Reaction of donor-acceptor cyclopropanes with 1,3-diphenylisobenzofuran. Lewis acid effect on the reaction pathway

Reaction of donor-acceptor cyclopropanes with 1,3-diphenylisobenzofuran in the presence of lanthanide triflates, as well as CuOTf, Sn(OTf)₂, SnCl₂, ZnCl₂, GaCl₃, and MgI₂, proceeds as a formal [3+4]-cycloaddition leading to a newly formed seven-membered ring. This reaction was found to be typical of cyclopropane-1,1-diesters and dinitriles, as well as 1-nitrocyclo-propanecarboxylates containing aromatic, heteroaromatic, and vinylic substituents at the C(2) atom of the small ring. When Me₃SiOTf, TiCl₄, SnCl₄, or BF₃·OEt₂ were used as initiators, unusual cyclic hemiacetals were formed via the conjugate 1,4-addition of a cyclopropane and a nucleophile to the diene moiety.     

On the generalized susceptibility of ferroelectric-dielectric nanocomposites

The linear response of ferroelectric-dielectric composite was studied and the frequency dependences of the real and imaginary parts of its susceptibility as functions of the ferroelectric granule sizes and temperature were found through exact consideration of electric fields and nonlocal effects. It is shown that the susceptibility dispersion can be described by Debye formulas with the parameters dependent on the ferroelectric granule size.     

Deuterium liner and multiparametric studies of the formation of an inverse Z-pinch

A method and results of measurements are presented of the ion energy distribution in a deuterium liner accelerated in the inverse Z-pinch, in which the plasma is accelerated electrodynamically from the liner axis. Knowledge of the deuteron energy distribution is of primary importance for the correct interpretation of the experimental results from the study of the dd-reaction in the range of infralow energies with the use of a liner plasma. Experiments were carried out in a high-current pulsed accelerator (I=950 kA, τ=80 ns) at the Institute of High-Current Electronics of the Siberian Division of the Russian Academy of Sciences (Tomsk, Russia). In the initial state, the liner is a supersonic hollow deuterium jet 32 mm in diameter and 20 mm in length. The liner parameters were measured with the help of optical detectors of H _α and H _β deuterium lines and magnetic probes arranged in a radial direction (along the direction the liner expansion). In addition, scintillation spectrometers and BF₃ counters were used to measure the intensity of the neutron flux produced in the d + d → ³He + n reaction. The results obtained by simultaneously analyzing the data from magnetic probes, optical detectors, and neutron detectors point to the possibility of using a rather simple method for measuring the parameters of the liner accelerated up to energies of 3–6 keV.     

Germanium carboxylates: the first X‐ray diffraction study of germanium(II) dicarboxylate and germanium(IV) tetracarboxylate

Germanium(II) dipropionate (1) has been synthesized and its crystal structure, as well as that of germanium(IV) tetrapropionate (2), has been determined. By contrast to monomeric 2 with monodentate propionate ligands, compound 1 is associated, forming a cyclotetramer [Ge(O₂CEt)₂]₄ (1a) via intermolecular dative C?O → Ge interactions. Copyright © 2005 John Wiley & Sons, Ltd.     

On a Boundary Value Problem for Pairs of Polyanalytic Functions

The necessary and sufficient conditions of Fredholmness and the index formula for a boundary value problems for a pair of polyanalytic functions, containing differential operators as well as operators with Carleman shift and conjugations, are obtained. Submitted: May 16, 2007. Accepted: November 5, 2007.     

AlGaN nanostructures with extremely high quantum yield at 300 K

Theoretical optimization of a quantum well heterostructure based on AlGaN solid solutions is implemented in order to attain the maximum charge carrier activation energy and the maximum exciton binding energy at a radiation wavelength of ~300 nm. An optimized structure sample with the radiative recombination dominating over the temperature range of 5 to 300 K and the room temperature internal quantum yield as high as 80% of the value measured at 5 K has been manufactured via plasma-assisted molecular beam epitaxy.     

Effect of ultraviolet radiation on polyethylene naphthalate films irradiated with high-energy heavy ions

The effect of UV radiation in the spectral range of 280–400 nm on polyethylene naphthalate (PEN) films has been studied. Changes in the optical absorption spectra of PEN after exposure to accelerated ions and UV radiation have been revealed. Changes in the surface properties have been explored, and the depth of the degraded polymer layer after long-term UV irradiation in air has been measured. Depending on the treatment time, the depth has made 0.1–0.9 μm. The photoablation rate and the quantum yield of monomer unit removal due to UV irradiation of the PEN films have been estimated at ~0.7 × 10^?4 molecule/photon. The possibility of the formation of asymmetric pores in PEN films using controlled photooxidative degradation has been shown.