bluuebunny/crossref_metadata_2025 huggingface dataset:
Cerebral Changes Following Carpal Tunnel Syndrome Treated with Guided Plasticity: A Prospective, Randomized, Placebo-Controlled Study
Authors: Flondell Magnus , Mannfolk Peter , Rosén Birgitta , Björkman-Burtscher Isabella M. , Björkman Anders
Published: November 2024

Background Compression neuropathy, such as carpal tunnel syndrome (CTS), results in changed afferent nerve signaling, which may result in changes in somatosensory brain areas. The purpose of this study was to assess cerebral changes following unilateral CTS and to assess short-term and long-term cerebral effects of guided plasticity treatment using ipsilateral cutaneous forearm deafferentation.

Methods Twenty-four patients with mild-to-moderate unilateral CTS were randomized to treatment with anesthetic cream (EMLA) or placebo. Patient-rated outcomes were assessed using Boston CTS questionnaire and disability of arm, shoulder, and hand questionnaire (QuickDASH). Patients were assessed for tactile discrimination and dexterity. Cortical activation during sensory stimulation was evaluated with functional magnetic resonance imaging at 3T. Assessments were performed at baseline, 90 minutes, and 8 weeks after treatment.

Results Functional magnetic resonance imaging showed that sensory stimulation of the hand with CTS resulted in significantly less cortical activation in the primary somatosensory cortex (S1) than stimulation of the healthy hand. Treatment with cutaneous forearm deafferentation on the side with CTS resulted in increased cortical activation in S1 both after the initial treatment and following 8 weeks of treatment. In addition, QuickDASH and tactile discrimination showed improvement in the EMLA group over time.

Conclusions Stimulation of median nerve-innervated fingers in patients with unilateral CTS results in smaller-than-normal activation in the contralateral S1. Cutaneous forearm anesthesia on the side with CTS results in larger activation in S1, suggesting recruitment of more neurons, and a slight improvement in sensory function.
Improving brand love through branded apps: is that possible?
Authors: Tran Trang P. , Zemanek James E. , Sakib Md. Nazmus
Published: November 2024

As organizations are gradually shifting their emphasis from customer acquisition to creating customer engagement and participation, mobile applications serve as an important tool for organizations to encourage and enhance customers’ active engagement and to serve as brand ambassadors. Previous research outlines that consumer engagement with branded mobile apps can lead to customer loyalty but has yet to examine the effects of branded mobile apps on brand love. Building on the Technology Acceptance Model (TAM) and consumers’ utilitarian and hedonic motivations of using technology, this study provides a comprehensive framework on how consumers’ brand love can be attained through branded apps. In this process, this research identified three primary app attributes namely perceived ease of use, perceived usefulness, and perceived entertainment and examined their direct and indirect influences on brand love through app attitude and app satisfaction. The results from 323 branded app users revealed that out of those three primary app attributes, only perceived usefulness serves as a key driver of brand love. Perceived entertainment may enhance the attitude towards the app but it does not improve brand love. And, perceived ease of use has no impact on either the attitude towards the app or brand love. These findings provide valuable insights and recommendations for researchers and managers alike.
Combating tax crimes in Indonesia: tackling the issue head-on
Authors: Nurferyanto Dwi , Takahashi Yoshi
Published: November 2024

Taxes are undeniably the lifeblood of a country’s financing. However, tax evasion is becoming increasingly rampant in Indonesia, resulting in substantial state losses. Enhanced tax enforcement policies are necessary to combat this crime. The Organization for Economic Cooperation and Development (OECD) has established principles for fighting tax crimes; however, the Indonesian government has been unable to integrate these principles into its tax enforcement policies, leading to gaps related to strategy, investigative powers, organizational structure, resources, and cooperation, which prevent the current measures from being fully effective. This article conducts a descriptive, evaluative, and comparative study of the Directorate General of Taxes’ (DGT) current tax enforcement policy and proposed practices based on the OECD’s principles to identify and elaborate on these gaps and analyse internal and external obstacles hindering effective implementation. This study’s findings reveal a fundamental difference between tax and legal interests that must be appropriately managed within their boundaries; therefore, the key to improving tax enforcement policy in Indonesia lies in combining Primum Remedium (criminal sanctions as the initial response) and Ultimum Remedium (criminal sanctions as the last resort) strategies. Additionally, the provision of adequate investigative powers, sufficient resources, gradual policy implementation, and necessary law amendments are also crucial factors. This study aims to provide the Indonesian government with insights and recommendations to enhance the tax enforcement policy, to combat tax crimes more comprehensively.
Nonlinear absorption of an electromagnetic wave in a London superconductor
Authors: Shumeiko V. S.
Published: November 2024

The kinetic equation is derived for low-lying excitations in a superconductor in the low-frequency range. For a London superconductor situated in an alternating electromagnetic field having an amplitude HcT/Δ≪H≪Hc, a solution is formulated which describes a strongly nonuniform distribution of excitations, and the magnitude of the absorption is calculated.
Transition from antiferromagnetic to ferromagnetic state in ferroelectric-magnetic crystals
Authors: Chupis I. E.
Published: November 2024

It is shown that in ferroelectric-antiferromagnetic crystals at temperatures below the ferroelectric and antiferromagnetic transition points exchange interaction between the electric and magnetic subsystems can give rise to phenomena such as the magnetoelectric effect and first- and second-order magnetic-field-induced phase transitions and can also result in a transition from the antiferromagnetic to the ferromagnetic state. The theoretical results are compared with experimental data, and the magnitude of the constant describing the exchange interaction between the subsystems is estimated.
Some new properties of the volt-ampere characteristics of bismuth in strong crossed fields
Authors: Bogod Yu. A. , Valeev R. G. , Onokienko G. P.
Published: November 2024

For the first time the volt-ampere characteristics of bismuth have been studied in electric fields of up to 350 V/cm. The magnetic field range is 20–190 kOe, and the experiments are conducted at liquid-helium and hydrogen temperatures. It is observed that under certain conditions the volt-ampere characteristics have two portions with a negative differential conductivity. In the postcritical region of E it is found that the differential and absolute resistances have a nonmonotonic dependence on the magnetic field. It is shown that the transition to the phonon generation regime is not uniquely determined by the drift velocity of the charge carriers and that the critical value of the electric field depends on the temperature and magnetic field.
Acoustical cyclotron resonance in nonextremal cross sections of the Fermi surface
Authors: Gokhfel’d V. M.
Published: November 2024

Acoustic cyclotron resonance in a metallic film, thin in comparison with the electron mean free path, was investigated in the case where the electrons are diffusely scattered by the metal’s boundaries. In a weak magnetic field, when the electron orbit with maximum Larmor period does not fit into the sample, electrons whose orbital diameters equal the thickness of the film and those in an jxtremal cross section of the Fermi surface near a reference point participate in the resonance.
Energy spectrum of quasiparticles in one-dimensional disordered systems (Review)
Authors: Gredeskul S. A. , Pastur L. A.
Published: November 2024

A review is presented of papers published over the last decade in which a study was made of the behavior of the density of states in one-dimensional disordered systems. The methods used in these papers seem fairly varied at first glance. Nevertheless, they are bare, simple and general ideas, and this allows currently available results to be stated within the framework of a unified approach. The one-dimensional nature of the problem allows closed dynamic equations to be written for any of the quantities which determine the spectral properties. The structure of these equations is always such that it provides the possibility of using them as the basis for obtaining other nonrandom equations for the probability densities of the corresponding quantities. The behavior of the solutions of these equations in all cases of interest is determined by the dynamics of the system, which leads to the derivation of asymptotic forms for the density of states in the investigated ranges of the spectrum. The density of one-electron states in a random field and the density of the squares of the vibration frequencies of a disordered chain are considered. Principal attention is devoted to the behavior of the density of states near singularities—in the neighborhood of the boundaries of the spectrum and in the impurity band.
Ultrasonic absorption in a current-carrying pure superconductor
Authors: Shklovskii V. A.
Published: November 2024

The absorption of ultrasound in a pure superconductor carrying a current js is considered for the case q1≫1 (q is the sound vector, l is the mean free path of the quasiparticles). The absorption depends substantially on the mutual orientation of js and q. When q⊥js and T≪Δ (Δ is the energy gap, practically independent of js), the absorption coefficient increases exponentially with the current owing to the narrowing of the “thermal” gap. At the same time, the frequency threshold for absorption is determined, as previously, by the condition ℏω>2Δ.
Subharmonic structure of the volt-ampere characteristics of superconducting tunnel junctions
Authors: Voloshkevich A. G. , Moiseenko V. A.
Published: November 2024

Amplitude beats of the subharmonics have been observed in the dV / dI— V characteristics of Pb–PbOx–Pb junctions. The reduction of the temperature to 0.75 °K during the measurements provided the basis for assuming that the beats are caused by interference between a series of minima (eV=2Δn−δV) shifted along the V axis and an unshifted series of odd peaks (eV=2Δ/nodd). Due to the shift δ V the certainties associated with the incomplete correspondence between the positions of the subharmonics along the V axis and the values of eV=2Δ/n are eliminated.
Influence of finite lifetime of excitations on the thermodynamical properties of helium II
Authors: Reut L. S. , Fisher I. Z.
Published: November 2024

The additional contribution to the density of the normal component of superfluid helium associated with the finite width of the roton level is calculated and compared with experiment.
Electrical resistivity of vanadium of various purities in the temperature range 4.2−47 °K
Authors: Aleksandrov B. N. , Semenova E. D. , Petrova O. I. , Chernyi B. P. , Azhazha V. M.
Published: November 2024

The temperature dependence of electrical resistivity in four specimens of vanadium with δ0=R0/R293=6.6⋅10−4−4.4⋅10−2 was studied in the temperature range 4.2−47 °K. It was found that from 4.2 to 22 °K ρ(T)∼T3 and in the range 22−58 °K ρ(T)∼α T2 + βT4 or ρ(T)∼ T3.75−3.4. In low purity specimens deviations from Mathiessen’s law were observed, increasing with growth in temperature and relative residual resistivity δ0.
Dopplerons in tungsten
Authors: Vitebskii I. M. , Vitchinkin V. T. , Galkin A. A. , Ostroukhov Yu. A. , Panchenko O. A. , Tsymbal L. T. , Cherkasov A. N.
Published: November 2024

A number of doppleron branches have been found experimentally in the spectrum of a compensated metal, namely tungsten. Some of the dopplerons are due to carriers of Fermi surface cross sections that were not observed experimentally before. Linear-polarization oscillations with a period conforming to the Gantmakher-Kaner effect are revealed.
The resistive state of thin tin films during the destruction of superconductivity by current
Authors: Musirenko L. E. , Shnyrkov V. I. , Volotskaya V. G. , Dmitrenko I. M.
Published: November 2024

The mechanism for the destruction of the superconductivity of thin films in a zero magnetic field is investigated. It is shown that in the range of temperatures close to the critical temperature T/Tc∼1÷0.99 the first derivatives of the smooth current-voltage characteristics are oscillatory in character. It is assumed that the cause of the oscillations is the development of a dynamic structure having alternating normal and superconducting regions in the sample.
Formation of bound states in the Kondo effect
Authors: Kadigrobov A. M.
Published: November 2024

The statistical sum of a metal having paramagnetic impurities with spin S = 1/2 is written by means of a functional integral whose form corresponds to the Nagaoka proposition concerning the formation of bound states between electrons and an impurity in the system. The method of steepest descent is used to calculate the first two terms in the expansion of this integral; the derived expressions coincide with the results of Abrikosov. However, the estimation of the subsequent terms of the expansion shows that, contrary to the assumption made by Abrikosov, they are not small in comparison with the preceding terms throughout the entire temperature range T≥ 0−, T ∼Tk (Tk is the Kondo temperature).
Calculation of distribution function of one-magnon excitations in a ferromagnet
Authors: Peresada V. I. , Afanas’ev V. N. , Borovikov V. S.
Published: November 2024

A method is proposed for constructing in general form an analytic approximation to the energy distribution function g(ϵ) of spin waves in an ideal Heisenberg ferromagnet. The method is based on the construction of subspaces which are invariant under the Heisenberg operator, which enables one to express the function g(ϵ) as the arithmetic mean of the spectral densities of some Jacobi matrices. The method is illustrated by the construction of the distribution function g(ϵ) for the three simplest ferromagnetic lattices: simple cubic, bcc and fcc. An analtyic approximation of the magnon distribution function is presented for a complex ferromagnetic lattice of the NaCl type, which has two bands in the energy spectrum.
Effect of low symmetry in ESR spectrum of Er3+ in potassium-yttrium molybdate KY(MoO4)2
Authors: Pshisukha A. M. , Chernyi A. S. , Zvyagin A. I.
Published: November 2024

The ESR of Er3+ on the ground and first-excited Kramers doublets is measured. It is shown that that difference in the angles at which the transitions on the different doublets are observed in extremal fields is due to monoclinic local symmetry of the crystal field. The angular difference is 47°.
An intermediate state in the region of sublattice inversion in an antiferromagnetic single crystal CuCl2⋅2H2O
Authors: Bar’yakhtar V. G. , Galkin A. A. , Telepa V. T.
Published: November 2024

The Nuclear Magnetic Resonance (NMR) features of protons in copper chloride dihydrate are investigated. A change of NMR frequencies is found, which takes place with change both of the size of the magnetic field and also its orientation relative to the “easy” axis. In a narrow interval of external magnetic fields (the size of the interval amounts to 150 Oersteds) and angles (ψk=20′to25′), a sharp broadening and amplification of the signal is observed. The line shape in this region of fields and angles is asymmetric. Outside this region, the dependence of NMR frequencies on fields remains the usual one. The anomalies observed are explained on the basis of the concept of an intermediate state in antiferromagnets.
Temperature dependence of the absorption of fourth sound in He II
Authors: Dyumin N. E. , Rudavskii E. Ya.
Published: November 2024

In the temperature range 0.4°K–Tλ the temperature dependence of the absorption coefficient of fourth sound in superfluid helium was investigated on the basis of measuring the amplitude of the sound signal. It was demonstrated that the principal contribution to the absorption of fourth sound is made by viscous losses associated with the slippage of the normal components along the channel walls.
Effects of defects on the electrical conductivity of single crystals of the complex tetrathiofulvalene 7,7,8,8-tetracyanoquinodimethane
Authors: Balabanov Ε. I. , Bespalov B. P. , Gakel’ V. R. , Isaeva R. V. , Titov V. V.
Published: November 2024

The electrical conductivity has been measured along the axis of maximum conduction; two methods have been employed (the usual 4-contact one and a four-contact style in which the specimen surface between the potential electrodes is coated with conducting silver paste); this enables one to distinguish the contributions from the intrinsic conductivity of the single crystal and the resistance of the defects, which has shown that surface defects have a substantial effect on the magnitude and temperature-dependence of the conductivity.
The motion of He3 impurity in solid He4
Authors: Richards M. G. , Smith J. H. , Tofts P.-S. , Mullin W. J.
Published: November 2024

Measurements of the NMR relaxation times T1 and T2 for He3 impurity in solid He4 at various impurity fractional concentrations x3, molar volumes V, and frequencies ω are reported. The ranges are 10−4<χ3<10−3,20.0cm3<V<21.0cm3 and 10−6sec−1<ω<3×107sec−1. The data suggest that the He3-He4 tunnelling frequency, J34,∼107⋅sec−1 rather than 104⋅sec−1 as previously indicated by measurements of the He3 spin diffusion coefficient, and that the density dependence of J34 is not anomalous as previously reported.
The energy spectrum of defectons in quantum crystals
Authors: Pushkarov D. I.
Published: November 2024

Based on microscopic theory the dispersion law for defectons in crystals of the solid-helium type is derived. The analysis is carried out in the tight binding approximation. Analytic expressions are derived for the width of the energy band, the effective mass, and other energy characteristics of defectons. A new method is developed which allows the effect of the phonon “cloud” to be taken into account without the use of perturbation theory. The final results are expressed in terms of the macroscopic characteristics of the crystal (Debye temperature, sound velocity, etc). The dependence of the width of the energy band on pressure is derived. The calculated values are in good agreement with the experimental results.
Ion motion in solid helium
Authors: Dahm A. J.
Published: November 2024

The temperature dependence of the positive and negative-ion mobilities has been measured at two molar volumes in hep He4 using a space charge limited-current technique. Near the melting curve, the mobilities of both carriers are characterized by an activation energy which differs for the two carriers. A comparison of the activation energy for positive ion motion with the vacancy activation energy as a function of molar volume suggests vacancy hopping as the mechanism for positive ion motion in hep He4. The data are consistent with a model for the negative ion in which the electron is trapped in a void of ∼ 10 Ǻ radius and moves by adatom surface diffusion on the void surface. Different mechanisms are responsible for the motion of carriers at lower temperatures. An attempt to detect vacancy waves with the use of positive ions as probes is also reported.
Hydrogen diffusion in the bcc metals
Authors: Wert C.
Published: November 2024

Hydrogen diffuses rapidly in the bcc metals even below room temperature. Thus, hydrides can easily form at low temperatures. We have determined the thermodynamic parameters of equilibrium between the bcc solid solutions and the hydride phases in the temperature range 150°K to 300°K for the V−H and Ta−H systems. The presence of other interstitials, especially oxygen, greatly affects the hydride formation, especially for the Ta−H binary system. The oxygen atoms, which are immobile, appear to trap the diffusing hydrogen atoms in O−H complexes, greatly retarding their diffusion rate. Thus, supercooling occurs readily, and the establishment of thermodynamic equilibrium requires very slow cooling and heating rates. In addition, the slower diffusion rate of deuterium, even in oxygen-free tantalum, demands slow cooling and heating rates for attainment of equilibrium. Data obtained in this experiment together with other information concerning the Nb−H system, shows significant trends in the binary systems V−H, Nb−H, and Ta−H.
Isotope and temperature dependence of the lattice expansion in metal-hydrogen systems
Authors: Wipf H.
Published: November 2024

The solution of hydrogen in metals leads to a lattice expansion. A model is proposed in this paper by which, due to anharmonic effects, an isotope-dependent lattice expansion is predicted. The anharmonicity is expressed by a Grüneisen constant for the hydrogen-induced localized mode. For low-hydrogen concentrations the lattice expansion should be greater for a lighter isotope than for a heavier one. At high temperatures the isotope effects disappear. From experimental results, high values for the Grüneisen constant o f the localized mode can be estimated.
Phase transitions in transition metal hydrides
Authors: Somenkov V. A. , Shil’shtein S. Sh.
Published: November 2024

Phase transitions associated with redistribution of hydrogen atoms injected into the metal lattice are treated as changes of state of the lattice gas (condensation, sublimation, crystallization). Based on structural data we study features of these transitions related to step transitions, appearance of metastable states, changes in type of interstitial sites, etc., as well as the role of interaction between the atoms implanted in the superstructures formed. Effects due to vibrations of light atoms are investigated by simple models. The existence of isotopic shifts of phase transition temperatures has been established, and the effect of isotopic “ordering” is predicted and displayed. The effect of high pressure on hydrogen atom ordering is discussed.
Heats of hydrogen absorption and phase transitions in the palladium–hydrogen system
Authors: McFall W. D. , Lewis F. A.
Published: November 2024

Among transition metal hydrides, which retain metallic characteristics, those of palladium and palladiumrich alloys are somewhat unique in substantially retaining the cohesiveness and mechanical robustness of the hydrogen-free metal—even over phase transition regions. This is a practical advantage in obtaining detailed relationships between hydrogen contents and physical properties such as electrical resistance. Latterly, increasingly detailed and accurate measurements have been obtained of equilibrium hydrogen pressures and related thermodynamic parameters over narrow ranges of hydrogen content. The present paper reports calculations from electrochemical measurements at closely spaced temperatures, of changes in the heats of absorption of hydrogen over ranges of hydride phase transitions—made in conjunction with electrical resistance measurements. Results suggest the possibility that, aided by the high mobility of hydrogen in these solids, phase transformations may be preceded by the formation o f a series of subphases which exist within narrow limits of closely similar nonstoichiometric composition.
Antiferromagnetic transition in holmium dihydride. Low temperature heat capacity studies
Authors: Biegański Z. , Opyrchal J. , Drulis M. , Staliński B.
Published: November 2024

Magnetic susceptibility measurements carried out for most of the Ln-H systems by W. E. Wallace et al. down to 4.2°K suggested antiferromagnetic transitions for Dy (8°K), Ho (8°K), and Tb (40-50°K) dihydrides and a ferromagnetic transition for the Nb (9.5°K) dihydride. Recently we started with a detailed calorimetric study of the magnetic transitions for obtaining closer insight into the magnetic interactions and electronic structure of these hydride phases. In this paper, results of specific heat measurements by adiabatic calorimetry in the range 2-30 °K for holmium dihydride HoH2 are reported. A λ-type anomaly with a critical temperature TN = (5.2 ± 0.2)°K has been discovered which may be compared with 8°K suggested by Wallace. The magnetic contribution to the total specific heat has been extracted and analysed. The experimentally determined entropy change has been compared with the theoretical value RIn (2J+1) for the tripositive Ho3+ ion with the 17-fold degenerated ground state 5I8. A conclusion is drawn that a great part of the entropy change is resolved in the high temperature range due to crystal-field effects. This result is in good agreement with our previously specific studies in the range 25−340°K where large Schottky contributions to the specific heat were found.
Singularities in the relaxation of electron excitations in neon crystals
Authors: Fugol’ I. Ya. , Savchenko E. V. , Belov A. G.
Published: November 2024

Results are presented of experimental measurements of the luminescence spectra of solid neon induced by slow electrons in the vacuum ultraviolet range. The temperature dependence of the spectra is studied. The dynamics of excitons in neon crystals is discussed, and the process of trapping the excitations in the lattice with the formation of quasifree centers of de-excitation of atomic and molecular types is examined.
Influence of impurities on the solidification temperature of hydrogen isotopes
Authors: Bereznyak N. G. , Sheinina A. A. , Karnatsevich L. V.
Published: November 2024

Melting diagrams of the systems n-D2-Ne and n-H2-Ne are measured in the low neon concentration domain. Both diagrams are eutectic in nature. It is established on the basis of the results obtained and of data about the system H2-He that neon and helium dissolution in liquid hygrogen causes a reduction in the solidification temperature, but the effect is slight because of the low equilibrium solubility of the impurities.
Thermal expansion and isothermal compressibility of solid hydrogen in the premelting range under pressures up to 200 atm. A new phase transformation
Authors: Manzhelii V. G. , Udovidchenko B. G. , Esel’son V. B.
Published: November 2024

An original method was used for studying the thermal expansion and the isothermal compressibility of solid parahydrogen in the premelting range of temperatures up to 200 atm. In the immediate vicinity of the melting curve a new kind of phase transformation has been discovered. The parameters of this transformation and their dependence on the history as well as the ortho-para constitution of a specimen are analyzed. A unified description is proposed of the temperature dependence of the coefficients of the thermal expansion of solid parahydrogen at various pressures. The temperature characteristics of the thermal expansivity of solid parahydrogen under various pressures are described by one universal relation. The pressure dependence of the compressibility is analyzed on the basis of the Gruneisen law.
Thermal conductivity of solid hydrogen at low orthohydrogen concentrations
Authors: Kokshenev V. B.
Published: November 2024

Lattice thermal resistance mechanisms are considered in solid parahydrogen containing o−H2 impurity molecules, in the temperature range (T < 4°K) below the heat conductivity maximum. It is shown that for o−H2 concentrations c < 1%, inelastic phonon scattering on isolated o−H2 molecules is significant, producing a contribution to thermal conductivity of K ∼ T/c. At c > 1% changes in thermal flux within the crystal are connected mainly with absorption or emission of phonons by the system formed of pairs of o−H2 (K∼ T3/c2). The results obtained are compared with experiment.
Transition of solid hydrogen into a metallic phase at high densities
Authors: Ostgaard E.
Published: November 2024

The ground-state energy, pressure, and compressibility of solid molecular hydrogen are calculated by means of a modified Brueckner theory. A Bethe–Goldstone-type equation is solved to give a reaction matrix or an effective interaction in coordinate space, and the ground-state energy of fcc hydrogen is calculated. Also, the pressure and the compressibility are estimated from the dependence of the ground-state energy on density or molar volume. The possibility of a phase transition from solid molecular hydrogen into a metallic atomic phase at high densities is then considered. The ground-state energy and the pressure for bcc atomic hydrogen is calculated, and a phase transition is found to occur at a pressure of approximately 1.2 or 1.9 Mbar.
Two-dimensional quantum solid phases of adsorbed monolayers
Authors: Dash J. G.
Published: November 2024

Monolayer films of helium and other gases adsorbed on basal plane surfaces of graphite exhibit phenomena that indicate numerous phases and phase transitions. He3 and He4 at high coverages form two-dimensional quantum solids whose structures are incommensurate with the underlying graphite, contrasting sharply with the (3×3) epitaxial ordered lattice solids occurring at lower coverage. The 2D solid phases melt in a continuous manner, while the lattice solids show a logarithmic second-order heat capacity peak. No monolayer displays a first-order melting transition indicated by a very high and narrow anomaly. This sharp melting point may be related to partial registry between the structure of the monolayer and that of the substrate. In N2 there is an apparent coupling between melting of the 2D type and the disordering of the lattice solid, with promotion of atoms to the second layer. Experimental methods include calorimetry, nuclear magnetic resonance, vapor pressure, and neutron diffraction.
Properties of submonolayer helium films from NMR measurements
Authors: Daunt J. G. , Hegde S. G.
Published: November 2024

NMR measurements have been made of He3 submonolayers adsorbed on Grafoil in the temperature range 0.35°K to 4.2°K with the following fractional monolayer coverages: x =0.20, 0.30, 0.57, 0.76, and 0.96. The cw measurements yielded linewidth and susceptibility data; For 0.20 ≤ x ≤ 0.76 the linewidth was temperature independent and equal to 0.22 G. For x = 0.96 the line broadened at and below 2°K to reach 35 G, a value which is about four times smaller than would be expected for a rigid He3 lattice. The three higher coverages showed a Curie law behavior in their susceptibility, whereas for x = 0.30 and 0.20 deviations occurred at the lowest temperatures. A discussion of these results in relation to other work is given.
Effects of fluctuational pairing on electron tunneling
Authors: Baramidze G. A. , Cheishvili O. D.
Published: November 2024

A theoretical study has been made of superconductor–insulator–normal metal contacts under conditions such that the normal metal is in the fluctuation state, which is close to the state of surface superconductivity. The current and its derivatives have been calculated as functions of temperature and of the magnetic field parallel to the surface of the insulator.
Superconductive transition temperature in rhenium and molybdenum films
Authors: Dmitriev V. P. , Milai A. K. , Orlov A. F.
Published: November 2024

Mo and Re films were produced by vacuum deposition on substrates cooled by liquid helium. The superconductive transition temperature Tc was studied as a function of film thickness and growth conditions. Formation of metastable phases with high Tc values, 16.7 and 8.5°K for Re and Mo respectively, was observed. Tc as a function of film thickness for Re showed saturation in the region of the maximum thickness studied, while the Mo films showed a maximum in Tc. It was concluded that the nature of the thickness dependence of Tc in superconductive films is determined by the strength of electron-phonon interaction in the equilibrium state.
Deviations from Mathiessen’s rule in dilute tin-based alloys at 4.2–12 °K
Authors: Aleksandrov B. N. , Petrova O. I.
Published: November 2024

It is shown that the extent of the effect is determined by Δρ/c, namely the change in the residual resistance per 1 at.% impurity, the effect being the larger the higher the impurity content. The results are explained qualitatively by Kagan and Zhernov’s theory. It is found that the temperature Tres, at which the resistance of the alloy can be taken as equal to the residual value Tres, is determined solely by ζ0 and is unaffected by the nature of the impurity.
Absorption spectrum of an oxygen isotope mixture at 1.5 °K. I. Visible and near ultraviolet regions (15,000-34,000 cm−1)
Authors: Glushkov L. P. , Prikhot’ko A. F. , Shanskii L. I.
Published: November 2024

The absorption spectrum over a range of 15,000 to 34,000 cm−1 of an oxygen isotope mixture at 1.5°K has been investigated. It has been shown that the exciton effects in crystals of different isotope composition are conserved. A doublet structure of the long-wave components of the system’s vibrational bands was discovered: (ΔΣ)←(3Σg−).
Plasmon and exciton superconductivity mechanics in layered structures
Authors: Gabovich A. M. , Pashitskii É. A. , Ovarova S. K.
Published: November 2024

The plasmon and exciton superconductivity mechanisms in a three-layered sandwich structure are examined in detail by using the temperature Green’s function of the longitudinal (Coulomb) field. The dependences of the superconducting transition temperature on the parameters of the system are obtained.
Conductivity fluctuations in layered superconductors
Authors: Golub A. A.
Published: November 2024

The paper studies the effect of a magnetic field, parallel to the layers of a layered superconductor, on the fluctuation conductivity. It is shown that the contribution of the fluctuations to the conductivity increases as a result of the formation of a nonuniform state or as a result of a spin-orbital interaction of the electrons in layered superconductors having a lattice without a center of inversion.
Spectral and magneto-optical studies concerning the magnetic-phase diagram of (Gd, Tb, Er)3(Al,Fe)5O12 at low temperatures
Authors: Belyaeva A. I. , Petrova G. P. , Potakova V. A. , Silaev V. I. , Stel’makhov Yu. N. , Vaishnoras R. A.
Published: November 2024

The characteristics of magnetization reversal in the (110) plane of a (Gd,Tb,Er)3(Al,Fe)5O12 ferrite-garnet were studied at the temperature T = 4.2 °K. This study was based on an analysis of the domain structure for which purpose the authors used, at the same time, the magneto-optical Faraday effect and the absorption spectra within the 4I15/2→4S3/2 transition of the Er3+ ion in each domain. The phase diagram has been established experimentally covering the 0–40 kOe range of magnetic field intensities. It appears that the magnetic anisotropy in the complex (Gd,Tb,Er)3(Al,Fe)5O12 garnet is the same as that in Er3Fe5O12.
Magnetic properties of a low-dimensional magnetic material with monoclinic crystal structure symmetry
Authors: Anders A. G. , Zvyagin A. I. , Kalinin P. S. , Khats’ko E. N. , Yurko V. G.
Published: November 2024

The magnetic and resonance properties of crystals of the monoclinic double tungstates NaFe(WO4)2 and LiFe(WO4)2, differing in the location of the magnetic ions in their crystal lattices, have been investigated. Because of this difference, sodium ferriferrous tungstate displays the properties of a low-dimensional magnetic material as well as the observed rotation of the magnetic axes over a broad energy range. The possible mechanisms for the rotation of the magnetic axes are considered by estimating the single-ion and dipole-dipole contributions to the magnetic anisotropy energy of the tungstates.
Singularities of electromagnetic field energy absorption by a system of electrons on a liquid helium surface
Authors: Rybalko S. A. , Kovdrya Yu. Z.
Published: November 2024

Electromagnetic field energy absorption by electrons on a liquid helium surface in the presence of a dc electric field clamping the electrons to the liquid-vapor interface was measured in the 1.5–2.6°K temperature range and 2.75–25.6 MHz frequency ranges. It is shown that for low surface electron concentrations the absorption is governed mainly by the interaction between the charges and the gaseous helium atoms. It is established that the energy being absorbed, converted to one electron, diminishes as the surface electron concentration increases (N = 108 el/cm2) while the temperature dependence of this quantity changes its nature. The surface electron concentration at which a liquid helium surface becomes unstable was measured.
Effect of lead impurities on the amplitude-dependent absorption in normal and in superconductive indium
Authors: Pal-Val L. N. , Platkov V. Ya.
Published: November 2024

A study was made concerning the effect of small concentrations of lead impurities on the amplitude dependence of ultrasound absorption in normal and in superconductive indium. The frequency of longitudinal vibrations was 7.5 MHz. The single-crystal specimens for this study had all the same orientation. The ultrasonic waves were propagated in the [110] direction. Measurements were made at 1.4 and 77°K. The lead content was varied from 1 × 10−3 to 3 × 10−1 at.%. In each case the transition to the n- state was accompanied by a shift of the absorption curve toward larger amplitudes. With the lead content increasing up to 3 × 10−1 at.%, the critical amplitude had increased more than 103 times. Implantation of impurity atoms had produced an appreciable change not dependent on the amplitude but nonmonotonically dependent on the impurity content: It first decreased and then slightly increased with increasing lead content. Unlike the amplitude-dependent absorption, this amplitude-independent absorption did not change during the s-transition at lead contents higher than c = 5 × l0−2 at.%. These results indicate that the dynamic interaction between impurity atoms and dislocations contributes to the quasiviscous braking of the latter. As a result, the damping in doped single crystals does not change significantly during the s- transition. The change in conditions under which pinning centers are overcome by dislocations during the s- transition is attributed to a quasistatic mechanism.
Experimental study of magnetic relaxation in certain solidified gases
Authors: Lazarev V. V.
Published: November 2024

The magnetic viscosity of solidified neon was investigated for the purpose of determining the possibility of the existence of diamagnetic component of the magnetic susceptibility χ", which characterizes relaxation processes, varied from sample to sample. Analogous measurements of χ" in solidified oxygen revealed that such variations are not related to the presence of paramagnetic impurities in the specimens. Possible causes of this phenomenon are discussed.
Peculiarities of the low-temperature luminescence of CsMnCl3 antiferromagnetic crystals
Authors: Bron R. Ya. , Matyushkin E. V. , Beznosikov B. V.
Published: November 2024

The luminescence of CsMnCl3 crystals is investigated in a broad temperature range. A strong polarization dependence of the luminescence spectrum and growth in the luminescence intensity and the frequency of its spectrum distribution maximum are observed as the temperature rises in the 20–100°K temperature band. Temperature changes in the crystal luminescence parameters are explained in the model of “doped” luminescence.
Nonlinear interaction between an alternating magnetic and an acoustic field in the “inverted” phase of antiferromagnetics
Authors: Genkin G. M. , Zil’berberg V. V.
Published: November 2024

Nonlinear interaction is considered between an electromagnetic wave and a longitudinal acoustic wave, both at close frequencies, propagating through antiferromagnetics with an axis of easy magnetization in the “inverted” phase. The method of many-times retarded Green’s functions yields expressions for the magnetization due to this interaction, namely for its component proportional to both the magnetic field and the acoustic field intensity, as well as for its component linear with respect to the magnetic field and quadratic with respect to the acoustic field. Two conditions of resonance are considered too, namely: ω=ωs(q)±ω(q) and ω=2ωs(q)±2ω(q) (where ω denotes the frequency of the alternating magnetic field, ω(q) denotes the frequency of the acoustic field, and ωs(q) denotes the frequency of magnons within the nonactivation branch. The magnetization of MnFe2 within the shf range is also evaluated.
The effects of mutual drag on the kinetic coefficients of bismuth at low temperatures
Authors: Medvedev É. S. , Kopylov V. N. , Mezhov-Deglin L. P.
Published: November 2024

The influence of mutual drag effects of phonons and charge carriers on the behavior of the kinetic coefficients of highly perfect bismuth crystals of d≤1 cm diameter are studied at liquid-helium temperatures. The kinetic coefficients were calculated by the variational method on a BÉSM-6 computer. The phonon drag thermo-emf α is calculated, and the values of the effective mean free paths of electrons lep and holes lhp are obtained for intravalley scattering by phonons which, together with scattering on the surface of the specimen, determine the conductivity in the case when the phonons are in thermal equilibrium. It is shown that the role of mutual-drag effects depends greatly on the temperature and dimensions of the specimen. The thermo-emf of bismuth at liquid-helium temperatures is practically completely determined by the drag of the carriers by the phonons. Furthermore, in sufficiently massive specimens, at T≥4°K under conditions of frequent normal collisions, a mutual phonon-phonon drag develops, which leads to an exponential dependence σ(T) similar to ϰ(T).
Nonlinear threshold effects in superconductors
Authors: Vugal’ter G. A. , Demikhovskii V. Ya.
Published: November 2024

Nonlinear threshold effects are considered which vary quadratically with the amplitude of an intense sound wave in a superconductor—second-harmonic generation and the acoustoelectric effect. It is shown that for a constant sound intensity in a crystal the amplitude of the second harmonic near the thresholds ω = Δ and ω = 2Δ for a given crystal length is several times higher than in a normal metal or a superconductor with ω≪Δ,qvF≪Δ. A discontinuity in the phase difference of the order parameter is found at ω = 2Δ(T), related to the discontinuity in the sound absorption coefficient at the pair creation threshold.
Large-radius surface ions in helium
Authors: Monarkha Yu. P.
Published: November 2024

Surface electron states in helium are investigated theoretically in the presence of a strong magnetic field normal to the fluid-vapor boundary for the case when the density of the gas phase is not small. It is shown that the electron in the ground state deforms the gas medium, which partially dislodges the helium atoms from the region of its localization, and is converted into a new quasiparticle (a large-radius surface ion) with low mobility and high effective mass. It is shown that magnetic fields and helium gas concentrations less than the fields and concentrations assuring the stability of large-radius bulk ions are necessary for the stability of such quasiparticles. The effective mass of the surface ions and their mobility along the fluid- vapor boundary are calculated.
Theory of heat conductivity of thin dielectric specimens
Authors: Gurzhi R. N. , II’evskii V. I. , Maksimov A. O.
Published: November 2024

An expression is obtained for the coefficient of heat conductivity of a thin dielectric plate at low temperatures, taking into account wave diffraction by a rough surface. Specific cases due to different relationships between the characteristic dimensions of the roughness, the temperature wavelength, the phonon mean free path relative to bulk collisions, and the specimen thickness are examined. The equations obtained differ substantially from those already known which are based on introducing a coefficient of diffuseness.
Influence of dislocations on the de Haas-van Alfven effect under magnetic breakdown conditions
Authors: Ginzburg VI. L.
Published: November 2024

The influence of dislocations on the amplitude of de Haas–van Alfven oscillations is studied. It is shown that a calculation of the Dingle factor of the harmonic corresponding to the j-th cooperative orbit can be carried out in terms of the “local Hamiltonian” H^(j)=H^0(j)+u(r) where H^0(j) is determined by the type of the j-th orbit, u(r) is the electron potential in a dislocation field (the coordinate r is a parameter, and u(r) is a c-number).
The selection rules for direct transitions in magnetic crystals having antirotation
Authors: Kovalev Ο. V.
Published: November 2024

The selection rules are established for transitions in magnetic crystals with coincident magnetic and crystallographic periods. The formulas found are used to find the points of zero slope.
Magnetic anisotropy in the model of a ferromagnetic Fermi liquid
Authors: Syshchenko V. G.
Published: November 2024

The ground state of an anisotropic ferromagnetic Fermi liquid with an arbitrary density of states function is studied. The Curie temperature and the temperature dependence of the magnetization are found. An expression is found for the high-frequency susceptibility of an anisotropic ferromagnetic Fermi liquid at an arbitrary temperature. The spin-wave spectrum in the paramagnetic and ferromagnetic phases is determined.
Low temperature paramagnetism of fine gadolinium particles
Authors: Morozov Yu. G. , Kostygov A. N. , Petinov V. I. , Chizhov P. E.
Published: November 2024

The magnetic properties and structure of small gadolinium particles, 1100 and 200 Å in size, are studied. It is shown that the particles with d = 1100 Å have an hcp structure and are ferromagnetic below 295°K, while the 200 Å particles have an fcc structure and are paramagnetic between 4.2 and 295°K.
Ultrasound studies of polycrystalline methane
Authors: Tarasenko L. M.
Published: November 2024

The longitudinal and transverse velocities of 1 MHz ultrasonic oscillations in polycrystalline methane have been measured at temperatures between 14 and 90°K. The adiabatic and isothermal compressibilities, Poisson’s coefficient, and 0°K Debye temperature of solid methane have been determined.
Relaxation of exciton states in lattices of light inert crystals
Authors: Savchenko E. V. , Ya. Fugol’ I.
Published: November 2024

Results of measuring the luminescence of crystalline films of argon, neon, and their mixtures in the vacuum ultraviolet radiation range are analyzed. The question of exciton-phonon interaction in inert crystals is discussed. Experimental data indicating that the binding of exciton states to lattice vibrations is weakened in making the transition from light inert to heavy elements are presented. Features of the exciton relaxation processes in argon and neon crystals are examined.
Structural fluctuations in superconducting paramagnetic alloys
Authors: Gvozdikov V. M. , Fal’ko I. I.
Published: November 2024

It is shown that inhomogeneity of the distribution of paramagnetic impurities in superconducting alloys leads to a decrease of Tc in comparison with the value predicted by the Abrikosov-Gor’kov theory. Expressions are obtained for Tc in alloys with homogeneous structural fluctuations and also for the case when the impurities are grouped in clusters distributed homogeneously throughout the crystal. It is important that in inhomogeneous alloys Tc depends both on the exchange and nonexchange parts of the electron-impurity interaction.
Cu2+ exchange pairs in zinc fluorosilicate
Authors: Kozhukhar’ A. Yu. , Lukin S. N. , Tsintsadze G. A.
Published: November 2024

ESR at 9.2−72 GHz has been used at low temperatures to examine the additional absorption lines for 0.1−5% Cu2+ in zinc fluorosilicate; the concentration, frequency, temperature, and angle dependences show that the additional spectrum is due to exchange pairs with isotropic interaction.