| 1621. |
- Larsson, Ragnar, 1960, et al.
(författare)
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A higher-order stress-resultant shell formulation based on multiscale homogenization
- 2009
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Ingår i: 10th International Conference on Computational Plasticity, COMPLAS X; Barcelona; Spain; 2 September 2009 through 4 September 2009. - 9788496736696
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Konferensbidrag (refereegranskat)abstract
- In this paper, a multiscale method for simulating the mechanical response of a thin porous structure subjected to loading is proposed. Shell kinematics is adopted for the structure on the macroscopic scale while the stress resultants pertaining to the shell model are attained from the underlying porous microstructure via computational homogenization of the microscale quantities. The microstructural response is in its turn evaluated by solving a boundary value problem involving a Representative Volume Element (RVE) that extends through the full thickness of the porous structure. The resulting nested computational scheme accommodates that microscopic variations of deformation, i.e. the micro-fluctuations, are accounted for. This is necessary when it cannot be assumed that there is a separation between the spatial scale on which the deformation fields vary and the spatial scale of the microstructure. It can for example be the case for a thin foam layer included in a vehicle reinforcing component.
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| 1622. |
- Larsson, Ragnar, 1960, et al.
(författare)
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A stress-resultant shell theory based on multiscale homogenization
- 2013
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Ingår i: Computer Methods in Applied Mechanics and Engineering. - : Elsevier BV. - 0045-7825. ; 263, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we propose a multiscale method based on computational homogenization for simulating the mechanical response of a thin–walled porous structure. Due to the inhomogeneous nature of the porous material in the thickness direction, the length scale of the deformation-field variations in the thickness direction is in the same order of magnitude as in the microstructure. To resolve this issue a higher-order stress-resultant shell formulation (with linear variation of the thickness stretch) based on multiscale homogenization is considered. The microscale is accounted for by calculating the micro-fluctuations from a boundary value problem over the domain of a 3D Representative Volume Element (RVE). The breadth and width of the RVE are determined by the representative microstructure of the porous material, whereas in the thickness direction of the shell the RVE completely resolves the microscopic variation. As a result the macroscopic stress resultants are obtained as volume averages through the entire thickness of the shell. The nested solution scheme is quite computationally demanding and it should only be applied where it is needed. The paper is concluded by a couple of numerical examples that illustrate the method and support the arguments put forward in the paper. Comparison is made to a 2D plane strain reference solution with complete resolution of the microstructure over the domain. Also a 3D case is considered, showing the significance of resolving the microscopic fluctuations.
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| 1623. |
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| 1624. |
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| 1625. |
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| 1626. |
- Larsson, Sofie, et al.
(författare)
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A microsimulation model projecting the health care costs for resistance to antibacterial drugs in Sweden
- 2019
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Ingår i: European journal of public health. - : Oxford University Press (OUP). - 1464-360X .- 1101-1262. ; 29:3, s. 392-396
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Previous studies have shown that increasing antibacterial resistance (ABR) globally will cause extensive morbidity, deaths and escalated health care costs. METHODS: To project economic consequences of resistance to antibacterial drugs for the Swedish health care sector, we used an individual-based microsimulation model, SESIM. Health care consumption was represented as increased numbers of hospital days, outpatient visits and contact tracing for individuals getting clinical infections or becoming asymptomatic carriers. The risk of contracting a resistant bacterium was calculated using the incidence of mandatorily notifiable ABR in Sweden. RESULTS: We estimate accumulated additional health care costs attributable to notifiable ABR from 2018 until 2030 to EUR 406 million and EUR 1, 503 million until 2050. Until 2030 the largest proportion, more than EUR 247 million (EUR 958 million until 2050), was due to ESBL, followed by methicillin resistant Staphylococcus aureus, carbapenemase-producing Enterobacteriaceae, vancomycin-resistant Enterococci and penicillin non-susceptible Pneumococci which incurred costs of EUR 128 million (EUR 453 million, 2050), EUR 15 million (EUR 58 million, 2050), EUR 13 million (EUR 28 million, 2050) and EUR 2 million (EUR 6 million, 2050), respectively. CONCLUSIONS: Projections concerning the future costs of ABR can be used to guide priorities and distribution of limited health care resources. Our estimates imply that costs in Sweden will have doubled by 2030 and increased more than 4-fold by 2050 if present trends continue and infection control practices remain unchanged. Still, indirect societal costs and costs for non-notifiable resistance remain to be added. © The Author(s) 2018. Published by Oxford University Press on behalf of the European Public Health Association.
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| 1627. |
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| 1628. |
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| 1629. |
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| 1630. |
- Larsson, Sune, et al.
(författare)
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Anti-osteoporosis therapy and fracture healing
- 2014
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Ingår i: Archives of Orthopaedic and Trauma Surgery. - : Springer Science and Business Media LLC. - 0936-8051 .- 1434-3916. ; 134:2, s. 291-297
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Tidskriftsartikel (refereegranskat)abstract
- A number of medications are approved for treatment of osteoporosis. As mode of action usually is anti-catabolic/anti-resorptive or anabolic, it is of interest to know whether these drugs affect not only normal bone remodeling, but also fracture healing. The purpose of this paper is to give a short overview of the potential effect of various anti-osteoporotic medication on fracture healing. A narrative literature review was performed to describe the current knowledge. Anti-catabolic/anti-resorptive drugs: for bisphosphonates, the most common class of drugs in this group, experimental studies have shown a larger and stronger callus and delayed remodeling but no evidence of delayed healing. A human monoclonal antibody to RANKL is another anti-catabolic drug, with the only report to date showing enhanced healing in an animal model. Strontium ranelate is a drug where both anti-catabolic and a weak anabolic effect have been proposed, with experimental data ranging from no effect to significant increase in both callus volume and strength. Anabolic drugs: PTH has demonstrated accelerated healing of various experimental fractures and of distal radius and pelvic fractures in humans. While the exact mechanism is not fully understood, PTH results in increased recruitment and differentiation of chondrocytes and enhancement of endochondral ossification. A monoclonal antibody to block sclerostin is another potential anabolic pathway, where animal data have shown increase in bone mass and strength. The potential effect on fracture healing is yet to be studied. There are still large gaps in the understanding of the potential effect of anti-osteoporotic drugs on fracture healing, although based on present knowledge a recent or present fracture should not be considered as a contraindication to such treatment.
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