Tether-controlled cycloadditions for the asymmetric synthesis of decalins: increased selectivity in acetonitrile solvent

[reaction: see text] The beneficial influence of cis-isopropylidene acetal tether control groups, to facilitate the asymmetric synthesis of substituted decalins by intramolecular Diels-Alder reactions, is described. Compared to trans-acetonides, these cases proceed under milder conditions to afford the cis-fused adducts from an endo transition state. An unusual acetonitrile solvent effect exerts a dramatic influence on the diastereoselectivity. This strategy leads to the chiral nonracemic bicyclo[4.4.0]decane core of diverse natural products.     

Possibilities of structural engineering in multilayer vacuum-arc ZrN/CrN coatings by varying the nanolayer thickness and application of a bias potential

The possibility of attaining an superhard state in multilayer vacuum-arc ZrN/CrN coatings with a layer thickness of about 20 nm has been established. It has been shown that the application of a constant negative potential for structural engineering during deposition leads to the formation of solid solutions due to mixing of interfaces. The hardness of these systems exceeds 30 GPa. The application of a pulsed high-voltage bias potential at which the ordering of atoms stimulated by elevated mobility is observed makes it possible to suppress the mixing of the interfaces and to attain elevated hardness (up to 42 GPa) for nanometer layer thicknesses.     

Generation of Surface Defects in Epitaxial Cd x Hg1–xTe Layers by Soft X-ray Radiation of Laser Plasma

Russian Physics Journal - The possibility is demonstrated of a selective action of soft X-ray radiation on atoms of an individual element on the surface of a crystal constructed of atoms of several...     

Explosion with plasma quasitrapping in a dipole field

Experiments using a powerful CO₂ amplifier were performed with the aim of developing a technique for simulating a space explosion in the magnetosphere of the Earth and other planets under laboratory conditions using laser plasma clouds. The amplifier radiation with an energy of about 300 J and a pulse duration of about 10^–7 sec focused on a Caprolon target of 4 mm diameter produced an exploding plasma in a dipole magnetic field with a characteristic dimension of 15 cm and a magnetic moment of 1.1·10⁷ Gs · cm³. The paper presents preliminary results of simulating a space explosion under quasitrapping conditions, where the energy of the explosion is much lower than the geomagnetic energy and the explosion point is located in the equatorial plane at a distance of two Earth's radii.     

Formation of Ion Fluxes of Laser Plasma by Azimuthally Symmetric Magnetic Fields

Physics of Atomic Nuclei - The formation of ion fluxes of the laser plasma by axially symmetric magnetic fields is studied. An algorithm for forming ion fluxes is developed and a computer...     

On optically detected ESR spectra from radical cations of liquid hydrocarbon solvents

The optically detected electron spin resonance (OD ESR) method has been employed to study the origin of radical-cation ESR signals in some saturated hydrocarbons with small amounts of 2.5-diphenyloxazol or p-terphenyl under radiolysis. In cyclohexane, the ESR, signal with resolved hyperfine structure was ascribed to c-C₆H₁₀⁺/PPO^? radical-ion pairs produced from primary c-C₆H₁₂⁺/PPO^? ones by monomolecular decay, of cyclohexane radical cations to cyclohexene radical cations. Cis- and trans-decalin under radiolysis accumulate 9,10-octalin which captures solvent holes and form 9,10-octalin radical cations giving a resolved OD ESR spectrum. 9,10-octalin is present in non-irradiated commercial decalin as an impurity. The OD ESR technique has been shown to be very sensitive to some impurities in hydrocarbon solvents.     

Fermi Surface of a Quasi–Two-Dimensional Electron Gas

A model of the energy state of a quasi–two-dimensional electron gas is constructed based on a rectangular potential well of finite depth. The form of the Fermi surface and the character of its transformation from the true two-dimensional gas to the three-dimensional one are determined.     

Charge exchange of laser-produced ions in a pulsed gas jet

Results of an experiment on the interaction of laser-produced plasma with a pulsed gas jet are reported. A resonant charge-exchange pumping of the n=3 level of the C³⁺ ion was observed. A spatial structure of the region of intensive interaction was obtained by a short time imaging of filtered plasma radiation. According to independent probe measurements, the interaction was realized at densities of ions and gas particles in excess of 10¹⁶ cm^-3. The obtained data provide a prospect for future experiments on laser gain in the EUV spectral range based on charge-exchange pumping of the C⁵⁺ ion. PACS 52.50.Jm; 52.25.Nr     

Torsional Alfvén and slow magnetoacoustic waves generated by a plasma in a magnetic field

An intense electron-antineutrino source with a hard spectrum (\(E_{{{\tilde v}_e}}^{\max }\) = 13 MeV and \(\left\langle {{E_{{{\tilde v}_e}}}} \right\rangle \) = 6.5MeV) can be created on the basis of the short-lived isotope ⁸Li (β^?-decay, T_1/2 = 0.84 s) formed via the (n, γ) activation of ⁷Li. In contrast to a reactor antineutrino spectrum whose uncertainty is large, particularly in the high-energy region \({E_{{{\tilde v}_e}}}\) > 6 MeV, which is experimentally relevant, the lithium \({\tilde v_e}\) spectrum is accurately determined. The proposed accelerator-driven experimental scheme with a neutron-producing target and a lithium converter as an intense \({\tilde v_e}\) source is an alternative to a nuclear reactor. The required amount of high-purity ⁷Li will be reduced in many times by using the suggested heavy-water LiOD solutions. A possible experiment involving the lithium source on search for sterile neutrinos in the mass region Δm² ≥ 0.2 eV² with a very high sensitivity to mixing-angle values down to sin²(2Θ) ≈ (7–10) × 10^–4 at the 95% C.L. has been considered.