Properties of ferromagnetic film hysteresis, on the surface of a hard-magnetic antiferromagnet, with a domain structure

This is a theoretical investigation of the exchange bias phenomenon, and the properties of a thin magnetic film's magnetization hysteresis loop, on the rough surface of a hard-magnetic antiferromagnet. An interface model with a periodic structure of atomic steps is presented. These atomic steps are associated with a spatially inhomogeneous distribution of the ferromagnetic film magnetization, akin to a system of domain walls. This structure leads to a complicated external field dependence of magnetization: the hysteresis curve can assume an asymmetrical shape and "fall apart" into two hysteresis loops, divided by a "horizontal plateau," or an area with constant field-independent magnetization. Such field dependence behavior has been recently observed experimentally in different ferro/antiferromagnet systems. The field dependence of magnetization has been obtained analytically using the long-wave approximation for various characteristics of ferromagnetic film (its thickness, values of exchange interaction, and magnetic anisotropy), and the interface (the period of the inhomogeneous structure, and exchange interaction through the interface). The analytical results are confirmed by numerical calculations for the corresponding discrete model with a more complex interface structure

Model of exchange bias in a trilayer FM/AFM/FM structure

A theoretical examination of the properties of the exchange bias phenomenon for sandwich FM/AFM/FM structures, which are actively studied in experiments. Magnetization dependences on the external magnetic field are obtained under the proposed discrete model of ferromagnetic layers of such multilayer structures. It is shown that the magnetization field dependences have a horizontal plateau, a splitting of the hysteresis loop, and asymmetry. We examine the influence of the interface defects on the exchange bias phenomenon and its features. The results are qualitatively consistent with experimental data

Коммуникативные технологии краудсорсинга в современной глобальной и российской публичной политике

Введение. Статья посвящена рассмотрению краудсорсинговых технологий публичной коммуникации в глобальном и региональном современных политических пространствах как средств мирного, ненасильственного разрешения конфликтов и снижения социальной напряженности в различных частях мира. Методы. Авторы концептуализируют краудсорсинговую технологию публичной политической коммуникации на основе классических и современных теорий политико-коммуникативного взаимодействия общества и власти (Ю. Хабермас, М. Кастельс, Г. Тард, Дж. Шуровьески, Дж. Хау и др.). Раскрыта специфика внедрения краудсорсинговых технологий в международной публичной политике на примере организации электронных дискуссий по формированию глобальной повестки дня Организацией Объединенных Наций, а также в политическом пространстве современной России в связи с распространением практик электронного управления, электронного участия индивидов и групп. Результаты. Акцентируется внимание на том факте, что внедрение краудсорсинга выступает одним из важных этапов в процессе повышения эффективности коммуникации между органами государственной власти, местного самоуправления, политическими и общественными объединениями, бизнесом при выработке и принятии наиболее значимых для граждан решений. Востребованность краудсорсинга в междуна- родной и российской публичной политике связана, с одной стороны, с признанием того, что огромное количество граждан обладает способностями, талантом, необходимыми компетенциями и качествами инновационной активности, а с другой стороны, со значимостью развития «человеческого капитала», понимаемого как совокупность знаний, умений, навыков, использующихся для удовлетворения многообразных потребностей граждан и социума в целом, в современных конкурентных и сложных мировых условиях. Обсуждение. Открытым и малоизученным остается вопрос об ограничениях использования краудсорсинговой технологии для реализации успешной публичной политики в контексте существующей социальной и культурной стратификации и неравенства, потенциала опосредованного коллективного действия.The paper studies crowdsourcing technologies of public communication that is an essential part of the global and regional contemporary political spaces as a method of nonviolent conflict resolution and reduction of social tensions in different parts of the world. Methods. The authors examine crowdsourcing technology of public political communication based on classical and modern concepts of political-communicative interaction of society and government (J. Habermas, M. Castells, G. Tarde, J. Shurovyeski, J. Howe). The paper reveals the specifics of implementation of crowdsourcing in the international public policy on the example of the United Nations Organization world agenda setting e-discussion projects, and in the political context of modern Russia with the spread of e-government practices, e-participation of individuals and groups. Results. The introduction of crowdsourcing is one of the important stages in the process of increasing the effectiveness of communication between government bodies, local authorities, business, political and public associations in developing and making the most important decisions for citizens all over the world. The demand for crowdsourcing in both international and Russian public policy is connected, on the one hand, with the recognition that a huge number of citizens have the abilities, talent, necessary competencies and qualities of innovative activity, and, on the other hand, with significance of development of ‘human capital’, understood as a set of knowledge and skills used to meet the diverse needs of citizens and society as a whole, for the modern competitive and challenging world. Discussion. The limits of crowdsourcing technology in public policy need to be evaluated from the perspective of social and cultural stratification and inequality, potential of mediated collective action

The magnetic structure of a thin ferromagnetic film on the rough surface of an antiferromagnet

The magnetic structure (including domanization) of a thin ferromagnetic film in contact with a rigid antiferromagnet is investigated under the assumption that the interface is rough and contains individual atomic steps of different signs, isolated "dipole of the steps," and a space-ordered periodic system of steps of alternate signs

Exchange bias effect in antiferromagnets containing ferromagnetic clusters

This study offers an explanation for the occurrence of magnetization exchange bias in antiferromagnets with ferromagnetic inclusions during pre-cooling the system in a magnetic field. The ferromagnetic (FM) subsystem ordered in this field at the Néel temperature leads to an inhomogeneous state of the antiferromagnetic (AFM) matrix with the finite mean effective field at the FM/AFM interface. This field causes exchange bias in the dependence M = M(H) during further remagnetization of the heterogeneous system. To describe the proposed scenario for such an effect, a simple model of a two-dimensional system with round inclusions of the FM phase was considered. Using numerical calculations and previously obtained analytical results, the study determines magnetization dependencies on the external field, which qualitatively explains the features of exchange bias in experimentally studied heterogeneous systems

Epobis is a Nonerythropoietic and Neuroprotective Agonist of the Erythropoietin Receptor with Anti-Inflammatory and Memory Enhancing Effects

The cytokine erythropoietin (EPO) stimulates proliferation and differentiation of erythroid progenitor cells. Moreover, EPO has neuroprotective, anti-inflammatory, and antioxidative effects, but the use of EPO as a neuroprotective agent is hampered by its erythropoietic activity. We have recently designed the synthetic, dendrimeric peptide, Epobis, derived from the sequence of human EPO. This peptide binds the EPO receptor and promotes neuritogenesis and neuronal cell survival. Here we demonstrate that Epobis in vitro promotes neuritogenesis in primary motoneurons and has anti-inflammatory effects as demonstrated by its ability to decrease TNF release from activated AMJ2-C8 macrophages and rat primary microglia. When administered systemically Epobis is detectable in both plasma and cerebrospinal fluid, demonstrating that the peptide crosses the blood-brain barrier. Importantly, Epobis is not erythropoietic, but systemic administration of Epobis in rats delays the clinical signs of experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis, and the peptide has long-term, but not short-term, effects on working memory, detected as an improved social memory 3 days after administration. These data reveal Epobis to be a nonerythropoietic and neuroprotective EPO receptor agonist with anti-inflammatory and memory enhancing properties

Field dependences of the magnetization and exchange bias in ferro/antiferromagnetic systems. II. Continuum model of a ferromagnetic layer

A model giving a qualitative explanation of the results of an experimental investigation of the field dependences of the magnetization in ferro- and antiferromagnetic media in contact with one another is proposed. In this model a thin ferromagnetic (FM) film with strong easy-plane anisotropy is described in the continuum approximation. It is shown that collinear and canted structures of the ferromagnetic layer can co-exist in the system studied. The ranges of the parameters (exchange interactions in the FM layer and through the FM/AFM interface, thickness of the FM layer, and magnitude of the external magnetic field) where a nonuniform state of the FM exists are found and explicit analytic expressions are obtained for the distribution of the magnetization in this state. The dependences of the total magnetization of the system on the magnitude of the external field are constructed in the physically important cases of "thin" and "thick" FM layers, and it is demonstrated that the experimentally observed unsymmetric dependence M (H) is possible. The results of the present work are compared with our previous results obtained using simpler model of a two-layer FM subsystem

Magnetization field-dependences and the "exchange bias" in ferro/antiferromagnetic systems. I. Model of a bilayer ferromagnetic

A qualitative model explanation of the experimentally obtained field dependences of the magnetization in ferro- and antiferromagnetic media in contact with one another is proposed. In this model a thin ferromagnetic (FM) film on an antiferromagnetic (AFM) substrate consists of only two ferromagnetic layers. This is the simplest model which admits a spatially nonuniform FM state. In this exactly solvable model it shown that a range of fields exists where a stable collinear (canted) structure of the FM subsystem obtains. This structure corresponds to inclined sections of the field dependence M (H) of the magnetization which are not associated with the kinetics of the magnetization reversal process. In the model proposed, for systems with large easy-plane anisotropy the magnetization reversal process with "exchange bias" taken into account is strictly symmetric as a function of the field provided that the additional weak FM anisotropy in the easy plane is neglected. When this anisotropy in the easy plane is taken into account hysteresis appears in the magnetization curve and the field dependence M (H) becomes asymmetric

A Riemann hypothesis analogue for invariant rings

AbstractA Riemann hypothesis analogue for coding theory was introduced by I.M. Duursma [A Riemann hypothesis analogue for self-dual codes, in: A. Barg, S. Litsyn (Eds.), Codes and Association Schemes (Piscataway, NJ, 1999), American Mathematical Society, Providence, RI, 2001, pp. 115–124]. In this paper, we extend zeta polynomials for linear codes to ones for invariant rings, and we investigate whether a Riemann hypothesis analogue holds for some concrete invariant rings. Also we shall show that there is some subring of an invariant ring such that the subring is not an invariant ring but extremal polynomials all satisfy the Riemann hypothesis analogue