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| 2. |
- Hansen, Steffen Foss, et al.
(författare)
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Nanotechnology meets circular economy
- 2022
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 17:7, s. 682-685
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Alonso-Vazquez, A, et al.
(författare)
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Initial stability of ankle arthrodesis with three-screw fixation. A finite element analysis
- 2004
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Ingår i: Clinical Biomechanics. - : Elsevier BV. - 0268-0033. ; 19:7, s. 751-759
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Compare the initial stability at the fusion site of ankle arthrodesis fixed with two and three screws. Design. Finite element models of ankle arthrodesis were developed from computed tomography images. Two-screw constructs were augmented with a third screw in different orientations and Subjected to loads likely to affect the ankle postoperatively. Background More stable fixation seems to increase the chance of fusion, as it minimises the motion between the tibiotalar interfaces. Methods. Non-linear elastic finite element analyses were performed in external torsion and dorsiflexion. The micromotions at the tibiotalar interface were computed to compare the two- and three-screw fixation in intact and flat-cut arthrodesis. Results. Adding a third screw reduced the micromotions at the fusion site. Inserting the third screw anteriorly predicted lower peak micromotions than inserting the screw posteriorly, except for the intact arthrodesis tested in dorsiflexion. Three-screw intact arthrodesis predicted lower peak micromotions than flat-cut arthrodesis. Conclusions. Better stability was predicted for three-screw ankle arthrodesis. In flat-cut arthrodesis, a third screw inserted anteriorly performed better than a posterior screw. In intact arthrodesis, a posterior screw seemed a better option when flexion stability was the main concern. Even with three-screw fixation, the configuration of the first two-crossed screws may still be important to improve the stability at the fusion site. Relevance The optimal number and placement of screws in ankle arthrodesis has yet to be determined. The differences in stability predicted between various screw configurations and Surface preparation techniques presented here may be the difference between success and failure. (C) 2004 Elsevier Ltd. All rights reserved.
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| 4. |
- Alonso-Vazquez, A, et al.
(författare)
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The effect of bone quality on the stability of ankle arthrodesis. A finite element study
- 2004
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Ingår i: Foot & Ankle International. - 1944-7876. ; 25:11, s. 840-850
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Tidskriftsartikel (refereegranskat)abstract
- Background: Despite uniform operating techniques, lack of fusion still occurs after ankle arthrodesis. Differences in the biological healing potential may be a factor but the mechanical performance of the arthrodesis construct because of varying bone quality also may be important. Internal compression techniques are preferred because of higher union rates, shorter fusion times, and fewer complications. A three-screw configuration has been shown to be more stable than a two-screw configuration, but it is not obvious when it should be used. Methods: Three-dimensional finite element models of intact and flat-cut ankle arthrodeses were built, using two and three screws in different configurations. Poor bone quality was simulated by decreasing Young's modulus of the bone. The constructs were loaded in torsion and dorsiflexion, and micromotions at the fusion site were measured. Results: Bone quality had a marked effect on the stability at the arthrodesis site. Inserting two screws at 30 degrees relative to the longitudinal axis of the tibia in an intact arthrodesis seemed the best option, especially as bone quality worsened. The addition of a third screw increased the stability at the arthrodesis site. Conclusions: Overall, intact joint surfaces and three-screw fixation, with the lateral and medial screws inserted produced the most stable arthrodesis constructs when bone quality was poor. Clinical Relevance. Ankle arthrodeses are technically demanding because of the shape and small size of the talus. Preoperative planning is an absolute necessity to determine placement and number of screws. This study shows that poor bone quality decreases the stability of the arthrodesis constructs, suggesting that an attempt should be made to create the most stable three-screw configuration. Finite element models can be used as an effective preoperative tool for planning screw number and placement.
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| 5. |
- Hansen, Steffen Foss, et al.
(författare)
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To be or not to be a nanomaterial
- 2022
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Ingår i: Journal of Nanoparticle Research. - : Springer Science and Business Media LLC. - 1388-0764 .- 1572-896X. ; 24:12
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Tidskriftsartikel (refereegranskat)abstract
- In early 2021, the new definition of the term “nanomaterial” proposed by the European Commission (EC) was subject to a stakeholder consultation and in June 2022, the EC published its updated definition. Based on an independent analysis of the different versions of the definition and the results of the stakeholder consultation, the aim of this paper is to identify key aspects to be considered when deciding whether a material should be regarded as a nanomaterial. More than 130 comments submitted during the stakeholder consultation by various organizations, companies, citizens, and authorities were analyzed. We find that the introduction of new terms such as “solid particles” has added clarity to terms used in the former definition. Our analysis shows that stakeholders seemed inclined to maintain the default number-based 50% threshold value, but were opposed to (1) the possible flexibility of varying the threshold in specific sectorial legislation, (2) the default inclusion of carbonaceous materials < 1 nm, and (3) the use of volume specific surface area (VSSA) other than for excluding materials from being defined as nanomaterials. Overall, we find that the updated definition addresses many of the limitations of the former definition. However, the updated definition also creates new challenges that will have to be addressed via development of new regulatory guidance. Apart from the relatively minor change of the VSSA threshold from 5 to 6 m2/cm3, it generally seems that no arguments from the stakeholder consultation made the EC reconsider its position. Graphical Abstract: [Figure not available: see fulltext.].
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| 6. |
- Nielsen, Maria, et al.
(författare)
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Nanomaterials in the European chemicals legislation-methodological challenges for registration and environmental safety assessment
- 2021
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Ingår i: Environmental Science: Nano. - : Royal Society of Chemistry. - 2051-8153 .- 2051-8161. ; 8:3, s. 731-747
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Tidskriftsartikel (refereegranskat)abstract
- In the European Union the Annexes of its chemical legislation (REACH) were revised and now clarify the technical data requirements for nanomaterials (NMs). These new provisions, effective from January 1, 2020, introduce requirements for manufacturers, importers and downstream users regarding registration and safety assessment of NMs. This study aims to assess the availability and suitability of methods needed to comply with the new regulatory provisions on NMs for physico-chemical characterisation and environmental fate and effects. The scientific literature and relevant test guideline frameworks were reviewed to identify applicable methods. These were subsequently evaluated and categorised as either: 'internationally accepted test guideline or standard (TGS)', 'internationally accepted test guideline or standard under development (TGSUD)', 'established as standard methods in scientific literature (SCI)', 'other methods and/or more research needed (O)' or 'no method (N)'. We find that 80% of the information requirements and a bit more than 40% of the waiving criteria in the new REACH Annexes are supported by methods that are available as TGS, TGSUD or SCI. Most of the relevant methods in the scientific literature are included in recent OECD guidance documents or ECHA guidance. We recommend that a targeted effort is made to develop protocols and guidelines for methods to determine NM adsorption/desorption, degradation, exposure scenarios and ability to cross biological membranes. Here methods to fulfil the information requirements and waiving criteria are currently lacking. Furthermore, we recommend that increasing attention is directed towards regulatory reliability and relevance of the information that is submitted by the registrants.
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| 7. |
- Thorsen, Lauge S., et al.
(författare)
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High pressure oxidation of NH3/n-heptane mixtures
- 2023
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Ingår i: Combustion and Flame. - 0010-2180. ; 254
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Tidskriftsartikel (refereegranskat)abstract
- Oxidation of NH3/n-heptane mixtures at pressures up to 100 atm and temperatures of 400–900 K was characterized experimentally in a laminar flow reactor and a jet-stirred reactor. A detailed chemical kinetic model was developed, updating the hydrogen and amine subsets and introducing a subset for the chemical coupling with emphasis on the NH2+n-heptane reaction. The kinetic model provided a good prediction of the ignition delay times measured in a rapid compression machine by Yu et al. (Combust. Flame 217 (2020) 2–11) as well as the high pressure experimental data obtained in the present work. The results show that it is important to include updated rate constants for NH2 + HO2 and NH2 + n-C7H16 to obtain reliable predictions for ignition and oxidation of NH3/n-heptane mixtures at high pressure. The effectiveness of implementing analogy rules for determining the rate constant of the key reaction NH2 + n-C7H16 was confirmed by the observed results.
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