Observations of internal undular bores on the Japan/East Sea shelf-coastal region     

Vadim Vasilevich Novotryasov  Dmitry Vadimovich Stepanov  Igor Olegovich Yaroshchuk 《Ocean Dynamics》2016,66(1):19-25

Observations are presented of internal undular bores (IUBs) on the Japan/East Sea coast. We found three types of IUB amplitude modulation functions. The first type (IUB₁) has a leading edge, which is formed by the soliton with maximal amplitude. The second type (IUB₂) has a soliton with maximal amplitude (SMA) located between the leading and trailing edges. The third type (IUB₃) consists of 2–3 solitons, which have identical amplitudes. The evolution of the IUB₂ from the moment of generation to the moment of maximal development was analyzed. The speed of the IUB₂ approached to the phase speed of linear internal waves with a period of 12.4 h. The amplitude modulation function of the IUB₂ is believed to be unique in ocean observations. Observations are discussed in the context of recently raised hypotheses concerning the evolution of IUBs in the coastal environment.  相似文献   

S 235 B explained: an accreting Herbig Be star surrounded by reflection nebulosity     

Paul A. Boley  rey M. Sobolev  Vadim V. Krushinsky  Roy van Boekel  Thomas Henning  Aleksei V. Moiseev  Maksim V. Yushkin 《Monthly notices of the Royal Astronomical Society》2009,399(2):778-782

The intent of this study is to determine the nature of the star and associated nebulosity S 235 B, which are located in a region of active star formation still heavily obscured by the parent molecular cloud. Low-resolution  ( R = 400)  long-slit spectra of the star and nebulosity, and medium-  ( R = 1800)  and high-resolution  ( R = 60 000)  spectra of the central star are presented along with the results of Fabry–Perot interferometric imaging of the entire region. Based on the long-slit and Fabry–Perot observations, the nebulosity appears to be entirely reflective in nature, with the stellar component S 235 B★ providing most of the illuminating flux. The stellar source itself is classified here as a B1V star, with emission-line profiles indicative of an accretion disc. S 235 B★ thus belongs to the relatively rare class of early-type Hebrig Be stars. Based on the intensity of the reflected component, it is concluded that the accretion disc must be viewed nearly edge-on. Estimates of the accretion rate of S 235 B★ from the width of the Hα profile at 10 per cent of maximum intensity, a method which has been used lately for T Tauri stars and Brown Dwarfs, appear to be inconsistent with the mass outflow rate and accretion rate implied from previous infrared observations by Felli et al., suggesting this empirical law does not extend to higher masses.  相似文献   

The SMART-1 Mission: Photometric Studies of the Moon with the AMIE Camera     

Yu. G. Shkuratov  M. A. Kreslavsky  D. G. Stankevich  V. G. Kaydash  P. Pinet  V. V. Shevchenko  B. H. Foing  J.-L. Josset 《Solar System Research》2003,37(4):251-259

We describe the future SMART-1 European Space Mission whose objective is to study the lunar surface from a polar lunar orbit. In particular, it is anticipated that selected regions of the Moon will be photographed using the AMIE camera with a mean spatial resolution of about 100 m in three spectral channels (0.75, 0.92, and 0.96 m) over a wide range of phase angles. Since these spectral channels and the AMIE resolution are close to those of the UVVIS camera onboard the Clementine spacecraft, the simultaneous processing of SMART-1 and Clementine data can be planned, for example, to obtain phase-ratio images. These images carry information on the structural features of the lunar surface. In particular, UVVIS/Clementine data revealed a photometric anomaly at the Apollo-15 landing site associated with the blowing of the lunar regolith by the lander engine. Anomalies were found in the ejection zones of several fresh craters.  相似文献   

Volatile Phase Separation in Silicic Magmas at Bajo de la Alumbrera Porphyry Cu-Au Deposit, NW Argentina   总被引：7，自引：0，他引：7  

Anthony C. Harris    Vadim S. Kamenetsky    Noel C. White  David A. Steele 《Resource Geology》2004,54(3):341-356

Abstract. At the Bajo de la Alumbrera porphyry Cu-Au deposit, NW Argentina, several key textural elements preserve evidence for volatile separation. Interconnected miarolitic cavities, while being studied extensively in granites, have now been recognized in intrusions related to porphyry Cu mineralization. Pods of saccharoidal quartz are connected by narrow, anastomosing zones of graphic quartz-alkali feldspar intergrowths and ragged biotite (with lesser apatite and magnetite). Their connectivity can be as much as 15 cm; however, more commonly, the interconnected miarolitic cavities are approximately 1 to 2 mm across and 5 cm or less, long. Features such comb-quartz layered textures and magmatic-hydrothermal veins (P veins), combined with aqueous fluid phase equilibria from fluid inclusions, better constrain physical models of exsolution. We interpret these textures in the context of vapour phase formation, coalescence and accumulation in an evolving silicic magma. Recognition of textures, such as the interconnected miarolitic cavities reported here, may provide a simple exploration tool for porphyry Cu deposits, helping explorers to recognize evidence for a potentially fertile intrusions.  相似文献   

Late Jurassic–Early Cretaceous closure of the Mongol-Okhotsk Ocean demonstrated by new Mesozoic palaeomagnetic results from the Trans-Baïkal area (SE Siberia)     

Jean-Pascal Cogné  Vadim A. Kravchinsky  Nadir Halim  Fatim Hankard 《Geophysical Journal International》2005,163(2):813-832

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Potassic primary melts of Vulsini (Roman Province): evidence from mineralogy and melt inclusions     

Vadim Kamenetsky  Nicole Métrich  Raffaello Cioni 《Contributions to Mineralogy and Petrology》1995,121(3):336-336

The online version of the original article can be found at  相似文献   

Quaternary high-Mg ultrapotassic rocks from the Qal’eh Hasan Ali maars,southeastern Iran: petrogenesis and geodynamic implications     

Kwan-Nang Pang  Sun-Lin Chung  Mohammad Hossein Zarrinkoub  Fei Wang  Vadim S. Kamenetsky  Hao-Yang Lee 《Contributions to Mineralogy and Petrology》2015,169(3):1-19

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Potential and limits of double-difference tomographic methods     

Jean-Luc Got  Vadim Monteiller  Jean Virieux  Stéphane Operto 《Geophysical Prospecting》2008,56(4):477-491

Double-difference tomographic methods use directly accurate time delays computed between similar signals. Such methods are designed to image very heterogeneous media, such as volcanoes or fault zones. In seismological applications, similar signals are recorded at a given station from earthquakes sharing similar and close-by sources. In seismic exploration experiments, similar signals are often recorded at neighbouring receivers. After a brief presentation of the tomographic algorithm used, a seismological application is summarized. The potential and limits of double-difference tomographic methods are explored using various numerical experiments. They show that two effects are competing in double-difference tomography: (i) the degradation of the stability of the inversion due to the geometrical proximity of the rays used in the differentiation and (ii) the decrease in modelling error, which allows improving the stability of the inversion and using smaller quantities of a priori information when data are sufficiently accurate. The best resolution is obtained for an optimal value of the inter-source or inter-receiver distance. For optimal values of these distances and a priori information, tomography using traveltime differences provides significantly better resolved results than using traveltimes.  相似文献   

Attenuation mechanisms in fractured fluid-saturated porous rocks: a numerical modelling study     

Eva Caspari  Mikhail Novikov  Vadim Lisitsa  Nicolás D. Barbosa  Beatriz Quintal  J. Germán Rubino  Klaus Holliger 《Geophysical Prospecting》2019,67(4):935-955

Seismic attenuation mechanisms receive increasing attention for the characterization of fractured formations because of their inherent sensitivity to the hydraulic and elastic properties of the probed media. Attenuation has been successfully inferred from seismic data in the past, but linking these estimates to intrinsic rock physical properties remains challenging. A reason for these difficulties in fluid-saturated fractured porous media is that several mechanisms can cause attenuation and may interfere with each other. These mechanisms notably comprise pressure diffusion phenomena and dynamic effects, such as scattering, as well as Biot's so-called intrinsic attenuation mechanism. Understanding the interplay between these mechanisms is therefore an essential step for estimating fracture properties from seismic measurements. In order to do this, we perform a comparative study involving wave propagation modelling in a transmission set-up based on Biot's low-frequency dynamic equations and numerical upscaling based on Biot's consolidation equations. The former captures all aforementioned attenuation mechanisms and their interference, whereas the latter only accounts for pressure diffusion phenomena. A comparison of the results from both methods therefore allows to distinguish between dynamic and pressure diffusion phenomena and to shed light on their interference. To this end, we consider a range of canonical models with randomly distributed vertical and/or horizontal fractures. We observe that scattering attenuation strongly interferes with pressure diffusion phenomena, since the latter affect the elastic contrasts between fractures and their embedding background. Our results also demonstrate that it is essential to account for amplitude reductions due to transmission losses to allow for an adequate estimation of the intrinsic attenuation of fractured media. The effects of Biot's intrinsic mechanism are rather small for the models considered in this study.  相似文献   

Magnetorotational and Tayler Instabilities in the Pulsar Magnetosphere     

Vadim Urpin 《Journal of Astrophysics and Astronomy》2017,38(3):41

The magnetospheres around neutron stars should be very particular because of their strong magnetic field and rapid rotation. A study of the pulsar magnetospheres is of crucial importance since it is the key issue to understand how energy outflow to the exterior is produced. In this paper, we discuss magnetohydrodynamic processes in the pulsar magnetosphere. We consider in detail the properties of magnetohydrodynamic waves that can exist in the magnetosphere and their instabilities. These instabilities lead to formation of magnetic structures and can be responsible for short-term variability of the pulsar emission.  相似文献