Determination of metabolic resistance mechanisms in pyrethroid-resistant and fipronil-tolerant brown dog ticks.

Rhipicephalus sanguineus (Latreille) (Ixodida: Ixodidae) is a three-host dog tick found worldwide that is able to complete its' entire lifecycle indoors. Options for the management of R. sanguineus are limited and its' control relies largely on only a few acaricidal active ingredients. Previous studies have confirmed permethrin resistance and fipronil tolerance in R. sanguineus populations, commonly conferred by metabolic detoxification or target site mutations. Herein, five strains of permethrin-resistant and three strains of fipronil-tolerant ticks were evaluated for metabolic resistance using synergists to block metabolic enzymes. Synergist studies were completed with triphenyl phosphate (TPP) for esterase inhibition, piperonyl butoxide (PBO) for cytochrome P450 inhibition, and diethyl maleate (DEM) for glutathione-S-transferase inhibition. Additionally, increased esterase activity was confirmed using gel electrophoresis. The most important metabolic detoxification mechanism in permethrin-resistant ticks was increased esterase activity, followed by increased cytochrome P450 activity. The inhibition of metabolic enzymes did not have a marked impact on fipronil-tolerant tick strains.

Photothermoelectric and photoelectric contributions to light detection in metal-graphene-metal photodetectors.

Graphene's high mobility and Fermi velocity, combined with its constant light absorption in the visible to far-infrared range, make it an ideal material to fabricate high-speed and ultrabroadband photodetectors. However, the precise mechanism of photodetection is still debated. Here, we report wavelength and polarization-dependent measurements of metal-graphene-metal photodetectors. This allows us to quantify and control the relative contributions of both photothermo- and photoelectric effects, both adding to the overall photoresponse. This paves the way for a more efficient photodetector design for ultrafast operating speeds.