Geology topics

Paul W. Davis

Publications and source records attributed to Paul W. Davis.

3 recordsLinked to original sources

USGS2022

Largest recent impact craters on Mars: Orbital imaging and surface seismic co-investigation

Two 130+ meter diameter impact craters formed on Mars during the later half of 2021. These are the two largest fresh impact craters discovered by the Mars Reconnaissance Orbiter since operations started 16 years ago. The impacts created two of the largest seismic events (magnitudes greater than 4) recorded by InSight during its three year mission. The combination of orbital imagery and seismic ground motion enables the investigation of subsurface and atmospheric energy partitioning of the impact process on a planet with a thin atmosphere and the first direct test of Martian deep-interior seismic models with known event distances.The impact at 35°N excavated blocks of water ice, which is the lowest latitude ice has been directly observed on Mars.

Science↗

USGS1972

Organochlorine insecticide, herbicide and polychlorinated biphenyl (PCB) inhibition of NaK-ATPase in rainbow trout

The current widespread presence of chlorinated insecticides, polychlorinated biphenyls (PCB's) and herbicides in world waterways has elicited much interest in the mechanisms of their toxicity in fishes. Inhibition of Na+,K+-activated adenosinetriphosphatase (NaK-ATPase) and Mg++-dependent ATPase (Mg-ATPase) by DDT, endosulfan and dicofol has been demonstrated in gill, brain and kidney microsomes of rainbow trout (1,2). Intestinal and gill ATPases in marine teleosts were recently reported to be sensitive to organochlorines (3). CutkonTp et al (4) noted inhibition of NaK-ATPase and Mg-ATPase in bluegill brain, liver, muscle and kidney by DDT and related chlorinated hydrocarbons. Inhibition of ATPases by PCB's has been recently shown in bluegill kidney, brain and liver (5). In the present study, we have further examined the NaK-ATPase enzyme system in trout gill as a site for the possible toxicity of selected organopolychlors, i.e., chlorinated insecticides, herbicides and PCB's.

Bulletin of Environmental Contamination and Toxico↗

USGS1971

Na+, K+-activated-ATPase inhibition in rainbow trout: A site for organochlorine pesticide toxicity?

1. The Na + , K + -activated, Mg 2+ -dependent-ATPase enzyme system in a heavy microsomal fraction of rainbow trout ( Salmo gairdneri ) brain was inhibited in vitro by chlorinated hydrocarbon pesticides. 2. T 50 (concentration at 50 per cent inhibition) values for dicofol, endosulfan and DDT were 5 × 10 −6 , 3 × 10 −5 and 1 × 10 −4 M respectively. Similar inhibition by these pesticides occurred in kidney and gill ATPase preparations. 3. An unexpected finding was a failure of the classic inhibitor, ouabain, to block the Na + , K + -activated component of ATPase activity in the gill. 4. It is suggested that inhibition of ATPase activity may be a causal factor in the toxic effects of organochlorine pesticides in fishes.

Comparative Biochemistry and Physiology, Part B: C↗