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Wyszukujesz frazę "Roberts, D. P." wg kryterium: Autor


Wyświetlanie 1-4 z 4
Tytuł:
The spectrum problem for digraphs of order 4 and size 5
Autorzy:
Bunge, R. C.
DeShong, S,
El-Zanati, S. I.
Fischer, A.
Roberts, D. P.
Teng, L.
Powiązania:
https://bibliotekanauki.pl/articles/255132.pdf
Data publikacji:
2018
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
spectrum problem
digraph decompositions
Opis:
The paw graph consists of a triangle with a pendant edge attached to one of the three vertices. We obtain a multigraph by adding exactly one repeated edge to the paw. Now, let D be a directed graph obtained by orientating the edges of that multigraph. For 12 of the 18 possibilities for D, we establish necessary and sufficient conditions on n for the existence of a [formula] design. Partial results are given for the remaining 6 possibilities for D.
Źródło:
Opuscula Mathematica; 2018, 38, 1; 15-30
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Cretaceous mammal from Tanzania
Autorzy:
Krause, D W
Gottfried, M.D.
O'Connor, P.M.
Roberts, E.M.
Powiązania:
https://bibliotekanauki.pl/articles/23042.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
mammal
Gondwana
Cretaceous
Mammalia
Africa
Tanzania
Gondwanatheria
paleontology
Opis:
We report here the discovery of a Cretaceous mammal from the “Red Sandstone Group” of southwestern Tanzania. This specimen is one of only a very few Cretaceous mammals known from Gondwana in general and Africa in particular. The specimen consists of a short, deep left dentary that bore a large, procumbent central incisor, and five single−rooted, hypsodont cheek−teeth. The specimen is very tentatively identified as a sudamericid, and thus may represent the first African record of an enigmatic clade of mammals, the Gondwanatheria, which is otherwise known from the Late Cretaceous and Paleogene of several other Gondwanan landmasses. Unfortunately, the precise age of the specimen could not be determined. If it is pre−Campanian and if its identity as a sudamercid is corroborated through subsequent discoveries, it represents the earliest known gondwanatherian. If the specimen is from the Campanian or Maastrichtian, and again assuming its identification is correct, it has the potential to refute a recently formulated biogeographic hypothesis predicting the absence of certain terrestrial and freshwater vertebrate taxa, including gondwanatherians, in Africa (i.e., those that evolved elsewhere on Gondwana after Africa became an isolated landmass).
Źródło:
Acta Palaeontologica Polonica; 2003, 48, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new mammal from the Turonian–Campanian (Upper Cretaceous) Galula Formation, southwestern Tanzania
Autorzy:
O’Connor, P.M.
Krause, D.W.
Stevens, N.J.
Groenke, J.R.
MacPhee, R.D.E.
Kalthoff, D.C.
Roberts, E.M.
Powiązania:
https://bibliotekanauki.pl/articles/20223.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Opis:
We here establish a new mammaliaform genus and species, Galulatherium jenkinsi (Mammalia), from the Upper Cretaceous Galula Formation in the Rukwa Rift Basin of southwestern Tanzania. This represents the first named taxon of a mammaliaform from the entire Late Cretaceous of continental Afro-Arabia, an interval of 34 million years. Preliminary study of the holotypic and only known specimen (a partial dentary) resulted in tentative assignation to the Gondwanatheria, a poorly known, enigmatic clade of Late Cretaceous–Paleogene Gondwanan mammals (Krause et al. 2003). The application of advanced imaging (μCT) and visualization techniques permits a more detailed understanding of key anatomical features of the new taxon. It reveals that the lower dentition consisted of a large, procumbent lower incisor and four cheek teeth, all of which were evergrowing (hypselodont). Importantly, all of the teeth appear devoid of enamel. Comparisons conducted with a range of Mesozoic and selected Cenozoic mammaliaform groups document a number of features (e.g., columnar, enamel-less and evergrowing teeth, with relatively simple occlusal morphology) expressed in Galulatherium that are reminiscent of several distantly related groups, making taxonomic assignment difficult at this time. Herein we retain the provisional referral of Galulatherium (RRBP 02067) to Gondwanatheria; it is most similar to sudamericids such as Lavanify and Bharratherium from the Late Cretaceous of Madagascar and India, respectively, in exhibiting relatively simple, high-crowned, columnar cheek teeth. Other features (e.g., enamel-less dentition) are shared with disparate forms such as the Late Jurassic Fruitafossor and toothed xenarthrans (e.g., sloths), here attributed to convergence. Revised analyses of the depositional context for the holotype place it as having lived sometime between the late Turonian and latest Campanian (roughly 91–72 million years ago). This enhanced geochronological context helps to refine the palaeobiogeographical significance of Galulatherium among Cretaceous mammals in general and those from Gondwanan landmasses specifically.
Źródło:
Acta Palaeontologica Polonica; 2019, 64, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Decomposing the Complete Symmetric Digraph into Orientations of K4 − e
Autorzy:
Bunge, Ryan C.
Darrow, Brian D.
Dubczuk, Toni M.
El-Zanati, Saad I.
Hao, Hanson H.
Keller, Gregory L.
Newkirk, Genevieve A.
Roberts, Dan P.
Powiązania:
https://bibliotekanauki.pl/articles/31343235.pdf
Data publikacji:
2019-11-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
digraph decompositions
orientations of K 4 − e
Opis:
Let $D$ be any of the 10 digraphs obtained by orienting the edges of $ K_4 − e $. We establish necessary and sufficient conditions for the existence of a $ (K_n^*, D)$-design for 8 of these digraphs. Partial results as well as some nonexistence results are established for the remaining 2 digraphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2019, 39, 4; 815-828
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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