Vol 118, No 3-4 (8) (2023)

Axions with an energy of 8.4 keV emitted in the М1 transition in ¹⁶⁹Tm nuclei in the Sun are sought in the A+169Tm">$A+{}^{169}\text{Tm}$ → ¹⁶⁹Tm* → 169Tm+(γ,e)">${}^{169}\text{Tm}+(\gamma ,e)$ (8.4 keV) reaction of resonant absorption by ¹⁶⁹Tm nuclei on the Earth using a Tm3Al5O12">$\text{T}{\text{m}}_{\text{3}}\text{A}{\text{l}}_{\text{5}}{\text{O}}_{\text{12}}$ thulium garnet crystal as a bolometric detector. The flux of monochromatic 8.4‑keV axions has been calculated. New constraints on the axion–nucleon coupling constants have been obtained and, as a result, new upper bounds on the axion mass mAKSVZ⩽141">$m_A^{\text{KSVZ}}⩽\text{141}$ eV and mADFSZ⩽244">$m_A^{\text{DFSZ}}⩽\text{244}$ eV have been obtained at 90% C.L. in the KSVZ and DFSZ models, respectively.

Recent discovery of neutral bremsstrahlung (NBrS) mechanism of electroluminescence (EL) in noble gases in two-phase detectors for dark matter searches has led to a prediction that NBrS EL should be present in noble liquids as well. A rigorous theory of NBrS EL in noble liquids was developed accordingly in the framework of Cohen–Leckner and Atrazhev formalism. It has been recently followed by the first experimental observation of NBrS EL in liquid argon, which however deviates significantly from the previous theory. Given these results, we revise previous theoretical calculations of EL NBrS in noble liquids to be consistent with experiment. In particular, NBrS EL yield and spectra were calculated in this work for argon, krypton, and xenon with momentum-transfer cross section for electron scattering (instead of energy-transfer one) being used for calculation of NBrS cross section. The results for light noble liquids, helium and neon, are also reexamined.

A method is proposed to calculate thermal effects induced by the heat treatment of high-entropy metallic glasses within the general thermodynamic approach. The experimental verification of the proposed method shows that the exothermic effect observed below the calorimetric glass transition temperature, the endothermic effect in the glass transition region, and the exothermic effect during the crystallization of a metallic glass can be quantitatively described using the general thermodynamic equation for the change in the entropy of the glass including the diaelastic effect.

The X-ray diffraction analysis of NbS₃ ribbon whiskers has revealed three structural features: (i) a fine-crystalline structure throughout the entire volume with the preferred orientation along the [001] direction perpendicular to the long b axis of the whisker, (ii) the combination of crystalline macroblocks with a length up to 0.5 mm with small crystallites of various orientations, and (iii) the combination of crystalline macroblocks with the left-hand twisting of planes around the b axis with a pitch angle of 1.25° per every 0.2 mm and with the return to the initial orientation in the next block. Structural features (ii) and (iii) of NbS₃ whiskers have not yet been observed, and inorganic crystals with such properties are absent to the best of our knowledge. All crystallites have a unit cell with almost right angles and approximately the same lattice constant c (18.130 Å), whereas the lattice constants a and b are noticeably different in a single sample. All crystallites can be referred to phase IV rather than to phase I, as expected. The right angle between the a and c axes can be explained by the twinning of phase I along the c axis. Differences in the lattice constants in macroblocks indicate large stresses in structures. Such stresses near twins (and/or stacking faults) can significantly affect the free electron density and play a key role in the formation of charge density waves in various phases of NbS₃.

Crumpled polymer further folded into random loops has been proposed as a minimal model of chromosome organization. How do loops affect spatial distances in such a polymer? Here we investigate the statistics of intrachain distances, R(s)">$R(s)$, at different length scales s in the ensemble of polymer configurations with frozen (quenched) disorder of loops. We delineate the effect of the loops by solving the model analytically for the crumpled polymer chain, which was long suggested as a null model of chromatin organization. As we show, the chain compacts across scales upon folding into loops and features a characteristic “toe” in R(s)">$R(s)$ at the length scale of several loop sizes λ. Quantitatively comparing R(s)">$R(s)$ with the behavior of the contact probability function, Pc(s)">$P_c(s)$, computed in our previous works K. Polovnikov and B. Slavov, Phys. Rev. E 107, 054135 (2023) [1] and K. E. Polovnikov, B. Slavov, S. Belan, M. Imakaev, H. B. Brandáo, and L. A. Mirny, bioRxiv: 2022.02.01.478588 [2], we further demonstrate breaking of the famous mean-field relation between the two observables. The latter result is a striking manifestation of the non-Gaussianity of the polymer ensemble, induced by the loops disorder. Altogether, our theoretical findings pave the way towards quantitative inference of parameters of loopy chromosomes from the microscopy data in vivo and warn researchers against using Gaussian methods of analysis of population-averaged conformation capture datasets (e.g., Hi-C).

Adiabatic superconducting logic circuits can ensure the practical implementation of operations with the energy dissipation below the Landauer limit. However, applications of the existing solutions are limited because of two contradictory requirements of a high energy efficiency and a sufficiently fast response of devices. Josephson junctions with a negative critical current (π junctions) allow one to obtain a certain form of the potential energy of superconducting circuits and, as a result, a practically required degree of control of dynamic processes in the proposed reversible logic cells. The features of the current transport and balance of Josephson phases in circuits with π junctions make it possible to improve the coupling between the parts of a reversible computer by a factor more than 2. At the same time, the continuous evolution of the state is ensured at higher critical currents and higher characteristic voltages of the main Josephson junctions of adiabatic superconducting logic cells, which allows an increase in the response rate.

We examine statistics of fluctuations of the laser beam intensity at its propagating in turbulent atmosphere. We are interested in relatively large propagating distances and the remote tail of the probability density function. The tail is determined by the stretched exponent, we find its index.

Fundamentals of surface-enhanced Raman spectroscopy/scattering have been developed and possibility of its application to analyze some structural characteristics of surfaces and agglomerates of plasmonic metal nanostructures has been considered. A remote nondestructive express method based on surface-enhanced Raman spectroscopy has been presented to control the degree of local cracking of a metal coating and the effect of defects/cracks on the conductivity of a thin metallized film (uniaxially stretched polyethylene terephthalate track-etched membrane with a 50-nm silver coating).

A magnetoelectric effect, which manifests itself as a “refraction” of domain walls at the location of an electrode deposited on the surface of an iron garnet film, is studied. The “refractive index” depends on the electric voltage applied to the electrode and varies from 0.6 to 1.2. An electrically induced change in the surface energy of a domain wall due to an inhomogeneous magnetoelectric coupling is suggested as the mechanism of this effect.

High (15–25) harmonic generation in the vacuum ultraviolet spectral range (83–50 nm) has been realized by focused (NA = 0.033) near-infrared femtosecond laser radiation (wavelength λ = 1.24 μm) with a vacuum intensity of ~7.5 × 10¹⁴ W/cm² irradiating a dense gas jet. It has been shown experimentally that the use of such a high-numerical aperture focusing requires high (up to 10 bar) gas jet pressures to optimize phase matching. The use of the dense gas jet results in a noticeable manifestation of nonlinear propagation effects for generating radiation, which affect the generation process through the change in the phase matching conditions. Furthermore, it has been shown that the prechirping of the generating pulse makes it possible to compensate a chirp appearing due to self-phase modulation and to increase the harmonic generation efficiency because of the nonlinear compression of the generating pulse. This approach has allowed 17th (73 nm) harmonic generation with an energy of 2 pJ in a pulse and a generation efficiency of 5.4 × 10^–9. The estimates obtained have shown that this radiation can be used for single-pulse maskless photolithography in the extreme ultraviolet range.

The development and implementation of modern experimental methods in interdisciplinary projects promote the solution of fundamental problems in molecular biology and medicine. One of these problems is the understanding of the physics of molecular interactions in a narrow (<1 nm) surface layer of cellular lipid membranes (hydration layer of the membrane), where most of the important electrochemical interactions with ions and proteins, transmembrane transport of molecules, and endocytosis occur. The solution of this problem requires noninvasive methods sensitive to changes in the molecular structure of the surface layer of membranes. The aims of this work are to describe advantages of nonlinear optical microscopy and spectroscopy for the study of structural and electrostatic features of lipid membranes, to present the developed method for the visualization of the hydration of lipid membranes, and to discuss the limits of applicability of this method.

The quasiclassical one-dimensional motion of a particle in a medium, where the drag force is proportional to the square of the particle velocity, is considered using the Caldirola–Kanai approach. The coherent state of the particle in the presence of a constant conservative force in addition to the drag force is studied. It has been shown that the wave packet undergoes quantum extension to a certain limit, forming a steady propagating profile. Thus, the drag force suppresses the quantum properties of the particle, and the classical features become more pronounced in its motion with time. This property allows one to consider such a medium as a classical instrument continuously measuring the state of the particle. For this reason, the restriction of the spatial extension of the wavefunction can be interpreted as one of the manifestations of the quantum Zeno effect.