Measurement of Effective Temperatures in an Aging Colloidal Glass

We study the thermal fluctuations of an optically confined probe particle, suspended in an aging colloidal suspension, as the suspension transforms from a viscous liquid into an elastic glass. The micron-sized bead forms a harmonic oscillator. By monitoring the equal-time fluctuations of the tracer, at two different laser powers, we determine the temperature of the oscillator, $T_{\text{o}}$. In the ergodic liquid the temperatures of the oscillator and its environment are equal while, in contrast, in a nonequilibrium glassy phase we find that $T_{\text{o}}$ substantially exceeds the bath temperature.Comment: 4 pages (minor changes, accepted Phys. Rev. Lett.

4. Wochenbericht SO242/1 DISCOL REVISITED

20. - 25. August 201

Rezente submarine Mineralbildungen : Abbild geochemischer Prozesse an aktiven Fluidaustrittsstellen im Aleuten- und Cascadia-Akkretionskomplex

Subduction zones with accretionary wedges are potential areas for active fluid transport and expulsion. Upward transport of relatively cold fluids is predominately caused by tectonic compression and usually occurs along geologically predefined conduits. These submarine fluid expulsions - also known as cold vents or seeps - may have a significant influence on the global geochemical mass balance because they transport dissolved matter and trigger the precipitation of carbonate, barite and sulfide minerals. Using petrographic and geochemical analyses of authigenic mineral precipitates and cemented sediments, one can obtain information about the environment of authigenic mineral formation and the composition of the fluids from which these minerals have formed. This thesis deals with three areas along the Aleutian subduction zone (study areas EDGE and SHUMAGIN) and the Cascadia subduction zone (study area CASCADIA), which are characterized by different types of authigenic precipitates and different fluid regimes. (orig.)SIGLEAvailable from TIB Hannover: RR 1846(87) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

3. Wochenbericht SO242/1 DISCOL REVISITED

12. - 19. August 201

Monitoring temporal variability of bubble release at seeps: The hydroacoustic swath system GasQuant

A lander-based hydroacoustic swath system, GasQuant, was deployed in an intensely bubbling seep area at the shelf west of the Crimea Peninsula, Black Sea. With its horizontally oriented swath (21 beams, 63° swath angle, 180 kHz) GasQuant operates in a sonar-like mode and monitors bubbles remotely, exploiting their strong backscattering when crossing the swath. All active seep spots were monitored simultaneously within the covered area (2075 m2). Even applying simple processing and visualization techniques (moving average for filtering, FFT for spectrum analyses; swath and trace plots) identified 17 seeps of different activity patterns that have been grouped as follows: (1) sporadically active with one to a few long bursts (up to 18 min) or randomly occurring short bursts (350 bursts or >20% active). Studying the bubble release variability of single seeps and of the entire area allows speculation about the external and internal processes that modulate the bubble release. In the study area none of the 17 seeps was found to be permanently active. Only one was active for 75% and another one for 45% of the time monitored. The rest only released bubbles during less than 20% of the time with an overall average of only 12%. This would have strong implications for flux extrapolations if these were based on very accurate but few short-term measurements. Both strong overestimates and underestimates are possible. High-resolution monitoring over at least one tidal cycle as with the GasQuant system might help to get an idea of the temporal variability. Thus flux extrapolations can be corrected to better reflect the real seep activity

2. Wochenbericht SO242/1 DISCOL REVISITED

12. - 19. August 201

1. Wochenbericht POS526

POSEIDON POS526 24.07.2018 - 12.08.2018 Dogger Bank und Tisler Ree