Seasonal Variation in the Phytoplanktonic Community,Seston and Environmental Variables During a 2-Year Period and Oyster Growth at Two Mariculture Sites,Southern Chile     

Jorge E. Toro  Pamela I. Paredes  Darío J. Villagra  Carolina M. Senn 《Marine Ecology》1999,20(1):63-89

Phytoplankton and its relationships with physical and chemical variables were analysed over a 2-year period in Hueihue and Linao Bays (southern Chile). Samples were collected on a monthly basis from May 1991 to May 1993. The growth rate of a single stock of hatchery-produced oysters (Ostrea chilensis) distributed between these two bays was also monitored monthly. The growth rate of oysters maintained at Linao Bay (site associated with a fish farm) was significantly higher, at every depth, compared with the oysters maintained at Hueihue Bay. Temperature and salinity values and their annual fluctuations were similar at both locations, presenting higher variations at the surface (1 m) due to the influence of air temperature and local precipitation than at depth. However, significant differences in phytoplankton abundance and composition were found between the two locations. The phytoplankton community was characterized by high biomass values during spring and summer, the dominance of diatoms and an inverse relationship between temperature and species diversity. However, phytoplankton cell abundance, biovolume and chlorophyll a concentration were significantly higher at Linao at every depth sampled. Cell abundance ranged between 4.49 × 10⁴ and 7.45 × 10⁶ cells · l^?1 in Hueihue and between 6.48 × 10⁴ and 8.71 × 10⁶ cells ·1^?1 in Linao. The influence of temperature on chlorophyll a concentration was significant except at 8 m at both locations. The instantaneous oyster growth rate was found to be positively correlated with temperature, chlorophyll a concentration and particulate organic matter at both locations. A significant negative relationship between oyster growth and amount of particulate inorganic matter was found; this confirms the important role played by seston composition in oyster growth. The demonstration of variation in oyster growth rate associated with differences in food availability between the two locations provides insight into the ecological role played by fish farms in southern Chile. The results suggest a strong link between food availability and oyster growth.  相似文献   

A new solution to the lagrange's case of the three‐body problem     

E. Piña 《Celestial Mechanics and Dynamical Astronomy》1999,74(3):163-174

The motion of three particles, interacting by gravitational forces, is studied in a new coordinate system given by the principal axes of inertia, as determined by Euler angles, and using the inertia principal moments and an auxiliar angle as coordinates. The solution to the particular Lagrange case of the three‐body problem is reviewed and solved in these new coordinates. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Mass and Metallurgical Balance Forecast for a Zinc Processing Plant Using Artificial Neural Networks     

Niquini  Fernanda Gontijo Fernandes  Costa  João Felipe Coimbra Leite 《Natural Resources Research》2020,29(6):3569-3580

Natural Resources Research - The forecasting of ore concentrate and tailings mass and metallurgical recovery at a processing plant is not a simple task. It starts with data collection, which is...  相似文献   

Respiration partitioning in contrasting subtidal sediments: seasonality and response to a spring phytoplankton deposition     

Maria de Assunção Franco  Jan Vanaverbeke  Dick Van Oevelen  Karline Soetaert  Maria José Costa  Magda Vincx  Tom Moens 《Marine Ecology》2010,31(2):276-290

Biomass and respiration rates of bacteria, nematodes and macrobenthos were estimated in relation to the deposition of the spring phytoplankton bloom at two contrasting sites in the Southern North Sea: one with fine‐grained sediment close to the coastline and another with highly permeable sediments. Sediment community oxygen consumption (SCOC) was also measured. Bacterial biomass was relatively similar at both stations, whereas nematode and macrobenthic biomass were higher in fine‐grained sediment. In fine sediments, bacterial biomass increased quickly after deposition of the phytoplankton bloom, whereas the response of nematodes and macrobenthos was delayed. In coarser sediments, nematodes and macrobenthos also showed a fast response in terms of density and biomass. Respiration in permeable sediments was mainly dominated by bacteria at all periods of the year. Hence, nematode and macrobenthic respiration did not contribute strongly to SCOC. This is in contrast to the patterns observed in finer sediments, where both macrofauna and nematodes were important oxygen consumers as well. Macrobenthos contributed more to total SCOC than did nematodes in winter. However, shortly after the arrival of phytodetritus at the sea floor, nematodes and macrobenthos contributed equally to the total SCOC, indicating that all benthic size classes should be taken into account when investigating marine benthic respiration rates.  相似文献   

On the design of beach nourishment projects using static equilibrium concepts: Application to the Spanish coast     

Mauricio González  Raul Medina  Miguel Losada 《Coastal Engineering》2010

The concept of equilibrium plan form and equilibrium profile has been widely used as an engineering tool in order to design beach nourishment projects. The scope of this paper is to further explore this “equilibrium beach” concept in crenulated bays, as a long-term tool for beach nourishment projects. The proposed methodology is based on González and Medina (2001) and combines the static equilibrium plan and profile for long-term analysis. This methodology includes a modified equilibrium plan form, which is able to define the orientation of the local wave front in the diffracting point, and also to locate the downcoast starting point of the static equilibrium beach from which the parabolic plan form of Hsu and Evans (1989) is valid. This methodology permits the application of any equilibrium profile formulation. An example of the application of this methodology and long-term formulations to the design of the Spanish nourishment project of Poniente Beach (Gijón) is presented. Ten years after its construction, the beach has still got a static equilibrium and remains pretty close to the predicted equilibrium beach in plan and profile.  相似文献   

Orbite de l'etoile double visuelle ADS 1538 = Σ 186     

Ronaldo Rogrio de Freitas Mouro 《Astronomische Nachrichten》1977,298(4):227-232

The physical and orbital elements of the binary star ADS 1538 = Σ 168 (α₁₉₀₀ = 01^h50^m.7, δ₁₉₀₀ = +01°21'; α₂₀₀₀ = 01^h55^m·8, δ₂₀₀₀ = +01°51') are determined. The absolute visual magnitudes of the two components are 4^m.04 resp. 4^m.17, the masses 1.34 M_⊙ resp. 1.29 M_⊙.  相似文献   

On biases in the predictions of stellar population synthesis models     

M. Cerviño  D. Valls-Gabaud 《Monthly notices of the Royal Astronomical Society》2003,338(2):481-496

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Gravitational collapse of gas clouds with spherical,cylindrical or plane symmetry in the linear wave flow approximation     

M. H. Ibañez S  L. Di G. Sigalotti 《Astrophysics and Space Science》1983,95(1):145-162

The equations of gas dynamics are solved, quasi-analytically by applying McVittie's method for spherical, cylindrical and plane configurations. The hypothesis of linear wave flow is applied and it is assumed that the final state of collapsing clouds is a hydrostatic equilibrium state, determined by complete polytropes. Complete analytical solutions are found when the generalized (to the three symmetries) Emden equation admits of analytical solutions. Otherwise the solutions are left in terms of the numerical solutions of the Emden equation. Numerical solutions to the Emden equation in the plane case are found and tabulated. A strong dependence of amplification, of density, pressure and temperature of the gas, on the symmetry is found. In addition, it is conclude that the flow remains subsonic, during the collapse, except toward the boundaries of the collapsing clouds.  相似文献   

Dwarf elliptical galaxies: structure, star formation and colour–magnitude diagrams     

Giovanni Carraro  Cesare Chiosi  Léo Girardi  Cesario Lia 《Monthly notices of the Royal Astronomical Society》2001,327(1):69-79

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Structure and Dynamics of NGC 1300     

J.A.L. Aguerri  M. Prieto  A.M. Varela  C. Muñoz-Tuñón 《Astrophysics and Space Science》2001,276(2-4):611-618

The isophotal profiles and colour maps of a sample of 12 spiral galaxies allowed us to analyse the different structural components that compose them. These components were parameterized by performing a decomposition of the galaxy brightness profiles. Inferring the geometry for each component, we have obtained the spatial mass distribution and the gravitational potential for each object. Here we present the detailed analysis for one of the galaxies in the sample, the barred galaxy NGC 1300. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献