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We have proposed a novel methodology using ultrasonic velocity profiling to estimate the effective viscosity of bubble suspensions that are accompanied by non-equilibrium bubble deformations in periodic shear flows. The methodology was termed "ultrasonic spinning rheometry" and validated on measurement of the effective viscosity of particle suspensions that has a semi-empirical formula giving good estimation of the actual viscosity. The results indicated that the proposed technique is valid for particle volume fractions below 3.0 %. Applying this to bubble suspensions suggested that the effective value of temporal variations in the capillary number, Ca rms , is an important indicator to distinguish regimes in estimating the effective viscosity: Unsteady flows having larger Ca rms number than the critical capillary number for the deformation of bubbles is categorized into Regime 2 that includes both highly unsteady conditions and large, steady deformation of bubbles.

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We discover two infrared objects that show deep absorption features of H2O, CO2, and CO ices in the AKARI/Infrared Camera slitless spectroscopic survey of the Galactic plane in 2.5–13 μm. Both objects are neither located in known star-forming regions nor in known dense clouds. For one of the objects, Object 1, we successfully extract spectrum from 2.5–13 μm, which also shows several absorption features in 5–13 μm, including deep silicate absorption at 10 μm. For the other object, Object 2, only spectrum from 3.1–5 μm is reliably extracted due to the presence of nearby overlapping objects and faint nebulosity. Both objects show warm (>100 K) CO gas absorption in addition to the ice absorption features, suggesting that they are embedded young stellar objects (YSOs). On the other hand, both objects have spectral energy distributions (SEDs) that peak at around 5 μm and decrease toward longer wavelengths. These characteristics of the SEDs and the presence of deep absorption features cannot easily be accounted for by standard YSO models. They may be explained as background stars behind dense clouds. We discuss possible nature of the objects and implications of the present discovery.

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