Measurement of the speed of sound by observation of the Mach cones in a complex plasma under microgravity conditions

We report the first observation of the Mach cones excited by a larger microparticle (projectile) moving through a cloud of smaller microparticles (dust) in a complex plasma with neon as a buffer gas under microgravity conditions. A collective motion of the dust particles occurs as propagation of the contact discontinuity. The corresponding speed of sound was measured by a special method of the Mach cone visualization. The measurement results are incompatible with the theory of ion acoustic waves. The estimate for the pressure in a strongly coupled Coulomb system and a scaling law for the complex plasma make it possible to derive an evaluation for the speed of sound, which is in a reasonable agreement with the experiments in complex plasmas.Comment: 5 pages, 2 figures, 1 tabl

Soviet Diplomacy and the All-Muslim Congress in Saudi Arabia

The article was submitted on 5.09.2018.В статье представлены малоизвестные страницы истории всемусульманских конгрессов и халифатистского движения XIX — первой трети XX вв. Автор раскрывает тесную взаимосвязь концепции халифата и идей мусульманского единства, а также причины провала попыток реализовать подобные проекты на практике в османскую эпоху. Историческая картина подготовки и проведения первых всемусульманских конгрессов в Каире и Мекке в 1926 г. представлена в контексте меняющейся системы международных отношений и процесса формировании нового геополитического пространства на Ближнем Востоке. Автор приходит к выводу о том, что исламский фактор стал эффективным инструментом внешней политики СССР, позволившим в 1920-е гг. усилить советские позиции в Аравии и в исламском мире.The article presents little-known chapters of the history of all-Muslim congresses and the caliphate movement of the XIX - the first third of the XX centuries. The author reveals a close link between the concept of the caliphate and the ideas of Muslim unity, as well as the cause of failed attempts to implement such projects in practice in the Ottoman era. The historical picture of the preparation and holding of the first all-Muslim congresses in Cairo and Mecca in 1926 is presented in the context of changing international relations’ system and formation of new geopolitical space in the Middle East. The author comes to conclusion that the Soviet diplomacy was able to use the Islamic factor as an effective instrument of Soviet foreign policy and thereby to promote the Soviet interests in Arabia and the Islamic world in the 1920s.Работа выполнена при под держке Международного дискуссионного клуба «Валдай»

Рецензия на книгу: Гусева Ю.Н., Сенюткина О.Н., Христофоров В.С. Пытаясь понять и вообразить ислам… (образ ислама в сознании российских элит 1880-х — 1920-х гг.): монография. М.: Медина, 2021. 460 с.

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Freezing and melting of 3D complex plasma structures under microgravity conditions driven by neutral gas pressure manipulation

Freezing and melting of large three-dimensional complex plasmas under microgravity conditions is investigated. The neutral gas pressure is used as a control parameter to trigger the phase changes: Complex plasma freezes (melts) by decreasing (increasing) the pressure. Evolution of complex plasma structural properties upon pressure variation is studied. Theoretical estimates allow us to identify main factors responsible for the observed behavior.Comment: Phys. Rev. Lett. (in press); 4 pages, 4 figure

Fluid-solid phase transitions in 3D complex plasmas under microgravity conditions

Phase behavior of large three-dimensional complex plasma systems under microgravity conditions onboard the International Space Station is investigated. The neutral gas pressure is used as a control parameter to trigger phase changes. Detailed analysis of structural properties and evaluation of three different melting/freezing indicators reveal that complex plasmas can exhibit melting by increasing the gas pressure. Theoretical estimates of complex plasma parameters allow us to identify main factors responsible for the observed behavior. The location of phase states of the investigated systems on a relevant equilibrium phase diagram is estimated. Important differences between the melting process of 3D complex plasmas under microgravity conditions and that of flat 2D complex plasma crystals in ground based experiments are discussed.Comment: 13 pages, 10 figures; submitted to Phys. Rev.

Phenomena in Complex (Dusty) Plasma Studied under Microgravity Conditions

Complex (dusty) plasmas are composed of weakly ionized gas and charged microparticles and represent the plasma state of soft matter. The investigations which are not available on ground have been per-formed onboard the International Space Station (ISS) with the help of the “Plasma Crystal-3 Plus” (PK-3 Plus) laboratory. A number of interesting phenomena has been observed. The phase transition from iso-tropic plasma into electrorheological plasma was initiated. The crystal-liquid phase transition was ob-tained in large 3D isotropic dusty plasma. The slow compression of the dust particle subsystem has been investigated

Сучасні "західні" та "східні" революції: класична складова і особливості здійснення

Наумкіна С. М., Кравець Г. В. Сучасні "західні" та "східні" революції: класична складова і особливості здійснення / С. М. Наумкіна, Г. В. Кравець // Актуальні проблеми політики зб. наук. пр. / редкол.: С. В. Ківалов (голов. ред.), Л. І. Кормич (заст. голов. ред.), М. А. Польовий (відп. секр.) [та ін.] ; НУ «ОЮА», Південноукр. центр гендер. проблем. – Одеса : Фенікс, 2015. – Вип. 56. – С. 173-181.Розглядається здійснення сучасних революцій, в межах яких виявляється те спільне, що поєднує сучасні та класичні революції, а також виявляє те нове, що привнесли «кольорові» революції в світовий політичний процес останніх десятиліть

Plasmon Resonance of Silver Nanoparticles as a Method of Increasing Their Antibacterial Action

In this article, a series of silver-containing dressings are prepared by metal-vapor synthesis (MVS), and their antibacterial properties are investigated. The antibacterial activity of the dressings containing silver nanoparticles (AgNPs) against some Gram-positive, and Gram-negative microorganisms (Staphylococcus aureus, Staphylococcus haemolyticus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Moraxella spp.) has been determined. Based on the plasmon resonance frequency of these nanoparticles, the frequency of laser irradiation of the dressing was chosen. The gauze bandage examined showed pronounced antibacterial properties, especially to Staphylococcus aureus strain. When 470 nm laser radiation, with a power of 5 mW, was applied for 5 min, 4 h after inoculating the Petri dish, and placing a bandage containing silver nanoparticles on it, the antibacterial effect of the latter significantly increased—both against Gram-positive and Gram-negative microorganisms. The structure and chemical composition of the silver-containing nanocomposite were studied by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS). The synthesized AgNPs demonstrate narrow and monomodal particle size distribution with an average size of 1.75 nm. Atoms of metal in Ag/bandage system are mainly in Ag0 state, and the oxidized atoms are in the form of Ag-Ag-O groups

Russia and the Arab Spring: supporting the counter-revolution

Russia’s response to the Arab Spring ranged from apprehension to deep anxiety and diverged significantly from the US and the EU responses. While initially welcoming the popular demands for political reform in North Africa, the Russian reaction rapidly became more critical as a result of Western military intervention into Libya and the threat of the spread of Islamist extremism. It was these twin fears which prompted the Russian leadership to adopt an uncompromizing stance towards Syria. While geopolitical factors certainly played a role in driving Russian strategy, domestic political factors were also more significant. As the Russian leadership felt internally threatened by the growing opposition within the country, conflict in the Middle East highlighted the perceived flaws of the imposition of Western liberal democracy and the virtues of Russia’s own model of state-managed political order. There was, as such, a significant ideational and ideological dimension to the Russian response to the Arab Spring