## 4 Results and Discussion
Once more, a note of caution is imparted to the reader that the \"headline measurement\" of a boost in DO, even if expressed in terms of per-Watt power efficiency, is further \"clouded\" by the precise number of residence-time recirculations, etc., in flow units from different manufacturers and different power draws and levels of internal turbulence and macrobubble dissipation prior to passage to an electric-field or porous-membrane chamber. Too often, the almost sole focus of actual or would-be NB-generator operators is on DO boost per se (or traditionally dissolved gas in general)--which does not capture NB production levels (unless the NBs destabilise within seconds to minutes after their birth) and does not consider the actual population or mass of NBs (and, even more subtly--and yet perhaps even more importantly--ORP/ROS, and wider oxidative benefits). Overly overt and prominent consideration of DO boost (or increase in any dissolved gas level), in the absence of considering other more subtle (and sometimes more difficult-to-measure) metrics (like ORP, although relatively straightforward to measure) [19] may shift the performance focus of NB generators instead to general hydrodynamic-/eddy-current-driven oxygen/CO\({}_{2}\)/gas mixing and transfer into the classically dissolved phase (i.e., Henry's Law of individually solvated guest molecules which electrical resistance and/or optical probes are trained to detect to the detriment of detecting NBs, ipso facto). Given that the focus of NB generators ought, logically, to be on NB generation per se, as opposed to producing larger bubbles in the bubble-size distribution (with their faster Stokes'-Law dissipation dynamics from the liquid to atmospheric discharge, or at least phase segregation into a headspace above the liquid in a scenario not open to atmosphere), it is not inappropriate to consider the portion of NB mass created, as opposed to those of larger bubbles. We may do this by comparing Tables 4 and 5--cf. Table 6; here, we also estimate the approximate percentage of conversion into NBs as a proportion of incoming gas (O\({}_{2}\)-in-air) flow, as well as the portion of classically dissolved versus \"nano-dissolved\" oxygen. It can be seen that the electrostriction NB generators lead to approximately a quarter of the incoming oxygen in the air feed, whether via Venturi or air-compressor, converting into NBs, with that proportion rising slightly with greater turbulence and concomitant upstream mesobubble generation. Even though there may well be a more severe underestimate of the level of mass of O\({}_{2}\) in NB form vis-a-vis the mechanical NB generators (1, 2, and 5), a level of mass conversion of no more than 1-2% into NBs--at best--is not ideal. Although a thorough analysis of turbidity has not been carried out in the present study, the greater level of cloudy turbidity observed for the just-generated waters emanating from the mechanical \"NB\" generators is an obvious visual clue of a larger portion of visual-range meso- and microbubbles, which is confirmed in the estimates of Table 6 of no more than \(\sim\)5-6% of the total dissolved O\({}_{2}\) mass being in NB form in those cases. The Stokes' Law escape of larger meso- and microbubbles over minutes to hours, as witnessed visually and anecdotally by less \"milkiness\", suggests that one should focus instead, and more usefully, on the time-resolved dissipation of NB populations per se via laser-light scattering--given that the present study is not concerned with Stokes' Lawdissipation of such larger bubbles over such short timescales. By carrying out \(\exp(-t/\tau)\) fits to time-resolved measurements of NB populations over hours to days, we estimate the negative-exponential NB dissipation \"relaxation times\", \(\tau\), as depicted in Table 7.  
It can be readily seen that the NB-dissipation kinetics are a good deal more sluggish for electric-field-produced NBs, owing in part to the more dense electric-field NBs and build-up of gas molecules at the liquid interface [10].