An improved Lorentzian technique for evaluating resonance characteristics of the Earth-ionosphere cavity     

Vadim C. Mushtak  Earle R. Williams   《Atmospheric Research》2009,91(2-4):188-193

The effectiveness of various formulations of the Lorentzian procedure for estimating Schumann resonance (SR) characteristics of the Earth-ionosphere waveguide from transient electromagnetic signals is tested in the limits of a simplified, spherically uniform model of the resonator. It is shown that the major improvement, in comparison with the “classic” Lorentzian formulation, is achieved by consideration of the intra-modal phase interference. The effect of the “limited frequency dispersion” inherent in the “classic” Lorentzian approach – that is of substantial importance at the lowest SR modes – can be effectively neutralized by interpolating the values for the propagation parameter between the adjacent modal frequencies. Several practical aspects of applying the Lorentzian procedure to transient signals are also discussed.  相似文献   

Selenium deficiency as a consequence of human activity and its correction     

Vadim Ermakov  Larisa Jovanović 《Journal of Geochemical Exploration》2010

Problems of sustainable development in connection with the change of biogeochemical cycle of selenium and overcoming its deficiency in Russia, Serbia, Belarus and other countries are reported. The history of the biological role of selenium as an essential trace element is discussed. A special program of «Overcoming of selenium deficiency» has been developed by researches of Russia, Serbia and Belarus in view of high morbidity rates for cardiovascular, tumor and endemic diseases affecting the population of both the above and some other countries, including children, prevalence of selenium deficiency among livestock species and aggravation of the environmental situation as a result of man-made processes.  相似文献   

Numerical simulation of tides in the World Ocean: 1. Parameterization of the shelf effects     

Dr. Vadim Yu. Gotlib  Prof. Boris A. Kagan 《Ocean Dynamics》1981,34(6):273-283

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Numerical simulation of tides in the World Ocean: 2. Experiments of the sensitivity of the solution to choice of the shelf effect parameterization and to variations in shelf parameters     

Dr. Vadim Yu. Gotlib  Prof. Boris A. Kagan 《Ocean Dynamics》1982,35(1):1-14

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Gaseous transport and deposition of gold in magmatic fluid: evidence from the active Kudryavy volcano, Kurile Islands     

Marina A. Yudovskaya  Vadim V. Distler  Ilya V. Chaplygin  Andrew V. Mokhov  Nikolai V. Trubkin  Sonya A. Gorbacheva 《Mineralium Deposita》2006,40(8):828-848

The distribution of gold in high-temperature fumarole gases of the Kudryavy volcano (Kurile Islands) was measured for gas, gas condensate, natural fumarolic sublimates, and precipitates in silica tubes from vents with outlet temperatures ranging from 380 to 870°C. Gold abundance in condensates ranges from 0.3 to 2.4 ppb, which is significantly lower than the abundances of transition metals. Gold contents in zoned precipitates from silica tubes increase gradually with a decrease in temperature to a maximum of 8 ppm in the oxychloride zone at a temperature of approximately 300°C. Total Au content in moderate-temperature sulfide and oxychloride zones is mainly a result of Au inclusions in the abundant Fe–Cu and Zn sulfide minerals as determined by instrumental neutron activation analysis. Most Au occurs as a Cu–Au–Ag triple alloy. Single grains of native gold and binary Au–Ag alloys were also identified among sublimates, but aggregates and crystals of Cu–Au–Ag alloy were found in all fumarolic fields, both in silica tube precipitates and in natural fumarolic crusts. Although the Au triple alloy is homogeneous on the scale of microns and has a composition close to (Cu,Ni,Zn)₃(Au,Ag)₂, transmission electron microscopy (TEM) shows that these alloy solid solutions consist of monocrystal domains of Au–Ag, Au–Cu, and possibly Cu₂O. Gold occurs in oxide assemblages due to the decomposition of its halogenide complexes under high-temperature conditions (650–870°C). In lower temperature zones (<650°C), Au behavior is related to sulfur compounds whose evolution is strongly controlled by redox state. Other minerals that formed from gas transport and precipitation at Kudryavy volcano include garnet, aegirine, diopside, magnetite, anhydrite, molybdenite, multivalent molybdenum oxides (molybdite, tugarinovite, and ilsemannite), powellite, scheelite, wolframite, Na–K chlorides, pyrrhotite, wurtzite, greenockite, pyrite, galena, cubanite, rare native metals (including Fe, Cr, Mo, Sn, Ag, and Al), Cu–Zn–Fe–In sulfides, In-bearing Pb–Bi sulfosalts, cannizzarite, rheniite, cadmoindite, and kudriavite. Although most of these minerals are fine-grained, they are strongly idiomorphic with textures such as gas channels and lamellar, banded, skeletal, and dendrite-like crystals, characteristic of precipitation from a gas phase. The identified textures and mineral assemblages at Kudryavy volcano can be used to interpret geochemical origins of both ancient and modern ore deposits, particularly gold-rich porphyry and related epithermal systems.  相似文献   

Pressure-induced phase transition in Mg0.8Fe0.2O ferropericlase     

Innokenty Kantor  Leonid Dubrovinsky  Catherine McCammon  Anastasia Kantor  Sakura Pascarelli  Giuliana Aquilanti  Wilson Crichton  Maurizio Mattesini  Rajeev Ahuja  Jailton Almeida  Vadim Urusov 《Physics and Chemistry of Minerals》2006,33(1):35-44

Combined X-ray powder diffraction, Mössbauer, and XANES spectroscopy in situ experiments revealed the transformation of cubic (Mg_0.8Fe_0.2)O ferropericlase to a rhombohedrally distorted phase at 35(1) GPa and room temperature. The Mössbauer spectroscopy results show that the rhombohedral distortion does not involve magnetic ordering. Combined with data from the literature, our results imply that the cubic to rhombodedral transition occurs in (Mg,Fe)O under conditions of non-hydrostatic stress over a wide range of composition (0.2≤x _Fe≤1).  相似文献   

A reconstruction of the tides in the paleocean: Results of a numerical simulation     

Dr. Vadim Yu. Gotlib  Prof. Boris A. Kagan 《Ocean Dynamics》1985,38(2):43-67

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Ferropericlase—a lower mantle phase in the upper mantle     

Gerhard P. Brey  Vadim Bulatov  Andrei Girnis  Jeff W. Harris  Thomas Stachel   《Lithos》2004,77(1-4):655-663

Experiments on compositions along the join MgO–NaA³⁺Si₂O₆ (A=Al, Cr, Fe³⁺) show that sodium can be incorporated into ferropericlase at upper mantle pressures in amounts commonly found in natural diamond inclusions. These results, combined with the observed mineral parageneses of several diamond inclusion suites, establish firmly that ferropericlase exists in the upper mantle in regions with low silica activity. Such regions may be carbonated dunite or stalled and degassed carbonatitic melts. Ferropericlase as an inclusion in diamond on its own is not indicative of a lower mantle origin or of a deep mantle plume. Coexisting phases have to be taken into consideration to decide on the depth of origin. The composition of olivine will indicate an origin from the upper mantle or border of the transition zone to the lower mantle and whether it coexisted with ferropericlase in the upper mantle or as ringwoodite. The narrow and flat three phase loop at the border transition zone—lower mantle together with hybrid peridotite plus eclogite/sediments provides an explanation for the varying and Fe-rich nature of the diamond inclusion suite from Sao Luiz, Brazil.  相似文献   

Cenozoic history of the Bering Sea and its northwestern margin     

Vadim Chekhovich  Dmitry Kovalenko  & Galina Ledneva 《Island Arc》1999,8(2):168-180

Tectonic reconstructions based on the geodynamic analysis of geologic, paleomagnetic, structural and kinematic data of Cenozoic age from the western Bering Sea region are proposed in the present paper. The most active tectonic and magmatic processes took place in the Komandorsky segment of the Bering Sea, exemplified by the Late Cretaceous–Early Eocene Olutorsky Arc and Eocene–Oligocene Govena–Karaginsky Arc, which was built on the structures of the Olutorsky Arc. A model of the complex collision of these two arcs with the paleocontinental margin, which considers rotations of the geological blocks from the various structural zones of the western margin of the Bering Sea in the horizontal plane (paleomagnetic data), was proposed by the authors. According to this model the collision of the flanks of the Olutorsky and Govena–Karaginsky arcs took place in the Eocene, before the collision of the central parts in the Miocene.  相似文献   

Local integrals and the plane motion of a point in rotating systems     

Vadim A. Antonov  Faziliddin T. Shamshiev 《Celestial Mechanics and Dynamical Astronomy》1993,56(3):451-469

This paper deals with the plane motion of a star in the gravitational field of a system which is in a steady state and rotates with a constant angular velocity. For these systems a class of potentials permitting a local integral, linear with respect to the velocity components, has been found. The concept of the local integral itself was introduced by one of the authors of the present paper (Antonov, 1981). A detailed model has been constructed. The corresponding domain of the particle motion and the form of the trajectory coils have been determined. The result is compared with the motion in a more realistic potential.  相似文献