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941.
Sebastian?D?ringEmail author Stefan?Schmidt David?Reifert Martin?Feltz Manuel?Monecke Noor?Hasan Volker?Tympel Frank?Schmidl Jan?Engelmann Fritz?Kurth Kazumasa?Iida Ingolf?M?nch Bernhard?Holzapfel Paul?Seidel 《Journal of Superconductivity and Novel Magnetism》2015,28(3):1117-1121
We investigate the iron-based superconductor Ba(Fe 1?x Co x ) 2As 2 (Ba-122) regarding its superconducting properties and possible applications. Therefore, Ba-122 thin films are used as base electrode to prepare different kinds of hybrid Josephson junctions with a counter electrode of the conventional superconductor Pb. Additionally, we use both c-axis and a b-plane transport geometries and different kinds of barriers like interface-engineered surfaces, sputtered titanium oxide and gold layers. Temperature dependent I– V characteristics as well as magnetic field dependence and microwave response of the junctions are shown. The examined I– V characteristics and I c R n– T behaviours of each junction type are compared and described according to the electrical behaviour of the respective normal conducting or insulating barrier. While the I c R n product of the interface-engineered barrier junction was 12 μV and the planar junction with Au barrier showed 18 μV, we could increase the I c R n to 90 μV for planar TiO x barrier junctions. 相似文献
942.
How Do MNC Headquarters Add Value? 总被引:1,自引:0,他引:1
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This focused issue examines the role of headquarters in modern multinational corporations (MNCs). We examine how headquarters
add value, which roles they play and how existing theory needs to be modified in light of recent developments. 相似文献
943.
We demonstrate depth-resolved spectral absorption measurements in the wavelength range from 750 to 850 nm using a broadband light source consisting of three spectrally shifted superluminescent light-emitting diode modules and a low-cost spectrometer-based Fourier-domain optical coherence tomography system. We present the theoretical model and experimental verification of interferences between autocorrelation terms and the signal carrying cross-correlation terms, strongly affecting the absorption measurements. A simple background subtraction, minimizing the artifacts caused by the interferences of autocorrelation and cross-correlation terms, is presented. 相似文献
944.
Inversion of the elution order of enantiomers caused by enthalpy-entropy compensation at the isoenantioselective temperature (Tiso) was experimentally observed by gas chromatography on the diamide-type chiral stationary phase (CSP), Chirasil-L-Val-C11, with N-ethoxycarbonyl propylamide (ECPA) derivatives of a number of alpha-amino acids. For the first time, a clear visual representation of the increase of the apparent enantioseparation factor alpha app from 1.00 to 1.08 as the temperature is raised from 120 to 170 degrees C is presented. The increase of alpha app is accompanied by a concomitant reduction of the retention factors of the enantiomers. The Tiso values were in the range from 110 to 130 degrees C depending on the nature of the alpha-amino acid. On the contrary, the Tiso values of the N(O)-trifluoroacetyl ethyl ester derivatives (TFA-Et) of the same alpha-amino acids were approximately 80 degrees higher than that of ECPA derivatives. The comprehensive thermodynamic investigation of the enantioseparation of ECPA and TFA-Et derivatives of valine and alanine using the retention increment method showed that the Delta L,D(DeltaH) difference between the diastereomeric selector-selectand associates was almost the same for ECPA and TFA-Et derivatives despite a much stronger bonded selector-selectand association taking place for the ECPA derivatives. On the other hand, the Delta L,D(DeltaS) values were found to be more negative in the case of ECPA derivatives, resulting in the unusually low values of Tiso. A temperature-dependent inversion of the elution order of enantiomers was also observed on the cyclodextrin-type CSP, Chirasil-Dex, with TFA-Et derivatives of several alpha-amino acids. The Tiso values were in the range from 20 to 170 degrees C depending on the nature of the alpha-amino acid. The results obtained demonstrate the necessity to conduct temperature-dependent studies in order to optimize the enantiomeric separation of single racemates isothermally or of mixtures of racemates in temperature-programmed runs using enantioselective GC. It is also shown that consideration of the elution order of enantiomers and the value of the apparent enantioseparation factor alpha app alone, without performing temperature-dependent measurements, can easily lead to wrong conclusions regarding the enantiorecognition mechanism. 相似文献
945.
The interconversion of E and Z isomers of acetaldoxime 1 and butyraldoxime 2 have been investigated by comprehensive two-dimensional dynamic gas chromatography (DGCxDGC) and computer simulation. Time-resolved cryogenic modulation is capable of revealing the precise isomeric ratio as a fine structure under the dynamic elution profile, which is characterized in one-dimensional experiments by a plateau formation or peak coalescence caused by interconversion of the isomers during the separation process. The chromatographic theoretical plate model has been extended for the computer simulation of comprehensive two-dimensional dynamic chromatographic experiments. A novel program, ChromWin 2D, based on the new algorithm has been developed for computer simulation to evaluate and predict the elution profiles of DGCxDGC experiments. ChromWin 2D allows the determination of rate constants and barriers of isomerization, epimerization, and enantiomerization processes occurring during chromatographic separations. The Eyring activation parameters of the E/Z and Z/E isomerization barriers in the presence of the stationary phase BP21 (poly(ethylene glycol) terephthalate terminated) were determined by temperature-dependent experiments between 80 and 90 degrees C for 1 and 70 and 130 degrees C for 2. The thermodynamic Gibbs free energy of the E/Z equilibrium of the isomers has been determined from the time-resolved chromatograms by cryogenic modulation. The method described here constitutes a new and important tool for the determination of isomerization barriers, which are of great interest, for example, for the quantitative determination of derivatized aldehydes, such as dinitrophenylhydrazine derivatives, in trace analysis. 相似文献
946.
Majda?Sfiligoj SmoleEmail author Zdenka?Per?in Tatjana?Kre?e Karin?Stana Kleinschek Volker?Ribitsch Susanne?Neumayer 《Materials Research Innovations》2003,7(5):275-282
Regenerated cellulose fibres have had an important role to play in the man-made fibre field. The very special characteristics of different types of regenerated cellulose fibres, e.g. mechanical properties, sorption characteristics, and aesthetics were conditioned by the differences in their fine structure due to fibre formation processes. Additionally, the finishing processes could influence the fibre structure. A study was done of the crystalline structures of a solvent-spun cellulose fibre type (Lenzing Lyocell), made according to the NMMO process, and two conventional cellulosic fibre types, made by the viscose process (Lenzing Viscose and Lenzing Modal). The fibres were pre-treated (bleached and slack mercerised) and structural changes were followed by wide angle and small angle x-ray scattering (WAXS and SAXS), respectively. The periodical structure, determined by long spacing, was nearly the same in all the different types of fibres. A slight increase was observed after the treatment of viscose and modal fibres, but an unpronounced fall of a long period accompanied the pre-treatment of lyocell fibres. Some changes in crystallinity and crystalline orientation occurred due to the treatment conditions. The structural changes were correlated to the iodinesorption and mechanical properties. 相似文献
947.
Speckle pattern decorrelation reduces the accuracy of interferometric shape and deformation measurements. We introduce a technique for the reduction of speckle noise in digital holography. The method is not based on classical filtering techniques such as median filters. Instead it utilizes the shift theorem of the Fourier transform. For this method several holograms of the same object under test are recorded. The reconstruction leads to a set of object wave fields with different speckle patterns. A proper averaging procedure, taking into account the properties of the wrapped phases, leads to an improvement of the accuracy in the resulting phase difference. The theory of the applied method is described and our first results for technical components with an improvement of accuracy up to 1/57 of the wavelength are presented. 相似文献
948.
Gideon P. A. G. van Zijl Volker Slowik Romildo D. Toledo Filho Folker H. Wittmann Hirozo Mihashi 《Materials and Structures》2016,49(4):1175-1189
Two of the main activities of RILEM Technical Committee 208-HFC Subcommittee 2 were the preparation and publication of the state-of-the-art report on durability of strain hardening cement-based composites (SHCC), and the performance of comparative laboratory testing on SHCC. In this paper the comparative mechanical tests are reported, as performed in laboratories of five participating institutions. The purpose was to investigate and compare the crack patterns in terms of crack widths and spacing, and subsequently to make recommendations for a suitable test setup and procedure towards characterizing cracking in this class of materials. Such standardized procedures are required for future systematic and objective research towards durability of these materials in their in-service conditions, i.e. their resistance to deterioration processes in the cracked state. Standardized test procedures are also required for durability testing and guidelines for structural design with SHCC, which is the focus of follow-up committee activity in TC 240-FDS. 相似文献
949.
Stephan Günzel Stefan Hickmann Christian Wittemeyer Volker Trappe 《Advanced Engineering Materials》2012,14(10):867-872
Short glass fiber reinforced polyamides are increasingly used in automotive applications. Concepts and models are needed, which enable the prediction of the structural durability. The fiber orientation and the content of moisture have a major influence on the fracture mechanical properties and on the damage mechanisms. The complex crack growth behavior was investigated and described in an empirical model. 相似文献
950.
Florez L Herrmann C Cramer JM Hauser CP Koynov K Landfester K Crespy D Mailänder V 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(14):2222-2230
Among several nanoparticle properties, shape is important for their interaction with cells and, therefore, relevant for uptake studies and applications. In order to further investigate such characteristics, fluorescently labeled spherical polymer nanoparticles are synthesized by free-radical polymerization via the miniemulsion process. The spherical nanoparticles are subsequently submitted to controlled mechanical deformation to yield quasi-ellipsoidal polymeric nanoparticles with different aspect ratios. The uptake behaviors of spherical and non-spherical particles with equal volume are investigated qualitatively and quantitatively by electron microscopy, confocal laser scanning microscopy, and flow cytometry measurements. Non-spherical particles show fewer uptake by cells than their spherical counterparts with a negative correlation between aspect ratio and uptake rate. This is attributed to the larger average curvature radius of adsorbed non-spherical particles experienced by the cells. 相似文献
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