Frequency Dependence of an Electromagnetic Absorption Coefficient in Magnetic Fluid

Technical Physics - The samples of water-based magnetic fluid, which contain Fe3O4–SiO2 particles with a spherical shape and sizes less than 100 nm, have been obtained. The method based on...     

Aggregate stability and magnetic characteristics of colloidal Fe m O n –SiO2 particles obtained by sol–gel method

Physics of the Solid State - Composite Fe m O n –SiO2 particles have been obtained by precipitation of iron oxide from aqueous solution with the addition of tetraethoxysilane. The shapes and...     

The preparation and properties of “porous silicon–nickel ferrite” nanoheterocomposites for gas detectors

This paper discusses the preparation and properties of gas detectors based on “porous silicon–nickel ferrite” nanocomposites. Impedance spectroscopy was used to measure sensitivity to ethanol and isopropanol vapours in the presence of an alternating electric field. The results were interpreted with the help of an equivalent electrical circuit. In the analysis of the resistive–capacitive properties in the equivalent circuit a constant phase element was used.     

The Study of Aggregation Processes in Colloidal Solutions of Magnetite–Silica Nanoparticles by NMR Relaxometry,AFM, and UV–Vis-Spectroscopy

Colloidal solutions of magnetic nanoparticles were studied as a promising magnetic resonance imaging (MRI) contrast agent. The problem of aggregative stability of solutions is considered. Sol-gel synthesis of magnetite colloidal solutions stabilized by silica is described. Transmittance spectra were measured to analyze sedimentation of nanoparticles in magnetite–silica solutions of different compositions and concentrations. It is shown that the synthesized nanoparticles can be used as MRI contrast agents. The surface morphology and particle size of Fe₃O₄/SiO₂ layers were estimated by atomic force mictroscopy (AFM) technique. The mechanism of magnetic-field-induced aggregation of Fe₃O₄/SiO₂ nanoparticles into chain-like and fractal structures is described.     

Mechanisms of Magnetoelectric Effects in Oxide Multiferroics with a Perovskite Praphase

Physics of the Solid State - Magnetoelectric effects in multiferroics with a perovskite structure, such as bismuth ferrite, rare-earth orthochromites, and Ruddlesden–Popper structures...     

Direct 13C-13C spin-spin coupling constants in the vinyl group of N-vinylazoles

The unshared electron pair of the dicoordinated nitrogen atom introduces a stereospecific contribution to the ¹³C-¹³C spin-spin coupling constant (SSCC) in the vinyl group of a series of N-vinylazoles, the value of which depends on the energetics of the unshared pair.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 197–200, February, 1989.     

On the total binding energy of spherical nuclei

The total binding energy of nuclei is determined by means of many-body field theory. The problem is then reduced to finding the energy-dependent average potential (mass operator) and solving the single-particle equations of motion. Such a potential can be established phenomenologically by using data on low excitations and reactions knocking out nucleons from deep “hole” levels. Calculations of the total binding energy of the nuclei ¹⁶O, ⁴⁰Ca and ⁵⁸Ni with this potential are in satisfactory agreement with experiment.     

A microscopical DWBA description of the charge-exchange reactions (7Li, 7Be)

The charge-exchange reaction (⁷Li, ⁷Be is described in the frame of a microscopical DWBA with central effective forces. The transition density for ⁷Li-⁷Be is calculated in two ways: with a one-particle model and with a cluster model, taking full account of recoil effects. The formalism is used for the cases of (⁷Li, ⁷Be reactions with ⁶Li and ⁴⁰Ca. Further cross sections for reactions on ¹²C and ¹⁶O with $\text{E(}{}^7\text{Li) = 78 MeV}$ and excitation energies around 4.5 and 6.2 MeV, respectively, are compared to new data obtained at the Kurchatov Institute. Here particle-hole states in an oscillator model were used to characterize the heavy system. Angular distributions are well reproduced, but absolute cross sections are 6–7 times too small. This indicates that the assumption of a direct one-step process is correct, but that tensor forces should be included as a component of the effective nucleon-nucleon force.     

A study of the 14C(6Li, 6He)14N reaction at 93 MeV

The reaction ¹⁴C(⁶Li, ⁶He)¹⁴N was investigated with 93 MeV ⁶Li ions in an angular interval of 7–26°. Angular distributions were analysed for the four most intense groups of ⁶He nuclei, corresponding to transitions to the ground (1₁⁺) and the excited (1₂⁺, 2₁^?, 4₁^?) states of ¹⁴N. In the theoretical analysis a mechanism of the spin-isospin excitation was suggested in the DWBA frame with the finite range of interaction and recoil in the light system (⁶Li⁶He) taken into account. In the calculations both shell-model wave functions and transition densities obtained in the theory of finite Fermi systems (FFS) were used. From the comparison between theory and experiment the Landau-Migdal force constant g′ is estimated in order to obtain some information on the degree of nuclear proximity to the threshold of pion condensation.