Orbite de L'Étoile Burnham 1164 – ADS 1156 B–765 (95 Piscium)     

R. R. de Freitas Mouro  H. Debehogne 《Astronomische Nachrichten》1982,303(2):157-159

The physical and orbital elements of the binary star ADS 1156 = B 1164 (α₁₉₀₀ = 01^h 22^m.0, δ₁₉₀₀ = + 04°50′) are determined. The absolute visual magnitudes of the two components are 3^m.72 resp. 3^m.97, the masses 1.43 M⊙ resp. 1.33 M⊙.  相似文献   

Characterisation and preliminary quantification of the methane reservoir in a coastal sedimentary source: San Simón Bay,Ría de Vigo,NW Spain     

S. García-Gil  E. de Blas  N. Martínez-Carreño  J. Iglesias  R. Rial-Otero  J. Simal-Gándara  A.G. Judd 《Estuarine, Coastal and Shelf Science》2011

Ría de Vigo is a river valley flooded by the sea, with a bay (San Simón Bay) at its innermost part. The accumulation of Holocene sediment in San Simón Bay has been studied by the integration of 1) large scale high resolution seismic data, and 2) detailed geochemical analysis of a gravity core. In San Simón Bay the majority of the seismic records are obscured by acoustic turbidity which represents gassy sediments, but on records from Rande Strait it is possible to distinguish two Quaternary seismic sequences; an Upper Pleistocene sequence (SQ1) and a Holocene sequence (SQ2). Only SQ2 is recognized in San Simón Bay where it is comprised of two seismic units; the upper unit represents the HST sediment, i.e. the period of highest sea level. A gravity core taken within the gassy zone at 10 m water depth provided 3.55 m of fine-grained sediments (muds) from the youngest seismic unit (4 m thick). Geochemical analysis show high values (4 to 10%) of TOC. Sediment and porewater analyses indicate a distinct sulphate–methane transition zone (SMTZ) between 60 and 80 cm where sulphate is depleted (to <1.7 mM) and methane increases (to >0.4 mM). The top of the acoustic turbidity (the gas front) at 80 cm corresponds to the lower limit of the SMTZ. The methane cannot have been derived from the underlying metamorphic and granitic rocks, but was probably derived by microbial degradation of the organic matter in the Holocene sediments. We estimate that the sediments of the Bay contain approximately 1.8 × 10⁶ m³ of organic carbon and 275 ton of methane.  相似文献   

Bistatic Radar Detection in the Luna-Resurs Mission     

O.?V.?YushkovaEmail author  A.?L.?Gavrik  V.?N.?Marchuk  V.?V.?Yushkov  V.?M.?Smirnov  M.?A.?Laptev  B.?V.?Chernyshev  I.?N.?Dutyshev  V.?P.?Lebedev  A.?V.?Medvedev  A.?A.?Petrukovich 《Solar System Research》2018,52(4):287-300

An overview of radiophysical investigations of the lunar soil and plasma shell by active radar detection with the use of spacecraft is presented. The possibility is analyzed of conducting bistatic measurements using the Irkutsk Incoherent Scattering Radar and the onboard radar system RLK-L which is being developed for the orbital station of the Luna-Resurs mission.  相似文献   

Limpets as prey: Lipophrys pholis choice for size     

Ana C. Silva  Ana C. Amador  Sónia Brazão  Claúdia Faria  Diana Boaventura 《Marine Ecology》2010,31(4):525-532

Patellid limpets are key species on rocky shores, structuring intertidal assemblages through their grazing. Their role as prey for fish is, however, often overlooked in studies of intertidal ecosystem functioning. The shanny Lipophrys pholis is a common predator of limpets on rocky shores in Northern Europe and, in this study, we examined the characteristics of its predation on limpets based on prey size. The limpet size range that adult L. pholis (10–12.5 cm) can eat was examined in the laboratory using Patella depressa in 0.2 cm classes, varying between 0.5 cm and 3.0 cm in maximum shell length. There was a limpet size refuge above 1.8 cm, while all smaller sizes were readily consumed by the shanny. The predator attacking behaviour was also examined and found to vary with prey size. Limpets up to 0.8 cm were crushed by the jaw‐constricting force and eaten whole, whereas larger prey were prised from the substratum and the body subsequently separated from the shell. To examine whether there was a L. pholis preference for P. depressa size, a two‐stage laboratory experiment was done using two size classes defined as small (0.7–0.8 cm maximum shell length) and large (1.5–1.6 cm maximum shell length). In the first stage, the predator was given each limpet size class separately. In the second stage, the fish was given a choice between the two classes. Lipophrys pholis was shown to have a preference for the large size class (1.5–1.6 cm). The average number of limpets consumed by the shanny was examined for the duration of one high‐tide typical of the central region of Portugal (≈ 4 h). On average, approximately five limpets (up to an eight limpet maximum) were consumed. The present study shows that L. pholis has a feeding preference based on limpet size, which suggests that the limpet population structure and intra‐ and inter‐specific interactions may be influenced by the shanny predation.  相似文献   

Diel and seasonal variability in the fish community structure of a mud‐bottom estuarine habitat in the Gulf of Mexico     

Manuel Castillo‐Rivera  Rocío Zárate‐Hernández  Selene Ortiz‐Burgos  José Zavala‐Hurtado 《Marine Ecology》2010,31(4):633-642

We hypothesized that temporal variation in fish species composition and community structure in a low complexity habitat in the Pueblo Viejo Lagoon, Mexico, is influenced by diel light/dark cycles and tidal stage, and by seasonal changes in salinity and temperature. We collected a total of 17,661 individuals during 2‐h interval sampling over six bi‐monthly 24‐h sampling cycles representing 53 species, of which 11 (～20%) were previously unknown in the system. Diel variation indicated that significantly higher numbers of individuals and species were caught at night, whereas diversity and evenness were higher during the day. Species richness was significantly higher in July and January, whereas diversity and evenness peaked around May; both were correlated with temperature. Diel variation in species composition was influenced primarily by the light/dark cycle. Cluster analyses of each diel cycle separated fish assemblages from midday samples from those of nocturnal samples, separated by an extended wide transition period as fish moved at dawn and during the late afternoon/dusk. Significant shifts (as determined by MANOVA) in assemblage structure occurred between months. Canonical correspondence analysis showed that temperature and day/night effects were the most important environmental variables structuring the fish community. This constrained ordination also defined species with specific habitat preferences as follows: (i) diurnal, warm temperature species (mainly planktivores) (Brevoortia gunteri, Cetengraulis edentulus, Diapterus auratus, and Membras martinica); (ii) nocturnal, warm temperature species (mainly predators) (Citharichthys spilopterus, Cathorops melanopus, and Bairdiella spp.); and (iii) low temperature, diurnal species (Brevoortia patronus and Mugil curema) or those with twilight and nocturnal distributions (Anchoa mitchilli, the most numerically abundant species). Our results indicate that diel and seasonal changes in fish community structure were mainly related to day/night cycles and temperature regimes.  相似文献   

Dynamics of arrays of floating point-absorber wave energy converters with inter-body and bottom slack-mooring connections     

Pedro C. Vicente  António F. de O. Falcão  Luís M.C. Gato  Paulo A.P. Justino 《Applied Ocean Research》2009,31(4):267-281

If point absorbers are employed in the extensive exploitation of the offshore wave energy resource, they should be deployed in arrays, the distance between the elements in the array being possibly tens of meters. In such cases, it may be more convenient that the array is spread moored to the sea bottom through only some of its elements, located in the periphery, while the other array elements are prevented from drifting and colliding with each other by connections to adjacent elements. An array of identical floating point absorbers located at the grid points of an equilateral triangular grid is considered in the paper. A spread set of slack-mooring lines connect the peripheric floaters to the bottom. A weight is located at the centre of each triangle whose function is to pull the three floaters towards each other and keep the inter-body mooring lines under tension. The power take-off system (PTO) is a linear damper activated by the buoy heaving motion. The whole system–buoys, moorings and power take-off systems–is assumed linear, so that a frequency domain analysis may be employed. Hydrodynamic interference between the oscillating buoys in array is accounted for. Equations are presented for a set of three identical point absorbers. This is then extended to more complex equilateral triangular grid arrays. Results from numerical simulations, with regular and irregular waves, are presented for the motions and power absorption of hemispherical converters in arrays of three and seven elements and for different mooring parameters and wave incidence angles. Comparisons are given with the unmoored and independently-moored buoy situations.  相似文献   

A predictive numerical model for potential mapping of the gas hydrate stability zone in the Gulf of Cadiz     

R. Len  L. Somoza  C.J. Gimnez-Moreno  C.J. Dabrio  G. Ercilla  D. Praeg  V. Díaz-del-Río  M. Gmez-Delgado 《Marine and Petroleum Geology》2009,26(8):1564-1579

This paper presents a computational model for mapping the regional 3D distribution in which seafloor gas hydrates would be stable, that is carried out in a Geographical Information System (GIS) environment. The construction of the model is comprised of three primary steps, namely: (1) the construction of surfaces for the various variables based on available 3D data (seafloor temperature, geothermal gradient and depth-pressure); (2) the calculation of the gas function equilibrium functions for the various hydrocarbon compositions reported from hydrate and sediment samples; and (3) the calculation of the thickness of the hydrate stability zone. The solution is based on a transcendental function, which is solved iteratively in a GIS environment.The model has been applied in the northernmost continental slope of the Gulf of Cadiz, an area where an abundant supply for hydrate formation, such as extensive hydrocarbon seeps, diapirs and fault structures, is combined with deep undercurrents and a complex seafloor morphology. In the Gulf of Cadiz, the model depicts the distribution of the base of the gas hydrate stability zone for both biogenic and thermogenic gas compositions, and explains the geometry and distribution of geological structures derived from gas venting in the Tasyo Field (Gulf of Cadiz) and the generation of BSR levels on the upper continental slope.  相似文献   

Reply to comments of G. Abril on “Underwater measurements of carbon dioxide evolution in marine plant communities: A new method” by J. Silva and R. Santos [Estuarine,Coastal and Shelf Science 78(2008) 827–830]     

João Silva  Rui Santos 《Estuarine, Coastal and Shelf Science》2009

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Distribution and spatial variation of hydrothermal faunal assemblages at Lucky Strike (Mid-Atlantic Ridge) revealed by high-resolution video image analysis     

Daphne Cuvelier  Joze Sarrazin  Ana Colao  Jon Copley  Daniel Desbruyres  Adrian G. Glover  Paul Tyler  Ricardo Serro Santos 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):2026-2040

Whilst the fauna inhabiting hydrothermal vent structures in the Atlantic Ocean is reasonably well known, less is understood about the spatial distributions of the fauna in relation to abiotic and biotic factors. In this study, a major active hydrothermal edifice (Eiffel Tower, at 1690 m depth) on the Lucky Strike vent field (Mid-Atlantic Ridge (MAR)) was investigated. Video transects were carried out by ROV Victor 6000 and complete image coverage was acquired. Four distinct assemblages, ranging from dense larger-sized Bathymodiolus mussel beds to smaller-sized mussel clumps and alvinocaridid shrimps, and two types of substrata were defined based on high definition photographs and video imagery. To evaluate spatial variation, faunal distribution was mapped in three dimensions. A high degree of patchiness characterizes this 11 m high sulfide structure. The differences observed in assemblage and substratum distribution were related to habitat characteristics (fluid exits, depth and structure orientation). Gradients in community structure were observed, which coincided with an increasing distance from the fluid exits. A biological zonation model for the Eiffel Tower edifice was created in which faunal composition and distribution can be visually explained by the presence/absence of fluid exits.  相似文献   

Adsorption of cobalt by using inorganic components of sediment samples from water bodies   总被引：2，自引：1，他引：1  

Rocío Montes de Oca-Palma  Marcos Solache-Ríos  Melania Jiménez-Reyes  JoséJuan García-Sánchez  Perla Tatiana Almazán-Sánchez 《国际泥沙研究》2021,36(4):524-531

The adsorption of cobalt ions was evaluated using sediment samples from water bodies to investigate the adsorption properties of sediment and the behavior of these natural materials in the presence of nuclear and industrial waste.The two sediments(S1 and S2)were treated to eliminate humic and fulvic acids and then they were characterized by several techniques.The minerals found in both the sediments(X-ray diffraction)were quartz and albite;plus,goethite and muscovite in S1,and kaolinite and montmorillonite in S2.Point of zero charge(PZC)of S1 and S2 was 6.00 and 5.22,respectively.The specific area of S1(63.3 m²/g)is higher than S2(1.5 m²/g).Adsorption kinetics data for S1 and S2 were best fitted to the pseudo second-order model.The removal efficiency of S1 for cobalt was 96%with an adsorption capacity(qe)of 0.93 mg/g,and for S2 was 45%with a qeof 0.40 mg/g.The experimental data of the adsorption isotherms were adjusted to Langmuir and Freundlich models for S1 and S2,respectively.The thermodynamic parameters(enthalpy,entropy,and Gibb’s free energy)indicated that the adsorption processes were endothermic,spontaneous,and chemisorption mechanism.The results show that the adsorption capacities of the sediments depend on their composition.These water sediments have important adsorption properties for cobalt,and they can be used in the treatment of nuclear and industrial aqueous wastes.  相似文献