Method of the phonon modulation of cryogenic hydrogen fuel structure in ITF targets

The possibility of spatial homogenization of the cryogenic hydrogen fuel structure in laser thermonuclear targets is considered. The results of a large cycle of experimental studies on low-temperature (T = 4.2 K) phonon modulation of the structure of solid hydrogen layers with various ortho-para compositions and its effect on the homogenization process rate are presented.     

Structure of bismuth oxoborate Bi<Subscript>4</Subscript>B<Subscript>2</Subscript>O<Subscript>9</Subscript> at 20, 200, and 450°C

Single crystals of bismuth oxoborate Bi₄B₂O₉ have been grown by slowly cooling the melt of a stoichiometric Bi₂O₃ + H₃BO₃ mixture. The structure of the borate (monoclinic space group P2₁/c, a = 11.107 Å, b = 6.629 Å, c = 11.044 Å, β = 91.04°, Z = 4) has been studied at 20, 200, and 450°C. The structure is described not only in terms of full BiO₆ ^? and BiO₇ polyhedra but also in terms of truncated BiO₃ ^? and BiO₄ ^? polyhedra and BO₃ triangles, as well as oxo-centered OBi₃ triangles and OBi₄ tetrahedra. It is shown that both the B-O and Bi-O bond lengths are practically unaffected by temperature. Only the angles between polyhedra change with temperature, being responsible for the strong anisotropy of Bi₄B₂O₆ thermal expansion, which was measured by high-temperature powder X-ray diffraction: α₁₁ = 20, α₂₂ = 15, α₃₃ = 6 × 10^?6 °C^?1, and μ = (c, α₃₃) = ?19°.     

Photonics of 18-crown-6-containing styryl dye and its complexes with metal cations

Using absorption, luminescence, ¹H NMR, and laser kinetic spectroscopies, the photophysical processes and photochemical reactions of 4-[(E)-2-(2,3,5,6,8,9,11,12,14,15-decahydro-1,4,7,10,13,16-benzohexaoxacyclooctadecin-18-yl)vinyl]-1-ethylpyridinium perchlorate and its complexes with lithium, sodium, potassium, calcium, barium, silver, and lead perchlorates in MeCN have been studied. The styryl dye and its complexes with metal cations are capable of emitting normal (prompt) and delayed fluorescence and enter into the trans–cis photoisomerization reaction. The dye molecules in the triplet state participate in the processes of degradation of electronic excitation energy. Triplet–triplet absorption is observed only in the presence of lead cations with a maximum at 470 nm and the deactivation rate constant of the triplet state k = 2.5 × 10⁴ s^–1 in a deoxygenated solution.     

Synthesis and electronic spectra of new low-molecular weight compounds with possible application in electroluminescent layers

Two new low-molecular weight compounds — (Z)-4-(4-(dimethylamino)benzylidene)-1-(9-ethyl-9H-carbazol-3-yl)-2-phenyl-1H-imidazol-5(4H)-one and 2-(6-hydroxyhexyl)-6-(pyrrolidin-1-yl)-1H-benzo[de]isoquinoline-1,3(2H)-dione) — with possible application in organic light-emitting devices were synthesized. Their photophysical properties in solution and in polymer films were investigated. The determined relative fluorescence quantum yields in solution for both compounds were 0.003 and 0.51, while those in poly(methyl methacrylate) films were around 0.10 and 1.0, respectively. For 1H-imidazol-5(4H)-one derivative, single-layer organic displays with one emitting layer were prepared by spin-coating technology. The applied voltage was 40 V (AC) with 1–3 KHz frequency. The emission maximum of the experimental AC display structures was at 600–630 nm. For displays with 2-(6-hydroxyhexyl)-6-(pyrrolidin-1-yl)-1H-benzo[de]isoquinoline-1,3(2H)-dione) the applied voltage was 60 V (AC) with 6-9 KHz frequency, but its future success will require more appropriate binding polymers. Based on the obtained experimental results, it is concluded that the investigated compounds could be applied for preparation of color electroluminescent structures.      

A Theoretical and Experimental Study of NMR Contrasting Properties of Nanocomposites Based on Ferric Oxides Stabilized by Arabinogalactan Matrix

Nuclear magnetic resonance relaxation properties of aqueous solution containing nanocomposites based on magnetite and maghemite nanoparticles stabilized by arabinogalactan obtained from Baikal larch (Larix sibirica) wood matrix were investigated. The relaxation properties of the solutions, namely, viscosity dependences of T ₁ and T ₂ and magnetic field dependence of T ₁, were studied experimentally. Two models of the nanocomposite granular structure corresponding to two limiting cases of ferromagnetic material distribution over the arabinogalactan matrix were considered. The first one assumes a homogeneous distribution of magnetite and maghemite nanoparticles over the spherical arabinogalactan matrix, while the second one considers a single hard ferromagnetic core at the center of the spherical arabinogalactan matrix. Theoretical fitting of the experimental results within these models was performed.     

Experimental study of the laminar-turbulent transition on a blunt cone

Results of an experimental study of the laminar-turbulent transition in a hypersonic flow around cones with different bluntness radii at a zero angle of attack, free-stream Mach number M _∞ = 6, and unit Reynolds number in the interval Re _∞,1 = 5.79 · 10⁶–5.66 · 10⁷ m^?1 are presented. Flow regimes in which a reverse of the laminar-turbulent transition (decrease in the length of the laminar segment with increasing bluntness radius) are studied. Heat flux distributions over the model surface are obtained with the use of temperature-sensitive paints. Lines of the beginning of the transition in the boundary layer are analyzed by using heat flux fields. The critical Reynolds number Re _∞,R ≈ 1.3 · 10⁵ beginning from which the laminar-turbulent transition substantially depends on uncontrolled disturbances, such as the model tip roughness, is found. In supercritical regimes, the line of the transition beginning is shifted in most cases toward the model tip (reverse of the transition). The results obtained are compared with available experimental data.     

Photonics of 18-crown-6-containing styryl dye and its complex with cucurbit[7]uril in the presence of lead cation

Russian Chemical Bulletin - The photophysical processes and photochemical reactions of...     

Determination of the Effective Surface of a Spent Spacecraft to Take into Account the Influence of Light Pressure on its Motion

Russian Physics Journal - A method for determining the effective surface area of a spent satellite depending on its spatial orientation is suggested on the example of the GLONASS spacecraft (SC)....     

Synthesis of quantum dot nanocrystals and plasmonic nanoparticles using a segmented flow reactor

The purpose of this research is to develop an automated method of synthesizing quantum dot nanocrystals and plasmonic nanoparticles using segmented flow rector synthesis as a new alternative to the batch method of synthesizing nanoparticles. A reactor was successfully applied to the synthesis of colloidal solutions of semiconductor (CdSe) and metal (Ag) nanoparticles. This instrument is applicable in both material science laboratories and industry.     

Microstructural study of He<Superscript>+</Superscript>-implanted and thermally annealed silicon-on-sapphire layers

The effect of He⁺ ion implantation and subsequent annealing on the silicon-on-sapphire microstructure is studied by transmission electron microscopy and X-ray diffraction analysis. It is established that He⁺ ion implantation leads to the formation of defects in the Si layer and α-Al₂O₃, while subsequent annealing causes dissociation of radiation defects in Si and formation of nanopores in α-Al₂O₃. The effect of implanted-ion dose and annealing temperature on the parameters of the porous α-Al₂O₃ layer and structural quality of the Si layer is investigated.