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排序方式: 共有71条查询结果,搜索用时 15 毫秒
1.
H. Jordan D. Hebert K. Fröhlich R.-P. Scholz R. Gellermann 《Isotopes in environmental and health studies》2013,49(3):79-82
The migration of radionuclides and other tracers in porous layers is determined by substance transport. The physical and hydraulic basis of retardation is investigated. A definition of a factor of retardation is given, describing the ratio between the pore velocity of the water and the velocity of tracer migration. Consequences to the groundwater protection are discussed. 相似文献
2.
Y. Davila A. PetitmanginC. Hebert J. PerrièreW. Seiler 《Applied Surface Science》2011,257(12):5354-5357
The incorporation of oxygen atoms in oxide films grown by pulsed laser deposition depends upon the oxygen pressure and laser power density. By carefully controlling these two parameters it is possible to control the oxygen deficiency in the samples, and thus to change their physical properties from insulating and transparent to absorbing and conducting. By using X-ray diffraction, Rutherford backscattering spectroscopy and resistivity measurements, we show that depending upon the oxide materials oxygen deficiency in the films can induce either the growth of stable sub-oxide phases or the formation of nanocomposite films by phase separation. The first case corresponds to oxides with a mixed valency cation like Ti, which leads to the formation of stable, crystalline and highly conductive TiOx sub-oxide phases. The second case is well described by the indium tin oxides (ITO) in which a large oxygen deficiency leads to metallic clusters embedded into a stoichiometric matrix, i.e. nanocomposite films. This phenomenon is due to the fact that sub-oxides of these compounds are not stable and thus the oxygen deficiency induced a phase separation. 相似文献
3.
Electron crystallography as a structural determination technique has grown dramatically in use over recent years. Improvements in microscopes, equipment, practical techniques, computation facilities and image processing methods are reflected in the increasing number of near-atomic resolution structures that have been published.In this review we shall summarize the techniques involved in structure determination of soluble proteins using electron crystallography. Many soluble protein structures have been investigated in this manner over the past two decades. Here we present several examples where a variety of approaches have been used to gradually increase the information obtained. 相似文献
4.
Ambrose D Arroyo C Bachman M Connor D Eckhause M Graessle S Hancock AD Hartman K Hebert M Hoff CH Hoffmann GW Irwin GM Kane JR Kanematsu N Kuang Y Lang K Lee R Martin RD McDonough J Milder A Molzon WR Pommot-Maia M Riley PJ Ritchie JL Rubin PD Vassilakopoulos VI 《Physical review letters》2000,84(7):1389-1392
We report results from Experiment 871, performed at the BNL AGS, of a measurement of the branching ratio K(0)(L)-->&mgr;(+)&mgr;(-) with respect to the CP-violating mode K(0)(L)-->pi(+)pi(-). This experiment detected over 6200 candidate &mgr;(+)&mgr;(-) events, a factor of 6 more than that seen in all previous measurements combined. The resulting branching ratio gamma(K(0)(L)-->&mgr;(+)&mgr;(-))/gamma(K(0)(L)-->pi(+)pi(-)) = (3. 474+/-0.057)x10(-6) leads to a branching fraction B(K(0)(L)-->&mgr;(+)&mgr;(-)) = (7.18+/-0.17)x10(-9), which is consistent with the current world average, and reduces the uncertainty in this decay mode by a factor of 3. 相似文献
5.
R. Mateva KR. Zhilkova G. Zamfirova R. Díaz‐Calleja A. Garcia‐Bernabé 《Journal of Polymer Science.Polymer Physics》2010,48(23):2518-2529
The molecular dynamics of new poly (ω‐dodecalactam‐co‐ε‐caprolactam‐co‐propylene oxide) copolymers (DL/CL/PAC) has been investigated by using dynamic mechanical thermal analysis (DMTA) and dielectric relaxation spectroscopy (DRS) measurements. The copolymers were synthesized via anionic polymerization of relevant lactams activated with carbamoyl derivatives of telechelic hydroxyl terminated polypropylene oxide with isophorone diisocyanate (PAC). The calorimetric, X‐ray diffraction, and DMTA measurements were performed to recognize the influence of the composition ratio and the type of PAC on the physical, thermal, and mechanical properties of the synthesized copolymers. The DRS was used to study the frequency dependence of the dielectric permittivity of some isotherms from ?110 to 145 °C. Copolymerization of ε‐caprolactam with about 10 wt % ω‐dodecalactam results in a copolymer that has lower water absorption, a melting point close to that of polyamide 6 and has a high enough degree of crystallinity in respect to high storage modulus. Five dielectric relaxations have been observed in the dielectric spectra, three at lower temperature and two at higher temperature. The copolymers have two glass transition temperatures for polyamide segments and polyether blocks, indicating microphase separation in the copolymers. Other studies directed toward molecular dynamics of polyamide DL/CL/PAC copolymers have not been reported. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010 相似文献
6.
G. Baroni S.Di. Liberto F. Meddi S. Petrera G. Romano M. Juric O. Adamovic I. Otterlund G. Baumann R. Devienne H. Areti C.J.D. Hebert J. Hebert J. Lory C. Meton D. Schune B. Willot G. Rey 《Nuclear Physics B》1976,103(2):213-220
The single- and two-particle inclusive rapidity distributions for proton-nucleus interactions at 300 GeV in nuclear emulsions are presented. The analysis of the data with the two-particle rapidity correlation function R(ν1, ν2) shows clear evidence of short range correlations. A remarkable asymmetry between projectile and target hemisphere is found. 相似文献
7.
The nature of asymmetry in reverse osmosis membranes 总被引:1,自引:0,他引:1
8.
The CIMPA Research School on Mathematical Models for Security Applications was dedicated to the memory of Emeritus Professor Mirka Miller, who suggested that it be held in Havana. Mirka Miller, member of the editorial board of Mathematics in Computer Science, devoted her research to Graph Theory and Data Security, fields where she made important and beautiful contributions. 相似文献
9.
K. Fröhlich T. Franke R. Gellermann D. Hebert H. Jordan 《Isotopes in environmental and health studies》2013,49(9):355-360
This paper presents results of a study carried out in order to assess the applicability of 32Si for groundwater dating. Measurements of 32Si in soil samples of the unsaturated zone, of drainage waters and plant material give a basis for estimating the 32Si initial concentration in groundwater. Different aquifers with groundwater of young and moderate ages have been selected for groundwater studies. For obtaining independent age information tritium was found to be a suitable reference isotope. A quantitative interpretation of the 32Si data is generally complicated by geochemical processes, preferably in the unsaturated zone. Favourable conditions concerning the use of 32Si in hydrogeology seem to exist in phreatic sandy aquifers, in limestone aquifers, and, depending on the thickness and composition of the unsaturated zone, in sandstone aquifers. Further improvements of the 32Si method needs a better understanding of the geochemical processes affecting this isotope. 相似文献
10.
D. Hebert K. Froöhlich A. Andreeff 《Isotopes in environmental and health studies》2013,49(10):358-361
Aufbau, Arbeitsweise und Eigenschaften einer Apparatur, mit der naturliche l4C-Aktiviäten in Grund- und Oberflächenwässern gemessen werden können, werden beschrieben. Die Messung erfordert 3 Arbeitsschritte: Probenahme, Synthese von Benzol, welches dann den Probenkohlenstoff enthält, und Messung der 14C-Aktivität in einem Flüssigkeitsszintillationszähler. Die Apparatur kann zur Datierung von Wasserproben im Altersbereich zwischen 200 und 37000 a verwendet werden. 相似文献