Thermohydrodynamics in Quantum Hall Systems

A theory of thermohydrodynamics in two-dimensional electron systems in quantizing magnetic fields is developed including a nonlinear transport regime. Spatio-temporal variations of the electron temperature and the chemical potential in the local equilibrium are described by the equations of conservation with the number and thermal-energy flux densities. A model of these flux densities due to hopping and drift processes is introduced for a random potential varying slowly compared to both the magnetic length and the phase coherence length. The flux measured in the standard transport experiment is derived and is used to define a transport component of the flux density. The equations of conservation can be written in terms of the transport component only. As an illustration, the theory is applied to the Ettingshausen effect, in which a one-dimensional spatial variation of the electron temperature is produced perpendicular to the current.Comment: 10 pages, 1 figur

Transport Phenomena of Inversion Layers in High Magnetic Fields

The discovery of the quantum Hall effect in 1980 has demonstrated the importance of two- dimensional electronic systems for application and fundamental research. In this paper a review of some transport phenomena in such systems in high magnetic fields is given

Multiscale Methods Application to Solve the Challenges of Field Development Optimization and Reservoir History Matching Problems

При проектировании разработки нефтяного месторождения часто приходится решать задачи, требующие большого числа расчетов на гидродинамическом симуляторе. К таким задачам относятся задачи выбора оптимальной системы разработки месторождения и адаптации гидродинамической модели на историю разработки. Однако при большом количестве ячеек в гидродинамической модели расчет требует больших временных затрат, т. к. задача подземной гидромеханики требует нахождения полей давления и водонасыщенности на каждом временном шаге. Для нахождения поля необходимо решить систему линейных алгебраических уравнений; размерность такой системы равна количеству расчетных блоков. В этой связи необходимо использовать методы, позволяющие ускорить расчет на симуляторе. Одним из таких методов является многомасштабный метод, позволяющий существенно сократить время расчета за счет снижения числа расчетных блоков для нахождения поля давления. В статье приведены примеры решения задач оптимизации системы разработки и адаптации гидродинамической модели с использованием многомасштабного метода. Задача оптимизации системы разработки решалась полным перебором всех вариантов назначения скважин c учетом исключения вариантов с одними нагнетательными и одними добывающими скважинами. Задача адаптации решалась итерационным методом с регуляризацией абсолютной проницаемости методом деления отрезка пополам. Абсолютная проницаемость настраивалась таким образом, чтобы накопленная добыча жидкости на каждой скважине совпадала с историей. Было получено хорошее совпадение результатов решения задач без использования многомасштабного метода с результатами решения задач с использованием многомасштабного метода. Показано, что применение многомасштабного метода позволяет в два раза сократить время расчета.In the design of the development of oil fields it is often necessary to solve problems that require a large number of hydrodynamic calculations on the simulator. These problems include the problem of choosing the optimal field development system, as well as the adaptation of hydrodynamic models on the development of the story. However, when there is a large number of cells in the simulation model, the calculation is time consuming. In this connection it is necessary to use the methods allowing to speed up the calculation of the simulator. One of these methods is the multiscale method to significantly reduce the time of calculation. This article provides examples of solving the challenges of field development optimization and solving the problem of reservoir history matching using multiscale method. The problem of optimizing the development of the system was considered a complete listing of all wells destination options. Adaptation problem is solved iteratively with regularization of absolute permeability by bisection of the segment. There was found a good agreement between the results of solving problems without using multiscale method with the results of solving problems with the use of multi-scale method. The article shows that the application of multiscale method allows to reduce the time of calculation in two times

SUCCESSFUL TREATMENT OF DISSECTION OF THE INTERNAL CAROTID ARTERY

The clinical observation of a successful treatment of a young patient with intima dissection of the internal carotid artery and thrombosis of the lumen of the internal carotid artery and the middle cerebral artery of traumatic genesis is presented. Injury of the internal carotid artery occurred with a large physical load of a rotational nature. Fracture of the styloid process caused a dissection of the internal carotid artery with its thrombosis on the extracranial level and the development of ischemic stroke in the basin of this artery. In an emergency order, a complex of diagnostics was performed-CT CT, CT angiography. The first stage was performed thrombextracion from the internal carotid artery and the middle cerebral artery by the X-ray endovascular method. To fix the intima in the internal carotid artery in the area of her injury we stented her. Complete revascularization was achieved in the basin of the internal carotid artery with almost complete regression of neurologic symptoms. The patient returned to work. The use of x-ray endovascular mini-invasive technologies, thrombus extraction and stenting in the next few hours after the development of AVCC allowed to achieve a good near and distant clinical result

Use of galvanic vestibular feedback to control postural orientation in decerebrate rabbits

In quadrupeds, the dorsal-side-up body orientation during standing is maintained due to a postural system that is driven by feedback signals coming mainly from limb mechanoreceptors. In caudally decerebrated (postmammillary) rabbits, the efficacy of this system is considerably reduced. In this paper, we report that the efficacy of postural control in these animals can be restored with galvanic vestibular stimulation (GVS) applied transcutaneously to the labyrinths. In standing intact rabbits, GVS causes a lateral body sway towards the positive electrode. We used this GVS-caused sway to counteract the lateral body sway resulting from a mechanical perturbation of posture. Experiments were performed on postmammillary rabbits that stood on the tilting platform with their hindlimbs. To make the GVS value dependent on the postural perturbation (i.e., on the lateral body sway caused by tilt of the platform), an artificial feedback loop was formed in the following ways: 1) Information about the body sway was provided by a mechanical sensor; 2) The GVS current was applied when the sway exceeded a threshold value; the polarity of the current was determined by the sway direction. This simple algorithm allowed the “hybrid” postural system to maintain the dorsal-side-up orientation of the hindquarters when the platform was tilted by ± 20°. Thus, an important postural function, i.e., securing lateral stability during standing, can be restored in decerebrate rabbits with the GVS-based artificial feedback. We suggest that such a control system can compensate for the loss of lateral stability of various etiologies, and can be used for restoration of balance control in patients with impaired postural functions

Effects of galvanic vestibular stimulation on postural limb reflexes and neurons of spinal postural network

Quadrupeds maintain the dorsal side up body orientation due to the activity of the postural control system driven by limb mechanoreceptors. Binaural galvanic vestibular stimulation (GVS) causes a lateral body sway toward the anode. Previously, we have shown that this new position is actively stabilized, suggesting that GVS changes a set point in the reflex mechanisms controlling body posture. The aim of the present study was to reveal the underlying neuronal mechanisms. Experiments were performed on decerebrate rabbits. The vertebral column was rigidly fixed, whereas hindlimbs were positioned on a platform. Periodic lateral tilts of the platform caused postural limb reflexes (PLRs): activation of extensors in the loaded and flexing limb and a decrease in extensor activity in the opposite (unloaded and extending) limb. Putative spinal interneurons were recorded in segments L4–L5 during PLRs, with and without GVS. We have found that GVS enhanced PLRs on the cathode side and reduced them on the anode side. This asymmetry in PLRs can account for changes in the stabilized body orientation observed in normal rabbits subjected to continuous GVS. Responses to platform tilts (frequency modulation) were observed in 106 spinal neurons, suggesting that they can contribute to PLR generation. Two neuron groups were active in opposite phases of the tilt cycle of the ipsi-limb: F-neurons in the flexion phase, and E-neurons in the extension phase. Neurons were driven mainly by afferent input from the ipsi-limb. If one supposes that F- and E-neurons contribute, respectively, to excitation and inhibition of extensor motoneurons, one can expect that the pattern of response to GVS in F-neurons will be similar to that in extensor muscles, whereas E-neurons will have an opposite pattern. We have found that ∼40% of all modulated neurons meet this condition, suggesting that they contribute to the generation of PLRs and to the GVS-caused changes in PLRs