Fate of rising methane bubbles in stratified waters: How much methane reaches the atmosphere?

There is growing concern about the transfer of methane originating from water bodies to the atmosphere. Methane from sediments can reach the atmosphere directly via bubbles or indirectly via vertical turbulent transport. This work quantifies methane gas bubble dissolution using a combination of bubble modeling and acoustic observations of rising bubbles to determine what fraction of the methane transported by bubbles will reach the atmosphere. The bubble model predicts the evolving bubble size, gas composition, and rise distance and is suitable for almost all aquatic environments. The model was validated using methane and argon bubble dissolution measurements obtained from the literature for deep, oxic, saline water with excellent results. Methane bubbles from within the hydrate stability zone (typically below ∼500 m water depth in the ocean) are believed to form an outer hydrate rim. To explain the subsequent slow dissolution, a model calibration was performed using bubble dissolution data from the literature measured within the hydrate stability zone. The calibrated model explains the impressively tall flares (>1300 m) observed in the hydrate stability zone of the Black Sea. This study suggests that only a small amount of methane reaches the surface at active seep sites in the Black Sea, and this only from very shallow water areas (<100 m). Clearly, the Black Sea and the ocean are rather effective barriers against the transfer of bubble methane to the atmosphere, although substantial amounts of methane may reach the surface in shallow lakes and reservoirs

The physiological and behavioral impact of sensory contact among unfamiliar adult mice in the laboratory

Housing mice in the laboratory in groups enables social interaction and is the way a laboratory should house mice. However, adult males show reciprocal aggression and are therefore frequently housed individually. Alternatively, a grid divider, which allows sensory contact by sight and smell but prevents fighting and injuries, can separate mice within 1 cage. This study examined the influence of this housing method on various physiological and behavioral parameters. Adult male mice housed for 10 days with sensory contact to an unfamiliar male displayed significant increases in heart rate (HR), body core temperature (BT), and motor activity (ACT). Furthermore, the mice suffered impaired nest-building behavior and significantly reduced body weight. Conversely, males housed in a similar manner with a female companion showed only a transient elevation of ACT, BT, and HR. Although no clear beneficial effect of housing males with sensory contact to females was evident, this study could not exclude it. On the other hand, housing of mature males in this way leads to sustained detrimental alterations of physiology and behavior, thus implying severe impairment of animal well-being

A time-domain terahertz spectrometer with 90 dB dynamic range

We present a time-domain terahertz spectrometer based on 1550 nm fiber laser technology and InGaAs photoconductive switches. The system features a voice-coil delay stage, which offers a high scanning speed of up to 60 traces per second. Owing to a precise reconstruction of the time axis, the system achieves a high dynamic range: a single pulse trace of 50 ps is acquired in only 44 ms, and transformed into a spectrum with a peak dynamic range of 60 dB. With 800 averages, the dynamic range increases to 90 dB and the measurement time still remains as short as 35 seconds

Dynamic Simulation of the Temporal Response of Microstructure Formation in Magnetorheological Fluids

this paper, a novel two-dimensional simulation of MR fluid microstructure dynamics is presented. This simulation treats the particle inclusions as twodimensional magnetic entities. The time evolution is considered to be magnetically quasi-static and magnetostatic forces are derived from the solution of (steady) Maxwell&apos;s equations, recomputed at each instant in time. For this we use a potential theoretic formulation where the boundary integral equations are solved with