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1.
The characteristic pattern of multiple colored layers in coastal stratified lakes in the process of separation from the White Sea 总被引:1,自引:1,他引:0
Krasnova Elena D. Matorin Dmitry N. Belevich Tatiana A. Efimova Ludmila E. Kharcheva Anastasiia V. Kokryatskaya Natalia M. Losyuk Galina N. Todorenko Daria A. Voronov Dmitry A. Patsaeva Svetlana V. 《中国海洋湖沼学报》2018,36(6):1962-1977
An unusual feature of the saline stratified lakes that were formed due to ongoing postglacial uplift on the White Sea coast is the presence of several differently colored thin layers in the zone with sharp gradients. Colored layers in five lakes at various stages of separation from the sea were investigated using optical microscopy, spectrophotometry, spectrofluorimetry, and photobiology. The upper greenish colored layer located in the aerobic strata of all lakes near the compensation depth of 1% light penetration contains green algae. In the chemocline, another layer, brightly green, red or pink, is dominated by mixotrophic flagellates. Despite the very low light intensities and the presence of H 2 S, active photosynthesis by these algae appears to be occurring, as indicated by high values of the maximum quantum yield of primary photochemistry, electron transport activity, photosynthetic activity of photosystem II, the fraction of active centers, and low values of heat dissipation. In the reduced zone of the chemocline, a dense green or brown suspension of anoxygenic phototrophs(green sulfur bacteria) is located. 相似文献
2.
Ezio Caroli Natalia Auricchio Lorenzo Amati Yuriy Bezsmolnyy Carl Budtz-JøRgensen Rui M. Curado da Silva Filippo Frontera Alessandro Pisa Stefano Del Sordo John B. Stephen Giulio Ventura 《Experimental Astronomy》2005,20(1-3):341-351
The energy range above 60 keV is important for the study of many open problems in high energy astrophysics such as the role of Inverse Compton with respect to synchrotron or thermal processes in GRBs, non thermal mechanisms in SNR, the study of the high energy cut-offs in AGN spectra, and the detection of nuclear and annihilation lines. Recently the development of high energy Laue lenses with broad energy bandpasses from 60 to 600keV have been proposed for a Hard X ray focusing Telescope (HAXTEL) in order to study the X-ray continuum of celestial sources. The required focal plane detector should have high detection efficiency over the entire operative range, a spatial resolution of about 1mm, an energy resolution of a few keV at 500keV and a sensitivity to linear polarization. We describe a possible configuration of the focal plane detector based on several CdTe/CZT pixelated layers stacked together to achieve the required detection efficiency at high energy.
Each layer can operate both as a separate position sensitive detector and polarimeter or work with other layers to increase the overall photopeak efficiency. Each layer has a hexagonal shape in order to minimize the detector surface required to cover the lens field of view. The pixels would have the same geometry so as to provide the best coupling with the lens point spread function and to increase the symmetry for polarimetric studies. 相似文献
3.
María Luisa García Vargas Angeles Díaz Roberto Terlevich Elena Terlevich 《Astrophysics and Space Science》1993,205(1):77-84
In the frame of the Starburst Model, we show that the evolution of a massive stellar cluster in a high metallicity environment can reproduce the observed emission-line spectrum and the UV-optical Spectral Energy Distribution of the Seyfert 2 galaxies and LINERs. We apply the results of our models to three objects: NGC 5506, NGC 5643 and Mk 348. 相似文献
4.
Natalia Orlova Vladimir Korchagin Nobuhiro Kikuchi Shoken. M. Miyama Aleksei Moiseev 《Astrophysics and Space Science》2003,284(2):739-742
We have tested the applicability of the global modal approach in the density wave theory of spiral structure for a sample
of spiral galaxies with measured axisymmetric background properties. We report here the results of the simulations for four
galaxies: NGC 488, NGC 628, NGC 1566, and NGC 3938. Using the observed radial distributions for the stellar velocity dispersions
and the rotation velocities we have constructed the equilibrium models for the galactic disks in each galaxy and implemented
two kinds of stability analyses - the linear global analysis and 2D-nonlinear simulations. In general, the global modal approach
is able to reproduce the observed properties of the spiral arms in the galactic disks. The growth of spirals in the galactic
disks can be physically understood in terms of amplification by over-reflection at the corotation resonance. Our results support
the global modal approach as a theoretical explanation of spiral structure in galaxies.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
E. García L. De Haro C. O'Sullivan G. Cahill J. A. López Fernández F. Tercero B. Galocha J. L. Besada 《Experimental Astronomy》2003,15(3):173-193
A classical radioastronomy receiver is fed with a corrugated horn and an independent lens, both placed in a cryostat to lower
the noise temperature. The beam is focused and directed using a combination of elliptical and plane mirrors. This paper proposes
modifying the initial feeding system by placing the lens onto the horn aperture, thereby allowing a size reduction of the
horn and lens, and a simplification of their mechanical design. The profiled lens is shaped to correct the phase error on
the horn aperture. A quasi-optical model of the horn-plus-lens system has been developed using a Beam Mode Expansion (BME).
Results using both a hyperbolic-planar lens and a spherical-elliptical lens, as well as results obtained by using Geometrical
Optics (GO) with a Kirchoff–Huygens integration to get the far-field pattern, have been compared with measurements. As a direct
application, a full focusing system for the new 40-m radiotelescope at the “Centro Astronómico de Yebes” is presented for
the 22, 30 and 45 GHz bands. This paper has developed a QO model for a corrugated conical horn with a phase-correcting lens.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Pablo Recabarren Pablo Recabarren Mirta Mosconi Hernán Muriel Hernán Muriel Diego García Lambas Diego García Lambas Marc Sarazin Riccardo Giovanelli 《Astrophysics and Space Science》2004,290(3-4):409-413
We present the preliminary results of the astronomical site testing, which the group IATE of the OAC is developing in northwest of Argentine in collaboration with ESO and the Department of Astronomy of Cornell University. We show the results, which we have obtained from the analysis of GOES 8 satellite images in the 10.7 μm band, which allowed us to configurate a map of clear sky regions in an area between 23° and 28° S, and 66° 30′ and 69° W. We also comment logistical and tectonic aspects, and discuss next steps to follow in the research. 相似文献
7.
Natalia Babkovskaia Juri Poutanen Anita M. S. Richards Ryszard Szczerba 《Monthly notices of the Royal Astronomical Society》2006,370(4):1921-1927
The silicate carbon star V778 Cyg is a source of 22-GHz water maser emission which was recently resolved by MERLIN. Observations revealed an elongated -like structure along which the velocities of the maser features show a linear dependence on the impact parameter. This is consistent with a doubly warped m = 2 disc observed edge-on. Water masers and silicate dust emission (detected by the Infrared Astronomical Satellite and Infrared Space Observatory ) have a common origin in O-rich material and are likely to be co-located in the disc. We propose a detailed self-consistent model of a masing gas–dust disc around a companion to the carbon star in a binary system, which allows us to estimate the companion mass of 1.7 ± 0.1 M⊙ , the disc radius of 40 ± 3 au and the distance between companions of ∼80 au. Using a dust–gas coupling model for water masing, we calculate the maser power self-consistently, accounting for both the gas and the dust energy balances. Comparing the simulation results with the observational data, we deduce the main physical parameters of the masing disc, such as the gas and dust temperatures and their densities. We also present an analysis of the stability of the disc. 相似文献
8.
M. M. Jordán S. Pina F. García-Orenes M. B. Almendro-Candel E. García-Sánchez 《Environmental Geology》2008,55(2):453-462
The ecologic restoration criteria in areas degraded from extraction activities require making use of their mine spoils. These
materials do not meet fertility conditions to guarantee restoration success and therefore, need the incorporation of organic
amendments to obtain efficient substratum. Reducing the deficiencies in the organic material and restoration material nutrients
with the contribution of treated sewage sludge is proposed in this work. This experiment was based on a controlled study using
columns. The work was conducted with two mine spoils, both very rich in calcium carbonate. The first mineral, of poor quality,
came from the formation of aggregates of crushed limestone (Z). The other residual material examined originated in limestone extraction, formed by the levels of interspersed non-limestone
materials and the remains of stripped soils (D). Two treatments were undertaken (30,000 and 90,000 kg/ha of sewage sludge), in addition to a control treatment. The water
contribution was carried out with a device that simulated either short-duration rain or a flooding irrigation system in order
to cover the surface and then percolate through the soil. The collection of leached water took place 24 h after the applications.
Different parameters of the leached water were determined, including pH, electrical conductivity, nitrate anions, ammonium,
phosphates, sulphates and chlorides. The values obtained for each irrigation application are discussed, and the nitrate values
obtained were very elevated. 相似文献
9.
Palynological characterization of the pollen assemblages from core ZV-01 offers a reliable age record of shallow ‘gas seal’
and ‘gas reservoir’ sediments from the Ría de Vigo (NW Spain). Gassy sediments show a direct correspondence with the palynological
assemblage zones (LPAZ) 2, 3 and 4, which range in age from 950 to 1510 a.d. for the interval 81–176 cm where gas is found. The facies acting as a seal would correspond to the sedimentation in the ria
starting from 1510 a.d. These assemblages also provide significant data which make it possible to reconstruct the palaeoenvironmental changes recorded
in the sedimentary infill of the Ría de Vigo. The gassy horizon corresponds to the phase when riparian and mesophilous forest
were better represented. This coincides with a relative high abundance of Lingulodinium machaerophorum, which indicates that the waters of the ria had been less renewed by oceanic waters and had a plentiful supply of continental
nutrients. At that time, anoxic conditions resulted from restricted vertical circulation of seawater and/or high biological
productivity. The dinocyst assemblages overlying and underlying the gassy horizon in core ZV-01 are clearly different from
those concomitant with the accumulation of the gassy sediments. This suggests that oceanographic conditions in the Ría de
Vigo may have changed several times during the time interval covered by our record. The weaker relationship between L. machaerophorum/Spiniferites spp., and simultaneous significant increases in Impagidinium spp. and Bitectatodinium tepikiense may indicate a greater intrusion of colder, more oceanic waters into the Ría de Vigo, which may have provoked intensification
in upwelling during two periods, ca. 700–850 a.d. and ca. 1500–1750 a.d. 相似文献
10.
Jue Lin-Ye Begoña Pérez-Gómez Enrique Álvarez-Fanjul Javier García-Valdecasas 《Marine Geodesy》2020,43(5):509-539
AbstractThe sea level station operating since 1996 at Mazagón (Huelva, Spain) has been progressively upgraded to fit tsunami warning requirements, due to its location in one of the main regions at risk. Its radar water level sensor was complemented in 2017, with the addition of a pressure sensor. The performance of both sea level sensors and their response to sea level oscillations, at different frequencies, is assessed. Particular emphasis is put on the effect of extreme events, such as Storm Emma, when alternative methods to obtain 1-min data are tested, in contrast to the one based on arithmetic means. The overall differences are small, for the whole period of study (centered-root-mean-square-error below 1?cm, for 5-min, and hourly data; similar tidal parameters and sea level oscillations with periods between 30?s and 5?min). However, during Storm Emma, the pressure sensor presents sensibly lower readings than the radar, with the centered-root-mean-square-error rising to 80?mm on the March 2nd 2018. A new method to compute 1-min data, based on medians, reduced this value to 10?mm for the same day. 相似文献