Latitudinal variability of the ionosphere and long-term prediction of the maximum usable frequency of the <Emphasis Type="Italic">F</Emphasis> region along direct and reverse paths

We present maximum usable frequency (MUF) calculation results when a radiowave, radiated at a zero angle, is reflected from the ionosphere along direct and reverse paths when the latitudinal variability of the medium is significant. As an example, we consider the Novorossiysk-California path. Calculations were carried out using a “two-point” method and data of the Monthly MUF Prediction for May 1980 and May 1991. The “two-point” method is validated based on a new way of approximated representation of the Watson integral, which is an exact solution of the benchmark problem related to the point source field in a spherically layered medium. It is shown that MUFs along a reverse path are several MHz higher than MUFs along a direct path during the whole day.     

Estimation of air temperature reproduction quality by the MM5 model in the Urals in July

The quality estimation of diurnal air temperature course reproduction by the hydrodynamical MM5 model in the Urals in July is carried out by means of the comparison with the station observational data. The MM5 model reproduces the temperature maximums better than the minimums which are considerably overestimated by the model. The highest accuracy of air temperature reproduction is demonstrated by the model at 03:00, 06:00, 09:00, 12:00, and 24:00, whereas the lowest one, at 15:00, 18:00, and 21:00. The correlation coefficients between the model and actual data vary from 0.74 at 21:00 to 0.87 at 09:00 and 12:00. The autocorrelation functions computed for the actual and model data indicate that the MM5 model reproduces the temperature field with higher quality than the technique based on the inertial properties of the atmosphere.     

Optical chemosensory films on the basis of a photon-crystal opal matrix

Doklady Earth Sciences -     

Gold in the weathering crust at the Suzdal' deposit (Kazakhstan)

A comparative analysis of morphology and geochemistry was made for gold from the primary ores and weathering crust of the Suzdal' gold deposit, Eastern Kazakhstan. The deposit is localized in Carboniferous carbonaceous-terrigenous strata and is of gold-sulfide type. Study of gold from primary ores showed that it occurs mainly in two species: free and so-called invisible. Free gold is crystallomorphic segregations and irregular-shaped grains up to tens of microns in size; it occurs in intergrowths with sulfides, quartz, carbonate, and mica-chlorite aggregate. Most of gold particles have a fineness of 930–980‰, with some grains showing wide variations in composition. Invisible gold (probably chemically combined) is present in fine-acicular arsenopyrite and, less frequently, pyrite.Being transported to the weathering crust, all this gold served as a source for “neogenic” gold of diverse morphologic forms. We recognized crystalline (isometric, prismatic, acicular, and tabular) particles and drusoid gold aggregates in the form of exotic intergrowths of crystallomorphic and sinter-shelly grains. The grains tend to coarsen from bottom to top of the weathering crust. Several generations of gold of different granulometric classes are observed. We have revealed seed and layer growth and dissolution structures in crystals of early generations overgrown with fine grains. All these gold varieties are associated with hypergene minerals. Most of this gold is of high fineness (on the average, 995‰). The hypergene gold particles are chemically homogeneous high-grade, without rims.The results of studies suggest that the high-grade hypergene gold formed in the weathering crust as a result of the dissolution of invisible gold of sulfides and its local redistribution and deposition in oxidizing media. This is also evidenced from the tendency of gold to coarsen from bottom to top of the weathering crust. A distinctive feature of secondary gold is well-expressed crystals and their great diversity.     

Heavy Metals in the Water and Bottom Sediments of the Selenga River Delta

The overall concentration of Cu, Pb, Zn, Cr, Mn, and Fe are determined in the water and bottom sediments of the Selenga River delta. The concentration of Cu, Pb, and Zn is found to decrease in the lower course of the river, at the delta outlet. The concentration of Mn and Fe is found to decrease in the downstream direction from the river's upper course along the investigated delta arms, whereas the concentration of Zn and Cr in certain arms exceeds their concentration in the upper section of the delta.     

LA–ICP–MS Isotopic U–Pb Age of Zircon from the Eldzhurty Granites and Rhyolites at the Tyrnyauz Mo–W Deposit (North Caucasus,Russia)

Doklady Earth Sciences - The isotopic U–Pb ages are estimated for zircons (for the first time by the LA–ICP–MS method) from biotite (Eldzhurty) granites and for the first time...     

U–Pb Isotope Age of Zircon (LA–ICP–MS Method) from Magmatic Rocks and Some Aspects of the Genesis of the Tyrnyauz Mo–W Deposit (North Caucasus)

Geology of Ore Deposits - The authors' determinations of the U–Pb isotopic age of zircon (LA–ICP–MS method) in the main types of igneous rocks emphasize the presence of both...