4-(4-Aminophenylsulfonyl)aniline–1,3,5-trinitrobenzene (1/2)

Cover vol. 12, no.4, August 2015-

In search of 4-(12, 6, 4) designs: Part II

In a 4-(12, 6, 4) design a block is either disjoint from one other block or it has five points in common with one other block. For a 4-(12, 6, 4) design with a pair of blocks of the second type it is shown that· another thirty blocks of the design can be completed in a unique way and these thirty blocks contain a copy of a 3-(10, 4, 1) design.

In search of 4-(12, 6, 4) designs: Part III

A 4-(12, 6, 4) design that is not also a 5-(12, 6, 1) design must have at least one pair of blocks with five points in common. It is shown that there are just nine non-isomorphic such designs; so, including the 5-(12, 6, 1) design, there are ten 4-(12, 6, 4) designs. These designs are characterised by the orders of their automorphism groups and they all contain a 4-(11, 5, 1) design.

In search of 4-(12, 6, 4) designs: Part I

Martin J. Sharry and Anne Penfold Street, Centre for Combinatorics, Department of Mathematics, The University of Queensland, Brisbane 4072, Australia. As a first step towards finding all 4-(12, 6, 4) designs which are not 5-(12, 6, 1) designs, it is shown that if such a design has a pair of blocks with five points in common, then there is a unique way of assigning the replicas of the seven poin...

Synthesis and structure of [ K – ( 12 - crown - 4 ) 2 ] 2 [ K – ( 12 - crown - 4 ) ] 2 [ Sn 9 ] · 4 en †

The new compound [K–(12C4)2]2[K–12C4]2[Sn9]·4en (1), where 12C4 is 12-crown-4 polyether, was crystallized from an ethylenediamine solution of an intermetallic precursor with nominal composition K4Li2Sn8. The structure of the compound (orthorhombic, Cmca, a = 21.763(4), b = 16.030(3), c = 51.85(1) Å, Z = 8) contains isolated deltahedral clusters of [Sn9]4−. The clusters are of Cs symmetry and ar...