Structure of the suprrnova remnant 3C 58 and its neighborhood     

G. G. Aivazyan  A. M. Aslanyan  A. G. Gulyan  V. P. Ivanov  R. M. Martirosyan  K. S. Stankevich  S. P. Stolyarov 《Astrophysics》1989,30(3):285-288

Institute of Radio Physics and Electronics, Armenian Academy of Sciences; Scientific Research Institute of Radio Physics and Physics of the Ionosphere, Gor'kii. Translated from Astrofizika, Vol. 30, No. 3, pp. 470–475, May–June, 1989.  相似文献   

First Palaeozoic arachnid from Portugal and implications for Carboniferous palaeobiogeography     

Pedro Correia  J. Brendan Murphy  Artur A. S  Rúben Domingos  Deolinda Flores 《Geological Journal》2013,48(1):101-107

The first occurrence of arachnids (Aphantomartus pustulatus) in the Carboniferous strata of Portugal is documented and its palaeobiogeographic significance is assessed. The Aphantomartidae species are thought to be native to Central Europe where its oldest example is recorded in Middle–Upper Mississippian strata. Known occurrences are preserved along the flanks of mountains such as the Appalachian Mountains, the Cantabrian Mountains and the Valongo Anticline (Portugal, Iberian Massif) and provide clear evidence that the Aphantomartidae species probably lived in upland or mountainous environments. The Iberian Massif may have served as a ‘link’ between the migration routes of several terrestrial animals from North America and Eurasia, and this linkage constrains the palaeogeographic and palaeoenvironmental conditions in equatorial Pangaea during the Carboniferous and Early Permian. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Geodetic monitoring of tectonic deformation in the Australian region     

Artur Stolz  Kurt Lambeck 《Australian Journal of Earth Sciences》2013,60(3-4):411-422

A number of geodetic techniques exist for measuring instantaneous crustal motions and deformations. Over distances of a few hundred kilometres, conventional terrestrial methods can achieve accuracies of about 1–2 parts in 10⁶ for horizontal positions, but most existing triangulation networks in Australia are of lower accuracies. Geodetic levelling can provide height‐difference measurements with an accuracy of a few mm for points separated by about 100 km, but actual accuracies are often much lower than this. For points separated by longer distances, from a few 100 km to several 1000 km, space techniques can provide precisions of 5–10 cm. Two experiments carried out in Australia confirm that these precisions can be reached. A laser ranging experiment between sites near Canberra and Perth produced a baseline that is precise to better than 10 cm, and a radio‐interferometry experiment between Canberra, Parkes and Sydney produced baselines with precisions of 10 cm. Further evaluation of both systems is required, but the present results indicate that crustal deformations of the order of 10 cm can be measured with repeat surveys.  相似文献   

Radio astronomical observations of the occulatation of the Crab nebula by the Moon on January 26, 1983     

M. I. Agafonov  A. M. Aslanyan  A. P. Barabanov  I. T. Bubukin  A. G. Gulyan  V. P. Ivanov  R. M. Martirosyan  I. A. Malyshev  K. S. Stankevich  S. P. Stolyarov 《Astrophysics》1984,21(2):503-507

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Fate of trace elements during alteration of uraninite in a hydrothermal vein-type U-deposit from Marshall Pass, Colorado, USA     

Artur P. Deditius 《Geochimica et cosmochimica acta》2007,71(20):4954-4973

Alteration of uraninite from a hydrothermal vein-type U-deposit in Marshall Pass, Colorado, has been examined by electron microprobe analysis in order to investigate the release and migration of trace elements W, As, Mo, Zr, Pb, Ba, Ce, Y, Ca, Ti, P, Th, Fe, Si, Al, during alteration, under both reducing and oxidizing conditions. The release of trace elements from uraninite is used to establish constraints on the release of fission product elements from the UO₂ in spent nuclear fuels. Uraninite occurs with two different textures: (1) colloform uraninite and (2) fine-grained uraninite. The colloform uraninite contains 1.04-1.75 wt% of WO₃, 0.16-1.70 wt% of As₂O₃, 0.06-0.88 wt% of MoO₃; whereas, the fine-grained uraninite retains 2.25-4.93 wt% of WO₃, up to 5.76 wt% of MoO₃, and 0.26-0.60 wt% of As₂O₃. The near constant concentration of incompatible W in the colloform uraninite suggests W-incorporation into the uraninite structure or homogeneous distribution of W-rich nano-domains. Incorporation of W and Mo into the uraninite and subsequent precipitation of uranyl phases bearing these elements are critically important to understanding the release and migration of Cs during the corrosion of spent nuclear fuel, as there is a strong affinity of Cs with W and Mo. Zoning in the colloform texture is attributed to variation in the amount of impurities in uraninite. For unaltered zones, the calculated amount of oxygen ranges from 2.08 to 2.32 [apfu, (atom per formula unit)] and defines the stoichiometry as UO_2+x and U₄O₉; whereas, for the altered zones of the colloform texture, the oxygen content is 2.37-2.48 [apfu], which is probably due to the inclusion of secondary uranyl phases, mainly schoepite. The supergene alteration resulted in precipitation of secondary uranyl minerals at the expense of uraninite. Four stages of colloform uraninite alteration are proposed: (i) formation of an oxidized layer at the rim, (ii) corrosion of the oxidized layer, (iii) precipitation of U⁶⁺-phases with well-defined cleavage, and (iv) fracture of the uraninite surface along the cleavage planes of the U⁶⁺-phases.  相似文献   

Genetic and metamorphic conditions constrained by fluid inclusions from Paleoproterozoic (c. 1.8 Ga) magnesite ore deposits, NE Brazil     

Luiz Henrique Ronchi  Clvis Vaz Parente  Kazuo Fuzikawa  Artur Bastos Neto 《Journal of South American Earth Sciences》2008,25(4):492-500

Precambrian magnesite occurrences hosted by metadolomites from the Orós belt, Ceará, Brazil, are part of a greenschist–amphibolite, metavolcano-sedimentary terrain, dated at 1.8 Ga, cut by Meso- to Neoproterozoic Brasiliano granites and Neoproterozoic basic sills. These rocks were affected by a shear zone between 580 and 500 Ma. The magnesite-bearing marbles can be grouped as medium-grained (1–9 mm) at the Riacho Fundo ore deposit or sparry magnesite (1–15 cm) at the Cabeça de Negro ore deposit. The sparry magnesite shows textural characteristics related to original sedimentary structures. Both types of magnesite-bearing marbles contain aqueous and aqueous-carbonic fluid inclusions that yield homogenization temperatures between 170 and 370 °C. Applying a pressure correction, these temperatures are compatible with the evolution from greenschist to amphibolite facies metamorphic conditions, as described in previous work on the Orós region. It also agrees with data in specialized literature on the metamorphism of carbonate rocks. Fluid inclusion distribution, composition, and physical-chemical characteristics suggest temperature increase, probably related to metamorphism on these rocks. The medium-grained magnesite records partial contamination of CO₂-rich inclusions by relict carbonaceous material (bitumen, hydrocarbons?) that favors, but does not confirm, a syngenetic sedimentary origin and could have caused the lowering of CO₂ melting point in these inclusions. Therefore, though textural evidence points to a sedimentary-diagenetic model, fluid inclusions record conditions of a metamorphic event.  相似文献   

Zur geomorphologischen und geologischen Entwicklungsgeschichte der Ostabdachung der Zentralalpen in der Miozänzeit     

Artur Winkler 《International Journal of Earth Sciences》1926,17(4):291-310

Ohne Zusammenfassung  相似文献   

The stability of annite+quartz: reversed experimental data for the reaction 2 annite+3 quartz=2 sanidine+3 fayalite +2 H2O     

E. Dachs  Artur Benisek 《Contributions to Mineralogy and Petrology》1995,121(4):380-387

Reversals for the reaction 2 annite+3 quartz=2 sanidine+3 fayalite+2 H₂O have been experimentally determined in cold-seal pressure vessels at pressures of 2, 3, 4 and 5?kbar, limiting annite +quartz stability towards higher temperatures. The equilibrium passes through the temperature intervals 500–540°?C (2?kbar), 550–570°?C (3?kbar), 570–590°?C (4?kbar) and 590–610°?C (5?kbar). Starting materials for most experiments were mixtures of synthetic annite +fayalite+sanidine+quartz and in some runs annite+quartz alone. Microprobe analyses of the reacted mixtures showed that the annites deviate slightly from their ideal Si/Al ratio (Si per formula unit ranges between 2.85 and 2.92, Al^VI between 0.06 and 0.15). As determined by Mössbauer spectroscopy, the Fe³⁺ content of annite in the assemblage annite+fayalite +sanidine+quartz is around 5–7%. The experimental data were used to extract the thermodynamic standard state enthalpy and entropy of annite as follows: H ⁰ _f,?Ann =?5125.896±8.319 [kJ/mol] and S ⁰ _Ann=432.62±8.89 [J/mol/K] (consistent with the Holland and Powell 1990 data set), and H ⁰ _f,Ann =?5130.971±7.939 [kJ/mol] and S ⁰ _Ann=424.02±8.39 [J/mol/K] (consistent with the TWEEQ data base, Berman 1991). The preceeding values are close to the standard state properties derived from hydrogen sensor data of the redox reaction annite=sanidine+magnetite+H ₂ (Dachs 1994). The experimental half-reversal of Eugster and Wones (1962) on the annite +quartz breakdown reaction could not be reproduced experimentally (formation of annite from sanidine+fayalite+quartz at 540°?C/1.035?kbar/magnetite-iron buffer) and probable reasons for this discrepancy remain unclear. The extracted thermodynamic standard state properties of annite were used to calculate annite and annite+quartz stabilities for pressures between 2 and 5?kbar.  相似文献   

Die Tektonik des Lüderich-Gangzuges im Bergischen Land     

Artur Jungfels 《International Journal of Earth Sciences》1955,44(1):422-442

Zusammenfassung Aufgrund struktureller Untersuchungen wurde versucht, Natur und Altersfolge der Störungen des variszischen Lüderich-Gangzuges und ihre Beziehungen zur Blei-Zinkerzführung zu klären.Träger der Vererzung sind ältere Auf- und Abschiebungen, in deren Bilbungszeit die Vererzung fällt. Die Erzgänge wurden durch jüngere Störungen zerstückelt und auseinandergezerrt.  相似文献   

The application of two‐dimensional hydrodynamic models for underwater archaeological finds from the Vistula River in Warsaw,Poland          下载免费PDF全文

Hubert Kowalski  Artur Magnuszewski  Artur Radecki‐Pawlik 《水文研究》2018,32(18):2888-2900

Low water levels occurring on the Warsaw section of the Vistula River during droughts in 2012 and 2015 stirred considerable interest by exposing parts of the riverbed. The river's low flow discharge created favourable conditions for archaeologists who, from the river's bottom, managed to salvage sculptures, architectural artefacts, and military accessories dating back to the middle of the 17th century. Literature shows that archaeological finds at the bottom of a major lowland river are unique and are attributed to very specific hydrological and geological conditions. Embankments and works meant to regulate the channel of the Vistula River in Warsaw narrowed the channel and accelerated the erosion of the river's bottom. A comparison of rating curves created between 1919 and 2015 shows that the river's bottom had lowered by 225 cm. The diameter of sediment particles that could be moved at maximum shear stress has been calculated using the Meyer–Peter and Muller formula. According to the calculated shear stress corresponding to the highest historical flood of 1844 particles smaller than 0.05 m were transported down the river, and it is true that artefacts of that size had not been collected at the site. Taking into consideration the very specific geological and hydrological conditions, we believe that finding so many 17th century artefacts with a well‐documented history at a site at the bottom of major lowland river with intensive channel processes is indeed unique. Additionally, it is the first time that results of hydrodynamic modelling have been successfully used for archaeological survey to define the critical shear stress and the smallest diameter of artefacts, which could remain stable on a river's bottom.  相似文献