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11.
Crystal and magnetic structure of the Sm0.55Sr0.45MnO3 and (Nd0.545Tb0.455)0.55Sr0.45MnO3 manganites
A. I. Kurbakov V. A. Trounov A. M. Balagurov V. Yu. Pomyakushin D. V. Sheptyakov O. Yu. Gorbenko A. R. Kaul 《Physics of the Solid State》2004,46(9):1704-1710
Neutron diffraction data are presented for the 152Sm0.55Sr0.45MnO3 (SSM) and (Nd0.545Tb0.455)0.55Sr0.45MnO3 (NTSM) manganites. The Nd and Tb contents in the latter composition are such that the average radius of the A cation 〈r
A
〉 in these two compounds is the same. The difference in local tolerance factor fluctuations was about 10%. It was found that
replacement of a rare-earth cation with leaving 〈r
A
〉 unchanged has practically no effect on the structural and transport properties; indeed, both compounds are metals at low
temperatures, have the same crystal structure from liquid-helium to room temperature, and exhibit the same pattern of structural
distortions at the onset of magnetic ordering. Magnetic moments of Mn ions in both compositions are ferromagnetically ordered
at low temperatures, with T
C
=122 and 90 K for the SSM and NTSM, respectively. Below 80 K, the rare-earth cation moments in NTSM undergo additional ordering.
In contrast to compositions that are close in Sr concentration (x
Sr=0.4, 0.5), which feature a phase-separated state with a mixture of the ferromagnetic metallic and antiferromagnetic insulator
phases, the ground state of both studied compositions with x
Sr=0.45 is uniformly ferromagnetic and metallic.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 9, 2004, pp. 1650–1656.
Original Russian Text Copyright ? 2004 by Kurbakov, Trounov, Balagurov, Pomyakushin, Sheptyakov, Gorbenko, Kaul. 相似文献
12.
The effect of solar features on geospheric conditions leading to geomagnetic storms (GMSs) with planetary index,A
P ≥ 20 and the range of horizontal component of the Earth’s magnetic fieldH such that 250γ <H < 400γ has been investigated using interplanetary magnetic field (IMF), solar wind plasma (SWP) and solar geophysical data
(SGD) during the period 1978–99. Statistically, it is observed that maximum number of GMSs have occurred during the maximum
solar activity years of 21st and 22nd solar cycles. A peculiar result has been observed during the years 1982, 1994 when sunspot
numbers (SSNs) decrease very rapidly while numbers of GMSs increase. No distinct association between yearly occurrence of
disturbed days and SSNs is observed. Maximum number of disturbed days have occurred during spring and rainy seasons showing
a seasonal variation of disturbed days. No significant correlation between magnitude (intensity) of GMSs and importance ofH
α
, X-ray solar flares has been observed. Maximum number of GMSs is associated with solar flares of lower importance, i.e.,
SF during the period 1978-93.H
α
, X-ray solar flares occurred within lower helio-latitudes, i.e., (0–30)°N to (0–30)°S are associated with GMSs. NoH
α
, X-ray solar flares have occurred beyond 40°N or 40°S in association with GMSs. In helio-latitude range (10–40)°N to (10–40)°S,
the 89.5% concentration of active prominences and disappearing filaments (APDFs) are associated with GMSs. Maximum number
of GMSs are associated with solar flares. Coronal mass ejections (CMEs) are related with eruptive prominences, solar flares,
type IV radio burst and they occur at low helio-latitude. It is observed that CMEs related GMS events are not always associated
with high speed solar wind streams (HSSWSs). In many individual events, the travel time between the explosion on the Sun and
maximum activity lies between 58 and 118 h causing GMSs at the Earth. 相似文献
13.
14.
Adamovich MI Aggarwal MM Alexandrov YA Ameeva ZV Andreeva NP Anzon ZV Arora R Badyal SK Bhalla KB Bhasin A Bhatia VS Bubnov VI Burnett TH Cai X Chasnikov IY Chernova LP Chernyavski MM Dressel B Eligbaeva GZ Eremenko LE Friedlander EM Gadzhieva SI Gaitinov AS Ganssauge ER Garpman S Gerassimov SG Gill A Grote JG Gulamov KG Gulyamov UG Gupta VK Hackel S Heckman HH Haung H Judek B Kachroo S Kadyrov FG Kalyachkina GS Kanygina EK Kaul GL Kaur M Kharlamov SP Koss T Kumar V Lal P Larionova VG 《Physical review letters》1990,65(4):412-415
15.
16.
Vishwakarma Santosh L. Bagul Milind S. Rajani M. Goyal Ramesh K. 《平面色谱法杂志一现代薄层色谱法》2004,17(2):128-131
JPC – Journal of Planar Chromatography – Modern TLC - Swertiamarin is a secoiridoid glucoside present in members of the Gentianaceae family, including Swertia chirata (Wall) Clarke, S.... 相似文献
17.
Vikas V. Vaidya Santosh M. Yetal Shikha M. N. Roy Noel A. Gomes Santosh S. Joshi 《Chromatographia》2007,66(11-12):925-928
A rapid, sensitive and specific method to quantify pregabalin in human plasma using metaxalone as the internal standard is described. Sample preparation involved simple protein precipitation by using acetronitrile as solvent. The extract was analyzed by high-performance liquid chromatography coupled to electrospray tandem mass spectrometry (LC-MS–MS). Chromatography was performed isocratically on Thermo Hypurity C18 5 μm analytical column, (50 mm × 4.6 mm i.d.). The assay of pegabalin was linear calibration curve over the range 10.000–10000.000 ng mL?1. The lower limit of quantification was 10.000 ng mL?1 in plasma. The method was successfully applied to the bioequivalence study of pregabalin capsules (150.0 mg) administered as a single oral dose. 相似文献
18.
Summary The kinetics of the RuIII-catalyzed oxidation of the hydroxy acids; lactic, tartaric, malic and citric acids byN-bromosuccinimide in HClO4 and in the presence of Hg(OAc)2 have been studied. The reactions exhibit a first order rate dependence with respect to the oxidant and zeroth order rate dependence with respect to substrate. The rate is retarded by [H+], accelerated at law RuIII concentrations but independent of [RuIII] at higher RuIII concentrations. A mechanism consistent with the observed kinetic data is proposed. 相似文献
19.
A simple, rapid, cost-effective and accurate high performance thin layer chromatographic method has been developed for quantification
of valerenic acid in Valeriana jatamansi and Valeriana officinalis which is one of the stable compounds of Valeriana officinalis and designated as a key marker compound. Valerenic acid makes substantial contribution to the sedative and spasmolytic activity
of the essential oil and extract of Valeriana officinalis. Separation and quantification was achieved by HPTLC using ternary mobile phase of hexane: ethyl acetate: acetic acid (80:20:0.5
v/v) on precoated silica gel 60F254 aluminium plates and densitometric determination was carried out after derivatization with anisaldehyde-sulphuric acid reagent
at 700 nm, in absorption-reflectance mode. The calibration curves were linear in the range of (500 ng–2.5 μg). This is the
first HPTLC report for the identification and quantification of valerenic acid in Valeriana jatamansi and Valeriana officinalis. 相似文献
20.
The formation of palladium(II) complexes with aliphatic amines and their oxidation by chloramine‐T in perchloric acid medium has been studied. The spectrophotometric studies showed the formation of 1:1 and 1:2 complexes between palladium(II) and amine in absence of HClO4. An increase in [HClO4] in reaction mixture suppresses the complex formation and in presence of [HClO4] ~10?3 mol dm?3 only a 1:1 complex between palladium(II) and amine has been observed. The effect of Cl? on the complex formation has also been studied. Palladium(II)‐catalyzed oxidation of these amines by chloramine‐T showed a first‐order dependence of rate with respect to each—oxidant, substrate, catalyst, and H+. The mechanism consistent with kinetic data for the oxidation process has been proposed in absence as well as in presence of initial [Cl?]. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 603–612, 2002 相似文献