title: Generator and Setup for Emulating Exposures of Biological Samples to Lightning Strokes.
abstract: OBJECTIVE
  We aimed to develop a system for controlled exposure of biological samples to conditions they experience when lightning strikes their habitats.
  
  
  METHODS
  We based the generator on a capacitor charged via a bridge rectifier and a dc-dc converter, and discharged via a relay, delivering arcs similar to natural lightning strokes in electric current waveform and similarly accompanied by acoustic shock waves. We coupled the generator to our exposure chamber described previously, measured electrical and acoustic properties of arc discharges delivered, and assessed their ability to inactivate bacterial spores.
  
  
  RESULTS
  Submicrosecond discharges descended vertically from the conical emitting electrode across the air gap, entering the sample centrally and dissipating radially toward the ring-shaped receiving electrode. In contrast, longer discharges tended to short-circuit the electrodes. Recording at 341 000 FPS with Vision Research Phantom v2010 camera revealed that initial arc descent was still vertical, but became accompanied by arcs leaning increasingly sideways; after 8-12 μs, as the first of these arcs formed direct contact with the receiving electrode, it evolved into a channel of plasmified air and short-circuited the electrodes. We eliminated this artefact by incorporating an insulating cylinder concentrically between the electrodes, precluding short-circuiting between them. While bacterial spores are highly resistant to electric pulses delivered through direct contact, we showed that with arc discharges accompanied by an acoustic shock wave, spore inactivation is readily obtained.
  
  
  CONCLUSIONS
  The presented system allows scientific investigation of effects of arc discharges on biological samples.
  
  
  CONCLUSIONS
  This system will allow realistic experimental studies of lightning-triggered horizontal gene transfer and assessment of its role in evolution.
authors.forename: Matej
authors.initials: M
authors.lastname: Rebersek
authors.forename: Igor
authors.initials: I
authors.lastname: Marjanovic
authors.forename: Samo
authors.initials: S
authors.lastname: Begus
authors.forename: Flavien
authors.initials: F
authors.lastname: Pillet
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Rols
authors.forename: Damijan
authors.initials: D
authors.lastname: Miklavcic
authors.forename: Tadej
authors.initials: T
authors.lastname: Kotnik
mesh_terms: D001407:Bacillus / Q000528:radiation effects; D004560:Electricity; D004867:Equipment Design; D022761:Gene Transfer, Horizontal / Q000528:radiation effects*; D008030:Lightning; D008962:Models, Theoretical; D012106:Research / Q000295:instrumentation*; D013016:Sound; D013171:Spores, Bacterial / Q000528:radiation effects*