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81.
Axially chiral benzamides and anilides were prepared by enantiotopic lithiation at the distinguished benzylic methyl of prochiral tricarbonylchromium complexes of N,N-diethyl 2,6-dimethylbenzamide (1) and N-methyl-N-acyl 2,6-dimethylaniline (14 and 21) with a chiral lithium amide base followed by electrophilic substitution in good yields with high optical purity. The resulting axially chiral chromium-complexed benzamides and anilides were oxidized under air to give chromium-free axially chiral benzamides and anilides in an enantiomerically active form without axial bond rotation at room temperature. 相似文献
82.
Prof. Nobutaka Fujieda Kyohei Umakoshi Yuta Ochi Dr. Yosuke Nishikawa Prof. Sachiko Yanagisawa Prof. Minoru Kubo Prof. Genji Kurisu Prof. Shinobu Itoh 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(32):13487-13492
The dinuclear copper enzyme, tyrosinase, activates O2 to form a (μ-η2:η2-peroxido)dicopper(II) species, which hydroxylates phenols to catechols. However, the exact mechanism of phenolase reaction in the catalytic site of tyrosinase is still under debate. We herein report the near atomic resolution X-ray crystal structures of the active tyrosinases with substrate l -tyrosine. At their catalytic sites, CuA moved toward l -tyrosine (CuA1 → CuA2), whose phenol oxygen directly coordinates to CuA2, involving the movement of CuB (CuB1 → CuB2). The crystal structures and spectroscopic analyses of the dioxygen-bound tyrosinases demonstrated that the peroxide ligand rotated, spontaneously weakening its O−O bond. Thus, the copper migration induced by the substrate-binding is accompanied by rearrangement of the bound peroxide species so as to provide one of the peroxide oxygen atoms with access to the phenol substrate's ϵ carbon atom. 相似文献
83.
84.
85.
Hosono E Fujihara S Honma I Zhou H 《Journal of the American Chemical Society》2005,127(39):13458-13459
We first fabricated the superhydrophobic film with a water contact angle of 178 degrees based on a perpendicular nanopin fractal structure by a bottom-up process. Until now, only materials with an original water contact angle larger than 90 degrees , which is classified as hydrophobicity, could be used to fabricate the superhydrophobic film (>170 degrees ) according to the possible fractal structure by a top-down process. Now, in this work, a water contact angle of about 178 degrees can be achieved using a lauric acid-coated film with an original contact angle of 75 degrees , which is classified as hydrophilicity, based on an ideal fractal structure for the superhydrophobic surface which is fabricated by the nanosize pin with 6.5 nm diameter. 相似文献
86.
We demonstrate 12-fs-pulse generation from a diode-pumped Kerr-lens mode-locked Cr:LiSAF laser. This is to our knowledge the shortest pulse ever produced from a mode-locked Cr:LiSAF laser. Based on an improved estimation of the intracavity dispersions, we utilized BK7 glass for the Brewster-prism-pair material. 相似文献
87.
88.
H. Ohyama E. Simoen C. Claeys K. Takakura H. Matsuoka T. Jono J. Uemura T. Kishikawa 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):533
Results are presented of a detailed study of the effects of high-temperature 4-MeV neutron irradiation on the performance degradation of Si pin photodiodes together with the radiation-induced defects, observed by deep level transient spectroscopy. The degradation of the device performance and the introduction rate of the lattice defects decrease with increasing sample temperature during irradiation. For a 250°C irradiation, the reduction of the reverse current is only 20% of the starting value. This result suggests that the creation and recovery of the radiation damage proceeds simultaneously at high temperatures. Carbon-related complex as hole capture levels is also mainly responsible for the device degradation for high-temperature neutron irradiation. 相似文献
89.
I. Mirebeau M. Hennion M.J.P. Gingras A. Keren K. Kojima M. Larkin G.M. Luke B. Nachumi W.D. Wu Y.J. Uemura I.A. Campbell G.D. Morris 《Hyperfine Interactions》1997,104(1-4):343-348
In the amorphous ( Fe1-x Mn_x)75 P16 B_6 Al_3 alloys, muon and neutron depolarization data, combined with the results of small angle neutron scattering, magnetization and Mössbauer spectroscopy, probe the existence of three distinct magnetic transitions at TC, TK and TF (TF < K < C). 相似文献
90.
R. F. Kiefl J. H. Brewer I. Affleck J. F. Carolan P. Dosanjh W. N. Hardy T. Hsu R. Kadono J. R. Kempton S. R. Kreitzman Q. Li A. H. O'Reilly T. M. Riseman P. Schleger P. C. E. Stamp H. Zhou L. P. Le G. M. Luke B. Sternlieb Y. J. Uemura H. R. Hart K. W. Lay 《Hyperfine Interactions》1991,63(1-4):139-144
We have searched for anomalous internal magnetic fields in highT
c materials which are predicted to occur in anyon and flux phase models of superconductivity. The magnitude, anisotropy and
temperature dependence of the observed fields inc-axis oriented samples of sintered YBa2CuO3O7 and of thick-film Bi2Sr2CaCu2O8 are consistent with a conventional nuclear dipolar origin. An upper limit of ≲0.08 mT is set for any anomalous magnetic fields
along thec-axis atμ
+ sites in bulk CuO2 superconductors. 相似文献