bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of plant density and biological products on the formation of seed yield of maize lines under irrigation conditions
Authors: Marchenko Tetiana , Piliarska Olena , Kiyamova Dilfuza , Musaev Sharof
Published: January 2025

Treatment with biological products resulted in an increase in the area of the assimilation apparatus by 1.7 to 2.4 thousand m²/ha.The application of Bio-gel led to an increase in leaf surface by 1.7 thousand m2/ha or 5.3%, and the treatment with Helafit combi by 2.4 thousand m2/ha or 7.5%. The treatment with biological products contributed to an increase in photosynthetic potential by 5.1% compared to the treatment with Bio- gel and by 7.2% compared to the treatment with Helafit combi. It was found that the treatment of parental lines with Bio-gel and Helafit combi caused an increase in laboratory germination of seeds. When using Bio-gel, the laboratory germination rate increased by an average of 1.5%. The treatment with Helafit combi was more effective, as the germination rate in this experimental variant increased by 2.4%. The increase in laboratory germination was observed due to a decrease in the infection of seeds of the lines by Fusarium moniliforme Scheld. The maximum seed yield in the early maturing line - the parent component of DK 281 was recorded at a density of 90 thousand plants/ha and treatment with Helafit combi - 3.65 t/ha. The maximum yield in the line - the parent component of DK 247 was observed at a density of 80 thousand plants/ha and treatment with Helafit combi - 4.89 t/ha. The medium-late line - the parent component DK 411 showed the highest yield at a density of 70 thousand plants/ha and treatment with Helafit combi - 4.65 t/ha. The maximum yield in the experiment was observed in the line
Peculiarities of Chickpea Growing Technology in the Steppe Zone of Ukraine
Authors: Zhuk Mykola , Rudenko Viacheslav , Khodjibekov S.
Published: January 2025

Chickpea is a valuable food crop. Among legumes, chickpea (Cicer arietinum) occupies a leading position in both quality and quantity of protein, which makes it a valuable food source. Its grain is widely used in human nutrition, especially in countries such as Turkey, Israel and other Middle Eastern countries. Research on chickpea breeding, seed production and cultivation technologies was carried out at the Odessa State Agricultural Research Station of the Institute of Climate-Oriented Agriculture of the National Academy of Agrarian Sciences of Ukraine from 2019 to 2022. These years provide grounds for highlighting a number of pressing issues in the modern vision of crop development. Growing demand and market prices have necessitated an increase in the cultivation area and promotion of chickpeas in the southern regions of Ukraine. Odessa region is a leader in expanding chickpea cultivation in the south of Ukraine. Several well-known farms, such as OOO AgroSvit (Belgorod-Dnestrovsky district, Petrovpavlovka village), KFH Svetlana (Bolgrad district) and others have been steadily growing chickpeas on areas of 400 to 500 hectares for the past ten years, receiving an average of 2.0–2.2 tons per hectare.
Comprehensive Analysis of Oil Sludge from The Absheron Peninsula to Solve Environmental Problems
Authors: Aliyev Goshgar , Aliyev Emin
Published: January 2025

The Absheron Peninsula, historically known for its oil production, is home to several key oil fields including Bibi-Eybet, Balakhani, Surakhani and Ramana. Decades of oil production have resulted in the accumulation of significant quantities of oil sludge, which poses significant environmental and economic challenges. The objective of this study is to conduct a comprehensive chemical analysis of oil sludge from these fields using an Agilent Technologies ICP-OES 5810 for elemental analysis and a Cary 630 FTIR for molecular characterization. The results provide valuable information on the composition of these sludges, which can facilitate more effective remediation and disposal strategies.
Inferior outcome of stand-alone short versus long tibial stem in revision total knee arthroplasty. A retrospective comparative study with minimum 2 year follow-up
Authors: Abdelatif Elsayed Ahmed , Abu Mukh Assala , Elsaid Ahmed Nady Saleh , Youssef Ahmed Omar , Foissey Constant , Servien Elvire , Lustig Sebastien
Published: January 2025

Introduction: Revision Total Knee Arthroplasty (RTKA) is complex, and induced bone loss might endanger implant fixation and joint stability. Intramedullary stems improve fixation throughout stress redistribution. The current study aims to compare the performance of short tibial stems with long tibial stems, investigating their intermediate-term radiographic and survival outcomes in RTKA. The main hypothesis is that the two types of tibial stems would exhibit similar complication and revision rates in mid-term follow-up. Methods: Patients who underwent RTKA for all causes in a specialized arthroplasty center from 2010 to 2022 with minimum 2-year follow-up were included in this study. Patients receiving mega prosthesis or implants associated with sleeves or cones were excluded. The final groups consisted of 234 knees: 110 patients with short stems (SS) and 124 with long stems (LS). The mean age at surgery was 65.96 ± 8.73 years in SS and 67.07 ± 8.64 years in LS. The mean Body Mass Index (BMI) was 28.95 is SS and 30.88 in LS (p < 0.05). The average follow-up for SS group was 4.24 years and for LS 5.16 years (p < 0.05). Results: Complications and re-revisions did not differ significantly between two groups (p > 0.05). Pathological radiolucency was present in 20.91% in SS group and 33.87% in LS group (p < 0.02). Time-to-re-revision was shorter in SS group and occurred at a mean of 3.1 years, while LS failed at a mean of 5.1 years (p < 0.001). Conclusions: The SS and LS may be comparable in terms of complications and re-revision. SS significantly fails almost 2 years earlier than long stem (p < 0.001). Additionally, there is a higher tendency for re-revision due to loosening in patients who present pathological radiolucency in SS group. To obtain the benefits of short stem and improve the longevity of the construct; adjuvant zone II (metaphyseal) fixation might be the clue.
Non covalent inhibitors of SARS-CoV-2 main protease, a rescaffolding attempt
Authors: Krischuns Tim , Paisant Sylvain , Chen Kuang-Yu , Thirion Laura N , Zettor Agnes , Chiaravalli Jeanne , Jacob Yves , Bellinzoni Marco , Naffakh Nadia , Janin Yves Louis
Published: January 2025

Out of the results of the sole large-scale screening for inhibitors of SARS-CoV-1 main protease reported in 2013, attempts to improve the 3-pyridyl-bearing hits found have been conducted in research laboratories, either on this enzyme or more recently on the closely related SARS-CoV-2 main protease. From the resulting structural information reported, we sought to design analogues featuring some of the components providing an affinity for the active site of these proteases along with a different scaffold which would allow for further structure-activity relationship studies and/or pharmacological improvements. We describe here the introduction of a bridging component aiming at the stabilization of the ligand conformation adopted when bound to these proteases. Accordingly, this led us to prepare 3,3-disubtituted piperazin-2-ones from an array of ketones, via either a Bargellini reaction or a multistage condensation/cyclization/hydrolysis involving ethylene diamine and potassium cyanide. However, even the most elaborate and lipophilic biphenyl-bearing analog made, displayed only a weak effect in a bioluminescence-based SARS-CoV-2 main protease inhibition assay.
Psychological reactance to vaccine mandates on Twitter: a study of sentiments in the United States
Authors: Hsieh Pei-Hsun
Published: January 2025

This study examines the relationship between vaccine mandates and public sentiment toward vaccines and health officials on Twitter. I analyzed 6.6 million vaccine-related tweets from July 2021 to February 2022 in the United States. Leveraging a large language model, BERT, I identified tweets discussing vaccine mandates even when lacking explicit keywords. Compared to non-mandate tweets, those mentioning mandates exhibit greater negativity, anger, and freedom-related language. Furthermore, increased state-level discussion of mandates correlates with rising levels of negativity and anger toward both vaccines and public health officials. Finally, greater disparity in vaccination progress across counties within a state is associated with increased anger in tweets directed toward both.
Acoustoelectronic size effects in metals (review)
Authors: Gokhfel’d V. M. , Kirichenko O. V. , Peschanskii V. G.
Published: January 2025

We consider acoustoelectronic phenomena in conductors with a high density of charge carriers under conditions when their mean free path compares to or exceeds the specimen thickness. In an external magnetic field, the scattering of electrons by the specimen boundary being close to the specular, a number of resonant and oscillatory effects occur that are due to the magneto-size quantization of the charge carrier energy or due to the effect of scattering at the conductor surface on their ballistics. These effects are analyzed over a wide range of acoustic frequencies for an arbitrary dispersion law of charge carriers. The oscillation period and the resonance magnetic field values contain more detailed information on the local characteristics of the Fermi surface as compared to acoustoelectronic phenomena in bulk specimens. Analysis of the smoothly (vs. H) varying part of the sound absorption decrement allows a detailed investigation into the dissipation mechanism in the system of electrons, which stems from their scattering by the specimen boundary. Acoustoelectronic phenomena have been analyzed for the condition of Andreev reflection of charge carriers by the normal metal–superconductor interface. Effect of the surface scattering of charge carriers on the electron-mediated transport of acoustic pulses is considered and the possibility is demonstrated of using a metal with open Fermi surfaces as a multiplier of sound pulses.
Self-diffusion in solid helium
Authors: Dyumin N. E. , Zuev N. V. , Grigor’ev V. N.
Published: January 2025

Based on measured rates of diffusion flow we have obtained data on the self-diffusion coefficients in hep 4He at molar volumes 20.30 to 20.82 cm3/mole. The experimental self-diffusion data in the working temperature range 1.3 to 1.7 K are shown to be consistently described by means of quantum mobility of thermal vacancies.
Vortex creep in Bi2Sr2Ca1Cu2O8+δ films
Authors: Grishin A. M. , Nikolaenko Yu. M. , Zinovuk A. V. , Vengalis B. Yu. , Flodström A.
Published: January 2025

We studied the magnetoresistance of thin, strongly textured BSCCO films deposited by the molecular-beam epitaxy method on MgO (100) substrates. It has been found that, within the temperature range 65 to 95 K, in magnetic fields up to 18 kOe, the magnetoresistance is due to thermally activated magnetic flux flow. The vortices have a macroscopic size of order 0.2 mcm. They are pinned in a shallow (the activation energy U∼940 K in a field of 1 kOe) and smoothly varying (at distances of the order of 50 mcm) potential relief. The temperature and field dependences of the activation energy, viz., U∝1−T/T0H, implies noncorrelated flux jumps by distances of the order of the average inter-vortex separation.
Effect of silver concentration on electric and magnetic properties of HTS composites YBa2Cu3Ox–Ag
Authors: Dotsenko V. I. , Kislyak I. F. , Pal’-Val’ P. P. , Pal’-Val’ L. N. , Natsik V. D.
Published: January 2025

The resistive and magnetic properties of the composites YBa2Cu3Ox–Ag are investigated in a wide range of silver concentration (c = 0–100%). It is found that the concentration dependences of the critical temperature Tcz and the critical density Jc are nonmonotonic, the peak values being attained for c = 5–15 vol.% Ag. A quantitative and qualitative correlation between the Jc(c) and the concentration dependence Jcj(c) of the critical current density in the weak coupling subsystem of a granulated superconductor is established. It is shown that the variation of the critical parameters of granulated HTS compounds is associated with the formation of intergranular silver layers of various thickness.
Effect of silver concentration on the structure and acoustic properties of the HTS composite YBa2Cu3Ox–Ag
Authors: Pal’-Val’ P. P. , Pal’-Val’ L. N. , Braude I. S. , Khomenko V. G. , Kislyak I. F. , Dotsenko V. I. , Natsik V. D.
Published: January 2025

Acoustic properties and structure of YBa2Cu3Ox–Ag composites are investigated in a wide range of silver concentration (c = 0–100%). An analysis of x-ray diffraction data and of the behavior of the structure-sensitive peak of ultrasound absorption reveals that the initial HTS phase 1:2:3 does not undergo any significant change in the technologically important concentration range c ≤ 20 vol.% Ag. In samples with c ≥ 10 vol.% Ag, a new relaxation absorption peak is observed, whose amplitude increases with c. It is shown that the microscopic mechanism responsible for this peak is the low-temperature dislocation relaxation in crystalline silver. The concentration dependence of the effective velocity of longitudinal sound is obtained for this composite for the first time, and its nonmonotonic nature is established. It is found that the formation of intergranular silver layers of various thickness determines the variation of elastic and relaxation properties of granulated HTS composites to a considerable extent.
Peculiarities of nuclear spin dynamics of bounded antiferromagnets
Authors: Stefanovskii E. P. , Tarasenko S. V.
Published: January 2025

It is shown by using a bounded cubic antiferromagnet as an example that if the thickness d of a magnetic film is smaller than a critical value d*, the linear spin dynamics of the nuclear spin subsystem of the antiferromagnet is characterized by some new peculiarities which are not observed for d≫d*.
On the dynamics of low-dimensional Heisenberg magnets with S = 1/2
Authors: Antsygina T. N. , Slyusarev V. A.
Published: January 2025

The thermodynamics and temperature dependence of spin correlation functions are analyzed for two- and quasi-two-dimensional Heisenberg magnets with a spin S-1/2 in an arbitrary temperature range. The method of Green’s functions uncoupling used for this purpose explicitly takes into account the short-range order and rules out long-range order in the system.
Absorption and velocity of ultrasound in plastically deformed tungsten
Authors: Rinkevich A. B.
Published: January 2025

The Doppler-shifted acoustic cyclotron resonance and the temperature dependence of absorption and velocity of transverse and longitudinal ultrasound waves in tungsten are measured in the temperature interval 4.2–90 K. It is shown that the temperature dependence of absorption may be explained by the dislocation-related umklapp processes occurring between the FS sheets.
Giant quantum-mechanical Hall effect in multichannel specular reflection of electrons at metal plate boundaries
Authors: Slutskin A. A. , Manzhelii E. V.
Published: January 2025

A quantum-interference effect is predicted in metal plates of thickness L≲l0 (l0 is the mean free path) upon multichannel specular reflection (MSR) of electrons at the metal surface in a weak magnetic field H perpendicular to the plate boundary. The effect consists in an increase in the Hall coefficient R (for small values of H) as compared to its normal value by a factor of pFL/ℏ (pF is the characteristic Fermi momentum). The expressions obtained for R are found to be valid for an arbitrary number of MSR channels.
Effect of pressure on the magnetic susceptibility of CeB6
Authors: Panfilov A. S. , Pushkar’ Yu. Ya. , Svechkarev I. V.
Published: January 2025

The effect of uniform compression on the magnetic susceptibility of CeB6 is investigated at 20.4, 78, and 296 K. The results are analyzed by using a theory taking into account the joint influence of the Kondo effect and crystal field on the susceptibility. The dependences of microscopic characteristics of the system, viz., the splitting of the 2F5/2 multiplet by the crystal field and of the Kondo interaction parameter, on the atomic volume are obtained.
Aharonov–Casher effect and a new type of magnetic oscillations in conductors
Authors: Zvyagin A. A. , Krive I. V. , Rozhavskii A. S.
Published: January 2025

A new type of magnetic oscillations with a period inversely proportional to the square of magnetic field is predicted in conductors. The effect is generated by a force-free topological interaction associated with the motion of electrons in closed Larmor orbits about linear edge dislocations playing the role of sources of the Aharonov–Casher field.
Heat capacity of dilute solid solutions of nitrogen in the matrix of inert gases
Authors: Antsygina T. N. , Slyusarev V. A.
Published: January 2025

A consistent theory has been developed to provide a qualitative description of the experimental data on the heat capacity of solid solutions of nitrogen molecules in the matrix of inert gases for impurity concentrations up to 1%.
Electron scattering on impurities in the two-band model of a superconductor with a narrow band near the Fermi level
Authors: Galaiko V. P.
Published: January 2025

From the physical viewpoint, the high-temperature superconducting metaloxides are substitution-type crystal solutions and should be treated in theory as “dirty” impurity systems. A technique is developed, in this paper, for averaging over randomly distributed impurities for the two-band model of a high-Tc superconductor with a wide conduction band and a local level near the Fermi level and with exchange of singlet electron pairs between the level and the band. This procedure accounts for the fact that electrons are broken up into two groups, mobile and immobile. It is shown that Anderson’s theorem remains formally valid in this model, viz., the collision frequency of the mobile electrons disappears from the equations that govern the critical temperature of the superconducting transition. Under normal skin-effect conditions at low frequencies, the impurity conductivity of the system has been calculated as a function of frequency and temperature. Owing to the resonance behavior of the collision frequency of mobile electrons, the conductivity (in the mean field approximation for the electron–electron interaction) reveals a number of anomalies at energies close to the local-level energy and, in particular, accounts for the crossover from the linear resistivity vs. temperature dependence to a semiconductor-like one observed experimentally at high enough frequencies.
Low-frequency anomalies in conductivity of superconducting metaloxides in the normal state
Authors: Galaiko V. P. , Dmitriev V. M. , Ofitserov M. N. , Prentslau N. N.
Published: January 2025

We have studied temperature and frequency dependence of the Ohmic resistance Rs of the YBa2Cu3Ox ceramic in the normal state (in the range of temperatures from Tc to 300 K and frequencies from 0 to 107 Hz). It is shown that the observed change of sign of the derivative ∂Rs/∂T in a certain frequency range is a consequence of the intrinsic properties of the ceramic rather than of the size effect. The observed phenomenon finds a qualitative explanation within the framework of the two-band superconductor model.
Interaction of current carriers with acoustic plasmons is a possible origin of high-temperature superconductivity in cuprate metaloxide compounds. I. Electron–plasmon and Coulomb interactions in layered metals
Authors: Pashitskii É. A.
Published: January 2025

The spectrum of low-frequency collective charge density excitations (acoustic plasmons) in a layered metal having a quasi-two-dimensional electron spectrum and a narrow band (a density-of-state peak) near the Fermi level is considered in the tight-binding approximation. Exchange of virtual acoustic plasmons is shown in this case to bring about an inter-electron attraction within the whole Brillouin zone. Hybridization between acoustic plasmons and optical phonons leads to an expansion of the region of attraction while local-field correlation effects and increasing number of conducting layers in the elementary (primitive) crystal lattice cell lead to enhanced electron–plasmon interaction.
Simulation of small magnetic particles of Cr2O3 and α-Fe2O3
Authors: Murtazaev A. K. , Favorskii I. A.
Published: January 2025

Equilibrium properties of small magnetic particles of Cr2O3 and α-Fe2O3 are investigated by using the Monte Carlo method. The temperatures of ordering are calculated. The results obtained for small Cr2O3 particles are compared with those for a system with periodic boundary conditions. The dynamic behavior of spins over short periods of time is studied by the molecular dynamics method.
Excitation of zeroth sound waves and quasiwaves in metals with a weak Fermi-liquid interaction
Authors: Kopeliovich A. I. , Churyukin M. S.
Published: January 2025

Various types of fast waves excited by an acoustic pulse in the Fermi liquid of a metal are considered by using a unified model. The conditions required for the formation of a zeroth sound wave are determined. It is shown, in particular, that, in the case of a weak Fermi-liquid interaction, zeroth sound is formed at a distance from the metal surface that is much larger than its wavelength. Besides, it is shown that a ballistic quasiwave existing in the model of Fermi gas is considerably affected by the Fermi-liquid interaction. For ωτ≪l, the quasiwave competes with a wave of nonequilibrium concentration of charge carriers of various types.
Phase transitions in the field of a laser wave
Authors: Aizenberg A. Ya. , Gufan Yu. M. , Pashinin P. P. , Prokhorov K. A.
Published: January 2025

A mechanism leading to a structural phase transition in crystals containing rare-earth ions in the field of high-intensity laser radiation is proposed. Dependences of the order parameter and transition temperature on the radiation intensity, frequency, and level structure are calculated. The model provides explanations for some well-known experiments.
Structure and thermodynamic properties of SF6
Authors: Isakina A. P. , Prokhvatilov A. I.
Published: January 2025

The structure and thermal expansion of the high-temperature phase of sulfur hexafluoride have been investigated by the x-ray diffraction technique. It is shown that the structure of SF6 corresponds to the bcc lattice with a space symmetry Im3m and molecular orientation along the main crystallographic directions. Extensive data are obtained on the temperature dependence of lattice parameters, molar volumes, and coefficients of thermal expansion. Other thermodynamic characteristics including the Grüneisen parameter, Debye temperature, and the components of the total heat capacity of the crystal are also analyzed. The effect of dynamic molecular disordering with increasing temperature on the structure and thermodynamic properties of SF6 is established.
Anomalies in low-temperature calorimetric properties of lead chalcogenides
Authors: Chernik I. A. , Berezin A. V.
Published: January 2025

The main results of investigations of calorimetric anomalies in PbTe, PbSe, and PbS are summarized. The data of calorimetric experiments, which are presented, compared, and analyzed in detail, point towards the existence of two serious anomalies in the low-temperature calorimetric properties of (undoped) lead chalcogenides with nearly stoichiometric composition. The observed anomalies and their characteristic features are interpreted by using the concept of tunnel states (configurational tunneling) associated with intrinsic defects (vacancies) and responsible for the formation of (multilevel) Schottky centers with low (∼ 0.1 − 1 meV) excitation energy.
Anomalies in physical and mechanical properties of Bi ceramics below the superconducting transition temperature
Authors: Gorbatenko V. M. , Karaseva E. V. , Krivenko L. F. , Lazareva M. B. , Starodubov Ya. D. , Frolov V. A. , Khaimovich P. A.
Published: January 2025

Inelastic deformation of Bi ceramics is investigated under active loading in the temperature range 4.2–77 K and at 300 K. The creep under axial compression of samples is studied upon a continuous increase in temperature from 4.2 to 60 K. A sharp change in acoustic emission registered during the deformation of the samples is accompanied by peculiarities in their mechanical behavior. It is shown that the ceramics under investigation exhibit activation of acoustic emission, variation of the creep rate, and anomalies in the system of free charge carriers in the temperature range below 35–40 K. On the whole, this is apparently an indication of a structural transformation in this temperature range.
Longitudinal magnetoplasma mode in conductors with quasilocal electron states
Authors: Ermolaev A. M. , Rashba G. I. , Shurduk A. I.
Published: January 2025

The effect of quasilocal electron states on plasma waves propagating in metals at right angles to a magnetic field is considered. It is shown that new branches of the spectrum of longitudinal waves exist in the vicinity of the resonance electron transitions between quasilocal level and Landau levels. The spectrum and the damping decrement of these waves are calculated.
Structural distortions of copper–oxygen layers and the nature of weak ferromagnetism in compounds of the R2CuO4 type
Authors: Vitebskii I. M. , Stepanov A. A.
Published: January 2025

Possible types of crystal structure distortions in copper–oxygen layers, which are responsible for weak ferromagnetism of compounds belonging to the R2CuO4 family are classified on the basis of the symmetry analysis. The most probable type of such distortions is indicated. The obtained results are compared with the experimental data.
Effect of short-wave surface excitations of liquid helium on momentum relaxation in a two-dimensional electron gas
Authors: Monarkha Yu. P.
Published: January 2025

Effect of the nonlinear terms in the Hamiltonian of the interaction of electrons with surface excitations of the liquid-vapor interface on the phenomena associated with the momentum relaxation in a two-dimensional electron gas on the liquid helium surface is considered theoretically. It is established that thermal (short-wave) ripplons, whose contribution to the momentum relaxation rate is very small in the traditional theories of transport, can, within the approach under consideration change essentially the quantum electron mobility in the region of low temperature as well as explain the previously observed discrepancies between theory and experiment in the variation of the mobility with concentration without a magnetic field.
Low-temperature thermodynamics of magnetically ordered states of a narrow-band Hubbard magnet
Authors: Zubov É. E.
Published: January 2025

The effect of exchange and doping on the structure of the ground state of a narrow-band Hubbard magnet is investigated by using the t-J model. The boundaries of ferro–, antiferro–, and paramagnetic phases are determined. The low-temperature thermodynamics of the ferromagnetic state is studied. It is found that thermal fluctuations affect the saturated ferromagnetic state and cause a concentration drop of magnetization to zero at temperatures T/W ≪ 1 (W is the band width). The experimentally observed peculiarities in the behavior of susceptibility, such as a paramagnetic increase in proportion to 1/T and the emergence of a Schottky-type peak, are explained qualitatively.
Electron absorption of flexural waves
Authors: Gokhfel’d V. M.
Published: January 2025

The contribution of free charge carriers to the absorption of flexural waves in a thin metal layer is calculated. The effect of surface electron scattering and the applicability of the results to quasiflexural waves in layered conductors are considered.
Current instability in metals with open Fermi surfaces
Authors: Peschanskii V. G. , Stepanenko D. I.
Published: January 2025

Nonlinear effects in thin conductors with open Fermi surfaces are investigated theoretically. It is shown that the intrinsic magnetic field of a steady-state current affects the dynamics of conduction electrons moving in open trajectories and interacting with the mirror surface of the sample, and generates low–frequency oscillations of the electric field. Analytic expressions for the oscillation frequencies are obtained, and a quantitative theory of this phenomenon is constructed.
Anisotropy of electronic excitations in crystals of inert elements and the self-localization barrier
Authors: Ratner A.M. , Fugol’ I. Ya.
Published: January 2025

Anisotropic properties of excitons and holes in cubic symmetry crystals are investigated and the quasiparticle polarization is assigned a preferred direction. Such an anisotropy is manifested clearly in insulators with an atomic type ground state since overlapping of valence p–states of neighboring atoms depends strongly on the angle between the lattice vector and the polarization direction. The anisotropy of the exciton- and hole dispersion relations is studied. It is shown that this anisotropy considerably affects the self-localization barrier.
Thermal conductivity of solid solutions of N2 in Ar
Authors: Gorodilov B. Ya. , Zholonko N. N. , Stahovjak P.
Published: January 2025

Thermal conductivity of argon crystals with nitrogen impurity is measured in the temperature range 2–20 K for impurity molecule concentrations between 0.05 and 1. The additional thermal conductivity associated with nitrogen impurity is proportional to T–2 for a linear concentration dependence. Possible mechanisms of phonon scattering by impurity are discussed.
Interaction of current carriers with acoustic plasmons is a possible origin of high-temperature superconductivity in cuprate metaloxide compounds. II. Critical temperature and isotope effect
Authors: Pashitskii É. A.
Published: January 2025

It is shown that high critical temperatures Tc and a weak isotope effect are characteristic of the plasmon mechanism of superconductivity due to the Cooper pairing of mobile “light” current carriers caused by exchange of virtual quanta of collective charge density excitations (acoustic plasmons) in the system of almost localized “heavy” carriers. The Tc is a nonmonotonic function of the doped carrier concentration while the index of the isotope shift in Tc decreases with increasing Tc in accord with experimental data for the high-temperature superconductors based on metaloxide cuprate compounds.
Analysis of low temperature properties of HTSC oxides La2–xMxCuO4–δ in the model of multi-well potential centers
Authors: Ivanov M. A. , Mitrofanov V. Ya. , Fishman A. Ya. , Fotiev A. A.
Published: January 2025

We consider thermodynamic properties of the crystals undergoing structural phase transitions because of a cooperative Jahn–Teller effect. Effect of random crystal fields produced by substitution atoms on the heat capacity, the elastic moduli, and the linear thermal expansion of such systems is studied in the framework of the molecular field theory. A build-up of the linear (in temperature) contribution to the heat capacity with increasing impurity concentration for x < xcr is demonstrated.
A study of spatial distribution of critical currents in high-T
c films by the laser scanning microscopy method
Authors: Dmitrenko I. M. , Grib P. A. , Sivakov A. G. , Turutanov O. G. , Zhuravel’ A. P.
Published: January 2025

Using low-temperature laser-scanning microscopy we have visualized the current-induced superconductivity destruction process in thin films of high-Tc materials of different quality. The critical current is shown to be controlled by local inhomogeneities and defects of the film, which need to be taken into account when analyzing current–voltage curves. A method is suggested for measuring critical currents in multiconnected superconducting circuits.
The dynamics of ions and the isotope effect in YBa2Cu3O7–δ
Authors: Kosov A. A.
Published: January 2025

Bose-condensation of local pairs of pz-holes on oxygen ions occupying the O4 positions in YBa2Cu3O7–δ compounds is studied by taking into account the interaction of holes with optical vibrations of atoms in the complex O4–Cul–O4. It is shown that the superconducting transition temperature Tc and the isotopic shift depend on the so-called resonance concentration of holes which is determined by the parameters of the vibrational subsystem and the efficiency of electron–phonon interaction. A possible explanation is offered for the weak isotope effect in YBa2Cu3O7–δ and for the increase in Tc observed in a number of cases upon an increase in the vibrational frequency of oxygen ions occupying the O4 positions.
A new nonlinear quantum effect in the propagation of a small-amplitude acoustic pulse in metals
Authors: Gorelik L. Yu. , Kovtun E. A.
Published: January 2025

Collisionless absorption of short one-dimensional acoustic pulses propagating in metals is considered. The size a of such pulses is much smaller than the electron mean free path, and the characteristic energy U0 of interaction between the sound and electrons is much smaller than the quantum uncertainty E0 = ℏ2/ma2 in the electron energy. It is shown that in view of the one-dimensional nature of electron scattering at a sound packet, the sound absorption coefficient does not tend to a constant in the limit U0 → 0 in some physically important situations, but increases according to the law ln (U0/E0). This anomaly is observed when the dispersion relation of an electron as a function of the electron momentum in the direction of sound propagation has closely spaced extrema separated by energies ⩽ (U0(U0/E0) (coherent magnetic breakdown). A universal expression is obtained from the first principles for the energy absorption in a moving localized perturbation of any origin in terms of the S-matrix of electron scattering. The predicted phenomenon is explained by using analytic properties of the S-matrix.
Electron–phonon scattering in thin bismuth films
Authors: Kashirin V. Yu. , Komnik Yu. F.
Published: January 2025

Comprehensive investigations of the weak localization and interaction of electrons and the electron overheating effect in thin bismuth films (∼ 100 Å) have been carried out at helium temperatures. Temperature dependences of inelastic electron relaxation times have been obtained from the magnetic field dependences of quantum corrections to the conductivity, and the variation of these corrections due to electron overheating has been used to find the temperature dependence of the electron–phonon scattering time in the temperature range where the electron–electron interaction processes dominate in the electron kinetics.
Simulation of activationless motion of dislocations through complex ensembles of forest dislocations and point obstacles
Authors: Loginov B. M. , Tolstykh S. V.
Published: January 2025

Computer simulation methods have been used to study the movement of slip dislocations in NaCl crystals through complex ensembles of forest dislocations and point obstacles by taking into account the finite structure of long-range internal stress fields. The complex ensembles are found to contain characteristic intervals of relative concentration of forest dislocations in which different types of obstacles affect the characteristics of motion of slip dislocations through these ensembles. It is shown that the sum of squares of stresses in the motion of slip dislocations through single-component ensembles constituting the complex ones are in best correspondence with the square of the total stresses of slip dislocation motion through complex ensembles.
Retardation of charged dislocations by impurity atoms in semiconducting crystals at low temperatures
Authors: Gestrin S. G.
Published: January 2025

It is shown that impurity atoms considerably affect the retardation of charged dislocations in semiconductors at low temperatures. The electric field of a moving dislocation excites the energy levels of impurity atoms, causing energy dissipation. The velocity dependence of the induced drag force acting on the dislocation is investigated.
Low-temperature plastic deformation of Al–Li solid solutions
Authors: Fomenko V. S. , Isaev N. V. , Pustovalov V. V.
Published: January 2025

Detailed investigations of plastic deformation of Al–Li solid solutions with equilibrium and nonequilibrium lithium concentrations have been carried out in the temperature range 293–4.2 K. The effect of temperature on the main parameters of the stress–strain curve is studied. The temperature dependence of the yield stress and the strain rate sensitivity of deforming stress at T < 140 K are analyzed in terms of the concept of thermally activated nature of plastic deformation of the alloys.
Resonance vibrations in three-dimensional and low-dimensional crystals containing two-parametric substitutional impurities
Authors: Ivanov M. A. , Kosevich A. M. , Syrkin E. S. , Gospodarev I. A. , Skripnik Yu. V. , Feodos’ev S. B.
Published: January 2025

The spectrum of quasilocal vibrations in three-dimensional and low-dimensional crystals containing two-parametric substitutional impurities is calculated analytically by using Green’s function technique. The results of analytic calculations are supplemented with a numerical analysis carried out for realistic lattice models in a wide range of defect parameters and anisotropy values of the crystal. Among other things, it is shown that well-defined resonance vibrations can emerge in low-dimensional systems practically in any spectral region.
Operating features of a dilution refrigerator with condensation pumping
Authors: Sivokon’ V. E. , Dotsenko V. V. , Pogorelov L. A. , Sobolev V. I.
Published: January 2025

Dilution refrigerators with a 3He cryogenic circulation cycle have a number of advantages over other models. The design of one of the most promising refrigerators of this type, viz., a dilution refrigerator with condensation pumping, is described and its operation is analyzed.
Temperature correlation of peculiarities of the impedance of a YBa2Cu3Ox film and an SrTiO3 substrate
Authors: Dmitriev V. M. , Kravchenko E. L. , Ofitserov M. N. , Prentslau N. N. , Svetlov V. N. , Stepanov V. B.
Published: January 2025

Temperature correlation has been established between the anomalies of ohmic losses and the reactive response of a SrTiO3 substrate and a YBa2Cu3Ox film. Impedance peculiarities that are characteristic for the substrate and material of the film separately are not observed in bulk samples of YBa2Cu3Ox and in metallic films deposited on a SrTiO3 substrate.
Dynamic properties of electrons in a single conducting channel on the surface of liquid helium
Authors: Kirichek O. I. , Monarkha Yu. P. , Kovdrya Yu. Z. , Grigor’ev V. N.
Published: January 2025

A simple method for creating a solitary conducting channel of high-mobility electrons on a liquid helium surface strongly distorted by capillary forces is described and experimentally realized. it is shown that this system can be used for effectively studying the influence of dimensional and correlation phenomena on the dynamic properties of electrons. The channel conductivity displays a strongly nonmonotonic dependence on the holding potential and the number of electrons in the channel.
The stability of van der Waals compounds at high pressure
Authors: Vos Willem L. , Schouten Jan A.
Published: January 2025

Recent experiments have revealed the existence of stoichiometric solid phases in nitrogen–helium and neon–helium mixtures at high pressures. An overview of the experimental and theoretical results is given. The stability of these compounds, formed by molecules interacting only through weak van der Waals forces is discussed and compared to the hard-sphere system. Contrary to that system, van der Waals compounds are probably stabilized by energy effects.
Heat transport in cryocrystals with impurities. Resonance impurity scattering and three-phonon processes
Authors: Antsygina T. N. , Slyusarev V. A.
Published: January 2025

A theoretical model is suggested for the heat transport in cryocrystals with heavy impurities without internal degrees of freedom. The theory is based on a consistent solution of the kinetic equation for the phonon gas. The large magnitude of the thermal resistance due to impurities and its nonlinear variation with point defect concentration are a consequence of an interference between the normal processes and the resonance scattering on impurity quasi-local levels. The parameters that are involved in the theory have been evaluated microscopically. The results obtained allow interpretation of experimental data on the thermal conductivity of solid para-hydrogen with rare gas impurities.
Thermodynamic properties of hydrogen (n-H2) in the dense fluid phase
Authors: Sheinina A. A. , Bereznyak N. G. , Vorob’eva V. P. , Khazhmuradov M. A.
Published: January 2025

Basic thermodynamic properties of hydrogen of normal ortho–para composition have been calculated for the dense fluid phase in the range of pressures 100 to 2000 MPa and temperatures from the respective solidification points to 500 K using the equation of state derived previously. Thermodynamic properties of n-H2 have been determined on the melting curve in the solid phase. Based on the data obtained, an entropy diagram of n-H2 is constructed.
Structure and energetics of fluid para-hydrogen
Authors: Scharf Daphna , Martyna Glenn J. , Klein Michael L.
Published: January 2025

The properties of neat fluid para-hydrogen from the low temperature liquid to the subcritical fluid (T = 14–25 K) are studied in the isothermal–isobaric ensemble using the Path Integral Monte Carlo method. The molecules are treated as spheres and are assumed to interact via a pair potential. This is a good approximation at low pressures as the anisotropic part of the potential surface is very small and the molecules are in J = 0 at the temperatures of interest. The volume and energy of the system are determined as a function of temperature and good agreement is found with experiment. In addition, radial distribution functions and structure factors are calculated for the molecular centers of mass. The extreme quantum nature of the system is illustrated by comparisons to the corresponding classical model of the system.
Quantum orientational melting
Authors: Brodyanskii A. P. , Sumarokov V. V. , Freiman Yu. A. , Jezowski A.
Published: January 2025

It is shown that under appropriate conditions, a novel physical phenomenon, viz., quantum orientational melting, can be observed in the system of rotors. Phase diagrams have been constructed for systems of symmetric and asymmetric linear rotors and they have shown that the diagram of the system of symmetric rotors resembles the P–T diagram of solid 3He, whereas that of asymmetric ones resembles that of 4He. A possibility is predicted for observing an effect similar to the Pomeranchuk effect in molecular crystals.
Temperature dependence of the phase transition in solid nitrogen from molecular to atomic phase
Authors: Yakub L. N.
Published: January 2025

Based on a simple molecular model for the atomic and molecular high-pressure crystal phases, a temperature dependence of the volume jump and the pressure of the phase transition from the molecular to atomic phase of nitrogen is predicted. The equilibrium pressure grows from 750 kbar at 0 K to 2 MBar at the melting temperature while the pressure jump is close to 1.5 cm3/mole.
Magnetic symmetry of β-oxygen
Authors: Vitebskii I. M. , Lavrinenko N. M.
Published: January 2025

The existence of a long-range magnetic order of the nonorientational (correlation) type in the rhombohedral modification of crystalline oxygen is predicted on the basis of symmetry analysis. In this phase, the time-averaged spin of each O2 molecule in the crystal is equal to zero. Nevertheless, the magnetic symmetry of the system is found to be half the symmetry of the true paramagnetic state. The existence of the long-range correlation spin ordering is determined by exchange intermolecular spin–spin interactions which are rather strong in crystalline oxygen (∼102 K). The absence of conventional orientational long-range order is associated in this case with the two-dimensional nature of spin–spin interactions and with a special symmetry of the system.
On the stability of triangular antiferromagnetic ordering in the rhombohedral lattice of β-oxygen
Authors: Vitebskii I. M. , Knigavko A. N. , Chabanov A. A.
Published: January 2025

The stability of the triangular antiferromagnetic ordering to the formation of an inhomogeneous superstructure in the rhombohedral lattice of β-oxygen is investigated by using the mean field theory. It is shown that a long-periodic modulation lowers the ground-state energy. Unlike in previous publications, the antiferromagnetic ordering with alternating polarity of adjacent X–Y layers is used as zeroth approximation in the present work, which apparently corresponds to β-oxygen.
Rotation of the methyl halides embedded in the rare gas solids
Authors: Smith David
Published: January 2025

The potential function for the rotation of a hindered methyl halide molecule in solid rare gas solids is derived from atom–atom potentials. The rotational energy levels of a symmetric top in an octahedral crystalline field have C¯3×O symmetry. The computed energy levels are different from schemes used for other problems. Each level consists of seven groups of states. The total degeneracy of each level is 96, if nuclear spin degeneracy is not considered. These groups of states within any level have large splittings for methyl fluoride and chloride in rare gas solids, but are nearly degenerate for methyl bromide and iodide in rare gas solids.
The derivation of the rotational potential function from atom–atom potentials. VI. Ammonium–oxygen compounds
Authors: Smith David
Published: January 2025

The rotational potential functions of a number of ammonium–oxygen compounds have been derived from atom–atom potentials of the Buckingham (exp-6) type. These solids usually have either orthorhombic or monoclinic crystal structures, which results in a low site symmetry for the ammonium ion. This complicates the analyses of these solids. The rotational potential functions for NH4ReO4, NH4IO4, (NH4)2C2O4 · H2O, NH4OOCCH3, (NH4)2H3IO6, and NH4ClO4, have been derived. For NH4ClO4, the low temperature librational and tunneling frequencies are determined from the derived rotational potential function and compared to observed values. An anomalous isotope effect for the librational frequency of ND4ClO4 to NH4ClO4 is computed. The low temperature heat capacity due to the hindered rotation of both ND4ClO4 and NH4ClO4 are computed from the hindered rotational energy levels and compared to the experimental results.
Molecular dynamics simulation of rare gas fullerene adducts
Authors: Cardini Gianni , Procacci Piero , Salvi Pier Remigio , Schettino Vincenzo
Published: January 2025

Molecular dynamics simulation studies of rare gases complexes with Buckminsterfullerene are reported in the low-temperature regime. A family of potential parameters is used to describe the C60-rare gas atom interactions and a comparison with different potential models in the case of Xe–C60 interaction is discussed. The effect on the structure and the internal frequencies of C60 is discussed.