Transport optimization on complex networks

We present a comparative study of the application of a recently introduced heuristic algorithm to the optimization of transport on three major types of complex networks. The algorithm balances network traffic iteratively by minimizing the maximum node betweenness with as little path lengthening as possible. We show that by using this optimal routing, a network can sustain significantly higher traffic without jamming than in the case of shortest path routing. A formula is proved that allows quick computation of the average number of hops along the path and of the average travel times once the betweennesses of the nodes are computed. Using this formula, we show that routing optimization preserves the small-world character exhibited by networks under shortest path routing, and that it significantly reduces the average travel time on congested networks with only a negligible increase in the average travel time at low loads. Finally, we study the correlation between the weights of the links in the case of optimal routing and the betweennesses of the nodes connected by them.Comment: 19 pages, 7 figure

Dynamical correlations in electronic transport through a system of coupled quantum dots

Current auto- and cross-correlations are studied in a system of two capacitively coupled quantum dots. We are interested in a role of Coulomb interaction in dynamical correlations, which occur outside the Coulomb blockade region (for high bias). After decomposition of the current correlation functions into contributions between individual tunneling events, we can show which of them are relevant and lead to sub-/supper-Poissonian shot noise and negative/positive cross-correlations. The results are differentiated for a weak and strong inter-dot coupling. Interesting results are for the strong coupling case when electron transfer in one of the channel is strongly correlated with charge drag in the second channel. We show that cross-correlations are non-monotonic functions of bias voltage and they are in general negative (except some cases with asymmetric tunnel resistances). This is effect of local potential fluctuations correlated by Coulomb interaction, which mimics the Pauli exclusion principle

Methods of thrombus age determination

Relevance: Venous thromboembolic complications are a formidable condition with a high mortality risk, that is rather common in the practice of a physician of any specialty. Therefore, timely diagnosis and correct management of patients with thromboembolic complications are key to a favorable outcome of the disease. An urgent problem for science nowadays is the search and development of diagnostic approaches that give a complete description of a thrombotic event. One of these characteristics is the determination of the age of thrombosis; it is a clear understanding of this criterion that makes it possible to choose a successful treatment strategy for patients with similar complications.Aim of study: To date, the assessment of the age of a thrombus is based mainly on the patient’s anamnestic data, which do not always correspond to the real situation, and imaging techniques based on indirect signs. Therefore, the ineffectiveness of therapy for the described conditions in some cases can be explained by an underestimation of the age of the thrombus. The development of scientific research in this direction seems promising and can lead to an improvement in the results of treatment of patients suffering from venous thromboembolic complications. This article is a review of the methods for thrombus age determination presented in the literature

Анализ распределения освещённости, генерируемой светодиодными матрицами

Сreation of indoor lighting systems with the possibility of changing its parameters in space and time is a promising direction within the framework of the intellectual environment system. The aim of this work was to create a methodology for calculating the illumination created by LED matrices which does not require the use of specialized software products and is adapted to the possibility of varying the parameters of LEDs and illuminated rooms.The urgency of creating a room lighting system that simulates the conditions of natural lighting taking into account the need to change its spectral composition in time, in space taking into account the physical and psychological state of a person is substantiated. The possibility of using well-known computer programs to calculate the distribution of illumination in the room is analyzed.A method has been developed for calculating the distribution of illumination on a plane using both a flat LED matrix and a matrix with an inclined arrangement of the planes of individual LEDs. It is shown that the distribution of illumination is a function of the indicatrix of the light intensity of the LED, its location in space, the number of LEDs in the matrix.Illumination distribution has been calculated for various light sources consisting of RGB LEDs both for desktop and ceiling lighting was calculated. It is established that when using matrices containing the same LEDs distribution of illumination is very nonuniform. The inclined arrangement of LED planes slightly increases uniformity reducing the maximum illumination. For ceiling lighting the option of uniform distribution of LEDs within the ceiling plane provides more uniform illumination than when the same number of LEDs are arranged in groups of matrices.Results of LED sources modeling indicate the need to modernize simple orthogonal matrices containing the same type of elements with the same power modes for all elements in order to increase the uniformity of illumination and efficiency. Such modernization can be carried out by changing the geometry of matrices differentiating the power modes of individual LEDs. The developed calculation program can be supplemented with options for introducing the above changes, as well as options for analyzing the spectral distribution of light in space. Создание систем освещения помещений с возможностью изменения его параметров в пространстве и во времени является перспективным направлением в рамках системы «интеллектуальная окружающая среда». Целью данной работы было создание методики расчёта освещённости, создаваемой светодиодными матрицами, которая не требует применения специализированных программных продуктов и адаптирована к возможности варьирования параметров светодиодов и освещаемых помещений. Обоснована актуальность создания системы освещения помещений, имитирующей условия естественного освещения с учётом необходимости его изменения по спектральному составу во времени, в пространстве с учётом физического и психологического состояния человека.Проанализирована возможность использования известных компьютерных программ для расчёта распределения освещённости в помещении.Разработана методика расчёта распределения освещённости на плоскости при использовании как плоской светодиодной матрицы, так и матрицы с наклонным расположением плоскостей отдельных светодиодов. Показано, что распределение освещённости является функцией индикатрисы силы света светодиода, расположения его в пространстве, количества светодиодов в матрице.Произведён расчёт распределения освещённости для различных источников света, состоящих из RGB светодиодов, как для настольного, так и для потолочного освещения. Установлено, что при использовании матриц, содержащих одинаковые светодиоды, велика неравномерность распределения освещённости. Наклонное расположение плоскостей светодиодов незначительно увеличивает равномерность, уменьшая максимальную освещённость. Для потолочного освещения вариант равномерного распределения светодиодов в пределах потолочной плоскости обеспечивает более равномерное освещение, чем при расположении такого же количества светодиодов в виде групп матриц.Результаты моделирования светодиодных источников свидетельствуют о необходимости модернизации простых ортогональных матриц, содержащих однотипные элементы с одинаковым для всех элементов режимом питания, с целью повышения равномерности освещённости и экономичности. Такая модернизация может осуществляться за счёт изменения геометрии матриц, дифференциации режимов питания отдельных светодиодов. Разработанная программа расчёта может дополняться опциями для введения перечисленных выше изменений, а также опциями для анализа спектрального распределения излучения в пространстве

Оценка неравномерности упругих свойств листов из закрытоячеистых пенополиолефинов акустическим методом

The widespread use of polyolefin foams in strategically important industries is due to their high thermal, sound and vibration insulation properties. The aim of the work was to evaluate the non-uniformity of elastic properties over the area of sheets of polyolefin foams of various types using the acoustic non-contact shadow amplitude method of testing and confirmation by the structural analysis method.The article presents the developed installation and a new method of non-contact acoustic testing of sheets made of closed-cell polyolefin foams based on recording the amplitude of the pulse that passed through the sheet and allowing to assess to the unevenness of its elastic properties during scanning. Studies of uneven elastic properties were carried out on sheets of closed-cell polyolefin foams of the ISOLON 500 and ISOLON 300 brands which differ in material and manufacturing technology (technique of cross-linking, method and multiplicity of foaming).It is shown that the absolute amplitude of the signal and its spread relative to the average value is affected by the structure of the foam polyolefin material and its heterogeneity over the area of the studied sheet determined by the production technology which is confirmed visually using microscopy.Studies have shown the effect on the indications unevenness of the method of obtaining and the apparent density of the material. It is shown that the most uneven elastic properties and structure belong to sheets of polyolefin foam obtained by chemical cross-linking technology (the unevenness of Δ was 6.5 %). Among the physically cross-linked sheets of polyolefin foam the most uniform in structure and elastic properties are samples made of ethylene vinyl acetate with Δ = 3.8 %, as well as sheets with a high foaming rate (Δ = 3.9 %). The unevenness of structure of the studied sheets of polyolefin foams was confirmed by optical microscopy of sections in two mutually perpendicular directions.Широкое использование пенополиолефинов в стратегически важных отраслях промышленности обусловлено их высокими тепло-, звуко- и виброизоляционными свойствами. Целью работы являлась оценка неравномерности упругих свойств по площади листов пенополиолефинов различных типов с использованием акустического бесконтактного теневого амплитудного метода контроля и подтверждением методом структурного анализа.Разработаны установка и новая методика бесконтактного акустического контроля листов из закрытоячеистых пенополиолефинов, основанная на регистрации амплитуды импульса, прошедшего сквозь лист, и позволяющая оценить неравномерность его упругих свойств в процессе сканирования. Исследования неравномерности упругих свойств проведены на листах из закрытоячеистых пенополиолефинов марки ISOLON 500 и ISOLON 300, различающиеся материалом и технологией изготовления (способ сшивки, метод и кратность вспенивания).Показано, что на абсолютную амплитуду сигнала и её разброс относительно среднего значения влияет структура материала пенополиолефина и её неоднородность по площади исследуемого листа, определяемая технологией производства, что подтверждено визуально с использованием микроскопии. Исследования показали влияние на неравномерность показаний способа получения и кажущейся плотности материала. Показано, что наиболее неравномерные упругие свойства и структуру имеют листы из пенополиолефинов, полученных по технологии химической сшивки (неравномерность Δ составила 6,5 %). Из физически сшитых листов пенополиолефинов наиболее равномерными по структуре и упругим свойствам являются образцы, изготовленные из этиленвинилацетата с Δ = 3,8 %, а также листы с высокой кратностью вспенивания (Δ = 3,9 %). Неравномерность структуры исследованных листов пенополиолефинов подтверждена оптической микроскопией срезов в двух взаимно перпендикулярных направлениях

Correlation Functions of Operators and Wilson Surfaces in the d=6, (0,2) Theory in the Large N Limit

We compute the two and three-point correlation functions of chiral primary operators in the large N limit of the (0,2), d=6 superconformal theory. We also consider the operator product expansion of Wilson surfaces in the (0,2) theory and compute the OPE coefficients of the chiral primary operators at large N from the correlation functions of surfaces.Comment: 34 pages, using utarticle.cls (included), array.sty, amsmath.sty, amsfonts.sty, latexsym.sty, epsfig. Bibtex style: utphys.bst (.bbl file included

Primacy of effective communication and its influence on adherence to artemether-lumefantrine treatment for children under five years of age: a qualitative study.

BACKGROUND\ud \ud Prompt access to artemesinin-combination therapy (ACT) is not adequate unless the drug is taken according to treatment guidelines. Adherence to the treatment schedule is important to preserve efficacy of the drug. Although some community based studies have reported fairly high levels of adherence, data on factors influencing adherence to artemether-lumefantrine (AL) treatment schedule remain inadequate. This study was carried-out to explore the provider's instructions to caretakers, caretakers' understanding of the instructions and how that understanding was likely to influence their practice with regard to adhering to AL treatment schedule.\ud \ud METHODS\ud \ud A qualitative study was conducted in five villages in Kilosa district, Tanzania. In-depth interviews were held with providers that included prescribers and dispensers; and caretakers whose children had just received AL treatment. Information was collected on providers' instructions to caretakers regarding dose timing and how to administer AL; and caretakers' understanding of providers' instructions.\ud \ud RESULTS\ud \ud Mismatch was found on providers' instructions as regards to dose timing. Some providers' (dogmatists) instructions were based on strict hourly schedule (conventional) which was likely to lead to administering some doses in awkward hours and completing treatment several hours before the scheduled time. Other providers (pragmatists) based their instruction on the existing circumstances (contextual) which was likely to lead to delays in administering the initial dose with serious treatment outcomes. Findings suggest that, the national treatment guidelines do not provide explicit information on how to address the various scenarios found in the field. A communication gap was also noted in which some important instructions on how to administer the doses were sometimes not provided or were given with false reasons.\ud \ud CONCLUSIONS\ud \ud There is need for a review of the national malaria treatment guidelines to address local context. In the review, emphasis should be put on on-the-job training to address practical problems faced by providers in the course of their work. Further research is needed to determine the implication of completing AL treatment prior to scheduled time

The low-energy limit of AdS(3)/CFT2 and its TBA

We investigate low-energy string excitations in AdS3 × S3 × T4. When the worldsheet is decompactified, the theory has gapless modes whose spectrum at low energies is determined by massless relativistic integrable S matrices of the type introduced by Al. B. Zamolodchikov. The S matrices are non-trivial only for excitations with identical worldsheet chirality, indicating that the low-energy theory is a CFT2. We construct a Thermodynamic Bethe Ansatz (TBA) for these excitations and show how the massless modes’ wrapping effects may be incorporated into the AdS3 spectral problem. Using the TBA and its associated Y-system, we determine the central charge of the low-energy CFT2 to be c = 6 from calculating the vacuum energy for antiperiodic fermions — with the vacuum energy being zero for periodic fermions in agreement with a supersymmetric theory — and find the energies of some excited states

Impurity-induced stabilization of solitons in arrays of parametrically driven nonlinear oscillators

Chains of parametrically driven, damped pendula are known to support soliton-like clusters of in-phase motion which become unstable and seed spatiotemporal chaos for sufficiently large driving amplitudes. We show that the pinning of the soliton on a "long" impurity (a longer pendulum) expands dramatically its stability region whereas "short" defects simply repel solitons producing effective partition of the chain. We also show that defects may spontaneously nucleate solitons.Comment: 4 pages in RevTeX; 7 figures in ps forma

Fano and Kondo resonance in electronic current through nanodevices

Electronic transport through a quantum dot strongly coupled to electrodes is studied within a model with two conduction channels. It is shown that multiple scattering and interference of transmitted waves through both channels lead to Fano resonance associated with Kondo resonance. Interference effects are also pronouncedly seen in transport through the Aharonov-Bohm ring with the Kondo dot, where the current characteristics continuously evolve with the magnetic flux.Comment: 4 pages, 3 figures,a typing error has been correcte