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121.
Toshiaki Taniike Binh Tien Nguyen Shougo Takahashi Thang Quoc Vu Mitsuhiro Ikeya Minoru Terano 《Journal of polymer science. Part A, Polymer chemistry》2011,49(18):4005-4012
We have kinetically elucidated the origins of activity enhancement because of the addition of comonomer in Ziegler‐Natta propylene polymerization, using stopped‐flow and continuously purged polymerization. Stopped‐flow polymerization (with the polymerization time of 0.1–0.2 s) enabled us to neglect contributions of physical phenomena to the activity, such as catalyst fragmentation and reagent diffusion through produced polymer. The propagation rate constant kp and active‐site concentration [C*] were compared between homopolymerization and copolymerization in the absence of physical effects. kp for propylene was increased by 30% because of the addition of a small amount of ethylene, whereas [C*] was constant. On the contrary, both kp (for propylene) and [C*] remained unchanged by the addition of 1‐hexene. Thus, only ethylene could chemically activate propylene polymerization. However, continuously purged polymerization for 30 s resulted in much more significant activation by the addition of comonomer, clearly indicating that the activation phenomenon mainly arises from the physical effects. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
122.
Yasuyuki Endo Kiminori Ohta Tomohiro Yoshimi Kentaro Yamaguchi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4-5):799-802
The inorganic cage compounds, dicarba-closo-dodecaboranes (carboranes), are chemical building blocks of remarkable thermal and chemical stability, with spherical geometry and exceptional hydrophobic character. We have focused on medicinal drug design using carboranes as a hydrophobic pharmacophore and have developed a potent estrogen agonist, BE120. We also have applied carboranes for structural chemistry, utilizing their specific three-dimensional character to obtain multilayer aromatic structures. 相似文献
123.
Yukari Tajika Yumi Yasuoka Hiroyuki Nagahama Toshiyuki Suzuki Yoshimi Homma Tetsuo Ishikawa Shinji Tokonami Takahiro Mukai Miroslaw Janik Atsuyuki Sorimachi Masahiro Hosoda 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(3):1709-1714
Gas-flow ionization chambers for radioisotope (RI) monitoring systems at RI institutes throughout Japan are commonly used to measure RIs which leak from the RI institutes. Before the Japan’s 2011 Tohoku earthquake [11 March 2011, moment magnitude (M w) 9.0], ionization current data measured with a gas-flow ionization chamber at the RI institute of Fukushima Medical University were found to change. The question we must raise is whether the variation ionization current can be considered to the variation of outdoor radon concentration. The conversion factors (from ionization current to radon concentration in air) of the gas-flow ionization chamber can be obtained by measuring four levels of radon concentration (outdoor air, indoor air, high level and radon-free gas) with an AlphaGUARD monitor and the chamber itself. The two gas-flow ionization chambers consist of the air intake and terminal exhaust duct of the RI institute. It was found that the radon concentration in the exhaust air was the same as that in the air intake. This study provided evidence that variations of outdoor radon concentration could be determined using gas-flow ionization chambers for RI monitoring systems. 相似文献
124.
Hajime Maeda Satoshi Nashihara Hirofumi Mukae Yasuharu Yoshimi Kazuhiko Mizuno 《Research on Chemical Intermediates》2013,39(1):301-310
Ultraviolet (UV) irradiation of 2-[(2,4,6-trimethylphenoxy)methyl]-1-(methoxycarbonyl)naphthalene promotes a photochemical reaction that gives a cyclohexa-2,4-dienone product arising from a photo-Claisen-type ortho-rearrangement and a phenol derivative arising from a meta-rearrangement, along with 1-methoxycarbonyl-2-methylnaphthalene and 1,2-bis[1-(methoxycarbonyl)naphthalen-2-yl]ethane. When this process is carried out in a microreactor/flow system, its efficiency is dramatically enhanced and selectivity of products is improved. The effects on efficiency and product selectivity caused by the microreactor/flow system are attributed to more efficient light absorption and the suppression of secondary reactions. 相似文献
125.
A simple method has been developed for the efficient synthesis of naphtho[b]furans from allyl bromonaphthyl ethers. The approach utilizes a novel photochemical process involving sequential radical cyclization and dehydrohalogenation. Because light is a readily available, environmentally friendly reagent that produces no by-products, the new process serves as a green synthetic method. 相似文献
126.
Analytical methods for arsine, silane and dichlorosilane by adsorption sampling and elemental analysis with graphite furnace AA were studied to establish convenient methods for atmospheric contamination surveys. This study included the following five items: (1) primary selection of adsorbents applicable to adsorption sampling; (2) examination of the adsorption capacities of the adsorbents for the gases; (3) improvement of the adsorbents by chemical modification; (4) desorption of the gases adsorbed on the adsorbents with solvents; and (5) quantitative analysis of arsenic and silicon in the solutions. Experimental results showed that active carbon made from synthetic thermosetting resin beads contained no aresenic and little silicon as impurities. This active carbon by itself was proved to adsorb arsine and dichlorosilane, but not silane. Impregnation with sodium hydroxide of the active carbon improved the adsorption capacity for all three gases. Refined silica gel, free from arsenic contamination, did not adsorb arsine by itself but potassium permanganate impregnation produced an adsorption capacity for arsine. The adsorbed arsine on the active carbon was desorbed into a hot dilute nitric acid solution with high efficiency (over 90%), but arsine adsorbed on sodium hydroxide impregnated active carbon or on potassium permanganate impregnated silica gel was dissolved into various solutions only at lower efficiencies. Silane adsorbed on sodium hydroxide-impregnated active carbon was desorbed with hot water with an efficiency higher than 90%. Dichlorosilane adsorbed on the active carbon with or without sodium hydroxide impregnation was desorbed with a nitric acid solution with efficiency of 85%. The lower determination limit for arsine able to discriminate from background interference of arsenie was 0.005 ppm, and those for silane and dichlorosilane were each 0.05 ppm for 3-dm3 air samples. 相似文献
127.
Y. Kobayashi H. Nonaka J. Miyazaki M. K. Kubo H. Ueno A. Yoshimi H. Miyoshi D. Kameda K. Shimada D. Nagae K. Asahi Y. Yamada 《Hyperfine Interactions》2005,166(1-4):357-361
The in-beam Mössbauer spectroscopy using a short-lived 57Mn (T 1/2=1.5 min) beam was carried out to study the production of the exotic chemical species of 57Fe atoms arising from 57Mn implanted into solid oxygen. The obtained spectra can be analyzed by four components of doublets at least, which are assigned to be novel Fe species of FeO, Fe(O2), (O2)FeO2, and Fe(O2)2, on the basis of ab initio molecular orbital calculations. 相似文献
128.
A light-weight portable electron spin resonance (ESR) spectrometer with the permanent magnet of Nd-B-Fe (Neomax) and field sweep coils was used as a demonstration tool of ESR microscopy for student’s experiments. Educational experiments on one-and two-dimensional ESR imaging are made by inserting field gradient coils or field scanning wire arrays into the cavity using test samples of DPPH. A preliminary work on double frequency modulation is described for two-dimensional imaging using microwire arrays. 相似文献
129.
130.
Tanaka T Nakatsuru R Kagari Y Saito N Okubo M 《Langmuir : the ACS journal of surfaces and colloids》2008,24(21):12267-12271
The effect of molecular weight on the morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA) composite particles was investigated. PS/PMMA composite particles with different molecular weights (M*=MwPS+MwPMMA)/2 approximately 2x10(4)-1x10(6) g.mol(-1)) were prepared by the release of toluene (T) from PS/PMMA/T (1/1/24, w/w/w) droplets dispersed in an aqueous solution of polyoxyethylene nonylphenyl ether nonionic surfactant (Emulgen 911). As T evaporated, the spherical droplets phase separated, resulting in snowmanlike composite particles with Janus morphology. The nonspherical shape was closely related to the morphology, which depended on M*. The interfacial tension between the phase-separated PS and PMMA phases increased with an increase in M*, and this would allow the formation of the snowmanlike shape to decrease the interfacial area between the PS and the PMMA phases. 相似文献