Publications by authors named "C Rude"
We report two analytical quantum mechanics (QM) models for approximating appropriately scaled harmonic zero-point energies (ZPEs) without Hessian calculations. Following our earlier bond energies from bond orders and populations model that takes a similar form as an extended Hückel model but uses well-conditioned orbital populations, this work demonstrates a proof of concept for approximating ZPEs, an important component in thermochemistry calculations, while eschewing unfavorably scaling algorithms involving Hessian matrices. The ZPE-BOP1 model uses Mulliken orbital populations from hybrid Kohn-Sham density functional theory calculations within an extended Hückel-type model that defines vibrational bond energy terms using two atom-pairwise parameters that are fit to reproduce ZPEs from B3LYP calculations.
View Article and Find Full Text PDFArticle Synopsis
- Zebra mussels are invasive species that can change aquatic ecosystems and food webs, potentially increasing mercury levels in fish, yet their impact in inland lakes hadn't been previously studied.
- In Minnesota lakes with zebra mussels, adult walleye and yellow perch showed mercury levels 72% and 157% higher, respectively, compared to lakes without them, with young fish also having elevated mercury concentrations.
- These higher mercury levels in invaded lakes raise concerns for fisheries management and human health, especially since many walleye exceeded safe consumption thresholds more frequently than in uninvaded lakes.
Article Synopsis
- Polycyclic aromatic hydrocarbons (PAHs) are diverse environmental compounds known for their varying toxic effects, often activating the aryl hydrocarbon receptor (AHR) and influencing gene expression, but their mechanisms can differ.
- The study specifically examined retene, which causes developmental toxicity in zebrafish by activating Ahr2 through its metabolites, rather than directly activating the AHR.
- Research found that the cyp1a enzyme plays a key role in the toxicity of retene, with cyp1a-null zebrafish showing heightened sensitivity, while exposure timing and metabolite presence were critical for understanding the toxicity's onset.
Article Synopsis
- Passive sampling devices combined with zebrafish toxicity tests effectively detect harmful non-polar organic mixtures in environmental sites.
- In a study of two locations in Portland Harbor, higher toxicity was noted at river mile 6.5W, linked to specific malformations in zebrafish development.
- RNA sequencing revealed significant gene expression changes due to exposure, suggesting that while some effects stem from known chemicals, other unidentified contaminants may also contribute to toxicity.
Interferometric synthetic aperture radar (InSAR) has become an essential technique to detect surface variations due to volcanoes, earthquakes, landslides, glaciers, and aquifers. However, Earth's ionosphere, atmosphere, vegetation, surface runoff, etc., introduce noise that requires post-processing to separate its components.
View Article and Find Full Text PDF