| 1. |
- Ebbers-Baumann, Annette, et al.
(författare)
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Embedding point sets into plane graphs of small dilation
- 2007
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Ingår i: International Journal of Computational Geometry and Applications. - 0218-1959. ; 17:3, s. 201-230
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Tidskriftsartikel (refereegranskat)abstract
- Let S be a set of points in the plane. What is the minimum possible dilation of all plane graphs that contain S? Even for a set S as simple as five points evenly placed on the circle, this question seems hard to answer; it is not even clear if there exists a lower bound > 1. In this paper we provide the first upper and lower bounds for the embedding problem. 1. Each finite point set can be embedded in to the vertex set of a finite triangulation of dilation <= 1.1247. 2. Each embedding of a closed convex curve has dilation >= 1.00157. 3. Let P be the plane graph that results from intersecting n infinite families of equidistant, parallel lines in general position. Then the vertex set of P has dilation >= 2/root 3 approximate to 1.1547.
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| 2. |
- Han, Xin, et al.
(författare)
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Approximating the maximum independent set and minimum vertex coloring on box graphs
- 2007
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Ingår i: Algorithmic Aspects in Information and Management / Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 9783540728689 ; 4508, s. 337-345
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Konferensbidrag (refereegranskat)abstract
- A box graph is the intersection graph of a finite set of orthogonal rectangles in the plane. The problem of whether or not the maximum independent set problem (MIS for short) for box graphs can be approximated within a substantially sub-logarithmic factor in polynomial time has been open for several years. We show that for box graphs on n vertices which have an independent set of size Ω(n/logO(1)n) the maximum independent set problem can be approximated within O(logn / loglogn) in polynomial time. Furthermore, we show that the chromatic number of a box graph on n vertices is within an O(logn) factor from the size of its maximum clique and provide an O(logn) approximation algorithm for minimum vertex coloring of such a box graph. More generally, we can show that the chromatic number of the intersection graph of n d-dimensional orthogonal rectangles is within an O(logd − 1n) factor from the size of its maximum clique and obtain an O(logd − 1n) approximation algorithm for minimum vertex coloring of such an intersection graph.
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| 3. |
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| 4. |
- Mattheos, Nikos, et al.
(författare)
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Assessing behavioural change support abilities of the oral healthcare team
- 2006
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Ingår i: Oral Health & Preventive Dentistry. - : Quintessence. - 1602-1622 .- 1757-9996. ; 4:1, s. 71-77
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Tidskriftsartikel (refereegranskat)abstract
- Competent behavioural change intervention can be learned, practised and developed. Therefore, the teaching and assessment of this ability should be within the scope of both the undergraduate and post-graduate curriculum. Assessment should target knowledge base and skills in the areas of counselling, communication and behaviour. Assessment of the knowledge base should ideally be conducted in a comprehensive, multidisciplinary, centrally based manner in the pre-clinical curriculum. Assessment of skills in the areas of communication, counselling and behaviour change is a wider aim that should be integral throughout the curriculum. In continuing education (CE) environments, an initial 'screening' assessment would help educators to adjust the course to the participants' background and needs. Furthermore, three major assessment schemes are proposed: (1) assessment of knowledge and skills, (2) evaluation of the whole course by the participants, and (3) assessment of the implementation process, four to six months after completion.
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| 5. |
- Post, Eric, et al.
(författare)
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Ecological Dynamics Across the Arctic Associated with Recent Climate Change
- 2009
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 325:5946, s. 1355-1358
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Forskningsöversikt (refereegranskat)abstract
- At the close of the Fourth International Polar Year, we take stock of the ecological consequences of recent climate change in the Arctic, focusing on effects at population, community, and ecosystem scales. Despite the buffering effect of landscape heterogeneity, Arctic ecosystems and the trophic relationships that structure them have been severely perturbed. These rapid changes may be a bellwether of changes to come at lower latitudes and have the potential to affect ecosystem services related to natural resources, food production, climate regulation, and cultural integrity. We highlight areas of ecological research that deserve priority as the Arctic continues to warm.
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