Interaction of microcracks with a macrocrack yielded in a narrow strip

Plastic zone growth of collinear cracks has had a longstanding interest in ductile fracture. This work further considers yield zone growth in an isotropic, homogeneous elastic–perfectly plastic infinite plate containing a macrocrack with several neighboring microcracks. Normal loading is considered at distances far away from the cracks. The strip yield is adopted where the plastic zone is assumed to be confined to two narrow strips extending from the ends of a finite length crack while the microcracks are assumed to be elastic. The plastic zone length and crack opening displacement are found from asymptotic solution and compared with finite element solution.     

High resolution study of the ν5 + ν12 band of C2H4

The combination band ν₅ + ν₁₂ of ethylene, C₂H₄, has been recorded for the first time with a high resolution Fourier transform spectrometer Bruker IFS 125HR. Assignments of transitions and preliminary rotational analysis are made. Two models (Hamiltonian of the isolated vibrational state and Hamiltonian that takes into account resonance interactions) are used. Influence of the local resonance interactions on the parameters and reproduction power of the models is discussed.     

Physicochemical interaction at the contact of higher manganese silicide with chromium

Diffusion processes taking place at the contact of higher manganese silicide MnSi_1.71?1.75 with chromium at elevated temperatures are considered. The microstructures of cast and annealed samples show a diffusion region that evolves at the HMS/Cr interface during the HMS melt crystallization on chromium flakes. As the temperature and time of annealing of HMS/Cr samples increase, the diffusion region grows thicker and new phases appear. It is shown that the diffusion is of reaction character. The diffusion coefficients of magnesium, chromium, and silicon in the solid solution based on manganese and chromium monosilicides and in the solid solution based on the Cr₃Si compound are calculated. It is also shown that, when the temperature of the HMS used as a thermoelement positive leg is optimal, the depletion time of a 10-µm-thick chromium layer exceeds 15000 h. Intermetallic phases forming in the diffusion region between the HMS and Cr are of metallic conduction and exhibit a high thermal conductivity, which minimizes energy losses in the contact layers of thermoelements.     

Vinylic nucleophilic substitution in functionalized 2-vinylpyrroles: a route to a new family of stable enols

2-(2-Cyano-1-ethylthioethenyl)pyrroles easy exchange their ethylthio group for hydroxyl (NaOH, H₂O-methanol, 40-45 °C, 1 h) to give 2-(2-cyano-1-hydroxyethenyl)pyrroles, a new family of stable enols, in 50-94% yields. The vinylic nucleophilic substitution proceeds at the double bond of both the starting pyrroles and their cyclic isomers, 3-iminopyrrolizines. X-ray structure analysis and NMR spectra show the enols to be stabilized by exceptionally strong intramolecular H-bonding.     

Numerical integration over a disc. A new Gaussian quadrature formula

Summary. We construct a quadrature formula for integration on the unit disc which is based on line integrals over distinct chords in the disc and integrates exactly all polynomials in two variables of total degree . Received August 8, 1996 / Revised version received July 2, 1997     

Physical methods for studying the effect of europium ions on lysozyme solutions

Metals play an important role in a human organism. Concentrations of metals, particularly, heavy metals, exceeding the maximum allowable level in the organism are dangerous for persons. At present, it is of topical interest to study molecular mechanisms of the effect of heavy metal ions on biological fluids, for instance, blood, and to develop sufficiently simple and reliable physical methods for environmental monitoring of the occurrence of heavy metals in natural environments, in the first place, in water.     

Incomparably easy migration of functionalized enol substituent in pyrrole ring

Functionalized pyrroleьvь? enols, 2-(1-hydroxy-2.2-dicyanoethenyl)-1-methylpyrroles, at heating (75–135°C) unexpectedly readily rearranged in high yield into 3-isomers. Evidently the migration of the enol fragment involves a mesomeric zwitterion formed as a result of an intra- and intermolecular autoprotonation of the pyrrole ring by the acidic enol hydroxy group. Under similar conditions no migration of the ethenyl moiety occurred in 2-(1-hydroxy-2-carbamoyl-2-cyanoethenyl)-1-methylpyrroles. The quantum-chemical calculations (MP2/6-311G**) show a clear-cut distinction in the relative stability of 2- and 3-isomers of 1H- and 1-methylhydroxyethenylpyrroles: in the former case the 2-isomer is more stable, whereas in the 1-methyl-substituted compound, the 3-isomer.     

Non-Linear Excitation and Decay of Low-Energy Nuclear Isomers Produced under Femtosecond Laser–Plasma Interaction

The properties of internal electronic conversion of nucleus excited in hot dense laser plasma are considered. The important role of dynamics of plasma charge state in residual gas is shown. We are also considering the role of multi-quanta photoexcitation of low-energy nuclear levels in this plasma. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of Allyl Substitution in Chitosan on the Structure of Graft Copolymers

The kinetics of graft polymerization of vinyl acetate on allyl chitosan samples with varied content of allyl groups, initiated with ammonium peroxodisulfate, was studied.