Showing papers by "David S. Smith published in 1990"
TL;DR: The remains of the omithomimid dinosaur Archaeomithomimus asiaticus from the Upper Cretaceous of the People's Republic of China are described and comparisons made with the bones of Elaphrosaurus, Gallimimus, Struthiomimus, Ornithomim, Dromiceiomim, Deinocheirus, and Allosaurus as mentioned in this paper.
Abstract: The remains of the omithomimid dinosaur Archaeomithomimus asiaticus from the Upper Cretaceous of the People's Republic of China are described and comparisons made with the bones of Elaphrosaurus, Gallimimus, Struthiomimus, Ornithomimus, Dromiceiomimus, Deinocheirus, and Allosaurus. The diagnosis of the Ornithomimidae of Russell (1972) is expanded to include the characters of Elaphrosaurus and Archaeomithomimus. Some of the remains from the Arundel Formation of Maryland that have been referred to Archaeomithomimus affinis are probably ornithomimid but are generically and specifically indeterminate.
41 citations
TL;DR: The similar proximal and distal attachments to the stereom of primary spine ligament in the echinoid Eucidaris tribuloides are described, from thin sections and SEM studies on frozen and fractured spine articulations and ligaments from decalcified material.
Abstract: The similar proximal and distal attachments to the stereom of primary spine ligament in the echinoid Eucidaris tribuloides are described, from thin sections and SEM studies on frozen and fractured spine articulations and ligaments from decalcified material. The orthogonal structure of the general stereom is modified on the attachment zones where bundles of collagen cylinders enter approximately hexagonally arranged channels. Straps of collagen extend in parallel series between adjacent bundles via regularly placed ports and collagen loops rather than non-striated 'tendons' pass over skeletal trabeculae. The regular pattern of collagen straps is most evident on the proximal and distal attachment zones. Mechanical features of the non-adhesive mode of attachment are considered, together with similarities and differences between insertion of muscle cells and mutable collagenous tissue (ligament) in echinoderms.
16 citations
01 Jan 1990
TL;DR: In this article, the role of the microstructure for the electrical properties of polycrystalline YBa2Cu3O7 03B4 was examined, showing the effect of variation in grain size and deviation from stoichiometry on the critical current density in zero field at 77 K and the room temperature resistivity.
Abstract: The role of the microstructure for the electrical properties of polycrystalline YBa2Cu3O7 03B4 is examined. Experimental data are presented showing the effect of (i) variation in grain size and (ii) deviation from stoichiometry for YBa2Cu3O7 03B4 on the critical current density in « zero » field at 77 K and the room temperature resistivity. Firstly a strong decrease in the critical current density has been observed when an average grain size of 15 03BCm is exceeded. Large grains promote microcracks due to anisotropic volume changes during cooling from the sintering temperature. This causes a reduction in the effective current carrying crosssection of the material. Ultrasonic measurements were used to confirm an increase in the microcrack density for large grained samples. Secondly, a significant modification of the electrical properties was achieved for deviations from stoichiometry greater than 0.5 mole %. Previous work has shown that the presence of minor phases due to incomplete calcination or poor mixing leads to reduced critical current density. Deviations from stoichiometry of the initial powder will also promote minor phases. These two aspects must be taken into account in the choice of a suitable ceramic processing route. Revue Phys. Appl. 25 (1990) 61-66 JANVIER 1990,
9 citations