54 research outputs found
Nonlinear dynamics of beta induced Alfv\'en eigenmode driven by energetic particles
Nonlinear saturation of beta induced Alfv\'en eigenmode, driven by slowing
down energetic particles via transit resonance, is investigated by the
nonlinear hybrid magnetohyrodynamic gyro-kinetic code (XHMGC). Saturation is
characterized by frequency chirping and symmetry breaking between co- and
counter-passing particles, which can be understood as the the evidence of
resonance-detuning. The scaling of the saturation amplitude with the growth
rate is also demonstrated to be consistent with radial resonance detuning due
to the radial non-uniformity and mode structure
Undamped electrostatic plasma waves
Electrostatic waves in a collision-free unmagnetized plasma of electrons with
fixed ions are investigated for electron equilibrium velocity distribution
functions that deviate slightly from Maxwellian. Of interest are undamped waves
that are the small amplitude limit of nonlinear excitations, such as electron
acoustic waves (EAWs). A deviation consisting of a small plateau, a region with
zero velocity derivative over a width that is a very small fraction of the
electron thermal speed, is shown to give rise to new undamped modes, which here
are named {\it corner modes}. The presence of the plateau turns off Landau
damping and allows oscillations with phase speeds within the plateau. These
undamped waves are obtained in a wide region of the plane
( being the real part of the wave frequency and the
wavenumber), away from the well-known `thumb curve' for Langmuir waves and EAWs
based on the Maxwellian. Results of nonlinear Vlasov-Poisson simulations that
corroborate the existence of these modes are described. It is also shown that
deviations caused by fattening the tail of the distribution shift roots off of
the thumb curve toward lower -values and chopping the tail shifts them
toward higher -values. In addition, a rule of thumb is obtained for
assessing how the existence of a plateau shifts roots off of the thumb curve.
Suggestions are made for interpreting experimental observations of
electrostatic waves, such as recent ones in nonneutral plasmas.Comment: 11 pages, 10 figure
Criticality in a Vlasov-Poisson system - a fermionic universality class
A model Vlasov--Poisson system is simulated close the point of marginal
stability, thus assuming only the wave-particle resonant interactions are
responsible for saturation, and shown to obey the power--law scaling of a
second-order phase transition. The set of critical exponents analogous to those
of the Ising universality class is calculated and shown to obey the Widom and
Rushbrooke scaling and Josephson's hyperscaling relations at the formal
dimensionality below the critical point at nonzero order parameter.
However, the two-point correlation function does not correspond to the
propagator of Euclidean quantum field theory, which is the Gaussian model for
the Ising universality class. Instead it corresponds to the propagator for the
fermionic {\it vector} field and to the {\it upper critical dimensionality}
. This suggests criticality of collisionless Vlasov-Poisson systems as
representative of the {\it universality class} of critical phenomena of {\it a
fermionic} quantum field description.Comment: 10 pages, 6 figures, Submitted to Phys. Rev.
Competitive complex of machinery and technologies for the production of grain and feed
The current situation in agricultural production is challenging. During the last 2 decades, the agrarian production system has been deteriorating. It concerns crop rotations, moisture accumulation and moisture conservation technologies, ways of increasing soil fertility and growing environmentally friendly grain, reducing production costs and increasing product profitability. But there are forced late sowings and artificial “drought”. All this provides reasons to consider domestic breeding and seed production obsolete and to introduce the foreign analogue, which has planned negative impacts not only on quantitative, but also on qualitative safety. The article provides the solution to this major strategic problem. Under the research program of the Russian Academy of Agricultural Sciences, a highly competitive technology for the production of grain and fodder was developed on the basis of only domestic equipment that 2-5 times predominates over the best foreign analogues in functional indicators. It was confirmed by a number of state tests in 1990-2016 and approved by numerous meetings of the Scientific and Technical Council of the Ministry of Agriculture of the Russian Federation, RAS. The units of domestic tractors and functional machines that can compete with the best foreign counterparts have been developed
Устройство для внутриполостного измерения механического импеданса биологических тканей
Analysis of infantile death- and illness-rate testifies that the majority of pathological cases are formed rather long prior to child’s birth and they are mainly interconnected with a mother’s illness. In order to measure the level of uterus cervix softening with measuring its mechanical impedance authors of the paper propose a device that consists of control probe, measuring block, automated system for tracing measurement methodology, calculation of the obtained results and block of data recording.Анализ младенческой смертности и заболеваемости свидетельствует о том, что большинство патологических состояний формируются задолго до рождения ребенка и во многом связаны с заболеваниями матери. Для измерения степени размягчения шейки матки путем измерения ее механического импеданса авторы предлагают устройство, состоящее из контрольного щупа, измерительного блока, автоматизированной системы слежения за методикой измерения, расчета получаемых результатов и блока регистрации данных
ПОЧВООБРАБАТЫВАЮЩАЯ ТЕХНИКА: ПУТИ ИМПОРТОЗАМЕЩЕНИЯ
The group of scientists in Russian Academy of Sciences system has finished the next stage of creation, test and widespread introduction of import-substituting competitive machinery for antidroughty technology. They created the complex of technologically functional completely closed upgraded soil-cultivating and sowing machines for all soil climatic conditions in Russia. The offered technology with a complex of the domestic technics is more profitable than foreign one. Crops cultivation on this technology under drought conditions promotes reduction of import of main types of agricultural production. The foreign machines can not always operate on stubble fields in Russia. They are adapted only for prior soil tillage minimum technology. Domestic agrotechnologies with the machines complex adapted to local conditions, in comparison with the best foreign analogs, allow to increase twice productivity and yield, by 3 times to lower expenses of fuel and capacity requirement, by 4 times - metal consumption and by 5 times - resources. The developed technics complexes can be used for moisture-power-resource-saving environmentally friendly production technologies. The cumulative economic effect of use of the upgraded equipment on 1 million hectares of wheat makes 8-45 billion rubles.Коллектив ученых в системе РАН завершил очередной этап создания, испытания и широкого внедрения импортозамещающей высококонкурентоспособной техники для противозасушливой технологии. Создан комплекс технологически функциональной цельнозамкнутой модернизированной почвообрабатывающей и посевной техники для всех почвенных климатических условий России. Показано, что предложенная технология с комплексом отечественной техники рентабельнее зарубежной. Доказано, что выращивание сельхозкультур по данной технологии в условиях засухи способствует сокращению импорта основных видов сельскохозяйственной продукции. Установлено, что зарубежная техника не всегда может работать по стерне в полевых условиях агропредприятий России. Она приспособлена только для предварительной минимальной технологии обработки почвы. Отмечено, что отечественные агротехнологии с адаптированным к местным условиям комплексом техники, по сравнению с лучшими зарубежными аналогами, позволяют в 2 раза повысить производительность и урожайность сельхозкультур, в 3 раза снизить затраты топлива и потребность в мощности, в 4 раза - металлоемкость и в 5 раз - ресурсы. Разработанные комплексы техники могут быть использованы для влаго-, энерго-, ресурсосберегающих экологически чистых технологий производства продукции растениеводства. Показано, что общий экономический эффект от использования модернизированной техники на 1 млн га посева пшеницы составляет 8-45 млрд руб
Exploring van der Waals materials with high anisotropy: geometrical and optical approaches
The emergence of van der Waals (vdW) materials resulted in the discovery of
their giant optical, mechanical, and electronic anisotropic properties,
immediately enabling countless novel phenomena and applications. Such success
inspired an intensive search for the highest possible anisotropic properties
among vdW materials. Furthermore, the identification of the most promising
among the huge family of vdW materials is a challenging quest requiring
innovative approaches. Here, we suggest an easy-to-use method for such a survey
based on the crystallographic geometrical perspective of vdW materials followed
by their optical characterization. Using our approach, we found As2S3 as a
highly anisotropic vdW material. It demonstrates rare giant in-plane optical
anisotropy, high refractive index and transparency in the visible range,
overcoming the century-long record set by rutile. Given these benefits, As2S3
opens a pathway towards next-generation nanophotonics as demonstrated by an
ultrathin true zero-order quarter-waveplate that combines classical and the
Fabry-Perot optical phase accumulations. Hence, our approach provides an
effective and easy-to-use method to find vdW materials with the utmost
anisotropic properties.Comment: 11 pages, 5 figure
Giant optical anisotropy in transition metal dichalcogenides for next-generation photonics
Large optical anisotropy observed in a broad spectral range is of paramount
importance for efficient light manipulation in countless devices. Although a
giant anisotropy was recently observed in the mid-infrared wavelength range,
for visible and near-infrared spectral intervals, the problem remains acute
with the highest reported birefringence values of 0.8 in BaTiS3 and h-BN
crystals. This inspired an intensive search for giant optical anisotropy among
natural and artificial materials. Here, we demonstrate that layered transition
metal dichalcogenides (TMDCs) provide an answer to this quest owing to their
fundamental differences between intralayer strong covalent bonding and weak
interlayer van der Walls interaction. To do this, we carried out a correlative
far- and near-field characterization validated by first-principle calculations
that reveals an unprecedented birefringence of 1.5 in the infrared and 3 in the
visible light for MoS2. Our findings demonstrate that this outstanding
anisotropy allows for tackling the diffraction limit enabling an avenue for
on-chip next-generation photonics.Comment: 20 pages, 5 figure
Gender differences in depressive disorders, cognitive functions impairments and life quality in elderly patients with cardiovascular diseases
Aim.To describe gender features of depressive disorders, cognitive and mnestic function impairments, life quality characteristic in elderly patients passing in-hospital rehabilitation course. Materials and methods. We investigated 26 men (23,6%) and 84 women (76,4%) with ischemic heart disease aged from 75 to 91 years old, average age - 83,9+3,3. Results. In elderly patients with cardio-vascular diseases predemential cognitive impairment and mild dementia was found in 76% of men and 91 % of women. Life quality proved to be low, estimated by every scale used for psychic and physical evaluation. Higher life quality was associated with male gender and in-hospital rehabilitation program raised both physical and psychic components for 19,9+2,4% и 8,3+1,8% respectively. Conclusion. In elderly patients with cardiovascular diseases more prominent life quality disorders and cognitive impairments are found in female group. This is most likely due to higher level of arterial hypertension prevalence in women.Цель исследования: Охарактеризовать гендерные особенности депрессив-ных расстройств, нарушений когнитивно-мнестической функции, качества жизни у лиц старческого возраста и их динамику на фоне стационарного этапа реабилитации. Материалы и методы: Обследовано 26 мужчин (23,6%) и 84 женщины (76,4%) с ишемической болезнью сердца в возрасте от 75 лет до 91 года, средний возраст 83,9+3,3 года. Результаты: У лиц старческого возраста с заболеваниями сердечно-сосудистой системы преддементные когнитивные нарушения и деменция легкой степени выраженности регистрируется у 76% мужчин и 91% женщин. Качество жизни характеризуется низкими значениями по всем шкалам как психического, так и физического компонента, при этом высокие значения качества жизни ассоциируются с мужским полом, а проведенное стационарное лечение в рамках комплексной реабилитационной программы способствует увеличениюфизического и психического компонента качества жизни на 8,3+1,8% и 19,9+2,4%, соответственно. Заключение:Гендерные особенности качества жизни и когнитивных функций у лиц старческого возраста с заболеваниями сердечно-сосудистой системы характеризуются более выраженными нарушениями в группе женщин, что, скорее всего, ассоциировано с большей распространенностью повышенного артериального давления
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