Campylobacter jejuni is a leading cause of bacterially derived gastroenteritis. A previous mutant screen demonstrated that the heme uptake system (Chu) is required for full colonization of the chicken gastrointestinal tract. Subsequent work identified a PAS domain-containing regulator, termed HeuR, as being required for chicken colonization. Here we confirm that both the heme uptake system and ...

In this paper we present a new hybrid heuristic for large geometric Traveling Salesman Problems. The method is based on the use of the Delaunay Triangulation of a set of cities. Many heuristics for the TSP are generally composed of two phases: a constructive heuristic followed by an iterative improvement step until a local minimum is reached. We think of this heuristic as a hybrid since, after ...

— We treat a discrete uncapacitated facility location problem where the installation cost per facility is a gênerai nonlinear function of the number of established facilities. Assuming a convexity proper ty, Mirchandani and Jagannathan developed a heur is tic solution procedure for this problem. Hère, we show how to modify their algorithm in order to get and prove exact solutions and, at the sa...

In high-performance A* searching to solve satisfici n g prob lems, there is a c r i t i ca l need to design heur is t ics which cause low t ime-complex i ty . In order for humans or machines to do this effectively, there mus t be an unders tand ing of the domainindependent properties that such heurist ics have. We snow that , contrary to common belief, accuracy is no t c r i t i c a l ; the key...

POPS ts a processor for a simple nondeterminist ic programming language, PSL. POPS accepts a problem stated in PSL and attempts to solve it by f inding a successfu l execut ion of the PSL program, POPS operates by ident i fy ing elements of the input program wi th elements of the heur is t ic search paradigm, analyzing the input program to obta in informat ion about the problem operat o r s , a...

The paper describes a heur is t ic scene descr ip t ion system. This system accepts as input a scene represented as a l ine drawing. Based on a set of known object models, the program attempts to determine the ident i ty and location of each object viewed. The most s igni f icant feature of the system is i t s a b i l i t y to deal with imperfect input data. This a b i l i t y appears essential...