Sparse approximation of multivariate functions from small datasets via weighted orthogonal matching pursuit

We show the potential of greedy recovery strategies for the sparse approximation of multivariate functions from a small dataset of pointwise evaluations by considering an extension of the orthogonal matching pursuit to the setting of weighted sparsity. The proposed recovery strategy is based on a formal derivation of the greedy index selection rule. Numerical experiments show that the proposed weighted orthogonal matching pursuit algorithm is able to reach accuracy levels similar to those of weighted $\ell^1$ minimization programs while considerably improving the computational efficiency for small values of the sparsity level

A dinosaur fauna from the Late Cretaceous (Cenomanian) of northern Sudan

A dinosaur fauna from the Cenomanian of northern Sudan (Wadi Milk Formation) is described. It comprises at least nine, probably ten to eleven taxa: a dicraeosaurid, a titanosaurid and another undetermined sauropod (possibly a titanosaurid), two charcharodontosaurids, a dromaeosaurid, a probable hypsilophodontid and two iguanodontian ornithopods. It is one of the most diverse dinosaur faunas known from the Cretaceous of Africa. The environment was probably a semiarid savanna with some rivers, lined by dense vegetation, with abundant sauropods, less abundant theropods and rare ornithopods. Gigantic carcharodontosaurids were at the top of the food chain. At the present state of knowledge, the dinosaur fauna from the middle to late Cretaceous of Africa can be characterized by the presence of carcharodontosaurids, spinosaurids, titanosaurids, diplodocoids, and possibly iguanodontian ornithopods.The Council's Research Committe, University of the Witwatersrand; National Science Foundation; EC, TMR grant ERBFMBICT 961013; DFG grant Kr 477/11 “Sudan-Wirbeltiere

Scanning electron microscopic study of the fibrous rings of the arterial orifices in embryos of the 7th and 8th weeks

The arterial fibrous rings were investigated in human embryos aged 7 and 8 weeks under light and scanning electron microscopes. In the present study it was shown that the arrangement of collagen and formation of fibres changes rapidly within one week. In the 7th week there are no collagen fibres and the netlike fibrils extend between processes of fibroblasts. At the end of the 8th week the collagen fibres are formed and they have different arrangements in the particular layers of the fibrous rings. (Folia Morphol 2010; 69, 3: 180-183

Re-evaluation of the Haarlem Archaeopteryx and the radiation of maniraptoran theropod dinosaurs

Archaeopteryx is an iconic fossil that has long been pivotal for our understanding of the origin of birds. Remains of this important taxon have only been found in the Late Jurassic lithographic limestones of Bavaria, Germany. Twelve skeletal specimens are reported so far. Archaeopteryx was long the only pre-Cretaceous paravian theropod known, but recent discoveries from the Tiaojishan Formation, China, yielded a remarkable diversity of this clade, including the possibly oldest and most basal known clade of avialan, here named Anchiornithidae. However, Archaeopteryx remains the only Jurassic paravian theropod based on diagnostic material reported outside China

First record of a Maastrichtian sauropod dinosaur from Egypt

Main articleA left femur of a small sauropod dinosaur was found in the Maastrichtian part of the Ammonite Hill Member of the Dahkla Formation of southwestern Egypt. it represents the first dinosaur remains of certain Maastrichtian age from Egypt and the second record of dinosaurs from this stage within Africa. Moreover, the Egyptian specimen shows similarities to femora of brachiosaurids, possibly extending the temporal range of this family up to the very end of the Mesozoic.TMR grant ERBFMBICT 961013 and the German Research Foundatio

Early trabeculation and closure of the interventricular foramen in staged human embryos

Internal differentiation of the ventricles was studied in staged serially sectioned human embryos of developmental stages 13-19 (postovulatory days 32-46). At stage 13 the trabeculation of both ventricles was advanced and the muscular part of the interventricular septum well marked. Dorsal and ventral endocardial cushions were fused and the atrioventricular canal was divided into two parts. In embryos at stage 18 the membranous interventricular septum was developing and the interventricular foramen was obliterated. At stage 19 the membranous part of the interventricular septum was becoming more cellular in structure. (Folia Morphol 2008; 67: 13–18

Restricted Isometries for Partial Random Circulant Matrices

In the theory of compressed sensing, restricted isometry analysis has become a standard tool for studying how efficiently a measurement matrix acquires information about sparse and compressible signals. Many recovery algorithms are known to succeed when the restricted isometry constants of the sampling matrix are small. Many potential applications of compressed sensing involve a data-acquisition process that proceeds by convolution with a random pulse followed by (nonrandom) subsampling. At present, the theoretical analysis of this measurement technique is lacking. This paper demonstrates that the $s$th order restricted isometry constant is small when the number $m$ of samples satisfies $m \gtrsim (s \log n)^{3/2}$, where $n$ is the length of the pulse. This bound improves on previous estimates, which exhibit quadratic scaling

A middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs

Abelisaurids are a clade of large, bizarre predatory dinosaurs, most notable for their high, short skulls and extremely reduced forelimbs. They were common in Gondwana during the Cretaceous, but exceedingly rare in the Northern Hemisphere. The oldest definitive abelisaurids so far come from the late Early Cretaceous of South America and Africa, and the early evolutionary history of the clade is still poorly known. Here, we report a new abelisaurid from the Middle Jurassic of Patagonia, Eoabelisaurus mefi gen. et sp. nov., which predates the so far oldest known secure member of this lineage by more than 40 Myr. The almost complete skeleton reveals the earliest evolutionary stages of the distinctive features of abelisaurids, such as the modification of the forelimb, which started with a reduction of the distal elements. The find underlines the explosive radiation of theropod dinosaurs in the Middle Jurassic and indicates an unexpected diversity of ceratosaurs at that time. The apparent endemism of abelisauroids to southern Gondwana during Pangean times might be due to the presence of a large, central Gondwanan desert. This indicates that, apart from continent-scale geography, aspects such as regional geography and climate are important to reconstruct the biogeographical history of Mesozoic vertebrates.Fil: Pol, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Rauhut, Oliver W. M.. Ludwig Maximilians Universitat; Alemani

Probable basal allosauroid from the early Middle Jurassic Canadon Asfalto Formation of Argentina highlights phylogenetic uncertainty in tetanuran theropod dinosaurs

Tetanurae, the most successful clade of theropod dinosaurs, including modern birds, split into three major clades early in their evolutionary history: Megalosauroidea, Coelurosauria, and Allosauroidea. The oldest tetanurans occur in the earliest Middle Jurassic, but the early fossil record of the clade is still poor. Here we report one of the oldest known and most complete pre-Late Jurassic tetanuran, the probable allosauroid Asfaltovenator vialidadi gen. et sp. nov., which has an unusual character combination, uniting features currently considered to be apomorphic of different tetanuran lineages. A phylogenetic analysis resulted in a monophyletic Carnosauria (Allosauroidea + Megalosauroidea), and the inclusion of the new taxon significantly changes topology within carnosaurs. The analysis shows concentrated homoplasy in proximal nodes at the base of Tetanurae, and a temporal peak at the Pliensbachian-Toarcian extinction event, recently identified as a potential driver of tetanuran radiation. These results highlight the complex morphological evolution in the early radiation of tetanuran theropods, in which convergences and parallelisms were extremely common. This pattern seems to be a common feature in rapid radiation events of major clades of vertebrates and might explain the common difficulties to unravel phylogenetic relationships of important lineages at the base of major clades