Influence of production variables and starting material on charcoal stable isotopic and molecular characteristics

We present a systematic study on the effect of starting species, gas composition, temperature, particle size and duration of heating upon the molecular and stable isotope composition of high density (mangrove) and low density (pine) wood. In both pine and mangrove, charcoal was depleted in o13C relative to the starting wood by up to 1.6% and 0.8%, respectively. This is attributed predominantly to the progressive loss of isotopically heavier polysaccharides, and kinetic effects of aromatization during heating. However, the pattern of o13C change was dependant upon both starting species and atmosphere, with different structural changes associated with charcoal production from each wood type elucidated by Solid-State o13C Nuclear Magnetic Resonance Spectroscopy. These are particularly evident at lower temperatures, where variation in the oxygen content of the production atmosphere results in differences in the thermal degradation of cellulose and lignin. It is concluded that production of charcoal from separate species in identical conditions, or from a single sample exposed to different production variables, can result in significantly different o13C of the resulting material, relative to the initial wood. These results have implications for the use of charcoal isotope composition to infer past environmental change

RMT: A dialog-based research methods tutor with or without a head

Abstract. RMT (Research Methods Tutor) is a dialog-based tutoring system that has a dual role. Its modular architecture enables the interchange and evaluation of different tools and techniques for improving tutoring. In addition to its research goals, the system is intended to be integrated as a regular component of a term-long Research Methods in Psychology course. Despite the significant technical challenges, this may help reduce our knowledge gap about how such systems can help students with long-term use. In this paper, we describe the RMT architecture and give the results of an initial experiment that compared RMT’s animated agent “talking head ” with a text-only version of the system.

Reliability of a Longitudinal Sequence of Scale Ratings

reliability, linear mixed model, longitudinal data, psychiatry, rating scale,