A system of slotted interconnected rings employing a combination of wavelength-division multiple access (WDMA) with time-division multiple access (TDMA) can serve a metropolitan area without electro-optical conversion and buffering of payload except at system entry points. The multiple rings overcome the power budget limitations of the single ring extending the reach of the system to even the l...

Introduction. A celebrated theorem of N. Jacobson [7] asserts that if (1) x*(x) =x for every x in a ring R, where n(x) is an integer greater than one, then R is commutative. In a recent paper [2], I. N. Herstein has shown that it is enough to require that (1) holds for those x in R which are commutators: x= [y, z]=yz — zy of two elements of R. The purpose of this note is to show that if R has n...

In the title mol-ecule [systematic name: 10-(prop-2-yn-1-yl)dipyrido[3,4-b:3',4'-e][1,4]thia-zine], C(13)H(9)N(3)S, the dihedral angle between the two pyridine rings is 146.33 (7)° and the angle between two halves of the thia-zine ring is 138.84 (8)°, resulting in a butterfly shape for the tricyclic system. The central thia-zine ring adopts a boat conformation, with the 2-propynyl substituent a...

In the polymeric title compound, {[Ag(C(8)H(10)N(4)S(4))]ClO(4)·1.5H(2)O}(n), the Ag(I) atom has a slightly distorted trigonal-planar coordination geometry provided by three N-atom donors from the thia-diazole rings of three symmetry-related 2,2'-[butane-1,4-diylbis(sulfanedi-yl)]bis-(1,3,4-thia-diazole) ligands. Centrosymmetrically related Ag(I) atoms are bridged by the N-N fragments of rings,...

In this work the definition of codes as modules over skew polynomial rings of automorphism type is generalized to skew polynomial rings, whose multiplication is defined using an automorphism and a derivation. This produces a more general class of codes which, in some cases, produce better distance bounds than module skew codes constructed only with an automorphism. Extending the approach of Gab...

The asymmetric unit of the title compound, C44H30O2, contains two independent mol-ecules in which the terminal rings of the terphenyl element are inclined at angles of 36.3 (1) and 22.5 (1)° with respect to the central ring and the dihedral angles between the fluorenyl units are 72.3 (1) and 62.8 (1)°. In the crystal, pairs of O-H⋯O hydrogen bonds link the mol-ecules into inversion dimers. The ...

In the title compound, C(15)H(14)O(2)S, the dihedral angle between the aromatic rings is 8.46 -(8)°. The central enone group is planar (r.m.s. deviation = 0.0267 Å) and is oriented at a dihedral angle of 1.20 (9)° with respect to the benzene ring and at 8.27 (9)° with respect to the thio-phene group. In the crystal, the mol-ecules are linked into polymeric chains extending along the b axis due ...

The title adduct, chlorido-(2,3-diphenyl-3,4,5,6-tetra-hydro-2H-1,3-thia-zin-4-one-κO)tri-phenyl-tin, [Sn(C6H5)3Cl(C16H15NOS)], resulted from reaction of 2,3-diphenyl-3,4,5,6-tetra-hydro-2H-1,3-thia-zin-4-one with tri-phenyl-tin chloride. The thia-zine ring has an envelope conformation with the S atom forming the flap. The mol-ecule has five phenyl rings, two of them attached to the thia-zine r...

Abstraet~High-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), annular dark-field scanning transmission electron microscope (STEM) images, and electron nanodiffraction were used to examine structures of synthetic 2and 6-line ferrihydrite specimens. HRTEM images of 2-line ferrihydrite (2LFh) show scattered small (-1-3 nm) areas with lattice fringes ...