Evaluation of an alternative spectroscopic approach for aflatoxin analysis: Comparative analysis of food and feed samples with UPLC-MS/MS

Increasing research has highlighted the effects of changing climates on the occurrence and prevalence of toxigenic Aspergillus species producing aflatoxins. There is concern of the toxicological effects to human health and animal productivity following acute and chronic exposure that may affect the future ability to provide safe and sufficient food globally. Considerable research has focused on the detection of these toxins, based on the physicochemical and biochemical properties of the aflatoxin compounds, in agricultural products for human and animal consumption. As improvements in food security continue more regulations for acceptable levels of aflatoxins have arisen globally; the most stringent in Europe. These regulations are important for developing countries as aflatoxin occurrence is high significantly effecting international trade and the economy. In developed countries analytical approaches have become highly sophisticated, capable of attaining results with high precision and accuracy, suitable for regulatory laboratories. Regrettably, many countries that are affected by aflatoxin contamination do not have resources for high tech HPLC and MS instrumentation and require more affordable, yet robust equally accurate alternatives that may be used by producers, processors and traders in emerging economies. It is especially important that those companies wishing to exploit the opportunities offered by lucrative but highly regulated markets in the developed world, have access to analytical methods that will ensure that their exports meet their customers quality and safety requirements. This work evaluates the ToxiMet system as an alternative approach to UPLC–MS/MS for the detection and determination of aflatoxins relative to current European regulatory standards. Four commodities: rice grain, maize cracked and flour, peanut paste and dried distillers grains were analysed for natural aflatoxin contamination. For B1 and total aflatoxins determination the qualitative correlation, above or below the regulatory limit, was good for all commodities with the exception of the dried distillers grain samples for B1 for which no calibration existed. For B1 the quantitative R2 correlations were 0.92, 0.92, 0.88 (<250 μg/kg) and 0.7 for rice, maize, peanuts and dried distillers grain samples respectively whereas for total aflatoxins the quantitative correlation was 0.92, 0.94, 0.88 and 0.91. The ToxiMet system could be used as an alternative for aflatoxin analysis for current legislation but some consideration should be given to aflatoxin M1 regulatory levels for these commodities considering the high levels detected in this study especially for maize and peanuts. (Résumé d'auteur

Epigenetic remodeling in B-cell acute lymphoblastic leukemia occurs in two tracks and employs embryonic stem cell-like signatures

We investigated DNA methylomes of pediatric B-cell acute lymphoblastic leukemias (B-ALLs) using whole-genome bisulfite sequencing and high-definition microarrays, along with RNA expression profiles. Epigenetic alteration of B-ALLs occurred in two tracks: de novo methylation of small functional compartments and demethylation of large intercompartmental backbones. The deviations were exaggerated in lamina-associated domains, with differences corresponding to methylation clusters and/or cytogenetic groups. Our data also suggested a pivotal role of polycomb and CTBP2 in de novo methylation, which may be traced back to bivalency status of embryonic stem cells. Driven by these potent epigenetic modulations, suppression of polycomb target genes was observed along with disruption of developmental fate and cell cycle and mismatch repair pathways and altered activities of key upstream regulators.This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by Oxford University Press on behalf of Nucleic Acids Research. The published article can be found at: http://nar.oxfordjournals.org/

Étude de l’effet des interactions élastiques et électroniques dans les théories de champs en basse dimension

This thesis explores the effect of interactions in several low-dimensional field theories with the help of both perturbative and non-perturbative analytic field-theory techniques. Our primary focus is on planar condensed matter physics systems and their interaction-induced, thermal or quantum, phase transitions. The latter are characterized by anomalous dimensions, or equivalently critical exponents, which are universal physical observables calculable with multiloop Feynman diagram techniques. A first part is devoted to the study of elastic fluctuations in several statistical field theories associated with the flat phase of polymerized membranes, ubiquitous in physics. We explore their critical mechanical properties, in particular the anomalous stiffness induced by long-range correlations that we compute at high loop order. A variant including disorder is also considered through the technique of replicas, unveiling a new wrinkling transition towards a glassy phase. A second part examines several abelian gauge field theories in low dimensions, which are particularly useful to describe strongly correlated planar fermionic quantum systems like graphene at low energies. We also consider a minimally supersymmetric extension in relation with a potential supergraphene material. For these models, we compute their critical exponents, in the loop or Nf expansion, and address the possibility of a metallic to insulating phase transition through the generation of a dynamical mass for the electron.Cette thèse explore l'effet des interactions dans plusieurs théories des champs de basse dimension à l'aide de techniques analytiques perturbatives et non perturbatives de la théorie des champs. Nous nous concentrons principalement sur les systèmes planaires de la physique de la matière condensée et leurs transitions de phase, thermiques ou quantiques, induites par les interactions. Ces dernières sont caractérisées par des dimensions anormales, ou de manière équivalente des exposants critiques, qui sont des observables physiques universelles calculables avec les techniques de diagramme de Feynman multi-boucles. Une première partie est consacrée à l'étude des fluctuations élastiques dans plusieurs théories statistiques des champs associées à la phase plate des membranes polymérisées, omniprésentes en physique. Nous explorons leurs propriétés mécaniques critiques, en particulier la rigidité anormale induite par les corrélations à longue portée que nous calculons à un ordre en boucles élevé. Une variante incluant du désordre est aussi considérée par la technique des répliques, dévoilant une nouvelle transition de plissement vers une phase de verre. Une deuxième partie examine plusieurs théories de jauge abéliennes en basse dimension, qui sont particulièrement utiles pour décrire les systèmes quantiques fermioniques planaires fortement corrélés comme le graphène à basse énergie. Nous considérons également une extension minimalement supersymétrique en relation avec un potentiel supergraphène. Pour ces modèles, nous calculons les exposants critiques, par un développement en boucles ou Nf, et abordons la possibilité d'une transition de phase métal isolant par la génération dynamique d'une masse pour l'électron

Study of elastic and electronic interaction effects in low-dimensional field theories

Cette thèse explore l'effet des interactions dans plusieurs théories des champs de basse dimension à l'aide de techniques analytiques perturbatives et non perturbatives de la théorie des champs. Nous nous concentrons principalement sur les systèmes planaires de la physique de la matière condensée et leurs transitions de phase, thermiques ou quantiques, induites par les interactions. Ces dernières sont caractérisées par des dimensions anormales, ou de manière équivalente des exposants critiques, qui sont des observables physiques universelles calculables avec les techniques de diagramme de Feynman multi-boucles. Une première partie est consacrée à l'étude des fluctuations élastiques dans plusieurs théories statistiques des champs associées à la phase plate des membranes polymérisées, omniprésentes en physique. Nous explorons leurs propriétés mécaniques critiques, en particulier la rigidité anormale induite par les corrélations à longue portée que nous calculons à un ordre en boucles élevé. Une variante incluant du désordre est aussi considérée par la technique des répliques, dévoilant une nouvelle transition de plissement vers une phase de verre. Une deuxième partie examine plusieurs théories de jauge abéliennes en basse dimension, qui sont particulièrement utiles pour décrire les systèmes quantiques fermioniques planaires fortement corrélés comme le graphène à basse énergie. Nous considérons également une extension minimalement supersymétrique en relation avec un potentiel supergraphène. Pour ces modèles, nous calculons les exposants critiques, par un développement en boucles ou Nf, et abordons la possibilité d'une transition de phase métal isolant par la génération dynamique d'une masse pour l'électron.This thesis explores the effect of interactions in several low-dimensional field theories with the help of both perturbative and non-perturbative analytic field-theory techniques. Our primary focus is on planar condensed matter physics systems and their interaction-induced, thermal or quantum, phase transitions. The latter are characterized by anomalous dimensions, or equivalently critical exponents, which are universal physical observables calculable with multiloop Feynman diagram techniques. A first part is devoted to the study of elastic fluctuations in several statistical field theories associated with the flat phase of polymerized membranes, ubiquitous in physics. We explore their critical mechanical properties, in particular the anomalous stiffness induced by long-range correlations that we compute at high loop order. A variant including disorder is also considered through the technique of replicas, unveiling a new wrinkling transition towards a glassy phase. A second part examines several abelian gauge field theories in low dimensions, which are particularly useful to describe strongly correlated planar fermionic quantum systems like graphene at low energies. We also consider a minimally supersymmetric extension in relation with a potential supergraphene material. For these models, we compute their critical exponents, in the loop or Nf expansion, and address the possibility of a metallic to insulating phase transition through the generation of a dynamical mass for the electron

Critical Properties of Three-Dimensional Many-Flavor QEDs

We review several variants of three-dimensional quantum electrodynamics (QED3) with Nf fermion (or boson) flavors, including fermionic (or spinorial) QED3, bosonic (or scalar) QED3, N=1 supersymmetric QED and also models of reduced QED (supersymmetric or not). We begin with an introduction to these models and their flow to a stable infra-red fixed point in the large-Nf limit. We then present detailed state-of-the-art computations of the critical exponents of these models within the dimensional regularization (and reduction) scheme(s), at the next-to-leading order in the 1/Nf expansion and in an arbitrary covariant gauge. We finally discuss dynamical (matter) mass generation and the current status of our understanding of the phase structure of these models

Characterization of major elements of insulin signaling cascade in chicken adipose tissue: apparent insulin refractoriness

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Vocalisation du poussin : développement d'une méthode d'enregistrement et d'analyse

International audienceThis study aims to develop a method for recording and analysing chicks vocalisations emitted during the first 3days of life (D0 to D3). First, a bibliographic review identified vocalizations categories emitted by chicks(comfort, distress, snuggle, fear or pleasure trills) and identified their sound characteristics. Then, two programsdeveloped under Matlab, made it possible (1) to automate the recording of sound sequences and (2) to detect andidentify comfort and distress vocalizations. The study defined optimal sound recording conditions allowing anoptimal analysis of sound signals: a group of ten chicks, omni-directional microphones, 2-minute recordingsequences. Between D0 and D3, chicks emit short sounds with a limited frequency range (2000 - 5000 Hz). Theprogram developed is functional to characterize the following sound indicators: the frequencial gravity center,spectral spreading and instantaneous frequency. It also allows, through a time-frequency analysis of theirsignature, to count the chicks' comfort and distress vocalizations.Cette étude vise à développer une méthode d’enregistrement et d’analyse des vocalisations émises par lespoussins lors des 3 premiers jours de vie (J0 à J3). Dans un premier temps, une analyse de la bibliographie apermis d'identifier les différentes catégories de vocalisations émises par les poussins (confort, détresse,blottissement, trille de peur ou de plaisir) et d'identifier leurs caractéristiques sonores. Ensuite, deux programmesdéveloppés sous Matlab, ont permis (1) d’automatiser les séquences d’enregistrement et (2) de détecter etd'identifier les vocalisations de confort et de détresse. L’étude a permis de définir des conditions optimales deprise de son permettant une analyse optimale des signaux : groupe d'une dizaine de poussins, des microphonesomni-directionnels, des séquences de 2 minutes d’enregistrement. Entre J0 et J3, les poussins émettent des sonscourts dont la bande de fréquence est limitée (2000 - 5000 Hz). Le programme développé est fonctionnel pourcaractériser les indicateurs sonores suivants : le centre de gravité fréquentiel, l’étalement spectral ainsi que lafréquence instantanée. Il permet également par une analyse temps-fréquence de leur signature, de dénombrer lesvocalisations de confort et de détresse des poussins

Chick vocalizations: development of a recording and analysis method

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First evidence of an insulin-sensitive glucose transporter in chicken

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