The results of geodesic acoustic mode (GAM) studies in the spherical torus Globus-M via Doppler reflectometry are presented. The intermittent character of the GAM evolution is similar to the ...limit-cycle oscillation behavior of zonal flows. The evident correlation between the GAM rotational velocity and both Dα emission and plasma density oscillations is exhibited and discussed. The obtained experimental results are compared with those from tokamaks with large aspect ratios.
Experimental data are presented that indicate the effect of the magnetohydrodynamic tearing mode in the Globus-M spherical tokamak on the occurrence of filamentary structures (filaments). The ...filaments are recorded by the Doppler backscattering method. The groups of filaments localized in the toroidal direction are discovered, the appearance of which is synchronized with the propagation of the tearing mode. Possible causes of the effect of low-frequency magnetohydrodynamic oscillations on the occurrence of filament groups are considered.
The first results of an investigation of geodesic acoustic modes (GAMs) in the Globus-M spherical tokamak are presented. The experiments were performed using Doppler reflectometry. The conditions of ...the appearance of GAMs, the nature of their development, and their radial localization have been studied. The obtained data are compared to experimental results obtained in tokamaks with large aspect ratios.
Magneto-Optics and Optomagnetism in Nanostructures Ignatyeva, D. O.; Prisyazhnyuk, A. V.; Krichevsky, D. M. ...
Bulletin of the Lebedev Physics Institute,
12/2023, Letnik:
50, Številka:
Suppl 12
Journal Article
Recenzirano
A transition from uniform materials to metamaterials structured at scales that are smaller than the radiation wavelength makes it possible to control the interaction of light with matter due to the ...excitation and rearrangement of various optical modes of the structure. New phenomena and effects that arise during the interaction of light with nanostructured magnetic materials are described. Nanostructuring plays an important role both for magneto-optics (effect of magnetization of a material on a light wave), leading to a significant enhancement of magnetooptical effects and even emergence of new effects, and for optomagnetism (effect of laser pulses on magnetization), opening up a possibility of three-dimensional magnetic recording and excitation of exchange spin waves. If the size of the structure becomes on the order of tens or even units of nanometers, then quantum properties begin to appear, which are promising for the use of magnetic nanostructures for quantum technologies.
La complex is the most effective catalyst towards the synthesis of cyanohydrin trimethylsilyl ethers from both aliphatic and aromatic aldehydes with yields up to 96.3 % in 6h at room temperature.
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A series of known metal complexes, LaL2(NO3)(H2O)2·5H2O (1), Zn(μ-L)(NO3)(H2O)n (2), {Cd2(μ-HL)(μ-L)(NO3)3(H2O)·H2O}n (3) and Hg(μ-L)(N3)n·nH2O (4), were synthesized from the corresponding metal salts and 2-pyridinecarboxaldehyde isonicotinoylhydrazone (HL), and demonstrated high activity and selectivity in the cyanosilylation of aldehydes. Although all the complexes are derived from the same HL hydrazone ligand, the catalytic activity of 1–4 is different and relates to the metal center and coordination environment, whereas complex 1 being the most effective homogeneous Lewis acid-base catalyst towards the synthesis of cyanohydrin trimethylsilyl ethers from both aliphatic and aromatic aldehydes with yields up to 96.3 % in 6 h in methanol solution and at room temperature. According to the proposed mechanism, both coordination and noncovalent interactions (hydrogen and tetrel bonds) play a significant role and account for the higher catalytic activity of complex 1.
Achiral, diamagnetic Ni(II) complexes 1 and 3 have been synthesized from Ni(II) salts and the Schiff bases, generated from glycine and PBP (7) and PBA (11), respectively, in MeONa/MeOH solutions. The ...requisite carbonyl-derivatizing agents pyridine-2-carboxylic acid(2-benzoyl-phenyl)-amide 7 (PBP) and pyridine-2-carboxylic acid(2-formyl-phenyl)-amide 11 (PBA) were readily prepared from picolinic acid and o-aminobenzophenone or picolinic acid and methyl o-anthranilate, respectively. The structure of 1 was established by X-ray crystallography. Complexes 1 and 3 were found to undergo C-alkylation with alkyl halides under PTC conditions in the presence of β-naphthol or benzyltriethylammonium bromide as catalysts to give mono- and bis-alkylated products, respectively. Decomposition of the complexes with aqueous HCl under mild conditions gave the required amino acids, and PBP and PBA were recovered. Alkylation of 1 with highly reactive alkyl halides, carried out under the PTC conditions in the presence of 10% mol of (S)- or (R)-2-hydroxy-2‘-amino-1,1‘-binaphthyl 31a (NOBIN) and/or its N-acyl derivatives and by (S)- or (R)-2-hydroxy-8‘-amino-1,1‘-binaphthyl 32a (iso-NOBIN) and its N-acyl derivatives, respectively, gave rise to α-amino acids with high enantioselectivities (90−98.5% ee) in good-to-excellent chemical yields at room temperature within several minutes. An unusually large positive nonlinear effect was observed in these reactions. The Michael addition of acrylic derivatives 37 to 1 was conducted under similar conditions with up to 96% ee. The 1H NMR and IR spectra of a mixture of the sodium salt of NOBIN and 1 indicated formation of a complex between the two components. Implications of the association and self-association of NOBIN for the observed sense of asymmetric induction and nonlinear effects are discussed.
In this paper, we present some indices for evaluating the effectiveness of information protection in an information interaction system when controlling complex distributed organizational objects and ...proposing a technique for determining these indices. The technique is based on a stochastic representation of the flow of destructive actions that affect the information interactions among controllers of the elements of a distributed organizational object.
Ferrimagnets containing several partially compensated magnetic sublattices are considered the most promising materials for all-optical data storage and for ultrafast communications based on spin ...waves. There are two magnetic phases of the ferrimagnets: collinear and non-collinear ones. Up to now spin dynamics in ferrimagnets has been studied mostly in the collinear state without paying much attention to the kind of the magnetic phase. Here we investigate laser induced ultrafast spin dynamics in a rare-earth iron garnet film in the noncollinear phase as well. We identify a crucial influence of the magnetic phase on the excited spin modes which allowed us to discover several prominent effects previously overlooked. In particular, the non-collinearity makes the quasi-antiferromagnetic mode sensitive to the external magnetic field and brings its frequency close to the frequency of the quasiferromagnetic mode. The latter maximizes near the magnetization compensation point and vanishes towards the collinear phase. Spectacularly, at the phase transition the quasiferromagnetic mode becomes soft and its amplitude significantly increases reaching 7{\deg}. This opens new opportunities for the ultrafast control of spins in ferrimagnets for nonthermal data storage and data processing.
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