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61.
Johan Kaarle Mikael Lindén Eeva-Leena Rautama Maarit Karppinen Hisao Yamauchi 《Hyperfine Interactions》2012,208(1-3):133-136
Polycrystalline samples of FeSe0.82 and FeSe0.5Te0.5 were synthesized using a solid-state reaction route. Bulk superconductivity was confirmed using SQUID magnetometry. The onset of T c was at 8.0 K for FeSe0.82 and 12.5 K for FeSe0.5Te0.5. Paramagnetic 57Fe Mössbauer spectra were recorded at temperatures between 5.4 and 320 K in transmission geometry. All spectra exhibited simple quadrupole splitting. For FeSe0.5Te0.5 a small drop in the quadrupole splitting was observed about T c upon cooling. Additionally, for both samples the isomer shift and the total absorption started to drop around T c , indicating a softening of the lattice. The drop is estimated to correspond to at least 60 K from the original Debye temperatures. 相似文献
62.
Esa Kokko Pirjo Pietikinen Jari Koivunen Jukka V. Seppl 《Journal of polymer science. Part A, Polymer chemistry》2001,39(21):3805-3817
Ethene was copolymerized (1) with 1,5‐hexadiene with rac‐ethylenebis(indenyl)zirconium dichloride/methylaluminoxane (MAO) used as a catalyst and (2) with 1,7‐octadiene with bis(n‐butylcyclopentadienyl)zirconium dichloride/MAO and rac‐ethylenebis(indenyl)hafnium dichloride (Et[Ind]2HfCl2)/MAO used as catalysts at 80 °C in toluene. The copolymer microstructure and the influence of diene incorporation on the rheological properties were examined. Ethene and 1,5‐hexadiene formed a copolymer in which a major fraction of the 1,5‐hexadiene was incorporated into rings and a small fraction formed 1‐butenyl branches. The copolymerization of ethene with 1,7‐octadiene resulted in a higher selectivity toward branch formation. Some of the branches formed long‐chain‐branching (LCB) structures. The ring formation selectivity increased with decreasing ethene concentration in the polymerization reactor. Melt rheological properties of the diene copolymers resembled those of metallocene‐catalyzed LCB homopolyethenes and depended on the vinyl content, the catalyst, and the polymerization conditions. At high diene contents, all three catalysts produced crosslinked polyethene. This was especially pronounced with Et[Ind]2HfCl2, where only 0.2 mol % 1,7‐octadiene in the copolymer was required to achieve significantly modified rheological properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3805–3817, 2001 相似文献
63.
Jari Toivanen 《PAMM》2007,7(1):1024001-1024002
Numerical methods are developed for pricing European and American options under Kou's jump-diffusion model which assumes the price of the underlying asset to behave like a geometrical Brownian motion with a drift and jumps whose size is log-double-exponentially distributed. The price of a European option is given by a partial integro-differential equation (PIDE) while American options lead to a linear complementarity problem (LCP) with the same operator. Spatial differential operators are discretized using finite differences on nonuniform grids and time stepping is performed using the implicit Rannacher scheme. For the evaluation of the integral term easy to implement recursion formulas are derived which have optimal computational cost. When pricing European options the resulting dense linear systems are solved using a stationary iteration. Also for pricing American options similar iterations can be employed. A numerical experiment demonstrates that the described method is very efficient as accurate option prices can be computed in a few milliseconds on a PC. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
64.
V.P.S. Awana Anurag Gupta E. Takayama-Muromachi M. Karppinen S.K. Malik V. Ganesan 《Solid State Communications》2004,129(2):117-121
A Tb-123 phase with the composition, TbSr2Cu2.7Mo0.3O7+δ, has been synthesized in single-phase form by the solid-state reaction route. Its phase purity has been confirmed from neutron powder diffraction studies. The as-synthesized Tb-123 sample does not show superconductivity down to 5 K. On the other hand, an unusually high antiferromagnetic ordering temperature (TN) of around 7 K is seen for the Tb moments. After 120-atm-O2 post-annealing, bulk superconductivity is achieved in this compound with a superconducting transition temperature (Tc) of about 30 K, without any significant effect on TN. To achieve higher oxygen content and higher Tc, the as-synthesized sample was subjected to high-pressure oxygenation, carried out in a closed cell, at 5 GPa and 400 °C in the presence of AgO as an excess-oxygen source. This sample exhibited superconductivity onset at around 80 K with a Meissner fraction larger than 10% at 5 K. Our observation of superconductivity at 80 K is the highest Tc to-date for the Tb-123 type compounds. 相似文献
65.
66.
Jari Häkkinen 《Zeitschrift fur Physik C Particles and Fields》1997,75(1):35-40
We show that experimental data are in very good agreement with predictions from the string fragmentation model by Bowler and Morris. We present a physical interpretation and discuss the relation to results obtained from Perturbative QCD and Local Hadron Parton Duality (LPHD). We also present implications for Bar correlations and the possibility to use these as a tag to study CP violation in B decays. 相似文献
67.
M. Karppinen M. Arai T.S. Chan J.M. Chen H. Yamauchi 《Journal of solid state chemistry》2005,178(5):1705-1711
Essentially single-phase Cu(Ba0.67Eu0.33)2(Ce0.33Eu0.67)2Cu2O9±δ samples of the Cu-1222 phase with a fluorite-structured (Ce,Eu)-O2-(Ce,Eu) block between the superconductive CuO2 planes were synthesized in O2 atmosphere to exhibit superconductivity with Tc around 25 K. Wide-range tuning of oxygen content and thereby the overall hole-doping level of the phase was found possible through (i) temperature-controlled oxygen-depletion (TCOD) annealing carried out in a thermobalance in N2 at various temperatures (for reduction), and (ii) high-pressure oxygenation (HPO) treatments carried out in a cubic-anvil-type high-pressure apparatus in the presence of various amounts of Ag2O2 as an excess oxygen source (for oxidation). For the HPO samples a record-high Tc value of 62 K was achieved. On the other hand, deoxygenation to the oxygen content less than 9±δ≈8.9 was found to kill superconductivity. The degree of hole doping (both in overall and for the CuO2 plane and CuO1±δ charge reservoir separately) in the samples is discussed on the bases of Cu L-edge and O K-edge XANES data. 相似文献
68.
H. Fjellvåg Y. Morita J.-M. Lee R.-S. Liu V.P.S. Awana Y. Matsui M. Karppinen 《Journal of solid state chemistry》2006,179(3):632-645
In this work, the first three members (s=1, 2, 3) of the Co-12s2 homologous series of multi-layered copper oxides are gradually doped with holes through high-pressure oxygenation (HPO). The phases differ from each other only by thickness of the fluorite-structured layer block, (Ce,Y,Ca)-[O2-(Ce,Y)]s−1, between two identical CuO2 planes. High-resolution transmission-electron microscopy (HRTEM) and electron diffraction (ED) analyses together with both synchrotron X-ray and neutron powder diffraction data, reveal that as a consequence of HPO the charge-reservoir CoO4-tetrahedra chains get broken and the lattice symmetry of the Co-12s2 phases changes from orthorhombic to tetragonal. Oxygen contents are analyzed for the samples with wet-chemical and thermogravimetric techniques. The valence state of copper in the CuO2 plane is determined from Cu L-edge X-ray absorption near-edge structure (XANES) spectra to be compared with the values estimated through bond-valence-sum (BVS) calculations from the crystal structure data. The positive charge induced by oxygen loading (or aliovalent CaII-for-YIII substitution in CoSr2YCu2O7+δ) is found not to be completely accommodated in the CuO2 planes but be rather effectively trapped at the charge-reservoir Co atoms. Superconductivity appears in the Co-1212 (CoSr2YCu2O7+δ) samples with the copper valence of 2.13 or higher, whereas in the Co-1222 (CoSr2(Ce0.25Y0.75)2Cu2O9+δ) and Co-1232 (CoSr2(Ce0.67Y0.33)3Cu2O11+δ) samples Cu valence does not increase high enough to induce superconductivity. 相似文献
69.
Jari Taskinen 《Proceedings of the American Mathematical Society》1997,125(8):2337-2346
We prove a universal mapping theorem for a large class of holomorphic mappings on a -space, stating that can be locally written in the form where and are bounded linear operators on certain Banach spaces consisting of functions on , and the division is taken pointwise.
70.
Harju K Vahermo M Mutikainen I Yli-Kauhaluoma J 《Journal of combinatorial chemistry》2003,5(6):826-833
The solid-phase synthesis of 1,2,3-triazoles via 1,3-dipolar cycloaddition of polymer-bound azides to various alkynes is reported. Polymer-bound azides were synthesized from polymer-bound halides and sodium azide and reacted with alkynes to produce polymer-bound 1,2,3-triazoles. Cleavage of the triazoles was performed with trifluoroacetic acid. A traceless synthesis of 1,2,3-triazoles was developed using 2-methoxy-substituted resin (polymer-bound 4-hydroxy-2-methoxybenzyl alcohol). In addition, a synthesis of 4-hydroxybenzyl-substituted 1,2,3-triazoles from the bromo-Wang resin (4-(bromomethyl)phenoxymethyl polystyrene) was achieved. 相似文献