排序方式： 共有20条查询结果，搜索用时 209 毫秒
1.
The characteristic pattern of multiple colored layers in coastal stratified lakes in the process of separation from the White Sea 总被引：1，自引：1，他引：0
Krasnova Elena D. Matorin Dmitry N. Belevich Tatiana A. Efimova Ludmila E. Kharcheva Anastasiia V. Kokryatskaya Natalia M. Losyuk Galina N. Todorenko Daria A. Voronov Dmitry A. Patsaeva Svetlana V. 《中国海洋湖沼学报》2018,36(6):1962-1977
An unusual feature of the saline stratified lakes that were formed due to ongoing postglacial uplift on the White Sea coast is the presence of several differently colored thin layers in the zone with sharp gradients. Colored layers in five lakes at various stages of separation from the sea were investigated using optical microscopy, spectrophotometry, spectrofluorimetry, and photobiology. The upper greenish colored layer located in the aerobic strata of all lakes near the compensation depth of 1% light penetration contains green algae. In the chemocline, another layer, brightly green, red or pink, is dominated by mixotrophic flagellates. Despite the very low light intensities and the presence of H 2 S, active photosynthesis by these algae appears to be occurring, as indicated by high values of the maximum quantum yield of primary photochemistry, electron transport activity, photosynthetic activity of photosystem II, the fraction of active centers, and low values of heat dissipation. In the reduced zone of the chemocline, a dense green or brown suspension of anoxygenic phototrophs(green sulfur bacteria) is located. 相似文献
2.
V. D. Mats D. Yu. Shcherbakov I. M. Efimova 《Stratigraphy and Geological Correlation》2011,19(4):404-423
Independent methods of geological and molecular-biological chronologies have made it possible to define generally corresponding
stages in the geological and biological evolution of the environments and communities of Lake Baikal since the Late Cretaceous,
i.e., during the last 70 myr. All the abiotic elements drastically changed during geological evolution, with destruction of
existing and formation of new natural complexes. Nevertheless, some specific zones retained relicts of former settings. The
resulting present-day natural complex includes elements of different ages and geneses. Similar to different natural zones
of the present-day Earth, which are populated by different biocoenoses, stages in the development of abiotic elements are
also characterized by different faunal and floral assemblages. Some taxa were replaced by others, and the resulting aqueous
biota of Lake Baikal includes different-age and ecologically different elements. The oldest groups of Baikal organisms appeared
approximately 70 Ma ago, although the largest proportion of the lake biota started forming 4–3 Ma ago in response to the most
drastic changes in the abiotic elements of the environment. The youngest taxa appeared 1.8 to 0.15 Ma ago, i.e., during the
period when superdeep lake environments and mountainous glaciations were developing. The chronological coincidence of main
stages in development of abiotic and biotic elements of the nature indicates their relationships. Particular transformations
of abiotic elements and the probable mechanism of their influence on the evolution of living communities are also considered. 相似文献
3.
Hagen-Thorn V. A. Troitskaya Yu. V. Hagen-Thorn E. I. Troitsky I. S. Savchenko S. S. Arharov A. A. Efimova N. V. Klimanov S. K. Volkov E. V. 《Astronomy Reports》2019,63(5):378-390
The results of multicolor photometric and polarization observations of the blazar 4C 38.41 (Q 1633+382) performed at St. Petersburg State University, the Pulkovo Astronomical Observatory of the Russian Academy of Sciences, Boston University, and Steward Observatory in 2006–2017 are analyzed. Separate variable sources responsible for the observed activity are distinguished, whose power-lawspectra and high degree of polarization confirm their synchrotron nature. The observed color variability of the object (redder when brighter) can be explained by an increase in the contribution to the total emission of a red component with variable flux and a constant relative spectral energy distribution. A close correlation between the optical and gamma-ray light curves is identified, suggesting the same location of the variable sources responsible for the radiation in these bands.
相似文献4.
V. P. Grinin O. Yu. Barsunova S. G. Sergeev A. A. Arkharov S. Yu. Shugarov A. O. Semenov N. V. Efimova 《Astronomy Reports》2018,62(10):677-688
The results of many-year photometric observations of the weak-line T Tauri star V715 Per in the optical (V RI) and infrared (JHK) photometric bands are presented. The period of the star’s lowamplitude brightness variations in the V RI bands detected earlier, 5.23d, is confirmed. This period persists during the entire 14-year time interval of the observations, but its amplitude varies with time. The same period was found in the variations of JHK infrared fluxes, with the brightness variations in the two ranges being almost synchronous. The most probable origin of these variations is periodic eclipses of the star by its own disk, perturbed by its interaction with the magnetosphere (AA Tau-type variations). In addition to the periodic brightness variations, the star also displayed sporadic Algol-like minima characteristic of UX Ori stars during several years (2005–2011). The amplitude of these variations increasedmonotonically, reaching approximately 1m in the V band by the end of 2010, after which the deep fadings ended. During this entire time interval, the amplitude of the periodic variations was observed to decrease. After 2011, the periodic component began to become stronger again. These changes of the photometric activity of V715 Per can be explained by an increasing rate of gas accretion onto the star, decreasing the radius of warped regions of the disk and leading to accompanying Algol-like fadings. This model assumes a low inclination of the circumstellar disk in V715 Per to the line of sight. 相似文献
5.
A. I. Tikhonov A. F. Ivanov N. E. Mironova V. P. Tikhonov S. V. Efimova 《Water Resources》2013,40(7):761-766
An integrated study with the use of uranium-isotope and microelement hydrogeochemical methods showed the possibility of studying changes in the dynamics and geoenvironmental condition of groundwater in an urban area by the indicator modeling of groundwater formation and circulation, as well as interaction of waters from different horizons, including water ingress from deeper aquifers. 相似文献
6.
7.
We discuss the chemistry of exceptionally rare phlogopite inclusions coexisting with ultramafic (peridotitic) and eclogitic minerals in kimberlite-hosted diamonds of Yakutia, Arkhangelsk, and Venezuela provinces. Phlogopite inclusions in diamonds are octahedral negative crystals following the diamond faceting in all 34 samples (including polymineralic inclusions). On this basis phlogopite inclusions have been interpreted as syngenetic and in equilibrium with the associated minerals. In ultramafic diamonds phlogopites coexist with subcalcic high-Cr2O3 pyrope and/or chromite, olivine and enstatite (dunite/harzburgite (H) paragenesis) or with clinopyroxene, enstatite, and/or olivine and pyrope (lherzolite (L) paragenesis). Ultramafic phlogopites have high Mg# [100?Mg/(Mg+Fe)] from 92.4 to 95.2 and Cr2O3 higher than TiO2 in H-phlogopites (1.5–2.5 wt.% versus 0.1–0.4 wt.%, respectively) but lower in L-phlogopites (0.15–0.5 wt.% versus 1.3–3.5 wt.%, respectively). Eclogitic (E) phlogopites show Mg# from 47.4 to 85.3 inclusive, and very broad ranges of TiO2 up to 12 wt.%. The primary syngenetic origin of phlogopite is indicated, besides other factors, by its compositional consistency with the associated minerals. The analyzed phlogopites are depleted in BaO (0.10–0.79 wt.%), and their F and Cl contents are highly variable reaching 1.29 and 0.49 wt.%, respectively. The latter is in line with high Cl enrichment in some unaltered kimberlites and in nanometric fluid inclusions from diamonds. The presence of syngenetic phlogopite in kimberlite-hosted diamonds provides important evidence that volatiles participated in diamond formation and that at least a part of diamonds may have been related to early stages of kimberlites formation. 相似文献
8.
V. A. Hagen-Thorn N. V. Efimova V. M. Larionov C. M. Raiteri M. Villata A. A. Arkharov E. I. Hagen-Thorn C. A. Gomez S. G. Jorstad L. V. Larionova L. O. Takalo A. Sillanpää 《Astronomy Reports》2009,53(6):510-518
We present an analysis of multicolor (U BV RI JH K) observations of the blazar 3C 454.3 made in 2004–2006. We used the light curves compiled at the Turin Observatory from coordinated observations in the framework of the WEBT program. We consider color variations in two time intervals, when an unprecedented strong outburst occurred (2004–2005), and when the object was in a post-eruptive state and a low-amplitude brightness increase was observed (2006). The spectral energy distribution (SED) of the variable component remained the same within each of these intervals, but differed between them. In both cases, this SED followed a power law after correction for extinction, suggesting the variable component has a synchrotron nature. We conclude that the variations in the optical and IR were due to the same variable source. The object’s unusual color behavior (the brighter, the redder) was due to an increasing contribution from a variable component that was redder than the constant component (big blue bump). 相似文献
9.
A. Pastorello S. Valenti L. Zampieri H. Navasardyan S. Taubenberger S. J. Smartt A. A. Arkharov O. Bärnbantner H. Barwig S. Benetti P. Birtwhistle M. T. Botticella E. Cappellaro M. Del Principe F. Di Mille G. Di Rico M. Dolci N. Elias-Rosa N. V. Efimova M. Fiedler A. Harutyunyan P. A. Höflich W. Kloehr V. M. Larionov V. Lorenzi J. R. Maund N. Napoleone M. Ragni M. Richmond C. Ries S. Spiro S. Temporin M. Turatto J. C. Wheeler 《Monthly notices of the Royal Astronomical Society》2009,394(4):2266-2282
We present the results of the one-year long observational campaign of the type II plateau SN 2005cs, which exploded in the nearby spiral galaxy M51 (the Whirlpool galaxy). This extensive data set makes SN 2005cs the best observed low-luminosity, 56 Ni-poor type II plateau event so far and one of the best core-collapse supernovae ever. The optical and near-infrared spectra show narrow P-Cygni lines characteristic of this SN family, which are indicative of a very low expansion velocity (about 1000 km s−1 ) of the ejected material. The optical light curves cover both the plateau phase and the late-time radioactive tail, until about 380 d after core-collapse. Numerous unfiltered observations obtained by amateur astronomers give us the rare opportunity to monitor the fast rise to maximum light, lasting about 2 d. In addition to optical observations, we also present near-infrared light curves that (together with already published ultraviolet observations) allow us to construct for the first time a reliable bolometric light curve for an object of this class. Finally, comparing the observed data with those derived from a semi-analytic model, we infer for SN 2005cs a 56 Ni mass of about 3 × 10−3 M⊙ , a total ejected mass of 8–13 M⊙ and an explosion energy of about 3 × 1050 erg . 相似文献
10.
Yu. K. Vasil’chuk N. L. Frolova E. D. Krasnova N. A. Budantseva A. C. Vasil’chuk L. V. Dobrydneva L. E. Efimova E. V. Terskaya Ju. N. Chizhova 《Water Resources》2016,43(5):828-838
The isotopic features of Lake Trekhtsvetnoe in the White Sea coast area were studied in 2012–2015 in both winter and summer. Lake Trekhtsvetnoe is a water body, separating from the sea, with constant vertical stratification throughout the observation period. Its isotopic, hydrophysical, and biological characteristics have been studied. By the isotopic profile of lake water body, three zones can be identified in the lake: (1) 0–1 m: mixolimnion zone with δ18O varying from–12 to–11.1‰; (2) 1.0–3.0 m: zone with transitional properties with δ18O varying from–11.1 to–5.5‰; (3) 3.0–7.6 m: monimolimnion zone with highest values of δ18O—from–5.5 to–4.7‰. 相似文献