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891.
We report an evidence for the precursor phenomena of the pion condensation, which is found in the enhancement of the spin longitudinal cross sections ID q of the quasielastic 12C, $^{40} Ca(\vec p, \vec n)$ , reactions at the incident energy 494 and 346 MeV around the momentum transfer q ≈ q c , the critical momentum of the pion condensation. We utilized the distorted wave impulse approximation incorporated with the continuum random phase approximation. We adjusted the Landau-Migdal parameters, g′ NN and g′ NΔ, and obtained g′ NN ≈ 0.6–0.7 and g′ N Δ ≈ 0.3–0.4, which are consistent with those obtained from the energy of the Gamov-Teller giant resonance and the quenching factor of the Gamov-Teller sum rule. 相似文献
892.
Interplay between nonlinearity,scan speed,damping, and electronics in frequency modulation atomic-force microscopy 总被引:1,自引:0,他引:1
Numerical simulations of the frequency modulation atomic force microscope, including the whole dynamical regulation by the electronics, show that the cantilever dynamics is conditionally stable and that there is a direct link between the frequency shift and the conservative tip-sample interaction. However, a soft coupling between the electronics and the nonlinearity of the interaction may significantly affect the damping. A resonance between the scan speed and the response time of the system can provide a simple explanation for the spatial shift and contrast inversion between topographical and damping images, and for the extreme sensitivity of the damping to a tip change. 相似文献
893.
Racemic indanofan [(+/-)-1] was efficiently converted to enantiopure (S)-indanofan [(S)-1] by a combination of enzymatic resolution and chemical inversion techniques. An additional important technique is the use of an o-xylene complex of a hemiketal (S)-3c as a precursor, which can be quantitatively converted to (S)-indanofan and easily purified by recrystallization from o-xylene. 相似文献
894.
The total syntheses of natural agelastatin A and agelastatin B were accomplished via a strategy that utilized an alkynyliodonium salt --> alkylidenecarbene --> cyclopentene transformation to convert a relatively simple amino alcohol derivative to the functionalized core of the agelastatin system. Subsequent manipulations delivered debromoagelastatin, which served as a precursor to both agelastatin A and agelastatin B. Alkylidenecarbene insertion chemoselectivity issues were explored en route to the final targets. 相似文献
895.
Ikushima Y Hatakeda K Sato M Sato O Arai M 《Chemical communications (Cambridge, England)》2002,(19):2208-2209
Our microreaction system using supercritical water solutions achieves nearly 100% yield and 100% selectivity for epsilon-caprolactam production at reaction times shorter than 1 s. 相似文献
896.
Carrettin S McMorn P Johnston P Griffin K Hutchings GJ 《Chemical communications (Cambridge, England)》2002,(7):696-697
Glycerol is oxidised to glyceric acid with 100% selectivity using either 1% Au/charcoal or 1% Au/graphite catalyst under mild reaction conditions (60 degrees C, 3 h, water as solvent). 相似文献
897.
Sakai K Ishigami E Konno Y Kajiwara T Ito T 《Journal of the American Chemical Society》2002,124(41):12088-12089
The first/second examples of partially oxidized 1-D platinum chain compounds consisting of cationic dimer units have been obtained from electro-oxidation of an aqueous solution containing cis-[Pt(NH3)2(OH2)2]2+ and acetate/propionate. The analytical and crystallographic studies reveal the mixed-valency of Pt(2.2+)infinity. The XPS confirms the presence of both Pt(II) and Pt(III). The solid-state physical measurements reveal that they are diamagnetic semiconductors and display a fairly broad, low-energy absorption band in the range of 500-3200 nm. 相似文献
898.
Takami Seiichi Suzuki Ken Kubo Momoji Miyamoto Akira 《Journal of nanoparticle research》2001,3(2-3):213-218
The fate of clusters emitted onto a substrate falls into several categories including repulsion, soft landing, migration, and explosion, depending on the interaction between the cluster and the substrate. This dynamic behavior of the clusters controls thin-film formation processes from clusters such as cluster ion beam deposition and chemical vapor deposition. Here we describe the collision processes of both Al and Au clusters with a kinetic energy of 0.56 eV/atom onto an amorphous SiO2 substrate studied by molecular dynamics simulation, focusing on the dissipation of translational kinetic energy during the collision process. The simulation elucidated that the activation of thermal vibrational energy of the substrate promoted the sticking of the colliding clusters on the substrate. This result suggests that the dissipation of the translational kinetic energy of the colliding cluster is one of the factors that determine the structure formed on a substrate from vapor phase. 相似文献
899.
Rapid analysis of amino sugars by microchip electrophoresis with laser-induced fluorescence detection. 总被引:1,自引:0,他引:1
Microchip electrophoresis for the short-time analysis of amino sugars is described. D-Glucosamine, D-galactosamine and their reduced forms were labeled with 4-nitro-2,1,3-benzoxadiazole 7-fluoride (NBD-F) at pH 6.0 and the fluorescent derivatives were purified on an octadecyl silica (ODS) gel plate. The derivatives were analyzed by electrophoresis on a microfabricated chip with a 33 mm long separation channel with argon laser-induced fluorescence detection. Under the established conditions, these amino sugarderivatives were well separated from each other within 60 s. Amino sugars of as small an amount as 0.5 fmol could be detected with a signal-to-noise (S/N) ratio of 3, and peak response showed good linearity between at least 0.8 and 8 fmol of samples with a relative standard deviation (RSD) of ca. 4%. This method was also applied to the analysis of amino sugar composition of O-linked glycans released from bovine submaxillary mucin with alkali in the presence of borohydride. The result of amino sugar composition analysis for individual O-glycans fractionated by high-performance liquid chromatography was quite useful for their identification. 相似文献
900.
The asymmetric conjugate addition of arylcopper reagents derived from aryl Grignard reagents and copper(I) iodide to a chiral 1-[2-(p-tolylsulfinyl)]pyrrolyl cinnamide proceeded smoothly to give (3R)-adducts with high diastereoselectivities (> or =92% de) in high yields. Conjugate additions either of the cinnamide with the alkyl Grignard reagent-copper(l) iodide combination or of the crotonamide derivative with aryl Grignard reagent-copper(l) iodide gave moderate to good diastereoselectivities. With these sulfinyl pyrrolyl alpha,beta-unsaturated amides, the chiral auxiliary was efficiently recovered without any loss of optical purity after asymmetric conjugate addition. 相似文献