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51.
Calculations are presented which show that, contrary to previous suggestions, ion flow velocity differences do not have a significant effect on the thermal structure of the midlatitude topside ionosphere. 相似文献
52.
D. Gorman-Lewis S. Skanthakumar M.P. Jensen S. Mekki K.L. Nagy L. Soderholm 《Chemical Geology》2008,253(3-4):136-140
Ambient-temperature environments in which dissolved silica and U(VI) are present may lack the conditions necessary to readily form crystalline uranyl-silicate phases; however amorphous phases, as defined by the absence of well-defined Bragg reflections in powder X-ray diffraction patterns, are kinetically favored when solution saturation levels are appropriate. Such amorphous uranyl-silicates may be related to the crystalline phases predicted to be thermodynamically stable and influence the mobility of U in the environment. To investigate amorphous uranyl-silicates and their relation to crystalline phases we precipitated solids from solutions containing 0.05 M UO2(ClO4)2 and 0.1 M Na2SiO3 adjusted to pH values from 2.2 to 9 and allowed the precipitates to age in their mother liquors for approximately 6 weeks at 22 °C. We compared the chemical composition, X-ray diffraction patterns, and Fourier transform infrared spectra of the precipitates to those of the crystalline phases predicted by thermodynamic modeling. The precipitates were amorphous with U:Si ratios of 0.8 ± 0.1. Their FTIR spectra revealed changes in the UO22+ and SiO44− vibrations as a function of pH that are consistent with a shift in mid-range structural linkages from those similar to soddyite to those more like Na-boltwoodite. Structural H2O, OH, and SiO3OH3− vibrations do not change as a function of pH and are consistent with a mixture of soddyite-like and Na-boltwoodite-like features. Six weeks of aging at ambient temperature is enough time for the precipitate structures to rearrange and adopt mid-range structural linkages characteristic of crystalline phases predicted by thermodynamic modeling. 相似文献
53.
Attila Demény Ramón Casillas Julio de La Nuez Géza Nagy 《Chemie der Erde / Geochemistry》2008,68(4):369-381
Carbonate xenoliths containing olivine and rimmed by kaersutitic amphibole were collected in basaltic rocks of the Basal Complex of La Palma. The mineralogical composition and microscopic appearance may suggest a relationship with carbonatites in general, thus a major element, trace element and stable isotope study was conducted to investigate the origin of the carbonate formation. Based on electron microprobe analyses, the carbonate is calcite with up to 6.3 wt% MgO and 7.2 wt% SiO2. The elevated SiO2 content may suggest a melt origin for the carbonate. However, the C and O isotope compositions of the carbonate xenoliths (δ13C and δ18O around −1‰ and 13‰, respectively) are similar to those of calcite veins and amygdales in basaltic rocks of the Basal Complexes of La Palma and Fuerteventura and are interpreted as produced by fluid degassing and metasomatism by CO2-H2O fluid derived from mobilization of sedimentary material. Trace element contents determined by laser-ablation ICP-MS analyses support the assumed origin, thus, the relationship with carbonatitic melts can be excluded. Based on trace element compositions, the amphibole surrounding the xenoliths is not related genetically to the carbonate. The elevated SiO2 content of the calcite can be attributed to submicron relics of pyroxene, thus, the use of this feature as an evidence for melt origin is questionable. 相似文献
54.
55.
Győző Szeidovitz Gergely Surányi Katalin Gribovszki Zoltán Bus Szabolcs Leél-Őssy Zsolt Varga 《Journal of Seismology》2008,12(1):21-33
The examination of speleothems in the Hajnóczy and Baradla caves (northeastern Hungary) allows estimating an upper limit for
horizontal peak ground acceleration generated by paleoearthquakes. The density, the Young’s modulus and the tensile failure
stress of the samples originating from a broken speleothem have been measured in a laboratory, whereas the natural frequency
of intact speleothems was determined by in situ observations. The value of horizontal ground acceleration resulting in failure,
the natural frequency and the inner friction coefficient of speleothems were assessed by theoretical calculations. The ages
of the samples taken from a stalagmite 5.1 m in height (Baradla cave) have been determined by inductively coupled plasma mass
spectrometry analysis and alpha spectrometry. The measured ages fall between 140,000 and 70,000 years; therefore, we assume
the speleothem has not been changed since the end of this time interval. According to our modeling results, this speleothem
has not been excited by a horizontal acceleration higher than 0.05 g during the last 70,000 years. 相似文献
56.
B. Érdi I. Nagy Zs. Sándor Á. Süli G. Fröhlich 《Monthly notices of the Royal Astronomical Society》2007,381(1):33-40
The size distribution of the stability region around the Lagrangian point L 4 is investigated in the elliptic restricted three-body problem as the function of the mass parameter and the orbital eccentricity of the primaries. It is shown that there are minimum zones in the size distribution of the stability regions, and these zones are connected with the secondary resonances between the frequencies of librational motions around L 4 . The results can be applied to hypothetical Trojan planets for predicting values of the mass parameter and the eccentricity for which such objects can be expected or their existence is less probable. 相似文献
57.
Arnold Gucsik Taro Endo Hirotsugu Nishido Kiyotaka Ninagawa Masahiro Kayama Szaniszló Bérczi Szabolcs Nagy Péter Ábrahám Yuki Kimura Hitoshi Miura Ildikó Gyollai Irakli Simonia Péter Rózsa József Posta Dániel Apai Krisztián Mihályi Mihály Nagy Ulrich Ott 《Meteoritics & planetary science》2013,48(12):2577-2596
Highly forsteritic olivine (Fo: 99.2–99.7) in the Kaba meteorite emits bright cathodoluminescence (CL). CL spectra of red luminescent forsterite grains have two broad emission bands at approximately 630 nm (impurity center of divalent Mn ions) in the red region and above 700 nm (trivalent Cr ions) in the red–IR region. The cores of the grains show CL blue luminescence giving a characteristic broad band emission at 400 nm, also associated with minor red emissions related to Mn and Cr ions. CL color variation of Kaba forsterite is attributed to structural defects. Electron probe microanalyzer (EPMA) analysis shows concentrations of Ca, Al, and Ti in the center of the forsterite grain. The migration of diffusible ions of Mn, Cr, and Fe to the rim of the Kaba meteoritic forsterite was controlled by the hydrothermal alteration at relatively low temperature (estimated at about 250 °C), while Ca and Al ions might still lie in the core. A very unusual phase of FeO (wüstite) was also observed, which may be a terrestrial alteration product of FeNi‐metal. 相似文献
58.
Edit Thamó-Bozsó Gábor Csillag László I. Fodor Pál M. Müller Attila Nagy 《Quaternary Geochronology》2010,5(2-3):120-124
Fluvial, colluvial, and aeolian sediments were dated by optically stimulated luminescence (OSL) on quartz to improve the chronological framework for Quaternary sedimentation and landscape evolution in the forelands of the Vértes Hills (central Hungary). The separated quartz was suitable for age determination based on an OSL SAR protocol. Most samples have asymmetric equivalent dose distributions and OSL ages were calculated by the mean, central, and minimum De values. Considering geomorphology and earlier age data from the area, the central De values seem most appropriate for age calculation. A fan on the geomorphological level QV in the western foreland of the Vértes Hills was deposited 79–75 (±8) ka ago. In the south-eastern foreland an alluvial fan on level QIIb is at most 42 ± 4 ka old. Fluvial incision and aggradation occurred 16–10 (±1) ka ago on the geomorphic surface QIIa. Loess is 14 ± 1 ka old, and slope sedimentation was active 11–9 (±1) ka ago. Our OSL data demonstrate that in the north-western foreland of the Vértes Hills wind remained an important agent after the last glacial times, into the early Holocene (9–8 ± 1 ka) and was able to accumulate large aeolian dunes. 相似文献
59.
Aaron W. Johnson Kevin L. Shelton Jay M. Gregg Ian D. Somerville Wayne R. Wright Zsolt R. Nagy 《Mineralogy and Petrology》2009,96(1-2):1-18
This study provides a regional framework within which studies of ore-related dolomite and dolomite cements may be placed. Fluid inclusion data indicate the presence of three distinct fluids following early dolomitization: 1) a ubiquitous low-temperature, higher salinity fluid found in saddle dolomite; 2) a low-temperature, lower salinity fluid limited to sub-Waulsortian and Waulsortian carbonates; and 3) a higher temperature, lower salinity fluid found in Waulsortian and supra-Waulsortian rocks. Similar fluids have been reported in ore-associated minerals and postmineralization dolomite (Type 1) and in ore-stage carbonates and sphalerite (Types 2 and 3). The halogen geochemistry of included fluids indicates genesis from evaporated seawater. Type 1 fluids are enriched in chloride relative to bromide, reflecting a component of salinity derived via dissolution of halite or from dehydration of seawater. These data suggest that dolomitization and mineralization of Mississippian rocks in the Midlands requires both regionally extensive and localized fluid flow. 相似文献
60.
U. Nagy 《Journal of Geodesy》1979,53(2):179-184
A recurrence relation has been derived to obtain the derivatives required for the Taylor expansion of the theoretical gravity
formula in powers of latitude. The computations using the relationship derived can provide easily all required derivatives
for any reference ellipsoid. 相似文献