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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ershov A. E., Isaev I. L., Semina P. N., Markel V. A., Karpov S. V.
Заглавие : Effects of size polydispersity on the extinction spectra of colloidal nanoparticle aggregates
Место публикации : Phys. Rev. B: American Physical Society, 2012. - Vol. 85, Is. 4. - Ст.045421. - P. - ISSN 1098-0121, DOI 10.1103/PhysRevB.85.045421
Примечания : Cited References: 41. - This work was supported by grants from the following foundations of the Russian Federation: Presidium of RAS, OFN RAS, and SB RAS.
Предметные рубрики: METAL FRACTAL CLUSTERS
OPTICAL-PROPERTIES
ABSORPTION
NONLINEARITIES
COMPOSITES
SCATTERING
PARTICLES
SPHERES
GRAINS
Аннотация: We investigate the effect of particle polydispersity on the optical extinction spectra of colloidal aggregates of spherical metallic (silver) nanoparticles, taking into account the realistic interparticle gaps caused by layers of stabilizing polymer adsorbed on the metal surface (adlayers). The spectra of computer-generated aggregates are computed using two different methods. The coupled-multipole method is used in the quasistatic approximation and the coupled-dipole method beyond the quasistatics. The latter approach is applicable if the interparticle gaps are sufficiently wide relative to the particle radii. Simulations are performed for two different particle size distribution functions (bimodal and Gaussian), varying the number of particles per aggregate, and different distribution functions of the interparticle gap width. The strong influence of the latter factor on the spectra is demonstrated and investigated in detail.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Merkushova E. M., Vtyurin A. N., Isaenko L. I.
Заглавие : Raman spectroscopic study of the lattice dynamics in the Rb2KMoO3F3 oxyfluoride
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 54, Is. 6. - P.1275-1280. - ISSN 1063-7834, DOI 10.1134/S1063783412060170
Примечания : Cited References: 24. - This study was supported by the Russian Foundation for Basic Research (project nos. 11-02-98002-r_sibir', 09-02-00062, and NSh-4645.2010.2).
Предметные рубрики: PHASE-TRANSITIONS
SCATTERING
(NH4)3WO3F3
CRYSTALS
DISORDER
Cs
Аннотация: The lattice dynamics of the Rb2KMoO3F3 oxyfluoride has been studied by Raman spectroscopy in the temperature range 7–400 K. A phase transition has been revealed at T ≈ 185 K with decreasing temperature. Anomalies of the frequencies and Raman line half-widths have been analyzed. No condensation of soft lattice modes has been found. The character of changes in the Raman spectra of the Rb2KMoO3F3 oxyfluoride shows that the phase transition is related to variations in the [MoO3F3]3− molecular octahedron.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sadreev A. F.
Заглавие : Feshbach projection formalism for transmission through a time-periodic potential
Место публикации : Phys. Rev. E: American Physical Society, 2012. - Vol. 86, Is. 5. - Ст.56211. - ISSN 1539-3755, DOI 10.1103/PhysRevE.86.056211
Примечания : Cited References: 33
Предметные рубрики: NUCLEAR REACTIONS
UNIFIED THEORY
QUANTUM
FIELD
SCATTERING
SYSTEM
STATES
Аннотация: The Feshbach projection formalism is applied to consider quantum transmission through a tight-binding wire subject to a time-periodic potential. The wire is coupled with two leads via the coupling constant v(C). The periodicity of the potential implies an additional temporal dimension that reduces the problem to stationary transmission through an effectively two-dimensional lattice system. The non-Hermitian effective Hamiltonian is formulated. Thist allows us to trace the redistribution of resonance positions and resonance widths with the growth of v(C) from the weak-coupling to the strong-coupling regime.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev A. F., Gerasimov V. P., Zyryanov V. Ya.
Заглавие : Resonant angular conversion in a Fabry-Perot resonator holding a dielectric cylinder
Коллективы : RFBR [13-02-00497, 43, 101, 24.29]
Место публикации : J. Opt. Soc. Am. A: Optical Society of America, 2014. - Vol. 31, Is. 2. - P.264-267. - ISSN 1084-7529, DOI 10.1364/JOSAA.31.000264. - ISSN 1520-8532
Примечания : Cited References: 8. - This work was partially supported by RFBR grant 13-02-00497, and grants no. 43, 101 and 24.29 of SB RAS, and NSCT-SB RAS. We thank D. N. Maksimov for critical reading of the manuscript.
Предметные рубрики: SCATTERING
SURFACE
Аннотация: Light transmission through a Fabry–Perot resonator (FPR) holding a dielectric cylinder rod is considered. For the cylinder parallel to mirrors of the FPR and the mirrors mimicked by the δ functions we present an exact analytical theory. It is shown that light transmits only for resonant incident angles, αm, similar to the empty FPR. However after transmission the light scatters into different resonant angles, αm′ , performing resonant angular conversion. We compare the theory with experiment in the FPR, exploring multilayer films as the mirrors and glass cylinder with diameter coincided with the distance between the FPR mirrors. The measured values of angular light conversion agree qualitatively with the theoretical results.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Rasskazov I. L., Karpov S. V., Markel V. A.
Заглавие : Waveguiding properties of short linear chains of nonspherical metal nanoparticles
Коллективы : U.S. National Science Foundation [DMS1216970]; Russian Academy of Sciences [24.29, 24.31, III.9.5, 43]; SFU [101]; Russian Ministry of Education and Science [1792]
Место публикации : J. Opt. Soc. Am. B: Optical Society of America, 2014. - Vol. 31, Is. 12. - P.2981-2989. - ISSN 0740-3224, DOI 10.1364/JOSAB.31.002981. - ISSN 1520-8540
Примечания : Cited References: 39. - This research was supported in part by the U.S. National Science Foundation under Grant DMS1216970; by the Russian Academy of Sciences under Grants 24.29, 24.31, III.9.5, 43, and SFU (101); and by the Russian Ministry of Education and Science under Contract 1792.
Предметные рубрики: DISPERSION-RELATIONS
MODES
SCATTERING
ARRAYS
GUIDES
LIGHT
GAIN
Аннотация: We study numerically the discrete dispersion relations and waveguiding properties of relatively short linear chains of spherical and spheroidal silver nanoparticles. Simulations are based on the Drude model for the dielectric permittivity of metal and on the dipole approximation for the electromagnetic interaction of particles. We also simulate the dynamics of femtosecond optical pulse propagation along such chains. In the case that we consider (10 particles per chain), reflections from the chain terminals play a significant detrimental role. We show that dissipative traps can be used to reduce the effects of reflections. We also show that chains composed of oblate spheroids with sufficiently small aspect ratio (nanodisks) have better waveguiding properties when compared to chains made of particles with other spheroidal shapes. This includes a slower rate of decay, larger group velocity, and larger bandwidth.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Aleksandrov K. S., Tressaud A., Fokina V. D.
Заглавие : Ferroelastic phase transitions in fluorides with cryolite and elpasolite structures
Место публикации : Crystallogr. Rep. - 2004. - Vol. 49, Is. 1. - P.100-107. - ISSN 1063-7745, DOI 10.1134/1.1643969
Примечания : Cited References: 43
Предметные рубрики: NUCLEAR MAGNETIC-RESONANCE
THERMODYNAMIC PROPERTIES
RB2KMIIIF6 ELPASOLITES
NEUTRON-DIFFRACTION
CRYSTALS
PEROVSKITES
DIAGRAM
SC
RB2KGAXSC1-XF6
SCATTERING
Аннотация: The ferroelastic phase transitions are investigated in several series of fluoride crystals belonging to the elpasolite and cryolite families (space group Fm (3) over barm) with the general formula A(2)BB'F-6. The influence of the size and shape of cations and anions on the entropy and the mechanism of structural distortions is discussed. (C) 2004 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Voronov V. N., Vtyurin A. N., Goryainov S. V., Zamkova N. G., Zinenko V. I., Krylov A. S.
Заглавие : Pressure-induced phase transitions in ScF3 crystal-Raman spectra and lattice dynamics
Коллективы : Russian-CIS-Baltic-Japanese symposium on ferroelectricity
Место публикации : Ferroelectrics. - 2003. - Vol. 284. - P.205-219. - ISSN 0015-0193, DOI 10.1080/00150190390204691
Примечания : Cited References: 24
Предметные рубрики: SCATTERING
Ключевые слова (''Своб.индексиров.''): scf3--high pressure--phase transitions--raman scattering--ab initio lattice dynamics
Аннотация: New pressure-induced phases are found in normally cubic ScF3 crystal using polarizing microscopy and micro-Raman spectroscopy. Their supposed space groups are R (3) over barc, Z = 2 and Pnma, Z = 4. Using ab initio model cubic phase was shown to be stable at ambient pressure down to T = 0 K, while hydrostatic pressure brings one of the phonon branches down to negative squared frequencies. R-5 soft mode condensation results in the rhombohedric distortion of the cubic lattice with cell volume doubling. Calculated squared frequencies of the high pressure phase are positive, their number and values agree with experimental results.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Voronov V. N., Vtyurin A. N., Goryainov S. V., Zamkova N. G., Zinenko V. I., Krylov A. S.
Заглавие : Lattice dynamics and hydrostatic-pressure-induced phase transitions in ScF3
Место публикации : J. Exp. Theor. Phys.: American Institute of Physics, 2002. - Vol. 94, Is. 5. - P.977-984. - ISSN 1063-7761, DOI 10.1134/1.1484991
Примечания : Cited References: 20
Предметные рубрики: RAMAN-SPECTROSCOPY
CRYSTALS
SCATTERING
Аннотация: New phase transitions induced by hydrostatic pressure in a cubic (under standard conditions) ScF3 crystal are discovered by the methods of polarization microscopy and Raman scattering. The space groups R (3) over barc for Z = 2 and Pnma for Z = 4 are proposed for the high-pressure phases. A nonempirical computation of the lattice dynamics of the crystal is carried out. It is shown that, under normal pressure, the cubic phase is stable down to T = 0 K, while the application of a hydrostatic pressure gives rise to a phonon branch in the vibrational spectrum (between points R and M of the Brillouin zone) with negative values of squares of frequencies. The condensation of soft mode R-5 at the boundary point of the Brillouin zone leads to rhombohedral distortion of the cubic structure with the unit cell volume doubling. The calculated frequencies at q = 0 of the ScF3 lattice in the distorted rhombohedral phase are real-valued; the number and position of frequencies active in Raman scattering are in accord with the experimental values. (C) 2002 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Петров, Михаил Иванович, Balaev D. A., Gokhfel'd D. M., Шайхутдинов, Кирилл Александрович, Aleksandrov K. S.
Заглавие : Temperature evolution of the hysteresis in the current-voltage characteristic of a polycrystalline high-temperature superconductor with 1-2-3 structure
Место публикации : Phys. Solid State: American Institute of Physics, 2002. - Vol. 44, Is. 7. - P.1229-1234. - ISSN 1063-7834, DOI 10.1134/1.1494614
Примечания : Cited References: 38
Предметные рубрики: WEAK LINKS
ANDREEV REFLECTIONS
SIMPLIFIED MODEL
EXCESS CURRENT
SNS JUNCTIONS
SCATTERING
COMPOSITES
TRANSPORT
Аннотация: The temperature evolution of the current-voltage (I-U) characteristic of a contact of the break-junction type with direct conduction is investigated on a polycrystalline HTSC of the Y-Ba-Cu-O system. The experimental I-U characteristics possessing a hysteresis are correctly described in the framework of the Kummel-Nicolsky theory for an S-N-S contact (S stands for a superconductor; N, for a normal metal) in which the Andreev reflection of quasiparticles from the N-S interface is considered. It is shown that the shape of the I-U curve, as well as the existence of a hysteresis, is determined by the ratio of the number of "long" and "short" intergranular boundaries in the polycrystal under investigation. The coincidence of the calculated and experimental I-U curves made it possible to estimate the effective length of "natural" intergranular boundaries in polycrystalline HTSC materials. The estimate is obtained from the experimental temperature dependence of the critical current in the sample under investigation. (C) 2002 MAIK "Nauka/Interperiodica".
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Petrov M. I., Balaev D. A., Ospishchev S. V., Aleksandrov K. S.
Заглавие : Transport properties of HTSC plus Ba(Pb, Met)O-3 composites as functions of the electrical and magnetic characteristics of nonsuperconducting components
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2000. - Vol. 42, Is. 5. - P.810-815. - ISSN 1063-7834, DOI 10.1134/1.1131294
Примечания : Cited References: 27
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTORS
CURRENT-VOLTAGE CHARACTERISTICS
NORMAL-METAL LAYER
WEAK LINKS
JUNCTIONS
SCATTERING
BAPB1-XBIXO3
TRANSITION
IMPURITIES
BREAKING
Аннотация: Composites simulating a network of weak metallic links and consisting of a classic 1-2-3 HTSC and a BaPbO3 metal oxide with incorporated Sn, Ni, and Fe impurities have been prepared. Experimental resistivity, magnetic, and Mossbauer studies of the BaPb(0.9)Met(0.1)O(3) nonsuperconducting components are presented. The transport properties of the HTSC + BaPb(0.9)Met(0.1)O(3) composites have been investigated. The superconducting properties of the composites are observed to be suppressed, both when the carrier mean free path in nonsuperconducting components with tin impurities decreases, and as a result of an additional interaction of the magnetic moments of (Fe, Ni) impurities with the spins of supercurrent carriers. The experimental temperature dependences of the composite critical current are analyzed in terms of the de Gennes theory for the superconductor-normal metal-superconductor structures. (C) 2000 MAIK "Nauka/Interperiodica".
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Melnikova S. V., Misyul S. V., Voronov V. N., Aleksandrov K. S.
Заглавие : Phase-transitions in elpasolite Rb2KSCF6
Место публикации : Fiz. Tverd. Tela. - 1992. - Vol. 34, Is. 7. - P.2185-2195. - ISSN 0367-3294
Примечания : Cited References: 24
Предметные рубрики: RB2KMIIIF6 ELPASOLITES
CS2NANDCL6
SCATTERING
RB2NADYF6
CS2RBDYF6
RB2KDYF6
CRYSTAL
MODE
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Voronov V. N., Vtyurin A. N., Krylov A. S., Molokeev M. S., Pavlovskii M. S., Goryainov S. V., Likhacheva A. Y., Ancharov A. I.
Заглавие : Pressure-induced phase transition in the cubic ScF3 crystal
Коллективы : Russian Academy of Sciences (Siberian Branch)
Место публикации : Phys. Solid State. - 2009. - Vol. 51, Is. 4. - P.810-816. - ISSN 1063-7834, DOI 10.1134/S1063783409040295
Примечания : Cited References: 22. - The authors are grateful to V.I. Zinenko for helpful discussion of the results.This work was conducted in the framework of Integration Project (no. 3.7) of the Russian Academy of Sciences (Siberian Branch).
Предметные рубрики: RAMAN-SPECTROSCOPY
POWDER DIFFRACTION
LATTICE-DYNAMICS
SCATTERING
Аннотация: Pressure-induced phase transitions in the ScF3 crystal were studied using synchrotron radiation diffraction, polarization microscopy, and Raman spectroscopy. The phase existing in the range 0.6-3.0 GPa is optically anisotropic; its structure is described by space group R (3) c (Z = 2), and the transition is due to rotation of ScF6 octahedra around a threefold axis. The pressure dependence of the structural parameters and angle of rotation are determined. The number of Raman spectral lines corresponds to that expected for this structure; above the phase transition point, a recovery of soft modes takes place. At a pressure of 3.0 GPa, a transition occurs to a new phase, which remains metastable as the pressure decreases. The results are interpreted using an ab initio method based on the Gordon-Kim approach.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev E. N.
Заглавие : Bloch bound states in the radiation continuum in a periodic array of dielectric rods
Коллективы : Russian Science Foundation [14-12-00266]
Место публикации : Phys. Rev. A: American Physical Society, 2014. - Vol. 90, Is. 5. - Ст.53801. - ISSN 1050-2947, DOI 10.1103/PhysRevA.90.053801. - ISSN 1094-1622
Примечания : Cited References: 35. - The work was supported by the Russian Science Foundation through Grant No. 14-12-00266. We acknowledge discussions with D. N. Maksimov.
Предметные рубрики: WAVE-GUIDE
SCATTERING
CYLINDERS
CHANNEL
Аннотация: We consider an infinite periodic array of dielectric rods in vacuum with the aim to demonstrate three types of Bloch bound states in the continuum (BSCs): symmetry protected with a zero Bloch vector, embedded in one diffraction channel with nonzero Bloch vector, and embedded in two and three diffraction channels. The first and second types of the BSC exist for a wide range of material parameters of the rods, while the third occurs only at a specific value of the radius of the rods. We show that the second type supports the power flux along the array. In order to find BSCs we put forward an approach based on the expansion over the Hankel functions. We show how the BSC reveals itself in the scattering function when the singular BSC point is approached along a specific path in the parametric space.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Tsikalov D. S.
Заглавие : Spectral properties of waves in superlattices with 2D and 3D inhomogeneities
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 113, Is. 2. - P.232-244. - ISSN 1063-7761, DOI 10.1134/S1063776111080061
Примечания : Cited References: 24. - This study was supported in part by the program of the Presidium of the Russian Academy of Sciences (grant no. 27.1), Federal Targeted Program (State contract no. 02.740.11.0220), and Targeted Programs "Development of the Higher School Scientific Potential" in 2009-2010 and 2011 years.
Предметные рубрики: X-RAY REFLECTION
PERTURBED FIELDS
MULTILAYERS
SUSCEPTIBILITY
PROPAGATION
INTERFACES
SCATTERING
SYSTEM
Аннотация: We investigate the dynamic susceptibility and one-dimensional density of states in an initially sinusoidal superlattice containing simultaneously 2D phase inhomogeneities simulating correlated rough-nesses of superlattice interfaces and 3D amplitude inhomogeneities of the superlattice layer materials. The analytic expression for the averaged Green's function of the sinusoidal superlattice with two phase inhomogeneities is derived in the Bourret approximation. It is shown that the effect of increasing asymmetry in the peak heights of dynamic susceptibility at the Brillouin zone boundary of the superlattice, which was discovered earlier [15] upon an increase in root-mean-square (rms) fluctuations, also takes place upon an increase in the correlation wavenumber of inhomogeneities. However, the peaks in this case also become closer, and the width and depth of the gap in the density of states decrease thereby. It is shown that the enhancement of rms fluctuations of 3D amplitude inhomogeneities in a superlattice containing 2D phase inhomogeneities suppresses the effect of dynamic susceptibility asymmetry and leads to a slight broadening of the gap in the density of states and a decrease in its depth. Targeted experiments aimed at detecting the effects studied here would facilitate the development of radio-spectroscopic and optical methods for identifying the presence of inhomogeneities of various dimensions in multilayer magnetic and optical structures.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Handunkanda S. U., Curry E. B., Voronov V. N., Said, Ayman H., Guzman-Verri G. G., Brierley R. T., Littlewood P. B., Hancock J. N.
Заглавие : Large isotropic negative thermal expansion above a structural quantum phase transition
Место публикации : Phys. Rev. B: American Physical Society, 2015. - Vol. 92, Is. 13. - Ст.134101. - ISSN 1098, DOI 10.1103/PhysRevB.92.134101. - ISSN 1550235X(eISSN)
Примечания : Cited References:35. - The authors also acknowledge the valuable conversations with Joe Budnick and Gabe Aeppli. Work at the University of Connecticut is supported by National Science Foundation Award No. DMR-1506825. Work at the University of Costa Rica is supported by Vicerrectoria de Investigacion under Project No. 816-B5-220, and work at Argonne National Laboratory is supported by the US Department of Energy, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357. R.T.B. acknowledges support from the Yale Prize Postdoctoral Fellowship. The construction of HERIX was partially supported by the NSF under Grant No. DMR-0115852.
Предметные рубрики: SCF3 CRYSTAL
CUBIC SCF3
DYNAMICS
SCATTERING
SRTIO3
Аннотация: Perovskite structured materials contain myriad tunable ordered phases of electronic and magnetic origin with proven technological importance and strong promise for a variety of energy solutions. An always-contributing influence beneath these cooperative and competing interactions is the lattice, whose physics may be obscured in complex perovskites by the many coupled degrees of freedom, which makes these systems interesting. Here, we report signatures of an approach to a quantum phase transition very near the ground state of the nonmagnetic, ionic insulating, simple cubic perovskite material ScF3, and show that its physical properties are strongly effected as much as 100 K above the putative transition. Spatial and temporal correlations in the high-symmetry cubic phase determined using energy- and momentum-resolved inelastic x-ray scattering as well as x-ray diffraction reveal that soft mode, central peak, and thermal expansion phenomena are all strongly influenced by the transition.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Oreshonkov A. S., Khodzhibaev A. K., Krylov A. S., Umarov M. F., Vtyurin A. N.
Заглавие : Raman spectroscopy study of the behavior of the soft mode in a structural phase transition in the Pr3Sb5O12 crystal
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 57, Is. 11. - P.2286-2289. - ISSN 1063-7834, DOI 10.1134/S1063783415110256
Примечания : Cited References: 15. - The study was supported in part by the Ministry for Education and Science of the Russian FederationErrutum: The fourth affiliation and e-mail of the corresponding author should read as follows: Vologda State University, ul. Lenina 15, Vologda, 160000 Russia *e-mail: oreshonkov@iph.krasn.ru
Предметные рубрики: SCATTERING
Аннотация: The structural phase transition in the Pr3Sb5O12 crystal has been studied using Raman spectroscopy. The phase transition is accompanied by the recovery of the soft mode below T = 735 K, which is associated with the displacements of the oxygen and antimony atoms. © 2015, Pleiades Publishing, Ltd.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Loiko V. A., Zyryanov V. Ya., Konkolovich A. V., Miskevich A. A.
Заглавие : Light transmission of polymer-dispersed liquid crystal layer composed of droplets with inhomogeneous surface anchoring
Место публикации : Opt. Spectrosc.: MAIK Nauka-Interperiodica / Springer, 2016. - Vol. 120, Is. 1. - P.143-152. - ISSN 0030-400X, DOI 10.1134/S0030400X16010112. - ISSN 1562-6911(eISSN)
Примечания : Cited References:43. - This work was supported by the National Academy of Sciences of Belarus and the Siberian Branch of the Russian Academy of Sciences (project no. 36) and the Belarusian Republican Foundation for Fundamental Research (project no. F15SO-039).
Предметные рубрики: NEMATIC DROPLETS
IONIC MODIFICATION
FIELD
TRANSITIONS
SCATTERING
PARTICLES
INTERFACE
DISPLAYS
Аннотация: We have developed a model and realized an algorithm for the calculation of the coefficient of coherent (direct) transmission of light through a layer of liquid crystal (LC) droplets in a polymer matrix. The model is based on the Hulst anomalous diffraction approximation for describing the scattering by an individual particle and the Foldy-Twersky approximation for a coherent field. It allows one to investigate polymer dispersed LC (PDLC) materials with homogeneous and inhomogeneous interphase surface anchoring on the droplet surface. In order to calculate the configuration of the field of the local director in the droplet, the relaxation method of solving the problem of minimization of the free energy volume density has been used. We have verified the model by comparison with experiment under the inverse regime of the ionic modification of the LC-polymer interphase boundary. The model makes it possible to solve problems of optimization of the optical response of PDLC films in relation to their thickness and optical characteristics of the polymer matrix, sizes, polydispersity, concentration, and anisometry parameters of droplets. Based on this model, we have proposed a technique for estimating the size of LC droplets from the data on the dependence of the transmission coefficient on the applied voltage.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Morozov E. V., Martyanov O. N.
Заглавие : Probing flocculant-induced asphaltene precipitation via NMR imaging: from model toluene-asphaltene systems to natural crude oils
Коллективы : Russian Science Foundation [15-19-00119]
Место публикации : Appl. Magn. Reson.: Springer, 2016. - Vol. 47, Is. 2. - P.223-235. - ISSN 0937-9347, DOI 10.1007/s00723-015-0741-9. - ISSN 1613-7507(eISSN)
Примечания : Cited References:46. - This research was performed with the financial support of Russian Science Foundation (project no. 15-19-00119).
Предметные рубрики: PETROLEUM ASPHALTENES
MOLECULAR-DYNAMICS
AGGREGATION
MICROSCOPY
SCATTERING
RESONANCE
SEDIMENTATION
ASSOCIATION
CALORIMETRY
RELAXATION
Аннотация: An nuclear magnetic resonance (NMR) imaging approach for studying flocculant-induced asphaltene precipitation processes is introduced in this report. Unlike commonly accepted techniques, which primarily measure aggregation processes on the submicron scale (the level of asphaltene molecules and their aggregates), NMR imaging demonstrates the capability to obtain new useful information about bulk system behavior on the macro scale. To reveal the capabilities of the method, the model toluene-asphaltene system and two samples of natural crude oils with different chemical composition and physical properties (such as asphaltene content and density) were employed for experiments. The process of colloidal suspension formation and two different patterns of its evolution were observed depending on both the asphaltene content and the flocculant concentration. In the first pattern, the flocculant-induced precipitation leads to the slow uniform compacting of the suspension and descent of the sedimentation front, whereas the second pattern is characterized by sediment accumulation and the upwards drift of the front. It was found that the behavior of the precipitated asphaltenes in the model system correlates well with those observed in natural crude oils. The results achieved in this work are in agreement with the data obtained previously via other techniques. Thus, NMR imaging proved to be an efficient method for probing flocculant-induced precipitation in crude oils.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Ignatchenko V. A., Tsikalov D. S.
Заглавие : Green's functions of the scalar model of electromagnetic fields in sinusoidal superlattices
Место публикации : Physica B: Elsevier, 2016. - Vol. 485. - P.94-102. - ISSN 09214526 (ISSN), DOI 10.1016/j.physb.2016.01.006
Примечания : Cited References: 30
Предметные рубрики: SCATTERING
MEDIA
PROPAGATION
GRATINGS
DENSITY
LIGHT
Ключевые слова (''Своб.индексиров.''): green's functions--electromagnetic waves--scalar model--sinusoidal superlattices--photonic crystals--ldos
Аннотация: Problems of obtaining Green's function and using it for studying the structure of scalar electromagnetic fields in a sinusoidal superlattice are considered. An analytical solution of equation in the k-space for Green's function is found. Green's function in the r-space is obtained by both the numerical and the approximate analytical Fourier transformation of that solution. It is shown, that from the experimental study of Green's function in the k-space the position of the plane radiation source relative to the extremes of the dielectric permittivity ?(z) can be determined. The relief map of Green's function in the r-space shows that the structure of the field takes the form of chains of islets in the plane ?z, the number of which increases with increasing the distance from a radiation source. This effect leads to different frequency dependences of Green's function at different distances from the radiation source and can be used to measure the distance to the internal source. The real component of Green's function and its spatial decay in the forbidden zones in the near field is investigated. The local density of states, depending on the position of the source in the superlattice, is calculated.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kagan M. Y., Val'kov V. V., Woelfle P.
Заглавие : Manifestation of the upper Hubbard band in the 2D Hubbard model at low electron density
Место публикации : Low Temp. Phys. - 2011. - Vol. 37, Is. 9-10. - P.834-839. - ISSN 1063-777X, DOI 10.1063/1.3670026; \b Физика низких температур
Примечания : Cited References: 31. - This work was supported by RFBR Grants No. 11-0200798 and 11-02-00741.
Предметные рубрики: 2-DIMENSIONAL FERMI GAS
LIQUID BEHAVIOR
SPECTRAL FUNCTIONS
TRANSITION METALS
SUPERCONDUCTIVITY
FERROMAGNETISM
DIMENSIONS
SCATTERING
STATE
Ключевые слова (''Своб.индексиров.''): electron density--electronic density of states--fermi liquid--green's function methods--hubbard model
Аннотация: We consider the 2D Hubbard model in the strong-coupling case (U W) and at low electron density (nd(2) ≪1). We find an antibound state as a pole in the two-particle T-matrix. The contribution of this pole in the self-energy reproduces a two-pole structure in the dressed one-particle Green-function similar to the Hubbard-I approximation. We also discuss briefly the Engelbrecht-Randeria mode which corresponds to the pairing of two holes below the bottom of the band for U W and low electron density. Both poles produce nontrivial corrections to Landau Fermi-liquid picture already at low electron density but do not destroy it in 2D.
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