| 1. |
- Barkefors, Irmeli, et al.
(författare)
-
Effect of fluid shear stress on endocytosis of heparan sulfate and low-density lipoproteins
- 2007
-
Ingår i: Journal of Biomedicine and Biotechnology. - : Hindawi Limited. - 1110-7243 .- 1110-7251. ; 2007
-
Tidskriftsartikel (refereegranskat)abstract
- Hemodynamic stress is a critical factor in the onset of atherosclerosis such that reduced rates of shear stress occurring at regions of high curvature are more prone to disease. The level of shear stress has direct influence on the thickness and integrity of the glycocalyx layer. Here we show that heparan sulfate, the main component of the glycocalyx layer, forms an intact layer only on cell surfaces subjected to shear, and not under static conditions. Furthermore, receptor-mediated endocytosis of heparan sulfate and low-density liporoteins is not detectable in cells exposed to shear stress. The internalized heparan sulfate and low-density lipoproteins are colocalized as shown by confocal imaging.
|
|
| 2. |
- Carrick, Christopher, et al.
(författare)
-
Native and functionalized micrometre-sized cellulose capsules prepared by microfluidic flow focusing
- 2014
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:37, s. 19061-19067
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulose capsules with average outer and inner radii of approximately 44 mu m and 29 mm respectively were prepared from cellulose dissolved in a mixture of lithium chloride and dimethylacetamide using a microfluidic flow focusing device (MFFD). The MFFD had three inlets where octane oil in a cellulose solution in silicone oil was used to produce a double emulsion containing a cellulose capsule. This technique enables the formation of capsules with a narrow size distribution which can be beneficial for drug delivery or controlled release capsules. In this respect, cellulose is a highly interesting material since it is known to cause no autoimmune reactions when used in contact with human tissue. Furthermore, by controlling the chemical properties of the cellulose, it is possible to trigger a swelling of the capsules and consequentially the release of an encapsulated substance, e. g. a model drug, when the capsule becomes exposed to an external stimulus. To demonstrate this, capsules were functionalized by carboxymethylation to be pH- responsive and to expand approximately 10% when subjected to a change in pH from 3 to 10. The diffusion constant of a model drug, a 4 kDa fluorescently labelled dextran, through the native capsule wall was estimated to be 6.5 X 10(-14) m(2) s(-1) by fitting fluorescence intensity data to Fick's second law.
|
|
| 3. |
|
|
| 4. |
- Howell, Aaron, et al.
(författare)
-
Black Liquor Falling Film Evaporation: Computational Model and Pilot Experiments
- 2014
-
Ingår i: Proceedings of International Chemical Recovery Conference, Tampere,Finland, June 8 – 13 2014. ; , s. 389-401
-
Konferensbidrag (refereegranskat)abstract
- The focus of this work is to improve our understanding of the black liquor evaporator fouling process. Theinvestigation method is two pronged, consisting of the development of a computational model paired withexperiments conducted in a pilot evaporator. Experiments for black liquor at solids up to 45% dry solids wereconducted and used to validate the computational model. It was found that for fixed Reynolds number, loweringpump frequency induces waves closer to the inlet. And, for fixed pumping frequency, increasing the Reynoldsnumber has the effect of inducing waves closer to the inlet. The numerical model reproduces the complex wavesstructures present in black liquor flow. The model and pilot plant are to be used to investigate the effect of relevantparameters for the hydrodynamics, heat transfer, and soluble scale fouling of black liquor, which is of specificconcern to the pulping industry.
|
|
| 5. |
- Lindström, Stefan B, 1974-
(författare)
-
Modelling and simulation of paper structure development
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A numerical tool has been developed for particle-level simulations of fibre suspension flows, particularly forming of the fibre network structure of paper sheets in the paper machine. The model considers inert fibres of various equilibrium shapes, and finite stiffness, interacting with each other through normal, frictional, and lubrication forces, and with the surrounding fluid medium through hydrodynamic forces. Fibre–fluid interactions in the non-creeping flow regime are taken into account, and the two-way coupling between the solids and the fluid phases is included by enforcing momentum conservation between phases. The incompressible three-dimensional Navier–Stokes equations are employed tomodel themotion of the fluid medium.The validity of the model has been tested by comparing simulation results with experimental data from the literature. It was demonstrated that the model predicts well the motion of isolated fibres in shear flow over a wide range of fibre flexibilities. It was also shown that the model predicts details of the orientation distribution of multiple, straight, rigid fibres in a sheared suspension. Furthermore, model predictions of the shear viscosity and first normal stress difference were in fair agreement with experimental data found in the literature. Since the model is based solely on first principles physics, quantitative predictions could be made without any parameter fitting. Based on these validations, a series of simulations have been performed to investigate the basic mechanisms responsible for the development of the stress tensor components for monodispersed, non-Brownian fibres suspended in a Newtonian fluid in shear flow. The effects of fibre aspect ratio, concentration, and inter-particle friction, as well as the tendency of fibre agglomeration, were examined in the nonconcentrated regimes. For the case of well dispersed suspensions, semi-empirical relationships were found between the aforementioned fibre suspension properties, and the steady state apparent shear viscosity, and the first/second normal stress differences. Finally, simulations have been conducted for the development of paper structures in the forming section of the paper machine. The conditions used for the simulations were retrieved from pilot-scale forming trial data in the literature, and from real pulp fibre analyses. Dewatering was simulated by moving two forming fabrics toward each other through a fibre suspension. Effects of the jet-to-wire speed difference on the fibre orientation anisotropy, the mass density distribution, and three-dimensionality of the fibre network, were investigated. Simulation results showed that the model captures well the essential features of the forming effects on these paper structure parameters, and also posed newquestions on the conventional wisdom of the forming mechanics.
|
|
| 6. |
|
|
| 7. |
- Rosén, Tomas, 1985-, et al.
(författare)
-
Orientational dynamics of a triaxial ellipsoid in simple shear flow : Influence of inertia
- 2017
-
Ingår i: Physical review. E. - : AMER PHYSICAL SOC. - 2470-0045 .- 2470-0053. ; 96:1
-
Tidskriftsartikel (refereegranskat)abstract
- The motion of a single ellipsoidal particle in simple shear flow can provide valuable insights toward understanding suspension flows with nonspherical particles. Previously, extensive studies have been performed on the ellipsoidal particle with rotational symmetry, a so-called spheroid. The nearly prolate ellipsoid (one major and two minor axes of almost equal size) is known to perform quasiperiodic or even chaotic orbits in the absence of inertia. With small particle inertia, the particle is also known to drift toward this irregular motion. However, it is not previously understood what effects from fluid inertia could be, which is of highest importance for particles close to neutral buoyancy. Here, we find that fluid inertia is acting strongly to suppress the chaotic motion and only very weak fluid inertia is sufficient to stabilize a rotation around themiddle axis. Themechanism responsible for this transition is believed to be centrifugal forces acting on fluid, which is dragged along with the rotational motion of the particle. With moderate fluid inertia, it is found that nearly prolate triaxial particles behave similarly to the perfectly spheroidal particles. Finally, we also are able to provide predictions about the stable rotational states for the general triaxial ellipsoid in simple shear with weak inertia.
|
|
| 8. |
- Rosén, Tomas, et al.
(författare)
-
Quantitative analysis of the angular dynamics of a single spheroid in simple shear flow at moderate Reynolds numbers
- 2016
-
Ingår i: Physical Review Fluids. - : American Institute of Physics (AIP). - 2469-990X. ; 1:4, s. 044201-1-044201-21
-
Tidskriftsartikel (refereegranskat)abstract
- A spheroidal particle in simple shear flow shows surprisingly complicated angular dynamics; caused by effects of fluid inertia (characterized by the particle Reynolds number Rep) and particle inertia (characterized by the Stokes number St). Understanding this behavior can provide important fundamental knowledge of suspension flows with spheroidal particles. Up to now only qualitative analysis has been available at moderate Rep. Rigorous analytical methods apply only to very small Rep and numerical results lack accuracy due to the difficulty in treating the moving boundary of the particle. Here we show that the dynamics of the rotational motion of a prolate spheroidal particle in a linear shear flow can be quantitatively analyzed through the eigenvalues of the log-rolling particle (particle aligned with vorticity). This analysis provides an accurate description of stable rotational states in terms of Rep,St, and particle aspect ratio (rp). Furthermore we find that the effect on the orientational dynamics from fluid inertia can be modeled with a Duffing-Van der Pol oscillator. This opens up the possibility of developing a reduced-order model that takes into account effects from both fluid and particle inertia.
|
|
