Spatial effects of Fano resonance in local tunneling conductivity in vicinity of impurity on semiconductor surface

We present the results of local tunneling conductivity spatial distribution detailed theoretical investigations in vicinity of impurity atom for a wide range of applied bias voltage. We observed Fano resonance in tunneling conductivity resulting from interference between resonant tunneling channel through impurity energy level and direct tunneling channel between the tunneling contact leads. We have found that interference between tunneling channels strongly modifies form of tunneling conductivity measured by the scanning tunneling microscopy/spectroscopy (STM/STS) depending on the distance value from the impurity.Comment: 4 pages, 3 figure

Spatial distribution of local density of states in vicinity of impurity on semiconductor surface

We present the results of detailed theoretical investigations of changes in local density of total electronic surface states in 2D anisotropic atomic semiconductor lattice in vicinity of impurity atom for a wide range of applied bias voltage. We have found that taking into account changes in density of continuous spectrum states leads to the formation of a downfall at the particular value of applied voltage when we are interested in the density of states above the impurity atom or even to a series of downfalls for the fixed value of the distance from the impurity. The behaviour of local density of states with increasing of the distance from impurity along the chain differs from behaviour in the direction perpendicular to the chain.Comment: 6 pages, 5 figure

Correlation induced switching of local spatial charge distribution in two-level system

We present theoretical investigation of spatial charge distribution in the two-level system with strong Coulomb correlations by means of Heisenberg equations analysis for localized states total electron filling numbers taking into account pair correlations of local electron density. It was found that tunneling current through nanometer scale structure with strongly coupled localized states causes Coulomb correlations induced spatial redistribution of localized charges. Conditions for inverse occupation of two-level system in particular range of applied bias caused by Coulomb correlations have been revealed. We also discuss possibility of charge manipulation in the proposed system.Comment: 6 pages, 4 figures Submitted to JETP Letter

Scanning tunneling microscopy and spectroscopy at low temperatures of the (110) surface of Te doped GaAs single crystals

We have performed voltage dependent imaging and spatially resolved spectroscopy on the (110) surface of Te doped GaAs single crystals with a low temperature scanning tunneling microscope (STM). A large fraction of the observed defects are identified as Te dopant atoms which can be observed down to the fifth subsurface layer. For negative sample voltages, the dopant atoms are surrounded by Friedel charge density oscillations. Spatially resolved spectroscopy above the dopant atoms and above defect free areas of the GaAs (110) surface reveals the presence of conductance peaks inside the semiconductor band gap. The appearance of the peaks can be linked to charges residing on states which are localized within the tunnel junction area. We show that these localized states can be present on the doped GaAs surface as well as at the STM tip apex.Comment: 8 pages, 8 figures, accepted for publication in PR

Basic principles of postgrowth annealing of CdTe:Cl ingot to obtain semi-insulating crystals

The process of annealing of a CdTe:Cl ingot during its cooling after growth was studied. The annealing was performed in two stages: a high-temperature stage, with an approximate equality of chlorine and cadmium vacancy concentrations established at the thermodynamic equilibrium between the crystal and vapors of volatile components, and a low-temperature stage, with charged defects interacting to form neutral associations. The chlorine concentrations necessary to obtain semi-insulating crystals were determined for various ingot cooling rates in the high temperature stage. The dependence of the chlorine concentration [Cl+Te] in the ingot on the temperature of annealing in the high-temperature stage was found. The carrier lifetimes and drift mobilities were obtained in relation to the temperature and cadmium vapor pressure in the postgrowth annealing of the ingot.Comment: 6 pages, 6 figure

Decay and Continuity of Boltzmann Equation in Bounded Domains

Boundaries occur naturally in kinetic equations and boundary effects are crucial for dynamics of dilute gases governed by the Boltzmann equation. We develop a mathematical theory to study the time decay and continuity of Boltzmann solutions for four basic types of boundary conditions: inflow, bounce-back reflection, specular reflection, and diffuse reflection. We establish exponential decay in $L^{\infty}$ norm for hard potentials for general classes of smooth domains near an absolute Maxwellian. Moreover, in convex domains, we also establish continuity for these Boltzmann solutions away from the grazing set of the velocity at the boundary. Our contribution is based on a new $L^{2}$ decay theory and its interplay with delicate $$ decay analysis for the linearized Boltzmann equation, in the presence of many repeated interactions with the boundary.Comment: 89 pages

Coulomb correlations effects on localized charge relaxation in the coupled quantum dots

We analyzed localized charge time evolution in the system of two interacting quantum dots (QD) (artificial molecule) coupled with the continuous spectrum states. We demonstrated that Coulomb interaction modifies relaxation rates and is responsible for non-monotonic time evolution of the localized charge. We suggested new mechanism of this non-monotonic charge time evolution connected with charge redistribution between different relaxation channels in each QD.Comment: 10 pages, 10 figure

Charge and spin configurations in the coupled quantum dots with Coulomb correlations induced by tunneling current

We investigated the peculiarities of non-equilibrium charge states and spin configurations in the system of two strongly coupled quantum dots (QDs) weakly connected to the electrodes in the presence of Coulomb correlations. We analyzed the modification of non-equilibrium charge states and different spin configurations of the system in a wide range of applied bias voltage and revealed well pronounced ranges of system parameters where negative tunneling conductivity appears due to the Coulomb correlations.Comment: 10 pages, 6 figure

Sun and shade leaf variability in Liquidambar chinensis and Liquidambar formosana (Altingiaceae): Implications for palaeobotany

© 2018 The Linnean Society of London. Many factors influence leaf anatomy and morphology in the crown of a tree, particularly those resulting from microclimatic differences between the periphery and the interior of the crown. These influences can be so strong that single species can produce different leaf forms in which shade and sun leaves exhibit consistently distinctive morphological and epidermal character sets. Here we show, using Liquidambar as a model system, that the principal morphological characters for distinguishing shade and sun leaves in two modern Liquidambar spp. with different lamina types (entire in L. chinensis and lobate in L. formosana) are the leaf lamina length to width ratio, the degree of development of venation networks, tooth size and tooth shape. The main epidermal characters are ordinary cell size and anticlinal wall outlines. Many fossils, however, are only preserved as impressions and morphological characters alone have been used to distinguish shade and sun leaf morphotypes. To evaluate the utility of our approach, populations of fossil Liquidambar leaves from the Eocene of southern China, preserved only as impressions, were categorized into sun and shade morphotypes. Recognition that sun and shade leaf morphological diversity exists in fossil populations will enable palaeobotanists to identify more reliably foliar polymorphisms that would otherwise be used to describe, incorrectly, different species

Создание новых форм томата с генами устойчивости к грибным болезням на основе маркерной селекции

Relevance. The presented studies are aimed at obtaining new forms of tomato with a complex of genes for resistance to fungal diseases in combination with a standard type of bush and dark coloring of fruits based on marker-mediated selection.Methodology. The biological objects of the study are varieties and hybrid forms of tomato from the collection of the Michurinsky SAU. Molecular genetic analysis was performed using the following methods. DNA extraction was carried out from young leaves using a kit for isolation of NC Sample NC manufactured by Agrodiagnostika LLC according to the manufacturer's protocol. Fermentas production kits were used for PCR. Identification of the cladosporosis resistance gene was Cf-19 performed using the DNA marker R7. The presence of a fusarious wilting resistance gene was determined by a I-2/5 marker. The amplification results were visualized by agarose gel electrophoresis.Results. During the research, a collection of varieties and hybrid forms of tomato of the Michurinsky GAU was analyzed in order to identify genes for resistance to cladosporiosis Cf-19 and fusarium wilt I-2. A total of 52 genotypes were analyzed. It was found that most samples (41 samples) are characterized by a heterozygous state of the Cf-19 gene. All indeterminant and semi-determinant forms had both alleles. Of the 23 determinant forms presented in the collection, 10 had only one allele corresponding to recessive homozygote. Among all analyzed tomato genotypes, no dominant homozygous forms were noted. The study of the collection revealed several alleles of the I-2 gene. In total, four fragments corresponding to various alleles were amplified. A total of 50 resistant genotypes have been identified in the collection. Two alleys of the I-2 gene (633/693 bp) were identified in 42 tomato samples. Four varieties are homozygous in one allele (633 bp), which determines resistance. Three varieties have a second resistance allele (566 bp). One genotype has only an allele defining susceptibility (693 bp). On the basis of molecular analysis, as well as an assessment of the type of bush and fetal color, initial forms were selected with subsequent hybridization. 67 hybrid tomato plants were obtained. Evaluation of the presence of resistance genes showed that most of the resulting hybrids are resistant to cladosporiosis and fuzariosis. This is due to the presence of dominant alleles of Cf-19 and I-2 genes in a heterozygous state. Among the resulting hybrids, plants with a bark type of bush were identified. A total of 13 such plants were obtained.Conclusion. Thus, the work carried out allowed to obtain hybrid forms of tomato combine the signs of resistance to two pathogens of fungal diseases and the stem type of the bush. These forms are planned to be used in further selection work.Цель. Исследования направлены на получение новых форм томата с комплексом генов устойчивости к грибным болезням в сочетании со штамбовым типом куста и темной окраской плодов на основе маркер-опосредованной селекции.Методы. Объект исследований – сорта и гибридные формы томата из коллекции Мичуринского ГАУ. Молекулярно-генетический анализ проводили с использованием следующих методов. Экстрагирование ДНК осуществляли из молодых листьев с применением набора для выделения НК «Проба НК» производства ООО «Агродиагностика» согласно протоколу производителя. Для проведения ПЦР использованы наборы производства компании Fermentas. Идентификацию гена устойчивости к кладоспоризу Cf-19 проводили с использованием ДНК-маркера Р7. Наличие гена устойчивости к фузариозному увяданию определяли с помощью маркера I-2/5. Визуализацию результатов амплификации осуществляли с помощью электрофореза в агарозном геле.Результаты. При проведении исследований была проанализирована коллекция сортов и гибридных форм томата Мичуринского ГАУ с целью идентификации генов устойчивости к кладоспориозу Cf-19 и фузариозному увяданию I-2. Всего проанализировано 52 генотипа. Установлено, что для большинства образцов (41 образец) характерно гетерозиготное состояние гена Cf-19. Все индетерминантные и полудетерминантные формы имели оба аллеля. Из 23 представленных в коллекции детерминантных форм у 10 отмечен только один аллель, соответствующий рецессивной гомозиготе. Среди всех анализируемых генотипов томата не отмечено доминантных гомозиготных форм. Изучение коллекции позволило выявить нескольких аллелей гена I-2. Всего амплифицировано четыре фрагмента, соответствующих различным аллелям. Всего устойчивых генотипов в коллекции выделено 50. У 42 образцов томата идентифицированы два аллея гена I-2 (633/693 п.н). Четыре сорта гомозиготны по одному аллелю (633 п.н.), обуславливающему устойчивость. Три сорта имеют второй аллель (566 п.н.) устойчивости. Один генотип имеет только аллель определяющий восприимчивость (693 п.н.).На основании молекулярного анализа, а также оценки типа куста и окраски плода был проведен отбор исходных форм с последующей гибридизацией. Получено 67 гибридных растений томата. Оценка наличия генов устойчивости показала, что большинство полученных гибридов являются устойчивыми к кладоспориозу и фузариозу. Это обусловлено наличием доминантных аллелей генов Cf-19 и I-2 в гетерозиготном состоянии. Среди полученных гибридов выделены растения со штамбовым типом куста. Всего таких растений получено 13. Проведенная работа позволила получить гибридные формы томата, сочетающие признаки устойчивости к двум возбудителям грибных болезней и штамбовый тип куста. Эти формы планируется использовать в дальнейшей селекционной работе