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901.
The separation of rare earth metals has been studied with a micro-column of 0.5 mm i.d.×75 mm length, packed with TSK LS-212
high-performance cation exchange resin 16 rare earth metals were separated within 38 min, using only 304 μl of 0.4M α-hydroxyisobutyric
acid solution adjusted to pH 3.1–6.0 with ammonia solution as gradient carrier solution. The gradient elution was successfully
performed by applying a new technique developed for microscale liquid chromatography.
Studies on micro-high-performance liquid chromatography, VII. 相似文献
902.
N‐Substituted Dicyanomethylphenyl Radicals: Dynamic Covalent Properties and Formation of Stimuli‐Responsive Cyclophanes by Self‐Assembly
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Toshiyuki Kobashi Dr. Daisuke Sakamaki Prof. Dr. Shu Seki 《Angewandte Chemie (International ed. in English)》2016,55(30):8634-8638
Dynamic covalent bonds and their chemistry have been of particular interest both from a fundamental and materials science aspect. Demonstrated herein is that triphenylamine (TPA) and carbazole (Cz), substituted with a dicyanomethyl radical, are useful motifs for dynamic covalent chemistry as they have the appropriate bond strength between monomer units as well as high stability and synthetic simplicity. TPA and Cz units substituted by two dicyanomethyl radicals formed macrocyclic oligomers classified as novel types of azacyclophanes, and in particular, the TPA‐based diradical gave a cyclic dimer in almost quantitative yield. The cyclic oligomers exhibited thermo‐ and mechanochromic behavior resulting from the generation of radical species by intermonomer C?C bond cleavage. 相似文献
903.
Particles of poorly water-soluble drugs were prepared to develop a dry powder inhaler (DPI). Spray freeze-drying (SFD) technique using a four-fluid nozzle (4N), which has been developed by authors, was applied in this research. Ciclosporin and mannitol were used as a poorly water-soluble model drug and a dissolution-enhanced carrier, respectively. The organic solution of ciclosporin and aqueous solution of mannitol were separately and simultaneously atomized through the 4N, and the two solutions were collided with each other at the tip of the nozzle edge. The spray mists were immediately frozen in liquid nitrogen to form a suspension. Then, the iced droplets were freeze-dried to prepare the composite particles of the drug and carrier. tert-Butyl alcohol (t-BuOH) was used as the organic spray solvent due to its relatively high freezing point. The resultant composite particles with varying drug content were characterized depending on their morphological and physicochemical properties. The particles contained amorphous ciclosporin and δ-crystalline mannitol. The characteristic porous structure of SFD particles potentially contributed to their good aerodynamic performance. A series of particles with a similar size distribution and different drug content revealed that the incorporation of mannitol successfully improved the cohesive behavior of ciclosporin, leading to enhanced aerosol dispersion. The dissolution test method using low-volume medium was newly established to simulate the release process from particles deposited on the surface of the bronchus and pulmonary mucosa. The composite with hydrophilic mannitol dramatically improved the in vitro dissolution behavior of ciclosporin in combination with the porous structure of SFD particles. 相似文献
904.
Phase-transfer-catalyzed alkylation of glycinate Schiff base with racemic secondary alkyl halides proceeded with excellent levels of syn- and enantioselectivities under the influence of chiral quaternary ammonium bromide 1d and 18-crown-6. The alkylation product can be selectively converted to the corresponding anti isomer, allowing the preparation of all the stereoisomers of beta-alkyl-alpha-amino acid derivatives, an extremely valuable chiral building block. 相似文献
905.
Daisuke Tomida Satoshi KenmochiKun Qiao Quanxi BaoChiaki Yokoyama 《Fluid Phase Equilibria》2011,307(2):185-189
The viscosities of the mixtures 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF6]) + CO2 and 1-octyl-3-methylimidazolium hexafluorophosphate ([OMIM][PF6]) + CO2 were measured with a rolling ball viscometer. The CO2 mole fraction for one mixture ranged up to 0.434 and the other up to 0.447. The viscosities were measured at 293.15-353.15 K and 10-20.0 MPa. The experimental uncertainty in viscosity was estimated to be within ±3.0%. The experimental data were compared with McAllister's three-body model, which correlated with the experimental data within average absolute deviations of 5.9%. 相似文献
906.
The spin dynamics of 2-dimensional ferromagnetic monolayers of [MnSb/Sb] were studied by the
+SR method using pulsed sub-surface muons with a momentum of 18 – 25 MeV/c. A gradual growth of a static field along the
+ spin below 200 K and a divergent increase of the relaxation rate at around 25 K were observed in the 1 monolayer sample, related to the critical fluctuations in this magnetic superlattice. 相似文献
907.
We investigate hadronic molecule states of $K \bar K N$ and $\bar K \bar K N$ systems with I?=?1/2 and J P ?=?1/2?+?, assuming that Λ(1405) and the scalar mesons, f 0(980), a 0(980), are reproduced as quasi-bound states of $\bar KN$ and $K \bar K$ . Performing non-relativistic three-body calculations for these systems, we find weakly bound states for $K \bar K N$ and $\bar K \bar K N$ around 1900 MeV, which correspond to new baryon resonances of N * and Ξ * with J P ?=?1/2?+?. We find that these resonances have cluster structure of the two-body bound state keeping its properties as in the isolated two-particle system. 相似文献
908.
Gold nanoclusters protected by 3-mercaptopropionic acid (MPA-Au nanoclusters) were prepared by citrate-reduction of hydrogen
tetrachloroaurate(III) in the presence of sodium 3-mercaptopropionate. Color of the dispersions of MPA-Au nanoclusters changed
from red to purple by addition of hydrochloric acid and returned from purple to red by addition of an aqueous sodium hydroxide
solution. This reversible response can be attributed to synchronized changes between dispersion and ordering of MPA-Au nanoclusters,
determined by transmission electron microscopy. Gold nanoclusters protected by poly(acrylic acid) (PAA-Au nanoclusters) were
prepared by UV irradiation of an aqueous solution of hydrogen tetrachloroaurate(III) in the presence of poly(sodium acrylate).
The pH-dependent spectral change observed for MPA-Au was not observed for PAA-Au. UV-Vis absorption spectra of colloidal dispersions
of PAA-Au nanoclusters after addition of hydrochloric acid and an aqueous sodium hydroxide solution were in good agreement
with each other, suggesting the stability of PAA-Au nanoclusters to pH change.
Received 18 October 2000 and Received in final form 10 April 2002 相似文献
909.
Daisuke Sasaki Yasushi Okada Toshiki Hagiwara Takashi Sawaguchi 《Polymer Degradation and Stability》2007,92(2):271-279
It was found that telechelic isotactic oligo(1-butene) and telechelic oligo(propylene-ran-1-butene) could be isolated as nonvolatile oligomers from polymer residues resulting from the thermal degradation of isotactic poly(1-butene) and poly(propylene-ran-1-butene), respectively. Their structures were determined by 1H and 13C NMR with attention being paid to their reactive end groups. The maximum average number of terminal vinylidene groups per molecule (fTVD) was 1.8, indicating that about 80 mol% were α,ω-diene oligomers having two terminal vinylidene groups. This useful new telechelic oligomer had a lower polydispersity than the original polymer, in spite of its lower molecular weight and Tm. The composition of end groups of nonvolatile oligomers obtained by thermal degradation of poly(propylene-ran-1-butene) could be explained by the differences in bond dissociation energy and activation energy of elementary reactions during thermal degradation, based on the monomer composition of the original polymer. 相似文献
910.
A method is described for the determination of traces of gold in copper and cadmium by neutron activation analysis, using
anion exchange resin as a preconcentration agent: gold was separated from large amount of copper or cadmium with Cl-form Dowex
1X8 AG, 100–200 mesh, resin. To reduce the interfering activities, the resin was irradiated in NO
3
−
-form and washed with dilute hydrochloric acid after irradiation.198Au in the resin was then counted with a Ge(Li) or NaI(Tl) detector. The chemical yields were more than 99%. The concentration
factors of gold for copper and cadmium samples were 1.1×108 and 2.7×106, respectively. The analytical results of gold in 99.99% copper and 99.999% cadmium were 65 and 0.15 ppb, respectively. The
blank was 0.05 ng Au per 200 mg of wet resin. 相似文献