Search

Sarahsaurus aurifontanalis is the most recent sauropodomorph dinosaur to be discovered and named from the Early Jurassic of North America. The dinosaur is represented by a mostly complete and articulated holotype specimen that preserves a unique manual phalangeal count of 2-3-4-2-2 and accessory pubic foramen adjacent to the obturator foramen. The holotype of Sarahsaurus comprises a braincase and isolated cranial elements, but the skull previously referred to this taxon, MCZ 8893, can only be provisionally referred to Sarahsaurus until additional crania are found associated with postcranial material. Sarahsaurus comes from the middle third of the Kayenta Formation, which is considered to be Early Jurassic in age despite the absence of a radiometric date from that unit. A new technique used to obtain a U-Pb radiometric date from the type quarry of Sarahsaurus in the Kayenta Formation was influenced by secondary uranium enrichment in the open system of the fossil bone. That suggests that uranium within the Kayenta Formation may be the result of the movement of groundwater during the Laramide orogeny in the Late Cretaceous and Early Eocene, and lends support to the hypothesis that the uplift of the Colorado Plateau began relatively early in Late Cretaceous to the Eocene.

This work was directed at improving the strength and durability of pultruded composites. Pultruded composites are being used in an increasingly wider range of applications, and, as a result, a higher demand has been placed on the performance capabilities of the various components.;One target area for improving composites is the fraction of voids in the final product. The presence of voids in a composite decreases the Interlaminar Shear Strength, provides a site for the formation of fractures, and increases the susceptibility of the part to outside contaminants.;In this work, the various steps of the pultrusion process are analyzed in order that the fraction of voids can be reduced. The goal is to promote uniform resin flow through the glass fibers, while the part is still in the die; this is because increasing resin flow in the die should result in fewer voids in the final product.;To achieve this objective, an existing pultrusion process was analyzed by modeling fluid mechanics, heat transfer and the chemical reactions involved in this process. From the results obtained, three conclusions could be drawn: (1) While pultruding at relatively low processing speeds, changes in processing speed do not have a significant influence in the final void fraction. (2) Void formation is suppressed by operating at the highest pull speed possible, without the exotherm being outside the end of the die. (3) A moderate variation in the temperature of the die will have a negligible impact on the void fraction of the component.;The void fraction of representative composite samples was measured with optical and scanning electron microscopy, and the results validated the above conclusions.