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

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

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

Identifying the Azobenzene/Aniline reaction intermediate on TiO2-(110) : a DFT Study

Density functional theory (DFT) calculations, both with and without dispersion corrections, have been performed to investigate the nature of the common surface reaction intermediate that has been shown to exist on TiO2(110) as a result of exposure to either azobenzene (C6H5N═NC6H5) or aniline (C6H5NH2). Our results confirm the results of a previous DFT study that dissociation of azobenzene into two adsorbed phenyl imide (C6H5N) fragments, as was originally proposed, is not energetically favorable. We also find that deprotonation of aniline to produce this surface species is even more strongly energetically disfavored. A range of alternative surface species has been considered, and while dissociation of azobenzene to form surface C6H4NH species is energetically favored, the same surface species cannot form from adsorbed aniline. On the contrary, adsorbed aniline is much the most stable surface species. Comparisons with experimental determinations of the local adsorption site, the Ti–N bond length, the molecular orientation, and the associated C 1s and N 1s photoelectron core level shifts are all consistent with the DFT results for adsorbed aniline and are inconsistent with other adsorbed species considered. Possible mechanisms for the hydrogenation of azobenzene required to produce this surface species are discussed

ОСОБЕННОСТИ ОНТОГЕНЕЗА СКЕЛЕТА ГОЛОВЫ САМЦОВ АМЕРИКАНСКОЙ НОРКИ ГЕНОТИПОВ STANDARD И LAVENDER (в норме и при воздействии препарата биостил)

The paper explores Biostil specimen on the American mink males of Standard and Lavender genotypes. The males selected were of different age from the experimental fur farm of theInstituteofCytologyand Genetics of Siberian Department ofRussianAcademyof Science. The paper is aimed at investigation of the influence on the growth and development of American mink males’ case brain skeleton of different genotypes aged 40–50; 86–90 and 176–180 days. The mink stock was bred by parents who were fed with Biostil dozed 0.05 ml/kg of body weight during 5 days before oestrum and during the oestrum. The authors observed the control animals who were not fed with Biostil. The mink stock was divided into the experimental and control groups according to the age and genotype features. The research was conducted by means of descriptive anatomic method and craniometric features. The authors found out 18 craniometric features. The research results show that Biostil influences positively morphogenesis of American mink males’ case brain of Standard genotype and some negative impact of Biostil on Lavender genotype. These impacts are mostly observed in the group of the males of reproductive age. Biostil impact on the morphogenesis of Lavender minks (a/a m/m) is followed by the changes in physiological parameters of growth and development of case brain that are mostly observed in the reproductive age. This impact is characterized by lower parameters of the case brain and lower growth of dorsal, ventral, cervical and sagittal crests.Проведены исследования препарата биостил на самцах американских норок генотипов Standard и Lavender разных возрастных групп на экспериментальной звероферме Института цитологии и генетики СО РАН. Целью работы являлось изучение влияния препарата биостил на рост и развитие скелета самцов американской норки разных окрасочных генотипов в возрасте 40–50; 86–90 и 176–180 дней на примере черепа. Поголовье норчат было получено от родительских пар, которым добавляли в корм биостил перед гоном в течение 5 дней и в период гона трёхкратно через день в дозе 0,05 мл/кг массы тела. Контролем служили животные, родители которых не получали с кормом биостил. Потомство было разделено на опытные и контрольные группы в соответствии с возрастными и генотипическими особенностями. Исследования проводили с помощью описательного анатомического метода и краниометрических измерений. Определено 18 краниометрических показателей. Результаты проведенных исследований позволяют сделать вывод о положительном влиянии препарата на морфогенез черепа самцов американской норки генотипа Standard и некотором угнетающем влиянии биостила на формирование черепа самцов американской норки генотипа Lavender. Указанные воздействия препарата наиболее выражены в группе самцов репродуктивного периода. Воздействие препарата на морфогенез черепа особей Lavender (a/a m/m) сопровождается изменением физиологических параметров роста и развития черепа, которые более четко проявляются в репродуктивном периоде и выражаются уменьшением размеров черепа, снижением активности роста дорсального, вентрального, затылочного и сагиттального гребней

Understanding Russia's return to the Middle East

Over recent years, there has been a significant resurgence of Russian power and influence in the Middle East, which has been evident in the diplomatic and military intervention into Syria. This article identifies the principal factors behind Russia’s return to the region. First, there are domestic political influences with the coincidence of the uprisings in the Middle East, the so-called ‘Arab Spring,’ with large-scale domestic opposition protests within Russia during the elections in 2011–2012. Second, there is the role of ideas, most notably the growing anti-Westernism in Putin’s third presidential term, along with Russia’s own struggle against Islamist terrorism. These ideational factors contributed to Russia’s resolve to support the Assad government against both Western intervention and its domestic Islamist opposition. Third, Russia has benefited from a pragmatic and flexible approach in its engagement with the region. Moscow seeks to ensure that it is a critical actor for all the various states and political movements in the Middle East