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| 2. |
- Sparrman, Anna, 1965-, et al.
(författare)
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Child Studies Multiple : Collaborative play for thinking through theories and methods
- 2023
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Ingår i: Culture Unbound. - : Linköping University Electronic Press. - 2000-1525. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- This text is an exploration of collaborative thinking and writing through theories, methods, and experiences on the topic of the child, children, and childhood. It is a collaborative written text (with 32 authors) that sprang out of the experimental workshop Child Studies Multiple. The workshop and this text are about daring to stay with mess, “un-closure” , and uncertainty in order to investigate the (e)motions and complexities of being either a child or a researcher. The theoretical and methodological processes presented here offer an opportunity to shake the ground on which individual researchers stand by raising questions about scientific inspiration, theoretical and methodological productivity, and thinking through focusing on process, play, and collaboration. The effect of this is a questioning of the singular academic ‘I’ by exploring and showing what a plural ‘I’ can look like. It is about what the multiplicity of voice can offer research in a highly individualistic time. The article allows the reader to follow and watch the unconventional trial-and-error path of the ongoing-ness of exploring theories and methods together as a research community via methods of drama, palimpsest, and fictionary.
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| 3. |
- Andersson, Johanna, 1984, et al.
(författare)
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Dynamics of capillary transport in semi-solid channels
- 2017
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Ingår i: Soft Matter. - 1744-683X .- 1744-6848. ; 13, s. 2562-2570
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Tidskriftsartikel (refereegranskat)abstract
- © The Royal Society of Chemistry. Capillary action has been described by Lucas and Washburn and extensively studied experimentally in hard materials, but few studies have examined capillary action in soft materials such as hydrogels. In tissue engineering, cells or dispersions must be often distributed within a hydrogel via microporous paths. Capillary action is one way to disperse such substances. Here, we examine the dynamics of capillary action in a model system of straight capillaries in two hydrogels. The channels had a circular cross-section in the micrometer size range (180-630 μm). The distance travelled over time was recorded and compared with the predictions of Lucas and Washburn. Besides water, we used a sucrose solution and a hydroxyethyl cellulose solution, both with viscosities slightly higher than that of water. The results showed that the distance travelled is proportional to the square root of time, , and that larger capillaries and lower viscosities result, as expected, in faster speeds. However, the absolute experimental values display large discrepancies from the predictions. We demonstrate that several possible reasons for these discrepancies can be ruled out and we describe a novel hypothesis for the cause of the retarded meniscus movement.
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| 4. |
- Andersson, Johanna, 1984
(författare)
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Evaluation of Capillary Flow in Gels - The Liquid Uptake of Capillaries and Gelation Mechanisms in Alginate Gels
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For centuries it has been known that wetting liquids penetrate porous materials if the pores are sufficiently small. In some cases the liquid penetration is desired, like in kitchen paper or diapers, in other systems the penetration should be minimised or avoided, like in water repellent textiles or paper printing. Either way capillary flow has been studied extensively starting from smooth to rough surfaces and from single capillaries to porous systems. However, one field, which is lacking attention is the behaviour of capillary flow in porous gels. How does a semi-solid material influence capillary flow? Possible applications could be to absorb solutes or cell solutions in porous gels with the aim to get an even distribution of those. In this thesis alginate and agarose gels are used to study capillary flow. A thorough study of the gel characteristics including rheology measurements and investigation of the microstructure using two different gelation mechanisms gave the basis to study capillary action in air filled capillaries in alginate gels. A fast method to create a single capillary of tailored diameter in an alginate gel as well as in agarose gel was developed. Pure water penetrated the 5–6 cm long horizontal channel in an alginate gel of 630 µm, containing predominantly water in just 0.8 seconds. With that I showed first (i), that it is possible to get spontaneous capillary flow in gels containing large amounts of water and second (ii), I showed that the penetration dynamics follow the expected behaviour in that the squared travelled distance is proportional to the time, x^2∝t. As anticipated smaller capillaries exhibit slower uptake and higher viscosities decrease the speed in addition, as tested with a sucrose and a hydroxyethyl cellulose solution. Yet, the predictions from Lucas and Washburn theory optimised for hard systems, like glass result in times of only 0.2 seconds for water in a diameter of 630 µm and 5 cm length compared to the experimentally determined value of 0.8 seconds. Also all other tested liquids and diameters result in slower speeds than predicted for tested alginate and agarose gels. The most common reasons to address discrepancies to the prediction like inertial forces and using the dynamic contact angle instead of static, fail to explain the observed discrepancy, as I will show in this thesis. Other reasons are given and analysed. Since the spreading speed of a liquid drop on a soft surface has shown to be decreased and a wetting ridge at the three-phase contact line has been observed, it is hypothesised that the capillary flow is slowed down by such a wetting ridge, occurring in the front of the moving meniscus in the capillary. Besides the known viscous energy dissipation in the liquid, a viscoelastic energy dissipation due to the wall has to be added, which is the object of further investigations.
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| 5. |
- Andersson, Johanna, 1983, et al.
(författare)
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Lifetime Heterogeneity of DNA-Bound dppz Complexes Originates from Distinct Intercalation Geometries Determined by Complex-Complex Interactions
- 2013
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 52:2, s. 1151-1159
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Tidskriftsartikel (refereegranskat)abstract
- Despite the extensive interest in structurally explaining the photophysics of DNA-bound [Ru(phen)(2)dppz](2+) and [Ru(bpy)(2)dppz](2+), the origin of the two distinct emission lifetimes of the pure enantiomers when intercalated into DNA has remained elusive. In this report, we have combined a photophysical characterization with a detailed isothermal titration calorimetry study to investigate the binding of the pure Delta and Lambda enantiomers of both complexes with [poly(dAdT)](2). We find that a binding model with two different binding geometries, proposed to be symmetric and canted intercalation from the minor groove, as recently reported in high-resolution X-ray structures, is required to appropriately explain the data. By assigning the long emission lifetime to the canted binding geometry, we can simultaneously fit both calorimetric data and the binding-density-dependent changes in the relative abundance of the two emission lifetimes using the same binding model. We find that all complex complex interactions are slightly unfavorable for Delta-[Ru(bpy)(2)dppz](2+), whereas interactions involving a complex canted away from a neighbor are favorable for the other three complexes. We also conclude that Delta-[Ru(bpy)(2)dppz](2+) preferably binds isolated, Delta-[Ru(phen)(2)dppz](2+) preferably binds as duplets of canted complexes, and that all complexes are reluctant to form longer consecutive sequences than triplets. We propose that this is due to an interplay of repulsive complex complex and attractive complex-DNA interactions modulated by allosteric DNA conformation changes that are largely affected by the nature of the ancillary ligands.
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| 6. |
- Andersson, Johanna, 1984, et al.
(författare)
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Stick–slip motion and controlled filling speed by the geometric design of soft micro-channels
- 2018
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 524, s. 139-147
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis Liquid can move by capillary action through interconnected porous materials, as in fabric or paper towels. Today mass transport is controlled by chemical modification. It is, however, possible to direct mass transport by geometrical modifications. It is here proposed that it is possible to tailor capillary flow speed in a model system of micro-channels by the angle, size and position of attached side channels. Experiments A flexible, rapid, and cost-effective method is used to produce micro-channels in gels. It involves 3D-printed moulds in which gels are cast. Open channels of micrometre size with several side channels on either one or two sides are produced with tilting angles of 10 – 170°. On a horizontal plane the meniscus of water driven by surface tension is tracked in the main channel. Findings The presence of side channels on one side slowed down the speed of the meniscus in the main channel least. Channels having side channels on both sides with tilting angles of up to 30° indicated tremendously slower flow, and the liquid exhibited a stick-slip motion. Broader side channels decreased the speed more than thinner ones, as suggested by the hypothesis. Inertial forces are suggested to be important in branched channel systems studied here.
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| 7. |
- Andersson, Johanna, 1984
(författare)
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Surface tension-driven flow in soft porous materials — An investigation of the mechanism of capillary flow in microchannels of hydrogels
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Spontaneous spreading of liquids in porous materials is of great industrial relevance and occurs in, for example, diapers, fabrics, paper or paint. Often, it is necessary to manipulate the spreading rate of liquids to result in the desired mass transport, for example to soak up large liquid volumes, as in a diaper. To do this, it is necessary to know the precise mechanism of surface tension driven flow. However, the process is complex and so are the porous materials in terms of both chemical composition and geometry. The mathematical and physical description of the process is often limited to specific cases – for example, the well-known Lucas-Washburn equation describes the speed of a meniscus in capillaries with circular cross-section in a hard material without interconnections. The objective of this thesis is to deepen the understanding of the mechanism with which a liquid spreads in a soft porous material only driven by surface tension. To this end, the liquid dynamics of water and water-based liquids were investigated in various model systems which are similar to porous 3D materials. In an alginate gel, capillaries with circular cross-sections were produced and the spreading rate of water was determined and compared to existing models. Using a method, which involves 3D printing, it was possible to fabricate open channels with rectangular cross-sections in the same alginate gel. The liquid spreading in these channels in geometries of branched channel systems was investigated. The results revealed that the spreading rate in capillaries of circular cross-sections in soft materials was much slower than that anticipated in existing models, which describe hard materials. In open channels of rectangular cross-sections, the presence of side channels slowed down the meniscus in the main channel; the meniscus stopped when it encountered junctions. The stop duration was longer when the side channels were longer, when they were wider, and when their tilting angle was low with respect to the main channel. An analysis of the volume flow indicated that those geometries that had long side channels but are few in number, resulted in faster volume flow. In a porous 3D material, this suggests that the interconnectivity could decrease the volume flow rate. Finally, a calcium alginate gel with straight-aligned pores was produced and characterised as an example of optimal liquid transport. The outcome of this thesis can be used to adjust the geometrical design of porous materials to result in desired liquid transport properties. The stiffness of the material may influence the liquid transport. The thesis also contributes to the discussion on how the liquid takes selective pathways in porous materials.
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| 8. |
- Andersson, Per, Professor, 1964-, et al.
(författare)
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Editorial: Autumn 2021
- 2022
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Ingår i: Nordic Journal of Vocational Education and Training. - : Linköping University Electronic Press. - 2242-458X. ; 11:3, s. iii-v
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Andersson, Per, Professor, 1964-, et al.
(författare)
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Editorial: Autumn 2022
- 2022
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Ingår i: Nordic Journal of Vocational Education and Training. - : Linköping University Electronic Press. - 2242-458X. ; 12:3, s. 3-6
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This is the third and last issue of our twelfth volume. It includes five researcharticles concerning vocational education and training (VET) in Finland, Ethiopia,Sweden, and Norway. We are happy to publish articles not only with studies ofVET in the Nordic countries, but also from other parts of the world. As long asthe findings are relevant for a Nordic and an international readership, studies ofVET in different contexts are welcome in this journal. The different contexts makeit possible to compare and learn from each other, and possible differences alsohelp us to discern things we did not see before in our own contexts. The fact thatfour of the five articles in this issue are written in English also helps readers fromoutside the Nordic countries to learn from and compare with VET in this part ofthe world. Still, we also publish articles in the Nordic languages, which makessuch international comparison and learning possible at least between the Nordiccountries. Furthermore, the English abstracts, keywords, and translated titles ofNordic language articles provide at least a glimpse of the findings to non-Nordicreaders.
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| 10. |
- Andersson, Per, Professor, 1964-, et al.
(författare)
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Editorial: Autumn 2023
- 2023
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Ingår i: Nordic Journal of Vocational Education and Training. - : Linköping University Electronic Press. - 2242-458X. ; :2, s. iii-v
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Welcome to a new issue of the Nordic Journal of Vocational Education and Training(NJVET), which completes volume 13 of our journal. We want to create an activeforum for critical research on vocational and professional education and training,and we are proud that so many researchers in this area choose to submit andpublish their work in this journal. We are also thankful for the work completedby all our anonymous reviewers, whose efforts are invaluable for the quality ofthe research articles that are published.This issue includes five research articles from four Nordic countries: two articles from Norway, one from Finland, one from Sweden, and one written in cooperation between Finland and Denmark – an example of the broad interest in disseminating research findings through NJVET.
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