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241.
Hofmann T Wallacher D Mayorova M Zorn R Frick B Huber P 《The Journal of chemical physics》2012,136(12):124505
We present incoherent quasi-elastic neutron scattering measurements in a wave vector transfer range from 0.4 A?(-1) to 1.6A? (-1) on liquid n-hexane confined in cylindrical, parallel-aligned nanochannels of 6 nm mean diameter and 260 μm length in monolithic, mesoporous silicon. They are complemented with, and compared to, measurements on the bulk system in a temperature range from 50 K to 250 K. The time-of-flight spectra of the bulk liquid (BL) can be modeled by microscopic translational as well as fast localized rotational, thermally excited, stochastic motions of the molecules. In the nano-confined state of the liquid, which was prepared by vapor condensation, we find two molecular populations with distinct dynamics, a fraction which is immobile on the time scale of 1 ps to 100 ps probed in our experiments and a second component with a self-diffusion dynamics slightly slower than observed for the bulk liquid. No hints of an anisotropy of the translational diffusion with regard to the orientation of the channels' long axes have been found. The immobile fraction amounts to about 5% at 250 K, gradually increases upon cooling and exhibits an abrupt increase at 160 K (20 K below bulk crystallization), which indicates pore freezing. 相似文献
242.
Andersen KK Andersen SL Esberg J Knudsen H Mikkelsen R Uggerhøj UI Sona P Mangiarotti A Ketel TJ Ballestrero S;CERN NA 《Physical review letters》2012,108(7):071802
We report the first observation of a shoulder in the radiation spectrum from GeV electrons in a structured target consisting of two thin and closely spaced foils. The position of the shoulder depends on the target spacing and is directly connected to the finite formation length of a low-energy photon emitted by an ultrarelativistic electron. With the present setup it is possible to control the separation of the foils on a μm scale and hence measure interference effects caused by the macroscopic dimensions of the formation length. Several theoretical groups have predicted this effect using different methods. Our observations have a preference for the modified theory by Blankenbecler but disagree with the results of Baier and Katkov. 相似文献
243.
244.
EHS/NA Collaboration N. M. Agababyan I. V. Ajinenko M. R. Atayan F. Botterweck M. Charlet P. V. Chliapnikov E. A. De Wolf K. Dziunikowska Z. C. Garutchava G. R. Gulkanyan R. Sh. Hakobyan J. K. Karamyan D. Kisielewska W. Kittel S. S. Mehrabyan L. C. S. Oliveira F. K. Rizatdinova L. A. Tikhonova A. Tomaradze F. Verbeure S. A. Zotkin 《Physics letters. [Part B]》1994,320(3-4):411-416
A collective “sea-gull” effect is observed for a system of fast hadrons produced in the fragmentation regions of nondiffractive π+p-interactions at 250 GeV/c. The effect is not reproduced by the FRITIOF fragmentation model in its details. It is demonstrated that hard-like processes, both in the collision phase and in the fragmentation phase, are not properly treated in the model. 相似文献
245.
通过模型化合物ArOArCOArArCOArOAr(Ar为苯基或1,4-亚苯基)的全优化模型,得到芳环之间的平均二面角为37.5°,由其结构参数建立了刚性链聚芳醚酮(砜)类均聚物分子结构与其熔点及玻璃化温度的关系式,据此较好地了预测了新品种均聚物的热性能。 相似文献
246.
BeiJIANG HuiYANG 《中国化学快报》2002,13(11):1083-1086
Two new ent-kauranc dierpenoids,sculponcatins L(1) and M (2) ,were isolated from the EtOAc extract of Isodon sculponeata.Their structures,were clucidated by spectroscopic cvidences.The cytotoxicities of 1 and 2 against human tumor cells k562 and T24 were tested. 相似文献
247.
Self-organization and chaos in a fluidized bed 总被引:1,自引:0,他引:1
Daw CS Finney CE Vasudevan M van Goor NA Nguyen K Bruns DD Kostelich EJ Grebogi C Ott E Yorke JA 《Physical review letters》1995,75(12):2308-2311
248.
Zhi NA Shuang Xi MEI Chao Ming LI Zhong Wen LIN Han Dong SUN* Laboratory of Phytochemistry Kunming Institute of Botany Chinese Academy of Sciences Kunming 《中国化学快报》2001,(3)
Isodon enanderianus (Hand.-Mazz.) H. W. Li, a perennial shrub plant of Labiatae family, is widely distributed in the southern part of Yunnan province. It has long been used as folk medicine to diminish inflammation and detoxify1. The Isodon genus is known to be rich in ent-kaurane diterpenoids, a series of new ent-kaurane diterpenoids have been isolated from the dried leaves of I. enanderianus2-4. During the course on a re-investigation of the chemical constituents of I. enanderianus, four… 相似文献
249.
250.
采取亲核取代反应合成了含有羟端基和不含羟端基的两种线性联苯型聚醚醚酮(PEDEK)齐聚物,并采用MS,1HNMR,ICP,IR,DSC和WAXD等方法对齐聚物进行表征.研究发现,含羟端基的齐聚物因分子间存在氢键,其X射线衍射峰峰位和峰形与聚合物十分相似,而不含羟端基齐聚物的X射线衍射峰与聚合物相差较大. 相似文献