Effect of exchange electron-electron interaction on conductivity of InGaAs single and double quantum wells in ballistic regime

We report an experimental study of quantum conductivity corrections for two-dimensional electron gas in a GaAs/InGaAs/GaAs single and double quantum wells in a wide temperature range (1.8-100) K. We perform a comparison of our experimental data for the longitudinal conductivity at zero magnetic field to the theory of interaction-induced corrections to th transport coefficients. In the temperature range from 10 K up to (45-60) K, wich covers the ballistic interaction regimes for our samples, a rather good agreement between the theory and our experimental results has been found

PRINCIPIOS DE DESARROLLO DE LA EDUCACIÓN SUPERIOR EN TRABAJOS DE FILOSÓFEROS Y CIENTÍFICOS RUSOS DEL SIGLO XX

Introducción: el artículo está dedicado a la investigación de la educación superior en diversos aspectos, se presentan los resultados de su reconocimiento en el pensamiento científico y filosófico nacional del siglo XX, se detecta la conexión con las tendencias europeas comunes de la escuela superior. Se consideran las opiniones de los filósofos y científicos rusos populares que hicieron su contribución a la base ideológica y los principios de la educación universitaria en Rusia en el siglo XX. Materiales y métodos: los métodos se basan en tradiciones de investigación del conocimiento humano: enfoque filosófico-antropológico de los problemas de la existencia humana, método comparativo de consideración de problemas educativos en relación con diversos contextos culturales e históricos del desarrollo de la existencia humana, método comparativo-histórico. Además de eso se reflejan los métodos de investigación fenomenológica y hermenéutica. Se detectan y comprenden filosóficamente las bases, los contenidos, los objetivos y las metas del sistema educativo, incluida la educación universitaria y la conexión de la educación con las investigaciones reales del ser humano y la sociedad contemporáneos. Resultados de la investigación: se presenta en el artículo que los principales enfoques de la educación y los resultados de su comprensión por parte de los pensadores rusos comprenden la unidad de contenido y resuenan con los problemas reales de su estructura y contenido en términos del mundo moderno, incluida la realidad rusa. Por lo tanto, se confirma la idea de la necesidad de una combinación óptima de conocimiento científico natural, especial y filosófico en el sistema educativo. Tal enfoque permite desarrollar la educación en términos de valores humanitarios, facilita la formación de la personalidad moral y espiritualmente orientada y socialmente responsable del especialista, ejerciendo una visión del mundo razonable. Discusión y conclusión: los resultados recibidos pueden usarse para ejercer los principios del desarrollo de la educación superior en términos de desafíos contemporáneos basados en el principio de sucesión y el mantenimiento de las mayores tradiciones culturales, y también para la planificación estratégica de los programas educativos de la Universidad.Introdução: o artigo é dedicado à pesquisa do ensino superior em vários aspectos, são apresentados os resultados do seu reconhecimento no pensamento científico e filosófico nacional do século XX, sendo detectada conexão com as tendências europeias comuns do ensino superior. Considerações de filósofos e cientistas russos populares que deram sua contribuição à base ideológica e aos princípios do ensino universitário na Rússia no século XX são consideradas.Materiais e métodos: Os métodos são baseados em tradições de pesquisa do conhecimento humano: abordagem filosóficoantropológica dos problemas da existência humana, método comparativo de consideração de problemas educacionais em conexão com vários contextos culturais e históricos do desenvolvimento da existência humana, método histórico-comparativo. Além disso, são refletidos os métodos de pesquisa fenomenológica e hermenêutica. A base, o conteúdo, as metas e os objetivos do sistema educacional, incluindo o ensino universitário e a conexão da educação com investigações reais do ser humano e da sociedade contemporâneos, são detectados e compreendidos filosoficamente.Resultados da pesquisa: É apresentado no artigo que as principais abordagens da educação e os resultados de sua compreensão pelos pensadores russos compreendem a unidade de conteúdo e ressoam com problemas reais de sua estrutura e conteúdo em termos do mundo moderno, incluindo a realidade russa.Portanto, a idéia da necessidade de uma combinação ótima de conhecimentos científicos, especiais e filosóficos naturais no sistema educacional é fundamentada. Essa abordagem permite desenvolver a educação em termos de valores humanitários, facilita a formação de personalidade moral e espiritualmente orientada e socialmente responsável do especialista, exercendo uma visão de mundo razoável. Discussão e conclusão: os resultados recebidos podem ser utilizados para o exercício dos princípios do desenvolvimento do ensino superior em termos de desafios contemporâneos, baseados no princípio da sucessão e na manutenção das maiores tradições culturais, e também no planejamento estratégico dos programas educacionais da Universidade.Introduction: the article is devoted to research of higher education various aspects, results of its recognition in national scientific and philosophical thought of 20th century are presented, connection with common European trends of higher school is detected. Views of popular Russian philosophers and scientists who made their contribution into ideologic basis and principles of University education in Russia in 20th century are considered. Materials and methods: Methods are based on research traditions of humane knowledge: philosophical-anthropologic approach to problems of human existence, comparative method of educational problems consideration in connection with various cultural and historical contexts of human existence development, comparative-historical method. Besides that phenomenological and hermeneutic research methods are reflected. Basis, contents, goals and targets of educational system including University education and connection of education with actual inquiries of contemporary human being and society are detected and philosophically comprehended. Results of research: It is presented in the article that major approaches to education and results of its comprehension by Russian thinkers comprise content unity and resonate with actual problems of its structure and contents in terms of modern world including Russian reality. Therefore the idea of necessity of optimal combination of natural scientific, special and philosophical knowledge in educational system is substantiated. Such approach allows to develop education in terms of humanitarian values, facilitates the formation of morally and spiritually oriented and socially responsible personality of the specialist, exercising reasonable world view. Discussion and conclusion: received results may be used in order to exercising the principles of higher education development in terms of contemporary challenges basing on principle of succession and keeping the greatest cultural traditions, and also for strategical planning of University educational programs

The key role of smooth impurity potential in formation of hole spectrum for p-Ge/Ge_{1-x}Si_x heterostructures in the quantum Hall regime

We have measured the temperature (0.1 <= T <= 15 K) and magnetic field (0 <= B <= 12 T) dependences of longitudinal and Hall resistivities for the p-Ge_0.93Si_0.07/Ge multilayers with different Ge layer widths 10 <= d_w <= 38 nm and hole densities p_s = (1-5)10^11 cm^-2. Two models for the long-range random impurity potential (the model with randomly distributed charged centers located outside the conducting layer and the model of the system with a spacer) are used for evaluation of the impurity potential fluctuation characteristics: the random potential amplitude, nonlinear screening length in vicinity of integer filling factors nu = 1 and nu = 2 and the background density of state (DOS). The described models are suitable for explanation of the unusually high value of DOS at nu = 1 and nu = 2, in contrast to the short-range impurity potential models. For half-integer filling factors the linear temperature dependence of the effective QHE plateau-to-plateau transition width nu_0(T) is observed in contrast to scaling behavior for systems with short-range disorder. The finite T -> 0 width of QHE transitions may be due to an effective low temperature screening of smooth random potential owing to Coulomb repulsion of electrons.Comment: Accepted for publication in Nanotechnolog

Parabolic negative magnetoresistance in p-Ge/Ge1-xSix heterostructures

Quantum corrections to the conductivity due to the weak localization (WL) and the disorder-modified electron-electron interaction (EEI) are investigated for the high-mobility multilayer p-Ge/Ge1-xSix heterostructures at T = (0.1 - 20.0)K in magnetic field B up to 1.5T. Negative magnetoresistance with logarithmic dependence on T and linear in B^2 is observed for B >= 0.1T. Such a behavior is attributed to the interplay of the classical cyclotron motion and the EEI effect. The Hartree part of the interaction constant is estimated (F_/sigma = 0.44) and the WL and EEI contributions to the total quantum correction /Delta /sigma at B = 0 are separated (/Delta /sigma_{WL} ~ 0.3/Delta /sigma; /Delta /sigma_{EEI} ~ 0.7/Delta /sigma).Comment: 3 pages, 4 figure

Dependence of the severity of pain in the lower back and degenerative changes in the lumbar spine in skydivers depending on the experience of training

Purpose of the study: to assess risk factors for the development of nonspecific back pain syndrome in skydivers.Materials and methods: A single-center, prospective, non-randomized study included 173 men aged 25 to 55 years who had been followed up with low back pain for 1 to 5 years. The main group included 89 people involved in parachuting (experience from 5 to 20 years, number of jumps — 276 (167; 387) times), the comparison group — 84 patients who had never jumped with a parachute. Depending on the total number of jumps, the main group was divided into 2 subgroups: less than 198 (n = 29) and more than 198 parachute jumps (n = 60). All patients underwent clinical neurological examination and magnetic resonance imaging (MRI) of the spine. MRI was used to quantify the presence of disc tissue displacements, the presence of straightening lordosis, and spondylolisthesis. Statistical processing of the obtained data was carried out using the IBM SPSS Statistics 25 program.Results: a correlation was established between the appearance of disc tissue displacement in the spine according to MRI and the number of parachute jumps in the main group (r = 0.430; p &lt; 0.001). The indicated pathological changes in the spine in paratroopers occurred when the total number of jumps was 198 or more. Among parachutists of the main group, displacement of disc tissue in the spine correlated with the level of pain intensity (r = 0.337; p &lt; 0.001) and the degree of functional impairment according to the results of the questionnaires Oswestry (r = 0.325; p &lt; 0.001) and Roland Morris (r = 0.292; p &lt; 0.001). The highest rate of pain syndrome and degree of disability was in the subgroup of paratroopers with extensive experience (p &lt; 0.05), while other groups of patients had no differences in this indicator.Conclusions: in skydiving athletes, the intensity of pain in the lower back and the degree of degenerative-dystrophic changes depended on the number of parachute jumps

Hole-hole interaction in a strained Inx_xGa1−x_{1-x}As two dimensional system

The interaction correction to the conductivity of 2D hole gas in strained GaAs/In$_x$Ga$_{1-x}$As/GaAs quantum well structures was studied. It is shown that the Zeeman splitting, spin relaxation and ballistic contribution should be taking into account for reliable determination of the Fermi-liquid constant $F_0^\sigma$. The proper consideration of these effects allows us to describe both th temperature and magnetic field dependences of the conductivity and find the value of $F_0^\sigma$.Comment: 7 pages, 6 figure