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351.
352.
Michio Aoyama Daisuke Tsumune Yasunori Hamajima 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(1):535-539
Impact of the TEPCO Fukushima-Daiichi NPP accident, FNPP1, to the North Pacific Ocean occurred through two pathways, namely direct release and atmospheric deposition to wide ocean surface. We collected more than 100 seawater samples in the North Pacific Ocean in April and May 2011 by seven commercial ships as VOS. Since the sample volume was 2 l each, we measured radiocaesium activity at Ogoya Underground Facility to obtain reliable activity. 137Cs was detected at all stations and 134Cs was detected at most of the stations in the North Pacific Ocean. The 137Cs activity ranged from around 1 to 1,000 Bq m?3 with activity ratios of 134Cs/137Cs close to 1 which is a signature of radiocaesium originated from the FNPP1 accident. At east of the International Date Line north of 40°N in the Pacific Ocean in April 2011, the 134Cs activity ranged from 2 to 12 Bq m?3. 相似文献
353.
Dr. Mitsuaki Suzuki Dr. Naomi Mizorogi Tao Yang Prof. Dr. Filip Uhlik Prof. Dr. Zdenek Slanina Prof. Dr. Xiang Zhao Prof. Dr. Michio Yamada Prof. Dr. Yutaka Maeda Prof. Dr. Tadashi Hasegawa Prof. Dr. Shigeru Nagase Prof. Dr. Xing Lu Prof. Dr. Takeshi Akasaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(50):17125-17130
Although all the pure‐carbon fullerene isomers above C60 reported to date comply with the isolated pentagon rule (IPR), non‐IPR structures, which are expected to have different properties from those of IPR species, are obtainable either by exohedral modification or by endohedral atom doping. This report describes the isolation and characterization of a new endohedral metallofullerene (EMF), La2@C76, which has a non‐IPR fullerene cage. The X‐ray crystallographic result for the La2@C76/[NiII(OEP)] (OEP=octaethylporphyrin) cocrystal unambiguously elucidated the Cs(17 490)‐C76 cage structure, which contains two adjacent pentagon pairs. Surprisingly, multiple metal sites were distinguished from the X‐ray data, which implies dynamic behavior for the two La3+ cations inside the cage. This dynamic behavior was also corroborated by variable‐temperature 139 La NMR spectroscopy. This phenomenon conflicts with the widely accepted idea that the metal cations in non‐IPR EMFs invariably coordinate strongly with the negatively charged fused‐pentagon carbons, thereby providing new insights into modern coordination chemistry. Furthermore, our electrochemical and computational studies reveal that La2@Cs(17 490)‐C76 has a larger HOMO–LUMO gap than other dilanthanum‐EMFs with IPR cage structures, such as La2@D3h(5)‐C78 and La2@Ih(7)‐C80, which implies that IPR is no longer a strict rule for EMFs. 相似文献
354.
To elucidate the reaction mechanism of the disulfide (SS) bond formation reaction of a polypeptide molecule with a water‐soluble selenoxide reagent, trans‐3,4‐dihydroxyselenolane oxide (DHSox), short‐term oxidation experiments were carried out for the reduced state (R) of a recombinant hirudin CX‐397 variant at pH 7.0 and 25 °C. In the reaction, R was oxidized sequentially to one‐SS, two‐SS, and three‐SS intermediate ensembles within 1 min. The kinetic analysis revealed that the three second‐order rate constants for the SS formation are proportional to the number of thiol groups existing in the reactant SS intermediates, indicating the stochastic nature of the SS formation. Ab initio calculation at the HF/6‐31++G(d,p) level in water by using the polarizable continuum model suggested that the SS formation reaction is highly exothermic and proceeds via a reactive thioselenurane intermediate with a distorted linear O‐Se‐S linkage. The results clearly demonstrated that the rate‐determining step of the SS formation reaction is the first bimolecular process between a thiol substrate and DHSox rather than the subsequent process to release a SS product. 相似文献
355.
Hashinokuchi M Fukuyama T Okada M Kasai T 《Physical chemistry chemical physics : PCCP》2011,13(14):6584-6589
We report a study of kinetics and dynamics in physisorption of CH(3)Cl on a highly-oriented pyrolytic graphite (HOPG). Thermal energy atom scattering (TEAS) was used to probe the kinetics of thermal CH(3)Cl adsorption on HOPG during the coverage evolution. The desorption energy of CH(3)Cl on HOPG changes from 0.25 to 0.30 eV with increasing surface coverage, suggesting the attractive interaction between CH(3)Cl molecules on the surface. On the other hand, the oriented molecular beam scattering was used to monitor the dynamical interaction of CH(3)Cl with HOPG at zero coverage, demonstrating that the CH(3)Cl scattering intensity depends on the molecular orientation of the incident CH(3)Cl. The observed steric preference is not sensitive to the surface temperature. These results suggest that the moderate anisotropy in the interaction potential induces the molecular-orientation dependence of energy dissipation during the transient trapping into the physisorption well. 相似文献
356.
Kasai Y Matsumori N Ueno H Nonomura K Yano S Michio M Oishi T 《Organic & biomolecular chemistry》2011,9(5):1437-1442
Two well-known antifungals, amphotericin B (AmB) and amphodinol 3 (AM3), are thought to exert antifungal activity by forming ion-permeable channels or pores together with sterol molecules. However, detailed molecular recognitions for AmB-sterol and AM3-sterol in lipid bilayers have yet to be determined. Toward (19)F NMR-based investigation of the molecular recognition underlying their potent antifungal activity, we synthesized 6-fluoro-ergosterol in five steps via ring opening of (5α,6α)-epoxide of ergosterol acetate with using novel combination of TiF(4) and n-Bu(4)N(+)Ph(3)SiF(2)(-). Then we evaluated its activity of promoting pore formation of AmB and AM3, and found that pore formation of AmB was barely promoted by 6-F-ergosterol in clear contrast to the dramatic promotion effect of unmodified ergosterol, whereas AM3 activity was markedly enhanced in the presence of 6-F-ergosterol, which was comparable to that of unmodified ergosterol. These results indicate that the introduction of an F atom at C6 position of ergosterol plays an inhibitory role in interacting with AmB, but it is not the case with AM3. 相似文献
357.
Michio Kobayashi Shin-ichi Komiya Toshiaki Maruyama Yasuhiro Kasahara Toshihiko Hoshi 《Monatshefte für Chemie / Chemical Monthly》2011,70(1):997-1003
Abstract
The bisazo dye Ponceau SS forms an acute oblique (V-type) dimer in dilute aqueous solution. In concentrated aqueous solution, these V-type dimers are considered to stack to form V-type blocks of chromonic liquid-crystalline (LC) columns. The weak interactions among these LC columnar V-type blocks have been spectroscopically investigated. On increasing the concentration of Ponceau SS at 25 °C, the V-type LC columnar blocks form a rhombus-type LC columnar block at 2 wt% concentration. These rhombus-type LC columnar blocks are further aligned at an acute angle at 5 and 10 wt% concentrations. The rapidly cooled 10 wt% LC sample shows an unusually sharp J-band-like peak in the electronic absorption spectrum. The emergence of this J-band-like peak has been analyzed from the viewpoint of an exciton model, suggesting that many nearest neighbor unique molecules belonging to many different rhombus-type LC columnar blocks are aligned in a head-to-tail manner to give a giant quasi-linear head-to-tail-type exciton. 相似文献358.
Abstract Kinetic studies on the radiation-induced polymerization and postpolymerization of tetrafiuoroethyiene were carried out using chlorofluorohydrocarbons as the solvents. The mechanism of the radiochemical formation of radicals and the kinetics of the radical decay during in-source and postpolymerization are discussed. The remarkable post-polymerization is explained by the unusually slow rate of the bimolecular chain termination. The mechanism of chain transfer reactions is also discussed. 相似文献
359.
Hasegawa Miki Terauchi Mayumi Kikuchi Yuko Nakao Akiko Okubo Jun Yoshinaga Tetsutaro Hiratsuka Hiroshi Kobayashi Michio Hoshi Toshihiko 《Monatshefte für Chemie / Chemical Monthly》2003,134(6):811-821
Monatshefte für Chemie - Chemical Monthly - ?The electronic absorption and polarized absorption spectra were measured at various pH conditions for ellagic acid. Comparison of these... 相似文献
360.
Tamotsu Hashimoto Michio Urushisaki 《Journal of polymer science. Part A, Polymer chemistry》2007,45(21):4855-4866
The living cationic polymerization of 5‐ethyl‐2‐methyl‐5‐(vinyloxymethyl)‐1,3‐dioxane ( 1 ), a vinyl ether with a cyclic acetal unit, was investigated with various initiating systems in toluene or methylene chloride at 0 to ?30 °C. With initiating systems such as hydrogen chloride (HCl)/zinc chloride (ZnCl2), isobutyl vinyl ether–acetic acid adduct [CH3CH(OiBu)OCOCH3]/tin tetrabromide (SnBr4)/di‐tert‐butylpyridine (DTBP), and CH3CH(OiBu)OCOCH3/ethylaluminum sesquichloride (Et1.5AlCl1.5)/ethyl acetate (CH3COOEt), the number‐average molecular weights (Mn's) of the obtained poly( 1 )s increased in direct proportion to the monomer conversion and produced polymers with relatively narrow molecular weight distributions [MWDs; weight‐average molecular weight/number‐average molecular weight (Mw/Mn) = 1.2–1.3]. To investigate the living nature of the polymerization with CH3CH(OiBu)OCOCH3/SnBr4/DTBP, a second monomer feed was added to the almost polymerized reaction mixture. The added monomer was completely consumed, and the Mn values of the polymers showed a direct increase against the conversion of the added monomer, indicating the formation of a long‐lived propagating species. The glass transition temperature and thermal decomposition temperature of poly( 1 ) (e.g., Mn = 13,600, Mw/Mn = 1.30) were 29 and 308 °C, respectively. The cyclic acetal group in the pendants of the polymer of 1 could be converted to the corresponding two hydroxy groups in a 65% yield by an acid‐catalyzed hydrolysis reaction. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4855–4866, 2007 相似文献