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排序方式: 共有409条查询结果,搜索用时 15 毫秒
401.
A novel selectable one-dimensional ((1)D) or two-dimensional ((2)D) gas chromatography-olfactometry/mass spectrometry with preparative fraction collection (selectable (1)D/(2)D GC-O/MS with PFC) system was developed. The main advantages of this system are the simple and fast selection of (1)D GC-O/MS or (2)D GC-O/MS or (1)D GC-PFC or (2)D GC-PFC operation with a mouse click (without any instrumental set-up change), and total transfer of enriched compounds with thermal desorption (TD) on the same system for identification with (2)D GC-O/MS analysis. Recovery of PFC enrichment with 20 injection cycles of 15 model compounds at 500pg each (e.g. alcohol, aldehyde, ester, lactone, and phenol) was very good with recoveries in the range of 98-116%. The feasibility and benefit of the proposed system was demonstrated with an identification of off-flavor compounds (e.g. 2,4,6-trichloroanisole (TCA), 2-isobutyl-3-methoxypyrazine (IBMP), and geosmin) in spiked wine at odor perception threshold level (5-50ngL(-1)). After parallel stir bar sorptive extraction (SBSE) for 20 aliquots of a sample and subsequent PFC enrichment for the odor-active fractions from the 20 stir bars, three off-flavor compounds were clearly resolved and detected with TD-(2)D GC-O/MS in scan mode. The good efficiency of SBSE-PFC enrichment in the range of 71-78% shows that all analytical steps, e.g. SBSE, TD, (1)D/(2)D GC-O/MS, and PFC, are quantitative and identification of off-flavor compounds at ngL(-1) level in wine is possible. 相似文献
402.
Midori Fukaya Ryuji Uesugi Hirokazu Ohashi Yuta Sakai Masaaki Sudo Atsushi Kasai Hidenari Kishimoto Masahiro Osakabe 《Photochemistry and photobiology》2013,89(2):424-431
Plant‐dwelling mites are potentially exposed to solar ultraviolet‐B (UVB) radiation that causes deleterious and often lethal effects, leading most mites to inhabit the lower (underside) leaf surfaces. However, in species of spider mite belonging to the Genus Panonychus, a substantial portion of individuals occur on upper leaf surfaces. We investigated whether the upper leaf surfaces of citrus trees are favorable for P. citri, and to what extent they are tolerant to UVB radiation. If eggs are not adequately protected from UVB damage, females may avoid ovipositing on the upper surfaces of sunny leaves. To test this, we conducted laboratory experiments using a UVB lamp, and semioutdoor manipulative experiments. As a result, P. citri eggs are tolerant to UVB. Field studies revealed that the ratio of eggs and adult females on upper leaf surfaces were larger for shaded than for sunny leaves. However, 64–89% of eggs hatched successfully even on sunny upper leaf surfaces. Nutritional evaluation revealed that whether on sunny or shaded leaves, in fecundity and juvenile development P. citri reaped the fitness benefits of upper leaf surfaces. Consequently, P. citri is tolerant to UVB damage, and inhabiting the upper surfaces of shaded leaves is advantageous to this mite. 相似文献
403.
Yoshihiko Takeda Oleg A. Plaksin Haisong Wang Kenichiro Kono Naoki Umeda Naoki Kishimoto 《Optical Review》2006,13(4):231-234
Optical properties of Au nanoparticle composites and a grid structure of Cu nanoparticle composite were studied. Negative
ion implantation was applied to synthesize Au and Cu nanoparticles in amorphous SiO2 and Al2O3. Au nanoparticles were embedded within a depth of 30 nm by 60keV Au− implantation. The surface plasmon resonance (SPR) of Au:SiO2 and Au: Al2O3 composites shifted to red and to blue, respectively, compared to calculated ones by the Mie theory. Optical nonlinearity
was measured with pump-probe femtosecond spectroscopy and the transient spectrum of Au: Al2O3 composite presented a large red shift from the SPR peak. Image mapping of far-field transmitted intensity of Cu-implanted
SiO2 with a fine grid structure drawn by laser-lithography was observed by a scanning near-field optical microscopy (SNOM) system. 相似文献
404.
Y. Kishimoto Y. Kawasaki Y. Ideta G. Ghosh L.C. Gupta 《Journal of Physics and Chemistry of Solids》2008,69(12):3153-3155
To investigate the electronic states in YRuB2 and LuRuB2, we have carried out 11B NMR measurements. In the normal state, the spin-lattice relaxation rates 1/T1's in these compounds are proportional to the temperature T. 1/T1's show a small coherence peak just below the superconducting transition temperature Tc and decrease exponentially well below Tc. YRuB2 and LuRuB2 are found to be BCS superconductors with the energy gap 2Δ(0)=3.52 kBTc. 相似文献
405.
N Tamura Y Matsushita T Iwama S Harada S Kishimoto K Itoh 《Chemical & pharmaceutical bulletin》1991,39(5):1199-1212
(S)-2-Amino-3-(2,5-dihydro-5-oxo-4-isoxazolyl)propanoic acid (TAN-950 A (1)) is a novel amino acid antibiotic which shows a high affinity for glutamate receptors of the central nervous system. To improve the affinity for glutamate receptors, the structure-activity relationships of TAN-950 A derivatives 6a--o, 15a--o were investigated. Optically active TAN-950 A analogs 15a--h were synthesized starting with methyl (S)- and (R)-N-Boc-pyroglutamate (8) via acylation at the C-4 position followed by isoxazolone formation with hydroxylamine and subsequent deprotection reactions. The lactam 16, prepared from (RS)-aminoadipic acid, and dimethyl esters 19 of (R)- and (S)-aspartic acid were converted to (RS)-3-methyl-homo-TAN-950 A (15i) and optically active nor-TAN-950 A derivatives 15j--o, respectively, utilizing a similar sequence of reactions. Most of TAN-950 A derivatives 6a--o, 15a--o showed an affinity for glutamate receptors. The 3-alkyl derivatives 15b, d--g, especially, showed a high affinity for the quisqualate subtype-receptor and had a strong activating effect on the hippocampal neurons (glutamate agonistic activity). The (R)-enantiomer 15a of TAN-950 A had increased selectivity for the N-methyl-D-aspartate (NMDA) subtype-receptor. This selectivity was further enhanced by removal of the methylene group in the amino acid moiety of 15a. The most potent and selective NMDA agonistic activity was observed with (R)-3-methyl-nor-TAN-950 A (15m). 相似文献
406.
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
407.
408.
We present the hexagonal digital moiré method for three-directional structural characterization of hexagonal packed nanostructures. A mismatch between a three-way grating and a nanoparticle assembly is shown to produce hexagonal moiré fringes due to the interference between three groups of parallel moiré patterns. The measuring principles of the pitches and the orientations of the three 1D arrays of the nanoparticles are presented. The structural information on a silica nanoparticle assembly is analyzed. 相似文献
409.