1,433 research outputs found
Hadwiger number of graphs with small chordality
The Hadwiger number of a graph G is the largest integer h such that G has the
complete graph K_h as a minor. We show that the problem of determining the
Hadwiger number of a graph is NP-hard on co-bipartite graphs, but can be solved
in polynomial time on cographs and on bipartite permutation graphs. We also
consider a natural generalization of this problem that asks for the largest
integer h such that G has a minor with h vertices and diameter at most . We
show that this problem can be solved in polynomial time on AT-free graphs when
s>=2, but is NP-hard on chordal graphs for every fixed s>=2
Open source software for semi-automated histomorphometry of bone resorption and formation parameters
Micro-CT analysis has become the standard method for assessing bone volume and architecture in small animals. However, micro-CT does not allow the assessment of bone turnover parameters such as bone formation rate and osteoclast (OC) number and surface. For these crucial variables histomorphometric analysis is still an essential technique. Histomorphometry however, is time consuming and, especially in mouse bones, OCs can be difficult to detect. The main purpose of this study was to develop and validate a relatively easy and rapid method to measure static and dynamic bone histomorphometry parameters. Here we present the adaptation of established staining protocols and three novel open source image analysis packages: TrapHisto, OsteoidHisto and CalceinHisto that allow rapid, semi-automated analysis of histomorphometric bone resorption, osteoid, and calcein double labelling parameters respectively. These three programs are based on ImageJ, but use a relatively simple user interface that hides the underlying complexity of the image analysis
Testing a consensus conference method by discussing the management of traumatic dental injuries in Tanzania
Objectives: To test the recommended consensus conference methods in Tanzania by discussing the management of traumatic dental injuries, and to reach consensus on the feasibility of the treatment modalities of traumatic dental injuries recommended in western countries in theTanzanian situation.Study participants: Fifteen dentists as representatives of the profession and two lay people as representative of potential consumers.Interventions: Presentation of treatment modalities for traumatic dental injuries recommended in western countries.Main outcome measure: Consensus on the feasibility of the recommended treatment modalities of traumatic dental injuries in the Tanzanian situation.Results: For most types of injuries, consensus on the feasibility of the recommended treatment methods for Tanzania was reached immediately. More time was spent to discuss management of some injuries where the members felt that the recommended managementregimes for these injuries are not feasible in the current Tanzanian situation. Panel members made three recommendations. First, parents and teachers should be provided with guidelines or instructions about self-care following trauma. Second, teaching on the management oftraumatic dental injuries at training institutions should be emphasised and third, dental practitioners at dental clinics in the country should get continuing education about the management of traumatic dental injuries.Conclusion: The methods for achieving consensus were useful in the Tanzanian dental situation, therefore it is recommended that the methods be adopted to reach consensus on other oral health issues
The Regulation of Household Debt Levels in the EU and Three of its Member States: Evaluating the Legal Preconditions for Effectiveness
High levels of household debt were at the heart of the financial crisis. They have created vulnerabilities for individual households and for the financial system as a whole. In response to the crisis, the European Union reformed the Capital Requirements Regulation and Directive, and added new possibilities to increase risk-weights for household loans. It also adopted the Mortgage Credit Directive, which obliges lenders to assess a consumer’s creditworthiness before providing credit. Many member stat
Editing to Eulerian Graphs
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
, and denote the operations edge addition, edge deletion and
vertex deletion respectively. For any , we define
Connected Degree Parity Editing (CDPE()) to be the problem that takes
as input a graph , an integer and a function , and asks whether can be modified into a connected
graph with for each , using
at most operations from . We prove that
1. if or , then CDPE() can be solved in polynomial
time;
2. if , then CDPE() is
NP-complete and W[1]-hard when parameterized by , even if .
Together with known results by Cai and Yang and by Cygan, Marx, Pilipczuk,
Pilipczuk and Schlotter, our results completely classify the classical and
parameterized complexity of the CDPE() problem for all . We obtain the same classification for a natural variant of the
CDPE() problem on directed graphs, where the target is a weakly connected
digraph in which the difference between the in- and out-degree of every vertex
equals a prescribed value. As an important implication of our results, we
obtain polynomial-time algorithms for the Eulerian Editing problem and its
directed variant.Comment: 33 pages. An extended abstract of this paper will appear in the
proceedings of FSTTCS 201
Organisatiecultuur, een nieuw wondermiddel?
Op 24 januari jongstleden werd in de sociale faculteit door de Haagse projectorganisatie Tangram een Bedrijfs/Organisatiecultuurdag gehouden. Op deze dag kwamen vijf sprekers aan het woord , die ingingen op het fenomeen organisatiecultuur . De dag werd geleid door prof. dr. A. Bekke, die een kort openingswoord hield. Vervolgens kwamen een cultureel antropoloog, een organisatiepsycholoog en een organisatiesocioloog aan het woord. Na dit theoretische gedeelte kwamen twee sprekers uit de praktijk verte1Ien over hun ervaringen met het wijzigen van een organisatiecultuur
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Scenarios as the basis for assessment of mitigation and adaptation
The possibilities and need for adaptation and mitigation depends on uncertain future developments with respect to socio-economic factors and the climate system. Scenarios are used to explore the impacts of different strategies under uncertainty. In this chapter, some scenarios are presented that are used in the ADAM project for this purpose. One scenario explores developments with no mitigation, and thus with high temperature increase and high reliance on adaptation (leading to 4oC increase by 2100 compared to pre-industrial levels). A second scenario explores an ambitious mitigation strategy (leading to 2oC increase by 2100 compared to pre-industrial levels). In the latter scenario, stringent mitigation strategies effectively reduces the risks of climate change, but based on uncertainties in the climate system a temperature increase of 3oC or more cannot be excluded. The analysis shows that, in many cases, adaptation and mitigation are not trade-offs but supplements. For example, the number of people exposed to increased water resource stress due to climate change can be substantially reduced in the mitigation scenario, but even then adaptation will be required for the remaining large numbers of people exposed to increased stress. Another example is sea level rise, for which adaptation is more cost-effective than mitigation, but mitigation can help reduce damages and the cost of adaptation. For agriculture, finally, only the scenario based on a combination of adaptation and mitigation is able to avoid serious climate change impacts
Editing to a planar graph of given degrees.
We consider the following graph modification problem. Let the input consist of a graph G=(V,E), a weight function w:V∪E→N, a cost function c:V∪E→N0 and a degree function δ:V→N0, together with three integers kv,ke and C . The question is whether we can delete a set of vertices of total weight at most kv and a set of edges of total weight at most ke so that the total cost of the deleted elements is at most C and every non-deleted vertex v has degree δ(v) in the resulting graph G′. We also consider the variant in which G′ must be connected. Both problems are known to be NP-complete and W[1]-hard when parameterized by kv+ke. We prove that, when restricted to planar graphs, they stay NP-complete but have polynomial kernels when parameterized by kv+ke
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