منابع مشابه
Characterizations of Transversal and Fundamental Transversal Matroids
A result of Mason, as refined by Ingleton, characterizes transversal matroids as the matroids that satisfy a set of inequalities that relate the ranks of intersections and unions of nonempty sets of cyclic flats. We prove counterparts, for fundamental transversal matroids, of this and other characterizations of transversal matroids. In particular, we show that fundamental transversal matroids a...
متن کاملTransversal Lattices
A flat of a matroid is cyclic if it is a union of circuits; such flats form a lattice under inclusion and, up to isomorphism, all lattices can be obtained this way. A lattice is a Tr-lattice if all matroids whose lattices of cyclic flats are isomorphic to it are transversal. We investigate some sufficient conditions for a lattice to be a Tr-lattice; a corollary is that distributive lattices of ...
متن کاملAn upper bound for the transversal numbers of 4-uniform hypergraphs
The main purpose of this paper is to prove that if H is a 4-uniform hypergraph with n vertices and m edges, then the transversal number r(H) <2(m +n)/9. All standard terminology of hypergraphs is from [ 11. Suppose H = (V, E) is a k-uniform hypergraph with n vertices and m edges. Tuza [2] proposed the problem of finding an upper bound for the transversal number r(H), of the form t(H) < ck(n + m...
متن کاملAn upper limit to the sodium layer longitudinal and transversal altitude structure function from MCAO data
The Gemini Multi-Conjugate Adaptive Optics System is the first sodium-based Multi-Laser Guide Star (LGS) Adaptive Optics system used for astronomy. It uses five LGSs distributed on a 1 arcmin2 constellation to measure and compensate for atmospheric distortions. In this Letter, we use the LGS wavefront sensor data to derive the amount of differential focus caused by horizontal sodium layer struc...
متن کاملTransversal Theory
1. Introduction. Transversal theory is a branch of combinatorial mathematics which is only just beginning to emerge as a reasonably connected and coherent subject. Whether this is yet rich enough or mature enough to be called a 'theory' may be a matter for debate; indeed, it is by no means certain that this part of mathematics may not finally be classified under some broader, more comprehensive...
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ژورنال
عنوان ژورنال: Annals of Surgical Oncology
سال: 2012
ISSN: 1068-9265,1534-4681
DOI: 10.1245/s10434-012-2596-8