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51.
Vu Quoc Thang Toshiaki Taniike Masaki Umemori Mitsuhiro Ikeya Yuichi Hiraoka Nguyen Duc Nghia Minoru Terano 《大分子反应工程》2009,3(8):467-472
Preservation of initial polymer/catalyst particle morphology under air, was examined using stopped‐flow Ziegler–Natta polymerization with various quenching conditions and post‐chemical treatments. The exposure of the initial particles to air caused the fast formation of cracks on the surface, finally leading to significant reformation of the particle shape, when polymerizing particles were washed with heptane at ?65 °C under N2 or under CO2. On the other hand, when the particles were washed with heptane containing an appropriate amount of tetrahydrofuran under CO2, the particle morphology under air was almost completely maintained even after 1 h exposure. The present results are useful for various ex situ characterizations of unstable initial polymer/catalyst particles.
52.
Two-photon near-infrared excitation-responsive amino acid was developed. It was incorporated into a peptide, and focused near-infrared pulsed laser irradiation-induced peptide bond cleavage reaction at the C-terminal position of the photo-responsive amino acid was observed. 相似文献
53.
Though preparation procedures of heterogeneous Ziegler‐Natta catalysts for propylene polymerization are sophisticated, it is uncertain whether the nature of the active sites is similar or different for different preparation procedures. In this study, the effects of preparation procedures on the nature of the active sites were investigated by stopped‐flow polymerization in combination with microstructure analysis of polymers. Both basic and advanced types of catalysts showed the same two kinds of isospecific active site, which indicated little influence of the preparation method on the active site structure. On the contrary, the ratios of the two kinds of isospecific sites were not the same, resulting in variation of average polymer properties.
54.
Tomohito Kameda Yuki Fubasami Toshiaki Yoshioka 《Journal of Thermal Analysis and Calorimetry》2012,110(2):641-646
The thermal properties of SO4 2?-intercalated Mg?CAl layered double hydroxide (SO4·Mg?CAl LDH) were investigated using simultaneous thermogravimetry?Cmass spectrometry (TG?CMS), and the elimination behavior of sulfur oxides from this double hydroxide was examined. The TG?CMS results showed that SO4·Mg?CAl LDH decomposed in five stages. The first stage involved evaporation of surface-adsorbed water and interlayer water in SO4·Mg?CAl LDH. In the second, third, and fourth stages, dehydroxylation of the brucite-like octahedral layers in SO4·Mg?CAl LDH occurred. The fifth stage corresponded to the elimination of SO4 2? intercalated in the interlayer of Mg?CAl LDH, producing SO2 and SO3. The thermal decomposition of SO4·Mg?CAl LDH resulted in the formation of SO2 and SO3 at 900?C1000?°C, which then reacted with H2O to form H2SO3 and H2SO4. The elimination of sulfur oxides increased with the decomposition time and temperature. Almost all of the intercalated SO4 2? was desulfurized from SO4·Mg?CAl LDH at 1000?°C; however, Mg?CAl oxide was not formed due to the production of MgO and MgAl2O4. 相似文献
55.
Ye J. Kojima N. Furuya K. Munakata F. Okada A. 《Journal of Thermal Analysis and Calorimetry》2002,69(3):1031-1036
A micro-thermal analysis technique was applied to investigate advanced silicon nitride materials, which exhibit high thermal
conductivity. Local thermal properties in the microstructure were evaluated, and the grain boundaries were observed to have
lower thermal conductance than the Si3N4 grains. It was found that thermal conductance both in the grains and boundaries was lowered by the addition of the sintering
aid Al2O3, which is soluble in Si3N4 grains. This indicates that high thermal conductivity in silicon nitride ceramics is achieved both by grain growth, leading
to a reduction in boundary density, and by eliminating soluble elements in silicon nitride grains.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
56.
Katoh K Okabayashi T Tanimoto M Sumiyoshi Y Endo Y 《The Journal of chemical physics》2004,120(17):7927-7932
The rotational spectra of the CrF and CrCl radicals in the X 6Sigma+ state were observed by employing a Fourier transform microwave spectrometer. The CrF and CrCl radicals were generated by the reaction of laser-ablated Cr with F2 and Cl2, respectively, diluted in Ar. A chromium rod made of chromium powder pasted with epoxy resin was ablated by a Nd:YAG laser. Rotational transitions were measured in the region between 8 and 26 GHz. Several hyperfine constants due to the halogen nuclei were determined by a least-squares analysis. The electronic properties of CrF and CrCl were derived from their hyperfine constants and were compared with those of other 3d transition metal monohalides: TiF, MnF, FeF, CoF, NiF, and FeCl. 相似文献
57.
Dobashi T Nobe M Yoshihara H Yamamoto T Konno A 《Langmuir : the ACS journal of surfaces and colloids》2004,20(16):6530-6534
Curdlan dissolved in aqueous sodium hydroxide was dialyzed to aqueous calcium chloride to form a gel. Transparent and turbid concentric layers observed in the gel cross section perpendicular to the long axis of the dialysis tube were identified as liquid crystalline gels with refractive index gradient and amorphous gels, respectively. The thickness of each layer was proportional to the diameter of the dialysis tube, and the gelation proceeded in proportion to the root of time. The unique pattern formation was attributed to the change of curdlan conformation and calcium-induced cross-linking resulting from a diffusion of calcium cations and hydroxide anions through the dialysis tube. It is suggested that the orderedness of the curdlan molecules decreases by the increase of the curvature of the concentric liquid crystal layers as the layer comes toward the center of the dialysis tube. 相似文献
58.
[reaction: see text] Chiral C(4)-substituted (E)- or (Z)-1-alkynyl-1-trimethylsilyloxy-2-butene systems provide anti-(Z) or syn-(Z) conjugated dienyne, with a very high level of stereocontrol, on treatment with BF(3).OEt(2) in CH(2)Cl(2) at -50 degrees C in the presence of allyltrimethylsilane. The Cieplak conformation for (E)-substrates and neighboring-group participation for (Z)-substrates are considered to be responsible for the stereochemical consequences. 相似文献
59.
A chiral water-soluble zinc porphyrin was optically resolved on a chiral HPLC column, and the binding of chiral amino acids and peptides to each of the enantiomers was examined spectrophotometrically in basic aqueous solution. The binding data apparently indicated that the zinc porphyrin has chiral selectivity for amino acids and dipeptides. This was reasonably explained in terms of the triple cooperation of coordination, Coulomb, and steric interactions of the chiral amino carboxylates with the porphyrin. A compensatory relationship among the thermodynamic parameters for chiral recognition was also shown. 相似文献
60.
Two new cytotoxic compounds, nakiterpiosin (1) and nakiterpiosinone (2), were isolated from the Okinawan sponge Terpios hoshinota. Their structures were determined by spectroscopic analysis. The absolute stereostructure of 1 was also determined by a modified Mosher's method. Nakiterpiosin (1) and nakiterpiosinone (2) showed potent cytotoxicity against mouse lymphocytic leukemia cell (P388). 相似文献