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91.
Yulia Krasheninnikova Alexander Ruzmaikin Dmitry Sokoloff Anvar Shukurov 《地球物理与天体物理流体动力学》2013,107(1-3):131-146
Abstract We discuss recent developments in the theory of large-scale magnetic structures in spiral galaxies. In addition to a review of galactic dynamo models developed for axisymmetric disks of variable thickness, we consider the possibility of dominance of non-axisymmetric magnetic modes in disks with weak deviations from axial symmetry. Difficulties of straightforward numerical simulation of galactic dynamos are discussed and asymptotic solutions of the dynamo equations relevant for galactic conditions are considered. Theoretical results are compared with observational data. 相似文献
92.
Dmitry Ponomarev Andrey Puzachenko Olga Bachura Pavel Kosintsev Johannes van der Plicht 《Boreas: An International Journal of Quaternary Research》2013,42(3):779-797
The paper summarises materials on the mammal remains in northeastern Europe, dated by radiocarbon. Altogether, 23 local faunas of small mammals and 47 local faunas of large mammals were analysed. Multidimensional statistical analysis shows a strong correlation between changes in small mammal fauna composition and climate changes throughout time. The correlations with the spatial gradients, however, are less pronounced. The faunas are classified into three groups: (1) faunas of Holocene age; (2) Late Pleistocene ‘stadial’ assemblages; and (3) Late Pleistocene ‘interstadial’ assemblages. In some cases, changes in species abundance are better understood in terms of biotic interrelations rather than of climatic effects. The most pronounced change in small mammal fauna composition and structure occurred at the Preboreal/Boreal boundary, and a less conspicuous alteration took place at the LGM/Lateglacial transition. The most noticeable transformation in the large mammal fauna composition is dated to the early Holocene. Less significant changes are observed at the Middle Weichselian/LGM transition and at the LGM/Lateglacial transition. It is safely concluded that variations in the faunas of small and large mammals recorded in NE Europe during the last 35 000 years occurred synchronously and unidirectionally. 相似文献
93.
94.
Hugues Lantuit Pier Paul Overduin Nicole Couture Sebastian Wetterich Felix Aré David Atkinson Jerry Brown Georgy Cherkashov Dmitry Drozdov Donald Lawrence Forbes Allison Graves-Gaylord Mikhail Grigoriev Hans-Wolfgang Hubberten James Jordan Torre Jorgenson Rune Strand ?deg?rd Stanislav Ogorodov Wayne H. Pollard Volker Rachold Sergey Sedenko Steve Solomon Frits Steenhuisen Irina Streletskaya Alexander Vasiliev 《Estuaries and Coasts》2012,35(2):383-400
Arctic permafrost coasts are sensitive to changing climate. The lengthening open water season and the increasing open water area are likely to induce greater erosion and threaten community and industry infrastructure as well as dramatically change nutrient pathways in the near-shore zone. The shallow, mediterranean Arctic Ocean is likely to be strongly affected by changes in currently poorly observed arctic coastal dynamics. We present a geomorphological classification scheme for the arctic coast, with 101,447?km of coastline in 1,315 segments. The average rate of erosion for the arctic coast is 0.5?m? year?1 with high local and regional variability. Highest rates are observed in the Laptev, East Siberian, and Beaufort Seas. Strong spatial variability in associated database bluff height, ground carbon and ice content, and coastline movement highlights the need to estimate the relative importance of shifting coastal fluxes to the Arctic Ocean at multiple spatial scales. 相似文献
95.
Quantification of geodiversity and its loss 总被引:1,自引:0,他引:1
Dmitry A. Ruban 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(3):326-333
Geodiversity, i.e., a diversity of geological heritage sites, can be quantified with an account of geosite types, type counterparts, and their ranks. Higher numbers of geosite types represented within a given territory and their higher ranks indicate a higher geodiversity. Two additional characteristics, namely geoabundance and georichness, allow measure of the quantity of geosites and the diversity-quantity relationship respectively. Geodiversity loss can be evaluated with an accounting of decreases in geosite type ranks linked to the damage of geosites. A calculation of relative and multi-dimensional geodiversity helps in quantitative assessment of the regional geological heritage. 相似文献
96.
Dmitry D. BADJUKOV Franz BRANDSTÄTTER Jouko RAITALA Gero KURAT 《Meteoritics & planetary science》2010,45(9):1502-1512
Abstract– A large number of micrometeorites (MMs) was recovered from glacier deposits located at the north‐eastern passive margin of the Novaya Zemlya glacier sheet. Melted, scoriaceous, and unmelted micrometeorites (UMMs) are present. Unmelted micrometeorites are dominated mostly by chondritic matter, but also a few achondritic MMs are present. Here we report the discovery of four UMMs that, according to their texture, mineralogy, and chemistry, are identified as basaltic breccias. Mineral chemistry and Fe/Mn ratios of two basaltic micrometeorites indicate a possible relationship with eucrites and/or mesosiderites, whereas two others seem to have parents, which appear not to be present in our meteorite collections. The basaltic breccia UMMs constitute 0.5% of the total population of the Novaya Zemlya MM suite. This content should be lowered to 0.25% because the Novaya Zemlya MM collection appears to be biased with carbonaceous UMMs being underrepresented. 相似文献
97.
Boris Shustov Ana I. Gómez de Castro Mikhail Sachkov Alexander Moisheev Evgeny Kanev Javier López-Santiago Oleg Malkov Dmitry Nasonov G. Belén Perea Néstor Sánchez Igor Savanov Andrey Shugarov Sergey Sichevskiy Oleg Vlasenko Javier Yañez 《Astrophysics and Space Science》2014,354(1):155-161
The World Space Observatory Ultraviolet (WSO-UV) is the space mission that will grant access to the ultraviolet (UV) range in the post Hubble epoch. WSO-UV is equipped with instrumentation for imaging and spectroscopy and it is fully devoted to UV astronomy. In this article, we outline the WSO-UV mission model and present the current status of the project. 相似文献
98.
99.
Dmitry A. Ruban 《Gondwana Research》2011,20(4):739-744
Global sea-level rise and consequent regional transgressions are hypothesized at the beginning of the Devonian. A brief review of lithostratigraphical data available from three regions of the “Tethyan” margin of Gondwana, namely Northern Africa, Arabia, and the Tethys Himalaya, suggests that all of them were characterized by a regressive setting in the Lochkovian. In contrast, data from some terranes of the Greater Galatian Superterrane provide evidence of early Lochkovian transgression. The regressive setting documented on the 'Tethyan' margin of Gondwana differs from the transgressive–regressive cycles of Euramerica and the norm of global sea-level rise followed by a highstand. Only regional tectonic processes including those linked with dynamic topography could explain these differences. These processes may have been associated with syn-rift uplift preceding the opening of the Palaeo-Tethys Ocean, mantle uplift at the supercontinent margin, or the Eo-Variscan orogenic phase. 相似文献
100.
We consider a conventional stellar α2 ω -dynamo with dynamo generators localized in two spherical shells separated by a passive layer. The signs of the α-effect as well as rotational shear in the dynamo active layers can be chosen to give dynamo waves that propagate in opposite directions (poleward and equatorward) if the layers are considered separately in the framework of the Parker migratory dynamo. In a sequence of numerical experiments we show that the variety of dynamo-generated magnetic configurations in the system under discussion is quite rich. We identify the possibility of almost independent dynamo waves existing in the two layers as well as enslavement of one layer by the other, and of activity waves generated by a joint action of the two layers. We suggest some qualitative explanations of the behaviour and discuss also the limited nature of these explanations. This variety of phenomena suggests previously underexploited freedoms to understand how predictions of dynamo theory may accommodate the observed solar and stellar activity phenomenology. 相似文献