| 1. |
- Avdeev, S. V., et al.
(author)
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Preliminary results of studying the effect of heavy charged particles on the human central nervous system in experiments SilEye and Alteino
- 2005
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In: Bulletin of the Russian Academy of Sciences: Physics. - 1062-8738. ; 69:3, s. 512-514
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Journal article (peer-reviewed)abstract
- A series of experiments were carried out in the period 1995 to 2002 to study the phenomenon of light flashes (LFs) which arose in the eyes of astronauts. These experiments were made onboard the Mir orbital station (SilEye, SilEye-2) and on the Russian segment of the International Space Station (SilEye-3/Alteino). As a result of investigation it is reliably demonstrated that the majority of light flashes under conditions of a space flight are caused by nuclei of cosmic rays. Electric signals from brain, recorded during LF occurrence, were an important final result of these studies.
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| 2. |
- Casolino, M., et al.
(author)
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Relative nuclear abundances inside ISS with Sileye-3/Alteino experiment
- 2006
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In: Advances in Space Research. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 37:9, s. 1685-1690
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Journal article (peer-reviewed)abstract
- The experiment Sileye-3/Alteino was first operational on board the international Space Station between 27/4 and 1/5/2002. It is constituted of a cosmic ray silicon detector and an electroencephalograph and is used to monitor radiation environment and study the light flash phenomenon in space. As a stand-alone device, Sileye-3/Alteino can monitor in real time cosmic ray nuclei. In this work, we report on relative nuclear abundance measurements in different regions of the orbit for nuclei from B to Fe in the energy range above similar or equal to 60 Mev/n. Abundances of nuclei such as 0 and Ne relative to C are found to be increased in respect to particle composition outside of the station, whereas the Fe group is reduced. This effect could be ascribed to nuclear interactions with the hull of the station.
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| 3. |
- Almessiere, M. A., et al.
(author)
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Review on functional bi-component nanocomposites based on hard/soft ferrites : Structural, magnetic, electrical and microwave absorption properties
- 2021
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In: Nano-Structures and Nano-Objects. - : Elsevier B.V.. - 2352-507X. ; 26
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Journal article (peer-reviewed)abstract
- Bi-component hard (H) (hexaferrite) and soft (S) (spinel) ferrites nanocomposites are gaining interest scientifically and technically, not only for combining the high magnetization of spinel ferrite nanomaterials and the high coercivity of hexaferrite magnetic nanomaterials but also for the outstanding exchange-coupling behavior among hard and soft magnetic phase. The improved magnetic features lead to produce a new nanocomposite with higher microwave absorption capacity in comparison with ferrites with a single absorption mechanism. Exchange-coupled effect has a potential application based on microwave absorption, recording media, permanent magnets, biomedical and other applications. Intensive studies have been conducted on this topic to produce hard/soft (H/S) ferrite nanocomposites with establishment of exchange coupled effect between the two phases. Preparation methods, microstructure, magnetics features, microwave and dielectric properties, and applications are elaborated. Consequently, a comprehensive effort has been made to contain an original reference investigating in detail the precise outcomes of the published papers.
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| 4. |
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| 5. |
- Almessiere, M. A., et al.
(author)
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Effects of Ce-Dy rare earths co-doping on various features of Ni-Co spinel ferrite microspheres prepared via hydrothermal approach
- 2021
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In: Journal of Materials Research and Technology. - : Elsevier BV. - 2238-7854 .- 2214-0697. ; 14, s. 2534-2553
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Journal article (peer-reviewed)abstract
- The effects of Ce-Dy co-doping on the crystal structure, optical, dielectric, magnetic properties, and hyperfine interactions of Ni-Co spinel ferrite microspheres synthesized hydrothermally have been studied. A series of ferrites with the general formula Ni0.5-Co0.5CexDyxFe2-2xO4 were synthesized with x values ranging from 0.00 to 0.10. The phase, crystallinity, and morphology of ferrite microspheres were analyzed by X-ray powder diffractometry (XRD), scanning and transmission electron microscopes (SEM and TEM), respectively. The structural analyses of the synthesized ferrite microspheres confirmed their high purity and cubic crystalline phase. The Diffuse reflectance spectroscopic (DRS) measurements were presented to calculate direct optical energy band gaps (E-g) and is found in the range 1.63 eV - 1.84 eV. Fe-57 Mossbauer spectroscopy showed that the hyperfine magnetic field of tetrahedral (A) and octahedral (B) sites decreased with the substitution of Dy3+-Ce3+ ions that preferrentially occupy the B site. The impact of the rare-earth content (x) on the magnetic features of the prepared NiCo ferrite microspheres was investigated by analyzing M-H loops, which showed soft ferrimagnetism. The magnetic features illustrate a great impact of the incorporation of Ce3+-Dy3+ ions within the NiCo ferrite structure. The saturation magnetization (M-s), remanence (M-r), and coercivity (H-c) increased gradually with increasing Ce-Dy content. At x = 0.04, M-s, M-r, and H-c attain maximum values of about 31.2 emu/g, 11.5 emu/g, and 512.4 Oe, respectively. The Bohr magneton (n(B)) and magneto-crystalline anisotropy constant (K-eff) were also determined and evaluated with correlation to other magnetic parameters. Further increase in Ce3+-Dy3+ content (i.e., x >= 0.06) was found to decrease M-s, M-r, and H-c values. The variations in magnetic parameters (M-s, M-r, and H-c) were largely caused by the surface spins effect, the variations in crystallite/particle size, the distribution of magnetic ions into the different sublattices, the evolutions of magneto-crystalline anisotropy, and the variations in the magnetic moment (n(B)). The squareness ratios were found to be lower than the predicted theoretical value of 0.5 for various samples, indicating that the prepared Ce-Dy substituted NiCo ferrite microspheres are composed of NPs with single-magnetic domain (SMD). Temperature and frequency-dependent electrical and dielectric measurements have been done to estimate the ac/dc conductivity, dielectric constant, and tangent loss values for all the samples. The ac conductivity measurements confirmed the power-law rules, largely dependent on Ce-Dy content. Impedance analysis stated that the conduction mechanisms in all samples are mainly due to the grains-grain boundaries. The dielectric constant of NiCo ferrite microspheres give rise to normal dielectric distribution, with the frequency depending strongly on the Ce-Dy content. The observed variation in tangential loss with frequency can be attributed to the conduction mechanism in ferrites, like Koop's phenomenological model.
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| 6. |
- Migas, Dmitry B., et al.
(author)
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Temperature induced structural and polarization features in BaFe12O19
- 2023
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In: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7526 .- 2050-7534. ; 11:36, s. 12406-12414
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Journal article (peer-reviewed)abstract
- We report the observation of a peculiar polarization behavior of BaFe12O19 in electric field where the linear polarization is detected at temperatures below 150 K whereas at higher temperatures a hysteresis-like polarization response is observed. At the same time, the performed neutron diffraction analysis shows no variations in crystal or magnetic structures with temperature. Based on the results of ab initio calculations we suggest the mechanism able to explain the experimentally observed behavior. We show that specific Fe atoms do not occupy the positions formally assigned to them by the conventional centrosymmetric P6(3)/mmc (#194) space group (z = 0.25; 0.75) as these positions correspond to local energy maxima. Instead, these Fe atoms are shifted along the z-axis to positions z = 0.259 (0.241) and z = 0.759 (0.741), which correspond to local energy minima. To an inversion center move between these minima Fe atoms need to overcome an energy barrier. This barrier is rather insignificant for smaller volumes but it becomes larger for expanded volumes due to coupling between the displacements of these Fe atoms. Additionally, our analysis suggests that the non-centrosymmetric and polar P6(3)mc (#186) space group could be appropriate for the description of the BaFe12O19 structure.
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