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排序方式: 共有310条查询结果,搜索用时 31 毫秒
91.
Various characteristics of dewetting of thin polystyrene (PS) films absorbed on highly cross-linked epoxy-coated and silicon oxide covered substrates are studied as a function of PS film thickness (20h(c1) whereas the spinodal dewetting (SD) occurs through the growth of surface undulations for hh(c2) while the SD mechanism is observed for h相似文献
92.
B. S. Garg R. Dixit A. L. Singh R. K. Sharma 《Journal of Thermal Analysis and Calorimetry》1991,37(11-12):2541-2554
Chromium(III) complexes of the type Cr(A)(A′)2, Cr(A)2(A′) and Cr(A)3 have been prepared (whereA is either piperidyldithiocarbamate or morpholyldithiocarbamate andA′ is glycine or oxine or acetylacetone moiety). The mixed ligand complexes have been charac terized by elemental analyses, magnetic susceptibility measurements and thermal studies. The complexes show magnetic moment in the range of 3.5–4.3 B.M. which corresponds to three unpaired electrons. TG studies have also been carried out, in order to study the mode of decomposition of the complexes and to evaluate various kinetic parameters. 相似文献
93.
Yu‐Chang Chen Ming‐Jen Cheng Shoiw‐Ju Lee AjayKumar Dixit Tsutomu Ishikawa Ian‐Lih Tsai Ih‐Sheng Chen 《Helvetica chimica acta》2004,87(11):2805-2811
Four new coumarinolignans, antidesmanin A (=7‐(1,1‐dimethylallyl)‐2,3‐dihydro‐3‐(4‐hydroxy‐3,5‐dimethoxyphenyl)‐10‐methoxy‐2‐methyl‐6H‐1,4,5‐trioxaphenanthren‐6‐one; 1 ), antidesmanin B (=3,7‐bis(1,1‐dimethylallyl)‐2,3‐dihydro‐2‐(4‐hydroxy‐3‐methoxyphenyl)‐10‐methoxy‐6H‐1,4,5‐trioxaphenanthren‐6‐one; 2 ), antidesmanin C (=2,7‐bis‐(1,1‐dimethylallyl)‐2,3‐dihydro‐3‐(4‐hydroxy‐3‐methoxyphenyl)‐10‐methoxy‐6H‐1,4,5‐trioxaphenanthren‐6‐one; 3 ) and antidesmanin D (=2‐(3,4‐dihydroxyphenyl)‐3,7‐bis(1,1‐dimethylallyl)‐2,3‐dihydroxy‐10‐methoxy‐6H‐1,4,5‐trioxaphenanthren‐6‐one or 3‐(3,4‐dihydroxyphenyl)‐2,7‐bis(1,1‐dimethylallyl)‐2,3‐dihydro‐10‐methoxy‐6H‐1,4,5‐trioxaphenanthren‐6‐one; 4 ) have been isolated from the root of the Formosan Antidesma pentandrum var. barbatum. The structures of these new compounds were elucidated by spectroscopic data. Compounds 1 – 3 exhibited marginal cytotoxicity against MCF‐7 (breast) and SF‐268 (CNS) cancer cell lines in vitro. 相似文献
94.
A regioselective approach for the synthesis of substituted naphthofurans and dibenzofurans has been demonstrated through a ring transformation reaction of suitably functionalized 2H-pyran-2-ones by reaction with 6,7-dihydro-5H-benzofuran-4-one and 7-methoxybenzofuran-3-one, respectively, in high yields. The novelty of the procedure lies in the creation of an aromatic ring transformed by 2H-pyran-2-one involving the -COCH2- moiety of a cyclic ketone. 相似文献
95.
A kinetic model for the nucleation of a crystalline phase consisting of particles experiencing short-range attractions is developed. Of particular significance is the proximity of the metastable fluid/fluid phase boundary. The model incorporates self-consistent thermodynamics, changes in gradient diffusivity, and density fluctuations in the vicinity of the critical point. Density fluctuations associated with the spinodal of this metastable phase transition greatly enhance nucleation rates, suggesting that experimental conditions may be found where rapid nucleation and slow crystal growth can be achieved by moving the metastable critical point relative to the solubility boundary. Copyright 2000 Academic Press. 相似文献
96.
Summary An XRF method for the determination of Y, Ce, Pr, Nd, Eu and Gd in high purity samarium oxide is described. Samples in oxalate form are mixed with boric acid in the ratio 31. About 800 mg of the mixture is pressed as a double layer pellet. Experimental parameters are selected to give maximum peak to noise ratio. The analysis lines are chosen after studying line interferences. The estimation limit ranges from 0.005% to 1% for most elements.
Röntgenfluorescenzanalyse von Y, Ce, Pr, Nd, Eu und Gd in Samariumoxid hoher Reinheit
Zusammenfassung Zur röntgenanalytischen Bestimmung von Spuren Seltener Erden in hochreinem Samariumoxid wird die Probe in die Oxalatform übergeführt, mit Borsäure im Verhältnis 31 gemischt und zu je 800 mg in Doppelschichttabletten (über Borsäure) gepreßt. Für ein maximales Peak/Untergrund-Verhältnis wurden die experimentellen Parameter entsprechend ausgewählt. Die benutzten Analysenlinien ergaben sich aus einer Untersuchung der Störungen. Die Erfassungsgrenze liegt zwischen 0,005% und 1%.相似文献
97.
A selective and sensitive technique has been developed for detecting and identifying 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) in human urine. Using a new, "mixed-mode", bonded silica gel, solid-phase extraction column cartridge, THC-COOH was selectively isolated from urine components. Following extraction, the presence of THC-COOH was confirmed and quantitated using gas chromatography-mass spectrometry (GC-MS) or gas chromatography-flame ionization detection. A linear quantitative response curve for THC-COOH was generated over a concentration range of 10 to 300 ng/ml. Overall extraction efficiency averaged greater than 85% and the quantitative response curve exhibited a correlation coefficient of 0.999. The limit of detection and identification using GC-MS for the drug metabolite was found to be six times below the present NIDA guidelines cut-off concentration of 15 ng/ml. 相似文献
98.
Summary An XRF method for the determination of Eu, Gd, Tb, Dy, Ho, Er and Yb in yttrium oxide has been developed. The samples are converted to yttrium oxalate and presented to the spectrometer in the form of pressed pellets. Philips PW-1220, semiautomatic X-ray spectrometer is used for analysis. Analysis lines have been chosen after careful study of line interferences. The lower estimation limit for Yb is 0.01% and for other elements it is 0.005%. The method has been tested for its accuracy by analysing synthetic samples with known composition.
Bestimmung von häufig vorkommenden Verunreinigungen an Seltenen Erden in Yttriumoxid hoher Reinheit mit Hilfe der Röntgenfluorescenzanalyse
Zusammenfassung Ein Verfahren zur röntgenfluorescenzanalytischen Bestimmung von Eu, Gd, Tb, Dy, Ho, Er und Yb in Yttriumoxid wurde ausgearbeitet. Die Probe wird zu Yttriumoxalat umgesetzt und in Form von Preßtabletten der RFA unterworfen. Das halbautomatische Röntgenfluorescenz-Spektrometer Philips PW-1220 wurde verwendet. Eine sorgfältige Untersuchung der Interferenzen führte zur Wahl der Analysenlinien. Die untere Bestimmungsgrenze liegt für Yb bei 0,01%, für die anderen Elemente bei 0,005%. Die Zuverlässigkeit des Verfahrens wurde anhand von synthetischen Proben bekannter Zusammensetzung geprüft.相似文献
99.
100.
Nicolas Delerue Sudhir Dixit Fred Gannaway David Howell Myriam Qurshi Grahame Blair Stewart Boogert Gary Boorman Chafik Driouichi Lawrence Deacon Alexander Aryshev Pavel Karataev Nobuhiro Terunuma Junji Urakawa Axel Brachmann Joe Frisch Marc Ross 《Pramana》2007,69(6):1147-1150
A new laser-wire has been installed in the extraction line of the ATF at KEK. It aims at demonstrating that laser-wires can
be used to measure micrometre scale beam size. In parallel, studies have been made to specify a laser suitable for the ILC
laser-wires.
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