The chapter covers methods for identifying islands of tractability for NP-hard combinatorial problems by exploiting suitable properties of their graphical structure. Acyclic structures are considered, as well as nearly acyclic ones identified by means of so-called structural decomposition methods. In particular, the chapter focuses on the tree decomposition method, which is the most powerful de...

* Partially supported by NSF under Grant No. DMS-9701598. † Research partially supported by NSF under Grant No. DMS-9401981 and by DIMACS Center, Rutgers University, New Brunswick, NJ 08903. ‡ Partially supported by ONR under Contract No. N00014-97-1-0512. §Partially supported by NSF under Grant No. DMS-9623031, by NSA under Contract No. MDA904-98-1-0517, and by DIMACS Center, Rutgers Universit...

background and aims. various methods are used to measure the size and form of the teeth, including the golden proportion, and the width-to-length ratio of central teeth, referred to as the golden standard. the aim of this study was to evaluate the occurrence of golden standard values and golden proportion in the anterior teeth. materials and methods. photographs of 100 dentistry students (50 ma...

the biologic width (bw) includes attached epithelial cells and connective tissue attachment complex being very important in the periodontal health during prosthetic treatments as invading this zone can cause bone resorption and gingival recession. the present study investigated biologic width values in the normal periodontium in anterior and posterior teeth. 30 patients that referred from resto...

An integer-valued function f on the set 2V of all subsets of a finite set V is a connectivity function if it satisfies the following conditions: (1) f(X) + f(Y ) ≥ f(X ∩Y )+ f(X ∪Y ) for all subsets X, Y of V , (2) f(X) = f(V \X) for all X ⊆ V , and (3) f(∅) = 0. Branch-width is defined for graphs, matroids, and more generally, connectivity functions. We show that for each constant k, there is ...