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411.
412.
Xenon isotopic studies confirm natural spontaneous chain reactions at the Oklo mine site (Republic of Gabon) with an integrated neutron flux of approximately 4 × 1020n/cm2 and a duration between 14,000 and 70,000 years. Similar studies for the Rabbit Lake deposit (Saskatchewan), a slightly younger site with some evidence of continued geologic activity, shows no evidence of self-supporting reactions. 相似文献
413.
V. G. Eselevich V. M. Bogod I. V. Chashey M. V. Eselevich Yu. I. Yermolaev 《Geomagnetism and Aeronomy》2009,49(1):133-135
The solar sources of the magnetic storms of November 8 and 10, 2004, are analyzed. The preliminary results of such an analysis [Yermolaev et al., 2005] are critically compared with the results of the paper [Tsurutani et al., 2008], where solar flares were put in correspondence with these magnetic storms. The method for determining solar sources that cause powerful magnetospheric storms is analyzed. It has been indicated that an optimal approach consists in considering coronal mass ejections (CMEs) as storm sources and accompanying flares as additional information about the location of CME origination. 相似文献
414.
In previous papers we have published preliminary results on the stellar oxygen-abundance gradient in M33 by using B-type supergiants.
In the present study, we include one new B-supergiant and derive effective temperatures and gravities for these stars. The
determination of atmospheric parameters is based on analyses of silicon ionisation balance.
Detailed non-LTE model atmospheres and non-LTE line formation calculations were used for the abundance determination of Si
and O. Careful differential analyses are used to quantify the differences in metal abundances between M33 stars and MK spectral
standards in our Galaxy.
We compare our results with the abundances expected from studies of HII regions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
415.
The photometric U orbital variations of the symbiotic binary AG Peg, caused by occultation of a bright gaseous region by the
M giant in this system, are used to determine the geometry of this region whose existence is explained in the framework of
the colliding winds model. The emission of the bright region varies and a particular value of its mean density of 2–3 1010 cm-3 has been derived. The causes for the irregular variations of the light in the orbital minimum and maximum are discussed.
It is also obtained, when the mass-loss rate of the hot companion of the system decreases to about 5 10-10
Ms
⊙ yr-1, this bright region will disappear.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
416.
D. R. Van Stempvoort T. W. D. Edwards M. S. Evans W. M. Last 《Journal of Paleolimnology》1993,8(2):135-147
This pilot study examines the potential of obtaining a sedimentary record of paleoenvironmental/climatic/hydrologic conditions for saline Redberry Lake in southern Saskatchewan, Canada. The tools are mineralogy, stable isotopes and pigments. The upper meter of an offshore sediment core contains 10 to 20% by weight aragonite (CaCO3), which apparently precipitated in the water column. The 18O and 13C of the bulk aragonite (corrected for content of detrital calcite) vary by 4 to 5. Enrichment in 18O in aragonite is significantly correlated with pigment concentrations (chlorophyll a, phaeophytin). The 18O and pigment data provide evidence for relatively dry and/or warm conditions and high limnetic productivity for the period 2500 to 1500 yrs B.P. After 1500 B.P., the climate was apparently similar to the present, with two episodes of relatively enhanced productivity, dryness and/or warmth, at around 1000 to 900 and 500 to 200 B.P. During the past century, Redberry Lake has decreased approximately 8 m in depth and its salinity has doubled. No clear sedimentary signal was observed in response to these recent hydrologic trends. These changes have not been associated with a significant climate trend in the region, but may have been induced by land use changes in the catchment.This publication is the third of a series of papers presented at the Conference on Sedimentary and Paleolimnological Records of Saline Lakes. This Conference was held August 13–16, 1991 at the University of Saskatchewan, Saskatoon, Canada. Dr. Evans is serving as Guest Editor for this series. 相似文献
417.
The Cryogenian succession of the Northern Flinders Ranges reveals a complex sedimentary record between the Sturtian and Marinoan glacial deposits. A major unconformity separates the Sturtian and Marinoan-aged sedimentary successions in the area. This forms a subaerial erosion surface with terrestrial and marginal marine infill directly above the Angepena and Balcanoona Formations in their respective localities. This exposure surface is here correlated with the previously documented submarine unconformity between the Yankaninna Formation and the underlying deep marine Tapley Hill Formation. This erosional event provides a chronostratigraphic marker horizon that coincides approximately with thepreviously defined Sturtian–Marinoan Time Series boundary in the Northern Flinders Ranges. These stratigraphic relationships also constrain lateral facies relationships between the Oodnaminta ReefComplex (Balcanoona Formation) and the Angepena Formation. Similarly, the shallow-water Weetootla Dolomite is correlated with the deeper water carbonates of the Yankaninna Formation. 相似文献
418.
E. K. Semenov N. N. Sokolikhina E. V. Sokolikhina 《Russian Meteorology and Hydrology》2013,38(10):661-668
The genetic and synoptic classifications of the Novorossiysk Bora are created using the data of daily observations at the Novorossiysk meteorological station and other available synoptic information. Obtained are the quantitative criteria of these classifications, and on this base worked out are the basic scenarios of the generation and evolution of this dangerous phenomenon on the Black Sea coast of Russia. According to the genetic classification, the Bora was divided into four types: frontal, air-mass, monsoon, and gravity. Quantitative criteria worked out for each type can be used for the more accurate forecast of this destructive phenomenon near Novorossiysk. According to the synoptic classification, four classes were distinguished: Azores, North Atlantic, Siberian, and Arctic. 相似文献
419.
V. V. Aristov I. I. Babarina A. V. Grigor’eva V. Yu. Alekseev V. Yu. Prokof’ev A. A. Uzyunkoyan O. V. Zabolotskaya S. G. Titov 《Geology of Ore Deposits》2017,59(1):68-101
Gold deposits and occurrences small in reserves and high in Au grade conventionally determine the line of prospecting in terrigenous sequences of the Verkhoyansk–Kolyma region. In this paper, the geological structure of such gold objects is considered with the example of the deposits and prospects making up the Zhdaninsky ore–placer cluster in the Republic of Sakha (Yakuia). From lithological, structural, and mineralogical–geochemical data, the formation conditions of ore-bearing complexes are specified, the geological evolution history of the northern Ol’chan Zone of the Kular–Nera Belt is reconstructed, and the zonal distribution of mineralization within the ore–placer cluster is revealed. The structural–compositional complexes were formed in the following succession: (1) sedimentation at the shelf of the passive margin accompanied by synsedimentation deformations; (2) metagenesis of sediments and the development of bedding-plane intraformational detachments of collision stage D1 under conditions of tangential compression and accompanied by the formation of carbon dioxide–aqueous metamorphic fluid at a temperature of 300°C and under a pressure of 1.4 kbar; (3) folding and faulting of orogenic stage D2 with the formation of synkinematic magmatic bodies, metasomatic alteration, and Au-bearig mineral assemblages. Small Au-bearing objects with veined mineralization and high Au grade are localized in structures of stage D2 transverse to bedding-plane schistosity S1. They form at the collision stage above intraformational detachment surfaces and are controlled by shear structures of the orogenic stage with misalignment of these deformations. The ore zoning is determined by the distribution of Co and Ni minerals and by variations in the anionic composition of ore (S, As, Sb). 相似文献
420.
M. N. Gnevyshev 《Solar physics》1977,51(1):175-183
Investigation of sunspots, coronal lines intensity, flares and other solar and geophysical data have confirmed the fact that the 11-year cycle consists of two events (maxima) having different features.During the first maximum (it coincides in time with the maximum of the Wolf numbers) the solar activity increases in all heliographic latitudes but it is maximal in latitude 25° in each hemisphere. The far UV radiation and number of small spots, flares and geomagnetic disturbances with sudden commencements and without 27-day recurrences are maximum at this time.During the second maximum, which appears 2–3 years after the first one, the activity is maximal in latitudes ± 10°. At this time the biggest spots, big flares, aurora and geomagnetic disturbances with the gradual commencements and long series of 27-day recurrences appear.The variations of averaged 5303 and 6374 Å coronal line intensities may be interpreted as an increase of coronal density and temperature during the first maximum and a sharp decrease of density and temperature rise during the second one. The temperature during the second maximum is higher than that during the first one.The distribution of activity on time-latitude diagrams (so-called butterflies) is a result of superposition of two random distributions corresponding to the two maxima mentioned above. 相似文献