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排序方式: 共有417条查询结果,搜索用时 15 毫秒
51.
Yoko Nunome Kenji Kodama Hyunkook Park Kozo Matsumoto Sang Chun Lee Kuniyuki Kitagawa 《Microchemical Journal》2011,99(2):470-477
A new system combining a soft plasma ionization (SPI) source with a time-of-flight mass spectrometer (TOFMS) has been successfully developed and applied to direct and on-line analysis of nanoparticles in smoke generated during combustion of mosquito coils with no sample preparation. The mass spectra of nanoparticles in smoke were examined in conjunction with the effects of species, pressure and current of the SPI discharge on fragmentation. The results indicated that a maximum mass of m/z 1576 was detectable when the following optima SPI conditions were satisfied: a He gas pressure of 1000 Pa with an air pressure of 1600 Pa and a discharge current of 110 mA. Furthermore, considering the results for emission spectra we suppose an ionization mechanism of SPI in which excitation and ionization of nitrogen molecule is promoted by the presence of He gas, leading to promote the smoke sample ionization. The mass spectrum of nanoparticles showed specific patterns of a peak interval of 74 which were assigned to triacetylene (1,3,5-hexatriyne). The most abundant peak in the mass spectrum, at m/z 452, was assigned to triacontanoic acid. 相似文献
52.
Oshima S Kashihara I Moritani K Inui N Mochiji K 《Rapid communications in mass spectrometry : RCM》2011,25(8):1070-1074
In secondary ion mass spectrometry (SIMS) of organic substances, the dissociation of the sample molecules is crucial. We have developed SIMS equipment capable of bombardment, where the primary ions are argon cluster ions with kinetic energy per atom controllable down to 1 eV. We previously reported the detection of intact ions of insulin and cytochrome C using this equipment. In this paper, we present a detailed characterization of the emission of secondary ions from insulin, focusing on the difference in secondary ion yield between intact ions and fragment ions by varying the incident angle of the cluster ions. The emission intensity of the intact ions was changed drastically due to the exposed dosage and incident angle of the cluster ions in contrast to the fragment ions. We discuss these results based on the manner in which the argon-cluster ions collide with the organic solid. 相似文献
53.
Yokoe H Mitsuhashi C Matsuoka Y Yoshimura T Yoshida M Shishido K 《Journal of the American Chemical Society》2011,133(23):8854-8857
Enantiocontrolled total syntheses of the breviones A, B, and C have been accomplished using a highly diastereoselective oxidative coupling of an α-pyrone with a tricyclic diene prepared from an optically pure Wieland-Miescher ketone derivative through the 7-endo-trig mode of acyl radical cyclization. 相似文献
54.
Hossain MZ Mukai K Yamashita Y Kawai H Yoshinobu J 《Chemical communications (Cambridge, England)》2011,47(37):10392-10394
The anisotropic correlation between buckled dimers on Si(100) was investigated by scanning tunneling microscopy. A bidentate ligand molecule was used to pin two neighboring dimers at 300 K. The chemically pinned dimer induces antiferromagnetic interaction along the dimer rows. Observed results agree well with Monte-Carlo simulations semi-quantitatively. 相似文献
55.
Kozo Matsumoto Hideki Matsuoka 《Journal of polymer science. Part A, Polymer chemistry》2005,43(17):3778-3787
Carbosilane fine particles were synthesized by core‐crosslinking of carbosilane block copolymer micelles and they were pyrolytically transformed into silica nanoparticles. The carbosilane block copolymer, poly(1‐(3‐butenyl)‐1‐methylsilacyclobutane)‐block‐polystyrene, (polyBMSB‐b‐polySt), [(m, n) = (31, 16), (54, 30), and (75, 28)], was synthesized by anionic polymerization of BMSB and St, where m and n represent polymerization degrees of BMSB and St segments, respectively. The block copolymer formed micelles in N,N‐dimethylformamide (DMF). The hydrodynamic diameters (Dh) of the micelles evaluated by dynamic light scattering ranged from 40 to 158 nm depending on the copolymer molecular weight. The core of the micelle was cross‐linked by Pt‐catalyzed hydrosilation with 1,2‐bis(dimethylsilylethane). The Dh of the core‐cross‐linked micelles in THF ranged from 56 to 164 nm. These precursor particles were pyrolyzed at 850 °C under N2 to give ceramic nanoparticles. The diameters of the spherical ceramic particles estimated by AFM ranged from 25 to 60 nm. X‐ray fluorescence analysis of the ceramic products revealed that it consisted of mainly SiO2 rather than SiC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3778–3787, 2005 相似文献
56.
Francisco A. Macías David Chinchilla Jose M.G. Molinillo Frank R. Fronczek Kozo Shishido 《Tetrahedron》2008,64(23):5502-5508
Both epimers of Heliannuol A, first heliannane reported in the literature, isolated from Heliannthus annuus, have been prepared individually in a stereoselective route using a ring closing metathesis (RCM) as a key step to obtain the eight-membered ring. Very good overall yield was obtained in both cases. 相似文献
57.
58.
Geoffrey B Edwards Kaoru Yamanouchi Kozo Kuchitsu Masaaki Sugie Harutoshi Takeo Chi Matsumura Keiichiro Ogawa Yoshito Takeuchi 《Journal of Molecular Spectroscopy》1985,111(2):301-319
The microwave spectrum of 1-pyrroline has been measured from 8 to 48 GHz. The transitions have been assigned to those of the ground state and the four lowest excited states of the ring-puckering vibration of monomer, which is a five-membered ring molecule with one CN double bond. The trimer, which exists in the liquid phase, has not been detected in the gas phase. The geometrical structure of the monomer has been estimated by an ab initio calculation and the trimer by a molecular mechanics calculation. The former is consistent with the experimental rotational constants. A gas-phase infrared spectrum has also been measured, and the ring-puckering potential has been determined by an analysis of the combination bands of the ring-puckering mode and the ring-stretching modes. The potential is described using a puckering coordinate, z, as V(z) = az2 + bz4, where and ; these values are intermediate of the corresponding values for cyclopentene and 1-pyrazoline. The nuclear quadrupole coupling constants, χaa = ?4.39(10), χbb = 1.04(10), and χcc = 3.35(10) MHz, have been determined by an analysis of well-resolved hyperfine splittings. These constants have been reproduced by an ab initio calculation with a 4-31G(N1) basis set. 相似文献
59.
60.
Summary By means of the filament heated in-beam method at 280–450° C, the series of sodium alkylsulphonates (RSO3Na, where R=C2H5 to n-C12H25) give very simple mass spectra: Na+, [RSO3Na2]+, which is the base peak except for R=n-C4H9, [(RSO3)2Na3]+ and, in most cases, [(RSO3)3Na4]+. Fragmentations other than these three or four peaks are observed only in the case of n-heptylsulphonate. The proposed method of analysis for simple alkylsulphonic acids is applicable to ordinary electron-impact mass spectrometers.
Analyse von Natrium-alkylsulfonaten durch Elektronenstoß-Massenspektrometrie mit Probenerhitzung im Elektronenstrahl
Zusammenfassung Mit Hilfe dieser Methode (280–450° C) erhält man für Natriumalkylsulfonate (RSO3Na mit R=C2H5 bis n-C12H25) sehr einfache Massenspektren: Na+, [RSO3Na2]+ (Basispeak mit Ausnahme von R=n-C4H9), [(RSO3)2Na3]+ und in den meisten Fällen [(RSO3)3Na4]+. Andere Fragmentierungen als diese 3 oder 4 Peaks wurden nur bei n-Heptylsulfonat beobachtet. Dieses Verfahren zur Analyse einfacher Alkylsulfonsäuren ist für übliche Elektronenstoß-Massenspektrometer verwendbar.相似文献