Giant magnetoresistance in semiconductor / granular film heterostructures with cobalt nanoparticles

We have studied the electron transport in SiO${}_2$(Co)/GaAs and SiO${}_2$(Co)/Si heterostructures, where the SiO${}_2$(Co) structure is the granular SiO${}_2$ film with Co nanoparticles. In SiO${}_2$(Co)/GaAs heterostructures giant magnetoresistance effect is observed. The effect has positive values, is expressed, when electrons are injected from the granular film into the GaAs semiconductor, and has the temperature-peak type character. The temperature location of the effect depends on the Co concentration and can be shifted by the applied electrical field. For the SiO${}_2$(Co)/GaAs heterostructure with 71 at.% Co the magnetoresistance reaches 1000 ($10^5$ %) at room temperature. On the contrary, for SiO${}_2$(Co)/Si heterostructures magnetoresistance values are very small (4%) and for SiO${}_2$(Co) films the magnetoresistance has an opposite value. High values of the magnetoresistance effect in SiO${}_2$(Co)/GaAs heterostructures have been explained by magnetic-field-controlled process of impact ionization in the vicinity of the spin-dependent potential barrier formed in the semiconductor near the interface. Kinetic energy of electrons, which pass through the barrier and trigger the avalanche process, is reduced by the applied magnetic field. This electron energy suppression postpones the onset of the impact ionization to higher electric fields and results in the giant magnetoresistance. The spin-dependent potential barrier is due to the exchange interaction between electrons in the accumulation electron layer in the semiconductor and $d$-electrons of Co.Comment: 25 pages, 16 figure

A New High Energy Photon Tagger for the H1 - Detector at HERA

The H1 detector at HERA has been upgraded by the addition of a new electromagnetic calorimeter. This is installed in the HERA tunnel close to the electron beam line at a position 8m from the interaction point in the electron beam direction. The new calorimeter extends the acceptance for tagged photoproduction events to the high y range, 0.85 < y < 0.95, and thus significantly improves the capability of H1 to study high energy gamma-p processes. The calorimeter design, performance and first results obtained during the 1996-1999 HERA running are described.Comment: 17 pages, 16 figure

Tagging High Energy Photons in the H1 Detector at HERA

Measures taken to extend the acceptance of the H1 detector at HERA for photoproduction events are described. These will enable the measurement of electrons scattered in events in the high y range 0.85 < y < 0.95 in the 1998 and 1999 HERA run period. The improvement is achieved by the installation of an electromagnetic calorimeter, the ET8, in the HERA tunnel close to the electron beam line 8 m downstream of the H1 interaction point in the electron direction. The ET8 will allow the study of tagged gamma p interactions at centre-of-mass energies significantly higher than those previously attainable. The calorimeter design and expected performance are discussed, as are results obtained using a prototype placed as close as possible to the position of the ET8 during the 1996 and 1997 HERA running.Comment: 13 pages, 13 figure

Characteristics of the Main Internet Services as a Means of Increasing the ICT Competence of Teachers

Сегодня важно уметь хранить, обрабатывать, передавать информацию, и интернет-сервисы становятся важным и актуальным инструментом для эффективной реализации этого умения. Внедрение интернет-инструментария в образовательный процесс - актуальная проблема. В статье рассмотрены некоторые наиболее популярные интернет-сервисы и их возможности в профессиональной деятельности преподавателя: Quizizz, Plickers, Learnis, Jamboard.Today it is important to be able to store, process, transmit information and Internet services are becoming an important and relevant tool for the effective implementation of this skill. The introduction of Internet tools into the educational process is an urgent problem. In the article we will consider some of the most popular Internet services and their capabilities in the professional activity of a teacher: Quizizz, Plickers, Learnis, Jamboard

Modern Trends in the Professional Training of Future Police Officers for the Performance of Service Task

В данной статье обосновывается необходимость перехода системы профессиональной подготовки будущих полицейских в области выполнения служебно-боевых задач от имитации к педагогическому моделированию. Выделены основные детерминанты низкой эффективности существующего симуляционного подхода в учебном процессе и приведены обоснованные предложения по реализации перехода к педагогическому моделированию. Кроме того, автор доказывает, что при помощи педагогического моделирования есть реальные возможности сформировать необходимые компетенции для эффективного выполнения служебно-боевых задач по отражению нападения правонарушителей на граждан и на полицейских.This article substantiates the need to transfer the system of professional training of future police officers in the field of performing service and combat tasks from imitation to pedagogical modeling. The main determinants of the low efficiency of the existing simulation approach in the educational process are identified and reasonable proposals are made for the implementation of the transition to pedagogical modeling. In addition, the author proves that with the help of pedagogical modeling there are real opportunities to form the necessary competencies for the effective performance of service and combat tasks to repel attacks by offenders on citizens and police officers

Petojezični rečnik termina metalurgije praha : (srpskohrvatsko-ruski, englesko-ruski, nemačko-ruski, francusko-ruski). Deo 2

Petojezični rečnik termina metalurgije praha : (srpskohrvatsko-ruski, englesko-ruski, nemačko-ruski, francusko-ruski). Deo 2 / I. I. Kovenski ... [i dr.] ; u redakciji M. M. Ristića i A. N. Piljankeviča. - Beograd : Srpska akademija nauka i umetnosti : Institut tehničkih nauka Srpske akademije nauka i umetnosti : Univerzitet u Beogradu, 1983 (Beograd : Zavod za grafičku tehniku Tehnološko-metalurškog fakulteta Univerziteta u Beogradu). - 442 p. ; 24 cm.- (Posebna izdanja / Srpska akademija nauka i umetnosti [i] Institut tehničkih nauka SANU ; t. 552.Odeljenje tehničkih nauka ; knj. 24

Ecosystem Approach in Education: Myth Or Reality?

Статья посвящена актуальным исследованиям в области экосистемного подхода в образовании. В ней рассмотрены основные характеристики образовательных экосистем, а также приведены примеры действующих инновационных и образовательных экосистем за рубежом и в России.The article outlines the problem of providing industry with graduates of educational organizations. The main characteristics of learning ecosystems are presented. Also examples of innovative and learning ecosystems abroad and in Russia are discussed

The Maslov index and nondegenerate singularities of integrable systems

We consider integrable Hamiltonian systems in R^{2n} with integrals of motion F = (F_1,...,F_n) in involution. Nondegenerate singularities are critical points of F where rank dF = n-1 and which have definite linear stability. The set of nondegenerate singularities is a codimension-two symplectic submanifold invariant under the flow. We show that the Maslov index of a closed curve is a sum of contributions +/- 2 from the nondegenerate singularities it is encloses, the sign depending on the local orientation and stability at the singularities. For one-freedom systems this corresponds to the well-known formula for the Poincar\'e index of a closed curve as the oriented difference between the number of elliptic and hyperbolic fixed points enclosed. We also obtain a formula for the Liapunov exponent of invariant (n-1)-dimensional tori in the nondegenerate singular set. Examples include rotationally symmetric n-freedom Hamiltonians, while an application to the periodic Toda chain is described in a companion paper.Comment: 27 pages, 1 figure; published versio

Foliations of Isonergy Surfaces and Singularities of Curves

It is well known that changes in the Liouville foliations of the isoenergy surfaces of an integrable system imply that the bifurcation set has singularities at the corresponding energy level. We formulate certain genericity assumptions for two degrees of freedom integrable systems and we prove the opposite statement: the essential critical points of the bifurcation set appear only if the Liouville foliations of the isoenergy surfaces change at the corresponding energy levels. Along the proof, we give full classification of the structure of the isoenergy surfaces near the critical set under our genericity assumptions and we give their complete list using Fomenko graphs. This may be viewed as a step towards completing the Smale program for relating the energy surfaces foliation structure to singularities of the momentum mappings for non-degenerate integrable two degrees of freedom systems.Comment: 30 pages, 19 figure

Singularities, Lax degeneracies and Maslov indices of the periodic Toda chain

The n-particle periodic Toda chain is a well known example of an integrable but nonseparable Hamiltonian system in R^{2n}. We show that Sigma_k, the k-fold singularities of the Toda chain, ie points where there exist k independent linear relations amongst the gradients of the integrals of motion, coincide with points where there are k (doubly) degenerate eigenvalues of representatives L and Lbar of the two inequivalent classes of Lax matrices (corresponding to degenerate periodic or antiperiodic solutions of the associated second-order difference equation). The singularities are shown to be nondegenerate, so that Sigma_k is a codimension-2k symplectic submanifold. Sigma_k is shown to be of elliptic type, and the frequencies of transverse oscillations under Hamiltonians which fix Sigma_k are computed in terms of spectral data of the Lax matrices. If mu(C) is the (even) Maslov index of a closed curve C in the regular component of R^{2n}, then (-1)^{\mu(C)/2} is given by the product of the holonomies (equal to +/- 1) of the even- (or odd-) indexed eigenvector bundles of L and Lmat.Comment: 25 pages; published versio