On the position of the maximum of the amplitude curves of reflected waves     

Vlastislav Červený 《Studia Geophysica et Geodaetica》1962,6(3):215-234

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Origin of the Zálesí U–Ni–Co–As–Ag/Bi deposit,Bohemian Massif,Czech Republic: fluid inclusion and stable isotope constraints     

Zdeněk Dolníček  Bohuslav Fojt  Walter Prochaska  Jan Kučera  Petr Sulovský 《Mineralium Deposita》2009,44(1):81-97

The Zálesí vein-type deposit is hosted by Early Paleozoic high-grade metamorphic rocks on the northern margin of the Bohemian Massif. The mineralization is composed of three main stages: uraninite, arsenide, and sulfide. The mineral assemblages formed at low temperatures (~80 to 130°C, locally even lower) and low pressures (<100 bars). The salinity of the aqueous hydrothermal fluids (0 to 27 wt.% salts) and their chemical composition vary significantly. Early fluids of the oldest uraninite stage contain a small admixture of a clathrate-forming gas, possibly CO₂. Salinity correlates with oxygen isotope signature of the fluid and suggests mixing of brines [δ ¹⁸O around +2‰ relative to standard mean ocean water (SMOW)] with meteoric waters (δ ¹⁸O around −4‰ SMOW). The fluid is characterized by highly variable halogen ratios (molar Br/Cl = 0.8 × 10⁻³ to 5.3 × 10⁻³; molar I/Cl = 5.7 × 10⁻⁶ to 891 × 10⁻⁶) indicating a dominantly external origin for the brines, i.e., from evaporated seawater, which mixed with iodine-enriched halite dissolution brine. The cationic composition of these fluids indicates extensive interaction of the initial brines with their country rocks, likely associated with leaching of sulfur, carbon, and metals. The brines possibly originated from Permian–Triassic evaporites in the neighboring Polish Basin, infiltrated into the basement during post-Variscan extension and were finally expelled along faults giving rise to the vein-type mineralization. Cenozoic reactivation by low-salinity, low-δ ¹⁸O (around −10‰ SMOW) fluids of mainly meteoric origin resulted in partial replacement of primary uraninite by coffinite-like mineral aggregates.  相似文献   

Variations in discharge and temperature of mineral springs at the Františkovy Lázně spa,Czech Republic,during a nearby earthquake swarm in 1985/1986     

V. Stejskal  J. Málek  O. Novotný 《Studia Geophysica et Geodaetica》2008,52(4):589-606

The western part of the Bohemian Massif (West-Bohemia/Vogtland region at the Czech-German border) is characterized by relatively frequent intraplate earthquake swarms and by other manifestations of present-day geodynamic activity. During the strong earthquake swarm at the turn of the years 1985 and 1986, significant changes in mineral spring parameters were observed at the spa of Františkovy Lázně. In this study, we present all available data on the mineral springs parameters, and we discuss them in terms of relations to seismic activity. Some changes in discharge were very distinct, amounting up to 40%, and had a co-seismic character. The changes in temperature were less noticeable, but preceded the beginning of the swarm by several months. Some hydrological changes persisted for nearly two years after the earthquake swarm. The character of the observed changes seems to support the hypothesis on an injection of mantle fluids, in particular of CO₂, as the main triggering mechanism of the earthquake swarm and the main cause of discharge anomalies.  相似文献   

On the uncertainty of the transmission function of the optically thick AGB dust shells     

Miroslav Kocifaj  Jozef Klačka  Thomas Posch 《Astrophysics and Space Science》2008,317(1-2):31-38

The uncertainty of the spectral transmission function due to the nonsphericity of cosmic dust particles is analysed for optically thick C-rich and O-rich dust shells. The transmission function directly prescribes the intensity of radiation that passes through a dust shell. It is shown that nonspherical particles affect the stellar spectra in a different way than a system of equally sized spherical particles. Discrepancies in the stellar spectra for both morphological models (spheres and irregular targets) grow with optical thickness of the dust shell and the spectral behaviour of the optical thickness depends on the particle size distribution function. In particular, two most frequently used distrubutions, a power law and Dirac’s delta function, are considered in the presented numerical runs. Light transmission through C-rich dust shells is strongly influenced by absorption which dominates in case of carbonaceous particles. Irregularly shaped carbonaceous particles reduce the intensity of stellar spectra more efficiently than spherical particles of the same composition (the difference is about 10–30%). MgO particles which may be present in O-rich dust shells are almost pure scatterers, thus the ratio of transmission functions for irregularly shaped particles and spherical ones show specific resonant features (especially at wavelengths below 0.4 μm).  相似文献   

On 17 – 22 January 2005 Events in Space Weather     

I. Dorotovič  K. Kudela  M. Lorenc  M. Rybanský 《Solar physics》2008,250(2):339-346

This contribution is a follow-up to the recent paper of Kuznetsov et al. (Contrib. Astron. Obs. Skalnaté Pleso 36, 85, 2006) on the ground level enhancement (GLE) on 20 January 2005. We focused on a study of Forbush decrease (FD) of 17 – 18 and 21 – 22 January 2005, respectively. The data from the neutron monitor at Lomnicky Štít (1 min counts) and from the Geomagnetic Observatory in Hurbanovo, both in Slovakia, were used as the basis for our investigation. The data on magnetic field and solar wind from GOES 10 and 12, SOHO-CELIAS, ACE and WIND satellites were used for better understanding of the global evolution of the event. The magnetic field is transformed to the RTN (Radial – Tangential – Normal) system where only the disturbed part of the field is compared, i.e., daily variations and a constant part are subtracted. The field reduction method is described. Our results are temporal vector diagrams of variation of all parameters at all positions from where we used the data. The amplitudes of |B| exceed 100 nT and variations during the arrival of the wavefront of CME take place simultaneously at the ground-based station and at GOES satellites. The character of the variations is as if there would be regions with the dominant electric charge of opposite signs, or electric currents with different orientations in the CME. On the basis of the values v _p and n _p and using certain assumptions we determined the mass of CME on 17 January and 21 January, respectively, of 10¹² kg. A decrease of the cosmic ray level runs suddenly (during 10 minutes), starting, however, about two hours after a sudden change of the magnetic field.  相似文献   

The Effect of Humic Acids on Zymogenous Microbial Consortia Growth          下载免费PDF全文

Srdjan B. Miletić  Snežana D. Spasić  Jelena Avdalović  Vladimir Beškoski  Mila Ilić  Gordana Gojgić‐Cvijović  Miroslav M. Vrvić 《洁净——土壤、空气、水》2014,42(9):1280-1283

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Outburst flood hazard: Case studies from the Tien-Shan Mountains, Kyrgyzstan   总被引：3，自引：0，他引：3  

Bohumír Janský  Miroslav Šobr  Zbyněk Engel 《Limnologica》2010,40(4):358-364

More than 2000 of mountain lakes covering more than 0.1 ha exist in a territory of Kyrgyzstan. Nearly 20% of them are dangerous because of instability of lake dams, frequent overflows and melting of buried ice inside the moraine dams. According to the Kyrgyz lake inventory, 328 lakes are at risk of outburst and 12 lakes are considered as actually dangerous. Since 1952 more than 70 disastrous cases of lake outbursts have occurred. The majority of the endangered lakes belong to one of the three genetic types: morainic-glacier, supraglacial and lake dammed by landslides and debris flows. Petrov, Adygine and Koltor lakes were selected and studied in the Tien-Shan Mountains as case studies of the most frequent genetic types of hazardous lakes. Observations were focused on the morphology of the lake basin and the surrounding relief, outflow pattern and processes controlling the development of lake. For the hazard assessment, evolution of glaciers and lakes was reconstructed using historical reports, aerial photographs and satellite images.  相似文献   

Sediment lithology and stable isotope composition of organic matter in a core from a cirque in the Krkonoše Mountains,Czech Republic     

Zbyněk Engel  Grzegorz Skrzypek  Debajyoti Paul  Wojciech Drzewicki  Daniel Nývlt 《Journal of Paleolimnology》2010,43(4):609-624

This study presents detailed lithostratigraphy and stable carbon and nitrogen isotopic variations in a 520-cm-long sediment core from a cirque basin in the Labsky důl Valley, Krkonoše Mountains, Czech Republic. Detailed study of the core reveals five major periods of sedimentation during the last 7600 years: silt and sand deposition during ~7.6–5.1 ka cal BP, Sphagnum peat accumulation during ~5.1–4.0 ka cal BP, sandy silt and sand during ~4.0–2.8 ka cal BP, raised peat bog during ~2.8–2.0 ka cal BP (Sphagnum peat), and sedimentation of sandy silt since ~2.0 ka cal BP. The δ¹³C values of the organic matter in the core vary in the range typical for C3 plants, from −24.35 to −27.68‰, whereas the δ¹⁵N values vary from −2.65 to +4.35‰. Core sections having ash contents ≥70% have δ¹⁵N > 1‰ and δ¹³C < −26‰, whereas those having ≤70% ash content have δ¹⁵N < 1‰ and δ¹³C > −26‰. Strong linear correlations are observed between δ¹³C and δ¹⁵N values as well as between C:N ratios and δ¹⁵N values in the horizons with ash content >10%, primarily for sand and silt horizons. On the other hand, poor correlations between δ¹³C and C:N ratio, as well as δ¹⁵N and C:N ratio, were observed in Sphagnum peat layers (45–125 and 185–265 cm). We conclude that the primary stable isotope variations are not preserved in the layers where significant correlation between δ¹⁵N and C:N ratio is observed. The relatively small δ¹³C variation in the uppermost Sphagnum peat layer suggests stable temperature during ~2.8–2.0 ka cal BP.  相似文献   

Chaotic transitions in resonant asteroidal dynamics     

S. Ferraz-Mello  J. C. Klafke  T. A. Michtchenko  D. Nesvorný 《Celestial Mechanics and Dynamical Astronomy》1996,64(1-2):93-105

The utilization of chaotic dynamics approaches allowed the identification of many modes of motion in resonant asteroidal dynamics. As these dynamical systems are not integrable, the motion modes are not separated and one orbit may transit from one mode to another. In some cases, as in the \31 resonance, these transitions may lead, in a relatively short time scale, to eccentricities so high that the asteroid may approach the Sun and be destroyed. In the \21 and \32 resonances these transitions are much slower and only indirect estimations of the time which is needed for a generic asteroid to leave the resonance are possible. It may reach hundreds of million years in the more robust regions of the \21 resonance and a time of the order of billions of years in those of the \32 resonance. These values are consistent with the observed depletion of the \21 resonance (only a few asteroids known while almost 60 asteroids are known in the \32 resonance).  相似文献   

Statistical field theory,volume 1: From brownian motion to renormalization and lattice gauge theory,volume 2: Strong coupling,monte carlo methods,conformal field theory,and random systems     

Roman Kotecký 《Astrophysics and Space Science》1992,187(1):163-163

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