| 61. |
- Lewin, Susanne, et al.
(författare)
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Mechanical behaviour of composite calcium phosphate-titanium cranial implants : Effects of loading rate and design
- 2020
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Ingår i: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier BV. - 1751-6161 .- 1878-0180. ; 104
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Tidskriftsartikel (refereegranskat)abstract
- Cranial implants are used to repair bone defects following neurosurgery or trauma. At present, there is a lack of data on their mechanical response, particularly in impact loading. The aim of the present study was to assess the mechanical response of a recently developed composite calcium phosphate-titanium (CaP-Ti) implant at quasi-static and impact loading rates. Two different designs were tested, referred to as Design 1 (D1) and Design 2 (D2). The titanium structures in the implant specimens were additively manufactured by a powder-bed fusion process and subsequently embedded in a self-setting CaP material. D1 was conceptually representative of the clinically used implants. In D2, the titanium structure was simplified in terms of geometry in order to facilitate the manufacturing. The mechanical response of the implants was evaluated in quasi-static compression, and in impact using a drop-tower. Similar peak loads were obtained for the two designs, at the two loading rates: 808 ± 29 N and 852 ± 34 for D1, and 840 ± 40 N and 814 ± 13 for D2. A strain rate dependency was demonstrated for both designs, with a higher stiffness in the impact test. Furthermore, the titanium in the implant fractured in the quasi-static test (to failure) but not in the impact test (to 5.75 J) for D1. For D2, the displacement at peak load was significantly lower in the impact test than in the quasi-static test. The main difference between the designs was seen in the quasi-static test results where the deformation zones, i.e. notches in the titanium structure between the CaP tiles, in D1 likely resulted in a localization of the deformation, compared to in D2 (which did not have deformation zones). In the impact test, the only significant difference between the designs was a higher maximum displacement of D2 than of D1. In comparison with other reported mechanical tests on osteoconductive ceramic-based cranial implants, the CaP-Ti implant demonstrates the highest reported strength in quasi-static compression. In conclusion, the titanium structure seems to make the CaP-Ti implant capable of cerebral protection in impact situations like the one tested in this study.
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| 62. |
- Lewin, Susanne, et al.
(författare)
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Monetite-based composite cranial implants demonstrate long-term clinical volumetric balance by concomitant bone formation and degradation
- 2021
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Ingår i: Acta Biomaterialia. - : Elsevier. - 1742-7061 .- 1878-7568. ; 128, s. 502-513
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Tidskriftsartikel (refereegranskat)abstract
- The use of calcium phosphates (CaPs) as synthetic bone substitutes should ideally result in a volumetric balance with concomitant bone formation and degradation. Clinical data on such properties is nevertheless lacking, especially for monetite-based CaPs. However, a monetite-based composite implant has recently shown promising cranial reconstructions, with both CaP degradation and bone formation. In this study, the volumetric change at the implant site was quantified longitudinally by clinical computed tomography (CT). The retrospective CT datasets had been acquired postoperatively ( n = 10), in 1-year ( n = 9) and 3-year ( n = 5) follow-ups. In the 1-year follow-up, the total volumetric change at the implant site was-8 +/- 8%. A volumetric increase (bone formation) was found in the implant-bone interface, and a volumetric decrease was observed in the central region (CaP degradation). In the subjects with 2-or 3-year follow-ups, the rate of volumetric decrease slowed down or plateaued. The reported degradation rate is lower than previous clinical studies on monetite, likely due to the presence of pyrophosphate in the monetite-based CaP-formulation. A 31-months retrieval specimen analysis demonstrated that parts of the CaP had been remodeled into bone. The CaP phase composition remained stable, with 6% transformation into hydroxyapatite. In conclusion, this study demonstrates successful bone-bonding between the CaP-material and the recipient bone, as well as a long-term volumetric balance in cranial defects repaired with the monetitebased composite implant, which motivates further clinical use. The developed methods could be used in future studies for correlating spatiotemporal information regarding bone regeneration and CaP degradation to e.g. patient demographics. Statement of significance In bone defect reconstructions, the use of calcium phosphate (CaP) bioceramics ideally results in a volumetric balance between bone formation and CaP degradation. Clinical data on the volumetric balance is nevertheless lacking, especially for monetite-based CaPs. Here, this concept is investigated for a composite cranial implant. The implant volumes were quantified from clinical CT-data: postoperatively, one year and three years postoperatively. In total,-8 +/- 8% ( n = 9) volumetric change was observed after one year. But the change plateaued, with only 2% additional decrease at the 3-year follow-up ( n = 5), indicating a lower CaP degradation rate. Osseointegration was seen at the bone-implant interface, with a 9 +/- 7% volumetric change after one year. This study presented the first quantitative spatiotemporal CT analysis of monetite-based CaPs.
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| 63. |
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| 64. |
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| 65. |
- Lundesjö Kvart, Susanne, 1969-
(författare)
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Konsten att undervisa ryttare : En studie om ridlärares pedagogiska praktik
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns how riding teachers’ reflect upon their teaching and how they teach. The overall aim of the thesis is to contribute with knowledge about how riding lessons are organized, regarding both the accomplishment of lessons as activity systems and the interactional organization of instructional work. Horseback riding can be understood as an embodied and practical knowledge, and includes communication and collaboration between horse and rider, sometimes referred to as equestrian feel (Dashper, 2016). Two different theoretical perspectives were applied to explore how such knowledge is taught. Activity theory (Engeström, 1987) was used to analyze interviews with and observations of ten riding teachers about their understanding and implementation of their pedagogical practice. Teachers’ and students’ interactions during riding lessons were examined using an ethnomethodological and conversation analytic approach (Goodwin, 2000; Schegloff, 1996). The analyses were based on video-recordings of ten group lessons and 40 one-on-one riding lessons.The results show that riding lessons can be conceptualized as activity systems where the focus of teaching constantly changes; from horse to student to routine. Traditions and safety regulations are shown to generate contradictions that may hinder the teachers from developing their teaching. However, the teachers express a wish to use more student collaborative methods, and display an intention to communicate with students about equestrian feel. Another result unveils how the teacher and the individual students, within the mobile context of riding lessons, make instructional sequences possible by co-creating instructional spaces. A third result illuminates the participants’ collaborative work to make equestrian feel available for instruction. The teacher molds equestrian feel through online instructions, i.e., instructions produced during the students’ active riding. These instructions shift focus between the students’ seat and influence, the horse’s actions and the student’s embodied feel. Moreover, the teachers are shown to use visual, verbal and embodied resources as they interpret equestrian feel for the student. In sum, the studies shed light on the complex art of teaching practical and embodied knowledge of riding.
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| 66. |
- Lundstedt, Rikard, et al.
(författare)
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Designing Virtual Natural Environments for Older Adults : Think-Aloud Study
- 2023
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Ingår i: JMIR Human Factors. - : JMIR Publications Inc.. - 2292-9495. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Background: Spending time in natural environments is beneficial for human health, but many older adults have limited or no access to natural environments. Virtual reality technology may be a means to facilitate nature experiences, and so, there is a need for knowledge on how to design virtual restorative natural environments for older adults. Objective: The aim of this study was to identify, implement, and test older adults’ preferences and ideas regarding virtual natural environments. Methods: A total of 14 older adults (mean age 75, SD 5.9 years) participated in an iterative process to design such an environment. We used think-aloud protocols and qualitative content analysis and established questionnaires that targeted usability, affective aspects, and side effects. These data guided the design decisions for incremental implementations of a prototype. Results: The participants’ preferences included trueness to reality in terms of rendition and behavior; traces of human activity and natural processes that trigger the imagination and provide believability; the ability to roam, explore, and interact with the environment; and a familiar, relatable environment that evokes memories. The iterative design process resulted in a prototype featuring many of the participants’ ideas and preferences, including a seated locomotion technique, animals, a boat ride, the discovery of a boat wreck, and apple picking. The questionnaire results indicated high perceived usability, interest, and enjoyment; low pressure and tension; moderate value and usefulness; and negligible side effects. Conclusions: We suggested 3 principles for virtual natural environments for older adults: realness, interactivity, and relatedness. Virtual natural environments should also provide a diversity of content and activities to accommodate the heterogeneity in older adults’ preferences. These results can contribute to a framework for designing virtual natural environments for older adults. However, these findings need to be tested and potentially revised in future studies.
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| 67. |
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| 68. |
- Malmgren Fänge, Agneta, et al.
(författare)
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Accessibility to the public environment as perceived by teenagers with functional limitations in a south Swedish town centre.
- 2002
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Ingår i: Disability and Rehabilitation. - : Informa UK Limited. - 0963-8288 .- 1464-5165. ; 24:6, s. 318-326
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Owing to physical inaccessibility persons with mobility restrictions and other functional limitations often face problems in public environments, leading to restrictions in activity and participation. To investigate general accessibility and perceived problems of accessibility to the public environment in a town centre, as well as visiting preferences to public facilities, among teenagers with functional limitations. METHODS: An interview questionnaire specific to a south Swedish town was constructed and used with 33 Swedish teenagers with functional limitations. RESULTS: To a varying degree, all 33 teenagers commented on accessibility problems, e.g. concerning uneven surface material outdoors, steps at entrances, heavy doors and restricted space indoors. The results also indicated that teenagers with functional limitations to a high extent want to visit the same environments as other teenagers, but that it is often impossible owing to accessibility problems. Furthermore, because of accessibility problems, many of the teenagers were dependent on personal assistance. CONCLUSION: Inaccessibility results in dependence, which might affect personal development negatively, and much effort are required in order to ensure activity and societal participation. Efficient priorities in public environment accessibility matters and discussions with the actors involved require valid and reliable data on local accessibility problems.
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| 69. |
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| 70. |
- Mani, K, et al.
(författare)
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Heparan/chondroitin/dermatan sulfate primer 2-(6-hydroxynaphthyl)-O-beta-D-xylopyranoside preferentially inhibits growth of transformed cells
- 1998
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Ingår i: Cancer Research. - 0008-5472. ; 58:6, s. 104-1099
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Tidskriftsartikel (refereegranskat)abstract
- Xylose forms the direct carbohydrate-protein link in extra- or pericellular proteoglycans (PGs) that are substituted with either chondroitin sulfate (CS)/dermatan sulfate (DS) and/or heparan sulfate (HS). Cell surface PGs carrying HS are important regulators of cell growth. Xylose coupled to an aromatic compound can enter cells and initiate either CS/DS synthesis or both HS and CS/DS synthesis, depending on the nature of the aromatic adduct. Here, we show that 2-(6-hydroxynaphthyl)-O-beta-D-xylopyranoside, which can prime both types of glycan chains, inhibits growth of a set of normal and transformed cells. Transformed cells are preferentially inhibited, and at a concentration of 0.15-0.20 mM xyloside, transformed cells are totally growth arrested, whereas normal cells are only < or = 50% inhibited. No inhibition of growth is observed with the stereoisomeric 2-(6-hydroxynaphthyl)-O-beta-L-xylopyranoside, which does not prime glycosaminoglycan synthesis at all; with the nonhydroxylated 2-naphthyl-O-beta-D-xylopyranoside, which only primes CS/DS synthesis under these conditions; or with p-nitrophenyl-O-beta-D-xylopyranoside, which is known to prime only CS/DS synthesis. We conclude that growth inhibition is due to priming of HS and/or CS/DS synthesis, which may either lead to the formation of specific antiproliferative glycans or glycan fragments or to interference with endogenous PG synthesis and turnover.
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