Numerical study of shock compression of graphite and its conversion to diamond in conical targets

The shock compression of carbon placed into lead conical targets that are subjected to a blow from aluminum strikers moving at a velocity of 4 km/s is numerically studied. The statement of the problem includes the hydrodynamic equations for compressed media, semi-empirical wide-range equations of state, and a kinetic model of nonequilibrium graphite-to-diamond conversion that is calibrated with known experimental data. All stages of the process are analyzed, starting from the cumulative effect at the symmetry axis of the target to the release of the sample due to the rarefaction wave coming from the rear side of the striker with allowance for spalling.     

Synthesis and study of vitrescent materials based on the alkoxybenzoic acids derivatives and triethanolamine

Fifteen new branched triethanolamine esters of the benzoic acid derivatives were designed and the mesomorphism typical of discotic mesogens was forecast for them. In eight of the obtained compounds a manifestation of liquid crystal properties was predicted, for four derivatives equiprobable prognosis was given, and only three compounds were predicted not to form a mesophase. The obtained esters were characterized by elemental analysis, NMR and IR spectroscopy, gas chromatography-mass spectrometry. The main thermal characteristics that allow accounting for their phase behavior were determined.     

Mechanism of amplification of convergent shock waves in porous media

The effect of amplification of moderate-intensity converging shock waves in porous media with decreasing initial density, revealed by numerically solving the hydrodynamics equations, was demonstrated for ID converging waves and for a 2D problem of the compression of porous material in conical solid targets. The latter problem was also treated within the framework of the simplest model of dynamic deformation of solids, with consideration given to shear stresses. The calculation results for porous graphite, aluminum, and Teflon samples are presented. Both closed targets and targets with an outlet orifice were considered. When modeling the intense shock loading of graphite, its transformation into diamond was taken into account.     

A metallographic and electron microscopic study of the structure of copper after dynamic pressing

Structural changes in copper samples subjected to severe plastic deformation with the use of the dynamic loading technique were studied. The deformation was caused by pressing blanks through two or three channels situated at an angle with respect to one another. The velocity of a blank before it got into the first channel was 280–450 m/s. Pressure in samples did not exceed 3–7 GPa. The microstructure of copper changed under the simultaneous action of high-velocity deformation and temperature increase. The formation of cellular dislocation structures, systems of microtwins, dynamic polygonization subgranular structures, and new recrystallized grains was observed. After two passes, the major part of a sample had a structure that consisted of thin fibers containing submicrodisperse (50–100 nm) grains.     

Numerical study of converging shock waves in porous media

The dependences of the solutions to the hydrodynamic equations of compressed media that describe converging shock waves on the density of a substance ahead of a wave front are studied. The properties of Hugoniot adiabats that can explain the qualitatively different characters of these dependences for the equations of state of perfect gas and condensed matter are analyzed. The one-dimensional problems of converging shock waves in graphite and aluminum are considered, and the two-dimensional problem of the compression of graphite in a steel target with a conical cavity is solved. The latter problem is also investigated in terms of a simple model for a deformable solid that takes into account shear stresses.     

On a certain nonstationary problem in a dihedral angle. II

An existence theorem is obtained for the initial-boundary value problem, considered in the previous paper, in the case of a positive parameter h in the boundary condition.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova Akademiya Nauk SSSR, Vol. 188, pp. 178–185, 1991.     

Chiral imines and amines based on 2-hydroxypinan-3-one

The new chiral derivatives of benzylamine and 2α-hydroxypinan-3-one (1R,2R,5R)-3-[(1S)-α-methylbenzylamino]-2,6,6-trimethylbicyclo[3.1.1]heptan-2-ol (2), (1S,2S,3S,5S)-3-(benzylamino)-2,6,6-trimethylbicyclo[3.1.1]heptan-2-ol (3), and (1R,2R,3R,5R)-3-[(1S)-α-methylbenzylamino]-2,6,6-trimethylbicyclo[3.1.1]heptan-2-ol (4) were synthesized and characterized. It was shown that reduction of the benzylimines by sodium triacetoxyborohydride formed stereoselectively 3β-substituted pinanamines.     

The nilpotency of Leibniz algebras with Engel condition

It is proved that a Leibniz algebra over a field of zero characteristic with the Engel condition is nilpotent.     

Effect of the nature of chiral fragment on mesomorphic properties of triphenylene ethers

A number of new 2,3,6,7,10,11-hexakis(heptyloxy)triphenylenes possessing a chiral substituent in position 1 of the triphenylene ring system and characterized by predictable mesomorphism were synthesized. The effect of the nature of the chiral fragment (dehydrocholic, lipoic, and d-tartaric acid residues) on the mesomorphic properties of triphenlylene ethers was studied. N-[2,3,6,7,10,11-hexakis(heptylozy)triphenylen-1-yl]amides derived from the above acids, unlike initial monomesomorphic amine, exhibit enantiotropic columnar polymorphism and give rise to helical columnar structure at reduced temperature. The newly synthesized amides are characterized by lower thermal stability and broader temperature range of the mesophase. Introduction of two chiral dehydrocholic acid fragments into the triphenylene core favors columnar (including chiral) mesomorphism.