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排序方式: 共有216条查询结果,搜索用时 15 毫秒
41.
Th. Arnd Kühne Sven Odén U. Pratolongo Th. Schloesing E. W. Hilgard G. Richter A. Atterberg J. König J. Hasenbäumer O. Kleine-Möllhof D. J. Hissink M. L. Plonski Ch. J. Moore W. H. Fry H. E. Middleton J. B. Rather O. Lemmermann L. Fresenius L. J. Gillespie L. E. Wise N. M. Comber Ch. Brioux E. A. Fisher Neuman O. Nolte 《Analytical and bioanalytical chemistry》1924,64(5-6):241-248
42.
A theoretical analysis of dynamic properties of freely suspended films of a SmC* α phase in an external electric field is performed within the ‘clock’ model, where the interactions up to nextnearest neighbours are considered. It is shown, that for an N-layer film, N amplitude and N phase fluctuation modes are present. The relaxation rates of the amplitude modes are in the MHz region, whereas the phase modes are typically in the kHz region. Magnitudes of the dielectric response and quasielastic light scattering cross-sections for individual modes are calculated as a function of an electric field applied along the smectic layers. 相似文献
43.
Th. Arnd Kühne Sven Odén U. Pratolongo Th. Schloesing E. W. Hilgard G. Richter A. Atterberg J. König J. Hasenbäumer O. Kleine-Möllhof D. J. Hissink M. L. Plonski Ch. J. Moore W. H. Fry H. E. Middleton J. B. Rather O. Lemmermann L. Fresenius L. J. Gillespie L. E. Wise N. M. Comber Ch. Brioux E. A. Fisher Neuman und O. Nolte 《Fresenius' Journal of Analytical Chemistry》1924,64(5-6):241-248
Ohne Zusammenfassung 相似文献
44.
Tamás Szücs Daniel Bemmerer Thomas Cowan Detlev Degering Zoltán Elekes Zsolt Fül?p Gy?rgy Gyürky Arnd Junghans Matthias K?hler Michele Marta Ronald Schwengner Andreas Wagner Kai Zuber 《The European Physical Journal A - Hadrons and Nuclei》2012,48(1):1-8
In order to reliably estimate the rate of a charged particle induced nuclear reaction in a non-explosive astrophysical scenario, its cross-section must be measured far below the Coulomb barrier. However, at the corresponding energies the cross-section values are very low, so that the experimental counting rate is dominated by cosmic-ray induced background, even if a suitable anticoincidence shield is applied. This problem can be overcome by performing an accelerator-based experiment in a deep underground site, as has been done with great success at the LUNA 0.4MV accelerator in Gran Sasso, Italy. Several underground accelerators with higher beam energy are in the planning phase worldwide. All of them are shielded by over 1000m of rock, a depth at which cosmic-ray effects are negligible for the purposes of nuclear astrophysics experiments. It is shown here that a combined approach, using a shallow-underground laboratory below 47m of rock and an active shield to veto surviving muons in simple detectors, results in a background level that is not far from that of deep underground sites. Data have been obtained using two ??traveling?? ??-detectors. They have been transported both shallow underground, to the Dresden Felsenkeller in Germany, and deep underground, to the Gran Sasso laboratory in Italy. As shallow-underground facilities are more easily accessible than deep-underground ones, the present finding holds the promise of greatly accelerated progress in the field of cross-section measurements for nuclear astrophysics. 相似文献
45.
Arnd Garsuch Alexander Panchenko Claudia Querner Andrey Karpov Sabine Huber Rüdiger Oesten 《Electrochemistry communications》2010,12(11):1642-1645
This paper reports about FeAgMo2O8 — a novel oxygen evolution catalyst material for secondary (rechargeable) metal–air batteries. Bifunctional air electrodes were made using FeAgMo2O8 as a charging catalyst for oxygen evolution reaction (OER) and silverized carbon black (Ag/C) was employed as a discharging catalyst for oxygen reduction reaction (ORR). Corresponding air electrodes were investigated using 10 M KOH as an electrolyte. At current densities between 20 and 50 mA per cm2 we observed discharging and charging voltages of 1.20 to 1.15 V and 1.96 to 2.05 V, respectively. 相似文献
46.
Simone Pentzien Andrea Conradi Robert Koter J?rg Krüger 《Applied Physics A: Materials Science & Processing》2010,101(2):441-446
Cleaning of cultural assets, especially fragile organic materials like paper, is a part of the conservation process. Laser
radiation as a non-contact tool offers prospects for that purpose. For the studies presented here, paper model samples were
prepared using three different paper types (pure cellulose, rag paper, and wood-pulp paper). Pure cellulose serves as reference
material. Rag and wood-pulp paper represent essential characteristics of the basic materials of real-world artworks. The papers
were mechanically soiled employing pulverized charcoal. Pure and artificially soiled paper samples were treated with laser
pulses of 28 fs (800 nm wavelength) and 8–12 ns (532 nm) duration in a multi pulse approach. Additionally, the cellulose reference
material was processed with 30 ps (532 nm) laser pulses. Damage and cleaning thresholds of pure and soiled paper were determined
for the different laser regimes. Laser working ranges allowing for removal of contamination and avoiding permanent modification
to the substrate were found. The specimens prior and after laser illumination were characterized by light-optical microscopy
(OM) and scanning electron microscopy (SEM) as well as multi spectral imaging analysis. The work extends previous nanosecond
laser cleaning investigations on paper into the ultra-short pulse duration domain. 相似文献
47.
In 1994, Jürgen Moser generalized Hénon’s area-preserving quadratic map to obtain a normal form for the family of four-dimensional, quadratic, symplectic maps. This map has at most four isolated fixed points. We show that the bounded dynamics of Moser’s six parameter family is organized by a codimension-three bifurcation, which we call a quadfurcation, that can create all four fixed points from none.The bounded dynamics is typically associated with Cantor families of invariant tori around fixed points that are doubly elliptic. For Moser’s map there can be two such fixed points: this structure is not what one would expect from dynamics near the cross product of a pair of uncoupled Hénon maps, where there is at most one doubly elliptic point. We visualize the dynamics by escape time plots on 2d planes through the phase space and by 3d slices through the tori. 相似文献
48.
We have measured the d.c. electric field dependence of the birefringence and conoscopic images for the smectic C* phase of a partially racemized ferroelectric chiral smectic liquid crystal CE-8. The experiments were performed using 50mu m thick homeotropic cells with lateral electrodes which created a d.c. electric field parallel to the smectic layers. The observed field induced birefringence shows a characteristic step-like behaviour which is due to the stepby-step unwinding of the helical structure in a sample with finite dimensions along the helical axis. In conoscopic observations we observe that these steps are associated with moving disclination lines that traverse the sample in the direction of the smectic layers. The observed electric field dependence of the birefringence is discussed in terms of the soliton-like unwinding of helical smectic structures and compared with the predictions of the Landau theory. A qualitatively good agreement is obtained. 相似文献
49.
50.
Reiner Figge Ute Patt-Siebel Elke Conradi Ulrich Müller Kurt Dehnicke 《无机化学与普通化学杂志》1988,558(1):107-113
Synthesis, I.R. Spectrum, and Crystal Structure of PPh4[OsCl4(NO)(NSCl)] Molten trithiazyl chloride reacts with OsCl3(NO) to yield a product mixture consisting mainly of S4N3[OsCl4(NO)(NSCl)] and S4N3Cl. Extraction of this mixture with a solution of tetraphenylphosphonium chloride in dichloromethane affords green (PPh4)2[OsCl5(NO)] · 2 CH2Cl2 and the red title compound. PPh4[OsCl4(NO)(NSCl)] was characterized by its IR spectrum and an X-ray crystal structure analysis (3001 independent observed reflexions, R = 0.048). Crystal data: monoclinic, space group P21/c, Z = 4, a = 1716, b = 1054, c = 1588 pm, β = 96.25°. The compound consists of PPh4⊕ cations and [OsCl4(NO)(NSCl)]? anions in which the nitrosyl and the chlorothionitrene ligands have a cis arrangement. Due to positional disorder the NO and NSCl groups are superimposed statistically in the structure model. 相似文献