A multi-proxy approach for revealing recent climatic changes in the Russian Altai   总被引：2，自引：0，他引：2  

Olga V. Sidorova  Matthias Saurer  Vladimir S. Myglan  Anja Eichler  Margit Schwikowski  Aleksander V. Kirdyanov  Marina V. Bryukhanova  Oksana V. Gerasimova  Ivan A. Kalugin  Andrey V. Daryin  Rolf T. W. Siegwolf 《Climate Dynamics》2012,38(1-2):175-188

For the first time we present a multi-proxy data set for the Russian Altai, consisting of Siberian larch tree-ring width (TRW), latewood density (MXD), δ¹³C and δ¹⁸O in cellulose chronologies obtained for the period 1779–2007 and cell wall thickness (CWT) for 1900–2008. All of these parameters agree well between each other in the high-frequency variability, while the low-frequency climate information shows systematic differences. The correlation analysis with temperature and precipitation data from the closest weather station and gridded data revealed that annual TRW, MXD, CWT, and δ¹³C data contain a strong summer temperature signal, while δ¹⁸O in cellulose represents a mixed summer and winter temperature and precipitation signal. The temperature and precipitation reconstructions from the Belukha ice core and Teletskoe lake sediments were used to investigate the correspondence of different independent proxies. Low frequency patterns in TRW and δ¹³C chronologies are consistent with temperature reconstructions from nearby Belukha ice core and Teletskoe lake sediments showing a pronounced warming trend in the last century. Their combination could be used for the regional temperature reconstruction. The long-term δ¹⁸O trend agrees with the precipitation reconstruction from the Teletskoe lake sediment indicating more humid conditions during the twentieth century. Therefore, these two proxies could be combined for the precipitation reconstruction.  相似文献   

Optical and near-infrared colours as a discriminant of the age and metallicity of stellar populations     

David Carter  Daniel J. B. Smith  Susan M. Percival  Ivan K. Baldry  Christopher A. Collins  Philip A. James  Maurizio Salaris  Chris Simpson  John P. Stott  Bahram Mobasher 《Monthly notices of the Royal Astronomical Society》2009,397(2):695-708

We present a comprehensive analysis of the ability of current stellar population models to reproduce the optical ( ugriz ) and near-infrared ( JHK ) colours of a small sample of well-studied nearby elliptical and S0 galaxies. We find broad agreement between the ages and metallicities derived using different population models, although different models show different systematic deviations from the measured broad-band fluxes. Although it is possible to constrain simple stellar population models to a well-defined area in age–metallicity space, there is a clear degeneracy between these parameters even with such a full range of precise colours. The precision to which age and metallicity can be determined independently, using only broad-band photometry with realistic errors, is  Δ[Fe/H]≃ 0.18  and  Δlog Age ≃ 0.25  . To constrain the populations and therefore the star formation history further, it will be necessary to combine broad-band optical–IR photometry with either spectral line indices, or else photometry at wavelengths outside this range.  相似文献   

Recovering the real-space correlation function from photometric redshift surveys     

Pablo Arnalte-Mur  Alberto Fernández-Soto  Vicent J. Martínez  Enn Saar  Pekka Heinämäki  Ivan Suhhonenko 《Monthly notices of the Royal Astronomical Society》2009,394(3):1631-1639

Measurements of clustering in large-scale imaging surveys that make use of photometric redshifts depend on the uncertainties in the redshift determination. We have used light-cone simulations to show how the deprojection method successfully recovers the real-space correlation function when applied to mock photometric redshift surveys. We study how the errors in the redshift determination affect the quality of the recovered two-point correlation function. Considering the expected errors associated with the planned photometric redshift surveys, we conclude that this method provides information on the clustering of matter useful for the estimation of cosmological parameters that depend on the large-scale distribution of galaxies.  相似文献   

Description and classification of RC 110, a new ordinary chondrite from Roosevelt County, New Mexico, USA     

Lena Boeck  Klaus Keil  Ivan E. Wilson 《Chemie der Erde / Geochemistry》2009,69(3):287-290

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Holocene environments and climate in the Mongolian Altai reconstructed from the Hoton-Nur pollen and diatom records: a step towards better understanding climate dynamics in Central Asia   总被引：1，自引：0，他引：1  

Natalia Rudaya  Pavel Tarasov  Nadezhda Dorofeyuk  Nadia Solovieva  Ivan Kalugin  Andrei Andreev  Andrei Daryin  Bernhard Diekmann  Frank Riedel  Narantsetseg Tserendash  Mayke Wagner 《Quaternary Science Reviews》2009,28(5-6):540-554

This study presents the results of the palynological and diatom analyses of the sediment core recovered in Hoton-Nur Lake (48°37′18″N, 88°20′45″E, 2083 m) in 2004. Quantitative reconstruction of the Holocene vegetation and climate dynamics in the semiarid Mongolian Altai suggests that boreal woodland replaced the primarily open landscape of northwestern Mongolia at about 10 kyr BP (1 kyr = 1000 cal yr) in response to a noticeable increase in precipitation from 200–250 mm/yr to 450–550 mm/yr. A decline of the forest vegetation and a return to a predominance of open vegetation types occurred after 5 kyr BP when precipitation sums decreased to 250–300 mm/yr. Prior to 11.5 kyr BP diatom concentrations are relatively low and the lake is dominated by planktonic Cyclotella and small Fragilariaceae, suggesting the existence of a relatively deep and oligotrophic/mesotrophic lake. The great abundance of Staurosirella pinnata from the beginning of the record until 10.7 kyr BP might imply intensified erosion processes in the catchment and this is fully consistent with the presence of scarce and dry vegetation and the generally arid climate during this period. From about 10.7 kyr BP, more planktonic diatom taxa appeared and increased in abundance, indicating that the lake became more productive as diatom concentration increased. This change correlates well with the development of boreal woodland in the catchment. Decrease in precipitation and changes in the vegetation towards steppe are reflected by the rapid increase in Aulacoseira distans from about 5 kyr BP. The Holocene pollen and diatom records do not indicate soil and vegetation cover disturbances by the anthropogenic activities, implying that the main transformations of the regional vegetation occurred as a result of the natural climate change. Our reconstruction is in agreement with the paleomonsoon records from China, demonstrating an abrupt strengthening of the summer monsoon at 12 kyr BP and an associated increase in precipitation and in lake levels between 11 and 8 kyr BP, followed by the stepwise attenuation of the monsoon circulation and climate aridization towards the modern level. The records from the neighboring areas of Kazakhstan and Russia, situated west and north of Hoton-Nur, demonstrate spatially and temporally different Holocene vegetation and climate histories, indicating that the Altai Mountains as a climate boundary are of pivotal importance for the Holocene environmental and, possibly, habitation history of Central Asia.  相似文献   

Robotic optical telescopes global network MASTER II. Equipment, structure, algorithms     

Victor G. Kornilov  Vladimir M. Lipunov  Evgeny S. Gorbovskoy  Aleksander A. Belinski  Dmitry A. Kuvshinov  Natalia V. Tyurina  Nikolai I. Shatsky  Anatoly V. Sankovich  Aleksander V. Krylov  Pavel V. Balanutsa  Vadim V. Chazov  Artem S. Kuznetsov  Dmitry S. Zimnuhov  Victor A. Senik  Andrey G. Tlatov  Aleksander V. Parkhomenko  Denis V. Dormidontov  Vadim V. Krushinsky  Ivan S. Zalozhnyh  Aleksander A. Popov  Sergey A. Yazev  Nikolai M. Budnev  Kirill I. Ivanov  Evgeny N. Konstantinov  Oleg A. Gress  Oleg V. Chvalaev  Vladimir V. Yurkov  Yury P. Sergienko  Irina P. Kudelina 《Experimental Astronomy》2012,33(1):173-196

Presented paper describes the basic principles and features of the implementation of a robotic network of optical telescopes MASTER, designed to study the prompt (simultaneous with gamma radiation) optical emission of gamma-ray bursts and to perform the sky survey to detect unknown objects and transient phenomena. With joint efforts of Sternberg astronomical institute, High altitude astronomical station of the Pulkovo observatory, Ural state university, Irkutsk state university, Blagoveshchensk pedagogical university, the robotic telescopes MASTER?II near Kislovodsk, Yekaterinburg, Irkutsk and Blagoveshchensk were installed and tested. The network spread over the longitudes is greater than 6?h. A further expansion of the network is considered.  相似文献   

Adiabatic chaos in the Prometheus–Pandora system     

Ivan I. Shevchenko 《Monthly notices of the Royal Astronomical Society》2008,384(3):1211-1220

The chaotic orbital motion of Prometheus and Pandora, the 16th and 17th satellites of Saturn, is studied. Chaos in their orbital motion, as found by Goldreich & Rappaport and Renner & Sicardy, is due to interaction of resonances in the resonance multiplet corresponding to the 121:118 commensurability of the mean motions of the satellites. It is shown rigorously that the system moves in adiabatic regime. The Lyapunov time (the 'time horizon of predictability' of the motion) is calculated analytically and compared to the available numerical–experimental estimates. For this purpose, a method of analytical estimation of the maximum Lyapunov exponent in the perturbed pendulum model of non-linear resonance is applied. The method is based on the separatrix map theory. An analytical estimate of the width of the chaotic layer is made as well, based on the same theory. The ranges of chaotic diffusion in the mean motion are shown to be almost twice as big compared to previous estimates for both satellites.  相似文献   

Panel Discussion on the Classification and Terminology of Stellar Populations     

Ivan R. King 《Astrophysics and Space Science》1999,267(1-4):373-384

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Effects of aperture on Marchenko focussing functions and their radiation behaviour at depth     

Yanadet Sripanich  Ivan Vasconcelos 《Geophysical Prospecting》2019,67(2):443-454

A focussing function is a specially constructed field that focusses on to a purely downgoing pulse at a specified subsurface position upon injection into the medium. Such focussing functions are key ingredients in the Marchenko method and in its applications such as retrieving Green's functions, redatuming, imaging with multiples and synthesizing the response of virtual sources/receiver arrays at depth. In this study, we show how the focussing function and its corresponding focussed response at a specified subsurface position are heavily influenced by the aperture of the source/receiver array at the surface. We describe such effects by considering focussing functions in the context of time-domain imaging, offering explicit connections between time processing and Marchenko focussing. In particular, we show that the focussed response radiates in the direction perpendicular to the line drawn from the centre of the surface data array aperture to the focussed position in the time-imaging domain, that is, in time-migration coordinates. The corresponding direction in the Cartesian domain follows from the sum (superposition) of the time-domain direction and the directional change due to time-to-depth conversion. Therefore, the result from this study provides a better understanding of focussing functions and has implications in applications such as the construction of amplitude-preserving redatuming and imaging, where the directional dependence of the focussed response plays a key role in controlling amplitude distortions.  相似文献   

Seismic performance of masonry walls retrofitted with steel reinforced grout          下载免费PDF全文

Stefano De Santis  Paolo Casadei  Gerardo De Canio  Gianmarco de Felice  Marialaura Malena  Marialuisa Mongelli  Ivan Roselli 《地震工程与结构动力学》2016,45(2):229-251

An innovative solution for the seismic protection of existing masonry structures is proposed and investigated through shake table tests on a natural scale wall assemblage. After a former test series carried out without reinforcement, the specimen was retrofitted using Steel Reinforced Grout. The strengthening system comprises horizontal strips of ultra‐high strength steel cords, externally bonded to the masonry with hydraulic lime mortar, and connectors to transversal walls, applied within the thickness of the plaster layer. In order to assess the seismic performance of the retrofitted wall, natural accelerograms were applied with increasing intensity up to failure. Test results provide a deep understanding of the effectiveness of mortar‐based composites for improving the out‐of‐plane seismic capacity of masonry walls, in comparison with traditional reinforcements with steel tie‐bars. The structural implications of the proposed solution in terms of dynamic properties and damage development under earthquake loads are also discussed.Copyright © 2015 John Wiley & Sons, Ltd.  相似文献