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Registros recuperados: 23 | |
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Nsiri, Benayad; Chonavel, Thierry; Boucher, Jean; Nouze, Herve. |
In seismic deconvolution, blind approaches must be considered in situations where reflectivity sequence, source wavelet signal, and noise power level are unknown. In the presence of long source wavelets, strong interference among the reflectors contributions makes the wavelet estimation and deconvolution more complicated. In this paper, we solve this problem in a two-step approach. First, we estimate a moving average (MA) truncated version of the wavelet by means of a stochastic expectation-maximization (SEM) algorithm. Then, we use Prony's method to improve the wavelet estimation accuracy by fitting an autoregressive moving average (ARMA) model with the initial truncated wavelet. Moreover, a solution to the wavelet initialization problem in the SEM... |
Tipo: Text |
Palavras-chave: Bernoulli Gaussian BG process; Blind deconvolution; Gibbs sampler; Maximum likelihood ML; Maximum posterior mode MPM; Monte Carlo Markov chains MCMCs methods; Prony algorithm; Seismic deconvolution; Stochastic expectation maximization SEM. |
Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/00000/11030/8978.pdf |
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Boucher, Jean. |
The main topic of the cruises ECOMANCHE I and II was to get the offshore data of a Reference Ecological State of the East Channel. This report dealing with the pelagic part of the cruise present the whole measurements carried out to characterize the phyto and zooplankton populations and the hydro biological conditions in 1978 and 1979. The descriptions of geographically distinct sub-systems and the characterization of the age of the populations in the annual cycle will allow in the future to realize similar observations. |
Tipo: Text |
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Ano: 1980 |
URL: https://archimer.ifremer.fr/doc/00431/54256/59120.pdf |
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Boucher, Jean; Razouls, Claude; Razouls, Suzanne. |
Variations of the amount and of the chemical composition in terms of Carbon and Nitrogen for both Copepods Centropages typicus and Temora stylifera sampled in Banyuls-sur-Mer neritic area are analysed in relation with physiological variations attached to annual cycle, sex, growth stage. Measurements on organisms sampled in the Mediterranean ecosystem are compared with equivalents from maroccan Atlantic coastal upwelling. It appears an adaptation of the organisms C/N ratio to the ecological conditions and variation from an ecosystem to the other. [NOT CONTROLLED OCR] |
Tipo: Text |
Palavras-chave: Histoire Ifremer. |
Ano: 1976 |
URL: http://archimer.ifremer.fr/doc/1976/publication-5471.pdf |
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Samain, Jean-francois; Boucher, Jean. |
A method for nutrition, production and ecological studies by calculation of amylase specific activity of zooplankton is described. The method's adjustment is based on the biochemical properties of the enzyme. The activity measurement of a single Artemia salina, a few Copepods, or of the whole contents of a net is possible with 5 % accuracy. Up to 15 samples can be analysed within one hour with good reproducible results. The method is well suited to in situ studies aboard oceanographic vessels. [NOT CONTROLLED OCR] |
Tipo: Text |
Palavras-chave: Histoire Ifremer. |
Ano: 1974 |
URL: http://archimer.ifremer.fr/doc/1974/publication-5424.pdf |
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Blanchard, Fabian; Thebaud, Olivier; Guyader, Olivier; Lorance, Pascal; Boucher, Jean; Chevaillier, Pierre. |
The populations of fishes dwelling near the sea bed (demersal species) on the continental shelf are usually the object of intense commercial exploitation. The Bay of Biscay shelf is no exception. Hence, populations suffer from this exploitation. Moreover, the general role played by hydro-climatic variations in the regulation of the abundance of demersal fish populations (population dynamics) is traditionally admitted. In the Bay of Biscay, a warming of the surface water has been observed over the three last decades (Koutsikopoulos et al., 1998). Climate change therefore has potential consequences on fish communities. Thus, the structure and dynamics of fish populations on the continental shelf of the Bay of Biscay are susceptible to suffer both from the... |
Tipo: Text |
Palavras-chave: Modèles individus centrés; Conséquences économiques; Réchauffement climatique; Impact de la pêche; Communautés de poissons. |
Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/rapport-6347.pdf |
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Boucher, Jean; Laurec, Alain; Samain, Jean-francois; Smith, S. L.. |
The amylase and trypsin activity of the most important zooplankton species has been measured in the upwelling zone of the Spanish Sahara during the "Gibraltar ecophysiological cruise" of the oceanographic vessel Jean Charcot. The analysis of the results was carried out for the double purpose of demonstrating the regulation by the nutrition of the activities of digestive enzymes and utilizing these results to study the feeding behavior under the natural environmental conditions of an ecosystem. With regard to its biological significance, the influence of the quality and quantity of food available has been demonstrated by a bouble experimental approach followed by a statistical one. Significant correlations were found between the specific amylase activity... |
Tipo: Text |
Palavras-chave: Histoire Ifremer. |
Ano: 1975 |
URL: http://archimer.ifremer.fr/doc/1975/publication-5105.pdf |
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Boucher, Jean; Samain, Jean-francois. |
The feeding of the zooplankton has been studied in the natural environment of an upwelling ecosystem by measurements of amylase and protease activities. The hypothesis of enzymatic specific activity as a nutritional index is extended by a correlation with Lorenzen's grazing index. There is no correlation between amylase and protease activity so the diet of the populations is described by the ratio of these two enzymatic activities. Variations of relative feeding rate for Calanus, Temora, Acartia, Podon, and for the total sample are discussed in relation to the ecological and trophic characteristics of the environment. |
Tipo: Text |
Palavras-chave: Histoire Ifremer. |
Ano: 1975 |
URL: http://archimer.ifremer.fr/doc/1975/publication-5463.pdf |
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Blanchard, Fabian; Le Loc'H, Francois; Hily, Christian; Boucher, Jean. |
Within the framework of the 'dynamic equilibrium model', we tested the hypothesis that fishing causes major disturbance to benthic communities on deeper bottoms of the continental shelf. Benthic megafauna on the Bay of Biscay coast of France was sampled on fishing grounds subject to various conditions of exploitation. Samples were taken at around 100 m depth to avoid strong natural disturbances. Species diversity and the largest body mass class of invertebrates were smaller in strongly exploited areas than in moderately exploited ones. Biomass size spectra in strongly exploited areas were characterised by a comparatively large biomass of small invertebrates, hence the K-dominance curve of abundance was either above the biomass curve, or the curves... |
Tipo: Text |
Palavras-chave: Benthic communities; Community dynamics; Disturbance; Diversity; Size spectrum. |
Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/00000/10896/7578.pdf |
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Boucher, Jean; Samain, Jean-francois. |
Specific amylase activity was measured during the CINECA III cruise in the moroccan upwelling area. In this region the population is homogeneous and in a steady state during the study. The hypothesis of enzymatic activity rate as a nutrition index is enlarged by a relation with diet, fast and feeding stock. A mathematical expression is given of the relationship between zooplankton digestive activity and phytoplankton biomass. Analysis of this equation shows a daily physiological rhythm of the amylase activity. [NOT CONTROLLED OCR] |
Tipo: Text |
Palavras-chave: Histoire Ifremer. |
Ano: 1974 |
URL: http://archimer.ifremer.fr/doc/1974/publication-5149.pdf |
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Brunel, Thomas; Boucher, Jean. |
Synchrony in population fluctuations have commonly been observed among a variety of species. They are generally attributed to the effect of common environmental forcings on population dynamics. Here, we investigate long term synchrony in the recruitment variations of the North East Atlantic fish populations. A PCA (principal component analysis) was performed to extract the main patterns of variation. The most significant one reflects the synchronous decrease of the recruitment for the majority of gadoids populations, in the Baltic Sea, Kattegat, North Sea, Irish Sea and West of Scotland. The inverse pattern was observed for half of the herring populations. Plaice populations also exhibit synchronous recruitment trends, characterised by strong year classes... |
Tipo: Text |
Palavras-chave: Synchrony; Regime shift; Recruitment variations; North Eastern Atlantic; Climate change. |
Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/acte-1145.pdf |
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Brunel, Thomas; Boucher, Jean. |
This study investigates the temporal correspondence between the main patterns of recruitment variations among north-east Atlantic exploited fish populations and large-scale climate and temperature indices. It is of primary importance to know what changes in fish stock productivity can be expected in response to climate change, to design appropriate management strategies. The dominant patterns of recruitment variation were extracted using a standardized principal component analysis (PCA). The first principal component (PC) was a long-term decline, with a stepwise change occurring in 1987. A majority of Baltic Sea, North Sea, west of Scotland and Irish Sea populations, especially the gadoids, have followed this decreasing trend. On the contrary, some herring... |
Tipo: Text |
Palavras-chave: North Atlantic; Global warming; Fishing impacts; Fish recruitment; Comparative approach; Climate change. |
Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2636.pdf |
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Brunel, Thomas; Boucher, Jean. |
It has long been argued that populations living on the edges of the species geographical range should exhibit stronger environmentally imposed variations in abundances than populations living near the centre of this range. This so-called 'Species Range Hypothesis' is tested here for the recruitment of 62 marine fish populations of the northeast Atlantic, belonging to 17 species. The pattern of increasing recruitment variability from the centre towards the edges of the species range was modelled by a quadratic linear regression between an index of interannual variability in recruitment and an index of population position in species range. The relationship between recruitment variability and exploitation rate was also investigated. A wide range of... |
Tipo: Text |
Palavras-chave: Environment; Comparative approach; Northeast Atlantic; Species range hypothesis; Recruitment variability. |
Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1119.pdf |
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Boucher, Jean. |
A comparative study of the copepod populations in the upwelling ecosystems of Cap Ghir (Morocco) and Cap Blanc (north Mauritania) was carried out. 187 different copepod species are identified for this north-eastern central part of Atlantic ocean. Among these, Diaixis pigmaea (T. Scott) in Morocco and Cap Blanc, and Temora longicornis (Müller) are new records. The biogeographical identity of this area is set in evidence by a comparison with other atlantic regions and is particularly well defined by the southern limit of distribution of Calanus helgolandicus, Temora longicornis and Oncaea curta. Among the 87 species currently present in the shelf area, dominant taxas are: Acartia clausi, Oncaea curta, Oithona nana, Paracalanus parvus, Clausocalanus jobei,... |
Tipo: Text |
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Ano: 1982 |
URL: http://archimer.ifremer.fr/doc/1982/publication-5349.pdf |
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Boucher, Jean. |
Le peuplement de copépodes des deux régions d'upwelling du Cap Ghir (Maroc) et du Cap Blanc (Nord-Mauritanie) a une composition spécifique, une définition des générations, une distribution spatiale conservées au cours des années successives d'observation. Ceci plaide en faveur d'un maintien de la localisation des individus. Le travail présenté ici a pour but de décrire par une méthode objective ces caractéristiques de distribution spatiale et d'analyser certains des comportements qui permettent ce maintien. Nous avons utilisé l'analyse en composantes principales (ACP) pour étudier de manière simultanée les variations spatiales et temporelles de la distribution des organismes, définir des groupes d'observations de composition faunistique similaire et... |
Tipo: Text |
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Ano: 1982 |
URL: http://archimer.ifremer.fr/doc/1982/publication-5377.pdf |
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Hellequin, Laurent; Boucher, Jean; Lurton, Xavier. |
Processing simultaneous bathymetry and backscatter data, multibeam echosounders (MBESs) show promising abilities for remote seafloor characterization. High-frequency MBESs provide a good horizontal resolution, making it possible to distinguish fine details at. the water-seafloor interface. However, in order to accurately measure the seafloor influence on the backscattered energy,the recorded sonar data must first be processed and cleared of various artifacts. generated by the sonar system itself. Such a preprocessing correction procedure along with the assessment of its validity limits is presented here and applied to a 95-kHz MBES (Simrad EM1000) data set. Beam pattern effects, uneven array sensitivities, and inaccurate normalization of the ensonified... |
Tipo: Text |
Palavras-chave: Seafloor classification; Multibeam echo sounder MBES; K distribution; Backscatter model. |
Ano: 2003 |
URL: http://archimer.ifremer.fr/doc/2003/publication-708.pdf |
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Packard, Théodore.; Harmon, Dana; Boucher, Jean. |
This paper presents measurements of the respiratory electron transport system (ETS) in the plankton from the upwelled waters of Morocco, Mauritania and Baja California. The ETS activity in the euphotic-zone phytoplankton is associated with chlorophyll-a, carbon and 14C-uptake, but not with nitrate reductase activity. Zooplankton respiration and excretion of phosphate and ammonium are calculated from zooplankton ETS measurements. The details of the method and significance of the results are discussed. [NOT CONTROLLED OCR] |
Tipo: Text |
Palavras-chave: Histoire Ifremer. |
Ano: 1974 |
URL: http://archimer.ifremer.fr/doc/1974/publication-5163.pdf |
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Boucher, Jean; De Bovee, Francis; Thiriot, Alain. |
Les échantillons ont été récoltés avec des filets W.P.2 (36) et un échantillonneur rapide, tube HAI (117). La campagne s'est déroulée du 10 mai au 22 juin 1970 en Méditerranée occidentale ; les prélèvements sont plus particulièrement groupés autour des Baléares, dans le golfe de Gênes et en mer d'Alboran. L'échantillonneur, traîné à 6 noeuds, était descendu jusqu'à 200 m et remonté avec quatre paliers. Sa facilité d'utilisation, sa fidélité de mode de pêche et la quantité de plancton récoltée, en font un engin bien adapté a une étude de répartition, même en Méditerranée. L'augmentation de la quantité de micronecton pendant la nuit est très sensible (1 à 8), celle du macroplancton est plus faible (1 à 2), le mésoplancton par contre ne présente pas de... |
Tipo: Text |
Palavras-chave: Histoire Ifremer. |
Ano: 1973 |
URL: http://archimer.ifremer.fr/doc/1973/publication-5025.pdf |
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Registros recuperados: 23 | |
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