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991.
Vlastimil Matějec Ivan Kašík Daniela Berková Miloš Hayer Jiří Kaňka 《Journal of Sol-Gel Science and Technology》1998,13(1-3):617-621
Optical cores of preforms for drawing optical fibers doped with Er3+ and Yb3+ were fabricated by the sol-gel method with the aim of increasing the thickness of glass layers coated in a single coating cycle and to determine the relation between the preparation conditions and optical properties of the fibers. Al2O3-P2O5-SiO2 and TiO2-P2O5-SiO2 glasses have been studied as matrices for entrapping the rare-earth elements. Input sols have been prepared from silicon and titanium alkoxides, AlCl3, ErCl3, YbCl3, POCl3, water and a modifier under acidic catalysis of HCl. The sols were coated on the inner wall of a silica substrate tube and the gel layers were sintered at high temperatures up to 2000°C after which the tube was collapsed into the preform. Continuous and homogenous glass films with the maximum thickness of about 8 m were fabricated. The influence of high-temperature heat treatment of the layers on their composition and optical attenuation was observed. The amplified stimulated emission of Er3+ around 1.55 m was measured under the excitation of the fibers by an Nd : YAG laser at 1.064 m. 相似文献
992.
Zs. Podolyák G.F. Farrelly P.H. Regan A.B. Garnsworthy S.J. Steer M. Górska J. Benlliure E. Casarejos S. Pietri J. Gerl H.J. Wollersheim R. Kumar F. Molina A. Algora N. Alkhomashi G. Benzoni A. Blazhev P. Boutachkov A.M. Bruce L. Caceres I.J. Cullen A.M. Denis Bacelar P. Doornenbal M.E. Estevez Y. Fujita W. Gelletly H. Geissel H. Grawe J. Gr?bosz R. Hoischen I. Kojouharov S. Lalkovski Z. Liu K.H. Maier C. Mihai D. Mücher B. Rubio H. Schaffner A. Tamii S. Tashenov J.J. Valiente-Dobón P.M. Walker P.J. Woods 《Physics letters. [Part B]》2009
993.
Mustafa Versan Kök Kiymet Gizem Gul 《Journal of Thermal Analysis and Calorimetry》2013,114(1):269-275
In this study, two Turkish crude oils from southeastern part of Turkey and their saturate, aromatic, resin fractions were analyzed by differential scanning calorimetry (DSC). The experiments were performed at three different heating rates (5, 10, 15 °C min?1) under air atmosphere. Two different reaction regions were observed from DSC curves due to the oxidative degradation of crude oil components. In the first reaction region, it was deduced that the free moisture, volatile hydrocarbons were evaporated from the crude oils, light hydrocarbons were burned, and fuel was formed. The second reaction region was the main combustion region where the fuel was burned. From DSC curves, it was observed that as the sample got heavier, the heat of the reaction increased. Saturates gave minimum heat of reaction. As the heating rate increased, shift of peak temperatures to high values and extended reaction region intervals were observed. The kinetic analysis of the crude oils and their fractions were also performed using ASTM E-698 and Borchardt and Daniels methods, respectively. Activation energy values of the crude oil samples and the fractions’ high-temperature oxidation region were close to each other and varied between 67 and 133 kJ mol?1 in ASTM and 35 and 154 kJ mol?1 in Borchardt and Daniels methods, respectively. 相似文献
994.
Muharrem Diner Namk
zdemir Sinan Saydam
zer Bekarolu Orhan Büyükgüngr 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(2):o89-o91
The molecule of the title compound, C18H24N2O2, resides on a crystallographic inversion centre. The molecule adopts a transoid conformation with respect to the central C—C single bond and is in the meso form. A polarimetric study of the compound did not show any optical activity, indicating that the compound is a racemic mixture entirely consistent with the centrosymmetric space group. In the molecule, there is one intramolecular N—H⋯O interaction, resulting in the formation of a five‐membered ring. In the crystal structure, intermolecular O—H⋯N and C—H⋯O interactions are also observed. These interactions form an R22(9) ring and one‐dimensional linear chains of edge‐fused rings running parallel to the [010] direction, which stabilize the crystal packing. 相似文献
995.
Local regularity of axially symmetric solutions to the Navier–Stokes equations is studied. It is shown that under certain natural assumptions there are no singularities of Type I. 相似文献
996.
M. Jelínek W. Kulisch M.P. Delplancke-Ogletree J. Lancok L. Jastrabík D. Chvostová C. Popov J. Bulír 《Applied Physics A: Materials Science & Processing》2001,73(2):167-170
Nitrogen-rich carbon nitride films were prepared by three different deposition methods on fused silica, stainless steel and
silicon cantilever substrates. Their optical properties were studied by spectroscopic ellipsometry and UV spectrometry. Mechanical
properties such as plastic and Vickers microhardness, Young’s modulus, adhesion and film stress were also tested. The results
were compared with the properties of films with lower nitrogen concentrations.
Received: 26 January 2001 / Accepted: 29 January 2001 / Published online: 3 May 2001 相似文献
997.
998.
Misfit‐Layered Bi1.85Sr2Co1.85O7.7−δ for the Hydrogen Evolution Reaction: Beyond van der Waals Heterostructures
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Dr. Chun Kiang Chua Prof. Zdeněk Sofer Ondřej Jankovský Prof. Martin Pumera 《Chemphyschem》2015,16(4):769-774
Recent research on stable 2D nanomaterials has led to the discovery of new materials for energy‐conversion and energy‐storage applications. A class of layered heterostructures known as misfit‐layered chalcogenides consists of well‐defined atomic layers and has previously been applied as thermoelectric materials for use as high‐temperature thermoelectric batteries. The performance of such misfit‐layered chalcogenides in electrochemical applications, specifically the hydrogen evolution reaction, is currently unexplored. Herein, a misfit‐layered chalcogenide consisting of CoO2 layers interleaved with an SrO–BiO–BiO–SrO rock‐salt block and having the formula Bi1.85Sr2Co1.85O7.7?δ is synthesized and examined for its structural and electrochemical properties. The hydrogen‐evolution performance of misfit‐layered Bi1.85Sr2Co1.85O7.7?δ, which has an overpotential of 589 mV and a Tafel slope of 51 mV per decade, demonstrates the promising potential of misfit‐layered chalcogenides as electrocatalysts instead of classical carbon. 相似文献
999.
Lísa M Netušilová K Franěk L Dvořáková H Vrkoslav V Holčapek M 《Journal of chromatography. A》2011,1218(42):7499-7510
Fatty acid (FA) and triacylglycerol (TG) composition of natural oils and fats intake in the diet has a strong influence on the human health and chronic diseases. In this work, non-aqueous reversed-phase (NARP) and silver-ion high-performance liquid chromatography with atmospheric pressure chemical ionization mass spectrometry detection and gas chromatography with flame-ionization detection (GC/FID) and mass spectrometry detection are used for the characterization of FA and TG composition in complex samples of animal fats from fallow deer, red deer, sheep, moufflon, wild boar, cock, duck and rabbit. The FA composition of samples is determined based on the GC/FID analysis of FA methyl esters. In total, 81 FAs of different acyl chain length, double bond (DB) number, branched/linear, cis-/trans- and DB positional isomers are identified. TGs in animal fats contain mainly monounsaturated and saturated FAs. High amounts of branched and trans-FAs are observed in the samples of ruminants. In NARP mode, individual TG species are separated including the separation of trans- and branched TGs. Silver-ion mode provides the separation of TG regioisomers, which enables the determination of their ratios. Great differences in the preference of unsaturated and saturated FAs in the sn-2 position on the glycerol skeleton are observed among individual animal fats. Unsaturated FAs are preferentially occupied in the sn-2 position in all animal samples except for wild boar with the strong preference of saturated FAs in the sn-2 position. 相似文献
1000.
Jaroslav Šesták 《Journal of Thermal Analysis and Calorimetry》2005,81(2):501-502
S. E. J_rgensen and Yu. M. Svirezhev Towards a Thermodynamic Theory for Ecological Systems Elsevier, Amsterdam 2004, Price: paperback 85€; hardbound 140€, 350 (A4 size) pages 相似文献