Approaches to Novel B-N Chemistry at the Boundary of Frustrated Lewis Pairs and Bifunctional Catalysis

This project is devoted to boron chemistry in two ways. Firstly, the development of the boron – nitrogen “Frustrated” Lewis Pairs (FLPs) was investigated by combining the principles of this approach with known bifunctional catalytic methods. This also included design and synthetic efforts towards new bifunctional catalysts 108 and 157 on the basis of L-proline connected to Lewis acidic borane or borinic derivatives, which revealed multiple peculiarities of boron chemistry. Catalyst 176 was successfully utilised in nitro-Michael addition reaction. Secondly, boronic acids are promising catalysts for the important process of direct amide formation, which is a much more atom efficient and sustainable alternative to the current industrial approaches to amide synthesis. However, the mechanism of action of boronic acids in this process is not yet well understood, while this is crucial for effective design and future application of catalysts for direct amide formation. Thus the roles of both borinic and boronic acids in direct amide formation reactions were investigated. This included isolation of multiple Lewis adducts formed as intermediates or byproducts in different reaction mixtures between amines, carboxylic acids and boron-containing compounds. These results have helped to better understand the reactivity of boron-based catalysts and allowed development of the new mechanistic understanding of boronic acids in direct amide formation. These finding underlined the complexity of boron-containing systems, the importance of boron-nitrogen Lewis adduct interactions and the high possibility of multiple boron atoms orchestrating the investigated processes. The non-catalytic thermal direct amide formation reaction was also studied both in flow and microwave reactors in order to better understand these complex multicomponent systems

Low Threshold Parametric Decay Instabilities in ECRH experiments at toroidal devices

The experimental conditions leading to substantial reduction of backscattering decay instability threshold in ECRH experiments in toroidal devices are analyzed. It is shown that drastic decrease of threshold is provided by non monotonic behaviour of plasma density, which is often observed due to so-called density-pump-out effect or presence of magnetic islands, and by poloidal magnetic field inhomogeniety making possible localization of ion Bernstein decay waves. The corresponding ion Bernstein wave gain and the parametric decay instability pump power threshold is calculated. The possible experimental consequences of easy backscattering decay instability excitation are discussed.Comment: 12 pages, 8 figures, submitted to Nuclear Fusio

Solitary waves on a ferrofluid jet

The propagation of axisymmetric solitary waves on the surface of an otherwise cylindrical ferrofluid jet subjected to a magnetic field is investigated. An azimuthal magnetic field is generated by an electric current flowing along a stationary metal rod which is mounted along the axis of the moving jet. A numerical method is used to compute fully-nonlinear travelling solitary waves and predictions of elevation waves and depression waves by Rannacher & Engel (2006) using a weakly-nonlinear theory are confirmed in the appropriate ranges of the magnetic Bond number. New nonlinear branches of solitary wave solutions are identified. As the Bond number is varied, the solitary wave profiles may approach a limiting configuration with a trapped toroidal-shaped bubble, or they may approach a static wave (i.e. one with zero phase speed). For a sufficiently large axial rod, the limiting profile may exhibit a cusp

Axisymmetric solitary waves on the surface of a ferrofluid

We report the first observation of axisymmetric solitary waves on the surface of a cylindrical magnetic fluid layer surrounding a current-carrying metallic tube. According to the ratio between the magnetic and capillary forces, both elevation and depression solitary waves are observed with profiles in good agreement with theoretical predictions based on the magnetic analogue of the Korteweg-deVries equation. We also report the first measurements of the velocity and the dispersion relation of axisymmetric linear waves propagating on the cylindrical ferrofluid layer that are found in good agreement with theoretical predictions.Comment: to be published in Phys. Rev. Let

Attention-Based Neural Networks for Sentiment Attitude Extraction using Distant Supervision

In the sentiment attitude extraction task, the aim is to identify > -- sentiment relations between entities mentioned in text. In this paper, we provide a study on attention-based context encoders in the sentiment attitude extraction task. For this task, we adapt attentive context encoders of two types: (1) feature-based; (2) self-based. In our study, we utilize the corpus of Russian analytical texts RuSentRel and automatically constructed news collection RuAttitudes for enriching the training set. We consider the problem of attitude extraction as two-class (positive, negative) and three-class (positive, negative, neutral) classification tasks for whole documents. Our experiments with the RuSentRel corpus show that the three-class classification models, which employ the RuAttitudes corpus for training, result in 10% increase and extra 3% by F1, when model architectures include the attention mechanism. We also provide the analysis of attention weight distributions in dependence on the term type.Comment: 10 pages, 9 figures. The preprint of an article published in the proceedings of the 10th International Conference on Web Intelligence, Mining and Semantics (WIMS 2020). The final authenticated publication is available online at https://doi.org/10.1145/3405962.3405985. arXiv admin note: substantial text overlap with arXiv:2006.1160

The influence of nitrogen admixture on concentration of an electronic–excited helium atoms in atmospheric pressure glow discharge

The concentrations of the low-excited helium atoms in states 2¹S, 2¹P, 2³S and 2³P were determined in the atmospheric pressure glow discharge in helium (99.98%He) and in helium with a nitrogen admixture (99.5%He + 0.5%N2). It was shown that the adding of nitrogen into helium leads to the drastically reduction of concentration of both the low-excited helium atoms and ions.Визначено концентрації низьких збуджених атомів гелію в станах 2¹S, 2¹P, 2³S і 2³P у тліючому розряді при атмосферному тиску в гелії (99.98%He) і в суміші гелію з азотом (99.5%He + 0.5%N2). Показано, що додавання азоту в гелій приводить до істотного зменшення як заселенностей нижніх збуджених рівнів гелію, так і концентрації іонів гелію.Определены концентрации низких возбужденных атомов гелия в состояниях 2¹S, 2¹P, 2³S и 2³P в тлеющем разряде при атмосферном давлении в гелии (99.98%He) и в смеси гелия с азотом (99.5%He + 0.5%N2). Показано, что добавление азота в гелий приводит к существенному уменьшению как заселенностей нижних возбужденных уровней гелия, так и концентрации ионов гелия

ДУГОВОЙ АТОМНО-ЭМИССИОННЫЙ АНАЛИЗ ОКСИДА ЛЮТЕЦИЯ

The requirements for the composition of initial oxides for the lutetium orthosilicate crystals are quite stringent: the content of the basic substance Lu2O3 is 99.999 wt%. Critical are coloring impurities: Fe, Ni, Cr, Co, Cu, V, Mn, the content of each should be no more than 0.0005 - 0.0010 wt%, Pr, Nd, Sm, Er, Tb, Yb no more than 0.0005 wt% for each one. It is also necessary to control the content of Al, As, Bi, Cd, Mg, Mo, Pb, Sb, Si, Sn, Ti, Zn, Y, La, Ce, Sc, Eu, Gd, Dy, Ho, Tm. To determine the impurity composition of lutetium oxide, one of the promising methods of analysis is direct arc atomic emission spectroscopy (DC Arc). The advantages of this method are the determination of the chemical composition without sample dissolution, a wide range of concentrations (10-6 - 10-1% wt%), a large number of determined elements. To realize the potential analytical capabilities of the method, the experimental conditions were studied: the interelectrode distance, the shape and size of graphite electrodes, the ratio of Lu2O3 to the spectral buffer, the type of carriers and operating modes of the generator. For most elements, the limits of determination are n ∙ 10-6 - n ∙ 10-4 wt%, that is significantly lower than in the current methods of DC Arc. The trueness of results is controlled by ICP-MS. The complex application of new approaches and modern capabilities of spectral equipment made it possible to develop a method with improved metrological characteristics.Keywords: Lutetium oxide, spectral analysis, direct current arc atomic emission spectrometry, method developmentDOI: http://dx.doi.org/10.15826/analitika.2021.25.2.008Elizaveta Sergeevna Koshel1, Arkhipenko Alexandra Alexandrovna2, Baranovskaya Vasilisa Borisovna21State Research and Design Institute of Rare Metal Industry Giredmet,ul. Elektrodnaya, 2, Moscow, 111524, Russian Federation2Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskij prospect, 31, Moscow, 119991, Russian FederationОртосиликат лютеция является перспективным сцинтилляционным материалом, оптические свойства которого напрямую зависят от его примесного состава. Требования к исходным оксидам, используемым для выращивания кристаллов состава Lu2SiO5:Ce достаточно жесткие: содержание основного вещества Lu2O3 – 99.999 % мас. Критическими являются красящие примеси: Fe, Ni, Cr, Co, Cu, V и Mn, содержание каждого из которых должно быть не более 0.0005 – 0.0010 % мас., Pr, Nd, Sm, Er, Tb, Yb – не более 0.0005 % мас. каждого. Также необходимо контролировать содержние Al, As, Bi, Cd, Ce, Dy Eu, Gd, Ho, La, Mg, Mo, Pb, Sb, Sc, Si, Sn, Tm. Ti, Zn, Y. Для определения примесного состава оксида лютеция одним из перспективных методов анализа является дуговая атомно-эмиссионная спектрометрия. Преимуществами данного метода являются анализ химического состава без перевода пробы в раствор и широкий диапазон определяемых концентраций (10-6 – 10-1 % мас.). Для реализации потенциальных аналитических возможностей метода исследованы следующие условия эксперимента: межэлектродное расстояние, форма и размер графитовых электродов, соотношение оксида лютеция и спектрального буфера (графитовый порошок), тип носителей (соединений, влияющих на испарение аналитов), режимы работы генератора. Для большинства элементов нижняя граница диапазона определяемых концентраций находится в интервале n∙10-6 – n∙10-4 % мас., что значительно ниже, чем в действующих методиках прямого дугового атомно-эмиссионного анализа. Контроль правильности результатов, которые были получены по разработанной методике, осуществлен с использованием метода масс-спектрального анализа с индуктивно связанной плазмой. Благодаря результатам, полученным с помощью современного спектрального оборудования и программных средств, разработана методика анализа оксида лютеция без предварительного растворения пробы, с улучшенными метрологическими показателями и расширенным кругом определяемых примесей по сравнению со стандартизованной методикой.Ключевые слова. Лютеция оксид, спектральный анализ, дуговая атомно-эмиссионная спектрометрия, оптимизация условий определенияDOI: http://dx.doi.org/10.15826/analitika.2021.25.2.00

The chaos control in parametric decay instability of stimulated backscattering by a pump frequency modulation

The chaotic behavior of nonlinear three-wave system in which the inhomogeneous plasma absolute parametric decay instability of stimulated backscattering l → l’ + s is excited is investigated. The possibility of transition threewave system from chaotic to regular behavior under influence of pump frequency modulation is demonstrated experimentally.Нелінійна трихвильова система, що приводить до абсолютної параметричної нестійкості змушеного розсіювання назад у неоднорідній замагніченій плазмі досліджується щодо стану динамічного хаосу. Експериментально продемонстровано перехід трихвольової системи зі стану хаотичного поводження в регулярне за допомогою гармонійної частотної модуляції хвилі накачування.Нелинейная трехволновая система, приводящая к абсолютной параметрической неустойчивости вынужденного рассеяния назад в неоднородной замагниченной плазме исследуется относительно состояния динамического хаоса. Экпериментально продемонстрирован переход трехволновой системы из состояния хаотического поведения в регулярное с помощью гармонической частотной модуляции волны накачки