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

Iodine content in running surface waters in areas with more intensive landscape management in the Czech Republic

The aim of this study has been to make an analysis and evaluation of iodine content in running surface waters in protected landscape areas (PLA) in the Czech Republic. Water samples were taken in 2009-2011 in Jeseníky PLA (Rapotín locality) and in Šumava PLA (Arnoštov and Lipno localities), and in 2009-2010 in the upper course of the Blanice River and its tributaries in and outside of Šumava PLA. Iodine was determined by the ICP-MS method. The average iodine content was 1.55±0.33 μg dm-3 (n = 41) in Jeseníky PLA and 2.58±0.33 μg dm-3 (n = 24) and 2.29±0.84 μg dm-3 (n = 30) in Šumava PLA. The average iodine content in water samples of the Blanice River and its tributaries localized in Šumava PLA was 2.27±0.65 and 2.38±0.66 μg dm-3 and outside of Šumava PLA it equalled 2.90±0.68 and 3.26±1.51 μg dm-3. The lowest concentration of 1.43 μg dm-3 was found out in a sample from the Spálenecký brook (Šumava PLA), and the highest one, 7.63 μg dm-3, was determined in a sample from the Živný brook, which flows below the town Prachatice. Higher concentrations were measured in the summer season: 3.05±0.35 (Blanice) and 3.63±1.24 μg dm-3 (tributaries), while lower ones were determined in the spring season: 1.48±0.30 (Blanice) and 2.37±1.12 μg dm-3 (tributaries). The results confirm the low iodine content in the environment of Jeseníky and Šumava Mts., and the self-purification capacity of the Blanice River even when it is stressed with anthropogenic iodine

Epitaxial VO<inf>2</inf> Nanostructures: A Route to Large-Scale, Switchable Dielectric Metasurfaces

Copyright © 2018 American Chemical Society. Metasurfaces offer unparalleled functionalities for controlling the propagation and properties of electromagnetic waves. But to transfer these functions to technological applications, it is critical to render them tunable and to enable fast control by external stimuli. In most cases, this has been realized by utilizing tunable materials combined with a top-down nanostructuring process, which is often complicated and time intensive. Here we present a novel strategy for fabricating a tunable metasurface comprising epitaxially grown nanobeams of a phase transition material, vanadium dioxide. Without the need for extensive nanolithographic fabrication, we prepared a large-area (>1 cm2), deep-subwavelength (thickness of ∼Λ/40) nanostructured thin film that can control light transmission with large modulation depth, exceeding 9 dB across all telecommunication wavelength bands. Furthermore, the transmission in the "on" state remains higher than 80% from near- to mid-infrared region. This renders our metasurface useful also as a phase-shifting element, which we demonstrate by carrying out cross-polarized transmission measurements. To provide insights about the relationship between metasurface morphology and its resulting optical properties, we perform full-field three-dimensional numerical simulations as a function of width, height, and edge-to-edge separation of the epitaxial VO2 nanobeams