We present a model of ultrasonic metafluids -acoustic metamaterials in the form of suspensions of discrete microscopic oscillators coupled to the embedding fluid. Contrary to a common assumption about metamaterials, and as already established in the field of metafluids, the metafluid concept need not be based on position periodicity or correlation of the suspended micro-oscillators, and in this case not even on ideally designed micro-oscillators. For the speculation that metafluids may one day be produced as solutions of macromolecules, it is essential that the micro-oscillators be allowed to be randomly distributed in the host fluid and generally have irregular (modal) shapes. We formulate the detailed operating principle of such a metafluid model, give explicit formulae for its effective dynamic moduli in terms of the modal structure of the micro-oscillators, and discuss basic practical issues of performance optimization in terms of their mass and size.

Characteristics of ammonia plasma sustained by inductively coupled radiofrequency discharge has been studied in the range of powers between 50 and 1000 W and pressures between 10 and 90 Pa. In such an experimental setup pronounced differences between the E‐ and H‐mode were observed and explained to some details. Plasma was characterized by optical emission spectroscopy (OES) and residual gas spectrometry (RGA). The plasma luminosity changed for four orders of magnitude and the NH2 band vanished at higher powers (H‐mode). The RGA results indicated high density of NH2 radicals in the E‐mode while in the H‐mode the ammonia molecules almost entirely dissociated to H and N atoms. The N and H atoms created in the plasma recombined to the nitrogen and hydrogen molecules rather than to parent ammonia molecules on the way to the RGA.

The article by Aljaž Draškovič‐Bračun et al. (ppap.201700105), published online on 18 September 2017, contains a wrong version of Figure . This corrigendum is published to correct this.