Search of low-dimensional magnetics on the basis of structural data: spin-1/2 antiferromagnetic zigzag chain compounds In2VO5, beta-Sr(VOAsO4)2,(NH4,K)2VOF4 and alpha-ZnV3O8

A new technique for searching low-dimensional compounds on the basis of structural data is presented. The sign and strength of all magnetic couplings at distances up to 12 A in five predicted new antiferromagnetic zigzag spin-1/2 chain compounds In2VO5, beta-Sr(VOAsO4)2, (NH4)2VOF4, K2VOF4 and alpha-ZnV3O8 were calculated. It was stated that in the compound In2VO5 zigzag spin chains are frustrated, since the ratio (J2/J1) of competing antiferromagnetic (AF) nearest- (J1) and AF next-to-nearest-neighbour (J2) couplings is equal to 1.68 that exceeds the Majumdar-Ghosh point by 1/2. In other compounds the zigzag spin chains are AF magnetically ordered single chains as value of ratios J2/J1 is close to zero. The interchain couplings were analyzed in detail.Comment: 14 pages, 6 figure, 1 table, minor change

Radiography of the Earth's Core and Mantle with Atmospheric Neutrinos

A measurement of the absorption of neutrinos with energies in excess of 10 TeV when traversing the Earth is capable of revealing its density distribution. Unfortunately, the existence of beams with sufficient luminosity for the task has been ruled out by the AMANDA South Pole neutrino telescope. In this letter we point out that, with the advent of second-generation kilometer-scale neutrino detectors, the idea of studying the internal structure of the Earth may be revived using atmospheric neutrinos instead.Comment: 4 pages, LaTeX file using RevTEX4, 2 figures and 1 table included. Matches published versio

Signatures of cosmic tau-neutrinos

The importance and signatures of cosmic tau--(anti)neutrinos have been studied for upward-- and downward--going $\mu^-+\mu^+$ and hadronic shower event rates relevant for present and future underground water or ice detectors, utilizing the unique and reliable ultrasmall--$x$ predictions of the dynamical (radiative) parton model. The upward--going $\mu^- +\mu^+$ event rates calculated just from cosmic $\nu_{\mu}+\bar{\nu}_{\mu}$ fluxes are sizeably enhanced by taking into account cosmic $\nu_{\tau}+ \bar{\nu}_{\tau}$ fluxes and their associated $\tau^- +\tau^+$ fluxes as well. The coupled transport equations for the upward--going $\stackrel{(-)}{\nu}_{\tau}$ flux traversing the Earth imply an enhancement of the attenuated and regenerated $\stackrel{(-)}{\nu}_{\tau}$ flux typically around $10^4-10^5$ GeV with respect to the initial cosmic flux. This enhancement turns out to be smaller than obtained so far, in particular for flatter initial cosmic fluxes behaving like $E_{\nu}^{-1}$. Downward--going $\mu^- +\mu^+$ events and in particular the background--free and unique hadronic `double bang' and `lollipop' events allow to test downward--going cosmic $\nu_{\tau} +\bar{\nu}_{\tau}$ fluxes up to about $10^9$ GeV.Comment: 32 pages, 6 figures; Added reference

Increasing the micromechanical and tribological characteristics of an austenitic steel by surface deformation processing

Frictional treatment (FT) with a sliding indenter forms highly dispersed (nano- and submicrocrystalline) austenitic structures with a hardness of 720 HV 0.025 in the surface layer of the 03Cr16Ni14Mo3Ti austenitic strain-resistant steel. According to the data on microindentation, FT increases the strength and of the surface layer of the austenitic steel and its resistance to elastic and plastic deformation. A high effectiveness of FT in the improvement of the tribological properties of the steel is demonstrated; namely, wear resistance increases 4 times under conditions of boundary friction as compared to the undeformed state. This is due to reduced plastic edging on the nanostructured surface. © 2018 Author(s)

Prompt neutrino fluxes from atmospheric charm

We calculate the prompt neutrino flux from atmospheric charm production by cosmic rays, using the dipole picture in a perturbative QCD framework, which incorporates the parton saturation effects present at high energies. We compare our results with the next-to-leading order perturbative QCD result and find that saturation effects are large for neutrino energies above 10^6 GeV, leading to a substantial suppression of the prompt neutrino flux. We comment on the range of prompt neutrino fluxes due to theoretical uncertainties.Comment: 13 pages with 11 figures; expanded discussion, added references, version to be published in Phys. Rev.

Phase equilibria, crystal structure and oxygen nonstoichiometry of the complex oxides in Sm – (Sr, Ba) – (Co, Fe) – O systems

Received: 18.01.2018. Accepted: 14.02.2018. Published: 10.05.2018.Present paper contains available information on the phase equilibria in the Sm – (Sr, Ba) – (Co, Fe) – O systems, including the synthesis routes used, crystal structure, which is often depended on oxygen nonstoichiometry, the data on thermodynamic stability of complex oxides, the obtained results on the homogeneity ranges of solid solutions, formed in the systems, and graphical presentation of phase relations in a form of phase diagrams

Neutrinos from Accreting Neutron Stars

The magnetospheres of accreting neutron stars develop electrostatic gaps with huge potential drops. Protons and ions, accelerated in these gaps along the dipolar magnetic field lines to energies greater than 100 TeV, can impact onto a surrounding accretion disc. A proton-induced cascade so develops, and $\nu$-emission is produced from charged pion decays. Using GEANT4, a computer code that tracks particles produced in high energy collisions, we have calculated the resulting $\nu$-spectrum with extensive disc shower simulations. We show that the $\nu$-spectrum produced out of the proton beam is a power law. We use this result to propose accretion-powered X-ray binaries (with highly magnetized neutron stars) as a new population of point-like $\nu$-sources for km-scale detectors, such as ICECUBE. As a particular example we discuss the case of A0535+26. We show that ICECUBE should find A0535+26 to be a periodic $\nu$-source: one for which the formation and loss of its accretion disc can be fully detected. Finally, we briefly comment on the possibility that smaller telescopes, like AMANDA, could also detect A0535+26 by folding observations with the orbital period.Comment: 7 pages, 5 figures. Updates to match accepted version in Astrophys.

Crystal chemistry aspects of the magnetically induced ferroelectricity in TbMn2O5 and BiMn2O5

The origin of magnetic frustration was stated and the ions whose shift is accompanied by emerging magnetic ordering and ferroelectricity in TbMn2O5 and BiMn2O5 were determined on the basis of calculation of magnetic coupling parameters by using the structural data. The displacements accompanying the magnetic ordering are not polar, they just induce changes of bond valence (charge disordering) of Mn1 and Mn2, thus creating instability of the crystal structure. To approximate again the bond valence to the initial value (charge ordering) under magnetic ordering conditions is possible only due to polar displacement of Mn2 (or O1) and O4 ions along the b axis that is the cause of ferroelectric transition.Comment: 17 pages, 3 figures, 5 table

Granular Rheology in Zero Gravity

We present an experimental investigation on the rheological behavior of model granular media made of nearly elastic spherical particles. The experiments are performed in a cylindrical Couette geometry and the experimental device is placed inside an airplane undergoing parabolic flights to cancel the effect of gravity. The corresponding curves, shear stress versus shear rate, are presented and a comparison with existing theories is proposed. The quadratic dependence on the shear rate is clearly shown and the behavior as a function of the solid volume fraction of particles exhibits a power law function. It is shown that theoretical predictions overestimate the experiments. We observe, at intermediate volume fractions, the formation of rings of particles regularly spaced along the height of the cell. The differences observed between experimental results and theoretical predictions are discussed and related to the structures formed in the granular medium submitted to the external shear.Comment: 10 pages, 6 figures to be published in Journal of Physics : Condensed Matte

Proteism in a cinematic portrait of a woman-philosopher

The article analyzes the image of a woman philosopher, created by modern culture, on the material of feature cinematography. Revealing a set of characteristics that belong to a woman-philosopher in the collective representations that are broadcast in motion pictures allows performing a double research vision: 1) analysis of the cultural era to which the heroine of the biopic belonged; a specific philosophical concept created by her; 2) diagnostics of the culture that created the cinematic portrait of a woman-philosophe