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排序方式: 共有228条查询结果,搜索用时 15 毫秒
1.
H. Ohta M. Kimata K. Koyama Y. Oshima M. Motokawa H. Nishikawa K. Kikuchi I. Ikemoto 《International Journal of Infrared and Millimeter Waves》2005,26(11):1525-1530
We have developed a new magneto-optical measurement system using a rotational cavity system equipped with a millimeter vector
network analyzer and a 14 T solenoid type super conducting magnet. The measurement can be performed in the transmission configuration
down to 1.6 K. The results of the precise angular dependence measurement of quasi-one-dimensional organic conductor (DMET)2I3 using the new system are shown, and its Fermi surface will be discussed in connection with the previous reports. 相似文献
2.
Spin-lattice relaxation mechanisms in kaolinite have been reinvestigated by magic-angle spinning (MAS) of the sample. MAS is useful to distinguish between relaxation mechanisms: the direct relaxation rate caused by the dipole-dipole interaction with electron spins is not affected by spinning while the spin diffusion-assisted relaxation rate is. Spin diffusion plays a dominant role in 1H relaxation. MAS causes only a slight change in the relaxation behavior, because the dipolar coupling between 1H spins is strong. 29Si relaxes directly through the dipole-dipole interaction with electron spins under spinning conditions higher than 2 kHz. A spin diffusion effect has been clearly observed in the 29Si relaxation of relatively pure samples under static and slow-spinning conditions. 27Al relaxes through three mechanisms: phonon-coupled quadrupole interaction, spin diffusion and dipole-dipole interaction with electron spins. The first mechanism is dominant, while the last is negligibly small. Spin diffusion between 27Al spins is suppressed completely at a spinning rate of 2.5 kHz. We have analyzed the relaxation behavior theoretically and discussed quantitatively. Concentrations of paramagnetic impurities, electron spin-lattice relaxation times and spin diffusion rates have been estimated. 相似文献
3.
Sontaya Limmatvapirat Etsuo Yonemochi Toshio Oguchi Keiji Yamamoto 《Journal of inclusion phenomena and macrocyclic chemistry》1998,31(4):367-379
A complex between deoxycholic acid (DCA) and salicylic acid (SA) was prepared by grinding and coprecipitation methods. The resultant complex was characterized by means of powder X-ray diffractometry, IR spectroscopy and thermal analysis. The stoichiometry (DCA : SA 1 : 1) of the complex obtained by grinding was identical to that obtained by coprecipitation. The powder X-ray diffraction pattern of the DCA–SA complex differed from the typical pattern of DCA–guest complexes such as DCA–camphor and DCA–phenanthrene complexes. IR spectra suggested that a different kind of hydrogen bonding was formed in the crystal of the DCA–SA complex, compared with the other DCA–guest complexes. This was in good agreement with data from the crystal structure. 相似文献
4.
Tsugikazu Tomono Etsuo Hasegawa Eishun Tsuchida 《Journal of polymer science. Part A, Polymer chemistry》1974,12(5):953-965
Active hydrogen compounds such as hydroquinone (HQ), cyclohexanone (CH), acetophenone (AP), and 4,4′-methylene bis-N-methylaniline (MNA) polymerized with formaldehyde (F) and secondary diamines to produce Mannich base polyamine polymers. The HQ-containing polymers were oxidized to benzoquinone (BQ)-containing polymers and their redox properties were investigated in the desulfurization of hydrogen sulfide. 相似文献
5.
Etsuo Watanabe Shunsuke Tokimatsu Kenzo Toyama Isao Karube Hideaki Matsuoka Shuichi Suzuki 《Analytica chimica acta》1984
A multielectrode enzyme sensor for the simultaneous determination of adenosine-5′-phosphate (AMP), inosine-5′-phosphate (IMP), inosine (HXR) and hypoxanthine (HX)in fish meat was developed by assembling four enzyme sensors for AMP, IMP, HXR and HX in a flow cell. These compounds were determined from oxygen consumption according to the following reactions: AMP IMP HXR HX Uric acid where AD is AMP deaminase, NT is 5′-nucleotidase, NP is nucleoside phosphorylase and XO is xanthine oxidase. Enzymes were covalently bound to a membrane prepared from cellulose triacetate, 1,8-diamino-4-aminomethyloctane and glutaraldehyde. Sensors for HX, HXR, IMP and AMP were prepared by attaching membranes of XO, XONP, XO NPNT, and of XONPNT and AD, respectively, to four oxygen electrodes. Samples extracted from sea bass, bream, flounder, abalone and arkshell were analyzed within 5 min, from the simultaneous response curves of the four electrodes. Results obtained by the multisensor system were in good agreement with those determined by each single electrode. 相似文献
6.
Nakamura T Ikemoto JY Fujitsuka M Araki Y Ito O Takimiya K Aso Y Otsubo T 《The journal of physical chemistry. B》2005,109(30):14365-14374
The dramatic changes of the lifetimes of the charge-separated (CS) states were confirmed in zinc porphyrin (ZnP)-oligothiophene (nT)-fullerene (C(60)) linked triads (ZnP-nT-C(60)) with the solvent polarity. After the selective excitation of the ZnP moiety of ZnP-nT-C(60), an energy transfer took place from the (1)ZnP moiety to the C(60) moiety, generating ZnP-nT-(1)C(60). In polar solvents, the CS process also took place directly via the (1)ZnP moiety, generating ZnP(*+)-nT-C(60)(*-), as well as the energy transfer to the C(60) moiety. After this energy transfer, an indirect CS process took place from the (1)C(60) moiety. In the less polar solvent anisole, the radical cation (hole) of ZnP(*+)-nT-C(60)(*-) shifted to the nT moiety; thus, the nT moiety behaves as a cation trapper, and the rates of the hole shift were evaluated to be in the order of 10(8) s(-1); then, the final CS states ZnP-nT(*+)-C(60)(*-) were lasting for 6-7 mus. In the medium polar solvent o-dichlorobenzene (o-DCB), ZnP-nT(*+)-C(60)(*-) and ZnP(*+)-nT-C(60)(*-) were present as an equilibrium, because both states have almost the same thermodynamic stability. This equilibrium resulted in quite long lifetimes of the CS states (450-910 mus) in o-DCB. In the more polar benzonitrile, the generation of ZnP-nT(*+)-C(60)(*-) was confirmed with apparent short lifetimes (0.6-0.8 mus), which can be explained by the fast hole shift to more stable ZnP(*+)-nT-C(60)(*-) followed by the faster charge recombination. It was revealed that the relation between the energy levels of two CS states, which strongly depend on the solvent polarity, causes dramatic changes of the lifetimes of the CS states in ZnP-nT-C(60); that is, the most appropriate solvents for the long-lived CS state are intermediately polar solvents such as o-DCB. Compared with our previous data for H(2)P-nT-C(60), in which H(2)P is free-base porphyrin, the lifetimes of the CS states of ZnP-nT-C(60) are approximately 30 times longer than those in o-DCB. 相似文献
7.
8.
Ogawa Y Ogawa K Kokufuta E 《Langmuir : the ACS journal of surfaces and colloids》2004,20(7):2546-2552
Polyampholyte gels were prepared by free radical polymerization of aqueous monomer solutions with the following composition: 69% N-isopropylacrylamide (thermosensitive neutral monomer), 1% N,N'-methylenebisacrylamide (cross-linker), 15% 1-vinylimidazole (cationic monomer), and either 15% acrylic acid (AAc, anionic monomer) or poly(acrylic acid) (PAAc, polyanion). We thus obtained two sorts of polyampholyte gels; that is, G1 with immobilized PAAc and G2 with randomly copolymerized AAc. The equilibrium swelling ratio (Qe) was studied as a function of the pH, NaCl concentration, and temperature. Also studied was the kinetics of swelling and shrinking in response to a sudden pH change. The significant results obtained were as follows: (i) A fully collapsed state was observed at pH 4.5-9.0 for G1 and at pH 4.5-7.0 for G2. (ii) Below and above these pH ranges, both gels were in a swollen state; therefore, an isoelectric point (pI) appeared in a wide pH range. (iii) At alkaline pH regions where a hysteresis was observed in the Qe versus pH curves of G1 and G2 as the pH was first increased then decreased, G1 exhibited very slow swelling-shrinking kinetics. (iv) An increase in the NaCl concentration allowed the gel to swell at pH approximately pI (antipolyelectrolyte behavior) but to shrink at pHs below and above the pI range (polyelectrolyte behavior). (v) The magnitude of the salt-induced shrinking of G1 is smaller than that of G2 at pH 10 and at NaCl concentrations > 0.01 M. (vi) At pH 10, an increase in the temperature from 35 to 50 degrees C led to a shrinking change of G1 but not of G2. These results were found to be explicable in terms of a different distribution of negative charges within the polyampholyte gel network. 相似文献
9.
Toru Tachihara Susumu Ishizaki Yoshiko Kurobayashi Hiroshi Tamura Youichi Ikemoto Atsushi Onuma Keisuke Yoshikawa Tetsuya Yanai Takeshi Kitahara 《Helvetica chimica acta》2003,86(2):274-279
All possible stereoisomers of imine derivatives 1 – 4 , which have the characteristic roast odor of seafood, were synthesized. As a result of odor evaluation of all isomers, we found that each isomer has a different and characteristic odor of roasted seafood. 相似文献
10.
M Mitsukuchi J Nakagami T Ikemoto S Higuchi Y Tarumoto H Yasui K Sota 《Chemical & pharmaceutical bulletin》1989,37(6):1534-1539
A series of 17-succinyl derivatives of four corticosteroids was prepared. They were tested for vasoconstrictive activity in humans, using 9 alpha-fluoro-11 beta, 21-dihydroxy-16 beta-methyl-17 alpha-valeryloxy-1,4-pregnadiene-3,20-dione (betamethasone 17-valerate, BV) as a standard. The activities of the 21-chloro 17-methylsuccinate compounds (6A, 6C and 6D) were greater than that of BV. A structure-activity relationship study showed that the activities of the 21-chloro 17-methylsuccinates were more potent than those of the corresponding 21-esters. 相似文献