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51.
52.
自行研制了电子碰撞离子化的飞行时间型质量分析器(TOFMS),用于物质的化学分析。用研制的TOFMS测量了Ar离子化的飞行时间谱和离子的部分电离截面积比与碰撞电子能量的依赖关系,将它与Stepshan等人的实验结果进行了比较。 相似文献
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Summary The members of the power divergence family of statistics
all have an asymptotically equivalent χ2 distribution (Cressie and Read [1]). An asymptotic expansion for the distribution function is derived which shows that the
speed of convergence to this asymptotic limit is dependent on λ. Known results for Pearson'sX
2 statistic and the log-likelihood ratio statistic then appear as special cases in a continuum rather than as separate (unrelated)
expansions. 相似文献
55.
Sánchez-Machado DI López-Cervantes J López-Hernández J Paseiro-Losada P Simal-Lozano J 《Biomedical chromatography : BMC》2004,18(2):90-97
A high-performance liquid chromatographic (HPLC) method is described for determination of the ratio of beta-d-mannuronic acid to alpha-l-guluronic acid (M/G ratio) in dietary fibre of edible seaweeds. Total dietary fibre (TDF) content was determined gravimetrically. The TDF fraction was hydrolysed with 12 m and 1 m H(2)SO(4), then neutralized with AG 4 x 4 resin. The uronic acids were separated in a Tracer Extrasil SAX 5 micro m column (25 cm x 4 mm) at 35 degrees C, with 2 mm KH(2)PO(4) containing 5% methanol as mobile phase at a fl ow rate of 1.5 mL/min. The detection wavelength was UV 210 nm. The chromatographic identifications of beta-d-mannuronic acid and alpha-l-guluronic acid were confirmed by liquid chromatography-mass spectrometry (LC-MS). The method precision was 1.4% for beta-d-mannuronic acid and 3.5% for alpha-l-guluronic acid. The method was used to determine M/G ratio in canned seaweeds (Saccorhiza polyschides and Himanthalia elongata) and in dried seaweeds (H. elongata, Laminaria ochroleuca, Undaria pinnatifida, Palmaria sp. and Porphyra sp.). 相似文献
56.
采用氢核磁共振(1H-NMR)、动态光散射(DLS)及透射电子显微镜(TEM)对聚乙二醇-嵌段-聚甲基丙烯酸N,N-二甲氨基乙酯(PEG-b-PDMAEMA)三种具有不同PEG/PDMAEMA嵌段比的PEG-b-PDMAEMA共聚物在水溶液中的自聚集行为进行了研究. 研究表明, 两嵌段比例是影响聚合物胶束化过程的关键因素: 只有当其中聚乙二醇含量较低(质量分数低于33%)时, 聚合物才具有其pH/温度敏感胶束化特性. 此外, 共聚物溶液随温度胶束化过程与共聚物嵌段比大小密切相关. PEG-b-PDMAEMA这种不同于传统双亲性嵌段共聚物(DHBCs)在选择性溶剂中独特的胶束化行为, 是由聚合物溶液体系中各种基团之间的氢键作用决定的. 相似文献
57.
用WAXD和SAXS研究交联1,4-顺式聚丁二烯的取向结晶。结果表明:该试样在拉伸状态时,形成折叠链片晶,而不是伸直链纤维晶。片晶之间断产生新的片晶,使长周期减小,并且片晶的横向尺寸不断增大,由此导致结晶度增大。 相似文献
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The complexes of poly(methacrylic acid-co-methyl methacrylate) network with poly(ethylene glycol) stabilized byhydrogen bonds were prepared. By introducing the poly(ethylene glycol), a large difference in storage modulus below andabove the glass transition temperature occurred and the complexes exhibited shape memory behaviors. The morphology ofcomplexes was studied by using DSC, WAXD, and DMA. The results indicate that the fixed phase of this kind of novelshape memory materials is the network, and the reversible phase is the amorphous state of PEG:PMAA complex phase. Theshape recoverability almost reaches 100%. This type of complexes can be regarded as a novel shape memory network. 相似文献
60.
The carborane–siloxane copolymers Dexsil 300, a 34.5% bis(dimethylsilyl)-m-carborane–65.5% dimethylsiloxane copolymer, and Dexsil 400, a 24.9% bis(dimethylsilyl)-m-carborane–50.8% dimethyl, 24.3% methylphenylsiloxane copolymer, were coated on fused silica capillary columns and their gas
chromatographic properties were evaluated. Their selectivity was evaluated using both Rohrschneider–McReynolds constants and
triacylglycerol indices. The bis(dimethylsilyl)-m-carborane unit turned out to be equivalent to two dimethylsiloxy units and one half of a diphenylsiloxy unit. The m-carborane unit was found to cause a 15–25 K shift in the elution temperature between 120 and 360 °C. The working range was
from 20 and 0 °C to 380 °C for Dexsil 300 and Dexsil 400, respectively. The column bleeding levels at 380 °C were below 20
and 15 pA for Dexsil 300 and Dexsil 400, respectively. 相似文献