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排序方式: 共有197条查询结果,搜索用时 62 毫秒
61.
Ken Sakakibara 《Tetrahedron letters》2005,46(6):959-962
Addition of a phosphenium dramatically improved the reaction yields in the carboxylation of arenes by formic acid catalyzed by Pd(II). Control experiments revealed that the majority of the phosphenium triflate was converted to a mixed anhydride of phosphonic acid and formic acid (7), which however did not substitute for the phosphenium to improve the reaction yield. 相似文献
62.
63.
Nagayama Y Kawahata K Inagaki S Peterson BJ Sakakibara S Tanaka K Tokuzawa T Watanabe KY Ashikawa N Chikaraishi H Emoto M Funaba H Goto M Hamada Y Ichiguchi K Ida K Idei H Ido T Ikeda K Imagawa S Isayama A Isobe M Iwamoto A Kaneko O Kitagawa S Komori A Kubo S Kumazawa R Masuzaki S Matsuoka K Mito T Miyazawa J Morisaki T Morita S Motojima O Murakami S Mutoh T Muto S Nakajima N Nakamura Y Nakanishi H Narihara K Narushima Y Nishimura A Nishimura K Nishizawa A Noda N Ohdachi S Ohkubo K Ohyabu N 《Physical review letters》2003,90(20):205001
Sawtooth oscillations have been observed in current-carrying helical plasmas by using electron-cyclotron-emission diagnostics in the Large Helical Device. The plasma current, which is driven by neutral beam injection, reduces the beta threshold of the sawtooth oscillation. When the central q value is increased due to the plasma current, the core region crashes, and, when it is decreased, the edge region crashes annularly. Observed rapid mixture of the plasma in the limited region suggests that these sawtooth crashes are reconnection phenomena. Unlike previous experiments, no precursor oscillation has been observed. 相似文献
64.
Chiva C Barthe P Codina A Gairí M Molina F Granier C Pugnière M Inui T Nishio H Nishiuchi Y Kimura T Sakakibara S Albericio F Giralt E 《Journal of the American Chemical Society》2003,125(6):1508-1517
The total synthesis and structural characterization of the MHCII-associated p41 invariant chain fragment (P41icf) is described. P41icf plays a crucial role in the maturation of MHC class II molecules and antigen processing, acting as a highly selective cathepsin L inhibitor. P41icf synthesis was achieved using a combined solid-phase/solution approach. The entire molecule (65 residues, 7246 Da unprotected) was assembled in solution from fully protected peptides in the size range of 10 residues. After deprotection, oxidative folding in carefully adjusted experimental conditions led to the completely folded and functional P41icf with a disulfide pairing identical to that of native P41icf. CD, NMR, and surface plasmon resonance (SPR) were used for the structural and functional characterization of synthetic P41icf. CD thermal denaturation showed clear cooperative behavior. Tight cathepsin L binding was demonstrated by SPR. (1)H NMR spectroscopy at 800 MHz of unlabeled P41icf was used to solve the three-dimensional structure of the molecule. P41icf behaves as a well-folded protein domain with a topology very close to the crystallographic cathepsin L-bound form. 相似文献
65.
Nobuyuki Mizuno Kenji Esaki Jinsaku Sakakibara Nobutoshi Murakami Shinichi Nagai 《Photochemistry and photobiology》1991,54(5):697-701
The chemical structure of the 8-methoxypsoralen oxidized product that inhibits the chemotactic activity of anaphylatoxin C5a was determined to be 2,3-dihydro-2,9-dimethoxy-3-hydroxy-7-oxo-7H-furo[3,2-g] [1]benzopyran. Its minimal concentration required to obtain the maximum inhibition of C5a des Arg (1 x 10(-8) M) chemotactic activity is 2.5 x 10(-8) M. Bioactivity of this substance was maintained for 2 weeks, stored in a dark room at room temperature under aerobic conditions. There is a possibility that this substance may be useful in the treatment of immune complex diseases. 相似文献
66.
Kajihara Y Suzuki Y Yamamoto N Sasaki K Sakakibara T Juneja LR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(4):971-985
We describe herein the preparation of 24 pure asparagine-linked oligosaccharides (Asn-oligosaccharides) from asparagine-linked biantennary complex-type sialylundecasaccharide [(NeuAc-alpha-2,6-Gal-beta-1,4-GlcNAc-beta-1,2-Man-alpha-1,6/1,3-)(2)-Man-beta-1,4-GlcNAc-beta-1,4-GlcNAc-beta-1-asparagine, 2] obtained from egg yolk. Our synthetic strategy aimed at adapting branch specific exo-glycosidases digestion (beta-D-galactosidase, N-acetyl-beta-D-glucosaminidase and alpha-D-mannosidase) of the individual asialo-branch after preparation of monosialyloligosaccharides obtained from 2 by acid hydrolysis of NeuAc. In order to perform branch specific exo-glycosidase digestion, isolation of pure monosialyloligosaccharides obtained was essential. However, isolation of two kinds of monosialyloligosaccharides are difficult by HPLC due to their highly hydrophilic nature. Therefore, we examined chemical protection with hydrophobic protecting (Fmoc and benzyl) groups. These chemical protection enabled us to separate the monosialyloligosaccharides by use of a HPLC column (ODS) on synthetic scales. Using these pure monosialiloligosaccharides enable us to obtain 24 Asn-linked oligosaccharides (100 mg scale) within a few weeks by branch specific exo-glycosidase digestions (alpha-D-neuraminidase, beta-D-galactosidase, N-acetyl-beta-D-glucosaminidase and alpha-D-mannosidase). In addition, solid-phase synthesis of glycopeptide having Asn-linked sialyl-undeca- and asialo-nonasaccharides thus obtained, was also performed on an acid labile HMPA-PEGA resin. 相似文献
67.
Ohyabu N Ida K Morisaki T Narihara K Komori A Watanabe K Narushima Y Nagayama Y Shoji M Ashikawa N Emoto M Funaba H Goto M Idei H Ikeda K Inagaki S Inoue N Isobe M Khlopenkov K Kobuchi T Kostrioukov A Kubo S Kumazawa R Liang Y Masuzaki S Minami T Miyazawa J Morita S Muto S Mutoh T Murakami S Nakamura Y Nakanishi H Nishimura K Noda N Notake T Ohkubo K Ohdachi S Oka Y Osakabe M Ozaki T Peterson BJ Sakamoto R Sakakibara S Sagara A Saito K Sasao M Sato K Sato M Seki T Shimozuma T Sudo S Suzuki H 《Physical review letters》2002,88(5):055005
In the Large Helical Device plasma discharges, the size of an externally imposed island with mode number ( n/m = 1/1) decreases substantially when the plasma is collisionless ( nu(*)< approximately 1) and the beta is finite ( > approximately 0.1%) at the island location. For the collisional plasmas with finite beta, on the other hand, the size of the island increases. However, there is a threshold in terms of the vacuum island size below which the island enlargement is not seen. 相似文献
68.
J.P. Zhao Z.Y. Chen T. Yano T. Ooie M. Yoneda J. Sakakibara 《Applied Physics A: Materials Science & Processing》2001,73(1):97-101
Carbon nitride films with high nitrogen content were prepared by reactive pulsed-laser deposition at nitrogen partial pressures
varying from 0.1 to 20.0 Torr. It was found that the nitrogen content in the films first increases with increase of the nitrogen
pressure, reaches a maximum of 46 at. % at 5.0 Torr, and then decreases to 37 at. % at 20.0 Torr. The almost pure carbon nitride
films were systematically characterized by using X-ray photoelectron spectroscopy (XPS) concerning the core-level and valence-band
structures. Some fingerprint information, which shows the role of nitrogen in controlling the electronic structure of carbon
nitride films, was found based on the XPS studies. With enhancing the nitrogen incorporation, both the binding energy and
the peak intensity of the core-level and the valence-band spectra vary systematically as a function of nitrogen content in
the films.
Received: 26 June 2000 / Accepted: 26 June 2000 / Published online: 20 September 2000 相似文献
69.
In order to elucidate the characteristic features of commercial methylcellulose precisely, O-methylcellulose model copolymers consisting of 2,3,6-tri-O-methylanhydroglucose unit (236MeAGU) and 2-O-methylanhydroglucose unit (2MeAGU) with various composition ratios were synthesized via cationic ring-opening copolymerization
of the corresponding glucose orthoester derivatives, subsequent removal of pivaloyl and allyl groups, and methylation. The
structure of the obtained copolymers was confirmed by 1H-, 13C-NMR, and FT-IR. Temperature-dependent turbidity measurement verified their thermoresponsive behavior in aqueous solution.
The lower critical solution temperature was tuned from 63 to 45 °C above 47 mol-% 236MeAGU content. The hydrophobicity along
the cellulose chain was dominant to determine their physical properties. However, the aqueous properties of the MC model copolymers
were strongly affected by the slight difference of the composition ratio. The present method would provide further details
of the structure–property relationship of O-methylcellulose. 相似文献
70.
The cross-correlation technique and Laser Induced Fluorescence (LIF) have been adopted to measure the time-dependent and two-dimensional velocity and temperature fields of a stably thermal-stratified pipe flow. One thousand instantaneous and simultaneous velocity and temperature maps were obtained at overall Richardson numberRi = 0 and 2.5, from which two-dimensional vorticity, Reynolds stress and turbulent heat flux vector were evaluated. The quasi-periodic inclined vortices (which connected to the crest) were revealed from successive instantaneous maps and temporal variation of vorticity and temperature. It has been recognized that these vortices are associated with the crest and valley in the roll-up motion.List of symbols
A
Fraction of the available light collected
-
C
Concentration of fluorescence
-
D
Pipe diameter
-
I
Fluorescence intensity
-
L
Sampling length along the incident beam
-
I
0
Intensity of an excitation beam
-
I
c
(T)
Calibration curve between temperature and fluorescence intensity
-
I
ref
Reference intensity of fluorescence radiation
-
Re
b
Reynolds number based on bulk velocity,U
b
D/v
-
Ri
Overall Richardson number based on velocity difference,gDT/U
2
-
t
Time
-
t
Time interval between the reference and corresponding matrix
-
T
Temperature
-
T
1,T
2
Temperature of lower and upper layer
-
T
*
Normalized temperature, (T–T
1)/T
-
T
c
(I)
Inverse function of temperature as a function ofI
c
-
T
ref
Reference temperature
-
T
Temperature difference between upper and lower flow,T
2 –T
1
-
U
1
Velocity of lower stream
-
U
2
Velocity of upper stream
-
U
b
Bulk velocity
-
U
c
Streamwise mean velocity atY/D=0
-
U
Streamwise velocity difference between upper and lower flow,U
1–U
2
-
u, v, T
Fluctuating component ofU, V, T
-
U, V
Velocity component of X, Y direction
-
X
Streamwise distance from the splitter plate
-
Y
Transverse distance from the centerline of the pipe
-
Z
Spanwise distance from the centerline of the pipe
-
Quantum yield
-
Absorptivity
-
vorticity calculated from a circulation
-
Kinematic viscosity
-
circulation 相似文献