The anomalously warm winter of 2005 follows similarly warm winters of 2003 and 2004. Although surface air temperature in the winter of 2002 was colder than 1961-2000 average, the depth-integrated temperatures at Mooring 2 indicate that the shift to warmer conditions in the Bering Sea began in the spring of 2000. This warming becomes comparable in its scale with major warm episodes in the late 1...

Starting with Einstein’s famous papers of 1905, we review some of the ensuing developments and their impact on present-day physics. We attempt to cover topics that are of interest to historians and philosophers of science as well as to physicists.

In this paper, we study a class of set cover problems that satisfy a special property which we call the small neighborhood cover property. This class encompasses several well-studied problems including vertex cover, interval cover, bag interval cover and tree cover. We design unified distributed and parallel algorithms that can handle any set cover problem falling under the above framework and ...

A new method for solving the hitting set problem is proposed. This method is based on the mapping of the problem onto an integer programming optimization problem. This new approach provides an algorithm with much better performance compare to the algorithms for the bitting set problem that currently are used for solving the diagnosis problem. The relation of this approach with the satisfiabilit...

When BDDs are used for propagation in a constraint solver with nogood recording, it is necessary to find a small subset of a given set of variable assignments that is enough for a BDD to imply a new variable assignment. We show that the task of finding such a minimum subset is NP-complete by reduction from the hitting set problem. We present a new algorithm for finding such a minimal subset, wh...

Covering is a widely used form of data structures. Covering-based rough set theory provides a systematic approach to this data. In this paper, graphs are connected with covering-based rough sets. Specifically, we convert some important concepts in graph theory including vertex covers, independent sets, edge covers, and matchings to ones in covering-based rough sets. At the same time, correspond...

In the hitting set problem one is given m subsets of a nite set N and one has to nd an X N of minimum cardinality that hits intersects all of them The problem is NP hard It is not known whether there exists a polynomial time approximation algorithm for the hitting set problem with a nite performance ratio Special cases of the hitting set problem are described for which nite performance ratios a...

This paper presents an O(1.2738 + kn)-time polynomialspace parameterized algorithm for Vertex Cover improving the previous O(1.286+kn)-time polynomial-space upper bound by Chen, Kanj, and Jia. The algorithm also improves the O(1.2745k+kn)-time exponentialspace upper bound for the problem by Chandran and Grandoni.

We establish almost tight upper and lower approximation bounds for the Vertex Cover problem on dense k-partite hypergraphs.