Challenging some tenets of Regional Climate Modelling   总被引：5，自引：0，他引：5  

R. Laprise  R. de Elía  D. Caya  S. Biner  P. Lucas-Picher  E. Diaconescu  M. Leduc  A. Alexandru  L. Separovic 《Meteorology and Atmospheric Physics》2008,100(1-4):3-22

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Magmagenesis in a subduction-related post-collisional volcanic arc segment: the Ukrainian Carpathians   总被引：6，自引：0，他引：6  

Ioan Seghedi  Hilary Downes  Zolt  n P  cskay  Matthew F. Thirlwall  Alexandru Szak  cs  Michail Prychodko  David Mattey 《Lithos》2001,57(4):237-262

Calc-alkaline magmatism in the south-west Ukraine occurred between 13.8 and 9.1 Ma and formed an integral part of the Neogene subduction-related post-collisional Carpathian volcanic arc. Eruptions occurred contemporaneously in two parallel arcs (here termed Outer Arc and Inner Arc) in the Ukrainian part of the Carpathians. Outer Arc rocks, mainly andesites, are characterized by LILE enrichment (e.g. K and Pb), Nb depletion, low compatible trace element abundances, high ⁸⁷Sr/⁸⁶Sr, high δ¹⁸O and low ¹⁴³Nd/¹⁴⁴Nd isotopic ratios (0.7085–0.7095, 7.01–8.53, 0.51230–0.51245, respectively). Inner Arc rocks are mostly dacites and rhyolites with some basaltic and andesitic lavas. They also show low compatible element abundances but have lower ⁸⁷Sr/⁸⁶Sr, δ¹⁸O and higher ¹⁴³Nd/¹⁴⁴Nd ratios (0.7060–0.7085, 6.15–6.64, 0.5125–0.5126, respectively) than Outer Arc rocks. Both high-Nb and low-Nb lithologies are present in the Inner Arc. Based on the LILE enrichment (especially Pb), a higher fluid flux is suggested for the Outer Arc magmas compared with those of the Inner Arc.

Combined trace element and Sr–Nd–O isotopic modelling suggests that the factors which controlled the generation and evolution of magmas were complex. Compositional differences between the Inner and Outer Arcs were produced by introduction of variable proportions of slab-derived sediments and fluids into a heterogeneous mantle wedge, and by different extents of upper crustal contamination. Degrees of magmatic fractionation also differed between the two arcs. The most primitive magmas belong to the Inner Arc. Isotopic modelling shows that they can be produced by adding 3–8% subducted terrigenous flysch sediments to the local mantle wedge source. Up to 5% upper crustal contamination has been modelled for fractionated products of the Inner Arc. The geochemical features of Outer Arc rocks suggest that they were generated from mantle wedge melts similar to the Inner Arc primitive magmas, but were strongly affected by both source enrichment and upper crustal contamination. Assimilation of 10–20% bulk upper crust is required in the AFC modelling, assuming an Inner Arc parental magma. We suggest that magmagenesis is closely related to the complex geotectonic evolution of the Carpathian area. Several tectonic and kinematic factors are significant: (1) hydration of the asthenosphere during subduction and plate rollback directly related to collisional processes; (2) thermal disturbance caused by ascent of hot asthenospheric mantle during the back-arc opening of the Pannonian Basin; (3) clockwise translational movements of the Intracarpathian terranes, which facilitated eruption of the magmas.  相似文献   

On the period variability of GP andromedae     

Alexandru Pop  Victor Liteanu  Dan Moldovan 《Astrophysics and Space Science》2003,284(4):1207-1222

The present paper deals with the pulsation period variability of the high-amplitude δ Scuti star GP Andromedae using a data set covering a time base of 26.9 years. The possibility of a periodic component (reflecting the light-time effect induced by a hypothetic binarity) in the O-C curve is inferred. The presence of this periodicity in the period variation of GP And leads to a diminution of the discrepancy between predicted and observed relative period change rates. The hypothesis of the existence of an unseen companion is discussed. The statistical analysis of the final O-C residuals distribution, indicates their normal or close to normal character. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Calculation of the cosmogenic nuclide production topographic shielding scaling factor for large areas using DEMs     

Alexandru T. Codilean 《地球表面变化过程与地形》2006,31(6):785-794

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The Stability of the Light Curve of DL Cassiopeiae Between 1959–1997     

Alexandru Pop  Vlad Turcu  Steliana Codreanu 《Astrophysics and Space Science》2004,293(4):393-413

A variability survey on the shape of the light curve of the classical Cepheid DL Cas has been performed on the basis of Johnson V photometry data covering about 38 years. The input parameters (mean magnitude, pulsation frequency and period, light curve amplitude, harmonics amplitudes, Fourier type structural parameters) for our study were determined through the Fourier decomposition technique applied to each data set. The analysis of the outcoming time series, using different and complementary methods, seems to indicate the constancy of these parameters within the precision limits of the available data, although the hypothesis of the presence of a low level variability cannot be excluded. The only exception is the pulsation period, which displays a possible increasing trend with a rate of 0.109 ± 0.037 s yr⁻¹. This trend may be, at least partly, an effect of the unequal precision of pulsation period estimated values, corresponding to each considered data set. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Biperiodic orbital period modulation of the W UMa binary system CK Bootis     

Alexandru Pop  Călin Vamoş 《New Astronomy》2012,17(7):667-672

A study of the orbital period variation of the W UMa system CK Bootis is made using an extended observational time base. The biperiodicity of the orbital period modulation is emphasized. Both detected periodicities (24.14 yr and 10.62 yr) cannot be explained through the light-time effect unless the companion would be a white dwarf as suggested by other authors, too. Moreover, we also argue that, nowadays at least, it seems that there is no causal relation between the orbital period variation and the recently discovered visual companion. Consequently, we infer that at least one of the two periodicities may be related to the magnetic activity cycles in the component stars of CK Boo, while the other periodicity could be related to the presence of a fourth companion in the system.  相似文献   

Short-lived eruptive episodes during the construction of a Na-alkalic basaltic field (Perşani Mountains,SE Transylvania,Romania)     

Ioan Seghedi  Răzvan-Gabriel Popa  Cristian G. Panaiotu  Alexandru Szakács  Zoltán Pécskay 《Bulletin of Volcanology》2016,78(10):69

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Assessment of vulnerability for rockfalls in Cozia Gorge (Southern Carpathians,Romania)     

Ovreiu  Adriana Bianca  Bărsoianu  Iulian Andrei  Nistor  Constantin  Nedelea  Alexandru  Comănescu  Laura 《Natural Hazards》2019,99(1):117-140

Natural Hazards - Rockfalls represents a sudden, extremely important geomorphological hazard and may become a threat for people’s life, as well as goods and transport. The present study aims...  相似文献   

Cosmogenic 21Ne analysis of individual detrital grains: Opportunities and limitations     

Alexandru T. Codilean  Paul Bishop  Trevor B. Hoey  Finlay M. Stuart  Derek Fabel 《地球表面变化过程与地形》2010,35(1):16-27

We use a numerical model describing cosmogenic nuclide acquisition in sediment moving through the upper Gaub River catchment to evaluate the extent to which aspects of source area geomorphology and geomorphological processes can be inferred from frequency distributions of cosmogenic ²¹Ne (²¹Ne_c) concentrations in individual detrital grains. The numerical model predicts the pathways of sediment grains from their source to the outlet of the catchment and calculates the total ²¹Ne_c concentration that each grain acquires along its pathway. The model fully accounts for variations in nuclide production due to changes in latitude, altitude and topographic shielding and allows for spatially variable erosion and sediment transport rates. Model results show that the form of the frequency distribution of ²¹Ne_c concentrations in exported sediment is sensitive to the range and spatial distribution of processes operating in the sediment's source areas and that this distribution can be used to infer the range and spatial distribution of erosion rates that characterise the catchment. The results also show that lithology can affect the form of the ²¹Ne_c concentration distribution indirectly by exerting control on the spatial pattern of denudation in a catchment. Model results further indicate that the form of the distribution of ²¹Ne_c concentrations in the exported sediment can also be affected by the acquisition of ²¹Ne_c after detachment from bedrock, in the diffusive (hillslope) and/or advective (fluvial) domains. However, for such post‐detachment nuclide acquisition to be important, this effect needs to at least equal the nuclide acquisition prior to detachment from bedrock. Copyright © 2009 John Wiley and Sons, Ltd.  相似文献   

(137)Cs baseline levels in the Mediterranean and Black Sea: a cross-basin survey of the CIESM Mediterranean Mussel Watch programme     

Thébault H  Rodriguez Y Baena AM  Andral B  Barisic D  Albaladejo JB  Bologa AS  Boudjenoun R  Delfanti R  Egorov VN  El Khoukhi T  Florou H  Kniewald G  Noureddine A  Patrascu V  Pham MK  Scarpato A  Stokozov NA  Topcuoglu S  Warnau M 《Marine pollution bulletin》2008,57(6-12):801-806

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify (137)Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured (137)Cs levels were found to be very low (usually < 1 Bq kg(-1) wet wt) (137)Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.  相似文献