| 1. |
- Björling, Marcus, et al.
(författare)
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Warm carbon coat reduces friction
- 2014
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 505:7483, s. 264-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A coating material made of carbon reduces friction not just by providing a slippery surface, but also by keeping the points of contact warm. Marcus Björling at Luleå University of Technology in Sweden and his team coated steel balls with ``diamond-like-carbon'' - a material in which carbon atoms have a bonding pattern similar to that of diamond. They rolled the balls against a metal disk with an oil lubricant in between, and showed that the carbon coating acts as an insulator, lowering the viscosity of the lubricant and thus reducing the fricion between the ball and the disk. These findings could encourage the development of lubricant coatings made from insulating materials.
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| 2. |
- Elming, Sten-Åke
(författare)
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Evidence for early Proterozoic plate tectonics from seismic reflection profiles in the Baltic Shield
- 1990
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 348, s. 34-38
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Tidskriftsartikel (refereegranskat)abstract
- Plate tectonics provides the linking framework for all tectonic and magmatic activity seen today, but it is not known when plate tectonics first developed on Earth. New deep seismic reflection and coincident refraction profiles across an exposed, 1.89-Gyr-old volcanic arc complex show a 10-km-thick offset in the Moho and bivergent reflectors in the crust, which were most probably created by plate convergence, subduction and accretion during the Early Proterozoic. Hence, plate tectonic models seem to be applicable for at least the second half of Earth's history.
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| 3. |
- Korablev, Oleg, et al.
(författare)
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No detection of methane on Mars from early ExoMars Trace Gas Orbiter observations
- 2019
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 568, s. 517-520
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Tidskriftsartikel (refereegranskat)abstract
- The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today1. A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations2,3,4,5. These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere6,7, which—given methane’s lifetime of several centuries—predicts an even, well mixed distribution of methane1,6,8. Here we report highly sensitive measurements of the atmosphere of Mars in an attempt to detect methane, using the ACS and NOMAD instruments onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter from April to August 2018. We did not detect any methane over a range of latitudes in both hemispheres, obtaining an upper limit for methane of about 0.05 parts per billion by volume, which is 10 to 100 times lower than previously reported positive detections2,4. We suggest that reconciliation between the present findings and the background methane concentrations found in the Gale crater4 would require an unknown process that can rapidly remove or sequester methane from the lower atmosphere before it spreads globally.
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| 4. |
- 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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| 5. |
- O’Carroll, Conor, et al.
(författare)
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Virtual mobility can drive equality
- 2014
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 511:292, s. 292-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 6. |
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| 7. |
- Parasnis, Dattatray S.
(författare)
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PhD theses
- 1988
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 333:6171, s. 294-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 8. |
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| 9. |
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| 10. |
- Vandaele, Ann Carine, et al.
(författare)
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Martian dust storm impact on atmospheric H2O and D/H observed by ExoMars Trace Gas Orbiter
- 2019
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Ingår i: Nature. - : Springer. - 1476-4687 .- 1476-4687 .- 0028-0836. ; 568:7753, s. 521-525
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Global dust storms on Mars are rare1,2 but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere3, primarily owing to solar heating of the dust3. In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars4. Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes5,6, as well as a decrease in the water column at low latitudes7,8. Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H2O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H2O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals3. The observed changes in H2O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere.
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