Nutrient limitation constrains tree growth in many managed forests. Nitrogen (N) is the most common limiting nutrient, but high N supply can shift limitation to other nutrients, particularly phosphorus (P) and the base cations calcium (Ca), magnesium (Mg), and potassium (K). As different soil minerals have different capacities to supply...
The continued development of organic semiconductor materials relies on an understanding of the relationship between optoelectronic properties, molecular structure, and molecular interaction. Several detailed studies of electronic properties in functionalized polyacene materials are presented. A computational model which allows the extraction of charge generation and transport properties from experimental data...
Several popular cultural movements emphasizing indigenous spirituality have arisen in the United States and Europe within the past thirty years. Spiritual discourses attributed to Native Americans, among other groups, are borrowed by Euro-Americans in search of alternatives to dominant ideologies. In such a circumstance, Native Americans become part of a...
In a search for designed materials that mimic those found in biological systems, combining polymers with inorganic materials in sol-gel chemistry processes has gained momentum in the research world since the 1990's. This work methodically investigated the properties of several related polymer-SiO₂ hybrids prepared by a simple methodology that could...
This work focuses primarily the development of methods for imaging microbial biofilms in opaque porous media using x-ray computed microtomography (CT). Two methods for evaluating biofilms in porous media are presented. The first focuses on the addition of silver-coated, hollow glass microspheres to a biofilm-containing micro-model. The silver-coated microspheres affix...
Cell-cell communication in bacteria is understood to facilitate the coordination of population-wide cooperative behavior in the form of concerted gene expression. The opportunistic pathogen Pseudomonas aeruginosa uses such a communication mechanism to regulate a large group of genes important to virulence strategies in this bacterium. This general mechanism of communication...
Marine sediments exceptionally rich in organic carbon, known as black shales, occur globally but intermittently in well correlated Cretaceous successions. The presence of black shales indicates that sporadic, ocean-wide interruption of normal respiration of marine organic matter during oxygen-deficient conditions has occurred. Submarine volcanism on a massive scale, related to...