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排序方式: 共有271条查询结果,搜索用时 15 毫秒
261.
Masayasu Sugiyama Katsuyuki Tsuzuki Kumi Matsumoto Ryohei Ogura 《Photochemistry and photobiology》1992,56(1):31-34
The effect of pretreatment with vitamin E on cytotoxicity, DNA single strand breaks, and chromosomal aberrations as well as on mutation induced by ultraviolet-B light (UV-B) was investigated in Chinese hamster V-79 cells. Cellular pretreatment with non-toxic levels of 25 microM alpha-tocopherol succinate (vitamin E) for 24 h prior to exposure resulted in a 10-fold increase in cellular levels of alpha-tocopherol. Using a colony-forming assay, this pretreatment decreased the cytotoxicity of UV-B light. However, alkaline elution assays demonstrated that pretreatment with vitamin E did not affect the number of DNA single strand breaks caused by UV-B light. In addition, UV-B exposure produced a dose-dependent induction of chromosomal aberrations and mutations at the HGPRT locus, and neither of these actions of UV-B was influenced by pretreatment with the vitamin. These results suggest that vitamin E protects cells from UV-B-induced cytotoxicity, possibly through its ability to scavenge free radicals. The results also suggest that the extent of genotoxicity induced by UV-B light may not correlate directly with the cytotoxic action of this wavelength region in sunlight. 相似文献
262.
Mizuno M Hayashi H Fujinami S Furutachi H Nagatomo S Otake S Uozumi K Suzuki M Kitagawa T 《Inorganic chemistry》2003,42(25):8534-8544
A new sterically hindered tetradentate tripodal ligand (Me2-etpy) and its labeled analogue having deuterated methylene groups (d4-Me2-etpy) were synthesized, where Me2-etpy is bis(6-methyl-2-pyridylmethyl)(2-pyridylethyl)amine. Copper(I) complexes [Cu(Me2-etpy or d4-Me2-etpy)]+ (1 and 1-d4, respectively) reacted with dioxygen at -80 degrees C in acetone to give bis(mu-oxo)dicopper(III) complexes [Cu2(O)2(Me2-etpy or d4-Me2-etpy)2](2+) (1-oxo and 1-d4-oxo, respectively), the latter of which was crystallographically characterized. Unlike a bis(mu-oxo)dicopper(III) complex with a closely related Me2-tpa ligand having a 2-pyridylmethyl pendant, 1-oxo possessing a 2-pyridylethyl pendant is not fully formed even under 1 atm of O2 at -80 degrees C and is very reactive toward the oxidation of the supporting ligand. Thermal decomposition of 1-oxo gave an N-dealkylated ligand in yield approximately 80% based on a dimer and a corresponding aldehyde. The deuterated ligand d4-Me2-etpy greatly stabilizes the bis(mu-oxo)dicopper(III) complex 1-d4-oxo, indicating that the rate determining step of the N-dealkylation is the C-H bond cleavage from the methylene group. The reversible conversion between 1-d4 and 1-d4-oxo in acetone is dependent on the temperature, and the thermodynamic parameters (DeltaH and DeltaS) of the equilibrium were determined to be -53 +/- 2 kJ mol(-1) and -187 +/- 10 J mol(-1) K(-1), respectively. The effect of the 2-pyridylethyl pendant in comparison with the 2-pyridylmethyl and 6-methyl-2-pyridylmethyl pendants on the physicochemical properties of the copper(I) and bis(mu-oxo)dicopper(III) species is discussed. 相似文献
263.
A new reliable analytical method, "Monochromatic X-ray Excitation X-ray Fluorescence Spectrometry", has been proposed. For validating the method, trace elements in sediment certified reference materials were determined. In the method X-ray fluorescence spectra are measured for specimens and pure metals; in addition the mass-attenuation coefficients of the specimens for various X-ray wavelengths are also measured. The data are analyzed by the fundamental parameter method and the uncertainty of the analysis is evaluated. The obtained results were in satisfactory agreement with the certified values within their uncertainties. This method will be applicable to the certification of reference materials, in the field of which reliable results with uncertainty statements are required. 相似文献
264.
Kaneko S Ito T Hirabayashi Y Ozawa T Okuda T Motoizumi Y Hirai K Naganuma Y Soga M Yoshimoto M Suzuki K 《Talanta》2011,84(2):579-582
Metal oxide nanoparticles prepared by pulsed laser deposition (PLD) were applied to nonenzymatic glucose detection. NiO nanoparticles with size of 3 nm were deposited on glassy carbon (GC) and silicon substrates at room temperature in an oxygen atmosphere. Transmission electron microscope (TEM) image showed nanoparticles with the size of 3 nm uniformly scattered on the Si(0 0 1) substrate. Unlike co-sputtering nanoparticle and carbon simultaneously, the PLD method can easily control the surface coverage of nanoparticles on the surface of substrate by deposition time. Cyclic voltammetry was performed on the samples deposited on the GC substrates for electrochemical detection of glucose. The differences between peak currents with and without glucose was used to optimize the coverage of nanoparticles on carbon electrode. The results indicated that optimal coverage of nanoparticles on carbon electrode. 相似文献
265.
We fabricated nanoscale GaN whiskers using photochemical etching. The fabricated GaN whiskers were conjugated and aligned
perpendicular to the incident light polarization used for photochemical etching in a self-assembling manner. Their far-field
photoluminescence spectra exhibited a blue-shifted photoluminescence peak at 3.60eV. Near-field photoluminescence spectra
of individual GaN whiskers were obtained, for the first time. The evaluation of the near-field spectra identified several
peaks from individual whiskers, corresponding to a diameter range of 5–10 nm, and revealed a stepwise change in the diameter
along the axis of individual whisker. 相似文献
266.
We performed time-resolved spectroscopy of ZnO quantum dots (QD), and observed exciton energy transfer and dissipation between
QD via an optical near-field interaction. Two different sizes of ZnO QD with resonant energy levels were mixed to test the
energy transfer and dissipation using time-resolved photoluminescence spectroscopy. The estimated energy transfer time was
144 ps. Furthermore, we demonstrated that the ratio of energy transfer between the resonant energy states could be controlled. 相似文献
267.
Prof. Dr. Suguru Ito Ryohei Sekine Masayasu Munakata Maho Yamashita Prof. Dr. Takashi Tachikawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(56):13982-13990
Despite recent extensive studies on mechanochromic luminescence (MCL), rational control over the magnitude of the emission-wavelength shift in response to mechanical stimuli remains challenging. In the present study, a two-component donor-acceptor approach has been applied to create a variety of organic MCL composites that exhibit remarkable emission-wavelength switching. Dibenzofuran-based bis(1-pyrenylmethyl)diamine and typical organic fluorophores have been employed as donor and acceptor dyes, respectively. Outstanding wide-range MCL with an emission-wavelength shift of over 300 nm has been achieved by mixing the diamine with 3,4,9,10-perylenetetracarboxylic diimide. Unprecedented two-step MCL in response to mechanical stimuli of different intensity has also been realized for a two-component mixture with 9,10-anthraquinone. Fluorescence microscopy observations at the single-particle level revealed that the segregation and mixing of the two-component dyes contribute to the stimuli-responsive emission-color switching of the MCL composites. 相似文献
268.
In this study, non-engineered RNAs were detected in living cells using bioluminescence. Two types of probe were utilized: a peptide inserted RLuc (PI-RLuc) probe and a split-RNA probe. Incorporation of the PI-RLuc and split-RNA probes enabled the direct detection of RNA introduced into living cells. 相似文献
269.
We evaluated the accuracy of an optical frequency comb in optical fibers by measuring the frequency shift after a sideband from an electro-optic modulator had passed through the fiber. We found that a frequency drift of a few hertz was due largely to a variation in the ambient temperature that corresponded to an increase in the square root of the Allan variance to 0.66 Hz. 相似文献
270.
Takashi Ohno Yutaka Kishimoto Kazuo Miyatani Masayasu Ishikawa 《Physica C: Superconductivity and its Applications》1995,250(3-4):227-234
The 63Cu NMR Knight shift K and spin-lattice relaxation rate 1/T1 have been measured to study the thiospinel superconductor Cu1.5Rh1.5S4 from a microscopic viewpoint. K is negative and has a weak dependence on temperature, and the hyperfine coupling constant Hhfd is estimated to be −52.4 kOe/μB. 1/T1 is proportional to the temperature in the normal state. In the superconducting state, 1/T1 takes a coherence peak just below Tc, and decreases exponentially well below Tc, from whose temperature dependence the superconducting energy gap has been proved to be close to 2Δ = 3.52kBTc given by the BCS theory. 相似文献