Hazards to golden-mantled ground squirrels and associated secondary hazard potential from strychnine baiting for forest pocket gophers

Radio telemetry and capture-recapture techniques were used to evaluate the hazards to golden-mantled ground squirrels (Spermophilus lateralis) from hand baiting with 0.5% strychnine-treated oats for western pocket gophers (Thomomys mazama) on conifer plantations in eastern Oregon. Toxicology data were collected on field-killed and caged ground squirrels and on caged mink (Mustela vison), great horned owls (Bubo virginianus), and red-tailed hawks (Buteo jamaicensis). Ground squirrel populations were reduced 50 to 75% following underground baiting for pocket gophers. Maximum amount of strychnine alkaloid found in cheek pouches and carcass of a field-killed golden-mantled ground squirrel was 2.88 mg. Mean amount of strychnine in carcasses was 0.35 mg; almost all occurred in the gut. The estimated LD50 for mink was 0.6 mg/kg. The lowest lethal dose for great horned owls and red-tailed hawks was 7.7 mg/kg and 10.2 mg/kg, respectively. The LD50 for owls and hawks was not determined. Long-term effects on golden-mantled ground squirrel populations and secondary hazard potential to owls and hawks were judged to be minimal. Wild mustelids as large as mink could be adversely affected by consuming the gut content of strychnine-killed golden-mantled ground squirrels

The multicommodity assignment problem: a network aggregation heuristic

AbstractWe present a network-based heuristic procedure for solving a class of large non-unimodular assignment-type problems. The procedure is developed from certain results concerning multi-commodity network flows and concepts of node-aggregation in networks. Computational experience indicates that problems with over fifteen thousand integer variables can be solved in well under ten seconds using state-of-the-art network optimization software

Fluctuation-Induced Transitions in a Bistable Surface Reaction: Catalytic CO Oxidation on a Pt Field Emitter Tip

Fluctuations which arise in catalytic CO oxidation on a Pt field emitter tip have been studied with field electron microscopy as the imaging method. Fluctuation-driven transitions between the active and the inactive branch of the reaction are found to occur sufficiently close to the bifurcation point, terminating the bistable range. The experimental results are modeled with Monte Carlo simulations of a lattice-gas reaction model incorporating rapid CO diffusion

Critical behavior in an atomistic model for a bistable surface reaction: CO oxidation with rapid CO diffusion

Critical behavior associated with the loss of bistability for an atomistic model for CO oxidation on surfaces in the limit of infinite diffusion of CO, was analyzed. A \u27hybrid\u27 treatment which incorporated a lattice-gas description of the O adlayer, and tracked just the number of adsorbed CO, was used. The study elucidated fluctuation effects observed in experiments of CO oxidation on the nanoscale facets of metal-field emitter tips

Anisotropy in Nucleation and Growth of Two-Dimensional Islands during Homoepitaxy on Hex Reconstructed Au(100)

We present results of a comprehensive scanning tunneling microscopy study of the nucleation and growth of Au islands on Au(100). It is shown that the reconstruction of the substrate produces strong anisotropic effects. Rate equation analysis of the experimental flux and temperature dependence of the island density suggests: (i) a critical size of i=3 for T=315−380 K, but i\u3e3 above 400 K; and (ii) strongly anisotropic diffusion, preferentially parallel to the reconstruction rows (activation energy ∼0.2 eV). We comment on energetic and kinetic aspects of the observed island shape anisotropy