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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Val'kov V. V.
Заглавие : Anomalous resistivity and the electron-polaron effect in the two-band hubbard model with one narrow band
Место публикации : J. Supercond. Nov. Magn.: SPRINGER, 2012. - Vol. 25, Is. 5. - P.1379-1382. - ISSN 1557-1939, DOI 10.1007/s10948-012-1523-3
Примечания : Cited References: 28. - We are grateful to P. Fulde, Yu. Kagan, K. I. Kugel, N.V. Prokof'ev, P. Nozieres, and C. M. Varma for the numerous stimulating discussions. We acknowledge financial support of the RFBR Grant No. 11-02-00741.
Предметные рубрики: FERMI GAS
SUPERCONDUCTIVITY
SUPERFLUIDITY
TEMPERATURE
REPULSION
SYSTEMS
Ключевые слова (''Своб.индексиров.''): electron-polaron effect--two-band hubbard model--marginality--anomalous resistivity
Аннотация: We search for anomalous normal and superconductive behavior in the two-band Hubbard model with one narrow band. We analyze the influence of the electron–polaron effect and the Altshuler–Aronov effect on effective mass enhancement and scattering times of heavy and light components in the clean case. We find anomalous behavior of resistivity at high temperatures TW∗hT W_{h}. *} both in 3D and 2D situations. The SC instability in the model is governed by an enhanced Kohn–Luttinger effect for p-wave pairing of heavy electrons via polarization of light electrons.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Udod L. V., Sitnicov M. N., Aplesnin S. S., Molokeev M. S.
Заглавие : Electrical and dielectrical propeties of gas-sensor resistive type Bi2Sn2O7
Коллективы : Euro-Asian Symposium "Trends in MAGnetism": Nanomagnetism
Место публикации : Solid State Phenom.: Selected, peer reviewed papers/ ed.: S. G. Ovchinnikov, A. Samardak: Trans Tech Publications, 2014. - Vol. 215: Trends in Magnetism: Nanomagnetism (EASTMAG-2013). - P.503-506. - ISSN 978-303835054-5, DOI 10.4028/www.scientific.net/SSP.215.503. - ISSN 1662-9779
Примечания : Cited References: 14. - This work was supported by the Russian Foundation for Basic Research projects no. 12-02-00125-а
Ключевые слова (''Своб.индексиров.''): crystallographic structure--polymorphic transformations--electrical resistivity--dielectric permeability
Аннотация: Polycrystalline samples of Bi2Sn2O7 have been synthesized by conventional solid-state reaction method. According to the X-ray powder diffraction research, our sample co-existing of two polymorphs phases: cubic and rhombic, concurrently. The real dielectric permeability Re (ε) monotonic grows versus temperature and the imaginary dielectric permeability Im (ε) nonmonotonic is increased at the heating. There are maxima at Т=450 K on both temperature dependences Im (ε) and Re (ε) reveal. Anomalies in the temperature dependence of electrical resistivity at temperatures are found and to be correlated with the α → β structural phase transition temperature.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Udod L. V., Aplesnin S. S., Sitnikov M. N., Eremin E. V., Molokeev M. S.
Заглавие : Effect of Mn doping on magnetic and dielectric properties of Bi2Sn2O7
Коллективы : Moscow International Symposium on Magnetism
Место публикации : Solid State Phenom.: Selected, peer reviewed papers/ ed.: N. Perov, A. Semisalova: Trans Tech Publications Ltd, 2015. - Vol. 233-234: Achievements in Magnetism. - P.105-108. - ISSN 1662-9779, DOI 10.4028/www.scientific.net/SSP.233-234.105. - ISSN 978-3-03835-482-6
Предметные рубрики: Achievements in magnetism
Ключевые слова (''Своб.индексиров.''): crystallographic structure--cubic phase--dielectric permeability--electrical resistivity--magnetic moment--martensitic phase transitions--orthorhombic phases--polymorphic transformation
Аннотация: The Bi2(Sn0.95Mn0.05)2O7 compound existing simultaneously in two polymorphic modifications, namely, orthorhombic and cubic has been synthesized for the first time by solid-phase synthesis. The magnetic, dielectric and electrical properties of the compound have been studied. Anomalies in the temperature dependences of the electrical resistance and magnetic propoties have been found. These features are explained as martensitic phase transitions.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Удод, Любовь Викторовна, Ситников, Максим Николаевич
Заглавие : Влияние катионного замещения на полиморфные переходы в пирасаннате висмута Bi2Sn2O7
Место публикации : Вестник СибГАУ. - Красноярск: СибГАУ, 2015. - Т. 16, № 4. - С. 975-982. - ISSN 1816-9724
Примечания : Библиогр.: 53. - Работа выполнена при финансовой поддержке Российского фонда фундаментальных исследований, грант № 15-42-04099 р_сибирь_а, и государственного задания № 114090470016
Ключевые слова (''Своб.индексиров.''): полиморфные переходы--диэлектрическая проницаемость--электросопротивление--катионное замещение--дифференциальная сканирующая калориметрия--polymorphic transitions--dielectric permeability--cation substitution--electrical resistivity--differential scanning calorimetry
Аннотация: Рассмотрена разработка технологии новых сенсорных материалов, необходимых для газочувствительных приборов, применяемых в ракетостроении. Целью данной работы является изучение влияния допирования разновалентными катионами на кристаллографическую структуру, диэлектрические и электрические свойства пирохлорного соединения Bi 2Sn 2O 7, обладающего селективной избирательностью к газам. Методом твердофазного синтеза впервые синтезированы соединения Bi2(Sn1-xMex)2O7, где Me = Mn, Cr, x = 0, 0,05, находящиеся сразу в двух полиморфных модификациях - орторомбической и кубической. В твердых растворах Bi2(Sn0,95Cr0,05)2O 7 методом сканирующей калориметрии обнаружено два новых структурных перехода, по сравнению со станнатом висмута Bi2Sn2O7. Ионы Mn 4+ сместили фазовые границы полиморфных переходов в сторону меньших температур, а фазовый α→β-переход около 370 К, характерный для Bi2(Sn1-xCrx)2O7, где x = 0, 0,05, подавили почти полностью. Полиморфный переход при Т = 543 К для Bi 2(Sn0,95Mn0,05) 2O 7 протекает с выделением тепла, в отличие от Bi2(Sn1-xCrx)2O7, где x = 0, 0,05. Исследована взаимосвязь структурных, электрических и диэлектрических свойств. Установлены аномалии в температурной зависимости электросопротивления и диэлектрической проницаемости (мнимой и реальной частями) как в области низких температур, так и при высоких температурах. Эти особенности объясняются в рамках модели мартенситных фазовых переходов. Методом сканирующей калориметрии найдены температуры структурных фазовых переходов, которые коррелируют с аномалиями электросопротивления в интервале температур 300 T 1000 К для Bi2(Sn1-xCrx)2O7, x The goal of this work is to develop a new technology of sensor materials required for gas sensing devices used in missile. The aim of this work is to study the effect of doping cations with different valency on the crystallographic structure, dielectric and electrical properties of pyrochlore compound Bi2Sn2O7 with selectivity to gases. Polycrystalline compounds Bi2(Sn1-xMex)2O7, where Me = Mn, Cr, x = 0, 0.05 have been synthesized by conventional solid-state reaction. According to the X-ray powder diffraction research, our sample consists of two polymorphs phases: cubic and rhombic. Two new structural transition are found in Bi2(Sn0.95Cr0.05)2O7 solid solutions by scanning calorimetry, as compared to bismuth pyrostannate Bi2Sn2O7. Ions Mn 4+ leads to shift of phase boundary of polymorphic transitions towards lower temperatures, and the phase α→β-transition at about 370 K, which is characteristic for Bi2(Sn1-xCrx)2O7, where x = 0, 0.05 is suppressed. The polymorphic transition at T = 543 K for Bi2(Sn0.95Mn0.05)2O7 occurs with calorification, in contrast to Bi2(Sn1-xCrx)2 7, where x = 0, 0.05. The relationship between structural, electrical and dielectric properties is investigated. Anomalies in the temperature dependence of electrical resistivity and dielectric permeability (real and imaginary part) as in the low region temperatures as in the high region temperature are found. These features are explained within a model of martensitic phase transitions. The temperature of the structural phase transitions correlates with temperature of maximum of the electrical resistivity in the temperature range 300 T 1000 K for Bi2(Sn1-xCrx)2O7, x
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Neznakhin D. S., Samoshkina Yu. E., Molokeev M. S., Semenov S. V.
Заглавие : Structural, electrical and magnetic study of manganites Pr0.6Sr0.4MnO3 thin films
Коллективы : Russian Youth Conference on Physics of Semiconductors and Nanostructures, Opto- and Nanoelectronics
Место публикации : J. Phys. Conf. Ser./ Russian Youth Conference on Physics of Semiconductors and Nanostructures, Opto- and Nanoelectronics (17 ; 23 - 27 Nov. 2015): IOP Publishing, 2016. - Vol. 690, Is. 1. - ISSN 17426588 (ISSN), DOI 10.1088/1742-6596/690/1/012002
Примечания : Cited References: 20. - The work was supported partly by RFBR, grant №14-02-01211, Grant of President of Russian Federation №NSh-2886.2014.2, and by The Ministry of Education and Science of the Russian Federation, project №2582.
Ключевые слова (''Своб.индексиров.''): magnetic materials--magnetization--manganese oxide--nanoelectronics--nanostructures--oxide films--field dependence--magnetization temperature curves--polycrystalline phase--polycrystalline pr--resistivity dependence--shape characteristics--structural parameter--zero-field cooling--thin films
Аннотация: Thin polycrystalline Pr0.6Sr0.4MnO3 films were grown on the Y stabilized zirconium oxide substrates by magnetron sputtering using RF power and off-axis sputtering scheme with double cathodes. Only one polycrystalline phase with structural parameters consistent with that for the corresponding bulk sample was revealed in the films. Electric resistivity dependence on temperature demonstrates the shape characteristic for the substances with the Mott transition. The difference between magnetization temperature curves measured in the zero field cooling and field cooling modes was revealed. Magnetization field dependences were presented by the hysteresis loops changing their form with temperature. © Published under licence by IOP Publishing Ltd.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gavrichkov V. A., Ovchinnikov S. G., Nekrasov I. A., Pchelkina Z. V.
Заглавие : Electronic Structure of p-Type La1-xMx2+MnO3 Manganites in the Ferromagnetic and Paramagnetic Phases in the LDA plus GTB Approach
Разночтения заглавия :авие SCOPUS: Electronic structure of p-Type La 1-x M x 2+ MnO 3 manganites in the ferromagnetic and paramagnetic phases in the LDA + GTB approach
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 112, Is. 5. - P860-876. - ISSN 1063-7761, DOI 10.1134/S1063776111030101
Примечания : Cited References: 47. - This study was supported financially by integration project no. 40 of the Ural and Siberian Branches of the Russian Academy of Sciences, the program "Strong Electron Correlations" of the Russian Academy of Sciences, and the Russian Foundation for Basic Research (project no. 10-02-00251-a).
Предметные рубрики: DOUBLE-EXCHANGE
COLOSSAL MAGNETORESISTANCE
THIN-FILMS
PHYSICS
LA1-XSRXMNO3
RESISTIVITY
SEPARATION
TRANSPORT
MODEL
Ключевые слова (''Своб.индексиров.''): complex structure--cubic materials--ferromagnetic phase--half metals--jahn teller effect--metal properties--metal types--orbitals--p-type--paramagnetic phase--paramagnetic phasis--quasi particles--spectral intensity--spin projections--strong electron correlations--barium--density functional theory--electron correlations--electron density measurement--electronic properties--electronic structure--fermi level--ferromagnetic materials--ferromagnetism--manganese oxide--manganites--paramagnetic materials--paramagnetism--valence bands--lanthanum
Аннотация: The band structure, spectral intensity, and position of the Fermi level in doped p-type La1-xMx2+ MnO3 manganites (M = Sr, Ca, Ba) is analyzed using the LDA + GBT method for calculating the electronic structure of systems with strong electron correlations, taking into account antiferro-orbital ordering and using the Kugel-Khomskii ideas and real spin S = 2. The results of the ferromagnetic phase reproduce the state of a spin half-metal with 100% spin polarization at T = 0, when the spectrum is of the metal type for a quasiparticle with one spin projection and of the dielectric type for the other. It is found that the valence band becomes approximately three times narrower upon a transition to the paramagnetic phase. For the paramagnetic phase, metal properties are observed because the Fermi level is located in the valence band for any nonzero x. The dielectrization effect at the Curie temperature is possible and must be accompanied by filling of d(x) orbitals upon doping. The effect itself is associated with strong electron correlations, and a complex structure of the top of the valence band is due to the Jahn-Teller effect in cubic materials. DOI: 10.1134/S1063776111030101
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaykhutdinov K. A., Semenov S. V., Popkov S. I., Balaev D. A., Bykov A. A., Dubrovskiy A. A., Petrov M. I., Volkov N. V.
Заглавие : Magnetoresistance of substituted lanthanum manganites La0.7Ca0.3MnO3 upon nonequilibrium overheating of carriers
Разночтения заглавия :авие SCOPUS: Magnetoresistance of substituted lanthanum manganites La 0.7Ca 0.3MnO 3 upon nonequilibrium overheating of carriers
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2011. - Vol. 109, Is. 8. - Ст.83711. - ISSN 0021-8979, DOI 10.1063/1.3573666
Примечания : Cited References: 15. - This study was partially supported by the Russian Foundation for Basic Research, project no. 08-02-00259a, and the Lavrent'ev's Competition of Young Scientists of the Siberian Branch of the RAS, project no. 12.
Ключевые слова (''Своб.индексиров.''): field dependence--lanthanum manganites--low thermal conductivity--manganite materials--negative differential resistivity--non equilibrium--non-linearity--nonequilibrium heating--polycrystalline--positive magnetoresistance--transport currents--electric resistance--electron gas--heating--lanthanum--lanthanum alloys--magnetic fields--magnetoelectronics--magnetoresistance--manganese oxide--manganites--thermal conductivity--current voltage characteristics
Аннотация: Current-voltage characteristics of the polycrystalline substituted lanthanum manganite La0.7Ca0.3MnO3 were experimentally studied at T - 77.4 K in magnetic fields up to 13 kOe. In these characteristics, a portion of negative differential resistivity was observed above a certain threshold value of critical current density j caused, in our opinion, by nonequilibrium heating of the electron gas due to low thermal conductivity of the manganite material. Because of the nonlinearity of the current-voltage characteristics, the field dependences of resistivity rho( H) appear extremely sensitive to the value of a transport current. In this case, the rho( H) dependences reveal both ordinary negative and positive magnetoresistance. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3573666]
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaykhutdinov K. A., Popkov S. I., Semenov S. V., Balaev D. A., Dubrovskiy A. A., Sablina K. A., Sapronova N. V., Volkov N. V.
Заглавие : Low-temperature resistance and magnetoresistance hysteresis in polycrystalline (La0.5Eu0.5)(0.7)Pb0.3MnO3
Разночтения заглавия :авие SCOPUS: Low-temperature resistance and magnetoresistance hysteresis in polycrystalline (La0.5Eu0.5)0.7Pb 0.3MnO3
Место публикации : J. Appl. Phys.: AMER INST PHYSICS, 2011. - Vol. 109, Is. 5. - Ст.53711. - ISSN 0021-8979, DOI 10.1063/1.3559303
Примечания : Cited References: 20. - This study was partially supported by the Russian Foundation for Basic Research, Project No. 08-02-00259a and the Lavrentyev Competition of the Young Scientists' Projects of the Siberian Branch of the Russian Academy of Sciences, Project No. 12.
Предметные рубрики: RESISTIVITY MINIMUM
MANGANITES
FILMS
Ключевые слова (''Своб.индексиров.''): antiferromagnets--electrical resistances--ferromagnets--field dependence--inter-grain--lanthanum manganites--low temperatures--low-temperature resistance--polycrystalline--temperature dependence--tunnel contacts--antiferromagnetic materials--europium--ferromagnetic materials--ferromagnetism--hysteresis--lead--magnetic field effects--magnetoelectronics--magnetoresistance--magnets--manganese oxide--paramagnetism--superconducting materials--electric resistance
Аннотация: The behavior of temperature dependences of electrical resistance and magnetoresistance of polycrystalline substituted lanthanum manganite (La0.5Eu0.5)(0.7)Pb0.3MnO3 at low temperatures was thoroughly studied. A broad hysteresis was found in the field dependences of electrical resistance in the low-temperature region. Above 40 K, no hysteresis feature was observed. The temperature T = 40 K corresponds to the temperature of minimum electrical resistance and the temperature T-N to the antiferromagnet-paramagnet phase transition of the material of the intergrain boundaries. In this work we propose a model which explains the observed features of the rho(T) and rho(H) curves at temperatures below T-N by the formation of a network of ferromagnet-antiferromagnet-ferromagnet tunnel contacts. (C) 2011 American Institute of Physics. [doi:10.1063/1.3559303]
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Valkov V. V.
Заглавие : Anomalous resistivity and superconductivity in the two-band Hubbard model with one narrow band (Review)
Место публикации : Low Temp. Phys. - 2011. - Vol. 37, Is. 1. - P.69-82. - ISSN 1063-777X, DOI 10.1063/1.3552118; \b Физика низких температур
Примечания : Cited References: 62. - We thank A.S. Alexandrov, A.F. Andreev, M.A. Baranov, Yu. Bichkov, A.V. Chubukov, D.V. Efremov, A.S. Hewson, K.A. Kikoin, F.V. Kusmartsev, P. Nozieres, T.M. Rice, A.O. Sboychakov, P. Thalmeer, C.M. Varma, D. Vollhardt, P. Woelfle, A. Yaresko and, especially, P. Fulde, Yu. Kagan, K.I. Kugel, and N.V. Prokof'ev for many simulating discussions on this subject and acknowledge the financial support of RFBR grants # 08-02-00224 and 08-02-00212. M.Yu.K. is also grateful to the Leverhulme trust for a grant to visit Loughborough University, where this work was completed.
Предметные рубрики: FERMI-LIQUID BEHAVIOR
MAGNETIC-ALLOYS
HEAVY
DENSITY
SYSTEMS
STATE
UPT3
MECHANISM
PARTICLE
VALENCE
Аннотация: We search for marginal Fermi-liquid behavior in the two-band Hubbard model with one narrow band. We consider the limit of low electron densities in the bands and strong intraband and interband Hubbard interactions. We analyze the influence of electron-polaron effects and other mechanisms for mass-enhancement (related to the momentum dependence of the self-energies) on the effective mass and scattering times of light and heavy components in the clean case (electron-electron scattering and no impurities). We find a tendency towards phase separation (towards negative partial compressibility of heavy particles) in the 3D case with a large mismatch between the densities of heavy and light bands in the strong coupling limit. We also find that for low temperatures and equal densities, the resistivity in a homogeneous state R(T) proportional to T-2 behaves as a Fermi-liquid in both 3D and 2D. For temperatures greater than the effective bandwidth for heavy electrons T W-h*, the coherence of the heavy component breaks down completely. The heavy particles move diffusively in the surrounding light particles. At the same time, light particles scatter on heavy particles as if on immobile (static) impurities. Under these conditions, the heavy component is marginal, while the light component is not. The resistivity approaches saturation for T W-h* in the 3D case. In 2D the resistivity has a maximum and a localization tail owing to weak-localization corrections of the Altshuler-Aronov type. This behavior of resistivity in 3D could be relevant for some uranium-based heavy-fermion compounds such as UNi2Al3 and in 2D, for some other mixed-valence compounds, possibly including layered manganites. We also consider briefly the superconductive (SC) instability in this model. The leading instability tends to p-wave pairing and is governed by an enhanced Kohn-Luttinger mechanism for SC at low electron densities. The critical temperature corresponds to the pairing of heavy electrons via polarization of the light electrons in 2D. (C) 2011 American Institute of Physics. [doi:10.1063/1.3552118]
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Eremin E. V., Sablina K. A., Sapronova N. V.
Заглавие : Dielectric properties of a mixed-valence Pb3Mn7O15 manganese oxide
Коллективы :
Разночтения заглавия :авие SCOPUS: Dielectric properties of a mixed-valence Pb3Mn7O 15 manganese oxide
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2010. - Vol. 22, Is. 37. - Ст.375901. - ISSN 0953-8984, DOI 10.1088/0953-8984/22/37/375901
Примечания : Cited References: 14. - This study was supported by the Russian Foundation for Basic Research 'Siberia', project No. 09-02-98003, and the Siberian Branch of the Russian Academy of Sciences, integration project No. 101.
Ключевые слова (''Своб.индексиров.''): cation--lead--manganese derivative--oxide--article--chemical model--chemistry--crystallization--electric conductivity--electronics--methodology--temperature--cations--crystallization--electric conductivity--electronics--lead--manganese compounds--models, chemical--oxides--temperature--ac electric field--analysis of resistivity--carrier hopping--charge ordering--complex dielectric constant--crystal site--debye models--dielectric constants--dielectric spectra--frequency windows--lattice sites--low frequency--manganese ions--mixed valence--mixed valence state--relaxation behaviors--temperature range--electric fields--manganese--manganese oxide--permittivity--single crystals--crystal symmetry
Аннотация: We investigated the low-frequency dielectric properties of a Pb3Mn7O15 single crystal with manganese ions in the mixed-valence state (Mn3+/Mn4+). Dielectric relaxation was found in the frequency window from 20 to 100 kHz in the temperature range 110-180 K. The dielectric spectra of the crystal were analyzed using a Debye model. Estimations made within the model and analysis of resistivity data suggest that the relaxation behavior of the dielectric constant is related to polaronic charge carrier hopping. Around 250 K, charge ordering occurs in the crystal when the Mn3+ and Mn4+ ions are arranged in a specific order among the crystal sites. With a decrease in temperature, an ac electric field can induce a charge hop between the equivalent lattice sites available, related to crystal symmetry. This hopping is equivalent to the reorientation of an electric dipole that yields Debye-type behavior of the complex dielectric constant. The observed anisotropy in the behavior of the dielectric properties and resistivity can be attributed to a pronounced two-dimensional character of the crystal structure.
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