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We call a partial Steiner triple system C (configuration) t-Ramsey if for large enough n (in terms of [ABSTRACT FROM AUTHOR]

Abstract: In this short survey, some approaches that can be used to solve the generalized -design problem are considered. Special cases of the generalized -design problem include well-known conjectures for -designs, degree sequences of graphs and hypergraphs, and partial Steiner systems. Also described are some related problems such as the characterization of -vectors of pure simplicial complexes, which are well known but little understood. Some suggestions how enumerative and polyhedral techniques may help are also described. [Copyright &y& Elsevier]

Abstract: A friendship 3-hypergraph is a 3-hypergraph in which for any 3 distinct vertices , and , there exists a unique fourth vertex such that , , are 3-hyperedges. Sós constructed friendship 3-hypergraphs using Steiner triple systems. Hartke and Vandenbussche showed that any friendship 3-hypergraph can be partitioned into ’s. (A is the set of four hyperedges of size three that can be formed from a set of 4 elements.) These ’s form a set of 4-tuples which we call a friendship design. We define a geometric friendship design to be a resolvable friendship design that can be embedded into an affine geometry. Refining the problem from friendship designs to geometric friendship designs allows us to state some structure results about these geometric friendship designs and decrease the search space when searching for geometric friendship designs. Hartke and Vandenbussche discovered 5 new examples of friendship designs which happen to be geometric friendship designs. We show the 3 non-isomorphic geometric designs on 16 vertices are the only such non-isomorphic geometric designs on 16 vertices. We also improve the known lower and upper bounds on the number of hyperedges in any friendship 3-hypergraph. Finally, we show that no friendship 3-hypergraph exists on 11 or 12 points. [Copyright &y& Elsevier]

This paper is a contribution to the study of a quasi-order on the set Ω of Boolean functions, the simple minor quasi-order. We look at the join-irreducible members of the resulting poset $\tilde{\Omega}$. Using a two-way correspondence between Boolean functions and hypergraphs, join-irreducibility translates into a combinatorial property of hypergraphs. We observe that among Steiner systems, those which yield join-irreducible members of $\tilde{\Omega}$ are the − 2-monomorphic Steiner systems. We also describe the graphs which correspond to join-irreducible members of $\tilde{\Omega}$. [ABSTRACT FROM AUTHOR]

A Steiner System, denoted S(t, k, υ), is a vertex set X containing υ vertices, and a collection of subsets of X of size k, called blocks, such that every t vertices from X are in exactly one of the blocks. A Steiner Triple System, or STS, is a special case of a Steiner System where t = 2, k = 3 and υ = 1 or 3 (mod6) [7]. A Bi-Steiner Triple System, or BSTS, is a Steiner Triple System with the vertices colored in such a way that each block of vertices receives precisely two colors. Out of the 80 BSTS(15)s, only 23 are colorable [1]. In this paper, using a computer program that we wrote, we give a complete description of all proper colorings, all feasible partitions, chromatic polynomial and chromatic spectrum of every colorable BSTS(15). [ABSTRACT FROM AUTHOR]

Abstract: A family of k-subsets of an n-set X is disjoint union-free (DUF) if all disjoint pairs of elements of have distinct unions; that is, if for every , and implies . DUF families of maximum size have been studied by Erdös and Füredi. Let be DUF with the property that is not DUF for any k-subset E of X not already in . Then is maximally DUF. We introduce the problem of finding the minimum size of maximally DUF families and provide bounds on this quantity for . [Copyright &y& Elsevier]