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71.
T. Kambara R. Schuch Y. Awaya T. Mizogawa H. Kumagai Y. Kanai H. Shibata K. Shima 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1992,22(2):451-456
We have measured the target thickness dependence ofK-vacancy production probabilities and total cross sections for 40.6 MeV Ar ions hitting Ca and Cu targets. The probabilities were measured as a function of the scattering angle between 0.13° and 1.4° by means of aK x-ray-particle coincidence. By integrating the measured probabilities over the impact parameter a significantly lower total cross section was obtained than the directly measured value. The maximum seen in the impact parameter dependent probability varies with decreasing target thickness towards the results obtained with molecular and atomic gas targets. From these observations a multiple collisionL-vacancy process prior to 2pπ-2pσ rational coupling is concluded. 相似文献
72.
Abstract Goldfish cells (RBCF-1) cultured at different cell densities were harvested and their photorepair (PR) abilities were examined in terms of survival. Photorepair ability gradually increased during the phase of logarithmic growth, reaching a maximum in cells at the confluent state. This enhancement of PR ability disappeared 12 h after replating of cells in fresh medium. A number of growth-inhibiting treatments (serum depletion, UVC, hydroxyurea [HU], change in incubation temperature) were tested for their ability to induce PR. The treatment of cells with HU and serum depletion induced PR while the other treatments did not. The increase in the ability to perform PR after treatment with HU or serum depletion returned to normal levels more rapidly than that after fluorescent light treatment. 相似文献
73.
Masahide Yasuda Yoshimasa Nishinaka Takumi Nakazono Takeshi Hamasaki Nobuya Nakamura Tsutomu Shiragami Chyongjin Pac Kensuke Shima 《Photochemistry and photobiology》1998,67(2):192-197
It was found that tetra-o-acyl riboflavins efficiently photosensitize the monomerization of the cis, syn-cyclobutane dimers of 1,3-dimethylthymine and 1,3-dimethyluracil in aqueous solution in the presence of such anionic surfactants as sodium dodecyl sulfate and sodium hexadecyl sulfate at concentrations higher than their critical micelle concentration, while little monomerization of the dimers was photosensitized by the flavins in the absence of the surfactants and even in the presence of cationic and nonionic surfactants. 相似文献
74.
Masaaki Yoshifuji Ichiro Shima Katsuhiro Shibayama Naoki Inamoto 《Tetrahedron letters》1984,25(4):411-414
Bis(2,4,6-tri--butylphenyl) diphosphene reacts with various halogens to give the corresponding phosphoric dihalides, haloarene, and arene depending upon the halogen and solvent used. 相似文献
75.
Arash Ghorbani-Choghamarani Hamid Goudarziafshar Somaieh Rezaee Saiedeh Shima Mortazavi 《中国化学快报》2009,20(4):415-419
A wide variety of secondary amines are chemoselectively subjected to N-nitrosation reaction with treatment of citric acid and NaNO2 in the presence of wet SiO2(50%,w/w)in dichloromethane at room temperatture under heterogeneous conditions.The N-nitrosation method is very simle and products can be easily isolated with good to high yields. 相似文献
76.
Mayr S Latkoczy C Krüger M Günther D Shima S Thauer RK Widdel F Jaun B 《Journal of the American Chemical Society》2008,130(32):10758-10767
Microbial mats collected at cold methane seeps in the Black Sea carry out anaerobic oxidation of methane (AOM) to carbon dioxide using sulfate as the electron acceptor. These mats, which predominantly consist of sulfate-reducing bacteria and archaea of the ANME-1 and ANME-2 type, contain large amounts of proteins very similar to methyl-coenzyme M reductase from methanogenic archaea. Mass spectrometry of mat samples revealed the presence of two nickel-containing cofactors in comparable amounts, one with the same mass as coenzyme F430 from methanogens (m/z = 905) and one with a mass that is 46 Da higher (m/z = 951). The two cofactors were isolated and purified, and their constitution and absolute configuration were determined. The cofactor with m/z = 905 was proven to be identical to coenzyme F430 from methanogens. For the m/z = 951 species, high resolution ICP-MS pointed to F430 + CH2S as the molecular formula, and LA-ICP-SF MS finally confirmed the presence of one sulfur atom per nickel. Esterification gave two stereoisomeric pentamethyl esters with m/z = 1021, which could be purified by reverse phase HPLC and were subjected to comprehensive NMR analysis, allowing determination of their constitution and configuration as (17(2)S)-17(2)-methylthio-F430 pentamethyl ester and (17(2)R)-17(2)-methylthio-F430 pentamethyl ester. The corresponding diastereoisomeric pentaacids could also be separated by HPLC and were correlated to the esters via mild hydrolysis of the latter. Equilibration of the pentaacids under acid catalysis showed that the (17(2)S) isomer is the naturally occurring albeit thermodynamically less stable one. The more stable (17(2)R) isomer (80% at equilibrium) is an isolation artifact generated under the acidic conditions necessary for the isolation of the cofactors from the calcium carbonate-encrusted mats. 相似文献
77.
Inokuchi T Takiuchi H Moriwaki Y Ka T Takahashi S Tsutsumi Z Shima H Hirota S Yamamoto T 《Magnetic resonance imaging》2006,24(10):1389-1393
A 35-year-old woman was referred to our institution for additional examinations to evaluate bilateral suprarenal masses incidentally found on abdominal ultrasonographic images obtained during an annual medical health checkup. Our computed tomographic scans showed bilateral and well-circumscribed low-density suprarenal masses, while MRI revealed the tumors to be heterogeneous with low intensity on T1-weighted images and high intensity on T2-weighted images. A laparoscopic adrenalectomy was performed under the suspicion of a malignant tumor, such as a malignant fibrous histiocytoma. Pathologic findings indicated a retroperitoneal ancient schwannoma of two histologic types: Antoni A and Antoni B. We considered that elucidation of the characteristic features of a schwannoma would provide helpful preoperative information for diagnosis. 相似文献
78.
Lyon EJ Shima S Boecher R Thauer RK Grevels FW Bill E Roseboom W Albracht SP 《Journal of the American Chemical Society》2004,126(43):14239-14248
The iron-sulfur-cluster-free hydrogenase Hmd (H(2)-forming methylenetetrahydromethanopterin dehydrogenase) from methanogenic archaea has recently been found to contain one iron associated tightly with an extractable cofactor of yet unknown structure. We report here that Hmd contains intrinsic CO bound to the Fe. Chemical analysis of Hmd revealed the presence of 2.4 +/- 0.2 mol of CO/mol of iron. Fourier transform infrared spectra of the native enzyme showed two bands of almost equal intensity at 2011 and 1944 cm(-)(1), interpreted as the stretching frequencies of two CO molecules bound to the same iron in an angle of 90 degrees . We also report on the effect of extrinsic (12)CO, (13)CO, (12)CN(-), and (13)CN(-) on the IR spectrum of Hmd. 相似文献
79.
Wang L Shima T Hampel F Gladysz JA 《Chemical communications (Cambridge, England)》2006,(39):4075-4077
trans-Rh(CO)(Cl)(P((CH(2))(14))(3)P) is prepared from trans-Rh(CO)(Cl)(P((CH(2))(6)CH[double bond, length as m-dash]CH(2))(3))(2) by a metathesis/hydrogenation sequence, and converted by substitution or addition reactions to Rh(CO)(I), Rh(CO)(2)(I), Rh(CO)(NCS), and Rh(CO)(Cl)(Br)(CCl(3)) species; the Rh(CO)(Cl) and Rh(CO)(I) moieties rapidly rotate within the cage-like diphosphine, but the other rhodium moieties do not. 相似文献
80.
The reaction of the tetranuclear rare earth metal polyhydrido complexes {Cp'Ln(mu-H)2}4(THF) (Cp' = C5Me4SiMe3, Ln = Y (1a), Lu (1b)) with carbon monoxide (1 atm) yielded ethylene and the corresponding tetraoxo cubane complexes (Cp'Ln)4(mu3-O)4 (Ln = Y (5a), Lu (5b)). Stepwise formation of some key reaction intermediates, such as oxymethylene complexes (Cp'Ln)4(mu-OCH2)(mu-H)6(THF) (Ln = Y (2a), Lu (2b)), enolate species (Cp'Y)4(OCH=CH2)(mu-O)(mu-H)5(THF) (3), and dioxo complex (Cp'Y)4(mu3-O)2(mu-H)4(THF) (4), was confirmed. The molecular structures of 2a, 4, and 5b were determined by X-ray diffraction studies. 相似文献