1,301 research outputs found
Astrid Lindgren and the Archives
No full textThe author Astrid Lindgren (1907-2002) is for many Swedes a genuine national icon. On several occasions, when the most popular and influential Swede is to be announced, Astrid Lindgren’s name is always one of the top names. Astrid Lindgren is for the Swedes known not only as a famous author, but also as a person who spoke out on things she found wrong in the Swedish society. In the history of Swedish literature 1945 is usually regarded as a milestone and Astrid Lindgren’s book Pippi Longstocking was published and revolutionised both children’s literature and the attitude to children and their upbringing. Astrid Lindgren also worked as editor-in-chief for the publishing house Rabén & Sjögren from 1946 to 1970 and for almost a quarter of a century she was responsible for the children’s literature while at the same time she was in practise her own editor. Today, ten years after she passed away 94 years old, her remaining papers, letters and manuscripts are kept in different archives where interesting research can be carried out. There is a substantial amount of material from her rich and prolific life and in this article I wish to illustrate how this material can be used to provide a deeper knowledge of Astrid Lindgren as a person and as an editor.</p
Sparsification Upper and Lower Bounds for Graphs Problems and Not-All-Equal SAT
No full textWe present several sparsification lower and upper bounds for classic problems in graph theory and logic. For the problems 4-Coloring, (Directed) Hamiltonian Cycle, and (Connected) Dominating Set, we prove that there is no polynomial-time algorithm that reduces any n-vertex input to an equivalent instance, of an arbitrary problem, with bitsize O(n^{2-epsilon}) for epsilon > 0, unless NP is a subset of coNP/poly and the polynomial-time hierarchy collapses. These results imply that existing linear-vertex kernels for k-Nonblocker and k-Max Leaf Spanning Tree (the parametric duals of (Connected) Dominating Set) cannot be improved to have O(k^{2-epsilon}) edges, unless NP is a subset of NP/poly. We also present a positive result and exhibit a non-trivial sparsification algorithm for d-Not-All-Equal-SAT. We give an algorithm that reduces an n-variable input with clauses of size at most d to an equivalent input with O(n^{d-1}) clauses, for any fixed d. Our algorithm is based on a linear-algebraic proof of Lovász that bounds the number of hyperedges in critically 3-chromatic d-uniform n-vertex hypergraphs by binom{n}{d-1}. We show that our kernel is tight under the assumption that NP is not a subset of NP/poly
Optimal Data Reduction for Graph Coloring Using Low-Degree Polynomials
No full textThe theory of kernelization can be used to rigorously analyze data reduction for graph coloring problems. Here, the aim is to reduce a q-Coloring input to an equivalent but smaller input whose size is provably bounded in terms of structural properties, such as the size of a minimum vertex cover. In this paper we settle two open problems about data reduction for q-Coloring.
First, we use a recent technique of finding redundant constraints by representing them as low-degree polynomials, to obtain a kernel of bitsize O(k^(q-1) log k) for q-Coloring parameterized by Vertex Cover for any q >= 3. This size bound is optimal up to k^o(1) factors assuming NP is not a subset of coNP/poly, and improves on the previous-best kernel of size O(k^q). Our second result shows that 3-Coloring does not admit non-trivial sparsification: assuming NP is not a subset of coNP/poly, the parameterization by the number of vertices n admits no (generalized) kernel of size O(n^(2-e)) for any e > 0. Previously, such a lower bound was only known for coloring with q >= 4 colors
Polynomial Kernels for Hitting Forbidden Minors under Structural Parameterizations
No full textWe investigate polynomial-time preprocessing for the problem of hitting forbidden minors in a graph, using the framework of kernelization. For a fixed finite set of graphs F, the F-Deletion problem is the following: given a graph G and integer k, is it possible to delete k vertices from G to ensure the resulting graph does not contain any graph from F as a minor? Earlier work by Fomin, Lokshtanov, Misra, and Saurabh [FOCS'12] showed that when F contains a planar graph, an instance (G,k) can be reduced in polynomial time to an equivalent one of size k^{O(1)}. In this work we focus on structural measures of the complexity of an instance, with the aim of giving nontrivial preprocessing guarantees for instances whose solutions are large. Motivated by several impossibility results, we parameterize the F-Deletion problem by the size of a vertex modulator whose removal results in a graph of constant treedepth eta.
We prove that for each set F of connected graphs and constant eta, the F-Deletion problem parameterized by the size of a treedepth-eta modulator has a polynomial kernel. Our kernelization is fully explicit and does not depend on protrusion reduction or well-quasi-ordering, which are sources of algorithmic non-constructivity in earlier works on F-Deletion. Our main technical contribution is to analyze how models of a forbidden minor in a graph G with modulator X, interact with the various connected components of G-X. Using the language of labeled minors, we analyze the fragments of potential forbidden minor models that can remain after removing an optimal F-Deletion solution from a single connected component of G-X. By bounding the number of different types of behavior that can occur by a polynomial in |X|, we obtain a polynomial kernel using a recursive preprocessing strategy. Our results extend earlier work for specific instances of F-Deletion such as Vertex Cover and Feedback Vertex Set. It also generalizes earlier preprocessing results for F-Deletion parameterized by a vertex cover, which is a treedepth-one modulator
Astrid Lindgren : Author and Publishing Editor
No full textI den tryckt boken felaktigt ISBN 978-91-89460-13-3 (print), 978-91-89460-14-0 (pdf)</p
Astrid Lindgren : Author and Publishing Editor
No full textI den tryckt boken felaktigt ISBN 978-91-89460-13-3 (print), 978-91-89460-14-0 (pdf)</p
Astrid Lindgren : Author and Publishing Editor
No full textI den tryckt boken felaktigt ISBN 978-91-89460-13-3 (print), 978-91-89460-14-0 (pdf)</p
The development of a SCAR marker for the identification of the potato cultivars Astrid and Mnandi
No full textM.Sc.Mnandi and Astrid are two commercially important potato cultivars in South Africa. These two cultivars are closely related and are morphological virtually identical. It is, however, necessary to be able to distinguish between these two cultivars, because each of these cultivars has certain desirable characteristics. It was decided to use DNA markers, since DNA markers are not influenced by the environment and the polymerase chain reaction (PCR) based DNA markers are relatively easy, cheap and fast. It was decided to develop a sequenced characterized amplified region (SCAR) due to the problems with the reproducibility of random amplified polymorphic DNA (RAPDs). SCARs are derived from RAPD fragments by using the sequence of a RAPD derived fragment to design a set of new longer primers (usually 20-24mer) which are less sensitive to PCR conditions. Ten commercial potato cultivars (Astrid, Mnandi. BP,, Buffelspoort, VanderPlank, Up-to-Date, Hoevelder, Hertha, Pimpernel and Agria) were used in this study. Commercially available RAPD primers (102) were evaluated to seek a polymorphism unique to either Mnandi or Astrid. Thirtyseven polymorphisms between Astrid and Mnandi were identified but only three were unique. The polymorphism obtained with OPH-15 was however, not reproducible. The polymorphisms obtained with UBC 509 and 582, corresponding to the presence in Mnandi of a 300 and 900 by fragment respectively, were reproducible. These two fragments, UBC 509 3" and UBC 582900, were cloned into the pMosBlue TA cloning vector and sequenced. The identity if the inserts in the recombinant plasmids were verified with PCR and Southern blotting. The sequences were used to develop two sets of SCAR primers, SCAR UBC 509 3" and SCAR UBC 582900 . The two SCAR primer pairs were then used in PCR reactions. The SCAR UBC 509 300 primer pair amplified a fragment of 230 by in both Astrid and Mnandi and a fragment of 260 by in Mnandi. The polymorphism is thus retained and SCAR UBC 509 3" can be used to distinguish between Astrid and Mnandi. The SCAR UBC 582' primer pair amplify a fragment of 500 by in both Astrid and Mnandi as well as some other longer fragments. It was not possible to regain a polymorphism by either elevating the annealing temperature or by digesting the amplification products with restriction enzymes. SCAR UBC 582' could thus not be used to distinguish between Astrid and Mnandi
Business Model Innovation and the Impact of Globalization
No full textAuthor Astrid LechnerMasterarbeit Universität Linz 201
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