bluuebunny/crossref_metadata_2025 huggingface dataset:
Contribution of dislocations to the low-temperature heat capacity of crystals
Authors: Natsik V. D. , Smirnov S. N.
Published: February 2025

The dislocation contribution to the low-temperature heat capacity of crystals is investigated theoretically. The change produced in the spectral density of the crystal by three basic factors is analyzed in detail: appearance of specific vibrational modes—dislocation phonons—in the vibrational spectrum; the presence of a static elastic field of the dislocations; and, appearance of quasilocal vibrations near dislocations. Expressions for the corresponding components of the dislocation contribution to the heat capacity are derived and analyzed. It was established that when the effect of impurities and Peierls relief are taken into account a complicated nontrivial dependence of this part of the heat capacity on the temperature and the parameters of the problem is obtained. The conditions necessary for observing dislocation effects experimentally are analyzed. The temperatures at which the dislocation contribution can be equal to the heat capacity of an ideal lattice are estimated for a number of substances. It is shown that superconducting metals are suitable for experimental investigations, since in such metals high dislocation densities can be achieved and the electronic part of the heat capacity decreases rapidly with decreasing temperature.
Modified random-phase approximation in the theory of low-dimensional Heisenberg magnets
Authors: Antsygina T. N. , Slyusarev V. A.
Published: February 2025

Takahashi’s approach for describing one- and two-dimensional magnetic systems is extended with the help of the random-phase approximation. The theory developed makes it possible to describe analytically the behavior of low-dimensional ferro- and antiferromagnets at all temperatures. The results are compared with other approximations.
Nonresonance coupling between ultrasonic and magnetoplasma waves in compensated metal
Authors: Gokhfel’d V. M.
Published: February 2025

A theoretical analysis is given of nonresonance coupling between ultrasound and a weakly attenuated magnetohydrodynamic wave in the electron–hole plasma of a compensated metal. It is shown that this interaction gives rise to an additional mechanical displacement wave with supersonic velocity. A calculation is made of the relative amplitude of the additional wave as a function of the external magnetic field strength, both for contact and electromagnetic excitation of the ultrasound.
Photoinduced changes in the absorption spectrum of superconducting YBa2Cu3O7–δ films in the 1.5–3 eV region
Authors: Fugol’ I. Ya. , Samovarov V. N. , Rybalko Yu. I. , Zhuravlev V. M. , Zaimann-lshchenko G. , Khol’tsapfel B. , Shtrebel’ I.
Published: February 2025

We have studied experimentally the absorption spectrum of crystalline superconducting films of YBa2Cu3O7–δ in the energy region 1.5–3 eV, for temperatures from 300 to 20 K. Magnetic characterization of the films using a SQUID magnetometer revealed the presence of two superconducting phases with critical temperatures 87.5 and ∝ 50 K. We find that the absorption spectrum is sensitive to both superconducting transitions. For the low temperature phase with Tc = 50 K, we observe long-lived photoinduced changes in the absorption spectrum (photochromic effect). We discuss the band structure of the electronic transitions responsible for the absorption spectrum and the photoinduced changes.
Formation of filament-type structures during growth of HTS thin films
Authors: Klitsova Zh. I. , Mateichenko P. V. , Mitina N. V. , Rozenberg G. Kh. , Rom M. A. , Rudenko E. N. , Usoskin A. I. , Chukanova I. N.
Published: February 2025

The formation of filaments during the growth of YBa2Cu3Ox HTS films on strontium titanate substrates obtained by pulsed laser ablation technique is described. The composition and critical parameters of such formations are analyzed.
Influence of fluorine on the superconducting properties of YBa2Cu3O7–y
Authors: Eremenko V. V. , Makarov V. I. , Zhukov V. V. , Krivoshei I. V. , Korsunskaya I. G. , Kleiner V. Z. , Ovcharenko O. N. , Tereshina N. S. , Khatsko E. N.
Published: February 2025

Complex investigations of yttrium-based HTS compounds containing 0<x <1.5 fluorine are investigated. Knight shift has been observed in 19F nuclei and may serve as a reliable indicator of fluorine in the crystal lattice of Y-based compounds. Fluorine was introduced into the compound by the method of solid phase diffusion by replacing a part of Y2O3 with YF3. Three samples of multiphase Y-based compounds have revealed a metastable superconducting state at a temperature of ∼240 K.
Effect of spin-wave spectral structure of antiferromagnetic crystals on thermal broadening of exciton absorption bands
Authors: Eremenko A. V. , Kachur I. S. , Piryatinskaya V. G. , Slavin V. V.
Published: February 2025

Temperature dependences of exciton absorption band half-widths are studied experimentally and theoretically for antiferromagnets with different dimensions of magnetic structures and spin wave spectra. In a 3D AFM with a gapless dispersion of spin waves, the exciton band half-width δ(T)∝T3 In the presence of an energy gap ε˙g in the magnon spectrum, δ(T)∝Tn−1Snεg/T , where Snεg/T=∑l=1∞l1−nexp−εgl/kBTn is the magnetic structure dimension, and kB is Boltzmann’s constant. The obtained expressions for AFM crystals with a gap in the spin-wave spectrum reflect the threshold nature of the δ(T) dependence. The experimental curves for compounds under investigation are in good agreement with the results of calculations.
Heat transfer in dilute solid solutions of neon in parahydrogen
Authors: Antsygina T. N. , Gorodilov B. Ya. , Zholonko N. N. , Krivchikov A. I. , Manzhelii V. G. , Slyusarev V. A.
Published: February 2025

The thermal conductivity of solid solutions of neon in parahydrogen of concentration ranging from 1 to 1000 ppm is measures in the temperature interval from 1.5 to 9 K. An extremely string effect of impurity on thermal conductivity and the absence of a linear region in the dependence of the impurity thermal resistance on neon concentration are observed. A quantitative theory is developed to explain these peculiarities by the interference of normal phonon–phonon processes, umklapp processes, and resonance scattering of phonons by the heavy isotopic impurity. An expression for relaxation rate due to normal phonon–phonon processes is obtained in the case of acoustic phonons. The calculated values of parameters of these processes are in good agreement with the experimental data.
Associated mass of a superfluid liquid in a vibrating vessel
Authors: Nadirashvili Z. Sh.
Published: February 2025

The associated moment of inertia of a superfluid in a vessel performing axial vibrations about an external axis is measured. The dependence of the measured effect on the geometry of the vessel is analyzed.
Interaction of bulk and surface waves with Abrikosov vortices in an external magnetic field
Authors: Gutlyanskii E. D.
Published: February 2025

Electrodynamic equations for moving superconductors are derived. It is shown that a direct interaction between ultrasonic waves and Abrikosov vortices takes place in an external magnetic field. This interaction is proportional to squared magnetic field and the deformation vector of the ultrasonic wave. If the vortex structure is pinned, the interaction changes the velocity of the ultrasonic wave. The change in the velocity of a surface acoustic wave is calculated in the planar structure consisting of a superconducting film deposited on a piezoelectric substrate and placed in a magnetic field perpendicular to its surface.
Internal field and EPR in Sm1.995Gd0.005CuO4 crystals
Authors: Anders A. G. , Volotskii S. V.
Published: February 2025

For a member of the family of double cuprates, which is an electron superconductor after doping (it has been found for the first time) that RE centers are in a strong internal field Hef ∼ 20 kOe. Possible sources of this effective field are considered.
Magnetotransport in point contacts
Authors: Bogachek E. N. , Kulik I. O.
Published: February 2025

The theory of point-contact resistivity in the presence of a magnetic field is developed. The resistance increases linearly with the field intensity in a strong field. The dependence of the nonlinear component of the contact current on magnetic field is calculated both in the classic and quantum limits. The latter includes de Haas–van Alphen and Aharonov–Bohm types oscillations of the contact resistance. The thermoelectric effects in point contacts in magnetic field are investigated.
Current–voltage characteristics of bismuth-based microbridges
Authors: Nikolayeva A. A. , Rybaltchenko L. F. , Wohlleben D.
Published: February 2025

An essentially nonlinear dependence of the differential resistance dV/dI on the bias V has been established in bismuth-based microbridges. At low temperatures when the mean drift velocity of electrons v¯ becomes of the order of the Fermi velocity vF a decrease of the differential resistance is observed with the increasing bias. Drop of resistance is due to ballistic charge carrier transit within the region of microbridge at large biases. For the first time the phonon spectrum of Bi has been observed in microbridges.
Point-contact spectroscopy of La1−xCexB6 compounds
Authors: Kunii S.
Published: February 2025

Point-contact spectroscopy of La1−xCexB6 (x = 0, 0.3, 0.1, 0.25, 0.5, 0.75, and 1) has been investigated in order to study the dense Kondo properties. It is shown that the so-called heating model failed to explain the experimental results for these systems. Experimental results for GaAs Schottky barrier tunneling of CeB6 also suggest that the heating model is not the case in this system. To explain the experimental results for point-contact spectra of these dense Kondo systems, a spin-flip model has been proposed. Non-local heating mechanism in dense Kondo system has been discussed.
Keeping track of conduction electrons
Authors: van Kempen H. , Hoevers H. F. C.
Published: February 2025

The method of transverse electron focusing allows the study of conduction electrons which move in precisely known cyclotron orbits. As the electrons are injected and detected by means of point contacts at fixed positions, the orbits in real space are known as well. This paper reports the results of spectroscopic experiments with ballistic electrons in electron focusing and related geometries.
Phonon-assisted resonance scattering effects in CeNi5 point-contact spectra
Authors: Akimenko A. I. , Ponomarenko N. M.
Published: February 2025

We have investigated the point-contact (PC) spectra of CeNi5–Cu heterocontacts. Special attention has been paid to an additional structure (peak or plateau) observed at 10–14 meV. The shape and the energy position of this structure considerably depend on the CeNi5 electrode polarity. The phonon densities of states in CeNi5 and Cu have no singularities in this region. It is shown that the conduction electron resonance scattering by Ce4+ and Ce3+ ions which accompanies the inelastic phonon scattering may result in an additional phonon structure. Analyzing the polarity influence on the PC spectrum, determined we see the 4f-level sceme. It was found that the 4f0-level, lying at 2–3 meV above EF, is long-lived with Γ < 2 meV and the 4f1-level is situated at the distance 4–5 meV below EF.
Electron–phonon coupling mechanism in Bi2Sr2Ca1Cu2Ox by tunneling
Authors: Samuely P. , Vedeneev S. I. , Meshkov S. V. , Éliashberg G. M. , Jansen A. G. M. , Wyder P.
Published: February 2025

In the measured conductance curves of a Bi2Sr2Ca1Cu2Ox–Nb tunnel junction we find evidence for strong electron-phonon coupling. Analysis of the tunneling data yields the spectral function α2F(ω) of the electron-phonon interaction with a coupling strength sufficiently large to explain the superconducitng critical temperature. The observed sharp BCS-like singularity at the superconducting gap edge points to conventional singlet-type pairing of electrons.
Nonlinear I–V characteristics of YBa2Cu3O7-x–In contacts
Authors: Harutunian S. R. , Sahakian S. R.
Published: February 2025

In this work we have investigated the I–V characteristics of point contacts, which were prepared by impressing of metallic indium into the bridge of a high-Tc superconducting YBa2Cu3O7–x film. The measurements of the I–V characteristics and their derivatives dI/dV(V) was performed in the temperature range 11–100 K by a standard modulation technique. The I–V characteristics obtained can be divided into three types (the character of contacts ranges from the tunnel to the metallic type). Such variation of the I–V characteristics vs the contact resistance is explained by the Blonder–Tinkham–Klapwijk theory.
Point-contact spectroscopy on oxygen-deficient YBa2Cu3O7–δ single crystals
Authors: Goll G. , Seemann K. , Bräuchle G. , van Löhneysen H. , Erb A. , Müller-Vogt G. , Akimenko A. I. , Yanson I. K.
Published: February 2025

Oxygen-deficient YBa2Cu3O7–δ single crystals are investigated by point-contact spectroscopy. For samples with Tc = 90.2 K (δ ≈ 0.07) and 78.1 K (δ ≈ 0.26) reproducible spectra with “metallic-like” behavior of the differential resistance dV/dI are obtained, while a sample with Tc = 70.6 K (δ ≈ 0.29) consistently shows “semiconducting-like” behavior. At 4.2 K the differential resistance dV/dI of the low-δ samples shows pronounced gap-related structures with a distribution of gaps with well-defined maximum and minimum values. The temperature dependence of dV/dI vs V which could be traced up to T > Tc shows that these structures vanish faster than expected from BCS theory. The dependence on δ of the position of gap-related structure at V = Δ/e suggests that the gap decreases faster than Tc. The samples with δ ≈ 0.29 possibility exhibits gapless superconductivity.
Influence of finite lifetime of quasiparticles on the I(V) characteristics of break junctions based on high-T
c superconductors
Authors: Pedyash M. V. , Petrov D. K. , Ponomarev Ya. G. , Rakhimov H. T.
Published: February 2025

The superconducting gas peculiarities of break junctions have been investigated within the framework of the Dynes model, which takes into account the finite lifetime of quasiparticle excitation τ, introducing the broadening parameter Γ = ħ/τ into the tunneling density of states. The Dynes model proved to be a good approximation not only for the low temperature interval but also for a wide range of temperatures up to Tc. The theoretical curves agree well with the experimental I(V) and dI/dV characteristics for temperatures as high as 93 K. The broadening parameter Γ for our samples has been changed from ∼ 1 up to 6 meV at T = 4.2 K. As the gap parameter Δ decreases with temperature and becomes comparable with Γ, peaks of the density of states are progressively smeared, which does not allow for the maxima on the dynamic conductance to describe the gap near Tc. This fact agrees with the calculations which have shown that at temperatures near Tc, where Γ is comparable with Δ, the distance between the maxima remain practically unchanged.
Tunneling spectroscopy of YBCO “break junctions”
Authors: Zimmermann U. , Keck K. , Thierauf A.
Published: February 2025

We present measurements at break junctions prepared of polycrystalline and texture YBCO pellets with different resistances. The higher-ohmic junctions show the well-known behavior of HTSC tunnel contacts with gap-like structures in their dI/dV (V) characteristics. Lower-ohmic junctioins show the behavior of point contacts. Their I(V) and dI/dV (V) characteristics indicate all properties of the Andreev reflection corresponding to the theory of Kümmel et al. [1] for BCS superconductors. For correcting the characteristics we took into consideration the influence of granular capacitive coupling; so we are able to compare the characteristics directly with theoretical calculations. We studied the influence of magnetic fields up to 8 T.
Irreversible phenomena in the absorption of electromagnetic field in HTSC plates
Authors: D’yachenko A. I. , Chabanenko V. V.
Published: February 2025

Temperature dependence of the impedance in the 4.2 to 300 K range and hysteresis phenomena in the absorption with the field varying from – 70 to 70 kOe were studied in the M–Ba–Cu–O (M = Y, Yb, Eu, Gd) superconductor systems. Ceramic plates were studied in the frequency range from 5·104 to 2·107 Hz. Absorption hysteresis loops revealed a minimum at a field Hmin whose value grew with increasing external field oscillation amplitude and then saturated. A transformation of the hysteresis curve was observed near the superconducting transition. Peculiarities in absorption hysteresis phenomena are explained on the basis of a theory that accounts for the effect of Abrikosov vortices in Josephson junction banks on the critical current through it.
Effect of recovery processes on the superconducting transition temperature of niobium deformed at 20 K
Authors: Borisova I. F. , Sokolenko V. I. , Starodubov Ya. D.
Published: February 2025

We studied the effect of annealing within the temperature interval corresponding to recovery stage III on the superconducting transition temperature Tc and the electrical resistivity ρn of niobium rolling deformed at 20 K. The nonmonotone variation of Tc, that we found which corresponds to a two-stage decrease of ρn is attributed to changes in the electron–phonon interaction due to the displacement of vacancy–oxygen complexes to sinks and to the growth of vacancy–oxygen clusters.
The spin density wave state in quasi-two-dimensional systems with nonsymmetric filled energy band
Authors: Palistrant M. E. , Vakalyuk V. M.
Published: February 2025

Thermodynamic properties of the spin density wave state are studied within the mean field approximation in quasi-two-dimensional systems with the energy band filling (μ) deviating from the median, which destroys the “nesting” condition. The cases of fixed μ and fixed charge carrier concentration x are considered.
Transient processes in Bi in the phonon generation mode
Authors: Bengus S. V. , Krasovitskii Vit. B. , Finkel’ P. E.
Published: February 2025

Electrical oscillations excited in Bi in the acoustic noise generation mode are investigated. For the first time, the periods of oscillations have been measured over a wide range of magnitudes and directions of the magnetic field at temperatures 4.2, 14, and 20.4 K. It is found that the dependence of the phonon distribution stabilization time on external parameters during a transition to the nonlinear regime is similar to the dependence of the oscillation period. It is concluded that the nonelectronic mechanisms of nonequilibrium phonon relaxation play a dominant role in the formation of the nonlinear conduction mode. It is found that the period of electrical oscillations is determined by the phonon–electron relaxation.
Electronic structure of intermetallic compounds in the Cd–Mg system
Authors: Khotkevich V. V. , Grechnev G. E.
Published: February 2025

The electronic structure of isostructural hexagonal crystals of Cd3Mg and Mg3Cd is studied. The detailed structure of the electron density of states and the Fermi surface of these compounds is determined and their electron energy spectra are calculated by the pseudopotential method. It is shown that the one-electron component of the total energy of the crystal dominates in the stabilization of the ordered states at low temperatures. The results of calculations of the Fermi surface characteristics of the ordered compounds Cd3Mg are compared with experimental data on the de Haas–van Alphen effect. An interpretation is proposed for the experimentally observed oscillations.
On the mobility of vacancies in solid 4He
Authors: Dyumin N. E. , Zuev N. V. , Svatko S. V.
Published: February 2025

It is shown that the experimental results concerning the self-diffusion coefficient in low-density fcc 4He can be described noncontradictorily by using the quantum mobility of bivacancies. The diffusion coefficient, energy gap and the width of the vacancion energy band are determined.
Effect of nonresonance interaction of a varying magnetic field with the magnon system on the parametric instability level
Authors: Zvyagin A. A. , Segal Ya. Yu. , Tsukernik V. M.
Published: February 2025

The parametric effect of a varying magnetic field on a magnon systems is investigated under longitudinal pumping conditions (the constant and the varying fields are directed along the easy axis) without using the resonance approximation. It is shown that the system is parametrically stable for a strong linear attenuation for any value of the pumping amplitude.
Monte Carlo calculations of phase transition temperatures on the triangular lattice of reorienting dipoles
Authors: Morozov A. N. , Grechko L. G. , Ogenko V. M. , Rozenbaum V. M.
Published: February 2025

We consider a triangular lattice of dipoles with several possible orientations within the lattice plane, the long-range dipole–dipole interactions being taken into account rigorously. Similar systems can be realized for polar surface groups of atoms. The Monte Carlo method is employed to calculate the orientational phase transition temperatures; these are consistent with theoretical estimates.
Effect of fluorine doping on the electrical properties of the Bi2Sr2CaCu2Oy superconductor
Authors: Petrukhnovskaya N. B. , Popova T. B. , Chernyaeva N. B.
Published: February 2025

A series of Bi2Sr2CaCu2OyFx samples has been synthesized with different fluorine contents (x = 0.2; 0.4; 0.6; 1.0). From x-ray data the samples are close to single-phase and have the parameters a = 5.4 Å; c = 30.6 Å. As the fluorine content increases the type of conduction changes from metallic to semiconducting which is likely to be related with a decreasing concentration of charge carriers, viz., doping-induced holes.
Electron focusing effects in metals (a review)
Authors: Kolesnichenko Yu. A.
Published: February 2025

This review contains original theoretical results that justify the use of the method of electron focusing by a magnetic field in metals for studying the interaction of charge carriers with the outer and inner boundaries of a conductor, as well as with phonons, and also for studying their energy spectrum.
Peculiarities of low-temperature lattice dynamics of layered crystals CsR(MoO4)2 (R = Dy, Gd)
Authors: Anders É. E. , Startsev S. V. , Kudryavtsev I. N. , Nemchenko K. É.
Published: February 2025

The results of investigations of the low-temperature heat capacity of layered crystals CsDy(MoO4)2 and CsCd(MoO4)2 in the temperature range from 2.5 to 40 K are considered. Various theoretical approaches used for describing the lattice heat capacity of layered crystals with a complex lattice are analyzed. A model taking into account optical phonons along with acoustic phonons is proposed. Various parameters of the phonon subsystem in the crystals under investigation are determined.
Diamagnetic susceptibility and magnetic flux creep in the YBa2Cu3Ox ceramic
Authors: Tsymbal L. T. , Cherkasov A. N.
Published: February 2025

Frequency and field dependence of the intergrain losses in the diamagnetic susceptibility of the YBa2Cu3Ox ceramic was studied experimentally. It is shown that the results obtained can be described by means of a critical state equation within the framework of Anderson’s magnetic flux creep model. The critical current density and the pinning potential have been determined as functions of temperature and magnetic field.
Magnetic structure and resonance properties of Nd2CuO4
Authors: Krivoruchko V. N. , Shestakov A. A. , Yablonskii D. A.
Published: February 2025

High-frequency properties of collinear and noncoliinear phases of Nd2CuO4, which are consistent with the space group 14/mmm, are studied. The influence of the rare-earth (RE) sublattice on the statics and dynamics of the system is analyzed over a wide temperature range, from low temperatures at which RE magnetic moments are in the ordered state, to high temperatures at which the RE subsystem is in the paramagnetic state. The effect of the applied magnetic field oriented along the tetragonal axis is considered.
Monte-Carlo investigations of pressure dependences of thermodynamic properties and exchange interactions of Heisenberg magnetodielectrics CuM2X4 · 2H2O
Authors: German B. R. , D’yakonov V. P. , Telezhkin V. A.
Published: February 2025

Thermodynamic characteristics of a group of Heisenberg-type crystals CuM2X4 · 2H2O (where M stands for K, Rb, NH4, and X for Cl or Br) are simulated by the Monte-Carlo method (the Metropolis scheme). A comparison of calculated and experimental results makes it possible to obtain the pressure dependences of the exchange constants for nearest magnetic coordination spheres. The complex competing nature of interactions, which is manifested with increasing pressure, is confirmed.
Effect of rotation of molecules on heat transport in solid SF6
Authors: Konstantinov V. A. , Manzhelii V. G. , Smirnov S. A.
Published: February 2025

The isochoric thermal conductivity and thermal pressure of solid SF6 are investigated in the temperature interval 180–250 K. It is found that the isochoric thermal conductivity increases with temperature, while the isobaric thermal conductivity decreases under the same conditions. The relation between the temperature dependence of thermal conductivity and the nature of orientational motion of molecules is discussed.
Cluster-approximation analysis of impurity-helium phase formation and stability
Authors: Gordon E. B. , Pel’menev A. A. , Popov E. A. , Pugachev O. F. , Khmelenko V. V. , Shestakov A. F.
Published: February 2025

A theoretical analysis of the model NeHe12 structure is carried out in view to the existence of a novel metastable phase of closely packed Van der Waals shells surrounding polarizable heavy impurities of Ne, Ar, Kr, Xe, N, and N2. The analysis makes it possible to assume that the violation of the quantum-mechanical behavior of helium atoms, i.e., strong suppression of the amplitudes of zero-point radial vibrations of helium atoms belonging to the Van der Waals shell in the field of dispersive forces of a central impurity particle is the physical reason behind the formation of this phase. The phase diagram of the substance consisting of NeHe12 clusters is constructed and the directions of further investigations are outlined.
A new type of spin waves in normal metals with quasilocal electron states
Authors: Ermolaev A. M. , Ul’yanov N. V.
Published: February 2025

A new type of spin waves is predicted in nonferromagnetic metals with quasilocal electron states in a quantizing magnetic field. These waves have frequencies lying in a narrow transparency band in the vicinity of frequencies of resonance transitions of localized electrons at the Landau levels accompanied by a spin flip. The energy-momentum relation and the wave decrement are calculated.
Electric resistance and estimate of skin effect in samarium cuprate single crystals
Authors: Anders É. E. , Startsev S. V. , Volotskii S. V. , Anders A. G.
Published: February 2025

The temperature dependences of the electrical resistance of Sm2CuO4 and Sm1.995Gd0.005CuO4 single crystals are measured in the temperature interval 4.2–300 K, and the data are compared with the results of measurements of the EPR spectrum. The skin-depth is estimated.
Security applications of metasurface holograms with color print features
Authors: Lange Katherine De
Published: February 2025

Dual-functional hybrid metasurfaces integrating color printing and holography generate high-quality tricolor images that enhance document security
Monte Carlo toolkit for designing and validating step-range-filter spectrometer designs
Authors: Johnson T. M. , Lahmann B. , Russell L. , Vanderloo N. L. , Cufari M. J. , Reichelt B. L. , Chang C. W. , Birkel A. , Kabadi N. V. , Sutcliffe G. D. , Adrian P. J. , Pearcy J. A. , Kunimune J. H. , Dannhoff S. G. , Evans T. E. , Johnson M. Gatu , Séguin F. H. , Petrasso R. D. , Li C. K. , Frenje J. A.
Published: February 2025

Here, we present a Monte Carlo toolkit for validating step range filter (SRF) spectrometer designs. Geant4 is used to transport charged particles through the SRF filters to generate synthetic SRF data that include realistic CR-39 effects. Synthetic SRF spectra generated by this method inherently account for instrument response and allow for the quantification of SRF performance before shots. The usefulness of this toolkit is demonstrated through its application to a number of problems. A new broadband SRF for the ∼10 MeV wide 3He3He proton spectrum is validated, and an analysis method for analyzing 3He3He-p SRF data that accounts for instrument response is put forth. In addition, an SRF design for the compact recoil-proton spectrometer (CRS) on the Z-machine is validated. Finally, a new calibration technique for the DD-p SRF is proposed and validated.
Electronic and adsorption characteristics of hydrogen cyanide (HCN) and isocyanide (HNC) on intrinsic and doped phosphorene
Authors: Sahithi A. , Sumithra K.
Published: February 2025

Density functional theory calculations are performed to investigate the electronic properties of the phosphorene that is substituted with the non-metals in different patterns and concentrations and to study the adsorption of the toxic gases, hydrogen cyanide (HCN) and isocyanides (HNC), on the intrinsic and nitrogen-doped phosphorene adsorbents. It has been established previously that the number of valence electrons in the dopant atoms considerably affects the electronic characteristics of phosphorene. Doping with B, S, Si, and other non-metals has resulted in drastic changes in the direct bandgap characteristics of the semiconductor, resulting in the conversion of the semiconductor into an indirect bandgap material (boron-doped) or metallic (Si/S doped). Of all the doped surfaces, only nitrogen-doped phosphorene shows a direct bandgap. Therefore, adsorption studies are conducted to investigate the sensitivity of the toxic gases hydrogen cyanide (HCN) and isocyanide (HNC) on intrinsic and nitrogen-doped adsorbents. The adsorption results are compared to those on graphene and doped graphene surfaces. Pure phosphorene is a good candidate for the moderate adsorption of HCN and HNC due to its low adsorption energy and charge transfer. We have also found that intrinsic phosphorene is a better adsorbent for these gases than intrinsic graphene and doped graphene. In addition, N-doped phosphorene shows moderate reactivity toward HCN and HNC gases, suggesting it may be used as a metal-free catalyst for the adsorption of these adsorbates. The 2p orbitals on the nitrogen of HCN are found to play a significant role in the strong physisorption.
The verification of the large dynamic range readout design for the charge detector of the very large area γ-rays space telescope
Authors: Liu Xiangman , Sun Zhiyu , Fang Fang , Yan Junwei , Yang Zuoqiao , An Yilang , Kong Jie , Guo Jianhua , Wan Qiang , Zhang Yan , Yang Peng , Yang Zhen , Chen Junling , Yu Yuhong , Zhang Yongjie , Hu Bitao
Published: February 2025

As a successor to the DArk Matter Particle Explorer (DAMPE), the Very Large Area γ-rays Space Telescope (VLAST) is being designed to strengthen γ-ray observations and extend the cosmic ray nuclei measurements up to Zr (Z = 40) and even heavier ions. Consequently, a large dynamic range is required by the charge detector of VLAST to cover the measurements of cosmic ray particles from the proton to ultra-heavy ions. To achieve the requirements, a readout design based on the three dynodes signal extracted from the photomultiplier tube has been proposed. In addition, a prototype VLAST charge detector has been developed and tested with cosmic rays, pulse UV laser, and relativistic heavy ion beams to verify this design. The test results illustrate that the dynamic range readout design can easily cover the required dynamic range of about five orders of magnitude.
Atomic force microscopy lateral force calibration using a V-shape scratch made by a nanoindenter
Authors: Mazeran Pierre-Emmanuel , Jaramillo-Isaza Sebastian , Baiti Risa-Nurin , Nguyen Anh Dung , El Kirat Karim , Noël Olivier
Published: February 2025

Measuring quantitative and accurate friction force at the nanoscale by means of atomic force microscopy is not straightforward. Numerous lateral force calibration methods have been proposed in the last decades. The most popular one is the wedge method that requires a specific calibration sample having areas that present constant slope and friction coefficient. In this paper, we propose to revisit the wedge method by using an original, cheap, and easy-to-make standard, which consists of a V-shaped scratch made by a Berkovich nanoindenter tip on a fused silica substrate. We show that the scratch has two large opposite facets characterized by the same moderate and constant friction coefficient and slope. This allows simplification of the data processing and a much more reliable and accurate lateral force microscopy calibration.
Characterization of AlF3-passivated aluminum mirrors using non-contact thermal metrology
Authors: Jones Andrew H. , Gaskins John T. , Hopkins Patrick E. , Walton Scott G. , Boris David R. , Murphy John P. , Rodriguez de Marcos Luis V. , Del Hoyo Javier , Quijada Manuel A.
Published: February 2025

We demonstrate the use of steady-state thermoreflectance (SSTR) as a technique for characterizing mirror surfaces. Due to the enhanced sensitivity of thermoreflectance compared to reflectance, SSTR provides the ability to assess the physical and chemical characteristics as well as the uniformity of thin films and coatings much more rapidly than common metrological methods such as x-ray photoelectron spectroscopy. The use of this technique is demonstrated on AlF3-passivated Al surfaces produced using a process developed for the fabrication of far ultraviolet reflectors. However, since SSTR is thermal in nature, this technique negates the need for a priori knowledge of the optical properties of the material. This is emphasized by interrogating both homogeneous and non-uniform AlF3 films.
Estimating infectious disease transmission risk: An analysis based on multi-scale modeling of respiratory droplet transport
Authors: Cavazzuti Marco , Campanelli Ludovico , Tartarini Paolo
Published: February 2025

In the present work, a multi-scale model is used to simulate the trajectory of exhaled droplets for different types of respiratory events. By estimating the saliva viral content, information on the exhaled droplet trajectory and size distribution are exploited to derive spatial maps of viral concentration. The maps are used to estimate the risk of infection by direct inhalation for a susceptible individual exposed to exhalations. Discriminating between the droplets falling to the ground and those remaining airborne, further estimates of the risks associated with fomite and airborne transmission routes are made possible. Simulations are based on an analytical model, recently developed by the authors, implementing the equations of droplet transport, evaporation, energy, and chemical composition. Turbulent dispersion is modeled with a random walk approach, whereas the droplets are released randomly within the exhalation time span and mouth/nose orifice cross section. Droplet transport within the respiratory cloud, a critical aspect in this kind of investigation, is evaluated by coupling the analytical model to the results of unsteady computational fluid dynamics simulations of the respiratory scenarios investigated, namely: mouth breathing, nose breathing, speaking, coughing, and sneezing. Results are compared to those obtained in a previous work where the respiratory cloud was simulated through a two-dimensional unsteady empirical model proposed by the authors based on momentum conservation. The multi-scale model provides better predictions of small droplet trajectories albeit at a higher computational cost. The risk maps provided constitute a useful tool for assessing prevention needs in controlling the spread of epidemics.
Synergistic effects of dielectrophoretic and magnetophoretic forces on continuous cell separation via pinched flow fractionation
Authors: Zare Mahdi , Khatibi Mahdi , Ashrafizadeh Seyed Nezameddin
Published: February 2025

The challenges of constraints and imprecision in chemical analysis and medical diagnosis are particularly evident in the separation of blood cells. Pinched flow fractionation, a passive microfluidic technique, has gained attention for its potential in size-based cell separation. Enhancing its efficiency is crucial, especially through integration with external forces or active methods. This study explores the use of dielectrophoresis (DEP) and magnetophoresis (MP) forces to separate platelet cells, red blood cells, white blood cells, and circulating tumor cells. These forces were analyzed both independently and simultaneously. To achieve optimal separation, the Navier–Stokes equations, Newton's second law, and the system's electric and magnetic fields were modeled. Experiments were conducted in a branched microchannel to assess the impact of various parameters, including buffer flow rate, pinched section width, applied voltage, electric field frequency, and magnetic field intensity. The analysis revealed optimal separation efficiency of approximately 99% under the conditions of Wp=20 μm, Q2=1250 μl/h, f=100 kHz, V=3 V, and M=1.5 T. The findings demonstrate that while DEP and MP forces individually enhance separation, their simultaneous application significantly improves precision, achieving complete separation. This optimized system holds great promise for applications in analytical chemistry and medical diagnostics, particularly in blood cell analysis.
Viscoelastic flow in converging-diverging pipes
Authors: Kadyirov Aidar
Published: February 2025

Point velocity measurement has been applied to analyze the flow field of dilute polymer solution in converging-diverging pipes with axial symmetry. Four geometries with various lengths of converging-diverging sections were considered. Special attention was given to stationarity and steadiness of investigated flows. It was observed that the amplitude of oscillating flow grows as the Deborah number increases and reaches the maximum at De ∼ 0.7, at which the vortex length has achieved its maximum value. Further increase in Deborah number leads to decrease in the vortex length and suppresses the amplitude of observed oscillation. Using time-averaged analysis, the velocity profiles at various cross sections of converging-diverging tubes are constructed and discussed. A comparison with the analytical solution for the pipe flow is also provided. For Deborah numbers in the range from 1 to 6, the fourth regime was observed for which the viscoelastic flow behaves like “purely divergent” without any vortex zone near the boundary wall in the converging section. The transition to this flow regime can be predicted by a modified version of extension rate distribution.
Comparative study for heat transfer characteristics of magnetohydrodynamic viscous fluid in a multilayer flow flanked between nanofluids
Authors: Rudrappa Mahesha , T Sravan Kumar , N Nalinakshi , Aly Emad H.
Published: February 2025

This article examines the mixed convection heat transfer analysis of magnetohydrodynamic (MHD) viscous fluid flow over a multilayer channel flanked between nanofluids comprising a porous medium. The research highlights the significance of multilayer nanofluid flow in practical applications such as petroleum filtration process, cooling of electronic systems, nuclear reactors, and solar thermal systems. Ethylene glycol (EG) serves as a coolant due to its excellent miscibility with copper (Cu), enhancing its corrosion resistance properties in the fluid flow system. The purpose of this study is to analyze the impact of magnetic fields on heat transfer in a multilayer flow of Cu-EG-based nanofluids with different nanoparticles. The comparative performance of copper, copper oxide, and silver nanoparticles in enhancing the heat transfer rate is investigated. The non-dimensional equations are highly coupled, and non-linear differential equations are resolved analytically by utilizing regular perturbation approaches to get a closed-form solution. A comparative analysis between analytical results and numerical methods was done, demonstrating excellent agreement for the fluid flow momentum profile. This study reveals the magnetic field reduces heat transfer in the fluid flow system EG as a base fluid, and silver nanoparticles outperform copper, and copper oxide nanoparticles in thermal conductivity. These findings give rise to optimizing nanofluid-based systems in engineering and industrial applications.
An interface accurate numerical method for liquid–gas phase change in the front-tracking framework
Authors: Ye Lijun , Zhang Xixi , Zhou Hongsheng , Tian Yuan , Zhang Ying , Li Peisheng , Lu Min
Published: February 2025

An interface accurate numerical method for phase-change processes is developed, and the velocity decomposition is introduced into the front-tracking framework. The method decomposes the velocity field into a potential part associated with phase change and a rotational part. The two parts are solved separately, which decouples the numerical errors in the potential and rotational parts during the advancement of the liquid–gas interface. The results of the present method are compared with the existing method at various density ratios, demonstrating more accurate representation of the interface and robust using the present method. Additionally, by explicitly tracking the interface, the method reduces the number of Poisson equations solved compared to the interface capturing framework, improving the computational efficiency during the interface advection process. The proposed method is validated through a series of benchmark tests, including the one-dimensional (1D) Stefan problem, the one-dimensional (1D) sucking problem, and two-dimensional (2D) droplet evaporation at both saturation and sub-saturation temperatures. Additionally, the method is tested by simulating one or two evaporating droplets falling under gravity in both two- and three-dimensional cases, further demonstrating its accuracy and robustness.
A possum’s cautionary tale: targeted surveys in north-eastern Victoria fail to detect Leadbeater’s possum in remnant forest within its historic range
Authors: Eyre Arabella C. , Harley Dan K. P. , Briscoe Natalie J. , Lumsden Lindy F. , McComb Leo B. , Lentini Pia E.
Published: February 2025

Endemic to Victoria, the range-restricted, Critically Endangered Leadbeater’s possum (Gymnobelideus leadbeateri) historically had a much broader distribution from south-east of Melbourne, through the wet forests of eastern Victoria, and extending into New South Wales. Undetected populations of this cryptic species may persist within forested sections of this historic range, despite these landscapes having been subject to significant disturbance through clearing, logging, and bushfires. The adoption of arboreal camera trapping has permitted targeted surveys for Leadbeater’s possum to be conducted with greater efficiency and reliability. Between 2017 and 2019, we conducted arboreal camera-trapping surveys for Leadbeater’s possum in seven patches of potentially suitable habitat, that were 13–145 km outside the species’ known range in Victoria’s Central Highlands. Site selection was informed by habitat suitability modelling. The species was detected at only one of seven areas surveyed, the patch closest to the possum’s current known range (~13 km). Notable occurrences of other cryptic arboreal mammals were recorded in rarely surveyed habitat types and at high elevations (>1000 m). Despite north-eastern Victoria’s significant remnant forest cover, the apparent loss of Leadbeater’s possum from its historic range in this region provides a cautionary tale regarding declining forest condition owing to major disturbance from fire and logging.
Physical activity and male reproductive function
Authors: Hamim Farhanah Mohd , Durairajanayagam Damayanthi , Daud Suzanna Binti , Singh Harbindar Jeet
Published: February 2025

Fecundity is declining in humans, which is partly due to male infertility. Poor sperm parameters, the main contributors to male infertility, are associated with sedentary, unhealthy lifestyle and poor dietary habits. Long periods of sedentary work lead to visceral adiposity and persistently elevated scrotal temperatures, which adversely affect spermatogenesis. Apart from increasing scrotal temperatures, excessive visceral adiposity exacerbates adipocyte dysfunction with increased pro-inflammatory adipokine release, like leptin. These, together with the increased scrotal temperature, are responsible for the poor sperm quality. The importance of regular physical activity in male fertility remains a matter of debate, as not all forms of exercises have been found to benefit sperm function. Sperm parameters are, nevertheless, somewhat better in active than in sedentary men. It now appears that low-to-moderate intensity exercises are more beneficial for male reproductive health than high-intensity exercises, which have a negative effect on spermatozoa. Low-to-moderate intensity exercises, in general, improve the overall organ-system function in the body, improve the management of body weight and oxidative stress, consequently improving sperm parameters. The detrimental effects of high-intensity exercises on spermatozoa result from disruption in the hypothalamus-pituitary-gonadal-axis, raised testicular temperature and increased oxidative stress. It, therefore, seems that not all types of exercises are beneficial for male reproductive health. Although some low-to-moderate intensity exercises improve male reproductive function, there remains a need to identify the best form of low-to-moderate intensity exercises, particularly those that do not increase testicular temperature or oxidative stress, to help maintain normal body weight and male reproductive health.
Biochemical and structural bases for talin ABSs–F-actin interactions
Authors: Biertümpfel Christian , Yamada Yurika , Vasquez-Montes Victor , Truong Thien Van , Cada A. King , Mizuno Naoko
Published: February 2025

Focal adhesions (FAs) are large intracellular macromolecular assemblies that play a critical role in cell polarization and migration. Talin serves as a direct connection between integrin receptor and actomyosin cytoskeleton within FAs. Talin contains three actin-binding sites (ABS1-3) that engage discreetly during the development of FAs, thus acting as a critical player in FA initiation and maturation. However, the molecular basis of the ABS–F-actin interactions remains unknown. Here, we explore interactions of ABSs with F-actin to understand the multivalent behavior of talin. Particularly, the cryo-EM structure of the F-actin–ABS3 complex at 2.9 Å shows ABS3 spanning through two actin monomers along the filament axis, each occupied by the R13 rod subdomain and the DD domain. The dimerization of ABS3 occurs through the DD domain where both protomers interact on the actin surface, and the dimerization of talin to the actin surface is necessary for the engagement to F-actin. The R13 helical bundle is distorted upon binding to F-actin and releases the H1 helix from the rest of the bundle. This phenomenon has also been observed with other tension-sensing proteins like vinculin and α-catenin, highlighting that unfolding is relevant for its force sensing activity. On the contrary, ABS2 (R4R8 subdomains), which is thought to be critical for the maintenance of mature FAs, had multiple F-actin-binding regions within ABS2 and the binding likely occurred by these subdomains running through the surface of F-actin, thus strengthening the interactions upon the maturation of FAs.