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921.
Isao Hashida Masato Nishimura 《Journal of polymer science. Part A, Polymer chemistry》1972,10(7):1975-1986
m-Aminophenol was condensed with formaldehyde in an acid medium in the presence of a water-soluble inorganic salt (NaCl, CaCl2 etc) and/or poly(ethylene glycol). The pore structure characteristics of the condensation products were investigated by measurements of average pore size, pore size distribution of channels, total pore volume, surface area, and electron microscopic observation. The type and concentration of inorganic salts appeared to be a significant variable for the resulting pore structure, while poly(ethylene glycol) had a little effect. The nongel interstices of products were channels between many agglomerates of minute spherical gel particles with narrow pore size distribution. The diameters of these spherical gel particles were 3–10 × 10?1µ from the scanning electron microscopic observation. Apparent dissociation constants of functional groups of resin, pKa and pKb, estimated by using the Henderson-Hasselbach equation, were 10.94 and 10.99, respectively. The resin had an ion-exchange capacity of 1.0 meq/g for base and 4.8 meq/g for acid. 相似文献
922.
923.
924.
We theoretically investigate electron transport in a one-dimensional conductor with a locally disordered potential by using the non-equilibrium Green's function theory. It is found that, by changing the energy of a site in a one-dimensional atomic chain, the electron conductivity can be larger when the modulated site energy is smaller than that of the other sites. This contradicts the conventional picture that an electron is scattered by the disorder of the potential, because such a scattering process usually causes resistivity. We show that the enhancement of conductivity that seems contradictory to the conventional picture of electron motion is explained by the change of energy of quasi bound states in the conductor. 相似文献
925.
In this paper, we determine completely the initial Fitting ideal of the minus part of the ideal class group of an abelian
number field over Q up to the 2-component. This answers an open question of Mazur and Wiles (Invent Math 76:179–330, 1984) up to the 2-component,
and proves Conjecture 0.1 in Kurihara (J Reine Angew Math 561:39–86, 2003). We also study Brumer’s conjecture and prove a
stronger version for a CM-field, assuming certain conditions, in particular on the Galois group. 相似文献
926.
Kazunori Kadota Takenobu Yamamoto Atsuko Shimosaka Yoshiyuki Shirakawa Jusuke Hidaka Masato Kouzu 《Journal of nanoparticle research》2011,13(12):7209-7218
The mechanism on aggregation of spindle granular particles of calcite was investigated for the carbonation of calcium hydroxide
in aqueous suspension for the purpose of controlling morphology of CaCO3. The experimental carbonation process was carried out in a semi-batch bubble column reactor under different conditions. Although,
fine rhombic nano-particles diameter ranged from 100 to 200 nm were obtained at 291 K, a higher temperature of 300 K provided
spindle granular particles with a length of 1.0–1.5 μm and a width of 0.3–0.5 μm. The average crystallite size was 28 nm for
the fine rhombic nano-particles and 43 nm for the spindle granules. Zeta potential measurement for the spindle granules indicated
that the suspension tended to be aggregated during the carbonation process. The effect of the degree of particle aggregation
on the shape of the obtained calcite particles was studied by Monte Carlo simulations. Our simulation results elucidated the
dependence of aggregation on unit particles, i.e., primary particles, on the experiment carbonation condition where the spindle
granules were formed out of the unit particles under the same condition as the experiments. In addition, the formation mechanism
of the granules was investigated by applying classical nucleation theory to the present simulations. 相似文献
927.
Takehiko Uematsu Yoshiaki Matsui Shusuke Kakiuchi Akira Isogai 《Cellulose (London, England)》2011,18(4):1129-1138
Carboxymethyl cellulose (CMC)-rich cellulose sheets were prepared with a cationic retention aid, poly[N,N,N-trimethyl-N-(2-methacryloxyethyl)ammonium chloride] (PTMMAC), using a papermaking technique. When 5% PTMMAC and 5% CMC were added to
cellulose slurries, approximately 94% of the polymers were retained in the sheets by formation of polyion complexes between
the two polymers. When the PTMMAC/CMC/cellulose sheets were soaked in solutions consisting of ethanol, water and calcium chloride
(EtOH/H2O/CaCl2) with a weight ratio of 75:24:1, almost all PTMMAC and CMC molecules remained in the sheets, forming the structures of PTMMAC-N+Cl− and CMC-COO−Ca2+Cl− without dissolution of these molecules in the soaking solution. Thus, PTMMAC, CMC and calcium contents in the sheets were
able to be determined on the basis of these PTMMAC and CMC structures from analytical data such as nitrogen, calcium and chlorine
contents. The trade-off properties between sufficient wet strength in use and water-disintegrability after use can be added
to the PTMMAC/CMC/cellulose sheets by selecting weight ratios of the EtOH/H2O/CaCl2 solution used as the impregnation liquid. 相似文献
928.
Takuya?Isogai Tsuguyuki?Saito Akira?IsogaiEmail author 《Cellulose (London, England)》2011,18(2):421-431
A softwood bleached kraft pulp (SBKP) was subjected to electro-mediated oxidation in water with TEMPO or 4-acetamido-TEMPO
without any chlorine-containing oxidant. Solid recovery ratios of water-insoluble fractions of the oxidized SBKPs were more
than 80%, and C6-carboxylate contents increased up to approximately 1 mmol g−1 after oxidation for 48 h. Significant amounts of C6-aldehyde groups (0.17–0.38 mmol g−1) were also formed in the oxidized SBKPs. The degree of polymerization decreased from 2,200 to 520 and 1,400 by the oxidation
for 48 h with TEMPO at pH 10 and 4-acetamido-TEMPO at pH 6.8, respectively. The original cellulose I crystal structure and
crystallinity of SBKP were maintained after the oxidation, indicating that all C6-oxidized groups were selectively formed
on crystalline cellulose microfibril surfaces. The oxidized SBKPs with carboxylate contents of more than 0.9 mmol g−1 were convertible to individual cellulose nanofibrils in yields of more than 80% by disintegration in water. 相似文献
929.
Fujii S Masuno H Taoda Y Kano A Wongmayura A Nakabayashi M Ito N Shimizu M Kawachi E Hirano T Endo Y Tanatani A Kagechika H 《Journal of the American Chemical Society》2011,133(51):20933-20941
We report here the design and synthesis of a novel vitamin D receptor (VDR) agonist whose hydrophobic core structure is p-carborane (1,12-dicarba-closo-dodecaborane, an icosahedral carbon-containing boron cluster having remarkable thermal and chemical stability and a characteristically hydrophobic B-H surface). This carborane-based VDR ligand exhibited moderate vitamin D activity, comparable to that of the natural hormone, despite its simple and flexible structure. X-ray structure analysis provided direct evidence that the carborane cage binds to the hydrophobic surface of the ligand-binding pocket of the receptor, promoting transition to the active conformation. These results indicate that the spherical B-H surface of carborane can function efficiently as a hydrophobic anchor in binding to the receptor surface, thereby allowing induced fitting of the three essential hydroxyl groups on the alkyl chains to the appropriate positions for interaction with the VDR binding site, despite the entropic disadvantage of the flexible structure. We suggest that carborane structure is a promising option in the design of novel drug candidates. 相似文献
930.
Ito M Ootsuka T Watari R Shiibashi A Himizu A Ikariya T 《Journal of the American Chemical Society》2011,133(12):4240-4242
A novel catalytic method for the straightforward hydrogenation of carboxamides and esters to primary alcohols has been developed. Chiral modification in the ligand sphere of the well-defined Cp*Ru catalyst molecule opens up a new possibility for the development of an enantioselective hydrogenation of racemic substrates via dynamic kinetic resolution. 相似文献