminescence measurements under a magnetic field in different configurations; the magnetic field perpendicular (g⊥) and parallel (g∥) to the quantum confinement direction. When the angle between the magnetic field and the confinement direction is 45°, we have found that g-factor varies depending on the direction of magnetic field and the circular polarization type of excitation light (σ+ or σ?). These dependences of g-factor exhibit main features of Overhauser effect that nuclear spins react back on electron spin precession. The value of g⊥ and g∥ corrected for the nuclear effects agree well with the results of four-band k·p perturbation calculations. 相似文献
493.
Wataru Sakai Motoi Kinoshita Minoru Nagata Naoto Tsutsumi 《Journal of polymer science. Part A, Polymer chemistry》2001,39(5):706-714
The photosensitized degradation of poly(L ‐lactic acid) (PLA) via an anionic reaction process was studied using spectrophotometry, electron spin resonance (ESR), and gel permeation chromatography (GPC) measurements. PLA film doped with N,N,N′,N′‐tetramethyl‐p‐phenylenediamine (TMPD) was irradiated at 77 K using UV light (λc = 356 nm) by which the PLA matrix itself cannot be directly excited. After photoirradiation, a new broad absorption band appeared over the original spectrum due to TMPD+ ·, which was produced by two‐photon ionization. The ESR spectrum of the irradiated sample indicated the presence of the TMPD+ · radical and main‐chain scission radical of PLA. During the thermal annealing at 0 °C, the latter radical changed to another radical species by dehydrogenation of the alpha hydrogen of the PLA main chain. TMPD+ · was extremely stable at room temperature for 7 d. However, by thermal annealing at 40 °C, all the radicals decayed due to the enhanced molecular motions near Tg of PLA (58.7 °C). Spectral simulation for the obtained ESR spectra revealed the relative amounts of four radicals: TMPD+ ·, a main‐chain scission radical, a main‐chain tertiary radical, and an unknown radical. The last one was tentatively assigned to the PLA radical anion because of its short decay time. GPC measurements clearly indicated a decrease in the molecular weight of PLA after irradiation. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 706–714, 2001 相似文献
494.
Fumiaki Ishii Wataru Hirahata Kazuaki Yokota Katsuyuki Tuda Akira Hirao Toyoji Kakuchi 《Journal of Polymer Science.Polymer Physics》1999,37(23):3319-3327
The crosslinking formation in the 8/92 mol % random copolymer of ethynyl- styrene and styrene is clarified quantitatively from the IR spectrum analysis on the basis of the thermally homogeneous reaction of ethynylstyrenes between the chains. The viscoelastic properties of the crosslinked polystyrene, CL-P(ESt/St), are investigated based on the temperature and frequency dependencies of the dynamic Young modulus. The relaxation spectrum of CL-P(ESt/St) drops deeply like the Wedge type with a slope of −½ in the glass transition region, and became a plateau without a terminal zone in the rubbery elasticity region. The effects of the ethynyl crosslinked junctions for the micro-Brownian motions of the segments in the strand are discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3319–3327, 1999 相似文献
495.
Minoru Nagata Tetsuya Machida Wataru Sakai Naoto Tsutsumi 《Journal of polymer science. Part A, Polymer chemistry》1999,37(13):2005-2011
Network copolyesters were prepared from glycerol (Yg) and sebacic acid (10) with 10–90 mol % of either succinic acid (4), 1,12-dodecanedicarboxylic acid (14), 1,18-octadecanedicarboxylic acid (20), or terephthalic acid (T). Prepolymers prepared by melt-polycondensation were cast from dimethylformamide solution and postpolymerized at 230–250°C for various periods of time to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network copolyesters obtained were characterized by infrared absorption spectra, wide angle X-ray diffraction analysis, density measurement, thermomechanical analysis, differential scanning calorimetry, and tensile test. The enzymatic degradation was estimated by weight loss of the network copolyester films in a buffer solution with Rhizopus delemar lipase at 37°C. The weight loss due to the enzymatic degradation was decreased with increasing comonomer content, and the copolyesters with Yg4, Yg20 and YgT more than 50 mol % were not degraded by lipase enzyme at all. On the contrary, Yg-10/14 films were degraded appreciably over whole range of comonomer composition. With increasing comonomer content, the heat distortion temperature increased gradually, while the tensile strength and Young's modulus were not changed much. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2005–2011, 1999 相似文献
496.
Minoru Nagata Takashi Morooka Wataru Sakai Naoto Tsutsumi 《Journal of polymer science. Part A, Polymer chemistry》2001,39(17):2896-2903
Regular‐network polyester‐amines were prepared from 1,1,1‐triethanolamine (YN) and various dicarboxylic acids [HOOC? (CH2)n?2? COOH, n = 6–14]. A prepolymer prepared by melt polycondensation was cast from dimethylformamide solution and postpolymerized at 220 °C in a nitrogen flow for various periods of time to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network polyester‐amines obtained were characterized by infrared absorption spectra, wide‐angle X‐ray diffraction analysis, density, DSC, and thermomechanical analysis. The biodegradation experiments for the network polyester‐amine films were carried out in enzymatic solution with Rhizopus delemar or Pseudomonas cepacia lipase and in an activated sludge. The degree and rate of biodegradation were estimated by the weight loss of the films. After incubation in Rhizopus delemar lipase solution for 24 h, weight loss was hardly observed for YN6–7, whereas it increased greatly for YN8–13 (13–51 g/m2), and then it decreased rapidly for YN14. The methylene‐chain dependence of degradation was essentially the same as in the case of network polyesters from glycerol and various aliphatic dicarboxylic acids reported previously. Psedomonas cepacia lipases also degraded YNn films, but the rate of degradation was much slower than Rhizopus delemar lipase. In the exposure to activated sludge for 30 days, the network polyester films with medium methylene‐chain lengths (YN7–11) showed the lager weight loss, as in the case of the enzymatic degradation, whereas the rate of biodegradation was much slower than that of the enzymatic degradation with Rhizopus delemar lipase. The effect of the protonation of the film with hydrochloric acid on the enzymatic degradation was also examined. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2896–2903, 2001 相似文献
497.
Akira Sugimoto Hideyuki Maruyama Wataru Takahashi Kazuhiko Mizuno Kaku Uehara Tomohiro Adachi 《Journal of heterocyclic chemistry》1999,36(4):849-856
The reaction of lithium salt of 5-methyl-5,10-dihydrophenazine anion with 4-nitrophenethyl bromide in 1,2-dimethoxyethane gave unexpected compounds, 1,2-bis[5-(10-methyl-5,10-dihydrophenazinyl)]-1-(4-nitrophenyl)ethane and 1,4-bis(4-nitrophenyl)-1,4-bis[5-(10-methyl-5,10-dihydrophenazinyl)]butane, while the reaction in dimethyl sulfoxide brought about the formation of 5-methyl-10-(4-nitrophenethyl)-5,10-dihydrophenazine. The successive electron transfer mechanism is proposed for the former reaction via 4-nitrostyrene. 相似文献
498.
Weak and Strong Convergence of Solutions to Accretive Operator Inclusions and Applications 总被引:7,自引:0,他引:7
Our purpose in this paper is to approximate solutions of accretive operators in Banach spaces. Motivated by Halpern's iteration and Mann's iteration, we prove weak and strong convergence theorems for resolvents of accretive operators. Using these results, we consider the convex minimization problem of finding a minimizer of a proper lower semicontinuous convex function and the variational problem of finding a solution of a variational inequality. 相似文献
499.
Let C be a closed, convex subset of a uniformly convex Banach space whose norm is uniformly Gâteaux differentiable and let T be an asymptotically nonexpansive mapping from C into itself such that the set F (T) of fixed points of T is nonempty. Let {an} be a sequence of real numbers with 0 £ an £ 10 \leq a_n \leq 1, and let x and x0 be elements of C. In this paper, we study the convergence of the sequence {xn} defined by¶¶xn+1=an x + (1-an) [1/(n+1)] ?j=0n Tj xn x_{n+1}=a_n x + (1-a_n) {1\over n+1} \sum\limits_{j=0}^n T^j x_n\quad for n=0,1,2,... . n=0,1,2,\dots \,. 相似文献
500.
Minoru Nagata Fujio Okano Wataru Sakai Naoto Tsutsumi 《Journal of polymer science. Part A, Polymer chemistry》1998,36(11):1861-1864
Blend films of poly(L -lactic acid) (PLLA) and cellulose with various composition was prepared by casting from trifluoroacetic acid solution. One hydroxyl group per each glucose unit was esterified by trifluoroacetic acid. The trifluoroacetyl group was hydrolyzed completely during the degradation. Weight losses for 90/10 and 75/25 PLLA/cellulose blends by proteinaze K were greatly increased compared with pure PLLA sample due to the large depression of the crystallinity of PLLA component, while cellulase was effective only for the degradation of pure cellulose film. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1861–1864, 1998 相似文献