Direct determination of the magnetic structure of the delta phase of oxygen

Simple diatomic molecules exhibit a variety of exciting physical phenomena under high pressures, including structural transitions, pressure induced metallization, and superconductivity. Oxygen is of particular interest because it carries a magnetic moment. For the first time we studied the magnetic structure in solid oxygen under very high pressure by a direct method, namely, neutron diffraction. A new type of magnetic order with ferromagnetic stacking of the antiferromagnetic O2 planes was discovered in delta-O2 at P=6.2 GPa. We show that all structural transformations at pressures <7 GPa are driven by spin interactions; therefore, high-pressure oxygen should be considered as a unique "spin-controlled crystal."     

The stability of the motion of a liquid,due to thermocapillary forces

A study is made of the stability of the plane-parallel flow of a viscous liquid in a layer with a free boundary, under weightless conditions. The motion of the liquid is due to the dependence of the surface tension on the temperature. An exact solution for an unperturbed boundary is obtained by the same method used in [1], but with a more general boundary condition for the temperature. A study of the stability was carried out by the method of small vibrations, taking account of the perturbation of the free boundary. The article discusses the asymptotic behavior of long waves at small Reynolds numbers, and the conditions for instability are found.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 94–98, November–December, 1971.     

Structure of the Sulfoxide Synthase EgtB from the Ergothioneine Biosynthetic Pathway

The non‐heme iron enzyme EgtB catalyzes O₂‐dependent C? S bond formation between γ‐glutamyl cysteine and N‐α‐trimethyl histidine as the central step in ergothioneine biosynthesis. Both, the catalytic activity and the architecture of EgtB are distinct from known sulfur transferases or thiol dioxygenases. The crystal structure of EgtB from Mycobacterium thermoresistibile in complex with γ‐glutamyl cysteine and N‐α‐trimethyl histidine reveals that the two substrates and three histidine residues serve as ligands in an octahedral iron binding site. This active site geometry is consistent with a catalytic mechanism in which C? S bond formation is initiated by an iron(III)‐complexed thiyl radical attacking the imidazole ring of N‐α‐trimethyl histidine.     

Influence of the Duration of Glow Discharge Treatment on the Microhardness of a Multicomponent Alloy

Russian Physics Journal -     

Mapping of n-connected region onto a plane with cuts along the arcs of logarithmic spirals

A univalent function is constructed that effects a conformal mapping of an n-connected circular region onto the entire plane with finite cuts along the arcs of logarithmic spirals. An approximate formula is obtained for this function, as well as the corresponding error.Translated from Matematicheskie Zametki, Vol. 21, No. 3, pp. 329–334, March, 1977.     

Motion of a nonlinear viscoelastic liquid in cylindrical channels of triangular cross section

The problem of the nonrectilinear steady-state flow of a nonlinear viscoelastic liquid in cylindrical channels is considered. It is established that in channels whose cross sections form an equilateral triangle or an isosceles right-angled triangle there are six transverse currents (eddies) in a plane perpendicular to the main longitudinal flow. In cylinders with cross sections in the form of an arbitrary triangle there may be four or six eddies, depending on the shape of the triangle.