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- Thapper, Johan, 1977-
(författare)
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Combinatorial Considerations on Two Models from Statistical Mechanics
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Interactions between combinatorics and statistical mechanics have provided many fruitful insights in both fields. A compelling example is Kuperberg’s solution to the alternating sign matrix conjecture, and its following generalisations. In this thesis we investigate two models from statistical mechanics which have received attention in recent years.The first is the fully packed loop model. A conjecture from 2001 by Razumov and Stroganov opened the field for a large ongoing investigation of the O(1) loop model and its connections to a refinement of the fully packed loop model. We apply a combinatorial bijection originally found by de Gier to an older conjecture made by Propp.The second model is the hard particle model. Recent discoveries by Fendley et al. and results by Jonsson suggests that the hard square model with cylindrical boundary conditions possess some beautiful combinatorial properties. We apply both topological and purely combinatorial methods to related independence complexes to try and gain a better understanding of this model.
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| 2. |
- Emtander, Eric, 1979-
(författare)
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On hypergraph algebras
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Fernaeus, Ylva, et al.
(författare)
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Beyond representations : Towards an action-centric perspective on tangible interaction
- 2008
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Ingår i: International Journal of Arts and Technology. - : Inderscience Publishers. - 1754-8853 .- 1754-8861. ; 1:3/4, s. 249-267
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Tidskriftsartikel (refereegranskat)abstract
- In the light of theoretical as well as concrete technical development, we discuss a conceptual shift from an information-centric to an action-centric perspective on tangible interactive technology. We explicitly emphasise the qualities of shareable use, and the importance of designing tangibles that allow for meaningful manipulation and control of the digital material. This involves a broadened focus from studying properties of the interface, to instead aim for qualities of the activity of using a system, a general tendency towards designing for social and sharable use settings and an increased openness towards multiple and subjective interpretations. An effect of this is that tangibles are not designed as representations of data, but as resources for action. We discuss four ways that tangible artefacts work as resources for action: (1) for physical manipulation; (2) for referential, social and contextually oriented action; (3) for perception and sensory experience; (4) for digitally mediated action.
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| 4. |
- Fernaeus, Ylva, et al.
(författare)
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Towards a new set of ideals : Consequences of the practice turn in tangible interaction
- 2008
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Ingår i: TEI'08 - Second International Conference on Tangible and Embedded Interaction - Conference Proceedings. - New York, NY, USA : ACM Press. - 9781605580043 ; , s. 223-230
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Konferensbidrag (refereegranskat)abstract
- The practice-oriented turn in social sciences has implied a series of fundamental consequences and design challenges for HCI in general, and particularly in tangible interaction research. This could be interpreted as a move away from scientific ideals based on a modernist tradition, reflected in four contemporary themes in tangible interaction research. The first theme concerns a shift from an information centric to an action centric perspective on interaction. The second concerns a broadened focus from studying properties of the system, to instead aim at supporting qualities of the activity of using a system. The third concerns the general shift towards supporting sharable use, rather than primarily individual use settings. The last theme concerns the shift towards multiple and subjective interpretation of how to use new technological artefacts. We discuss how these themes are grounded in theoretical as well as more concrete technical developments in the area of tangible computing.
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| 6. |
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| 7. |
- Jonsson, Andreas, 1974-, et al.
(författare)
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Engineering of a femtomolar affinity binding protein to human serum albumin
- 2008
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Ingår i: Protein Engineering Design & Selection. - : Oxford University Press (OUP). - 1741-0126 .- 1741-0134. ; 21:8, s. 515-527
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Tidskriftsartikel (refereegranskat)abstract
- We describe the development of a novel serum albumin binding protein showing an extremely high affinity (K(D)) for HSA in the femtomolar range. Using a naturally occurring 46-residue three-helix bundle albumin binding domain (ABD) of nanomolar affinity for HSA as template, 15 residues were targeted for a combinatorial protein engineering strategy to identify variants showing improved HSA affinities. Sequencing of 55 unique phage display-selected clones showed a strong bias for wild-type residues at nine positions, whereas various changes were observed at other positions, including charge shifts. Additionally, a few non-designed substitutions appeared. On the basis of the sequences of 12 variants showing high overall binding affinities and slow dissociation rate kinetics, a set of seven 'second generation' variants were constructed. One variant denoted ABD035 displaying wild-type-like secondary structure content and excellent thermal denaturation/renaturation properties showed an apparent affinity for HSA in the range of 50-500 fM, corresponding to several orders of magnitude improvement compared with the wild-type domain. The ABD035 variant also showed an improved affinity toward serum albumin from a number of other species, and a capture experiment involving human serum indicated that the selectivity for serum albumin had not been compromised from the affinity engineering.
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| 8. |
- Jonsson, Jakob, et al.
(författare)
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A spherical initial ideal for Pfaffians
- 2007
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Ingår i: Illinois Journal of Mathematics. - : Duke University Press. - 0019-2082 .- 1945-6581. ; 51:4, s. 1397-1407
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Tidskriftsartikel (refereegranskat)abstract
- We determine a term order on the monomials in the variables X-ij, 1 <= i <= j <= n, such that corresponding initial ideal of the ideal of Pfaffians of degree r of a generic n by n skew-symmetric matrix is the Stanley-Reisner ideal of a join of a simplicial sphere and a simplex. Moreover, we demonstrate that the Pfaffians of the 2r by 2r skew-symmetric submatrices form a, Grobner basis for the given term order. The same methods and similar term orders as for the Pfaffians also yield squarefree initial ideals for certain determinantal ideals. Yet, in contrast to the case of Pfaffians, the corresponding simplicial complexes are balls that do not decompose into a join as above.
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| 9. |
- Jonsson, Jakob, et al.
(författare)
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COMPLEXES OF INJECTIVE WORDS AND THEIR COMMUTATION CLASSES
- 2009
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Ingår i: Pacific Journal of Mathematics. - : Mathematical Sciences Publishers. - 0030-8730 .- 1945-5844. ; 243:2, s. 313-329
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Tidskriftsartikel (refereegranskat)abstract
- Let S be a finite alphabet. An injective word over S is a word over S such that each letter in S appears at most once in the word. For an abstract simplicial complex Delta, let Gamma(Delta) be the Boolean cell complex whose cells are indexed by all injective words over the sets forming the faces of Delta. The boundary of a cell indexed by a given word w consists of those cells that are indexed by subwords of w. For a partial order P on S, we study the subcomplex Gamma(Delta, P) of Gamma(Delta) consisting of those cells that are indexed by words whose letters are arranged in increasing order with respect to some linear extension of the order P. For a graph G = (S, E) on vertex set S and a word w over S, let [w] be the class of all words that we can obtain from w via a sequence of commutations ss' -> s's s such that {s, s'} g is not an edge in E. We study the Boolean cell complex Gamma/G(Delta) whose cells are indexed by commutation classes [w] of words indexing cells in Gamma(Delta). We prove: If Delta is shellable then so are Gamma(Delta, P) and Gamma/G(Delta). If Delta is Cohen-Macaulay (respectively sequentially Cohen-Macaulay) then so are Gamma(Delta, P) and Gamma/G(Delta). The complex Gamma(Delta) is partitionable. Our work generalizes work by Farmer and by Bjorner and Wachs on the complex of all injective words.
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| 10. |
- Jonsson, Jakob
(författare)
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Exact sequences for the homology of the matching complex
- 2008
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Ingår i: Journal of combinatorial theory. Series A (Print). - : Elsevier BV. - 0097-3165 .- 1096-0899. ; 115:8, s. 1504-1526
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Tidskriftsartikel (refereegranskat)abstract
- Building on work by Bouc and by Shareshian and Wachs, we provide a toolbox of long exact sequences for the reduced simplicial homology of the matching complex M., which is the simplicial complex of matchings in the complete graph K-n. Combining these sequences in different ways, we prove several results about the 3-torsion part of the homology of M, First, we demonstrate that there is nonvanishing 3-torsion in (H) over bar (d)(M-n : Z) whenever v(n) <= d <= [n-6/2], where v(n) =[n-4/3]. By results due to Bouc and to Shareshian and Wachs, (H) over bar (d)(M-n : Z) is a nontrivial elementary 3-group for almost all n and the bottom nonvanishing homology group of M. for all n 0 2. Second, we prove that (H) over bar (d)(M-n : Z) is a nontrivial 3-group whenever v(n) <= d <= [2n-9/5]. Third, for each k >= 0, we show that there is a polynomial f(k)(r) of degree 3k such that the dimension of (H) over bar (k-1+r) (M2k+1+3r:Z(3)), viewed as a vector space over Z(3), is at most f(k)(r) for all r >= k + 2.
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