Design of a rotating disk reactor to assess the colonization of biofilms by free-living amoebae under high shear rates

<p>The present study was aimed at designing and optimizing a rotating disk reactor simulating high hydrodynamic shear rates (<i>γ</i>), which are representative of cooling circuits. The characteristics of the hydrodynamic conditions in the reactor and the complex approach used to engineer it are described. A 60 l tank was filled with freshwater containing free-living amoebae (FLA) and bacteria. Adhesion of the bacteria and formation of a biofilm on the stainless steel coupons were observed. FLA were able to establish in these biofilms under <i>γ</i> as high as 85,000 s⁻¹. Several physical mechanisms (convection, diffusion, sedimentation) could explain the accumulation of amoeboid cells on surfaces, but further research is required to fully understand and model the fine mechanisms governing such transport under <i>γ</i> similar to those encountered in the industrial environment. This technological advance may enable research into these topics.</p

First far-infrared high-resolution analysis of the ν₂ band of sulphur dioxide ³²S¹⁶O¹⁸O and ³²S¹⁸O₂

<p>High-resolution Fourier transform spectra of ¹⁸O-enriched isotopic samples of sulphur dioxide (³²S¹⁶O¹⁸O and ³²S¹⁸O₂) have been recorded at 0.00102 cm⁻¹ resolution in the 400–620 cm⁻¹ region at Synchrotron SOLEIL. These spectra have been recorded at low temperature 185 K using a 3.14 m optical path length cryogenic cell. This enables the first detailed infrared analysis of the ν₂ bands of the ³²S¹⁶O¹⁸O and ³²S¹⁸O₂ isotopologues of sulphur dioxide located at 507.36541(1) and 496.59988(1) cm⁻¹, respectively. Using a Watson-type Hamiltonian model to compute the upper and lower state energy levels, it was possible to reproduce the observed transitions. For both species, accurate rotational and centrifugal distortion constants were derived for the upper (0,1,0) vibrational state, while those of the (0,0,0) ground state were significantly updated. For this task, we combined the results of the present infrared measurements with the available literature microwave data in the (0,0,0) and (0,1,0) vibrational states. Finally, we took the opportunity of this study to compare the quality of the fit using an A- and S-type reduction for the Watson Hamiltonian.</p