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排序方式: 共有155条查询结果,搜索用时 15 毫秒
51.
Haruhisa Kikuchi 《Tetrahedron letters》2004,45(2):367-370
Oriental crude drug, Bombyx Batryticatus, is dried silkworm larva, Bombyx mori L., which are dead and stiffened due to a Beauveria bassiana infection. In traditional Japanese, Korean, and Chinese medicine, it is employed as analgesic and anticonvulsant. We investigated the constituents of Bombyx Batryticatus and isolated four novel aromatics bearing 4-O-methylglucose moiety, BB-1, 2, 3, and 4 (1-4). It is speculated that these compounds are produced by an interaction between plants, insects, and microorganisms. 相似文献
52.
We present measurements and a theoretical concept of the nonlinear transport in the two-dimensional Wigner solid on the free surface of normal and superfluid 3He. We have observed the transition from Ohmic to nonlinear transport over a wide temperature range, from 200 microK to 200 mK at low electron velocities. The field-velocity (E-nu) characteristics show a nonmonotonic structure with a particular local maxima. We attribute this nonlinearity to the velocity-induced deformation of the periodic surface displacement due to the extremely strong damping in Fermi-liquid 3He. The calculated E-nu curves and thresholds are in good agreement with experiment. 相似文献
53.
Highly luminescent silica-coated ZnO nanoparticles dispersed in an aqueous medium were synthesized using the sol-gel process. The samples prepared at various temperatures exhibited an emission peak at around 480 nm (blue color) and a quantum efficiency of 60% at maximum by the quantum confinement effect of ZnO nanoparticles, with diameters ranging from 3.1 to 3.5 nm, under ultraviolet excitation. No degradation of the quantum efficiencies and no peak shifting in the emission spectra were observed for 7 days following the preparation, which indicated no growth of ZnO nanoparticles in the aqueous medium. 相似文献
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56.
Haruhisa Ueda Masahiro Wakisaka Hiromasa Nagase Takeshi Takaha Shigetaka Okada 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):403-405
Cyclomaltooctadecaose(CD18),cyclomaltononadecaose(CD19),cyclomaltoeicosaose(CD20) andcyclomaltoheneicosaose(CD21) are cyclic oligosaccharides composed of 18, 19, 20 and 21 D-glucose units, respectively. This report describes the physicochemical properties of CD18, CD19, CD20 and CD21 in terms of aqueous solubility, surface tension, optical rotation and acid-catalyzed hydrolysis. 相似文献
57.
Kunihioro Ichimura Haruhisa Akiyama Kazuaki Kudo Norio Ishizuki Shigeo Yamamura 《Liquid crystals》1996,20(4):423-435
In-plane alignment of nematic liquid crystals was regulated by polarized-light-irradiation of a cell assembled with a silica plate, the surface of which was modified by attaching 4-hexyl-4'-hexyloxyazobenzene at its o-position through surface silylation. The photoisomerizability of the chemisorbed azo-chromophore was affected by their surface density and the nature of photoinactive co-modifiers. The efficiency of the photoregulation of liquid crystal alignment was optimized by two-dimensional dilution of the chromophore with ethyltriethoxysilane (ETS) or 3-aminopropyltriethoxysilane (ATS). As a result, favourable procedure was to modify a silica surface with a crude azo-silylating reagent contaminated by ATS. The rate of the photoinduced reorientation of liquid crystals was followed by monitoring the alteration of the alignment direction of a dichroic dye dissolving in a mesophasic layer upon exposure to linearly polarized light. Exposure energy for the in-plane reorientation of a liquid crystal was about 100mJcm-2 of 445 nm light at elevated temperatures close to TNI. The effect of positional isomerism on the photoregulation was determined with the use of 4-cyano-4'-hexyloxyazobenzene as a commander molecule. It was confirmed that the photoalignment efficiency was markedly enhanced by attaching the chromophore at the ortho- or meta-position. The exposure energy for the reorientation of a liquid crystal was reduced by linking the p-cyanoazobenzene at the meta-position so that the reorientation was complete with an exposure energy of 20mJcm-2. 相似文献
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Rahman SM Seki S Obika S Yoshikawa H Miyashita K Imanishi T 《Journal of the American Chemical Society》2008,130(14):4886-4896
The novel bridged nucleic-acid analogue 2',4'-BNA(NC) (2'-O,4'-C-aminomethylene bridged nucleic acid), containing a six-membered bridged structure with an N-O linkage, was designed and synthesized efficiently, demonstrating a one-pot intramolecular NC bond-forming key reaction to construct a perhydro-1,2-oxazine ring (11 and 12). Three monomers of 2',4'-BNA(NC) (2',4'-BNA(NC)[NH], [NMe], and [NBn]) were synthesized and incorporated into oligonucleotides, and their properties were investigated and compared with those of 2',4'-BNA (LNA)-modified oligonucleotides. Compared to 2',4'-BNA (LNA)-modified oligonucleotides, 2',4'-BNA(NC) congeners were found to possess: (i) equal or higher binding affinity against an RNA complement with excellent single-mismatch discriminating power, (ii) much better RNA selective binding, (iii) stronger and more sequence selective triplex-forming characters, and (iv) immensely higher nuclease resistance, even higher than the S(p)-phosphorthioate analogue. 2',4'-BNA(NC)-modified oligonucleotides with these excellent profiles show great promise for applications in antisense and antigene technologies. 相似文献
60.
Takahashi K Kishine K Matsuyama S Saito T Kato H Kinugasa S 《Analytical and bioanalytical chemistry》2008,391(6):2079-2087
Poly(ethylene glycol) (PEG) is a useful water-soluble polymer that has attracted considerable interest in medical and biological
science applications as well as in polymer physics. Through the use of a well-calibrated evaporative light-scattering detector
coupled with high performance supercritical fluid chromatography, we are able to determine exactly not only the average mass
but also all of the molecular mass fractions of PEG samples needed for certified reference materials issued by the National
Metrology Institute of Japan. In addition, experimental uncertainty was determined in accordance with the Guide to the expression of uncertainty in measurement (GUM). This reference material can be used to calibrate measuring instruments, to control measurement precision, and to confirm
the validity of measurement methods when determining molecular mass distributions and average molecular masses. Especially,
it is suitable for calibration against both masses and intensities for matrix-assisted laser desorption/ionization time-of-flight
mass spectrometry.
Figure Comparison between the molecular mass fractions of PEG 1000 before calibration (si) (○) and after calibration (wi) (⧫). The error bar shows the expanded uncertainty of k = 2 of each mass fraction 相似文献