Earth rotation in the hipparcos reference frame     

J. Vondrak  C. Ron  I. Pešek 《Celestial Mechanics and Dynamical Astronomy》1996,66(1):115-122

New determination of the Earth orientation parameters (EOP), based on optical astrometry observations since the beginning of the century, is now under preparation by the Working group established by Commission 19 of the IAU. The Hipparcos catalog is to define the celestial reference frame in which the new series of EOP are to be described, The novelties of the prepared solution are the higher resolution (5 days) and more parameters estimated from the solution (celestial pole offsets, rheological parameters of the Earth, certain instrumental constants). The mathematical model of the solution is described, and the results based on the observations made with 46 instruments at 29 observatories and a preliminary Hipparcos catalog are presented.  相似文献   

Terminal Outflow Velocities from the Mass-Losing AGB Stars     

A. Kučinskas 《Astrophysics and Space Science》1997,251(1-2):231-234

We have calculated terminal gas outflow velocities from the circumstellar shells of the AGB stars. Our results confirm that, in case of the stationary dust driven winds, the dynamics of the outflow is governed essentially by the dust properties and stellar luminosities, while only marginally by other stellar parameters. Although being far from comprehensive, our calculations also indicate that the dust driven winds may only occur in cool, luminous, low mass objects. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

Radar observations of the Geminid meteoroid stream     

G. Cevolani  G. Bortolotti  L. Foschini  C. Franceschi  G. Grassi  G. Trivellone  A. Hajduk  V. Porubčan 《Earth, Moon, and Planets》1995,68(1-3):247-255

Continuous radio-wave monitoring of the Geminid activity in December 1992 and 1993 by using a forward scatter (FS) bistatic radar over the Bologna-Lecce baseline (700 km) in Italy, reveals peculiar structural aspects of the stream in terms of signal amplitude-rate and duration-rate dependence. The observational results of the Geminid display obtained in the two consecutive years with differentiated peak levels of transmitted power, exhibit different time distributions of underdense meteors against the signal received power. Both sets of the data relative to the peak activity in December 12–14, show reflection properties of Geminids which are atypical if compared with echoes from cometary-type showers, with really high echo counts at mid-upper levels of the peak received power. An assymmetric curve of activity of the Geminids complex is evidenced, with the peak flux of smaller particles occurring earlier than that of larger ones.  相似文献   

Interplanetary dust particles and solar radiation     

J. Klačka 《Earth, Moon, and Planets》1994,64(2):125-132

The problem of the action of the solar radiation on the motion of interplanetary dust particle is discussed. Differences between the action of electromagnetic solar radiation and that of the solar wind are explained not only from the point of view of the physical nature of these phenomena but also from the point of view of dust particle's orbital evolution. As for the electromagnetic solar radiation, general equation of motion for the particle is written and the most important consequences are: (i) the process of inspiralling toward the Sun is not the only possible motion - even spiralling from the Sun is also possible, and, (ii) the orbital plane of the particle (its inclination) may change in time. As for the solar wind, the effect corresponding to the fact that solar wind particles spread out from the Sun in nonradial direction causes that the process of inspiralling toward the Sun is in more than 50% less effective than for radial spread out; in the region of the asteroid belt (long period orbits) the process of inspiralling is changed into offspiralling. Also shift in the perihelion of dust particle's orbit exists.  相似文献   

Results from several persistent train spectra intercompared     

J. Rajchl  J. Bočcek  D. Očenáš  J. Škvarka  P. Zimnikoval  H. Murayama  K. Ohtsuka 《Earth, Moon, and Planets》1995,68(1-3):479-486

Some results following from two contemporary photographical programs (Slovakia and Japan) for persistent meteor train spectra are compared. It shows that even though both programs are not too different according to their lenses and films used, the spectral interval detected is very different. In this respect prism as a dispersion element is more favourable than the grating with blaze wavelength near 610 nm. However, some results previously assumed as typicai for presented persistent trains-e.g. the forbidden Herzberg O₂ emission, the NO₂ continuum and OH red emissions-seem to be substanciated especially due to higher and linear dispersion of those grating spectra.  相似文献   

Emission features in the solar corona after the perihelion passage of Comet 1979 XI     

D. Chochol  V. Rušín  L. Kulčár  V. Vanýsek 《Astrophysics and Space Science》1983,91(1):71-77

On the coronograph spectrophotographic records taken on 31.372 UT, August 1979, some faint emission features were found which can be ascribed to Siii and Niii. These emissions were obviously a transient phenomena which were detected only 10 hr after the supposed fall of Comet 1979 XI in the Sun's photosphere. It cannot be excluded that the appearance of Si and Ni lines was triggered by the evaporation of dust particles with a high abundance of heavier elements in the solar corona. This assumption is also supported by intensity distribution of the Fex coronal line around the Sun's limb. The maximum coincide with the position angle of the projected path of the comet.  相似文献   

The largest karst cave discovered in a tunnel during motorway construction in Slovenia’s Classical Karst (Kras)   总被引：1，自引：0，他引：1  

Martin Knez  Tadej Slabe  Stanka Šebela  Franci Gabrovšek 《Environmental Geology》2008,54(4):711-718

Karst researchers of the Karst Research Institute ZRC SAZU are regularly consulted during the planning of Slovenia’s motorways and invited to observe and monitor construction in the karst areas. More than 350 caves have been discovered in the course of building 60 km of new motorways over the past decade. Access to the most important caves is preserved by concrete tubes closed with metal covers at the roadside. The largest cave system in a tunnel, named LC-S647, is almost entirely preserved. The protection of this cave will serve as a good example for the preservation of natural heritage in the future. Construction work for the motorway uncovered a high degree of karstification. In particular, the discovery of this cave in the Kastelec tunnel LC-S647 showed the existence of a major cave system in the geological and speleological past. A number of unconnected passages have also been found. Caves discovered during highway construction have brought new knowledge about the cavernosity and the geological history of this part of the karst.  相似文献   

Anthropogenic influence on trace element geochemistry of healing mud (peloid) from Makirina Cove (Croatia)     

S. Miko  G. Koch  S. Mesić  M. Šparica-Miko  M. Šparica  R. Čepelak  A. Bačani  P. Vreča  T. Dolenec  S. Bergant 《Environmental Geology》2008,55(3):517-537

Due to their balneotherapeutic features, the organic-rich sediments in Makirina Cove are an important source of healing mud. An environmental geochemistry approach using normalization techniques was applied to evaluate the anthropogenic contribution of trace metals to sediments used as healing mud. Sediment geochemistry was found to be associated with land-use change and storm events, as well as with proximity of a road with heavy traffic in the summer months. Local valley topography preferentially channels lithogenic and pollutant transport to the cove. Concentrations and distribution of trace metals indicate lithogenic (Ni, Cr, Co) and anthropogenic (Pb, Cu, Zn and Se) contributions to the sediments. The calculation of enrichment factors indicates a moderate (EFs between 2–3.5) input of anthropogenic Cu and Pb in surficial sediments to a depth of 10 cm. Patients using the Makirina Cove sediments as healing mud could be to some extent exposed to enhanced uptake of metals from anthropogenic sources via dermal contact.  相似文献   

Biomarker distributions as indicators for the depositional environment of lacustrine sediments in the Valjevo-Mionica basin (Serbia)     

Aleksandra Šajnović  Ksenija Stojanović  Branimir Jovančićević  Olga Cvetković 《Chemie der Erde / Geochemistry》2008,68(4):395-411

In this study, the molecular composition and biomarker distribution of lacustrine sediments from Val-1 drillhole in the central zone of the western part of the Valjevo-Mionica basin were investigated at depth interval of 0–400 m. Former investigations have shown that the core material can be separated into six depth intervals based on bulk geochemical, mineralogical and sedimentological characteristics. Concerning the quality of organic matter, presence of specific minerals, and high salinity and anoxicity, or alkalinity, three zones are of highest interest, defined at depth intervals of 15–75 m (A), 75–200 m (B) and 360–400 m (F). The first aim of the study was to identify which biomarkers characterize these specific intervals. The second aim, addressing the transitions zones of these intervals, was to extend the changes in the characteristics of the organic substance, to reflect the changes of conditions in the depositional environment as well as to define biomarker parameters which are the most sensitive sedimentological indicators.The sediments from the hypersaline anoxic and alkaline environment show high contribution of algal precursor biomass, what is in accordance with the good quality of organic substances in the sediments from these zones. High squalane content and low content of regular isoprenoid C₂₅ are typical for hypersaline anoxic environment, whereas sediments from alkaline environment have high regular isoprenoid C₂₅ content.Transition to specific sedimentation zones is characterized by change in total organic matter content, and of both free and pyrolysis-derived, and change in hydrogen index value. In the biomarker distributions, more significant changes were detected in distributions of n-alkanes and isoprenoids, compared to polycyclic alkanes. The most intensive changes in alkane distribution are reflected in changes in n-C₁₇ content compared to n-C₂₇, and phytane compared to n-C₁₈. In addition, significant sensitivity was seen in ratios between squalane and n-alkane C₂₆ (hypersaline depositional environment), or isoprenoid C₂₅ and n-alkane C₂₂ for high alkalinity environment.This study showed that Sq/n-C₂₆ ratio can be used to assess the quality of organic substance in immature lacustrine sediments.  相似文献   

On the types and dispersions of whistlers as observed in czechoslovakia     

František Jiříček 《Studia Geophysica et Geodaetica》1962,6(1):98-101

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