Uspehi fizičeskih nauk
ISSN (print): 0042-1294, ISSN (online): 1996-6652
Media registration certificate: ПИ № ФС 77 – 28253 from 11.06.2007
Founders: P.N. Lebedev Physical Institute of the RAS, Uspekhi Fizicheskikh Nauk, RAS
Editor-in-Chief: Rudenko O.V., academician RAS
Frequency / Assess: 12 issues per year / Subsription
Included in: White List (1st level), Higher Attestation Commission List, RISC, Scopus
Current Issue
Vol 193, No 12 (2023)
Reviews of topical problems
Atomic processes involving highly charged ions
Abstract
Atomic processes of ionization, recombination, and electron capture in collisions of positive ions with atoms, ions, electrons, and molecules are considered. The impact of these processes on the interaction of ion beams with media in a wide range of energies—from low to super-relativistic—is discussed, focusing primarily on energies $E \sim 10$ keV–100 GeV per nucleon. The main features of the effective cross sections of the processes are described as a function of the collision energy, atomic structure, and density effects in gases, solids, and plasmas. The role of dielectronic recombination in the interaction of beams of heavy multi-electron ions with a plasma is considered in detail. The progress in experimental and theoretical studies in accelerator physics and the physics of collisions of heavy ions with atomic systems, achieved over the last five to ten years is reviewed.
Uspehi fizičeskih nauk. 2023;193(12):1249-1283
1249-1283
Photonics approaches to the implementation of neuromorphic computing
Abstract
Physical limitations on the operation speed of electronic devices has motivated the search for alternative ways to process information. The past few years have seen the development of neuromorphic photonics—a branch of photonics where the physics of optical and optoelectronic devices is combined with mathematical algorithms of artificial neural networks. Such a symbiosis allows certain classes of computation prob„lems, including some involving artificial intelligence, to be solved with greater speed and higher energy efficiency than can be reached with electronic devices based on the von Neumann architecture. We review optical analog computing, photonic neural networks, and methods of matrix multiplication by optical means, and discuss the advantages and disadvantages of existing approaches.
Uspehi fizičeskih nauk. 2023;193(12):1284-1297
1284-1297
Stochastic processes in the brain's neural network and their impact on perception and decision-making
Abstract
The article deals with the influence of stochastic dynamics of the brain's neural ensembles on the perception and processing of sensory information, as well as on decision-making based on it. The review considers sources of noise in the nervous system during sensory information processing, as well as some nervous system strategies of compensating for or taking into account stochastic processes. Experiments and mathemat„ical models are discussed in which stochastic brain dynamics begins to play a significant role in the perception of sensory information. Particular attention is paid to brain noise research paradigms such as the perception of weak stimuli close to the sensitivity threshold and bistable ambiguous stimuli. Methods for assessing brain noise using both psychophysical experiments and direct analysis of neuroimaging data are described. Finally, some issues in applying the concept of stochastic brain dynamics to problems in the biomedical diagnosis of various neurological diseases are considered.
Uspehi fizičeskih nauk. 2023;193(12):1298-1324
1298-1324
Instruments and methods of investigation
Potential of the microwave method for the activation of carbon materials in comparison with the traditional thermal method
Abstract
Microwave exposure is one possible promising heating method that can be used to create porous carbon materials. Activated carbon materials obtained by microwave heating can serve as an adsorbent or electrode material in energy storage devices such as supercapacitors. The paper investigates the processes of carbonization and activation of cotton lint using microwaves. A comparison is made with the traditional thermal method of heating, as well as with the mass-produced highly porous carbon fiber Busofit T1.
Uspehi fizičeskih nauk. 2023;193(12):1325-1334
1325-1334
Investigation of the dynamics of the Belousov–Zhabotinsky reaction by time-resolved X-ray absorption spectroscopy using adaptive X-ray optical elements
Abstract
We performed an in-situ study of the Belousov–Zhabotinsky self-oscillatory chemical reaction using the developed technique of time-resolved X-ray absorption spectroscopy implemented with the help of adaptive X-ray optical elements (AXOEs). The dynamics of the K-edge absorption of bromine (Br), which is found in various substances during the reaction, were monitored. We carried out sequential recordings of the K-edge absorption spectrum of bromine in the vicinity of 275 eV with a spectral resolution of better than 1.4 eV, an accumulation time of 1 s per spectrum, and a repetition rate of 0.71 Hz. The acquired series of spectra allow us to trace the kinetics of the Belousov–Zhabotinsky reaction, in particular, the kinetics of chemical self-oscillations taking place in it.
Uspehi fizičeskih nauk. 2023;193(12):1335-1339
1335-1339
Methodological notes
Magnetorotational instability in Keplerian disks: a nonlocal approach
Abstract
We revisit the modal analysis of small perturbations in Keplerian ideal gas flows with a constant vertical magnetic field leading to magnetorotational instability (MRI) using the nonlocal approach. In the general case, MRI modes are described by a Schr$\ddot o$dinger-like differential equation with some effective potential, including ‘repulsive’ ($1/r^{2}$) and ‘attractive’ ($-1/r^{3}$) terms, and are quantized. In shallow potentials, there are no stationary ‘energy levels.’ In thin Keplerian accretion discs, the perturbation wavelengths $\lambda =2\pi /k_{z}$ are smaller than the disc semi-thickness $h$ only in ‘deep’ potential wells. We find that there is a critical magnetic field for the MRI to develop. The instability arises for magnetic fields below this critical value. In thin accretion discs, at low background Alfv$\acute e$n velocity $c_A\ll (c_A)_cr$, the MRI instability increment $\omega $ is suppressed compared to the value obtained in the local perturbation analysis, $\omega \approx -\sqrt {3}ic_Ak_{z}$. We also investigate for the first time the case of a radially variable background magnetic field.
Uspehi fizičeskih nauk. 2023;193(12):1340-1355
1340-1355
Personalia
In memory of Vladimir Evgen'evich Zakharov
Uspehi fizičeskih nauk. 2023;193(12):1356-1357
1356-1357
Bibliography
New books on physics and related sciences: December 2023
Uspehi fizičeskih nauk. 2023;193(12):1358-1359
1358-1359
Physics news on the Internet: December 2023
Uspehi fizičeskih nauk. 2023;193(12):1360-1360
1360-1360