Forbidden induced subgraphs and the price of connectivity for feedback vertex set.

Let fvs(G) and cfvs(G) denote the cardinalities of a minimum feedback vertex set and a minimum connected feedback vertex set of a graph G, respectively. For a graph class G, the price of connectivity for feedback vertex set (poc-fvs) for G is defined as the maximum ratio cfvs(G)/fvs(G) over all connected graphs G in G. It is known that the poc-fvs for general graphs is unbounded. We study the poc-fvs for graph classes defined by a finite family H of forbidden induced subgraphs. We characterize exactly those finite families H for which the poc-fvs for H-free graphs is bounded by a constant. Prior to our work, such a result was only known for the case where |H|=1

Vooral kinderen uit bijstandsgezinnen geen kansrijke start:Ouderlijke hulpbronnen in de eerste duizend dagen tot en met de basisschoolperiode

De aanwezigheid van hulpbronnen in gezinnen is van belang voor een goede start van een kind. In dit artikel is gekeken naar onderwijsniveau, arbeidsparticipatie, welvaart, gezinsstabiliteit en mentale gezondheid van ouders in de eerste duizend dagen. Gekeken is naar de periode van conceptie tot de tweede verjaardag van in 2006 geboren kinderen en beslaat de periode van 2005 tot en met 2007. Vooral het ontbreken van meerdere hulpbronnen tegelijkertijd kan een risico betekenen voor de ontwikkeling van kinderen. Bij kinderen die opgroeien in een gezin met een bijstandsuitkering is bij 9 procent sprake van een opeenstapeling van vier risicofactoren. Bij kinderen in een gezin zonder bijstand is dat bij 0,2 procent het geval

The price of connectivity for feedback vertex set

Let View the MathML source and View the MathML source denote the cardinalities of a minimum feedback vertex set and a minimum connected feedback vertex set of a graph G, respectively. The price of connectivity for feedback vertex set (poc-fvs) for a class of graphs G is defined as the maximum ratio View the MathML source over all connected graphs G∈G. We study the poc-fvs for graph classes defined by a finite family H of forbidden induced subgraphs. We characterize exactly those finite families H for which the poc-fvs for H-free graphs is upper bounded by a constant. Additionally, for the case where ∣H∣=1, we determine exactly those graphs H for which there exists a constant cH such that View the MathML source for every connected H-free graph G, as well as exactly those graphs H for which we can take cH=0

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

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