Carbon, oxygen, and sulfur isotope compositions of carbonate and sulfate rocks from the Famennian potassium-bearing subformation of the Pripyat trough     

A. A. Makhnach  V. N. Kuleshov  V. I. Vinogradov  B. G. Pokrovsky  N. S. Petrova  M. I. Bujakaite  S. V. Antipenko  O. V. Murashko 《Lithology and Mineral Resources》2013,48(4):327-342

Peculiar features of evaporitic process at the stage of potassium accumulation are considered on the basis of carbon and oxygen isotope data on carbonate rocks and sulfur isotope data on anhydrite from the Famennian potassium-bearing subformation of the Starobin potassic salt deposit in the Pripyat trough. It was found that potassium accumulation was accompanied by the influx of continental waters and highly concentrated brines, while the formation of thick salt-free units was related to the replenishment of fresh seawater to the basin.  相似文献   

Light Scattering by Aggregate Particles Comparable in Size to Wavelength: Application to Cometary Dust     

Petrova  E. V.  Jockers  K.  Kiselev  N. N. 《Solar System Research》2001,35(1):57-69

Many naturally occurring particles (including, most likely, cometary dust) have an aggregate structure. We study the scattering properties of polydisperse independent aggregate particles (clusters) comparable in size to visible wavelengths. The sizes of the monomers constituting a cluster play a significant role in forming the angular dependences of intensity and linear polarization of the scattered light. Irregularly structured aggregates composed of a moderate number of spheres (<50) with size parameters 1.3–1.65 exhibit properties typical of cometary dust particles: a slight increase in backscattering intensity, a negative polarization at small phase angles, an inversion phase angle close to the observed one, an increase in brightness, and a linear polarization with increasing wavelength. In this case, the imaginary part of the refractive index for particles can increase with decreasing wavelength in the visible spectral range, which is typical of silicates with an admixture of iron or organic material. The spectral dependence of extinction efficiency for aggregates is less steep than that for equivalent spherical particles, and its maximum is shifted to larger size parameters. Therefore, when analyzing extinction measurements, the scatterer shape must be taken into account to avoid underestimation of the scattering-particle sizes.  相似文献   

Apsidal Motion in Detached Binary Stars: Comparison of Theory and Observations     

A. V. Petrova  V. V. Orlov 《Astrophysics》2002,45(3):334-341

A list of 62 detached binaries having reliable data on the rotation of the line of apsides is considered. Theoretical estimates of the rate of apsidal motion are obtained. These estimates are compared with observational data. It is shown that cases in which the theoretical estimate exceeds the observed value are several times more frequent than cases in which the theoretical value is lower than the observed one. This discrepancy increases when systems with more reliable observational data are considered.  相似文献   

Modeling of opposition effects with ensembles of clusters: Interplay of various scattering mechanisms     

Elena V. Petrova  Victor P. Tishkovets 《Icarus》2007,188(1):233-245

Although the opposition phenomena observed in brightness and polarization for various astronomical objects and laboratory samples have been under intense study for many years, their explanation is still far from being complete. The shadow hiding and coherent backscattering effects are mentioned most frequently in this connection. In the present work we first discuss how other coherent scattering mechanisms, in particular interference and interaction between scatterers in the near field, influence brightness and polarization of complex ensembles of particles at small phase angles. Then we demonstrate the contribution of the different mechanisms to the scattering process in a model regolith described as an ensemble of wavelength-sized clusters as constituents. While the clusters are always densely packed, the porosity of the ensemble itself, i.e., the average distances between the clusters within the ensemble, is allowed to vary. The modeling confirms that the phase dependence of intensity and polarization of light scattered by complex structures in the backscattering domain is mainly caused by the interplay of (1) the constructive interference of waves traveling through the particle ensemble along similar paths but in opposite directions and (2) the near-field effect caused by the inhomogeneity of waves in the immediate vicinity of constituent particles. The first mechanism works more effectively in sparse ensembles, while the second one manifests itself in more compact structures of wavelength-sized scatterers at distances comparable to the wavelength. It is difficult to distinguish quantitatively their contributions in models of simple structures and even more in measurements. A number of observations, especially of moderate and low albedo objects, can, however, be explained only by invoking the near-field effect.  相似文献   

Approach-ejection correlation in the general three-body problem     

V. V. Orlov  A. V. Petrova  A. I. Martynova 《Astronomy Letters》2001,27(7):470-474

The relations between parameters of triple approaches and the lengths of subsequent ejections are analyzed for the general three-body problem with components of equal masses and zero initial velocities. A statistically significant correlation is shown to exist between the closeness of approaches and the lengths of subsequent ejections: closer approaches generally result in longer ejections. We have found several systems that evolve to a temporary quasi-stable chain-like configuration.  相似文献   

Characterization of Bulgarian oil shale kerogen revealed by oxidative degradation   总被引：1，自引：0，他引：1  

Temenuzhka Budinova  Maria Razvigorova  Bilyana Petrova  M. Ferhat Yardim 《Chemie der Erde / Geochemistry》2009,69(3):235-245

A 13-step alkaline permanganate degradation of Bulgarian oil shale kerogen concentrate at ambient temperature was carried out. A high yield of oxidation products (90.1%) and a low yield of gaseous products (2.79%) were obtained. IR and ¹H NMR spectroscopic studies have shown that two significantly different types of high molecular products are present in kerogen. Further oxidation of these structures leads to the formation of low molecular aliphatic and aromatic acids, proven by gas chromotography (GC) and gas chromatography-mass spectrometry (GC-MS). The data obtained at these mild conditions allow us to acquire detailed information about the aromatic structures and polymethylene chain lengths in kerogen.The 5-step oxidation of the kerogen at 90 °C provides information about stable aromatic structures. Soluble and insoluble polyfunctional acids in acid medium have close molecular masses and spectral characteristics. The amount of benzene and naphthalene carboxylic acids is 11.3% of the organic matter of the oil shale.  相似文献   

The provenance of terrigenous rocks of the basal horizons of the Uralides of the Baidarata Allochthon (Polar Urals) according to the U–Pb isotope age of detrital zircons     

S. N. Sychev  A. S. Ivleva  S. Yu. Petrov  M. N. Petrova  V. B. Ershova  R. B. Veselovskii  A. G. Konnov 《Moscow University Geology Bulletin》2017,72(3):172-180

The U–Pb (LA–ICP–MS) age of detrital zircons from the Upper Cambrian–Lower Ordovician terrigenous rocks of the Baidarata Allochthon, which is located in the northern part of the Polar Urals, is determined. The analysis of the youngest zircon population indicates a broad occurrence of the Uralides in this area rather than Pre-Uralides, as was considered previously. The Bedamel island-arc rocks (rather than Timan orogen) were probably the major provenance for the studied sequences. The results of statistical processing of the U–Pb ages of zircons from coeval rocks of Arctic regions suggest similar provenances for the Baidarata Allochthon and Novaya Zemlya and Severnaya Zemlya archipelagoes.  相似文献   

Neoproterozoic riftogenic subalkali basites of the Central Urals: Geochemical specifics of clinopyroxene     

L. V. Sazonova  A. A. Nosova  L. G. Petrova 《Geochemistry International》2010,48(3):260-279

Trace-element distribution in clinopyroxenes of different generations was used to decipher the intricate melt fractionation history of the trachybasalts, trachyandesites, and gabbroids from different rift-related magmatic complexes, which were formed during evolution of the Neoproterozoic passive margin of the East European craton (western slope of the Central Urals). It was established that chromian and high-magnesian cores of the early Cpx phenocrysts in the trachybasalts are not xenogenic, but represent relict minerals that were formed at the early stage of fractionation of a high-Mg melt. The fact that the trachybasalts and trachybasaltic andesites contain high-Mg Cpx with trace-element patterns similar in shape and element abundance indicates their formation via differentiation of a common melt. However, their subsequent evolution was different: trachybasaltic andesites were subjected to significant crustal contamination, which was recorded in composition of late Cpx. All subalkali basites were presumably formed from comparatively deepseated melts, because, according to thermodynamic calculations, early cores in the gabbroids crystallized at temperature more than 1200°C and pressure between 10 and 14–15 kbar, i.e., at depths of approximately 35–50 km. Some differences observed between trace-element composition of Cpx from the studied subalkali basatoids and gabbroids are inconsistent with their derivation from a common source, but similarity of their Cpx in many characteristics undoubtedly indicates close depths and compositions of their sources. Geochemical peculiarities of Cpx in the Neoproterozoic rift rocks from the western slope of the Central Urals testify that they were derived from melts formed by relatively low degree partial melting with garnet in residue. The geochemical specifics of clinopyroxenes from the Neoproterozoic riftogenic subalkali basites of the Central Urals and basaltoids from the Paleozoic Tagil structure of the same region showed that this island-arc system reflects the composition of melt source and its reworking by mantle fluids, which were different in the course of plume-lithosphere interaction and suprasubduction processes.  相似文献   

Modeling of Lake Ladoga ecosystem transformation under decreased phosphorus load     

L. A. Rukhovets  N. A. Petrova  V. V. Menshutkin  G. P. Astrakhantsev  T. R. Minina  V. N. Poloskov 《Doklady Earth Sciences》2010,434(2):1373-1376

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Penetration of the Earth’s free oscillations at 54 minute period into the atmosphere     

G. M. Shved  L. N. Petrova  O. S. Polyakova 《Annales Geophysicae》2000,18(5):566-572

It is known that the fundamental spheroidal mode ₀S₂ of the Earth free oscillation with a period of about 54 min forces atmospheric oscillations. We present a certain phase relationship for components of the ₀S₂ multiplet, which is based on synchronous collocated microbarograph and seismograph observations. This relationship is both the first observational manifestation of the Pekeris mode of global atmospheric oscillations with the 54 min period and a further proof of the Earths ₀S₂ mode penetrating into the atmosphere. We show that the linear non-dissipative model of steady forced oscillations in isothermal atmosphere at rest does not describe the penetration of the ₀S₂ mode into the atmosphere adequately.  相似文献