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1.
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
2.
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
3.
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
4.
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
5.
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
6.
The title hydride and its deuteride were successfully synthesized. The crystal structure of the deuteride was determined by time-of-flight neutron powder diffraction. BaAlD(5) crystallizes with a new orthorhombic structure in space group Pna2(1) (No. 33), cell parameters a = 9.194(1) A, b = 7.0403(9) A, and c = 5.1061(6) A, Z = 4. BaAlH(5) is the first example that contains one-dimensional zigzag chains of [AlH(6)] along the crystallographic c axis. 相似文献
7.
Fukami J Ozawa A Yoshihashi Y Yonemochi E Terada K 《Chemical & pharmaceutical bulletin》2005,53(12):1536-1539
A fast disintegrating compressed tablet was formulated using amino acids, such as L-lysine HCl, L-alanine, glycine and L-tyrosine as disintegration accelerator. The tablets having the hardness of about 4 kgf were prepared and the effect of amino acids on the wetting time and disintegration time in the oral cavity of tablets was examined on the basis of surface free energy of amino acids. The wetting time of the tablets increased in the order of L-lysine HCl, L-alanine, glycine and L-tyrosine, whereas the disintegration time in the oral cavity of the tablets increased in the order of L-alanine, glycine, L-lysine HCl and L-tyrosine. These behaviors were well analyzed by the introduction of surface free energy. When the polar component of amino acid was large value or the dispersion component was small value, faster wetting of tablet was observed. When the dispersion component of amino acid was large value or the dispersion component was small value, faster disintegration of tablet was observed, expect of L-tyrosine tablet. The fast disintegration of tablets was explained by the theory presented by Matsumaru. 相似文献
8.
Tomihiro Nishiyama Yasushi Nakai Masataka Kushiyama Etsuo Ikemoto Fukiko Yamada 《Journal of heterocyclic chemistry》1982,19(5):1223-1226
The mass spectral fragmentation of 4-, 5-, and 4,8-disubstituted derivatives of 6-aryl-5,6,7,8-tetrahydro-4H-1,3,2,6-dioxathiazocine 2-oxides is reported. 相似文献
9.
K. Terada T. Masuda Y. Yoshihashi E. Yonemochi 《Journal of Thermal Analysis and Calorimetry》2006,85(3):675-680
Isothermal
microcalorimetry was used to evaluate excipient compatibility of solid dosage
form. Oxybutynin hydrochloride and cefaclor were used as model drugs for compatibility
test with excipients. The calorimetric data for compatibility test were compared
with those of HPLC data. Evaluation of compatibility between drug and excipient
of solid dosage form might be possible to use isothermal microcalorimetry
instead of conventional method. By using microcalorimetric method, the evaluation
of the compatibility between drug and excipient could be successfully performed
with a simple operation in a short time. The application of the isothermal
microcalorimetry would be useful for the screening test of the drug compatibility
with excipients. 相似文献
10.
We synthesized the glutaraldehyde cross-linked hydrogels using four kinds of poly(lysine)s (PLs) and measured the equilibrium swelling ratio (Q) as a function of pH. Also measured was the temperature change of Q at a fixed pH (11.6) in the absence and presence of additives (LiBr, methanol and urea) that affect the secondary structure of PLs. The swelling data were examined using a force balance approach in which the repulsive and attractive interactions among the cross-linked PL chains were considered based on the conformational properties of PLs in aqueous solutions. It was found that the formation of the helical segments in the cross-linked chain has little effect in the gel collapse, but their association acts as the attractive interaction causing the gel to shrink. The formation of the beta-sheet structure within the network also acts as the attractive interaction. These attractive interactions are mainly due to the hydrogen bonding, but hydrophobic interactions between the lysine side chains should be considered. In addition, in the swelling behavior of all the PL gels the polyampholyte nature appears due to electrostatic interactions of the basic groups with the C-terminal carboxyl group. 相似文献