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181.
Summary Relatively good correlation between such remote phenomena as microseisms, geomagnetic activity and ionospheric absorption of radio waves has been observed. These phenomena are probably connected by a considerably increased penetration of energetic particles into the atmosphere under conditions of geomagnetic activity. 相似文献
182.
Summary As a result of investigating the energy flow, transmitted by short-period HM waves, the existence of a frequency limitation was found at the theoretical investigation of the propagation of these HM waves. 相似文献
183.
184.
185.
On 13 May 2000 parts of a penumbra were observed in an active region NOAA 8990 with the La Palma Stokes Polarimeter attached
to the Swedish Vacuum Solar Telescope. The stratification over the solar atmosphere of different physical parameters is retrieved
from these data by using the Stokes inversion based on response functions. The results confirm the previous findings of the
penumbral structure. In general, the magnetic field becomes weaker and more horizontal with increasing distance from the umbra
and the line-of-sight velocities are increasing towards the outer boundary of the penumbra. The results also suggest the existence
of the unresolved fine structure of the penumbra. The stratifications of the temperature and of the magnetic field strength
indicate the presence of rising flux tubes, which were predicted theoretically by Schlichenmaier, Jahn and Schmidt (1998,
Astron. Astrophys.
337, 897). 相似文献
186.
187.
We calculate NLTE models of stellar winds of hot compact stars (central stars of planetary nebulae and subdwarf stars). The studied range of subdwarf parameters is selected to cover a large part of these stars. The models predict the wind hydrodynamical structure and provide mass-loss rates for different abundances. Our models show that CNO elements are important drivers of subdwarf winds, especially for low-luminosity stars. We study the effect of X-rays and instabilities on these winds. Due to the line-driven wind instability, a significant part of the wind could be very hot. 相似文献
188.
B. Košt’ák S. Cacoń N. D. Dobrev E. Avramova-Tačeva E. Fecker J. Kopecký L. Petro R. Schweitzer A. A. Nikonov 《Izvestiya Physics of the Solid Earth》2007,43(6):503-516
Long-term repeated measurements of microdisplacements in tectonic fault structures of various parts of Central Europe and the Balkan Mountains showed that displacement trends changed significantly at several points in the period from 1997 through 2000; afterward, long-term trends were restored. This phenomenon took place in the periods of strong (M > 7) earthquakes in Iran (1997) and in the North Anatolian fault zone in Turkey (1999). Two strong Izmit earthquakes of 1999 in Turkey at distances of 600 km from the Balkan Peninsula and 1400 km from observation points in Central Europe were the main seismic events of the period studied. Apparently, the crustal deformation due to the sources of the aforementioned earthquakes reaches the central part of the European craton. Anomalous displacements in some areas occurred due to deformation propagating for great distances in the heterogeneous block medium of the West European part of the Eurasian plate. Changes in stresses can be caused by impulsive deformations of various intensities acting on some structural units (fault segments) at various distances. 相似文献
189.
A. Sajnović K. Stojanović G. S. Pevneva A. K. Golovko B. Jovančičević 《Geochemistry International》2010,48(7):678-694
This paper reports an investigation of 60 samples of lacustrine sedimentary rocks of Neogene age lying at depths of 0–400
m in the Valjevo-Mionica Basin, Serbia. The goal of the study was to determine the origin and type of primary organic matter
(OM), the degree of thermal alteration, the generation potential of OM from the rocks of this basin, and conditions in the
sedimentation environment during the formation of the rocks. The potential of OM of the rocks was estimated on the basis of
the thermolysis of a representative sample after its preliminary debituminization. 相似文献
190.
The Mississippi Valley-type (MVT) Pb–Zn ore district at Mežica is hosted by Middle to Upper Triassic platform carbonate rocks
in the Northern Karavanke/Drau Range geotectonic units of the Eastern Alps, northeastern Slovenia. The mineralization at Mežica
covers an area of 64 km2 with more than 350 orebodies and numerous galena and sphalerite occurrences, which formed epigenetically, both conformable
and discordant to bedding. While knowledge on the style of mineralization has grown considerably, the origin of discordant
mineralization is still debated. Sulfur stable isotope analyses of 149 sulfide samples from the different types of orebodies
provide new insights on the genesis of these mineralizations and their relationship. Over the whole mining district, sphalerite
and galena have δ
34
S values in the range of –24.7 to –1.5‰ VCDT (–13.5 ± 5.0‰) and –24.7 to –1.4‰ (–10.7 ± 5.9‰), respectively. These values are
in the range of the main MVT deposits of the Drau Range. All sulfide δ
34
S values are negative within a broad range, with δ
34
S
pyrite <δ
34
S
sphalerite <δ
34
S
galena for both conformable and discordant orebodies, indicating isotopically heterogeneous H2S in the ore-forming fluids and precipitation of the sulfides at thermodynamic disequilibrium. This clearly supports that
the main sulfide sulfur originates from bacterially mediated reduction (BSR) of Middle to Upper Triassic seawater sulfate
or evaporite sulfate. Thermochemical sulfate reduction (TSR) by organic compounds contributed a minor amount of 34S-enriched H2S to the ore fluid. The variations of δ
34
S values of galena and coarse-grained sphalerite at orefield scale are generally larger than the differences observed in single
hand specimens. The progressively more negative δ
34
S values with time along the different sphalerite generations are consistent with mixing of different H2S sources, with a decreasing contribution of H2S from regional TSR, and an increase from a local H2S reservoir produced by BSR (i.e., sedimentary biogenic pyrite, organo-sulfur compounds). Galena in discordant ore (–11.9
to –1.7‰; –7.0 ± 2.7‰, n = 12) tends to be depleted in 34
S compared with conformable ore (–24.7 to –2.8‰, –11.7 ± 6.2‰, n = 39). A similar trend is observed from fine-crystalline sphalerite I to coarse open-space filling sphalerite II. Some variation
of the sulfide δ
34
S values is attributed to the inherent variability of bacterial sulfate reduction, including metabolic recycling in a locally
partially closed system and contribution of H2S from hydrolysis of biogenic pyrite and thermal cracking of organo-sulfur compounds. The results suggest that the conformable
orebodies originated by mixing of hydrothermal saline metal-rich fluid with H2S-rich pore waters during late burial diagenesis, while the discordant orebodies formed by mobilization of the earlier conformable
mineralization. 相似文献