2,890 research outputs found

    Pairwise likelihood estimation for multivariate mixed Poisson models generated by Gamma intensities

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    Estimating the parameters of multivariate mixed Poisson models is an important problem in image processing applications, especially for active imaging or astronomy. The classical maximum likelihood approach cannot be used for these models since the corresponding masses cannot be expressed in a simple closed form. This paper studies a maximum pairwise likelihood approach to estimate the parameters of multivariate mixed Poisson models when the mixing distribution is a multivariate Gamma distribution. The consistency and asymptotic normality of this estimator are derived. Simulations conducted on synthetic data illustrate these results and show that the proposed estimator outperforms classical estimators based on the method of moments. An application to change detection in low-flux images is also investigated

    Rapid and concomitant gut microbiota and endocannabinoidome response to diet-induced obesity in mice

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    The intestinal microbiota and the expanded endocannabinoid (eCB) system, or endocannabinoidome (eCBome), have both been implicated in diet-induced obesity and dysmetabolism. These systems were recently suggested to interact during the development of obesity. We aimed at identifying the potential interactions between gut microbiota composition and the eCBome during the establishment of diet-induced obesity and metabolic complications. Male mice were fed a high-fat, high-sucrose (HFHS) diet for 56 days to assess jejunum, ileum, and cecum microbiomes by 16S rRNA gene metataxonomics as well as ileum and plasma eCBome by targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS). The HFHS diet induced early (3 days) and persistent glucose intolerance followed by weight gain and hyperinsulinemia. Concomitantly, it induced the elevation of the two eCBs, anandamide, in both ileum and plasma, and 2-arachidonoyl-glycerol, in plasma, as well as alterations in several other N-acylethanolamines and 2-acylglycerols. It also promoted segment-specific changes in the relative abundance of several genera in intestinal microbiota, some of which were observed as early as 3 days following HFHS diet. Weight-independent correlations were found between the relative abundances of, among others, Barnesiella, Eubacterium, Adlercreutzia, Parasutterella, Propionibacterium, Enterococcus, and Methylobacterium and the concentrations of anandamide and the anti-inflammatory eCBome mediator N-docosahexaenoyl-ethanolamine. This study highlights for the first time the existence of potential interactions between the eCBome, an endogenous system of multifunctional signaling lipids, and several intestinal genera during early and late HFHS-induced dysmetabolic events, with potential impact on the host capability of adapting to increased intake of fat and sucrose

    Gene expression signature discriminates sporadic from post-radiotherapy-induced thyroid tumors

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    Both external and internal exposure to ionizing radiation are strong risk factors for the development of thyroid tumors. Until now, the diagnosis of radiation-induced thyroid tumors has been deduced from a network of arguments taken together with the individual history of radiation exposure. Neither the histological features nor the genetic alterations observed in these tumors have been shown to be specific fingerprints of an exposure to radiation. The aim of our work is to define ionizing radiation-related molecular specificities in a series of secondary thyroid tumors developed in the radiation field of patients treated by radiotherapy. To identify molecular markers that could represent a radiation-induction signature, we compared 25K microarray transcriptome profiles of a learning set of 28 thyroid tumors, which comprised 14 follicular thyroid adenomas (FTA) and 14 papillary thyroid carcinomas (PTC), either sporadic or consecutive to external radiotherapy in childhood. We identified a signature composed of 322 genes which discriminates radiation-induced tumors (FTA and PTC) from their sporadic counterparts. The robustness of this signature was further confirmed by blind case-by-case classification of an independent set of 29 tumors (16 FTA and 13 PTC). After the histology code break by the clinicians, 26/29 tumors were well classified regarding tumor etiology, 1 was undetermined, and 2 were misclassified. Our results help shed light on radiation-induced thyroid carcinogenesis, since specific molecular pathways are deregulated in radiation-induced tumors

    Compressed representation of a partially defined integer function over multiple arguments

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    In OLAP (OnLine Analitical Processing) data are analysed in an n-dimensional cube. The cube may be represented as a partially defined function over n arguments. Considering that often the function is not defined everywhere, we ask: is there a known way of representing the function or the points in which it is defined, in a more compact manner than the trivial one

    Search for neutral color-octet weak-triplet scalar particles in proton-proton collisions at √s= 8TeV