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91.
Yuzo Yamazawa Tadashi Iwai Akihiko Ito Koichiro Hayashi 《Journal of polymer science. Part A, Polymer chemistry》1971,9(2):257-263
The in-source polymerization of trioxane in the solid state was investigated over a wide range of temperature and pressure, i.e., from 30 to 140°C and up to 7000 kg/cm2, respectively. In the polymerization that was carried out slightly below the melting point under pressure, the higher the pressure, the higher the rate of polymerization. It was confirmed that the maximum rate of solid-state polymerization of trioxane occurs near the melting points, even under elevated pressure. The rate of polymerization decreased with increasing pressure at constant temperature. The shape of the time–conversion curves may be classified into two types, i.e., one which is typical of high pressure and low temperature, and the other which is typical of low pressure and high temperature. Changes in the shape of the conversion—intrinsic viscosity curves occurred coincidentally. Thus, three regions for the different “polymerization characteristic” were determined as functions of polymerization temperature and pressure. Explanations are given for the above-mentioned polymerization characteristic. 相似文献
92.
Shimizu K Suzuki H Hayashi E Kodama T Tsuchiya Y Hagiwara H Kitayama Y 《Chemical communications (Cambridge, England)》2002,(10):1068-1069
Direct 1,4-conjugate addition of naked aldehydes to vinylketones is catalysed effectively by N-methyl-3-aminopropylated FSM-16 mesoporous silica, which can be regarded as a novel heterogeneous catalysis for a practical C-C bond formation reaction. 相似文献
93.
Comparative characterization study of microporous carbons by HRTEM image analysis and gas adsorption 总被引:1,自引:0,他引:1
Lozano-Castello D Cazorla-Amoros D Linares-Solano A Oshida K Miyazaki T Kim YJ Hayashi T Endo M 《The journal of physical chemistry. B》2005,109(31):15032-15036
The present work presents a useful comparison of micropore size distributions (MPSDs) obtained from gas adsorption and image analysis of high-resolution transmission electron micrographs. It is shown that the MPSD obtained for a chemical activated carbon is concordant with that obtained from CO2 adsorption. In addition, this technique has allowed us to obtain the MPSD of a carbon molecular sieve (CMS) prepared in our laboratory by a copyrolysis process, which could only be characterized by CO2 adsorption at 273 K (not by N2 adsorption at 77 K due to diffusional problems). The MPSD obtained by high-resolution transmission electron microscopy (HRTEM) for the CMS is wider than that obtained by CO2 adsorption, suggesting that HRTEM is detecting the closed porosity existing in this sample, which is not accessible to gas adsorption. The existence of closed porosity in the CMS is explained considering the preparation method used. Thus, HRTEM combined with image analysis seems to be useful for structural analysis of narrow micropores including closed porosity. 相似文献
94.
Talukder MM Takeyama T Hayashi Y Wu JC Kawanishi T Shimizu N Ogino C 《Applied biochemistry and biotechnology》2003,110(2):101-112
The activity and stability of Chromobacterium viscosum lipase (glycerolester hydrolase, EC 3.1.1.3)-catalyzed olive oil hydrolysis in sodium bis (2-ethyl-1-hexyl)sulfosuccinate (AOT)/isooctane reverse micelles is increased appreciably when low molecular weight polyethylene
glycol (PEG 400) is added to the reverse micelles. To understand the effect of PEG 400 on the phase behavior of the reverse
micellar system, the phase diagram of AOT/PEG 400/water/isooctane system was studied. The influences of relevant parameters
on the catalytic activity in AOT/PEG 400 reverse micelles were investigated and compared with the results in the simple AOT
reverse micelles. In the presence of PEG 400, the linear decreasing trend of the lipase activity with AOT concentration, which
is observed in the simple AOT reverse micelles, disappeared. Enzyme entrapped in AOT/PEG reverse micelles was very stable,
retaining>75% of its initial activity after 60 d, whereas the half-life in simple AOT reverse micelles was 38 d. The kinetics
parameter maximum velocity (V
max)exhibiting the temperature dependence and the activation energy obtained by Arrhenius plot was suppressed significantly by
the addition of PEG 400. 相似文献
95.
The relative standard deviation (RSD) of measurements in high-performance liquid chromatography with electrochemical detection (HPLC-ECD) was predicted by a chemometric tool based on the 1/f fluctuation model which is made up of white noise and a Markov process, called the Function of Mutual Information (FUMI) theory. FUMI theory can provide aprecise and reliable detection limit from a single measurement of noise and signal in HPLC-ECD. To obtain RSD (n = 5) for determination of (-)-epicatechin at five concentrations required 12.5 h, while the predicted RSD by FUMI theory required only 0.5 h (one measurement). Moreover, to trace the source of instrumental noise, power spectra of chromatographic baseline were used. Selection of a suitable apparatus in HPLC-ECD system, acquisition of RSD, and detection limits for determination of catechins by HPLC-ECD were simply and easily made by this chemometric tool within a very short time. The use of the FUMI theory for the prediction of measuring precision was more efficient and the optimization was less time-consuming to be suited for determination. 相似文献
96.
In order to obtain a highly concentrated, pure and super-hot [gamma-32P]ATP, we improved the purification method of super-hot [gamma-32P]ATP which was synthesized by the method of Johnson and Walseth (1979). The super-hot [gamma-32P]ATP was synthesized in a relatively large volume (2 ml) of reaction mixture and purified using semi-micro scale anion exchange chromatography (Dowex 1 X 2, 60-70 microliters column volume). In combination with washing the reaction product with certain organic solvents, this chromatography technique makes it possible to obtain a highly concentrated and pure super-hot [gamma-32P]ATP (approx. 7,000 Ci/mmol; 20-30 mCi/ml) from [32P]Pi of any commercial source in a good yield. 相似文献
97.
Optimization of HPLC-ECD conditions for determination of catechins with precision and efficiency based on the FUMI theory. 总被引:1,自引:0,他引:1
A chemometric tool based on the Function of Mutual Information (FUMI) theory can provide a relative standard deviation (RSD) without repetitive measurements in high-performance liquid chromatography with electrochemical detection (HPLC-ECD). Two parameters: precision (= information content) phi and efficiency (= information content/time) theta, which were calculated from predicted RSD based on the FUMI theory, were used to optimize HPLC-ECD conditions, such as applied potential, flow rate, column length, and size of ODS porous packing. We selected catechins as analytes, and found that the most optimum applied potential and flow rate were +600 mV vs. SCE and 0.9 mL/min, respectively, because they gave the largest phi and theta values. Buffer concentration in mobile phase is less effective for giving large phi and theta values. Since the FUMI theory makes it possible to predict RSD without repetitive measurements, the present method saves considerable amounts of chemicals and experimental time, and was found to be useful for the optimization of experimental conditions for determination by HPLC-ECD. 相似文献
98.
Kanae Hayashi Noritaka Kotani 《Journal of polymer science. Part A, Polymer chemistry》1980,18(1):191-202
Bulk polymerization of α-methylstyrene was carried out in a wide dose rate range, 7.6–256 rad/sec by γ rays and 8.5 × 103–2.1 × 105 rad/sec by electron beams. At high dose rate by electron beams, cationic polymerization took place along with formation of oligomeric product of DP n = ~4. At low dose rate by γ rays, radical polymerization was found to occur in water-saturated monomer. The cationic polymerization at high dose rate proceeds with essentially the same mechanism as was already known in γ-ray polymerization of dry monomers. Relatively low reaction rate of the cationic polymerization compared with that of styrene is explained with the fact that the propagation of α-methylstyrene is much more easily inhibited by a slight amount of water. 相似文献
99.
Moriya Y Hasegawa T Hayashi K Maruyama M Nakata S Ogawa N 《Analytical and bioanalytical chemistry》2003,376(3):374-378
Visible reflection spectra of diprotonated meso-tetraphenylporphyrin adsorbates spontaneously formed at a dodecane-aqueous sulfuric acid interface have been measured using a home-made device comprising a prism-cell and variable-angle optics. The tilt angle of the pyrrole ring plane was estimated to be 47 degrees from the interface normal by use of an experimentally evaluated molecular density (1.20x10(-10) mol cm(-2)) of the diprotonated molecule in a monolayer form at the liquid-liquid interface. Positive and negative bands have been observed in the p-polarized partial internal reflection (p-PIR) spectra, whose band locations correspond to those in p-polarized external reflection (p-ER) spectra. Nevertheless, the bands in the p-PIR exhibited reversed sign to those of p-ER spectra. These suggest that the surface selection rule of the p-PIR spectrometry has a reversal rule of p-ER and p-PIR can also be used for the analysis of molecular orientation. 相似文献
100.
Chemiluminescence from HgBr(B) formed in the reaction of Hg(63Po with Br2 has been observed using a N2-seeded nozzle beam of metastable Hg3Po) atoms. The cross section has been estimated to be 3+3?2 at a collission energy of 0.33 eV. This value is smaller by more than an order of magnitude than the corresponding value for Hg(3P2) atoms measured by Krause et al., in accordance with their inference based on less direct evidence. 相似文献