Le potentiel du saule pour la phytostabilisation des sols pollués par les éléments-traces métalliques

Doctoral thesis (2013)

Since the ‘80s, when the concept of phytoremediation first appeared, a lot of research has been put into studying the efficiency of woody plants in metal extraction. Willows, as fast growing plants and ... [more ▼]

Since the ‘80s, when the concept of phytoremediation first appeared, a lot of research has been put into studying the efficiency of woody plants in metal extraction. Willows, as fast growing plants and because of their tolerance to difficult edaphic conditions, have been particularly well investigated. In this investigation, the essays were done on Salix clones, which come from a Walloon collection provided by ECOLIRI and ECOLIRIMED projects. The first objective was to study the potential of these local clones by considering not only their ability to extract their pollutants, but also by adding their biomass production to this parameter. We have called the study of these criteria the phenotypic approach to the tolerance of Salix clones to metals. The second added value of this investigation lies in the second objective which aims to complete these phenotypic criteria with physiological and proteomic criteria. These last criteria are often used to study the metal tolerance of plant species, but rarely for willows. The combination of these different approaches gives a expand view of metal tolerance in Salix clones studied in this investigation. As the phenotypical parameters help to answer the extraction ability challenge, the physiological and proteomic approaches give answers linked to the “health” of the willow trees when they grow in the presence of metals. Our results indicate that the clones that produced more biomass were the ones that showed the highest metal concentrations. The clones with lower biomass production showed the same tolerance as the highest producers and our results revealed that growth reduction indicates metal tolerance. Finally, after comparing our results of the metal concentrations obtained in the twigs, to results obtained during the last two decades of research papers, we have concluded that we should reconsider the use of Salix potential in phytoextraction. The first chapter of this investigation was about Salix clones exposed to metals, but, in natural conditions, their roots are colonized by fungi. Thus, their rhizosphere constitutes a separate ecosystem, which is interesting to investigate. The rhizospheric fungi, the first interface between roots and soil pollutants, play an important role in metal tolerance in woody plants. For this reason, the second chapter of this thesis aimed to test the in vitro growth of rhizospheric fungi collected on woody plant roots in the presence of cadmium. The outcome of these essays is that fungal strains have been identified and classified as tolerant to this metal. This chapter thus constitutes a first step in a future study aiming to analyze these strains in association with woody plant roots in the presence of metals. [less ▲]

Quasi-One-Dimensional Numerical Simulations of Post-Stall Compression Systems

Doctoral thesis (2013)

Hygrothermal behavior modeling of different Lime-Hemp Concrete mixes

Conference (2013, May 27)

This paper studies the specific hygrothermal behavior of Lime-Hemp concretes through analysis of non-linear coupled heat and moisture transfer using a research model. Three compositions were studied ... [more ▼]

This paper studies the specific hygrothermal behavior of Lime-Hemp concretes through analysis of non-linear coupled heat and moisture transfer using a research model. Three compositions were studied, varying the type of binder. First Moisture Buffer Value determination tests are lead experimentally using the NORDTEST protocol. These dynamic experiments, which reveal the moisture storage and exchange capacity together with latent heat effects, are then modeled using a set of partial differential equations. The reduction of humidity buffering capacity induced by hydraulic binder incorporation is properly evaluated and the hygrothermal parameters can be assessed by inverse modeling. [less ▲]

Blattmaske. Figure du rinceau peuplé dans les mosaïques d'Asie Mineure

Scientific conference (2013, May 25)

Expliquer et illustrer Prospéro. Suivre le marqueur temporel "le-pire-est-à-venir" au sein des agendas politiques climatiques belges (1980-2012)

Conference (2013, May 24)

Variabilité de la respiration hétérotrophe du sol dans des écosystèmes agricoles: Analyse à différentes échelles spatiales et temporelles.

Doctoral thesis (2013)

Soil heterotrophic respiration (HR) was studied at different spatial and temporal scales in agricultural ecosystems in Belgium (loamy region). Results from both laboratory and field experiments conducted ... [more ▼]

Soil heterotrophic respiration (HR) was studied at different spatial and temporal scales in agricultural ecosystems in Belgium (loamy region). Results from both laboratory and field experiments conducted at short and long timescales were analysed with the aim to better understand the influence of driving variables such as temperature, substrate input quantity and quality on HR. Both empirical and semi-mechanistic models were used in order to help interpret experimental results. Our observations showed that temperature is an important HR driving variable in agricultural ecosystems in temperate regions. HR sensitivity to temperature, characterized by a Q10 differing from 2 in our experiments, was very likely influenced by substrate availability and quality. The impact of these last two factors was however never observed through our measurements. Good agreement between modelled and observed CO2 fluxes in the incubation experiment, where carbon substrate was limited, suggested that temperature played a role both directly (enzymatic response) and indirectly (labile carbon stock depletion) at a relatively short term, and confirmed the hypothesis of occurrence of abiotic fluxes linked to the presence of carbonates in the samples taken from a limed agricultural field. Crop residue management (in both quantity and quality), as characterized by relatively low input levels in our experiment, influenced soil carbon stocks in the long term. However, HR, microbial biomass, labile carbon and metabolic diversity were not affected by the investigated treatments. Besides, results from both soil carbon budgets and short term HR measurements showed that supposedly large differences were likely to be reduced due to the relatively large proportion of root residues, weeds and residues unexported at harvest. [less ▲]

Introduction

Conference (2013, May 23)

Influence of dipole-dipole interactions on the superradiant pulse

Poster (2013, May 23)

Superradiance, known as the cooperative spontaneous emission of a directional light pulse by excited atoms placed in vacuum, has recently regained attention in the context of photon localization [1] and ... [more ▼]

Superradiance, known as the cooperative spontaneous emission of a directional light pulse by excited atoms placed in vacuum, has recently regained attention in the context of photon localization [1] and single photon cooperative emission [2]. The dissipative dynamics of the atoms is known to depend dramatically on the ratio between the typical inter-atomic distance and the atomic transition wavelength, notably because of dipole-dipole interactions [3]. In this work, we study the effects of these interactions on superradiance as in [4] by solving numerically the corresponding master equation. In particular, by averaging over many realizations of the randomly distributed atomic positions, we show that the decay of the radiated energy pulse height with the intensity of the dipolar coupling follows a power law. [1] E. Ackermans, A. Gero & R. Kaiser, Phys. Rev. Lett. 101, 103602 (2008). [2] R. Friedberg & J. T. Manassah, J. Phys. B 43, 035501 (2010). [3] M. Gross & S. Haroche, Physics reports 93, 301-396 (1982). [4] B. Coffey & R. Friedberg, Phys. Rev. A 17, 1033 (1978). [less ▲]

Défaire le discours d'autorité. Les Physiologies à la limite de l'essai

Conference (2013, May 23)

Un siècle après l’essoufflement de la mode panoramique des années 1830-1840, l’emprunt littéraire à la « physiologie » constitue encore un effet de titre pour un essai théorique tel que Physiologie de la ... [more ▼]

Un siècle après l’essoufflement de la mode panoramique des années 1830-1840, l’emprunt littéraire à la « physiologie » constitue encore un effet de titre pour un essai théorique tel que Physiologie de la critique d’Albert Thibaudet. Pourtant, sous la Monarchie de Juillet, le petit genre du même nom, qui présente d’autres caractéristiques formelles et thématiques, n’est pas nettement défini par rapport à une conception et une pratique de l’essai. Au mieux peut-on lui découvrir des parentés significatives avec une certaine écriture journalistique. Les Physiologies se rapprochent en effet de la chronique sous la forme de la notation des faits-Paris et développent une fiction d’actualité féconde en savoir culturel et social. Leur engagement satirique contre le gouvernement en place et leur inscription dans un contexte de vulgarisation scientifique accrue sous l’influence londonienne de la « connaissance utile » ne suffisent pas à apparenter ces Physiologies à de la prose d’idées. Au contraire, elles contournent volontiers les conventions d’écriture du texte d’idées à travers des formes parodiques et déceptives. Il s’agit, de la sorte, d’empêcher le dogmatisme de prendre consistance en oeuvrant contre le discours d’autorité, en particulier scientifique, et contre l’assertivité qui lui est inhérente. Les informations traitées sont non seulement modelées par la distanciation humoristique et la saturation polyphonique, mais elles se trouvent également travaillées en profondeur par la contamination volontaire avec la rhétorique publicitaire dans un contexte de prolifération journalistique de la « réclame ». Le genre physiologique résiste de la sorte aux structures textuelles normatives et assertives d’exposition du savoir. Il ne se les approprie que pour mieux les disqualifier par l’humour et le raisonnement paralogique. Cette caractéristique se traduit par certaines postures discursives récurrentes, en particulier celle du faux spécialiste exhibé comme tel, posture qui consiste à feindre de se rendre ponctuellement expert d’une fraction réduite et caricaturalement recréée de la société, tout en opérant des décrochages réguliers par rapport à cette position énonciative investie d’une autorité. L’étude discursive et générique de tels modes d’expression biaisée du discours d’autorité doit permettre d’éclairer la dynamique d’écriture de l’essai dans les Physiologies parisiennes des années 1830-1840. Cet examen sera orienté par la question des redistributions qui sont ainsi rendues possibles à propos de la frontière entre l’essai-cognitif, caractérisé par une structuration théorique à vocation objectivante, et l’essai-méditation, centré sur une expressivité individualisante de l’instance énonciative. [less ▲]

A BAYESIAN PROBABILITY CRITERION TO ASSESS ANALYTICAL RESULTS RELIABILITY

Conference (2013, May 21)

In pharmaceutical and biomedical industries, quantitative analytical methods such as HPLC play a key role. Indeed, the analytical results obtained from them are used to make crucial decisions such as the ... [more ▼]

In pharmaceutical and biomedical industries, quantitative analytical methods such as HPLC play a key role. Indeed, the analytical results obtained from them are used to make crucial decisions such as the release of batches of drugs, the evaluation of safety and efficacy of new drug candidates or the monitoring of patients health. Prior to their routine use, analytical methods are submitted to a stringent validation study [1] where they have to demonstrate that they are fit for their final purpose, i.e. providing accurate results: where is the analytical result, is the theoretical unknown true concentration of analyte in the sample analyzed and a regulatory acceptance limit. Typically this demonstration is made by either providing point estimates of systematic error (bias) and random error (variance) or sometimes by providing interval estimates of these statistical parameters at several well defined concentration levels of the target analyte [2]. They are then compared to maximum acceptable levels. More recently, tolerance intervals approaches have been proposed that are evaluated in a similar way at these key concentration levels [3]. However none of these decision approaches allow knowing the probability to obtain accurate results over the whole concentration range of interest: is a vector of parameters and Pmin is a minimum reliability probability. Frequentist approximations have been proposed to estimate this probability but only at the concentration levels experimentally tested [4,5]. In this work, a linear hierarchical Bayesian approach is proposed. It takes into account the potential random characteristic of the slope and intercept observed from one analytical run to the other, but it also integrates the possible covariance between the parameters. Additionally, heteroscedasticity of the residual variance over the concentration range investigated is taken into account. A situation regularly observed in practice. Finally a reliability profile for the whole concentration range studied is obtained using MCMC sampling. This profile provides the probability (Prel) to obtain accurate results over the full concentration range investigated. This profile is then compared to a minimum reliability probability (Pmin) that will define the valid concentration range of the analytical method. The usefulness of this approach is illustrated through the validation of a bioanalytical method and also compared with one concentration level at a time frequentist approaches [4,5]. [1] International Conference on Harmonization (ICH) of Technical Requirements for registration of Pharmaceuticals for Human Use Topic Q2 (R1): Validation of Analytical Procedures: Text and Methodology, Geneva, 2005. [2] A. Bouabidi and al., J. Chromatogr. A, 1217 (2010) 3180. [3] Ph. Hubert and al., J. Pharm. Biomed. Anal., 36 (2004) 579. [4] W. Dewé and al., Chemometr. Intell. Lab. Syst. 85 (2007) 262. [5] B. Govaerts and al., Qual. Reliab. Engng. Int. 24 (2008) 667. [less ▲]