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- Keppler, M., et al.
(författare)
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Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 617
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Tidskriftsartikel (refereegranskat)abstract
- Context. Young circumstellar disks are the birthplaces of planets. Their study is of prime interest to understand the physical and chemical conditions under which planet formation takes place. Only very few detections of planet candidates within these disks exist, and most of them are currently suspected to be disk features.Aims. In this context, the transition disk around the young star PDS 70 is of particular interest, due to its large gap identified in previous observations, indicative of ongoing planet formation. We aim to search for the presence of an embedded young planet and search for disk structures that may be the result of disk-planet interactions and other evolutionary processes.Methods. We analyse new and archival near-infrared images of the transition disk PDS 70 obtained with the VLT/SPHERE, VLT/NaCo, and Gemini/NICI instruments in polarimetric differential imaging and angular differential imaging modes.Results. We detect a point source within the gap of the disk at about 195 mas (similar to 22 au) projected separation. The detection is confirmed at five different epochs, in three filter bands and using different instruments. The astrometry results in an object of bound nature, with high significance. The comparison of the measured magnitudes and colours to evolutionary tracks suggests that the detection is a companion of planetary mass. The luminosity of the detected object is consistent with that of an L-type dwarf, but its IR colours are redder, possibly indicating the presence of warm surrounding material. Further, we confirm the detection of a large gap of similar to 54 au in size within the disk in our scattered light images, and detect a signal from an inner disk component. We find that its spatial extent is very likely smaller than similar to 17 au in radius, and its position angle is consistent with that of the outer disk. The images of the outer disk show evidence of a complex azimuthal brightness distribution which is different at different wavelengths and may in part be explained by Rayleigh scattering from very small grains.Conclusions. The detection of a young protoplanet within the gap of the transition disk around PDS 70 opens the door to a so far observationally unexplored parameter space of planetary formation and evolution. Future observations of this system at different wavelengths and continuing astrometry will allow us to test theoretical predictions regarding planet-disk interactions, planetary atmospheres, and evolutionary models.
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| 2. |
- Frykberg, Lars, et al.
(författare)
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Antiphagocytic Function of an IgG Glycosyl Hydrolase from Streptococcus equi subsp equi and Its Use as a Vaccine Component
- 2012
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Ingår i: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 80, s. 2914-2919
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Tidskriftsartikel (refereegranskat)abstract
- Endo Se from Streptococcus equi subsp. equi is an enzyme hydrolyzing glycosyl groups on IgG, analogous to EndoS from Streptococcus pyogenes. We here show that the activity of EndoSe leads to an antiphagocytic function and may thus be a contributory factor to immune evasion of S. equi. Despite the damaging effect that EndoSe has on IgG, antibodies against EndoSe can neutralize its function. Antibodies against EndoSe restored the opsonic activity of specific opsonizing antibodies. Mice infected with either S. equi subsp. equi or subsp. zooepidemicus or S. pyogenes could be protected by vaccination with EndoSe. It is speculated that EndoSe could be a suitable vaccine candidate against streptococcal infections.
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| 5. |
- Ulfendahl, M., et al.
(författare)
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Mechanical response characteristics of the hearing organ in the low-frequency regions of the cochlea
- 1996
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 76:6, s. 3850-3862
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Tidskriftsartikel (refereegranskat)abstract
- 1. With the use of an in vitro preparation of the guinea pig temporal bone, in which the apical turns of the cochlea are exposed, the mechanical and electrical responses of the cochlea in the low-frequency regions were studied during sound stimulation. 2. The mechanical characteristics were investigated in the fourth and third turns of the cochlea with the use of laser heterodyne interferometry, which allows the vibratory responses of both sensory and supporting cells to be recorded. The electrical responses, which can be maintained for several hours, were recorded only in the most apical turn. 3. In the most apical turn, the frequency locations and shapes of the mechanical and electrical responses were very similar. 4. The shapes of the tuning curves and the spatial locations of the frequency maxima in the temporal bone preparation compared very favorably with published results from in vivo recordings of hair cell receptor potentials and sound-induced vibrations of the Reissner's membrane. 5. Compressive nonlinearities were present in both the mechanical and the electrical responses at moderate sound pressure levels. 6. The mechanical tuning changed along the length of the cochlea, the center frequencies in the fourth and third turns being approximately 280 and 570 Hz, respectively. 7. The mechanical responses of sensory and supporting cells were almost identical in shape but differed significantly in amplitude radially across the reticular lamina.
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| 9. |
- Elbir, H, et al.
(författare)
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Ovine clone ST1464: a predominant genotype of Staphylococcus aureus subsp. anaerobius isolated from sheep in Sudan
- 2010
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Ingår i: Journal of infection in developing countries. - : Journal of Infection in Developing Countries. - 1972-2680. ; 4:4, s. 235-238
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Tidskriftsartikel (refereegranskat)abstract
- Background: The aim of the present study was to examine the phenotypic and genotypic relatedness of 17 Staphylococcus aureus subsp. anaerobius isolates recovered from sheep abscesses in Khartoum state, Sudan, during the period 2007-2008. Methodology: This sample was characterised using antibiogram typing, biochemical typing with the commercial PhenePlate system (PhP-CS) and multilocus sequence typing (MLST). Results: Low levels of resistance were noted to the 11 antimicrobial agents tested. All the isolates corresponded to a single PhP type, and to a single, novel, multilocus sequence type, designated ST1464. Conclusion: These results demonstrate that the vast majority of cases of sheep abscess disease in Khartoum state are caused by a single novel clone of S. aureus subsp. anaerobius.
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