The harmonic oscillations of water level changes with several hundred nanometers amplitudes and 10-3 [Hz] frequencies are irregularly observed with the water-tube tiltmeter. The effects are observed only by one of four gauges - the one closest to the entrance to underground. The other three gauges of water-tube tiltmeters are situated at the ends of the corridors and are significantly more distant from the entrance to the underground. The atmospheric pressure signals affect level of water in the instrument by inverse barometric effect. The water-tube tiltmeters can register water level variations associated with inverse barometric effects, which were produced by air pressure signals until 10-5 [Pa] magnitude. The amplitude of harmonic oscillations of water level is significantly large and amounts to 1/10 of tidal amplitude, that is 300 to 500 nanometers, which corresponds to 5 x 10-3 [Pa] of air pressure variations. Harmonic oscillations appear irregularly and their time of duration changes from few days until several weeks. The length of atmospheric wave of 10-3 [Hz] frequencies is of 1000 [km] and cannot be explained by any phenomenon from the outside surroundings or the inside of the underground. Resonance frequencies of air column in the hundred meters long underground corridors are of the order of single Hz. Absence of similar signals in measurements from the other three gauges suggests that the harmonic signals are not propagated through the Earth’s solid body but through the atmospheric medium. The observed micro-vibrations of air pressure are very low infrasounds which can be produced in large dimension space of thousand kilometers size. The open question is what is the origin of micro-vibrations registered by the water-tube tiltmeter., Marek Kaczorowski., and Obsahuje bibliografii
The induced unsteady flow due to a stretching porous surface in a rotating fluid, where the unsteadiness is caused by the suddenly stretched surface is studied in this paper. After a similarity tranformation, the unsteady Navier-Stokes equations have been solved numerically using the Adams Predictor Corrector Method. It is found that there is a smooth transition from the small time solution to the large time or steady state solution. and Obsahuje seznam literatury a názvosloví
The unsteady Hartmann flow of a conducting incompressible non-Newtonian viscoelastic fluid between two parallel horizontal insulating porous plates is studied with heat transfer. A uniform pressure gradient which decays exponentially is imposed in the axial direction. An external uniform magnetic field and uniform suction and injection through the surface of the plates are applied in the vertical direction. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are considered in the energy equation. Numerical solutions for the governing momentum and energy equations are obtained using finite differences. The effect of the magnetic field, the parameter describing the non-Newtonian behavior, and the velocity of suction and injection on both the velocity and temperature distributions is investigated. and Obsahuje seznam literatury
Research on the diet of barn owls on some of the lesser Pityusic Islands (Formentera, s’Espalmador and s’Espartar) reveals a previously undescribed opportunistic trophic behaviour based on regular foraging in patches of territory separated by relatively broad sea channels. Individually, small islets with reduced human influence do not usually provide enough food for the barn owl. Consequently, the species expands its home range to include multiple islands or islets. This study is the first to document the regular
crossing of broad sea channels (one of which exceeds 4.5 km) by barn owls in order to hunt. The islets provide the barn owls with prey otherwise considered as marginal (such as Oryctolagus cuniculus and Hydrobates pelagicus).
The advertisement calls of Nathusius’ pipistrelle (Pipistrellus nathusii) show an unified structure: three main motifs which can be supplemented with additional two motifs especially during mating season. In May and June, a continuous social vocalization of quite unusual structure and composition was recorded apart from these standard calls. Most of these calls were designed in a long “wavy line” pattern with the peak frequency of 14–36 kHz, and were accompanied by standard or modified echolocation calls. In one case we succeeded to supplement the acoustic records with a complete record of behavioural details: two bats slowly flew and followed one another in a circular path in front of the roost, where they repeatedly performed false landings, and during approaching one of them emitted the unusual social calls. This behaviour lasted for about 40% of the whole-night activity. The possible meaning is discussed.
The Czech ''Silesian identity'', obvious throughout the twentieth century, was based on a mixture of strong regional, even local, patriotism, which was determined by historical developments. This patriotism developed on the ethnically mixed territory of Czech Silesia (formerly Austrian Silesia). After the Second World War, this phenomenon was quickly revived, but unlike in the pre-war period, it took a clearly Czech national form. The territorial factor, by contrast, receded into the background. Behind this activity and new interpretation stood intellectual circles and institutions in Opava, some leading fi gures from Ostrava, and the Silesian Cultural Institute in Prague. In addition to cultural-educational activity, their efforts were concentratedon claiming some border areas of Polish and German Silesia as being historically Czech, and also on ensuring the distinctive administrative status of the territory of Silesia in Czechoslovakia, the seed of which they saw in the Ostrava branch of the Moravian National Committee (Zemský národní výbor) in Brno. During the Communist regime, according to the authors, the top state authorities showed an intentional lack of interest in the problems of Silesia when solving related economic and other questions. A consequence of this was a ''silencing of the offi cial sources'' about Silesia. In the 1950s, the ''Silesian-ness'' was condemned as a form of ''bourgeois nationalism'' and was identifi ed with the period of Czech-Polish national friction in the region. From the administrative point of view, Silesia was dissolved in the Ostrava area, later in the North Moravian Region, and was recalled practically only by artistic expressions of an ''Old Silesian-ness'', such as folklore and museum exhibitions. Silesian organizations and societies were, with few exceptions, dissolved or renamed and the newly established Silesian Research Institute in Opava had to orient its historical research chiefl y to the labour movement. The works of the poet Petr Bezruč (born Vladimír Vašek, 1867-1958) and his collection of verses, Slezské písně (Silesian Songs), presented a problem because of their questionable depiction of Silesian identity, and the publication of the complete collection led to disputes in cultural policy. The Ostrava-based arts and politics periodical Červený květ (Red Flower), which repeatedly included debates about regionalism, began to be published in the mid-1950s. At the end of the decade, however, the Communist Party launched a campaign against parochialism (lokálpatriotismus), which was refl ected also in the condemnation of publications seeking to exonerate the poems and ideas of Óndra Łysohorsky (born Ervín Goj, 1905-1989), who during the war promoted the theory of a ''Lach nation.'' In the 1960s, the local authorities and fi gures of Opava again began to emphasize the role of their town as a regional centre. During the Prague Spring of 1968, there were calls for the restoration of Silesian self-government, but that remained more or less limited to the Opava region, and consequently some ''Silesian'' cultural initiatives from this period were of greater importance.