An unusual conformation of 1,1′-dimethyl-isoindigo in crystals

The crystal and molecular structure of 1,1′-dimethyl-isoindigo is studied by single crystal X-ray diffraction analysis. It is shown that the molecules of 1,1′-dimethyl-isoindigo are nonplanar due to the rotation of two oxindole rings relative to the double bond.     

On the extraction of gold(III) with dibutyl carbitol

Extraction of HAuCl₄ with diethylene glycol dibutyl ether (dibutyl carbitol) was studied in the gold(III) concentration range 10^?6?1.5 mol/L at c _HCl = 1 mol/L and T = 25°C, distribution ratios were determined. Experiments were made at other c _HCl. A unified extraction isotherm was obtained with the use of activity coefficients of HAuCl₄. The main extraction equilibrium is H _aq ⁺ + AuCl _4aq ^? = HAuCl_{4 org}, K ₀ (extractant and water molecules are omitted). For low c _AulogK ₀ = 1.89 ± 0.06. Dimerization equilibrium 2HAuCl_{4 org} = (HAuCl₄)_{2 org} has logK ₂ = 2.1. Extracts are electrically conducting, the share of ionic subsystem increases with C _Au and reaches about 10% at c _{Au org} = 0.1 mol/L. Alteration of phase volumes on extraction was studied: ??V _aq ?? ?0.20n _Au, ??V _org = ?0.8??V _aq, where n _Au is the number of moles of gold(III) that transfer from aqueous into organic phase. It was shown that 6 ± 1 water molecules are co-extracted with each HAuCl₄ molecule.     

Propagation and annihilation of vortex pairs in a smoothly inhomogeneous Bose-Einstein condensate

An asymptotic theory has been developed to describe the propagation and annihilation of vortex pairs in a smoothly inhomogeneous Bose-Einstein condensate with the repulsive interaction between atoms. It has been shown that the trajectories of vortex pairs coincide with geometric-optical rays in an equivalent isotropic medium with the refractive index depending both on the density of the unperturbed inhomogeneous condensate and on the energy of structures under study. The transformation of vortex pairs to vortex-free quasisolitons and back has been described.     

Osmium thioselenochloride Os<Subscript>2</Subscript>S<Subscript>6</Subscript>Se<Subscript>2</Subscript>Cl<Subscript>8</Subscript>: Synthesis,cluster isolation,and structure

The quaternary thioselenochloride complex Os₂S₆Se₂Cl₈ (I) was obtained by a reaction of OsO₄ with a solution of Se in S₂Cl₂ at 100°C and identified by combination of X-ray diffraction (polycrystalline approach) and cluster framework isolation. A reaction of complex I with melted 4-cyanopyridine (4-CNPy) at 165°C gave the complex Os₂S₂Cl₄(4-CNPy)₄, which confirms the integrity of the binuclear cluster frame-work [Cl₂OsS₂OsCl₂] in complex I.     

Synthetic transformations of higher terpenoids: XXVIII. Diels-Alder reactions of 16-(trimethylsiloxybutadienyl) labdanoids

15,16-Epoxy-16-(3-trimethylsiloxybuta-1,3-dien-1-yl)labdanoids were synthesized, and their reactions with cyclic dienophiles (1,4-benzoquinone, 1,4-toluquinone, 2-bromo-6-methyl-1,4-benzoquinone, and N-methylmaleimide) were studied. The reactions with unsymmetrically substituted benzoquinones were not selective. Methods for the preparation of hybrid compounds containing furan diterpenoid and substituted naphthoquinone, octahydroisoindoletrione, or hexahydroisoindoledione fragments were proposed.     

Supercritical fluid micronization of risperidone pharmaceutical substance

A comparative study of the supercritical fluid micronization of risperidone pharmaceutical substance with an initial particle size of 50 to 100 μm by the RESS and SAS methods aimed at increasing the bioavailability of risperidone as a drug was performed. Both methods makes it possible to prepare risperidone particle of various forms, 5–20 μm in size. However, the SAS method is preferable, because in contrast to RESS, it does not cause contamination of risperidone with organic solvents used in both processes or any other impurities and also makes it possible to vary the shape and size of particles. It is shown that, during SAS micronization, the polymorphic form of risperidone changes from triclinic to monoclinic.     

Wave processes in the shock layer on a flat plate at an angle of attack

A numerical and experimental study of receptivity of the viscous shock layer on a flat plate aligned at an angle of attack to external acoustic perturbations is performed. Density and pressure fluctuations are measured in experiments at the free-stream Mach number M _∞ = 21 and Reynolds number Re ₁ = 6·10 ⁵ m ⁻¹ . Direct numerical simulations of receptivity of the viscous shock layer to external acoustic perturbations in wide ranges of the governing parameters are performed by solving the Navier-Stokes equations with the use of high-order shock-capturing schemes. The calculated intensities of density and pressure fluctuations are found to be in good agreement with experimental data. Results of the study show that entropy-vortex disturbances dominate in the shock layer at small angles of attack, whereas acoustic perturbations prevail at angles of attack above 20°.     

Crystal and molecular structure of 11,12-dihydroxydrim-8(9)-en-7-one

The crystal structure of 11,12-dihydroxydrim-8(9)-en-7-one was determined by X-ray diffraction. The unit cell parameters are a = 7.534(3), b = 12.192(5), c = 8.067(4) Å, β = 98.01(3) Å, space group P2₁, and Z = 2 for C₁₅H₂₄O_3. The structure was solved by direct methods and refined in the anisotropic approximation to R = 0.051 and R _w = 0.113. The intramolecular O-H?O hydrogen bond [2.892(6) Å] between the hydroxy groups closes an additional seven-membered H-ring in the molecule. In the crystal, the intermolecular O-H?O hydrogen bond [2.857(4) Å] between the hydroxyl group and the carbonyl oxygen atom links the molecules related by the translation along the c-axis to form infinite chains.     

Ultrahigh-spatial-resolution field-emission projection microscopy of insulating samples

The method of ultrahigh-spatial-resolution field-emission projection imaging of nonconducting tips is implemented experimentally. An image of a glass microcapillary tip was obtained for the first time by the nonscanning method with spatial resolution no worse than 20 nm.     

New Cysteine-Containing PEG-Glycerolipid Increases the Bloodstream Circulation Time of Upconverting Nanoparticles

Upconverting nanoparticles have unique spectral and photophysical properties that make them suitable for development of theranostics for imaging and treating large and deep-seated tumors. Nanoparticles based on NaYF₄ crystals doped with lanthanides Yb³⁺ and Er³⁺ were obtained by the high-temperature decomposition of trifluoroacetates in oleic acid and 1-octadecene. Such particles have pronounced hydrophobic properties. Therefore, to obtain stable dispersions in aqueous media for the study of their properties in vivo and in vitro, the polyethylene glycol (PEG)-glycerolipids of various structures were obtained. To increase the circulation time of PEG-lipid coated nanoparticles in the bloodstream, long-chain substituents are needed to be attached to the glycerol backbone using ether bonds. To prevent nanoparticle aggregation, an L-cysteine-derived negatively charged carboxy group should be included in the lipid molecule.