IPG Photonics

About: IPG Photonics is a based out in . It is known for research contribution in the topics: Laser & Fiber laser. The organization has 903 authors who have published 1241 publications receiving 63339 citations.

Immobilization of Arsenite and Ferric Iron by Acidithiobacillus ferrooxidans and Its Relevance to Acid Mine Drainage

Abstract: Weathering of the As-rich pyrite-rich tailings of the abandoned mining site of Carnoules (southeastern France) results in the formation of acid waters heavily loaded with arsenic. Dissolved arsenic present in the seepage waters precipitates within a few meters from the bottom of the tailing dam in the presence of microorganisms. An Acidithiobacillus ferrooxidans strain, referred to as CC1, was isolated from the effluents. This strain was able to remove arsenic from a defined synthetic medium only when grown on ferrous iron. This A. ferrooxidans strain did not oxidize arsenite to arsenate directly or indirectly. Strain CC1 precipitated arsenic unexpectedly as arsenite but not arsenate, with ferric iron produced by its energy metabolism. Furthermore, arsenite was almost not found adsorbed on jarosite but associated with a poorly ordered schwertmannite. Arsenate is known to efficiently precipitate with ferric iron and sulfate in the form of more or less ordered schwertmannite, depending on the sulfur-to-arsenic ratio. Our data demonstrate that the coprecipitation of arsenite with schwertmannite also appears as a potential mechanism of arsenite removal in heavily contaminated acid waters. The removal of arsenite by coprecipitation with ferric iron appears to be a common property of the A. ferrooxidans species, as such a feature was observed with one private and three collection strains, one of which was the type strain.

Origin of the sound generated by Strombolian explosions

Abstract: During strombolian eruptions, large bubbles break at the surface of the lava column and produce sound. Acoustic pressure recorded during several explosions on the Eastern vent of Stromboli volcano, shows a pattern consistent between explosions. The well-marked oscillation contains only very low frequencies (around 7 Hz), and is followed by a signal containing now both higher frequencies and lower frequency (less than 4 Hz). The generation of sound is explained by the vibration (7 Hz) and bursting (higher frequencies) of large bubbles, followed by the drainage of magma down in the conduit (less than 4 Hz). The interpretation suggests that: (1) the bubble vibrates before bursting and (2) the vibration prior to bursting yields more energy than the bursting itself. The radius of bubbles responsible for explosions is determined to be close to 1 meter, in agreement with observations of a few conduit sizes.