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151.
Kreshimir Nenadovitch Malitch Elena A. Belousova William L. Griffin Inna Yu Badanina Norman J. Pearson Sergey L. Presnyakov Evgeniya V. Tuganova 《Contributions to Mineralogy and Petrology》2010,159(6):753-768
The ultramafic–mafic Kharaelakh intrusion in the northwestern part of the Siberian Craton (Russia) hosts major economic platinum-group-element
(PGE)–Cu–Ni sulphide deposits. In situ U–Pb, REE and Hf-isotope analyses of zircon from these rocks, combined with detailed
study of crystal morphology and internal structure, identify four zircon populations. U–Pb ages of these populations cover
a significant time span (from 347 ± 16 to 235.7 ± 6.1 Ma) suggesting multiple magmatic events that cluster around 350 and
250 Ma, being consistent with two recognised stages of active tectonism in the development of the Siberian Craton. The oldest
zircon population, however, represents previously unknown stage of magmatic activity in the Noril’sk area. Epsilon-Hf values
of +2.3 to +16.3 in the analysed zircons reflect a dominant role of mantle-derived magmas and suggest that juvenile mantle
material was the main source for the ultramafic–mafic Kharaelakh intrusion. A significant range in initial 176Hf/177Hf values, found in zircons that cluster around 250 Ma, indicate mixing between mantle and crustal magma sources. Our findings
imply that economic intrusions hosting PGE–Cu–Ni deposits of the Noril’sk area have a far more complex geological history
than is commonly assumed. 相似文献
152.
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
153.
Sergey Paltsev Valerie Karplus Henry Chen Ioanna Karkatsouli John Reilly Henry Jacoby 《Climate Policy》2013,13(4):438-457
Passenger vehicles and power plants are major sources of GHG emissions. While economic analyses generally indicate that a broader market-based approach to GHG reduction would be less costly and more effective, regulatory approaches have found greater political success. We evaluate a global regulatory regime that replaces coal with natural gas in the electricity sector and imposes technically achievable improvements in the efficiency of personal transport vehicles. Its performance and cost are compared with other scenarios of future policy development including a no-policy world, achievements under the Copenhagen Accord, and a price-based policy to reduce global emissions by 50% by 2050. The assumed regulations applied globally achieve a global emissions reduction larger than projected for the Copenhagen agreements, but they do not prevent global GHG emissions from continuing to grow. The reduction in emissions is achieved at a high cost compared to a price-based policy. Diagnosis of the reasons for the limited yet high-cost performance reveals influences including the partial coverage of emitting sectors, small or no influence on the demand for emissions-intensive products, leakage when a reduction in fossil use in the covered sectors lowers the price to others, and the partial coverage of GHGs. If these regulatory measures are in part correcting other barriers or behavioural limitations consumers face, the benefits of overcoming these could offset at least some of the costs we estimate. The extent of any efficiency gap – the difference between engineering estimates of best practice and what actually happens – is highly contested, and offers an important avenue for future research.Policy relevanceWhile analysts concerned with national cost of GHG control have long advocated a GHG pricing policy, by a cap-and-trade system or a tax, covering all emissions sources and gases, governments more often pursue sectoral policies and technology standards. Given these political realities, the regulations represent a more politically practical approach to GHG reductions, focusing on solutions that are within reach and that do not depend on technological breakthroughs. If regulations are imposed as a way to get started on larger emissions reductions, and then combined with a broader GHG pricing policy pursuing a deep global cut in emissions, its requirements will eventually be overtaken by the pricing policy. The remaining higher costs of the regulatory targets become diluted so that in later years the difference in average cost per ton between a least-cost approach and one preceded by a period of regulatory action becomes very small. 相似文献
154.
155.
156.
Galina V. Ledneva Victoria L. Pease Sergey D. Sokolov 《Journal of Asian Earth Sciences》2011,40(3):737-745
In order to test tectonic hypotheses regarding the evolution of the Arctic Alaska–Chukotka microplate prior to the opening of the Amerasian basin, we investigated rocks exposed near Kolyuchinskaya Bay, eastern Chukotka. Hypabyssal mafic rocks and associated basaltic flows enclose terrigenous sediments, minor cherts and limestones in pillow interstices. The hypabyssal mafic rock yields a U–Pb zircon age of 252 ± 4 Ma and indicates intrusion of basic magma at the Permo-Triassic boundary, contemporaneous with voluminous magmatism of the Siberian large igneous province (LIP). The lava flows and hypabyssal mafic rocks of the Kolyuchinskaya Bay region have trace elements, Sm–Nd and Rb–Sr isotope compositions identical to the tholeiitic flood basalts of the main plateau stage of the Siberian LIP, but differ from the latter in the major-element variations. We conclude that compositional variations in the hypabyssal rocks studied reflect their generation in an extensional environment that might be related to the Siberian super-plume activity at the time. Although the genetic and temporal links between intrusive mafic rocks and lavas are not well proved, compositional variations of the eruptive rocks still indicate their generation in an extensional environment. 相似文献
157.
Pavel Ya. Groisman Sergey A. Bartalev The NEESPI Science Plan Development Team 《Global and Planetary Change》2007,56(3-4):215
Northern Eurasia Earth System Partnership Initiative, NEESPI, was established to address the global change processes associated with and/or originated within Northern Eurasia as well as to study the major socially-important processes within the region. NEESPI began as a US–Russian initiative but has quickly broadened into a fully international program. Scientists from 11 countries participated in preparing the NEESPI Science Plan. Current version of the Science Plan was released for public review on the World Wide Web in summer 2004 and finalized in December 2004. This paper provides an Overview of the Plan and is based, mainly, on its Executive Summary. The Overview describes the Plan's science themes and key science questions, provides a justification of the urgency studying Northern Eurasia from the global change prospective, and outlines research strategy and tools to address NEESPI science questions, as well as projected deliverables of the Initiative. 相似文献
158.
Capture and escape in the elliptic restricted three-body problem 总被引:1,自引:0,他引:1
Sergey A. Astakhov David Farrelly 《Monthly notices of the Royal Astronomical Society》2004,354(4):971-979
159.
Sergey P. Trudolyubov Konstantin N. Borozdin William C. Priedhorsky 《Monthly notices of the Royal Astronomical Society》2001,322(2):309-320
We present an analysis of the RXTE observations of 4U 1630−47 during its 1998 outburst. The light curve and the spectral evolution of the outburst were significantly different from the outbursts of the same source in 1996 and 1999. Special emphasis was placed on observations taken during the initial rise and during the maximum of the outburst. The maximum of the outburst was divided into three plateaux, with almost constant flux within each plateau, and fast jumps between them. The spectral and timing parameters are stable for each individual plateau, but significantly different between the plateaux. The variability detected on the first plateau is of special interest. During these observations the source exhibits quasi-regular oscillations with a period of ∼ 10–20 s. Our analysis revealed a difference in temporal behaviour of the source at high and low fluxes during this period of time. The source behaviour can be generally explained in the framework of the two-phase model of accretion flow, involving a hot inner Comptonization region and surrounding optically thick disc.
The variability and spectral evolution of the source were similar to what was observed earlier for other X-ray novae. We show that 4U 1630−47 resembles, in several aspects, other transient and persistent black hole binaries. 相似文献
The variability and spectral evolution of the source were similar to what was observed earlier for other X-ray novae. We show that 4U 1630−47 resembles, in several aspects, other transient and persistent black hole binaries. 相似文献
160.
We present the results of polarimetric and photometricobservations of split Comet C/2001 A2 (LINEAR), which wereobtained at
the 70-cm telescope of the Astronomical Observatoryof Kharkiv National University between 30 June and 31 July 2001.The brightest
fragment of the comet, nucleus B, was observed.Eight narrowband cometary filters in the continuum and in emissionbands and
a wideband red filter have been used. The comet wasobserved through apertures of 88, 33, and 19 arcsec. Polarizationphase
curves were obtained for the continuum and for the firsttime, for NH2(0, 7, 0) emission. The degree of polarization ofthe light scattered by the dust decreases with the increase ofaperture size.
An important temporal variation of the polarizationwith a rotation of the polarization plane was observed at twophase angles
(26.5° and 36.2°). Molecular column densities and production rates of CN, C2,C3, and NH2 species are calculated in the framework of theHaser model. A comparative analysis of the temporal variations ofthe visual
magnitudes, gas and dust production rates, dust colorand polarization are presented. 相似文献