Transport Properties of Highly Aligned Polymer Light-Emitting-Diodes

We investigate hole transport in polymer light-emitting-diodes in which the emissive layer is made of liquid-crystalline polymer chains aligned perpendicular to the direction of transport. Calculations of the current as a function of time via a random-walk model show excellent qualitative agreement with experiments conducted on electroluminescent polyfluorene demonstrating non-dispersive hole transport. The current exhibits a constant plateau as the charge carriers move with a time-independent drift velocity, followed by a long tail when they reach the collecting electrode. Variation of the parameters within the model allows the investigation of the transition from non-dispersive to dispersive transport in highly aligned polymers. It turns out that large inter-chain hopping is required for non-dispersive hole transport and that structural disorder obstructs the propagation of holes through the polymer film.Comment: 4 pages, 5 figure

Bark beetle population dynamics in the Anthropocene: Challenges and solutions

Tree-killing bark beetles are the most economically important insects in conifer forests worldwide. However, despite N200 years of research, the drivers of population eruptions and crashes are still not fully understood and the existing knowledge is thus insufficient to face the challenges posed by the Anthropocene. We critically analyze potential biotic and abiotic drivers of population dynamics of an exemplary species, the European spruce bark beetle (ESBB) (Ips typographus) and present a multivariate approach that integrates the many drivers governing this bark beetle system. We call for hypothesis-driven, large-scale collaborative research efforts to improve our understanding of the population dynamics of this and other bark beetle pests. Our approach can serve as a blueprint for tackling other eruptive forest insects

Fungi and lichens recorded during the Cryptogam Symposium on Natural Beech Forests, Slovakia 2011

In September 2011, an international team of cryptogam experts visited seven national nature reserves in five mountain areas of Slovakia: Havešová and Stužica in the Poloniny Mts., Vihorlat in the Vihorlatské vrchyMts., Oblík in the Slanské vrchyMts., Dobročský prales and Klenovský Vepor in the Veporské vrchy Mts. and Badínsky prales in the Kremnické vrchy Mts. The reserves were selected to represent examples of the best protected old-growth beech forests in the country. The aim was to study the diversity of wood-inhabiting fungi on fallen beech logs and epiphytic lichens on standing beech trees. In total, 215 fungal species and 128 lichens were recorded on beech wood and bark, and 27 fungi and 26 lichens on additional substrates. The site of the highest conservation value is Stužica with 126 fungi and 79 lichens recorded on beech, of which 12 fungi and 19 lichens are indicators of high nature conservation value. Combined with historical records, a total of 19 non-lichenised fungal indicators are now reported from the site, making it the highest ranked natural beech forest in Europe. The second most important reserve for fungal diversity is Havešová with 121 species, including 14 indicator species recorded on beech wood. For lichens, the second most important reserve is Klenovský Vepor with 69 species including 18 lichen indicators recorded on beech. Nine fungus species are here reported as new to Slovakia: Asterostroma medium, Entoloma hispidulum, E. pseudoparasiticum, Gloeohypochnicium analogum, Hohenbuehelia valesiaca, Hymenochaete ulmicola, Hypocrea parmastoi, Melanomma spiniferum and Scutellinia colensoi. Lichen species Alyxoria ochrocheila is reported as new to Slovakia and Lecanographa amylacea, which was considered extinct in the Slovak Red list, was also recorded. This is the first list of wood-inhabiting fungi and epiphytic lichens of old-growth beech forests in Slovakia, and hence an important contribution to the exploration of biodiversity in Slovakia

Theory of Electric Field-Induced Photoluminescence Quenching in Disordered Molecular Solids

The dynamics of excitons in disordered molecular solids is studied theoretically, taking into account migration between different sites, recombination, and dissociation into free charge carriers in the presence of an electric field. The theory is applied to interpret the results of electric field-induced photoluminescence (PL) quenching experiments on molecularly doped polymers by Deussen et al. [Chem. Phys. 207, 147 (1996)]. Using an intermolecular dissociation mechanism, the dependence of the PL quenching on the electric field strength and the dopant concentration, and the time evolution of the transient PL quenching can be well described. The results constitute additional proof of the distinct exciton dissociation mechanisms in conjugated polymer blends and molecularly doped polymers.Comment: 4 pages RevTeX, 3 Postscript figure

Theory of Exciton Migration and Field-Induced Dissociation in Conjugated Polymers

The interplay of migration, recombination, and dissociation of excitons in disordered media is studied theoretically in the low temperature regime. An exact expression for the photoluminescence spectrum is obtained. The theory is applied to describe the electric field-induced photoluminescence-quenching experiments by Kersting et al. [Phys. Rev. Lett. 73, 1440 (1994)] and Deussen et al. [Synth. Met. 73, 123 (1995)] on conjugated polymer systems. Good agreement with experiment is obtained using an on-chain dissociation mechanism, which implies a separation of the electron-hole pair along the polymer chain.Comment: 4 pages, RevTeX, 2 Postscript figure

Temperature Dependence of Exciton Diffusion in Conjugated Polymers

The temperature dependence of the exciton dynamics in a conjugated polymer is studied using time-resolved spectroscopy. Photoluminescence decays were measured in heterostructured samples containing a sharp polymer-fullerene interface, which acts as an exciton quenching wall. Using a 1D diffusion model, the exciton diffusion length and diffusion coefficient were extracted in the temperature range of 4-293 K. The exciton dynamics reveal two temperature regimes: in the range of 4-150 K, the exciton diffusion length (coefficient) of ~3 nm (~1.5 × 10-4 cm2/s) is nearly temperature independent. Increasing the temperature up to 293 K leads to a gradual growth up to 4.5 nm (~3.2 × 10-4 cm2/s). This demonstrates that exciton diffusion in conjugated polymers is governed by two processes: an initial downhill migration toward lower energy states in the inhomogenously broadened density of states, followed by temperature activated hopping. The latter process is switched off below 150 K.

Анализ современных технологий заводнения при разработке нефтяных месторождений

Объектом исследования являются системы заводнения применяемые на месторождениях России Цель работы – анализ современных технологий заводнения при разработке нефтяных месторождений, а также обоснование применения технологий заводнения с целью увеличения темпов отбора, коэффициента нефтеизвлечения, технико-экономических показателей. В выпускной квалификационной работе приведены сведения о современных технологиях заводнения, применяемых на месторождениях России. Проведены расчеты экономической эффективности при внедрении нестационарного метода заводнения. Проанализирован процесс работы методов заводнения в условиях месторождений России. Бакалаврская работа выполнена в текстовом редакторе Microsoft Word, и Microsoft Excel.The object of the study are the waterflooding systems used in the fields of Russia The aim of the work is the analysis of modern flooding technologies in the development of oil fields, as well as the rationale for using flooding technologies to increase the rate of selection, the oil recovery factor, and the technical and economic indicators. In the final qualification work information on modern water flooding technologies used in the fields of Russia is given. Calculations of economic efficiency are implemented in the introduction of the non-stationary flooding method. The process of work of flooding methods in the conditions of Russian deposits is analyzed. Bachelor's work is executed in the text editor Microsoft Word, and Microsoft Excel

Temperature and Field Dependence of the Mobility in Liquid-Crystalline Conjugated Polymer Films

The transport properties of organic light-emitting diodes in which the emissive layer is composed of conjugated polymers in the liquid-crystalline phase have been investigated. We have performed simulations of the current transient response to an illumination pulse via the Monte Carlo approach, and from the transit times we have extracted the mobility of the charge carriers as a function of both the electric field and the temperature. The transport properties of such films are different from their disordered counterparts, with charge carrier mobilities exhibiting only a weak dependence on both the electric field and temperature. We show that for spatially ordered polymer films, this weak dependence arises for thermal energy being comparable to the energetic disorder, due to the combined effect of the electrostatic and thermal energies. The inclusion of spatial disorder, on the other hand, does not alter the qualitative behaviour of the mobility, but results in decreasing its absolute value.Comment: 9 pages, 8 figures, submitted to Phys. Rev.

Photoinduced transient stark spectroscopy in organic semiconductors: a method for charge mobility determination in the picosecond regime.

Published versio

Технологические решения для реконструкции добывающей скважины глубиной 2170 метров методом зарезки бокового ствола на нефтяном месторождении Томской области

Обоснование технологических решений для реконструкции добывающей скважины глубиной 2170 метров методом зарезки бокового ствола на нефтяном месторождении Томской области. В процессе исследования проводился анализ предоставленных геологических данных для принятия решений при разработке проекта. В результате исследования представлен комплекс технологических решений для строительства бокового ствола. Основные конструктивные, технологические и технико-эксплуатационные характеристики: обоснование и расчет профиля бокового ствола, расчет процессов углубления и заканчивания скважины, определение времени и стоимости проведения работ. Область применения: работа может быть использованы при составлении проектов на скважины, а данные из специальной части – при разработке состава эластомера ВЗД.Substantiation of technological solutions for reconstruction of a production well with a depth of 2,170 meters by the method of sidetracking at an oil field in the Tomsk region. In the course of the study, the analysis of the provided geological data for decision making during project development was carried out. As a result of the research, a set of technological solutions for the construction of the lateral trunk is presented. The main design, technological and technical and operational characteristics: justification and calculation of the sidetrack profile, calculation of the deepening and completion of the well, determination of the time and cost of work. Scope: the work can be used in the design of wells, and data from a special part - when developing the composition of an elastomer