We have measured voltage-current characteristics for YBa₂Cu₃O₇ thin films in magnetic fields from 5
T to ambient, including some in the millitesla range. In all cases, the resistivity —current density isotherms
can be separated into two classes: those which exhibit upward curvature, and have constant
resistivity at low currents, and...
Most climate models predict a weakening of the North Atlantic thermohaline circulation for the 21st century when forced by increasing levels of greenhouse gas concentrations. The model spread, however, is rather large, even when the forcing scenario is identical, indicating a large uncertainty in the response to forcing. In order...
A shell model for ferroelectric perovskites fitted to results of first-principles density functional theory (DFT) calculations is strongly affected by approximations made in the exchange-correlation functional within DFT, and in general not as accurate as a shell model derived from experimental data. We have developed an isotropic shell model for...
Native point defects, defect complexes, and oxygen impurities in BaCuChF were studied using density
functional theory calculations, self-consistent thermodynamic simulations, and various experimental techniques.
Unintentional p-type conductivity in BaCuChF is explained by the presence of copper vacancies with
transition levels in the valence band. These acceptor-like defects are partially compensated...
Climate models predict a gradual weakening of the North Atlantic meridional overturning circulation (MOC) during the twenty-first century due to increasing levels of greenhouse gas concentrations in the atmosphere. Using an ensemble of 16 different coupled climate models performed for the Fourth Assessment Report (AR4) of the Intergovernmental Panel on...
Double excitonic absorption peaks are observed in textured BaCuSF and BaCuSeF thin films. The excitonic doublet separation increases with increasing fraction of heavy chalcogen in the thin-film solid solutions, in good agreement with the spin-orbit splitting of the valence bands calculated by density-functional theory. In BaCuSF and BaCuSeF, the excitons...
The p-type semiconductor Cu₃PSe₄ has recently been established to have a direct band gap of 1.4 eV and an optical absorption spectrum similar to GaAs [Foster et al., Appl. Phys. Lett. 99, 181903 (2011)], suggesting a possible application as a solar photovoltaic absorber. Here we calculate the thermodynamic stability, defect...
Wood that is submerged in fresh water for long periods has increased permeability and other changed properties. Wood that is submerged in salt water may absorb considerable quantities of salts, which may render the wood resistant to microbial colonization. In this report, we describe decay tests on Douglas-fir sapwood and...
The development of pressure inside wood during preservative impregnation was studied using Douglas-fir heartwood and ponderosa pine sapwood. Pressure sensors mounted on sample holders provided the most reliable measurements. As expected, pressure equilibrated most rapidly with air as the treatment medium and ponderosa pine as the test species. Pressure changes...
Biological invasion potential can be strongly influenced by abiotic factors such as temperature, water availability, and solar radiation. Invasive species that possess phenotypically plastic traits can mediate impacts from these stressors, but may be unable to recognize and respond to dangerous levels in a novel environment. Understanding potential constraints on...