Let P be a hereditary property. Let kP(G) denote the number of forbidden subgraphs, which are contained in G. A graph G is said to be weakly P-saturated, if G ∈ P and the edges of the complement of G can be labelled e1, e2, . . . , el in such way that for i= 0, 1, . . . , l− 1 the inequality kP(Gi+1)> kP(Gi) holds, whereG0=G,Gi+1=Gi + ei andGl =Kn. The minimum possible size of weakly P-saturate...

This paper presents a fully automated microrobotic system based on force/vision referenced control designed for cell mechanical characterization. The design of the prototype combines Scanning Probe Microscopy (SPM) techniques with advanced robotics approaches. As a result, accurate and non-destructive mechanical characterization based on soft contact mechanisms are achieved. The in vitro workin...

In this paper we propose a multipartite version of the classical Turán problem of determining the minimum number of edges needed for an arbitrary graph to contain a given subgraph. As it turns out, here the non-trivial problem is the determination of the minimal edge density between two classes that implies the existence of a given subgraph. We determine the critical edge density for trees and ...

This paper is concerned with the fixed-parameter tractability of the problem of deciding whether a graph can be made into a graph with a specified hereditary property by deleting at most i vertices, at most j edges, and adding at most k edges, where i, j, k are fixed integers. It is shown that this problem is fixed-parameter tractable whenever the hereditary property can be characterized by a f...

Tucker characterized the minimal forbidden submatrices of binary matrices that do not have the consecutive-ones property. We give a linear-time algorithm to find such a minimal one in any binary matrix that does not have the consecutive-ones property. Lekkerkerker and Boland characterized the minimal forbidden induced subgraphs for the class of interval graphs. We give a linear-time algorithm t...

Interval p-graphs were introduced by Brown et al. in 2002 as a generalization of interval bigraphs [D.E. Brown, S.C. Flink and J.R. Lundgren, Congr. Numer. 157 (2002), 79–93]. Little work has been done towards characterizing them. For interval bigraphs the only known forbidden subgraph characterization is for trees. As it appears to be quite difficult to find a forbidden subgraph characterizati...

We examine two criteria for balance of a gain graph, one based on binary cycles and one on circles. The graphs for which each criterion is valid depend on the set of allowed gain groups. The binary cycle test is invalid, except for forests, if any possible gain group has an element of odd order. Assuming all groups are allowed, or all abelian groups, or merely the cyclic group of order 3, we ch...

This paper investigates the dynamics of corruption at the top (i.e., by politicians). For this purpose a dynamic, politico-economic framework is developed and analyzed. A particular feature of this investigation is an analytical characterization of the dynamic properties of the system. This allows one to interpret these properties in terms of economic and institutional parameters. As an example...

Semiorders may form the simplest class of ordered sets with a not necessarily transitive indifference relation. Their generalization has given birth to many other classes of ordered sets, each of them characterized by an interval representation, by the properties of its relations or by forbidden configurations. In this paper, we are interested in preference structures having an interval represe...

A graph is probe (unit) interval if its vertices can be partitioned into two sets: a set of probe vertices and a set of nonprobe vertices, so that the set of nonprobe vertices is a stable set and it is possible to obtain a (unit) interval graph by adding edges with both endpoints in the set of nonprobe vertices. Probe (unit) interval graphs form a superclass of (unit) interval graphs. Probe int...