Extracting a common high frequency signal from Northern Quebec black spruce tree-rings with a Bayesian hierarchical model

in Climate of the Past (2009), 5

One basic premise of dendroclimatology is that tree rings can be viewed as climate proxies, i.e. rings are assumed to contain some hidden information about past climate. From a statistical perspective ... [more ▼]

One basic premise of dendroclimatology is that tree rings can be viewed as climate proxies, i.e. rings are assumed to contain some hidden information about past climate. From a statistical perspective, this extraction problem can be understood as the search of a hidden variable which represents the common signal within a collection of tree-ring width series. Classical average-based techniques used in dendrochronology have been applied to estimate the mean behavior of this latent variable. Still, depending on tree species, regional factors and statistical methods, a precise quantification of uncertainties associated to the hidden variable distribution is difficult to assess. To model the error propagation throughout the extraction procedure, we propose and study a Bayesian hierarchical model that focuses on extracting an inter-annual high frequency signal. Our method is applied to black spruce (Picea mariana) tree-rings recorded in Northern Quebec and compared to a classical average-based techniques used by dendrochronologists. [less ▲]

Extracting Intra-Domain Topology from mrinfo Probing

in 11th international Conference on Passive and active Measurement (2010, April)

Activeandpassivemeasurementsfortopologydiscoveryhave known an impressive growth during the last decade. If a lot of work has been done regarding inter-domain topology discovery and modeling, only a few ... [more ▼]

Activeandpassivemeasurementsfortopologydiscoveryhave known an impressive growth during the last decade. If a lot of work has been done regarding inter-domain topology discovery and modeling, only a few papers raise the question of how to extract intra-domain topologies from measurements results. In this paper, based on a large dataset collected with mrinfo, a multicast tool that silently discovers all interfaces of a router, we provide a mechanism for retrieving intra-domain topologies. The main challenge is to assign an AS number to a border router whose IP addresses are not mapped to the same AS. Our algorithm is based on probabilistic and empirical IP allocation rules. The goal of our pool of rules is to converge to a consistent router to AS mapping. We show that our router-to-AS algorithm results in a mapping in more than 99% of the cases. Furthermore, with mrinfo, point-to-point links between routers can be distinguished from multiple links attached to a switch, providing an accurate view of the collected topologies. Finally, we provide a set of large intra-domain topologies in various formats. [less ▲]

Extraction and characterisation of a dietary fibre concentrate from date pulp

Poster (2006, June)

Extraction And Characterization Of Water-Extractable And Water-Unextractable Arabinoxylans From Spelt Bran: Study Of The Hydrolysis Conditions For Monosaccharides Analysis.

in Journal of Cereal Science (2011)

Extraction and fractionation of cytotoxic metabolites from Galanthus lagodechianus Kem.-Nath

in Allergology and Immunology (Moscou) (2006), 7

Extraction conditions can greatly influence antioxidant capacity assays in plant food matrices

in Food Chemistry (2011)

The estimated antioxidant capacity of different matrices can vary considerably between research reports. Besides intrinsic factors (not studied here), our work showed that may have various causes. Firstly ... [more ▼]

The estimated antioxidant capacity of different matrices can vary considerably between research reports. Besides intrinsic factors (not studied here), our work showed that may have various causes. Firstly, different methods are used to measure antioxidant capacity. Secondly, the results obtained for a single matrix by one method (such as ORAC) can vary with the extraction conditions. Parameters having a great impact on the amount and composition of antioxidants in extracts, and thus on the measured antioxidant capacity, notably include the extraction solvent composition, temperature, extraction time (duration), solvent-to-solid ratio, and storage conditions. Standardization of the extraction procedure is thus necessary for accurate and reproducible determination of the antioxidant capacity and phenolics in different food matrices by different laboratories. In this study we optimised such a procedure for four fresh plant matrices (orange, apple, leek, and broccoli). The optimised procedure requires extraction in a mixture of acetone/water/acetic acid (70/28/2, v/v/v) for 1 h at 4°C, with a solvent-to-solid ratio of 20 mL per 1 g. Fresh material should be used, but if this is not possible, one may lyophilise the plant matrices or store the extracts for a few days at -20°C before analysis. [less ▲]

Extraction d'une canine chez un ours polaire

in Annales de Médecine Vétérinaire (1995)

L'extraction de matrices solides

Learning material (2007)

La préparation de l'échantillon est une étape clé et indispensable au dosage de l'analyte dans la matrice solide. Les principes de base et applications des procédés dits "conventionnels" (macération ... [more ▼]

La préparation de l'échantillon est une étape clé et indispensable au dosage de l'analyte dans la matrice solide. Les principes de base et applications des procédés dits "conventionnels" (macération, percolation et soxhlet) et "modernes" (micro-ondes,assistée par solvant et en phase supercritique) sont repris dans le document. Compte tenu de l'utilisation et des avantages de l'extraction par les fluides supercritiques, ce procédé est présenté plus en détails. [less ▲]

Extraction of ferulic acid from Walloon agro-industrial by-products.

Poster (2007, October 11)

Extraction of land use / landcover – related information from very high resolution data in urban and suburban areas

in Goossens, Rudi (Ed.) Remote Sensing in Transition (2004)

Very High Resolution (VHR) satellite images offer a great potential for the extraction of landuse and land-cover related information for urban areas. The available techniques are diverse and need to be ... [more ▼]

Very High Resolution (VHR) satellite images offer a great potential for the extraction of landuse and land-cover related information for urban areas. The available techniques are diverse and need to be further examined before operational use is possible. In this paper we applied two pixel-by-pixel classification techniques and the object-oriented image analysis approach (eCognition) for a land-cover classification of a Quickbird image of a study area in the northern part of the city of Ghent (Belgium). Only small differences in overall Kappa were noted between the best results of the pixel-based approach (neural network classification with Haralick texture measures) and the object-oriented classification (eCognition). A rule-based procedure using ancillary information on elevation derived from a digital surface model was applied on the pixel-based land-cover classification in order to obtain information on the spatial distribution of buildings and artificial surfaces. [less ▲]