5,506 research outputs found
Applications of canonical relations in generic differential geometry
Conflict sets are loci of intersecting wavefronts emanating from
different surfaces. We show that generically conflict sets are Legendrian:
locally they admit the structure of wavefronts. Simple stable singularities for
this problem in occur when . Other related sets, such
as kite curves and centre sets are also defined and discussed. Throughout
canonical relations are used as an essential tool to carry out several of these
geometrical constructions.Comment: 20 pages, 12 figure
La production céramique de Pont de Roque-Haute : synthèse et comparaisons
La production céramique du gisement languedocien de Pont de Roque-Haute est replacée dans le cadre des plus anciennes productions céramiques de Méditerranée occidentale. Des liens avec l'Italie centro-méridionale sont privilégiés
La production céramique : caractérisation technique et typologique
La production céramique du gisement languedocien de Pont de Roque-Haute fait l'objet d'une caractérisation typologique, technologique et spatiale
Henri Temianka Correspondence; (manen)
https://digitalcommons.chapman.edu/temianka_correspondence/2344/thumbnail.jp
Interferometric modeling of wave propagation in inhomogeneous elastic media using time reversal and reciprocity
On dangerous self-tangencies in families of conflict sets
In this note we observe an interesting link between
an intersection of two Legendrian manifolds in -
or dangerous self-tangencies, on the one hand
and hyperbolic Morse transition of immersed curves on a torus on the
other hand. The connection between these two arises naturally in the
study of one-parameter families of conflict sets
Are both sympatric species Ilex perado and Ilex canariensis secretly hybridizing? Indication from nuclear markers collected in Tenerife
BACKGROUND: Intra-specific and intra-individual polymorphism is frequently observed in nuclear markers of Ilex (Aquifoliaceae) and discrepancy between plastid and nuclear phylogenies is the rule in this genus. These observations suggest that inter-specific plastid or/and nuclear introgression played an important role in the process of evolution of Ilex. With the aim of a precise understanding of the evolution of this genus, two distantly related sympatric species collected in Tenerife (Canary Islands), I. perado and I. canariensis, were studied in detail. Introgression between these two species was previously never reported. One plastid marker (the atpB-rbcL spacer) and two nuclear markers, the ribosomal internal transcribed spacer (ITS) and the nuclear encoded plastid glutamine synthetase (nepGS) were analyzed for 13 and 27 individuals of I. perado and I. canariensis, respectively. RESULTS: The plastid marker is intra-specifically constant and correlated with species identity. On the other hand, whereas the nuclear markers are conserved in I. perado, they are highly polymorphic in I. canariensis. The presence of pseudogenes and recombination in ITS sequences of I. canariensis explain this polymorphism. Ancestral sequence polymorphism with incomplete lineage sorting, or past or recent hybridization with an unknown species could explain this polymorphism, not resolved by concerted evolution. However, as already reported for many other plants, past or recent introgression of an alien genotype seem the most probable explanation for such a tremendous polymorphism. CONCLUSIONS: Data do not allow the determination with certitude of the putative species introgressing I. canariensis, but I. perado is suspected. The introgression would be unilateral, with I. perado as the male donor, and the paternal sequences would be rapidly converted in highly divergent and consequently unidentifiable pseudogenes. At least, this study allows the establishment of precautionary measures when nuclear markers are used in phylogenetic studies of genera having experienced introgression such as the genus Ilex
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