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- Li, Jian-Yang, et al.
(författare)
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Ejecta from the DART-produced active asteroid Dimorphos
- 2023
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 616, s. 452-456
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Tidskriftsartikel (refereegranskat)abstract
- Some active asteroids have been proposed to be formed as a result of impact events1. Because active asteroids are generally discovered by chance only after their tails have fully formed, the process of how impact ejecta evolve into a tail has, to our knowledge, not been directly observed. The Double Asteroid Redirection Test (DART) mission of NASA2, in addition to having successfully changed the orbital period of Dimorphos3, demonstrated the activation process of an asteroid resulting from an impact under precisely known conditions. Here we report the observations of the DART impact ejecta with the Hubble Space Telescope from impact time T + 15 min to T + 18.5 days at spatial resolutions of around 2.1 km per pixel. Our observations reveal the complex evolution of the ejecta, which are first dominated by the gravitational interaction between the Didymos binary system and the ejected dust and subsequently by solar radiation pressure. The lowest-speed ejecta dispersed through a sustained tail that had a consistent morphology with previously observed asteroid tails thought to be produced by an impact4,5. The evolution of the ejecta after the controlled impact experiment of DART thus provides a framework for understanding the fundamental mechanisms that act on asteroids disrupted by a natural impact1,6.
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| 2. |
- Maffulli, N., et al.
(författare)
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Free tendon grafts for surgical management of chronic tears of the main body of the Achilles tendon: a systematic review
- 2023
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Ingår i: Knee Surgery Sports Traumatology Arthroscopy. - 0942-2056. ; 31:10, s. 4526-38
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Tidskriftsartikel (refereegranskat)abstract
- PurposeAfter four weeks from injury, tears of the Achilles tendon are considered chronic. Their management is challenging, and the use of a graft is suggested when the gap between proximal and distal stumps is greater than 6 cm. The present study systematically reviews the outcome of free tendon grafts in chronic ruptures of the Achilles tendon, evaluating clinical outcomes, complications and return to sport.MethodsThe present study was conducted according to the PRISMA 2020 guidelines. PubMed, Google Scholar, Embase, and Web of Science databases were accessed in February 2023. All the published clinical studies reporting clinical outcome, return to sport and complications of free tendon grafts used the treatment of chronic rupture of the midportion of the Achilles Tendon were accessed. The mean CMS (Coleman Methodology Score) of 65.7 suggested an overall good quality of the available published articles, attesting to the low risk of bias.ResultsData from 22 articles (368 patients with a mean age of 47 years) were retrieved. The average time from rupture to surgery was 25.1 week. At last follow-up, the AOFAS (American Orthopaedic Foot and Ankle Surgery) and ATRS (Achilles Tendon Total Rupture Score) scores improved of 33.8 (P = 0.0004), and 45.1 points (P = 0.0001) respectively. Return to activity was reported in 105 patients, and 82 (78.1%) had no activity limitations, while 19 (18.1%) had limited recreational but not daily activity limitations, and 4 (3.8%) reported limitations in daily activities. Return to sport data was reported in six studies, and 45 of 93 (48.4%) patients returned to sport at an average of 22.6 weeks.ConclusionIn chronic tears of the Achilles tendon, with a gap of at least 6 cm, free tendon grafts allow predictable return to sport and acceptable recovery function.
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