Tracking suspended particle transport via radium isotopes ((226)Ra and (228)Ra) through the Apalachicola-Chattahoochee-Flint River system.

Suspended particles in rivers can carry metals, nutrients, and pollutants downstream which can become bioactive in estuaries and coastal marine waters. In river systems with multiple sources of both suspended particles and contamination sources, it is important to assess the hydrologic conditions under which contaminated particles can be delivered to downstream ecosystems. The Apalachicola-Chattahoochee-Flint (ACF) River system in the southeastern United States represents an ideal system to study these hydrologic impacts on particle transport through a heavily-impacted river (the Chattahoochee River) and one much less impacted by anthropogenic activities (the Flint River).

Lithium isotope history of Cenozoic seawater: changes in silicate weathering and reverse weathering.

Weathering of uplifted continental rocks consumes carbon dioxide and transports cations to the oceans, thereby playing a critical role in controlling both seawater chemistry and climate. However, there are few archives of seawater chemical change that reveal shifts in global tectonic forces connecting Earth ocean-climate processes. We present a 68-million-year record of lithium isotopes in seawater (δ(7)Li(SW)) reconstructed from planktonic foraminifera.

Collisions between metastable hydrogen atoms at thermal energies.

The complex interaction potentials arising in the approach of two metastable hydrogen 2s atoms are calculated and the cross sections for ionization, excitation transfer, and elastic scattering are predicted. The measured cross section for associative ionization at E = 4.1 meV equals 2x10(-15) cm (2).

Improved molecular final-state distribution of HeT+ for the beta-decay process of T2.

An improved theoretical final-state distribution of HeT+ (and HeH+) resulting from the beta decay of molecular tritium T2 (HT) is presented to accommodate the needs of increased accuracy in the analysis of ongoing and future tritium neutrino-mass experiments. The previously available theoretical spectrum has been improved in many respects, and adopted approximations have been validated.

Hydrogen-antihydrogen collisions.

Matter-antimatter interactions are investigated using hydrogen-antihydrogen collisions as an example. Cross sections for elastic scattering and for the antihydrogen loss (either through the rearrangement reaction, resulting in formation of protonium and positronium according to H+&Hmacr;-->p&pmacr;+e(+)e(-), or via annihilation in flight) are calculated for the first time in a fully quantum mechanical approach. Implications for experiments intending to trap and cool antihydrogen are discussed.