staphylococcus aureus is a major causative pathogen of clinical and subclinical mastitis of dairy domestic ruminants. this agent produces a variety of extracellular toxins and virulence factors including toxic shock syndrome toxin-1 (tsst-1) which is the major cause of toxic shock syndrome (tss). in this study 58 s. aureus isolates obtained from 9 dairy herds in east and west azerbaijan prov...

Let G be an edge-colored graph. A tree T in G is a proper tree if no two adjacent edges of it are assigned the same color. Let k be a fixed integer with 2 ≤ k ≤ n. For a vertex subset S ⊆ V (G) with |S| ≥ 2, a tree is called an S-tree if it connects the vertices of S in G. A k-proper coloring of G is an edge-coloring of G having the property that for every set S of k vertices of G, there exists...

Railway optimization problems have been studied from a mathematical programming perspective for decades. This approach is particularly well suited to model the multitude of constraints that typically arises in the context of a railway system. In recent years, these problems have attracted some attention in the algorithms community, with a focus on individual problem aspects, in an attempt to un...

A sequence X = {xi}i=1 over an alphabet containing t symbols is t-universal if every permutation of those symbols is contained as a subsequence. Kleitman and Kwiatkowski showed that the minimum length of a t-universal sequence is (1−o(1))t2. In this note we address a related Ramsey-type problem. We say that an r-coloring χ of the sequence X is canonical if χ(xi) = χ(xj) whenever xi = xj . We pr...

In [5], we presented a lower bound for the chromatic numbers of hypergraphs KG sS, “generalized r-uniform Kneser hypergraphs with intersection multiplicities s.” It generalized previous lower bounds by Kř́ıž [1, 2] for the case s = (1, . . . , 1) without intersection multiplicities, and by Sarkaria [4] for S = ([n] k ) . The following two problems that arise for intersection multiplicities si > ...

Let G be a plane graph whose vertices are to be colored subject to constraints on some of the faces. There are 3 types of constraints: a C indicates that the face must contain two vertices of a Common color, a D that it must contain two vertices of a Different color and a B that Both conditions must hold simultaneously. A coloring of the vertices of G satisfying the facial constraints is a stri...

In this paper we present a hybrid technique that applies a genetic algorithm followed by wisdom of artificial crowds approach to solving the graph-coloring problem. The genetic algorithm described here utilizes more than one parent selection and mutation methods depending on the state of fitness of its best solution. This results in shifting the solution to the global optimum more quickly than ...

Let Ω be a space with probability measure μ for which the notion of symmetry is defined. Given A ⊆ Ω, let ms(A) denote the supremum of μ(B) over symmetric B ⊆ A. An r-coloring of Ω is a measurable map χ : Ω → {1, . . . , r} possibly undefined on a set of measure 0. Given an r-coloring χ, let ms(Ω;χ) = max1≤i≤r ms(χ (i)). With each space Ω we associate a Ramsey type number ms(Ω, r) = infχ ms(Ω;χ...