Two-component model of a spin-polarized transport

Effect of the spin-involved interaction of electrons with impurity atoms or defects to the transport properties of a two-dimensional electron gas is described by using a simplifying two-component model. Components representing spin-up and spin-down states are supposed to be coupled at a discrete set of points within a conduction channel. The used limit of the short-range interaction allows to solve the relevant scattering problem exactly. By varying the model parameters different transport regimes of two-terminal devices with ferromagnetic contacts can be described. In a quasi-ballistic regime the resulting difference between conductances for the parallel and antiparallel orientation of the contact magnetization changes its sign as a function of the length of the conduction channel if appropriate model parameters are chosen. The effect is in agreement with recent experimental observations.Comment: 4 RevTeX pages with 4 figure

Spin rotation for ballistic electron transmission induced by spin-orbit interaction

We study spin dependent electron transmission through one- and two-dimensional curved waveguides and quantum dots with account of spin-orbit interaction. We prove that for a transmission through arbitrary structure there is no spin polarization provided that electron transmits in isolated energy subband and only two leads are attached to the structure. In particular there is no spin polarization in the one-dimensional wire for which spin dependent solution is found analytically. The solution demonstrates spin evolution as dependent on a length of wire. Numerical solution for transmission of electrons through the two-dimensional curved waveguides coincides with the solution for the one-dimensional wire if the energy of electron is within the first energy subband. In the vicinity of edges of the energy subbands there are sharp anomalies of spin flipping.Comment: 9 oages, 7 figure

Investigation of shock waves in explosive blasts using fibre optic pressure sensors

The published version of this article may be accessed at the link below. Copyright @ IOP Publishing, 2006.We describe miniature all-optical pressure sensors, fabricated by wafer etching techniques, less than 1 mm(2) in overall cross-section with rise times in the mu s regime and pressure ranges typically 900 kPa (9 bar). Their performance is suitable for experimental studies of the pressure-time history for test models exposed to shocks initiated by an explosive charge. The small size and fast response of the sensors promises higher quality data than has been previously available from conventional electrical sensors, with potential improvements to numerical models of blast effects. Results from blast tests are presented in which up to six sensors were multiplexed, embedded within test models in a range of orientations relative to the shock front.Support from the UK Engineering&Physical Sciences Research Council and Dstl Fort Halstead through the MoD Joint Grants Scheme are acknowledged. WN MacPherson is supported by an EPSRC Advanced Research Fellowship

К ВОПРОСУ О РАЦИОНАЛЬНОМ ИСПОЛЬЗОВАНИИ КОРМОВОЙ БАЗЫ В РАЗВИТИИ ЖИВОТНОВОДСТВА РЕГИОНА СИБИРИ

The paper considers development of forage production in agribusiness to be the important socioeconomic task due to complicated and difficult geopolitical situation. The task assumes systematic studies on the industry from the point of view of development and efficient applying of forage by means of innovations and further development of business mechanism aimed at supply with high-energy cheep forages. The authors suggest it is necessary to found the main directions and methods aimed at productivity of natural forage grasslands; prepare scientific recommendations on development of forage grasslands, applying of cultivated grasslands, soil-conservation measures in meadows and pastures, applying mineral and organic fertilizers. The article mentions necessity to develop measures on forages quality increasing, reducing losses of nutrition forages when harvesting and storing. The authors suggest it is significant to specify recommendations on applying progressive ways of forages preparing and storing in respect to the regional conditions and efficient applying of hayfields, pastures and perennial plantings. It is necessary to build regional variants of technological schemes aimed at forage production and demand in the main industrial resources. The research analyzes areas which can be applied as natural forage grasslands and areas for specific sub-industries of livestock farming in the region. The authors declare there is no well-defined strategy of regional forage production development.В условиях геополитической нестабильности устойчивое развитие кормопроизводства в АПК представляет собой стратегически важную социально-экономическую задачу, предполагающую системные исследования организации отрасли как с точки зрения наращивания и  эффективного использования кормов на основе инновационных технологий, так и  дальнейшего совершенствования организационно-экономического механизма системы обеспечения высоко- энергетическими дешевыми кормами. В этих целях необходимо обосновать основные направления и методы повышения продуктивности естественных кормовых угодий, подготовить научно обоснованные предложения по их улучшению, созданию и использованию культурных пастбищ, проведению почвозащитных мероприятий на лугах и пастбищах, внесению минеральных и органических удобрений. Следует разработать систему мероприятий по улучшению качества всех видов кормов, уменьшению потерь их питательной ценности при уборке и хранении. Целесообразно конкретизировать рекомендации по использованию прогрессивных способов заготовки и хранения кормов для условий региона, эффективному использованию сенокосов и пастбищ и многолетних насаждений. Необходимо сформировать зональные варианты технологических схем производства кормов, потребность в основных видах производственных ресурсов. В результате исследования проведен анализ зон, благоприятных для использования в качестве естественных кормовых угодий и размещения определенных подотраслей животноводства в регионе. Также установлено, что в настоящее время отсутствует четко аргументированна

Влияние НКО на деятельность местного сообщества

The country’s economy and its social sphere, including education and the formation of a person, are directly dependent on the possibilities of the social orientation of all creative and material forces. At the same time, regardless of the forms of management in a given territory, various public non-profit organizations and associations manifest themselves and can play an important role in improving the municipal government. The article examines some types of public organizations in the form of NGOs, which contributes to the manifestation of a sense of pride in their fellow countrymen, in history and nature, which the locality has presented. The observed changes in the number of inhabitants of rural areas in the direction of reduction, not exceeding the parameters of natural loss without the migratory component. The most important characteristics of the local community have been determined: population with an established history, way of life, traditions and accepted rules. It is shown that the activities and relationships of people have spatial and temporal dimensions associated with the boundaries of the interaction or the boundaries of the local community. Taking into account the domestic practices and experience of foreign countries, specific examples presented the possibility of a positive influence of a developed system of non-profit organizations on local authorities in order to solve such important issues for the population as: material and moral support and protection of citizens; overcoming the consequences of natural disasters, environmental, technological or other disasters; environmental protection and animal welfare; activities in the field of education, science, culture, health care, improving the moral and psychological state of citizens, physical culture and sports, promoting spiritual development of the individual; activities in the field of military-patriotic education of the younger generation. All this contributes to the strengthening of the role of local authorities and raising the status of municipalities, which has a positive effect on improving the efficiency of local government and improving the socio-economic environment.Экономика страны и ее социальная сфера, включая образование и формирование человека, находятся в прямой зависимости от возможностей социальной ориентации всех творческих и материальных сил. При этом, независимо от форм хозяйствования на данной территории, различные общественные некоммерческие организации и объединения проявляют себя и могут сыграть важную роль в деле совершенствования муниципального управления. В статье рассмотрены некоторые виды общественных организаций в виде НКО, которые способствуют проявлению чувства гордости за своих земляков, за историю и природу, которые подарила местность. Отмечены произошедшие изменения численности жителей сельских районов в сторону уменьшения, не превышающие параметров естественной убыли без миграционной составляющей. Определены важнейшие характеристики местного сообщества население со сложившейся историей, укладом жизни, традициями и принятыми правилами. Показано, что деятельность и взаимоотношения людей имеют пространственное и временное измерения, связанные с границами взаимодействия или границами местного сообщества. С учетом отечественных практик и опыта зарубежных стран на конкретных примерах представлена возможность положительного влияния развитой системы некоммерческих организаций на местные органы власти в целях решения таких важных для населения вопросов, как: материальная и моральная поддержка и защита граждан; преодоление последствий стихийных бедствий, экологических, техногенных или иных катастроф; охрана окружающей среды и защита животных; деятельность в области просвещения, науки, культуры, здравоохранения, улучшения морально-психологического состояния граждан, физической культуры и спорта, содействие духовному развитию личности; деятельность в сфере военно-патриотического воспитания молодого поколения. Всё это способствует упрочнению роли местных органов власти и повышению статуса муниципалитетов, что положительно сказывается на повышении эффективности местного управления и улучшении социально-экономической среды

Hall-like effect induced by spin-orbit interaction

The effect of spin-orbit interaction on electron transport properties of a cross-junction structure is studied. It is shown that it results in spin polarization of left and right outgoing electron waves. Consequently, incoming electron wave of a proper polarization induces voltage drop perpendicularly to the direct current flow between source and drain of the considered four-terminal cross-structure. The resulting Hall-like resistance is estimated to be of the order of 10^-3 - 10^-2 h/e^2 for technologically available structures. The effect becomes more pronounced in the vicinity of resonances where Hall-like resistance changes its sign as function of the Fermi energy.Comment: 4 pages (RevTeX), 4 figures, will appear in Phys. Rev. Let

S-matrix theory for transmission through billiards in tight-binding approach

In the tight-binding approximation we consider multi-channel transmission through a billiard coupled to leads. Following Dittes we derive the coupling matrix, the scattering matrix and the effective Hamiltonian, but take into account the energy restriction of the conductance band. The complex eigenvalues of the effective Hamiltonian define the poles of the scattering matrix. For some simple cases, we present exact values for the poles. We derive also the condition for the appearance of double poles.Comment: 29 pages, 9 figures, submitted to J. Phys. A: Math. and Ge

Conductance of Open Quantum Billiards and Classical Trajectories

We analyse the transport phenomena of 2D quantum billiards with convex boundary of different shape. The quantum mechanical analysis is performed by means of the poles of the S-matrix while the classical analysis is based on the motion of a free particle inside the cavity along trajectories with a different number of bounces at the boundary. The value of the conductance depends on the manner the leads are attached to the cavity. The Fourier transform of the transmission amplitudes is compared with the length of the classical paths. There is good agreement between classical and quantum mechanical results when the conductance is achieved mainly by special short-lived states such as whispering gallery modes (WGM) and bouncing ball modes (BBM). In these cases, also the localization of the wave functions agrees with the picture of the classical paths. The S-matrix is calculated classically and compared with the transmission coefficients of the quantum mechanical calculations for five modes in each lead. The number of modes coupled to the special states is effectively reduced.Comment: 19 pages, 6 figures (jpg), 2 table

Interfering resonances in a quantum billiard

We present a method for numerically obtaining the positions, widths and wavefunctions of resonance states in a two dimensional billiard connected to a waveguide. For a rectangular billiard, we study the dynamics of three resonance poles lying separated from the other ones. As a function of increasing coupling strength between the waveguide and the billiard two of the states become trapped while the width of the third one continues to increase for all coupling strengths. This behavior of the resonance poles is reflected in the time delay function which can be studied experimentally.Comment: 2 pages, 3 figure

Observation of Quantum Asymmetry in an Aharonov-Bohm Ring

We have investigated the Aharonov-Bohm effect in a one-dimensional GaAs/GaAlAs ring at low magnetic fields. The oscillatory magnetoconductance of these systems are for the first time systematically studied as a function of density. We observe phase-shifts of $\pi$ in the magnetoconductance oscillations, and halving of the fundamental $h/e$ period, as the density is varied. Theoretically we find agreement with the experiment, by introducing an asymmetry between the two arms of the ring.Comment: 4 pages RevTex including 3 figures, submitted to Phys. Rev.