Browsing Department of Informatics by Subject "VDP::Matematikk og Naturvitenskap: 400"
Now showing items 120 of 28

Additive Schwarz preconditioner for the finite volume element discretization of symmetric elliptic problems
(Peer reviewed; Journal article, 20150925)A symmetric and a nonsymmetric variant of the additive Schwarz preconditioner are proposed for the solution of a class of finite volume element discretization of the symmetric elliptic problem in two dimensions, with large ... 
Aligning a Splice Graph to a Genomic Sequence
(Master thesis, 20050601) 
Bchromatic number: Beyond NPhardness
(Peer reviewed; Journal article, 2015)The bchromatic number of a graph G, chi_b(G), is the largest integer k such that G has a kvertex coloring with the property that each color class has a vertex which is adjacent to at least one vertex in each of the other ... 
Chromatin and epigenetic features of longrange gene regulation
(Peer reviewed; Journal article, 20130613)The precise regulation of gene transcription during metazoan development is controlled by a complex system of interactions between transcription factors, histone modifications and modifying enzymes and chromatin conformation. ... 
Connecting Vertices by Independent Trees
(Journal article; Peer reviewed, 2014)We study the paramereteized complexity of the following connectivity problem. For a vertex subset U of a graph G, trees T1, . . . , Ts of G are completely independent spanning trees of U if each of them contains U , and ... 
Editing to Eulerian Graphs
(Journal article; Peer reviewed, 2014)We investigate the problem of modifying a graph into a connected graph in which the degree of each vertex satisfies a prescribed parity constraint. Let ea, ed and vd denote the operations edge addition, edge deletion and ... 
The EMBRACE web service collection
(Peer reviewed; Journal article, 20100510)The EMBRACE (European Model for Bioinformatics Research and Community Education) web service collection is the culmination of a 5year project that set out to investigate issues involved in developing and deploying web ... 
Enumerating minimal connected dominating sets in graphs of bounded chordality
(Peer reviewed; Journal article, 2015)Listing, generating or enumerating objects of specified type is one of the principal tasks in algorithmics. In graph algorithms one often enumerates vertex subsets satisfying a certain property. We study the enumeration ... 
Fast biclustering by dual parameterization
(Peer reviewed; Journal article, 2015)We study two clustering problems, Starforest Editing, the problem of adding and deleting edges to obtain a disjoint union of stars, and the generalization Bicluster Editing. We show that, in addition to being NPhard, none ... 
Finding even subgraphs even faster
(Peer reviewed; Journal article, 2015)Problems of the following kind have been the focus of much recent research in the realm of parameterized complexity: Given an input graph (digraph) on n vertices and a positive integer parameter k, find if there exist k ... 
Finding Induced Subgraphs via Minimal Triangulations
(Peer reviewed; Journal article, 2010)Potential maximal cliques and minimal separators are combinatorial objects which were introduced and studied in the realm of minimal triangulation problems in cluding Minimum Fillin and Treewidth. We discover unexpected ... 
The Genomic HyperBrowser: an analysis web server for genomescale data
(Peer reviewed; Journal article, 20130430)The immense increase in availability of genomic scale datasets, such as those provided by the ENCODE and Roadmap Epigenomics projects, presents unprecedented opportunities for individual researchers to pose novel falsifiable ... 
Investigating Streamless Sets
(Journal article; Peer reviewed, 2015)In this paper we look at streamless sets, recently investigated by Coquand and Spiwack. A set is streamless if every stream over that set contain a duplicate. It is an open question in constructive mathematics whether the ... 
Kernel(s) for Problems with No Kernel: On OutTrees with Many Leaves
(Peer reviewed; Journal article, 2009)The {\sc \(k\)Leaf OutBranching} problem is to find an outbranching, that is a rooted oriented spanning tree, with at least \(k\) leaves in a given digraph. The problem has recently received much attention from the ... 
Largest chordal and interval subgraphs faster than 2n
(Peer reviewed; Journal article, 20150822)We prove that in a graph with n vertices, induced chordal and interval subgraphs with the maximum number of vertices can be found in time O(2λn) for some λ< 1. These are the first algorithms breaking the trivial 2nnO(1) ... 
Maximum matching width: New characterizations and a fast algorithm for dominating set
(Peer reviewed; Journal article, 2015)We give alternative definitions for maximum matching width, e.g., a graph G has mmw(G) <= k if and only if it is a subgraph of a chordal graph H and for every maximal clique X of H there exists A,B,C \subseteq X with A ... 
Minimizing Fillin Size and Elimination Tree Height in Parallel Cholesky Factorization
(Master thesis, 1992) 
Model Checking Healthcare Workflows Using Alloy
(Journal article; Peer reviewed, 2014)Workflows are used to organize business processes, and workflow management tools are used to guide users in which order these processes should be performed. These tools increase organizational efficiency and enable users ... 
New Results on Minimal Triangulations
(Doctoral thesis, 20060425) 
NonConstructivity in Kan Simplicial Sets
(Journal article; Peer reviewed, 2015)We give an analysis of the nonconstructivity of the following basic result: if X and Y are simplicial sets and Y has the Kan extension property, then Y X also has the Kan extension property. By means of Kripke countermodels ...