Magnetic resonance study of the spin-reorientation transitions in the quasi-one-dimensional antiferromagnet BaCu2Si2O7

A quasi-one dimensional antiferromagnet with a strong reduction of the ordered spin component, BaCu2Si2O7, is studied by the magnetic resonance technique in a wide field and frequency range. Besides of conventional spin-flop transition at the magnetic field parallel to the easy axis of spin ordering, magnetic resonance spectra indicate additional spin-reorientation transitions in all three principal orientations of magnetic field. At these additional transitions the spins rotate in the plane perpendicular to the magnetic field keeping the mutual arrangement of ordered spin components. The observed magnetic resonance spectra and spin-reorientation phase transitions are quantitatively described by a model including the anisotropy of transverse susceptibility with respect to the order parameter orientation. The anisotropy of the transverse susceptibility and the strong reduction of the anisotropy energy due to the quantum spin fluctuations are proposed to be the reason of the spin reorientations which are observed.Comment: RevTeX, 9 pages, 7 figure

Magnetoelastic Coupling and Possibility of Spintronic Electromagnetomechanical Effects

Nanoelectromangetomechanical systems (NEMMS) open up a new path for the development of high speed autonomous nanoresonators and signal generators that could be used as actuators, for information processing, as elements of quantum computers etc. Those NEMMS that include ferromagnetic layers could be controlled by the electric current due to effects related with spin transfer. In the present paper we discuss another situation when the current-controlled behaviour of nanorod that includes an antiferro- (instead of one of ferro-) magnetic layer. We argue that in this case ac spin-polarized current can also induce resonant coupled magneto-mechanical oscillations and produce an oscillating magnetization of antiferromagnetic (AFM) layer. These effects are caused by \emph{i}) spin-transfer torque exerted to AFM at the interface with nonmagnetic spacer and by \emph{ii}) the effective magnetic field produced by the spin-polarized free electrons due to $sd$-exchange.The described nanorod with an AFM layer can find an application in magnetometry and as a current-controlled high-frequency mechanical oscillator.Comment: 8 pages, 2 figures, submitted to Low Temp. Physic

Fast escaping points of entire functions: A new regularity condition

Let ƒ be a transcendental entire function. The fast escaping set, A(ƒ), plays a key role in transcendental dynamics. The quite fast escaping set, Q(ƒ), defined by an apparently weaker condition is equal to A(ƒ) under certain conditions. Here we introduce Q2(ƒ) defined by what appears to be an even weaker condition. Using a new regularity condition we show that functions of finite order and positive lower order satisfy Q2(ƒ) = A(ƒ). We also show that the finite composition of such functions satisfies Q2(ƒ) = A(ƒ). Finally, we construct a function for which Q2(ƒ) ≠ Q(ƒ) = A(ƒ)

Uncertainty of the implementation time of geodynamic monitoring system in multi-criteria ranking of alternatives

The paper deals with the problem of ranking alternatives to geodynamic monitoring systems in the case of uncertainty of their implementation time. The problem is characterized by the fact that the choice of alternatives and the effect of it depends on the quality properties of the applied organizational and technical solutions, taking into account the time of implementation. The ordering of alternatives is proposed taking into account the uncertainty of the implementation time factors. Ranking is realized by comparing the trees of functional characteristics of alternatives taking into account the compliance of their characteristics with time-varying requirement

Electrokinetic potential and stability of SiC suspensions in electrolyte solutions

The dependence of zeta potential on pH of an aqueous Si carbide suspension was studied by an electroosmosis method. The effect of pH on the Si carbide electrical double layer is attributed to the participation of H and OH ions in the surface dissociation reactions of weak acid OH groups on an oxidized carbide surface. Maximum stability of the suspensions was observed at maximum negative zeta potentials

Reality property of discrete Wronski map with imaginary step

For a set of quasi-exponentials with real exponents, we consider the discrete Wronskian (also known as Casorati determinant) with pure imaginary step 2h. We prove that if the coefficients of the discrete Wronskian are real and for every its roots the imaginary part is at most |h|, then the complex span of this set of quasi-exponentials has a basis consisting of quasi-exponentials with real coefficients. This result is a generalization of the statement of the B. and M. Shapiro conjecture on spaces of polynomials. The proof is based on the Bethe ansatz for the XXX model.Comment: Latex, 9 page

Самореалізація обдарованих учнів у сучасній Україні: основні чинники та ризики

The main theoretical and methodological approaches to the study of giftedness are regarded in the research, their analysis is carried out. It is suggested to use the theoretical and methodological positions of analysis of giftedness on two levels: the first level is the theoretical approaches that allow to position giftedness in society, the second one is those that expose the essential features of this phenomenon. The analysis of various definitions of giftedness led to the conclusion that giftedness represents the integration of abilities, social and personal preconditions, that allows to achieve higher results (higher of conditionally «average») in a certain area of activity. The analysis of the key models of giftedness is done in the research. It is suggested to use three groups of characteristics to portray gifted students. The first group is social characteristics. The second group of characteristics is intellectually mental. The third group of characteristics is psychological. The analysis of these groups of characteristics has shown that all these features of gifted pupils are manifested differently and can encounter specific obstacles in the way of their development depending on individual characteristics and their environment. The generalization of the results of own researches and studies of a wide range of domestic and foreign scholars allowed us to group the problem areas of self-realization of gifted pupils. These include: the state of the social environment, problems of social interaction, communicative and psychological-personal. It is shown that social expectations play a special role in the self-realization of gifted students and overcoming / non-overcoming their identified problem areas. Considering different approaches to the analysis of factor determination of giftedness (genetic, functional, adaptive, and probabilistic) and on the basis of empirical data analysis, four key groups of factors of self-realization of gifted pupils are singled out: general public factors; personal factors; the immediate environment; the educational local environment; cultural and educational macro environment. The generalization of the different aspects of self-realization of gifted pupils allowed us to propose a typology of the risks of this process. These risks include social risks, school risks, family risks and individual risks. The analysis of working experience in Ukraine and other countries on working with gifted children has demonstrated the presence of two main areas of such work: research-modeling and practical-oriented. On the basis of the analysis of the characteristics of gifted pupils, the factor determination of their self-realization and the risks of this process, a program of support for gifted pupils that includes normative and scientific-methodological basis, training of educational institutions for work with gifted pupils, resource support, public recognition of gifted pupils and their material encouragement is proposed. It is shown that the effective solution of the questions of self-realization of gifted pupils is associated with the use of the potential of stakeholder management, which provides for the audit stakeholders through the prism of their interests to the gifted pupils, the opportunities to participate in various stages of integrative approach of their education and others.У роботі розглянуто основні теоретичні та методологічні підходи до дослідження обдарованості, окреслено їх можливості та обмеження. Здійснено аналіз сутності обдарованості та її видів. На основі опрацювання моделей обдарованості визначено її елементи, що мають принципове значення для самореалізації особистості як процесу втілення у життя свого індивідуального потенціалу. Розглянуто три групи характеристик обдарованих учнів: соціокультурні, інтелектуально-розумові та психологічні. На основі аналізу різних підходів до факторної детермінації обдарованості виокремлено чотири групи чинників самореалізації обдарованих учнів. Здійснено систематизацію проблемних зон даного процесу та запропоновано типологію його ризиків. Розглянуто зарубіжний і вітчизняний досвід роботи з обдарованими дітьми та на основі розкриття потенціалу стейкхолдер-менеджменту удосконалено програмні основи супроводу обдарованих учнів

Androgynous plot in the oeuvre of Z.N. Gippius and its reflection in the novel by V.V. Nabokov "The gift"

This article considers androgynous plot in fictional prose of Z.N. Gippius, exemplified with the short novel “The mirrors” (1896) and the novel “Roman-tzarevitch” (1913), within the frameworks of studying of creative life model of this prominent representative of Russian Silver Age. Androgynous plot as an creative life allusion by Z.N. Gippius created the base for so-called “History if Yasha Chernyshevskiy” , which from hearsay is retold by the main character of V.V. Nabokov’s novel “The Gift” F.K.Godunov-Cherdyntsev. This text vividly expresses author’s polemical attitude to Z.N. Gippius’ creativeyesBelgorod State Universit