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排序方式: 共有3785条查询结果,搜索用时 15 毫秒
1.
Dr. Nozomi Mihara Dr. Yasuyuki Yamada Dr. Hikaru Takaya Prof. Yasutaka Kitagawa Dr. Kazunobu Igawa Prof. Katsuhiko Tomooka Prof. Hiroshi Fujii Prof. Kentaro Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(13):3369-3375
Development of supramolecular methods to further activate a highly reactive intermediate is a fascinating strategy to create novel potent catalysts for activation of inert chemicals. Herein, a supramolecular approach to enhance the oxidizing ability of a high-valent oxo species of a nitrido-bridged iron porphyrinoid dimer that is a known potent molecular catalyst for light alkane oxidation is reported. For this purpose, a nitrido-bridged dinuclear iron complex of porphyrin-phthalocyanine heterodimer 3 5+, which is connected through a fourfold rotaxane, was prepared. Heterodimer 3 5+ catalyzed ethane oxidation in the presence of H2O2 at a relatively low temperature. The site-selective complexation of 3 5+ with an additional anionic porphyrin (TPPS4−) through π–π stacking and electrostatic interactions afforded a stable 1:1 complex. It was demonstrated that the supramolecular post-synthetic modification of 3 5+ enhances its catalytic activity efficiently. Moreover, supramolecular conjugates achieved higher catalytic ethane oxidation activity than nitrido-bridged iron phthalocyanine dimer, which is the most potent iron-oxo-based molecular catalyst for light-alkane oxidation reported so far. Electrochemical measurements proved that the electronic perturbation from TPPS4− to 3 5+ enhanced the catalytic activity. 相似文献
2.
Homohelicity induction of a series of propylene-linked zinc bilinone (ZnBL; linear tetrapyrrople-zinc(II) complex) dimers upon complexation with chiral amine and α-amino esters was investigated. Introduction of substituents such as dimethyl and diisobutyl to the central carbon of the propylene spacer gave rise to stabilization of the homohelical (PP and MM) conformers rather than the heterohelical (PM) conformer. As bulkiness of the substituent increased, stability of the homohelical conformers was raised. The preorganization of the homohelical structures led to significantly amplified homohelicity induction upon complexation with chiral amine and α-amino esters. 相似文献
3.
Kosuke Morita Kouji Morimoto Daiya Kaji Yu Liang Zhao Atsushi Yoshida Toshimi Suda Akira Yoneda Tetsuya Ohnishi Hiromitsu Haba Eiji Ideguchi Hu Shan Xu Tao Zheng Hisaaki Kudo Keisuke Sueki Kenji Katori Isao Tanihata 《Acta Physica Hungarica A》2004,19(1-2):53-60
A gas-filled type of recoil separator for heavy element research was installed at an experimental hall of RIKEN Linear Accelerator facility to realize getting higher intensity of primary beam and long beam time. Performance of the separator was studied using target recoils and various nuclear reactions. The results show the high performance of the separator for heave element research. As an application of the GARIS, production and identification of an isotope of the 110th element 271[110] have been performed using the 208Pb(64Ni,1n)271[110] reaction. Three decay chains coincide well both in decay times and energies with the ones reported by the group of SHIP experiment at GSI, Germany. Our results provide a confirmation of the synthesis of an isotope 271[110] of element 110. 相似文献
4.
Ryoichi Kizu Naoki Otsuki Yoshiko Kishida Akira Toriba Atsushi Mizokami Kerry L Burnstein Carolyn M Klinge Kazuichi Hayakawai 《Analytical sciences》2004,20(1):55-59
We developed a new mammalian cell-based luciferase reporter gene assay for androgenic and antiandrogenic activities of chemicals and environmental samples. Environmental samples usually have a complex matrix that may contain the constituents acting as androgen receptor (AR) agonists, AR antagonists or aryl hydrocarbon receptor (AhR) agonists. AhR agonists are known to elicit the antiandrogenic effect through cross-talk between AR and AhR signal transduction pathways. In this study, PC3/AR human prostate carcinoma cells were transiently transfected with a prostate-specific antigen (PSA) promoter-driven luciferase expression plasmid. The cells were treated with a test compound or an environmental sample for 24 h at 37 degrees C and then measured for luciferase activity. The luciferase activity was induced by dihydrotestosterone (DHT) in a concentration-dependent manner in a concentration range from 10 fM to 1 nM. R1881, a synthetic androgen receptor agonist, induced luciferase activity and its inductive effects was additive to that of DHT. The luciferase activity was not induced by cortisol, a glucocorticoid, progesterone, a progestin, and 17beta-estradiol, an estrogen in a concentration range of up to 1 microM. DHT-induced luciferase activity was reduced by bicalutamide and cyproterone acetate, AR antagonists, and also by benzo[a]pyrene, an aryl hydrocarbon receptor agonist, through AhR-mediated pathways. All of these findings indicate that the present assay system correctly responds to AR agonists, AR antagonists and AhR agonist and, therefore, it is a powerful tool for the sensitive and selective screening of chemicals and environmental samples for their androgenic and antiandrogenic activities. We developed the first assay system, in which the expression of luciferase was driven by the promoter of a prostate-specific antigen gene, a typical human androgen-regulated gene. 相似文献
5.
Mineo Hashizume Hiroaki Inoue Kiyofumi Katagiri Atsushi Ikeda Jun-Ichi Kikuchi 《Journal of Sol-Gel Science and Technology》2004,31(1-3):99-102
Morphological characterization of the organic-inorganic vesicular nanohybrids, Cerasomes, was performed in aqueous media from two aspects. Firstly, a novel Cerasome-forming lipid having two triethoxysilyl groups in the head moiety was synthesized and the physical property of the Cerasome was investigated. While the morphological stability of the Cerasomes, as evaluated from the vesicular collapse behavior against a micelle-forming nonionic surfactant, Triton-X 100, was extremely higher than that of the conventional phospholipid liposome, the stabilities were comparable to each other for the Cerasomes derived from the dual- and single-head lipids. On the other hand, the surface property of the Cerasome formed with the dual-head lipid more closely resembled the colloidal silica particles rather than that derived from the single-head lipid, as suggested by zeta-potential measurements. Secondly, the effect of the media pH on the morphological stability of the Cerasome formed with the single-head lipid was evaluated and appeared as a time difference in obtaining the morphological stability of the Cerasome. These morphological characteristics of the Cerasomes could be mainly owing to the development of the siloxane network on the vesicular surface. 相似文献
6.
Yukinobu Mild Atsushi Onae Tomizo Kurosawa Eiichi Sakuma 《International Journal of Infrared and Millimeter Waves》1993,14(11):2345-2359
A system for measuring the absolute frequency of a far-infrared (FIR) laser is described. Josephson point contacts have been utilized in the system as a frequency harmonic mixer connecting microwaves and optically pumped CH3OH laser lines. The Josephson point contacts are capable of generating beat signals of 90 GHz microwaves and FIR waves of up to 4.25 THz. To measure the frequency of the beat signals from the Josephson junction with a frequency counter, tracking oscillators have been developed, which tracks the beat signals by phase locking and regenerate clean signals for frequency counting. It is shown that the absolute frequency can be measured to an accuracy of about 100 Hz by using the tracking oscillators. 相似文献
7.
It is shown that if in a simple graph G of order n the sum of degrees of any three pairwise non-adjacent vertices is at least n, then there are two cycles (or one cycle and an edge or a vertex) of GF that contain all the vertices. © 1995 John Wiley & Sons, Inc. 相似文献
8.
9.
Atsushi Yamagami 《Journal of Number Theory》2003,99(1):120-138
In this article, for a residual modular representation defined over an arbitrary finite field, Gouvêa's conjecture which says that the universal deformation ring is isomorphic to a certain Hecke algebra is proven in the unobstructed case. 相似文献
10.
Yutaka Miura Toshifumi Satoh Atsushi Narumi Osamu Nishizawa Yoshio Okamoto Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2006,44(4):1436-1446
The copper‐mediated atom transfer radical polymerization of methyl methacrylate (MMA) in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) was studied to simultaneously control the molecular weight and tacticity. The polymerization using tris[2‐(dimethylamino)ethyl]amine (Me6TREN) as a ligand was performed even at ?78°C with a number‐average molecular weight (Mn) of 13,400 and a polydispersity (weight‐average molecular weight/number‐average molecular weight) of 1.31, although the measured Mn's were much higher than the theoretical ones. The addition of copper(II) bromide (CuBr2) apparently affected the early stage of the polymerization; that is, the polymerization could proceed in a controlled manner under the condition of [MMA]0/[methyl α‐bromoisobutyrate]0/[CuBr]0/[CuBr2]0/[Me6TREN]0 = 200/1/1/0.2/1.2 at ?20°C with an MMA/HFIP ratio of 1/4 (v/v). For the field desorption mass spectrum of CuIBr/Me6TREN in HFIP, there were [Cu(Me6TREN)Br]+ and [Cu(Me6TREN)OCH(CF3)2]+, indicating that HFIP should coordinate to the CuI/Me6TREN complex. The syndiotacticity of the obtained poly(methyl methacrylate)s increased with the decreasing polymerization temperature; the racemo content was 84% for ?78°C, 77% for ?30°C, 75% for ?20°C, and 63% for 30°C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1436–1446, 2006 相似文献