The Theory of Propagation of Acoustic Waves in a Vapor-gas Mixture with Polydispersed Droplets and Particles

The propagation of small disturbances in a two-component gas-vapor mixture with polydispersed particles and drops in the presence of phase transitions is studied. A mathematical model is proposed, the dispersion relation is obtained. The effect of the droplets and particles polydispersity on the dispersion and dissipation of small disturbances is analyzed. Comparison of the theory with experimental data is presented.The propagation of small disturbances in a two-component gas-vapor mixture withpolydispersed particles and drops in the presence of phase transitions is studied. A mathematicalmodel is proposed, the dispersion relation is obtained. The effect of the droplets and particlespolydispersity on the dispersion and dissipation of small disturbances is analyzed. Comparison ofthe theory with experimental data is presented

Дослідження властивостей ресурсозберігаючої хромвмісної брикетованої легуючої добавки із рудної сировини

It was determined that the original oxide chromium-containing ore raw material is represented by granules of rounded shape the size of 250–600 µm. Along with Cr and Fe, it revealed Mg, Al, Si, Ca, and Ti. They probably were included in the composition of oxide ore impurities and can exert an indirect influence on the reducing processes. Phase composition of the briquetted raw material after the carbon thermal treatment consisted mainly of Cr2O3 and metal Cr with the presence of carbides Cr7C3 and Cr2C3. Diffraction maxima of metal Fe and its compounds had no explicit manifestation, indicating the presence of Fe as substitution atoms in the chromium-containing phases and compounds. The structure is heterogeneous.The content of residual oxygen confirms the presence, along with metal Cr, under-reduced oxide or oxy-carbide compounds. The residual oxygen could also be contained in the composition of oxide related ore impurities. This is confirmed by detection of the specified elements in the examined areas in the images of the microstructure. Excessive carbon content ensures the post-reduction of residual oxide component in a liquid metal in the process of alloying and enables protection against secondary oxidation of chromiumИсследованы фазовый состав, микроструктура хромсодержащего оксидного рудного сырья и соответствующих продуктов углеродотермического восстановления. Опытно-промышленным путем получен ресурсосберегающий хромсодержащий брикетированный легирующий материал с качественно новыми свойствами. Выявлена неоднородная оксикарбидная структура с избыточным содержанием углерода, что обеспечивает довосстановление остаточной оксидной составляющей при легировании и защиту от вторичного окисления хромаДосліджено фазовий склад, мікроструктуру хромвмісної оксидної рудної сировини і відповідних продуктів вуглецевотермічного відновлення. Дослідно-промисловим шляхом отримано ресурсозберігаючий хромвмісний брикетований легуючий матеріал з якісно новими властивостями. Виявлено неоднорідну оксикарбідну структуру з надлишковим вмістом вуглецю, що забезпечує довідновлення залишкової оксидної складової при легуванні та захист від вторинного окислення хром

Optical Properties and In Vitro Biological Studies of Oligonucleotide-Modified Quantum Dots

Water-soluble semiconducting nanocrystals or quantum dots (QDs) have attracted much interest in recent years due to their tuneable emission and potential applications in photonics and biological imaging. Fluorescence resonance energy transfer (FRET) processes are very important for elucidating biochemical mechanisms in vitro, and QDs constitute an excellent substrate for this purpose. In this work, new oligonucleotide-functionalised CdTe-based QDs were prepared, characterised and biologically tested. These QDs demonstrated interesting optical properties as well as remarkable in vitro behaviour and potential for a range of biological applications

Chiral quantum supercrystals with total dissymmetry of optical response

Since chiral nanoparticles are much smaller than the optical wavelength, their enantiomers show little difference in the interaction with circularly polarized light. This scale mismatch makes the enhancement of enantioselectivity in optical excitation of nanoobjects a fundamental challenge in modern nanophotonics. Here we demonstrate that a strong dissymmetry of optical response from achiral nanoobjects can be achieved through their arrangement into chiral superstructures with the length scale comparable to the optical wavelength. This concept is illustrated by the example of the simple helix supercrystal made of semiconductor quantum dots. We show that this supercrystal almost fully absorbs light with one circular polarization and does not absorb the other. The giant circular dichroism of the supercrystal comes from the formation of chiral bright excitons, which are the optically active collective excitations of the entire supercrystal. Owing to the recent advances in assembly and self-organization of nanocrystals in large superparticle structures, the proposed principle of enantioselectivity enhancement has great potential of benefiting various chiral and analytical methods, which are used in biophysics, chemistry, and pharmaceutical science

Annelated tricyclic thiophenes and their photophysical properties

Photochemical oxidative cyclization of 3-[(E)-2-(3,4-di-methoxyphenyl)vinyl]thiophene and its 15-crown-5-analogue (15-[(E)-2-(3-thienyl)vinyl]-2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecine) affords the isomeric thiophene-containing fused aromatic compounds demonstrating photophysical properties different from those of initial styryl derivatives. E-Configuration of the initial styryl dye, 3-[(E)-2-(3,4-dimethoxyphenyl)vinyl]thiophene, has been proved by X-ray analysis

Engineering Optical Activity of Semiconductor Nanocrystals via Ion Doping

Controlling the strength of enantioselective interaction of chiral inorganic nanoparticles with circularly polarized light is an intrinsically interesting subject of contemporary nanophotonics. This interaction is relatively weak, because the chirality scale of nanoparticles is much smaller than the optical wavelength. Here we theoretically demonstrate that ion doping provides a powerful tool of engineering and enhances optical activity of semiconductor nanocrystals. We show that by carefully positioning ionic impurities inside the nanocrystals, one can maximize the rotatory strengths of intraband optical transitions, and make them 100 times larger than the typical rotatory strengths of small chiral molecules