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Author  |
Bart Van de Vijver, Luc Ector |
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Title |
Microcostatus elisabethianus, a new limnoterrestrial diatom species (Bacillariophyta) from the sub-Antarctic region |
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Journal |
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Year |
2019 |
Publication |
Plant Ecology and Evolution |
Abbreviated Journal |
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Volume |
152 |
Issue |
3 |
Pages |
539-545 |
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Abstract |
Background and aims – During a survey of the soil diatom flora of the sub-Antarctic islands in the southern Indian Ocean, an unknown small-celled naviculoid taxon was discovered living in small cracks in cliffs bordering the ocean. The taxon showed a set of morphological features only found in the genus Microcostatus. However, the unknown taxon could not be identified using the currently available literature. Methods – Using both light microscopical and scanning electron microscopical techniques, the morphology of the unknown Microcostatus taxon was documented. The new taxon is described, illustrated and compared with all other similar Microcostatus taxa worldwide. Key results – Microcostatus elisabethianus possesses a unique combination of morphological features that excludes conspecificity with all other members of the genus. It is characterized by a lanceolate valve outline with protracted, elongate apices, a very large, porous conopeum reaching the valve margins and uniseriate striae composed of only one macroareola and mantle areolae restricted to the valve apices. The morphological features of the genus Microcostatus are evaluated and discussed. Notes on the occurrence and ecology of the new taxon are added. |
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136 |
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2032-3921 |
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yes |
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7713 |
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Author |
Bart Van de Vijver, Pieter Scholberg, Marc Lebouvier |
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Title |
Pinnularia schoelynckiana, a new limnoterrestrial diatom species (Bacillariophyta) from the sub-Antarctic Iles Kerguelen (southern Indian Ocean) |
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Year |
2019 |
Publication |
Botany Letters |
Abbreviated Journal |
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Volume |
167 |
Issue |
1 |
Pages |
42-49 |
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Keywords |
hot springs morphology new species Pinnularia sub-Antarctica |
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Abstract |
An unknown Pinnularia taxon was recorded during a survey of the limno-terrestrial diatom flora of some hot springs in the Val Travers area (Grande Terre, Iles Kerguelen, sub-Antarctic region). The morphology of the species was investigated using both light and scanning electron microscopy. Based on these results, the species could not be identified using the currently available literature and is therefore described as a new species: Pinnularia schoelynckiana sp. nov. The new species is characterized by rhombic-lanceolate valves, radiate, geniculate striae changing into strongly convergent near the apices and an undulating, lateral raphe. A detailed morphological comparison is made with similar Pinnularia species, described from the Antarctic Region and worldwide. Brief notes on the associated diatom flora and its ecology are added. |
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136 |
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2381-8107 |
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yes |
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7716 |
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Author |
Bart Van de Vijver, Richard M. Crawford |
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Title |
Melosira jeanbertrandiana, a new Melosira species (Bacillariophyceae) from the sub-Antarctic region |
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Journal |
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Year |
2019 |
Publication |
Botany Letters |
Abbreviated Journal |
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Volume |
167 |
Issue |
1 |
Pages |
50-56 |
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Keywords |
Melosira melosiroid genera morphology new species Sub-Antarctica |
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Abstract |
During a survey of the soil diatom flora of the sub-Antarctic Ile de la Possession (Iles Crozet), located in the southern Indian Ocean, an unknown Melosira species was found that could not be identified using the currently available literature on the genus. The species is described as Melosira jeanbertrandiana sp. nov. based on detailed light and scanning electron microscopy observations. The new species is characterized by a relatively high mantle, the presence of several marginal rings of acute, never bifurcating spines and a series of eight rimoportulae near the central area with several others scattered over the rest of the valve face and mantle. The girdle comprising several large, ligulate open copulae and the position of the rimoportulae clearly place this new species within the genus Melosira C.Agardh. The species was observed in bare, moist soil in scratches in cliffs bordering the ocean where the influence of sea spray is obvious. The description of this new species further increases the number of species of the Melosirales compared to other centric freshwater diatoms which are infrequently found on the sub-Antarctic islands. |
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136 |
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2381-8107 |
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yes |
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Serial |
7712 |
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Author |
Bart Van De Vijver, Steven Dessein |
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Title |
Cyclotella deceusteriana , a new centric diatom species (Bacillariophyta) from the sub-Antarctic Region |
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Journal |
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Year |
2018 |
Publication |
Phytotaxa |
Abbreviated Journal |
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Volume |
333 |
Issue |
1 |
Pages |
108-116 |
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Keywords |
Algae centric diatoms Cyclotella morphology new species Sub-Antarctica |
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Abstract |
During a survey of the freshwater diatom flora of the sub-Antarctic region (Iles Kerguelen and Iles Crozet) in the southern Indian Ocean, an unknown Cyclotella taxon was observed that was formerly identified as the presumed cosmopolitan C. meneghinana. Detailed morphological analysis based on light and scanning electron microscopical observations and comparison with several similar Cyclotella taxa worldwide justified the description of this unknown taxon as a new species: Cyclotella deceusteriana sp. nov. The new taxon is characterized by the presence of marginal fultoportulae on every costa, hyaline furrows between the raised marginal parts on which the striae are located, 2, occasionally 1, 3 or 4 central fultoportulae and an entirely flat, smooth, relatively small central area. The new species is described and compared with other Cyclotella taxa. Notes on its distribution and ecology are added. |
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136 |
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ISSN |
1179-3163 |
ISBN |
1179-3163 |
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yes |
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Call Number |
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Serial |
7469 |
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Author |
Barthelemy M, Lystrup M B, Menager H, Miller S, Lilensten J, |
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Title |
First detection of polarization in jovian auroral H+3 emissions |
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Journal Article |
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Year |
2011 |
Publication |
A&A |
Abbreviated Journal |
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Volume |
530 |
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Keywords |
polarization / molecular data / planets and satellites: aurorae / planets and satellites: individual: Jupiter |
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Abstract |
Context. The recent measurement of linear polarization in the Earth thermospheric oxygen red line shows that it can be a useful observable quantity to characterise the upper atmospheres conditions. Therefore, polarimetry measurements are extended to other planets. Considering that FUV emissions are not observable from the ground, the best candidates for Jupiter auroral emissions are
H3+ infrared emissions around 4µm. This ion is created after a chemical process in the jovian upper atmosphere. Then, the anisotropy responsible of the polarization cannot be the particle impact as in the Earth case
Aims. The goal of this study is to detect some potential linear polarisation in the H3+ emissions of the jovian auroral oval.
Methods. Measurements of the H3+ emissions from the south auroral oval have been performed at the UKIRT during the beginning of August 2008, using the UIST-IRPOL spectro-polarimeter. The slit have been positioned perpendicularly to the jovian rotation axis.
Data were processed by dividing the slit in 24 bins. Stokes parameters u and q, polarization degree and direction are extracted for
each bin and debiased.
Results. Polarization up to 8% is detected. More than 7 bins show polarization with confidence level above 3σ. The better signal to noise ratio appears in the main auroral oval but no clear link appears between the polarization degrees and angles and the local known
anisotropies. The angles are a bit higher than 90° in the West part of the oval and mostly around 90° for the East part.
Conclusions. This study shows that polarization is detectable in the jovian infrared auroras. However, it is impossible to link it with electric or magnetic field for the moment due to the lack of theoretical work and laboratory experiments concerning the polarization of H3+. |
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1026 |
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ISSN |
1895-6572 |
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yes |
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220 |
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Author |
Barthelémy, M., Culot, F., Kofman, W., Lathuillère, Ch., Lilensten, J., Perrin, J. M., Simon, C., and Thuillier, G. |
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Title |
Response of the polar ionosphere to ICME's observed on October 29-30, 2003 |
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Conference - International - Communication |
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Year |
2004 |
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Abstract |
COSPAR PARIS July 2004 |
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384 |
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yes |
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3527 |
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Author |
Barthélémy, M.; Lilensten, J.; Pitout, F.; Simon Wedlund, C.; Thissen, R.; Lorentzen, D.; Sigernes, F.; Moen, J.; Gronoff, G.; McCrea, I.; Rothkael, H.; Ménager, H.; Aruliah, A. |
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Title |
Polarisation in the auroral red line during coordinated EISCAT Svalbard Radar/optical experiments |
Type |
Journal Article |
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Year |
2011 |
Publication |
Ann. Geophys. |
Abbreviated Journal |
ANGEO |
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Volume |
29 |
Issue |
6 |
Pages |
1101-1112 |
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Abstract |
The polarisation of the atomic oxygen red line in the Earth's thermosphere is observed in different configurations with respect to the magnetic field line at high latitude during several coordinated Incoherent Scatter radar/optical experiment campaigns. When pointing northward with a line-of-sight nearly perpendicular to the magnetic field, we show that, as expected, the polarisation is due to precipitated electrons with characteristic energies of a few hundreds of electron Volts. When pointing toward the zenith or southward with a line-of-sight more parallel to the magnetic field, we show that the polarisation practically disappears. This confirms experimentally the predictions deduced from the recent discovery of the red line polarisation. We show that the polarisation direction is parallel to the magnetic field line during geomagnetic activity intensification and that these results are in agreement with theoretical work. |
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1026 |
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Copernicus Publications |
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1432-0576 |
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yes |
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Call Number |
IPEV @ Thierry.Lemaire @ |
Serial |
6063 |
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Author |
Barthes L., Andre R., Cerisier J.C. & Villain J.P. |
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Title |
Separation of multiple echoes using a high-resolution spectral analysis for SuperDARN HF rdars. |
Type |
Journal Article |
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Year |
1998 |
Publication |
Radio science |
Abbreviated Journal |
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Volume |
33 |
Issue |
4 |
Pages |
1005-1017 |
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Programme |
312 |
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Bachelor's thesis |
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ISSN |
0048-6604 |
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yes |
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1410 |
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Author |
Bartish Igor V, Aïnouche Abdelkader, Jia Dongrui, Bergstrom Dana, Chown Steven L, Winkworth Richard C, Hennion Françoise, |
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Title |
Phylogeny and colonization history of Pringlea antiscorbutica (Brassicaceae), an emblematic endemic from the South Indian Ocean Province
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Journal Article |
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Year |
2012 |
Publication |
Molecular Phylogenetics and Evolution |
Abbreviated Journal |
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Volume |
65 |
Issue |
2 |
Pages |
748-756 |
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Keywords |
Ancestral area reconstruction, Biogeography, Long-distance dispersal, Molecular dating, PliocenePleistocene glaciation, Sub-Antarctic islands, |
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Abstract |
The origins and evolution of sub-Antarctic island floras are not well understood. In particular there is uncertainty about the ages of the contemporary floras and the ultimate origins of the lineages they contain. Pringlea R. Br. (Brassicaceae) is a monotypic genus endemic to four sub-Antarctic island groups in the southern Indian Ocean. Here we used sequences from both the chloroplast and nuclear genomes to examine the phylogenetic position of this enigmatic genus. Our analyses confirm that Pringlea falls within the tribe Thelypodieae and provide a preliminary view of its relationships within the group. Divergence time estimates and ancestral area reconstructions imply Pringlea diverged from a South American ancestor 5 Myr ago. It remains unclear whether the ancestor of Pringlea dispersed directly to the South Indian Ocean Province (SIOP) or used Antarctica as a stepping-stone; what is clear, however, is that following arrival in the SIOP several additional long-distance dispersal events must be inferred to explain the current distribution of this species. Our analyses also suggest that although Pringlea is likely to have inherited cold tolerance from its closest relatives, the distinctive morphology of this species evolved only after it split from the South American lineage. More generally, our results lend support to the hypothesis that angiosperms persisted on the sub-Antarctic islands throughout the Pliocene and Pleistocene. Taken together with evidence from other sub-Antarctic island plant groups, they suggest the extant flora of sub-Antarctic is likely to have been assembled over a broad time period and from lineages with distinctive biogeographic histories. |
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136 |
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ISSN |
1055-7903 |
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yes |
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4015 |
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Author |
Bas J. H. Van de Wiel, Etienne Vignon, Peter Baas, Ivo G. S. van Hooijdonk, Steven J. A. van der Linden, J. Antoon van Hooft, Fred C. Bosveld, Stefan R. de Roode, Arnold F. Moene, Christophe Genthon |
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Title |
Regime Transitions in Near-Surface Temperature Inversions: A Conceptual Model |
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Year |
2017 |
Publication |
Journal of the atmospheric sciences |
Abbreviated Journal |
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Volume |
74 |
Issue |
4 |
Pages |
1057-1073 |
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Abstract |
A conceptual model is used in combination with observational analysis to understand regime transitions of near-surface temperature inversions at night as well as in Arctic conditions. The model combines a surface energy budget with a bulk parameterization for turbulent heat transport. Energy fluxes or feedbacks due to soil and radiative heat transfer are accounted for by a ?lumped parameter closure,? which represents the ?coupling strength? of the system.Observations from Cabauw, Netherlands, and Dome C, Antarctica, are analyzed. As expected, inversions are weak for strong winds, whereas large inversions are found under weak-wind conditions. However, a sharp transition is found between those regimes, as it occurs within a narrow wind range. This results in a typical S-shaped dependency. The conceptual model explains why this characteristic must be a robust feature. Differences between the Cabauw and Dome C cases are explained from differences in coupling strength (being weaker in the Antarctic). For comparison, a realistic column model is run. As findings are similar to the simple model and the observational analysis, it suggests generality of the results.Theoretical analysis reveals that, in the transition zone near the critical wind speed, the response time of the system to perturbations becomes large. As resilience to perturbations becomes weaker, it may explain why, within this wind regime, an increase of scatter is found. Finally, the so-called heat flux duality paradox is analyzed. It is explained why numerical simulations with prescribed surface fluxes show a dynamical response different from more realistic surface-coupled systems. |
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Programme |
1013 |
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Bachelor's thesis |
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0022-4928 |
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0022-4928 |
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yes |
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6570 |
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