Cellulose destruction by electron-beam-induced heating

An efficient method for producing furfural and other furan derivatives from cellulose was proposed. Radiolytic destruction of cotton cellulose, sulfate and sulfite pine celluloses, and carboxymethylcellulose was studied under electron-beam-induced distillation conditions. The yield of the liquid distillate from cellulose of various origin was about 60%. Furfural and its derivatives with the molecular weight up to 140 were the predominant products. Grinding and preheating of cellulose increase the fraction of furan derivatives in the condensate. The liquid products are partially transformed into high-molecular-weight compounds that are distilled with difficulty and that are involved in the formation of wood charcoal in the yield of about 20%.     

Preparation of fragrant substances from bornyl chloride

Organocuprate reagents were used for introducing bornane (1,7,7-trimethylbicyclo[2.2.1]heptane) moiety into the carbon skeleton of α,β-unsaturated carbonyl compounds. Prospects for use of the products obtained as fragrant substances were assessed.     

Structural and electrical properties of quantum wells with nanoscale InAs inserts in InyAl1 ? yAs/InxGa1 ? xAs heterostructures on InP substrates

A complex study of the effect ofintroduction of nanoscale InAs inserts of different thicknesses into an In_0.53Ga_0.47As quantum well on the electrical properties and structural features of In_0.50Al_0.50As/In_0.53Ga_0.47As/In_0.50Al_0.50As nanoheterostructures with bilateral δ-Si doping grown on InP substrates has been performed. The layers of nanoheterostructures with a weak lattice mismatch are found to be equally (cube-on-cube) oriented. The introduction of a nanoscale InAs insert leads to an increase in mobility. At an insert thickness of about 1.8 nm, the effect of increasing mobility is saturated due to structural deterioration. The segregation of the second (apparently, wurtzite) phase is revealed; this process, as well as the formation of other defects in the nanoheterostructure layers, is due to local strains caused by variations of the indium content in the layers.     

The mechanism of formation of copper aluminide in the thermal explosion mode

The mechanism of formation of copper aluminides in the thermal explosion mode was studied. A molded mixture of copper and aluminum powders was heated to the self-ignition temperature by the radiation of a tungsten heater. The phase transformations were detected by time-resolved X-ray diffraction (TRXRD). The kinetics of heat release due to the chemical reaction was studied by measuring the temperature of the sample. The macrokinetic stages of the process were revealed, and the apparent activation energy of each stage was estimated.     

Determination of pesticides and other physiologically active compounds by capillary gas chromatography with an atomic-emission detector without using standard reference materials

It was shown that organic substances can be determined by gas chromatography with an atomicemission detector without using standard reference materials of these substances or information on their toxicity, but using reference materials of other compounds containing similar hetero-atoms     

Penetration depth and pinning effects in high-Tc superconductors La-Sr-Cu-O and (Er,Ho)-Ba-Cu-O studies by μSR

We report the results of μSR investigations of the ceramic samples La_2-xSr_xCuO_4-σ (x=0.1, 0.15, 0.25) and ReBa₂Cu₃O_7-σ (Re=Er, Ho, Y_0.5Ho_0.5) in the external magnetic field 0–800 Oe. The measurements were performed by the ZFC and FC methods. The irreversibility effects were studied at several temperatures by measuring the mean value and the width of the magnetic field distribution on the muon in the step by step procedure of increasing and subsequent decreasing of the external field. The temperature dependences of the magnetic penetration depth perpendicular to the basal plane λ_⊥ were obtained. For the lanthanum sample with 0.15 of Sr its value at the zero temperature is λ_⊥ (0)=2400 Å, for Er-Ba-Cu-O λ_⊥ (0)=1600 Å.     

Adhesive ability of a heat-resistant double-chain polymer and the strength of CFRP based on it

The adhesive ability of a heat-resistant polyiminoquinazolindione (PIQD) binder, based on a double-chain polymer, and the physicomechanical characteristics of unidirectional CFRPs made with it are investigated. It is shown that, at room temperature, the strength of model adhesive joints (PIQD-steel wire) and of the CFRPs in shear and bending is rather low — about half of that of similar specimens based on an epoxy binder. At the same time, all their mechanical characteristics, to a large measure (50%), are retained at temperatures up to 450°C, which considerably exceeds the heat resistance of all polymer matrices used at the present time. The elastic modulus of the CFRPs in bending practically remains the same up to 450°C. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 535–546, July–August, 2008.     

Potential barriers of internal rotation in halogen-substituted ethanes

A simple model is proposed for calculating torsional vibrational frequencies and torsion potentials in ethane-type molecules. The model is based on internuclear coulomb electrostatic interactions of the end atoms in molecular groups undergoing rotations. The effective charges on the nuclei are considered to be the model parameters. The results of calculations show that the model can reliably reproduce the frequencies of torsional vibrations for rotational conformers and that the effective charges are transferable among halogen-substituted ethanes, both symmetrical and asymmetrical.Orenburg Pedagogical Institute. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 1, pp. 39–43, January–February, 1993.