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91.
Spectroscopic, chemical, thermal, and voltammetric analyses on six kinds of alkylcarboxylate-stabilized silver nanoparticles 4.7 nm in diameter were carried out with an aim to reveal the effect of alkylcarboxylates on the optical, thermal, geometric, and electrochemical properties of the nanoparticles. These nanoparticles are composed of silver atoms and silver alkylcarboxylates having even numbers, m, of carbon atoms from 8 to 18. As a measure of the structure of the nanoparticles, the ratio of the number of silver atoms (nAg) to that of alkylcarboxylates (ns) per nanoparticle was evaluated by means of titration through chemical oxidation, voltammetric currents, and thermal gravimetric analysis. It increased with an increase in m and ranged from 1.3 to 9.8. Properties of the nanoparticle have been exhibited in absorbance of the UV-vis spectra at the point of the proportionality to n(Ag), voltammetric currents of which values were close to the theoretical values at the diffusion of particle itself, and the m-independent kinetic energy of the thermal decomposition and the overpotential of the reduction. They are not observed for the composed species, that is, silver atoms and silver alkylcarboxylate molecules. 相似文献
92.
Since the physical properties of lithium borate glasses xLi2O-(1-x)B2O3 (0<x< 0.28) vary over a wide range with the composition, this binary system is particularly suitable for studying the relationship
between vibrational anharmonicity and fragility. The density, the linear expansion coefficient, the longitudinal and transverse
ultrasonic velocities and their respective temperature coefficients of the velocities are measured, from which the vibrational
anharmonicity in lithium borate glasses is evaluated with the help of the Grüneisen parameter at the Debye cut-off frequency
and the Anderson-Grüneisen parameter: these two parameters plotted vs. composition have the same characteristics with minima at x≈0.08. The fragility is evaluated from the temperature width of the glass transition; the fragility also shows a minimum at
x≈0.08. The presence of minima at x≈0.08 is ascribable to the fact that the crosslinking density between six-membered rings in the glass reaches a maximum at
this composition. We show that the anharmonic parameters strongly correlate with the fragility metrics.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
93.
A new C3-unit substitution reaction at C-4 position of 4- acetoxyazetidinone derivative ( and ) by tetraallyltin () in the presence of 1/10 eq. of BF3-ether in methylene chloride is described. From 4-allylazetidinone derivative () via ylid intermediate () dethiathienamycin () was synthesized. 相似文献
94.
[reaction: see text] On treatment of 5-siloxyhexa-1,2,5-trienes with a catalytic amount of W(CO)(6) under photoirradiation, formal Cope rearrangement proceeded to give 2-siloxyhex-1-en-5-ynes in good yield. The electrophilic activation of the allenyl moiety by W(CO)(5) triggers the intramolecular attack of the silyl enol ether in a 6-endo manner to produce a cyclohexenyl tungsten species. Carbon-carbon bond cleavage occurs by electron donation from the anionic W(CO)(5) into the silyloxonium moiety to afford the products with regeneration of the W(CO)(5)(L). 相似文献
95.
K Maruyama T Yuda A Okamoto C Ishikura S Kojima M Iwatsuru 《Chemical & pharmaceutical bulletin》1991,39(6):1620-1622
The effect in mice of the molecular weight of polyethyleneglycol on prolonging the circulation time of large unilamellar liposomes (LUVs) was examined using four different distearoyl N-(monomethoxy polyethyleneglycol succinyl) phosphatidylethanolamines (DSPE-PEGs). The molecular weights tested were 1000, 2000, 5000 and 12000. Incorporation of 6 mol% of DSPE-PEG in LUV composed of distearoylphosphatidylcholine (DSPC) / cholesterol (CH) (1:1 in molar ratio) increased the blood circulation half-life significantly more than those without DSPE-PEG derivatives. DSPE-PEGs with molecular weights of 1000 and 2000 prolonged the circulation time of liposomes more than other DSPE-PEGs with higher molecular weights, such as 5000 and 12000. Their effects are also higher than ganglioside GM1, a well described glycolipid with this effect. DSPC/CH LUV-incorporated DSPE-PEG with a molecular weight of 2000 displayed a high concentration in the blood, approximately 40% of the dose, 6 h after the injection. 相似文献
96.
97.
Two kinds of adsorbents (Si adsorbent and Al adsorbent) for the removal of silicic acid from geothermal water to retard the formation of silica scales were prepared using silicic acid contained in geothermal water. The Si adsorbent was prepared by evaporating geothermal water, and the Al adsorbent was prepared by evaporating geothermal water after the addition of aluminum chloride. The specific surface area of the Si adsorbent was small and it's adsorption capacity of silicic acid was low. Although the specific surface area of the Al adsorbent was also small, it was significantly increased by the adsorption of silicic acid and it's adsorption capacity was high. Based on the change in the local structure of aluminum ion by the adsorption of silicic acid, the Al adsorbent was considered to be silica particles covered with crystalline aluminum hydroxide. Moreover, it was concluded that the increase in the specific surface area of the Al adsorbent and the decrease in the zeta potential were due to the formation of an amorphous aluminosilicate with a large surface area and a negative charge (one 4-coordinated Al) by the reaction between aluminum ions and silicic acids. 相似文献
98.
Yamaguchi T Sunatsuki Y Kojima M Akashi H Tsuchimoto M Re N Osa S Matsumoto N 《Chemical communications (Cambridge, England)》2004,(9):1048-1049
Dinuclear [(NiL)Gd(hfac)(2)(EtOH)](H(3)L = 1,1,1-tris(N-salicylideneaminomethyl)ethane, Hhfac = hexafluoroacetylacetone), trinuclear [(NiL)(2)Gd(NO(3))], and tetranuclear [(NiL)Gd(CH(3)CO(2))(2)(MeOH)](2) complexes, were prepared by treating [Ni(HL)] with [Gd(hfac)(3)(H(2)O)(2)], Gd(NO(3))(3).6H(2)O, and Gd(CH(3)CO(2))(3).4H(2)O, respectively, in the presence of Et(3)N. All the complexes show that ferromagnetic interactions occur between the Ni(II) and Gd(III) ions. 相似文献
99.
T Takahashi N Kakuhara S Katsuragawa Y Kojima A Hirose T Nakasato K Yoshioka K Kato T Yanagisawa 《Radioisotopes》1987,36(10):519-522
Patients with diffuse increased accumulation in both kidneys on 99mTc-MDP bone scintigram were evaluated quantitatively. Among 1,100 cases, 7 (0.63%) showed this finding. The accumulation density ratios of kidneys/lumbal vertebra in A/D exchanged images of these patients were compared with control group, so that these ratios of patient group were higher than control group statistically. In conclusion, the accumulation density ratio was made the index of diffuse increase accumulation in both kidneys on 99mTc-MDP bone scintigram. 相似文献
100.
Yasushi Joh Koichi Harada Heimei Yuki Shunsuke Murahashi 《Journal of polymer science. Part A, Polymer chemistry》1971,9(4):1089-1102
The polymerization of isobutyl vinyl ether by vanadium trichloride in n-heptane was studied. VCl3 ? LiCl was prepared by the reduction of VCl4 with stoichiometric amounts of BuLi. This type of catalyst induces stereospecific polymerization of isobutyl vinyl ether without the action of trialkyl aluminum to an isotactic polymer when a rise in temperature during the polymerization was depressed by cooling. It is suggested that the cause of the stereospecific polymerization might be due to the catalyst structure in which LiCl coexists with VCl3, namely, VCl3 ? LiCl or VCl2 ? 2LiCl as a solid solution in the crystalline lattice, since VCl3 prepared by thermal decomposition of VCl4 and a commercial VCl3 did not produce the crystalline polymer and soluble catalysts such as VCl4 in heptane and VCl3 ? LiCl in ether solution did not yield the stereospecific polymer. It was found that some additives, such as tetrahydrofuran or ethylene glycol diphenyl ether, to the catalyst increased the stereospecific polymerization activity of the catalysts. Influence of the polymerization conditions such as temperature, time, monomer and catalyst concentrations, and the kind of solvent on the formed polymer was also examined. 相似文献