Photoelectric, nonlinear optical, and photorefractive properties of polymer composites including carbon nanotubes and cyanine dyes

The effect of cyanine dye additives on the photoelectric, nonlinear optical, and photorefractive properties of polyvinyl carbazole composites based on closed single-walled carbon nanotubes has been investigated. It has been found that these characteristics are affected by the dye in which the lowest unoccupied molecular orbital (LUMO) lies below the level of the photoexcited nanotube. The addition of this dye to the composite leads to a 14-fold increase in the quantum efficiency of the generation of mobile charge carriers under irradiation by a laser (1064 nm) in the absorption region of the nanotubes. Moreover, the addition of the dye to the composite decreases the third-order susceptibility χ (3) , presumably, due to the opposite orientations of dipoles of the dye and the nanotube upon adsorption of the dye on the nanotube. The addition of the dye to the composite also provides a twofold increase in the two-beam photorefractive amplification factor of the laser beam with a wavelength of 1064 nm. The obtained values of the two-beam photorefractive amplification factor reach 120 cm -1 . \ua9 2013 Pleiades Publishing, Ltd

Photoelectric, nonlinear optical, and photorefractive properties of polyvinylcarbazole composites with graphene

Polyvinylcarbazole (PVK) composites containing graphene in an amount of somewhat less than 0.15 wt % exhibit third-order dielectric susceptibility due to the presence of graphene, as well as photoelectric and photorefractive sensitivity at 1064 nm. The photorefractive (PR) effect is known to occur in a polymer composite that possesses both photoelectric sensitivity and nonlinear optical properties. The photoelectric, nonlinear optical, and PR properties of PVK composites with graphene have been considered in this paper

Long-range dynamics of magnetic impurities coupled to a two-dimensional Heisenberg antiferromagnet

We consider a two-dimensional Heisenberg antiferromagnet on a square lattice with weakly coupled impurities, i.e. additional spins interacting with the host magnet by a small dimensionless coupling constant g<<1. Using linear spin-wave theory, we find that the magnetization disturbance at distance r from a single impurity behaves as g/r for 1>1/g. Surprisingly the disturbance is inversely proportional to the coupling constant! The interaction between two impurities separated by a distance r is proportional to g^2/r for 1>1/g. Hence at large distances, the interaction is universal and independent of the coupling constant. We also find that the frequency of Rabi oscillations between two impurities is proportional to g^2 ln(gr) at 1<<r<<1/g, logarithmically enhanced compared to the spin-wave width. This leads to a new mechanism for NMR, NQR and EPR line broadening. All these astonishing results are due to the gapless spectrum of the magnetic excitations in the quantum antiferromagnet.Comment: 6 pages, 5 figure

Unconventional Hund Metal in a Weak Itinerant Ferromagnet

The physics of weak itinerant ferromagnets is challenging due to their small magnetic moments and the ambiguous role of local interactions governing their electronic properties, many of which violate Fermi-liquid theory. While magnetic fluctuations play an important role in the materials’ unusual electronic states, the nature of these fluctuations and the paradigms through which they arise remain debated. Here we use inelastic neutron scattering to study magnetic fluctuations in the canonical weak itinerant ferromagnet MnSi. Data reveal that short-wavelength magnons continue to propagate until a mode crossing predicted for strongly interacting quasiparticles is reached, and the local susceptibility peaks at a coherence energy predicted for a correlated Hund metal by first-principles many-body theory. Scattering between electrons and orbital and spin fluctuations in MnSi can be understood at the local level to generate its non-Fermi liquid character. These results provide crucial insight into the role of interorbital Hund’s exchange within the broader class of enigmatic multiband itinerant, weak ferromagnets

EFFECT OF ELECTROLYTE COMPOSITION ON ELECTROCATALYTIC PROPERTIES OF NICKEL FOAMS

В работе установлено, что пористость никелевых пен оказывает влияние на каталитические свойства электрода по отношению к реакции выделения водорода. Показано, что пена, полученная из сульфат-хлоридного электрода обладает наибольшей пористостью. Величина перенапряжения водорода на данной пене была наименьшей среди исследованных образцов, что согласуется с результатами расчета пористости.It was found that the porosity of nickel foams affects the electrode catalytic activity for the hydrogen evolution reaction. It is shown that the foam obtained from the sulfate-chloride electrode has the highest porosity. The hydrogen overvoltage on this foam was the lowest among the samples studied, which correlates with the results of the porosity calculation

ПЕРЕВАГИ ВИКОРИСТАННЯ ОНЛАЙН-ФОРМ ЯК ЗАСОБУ ВИКЛАДАННЯ В ІНТЕРНАТУРІ

The article deals with the results of the analysis of the effectiveness of using online forms in the process of mastering the discipline «internal diseases». A pedagogical experiment was conducted with the inclusion of 46 interns who were engaged in the department during the period 2016-2017. It was found that the use of online forms to improve the efficiency of the educational process at the expense of, firstly, reducing the time spent on processing of the survey results, and, secondly, the optimization of the material assimilation level and «survival» knowledge of medical interns using a visual representation the results of the initial test and the substantive discussion on problematic issues. The combination of the online interviewing as a form of testing with the traditional way of control, and with self-control, can lead to a real system of objective assessment of the knowledge and realization of the main task of the educational process — the formation of strong knowledge and provide high-quality training of future specialists.В статье представлены результаты анализа эффективности использования онлайн-форм в процессе освоения дисциплины «внутренние болезни». Проведен педагогический эксперимент с включением 46 врачей-интернов, которые занимались на кафедре в период 2016-2017 годов. Установлено, что использование онлайн-форм позволяет повысить эффективность учебного процесса за счет, во-первых, уменьшения времени, затрачиваемого на обработку результатов опроса, и, во-вторых, оптимизации уровня усвоения материала и «выживаемости» знаний врачей-интернов с помощью наглядного представления результатов исходного испытания и предметной дискуссии по проблемным вопросам. Онлайн-опрос характеризуется большей объективностью и, как следствие, более выраженным положительным стимулирующим влиянием на познавательную деятельность врача-интерна. В предлагаемой методике проверка выполнения ситуационных задач выполняется централизованно, по единым критериям, что позволяет с достаточным основанием судить об общей степени овладения соответствующими знаниями и навыками, выявлять типичные ошибки и на этом основании корректировать, а в дальнейшем — совершенствовать учебный процесс. Сочетание онлайн-опроса как формы проверки с традиционными средствами контроля, а также с самоконтролем может способствовать выработке реальной системы объективной оценки знаний и реализации главной задачи образовательного процесса — формированию прочных знаний и обеспечению высокого качества подготовки будущих специалистов.У статті наведено результати аналізу ефективності використання онлайн-форм у процесі опанування дисципліни «внутрішні хвороби». Проведено педагогічний експеримент із включенням 46 лікарів-інтернів, які займалися на кафедрі в період 2016-2017 років. Встановлено, що використання онлайн-форм дозволяє підвищити ефективність навчального процесу за рахунок, по-перше, зменшення часу, який витрачається на обробку результатів опитування, і, по-друге, поліпшення рівня засвоєння матеріалу та «виживаності» знань лікарів-інтернів за допомогою наочного представлення результатів вихідного випробування і предметної дискусії з проблемних питань. Онлайн-опитування характеризується більшою об'єктивністю і, як наслідок, більш позитивним стимулюючим впливом на пізнавальну діяльність лікаря-інтерна. У запропонованій методиці перевірка виконання ситуаційних завдань виконується централізовано, за єдиними критеріями, що дозволяє з достатньою підставою судити про загальний ступінь сформо-ваності відповідних знань та навиків, виявляти типові помилки і на цій основі корегувати та надалі вдосконалювати навчальний процес. Поєднання онлайн-опитування як форми перевірки з традиційними засобами контролю, а також із самоконтролем може сприяти виробленню реальної системи об'єктивної оцінки знань і реалізації головного завдання освітнього процесу — формуванню міцних знань і забезпеченню високої якості підготовки майбутніх фахівців

Estudo comparativo da análise de ciclo de vida de concretos geopoliméricos e de concretos à base de cimento Portland composto (CP II)

A Análise de Ciclo de Vida (ACV) é um método que inclui a compilação e avaliação das entradas, saídas e dos impactos de um produto ao longo do seu ciclo de vida. Os resultados desta análise são utilizados para escolher alternativas favoráveis para uma aplicação específica. Este artigo utilizou as ferramentas de ACV, apoiada pelo software Umberto, para comparar o processo de obtenção de concretos de cimento Portland com o de concretos geopoliméricos, obtidos da ativação alcalina de aluminossilicatos. O impacto ambiental foi avaliado considerando 1 m³ de cada concreto, sendo (i) as emissões de CO2 (kg CO2/ m³) e (ii) a demanda energética (MJ/m³) as variáveis para determinar o potencial sustentável de ambos materiais. O objetivo principal foi avaliar se os concretos geopoliméricos são mais sustentáveis do que os concretos tradicionais. Os resultados obtidos mostraram que o consumo energético é reduzido em 45,8% na produção do concreto geopolimérico, quando comparado à produção do concreto de cimento Portland de desempenho mecânico equivalente. Com relação às emissões de CO2, o concreto geopolimérico reduz as emissões em 72,4%, em comparação ao concreto tradicional de cimento Portland CPII. Assim, o primeiro se mostra uma alternativa a ser considerada, na produção de materiais de construção de menor impacto ambiental

Nootropic and Antihypoxic Properties of Novel Derivatives of 1,2-Dihydro-3H-1,4-Benzodiazepin-2-one

Among eight recently synthesized 3-phthalimidoacyloxy- and phthalimidoacyloxyethoxy-1,2-dihydro-3H-1,4-benzodiazepin-2-ones, three compounds that enhanced the indices of cognitive functions in albino rats by 24–43%, as compared with those in control animals, were found. In the Morris water maze test, these agents used in doses of 10 mg/kg positively influenced the index of long-term memory in contrast to the hormone leptin (10 nM) that enhanced the index of short-term memory but did not influence long-term memory. Pyracetam enhanced the indices of both short-term memory and long-term memory, but only in a much greater dose (400 mg/kg). Injections of the above-mentioned three tested compounds into rats resulted in a decrease in the power of the delta EEG rhythm and also in rises in the powers of theta and (especially) beta oscillations. All eight tested compounds (in doses 10 mg/kg) demonstrated clearly pronounced antihypoxic effects under conditions of acute hypoxia in a closed space test in experiments on mice. Two compounds showed the maximum efficiency; those increased the survival time of mice by 76% and 50%, respectively, as compared with the control. Therefore, the eight tested compounds demonstrate, along with high antihypoxic efficiency, a specific aspect of pharmacological activity somewhat unusual for benzodiazepins; these compounds improve the longterm memory and learning capability and exert specific effects on the EEG characteristics. These compounds are characterized by low toxicity; their LD50 exceeds 550 mg/kg

Lossy Compression of Noisy Images Based on Visual Quality: A Comprehensive Study

This paper concerns lossy compression of images corrupted by additive noise. The main contribution of the paper is that analysis is carried out from the viewpoint of compressed image visual quality. Several coders for which the compression ratio is controlled in different manner are considered. Visual quality metrics that are the most adequate for the considered application (WSNR, MSSIM, PSNR-HVS-M, and PSNR-HVS) are used. It is demonstrated that under certain conditions visual quality of compressed images can be slightly better than quality of original noisy images due to image filtering through lossy compression. The &#8220;optimal&#8221; parameters of coders for which this positive effect can be observed depend upon standard deviation of the noise. This allows proposing automatic procedure for compressing noisy images in the neighborhood of optimal operation point, that is, when visual quality either improves or degrades insufficiently. Comparison results for a set of grayscale test images and several variances of noise are presented