Commune de Cazavet

Le deuxième volet de l’opération de prospection réalisée sur la commune, a consisté au relevé de différents types d’empreintes de nature anthropique répartis sur 1 793 ha. Ces aménagements ou traces rencontrés dans les milieux forestiers, pastoraux ou agraires sont marqués par une géologie au caractère karstique (lapiaz, dolines, poljés et cours d’eau temporaires). L’exhaustivité n’est pas visée et l’approche est sans parti pris chronologique. Du point de vue de la prospection en milieu soute..

Neurocomputational model for learning, memory consolidation and schemas

This thesis investigates how through experience the brain acquires and stores memories, and uses these to extract and modify knowledge. This question is being studied by both computational and experimental neuroscientists as it is of relevance for neuroscience, but also for artificial systems that need to develop knowledge about the world from limited, sequential data. It is widely assumed that new memories are initially stored in the hippocampus, and later are slowly reorganised into distributed cortical networks that represent knowledge. This memory reorganisation is called systems consolidation. In recent years, experimental studies have revealed complex hippocampal-neocortical interactions that have blurred the lines between the two memory systems, challenging the traditional understanding of memory processes. In particular, the prior existence of cortical knowledge frameworks (also known as schemas) was found to speed up learning and consolidation, which seemingly is at odds with previous models of systems consolidation. However, the underlying mechanisms of this effect are not known. In this work, we present a computational framework to explore potential interactions between the hippocampus, the prefrontal cortex, and associative cortical areas during learning as well as during sleep. To model the associative cortical areas, where the memories are gradually consolidated, we have implemented an artificial neural network (Restricted Boltzmann Machine) so as to get insight into potential neural mechanisms of memory acquisition, recall, and consolidation. We analyse the network’s properties using two tasks inspired by neuroscience experiments. The network gradually built a semantic schema in the associative cortical areas through the consolidation of multiple related memories, a process promoted by hippocampal-driven replay during sleep. To explain the experimental data we suggest that, as the neocortical schema develops, the prefrontal cortex extracts characteristics shared across multiple memories. We call this information meta-schema. In our model, the semantic schema and meta-schema in the neocortex are used to compute consistency, conflict and novelty signals. We propose that the prefrontal cortex uses these signals to modulate memory formation in the hippocampus during learning, which in turn influences consolidation during sleep replay. Together, these results provide theoretical framework to explain experimental findings and produce predictions for hippocampal-neocortical interactions during learning and systems consolidation

Parametric Copula-GP model for analyzing multidimensional neuronal and behavioral relationships

One of the main goals of current systems neuroscience is to understand how neuronal populations integrate sensory information to inform behavior. However, estimating stimulus or behavioral information that is encoded in high-dimensional neuronal populations is challenging. We propose a method based on parametric copulas which allows modeling joint distributions of neuronal and behavioral variables characterized by different statistics and timescales. To account for temporal or spatial changes in dependencies between variables, we model varying copula parameters by means of Gaussian Processes (GP). We validate the resulting Copula-GP framework on synthetic data and on neuronal and behavioral recordings obtained in awake mice. We show that the use of a parametric description of the high-dimensional dependence structure in our method provides better accuracy in mutual information estimation in higher dimensions compared to other non-parametric methods. Moreover, by quantifying the redundancy between neuronal and behavioral variables, our model exposed the location of the reward zone in an unsupervised manner (i.e., without using any explicit cues about the task structure). These results demonstrate that the Copula-GP framework is particularly useful for the analysis of complex multidimensional relationships between neuronal, sensory and behavioral variables

AComDim applied to evaluate gamma irradiation impact on multilayer PE based films

The use of single-use systems is becoming increasingly common in the biopharmaceutical and biotechnology industries. These systems are manufactured from polymers such as polyethylene (PE) and ethylene vinyl acetate (EVA). For their future applications, these devices are sterilized by γ-irradiation with a dose between 25 and 45kGy. C. Artandi and W.V. Winkle[i] determined that 25kGy is the dose to be at 40% above the minimum needed to kill the most resistant microorganisms. The purpose of this study is to understand what happens on the surface of polymers after γ-sterilization. Optical spectroscopy are of great interest for chemical analysis and are used to obtain information on the composition of materials, such as polymers. The Fourier Transform Infrared (FTIR) spectroscopy provides information on the fundamental vibrations of the molecules using an excitation in the visible. The surface of films is analyzed after being sterilized with different radiation doses and after a natural ageing of few months to check their composition and stability by FTIR spectroscopy. As the number of data is important, the use of chemometric methods, like Principal Component Analysis (PCA) and AComDim (ANOVA Common Dimensions), has many advantages, such as identification of shift and intensity modification, detection and highlighting of the influential factors and interactions between several elements (γ-doses, aging, and film batches)

Discrimination by Infrared Spectroscopy: Application to Micronized Locust Bean and Guar Gums

The authentication of locust bean and guar powder gums requires usually the use of sophisticated and time-consuming analytical techniques. There is a need for fast and simple analytical techniques for the objective of a quality control methodology. Commercial locust bean and guar micronized powder gums present characteristic MIR spectra. Principal component analysis of the infrared spectra of these micronized powder gums allowed to distinguish locust bean from guar samples and to perform good classification results. The prediction of the two varieties was done without any ambiguity with a partial least square regression-discriminant analysis (PLS-DA). A simplex approach was used to generate binary blends mathematically taking into account the intrinsic variability of chemical composition of commercial products. The simulated spectral profiles allowed to develop predictive model of the percentage of gums in blends

Identification of antioxidant by-products based on their specific chemistry and their potential detection during SUS extractable study

Single-use films in biopharmaceutical and biotechnology industries are mainly made from polymers such as PE, EVA and EVOH. Depending upon the environmental aggressiveness during various stages of the polymer lifetime, additives are added to protect them such as substituted hindered phenols acting as antioxidants, melt (processing) stabilizers, and to some extent as photo-antioxidants. Ionizing radiation effects on polymers have been widely investigated. They consist mainly of free radicals production. These free radicals can in turn lead to degradation and or crosslinking phenomena (release of gases, discoloration, changes in mechanical properties and gas permeability, degradation and leaching of polymer additives into solvents, etc.) whose extent depends on many factors. In contrast, there is little information on the effect of ionizing radiation on the additive package properties used in multilayer packaging films. A specific influence on chemical transformations of phenols is induced as well. Strong discoloration of the polymer stabilized with phenolic antioxidants originates for instance mainly from the reaction products of the stabilizers. The color development can be attributed to the formation of conjugated diene compounds, arising as a consequence of trapping of radicals by phenolics. The discoloration depends on the structure and concentration of the phenolic transformation products. As a result of the described complexity, a huge variety of potential extractable compounds can be expected from antioxidants. This work focuses of highlighting the degradation products we may expect from the thermal and radiative degradation of the primary and secondary anti-oxidants and to address complexity of identifying properly the by-products one may detect in extractable study applied to pharmaceutical single use products

pH evolution in solution after contact with multilayer films after different g- irradiation doses and thus reconciliation of pH and TOC with carboxylic acids detected by ion chromatography

For a number of various uses (storage, mixing, freezing, transportation, formulation, and filling) biopharmaceutical solutions are stored in sterile single-use plastic bags. Material transfers can then occur between containers and contents. These migrations, of different types, depend on the physicochemical characteristics of the material (composition, pH, solubility, viscosity, molecular weight, etc.), the nature of the product (solid, semi-solid and liquid) and the conditions of the material utilization. In the case of single-use polymers, γ-irradiation sterilization of the polymer is often carried out. The interactions could be therefore influenced by the dose and the contact time between the container and the contents. γ-sterilization of single-use systems initiates chemical reactions and complex modifications inside the plastic material, In this study, γ-irradiation doses investigated are up to 270 kGy in order to emphazise the γ-irradiation effect and to better investigate the modifications of commercial PE(Polyethylene)/EVOH(Ethylene Vinyl Alcohol)/PE-film and commercial EVA(Ethylene Vinyl Acetate)/EVOH/EVA film. This study is a part of a global investigation on γ-irradiation on multilayer films Non-specific (TOC, pH, conductivity) or specific (e.g. chromatographic, spectroscopic, gravimetric) analytical methods can be used. several approaches were used to study the impact of γ-irradiation on multilayer films, as ion chromatography to detect and quantify the ionic species, and as pH and conductivity measurements to observe the consequences of the chemical modifications.. There are few references available on the leaching of carboxylic acid species impacting aqueous solutions used in biopharmaceutical applications in contact with plastic single-use systems [[i]]. Stability studies under accelerated or real-time degradation conditions make it possible to define the shelf life and storage conditions in order to guarantee the quality of the product. The aim of the study is to identify and quantify the acid compounds that can be released from the container under normal conditions of use of the materials: the extractables. [[1]] D. Jenke, D and V.J. Barge. Factors affecting the release of extractable acetic acid from multi-layered plastic films containing ethylene vinyl acetate (EVA) and polyethylene (PE) layers. Pharm Outsourcing. 15 (2014) 56-59

Influence of γ-irradiated biopharmaceutical films

Preventing cross-contamination, saving costs and increasing configuration flexibility make the adoption of single-use technologies very attractive for the biopharmaceutical industry. The integrity and the security of bags are due to appropriate flexible and barrier polymeric materials, such as polyethylene (PE) or ethylene vinyl acetate (EVA) and polyethylene-co-vinyl alcohol (EVOH), which are barrier to water vapor and oxygen, respectively. Conventional stainless steel tanks are sterilized by steam sterilization by the end-users, whereas plastic containers are sterilized by gamma-irradiation before delivery. The major advantage of radio-sterilization is the penetration power of the γ-radiation. It is known that γ -sterilization of polyolefin based polymer leads to alterations of the material: changes in the additives or potential damage to the polymer, as reported in the literature. Irradiation of polymeric materials has been proven to initiate radiation chemical reactions inside the polymeric material, leading to either an increase or a decrease in the polymer molecular weight. The effects of γ-irradiation on polymers are well known whereas the effects of γ-irradiation on multilayer films have been little investigated. In the case of multilayer films, the acidity of the stored solution increased after gamma irradiation for instance. In another case oxidation of the solution occurred. Such observations denote the presence of acidic and oxidant compounds, which are issued either from modification of surface of the film or from the migration of by-products from core to surface. A global investigation on γ-irradiation on multilayer films is performed to investigate the γ-irradiation based modifications on PE(Polyethylene)/EVOH(Ethylene Vinyl Alcohol)/PE film and EVA(Ethylene Vinyl Acetate)/EVOH/EVA film to assess the multilayer film robustness. Several approaches could be used to study the impact of γ-irradiation on multilayer films, as ESR (Electron Spin Resonance) to observe the radicals formation, ATR-FTIR (Attenuated Total Reflection-Fourier Transform Infrared) and Raman spectroscopies to observe the structural modifications, the measurement of yellowing, the measurement of O2 transmission rate (O2TR) and water vapor transmission rate (WVTR), the measurement of pH to follow the acidity change of solution contained in the bag and the mechanical test to evaluate the toughness of film. Due to the number of data recorded, chemometric methods, such as Principal Component Analysis (PCA), are applied to enhance the weak variations brought to the γ-irradiation of the multilayer films in the different data sets. Results show that films undergo modifications at microscopic level and that they are not altered from macroscopic and application viewpoints. Results are equivalent from batch to batch assuring then a reproducibility of the films behavior for their integration in single-use systems

Bacterivory by benthic organisms in sediment: quantification using 15N enriched bacteria

International audienceThe fate of benthic bacterial biomass in benthic food webs is a topic of major importance but poorly described. This paper describes an alternative method for evaluation of bacterial grazing rate by meiofauna and macrofauna using bacteria pre-enriched with stable isotopes. Natural bacteria from the sediment of an intertidal mudflat were cultured in a liquid medium enriched with 15NH4Cl. Cultured bacteria contained 2.9 % of 15N and were enriched sufficiently to be used as tracers during grazing experiments. Cultured-bacteria presented a biovolume (0.21 µm3) and a percentage of actively respiring bacteria (10 %) similar to those found in natural communities. The number of Operational Taxon Units found in cultures fluctuated between 56 and 75 % of that found in natural sediment. Despite this change in community composition, the bacterial consortium used for grazing experiments exhibited characteristics of size, activity and diversity more representative of the natural community than usually noticed in many other grazing studies. The bacterial ingestion rates of three different grazers were in the range of literature values resulting from other methods: 1149 ngC ind-1 h-1 for the mud snail Hydrobia ulvae, 0.027 ngC ind-1 h-1 for the nematode community, and 0.067 ngC ind-1 h-1 for the foraminifera Ammonia tepida. The alternative method described in this paper overcomes some past limitations and it presents interesting advantages such as short time incubation and in situ potential utilisation

Une approche par dissimilarité pour la caractérisation de jeux de données

La caractérisation de jeu de données reste un verrou majeur de l'analyse de données intelligente. Une majorité d'approches à ce problème agrègent les informations décrivant les attributs individuels des jeux de données, ce qui représente une perte d'information. Nous proposons une approche par dissimilarité permettant d'éviter cette agrégation, et étudions son intérêt dans la caractérisation des performances d'algorithmes de classifications, et dans la résolution de problèmes de méta-apprentissage