Charge carrier injection into insulating media: single-particle versus mean-field approach

Self-consistent, mean-field description of charge injection into a dielectric medium is modified to account for discreteness of charge carriers. The improved scheme includes both the Schottky barrier lowering due to the individual image charge and the barrier change due to the field penetration into the injecting electrode that ensures validity of the model at both high and low injection rates including the barrier dominated and the space-charge dominated regimes. Comparison of the theory with experiment on an unipolar ITO/PPV/Au-device is presented.Comment: 32 pages, 9 figures; revised version accepted to PR

АНАЛІЗ РЕЗУЛЬТАТІВ СКЛАДАННЯ СТУДЕНТАМИ ГРОМАДЯНАМИ УКРАЇНИ СУБТЕСТУ З ІНОЗЕМНОЇ МОВИ ПРОФЕСІЙНОГО СПРЯМУВАННЯ ЛІЦЕНЗІЙНОГО ІСПИТУ “КРОК 1. СТОМАТОЛОГІЯ” 20.02.2018 РОКУ

The aim of the work – to analyze the results of passing by native Ukrainian students the subtest from English of professional orientation “Krok-1. Dentistry”.The main body. It was analyzed the results of passing the exam from each discipline of “Krok-1. Dentistry”(English of professional orientation) by students of specialty “Dentistry”, Field of Study 22 “Health Care”. All students studied English at a higher education institution.Conclusion. The average score of successful passing exam of English of professional orientation was 36.6 %. It testifies low level, and in some higher educational institutions – very low level, of English proficiency by native Ukrainian students, who study in Ukrainian.Мета роботи – аналіз результатів складання студентами громадянами України субтесту з іноземної мови професійного спрямування ліцензійного іспиту “Крок 1. Стоматологія”.Основна частина. Проаналізовано результати складання студентами громадянами України, які навчаються за спеціальністю “Стоматологія”, галузі знань 22 “Охорона здоров’я”, субтесту з тестових завдань іноземною мовою професійного спрямування, яку вивчали студенти у закладі вищої освіти, з кожної дисципліни, що входить до змісту ліцензійного іспиту “Крок 1. Стоматологія”.Висновок. Середній результат складання субтесту з іноземної мови професійного спрямування 36,6 % свідчить про низький, а в окремих закладах вищої освіти дуже низький, рівень володіння студентами громадянами України іноземною мовою професійного спрямування

Nonliner damping of electron beam-driven Langmuir waves due to Langmuir-kinetic Alfvén-whistler coupling in the solar corona

We present a coherent nonlinear theory of three-wave coupling involving Langmuir, kinetic Alfvén and whistler waves. The initial stage of the energy exchange among these modes and the following nonlinear temporal dynamics are studied. The role of pump depletion, dissipation and frequency mismatch in the nonlinear wave dynamics is analyzed. Depending on the relative damping rates of the waves, the initial Langmuir waves can be nonlinearly transformed either into whistlers, or into KAWs. The theory is applied to the Langmuir waves excited by electron beams in a diluted solar corona where the local electron-cyclotron frequency is higher than the local electron plasma frequency.Представлена когерентна нелінійну теорія трихвильової взаємодії, що включає ленгмюрівську, кінетичну альфвенівську хвилі та вістлер. Вивчена початкова стадія енергетичного обміну між даними хвилями та його наступна часова динаміка. Проаналізовано вплив зміни амплітуди хвилі накачки, вплив диссипації та частотного зсуву на нелінійну хвильову динаміку. В залежності від відносного затухання хвиль, початкові ленгмюрівські хвилі можуть бути нелінійно трансформовані або в вістлери, або в кінетичні альфвенівські хвилі. Результати теорії застосовані для ленгмюрівських хвиль, що збуджуються електронним пучком в розрідженій корональній плазмі, де локальна електронно-циклотронна частота більша за локальну електронну плазмову частоту.Представлена когерентная нелинейная теория трехволнового взаимодействия ленгмюровской, кинетической альфвеновской волн и вистлера. Изучена начальная стадия энергообмена между данными волнами и его последующая временная динамика. Проанализировано влияние изменения амплитуды волны накачки, влияние диссипации и частотного сдвига на нелинейную волновую динамику. В зависимости от относительного затухания волн начальные легмюровские волны могут быть нелинейно трансформированы или в вистлеры, или в кинетические альфвеновские волны. Результаты теории применены для ленгмюровской волны, которая возбуждается электронным пучком в разреженной корональной плазме, где локальная электронно-циклотронная частота больше, чем локальная электронная плазменная частота

Morphogenesis, pigment content, phytohormones and yield of tomatoes under the action of gibberellin and tebuconazole

One of the main tasks of contemporary plant physiology is regulation of growth and development of cultivated plants in order to optimize the productive process. The scientific community focuses its attention on the use of natural activators and growth inhibitors. We investigated the effect of foliar treatment with 0.005% solution of gibberellic acid and 0.025% solution of the anti-gibberellic preparation tebuconazole on morphogenesis, leaf mesostructure, content of photosynthetic pigments, balance of endogenous phytobrybrides and lymphocyte B and productivity of tomatoes. The vegetation experiment was carried out in the conditions of soil-sand culture in vessels with a 10-liter volume. The treatment was carried out in the budding phase. Morphometric parameters were measured every 10 days. The mesostructure of the middle tier leaves was studied in the fruit formation phase, and the chlorophyll content was determined in the raw material by spectrophotometric method. Analytical determination of endogenous phytohormones – indolyl-3-acetic (IAA), gibberellic acid and abscisic (ABA) acids and cytokinins – zeatin (Z), zeatin-O-glucoside (ZG), zeatinribozide (Znila) and isopentenyladenosine (iPA) was performed by high performance liquid chromatography – mass spectrometry (HPLC-MS). With gibberellic acid treatment plant height increased significantly, while with tebuconazole it decreased. Gibberellic acid increased the number of leaves per plant, and tebuconazole did not change it. The preparations increased the number of leaf blades per leaf, the total number of leaf blades per plant, the weight of the raw material of leaves, the area of leaf blades and the area of the leaves at the end of the study period. The dry matter weight of stems and roots under the action of gibberellic acid increased, and during the treatment of tebuconazole decreased. Gibberellic acid increased the dry matter of the whole plant, and tebuconazole did not change it. Under the action of tebuconazole the content of chlorophyll in the leaves increased, while under the action of gibberellic acid it decreased. Both regulators increased the volume of columnar parenchyma cells. Gibberellic acid increased the size of spongy parenchyma cells, while tebuconazole did not change them. It is revealed that the action of exogenous gibberellic acid in stems and leaves increased the content of endogenous IAA and gibberellic acid, and tebuconazole decreased their content. The ABA content in stems and leaves increased with tebuconazole treatments and decreased with exogenous gibberellic acid. The total cytokinin content in the leaves was higher than in the stems in both the control and the experiment samples. Growth regulators induced an increase in the cytokinin pool in leaves and a decrease in stems. Gibberellic acid increased the content of all five forms of cytokinins in the leaves, and tebuconazole increased only two isoforms. In the stems under the action of both growth regulators the content of Z decreased and iP increased. The content of ZR and iPA in stems increased after the application of the retardant and decreased under the action of growth stimulant. The ZG content exceeded the control after gibberellic acid treatment and was in trace concentrations under the action of tebuconazole. Growth regulators optimized the productivity of tomato plants: under the action of gibberellic acid there was a considerable increase in the number of fruits per plant, and after the use of tebuconazole the average weight of one fruit significantly increased. The obtained results demonstrated that anatomical-morphological and structural-functional rearrangements in tomato plants under the action of exogenous gibberellic acid and tebuconazole occurred against the background of changes in the balance and distribution of endogenous hormones. Increased photosynthetic activity, stimulation of growth processes of some plant organs and inhibition of others increased the biological crop capacity

Nonlinear excitation of kinetic Alfven waves and whistler waves by electron beam-driven Langmuir waves in the solar corona

© ESO 2003We study a new nonlinear excitation mechanism of kinetic Alfvén waves (KAWs) and whistler waves (Ws) by electron beam-driven Langmuir waves (Ls). The generation conditions for the parametric decay instability L W + KAW are determined and the growth rate is calculated. We show that the resonant pairs of KAWs and whistler waves are nonlinearly coupled to the pump Langmuir waves and their amplitudes undergo exponential growth from the thermal level. The perpendicular dispersion of KAWs strongly increases the coupling due to the nonlinear current parallel to the ambient magnetic field. Our study suggests that the nonlinear coupling of Langmuir wave energy into KAWs and whistlers can provide an efficient sink for weakly dispersive Langmuir waves excited by fast electron beams in the solar corona when the electron plasma frequency is lower than the electron gyrofrequency. This condition can be satisfied in the low-density magnetic filaments that are rooted in the depleted patches at the coronal base and extend to the high corona. At the same time, the Langmuir-driven KAWs and whistlers give rise to scattering and/or thin structures of radio emission penetrating through, or generated in these regions. Since the decay into sunward propagating KAWs is strongest, the nonlinearly driven KAWs can be easily distinguished from the waves generated at the coronal base and propagating away from the Sun. Our results may be used in the analysis of solar radio data and for remote probing of the coronal plasma, magnetic fields, and waves.Yu. Voitenko, M. Goossens, O. Sirenko and A. C.-L. Chia

Constructing an index of physical fitness age for Japanese elderly based on 7-year longitudinal data: sex differences in estimated physical fitness age

A standardized method for assessing the physical fitness of elderly adults has not yet been established. In this study, we developed an index of physical fitness age (fitness age score, FAS) for older Japanese adults and investigated sex differences based on the estimated FAS. Healthy elderly adults (52 men, 70 women) who underwent physical fitness tests once yearly for 7 years between 2002 and 2008 were included in this study. The age of the participants at the beginning of this study ranged from 60.0 to 83.0 years. The physical fitness tests consisted of 13 items to measure balance, agility, flexibility, muscle strength, and endurance. Three criteria were used to evaluate fitness markers of aging: (1) significant cross-sectional correlation with age; (2) significant longitudinal change with age consistent with the cross-sectional correlation; and (3) significant stability of individual differences. We developed an equation to assess individual FAS values using the first principal component derived from principal component analysis. Five candidate fitness markers of aging (10-m walking time, functional reach, one leg stand with eyes open, vertical jump and grip strength) were selected from the 13 physical fitness tests. Individual FAS was predicted from these five fitness markers using a principal component model. Individual FAS showed high longitudinal stability for age-related changes. This investigation of the longitudinal changes of individual FAS revealed that women had relatively lower physical fitness compared with men, but their rate of physical fitness aging was slower than that of men

Self-consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence

We present a series of models for the plasma properties along open magnetic flux tubes rooted in solar coronal holes, streamers, and active regions. These models represent the first self-consistent solutions that combine: (1) chromospheric heating driven by an empirically guided acoustic wave spectrum, (2) coronal heating from Alfven waves that have been partially reflected, then damped by anisotropic turbulent cascade, and (3) solar wind acceleration from gradients of gas pressure, acoustic wave pressure, and Alfven wave pressure. The only input parameters are the photospheric lower boundary conditions for the waves and the radial dependence of the background magnetic field along the flux tube. For a single choice for the photospheric wave properties, our models produce a realistic range of slow and fast solar wind conditions by varying only the coronal magnetic field. Specifically, a 2D model of coronal holes and streamers at solar minimum reproduces the latitudinal bifurcation of slow and fast streams seen by Ulysses. The radial gradient of the Alfven speed affects where the waves are reflected and damped, and thus whether energy is deposited below or above the Parker critical point. As predicted by earlier studies, a larger coronal ``expansion factor'' gives rise to a slower and denser wind, higher temperature at the coronal base, less intense Alfven waves at 1 AU, and correlative trends for commonly measured ratios of ion charge states and FIP-sensitive abundances that are in general agreement with observations. These models offer supporting evidence for the idea that coronal heating and solar wind acceleration (in open magnetic flux tubes) can occur as a result of wave dissipation and turbulent cascade. (abridged abstract)Comment: 32 pages (emulateapj style), 18 figures, ApJ Supplement, in press (v. 171, August 2007

Evidence for electron Landau damping in space plasma turbulence

How turbulent energy is dissipated in weakly collisional space and astrophysical plasmas is a major open question. Here, we present the application of a field-particle correlation technique to directly measure the transfer of energy between the turbulent electromagnetic field and electrons in the Earth's magnetosheath, the region of solar wind downstream of the Earth's bow shock. The measurement of the secular energy transfer from the parallel electric field as a function of electron velocity shows a signature consistent with Landau damping. This signature is coherent over time, close to the predicted resonant velocity, similar to that seen in kinetic Alfven turbulence simulations, and disappears under phase randomisation. This suggests that electron Landau damping could play a significant role in turbulent plasma heating, and that the technique is a valuable tool for determining the particle energisation processes operating in space and astrophysical plasmas.STFC Ernest Rutherford Fellowship [ST/N003748/2]; NASA HSR grant [NNX16AM23G]; NSF CAREER Award [AGS-1054061]; NASA HGI grant [80NSSC18K0643]; NASA MMS GI grant [80NSSC18K1371]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]