Semigroups, rings, and Markov chains

We analyze random walks on a class of semigroups called ``left-regular bands''. These walks include the hyperplane chamber walks of Bidigare, Hanlon, and Rockmore. Using methods of ring theory, we show that the transition matrices are diagonalizable and we calculate the eigenvalues and multiplicities. The methods lead to explicit formulas for the projections onto the eigenspaces. As examples of these semigroup walks, we construct a random walk on the maximal chains of any distributive lattice, as well as two random walks associated with any matroid. The examples include a q-analogue of the Tsetlin library. The multiplicities of the eigenvalues in the matroid walks are ``generalized derangement numbers'', which may be of independent interest.Comment: To appear in J. Theoret. Proba

Four Clovis Points from San Augustine County, Texas

Four surface-collected Clovis points (two complete, two fragmentary) from the northeastern valley margin of the Angelina River in San Augustine County are described. One specimen is made from Manning fused glass and is the oldest artifact known to have been made of that rock type. The others appear to be made of chert from the Edwards Plateau

The Mental Database

This article uses database, evolution and physics considerations to suggest how the mind stores and processes its data. Its innovations in its approach lie in:- A) The comparison between the capabilities of the mind to those of a modern relational database while conserving phenomenality. The strong functional similarity of the two systems leads to the conclusion that the mind may be profitably described as being a mental database. The need for material/mental bridging and addressing indexes is discussed. B) The consideration of what neural correlates of consciousness (NCC) between sensorimotor data and instrumented observation one can hope to obtain using current biophysics. It is deduced that what is seen using the various brain scanning methods reflects only that part of current activity transactions (e.g. visualizing) which update and interrogate the mind, but not the contents of the integrated mental database which constitutes the mind itself. This approach yields reasons why there is much neural activity in an area to which a conscious function is ascribed (e.g. the amygdala is associated with fear), yet there is no visible part of its activity which can be clearly identified as phenomenal. The concept is then situated in a Penrosian expanded physical environment, requiring evolutionary continuity, modularity and phenomenality.Several novel Darwinian advantages arising from the approach are described

A Framework for Assessing the Rationality of Judgments in Carcinogenicity Hazard Identification

Arguing that guidelines for identifying carcinogens now lack a philosophically rigorous framework, the authors present an alternative that draws clear attention to the process of reasoning towards judgments of carcinogenicity

Optimization of the tungsten oxide technique for measurement of atmospheric ammonia

Hollow tubes coated with tungstic acid have been shown to be of value in the determination of ammonia and nitric acid in ambient air. Practical application of this technique was demonstrated utilizing an automated sampling system for in-flight collection and analysis of atmospheric samples. Due to time constraints these previous measurements were performed on tubes that had not been well characterized in the laboratory. As a result the experimental precision could not be accurately estimated. Since the technique was being compared to other techniques for measuring these compounds, it became necessary to perform laboratory tests which would establish the reliability of the technique. This report is a summary of these laboratory experiments as they are applied to the determination of ambient ammonia concentration

Their memory:exploring veterans’ voices, virtual reality and collective memory

This paper focuses on the virtual reality (VR) project Their Memory and details the development and evaluation of virtual reality environments and experiences with respect to its impact on young people (14-35 demographic) with the narratives of veterans in Scotland. As part of the AHRC Immersive Experiences program, Their Memory was created to explore how game design techniques and immersive technology could be used to enhance existing historical research and enrich narratives to bring expansive experiences to hard-to-reach audiences. The project worked directly with the veterans’ charity, Poppyscotland, to create an environment and experience that would resonate with new audiences, and explore documentary and storytelling techniques for the commemoration of war and conflict. The design of the project evolved through co-design sessions with veterans and young people and culminated in the creation of a short, thought-provoking, narrative-driven experience. The VR experience enabled players to connect with the memories of veterans in Scotland and exploring the different conflicts or situations they experienced and how they make sense of them. The project brought together cross-sector expertise to research how immersive experiences can help memory-based organizations in engaging with wider audiences, raise awareness, and diversify current learning outputs. The paper details the design and development of the Virtual Reality project, through co-design, and how this engaged the audience and evolved the experience created. The paper includes a summative evaluation of events conducted with schoolchildren to assess the project and concludes with how the project evidences impact upon audiences and the potential for both technology and the experience