| 1. |
- Bateman, A, et al.
(författare)
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The Pfam protein families database
- 2004
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Ingår i: Nucleic acids research. - : Oxford University Press (OUP). - 1362-4962. ; 32:Database issue, s. D138-D141
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Björklund, Andreas, et al.
(författare)
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Approximating longest directed paths and cycles
- 2004
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Ingår i: Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349. ; 3142, s. 222-233
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the hardness of approximating the longest path and the longest cycle in directed graphs on n vertices. We show that neither of these two problems can be polynomial time approximated within n(1-epsilon)for any epsilon > 0 unless P = NP. In particular, the result holds for digraphs of constant bounded outdegree that contain a Hamiltonian cycle. Assuming the stronger complexity conjecture that Satisfiability cannot be solved in subexponential time, we show that there is no polynomial time algorithm that finds a directed path of length Omega(f(n) log(2) n), or a directed cycle of length Omega(f(n) log n), for any nondecreasing, polynomial time computable function f in w(1). With a recent algorithm for undirected graphs by Gabow, this shows that long paths and cycles are harder to find in directed graphs than in undirected graphs. We also find a directed path of length Omega(log(2) n/log log n) in Hamiltonian digraphs with bounded outdegree. With our hardness results, this shows that long directed cycles are harder to find than a long directed paths. Furthermore, we present a simple polynomial time algorithm that finds paths of length Omega(n) in directed expanders of constant bounded outdegree.
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| 3. |
- Johansson, C, et al.
(författare)
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Critical test of the validity of Monin-Obukhov similarity during convective conditions
- 2001
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Ingår i: Journal of the Atmospheric Sciences. - 0022-4928 .- 1520-0469. ; 58:12, s. 1549-1566
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Tidskriftsartikel (refereegranskat)abstract
- A recent study of convective boundary layer characteristics performed with large eddy simulation technique (LES) has demonstrated unexpected influence of the depth of the boundary layer on surface layer characteristics. The present study tests some of the
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| 4. |
- Johansson, Göran A., et al.
(författare)
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Exploring the use of soft X-ray microscopy for imaging subcellular structures of the inner ear
- 2004
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Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 215, s. 203-212
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Tidskriftsartikel (refereegranskat)abstract
- The soft X-ray microscope at the Lawrence Berkeley National Laboratory was developed for visualization of biological tissue. Soft X-ray microscopy provides high-resolution visualization of hydrated, non-embedded and non-sectioned cells and is thus potentially an alternative to transmission electron microscopy. Here we show for the first time soft X-ray micrographs of structures isolated from the guinea-pig inner ear. Sensory outer hair cells and supporting pillar cells are readily visualized. In the hair cells, individual stereocilia can easily be identified within the apical hair bundle. The underlying cuticular plate is, however, too densely composed or too thick to be clearly visualized, and thus appears very dark. The cytoplasmic structures protruding from the cuticular plates as well as the fibrillar material surrounding and projecting from the cell nuclei can be seen. In the pillar cells the images reveal individual microtubule bundles. Soft X-ray images of the acellular tectorial membrane and thin two-layered Reissner's membrane display a level of resolution comparable to low-power electron microscopy.
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| 5. |
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