Solving satisfiability problems by fluctuations: the dynamics of stochastic local search algorithms.

Stochastic local search algorithms are frequently used to numerically solve hard combinatorial optimization or decision problems. We give numerical and approximate analytical descriptions of the dynamics of such algorithms applied to random satisfiability problems. We find two different dynamical regimes, depending on the number of constraints per variable: For low constraintness, the problems are solved efficiently, i.

Clustering analysis of the ground-state structure of the vertex-cover problem.

Vertex cover is one of the classical NP-complete problems in theoretical computer science. A vertex cover of a graph is a subset of vertices such that for each edge at least one of the two endpoints is contained in the subset. When studied on Erdo s-Re nyi random graphs (with connectivity c) one observes a threshold behavior: In the thermodynamic limit the size of the minimal vertex cover is independent of the specific graph.

Hiding solutions in random satisfiability problems: a statistical mechanics approach.

A major problem in evaluating stochastic local search algorithms for NP-complete problems is the need for a systematic generation of hard test instances having previously known properties of the optimal solutions. On the basis of statistical mechanics results, we propose random generators of hard and satisfiable instances for the 3-satisfiability problem. The design of the hardest problem instances is based on the existence of a first order ferromagnetic phase transition and the glassy nature of excited states.

Bioequivalence of allopurinol-containing tablet preparations.

Aim: The study was undertaken to prove the bioequivalence of two allopurinol tablet preparations.

Subjects, Materials And Methods: The relative bioavailability of allopurinol from two tablet preparations (Uribenz vs. Zyloric 300) was estimated on 18 volunteers of both sexes in an open randomized study by administering one tablet of each preparation at an interval of 2 weeks.

Effects of a supersulfated low molecular weight heparin (IK-SSH) on different hemostatic parameters.

In a phase I trial effects of a new supersulfated low molecular weight heparin (IK-SSH) on different hemostatic parameters were investigated in healthy volunteers. Parameters studied were activated partial thromboplastin time (aPTT), thrombin time, Heptest, anti-activated factor II (anti-FIIa) and anti-activated factor X (anti-FXa) activity, platelet adhesion, platelet count, platelet-induced thrombin generation time (PITT), bleeding time, antithrombin III, fibrinogen and several safety parameters. After single intravenous (i.