Models of G time variations in diverse dimensions

A review of different cosmological models in diverse dimensions leading to a relatively small time variation of the effective gravitational constant G is presented. Among them: 4-dimensional general scalar-tensor model, multidimensional vacuum model with two curved Einstein spaces, multidimensional model with multicomponent anisotropic "perfect fluid", S-brane model with scalar fields and two form field etc. It is shown that there exist different possible ways of explanation of relatively small time variation of the effective gravitational constant G compatible with present cosmological data (e.g. acceleration): 4-dimensional scalar-tensor theories or multidimensional cosmological models with different matter sources. The experimental bounds on G-dot may be satisfied ether in some restricted interval or for all allowed values of the synchronous time variable.Comment: 27 pages, Late

Hadronic Light-by-Light Scattering in the Muonium Hyperfine Splitting

We consider an impact of hadronic light-by-light scattering on the muonium hyperfine structure. A shift of the hyperfine interval $\Delta \nu({\rm Mu}) _{\rm\tiny HLBL}$ is calculated with the light-by-light scattering approximated by exchange of pseudoscalar and pseudovector mesons. Constraints from the operator product expansion in QCD are used to fix parameters of the model similar to the one used earlier for the hadronic light-by-light scattering in calculations of the muon anomalous magnetic moment. The pseudovector exchange is dominant in the resulting shift, $\Delta \nu({\rm Mu})_{\rm\tiny HLBL}= -0.0065(10) {Hz}$. Although the effect is tiny it is useful in understanding the level of hadronic uncertainties.Comment: 16 pages, 7 figures, a reference adde

Angular dependence of the ferromagnetic resonance parameters of [Ti/FeNi]6/Ti/Cu/Ti/[FeNi/Ti]6 nanostructured multilayered elements in the wide frequency range

Magnetically soft [Ti(6)/FeNi(50)]6/Ti(6)/Cu(500)/Ti(6)/[FeNi(50)/Ti(6)]6 nanostructured multilayered elements were deposited by rf-sputtering technique in the shape of elongated stripes. The easy magnetization axis was oriented along the short size of the stripe using deposition in the external magnetic field. Such configuration is important for the development of small magnetic field sensors employing giant magnetoimpedance effect (GMI) for different applications. Microwave absorption of electromagnetic radiation was experimentally and theoretically studied in order to provide an as complete as possible high frequency characterization. The conductor-backed coplanar line was used for microwave properties investigation. The medialization for the precession of the magnetization vector in the uniformly magnetized GMI element was done on the basis of the Landau–Lifshitz equation with a dissipative Bloch–Bloembergen term. We applied the method of the complex amplitude for the analysis of the rotation of the ferromagnetic GMI element in the external magnetic field. The calculated and experimental dependences for the amplitudes of the imaginary part of the magnetic susceptibility tensor x-component and magnetoabsorption related to different angles show a good agreement. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 18-19-00090Funding: This research was funded by the Russian Science Foundation, grant number 18-19-00090

Personality regulation of students’ cognitive states during sports and educational activities

The article is devoted to the study of cognitive mental states and personality properties relationship during educational activities. In practical terms, the most important task in the field of educational psychology is to develop methods for updating and regulation of cognitive states. The study of cognitive states carried out in various forms of educational activity: in an ordinary situation (a lecture) and in a tense situation of training (an exam). N = 90, 1-st year students at the Kazan Federal University. During the research used different questionnaires to diagnose the personality traits and the intensity of students’ cognitive states, such as interest, reflection, concentration, mental stress etc. The data analysis included frequency analysis, the polar group method and the MANOVA method. Revealed that in an everyday situation of educational activity (lecture) the most often experienced states are thoughtfulness, interest and concentration, while in a tense situation of an exam - mental stress, doubt and concentration. In everyday situations, a state of thoughtfulness is observed in individuals with high Conscientiousness, and prevails in friendly, open-minded and emotionally stable students with a focus on the task. During the exam students with high activity, extraversion, and focus on the task experience the state of mental stress. Results of this research will find application in educational systems increasing the effectiveness of educational, scientific and creative activities, through the updating of students’ positive cognitive states. Cognitive states stimulate and regulate cognitive activity, performing the function of development of cognitive processes and intellectual abilities. The influence of personality properties on cognitive states is mediated by both the intensity of educational activity and the interaction of the personality traits.The study was carried out with the financial support of the Russian Foundation for Basic Research, project No. 19-013-00325

Influence of Sintering Conditions on Specific Electrical Conductivity in Aluminum-Graphene Composite

Dependence of specific electrical resistance on temperature (20 - 1600 ∘C) and processing method in an aluminum-graphene (up to 2wt.%) composite is investigated. It is established that spark plasma sintering (SPS) under pressure 40 MPа does not influence on electrical resistance, whereas SPS at low pressure (<10 MPa) reduces electrical resistance at a room temperature on 6 orders. Lower values of electrical resistance (up to 90 Ω *mm) received at sintering in hot pressing set at radiating heating. It is supposed that the reason of sharp decrease in electrical resistance at the lowered pressure is presence of current pulsations during SPS. They induces magnetic fields in graphene flake which lead to their moving and forming of particles to electroconductive chains or their capture in arched cells at applied pressure. Keywords: composite, aluminum, graphene, electrical resistance, temperature dependence

Chemical analysis of aerosol in the Venusian cloud layer by reaction gas chromatography on board the Vega landers

The experiment on sulfuric acid aerosol determination in the Venusian cloud layer on board the Vega landers is described. An average content of sulfuric acid of approximately 1 mg/cu m was found for the samples taken from the atmosphere at heights from 63 to 48 km and analyzed with the SIGMA-3 chromatograph. Sulfur dioxide (SO2) was revealed in the gaseous sample at the height of 48 km. From the experimental results and blank run measurements, a suggestion is made that the Venusian cloud layer aerosol consists of more complicated particles than the sulfuric acid water solution does