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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Юмашев, Владимир Витальевич, Кирик, Надежда Павловна, Шишкина, Нина Николаевна, Князев, Юрий Владимирович, Жижаев, Анатолий Михайлович, Соловьев, Леонид Александрович
Заглавие : Состав, структура и реакционная способность при восстановлении водородом композиционных материалов системы α-Fe2O3–CaFe2O4
Место публикации : Журнал СФУ. Химия. - 2019. - Т. 12, Вып. 1. - С. 54-72. - ISSN 1998-2836, DOI 10.17516/1998-2836-0108; J. Sib. Fed. Univ. Chem. - ISSN 2313-6049(eISSN)
Примечания : Библиогр.: 37
Предметные рубрики: CHEMICAL LOOPING GASIFICATION
OXYGEN CARRIER
PARTIAL OXIDATION
Аннотация: В работе изучены композиционные материалы системы α-Fe2O3-CaFe2O4, полученные методом высокотемпературного твердофазного синтеза из оксидов Са и Fe(III) с вариацией мольного отношения СаО/Fe2O3 от 0.15 до 1.00. Материалы охарактеризованы методами рентгеновской дифракции (РФА), сканирующей электронной микроскопии с системой энергодисперсионного микроанализа (СЭМ-ЭДС) и синхронного термического анализа (СТА) в режиме термопрограммируемого восстановления водородом (H2-ТПВ). СЭМ-ЭДС - исследование образцов выявило формирование сложной микроструктуры материала по типу «ядро-оболочка» с фазой гематита в качестве «ядра». H2-ТПВ образцов позволило установить, что с увеличением содержания фазы CaFe2O4 (от 33.4 до 97.5 мас. %) наблюдается снижение вклада низкотемпературных форм решеточного кислорода в областях 350-510 °С (до 2.6 раза) и 510-650 °С (до 1.7 раза) и рост вклада высокотемпературной формы кислорода в интервале 650-900 °С (до 2 раз). На основе оценки подвижности решеточного кислорода высказано предположение о перспективности использования полученных композиционных материалов с содержанием фазы CaFe2O4 более 55.2 мас. % в качестве носителей кислорода в химических циклических процессах получения синтез-газа.In this paper, α-Fe2O3–CaFe2O4 composite materials obtained by high-temperature solid-phase synthesis from Ca and Fe (III) oxides with varying molar ratio CaO/Fe2O3 in the range 0.15-1.00 were investigated. The materials are characterized by Х-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDS) and simultaneous thermal analysis (STA) in the hydrogen temperature-programmed reduction mode (H2-TPR). SEM-EDS studies of the specimens were revealed a formation of the “core-shell” type complex microstructure of material with the hematite phase as the “core”. H2-TPR of the specimens allowed to establish a decrease of the contribution of low-temperature forms of lattice oxygen in areas of 350-510 °С (up to 2.6 times) and 510-650 °С (up to 1.7 times), and the growth of the contribution of the high-temperature oxygen form in the range of 650-900 °С (up to 2 times) with an increase in the content of the phase CaFe2O4 from 33.4 to 97.5 wt. %. Relying on the assessment of lattice oxygen mobility, it was suggested, that the samples with content of CaFe2O4 phase more than 55.4 wt. % are promising for use as oxygen carriers in chemical looping processes of syngas production.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Шишацкая, Екатерина Игоревна, Николаева Е. Д., Шумилова А. А., Шабанов, Александр Васильевич, Волова, Татьяна Григорьевна
Заглавие : Культивирование мультипотентных мезенхимных стромальных клеток костного мозга на носителях из резорбируемого биопластотана
Разночтения заглавия :Загл. в Scopus: Cultivation of multipotent mesenchymal bone marrow cells on matrixes made of resorbable bioplastotan
Место публикации : Клеточная трансплантология и тканевая инженерия. - 2013. - Т. 8, Вып. 1. - P.57-65. - ISSN 1815-445X; Cell. Transplant. Tissue Eng. - 2013. - Vol. 8, Is. 1. - P.57-65
Ключевые слова (''Своб.индексиров.''): alkaline phosphatase--differentiation--extracellular calcium precipitates--multipotent mesenchymal stromal cells--osteopontin--resorbable bioplastotan
Аннотация: В работе охарактеризовано «семейство» клеточных носителей из резорбируемого полиэфира Биопластотан, представляющего собой сополимер 3- и 4-гидроксипро-изводных масляной кислоты. С применением различных технологий сконструированы пленочные и 3D носители, а также наноматриксы, образованные ультратонкими волокнами, полученные методом электростатического формования. Все типы носителей обеспечивают адгезию муль-типотентных мезенхимных стромальных клеток костного мозга и пригодны для культивирования и дифференцировки мультипотентных мезенхимных стромальных клеток в клетки остеобластического ряда. Последнее подтверждено детектированием в культуре клеток внеклеточных преципитатов кальция, активности щелочной фосфатазы и продукции остеопонтина.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen M., Xia Z., Molokeev M. S., Wang T., Liu Q.
Заглавие : Tuning of photoluminescence and local structures of substituted cations in xSr2Ca(PO4)2-(1 - x)Ca10Li(PO4)7:Eu2+ phosphors
Место публикации : Chem. Mater.: American Chemical Society, 2017. - Vol. 29, Is. 3. - P.1430-1438. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.7b00006
Примечания : Cited References: 37. - The present work was supported by the National Natural Science Foundation of China (Grants 91622125 and 51572023), Natural Science Foundations of Beijing (2172036), and Fundamental Research Funds for the Central Universities (FRF-TP-15-003A2).
Ключевые слова (''Своб.индексиров.''): calcium--energy transfer--europium--light emission--lithium--luminescence--phosphors--photoionization--photoluminescence--single crystals--composition ranges--crystal-field splitting--luminescence measurements--non-linear variation--photoionization process--polyhedra distortion--rare earth doped solids--temperature dependent--solid solutions
Аннотация: Local structure modification in solid solution is an essential part of photoluminescence tuning of rare earth doped solid state phosphors. Herein we report a new solid solution phosphor of Eu2+-doped xSr2Ca(PO4)2-(1 - x)Ca10Li(PO4)7 (0 ≤ x ≤ 1), which share the same β-Ca3(PO4)2 type structure in the full composition range. Depending on the x parameter variation in xSr2Ca(PO4)2-(1 - x)Ca10Li(PO4)7:Eu2+, the vacancies generated in the M(4) site enable the nonlinear variation of cell parameters and volume, and this increases the magnitude of M(4)O6 polyhedra distortion. The local structure modulation around the Eu2+ ions causes different luminescent behaviors of the two-peak emission and induces the photoluminescence tuning. The shift of the emission peaks in the solid solution phosphors with different compositions has been discussed. It remains invariable at x ≤ 0.5, but the red-shift is observed at x 0.5 which is attributed to combined effect of the crystal field splitting, Stokes shift, and energy transfer between Eu2+ ions. The temperature-dependent luminescence measurements are also performed, and it is shown that the photoionization process is responsible for the quenching effect.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ivanova N. B., Ovchinnikov S. G., Korshunov M. M., Eremin I. M., Kazak N. V.
Заглавие : Specific features of spin, charge, and orbital ordering in cobaltites
Коллективы : RFBR [09-02-00171-a, 07-02-00226, 09-02-00127]; Federal Agency of Science and Innovation [MK-4278.2008.2]; Presidium of the Russian Academy of Sciences [5, 7]; Leading Science Schools of the Ministry of Education and Science of the Russian Federation [2.1.1/3199]
Место публикации : Phys. Usp.: Turpion Ltd, 2009. - Vol. 52, Is. 8. - P.789-810. - ISSN 1063-7869, DOI 10.3367/UFNe.0179.200908b.0837
Примечания : Cited References: 278. - This work was financially supported by the RFBR (projects 09-02-00171-a, 07-02-00226, and 09-02-00127), the Federal Agency of Science and Innovation (grant MK-4278.2008.2), and the Presidium of the Russian Academy of Sciences Program No. 5, Quantum Physics of Condensed Media (project No. 7). I.M.E.'s work was supported by the program for Leading Science Schools of the Ministry of Education and Science of the Russian Federation (grant 2.1.1/3199).
Предметные рубрики: PEROVSKITE-TYPE OXIDES
METAL-INSULATOR-TRANSITION
HIGH-TEMPERATURE SUPERCONDUCTIVITY
ONE-DIMENSIONAL CA3CO2O6
ELECTRONIC-STRUCTURE
MAGNETIC-PROPERTIES
TRANSPORT-PROPERTIES
STATE TRANSITION
FUEL-CELLS
CRYSTAL-STRUCTURE
Ключевые слова (''Своб.индексиров.''): cobalt oxides--lanthanides--orbital degrees of freedom--orbital ordering--quasi-one-dimensional--spin state--superconducting compounds--theoretical result--calcium--cobalt--lanthanum--oxide minerals--perovskite--spin dynamics--superconductivity--cobalt compounds
Аннотация: Complex cobalt oxides known as cobaltites are reviewed, including LnCoO(3)-based perovskite-structured rare-earth cobaltites (where Ln is lanthanum or a lanthanide), quasi-two-dimensional and quasi-one-dimensional cobaltites of the types LnCo(2)O(5+delta), La2CoO4, and Ca3Co2O8, and NaxCoO2 center dot yH(2)O superconducting compounds. Key experimental and theoretical results are presented, with emphasis on the interplay between charge, spin, and orbital degrees of freedom. Two problems of specific relevance to cobaltites - the spin state instability of Co3+ ions in LnCoO(3), and the nature of superconductivity in NaxCoO2 center dot yH(2)O - are also given significant attention.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen M., Xia Z., Molokeev M. S., Lin C. C., Su C., Chuang Y. -C., Liu Q.
Заглавие : Probing Eu2+ luminescence from different crystallographic sites in Ca10M(PO4)7:Eu2+ (M = Li, Na, and K) with β-Ca3(PO4)2-type structure
Место публикации : Chem. Mater.: American Chemical Society, 2017. - Vol. 29, Is. 17. - P.7563-7570. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.7b02724
Примечания : Cited References: 34. - The present work was supported by the National Natural Science Foundation of China (Grants 51722202, 91622125, and 51572023), Natural Science Foundations of Beijing (2172036), and Fundamental Research Funds for the Central Universities (FRF-TP-16-002A3). C.C.L. and C.C.S. acknowledge the financial support from the Ministry of Science and Technology of Taiwan (Contract No. MOST 104-2113-M-027-007-MY3), and M. Molokeev acknowledges support of the Russian Foundation for Basic Research (17-52-53031).
Ключевые слова (''Своб.индексиров.''): calcium--doping (additives)--excited states--light emission--lithium--luminescence--phosphors--photoluminescence--positive ions--rietveld refinement--single crystals--color tuning--crystallographic sites--different distributions--emission bands--local environments--long wavelength bands--luminescent centers--power diffraction data--europium
Аннотация: Eu2+ local environments in various crystallographic sites enable the different distributions of the emission and excitation energies and then realize the photoluminescence tuning of the Eu2+ doped solid state phosphors. Herein we report the Eu2+-doped Ca10M(PO4)7 (M = Li, Na, and K) phosphors with β-Ca3(PO4)2-type structure, in which there are five cation crystallographic sites, and the phosphors show a color tuning from bluish-violet to blue and yellow with the variation of M ions. The difference in decay rate monitored at selected wavelengths is related to multiple luminescent centers in Ca10M(PO4)7:Eu2+, and the occupied rates of Eu2+ in Ca(1), Ca(2), Ca(3), Na(4), and Ca(5) sites from Rietveld refinements using synchrotron power diffraction data confirm that Eu2+ enters into four cation sites except for Ca(5). Since the average bond lengths d(Ca-O) remain invariable in the Ca10M(PO4)7:Eu2+, the drastic changes of bond lengths d(M-O) and Eu2+ emission depending on the variation from Li to Na and K can provide insight into the distribution of Eu2+ ions. It is found that the emission band at 410 nm is ascribed to the occupation of Eu2+ in the Ca(1), Ca(2), and Ca(3) sites with similar local environments, while the long-wavelength band (466 or 511 nm) is attributed to Eu2+ at the M(4) site (M = Na and K). We show that the crystal-site engineering approach discussed herein can be applied to probe the luminescence of the dopants and provide a new method for photoluminescence tuning.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrov M. I., Belozerova I. L., Shaikhutdinov K. A., Balaev D. A., Dubrovskii A. A., Popkov S. I., Vasil'ev A. D., Mart'yanov O. N.
Заглавие : Preparation, microstructure, magnetic and transport properties of bulk textured Bi(1.8)Pb(0.3)Sr(1.9)Ca(2)Cu(3)O(x) and Bi(1.8)Pb(0.3)Sr(1.9)Ca(2)Cu(3)O(x)+Agceramics
Коллективы :
Разночтения заглавия :авие SCOPUS: Preparation, microstructure, magnetic and transport properties of bulk textured Bi1.8Pb0.3Sr1.9Ca2Cu 3Ox and Bi1.8Pb0.3Sr 1.9Ca2Cu3Ox+Ag ceramics
Место публикации : Supercond. Sci. Technol.: IOP PUBLISHING LTD, 2008. - Vol. 21, Is. 10. - Ст.105019. - ISSN 0953-2048, DOI 10.1088/0953-2048/21/10/105019
Примечания : Cited References: 22. - This work is supported by program of RAS 'Quantum macrophysics' No. 3.4 and integration project of SB RAS No. 3.4 and in part by Krasnoyarsk Regional Scientific Foundation (KRSF), Grants 17G057, 18G148 and 18G011. DAB and AAD acknowledge the Russian Science Support Foundation.
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
CRITICAL-CURRENT DENSITY
BI-2223 TAPES
BI2223
SILVER
DISCS
(BI
Ключевые слова (''Своб.индексиров.''): building materials--calcium--copper--crystallites--diamagnetic materials--lead--lead alloys--magnetic anisotropy--magnetic properties--nanocrystalline alloys--silver--textures--transport properties--bi-2223--bulk samples--degree of textures--diamagnetic responses--liquid mediums--magnetic and transport properties--magnetic measurements--room temperatures--ceramic materials
Аннотация: A new method of preparation of bulk textured Bi2223 ceramics and Bi2223 + Ag composites, based on room temperature pressing of foamed precursor (Bi2223, Bi2223 + Ag) in a liquid medium, is proposed. SEM and XRD data prove a high degree of texture of the bulk samples obtained. Magnetic measurements performed in directions H parallel to c-axis and H parallel to a-b-planes of Bi2223 crystallites demonstrates anisotropy of magnetization confirming the texture of the ceramics. The materials obtained possess large diamagnetic response in the direction H parallel to a-b-planes of Bi2223 crystallites at both 77.4 and 4.2 K.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shtarev D. S., Ryabchuk V. K., Rudakova A. V., Shtareva A. V., Molokeev M. S., Kirichenko E. A., Serpone N.
Заглавие : Phenomenological rule from correlations of conduction/valence band energies and bandgap energies in semiconductor photocatalysts: calcium bismuthates versus strontium bismuthates
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [19-73-10013]; Saint-Petersburg State University [39054581]
Место публикации : ChemCatChem. - 2020. - Vol. 12, Is. 6. - P.1551-1555. - ISSN 1867-3880, DOI 10.1002/cctc.201902236. - ISSN 1867-3899(eISSN)
Примечания : Cited References: 13. - The research was supported from a grant from the Russian Science Foundation (project No. 19-73-10013). We are very grateful to the staff of the Khabarovsk Innovation and Analytical Center of the Yu. A. Kosygin Institute of Tectonics and Geophysics FEB RAS, and of the Research Center on Nanophotonics and the Center for Physical Methods of Surface Investigation (to Dr. Alexandra Koroleva) of the Research Park at Saint-Petersburg State University for their valuable assistance in carrying out the research and in providing the needed equipment. VKR and AVR acknowledge financial support from a grant by the Saint-Petersburg State University (Pure ID 39054581). One of us (NS) thanks Prof. A. Albini and the staff of the PhotoGreen Laboratory of the University of Pavia for their continued hospitality
Предметные рубрики: STRUCTURAL-PROPERTIES
Аннотация: A number of calcium bismuthates were synthesized (25 to 50 mol% in Ca) and characterized by XRD, SEM, EDX, XPS and DRS techniques; the latter provided an estimate of the bandgap energies (Ebg=2.41 to 3.29 eV) via Tauc plots for indirect transitions, whereas XPS established the potentials (vs NHE) of their respective valence bands (and thus the conduction bands). Linear correlations existed between EVB/ECB and Ebg that when compared with those of strontium bismuthates (reported earlier) showed that differences in energies at Ebg=0 eV are related to the difference in the absolute electronegativities of Ca and Sr, from which the following empirical phenomenological rule is postulated: replacing one alkaline earth metal in bismuthates by another causes the points of intersection of the linear correlations ECB(Ebg) and EVB(Ebg) to be displaced by an amount equal to twice the difference in absolute electronegativities of these metals.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrovsky A. S., Arkhipkin V. G., Bezmaternykh L. N., Gudim I. A., Krylov A. S., Vagizov F.
Заглавие : Origin of color centers in the flux-grown europium gallium garnet
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2008. - Vol. 103, Is. 8. - Ст.83102. - ISSN 0021-8979, DOI 10.1063/1.2902365
Примечания : Cited References: 7
Предметные рубрики: SPECTRA
IONS
Ключевые слова (''Своб.индексиров.''): absorption--europium alloys--garnets--ultraviolet radiation--calcium-free flux--flux-grown europium gallium garnet--color centers
Аннотация: Europium gallium garnet (EuGG) single crystals were grown from fluxes with various contents. Optical absorption spectra of EuGG grown from a flux containing calcium show an additional band in the ultraviolet and blue regions of the spectra as compared to the case of a calcium-free flux. Mossbauer spectra of the samples grown from the fluxes with different additives show no signs of other valence states of the europium ions except for 3+. However, they indicate changes in the crystal field due to the entrance of additive ions. The nature of the additional absorption must be the same as that for calcium-doped gadolinium gallium garnet, i.e., anion vacancies. Mossbauer isotope shifts and quadrupole splitting for EuGG are determined. (C) 2008 American Institute of Physics.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhang M., Xia Z., Molokeev M. S., Shi L., Liu Q.
Заглавие : New insight into the crystal structure of Sr4Ca(PO4)2SiO4 and the photoluminescence tuning of Sr4Ca(PO4)2SiO4:Ce3+,Na+,Eu2+ phosphors
Место публикации : J. Mater. Chem. C: Royal Society of Chemistry, 2016. - Vol. 4, Is. 38. - P.9078-9084. - ISSN 20507534 (ISSN), DOI 10.1039/c6tc03373c
Примечания : Cited References: 31
Ключевые слова (''Своб.индексиров.''): calcium--energy transfer--europium--light emission--light emitting diodes--luminescence--phosphate minerals--phosphors--photoluminescence--positive ions--rietveld refinement--tuning--chemical compositions--energy transfer mechanisms--green component--hexagonal cells--luminescence properties--single phase--solid state method--white lightemitting diodes (wleds)--crystal structure
Аннотация: A new single phase based on the substitution of a Sr cation by a Ca cation in the apatite-type Sr5(PO4)2(SiO4) has been fabricated with the nominal chemical composition of Sr4Ca(PO4)2(SiO4), which appears as a definite compound rather than a solid solution between (Sr,Ca)3(PO4)2 and (Sr,Ca)2SiO4. The crystal structure of Sr4Ca(PO4)2(SiO4) has been firstly analysed by the difference electron map, and further resolved by the Rietveld refinement, and the final composition has been determined as Sr4Ca(PO4)(2+x)(SiO4)(1-x)(OH)x (x = 0.64) with a hexagonal cell (P63/m). The Ce3+/Eu2+ codoped Sr4Ca(PO4)2SiO4 phosphors have been designed and prepared by the solid state method, and the photoluminescence tuning from blue to green upon 365 nm ultraviolet (UV) radiation can be realized, which is ascribed to the energy transfer from Ce3+ to Eu2+ ions. The luminescence properties and the energy transfer mechanism in Ce3+/Eu2+ codoped Sr4Ca(PO4)2SiO4 phosphors have been discussed, which might act as potential candidates for blue-green components in UV-pumped white light emitting diodes (WLEDs). © 2016 The Royal Society of Chemistry.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Dubrovskii A. A., Shaikhutdinov K. A., Popkov S. I., Gokhfeld D. M., Gokhfeld Yu. S., Petrov M. I.
Заглавие : Mechanism of the hysteretic behavior of the magnetoresistance of granular HTSCs: The universal nature of the width of the magnetoresistance hysteresis loop
Коллективы : Quantum Macrophysics of the Russian Academy of Sciences [3.4]; Krasnoyarsk Regional Science Foundation [18G011]; Foundation for Supporting National Science Projects
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2009. - Vol. 108, Is. 2. - P241-248. - ISSN 1063-7761, DOI 10.1134/S106377610902006X
Примечания : Cited References: 32. - This study was carried out under the program "Quantum Macrophysics" of the Russian Academy of Sciences and complex integration project no. 3.4 of the Siberian Branch of the Russian Academy of Sciences, and was partly supported by the Krasnoyarsk Regional Science Foundation (grant no. 18G011). D. A. B. and A. A. D. are grateful to the Foundation for Supporting National Science Projects.
Предметные рубрики: CRITICAL-CURRENT-DENSITY
HIGH-TEMPERATURE SUPERCONDUCTOR
CURRENT-VOLTAGE CHARACTERISTICS
EXTERNAL MAGNETIC-FIELD
BA-CU-O
JOSEPHSON MEDIUM
CRITICAL-STATE
FLUX
COMPOSITES
YBA2CU3O7-DELTA
Ключевые слова (''Своб.индексиров.''): barium--calcium--damping--electric resistance--high temperature superconductors--magnetic field effects--magnetic materials--magnetoelectronics--magnetoresistance--stiffness--classical systems--critical densities--experimental datum--external conditions--flux trapping--hysteretic behaviors--josephson vortices--residual resistances--transport currents--universal behaviors--y-ba-cu-o--hysteresis
Аннотация: The hysteretic behavior of the magnetoresistance R(H) of granular high-temperature superconductors (HTSCs) of the Y-Ba-Cu-O, Bi-Ca-Sr-Cu-O, and La-Sr-Cu-O classical systems is investigated for transport current densities lower and higher than the critical density (at H = 0). All systems exhibit universal behavior of the width of the magnetoresistance hysteresis loop: independence of transport current under identical external conditions. This means that flux trapping in HTSC grains is the main mechanism controlling the hysteretic behavior of the magnetoresistance of granular HTSCs, while pinning of Josephson vortices in the intragranular medium makes no appreciable contribution to the formation of magnetoresistance hysteresis (when transport current flows through the sample). Experimental data on relaxation of residual resistance after the action of a magnetic field also confirm this conclusion.
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