Constructing tree decompositions of graphs with bounded gonality

In this paper, we give a constructive proof of the fact that the treewidth of a graph is at most its divisorial gonality. The proof gives a polynomial time algorithm to construct a tree decomposition of width at most k, when an effective divisor of degree k that reaches all vertices is given. We also give a similar result for two related notions: stable divisorial gonality and stable gonality

Is de rode Amerikaanse rivierkreeft een ernstige bedreiging voor het veenweidegebied?

Sinds 2010 worden in het veenweidegebied van Zuid Holland en Utrecht zeer hoge dichtheden van de rode Amerikaanse rivierkreeft (Procambarus clarckii) aangetroffen. Deze exoot uit Mexico en het zuiden van de Verenigde Staten werd in 1973 uitgezet in Spanje, vooral om de lokale visserij te stimuleren. Van hier uit heeft deze soort zich snel over Europa verspreid. In dit artikel wordt aan de hand van gegevens over juffers en libellen in de Molenpolder bij Utrecht ingegaan op de effecten en mogelijke aanpak van deze soort

Is de rode Amerikaanse rivierkreeft een ernstige bedreiging voor het veenweidegebied?

Sinds 2010 worden in het veenweidegebied van Zuid Holland en Utrecht zeer hoge dichtheden van de rode Amerikaanse rivierkreeft (Procambarus clarckii) aangetroffen. Deze exoot uit Mexico en het zuiden van de Verenigde Staten werd in 1973 uitgezet in Spanje, vooral om de lokale visserij te stimuleren. Van hier uit heeft deze soort zich snel over Europa verspreid. In dit artikel wordt aan de hand van gegevens over juffers en libellen in de Molenpolder bij Utrecht ingegaan op de effecten en mogelijke aanpak van deze soort

Developments in deriving critical limits and modelling critical loads of nitrogen for terrestrial ecosystems in Europe

This collaborative report of Alterra and the Coordination Center for Effects (MNP-CCE), in cooperation with various participants of the International Cooperative programme on Modelling and Mapping (ICP-MM) includes: 1. A summarizing overview of adverse nitrogen deposition effects on terrestrial ecosystems in terms of impacts on plant species and faunal biodiversity, forest nutrient status in relation to impacts on soil and solution chemistry and on ground water quality. 2. An overview of integrated dynamic biogeochemical models with plant species diversity models, that allow the assessment of critical loads and target loads of nitrogen in view of plant species diversity impacts. 3. A review of currently used critical limits for N concentrations in soil solution and derivation of new critical limits, based on field (literature) data and integrated soil vegetation models, that can be used in the computation of critical loads by steady state soil models. This updated knowledge of N effects, critcal N load methodologies (integrated models) and critical N limits a can contribute to a more appropriate data submission on critical N loads by the National Focal Centres to the CCE, specifically in view of biodiversity impacts, to be used for support of the UNECE and EU air pollution policies

Constructing tree decompositions of graphs with bounded gonality

In this paper, we give a constructive proof of the fact that the treewidth of a graph is at most its divisorial gonality. The proof gives a polynomial time algorithm to construct a tree decomposition of width at most k, when an effective divisor of degree k that reaches all vertices is given. We also give a similar result for two related notions: stable divisorial gonality and stable gonality.Optimizatio

X-ray collinator having plates with periodic rectangular openings

An X-ray collimator in an X-ray analysis apparatus, consisting of plates of X-ray absorbing material, for example tungsten, which are arranged transversely of the X-ray beam. The plates are identical and provided with a pattern of rows and columns of rectangular openings 40, 42 which have a vertical period p1 and a horizontal period p2. The openings take up an opening fraction t1 and t2 of the periods p1 and p2, respectively. The plates are arranged in the collimator in a series in which the ratio between two successive distances (di, di+1) between the plates of the series is equal to the given opening fractions t1 and t2 of the periods p1 and p2, respectively. It has been found that all directions in the X-ray beam are then intercepted except for the direction to be collimated. Moreover, this configuration also enables transverse collimation. The collimator thus formed has a substantially smaller weight and also offers space to accommodate further elements for influencing the X-ray beam

Constructing tree decompositions of graphs with bounded gonality

In this paper, we give a constructive proof of the fact that the treewidth of a graph is at most its divisorial gonality. The proof gives a polynomial time algorithm to construct a tree decomposition of width at most k, when an effective divisor of degree k that reaches all vertices is given. We also give a similar result for two related notions: stable divisorial gonality and stable gonality

Constructing tree decompositions of graphs with bounded gonality

In this paper, we give a constructive proof of the fact that the treewidth of a graph is at most its divisorial gonality. The proof gives a polynomial time algorithm to construct a tree decomposition of width at most k, when an effective divisor of degree k that reaches all vertices is given. We also give a similar result for two related notions: stable divisorial gonality and stable gonality.</p