Selective spectroscopy of tunneling transitions between the Landau levels in vertical double-gate graphene–boron nitride–graphene heterostructures

The spectral and total electron densities of states in two-dimensional FeAs clusters, which simulate iron-based superconductors, have been calculated using the generalized quantum Monte Carlo algorithm within the full two-orbital model. Spectra have been reconstructed by solving the integral equation relating the Matsubara Green’s function and spectral density by the method combining the gradient descent and Monte Carlo algorithms. The calculations have been performed for clusters with dimensions up to 10 × 10 FeAs cells. The profiles of the Fermi surface for the entire Brillouin zone have been presented in the quasiparticle approximation. Data for the total density of states near the Fermi level have been obtained. The effect of the interaction parameter, size of the cluster, and temperature on the spectrum of excitations has been studied.     

Dissociation of LiAlO2 and LiGaO2

The thermodynamic calculations of dissociation of LiAlO₂ and LiGaO₂ as function of temperature and oxygen pressure are presented. It has been found that LiGaO₂ evaporates congruently at the melting point under the oxygen pressure equal to 1 · 10^—5 atm. LiAlO₂ evaporates incongruently, the equilibrium oxygen partial pressure at the melting point is equal to 9.6 · 10^—5 atm and the partial pressure of Li and Al oxides decrease with increasing of oxygen pressure.     

Lenar Timofeevich Bugaenko (1930–2005)

Obituary

Lenar Timofeevich Bugaenko (1930–2005)     

Dissolution of Silk Fibroin in N-methylmorpholine-N-oxide and Its Mixtures with Organic Solvents

Preparation of concentrated solutions of natural silk fibroin in N-methylmorpholine-N-oxide and its mixtures with protonic and aprotic solvents was experimentally studied. Solutions with the fibroin concentration of 6 wt % and more were prepared.     

Thermoluminescence of a polyethylene surface after plasma treatment with a high-frequency glow discharge

The plasma treatment of polyethylene (PE) gives a specific pattern of thermoluminescence (TL). The qualitative difference between the TL curves of PE after plasma treatment and the curves for radioluminescence appears to be due both to specific features of the plasma treatment (attack on the surface of the sample and the unavoidable effect of photobleaching) and to the particular structure of the surface of the polymer (the existence or formation in the surface layer of special low-molecular structures). TL after plasma treatment can therefore be used to investigate the surface structure of polymers.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1742–1744, August, 1990.     

Specific features of cellulose and chitin dissolution in ionic liquids of varied structure and the structural organization of regenerated polysaccharides

Solubility of cellulose, chitin, and chitosan in seven ionic liquids of varied structure was studied. It was found that pressure, temperature, and amount of an aprotic diluent (dimethyl sulfoxide) affect the dissolution of cellulose and chitin in an ionic liquid. The variation of the degree of polymerization of cellulose and chitin in ionic liquid solutions was studied. IR Fourier spectroscopy and X-ray diffraction analysis were used to examine the structural organization of hydrated cellulose and chitin films obtained.     

Use of the CNDO method with modified shell repulsion potential for calculation of interactions in solutions

Theoretical and Experimental Chemistry -     

Effect of structure of ionic liquids on their dissolving power toward natural polymers

Experimental and calculated data on the effect of anion and cation structure on the dissolving power of ionic liquids based on imidazole toward the natural polymers cellulose, fibroin and keratin are presented.     

Oxidative Dearomatization of 4,5,6,7‐Tetrahydro‐1H‐indoles Obtained by Metal‐ and Solvent‐Free Thermal 5‐endo‐dig Cyclization: The Route to Erythrina and Lycorine Alkaloids

A facile one‐pot approach based on a thermally induced metal‐ and solvent‐free 5‐endo‐dig cyclization reaction of the amino propargylic alcohols in combination with Dess–Martin periodinane‐promoted oxidative dearomatization of 4,5,6,7‐tetrahydroindole intermediates provides an efficient and robust access to 5,6‐dihydro‐1H‐indol‐2(4H)ones. Green, relatively mild and operationally simple characteristics of the synthetic sequence are the major advantages, which greatly amplify the developed methodology. The utility of obtained indolones as unified key precursors is demonstrated by the application of these products to the formal total syntheses of a whole pleiad of Erythrina‐ and Lycorine‐type alkaloids, namely (±)‐erysotramidine, (±)‐erysotrine, (±)‐erythravine, (±)‐γ‐lycorane, and abnormal erythrinanes (±)‐coccoline and (±)‐coccuvinine.     

Study of a possibility of applying the films of the silk fibroin and its mixtures with synthetic polymers for creating the materials of contact lenses

Russian Journal of Applied Chemistry - Light and gas permeability, antimicrobic and physico-mechanical properties are studied of the films from the mixtures of fibroin with the synthetic polymers.