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In this paper we consider the approximability of the maximum induced matching problem. We prove that there is some xed constant c such that the problem of approximating a maximum induced matching in 3s-regular graphs within a factor of c is NP-hard, for each s 1. In addition we give an approximation algorithm with asymptotic performance ratio d ? 1 for the(More)
BACKGROUND The prognostic impact of masked hypertension is not yet completely clear. The aim of this study was to evaluate the prognostic relevance of masked hypertension in subjects with prehypertension. METHODS The occurrence of fatal and nonfatal cardiovascular events was evaluated in 591 subjects with prehypertension defined as clinic blood pressure(More)
Graph mining is an important research area within the domain of data mining. The field of study concentrates on the identification of frequent subgraphs within graph data sets. The research goals are directed at: (i) effective mechanisms for generating candidate subgraphs (without generating duplicates) and (ii) how best to process the generated candidate(More)
Geographic profilers have access to a repertoire of strategies for predicting a serial offender's home location. These strategies range in complexity—some involve more calculations to implement than others—and the assumption often made is that more complex strategies will outperform simpler strategies. In the present study, we tested the relationship(More)
The problem of determining the unsatisfiability threshold for random 3-SAT formulas consists in determining the clause to variable ratio that marks the experimentally observed abrupt change from almost surely satisfiable formulas to almost surely unsatisfiable. Up to now, there have been rigorously established increasingly better lower and upper bounds to(More)
The problem of determining the unsatisfiability threshold for random 3-SAT formulas consists in determining the clause to variable ratio that marks the (experimentally observed) abrupt change from almost surely satisfiable formulas to almost surely unsatisfiable. Up to now, there have been rigorously established increasingly better lower and upper bounds to(More)
Web traversal robots are used by search engines and in other applications to gather information periodically from large numbers of documents distributed throughout the Web. In this paper we study the issues involved in the design of algorithms for performing information gathering of this kind more eeciently, by taking advantage of anticipated variations in(More)