Estimating the upper limit of prehistoric peak ground acceleration using an in situ, intact and vulnerable stalagmite from Plavecka priepast cave (Detrekoi-zsomboly), Little Carpathians, Slovakia-first results

Earthquakes hit urban centres in Europe infrequently, but occasionally with disastrous effects. Obtaining an unbiased view of seismic hazard (and risk) is therefore very important. In principle, the best way to test probabilistic seismic hazard assessments (PSHAs) is to compare them with observations that are entirely independent of the procedure used to produce PSHA models. Arguably, the most valuable information in this context should be information on long-term hazard, namely maximum intensities (or magnitudes) occurring over time intervals that are at least as long as a seismic cycle. The new observations can provide information of maximum intensity (or magnitude) for long timescale as an input data for PSHA studies as well. Long-term information can be gained from intact stalagmites in natural caves. These formations survived all earthquakes that have occurred over thousands of years, depending on the age of the stalagmite. Their 'survival' requires that the horizontal ground acceleration (HGA) has never exceeded a certain critical value within that time period. Here, we present such a stalagmite-based case study from the Little Carpathians of Slovakia. A specially shaped, intact and vulnerable stalagmite in the Plavecka priepast cave was examined in 2013. This stalagmite is suitable for estimating the upper limit of horizontal peak ground acceleration generated by prehistoric earthquakes. The critical HGA values as a function of time going back into the past determined from the stalagmite that we investigated are presented. For example, at the time of Joko event (1906), the critical HGA value cannot have been higher than 1 and 1.3 m/s(2) at the time of the assumed Carnuntum event (similar to 340 AD), and 3000 years ago, it must have been lower than 1.7 m/s(2). We claimed that the effect of Joko earthquake (1906) on the location of the Plavecka priepast cave is consistent with the critical HGA value provided by the stalagmite we investigated. The approach used in this study yields significant new constraints on the seismic hazard, as tectonic structures close to Plavecka priepast cave did not generate strong earthquakes in the last few thousand years. The results of this study are highly relevant given that the two capitals, Vienna and Bratislava, are located within 40 and 70 km of the cave, respectively.Web of Science2151130111

Adsorption of benzene on Si(100) from first principles

Adsorption of benzene on the Si(100) surface is studied from first principles. We find that the most stable configuration is a tetra-$\sigma$-bonded structure characterized by one C-C double bond and four C-Si bonds. A similar structure, obtained by rotating the benzene molecule by 90 degrees, lies slightly higher in energy. However, rather narrow wells on the potential energy surface characterize these adsorption configurations. A benzene molecule impinging on the Si surface is most likely to be adsorbed in one of three different di-$\sigma$-bonded, metastable structures, characterized by two C-Si bonds, and eventually converts into the lowest-energy configurations. These results are consistent with recent experiments.Comment: 4 pages, RevTex, 2 PostScript gzipped figure

Development of Wax Fuel Grain for Hybrid Rocket Motor

Abstract: The paper deals with development of wax fuel grain for testing of small hybrid rocket motor. The possible wax composition is selected as solid fuel which in combination with nitrous oxide as oxidizer creates hybrid propellant. Rotary casting system specially developed for this case and wax grain manufacturing is described. The first practice with such hybrid rocket motor testing is introduced

Analysis of social networks in rodents under different environmental conditions

During the last decade social network analysis has increased in importance as a methodological framework to study inter- and intra-specific relations between animals. Understanding patterns in social network structure have important consequences in biological control, conservation and help us make inferences about parasite/pathogen transmission dynamics in animal systems. Rodents are reservoirs and vectors of several important diseases in Europe and are sensitive to environmental change. As such, we use rodents as model organisms to study the effects of altitude (proxy for global climate change) and habitat disturbance on structure of social networks. Capture-mark-recapture (CMR) sampling was carried out using 16 replicated grids in an 8x8 live-trap array set in both disturbed and undisturbed forests (in terms of recent or former tree cutting) in low (ca. 650 m a.s.l.) and high altitude (ca. 1250 m a.s.l.) in the Italian Dolomites. During 14,336 trap-nights separated to seven two-night sessions every month (April – October 2012), a total of 1,280 rodent individuals were captured, belonging to four species: Apodemus flavicollis, A. sylvaticus, Myodes glareolus and Microtus multiplex. Rodent communities of high-altitude forests were significantly richer and more abundant having two main species (A. flavicollis and M. glareolus) in contrast to communities of low-altitude ones highly predominated by A. flavicollis. In this contribution, we describe the practicalities of constructing contact networks of rodents based on space sharing as revealed from CMR sampling. We present the social network structure of wild rodents under different environmental conditions, both visually and statisticall