Density and Distribution Function estimation through iterates of fractional Bernstein Operators

International audienceWe describe a method for distribution function and density estimation with Bern- stein polynomials. We take advantage of results about the eigenstructure of the Bernstein operator to re ne the Sevy's convergence acceleration method, based on iterates of this opera- tor; the original Sevy's algorithm is improved by introducing fractional operators. The proposed algorithm has better convergence properties than the classical one; the price to pay is a control- lable loss of the shape-preserving properties of the Bernstein approximation (monotonicity and positivity in the Density Estimation setting). The method is tested on simulated data

Global Production Increased by Spatial Heterogeneity in a Population Dynamics Model

Spatial and temporal heterogeneity are often described as important factors having a strong impact on biodiversity. The effect of heterogeneity is in most cases analyzed by the response of biotic interactions such as competition of predation. It may also modify intrinsic population properties such as growth rate. Most of the studies are theoretic since it is often difficult to manipulate spatial heterogeneity in practice. Despite the large number of studies dealing with this topics, it is still difficult to understand how the heterogeneity affects populations dynamics. On the basis of a very simple model, this paper aims to explicitly provide a simple mechanism which can explain why spatial heterogeneity may be a favorable factor for production.We consider a two patch model and a logistic growth is assumed on each patch. A general condition on the migration rates and the local subpopulation growth rates is provided under which the total carrying capacity is higher than the sum of the local carrying capacities, which is not intuitive. As we illustrate, this result is robust under stochastic perturbations

The Rao's distance between negative binomial distributions for Exploratory Analyses and Goodness-of-Fit Testing

International audienceThe statistical analysis of counts of living organisms brings information about the collective behavior of species (schooling, habitat preference, etc), possibly depending on their biological characteristics (growth rate, reproductive power, survival rate, etc). The negative binomial distribution (NB) is widely used to model such data but the parametric approach is ill-suited from an exploratory point of view. Indeed, the visual distance between parameters is not relevant, because it depends on the chosen parametrization! On the contrary, considering the Riemannian manifold N B(D R) of negative binomial distributions equipped with the Fisher-Rao metrics, it is possible to compute intrinsic distances between species. In this work, we focus on geometrical aspects of the χ 2 goodness-of-t (GOF) test for distributions in N B(D R), in connection with the position of the reference distribution. We show that this position is critical for performances of this test, as Critchley & Marriott (2016) noticed in a dierent setting

Application of Ordinal Correspondence Analysis for Submerged Aquatic Vegetation Monitoring

International audienceThe European Water Framework states that macrophyte communities (seaweeds and seagrass) are key indicators of the ecological health of lagoons. Furthermore the restoration of these communities, especially the Zostera meadows, is one of the main objectives of the Berre lagoon restoration plan. Consequently a monitoring program of the main macrophyte species still present in the lagoon was initiated in 1996. This monitoring resulted in a sequence of eleven spatially structured annual tables consisting of the observed density of these species. These tables are processed in this study. First, we specify the principles of Beh's Ordinal Correspondence Analysis (OCA), designed for ordered row/column categories, and compare this method to classical Correspondence Analysis (CA). Then, we show that OCA is straightforwardly adaptable for processing a sequence of ordered contingency tables like ours. Both OCA and CA are afterwards used to reveal and test the main patterns of spatiotemporal changes of two macrophyte species in the Berre lagoon: Ulva and Zostera. The results we obtained are compared and discussed

Fairly processing rare and common species in multivariate analysis of ecological series - Application to macrobenthic communities from Algiers harbour

International audienceSystematic sampling of communities gives rise to large contingency tables summing up possible changes in the assemblages' structure. Such tables are generally analysed by multivariate statistical methods, which are ill-suited for simultaneously analysing rare and common species (Field et al., 1982). In order to separately process species belonging to either of these categories, we propose a statistical method to select common species in a sequence of ecological surveys. It is based on a precise definition of rarity, and depends on a rarity parameter.;In this work, this parameter will be optimised so that the sub-table of common species captures the essential features of the complete table as well as possible. In this way we analysed the spatio-temporal evolution of macrobenthic communities from the Algiers harbour to study the pollution influence during a year. The examination of the communities' structuring was done through Principal Components Analysis (PCA) of the species proportions table. Environmental variables were simultaneously sampled. We show that the data structure can be explained by about 25% of the total number of present species. Two environmental gradients were brought to the fore inside the harbour, the first one representing pollution, and the second one representing hydrological instabilities.;Since rare species can also convey information, the complete table was also coded according to a generalised presence/absence index and submitted to Correspondence Analysis. The results were consistent with those of PCA, but they depended on more species, and highlighted the influence of sedimentology on the assemblages composition

Dosis respuesta en la actividad analgésica periférica de la metformina en la prueba de contorsiones abdominales en ratones

Objective: To evaluate the dose-response analgesic effect of metformin in an acute pain event in rodents. Materials and methods: Eighty (80) mice were used. The analgesic effect was evaluated using the abdominal writhing test in mice. Eight (8) groups of 10 mice each were formed: one diclofenac 8 mg/kg group, one tramadol group, one target group, and five experimental groups of metformin at doses of 50, 100, 150, 200 and 250 mg/kg. For the statistical analysis, the D'Agostino-Pearson test, one-tailed ANOVA test, Tukey's test, and Pearson's correlation coefficient were used. Results: The D'Agostino-Pearson normality test revealed a p-value < 0.05 in all groups. The ANOVA test showed a p-value < 0.0001. The Tukey's range test obtained a p-value < 0.05 between the target group and metformin groups at all doses, and between the diclofenac group and metformin groups at doses of 100, 150, 200 and 250 mg/kg, and a p-value > 0.05 between the tramadol group and metformin groups at doses of 100, 150, 200 and 250 mg/kg. The Pearson's correlation coefficient was r = -0.6897 and R = 0.4756, and yielded a p-value < 0.0001. Metformin showed a pain inhibition percentage in the range of 34.89 % to 92.62 %. Conclusions: It has been demonstrated that metformin at doses of 100, 150, 200 and 250 mg/kg had an acute analgesic effect in the abdominal writhing test in mice, with the 250 mg/kg dose being the one that showed the best effect. In addition, a dose-response effect was obtained in escalated doses of metformin.Objetivo: Evaluar el efecto analgésico dosis respuesta de la metformina en un evento de dolor agudo en roedores.Materiales y métodos: Se utilizaron 80 ratones. Se evaluó el efecto analgésico con la prueba de contorsiones abdominalesen ratones. Se formaron 8 grupos de 10 ratones cada uno: 3 grupos recibieron diclofenaco 8 mg/kg, tramadol y un grupoblanco, y 5 grupos experimentales de metformina a dosis de 50, 100, 150, 200 y 250 mg/kg. Para el análisis estadístico seempleó la prueba de D'Agostino-Pearson, prueba de ANOVA de una cola, prueba de Tukey, y correlación de Pearson.Resultados: Prueba de normalidad de D'Agostino-Pearson reveló un valor p0.05 entre tramadoly metformina a dosis de 100, 150, 200 y 250 mg/kg, la prueba de correlación de Pearson obtuvo un r=-0.6897 y R=0.4756con valor p<0.0001. metformina presentó un porcentaje de inhibición del dolor en rango de 34.89 % - 92.62 %.Conclusiones: Se demuestra que metformina a dosis 100, 150, 200 y 250 mg/kg presentó efecto analgésico agudo en laprueba de contorsiones abdominales en ratón, siendo la dosis de 250 mg/kg la que tuvo mejor efecto. Además, se obtuvoefecto dosis-respuesta en dosis escalonada de metformina

Spatio-temporal dynamics of exploited groundfish species assemblages faced to environmental and fishing forcings : insights from the mauritanian exclusive economic zone

Environmental changes and human activities can have strong impacts on biodiversity and ecosystem functioning. This study investigates how, from a quantitative point of view, simultaneously both environmental and anthropogenic factors affect species composition and abundance of exploited groundfish assemblages (i.e. target and non-target species) at large spatio-temporal scales. We aim to investigate (1) the spatial and annual stability of groundfish assemblages, (2) relationships between these assemblages and structuring factors in order to better explain the dynamic of the assemblages' structure. The Mauritanian Exclusive Economic Zone (MEEZ) is of particular interest as it embeds a productive ecosystem due to upwelling, producing abundant and diverse resources which constitute an attractive socio-economic development. We applied the multi-variate and multi-table STATICO method on a data set consisting of 854 hauls collected during 14-years (1997-2010) from scientific trawl surveys (species abundance), logbooks of industrial fishery (fishing effort), sea surface temperature and chlorophyll a concentration as environmental variables. Our results showed that abiotic factors drove four main persistent fish assemblages. Overall, chlorophyll a concentration and sea surface temperature mainly influenced the structure of assemblages of coastal soft bottoms and those of the offshore near rocky bottoms where upwellings held. While highest levels of fishing effort were located in the northern permanent upwelling zone, effects of this variable on species composition and abundances of assemblages were relatively low, even if not negligible in some years and areas. The temporal trajectories between environmental and fishing conditions and assemblages did not match for all the entire time series analyzed in the MEEZ, but interestingly for some specific years and areas. The quantitative approach used in this work may provide to stakeholders, scientists and fishers a useful assessment for the spatio-temporal dynamics of exploited assemblages under stable or changing conditions in fishing and environment