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171.
Effect of low-energy ion bombardment on the crystal structure and superconductivity of niobium films
V. V. Naumov V. F. Bochkarev A. A. Goryachev A. S. Kunitsyn E. I. Il’yashenko P. E. Goa T. H. Johansen 《Technical Physics》2004,49(4):426-430
The effect of ion bombardment on the growth of Nb films and their crystal structure is investigated. Epitaxial niobium films with the (001) orientation are grown on (01i2) Al2O3 substrates heated to 600°C and biased at ?20 V. Niobium films with pronounced axial texture in the [110] direction are grown on water-cooled Sitall (devitrified glass such as Pyroceram) substrates. In Nb films biased at ?50 V, which are in the superconducting state, the motion of individual magnetic vortices is observed with a magnetooptic indicator. 相似文献
172.
The problem of determining directional coupling between neuronal oscillators from their time series is addressed. We compare performance of the two well-established approaches: partial directed coherence and phase dynamics modeling. They represent linear and nonlinear time series analysis techniques, respectively. In numerical experiments, we found each of them to be applicable and superior under appropriate conditions: The latter technique is superior if the observed behavior is "closer" to limit-cycle dynamics, the former is better in cases that are closer to linear stochastic processes. 相似文献
173.
Landa A Richter B Johansen RL Minkkilä A Jørgensen KA 《The Journal of organic chemistry》2007,72(1):240-245
A general catalytic oxo-hetero-Diels-Alder reaction for pro-chiral aldehyde and ketone N-oxy-pyridines is presented. The catalytic and asymmetric oxo-hetero-Diels-Alder reaction of electron-rich dienes with N-oxy-pyridine-2-carbaldehyde and ketone derivatives, catalyzed by chiral copper(II)-bisoxazoline complexes, gives optically active six-membered oxygen heterocycles in moderate to good yields and with excellent enantioselectivities. 相似文献
174.
By using Solid Phase Micro-Extraction (SPME) and Capillary Gas Chromatography (CGC) a method was developed to analyze hetero aromatic compounds (NSO) in water. Compounds with nitrogen, sulfur, or oxygen in the aromatic ring system are found in creosotecontaminated groundwater. NSO are highly water-soluble, toxic, and have adverse organoleptic characteristics. SPME is a fast, simple, and solvent-free sample preparation technique that involves exposing a polymer coated fiber to a sample to extract contaminants. Different fiber coatings were tested, and polyacrylate was found to extract NSO in the highest amounts and to be most versatile. Extraction was strongly enhanced by salting. The optimized SPME method combined with CGC coupled to an ion trap mass spectrometer (ITMS) has detection limits of 20–40 ng/L for the semi-volatile and 1–10 μg/L for the volatile NSO, response linear with respect to concentrations over three orders of magnitude, and precision of 3–14% relative standard deviation. The method was evaluated using real creosote-contaminated groundwater samples and feasibility was demonstrated. SPME-CGC/ITMS allows an unequivocal identification and quantification at a low NSO level in environmental samples. 相似文献
175.
We propose MultiScale Singularity Trees (MSSTs) as a structure to represent images, and we propose an algorithm for image comparison based on comparing MSSTs. The algorithm is tested on 3 public image databases and compared to 2 state-of-theart methods. We conclude that the computational complexity of our algorithm only allows for the comparison of small trees, and that the results of our method are comparable with state-of-the-art using much fewer parameters for image representation. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
176.
177.
A. Johansen D. Sornette 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):319-328
The Nasdaq Composite fell another % on Friday the 14'th of April 2000 signaling the end of a remarkable speculative high-tech bubble starting in spring 1997.
The closing of the Nasdaq Composite at 3321 corresponds to a total loss of over 35% since its all-time high of 5133 on the
10'th of March 2000. Similarities to the speculative bubble preceding the infamous crash of October 1929 are quite striking:
the belief in what was coined a “New Economy” both in 1929 and presently made share-prices of companies with three digits
price-earning ratios soar. Furthermore, we show that the largest draw downs of the Nasdaq are outliers with a confidence level
better than 99% and that these two speculative bubbles, as well as others, both nicely fit into the quantitative framework
proposed by the authors in a series of recent papers.
Received 3 May 2000 相似文献
178.
179.
Indoles, when treated with dimethyl diazomalonate under catalysis by Cu(acac)(2), undergo C-H insertion reactions regioselectively depending on the substitution pattern on the indole moiety. Indoles where the 3-position is substituted give high yields of the C2-H insertion product. Microwave conditions are also disclosed which show comparable yields with reduced reaction times. 相似文献
180.
Humberto Rodriguez-Alvarez Roland Mainz Bjoern Marsen Hans-Werner Schock 《Journal of solid state chemistry》2010,183(4):803-7196
We monitor the recrystallization of Cu-poor CuInS2 thin films assisted by pure Cu or pure Ag by means of real-time synchrotron-based polychromatic X-ray diffraction. In both cases a new microstructure is formed accompanied by an increase in grain size. In the case of Cu, the onset temperature of the thin-film recrystallization is higher than 370 °C. In the case of Ag, the thin-film recrystallization comes to an end at 270 °C. The Ag-assisted recrystallization occurs in the presence of the body-centered cubic β-Ag2S phase. We find that domain growth and diffusion of silver into the film occur simultaneously. 相似文献