Heavy-ion irradiation on crystallographically oriented cordierite and the conversion of molecular CO2 to CO: a Raman spectroscopic study

Crystallographically oriented sections of natural gemstone quality cordierite single-crystals have been irradiated with swift heavy ions of GeV energy and various fluences. Irradiation effects on the crystal lattice were investigated by means of Raman spectroscopy. Raman line scans along the trajectory of the ions reveal a close correlation of beam parameters (such as fluence and energy loss dE/dx along the ion path) to strain due to associated changes in lattice dimensions and defect concentration. The luminescence background also scales with the ion fluence and suggests the formation of point defects, which could also account for the macroscopically observable colouration of the irradiated samples. In addition, changes in the amount and nature of volatile species inside the structural channels are observed. They also scale with dE/dx and confirm the previously postulated irradiation-induced conversion of CO₂ to CO. Irradiations along the crystallographic a-, b- and c-axis reveal no significant anisotropy effect with respect to lattice alterations. The polarisation characteristics of the Raman-active modes confirm the preferred molecular alignment of CO and CO₂ along the a-axis direction.     

Umbrella structure and channel-wall stoping in the Cambrian St. Roch Formation,Quebec Appalachians: significance for particle support mechanisms and turbulence development in hyper-concentrated sediment gravity flows

Umbrella structure is a newly recognized sedimentary structure associated with large platy clasts in resedimented boulder-bearing pebble conglomerate with a sandy matrix. It consists of a sand rim that lacks pebbles on parts or the entire underside of platy boulders, whereas on the upper side, pebbles are in direct contact with the boulders. The depositing processes were high- to hyper-concentrated sediment gravity flows in a submarine channel or canyon on the Cambrian continental slope of North America bordering the Iapetus Ocean. The structure occurs predominantly where clasts dip moderately in the down-current direction. Based on the association of the structure with slightly forward dipping slabs, it is proposed that these down-current dipping slabs may have been in the process of counter-clockwise rotation that was aborted and may have generated a pressure shadow on the underside enabling the inrush of fluid and the infiltration of sand into the anomalous low-pressure zone. The structure has implications for particle support mechanisms in high- to hyper-concentrated sedimentary gravity flows, in that it redirects attention to the much debated mechanism of dispersive pressure and alternatives. It provides an observable sediment structure that supports dispersive pressure which so far depended on experimental evidence and theoretical arguments alone. Vrolijk and Southard’s (1997) concept of a ‘laminar sheared layer’ is here for the first time interpreted as having an upward-moving ‘free-surface’ layer effect during deposition from hyper-concentrated flows. Channel-wall stoping involves unlithified turbiditic spillover sand in the levee sediment of the canyon wall that was washed out by the upper diluted parts of the high-concentration flows coming down the channel and leaving a niche in the wall that was filled with coarser channel-axis facies by the same flow (or later flows) when its aggradation reached the level of the niche. The contact between turbidite and pebble conglomerate occurs now more than 2 m laterally into the exposed channel wall. Channel-wall stoping tracks turbulence development in hyper-concentrated gravity flows.     

Statistical Investigations of Earthquake Swarms within the Vogtland/NW-Bohemian Area

The microseismicity of the Vogtland/NW-Bohemian region has been continually recorded since 1962. Earthquakes mostly occur in single clusters as swarms. The long-term data set has been analysed by statistical methods dividing the whole seismic region into significant clusters. The b-value and fractal dimension D of epicentre distribution, as well as the distribution of times between events for particular swarms has been determined for each cluster to find the parameters characteristic for swarm-like occurrence. The correlation between b and D is discussed with a view to the changing data quality of location and magnitude calculation.     

Multiband photometric detection of a huge flare on the M9 dwarf 2MASSW J1707183+643933

We present simultaneous UV , G , R and I monitoring of 19 M dwarfs that reveal a huge flare on the M9 dwarf with an amplitude in the UV of at least 6 mag. This is one of the strongest detections ever of an optical flare in an M star and one of the first in an ultracool dwarf (spectral types later than about M7). Four intermediate-strength flares  (Δ m _UV < 4 mag)  were found in this and three other targets. For the whole sample we deduce a flare probability of 0.013 (rate of  0.022 h⁻¹  ), and  0.049 (0.090 h⁻¹)  for 2M1707+64 alone. Deviations of the flare emission from a blackbody is consistent with strong  Hα  line emission. We also confirm our previously found rotation period for 2M1707+64 and determine it more precisely to be  3.619 ± 0.015 h  .     

Dynamics of initial ecosystem development at the artificial catchment Chicken Creek, Lusatia, Germany

In autumn 2005, the artificial catchment Chicken Creek was completed in an open-cast lignite mine in Lusatia, Germany. The 6 ha area has been constructed as a two-layer system consisting of a clay aquiclude and a sandy aquifer at the top. After construction, the site was left to an unrestricted and unmanaged succession. A comprehensive environmental monitoring program started immediately after the site was completed. Time series of essential environmental parameters were recorded with high temporal and spatial resolution. This paper presents selected time series of the past 6-year ecosystem development. Important changes registered in this period allow for the definition of distinctive phases of the still ongoing initial ecosystem evolution. A primary, short, but pronounced geo-phase—characterized by surface runoff, excessive erosion and sedimentation as well as very rapid immigration of biota—was followed by a hydrological dominated phase with processes, such as groundwater recharge. At the end of the study period, biotic processes became more evident. It can be concluded that the artificial catchment offers unique opportunities for interdisciplinary research on the establishment of an ecological system with rapidly growing complexity. The highly dynamic development of the Chicken Creek catchment provides the possibility to observe manifold changes within short time and to detect feedbacks and their modifications between different ecosystem compartments.