90 resultados para Sr^2
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xLa2 -xSrxCuO4( 0 .0x 0 .1 )La2 -xThxCuO4( 0 .0x 0 .4)K2 NiF4 ,XRDIR .XPSCuCu () .BCu ,NO +CO ;MS TPDNOCO +NO ,CuA2 BO4NO +CO . ,NO , . ,NO ,
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(,),,70,,,,,,(<0.9 nm),,
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Two systems of La2-xSrxCuO4+/-lambda and La2-xThxCuO4+/-lambda, mixed oxides with K2NiF4 structure were synthesized. The compositions and structures of the catalysts were characterized by means of XRD, XPS, chemical analysis and so on. The catalytic behavior for the direct decomposition of NO has been investigated. The results show that the catalytic activity is closely related to the oxygen vacancy and lower valence metallic ion in the direct decomposition of NO. The presence of oxygen vacancy is necessary for mixed oxide to have steady activity in NO decomposition.
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Three new oxides Sm2SrCo2O7, Sm2BaCo2O7 and Gd2SrCo2O7 have been synthesized successfully by solid state reaction mathod. The X-Ray diffraction spectra show that they are all isostructural with Sr3Ti2O7, and Ln(2)SrCo(2)O(7)(Ln=Sm,Gd) crystallized in tetragonal system, Sm2BaCo2O7 in orthrhombic system. The Co-O bonds in CoO2 planes of Ln(2)SrCo(2)O(7) are shorter than those of LnSrCoO(4)(Ln=Sm, Gd), and so their delectrons are more delocalized and their electrical resistivities are smaller. The electrical resistivities versus temperature in the range 300 similar to 1100K showed that the five brides show the characters of weakly localized systems. In the lower temperature range, the magnetic behaviors of Gd2SrCo2O7 and GdSrCoO4 fit Curie-Weiss law well, and the magnetic exchange reaction in CoO2 sublattices of Gd2SrCo2O7 is ferromagnetic, but that of GdSrCoO4 is antiferromagnetic. The other three oxides with Sm3+ showed complex magnetic behaviors which is perhaps related with the complexity of Sm3+.
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Three new oxides Ln(2)MCo(2)O(7) (Ln = Sm, Gd; M = Sr, Ba) have been synthesized in solid state reaction method. The powder X-ray diffraction spectra show that they are all isostructural with Sr3Ti2O7. The electrical resistivities in the temperature range 300-1100 K show that they are all semiconductors, and a transition to metals is observed at 1053, 1053, and 573 K for Sm2SrCo2O7, Gd2SrCo2O7, and Sm2BaCo2O7, respectively. The magnetic suspectivities of Gd2SrCo2O7 in the temperature range 300-673 K fit the Curie-Weiss law well. A plateau is observed in the curves of Sm(2)MCo(2)O(7) (M = Sr, Ba) which is attributed to the configuration state change of Co(III) from low spin to high spin. (C) 1995 Academic Press, Inc.
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:Sm_2SrCo_2O_7,Gd_2SrCO_2O_7Sm_2BaCo_2O_7.Sr_3Ti_2O_7,Sm_2BaCo_2O_7,.LnSrCoO_4,Ln_2SrCo_2O_7(Ln=Sm,Gd)CoO_2Co-O,,.3001100K,,. 3001100K,,GdSrCoO_4Gd_2SrCo_2O_7Curie-Weiss,CoO_2,;Sm~(3+),Sm~(3+).
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The phosphors MMgF(4)(M = Ca, Sr, Ba) doped with samarium ions are synthesized in different atmospheres using solid phase reaction at high temperature. Samarium has been first stabilized in the divalent state in SrMgF4 and BaMgF4 matrices. Effects of matrices on the valent state of samarium ions are briefly discussed.
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Er3+ doped multicomponent fluoride based glass was prepared. These precursor fluoride glass samples were then heated using different schedules. Crystalline phase particles were successfully precipitated in the multicomponent fluoride glass samples after heat treatment. The influence of heat treatment on the spectroscopic properties of Er3+ in multicomponent fluoride based glass samples were discussed. Small changes of the Judd-Ofelt parameters Omega(i) (i = 2,4,6) were found in multicomponent fluoride glass samples before and after heat treatment compared to oxyfluoride telluride glass. Preparation conditions used to produce transparent multicomponent fluoride glass ceramics doped with rare-earth ions are discussed. (c) 2007 Elsevier B.V. All rights reserved.
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A new laser crystal Nd3+:(La, Sr)(Al, Ta)O-3 (abbreviated as Nd3+:LSAT) has been grown by the conventional Czochralski method. The absorption and luminescence spectra of trivalent neodymium in Nd3+:LSAT crystal were measured at room temperature. The value of absorption and emission cross-section was calculated. The Judd-Ofelt analysis was applied to the crystal to get the phenomenological parameters (Omega(i), i = 2,4,6), the line strengths, the radiative transition rates, the branching ratios and the radiative lifetime. (C) 2006 Elsevier B.V. All rights reserved.
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<> 1977,PhillipSharpRichard Roberts(adenov-irus)mRNA(split),,RNASplicing,16,,Phillip SharpRichard Roberts1993
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The SR-protein kinase activity was analyzed and the cytological changes were observed during oocyte maturation in bisexual transparent color crucian carp ( Carassius auratus color variety). The results revealed that the SR-protein kinase activity was sensitive to the artificially induced spawning hormones, and the change of oscillatory activity was similar to that of the maturation-promoting factor (MPF) kinase that regulates meiotic cell cycle in fish.
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The luminescence from Eu2+ ions in MF2 (M = Ca, Sr, Ba) fluorides has been investigated under the pressure range of 0-8 GPa. The emission band originating from the 4f(6)5d(1) -> 4f(7) transition of Eu2+ ions in CaF2 and SrF2 shows the red-shift as increasing pressure with pressure coefficients of -17 meV/GPa for CaF2 and -18 meV/GPa for SrF2. At atmospheric pressure, the emission spectrum of BaF2:Eu2+ comprises two peaks at 2.20 and 2.75 eV from the impurity trapped exciton (ITE) and the self-trapped exciton (STE), respectively. As the pressure is increased, both emission peaks shift to higher energies, and the shifting rate is slowed by the phase transition from the cubic to orthorhombic phase at 4 GPa. Due to the phase transition at 4-5 GPa pressure, the ITE emission disappears gradually, and the STE emission is gradually replaced by the 4f(6)5d(1) -> 4f(7) transition of Eu2+. Above 5 GPa, the pressure behavior of the 4f(6)5d(1) -> 4f(7) transition of EU2+ in BaF2: EU2+ is the same as the normal emission of Eu2+ in CaF2 and SrF2 phosphors.
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3m~(2+)4f~6f-fd-fd-f4f~nf-f4f~nf-f3m~(2+)3m~(2+)3m~(2+)xBaMgF_4:3m~(2+)3m~(2+)ff3m~(2+)ff~5Do~7F_13m~(2+)ff~5Do~7FoKMgF_3:3m~(2+)3m~(2+)ff3m~(2+)3m~(2+)ffNaMgF_4:3m~(2+)3m~(2+)ffNaMgF_3:3m~(2+)3m~(2+)~5Do~7F_3~5Do~7F_43m~(2+)3m~(2+)3mFd-fffS3m~(2+)3m~(2+)d-fKxNo_1-xMgF_3:3m~(2+)KMgF_3-xClx:3m~(2+)KMgF_(2.9)*0.1:3m~(2+) (X=FClBrI)3m~(2+)ff3m~(2+)3m~(2+)ff3m~(2+)ff3m~(2+)ffBaCl_2:3m~(2+)3m~(2+)3m~(2+)0.02mol3m~(2+)3mF_3KMgF_3:3m~(2+)3m(III)3m(II)3mF_33m(III)3m(II)S3m~(2+)3m~(2+)3m~(2+) KMgF_3NaMgF_3BaClFBaBrF3m~(2+)MLnFs(M=Ca Sr Ba Ln=La Crd)3m(III)3m(II)3m
