| 1. |
- Claesson, Julia, 1985, et al.
(författare)
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An experimental study of the turbulent mixing layer in concentrated fiber suspensions.
- 2012
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Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 27:5, s. 940-946
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Tidskriftsartikel (refereegranskat)abstract
- Turbulence structures in a free mixing layer after a backward-facing step were studied in concentrated pulp suspensions (0.5-3% by weight) using Laser Doppler Anemometry (LDA) at two predetermined average inflow velocities (0.9 and 1.8 m/s). Both average and fluctuating velocities were investigated and the findings were compared with measurements in water. The experimental findings show that both the average velocities and the RMS velocities in the mixing layer decreased with an increase in concentration. Furthermore, by analyzing the energy spectra at the center of the mixing layer, it was possible to extract the inertial sub-range of pulp suspensions with a concentration of 0.5% at the lower inflow velocity and in suspensions up to a concentration of 1% at the higher inflow velocity. At higher concentrations the turbulence was damped by the fiber network and no turbulence structures could be extracted. The energy content at lower frequencies was higher in the pulp suspensions than in the experiments in pure water.
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| 2. |
- Claesson, Julia, 1985, et al.
(författare)
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Flow of concentrated fiber suspensions over a backward facing step studied using LDA
- 2012
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Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 27:3, s. 653-661
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Tidskriftsartikel (refereegranskat)abstract
- Laser Doppler Anemometry (LDA) was used to study the flow structures of pulp suspensions over a backward facing step at two step heights (5 and 10 mm). Experiments were conducted at four consistencies (1, 1.5, 2 and 3%) and two pre-determined free stream velocities (1.3 and 1.8 m/s). The flow structures in the suspensions were compared with measurements made in water. The experimental results showed that it was possible to measure recirculation flow, mixing layers, reattaching flows as well as different flow regimes with LDA. Further measurements in turbulent concentrated pulp flows are needed to distinguish and characterize turbulent structures. Results show that the reattachment length decreased along with a decrease in velocity or an increase in consistency in pulp suspensions with a consistency of at least 1.5%. At 1% a decrease in velocity gave an increase in the reattachment length probably due to a change in the flow regime from laminar to transition or turbulent.
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| 3. |
- Claesson, Julia, 1985, et al.
(författare)
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The development of a near-wall boundary layer over a flat plate in concentrated pulp fiber suspensions
- 2013
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 28:3, s. 399-406
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Tidskriftsartikel (refereegranskat)abstract
- The development of a boundary layer over a flat plate placed in a square pipe was studied in pulp suspensions at concentrations of 0.5, 1 and 1.8% at flow velocities of 0.24-0.96 m/s. Laser Doppler Anemometry (LDA) was used to measure velocities in the boundary layer from y=0-3 mm at x=0, 5, 10, 20 and 30 mm, where x=0 mm was the position where the flow met the plate. During the measurement time the pressure drop over the plate was also measured and it was concluded that the flow was in the rolling friction regime. The results of boundary layer thickness show that an increase in velocity or a decrease in concentration gave a thicker boundary layer in contrast to a laminar Newtonian boundary layer. In a power law fluid, boundary layer thickness decreases with an increase in shear thinning or velocity. Furthermore, in the pulp suspensions, a boundary layer with a constant thickness was reached 20 mm from the plate edge in contrast to a Newtonian and a shear thinning boundary layer which continued to increase along the plate. The difference in boundary layer development is believed to depend on the two-phase effects in pulp suspensions.
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| 4. |
- Claesson, Kjersti, et al.
(författare)
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Counting the platelets: a robust and sensitive quantification method for thrombus formation
- 2016
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Ingår i: Thrombosis and Haemostasis. - : SCHATTAUER GMBH-VERLAG MEDIZIN NATURWISSENSCHAFTEN. - 0340-6245 .- 2567-689X. ; 115:6, s. 1178-1190
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Tidskriftsartikel (refereegranskat)abstract
- Flow chambers are common tools used for studying thrombus formation in vitro. However, the use of such devices is not standardised and there is a large diversity among the flow chamber systems currently used, and also in the methods used for quantifying the thrombus development. It was the study objective to evaluate a new method for analysis and quantification of platelet thrombus formation that can facilitate comparison of results between research groups. Whole blood was drawn over a collagen patch in commercial Ibid or in-house constructed PDMS flow chambers. Five percent of the platelets were fluorescently labelled and z-stack time-lapse images were captured during thrombus formation. Images were processed in a Python script in which the number of platelets and their respective x-, y- and z-positions were obtained. For comparison with existing methods the platelets were also labelled and quantified using fluorescence intensity and thrombus volume estimations by confocal microscopy. The presented method was found less sensitive to microscope and image adjustments and provides more details on thrombus development dynamics than the methods for measuring fluorescence intensity and thrombus volume estimation. The platelet count method produced comparable results with commercial and PDMS flow chambers, and could also obtain information regarding the stability of each detected platelet in the thrombus. In conclusion, quantification of thrombus formation by platelet count is a sensitive and robust method that enables measurement of platelet accumulation and platelet stability in an absolute scale that could be used for comparisons between research groups.
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| 5. |
- Ghaffarpour, Nader, et al.
(författare)
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Long-term health-related quality of life in children with lymphatic malformations treated with sclerotherapy generally matched age-appropriate standardised population norms
- 2019
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Ingår i: Acta Paediatrica. - : Wiley. - 0803-5253 .- 1651-2227. ; 108:8, s. 1499-1506
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Tidskriftsartikel (refereegranskat)abstract
- Aim: We assessed the long-term health-related quality of life (HRQoL) of children who received sclerotherapy for lymphatic malformations. This treatment involved injecting drugs into the blood vessels to make them shrink.Methods: Our cross-sectional study retrospectively reviewed patients who received OK-432 sclerotherapy injections at Karolinska University Hospital, Stockholm, Sweden, from 1998 to 2013. We studied 49 patients (63% female) aged 8-18 at least five years after their first injection. HRQoL was assessed with the KIDSCREEN-52 questionnaire and a study-specific questionnaire addressed disease consequences and patient satisfaction. We determined associations between HRQoL and disease and treatment and the patient's sex.Results: Overall HRQoL paralleled age-appropriate norms in the general population, but some subgroups had lower levels. Regression-based estimates showed that larger numbers of injections were negatively associated with HRQoL in the dimensions autonomy, parent relations and home life, financial resources and school environment (p = 0.01-0.03). Malformations in the head and neck area were negative predictors across dimensions and were strongest for psychological well-being (p = 0.009), parent relations and home life (p = 0.017) and school environment (p = 0.006).Conclusion: Despite generally positive outcomes, multiple injections and malformations in the head and neck were associated with impaired HRQoL.
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| 6. |
- He, Yunjuan, et al.
(författare)
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Comparative study of CNC and CNF as additives in waterborne acrylate-based anti-corrosion coatings
- 2020
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Ingår i: Journal of Dispersion Science and Technology. - : Taylor & Francis. - 0193-2691 .- 1532-2351. ; 41:13, s. 2037-2047
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposite coatings are of great interest as barrier coatings since synergy effects between matrix and additive properties can be achieved. This, however, requires favorable additive-matrix interactions to provide a strong interphase (interface region). In this work we elucidate the properties of two environmentally benign nanocomposite coatings based on a waterborne acrylate formulation with additives from renewable sources, i.e. either cellulose nanocrystals, CNC; or, alternatively, cellulose nanofibrils, CNF. We focus on the corrosion protective properties of these coatings and discuss the reason why the nanocomposite with CNC displays favorable corrosion protection properties whereas that with CNF does not. To this end we utilized scanning electron microscopy, water contact angle measurement, Fourier transform infrared spectroscopy and electrochemical impedance spectroscopy techniques to investigate the microstructure, surface wetting, interactions between cellulosic materials and matrix as well as corrosion protective properties of both composite coatings.
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| 7. |
- He, Yunjuan, 1987-, et al.
(författare)
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Corrosion protective properties of cellulose nanocrystals reinforced waterborne acrylate-based composite coating
- 2019
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Ingår i: Corrosion Science. - : Elsevier Ltd. - 0010-938X .- 1879-0496. ; 155, s. 186-194
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Tidskriftsartikel (refereegranskat)abstract
- The present investigation highlights corrosion protection of carbon steel by a waterborne acrylate-based matrix coating, with and without reinforcement by cellulose nanocrystals, by using electrochemical impedance spectroscopy in 0.1 M NaCl solution over a period of 35 days. Interactions between cellulose nanocrystals and the matrix coating were demonstrated by Fourier transform infrared spectroscopy. The results show that both coatings have high barrier performance but different protective characteristics during long-term exposure. The differences can be attributed to the reinforcement effect of cellulose nanocrystals caused by hydrogen bonding interactions between cellulose nanocrystals and the matrix coating.
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| 8. |
- He, Yunjuan, et al.
(författare)
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Nano-scale mechanical and wear properties of a waterborne hydroxyacrylic-melamine anti-corrosion coating
- 2018
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 457, s. 548-558
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion protection is commonly achieved by applying a thin polymer coating on the metal surface. Many studies have been devoted to local events occurring at the metal surface leading to local or general corrosion. In contrast, changes occurring in the organic coating after exposure to corrosive conditions are much less studied. In this article we outline how changes in the coating itself due to curing conditions, environmental and erosion effects can be investigated at the nanometer scale, and discuss how such changes would affect its corrosion protection performance. We focus on a waterborne hydroxyacrylic-melamine coating, showing high corrosion protection performance for carbon steel during long-term (≈35 days) exposure to 0.1 M NaCl solution. The effect of curing time on the conversion of the crosslinking reaction within the coating was evaluated by fourier transform infrared spectroscopy (FTIR); the wetting properties of the cured films were investigated by contact angle measurement, and the corrosion resistance was studied by electrochemical impedance spectroscopy (EIS). In particular, coating nanomechanical and wear properties before and after exposure to 0.1 M NaCl, were evaluated by atomic force microscopy (AFM). Fiber-like surface features were observed after exposure, which are suggested to arise due to diffusion of monomers or low molecular weight polymers to the surface. This may give rise to local weakening of the coating, leading to local corrosion after even longer exposure times. We also find a direct correlation between the stick-slip spacing during shearing and plastic deformation induced in the surface layer, giving rise to topographical ripple structures on the nanometer length scale.
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| 9. |
- Olsen Faresjö, Åshild, et al.
(författare)
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Higher Perceived Stress but Lower Cortisol Levels Found among Young Greek Adults Living in a Stressful Social Environment in Comparison with Swedish Young Adults
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 8:9
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Tidskriftsartikel (refereegranskat)abstract
- The worldwide financial crisis during recent years has raised concerns of negative public health effects. This is notably evident in southern Europe. In Greece, where the financial austerity has been especially pronounced, the prevalence of mental health problems including depression and suicide has increased, and outbreaks of infectious diseases have risen. The main objective in this study was to investigate whether different indicators of health and stress levels measured by a new biomarker based on cortisol in human hair were different amongst comparable Greek and Swedish young adults, considering that Sweden has been much less affected by the recent economic crises. In this cross-sectional comparative study, young adults from the city of Athens in Greece (n = 124) and from the city of Linkoping in Sweden (n = 112) participated. The data collection comprised answering a questionnaire with different health indicators and hair samples being analyzed for the stress hormone cortisol, a biomarker with the ability to retrospectively measure long-term cortisol exposure. The Greek young adults reported significantly higher perceived stress (p<0.0001), had experienced more serious life events (p = 0.002), had lower hope for the future (p<0.0001), and had significantly more widespread symptoms of depression (p<0.0001) and anxiety (p<0.0001) than the Swedes. But, the Greeks were found to have significantly lower cortisol levels (p<0.0001) than the Swedes, and this difference was still significant in a multivariate regression (p<0.0001), after adjustments for potential intervening variables. A variety of factors related to differences in the physical or socio-cultural environment between the two sites, might possibly explain this finding. However, a potential biological mechanism is that long-term stress exposure could lead to a lowering of the cortisol levels. This study points out a possible hypothesis that the cortisol levels of the Greek young adults might have been suppressed and their HPA-axis down-regulated after living in a stressful environment with economic and social pressure.
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| 10. |
- Pettersson, Charlotta, 1972-
(författare)
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Kursplaners möjlighetsrum : om nationella kursplaners transformation till lokala
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study explores the transformation of national syllabuses into local ones, as expressed in teachers’ organized conversations. It also investigates what view of knowledge is expressed in local syllabuses and what implications that view has for the educational task entrusted to schools by society. The data collected consist of six focus-group conversations in which teachers discuss national and local syllabuses. The thesis takes its theoretical point of departure in relational curriculum theory, with support from Ricoeur. These perspectives form the basis for the model that is used to study the transformation of national syllabuses are transformed into local ones – and what they are transformed in relation to. This transformation process results in four local ‘spaces of possibilities’: The analysis shows that teachers interpret the national syllabuses as documents which open up unlimited freedom in their teaching. The teachers use this freedom to turn from the content of national syllabuses towards other texts. Teachers feel that the only thing limiting them in their teaching is the grading of students, which places many different kinds of demands on them. The view of knowledge that emerges from the spaces of possibilities described is an individualistic one. The teachers fall back on their own experience, rather than reading, interpreting and developing an understanding of what the national syllabuses mean in relation to their experience and knowledge. In terms of content, the education provided is directed inwards towards the teacher’s own individual view of knowledge, rather than outwards towards the task given to schools by society. It is concluded that it is the teachers who, individually and based on their personal points of view, decide what knowledge students need to prepare them for life, rather than the goals set out in national syllabuses.
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