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排序方式: 共有329条查询结果,搜索用时 15 毫秒
1.
Dušan Hemzal 《Czechoslovak Journal of Physics》2006,56(12):1467-1479
In this article, general idea of focusing is studied within the framework of optics extension into general relativity (covariant optics). In a configuration of static spacetime, the general, mathematically rigorous treatment of rays, wavefronts and caustics
of spherical symmetry is presented, particularly with regard to problems of obtaining them within general relativity. An original
result is the aberration formulation to covariant optics, whose application is given in this paper; a particular solution
of Einstein equations is finally chosen to provide concrete, exact results of cluster focal length and its aberration structure.
In this way, a gravitational lensing situation is shown to be a true lens. 相似文献
2.
Phase-Locked Fibre Array for Coherent Combination and Atmosphere Aberration Compensation 总被引:1,自引:0,他引:1
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We report a fibre amplifier array that not only achieves coherent beam combination by compensation of phase noises of fibre amplifier, but also accomplishes correction of atmosphere aberration. It is of master-oscillatormultiple-amplifier (MOPA) configuration, which can be phase-locked by the multidither principle or heterodyne detection principle. First laboratory experiments of atmosphere aberration compensation of a three-element fibre amplifier array are reported. The atmosphere aberration is created by a phase screen in the experiment. The phase changes of the beam, which are introduced by the fibre amplifier and the phase screen, are both detected by the heterodyne detection method. Phase modulators are controlled to compensate for the phase in the three paths. No matter whether there is a phase screen producing atmosphere aberration or not, the dim dynamic interference fringes in the far field turn to a clear and stable pattern, and the peak intensity is maximized. It is indicated that the fibre amplifier array is phase-locked, and coherent combination of the three beams is achieved. It can be used not only to obtain high power fibre laser array but also in laser space communication. 相似文献
3.
B. Aspacher W. Frank P. Kizler K. Maier 《Applied Physics A: Materials Science & Processing》1994,59(4):339-348
In previous Perturbed-Angular-Correlation (PAC) studies of the - emission of 111In probe nuclei in cold-worked or particle-irradiated nickel, it has been found that thermal annealing in the temperature regime of recovery stage III leads to the formation of so-called C-defects (Cubic defects). This is indicated by the occurrence of a new frequency of about 80 Mrad/s, in addition to the frequency (200 Mrad/s) that is due to 111In on substitutional sites. Obviously, the C-defects are complexes consisting of 111In and the intrinsic point-defect species that migrates freely in recovery stage III. Therefore, they have played an important rôle in the long-standing controversy on whether the recovery-stage-III defects are vacancies (one-interstitial model) or self-interstitials (two-interstitial model). The present paper reports on a novel experimental effort to reveal the nature of the C-defects by combining PAC studies on nickel samples differently pretreated in a systematic way, investigations of the Extended X-ray Absorption Fine Structure (EXAFS) on In-doped nickel, and measurements of the decay rate of 111In nuclei in the Electron-Capture-Induced Decay (ECID). On the basis of the results of these experiments it is concluded that the defects trapped by substitutional 111In atoms (Ins) in recovery stage III are self-interstitials (I), as expected according to the two-interstitial model. Moreover, there is evidence that the C-defects are In interstitials on tetrahedral sites (Ini) that form exclusively in the vicinity of the specimen surface from Ins – I pairs via the reaction Ins+I Ini. 相似文献
4.
R. Schaub G. Pensl M. Schulz C. Holm 《Applied Physics A: Materials Science & Processing》1984,34(4):215-222
Hall effect and conductivity measurements are performed on Te-doped silicon in the temperature range 30KT800K. A Hall equipment suited for high temperatures up to 800 K has been constructed. The temperature dependence of the free electron concentration is analyzed for Te-doped silicon including one double-donor and several monovalent donor species. A deep level with an electrical activation energy of 200 meV is determined from the saturation of the free electron concentration at temperatures above 400 K. This level represents the first ionization stage of the Te double-donor. The second ionization stage is estimated to have an activation energy of 440 meV. The maximum electrically active Te concentration obtained is 5×1016cm–3. Three different shallow donor states are resolved in the low-temperature range. The concentrations of these shallow donors are partially sensitive to a subsequent heat-treatment. 相似文献
5.
Leitner Christian Hess Johann Galhaup Christiane Ludwig Roland Nidetzky Bernd Kulbe Klaus D. Haltrich Dietmar 《Applied biochemistry and biotechnology》2002,98(1-9):497-507
The wood-degrading fungus Trametes multicolor secretes several laccase isoforms when grown on a simple medium containing copper in the millimolar range for stimulating
laccase synthesis. The main isoenzyme laccase II was purified to apparent homogeneity from the culture supernatant by using
anion-exchange chromatography and gel filtration. Laccase II is a monomeric glycoprotein with a molecular mass of 63 kDa as
determined by sodium dodecylsulfate polyacrylamide gel electrophoresis, contains 18% glycosylation, and has a pI of 3.0. It oxidizes a variety of phenolic substrates as well as ferrocyanide and iodide. The pH optimum depends on the substrate
employed and shows a bell-shaped pH activity profile with an optimum of 4.0 to 5.0 for the phenolic substrates, while the
nonphenolic substrates ferrocyanide and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonate) show a monotonic pH profile with
a rate decreasing with increasing pH. 相似文献
6.
Thaís Silva da Rocha Alessandro de Lima Jurandy do Nascimento Silva Geni Rodrigues Sampaio Rosana Aparecida Manlio Soares Freitas Renan Danielski Adriano Costa de Camargo Fereidoon Shahidi Elizabeth Aparecida Ferraz da Silva Torres 《Molecules (Basel, Switzerland)》2022,27(3)
Jua (juá in Portuguese) is an underexplored fruit from Brazil’s northeast. This fruit is rich in antioxidant substances. However, there is a dearth of information about jua’s bioactive potential. The present study evaluated two extraction methods (continuous agitation and ultrasound-assisted extraction—UAE) and employed three different solvents (water, ethanol, and acetone) to efficiently recover soluble phenolic compounds. Aqueous extracts obtained by UAE showed the highest total phenolic content (TPC) and antiradical activity. Besides being an eco-friendly procedure, extraction and/or solubility in an aqueous medium is also important for food application. Ellagic acids were the predominant phenolics (80%) found in aqueous jua pulp extract obtained by UAE, as determined by HPLC, while its TPC was 405.8 gallic acid equivalent per gram of fruit. This extract also exhibited a higher scavenging activity towards peroxyl radicals when compared to that of several other fruits from the literature, including grape, strawberry, cranberry, and walnuts, which are known references in terms of antioxidants. This is the first report that demonstrates jua pulp’s potential as an alternative source of ellagic acid and other phenolic acids and flavonoids. Therefore, the outcome of this study provides new information that can be useful for functional food and nutraceutical industries. 相似文献
7.
六味地黄丸的高效液相色谱/电喷雾电离-质谱分析 总被引:15,自引:0,他引:15
建立了高效液相色谱/电喷雾电离-质谱定性分析六味地黄丸的方法,通过2级质谱识别了其中的9种化学成分。色谱条件为:Zorbax SB-C18色谱柱;乙腈-水二元高压梯度洗脱;二极管阵列检测器,设定波长254 nm;流速1 mL/min。质谱条件为:Agilent离子阱质谱仪;电喷雾电离(ESI)离子源;负离子检出模式。结果表明,六味地黄丸的总离子流色谱图比紫外色谱图具有更强的特征性,以质谱作为检测器是一种很好的研究中药指纹图谱的方法。 相似文献
8.
N. G. Fytas A. Malakis 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(1):111-120
The one-parametric Wang-Landau (WL) method is
implemented together with an extrapolation scheme to yield
approximations of the two-dimensional (exchange-energy,
field-energy) density of states (DOS) of the 3D bimodal
random-field Ising model (RFIM). The present approach generalizes
our earlier WL implementations, by handling the final stage of the
WL process as an entropic sampling scheme, appropriate for the
recording of the required two-parametric histograms. We test the
accuracy of the proposed extrapolation scheme and then apply it to
study the size-shift behavior of the phase diagram of the 3D
bimodal RFIM. We present a finite-size converging approach and a
well-behaved sequence of estimates for the critical disorder
strength. Their asymptotic shift-behavior yields the critical
disorder strength and the associated correlation length's
exponent, in agreement with previous estimates from ground-state
studies of the model. 相似文献
9.
Vollmer A Jurchescu OD Arfaoui I Salzmann I Palstra TT Rudolf P Niemax J Pflaum J Rabe JP Koch N 《The European physical journal. E, Soft matter》2005,17(3):339-343
We use ultraviolet photoelectron spectroscopy to investigate the effect of oxygen and air exposure on the electronic structure of pentacene single crystals and thin films. It is found that O2 and water do not react noticeably with pentacene, whereas singlet oxygen/ozone readily oxidize the organic compound. Also, we obtain no evidence for considerable p-type doping of pentacene by O2 at low pressure. However, oxygen exposure lowers the hole injection barrier at the interface between Au and pentacene by 0.25 eV, presumably due to a modification of the Au surface properties. 相似文献
10.
Van Roie B Denolf K Pitsi G Thoen J 《The European physical journal. E, Soft matter》2005,16(4):361-364
We investigated the smectic-A-hexatic-B (SmA-HexB) transition in the liquid-crystal n-hexyl-4-n-pentyloxybiphenyl-4-carboxilate (65OBC) with adiabatic scanning calorimetry. We were able to prove in a direct way that this transition is indeed very weakly first order, as was already suggested in the literature. The latent heat at the transition was determined to be HL = 0.04±0.02 J/g. Our experiments confirm the high value for the heat capacity critical exponent earlier reported, yielding = 0.64±0.05. 相似文献