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41.
Two series of nano-sized N-containing MOx–ZnO (M: Fe, W) composite powders were synthesized by spray pyrolysis. The nitrogen content was controlled from 500 to 2100 ppm by changing the powder ingredients and spray pyrolysis temperature. Ultraviolet-visible (UV-Vis) spectra indicated that the N-containing MOx–ZnO powders absorbed not only ultraviolet light (λ<387 nm) like pure ZnO powder, but also part of visible light (λ<650 nm). Acetaldehyde decomposition was used as a probe reaction to evaluate the photocatalysis of these composite powders. The photocatalytic activity of the N-containing ZnO powder was pronouncedly enhanced by the WO3 addition under both UV and visible-light irradiation. However, that of the N-containing ZnO powder was suppressed by the Fe2O3 addition. A model of the semiconductor energy-band structure is proposed to explain the enhancement and suppression of photocatalytic activity. 相似文献
42.
The chelation controlled radical reactions of ethyl γ-benzyloxy-α-methylenecarboxylates bearing a bulky γ-substituent, such as CHMe2, CHPh2, c-C6H11 and CH(Ph)OTBDMS, with alkyl iodides gave the syn-adducts with high diastereoselectivities. However, the diastereoselectivity for the substrates bearing a γ-substituent CH(i-Pr)OTBDMS depended critically on the configuration of the substituent; the substrate bearing the OTBDMS group anti to the γ-benzyloxy group showed poor diastereoselectivity, but its diastereomer gave syn-adduct exclusively. The high syn-selectivitiy is referred to the H-atom transfer to the outside face of radical center in the sharply folded seven-membered chelate intermediate bearing the ethoxy group with Z-geometry. The corner flapping of the radical center atom of the global minimum energy conformer generates a local minimum conformer and the H-atom transfer to the outside face of the radical center of the newly formed structure gives the anti-adduct. The poor diastereoselectivity is due to the very small energy difference between the two conformers and consequently both the syn- and anti-adducts are yielded in nearly equal amounts. 相似文献
43.
The free-radical-induced reactions of cyclohexene oxide in the presence of maleic anhydride have been found to lead to polyether in presence of AIBN and to a mixture of polyether, ester, and maleic anhydride adduct of polyether with di-tert-butyl peroxide (DTBP), the amounts of the mixture components depending on the concentration of DTBP and the temperature. Analogous reactions in the presence of succinic anhydride lead to no polyether. The obtained polyether has no hydroxyl group. The reaction appears to consist of three different steps, radical initiation, cationic propagation, and radical termination. 相似文献
44.
Kitano H Tada S Mori T Takaha K Gemmei-Ide M Tanaka M Fukuda M Yokoyama Y 《Langmuir : the ACS journal of surfaces and colloids》2005,21(25):11932-11940
The structure and hydrogen bonding of water in the vicinity of carboxybetaine homopolymer (poly[1-carboxy-N,N-dimethyl-N-(2'-methacryloyloxyethyl)methanaminium inner salt] (PolyCMB), and a random copolymer of CMB and n-butyl methacrylate, Poly(CMB-r-BMA), with various molecular weights were analyzed in their aqueous solutions and thin film with contours of O-H stretching of Raman and attenuated total reflection infrared (ATR-IR) spectra, respectively. The relative intensity of the collective band (C value) corresponding to a long-range coupling of O-H stretchings of the Raman spectra for aqueous solution of Poly(CMB-r-BMA) was very close to that for pure water, which is in contrast with the smaller C value in aqueous solution of ordinary polyelectrolytes. The number of hydrogen bonds collapsed by the presence of one monomer residue (N(corr) value) of PolyCMB and Poly(CMB-r-BMA) (CMB, 45 mol %) (M(w), 1.14 x 10(4) and 1.78 x 10(4), respectively) could be calculated from the C value. The N(corr) values were much smaller than those for ordinary polyelectrolytes and close to those for nonionic water-soluble polymers such as poly(ethylene glycol) and poly(N-vinylpyrrolidone). Furthermore, a water-insoluble Poly(CMB-r-BMA) with a large BMA content (M(w) = 347 kD, CMB 27 mol %) could be cast as a thin film (thickness, ca. 10 microm) on a ZnSe crystal for the ATR-IR analyses. At an early stage of sorption of water into the Poly(CMB-r-BMA) film, the O-H stretching band of IR spectra for the water incorporated in the film was similar to that for free water, which is in contrast with the drastic change in the O-H stretching band of water incorporated in polymer films such as poly(methyl methacrylate) (PMMA) and poly(n-butyl methacrylate) (PBMA). The theoretical vibrational frequency for water molecules hydrating a betaine molecule calculated by using a density functional method supported the experimental results. The adhesion of human platelets to Poly(CMB-r-BMA) films was much less than that to PMMA and PBMA. With an increase in the content of CMB residue, the number of platelets adhered to the Poly(CMB-r-BMA) film drastically decreased and then gradually increased, probably due to the increase in the roughness of the film surface. These results suggest that the carboxybetaine monomer residues with a zwitterionic structure do not significantly disturb the hydrogen bonding between water molecules in both aqueous solution and thin film systems, resulting in the excellent blood-compatibility of the carboxybetaine polymers. 相似文献
45.
A gas chromatographic-mass spectrometric procedure has been developed for the quantitation of the benzodiazepine antagonist flumazenil in human plasma. The assay utilizes an extraction at alkaline pH with benzene-dichloroethane (80:20), selective ion monitoring, isobutane positive-ion chemical ionization mass spectrometry and stable isotope dilution. The method has been used to measure plasma concentrations of flumazenil in over 1500 clinical samples over a range of 0.5-200 ng/ml (using 2 ml of plasma). 相似文献
46.
We give a lower bound for the number of vertices of a generald-dimensional polytope with a given numberm ofi-faces for eachi = 0,..., d/2 – 1. The tightness of those bounds is proved using McMullen's conditions. Form greater than a small constant, those lower bounds are attained by simpliciali-neighbourly polytopes. 相似文献
47.
F. Kokai Y. Koga Y. Kakudate M. Kawaguchi S. Fujiwara M. Kubota K. Fukuda 《Applied Physics A: Materials Science & Processing》1994,59(3):299-304
Laser-ionization Time-Of-Flight (TOF) mass-spectrometric studies have been carried out on the 532 nm and 1064 nm laser ablation products from a nitrogen-rich polymer. The polymer used had an elemental composition of C6.0N8.9H3.4 and consisted of C=N, C-N, and N-H chemical bonds. The TOF mass spectra observed were composed of various peaks (150 amu) depending on the ablation laser wavelength. The primary peaks were assigned to C+, CN+, CHnN+
2 (n=1–3) and C2H2N+
3 for 532 nm ablation, and C+, C+
3, HCN+, HCCN+, CH2NH+, HNCN+, H3NCN+, and C4H4N+
7 for 1064 nm ablation. The flight velocity distributions with peak velocities ranging from 8.6×103 cm/s to 3.8×104 cm/s were measured for these products. The distinct velocity distributions observed between small and large products indicate the presence of two origins in the fragment ejection process from the polymer for both 532 nm and 1064 nm ablation. Furthermore, we suggest an importance of the translational energy of the fragments for the product generation in the laser plume. 相似文献
48.
S. Momota Y. Nojiri M. -B. Tanaka T. Yanagisawa M. Fukuda K. Matsuta T. Minamisono 《Hyperfine Interactions》1993,80(1-4):1275-1279
To disclose the basic mechanisms of nuclear polarization creation realized by the tilted foil technique, hyperfine quantum beats of the nuclear polarization of the short-lived beta-emitter8Li(I
=2+,T
1/2=840 ms) were measured as a function of the distance between two tilted foils. From the observed beats of the8Li nuclear polarization, it was found that the Fermi-contact interaction of the8Li nucleus with the ground 1s-electron in LiIII plays a main role in the final stage of polarization transfer from polarized orbital electrons to the8Li nucleus. 相似文献
49.
T. Minamisono S. Fukuda T. Ohtsubo M. Tanigaki A. Kitagawa M. Fukuda K. Matsuta Y. Nojiri S. Takeda 《Hyperfine Interactions》1993,78(1-4):191-194
Quadrupole effects in -NMR spectra of41Sc(I
=7/2–,T
1/2=0.596 s) implanted in a TiO2 single crystal were detected by use of a modified -NMR technique. Using the field gradient in the crystal determined by the pulsed-Fourier-transformed NMR of45Sc in TiO2, the quadrupole moment of41Sc has been determined as |Q(41Sc; 7/2–)|=166±8 mb. 相似文献
50.
S. Momota Y. Nojiri M. -B. Tanaka T. Yanagisawa M. -Y. Tanaka M. Fukuda K. Matsuta T. Minamisono 《Hyperfine Interactions》1993,80(1-4):1281-1286
In order to study the basic mechanism of polarization enhancement realized by the multitilted foil technique, nuclear polarization of short-lived beta-emitter8B(T1/2=769 ms,I
=2+) was induced. Utilizing up to ten tilted foils, the polarization enhancement was measured as a function of the foil numbers. The observed enhancement for8B was combined with the previous results for12B(I
=1+,T
1/2=20 ms) which has the same atomic configurations but different nuclear spin. Analyzing these results in the framework of the classical vector model, the essential features of the enhancement depending on the nuclear spin was disclosed. 相似文献