| 1. |
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| 2. |
- Allain, J. P., et al.
(författare)
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Evolutionary rate and genetic drift of hepatitis C virus are not correlated with the host immune response : Studies of infected donor-recipient clusters
- 2000
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Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 74:6, s. 2541-2549
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Tidskriftsartikel (refereegranskat)abstract
- Six donor-recipient clusters of hepatitis C virus (HCV)-infected individuals were studied. For five clusters the period of infection of the donor could be estimated, and for all six clusters the time of infection of the recipients from the donor via blood transfusion was also precisely known. Detailed phylogenetic analyses were carried out to investigate the genomic evolution of the viral quasispecies within infected individuals in each cluster. The molecular clock analysis showed that HCV quasispecies within a patient are evolving at the same rate and that donors that have been infected for longer time tend to have a lower evolutionary rate. Phylogenetic analysis based on the split decomposition method revealed different evolutionary patterns in different donor-recipient clusters. Reactivity of antibody against the first hypervariable region (HVR1) of HCV in donor and recipient sera was evaluated and correlated to the calculated evolutionary rate. Results indicate that anti-HVR1 reactivity was related more to the overall level of humoral immune response of the host than to the HVR1 sequence itself, suggesting that the particular sequence of the HVR1 peptides is not the determinant of reactivity. Moreover, no correlation was found between the evolutionary rate or the heterogeneity of the viral quasispecies in the patients and the strength of the immune response to HVR1 epitopes, Rather, the results seem to imply that genetic drift is less dependent on immune pressure than on the rate of evolution and that the genetic drift of HCV is independent of the host immune pressure.
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| 3. |
- Cieslik, D, et al.
(författare)
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Connectivity calculus
- 2003
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Ingår i: Applied Mathematics Letters. - 0893-9659 .- 1873-5452. ; 16:3, s. 395-399
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Tidskriftsartikel (refereegranskat)abstract
- Given a finite hypergraph H = (V, E) and, for each e E E, a collection of nonempty subsets pi(e) of e, Mobius inversion is used to establish a recursive formula for the number of connected components of the hypergraph H = (V, boolean OR(eis an element ofE)pi(e)). As shown elsewhere, this formula is an essential ingredient in the context of a certain divide-and-conquer strategy that allows us to define a dynamical programming scheme solving Steiner's problem for graphs in linear time (however, with a constant depending hyperexponentially on their tree width).
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| 4. |
- Cieslik, D., et al.
(författare)
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Connectivity calculus
- 2003
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Ingår i: Applied Mathematical Letters. ; 16, s. 395-399
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Tidskriftsartikel (refereegranskat)
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| 5. |
- Dress, A., et al.
(författare)
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Affine maps that induce polyhedral complex isomorphisms
- 2000
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Ingår i: Discrete & Computational Geometry. - 0179-5376 .- 1432-0444. ; 24:1, s. 49-60
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we show that an affine bijection f: T-1 --> T-2 between two polyhedral complexes T-1, T-2, both of which consist of a union of faces of two convex polyhedra P-1 and P-2, necessarily respects the cell-complex structure of T-1 and T-2 inherited from P-1 and P-2, respectively, provided f extends to an affine map from P-1 into P-2. In addition, we present an application of this result within the area of T-theory to obtain a far-reaching generalization of previous results regarding the equivalence of two distinct constructions of the phylogenetic tree associated to "perfect" (that is, treelike) distance data.
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| 6. |
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| 7. |
- Dress, A, et al.
(författare)
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Antipodal metrics and split systems
- 2002
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Ingår i: European Journal of Combinatorics. - : Elsevier BV. - 0195-6698 .- 1095-9971. ; 23:2, s. 187-200
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Tidskriftsartikel (refereegranskat)abstract
- Recall that a metric d on a finite set X is called antipodal if there exists a map sigma : X --> X: x --> (x) over bar so that d(x, (x) over bar) = d(x, y) + d(y, (x) over bar) holds for all x, y epsilon X. Antipodal metrics canonically arise as metrics induced on specific weighted graphs, although their abundance becomes clearer in light of the fact that any finite metric space can be isometrically embedded in a more or less canonical way into an antipodal metric space called its full antipodal extension. In this paper, we examine in some detail antipodal metrics that are, in addition, totally split decomposable. In particular, we give an explicit characterization of such metrics, and prove that-somewhat surprisingly-the full antipodal extension of a proper metric d on a finite set X is totally split decomposable if and only if d is linear or #X = 3 holds.
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| 8. |
- Dress, A., et al.
(författare)
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On line arrangements in the hyperbolic plane
- 2002
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Ingår i: European journal of combinatorics (Print). - : Elsevier BV. - 0195-6698 .- 1095-9971. ; 23:5, s. 549-557
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Tidskriftsartikel (refereegranskat)abstract
- Given a finite collection L of lines in the hyperbolic plane H, we denote by k = k(L) its Karzanov number, i.e., the maximal number of pairwise intersecting lines in L, and by C(L) and n = n(L) the set and the number, respectively, of those points at infinity that are incident with at least one line from L. By using purely combinatorial properties of cyclic seta:, it is shown that #L less than or equal to 2nk - ((2k+1)(2)) always holds and that #L equals 2nk - ((2k+1)(2)) if and only if there is no collection L' of lines in H with L subset of or equal to L', k(L') = k(L) and C(L') = C(L).
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| 9. |
- Dress, A., et al.
(författare)
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Six points suffice : How to check for metric consistency
- 2001
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Ingår i: European journal of combinatorics (Print). - : Elsevier BV. - 0195-6698 .- 1095-9971. ; 22:4, s. 465-474
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Tidskriftsartikel (refereegranskat)abstract
- In many areas of data analysis, it is desirable to have tools at hand for analyzing the structure of distance tables-or, in more mathematical terms, of finite metric spaces. One such tool, known as split decomposition theory has proven particularly useful in this respect. Tbe class of so-called totally decomposable metrics forms a cornerstone for this theory, and much work has been devoted to their study. Recently, it has become apparent that a particular subclass of these metrics, the consistent metrics, are also of fundamental importance. In this paper, we give a six-point characterization of consistent metrics amongst the totally decomposable ones.
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| 10. |
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