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- Meister, Mikael, 1969, et al.
(författare)
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High-energy breakup of 8B
- 2003
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Ingår i: Nucl. Phys. A. ; 718, s. 431-433
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Konferensbidrag (refereegranskat)
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| 5. |
- Abad, JM, et al.
(författare)
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Immobilization of peroxidase glycoprotein on gold electrodes modified with mixed epoxy-boronic acid monolayers
- 2002
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 124:43, s. 12845-12853
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Forskningsöversikt (refereegranskat)abstract
- The development of bioelectronic enzyme applications requires the immobilization of active proteins onto solid or colloidal substrates such as gold. Coverage of the gold surface with alkanethiol self-assembled monolayers (SAMS) reduces nonspecific adsorption of proteins and also allows the incorporation onto the surface of ligands with affinity for complementary binding sites on native proteins. We present in this work a strategy for the covalent immobilization of glycosylated proteins previously adsorbed through weak, reversible interactions, on tailored SAMS. Boronic acids, which form cyclic esters with saccharides, are incorporated into SAMS to weakly adsorb the glycoprotein onto the electrode surface through their carbohydrate moiety. To prevent protein release from the electrode surface, we combine the affinity motif of boronates with the reactivity of epoxy groups to covalently link the protein to heterofunctional boronateepoxy SAMS. The principle underlying our strategy is the increased immobilization rate achieved by the weak interaction-induced proximity effect between slow reacting oxyrane groups in the SAM and nucleophilic residues from adsorbed proteins, which allows the formation of very stable covalent bonds. This approach is exemplified by the use of phenylboronates-oxyrane mixed monolayers as a reactive support and redox-enzyme horseradish peroxidase as glycoprotein for the preparation of peroxidase electrodes. Quartz crystal microbalance, atomic force microscopy, and electrochemical measurements are used to characterize these enzymatic electrodes. These epoxy-boronate functional monolayers; are versatile, stable interfaces, ready to incorporate glycoproteins by incubation under mild conditions.
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- Alonso-Vazquez, A, et al.
(författare)
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Initial stability of ankle arthrodesis with three-screw fixation. A finite element analysis
- 2004
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Ingår i: Clinical Biomechanics. - : Elsevier BV. - 0268-0033. ; 19:7, s. 751-759
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Compare the initial stability at the fusion site of ankle arthrodesis fixed with two and three screws. Design. Finite element models of ankle arthrodesis were developed from computed tomography images. Two-screw constructs were augmented with a third screw in different orientations and Subjected to loads likely to affect the ankle postoperatively. Background More stable fixation seems to increase the chance of fusion, as it minimises the motion between the tibiotalar interfaces. Methods. Non-linear elastic finite element analyses were performed in external torsion and dorsiflexion. The micromotions at the tibiotalar interface were computed to compare the two- and three-screw fixation in intact and flat-cut arthrodesis. Results. Adding a third screw reduced the micromotions at the fusion site. Inserting the third screw anteriorly predicted lower peak micromotions than inserting the screw posteriorly, except for the intact arthrodesis tested in dorsiflexion. Three-screw intact arthrodesis predicted lower peak micromotions than flat-cut arthrodesis. Conclusions. Better stability was predicted for three-screw ankle arthrodesis. In flat-cut arthrodesis, a third screw inserted anteriorly performed better than a posterior screw. In intact arthrodesis, a posterior screw seemed a better option when flexion stability was the main concern. Even with three-screw fixation, the configuration of the first two-crossed screws may still be important to improve the stability at the fusion site. Relevance The optimal number and placement of screws in ankle arthrodesis has yet to be determined. The differences in stability predicted between various screw configurations and Surface preparation techniques presented here may be the difference between success and failure. (C) 2004 Elsevier Ltd. All rights reserved.
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- Alonso-Vazquez, A, et al.
(författare)
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The effect of bone quality on the stability of ankle arthrodesis. A finite element study
- 2004
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Ingår i: Foot & Ankle International. - 1944-7876. ; 25:11, s. 840-850
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Tidskriftsartikel (refereegranskat)abstract
- Background: Despite uniform operating techniques, lack of fusion still occurs after ankle arthrodesis. Differences in the biological healing potential may be a factor but the mechanical performance of the arthrodesis construct because of varying bone quality also may be important. Internal compression techniques are preferred because of higher union rates, shorter fusion times, and fewer complications. A three-screw configuration has been shown to be more stable than a two-screw configuration, but it is not obvious when it should be used. Methods: Three-dimensional finite element models of intact and flat-cut ankle arthrodeses were built, using two and three screws in different configurations. Poor bone quality was simulated by decreasing Young's modulus of the bone. The constructs were loaded in torsion and dorsiflexion, and micromotions at the fusion site were measured. Results: Bone quality had a marked effect on the stability at the arthrodesis site. Inserting two screws at 30 degrees relative to the longitudinal axis of the tibia in an intact arthrodesis seemed the best option, especially as bone quality worsened. The addition of a third screw increased the stability at the arthrodesis site. Conclusions: Overall, intact joint surfaces and three-screw fixation, with the lateral and medial screws inserted produced the most stable arthrodesis constructs when bone quality was poor. Clinical Relevance. Ankle arthrodeses are technically demanding because of the shape and small size of the talus. Preoperative planning is an absolute necessity to determine placement and number of screws. This study shows that poor bone quality decreases the stability of the arthrodesis constructs, suggesting that an attempt should be made to create the most stable three-screw configuration. Finite element models can be used as an effective preoperative tool for planning screw number and placement.
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- Wilson, W G, et al.
(författare)
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Biodiversity and species interactions: extending Lotka-Volterra community theory
- 2003
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 6:10, s. 944-952
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Tidskriftsartikel (refereegranskat)abstract
- A new analysis of the nearly century-old Lotka-Volterra theory allows us to link species interactions to biodiversity patterns, including: species abundance distributions, estimates of total community size, patterns of community invasibility, and predicted responses to disturbance. Based on a few restrictive assumptions about species interactions, our calculations require only that the community is sufficiently large to allow a mean-field approximation. We develop this analysis to show how an initial assemblage of species with varying interaction strengths is predicted to sort out into the final community based on the species' predicted target densities. The sorting process yields predictions of covarying patterns of species abundance, community size, and species interaction strengths. These predictions can be tested using enrichment experiments, examination of latitudinal and productivity gradients, and features of community assembly.
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