Comment on "Interaction Effects in Conductivity of Si Inversion Layers at Intermediate Temperatures"

We show that the comparison between theory and experiment, performed by Pudalov et al. in PRL 91, 126403 (2003), is not valid.Comment: comment on PRL 91, 126403 (2003) by Pudalov et a

Instability of the Two-Dimensional Metallic Phase to Parallel Magnetic Field

We report on magnetotransport studies of the unusual two-dimensional metallic phase in high mobility Si-MOS structures. We have observed that the magnetic field applied in the 2D plane suppresses the metallic state, causing the resistivity to increase dramatically by more than 30 times. Over the total existence range of the metallic state, we have found three distinct types of the magnetoresistance, related to the corresponding quantum corrections to the conductivity. Our data suggest that the unusual metallic state is a consequence of both spin- and Coulomb-interaction effects.Comment: 6 pages, Latex, 4 ps fig

On a complex differential Riccati equation

We consider a nonlinear partial differential equation for complex-valued functions which is related to the two-dimensional stationary Schrodinger equation and enjoys many properties similar to those of the ordinary differential Riccati equation as, e.g., the famous Euler theorems, the Picard theorem and others. Besides these generalizations of the classical "one-dimensional" results we discuss new features of the considered equation like, e.g., an analogue of the Cauchy integral theorem

Flow diagram of the metal-insulator transition in two dimensions

The discovery of the metal-insulator transition (MIT) in two-dimensional (2D) electron systems challenged the veracity of one of the most influential conjectures in the physics of disordered electrons, which states that `in two dimensions, there is no true metallic behaviour'; no matter how weak the disorder, electrons would be trapped and unable to conduct a current. However, that theory did not account for interactions between the electrons. Here we investigate the interplay between the electron-electron interactions and disorder near the MIT using simultaneous measurements of electrical resistivity and magnetoconductance. We show that both the resistance and interaction amplitude exhibit a fan-like spread as the MIT is crossed. From these data we construct a resistance-interaction flow diagram of the MIT that clearly reveals a quantum critical point, as predicted by the two-parameter scaling theory (Punnoose and Finkel'stein, Science 310, 289 (2005)). The metallic side of this diagram is accurately described by the renormalization group theory without any fitting parameters. In particular, the metallic temperature dependence of the resistance sets in when the interaction amplitude reaches gamma_2 = 0.45 - a value in remarkable agreement with the one predicted by the theory.Comment: as publishe

A New Liquid Phase and Metal-Insulator Transition in Si MOSFETs

We argue that there is a new liquid phase in the two-dimensional electron system in Si MOSFETs at low enough electron densities. The recently observed metal-insulator transition results as a crossover from the percolation transition of the liquid phase through the disorder landscape in the system below the liquid-gas critical temperature. The consequences of our theory are discussed for variety of physical properties relevant to the recent experiments.Comment: 12 pages of RevTeX with 3 postscript figure

Magnetoresistance of a two-dimensional electron gas in a parallel magnetic field

The conductivity of a two-dimensional electron gas in a parallel magnetic field is calculated. We take into account the magnetic field induced spin-splitting, which changes the density of states, the Fermi momentum and the screening behavior of the electron gas. For impurity scattering we predict a positive magnetoresistance for low electron density and a negative magnetoresistance for high electron density. The theory is in qualitative agreement with recent experimental results found for Si inversion layers and Si quantum wells.Comment: 4 pages, figures included, PDF onl

Spin polarization of strongly interacting 2D electrons: the role of disorder

In high-mobility silicon MOSFET's, the $g^*m^*$ inferred indirectly from magnetoconductance and magnetoresistance measurements with the assumption that $g^*\mu_BH_s=2E_F$ are in surprisingly good agreement with $g^*m^*$ obtained by direct measurement of Shubnikov-de Haas oscillations. The enhanced susceptibility $\chi^* \propto (g^*m^*)$ exhibits critical behavior of the form $\chi^* \propto (n - n_0)^{-\alpha}$. We examine the significance of the field scale $H_s$ derived from transport measurements, and show that this field signals the onset of full spin polarization only in the absence of disorder. Our results suggest that disorder becomes increasingly important as the electron density is reduced toward the transition.Comment: 4 pages, 3 figure

Funcionamento do mercado de serviços de transporte de passageiros e gestão do desenvolvimento em aglomerações urbanas baseadas em abordagem integrada

In this article, according to the results of urban agglomeration study of the Krasnodar Territory, they revealed global and local problems of passenger transport service market functioning and development affecting the quality of transport services. A new classification of passenger transport services markets is proposed, which allows to differentiate and optimize a route network in accordance with the requirements of consumer demand. An integrated approach has been formulated that integrates SWOT analysis and PEST analysis toolsinto a single coherent system that allows to take into account the global and the local aspects of passenger transport service market functioning and development to solve the problems of management in urban agglomerations. The matrix model "CTON" ("Coordination of public transport services") is developed, which includes a substantial part of SWOT and PEST analysis tools, the use of which allows to identify the components that affect an effective functioning and the development of PTS markets systematically and purposefully. SWOT and PEST analysis was carried out, on the basis of which the components of KTON matrix were determined and structured in the issue of various types of markets for PTS functioning and development management on the example of urban agglomerations of the Krasnodar Territory. They developed universal script nomograms to optimize a route network, taking into account the seasonal factor of PTS provision to the population and allowing adjust the process of transport services for population in a functional way on the basis of a balance of benefits observation for all interested parties-participants of PTS markets (Customer-Carrier-Consumer). They proposed an estimated economic-mathematical model, on the basis of which an absolute integral economic effect from a route network optimization is determined.En este artículo, de acuerdo con los resultados del estudio de aglomeración urbana del territorio de Krasnodar, revelaron los problemas globales y locales del funcionamiento del mercado de servicios de transporte de pasajeros y el desarrollo que afectan la calidad de los servicios de transporte. Se propone una nueva  clasificación de los mercados de servicios de transporte de pasajeros, que permite diferenciary optimizar una red de rutas de acuerdo con los requisitos de la demanda del consumidor. Se haformulado un enfoque integrado que integra el análisis FODA y las herramientas de análisis PESTen un único sistema coherente que permite tener en cuenta los aspectos globales y locales del funcionamiento y desarrollo del mercado de servicios de transporte de pasajeros para resolver los problemas de gestión en las aglomeraciones urbanas. Se desarrolla el modelo matricial "CTON" ("Coordinación de servicios de transporte público"), que incluye una parte sustancial de las herramientas de análisis FODAy PEST, cuyo uso permite identificar los componentes que afectan un funcionamiento eficaz y el desarrollo de los mercados de PTS sistemática y a propósito. Se llevaron a cabo análisis FODA y PEST, sobre la base de los cuales se determinaron y estructuraron los componentes de la matriz de KTON en el tema de varios tipos de mercados para el funcionamiento de PTS y la gestión del desarrollo en el ejemplo de las aglomeraciones urbanas del territorio de Krasnodar. Desarrollaron nomogramas de guiones universales paraoptimizar una red de rutas, teniendo en cuenta el factor estacional de provisión de STP a la población y permitiendo ajustar el proceso de servicios de transporte para la población de manera funcional sobre la base de un balance de observación de beneficios para todas las partes interesadas -participantes de los mercados PTS (Cliente-Transportista-Consumidor). Propusieron un modelo económico-matemático estimado, sobre la base del cual se determina un efecto económico integral absoluto a partir de una optimización de la red de rutas.Neste artigo, de acordo com os resultados do estudo da aglomeração urbana do território de Krasnodar,eles revelaram os problemas globais e locais da operação do mercado de serviços de transporte depassageiros e desenvolvimento que afetam a qualidade dos serviços de transporte. Propõe-se uma novaclassificação dos mercados de serviços de transporte de passageiros, que permite diferenciar e otimizaruma rede de rotas de acordo com as exigências da demanda do consumidor. Uma abordagem integradafoi formulada que integra a análise SWOT e as ferramentas de análise PEST em um único sistema coerenteque permite levar em conta os aspectos globais e locais da operação e desenvolvimento do mercado deserviços de transporte de passageiros para resolver os problemas de gerenciamento. em aglomeraçõesurbanas. O modelo matricial "CTON" ("Coordenação dos serviços de transporte público") é desenvolvido,o qual inclui uma parte substancial das ferramentas de análise SWOT e PEST, cujo uso permite identificaros componentes que afetam uma operação eficiente e o desenvolvimento dos mercados. de PTSsistemática e propositalmente. Análises SWOT e PEST foram realizadas, com base nas quais oscomponentes da matriz KTON foram determinados e estruturados sobre o tema de vários tipos demercados para a operação de PTS e o gerenciamento do desenvolvimento no exemplo das aglomerações.áreas urbanas do território de Krasnodar. Desenvolveram nomogramas de roteiros universais para otimizaruma rede de rotas, levando em consideração o fator sazonal de provisão de LTS para a população epermitindo ajustar o processo de serviços de transporte para a população de forma funcional com base emum balanço de observação de benefícios para todas as partes interessadas - participantes dos mercadosPTS (Customer-Carrier-Consumer). Eles propuseram um modelo econômico-matemático estimado, combase no qual um efeito econômico integral absoluto é determinado a partir de uma otimização da rede derotas

Technique of automated hypnogram construction

The technique of automated sleep stage recognition and hypnogram construction has been considered. For partition of initial polysomnogram by segments obtained as a result of patient sleep monitoring the signal energy is analyzed using nonlinear energy controller. Frequency weighted energy is calculated for all registered signals then averaging and segmentation occur according to monitored signals behavior. Secondary index vector which is used at transition from segments to fixed duration periods is formed for segments. One or another sleep stage is finally assigned to the period by correlation analysis. Accuracy of the developed algorithm is connected with quantity of considered secondary indices, maximally detailed description of sleep stage characteristics and realization of training by manually prepared example