Thermodynamic nonequilibrium effects in bubble coalescence: A discrete Boltzmann study.

The thermodynamic nonequilibrium (TNE) effects in a coalescence process of two initially static bubbles under thermal conditions are investigated by a discrete Boltzmann model. The spatial distributions of the typical nonequilibrium quantity, i.e., nonorganized momentum fluxes (NOMFs), during evolutions are investigated in detail. The density-weighted statistical method is used to highlight the relationship between the TNE effects and the morphological and kinetics characteristics of bubble coalescence. The results show that the xx component and yy component of NOMFs are antisymmetrical; the xy component changes from an antisymmetric internal and external double quadrupole structure to an outer octupole structure during the coalescence process. Moreover, the evolution of the averaged xx component of NOMFs provides two characteristic instants, which divide the nonequilibrium process into three stages. The first instant, when the averaged xx component of the NOMFs reaches its first local minimum, corresponds to the moment when the mean coalescence speed gets the maximum, and at this time the ratio of minor and major axes is about 1/2. The second instant, when the averaged xx component of the NOMFs gets its second local maximum, corresponds to the moment when the ratio of minor and major axes becomes 1 for the first time. It is interesting to find that the three quantities, TNE intensity, acceleration of coalescence, and the slope of boundary length, show a high degree of correlation and attain their maxima simultaneously. The surface tension and the heat conduction accelerate the process of bubble coalescence, while the viscosity delays it. Both the surface tension and the viscosity enhance the global nonequilibrium intensity, whereas the heat conduction restrains it. These TNE features and findings present some insights into the kinetics of bubble coalescence.

Dual-Phosphorescent Iridium(III) Complexes Extending Oxygen Sensing from Hypoxia to Hyperoxia.

Hypoxia and hyperoxia, referring to states of biological tissues in which oxygen supply is in sufficient and excessive, respectively, are often pathological conditions. Many luminescent oxygen probes have been developed for imaging intracellular and in vivo hypoxia, but their sensitivity toward hyperoxia becomes very low. Here we report a series of iridium(III) complexes in which limited internal conversion between two excited states results in dual phosphorescence from two different excited states upon excitation at a single wavelength. Structural manipulation of the complexes allows rational tuning of the dual-phosphorescence properties and the spectral profile response of the complexes toward oxygen. By manipulating the efficiency of internal conversion between the two emissive states, we obtained a complex exhibiting naked-eye distinguishable green, orange, and red emission in aqueous buffer solution under an atmosphere of N2, air, and O2, respectively. This complex is used for intracellular and in vivo oxygen sensing not only in the hypoxic region but also in normoxic and hyperoxic intervals. To the best of our knowledge, this is the first example of using a molecular probe for simultaneous bioimaging of hypoxia and hyperoxia.

Utilization of Electrochromically Luminescent Transition-Metal Complexes for Erasable Information Recording and Temperature-Related Information Protection.

Transition metal complexes containing pyrazinium or pyridinium moieties display reversible luminescence changes in response to electrical stimuli, which is useful in the development of erasable information recording electric devices. These complexes are also suitable for temperature-related information protection, since chemically-induced luminescence turn-on is temperature-dependent.