The title compound, C(19)H(20)O(5), is approximately planar; the dihedral angle between the benzene rings is 3.82 (8)°, and the central propenone C(=O)-C=C plane makes dihedral angles of 1.95 (10) and 3.17 (11)° with the two benzene rings. In the crystal structure, intra- and inter-molecular C-H⋯O hydrogen bonds are observed.

Ring stacking in some closo-borane dianions and the hypothetical capped borane nanotubes, predicted to be stable earlier, is analyzed in a perturbation theoretic way. A "staggered" building up of rings to form nanotubes is explored for four- and five-membered B(n)H(n) rings. Arguments are given for the stacking of B(5)H(5) rings being energetically more favorable than the stacking of B(4)H(4) r...

Problem statement: Algebraic K-theory of projective modules over commutative rings were introduced by Bass and central simple superalgebras, supercommutative super-rings were introduced by many researchers such as Knus, Racine and Zelmanov. In this research, we classified the projective supermodules over (torsion free) supercommutative super-rings and through out this study we forced our selves...

for any reduced commutative $f$-ring with identity and bounded inversion, we show that a condition which is obviously necessary for the socle of the ring to coincide with the socle of its bounded part, is actually also sufficient. the condition is that every minimal ideal of the ring consist entirely of bounded elements. it is not too stringent, and is satisfied, for instance, by rings of conti...

PURPOSE To evaluate the safety and efficacy of Ferrara intrastromal corneal rings in the treatment of eyes with keratoconus without central corneal scarring. SETTING Vlemma Eye Institute, Athens, Greece. METHODS Twenty-six patients with bilateral keratoconus, clear central corneas, and contact lens intolerance participated in the study. Videokeratographic corneal topography and ultrasonic p...

The tripodal character of the title compound, C(33)H(30)N(10)S(3), arises from the three thio-ether arms surrounding a central amine N atom. The three arms have approximately the same conformation but distinct geometries in a trans-trans-cis conformation, resulting in a short pyridine-sulfanyl N⋯S distance of 4.320 (7) Å. The distances of the central N atom to the N atoms of three pyridine ring...

for a fixed positive integer , we say a ring with identity is n-generalized right principally quasi-baer, if for any principal right ideal of , the right annihilator of is generated by an idempotent. this class of rings includes the right principally quasi-baer rings and hence all prime rings. a certain n-generalized principally quasi-baer subring of the matrix ring are studied, and connections...

The title compound, C(22)H(22)O(5), crystallizes with two independent mol-ecules in the asymmetric unit, both of which possess pseudo-C(s) symmetry. The central 1,3-dioxanone rings have envelope conformations, with the C atom bearing the two methyl groups at the flap. The benzene rings of the meth-oxy-benzyl-idene units, attached in the 4- and 6-positions on the central 1,3-dioxanone rings, are...

The central residue in the title compound, C(21)H(21)N(3)O(3), is close to planar (r.m.s. deviation = 0.0753 Å for all non-H atoms from OH to NH inclusive): the hy-droxy, amino and carbonyl groups all lie to the same side of the mol-ecule (the conformation about the ethene bond is Z), facilitating the formation of intra-molecular O-H⋯O and N-H⋯O hydrogen bonds that close S(6) rings. However, ov...

The title compound, C27H26O3, crystallized with two independent mol-ecules (A and B) in the asymmetric unit. In mol-ecule A, the plane of the central benzene ring forms dihedral angles of 75.78 (14) and 52.75 (16)° with that of the terminal benzene rings, and the dihedral angle between the planes of the terminal benzene rings is 51.49 (17)°. The corresponding values for mol-ecule B are 75.18 (1...