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991.
A novel route to (±)-platencin is reported, in which the highly stereoselective alkylative quaternization of a cyclohexenone scaffold via 1,4-diastereoinduction and two radical carbon-carbon bond-forming reactions that involve titanium(III)-mediated cyclization and stannyl-radical-mediated skeletal rearrangement are utilized. 相似文献
992.
Anthranilamide (AAM) serves as a bifunctional modifier on the boron atom in catalytic transformations of arylboronic acids. It makes boronyl groups unreactive in Suzuki-Miyaura coupling and promotes Ru-catalyzed ortho-silylation. Suzuki-Miyaura coupling of AAM-modified bromophenylboronic acids with tolylboronic acid gave 1,1'-biaryl-4-boronic acid bearing AAM on the boron atom, which subsequently underwent Ru-catalyzed ortho-silylation at the 3-position by virtue of the ortho-directing effect of the AAM group. 相似文献
993.
Han H Miyoshi Y Oyama T Konishi R Mita M Hamase K 《Journal of separation science》2011,34(20):2847-2853
Enantioselective determination of aspartic acid (Asp) in the pineal gland of rodents with various melatonin contents was performed using a highly sensitive and selective two-dimensional HPLC system. After derivatization of the amino group with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), NBD-Asp was separated using a capillary monolithic ODS column in the first dimension. The fraction of NBD-Asp was automatically collected and transferred to the second dimension, and the D- and L-Asp were separated and determined using a narrowbore enantioselective column. Large amounts of D-Asp were observed in the pineal gland of the rats and specific strains of mice (C3H and CBA) possessing a high concentration of melatonin in their pineal gland. On the other hand, the amounts of D-Asp were small in the pineal gland of mice possessing a trace or no melatonin in their pineal gland (ddY, ICR, C57BL and BALB/c). In other tissues and physiological fluids, no significant strain-dependent changes of the D-Asp amounts were observed. These results indicate that large amounts of D-Asp are present only in the pineal gland containing large amounts of melatonin, and special care should be taken when selecting mouse strains for the investigation of D-Asp. 相似文献
994.
Maruyama M Guo JD Nagase S Nakamura E Matsuo Y 《Journal of the American Chemical Society》2011,133(18):6890-6893
As a new class of neutral closed-shell aromatic four-membered ring systems, CoE(3) (E = S, Se) was constructed inside the bowl-shaped space of pentaaryl[60]fullerene. X-ray crystallographic analysis of CoS(3)(η(5)-C(60)Ar(5)) revealed that the CoS(3) unit is planar, and DFT calculations suggested an aromatic 6π-electron system. Steric protection by the pentaaryl[60]fullerene ligand is critical for isolation and characterization of the aromatic hetero cobaltacyclobutane. Unique reactivity of the CoS(3) unit was demonstrated by disruption of 6π-conjugation with abstraction of the sulfur atom, affording a dimer, [CoS(2)(η(5)-C(60)Ar(5))](2). This work provides new insight into the aromaticity of four-membered ring systems and advances the understanding of aromatic organometallic compounds. 相似文献
995.
Density functional theory (DFT) calculations at the B3LYP/6-31G(d) and B3LYP/6-31G+(d) levels demonstrated that O-furfuryl S-alkyl dithiocarbonate (1) undergoes aromatic [3,3]-sigmatropic rearrangement to the energetically unfavorable S-(2-methylene-2,3-dihydrofuran-3-yl) S-alkyl dithiocarbonate (2'), which then rearranges to furfuryl alkyl sulfide (3) with COS extrusion to regain the aromaticity lost in the first step. 相似文献
996.
Julie?LelouvetelEmail author Masashi?Nakagawa Yohei?Sato Koichi?Hishida 《Experiments in fluids》2011,50(4):813-823
A time-resolved particle tracking velocimetry (PTV) system and a shape projection imaging system were used to investigate
the turbulence modifications by bubbles in a downward bubbly flow. Two bubble sizes and three mean void fractions were tested
at a Reynolds number of about 20,000. The strong modifications in the mean velocity, turbulent kinetic energy (TKE) budget,
and velocity spectra are observed in the central region of the pipe that has a high local void fraction. In particular, kinetic
energy production decreased, whereas the TKE dissipation rate increased. This suggests that the transfer of energy due to
bubbles has a very large effect on the TKE budget. Moreover, velocity spectra reveal that the presence of bubbles modifies
the length scales of turbulent eddies, which contain, transfer, and dissipate energy. 相似文献
997.
Masashi Eto Koki YamaguchiItaru Shinohara Fumikazu ItoYasuyuki Yoshitake Kazunobu Harano 《Tetrahedron》2011,67(38):7400-7405
(4-Nitrophenyl- and 4-chlorophenyl)(2-hydroxy-3,3-dimethylindolin-1-yl)methanone (4a,b) serve as clathrate hosts for benzene guests. X-ray crystal analyses of the inclusion compounds of 4a and 4b with benzene indicate that the ‘edge-to-face interaction’ plays an important role in the formation of the inclusion complexes with benzene as well as in the host-host interactions. PM6 molecular orbital calculations were found to reproduce the characteristic structural features of both intra- and intermolecular edge-to-face interactions. 相似文献
998.
Masashi Kato 《Applied Acoustics》2011,(10):732-736
Conventional active noise control (ANC) in ducts has been realized with digital signal processing. The physical size of the conventional ANC systems is usually large owing to the signal processing interval, and the cost of the system depends on the price of the digital signal processor (DSP). This paper proposes a new ANC system with an analog neural network circuit, which will process signals in short time periods without DSP. The proposed neural network circuit has a simple structure consisting of analog multipliers and an integrator, and we simulated the performance of the circuit by HSPICE. We also fabricated a circuit connected to a real duct and confirmed operation of the proposed ANC system. 相似文献
999.
Jean Cardinal Erik D. Demaine Martin L. Demaine Shinji Imahori Tsuyoshi Ito Masashi Kiyomi Stefan Langerman Ryuhei Uehara Takeaki Uno 《Graphs and Combinatorics》2011,27(3):341-351
How do we most quickly fold a paper strip (modeled as a line) to obtain a desired mountain-valley pattern of equidistant creases (viewed as a binary string)? Define the folding complexity of a mountain-valley string as the minimum number of simple folds required to construct it. We first show that the folding complexity of a length-n uniform string (all mountains or all valleys), and hence of a length-n pleat (alternating mountain/valley), is O(lg2 n). We also show that a lower bound of the complexity of the problems is ??(lg2 n/lg lg n). Next we show that almost all mountain-valley patterns require ??(n/lg n) folds, which means that the uniform and pleat foldings are relatively easy problems. We also give a general algorithm for folding an arbitrary sequence of length n in O(n/lg n) folds, meeting the lower bound up to a constant factor. 相似文献
1000.
Rother W Dewald A Iwasaki H Lenzi SM Starosta K Bazin D Baugher T Brown BA Crawford HL Fransen C Gade A Ginter TN Glasmacher T Grinyer GF Hackstein M Ilie G Jolie J McDaniel S Miller D Petkov P Pissulla T Ratkiewicz A Ur CA Voss P Walsh KA Weisshaar D Zell KO 《Physical review letters》2011,106(2):022502
The transition rates for the 2(1)+ states in (62,64,66)Fe were studied using the recoil distance Doppler-shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N = 40. The results are interpreted using the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N = 40 as governed by the number of valence protons with respect to Z ≈ 30. The trend of collectivity suggested by the experimental data is described by state-of-the-art shell-model calculations with a new effective interaction developed for the fpgd valence space. 相似文献