| 1. |
- Cho, H., et al.
(författare)
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Ultradeep, low-damage dry etching of SiC
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 76:6, s. 739-741
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Tidskriftsartikel (refereegranskat)abstract
- The Schottky barrier height (Phi(B)) and reverse breakdown voltage (V-B) of Au/n-SiC diodes were used to examine the effect of inductively coupled plasma SF6/O-2 discharges on the near-surface electrical properties of SiC. For low ion energies (less than or equal to 60 eV) in the discharge, there is minimal change in Phi(B) and V-B, but both parameters degrade at higher energies. Highly anisotropic features typical of through-wafer via holes were formed in SiC using an Al mask.
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| 2. |
- Hays, Graeme C., et al.
(författare)
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Island-finding ability of marine turtles
- 2003
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 270:Suppl. 1, Aug 7, s. 5-7
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Tidskriftsartikel (refereegranskat)abstract
- Green turtles (Chelonia mydas) swim from foraging grounds along the Brazilian coast to Ascension Island to nest, over 2200 km distant in the middle of the equatorial Atlantic. To test the hypothesis that turtles use wind-borne cues to locate Ascension Island we found turtles that had just completed nesting and then moved three individuals 50 km northwest (downwind) of the island and three individuals 50 km southeast (upwind). Their subsequent movements were tracked by satellite. Turtles released downwind returned to Ascension Island within 1, 2 and 4 days, respectively. By contrast, those released upwind had far more difficulty in relocating Ascension Island, two eventually returning after 10 and 27 days and the third heading back to Brazil after failing to find its way back to the island. These findings strongly support the hypothesis that wind-borne cues are used by turtles to locate Ascension Island.
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| 3. |
- Hays, G. C., et al.
(författare)
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The diving behaviour of green turtles undertaking oceanic migration to and from Ascension Island: dive durations, dive profiles and depth distribution
- 2001
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Ingår i: Journal of Experimental Biology. - 1477-9145. ; 204:23, s. 4093-4098
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Tidskriftsartikel (refereegranskat)abstract
- Satellite telemetry was used to record the submergence duration of green turtles (Chelonia mydas) as they migrated from Ascension Island to Brazil (N=12 individuals) while time/depth recorders (TDRs) were used to examine the depth distribution and dive profiles of individuals returning to Ascension Island to nest after experimental displacement (N=5 individuals). Satellite telemetry revealed that most submergences were short (<5 min) but that some submergences were longer (>20 min), particularly at night. TDRs revealed that much of the time was spent conducting short (24 min), shallow (approximately 0.91.5 m) dives, consistent with predictions for optimisation of near-surface travelling, while long (typically 2030 min), deep (typically 1020 m) dives had a distinctive profile found in other marine reptiles. These results suggest that green turtles crossing the Atlantic do not behave invariantly, but instead alternate between periods of travelling just beneath the surface and diving deeper. These deep dives may have evolved to reduce silhouetting against the surface, which would make turtles more susceptible to visual predators such as large sharks.
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| 4. |
- Luschi, P, et al.
(författare)
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Testing the navigational abilities of ocean migrants: displacement experiments on green sea turtles (Chelonia mydas)
- 2001
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Ingår i: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 1432-0762 .- 0340-5443. ; 50:6, s. 528-534
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Tidskriftsartikel (refereegranskat)abstract
- Like many animals migrating through the oceans, sea turtles face difficult navigational tasks when they have to reach distant, specific sites. The paradigmatic case of Brazilian green turtles (Chelonia mydas), which nest on the tiny Ascension Island in the middle of the Atlantic Ocean, has often been the subject of hypotheses concerning their navigational mechanisms. To investigate their nature, we displaced 18 females from Ascension and tracked them by satellite after release from eight different points in the ocean, 60-450 km away from the island. Four turtles moved to Brazil soon after the release, 4 moved in various directions before heading to Brazil, and 10 reached the island. All the successful trips, bar 1, were winding but ended with a final straight segment of variable length, as if the turtles were searching for a sensory contact with the island which they obtained at various distances. The approach to Ascension mostly occurred from the direction opposite to the trade wind, suggesting a navigational role of wind-borne information originating from the island.
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| 5. |
- Åkesson, Susanne, et al.
(författare)
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Navigation by green turtles: which strategy do displaced adults use to find Ascension Island?
- 2003
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 103:2, s. 363-372
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Tidskriftsartikel (refereegranskat)abstract
- Sea turtles are known to perform long-distance, oceanic migrations between disparate feeding areas and breeding sites, some of them located on isolated oceanic islands. These migrations demonstrate impressive navigational abilities, but the sensory mechanisms used are still largely unknown. Green turtles breeding at Ascension Island perform long oceanic migrations (>2200 km) between foraging areas along the Brazilian coast and the isolated island. By performing displacement experiments of female green turtles tracked by satellite telemetry in the waters around Ascension Island we investigated which strategies most probably are used by the turtles in locating the island. In the present paper we analysed the search trajectories in relation to alternative navigation strategies including the use of global geomagnetic cues, ocean currents, celestial cues and wind. The results suggest that the turtles did not use chemical information transported with ocean currents. Neither did the results indicate that the turtles use true bi-coordinate geomagnetic navigation nor did they use indirect navigation with respect to any of the available magnetic gradients (total field intensity, horizontal field intensity, vertical field intensity, inclination and declination) or celestial cues. The female green turtles successfully locating Ascension Island seemed to use a combination of searching followed by beaconing, since they searched for sensory contact with the island until they reached positions NW and N of the Island and from there presumably used cues transported by wind to locate the island during the final stages of the search.
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| 6. |
- Åkesson, Susanne, et al.
(författare)
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Oceanic long-distance navigation: Do experienced migrants use the Earth's magnetic field?
- 2001
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Ingår i: Journal of Navigation. - 0373-4633. ; 54:3, s. 419-427
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Albatrosses and sea turtles are known to perform extremely long-distance journeys between disparate feeding areas and breeding sites located on small, isolated, oceanic islands or at specific coastal sites. These oceanic journeys, performed mainly over or through apparently featureless mediums, indicate impressive navigational abilities, and the sensory mechanisms used are still largely unknown. This research used three different approaches to investigate whether bi-coordinate navigation based on magnetic field gradients is likely to explain the navigational performance of wandering albatrosses in the South Atlantic and Indian Oceans and of green turtles breeding on Ascension Island in the South Atlantic Ocean. The possibility that magnetic field parameters can potentially be used in a bi-coordinate magnetic map by wandering albatrosses in their foraging area was investigated by analysing satellite telemetry data published in the literature. The possibilities for using bi-coordinate magnetic navigation varied widely between different areas of the Southern Oceans, indicating that a common mechanism, based on a bi-coordinate geomagnetic map alone, was unlikely for navigation in these areas. In the second approach, satellite telemetry was used to investigate whether Ascension Island green turtles use magnetic information for navigation during migration from their breeding island to foraging areas in Brazilian coastal waters. Disturbing magnets were applied to the heads and carapaces of the turtles, but these appeared to have little effect on their ability to navigate. The only possible effect observed was that some of the turtles with magnets attached were heading for foraging areas slightly south of the control turtles along the Brazilian coast. In the third approach, breeding female green turtles were deliberately displaced in the waters around Ascension Island to investigate which cues these turtles might use to locate and return to the island; the results suggested that cues transported by wind might be involved in the final stages of navigation.
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| 7. |
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