Search results for "Graph theory"
showing 10 items of 784 documents
Algorithms for the Maximum Weight Connected $$k$$-Induced Subgraph Problem
2014
Finding differentially regulated subgraphs in a biochemical network is an important problem in bioinformatics. We present a new model for finding such subgraphs which takes the polarity of the edges (activating or inhibiting) into account, leading to the problem of finding a connected subgraph induced by \(k\) vertices with maximum weight. We present several algorithms for this problem, including dynamic programming on tree decompositions and integer linear programming. We compare the strength of our integer linear program to previous formulations of the \(k\)-cardinality tree problem. Finally, we compare the performance of the algorithms and the quality of the results to a previous approac…
Analytical properties of horizontal visibility graphs in the Feigenbaum scenario
2012
Time series are proficiently converted into graphs via the horizontal visibility (HV) algorithm, which prompts interest in its capability for capturing the nature of different classes of series in a network context. We have recently shown [1] that dynamical systems can be studied from a novel perspective via the use of this method. Specifically, the period-doubling and band-splitting attractor cascades that characterize unimodal maps transform into families of graphs that turn out to be independent of map nonlinearity or other particulars. Here we provide an in depth description of the HV treatment of the Feigenbaum scenario, together with analytical derivations that relate to the degree di…
Structural brain network fingerprints of focal dystonia
2019
Background: Focal dystonias are severe and disabling movement disorders of a still unclear origin. The structural brain networks associated with focal dystonia have not been well characterized. Here, we investigated structural brain network fingerprints in patients with blepharospasm (BSP) compared with those with hemifacial spasm (HFS), and healthy controls (HC). The patients were also examined following treatment with botulinum neurotoxin (BoNT). Methods: This study included matched groups of 13 BSP patients, 13 HFS patients, and 13 HC. We measured patients using structural-magnetic resonance imaging (MRI) at baseline and after one month BoNT treatment, at time points of maximal and minim…
Effective Field Theory
2015
Effective field theories (EFTs) are a highly important topic in Quantum Field Theory. Here we are going to shortly present some important highlights as well as the renormalization group equations for the Wilson coefficients. Afterwards we shall focus on one illustrative example and present the \(\textit{matching}\) procedure at the one-loop level. The infrared behaviour of EFTs is also covered with this example.
Walking on exoplanets: Is Star Wars right?
2016
As the number of detected extrasolar planets increases, exoplanet databases become a valuable resource, confirming some details about planetary formation, but also challenging our theories with new unexpected properties.
The Logical Sequence of Regional Economic Integration
2021
Globally, regional economic communities are classified in what is customarily called the linear model of integration. The question arises as to where African RECs stand on a stylized linear path of economic integration and to what extent this model can provide guidance for further integration steps. The factual nonlinearity of the ‘model’ is discussed and the ensuing challenges for economic integration are identified in terms of monetary unions, non-tariff measures/barriers (with a new typology) and harmonization of standards. In a final step, the ‘model’ itself is amended and critically discussed in the light of the question of whether a scheme largely inspired by the European experience c…
An Ecology and Economy Coupling Model. A global stationary state model for a sustainable economy in the Hamiltonian formalism
2020
Abstract The severity of the two deeply correlated crises, the environmental and the economic ones, needs to be faced also in theoretical terms; thus, the authors propose a model yielding a global “stationary state”, following the idea of a “steady-state economics” by Georgescu-Rogen and Herman Daly, by constructing only one dynamical system of ecological and economic coupled variables. This is possible resorting to the generalized Volterra model, that, translated in the Hamiltonian formalism and its Hamilton equations, makes possible to “conjugate” every pair of variables, one economic, the other one ecological, in describing the behavior in time of a unique dynamical system. Applying the …
Industrial development in thin regions: trapped in path extension?
2014
Recent theorizing of path dependence supplements the traditional view of regional path-dependent industrial development characterized by lock-in effects with paths dealing with change, that is, path renewal and path creation. Few studies, however, examine why different types of regions experience diverse path-dependent development. This article examines why organizationally thin regions are much less likely to achieve path renewal and path creation than core regions. By use of a case study of industrial development in an organizationally thin and rather peripheral region in Norway the article contends that thin regions often need external investments to avoid being trapped in path extension.
The path of R&D efficiency over time
2015
Abstract In this paper we investigate the pattern of R&D efficiency in terms of the number of product innovations achieved by firms over time. Using a panel dataset of Spanish manufacturing firms for the period 1990–2006, we follow the innovative performance of R&D active firms and observe that innovation rates change over firms' R&D histories. To explain these facts we propose a model that explicitly acknowledges the twofold composition of firms' R&D expenditures, comprising spending on both physical capital for R&D projects and payments to researchers. We regard this latter component of R&D as a source for dynamic returns to firms' R&D investments. Consequently firms' innovation outcomes …
Exogenously Led and Policy-Supported New Path Development in Peripheral Regions: Analytical and Synthetic Routes
2016
AbstractThe aim of this article is to explore how new industrial paths emerge and grow in peripheral regional economies. Current conceptualizations of regional path development are based on experiences from core regions and fail to provide satisfactory theoretical explanations of new path-creating activities in peripheral areas. Our conceptual approach combines the notions of path development and knowledge bases, enabling us to distinguish between an analytic and a synthetic route of path creation. We argue that due emphasis should be given to exogenous sources of new path development and policy actions in order to understand how analytical and synthetic routes unfold in peripheral regions.…