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| 2. |
- Andersson, Sören, et al.
(författare)
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Frictions models for sliding dry, boundary and mixed lubricated contacts
- 2007
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 40, s. 580-587
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Tidskriftsartikel (refereegranskat)abstract
- Friction, lubrication, and wear have a strong influence on the performance and behavior of mechanical systems. This paper deals with different friction models for sliding contacts running under different conditions. The models presented are suited to different situations, depending on the type of contact, running conditions, and the behavior of interest. The models will be discussed from simulation and tribological points of view. The different types of friction models considered are:center dot friction models for transient sliding under dry, boundary and mixed lubrication conditions,center dot friction models for micro-displacements of engineering surfaces subjected to transient sliding,center dot friction models often used in the simulation and control of technical systems,center dot combined friction models that represent physical behaviors fairly well but are also suitable for use in simulating systems,center dot friction models that take into account the stochastic nature of interacting surface asperities
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| 3. |
- Lundell, Fredrik, et al.
(författare)
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THE EFFECT OF FIBRES ON LAMINAR-TURBULENT TRANSITION AND SCALES IN TURBULENT DECAY
- 2005
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Ingår i: ADVANCES IN PAPER SCIENCE AND TECHNOLOGY. - BURY : PULP & PAPER FUNDAMENTAL RESEARCH SOCIETY. - 9780954527235 ; , s. 19-34
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Konferensbidrag (refereegranskat)abstract
- Two physical phenomena which determine fundamental possibilities of paper forming are studied. The two phenomena are (i) laminar/turbulent transition and (ii) decay of turbulence. At first, the relevance of the processes to paper making is reviewed and discussed. The state of the boundary layers (laminar or turbulent) on split vanes and the decay of turbulence in the free stream are found to be of uttermost importance for the control of layer purity, formation and other properties of the final paper. Experiments in which these two processes are studied by visualisations are presented. The experiments emphasize the impact of fibres on these processes, as compared to what is found with pure water. All experiments are performed in model experiments were the structures in the flow are visualised by the addition of small, flake-like particles. It is shown that the addition of fibres radically change the physics of the flow. In a water table experiment, the addition of fibres is seen to promote the production of turbulent spots. At high enough fibre concentrations, the flow of water and fibres is fully turbulent even if a flow of pure water is laminar. In decay of turbulence, the fibres are seen to radically change the energy transfer between different scales so that intermediate and small scales remain active for longer times. It is concluded that fibres have large effects on laminar-turbulent transition and turbulence decay and that improved knowledge of these effects are a corner stone in the understanding of head box flow and its relations to the resulting paper quality.
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| 5. |
- Nordenström, Malin, et al.
(författare)
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The structure of cellulose nanofibril networks at low concentrations and their stabilizing action on colloidal particles
- 2022
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 297, s. 120046-
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Tidskriftsartikel (refereegranskat)abstract
- The structure and dynamics of networks formed by rod-shaped particles can be indirectly investigated by measuring the diffusion of spherical tracer particles. This method was used to characterize cellulose nanofibril (CNF) networks in both dispersed and arrested states, the results of which were compared with coarse-grained Brownian dynamics simulations. At a CNF concentration of 0.2 wt% a transition was observed where, below this concentration tracer diffusion is governed by the increasing macroscopic viscosity of the dispersion. Above 0.2 wt%, the diffusion of small particles (20-40 nm) remains viscosity controlled, while particles (100-500 nm) become trapped in the CNF network. Sedimentation of silica microparticles (1-5 mu m) in CNF dispersions was also determined, showing that sedimentation of larger particles is significantly affected by the presence of CNF. At concentrations of 0.2 wt%, the sedimentation velocity of 5 mu m particles was reduced by 99 % compared to pure water.
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| 6. |
- Parks, Luke
(författare)
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Development of directed-evolution methods utilizing combinatorial protein libraries in Escherichia coli
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Directed evolution using combinatorial protein libraries is a tremendously powerful technique for the generation of proteins with new or improved properties. A key aspect in such techniques is the link between individual protein variants and their corresponding genetic information. To provide this link, the most successful combinatorial protein engineering methods employ microorganisms, such as bacteriophages, bacteria or yeast for the production and display of libraries. This thesis focuses on the development and application of new directed evolution methods utilizing the bacterium Escherichia coli (E. coli), for the engineering of affinity proteins and proteases.The first study aimed to engineer the substrate specificity of a protease from tobacco etch virus (TEV). For this purpose, a novel method was devised based on expression of intracellular protease libraries, and employed a reporter fusion protein consisting of amyloid β peptide fused to the N-terminus of enhanced green fluorescent protein (EGFP). Variants were screened for proteolytic activity on co-expressed target substrate by means of fluorescence-activated cell sorting (FACS). After three rounds of FACS, a set of TEV protease variants were enriched that exhibited improved proteolytic activity on the novel substrate.Studies two to four describe the development of an E. coli surface expression system that was explored for directed evolution applications. The method is based on display of recombinant proteins on the outer membrane via fusion to a bacterial autotransporter, adhesin involved in diffuse adherence I (AIDA-I). The second study focused on the optimization of the surface display system and its application to directed evolution. In this effort, several affinity protein classes were evaluated for surface display via AIDA-I in a panel of E. coli strains. Results showed that smaller and less complicated affibody molecules were displayed at high levels, while more complex proteins, such as antibody fragments, varied in their performance and functioned best in certain engineered strains. A mock affibody library was used to develop a high-throughput magnetic-assisted cell sorting (MACS) protocol for enrichment of binders from very large libraries.In the third and fourth study, the new E. coli display method combined with the MACS protocol was evaluated for generation of new affibody molecules.In the third study, a large naïve affibody library (>1.5×1011 members) was constructed, displayed on E. coli and characterized. The performance of the method and library was evaluated by selection of binders against two cancer-associated targets, tumor-associated calcium signal transducer 2 (TROP-2) and lymphocyte-activation gene 3 (LAG-3). MACS and FACS were performed, with flow cytometry assessment between rounds to monitor enrichment. Both selections produced high affinity binders to their respective targets.In the fourth study, a maturation library was constructed for improving the properties of an affibody molecule toward the renal cell carcinoma biomarker carbonic anhydrase IX (CAIX). Selections included stringent off-rate procedures and yielded variants with improved affinities and folding stability compared to previously reported binders.In summary, the work in this thesis demonstrate the potential of E. coli-based directed evolution methods for selection of new proteins with altered or improved properties.
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| 7. |
- Ritsinger, V., et al.
(författare)
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Elevated levels of adipokines predict outcome after acute myocardial infarction : A long-term follow-up of the Glucose Tolerance in Patients with Acute Myocardial Infarction cohort
- 2017
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Ingår i: Diabetes & Vascular Disease Research. - : Sage Publications. - 1479-1641 .- 1752-8984. ; 14:2, s. 77-87
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Adiponectin and leptin are associated with insulin resistance and cardiovascular disease. Information on the prognostic value after an acute myocardial infarction is still conflicting. Methods: Patients (n = 180) without known diabetes and with admission glucose of <11 mmol/L admitted for an acute myocardial infarction in 1998-2000 were followed for mortality and cardiovascular events (first of cardiovascular mortality/acute myocardial infarction/stroke/heart failure) until the end of 2011 (median: 11.6 years). Plasma adiponectin and leptin were related to outcome in Cox proportional-hazard regression analyses. Results: Median age was 64 years and 69% were male. Total mortality was 34% (n = 61) and 44% (n = 80) experienced a cardiovascular event. Adiponectin at discharge predicted cardiovascular events (hazard ratio; 95% confidence interval; 1.45; 1.02-2.07, p = 0.038), total mortality (2.53; 1.64-3.91, p < 0.001) and cancer mortality (3.64; 1.51-8.74, p = 0.004). After adjustment for age, sex, body mass index, previous myocardial infarction and heart failure, adiponectin predicted total mortality (1.79; 1.07-3.00, p = 0.027) but not cardiovascular events. High levels of leptin were associated with cardiovascular events during the first 7 years, after which the association was attenuated. Leptin did not predict total mortality. Conclusion: In patients with acute myocardial infarction but without previously known diabetes, high levels of adiponectin at discharge predicted total mortality. The present results support the hypothesis that high rather than low levels of adiponectin predict mortality after acute myocardial infarction.
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| 8. |
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| 9. |
- Ritsinger, V., et al.
(författare)
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Elevated levels of insulin-like growth factor-binding protein 1 predict outcome after acute myocardial infarction : A long-term follow-up of the glucose tolerance in patients with acute myocardial infarction (GAMI) cohort
- 2018
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Ingår i: Diabetes & Vascular Disease Research. - : SAGE Publications Ltd. - 1479-1641 .- 1752-8984. ; 15:5, s. 387-395
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To investigate the long-term prognostic value of insulin-like growth factor-binding protein 1 in patients with acute myocardial infarction. Methods: Patients (n = 180) with admission glucose < 11 mmol/L without previously known diabetes admitted for an acute myocardial infarction in 1998–2000 were followed for mortality and cardiovascular events (first of cardiovascular mortality/acute myocardial infarction/stroke/severe heart failure) until the end of 2011 (median 11.6 years). Fasting levels of insulin-like growth factor-binding protein 1 at day 2 were related to outcome in Cox proportional hazard regression analyses. Results: Median age was 64 years, 69% were male and median insulin-like growth factor-binding protein 1 was 20 µg/L. Total mortality was 34% (n = 61) and 44% (n = 80) experienced a cardiovascular event during a median follow-up time of 11.6 years. After age adjustment, insulin-like growth factor-binding protein 1 was associated with all-cause (1.40; 1.02–1.93, p = 0.039) and cancer mortality (2.09; 1.15–3.79, p = 0.015) but not with cardiovascular death (p = 0.29) or cardiovascular events (p = 0.57). After adjustments also for previous myocardial infarction, previous heart failure and body mass index, insulin-like growth factor-binding protein 1 was still associated with all-cause mortality (1.38; 1.01–1.89, p = 0.046). Conclusion: In patients with acute myocardial infarction without previously known diabetes, high insulin-like growth factor-binding protein 1 was associated with long-term all-cause and cancer mortality but not with cardiovascular events.
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