A Specification of the Soar Cognitive Architecture in Z

A formal specification of the sixth revision of the Soar architecture in the Z notation was constructed to elucidate and clarify the definition of Soar and to guide its implementation. Soar is a cognitive architecture that has been successfully applied to many domains and has been proposed as an exemplar unified theory of cognition. Z is a model theoretic specification language based in set theory that has syntax and type checking programs available. The specification has a complete coverage of the architecture, a low level of abstraction and a considerable implementation bias

Structural discordance between neogene detachments and frontal Sevier thrusts, central Mormon Mountains, southern Nevada

Detailed geologic mapping in the Mormon Mountains of southern Nevada provides significant insight into processes of extensional tectonics developed within older compressional orogens. A newly discovered, WSW-directed low-angle normal fault, the Mormon Peak detachment, juxtaposes the highest levels of the frontal most part of the east-vergent, Mesozoic Sevier thrust belt with autochthonous crystalline basement. Palinspastic analysis suggests that the detachment initially dipped 20–25° to the west and cut discordantly across thrust faults. Nearly complete lateral removal of the hanging wall from the area has exposed a 5 km thick longitudinal cross-section through the thrust belt in the footwall, while highly attenuated remnants of the hanging wall (nowhere more than a few hundred meters thick) structurally veneer the range. The present arched configuration of the detachment resulted in part from progressive “domino-style” rotation of a few degrees while it was active, but is largely due to rotation on younger, structurally lower, basement-penetrating normal faults that initiated at high-angle. The geometry and kinematics of normal faulting in the Mormon Mountains suggest that pre-existing thrust planes are not required for the initiation of low-angle normal faults, and even where closely overlapped by extensional tectonism, need not function as a primary control of detachment geometry. Caution must thus be exercised in interpreting low-angle normal faults of uncertain tectonic heritage such as those seen in the COCORP west-central Utah and BIRP's MOIST deep-reflection profiles. Although thrust fault reactivation has reasonably been shown to be the origin of a very few low-angle normal faults, our results indicate that it may not be as fundamental a component of orogenic architecture as it is now widely perceived to be. We conclude that while in many instances thrust fault reactivation may be both a plausible and attractive hypothesis, it may never be assumed

Sequencing three crocodilian genomes to illuminate the evolution of archosaurs and amniotes

The International Crocodilian Genomes Working Group (ICGWG) will sequence and assemble the American alligator (Alligator mississippiensis), saltwater crocodile (Crocodylus porosus) and Indian gharial (Gavialis gangeticus) genomes. The status of these projects and our planned analyses are described

The responses of Briza media and Koeleria manrantha to drought and re-watering.

1. To test whether differences in response to drought can help to explain the differing distributions of Briza media and Koeleria macrantha, changes in their leaf growth and water relations during soil drying were measured. After droughting, plants were re-watered and recovery recorded. 2. Leaf growth of the two species showed a similar sensitivity to drought with respect to duration of soil drying and soil moisture content. 3. In both species tiller base relative water content (RWC) was maintained at similar levels to controls until soil moisture content had fallen to less than 9%. This may aid survival in habitats subject to periodic droughting by preventing damage to the meristems. 4. Briza media did not respond to re-watering. However, plants of K. macrantha re-grew after periods of over 20 days of drought, when tiller base RWCs had fallen as low as 13%. This ability to resurrect may explain the occurrence of K. macrantha in xeric calcicolous grasslands subject to episodes of severe droughting, from which B. media is absent

The challenges in predicting the fatigue life of dissimilar brazed joints and initial finite element results for a tungsten to EUROFER97 steel brazed joint

This paper summarises the challenges in accurately predicting stress states in dissimilar brazed joints and presents initial results from a finite element analysis of a tungsten to EUROFER97 brazed joint. The residual stresses due to joint manufacture are presented and differences in stress distribution due to thermal and mechanical loading highlighted. The results from this analysis correlate well to experimental results from previous research however further validation is required. The challenges in developing fatigue assessment procedures for dissimilar brazed joints are also discussed. These fatigue assessment procedures are introduced and a validation strategy for such procedures is proposed