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951.
Gruber JW Kittipongpatana N Bloxton JD Der Marderosian A Schaefer FT Gibbs R 《Journal of chromatographic science》2004,42(4):196-199
Devil's root, Oplopanax horridus, is a widely used folk medicine in Alaska and British Columbia. The inner bark of the root and stem has been used to treat colds, cough, fever, and diabetes. The present study involves the development of high-pressure liquid chromatography (HPLC) and thin-layer chromatography (TLC) methods to detect the presence of trans-nerolidol and sterols in the root bark. The HPLC and TLC analytical methods presented are suitable for the characterization and identification of Oplopanax horridus. 相似文献
952.
Effect of methanol dilution on H-ZSM-5 zeolite deactivation in the process of light olefin formation
A. .A. Cichowlas P. T. Wierzchowski L. W. Zatorski 《Reaction Kinetics and Catalysis Letters》1986,32(2):341-346
Conversion of methanol in the presence of H2O, O2, H2, CO, CO2 and He was studied at 733 K on H-ZSM-5 zeolite. The effect of diluent on the selectivity to light olefins and resistance to coking of H-ZSM-5 were observed. Among the diluents studied only water exerts a promoting effect on prolonged activity of the catalyst. Some explanations of the deactivation process are given.
H2O, O2, H2, CO, CO2 He H-ZSM-5 733K. H-ZSM-5. . .相似文献
953.
Strong, low-energy two-photon absorption in extended amine-terminated cyano-substituted phenylenevinylene oligomers 总被引:8,自引:0,他引:8
Chung SJ Rumi M Alain V Barlow S Perry JW Marder SR 《Journal of the American Chemical Society》2005,127(31):10844-10845
Three quadrupolar oligophenylenevinylenes with five rings in the conjugated backbone, terminal donor groups, and various acceptors and/or donors along the backbone were synthesized and their two-photon spectroscopic properties investigated. These chromophores exhibit large two-photon absorption cross sections over a wide wavelength range and two distinct peaks, the strongest of which (deltamax > 3600 GM) is observed at 960-970 nm, a wavelength close to twice the value of the linear absorption maximum (2lambda(1)max). The findings on these chromophores are compared with those for analogous molecules with shorter conjugation length, for which the main two-photon band is at significantly shorter wavelength than 2lambda(1)max. 相似文献
954.
The valence band and core-level X-ray photoelectron spectroscopy (XPS) of iron and its oxides are reported, and the valence band spectra interpreted by various calculation models. The paper focuses upon the valence band region, which shows significant differences between the metal and the following oxidized iron species: FeO, Fe(3)O(4), alpha-Fe(2)O(3), gamma-Fe(2)O(3), alpha-FeOOH and gamma-FeOOH. The core region is of little analytical value as a means of distinguishing between these species, but the valence band region shows significant differences. These differences are consistent with spectra predicted by cluster and band structure calculations. Cluster calculations are valuable as a means for interpreting the spectra of iron oxides with multiple iron sites and defect characteristics. 相似文献
955.
Takuji Hirose Kumiko Naito Megumi Nakahara Hiroaki Shitara Yoshio Aoki Hiroyuki Nohira Bruce W. Baldwin 《Journal of inclusion phenomena and macrocyclic chemistry》2002,43(1-2):87-93
Two Kemp's acid diamides were synthesized and applied to chiral amine recognition using 1H NMR analysis. One derivative based on 1-(1-naphthyl)ethylamine had good chiral recognition of six amines and was useful to determine the optical purity for three amines, i.e., methylbenzylamine, 1-(1-naphthyl)ethylamine and 1- henylpropylamine,however, the cyclohexylethylamine derivative showed little discrimination for the amines studied. Together with the results for alkylamines, it was shown that aromatic structure was important for aromatic shielding anisotropy and –– interactions between host and guest. The structure of the 1-(1-naphthyl)ethylamine derivative in solution was also considered based on 1H NMR data and computer simulation. 相似文献
956.
E. W. Chung E. N. M. Ho D. K. K. Leung F. P. W. Tang K. C. H. Yiu T. S. M. Wan 《Chromatographia》2004,59(1):S29-S38
This paper describes a convenient method for the extraction and detection of eight anti-ulcer drugs simultaneously in horse urine, a relatively complex and viscous matrix, using a single-step liquid-liquid extraction followed by high-performance liquid chromatography – mass spectrometry (LC-MS). Anti-ulcer drugs were isolated from horse urine by salting out and liquid-liquid extraction. Detection of these drugs at concentrations below 1 ng mL?1 could be achieved using LC-MS-MS in the positive atmospheric pressure chemical ionisation (APCI) mode. The above analysis was also extended to elimination studies of horses administered with ranitidine and omeprazole. The urinary elimination data of these two drugs suggest that ranitidine was eliminated from horse urine at a much slower rate than omeprazole. In addition, three ranitidine metabolites and six omeprazole metabolites were identified for the first time in equine urine samples. 相似文献
957.
Mechanical analysis on rocket propellants 总被引:2,自引:0,他引:2
Herder G. Weterings F. P. de Klerk W. P. C. 《Journal of Thermal Analysis and Calorimetry》2003,72(3):921-929
The mechanical properties of solid rocket propellants are very important for good functioning of rocket motors. During use
and storage the mechanical properties of rocket propellants are changing, due to chemical and mechanical influences such as
thermal reactions, oxidation reactions or vibrations. These influences can result in malfunctioning, leading to an unwanted
explosion of the rocket motor. Most of modern rocket propellants consist of a polymer matrix (i.e. HTPB) filled with a crystalline
material (i.e. AP, AN). However, the more conventional double base propellants consist of a solid gel matrix with additives,
such as stabilizers. Both materials show a mechanical behaviour, quite similar to that of general polymers. To describe the
material behaviour of both propellants a linear visco-elastic theory is often used to describe the mechanical behaviour for
small deformations. Because the time-temperature dependency is also valid for these materials a mastercurve can be constituted.
With this mastercurve the response properties (stiffness) under extreme conditions can be determined. At TNO-PML a mastercurve
of a double base propellant was constituted using dynamical mechanical analysis (DMA) and compared with a mastercurve reduced
from conventional (static) stress relaxation tests. The mechanical properties of this double base propellant determined by
DMA were compared with conventional (quasi-static) tensile test results.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
958.
Gerald J. Smith Kenneth R. Markham W. Hugh Melhuish 《Photochemistry and photobiology》1994,60(3):196-198
Abstract Solvent-cleaned Merino wool, which was enzymatically digested with protease K, displayed a fluorescence maximum at 500 nm when excited at 430 nm. The yield of this emission was approximately 15 times greater for a fiber tips digest than for a digest of the mid-length region of the same fibers.
Separation of the components in the wool tip digest by silica gel thin-layer chromatography revealed the presence of several fluorescent species. The chromatographic mobility of these species was similar to the behavior observed in a preparation of authentic 1-methyltetrahydro-P-carboline, 1,3-dicarboxylic acid.
Mass spectroscopy of the fluorescent compounds in the wool tip digest displayed molecular ions, [M + H]+ with m/z = 273.0890 and 257.0560, and molecular weights that define the formulae C14 H12 N2 O4 and C11 H8 O4 N2 , respectively, which correspond to β-carboline 1,3-dicarboxylic acids. Mass spectral evidence also indicates the presence of two other β-carbolines. 相似文献
Separation of the components in the wool tip digest by silica gel thin-layer chromatography revealed the presence of several fluorescent species. The chromatographic mobility of these species was similar to the behavior observed in a preparation of authentic 1-methyltetrahydro-P-carboline, 1,3-dicarboxylic acid.
Mass spectroscopy of the fluorescent compounds in the wool tip digest displayed molecular ions, [M + H]
959.
William W. Paudler Richard A. Vandahm Young N. Park 《Journal of heterocyclic chemistry》1972,9(1):81-85
The diazaanalog of “cycl[3,2,2]azine”, “1,4-diazacycl[3,2,2]azine” (1,4,7b-triazacyclopent-[cd]indene) and its 2-methyl derivative were prepared. These compounds are subject to facile acid-catalyzed hydrolysis affording substituted imidazo[1,2-a]pyridines. 相似文献
960.