A graph G is said to be 1-tough if for every vertex cut S of G, the number of components of G − S does not exceed |S|. Being 1-tough is an obvious necessary condition for a graph to be hamiltonian, but it is not sufficient in general. We study the problem of characterizing all graphs H such that every 1-tough H-free graph is hamiltonian. We almost obtain a complete solution to this problem, lea...

A graph G is a chordal-k-generalized split graph if G is chordal and there is a clique Q in G such that every connected component in G[V \ Q] has at most k vertices. Thus, chordal-1-generalized split graphs are exactly the split graphs. We characterize chordal-k-generalized split graphs by forbidden induced subgraphs. Moreover, we characterize a very special case of chordal-2-generalized split ...

A graph is a probe interval graph (PIG) if its vertices can be partitioned into probes and nonprobes with an interval assigned to each vertex so that vertices are adjacent if and only if their corresponding intervals intersect and at least one of the vertices is a probe. When all intervals have the same length (or equivalently, no interval contains another properly) the graph is a unit probe in...

In this paper we extend the work of Rautenbach and Szwarcfiter [8] by giving a structural characterization of graphs that can be represented by the intersection of unit intervals that may or may not contain their endpoints. A characterization was proved independently by Joos in [6], however our approach provides an algorithm that produces such a representation, as well as a forbidden graph char...

Probe interval graphs (PIGs) are used as a generalization of interval graphs in physical mapping of DNA.G= (V ,E) is a probe interval graph (PIG) with respect to a partition (P,N) ofV if vertices of G correspond to intervals on a real line and two vertices are adjacent if and only if their corresponding intervals intersect and at least one of them is in P; vertices belonging to P are called pro...

Many studies on detection and classification of web robots have focused their attention mostly on text crawlers, and empirical experiments used relatively small data collected at universities. In this paper, we analyzed more than one billion requests to www.microsoft. com in 24 h. Web logs were made anonymous to eliminate potential privacy concerns while preserving essential characteristics (e....

omega-3 fatty acids (fas) have been shown to prevent cardiovascular disease. the most commonly used omega-3 fatty acids like eicosapentaenoic acid (epa) and docosahexaenoic acid (dha) are highly vulnerable to oxidation and therefore, have short shelf life. recent advances in nanoliposomes provided a biocompatible system for stabilizing omega-3 fas. several methods could be implemented to prepar...

metal oxides play a very important role in many areas of chemistry, physics and materials science.the metal elements are able to form a large diversity of oxide compounds. in this investigation, wesynthesis sno2 and c,n,s-tridoped sno2 nanoparticles by precipitation method. the synthesizedsno2 and c,n,s-tridoped sno2 nanoparticles were characterized by instrumental analysis methods,such as x-ra...

filariasis in dogs is caused by several species of filariids. because of importance of this infection in veterinary medicine and public health, it is necessary to carry out an epidemiological and cross sectional studies in various geographical areas and use of well-adapted diagnosis methods. in this study 205 capillary and whole blood samples were collected from doges in various counties of eas...

virulence of the opportunistic yeast, candida albieans, involves the interplay of many complex changes including the yeast-hyphae transition, which mainly involves protein changes. cell wall mannoproteins are found to be the main cause of adherence of c. albieans to epithel ial cells in the first step of an infection process. in the present study, cell wall mannoproteins of intact yeast were pu...