Bienzymatic-based electrochemical DNA biosensors: a way to lower the detection limit of hybridization assays

5 pagesInternational audienceThe use of the alkaline phosphatase (AP) as enzyme label and the amplification of its analytical response with a diaphorase (DI) secondary enzyme were investigated in an electrochemical hybridization assay involving arrays of carbon screen-printed DNA biosensors for the sensitive quantification of an amplified 406-base pair human cytomegalovirus DNA sequence (HCMV DNA). For this purpose, PCR-amplified biotinylated HCMV DNA targets were simultaneously bound to a monolayer of neutravidin irreversibly adsorbed on the surface of the electrodes and hybridized to complementary digoxigenin-labeled detection probes. The amount of hybrids immobilized on the electrode surface was labeled with an anti-digoxigenin AP conjugate and quantified electrochemically by measuring the activity of the AP label through the hydrolysis of the electroinactive p-aminophenylphosphate (PAPP) substrate into the p-aminophenol (PAP) product. The intensity of the cyclic voltammetric anodic peak current resulting from the oxidation of PAP into p-quinoneimine (PQI) was related to the number of viral amplified DNA targets present in the sample, and a detection limit of 10 pM was thus achieved. The electrochemical response of the AP label product was further enhanced by adding the diaphorase enzymatic amplifier in the solution. In the presence of the auxiliary enzyme DI, the PQI was reduced back to PAP and the resulting oxidized form of DI was finally regenerated in its reduced native state by its natural substrate, NADH. Such bienzymatic amplification scheme enabled a 100-fold lowering of the HCMV DNA detection limit obtained with the monoenzymatic system

A Low Complexity Block Turbo Decoder Architecture

International audienceWe present a low-complexity architecture designed for the decoding of block turbo codes. In particular we simplify the implementation of Pyndiah's algorithm by not memorizing any of the concurrent codewords generated by the Chase search

Analytic and Asymptotic Analysis of Bayesian Cramér-Rao Bound for Dynamical Phase Offset Estimation

International audienceIn this paper, we present a closed-form expression of a Bayesian Cramér-Rao lower bound for the estimation of a dynamical phase offset in a non-data-aided BPSK transmitting context. This kind of bound is derived considering two different scenarios: a first expression is obtained in an off-line context and then, a second expression in an on-line context logically follows. The SNR-asymptotic expressions of this bound drive us to introduce a new asymptotic bound, namely the Asymptotic Bayesian Cramér-Rao Bound. This bound is close to the classical Bayesian bound but is easier to evaluate

Geneviève Jourdain : Sa carrière et son oeuvre

Geneviève Jourdain, comment décrire simplement et complètement sa carrière et son œuvre si riches, si larges et si diverses? Chercheur de renom, elle a bâti une œuvre considérable et diverse. Enseignante de talent et de conviction, elle a formé plusieurs générations d'ingénieurs. Femme de communication et d'action, elle a marqué de son empreinte la communauté de recherche en lui apportant sa connaissance du terrain et sa vision prospective de l'évolution de la recherche et de l'enseignement. Guide sûr et bienveillant, elle a été un maître au sens classique. Elle a formé de nombreux élèves, stagiaires, thésards, qu'elle a pris sous son aile et qui lui ont été chers. Elle les a guidés, conseillés, leur a ouvert des portes. Ils sont venus enrichir la famille, selon la belle image du Professeur Blanc-Lapierre, du GRETSI, contribuant ainsi à la vie de l'École française de traitement du signal

Improving sea level simulation in Mediterranean regional climate models

For now, the question about future sea level change in the Mediterranean remains a challenge. Previous climate modelling attempts to estimate future sea level change in the Mediterranean did not meet a consensus. The low resolution of CMIP-type models prevents an accurate representation of important small scales processes acting over the Mediterranean region. For this reason among others, the use of high resolution regional ocean modelling has been recommended in literature to address the question of ongoing and future Mediterranean sea level change in response to climate change or greenhouse gases emissions. Also, it has been shown that east Atlantic sea level variability is the dominant driver of the Mediterranean variability at interannual and interdecadal scales. However, up to now, long-term regional simulations of the Mediterranean Sea do not integrate the full sea level information from the Atlantic, which is a substantial shortcoming when analysing Mediterranean sea level response. In the present study we analyse different approaches followed by state-of-the-art regional climate models to simulate Mediterranean sea level variability. Additionally we present a new simulation which incorporates improved information of Atlantic sea level forcing at the lateral boundary. We evaluate the skills of the different simulations in the frame of long-term hindcast simulations spanning from 1980 to 2012 analysing sea level variability from seasonal to multidecadal scales. Results from the new simulation show a substantial improvement in the modelled Mediterranean sea level signal. This confirms that Mediterranean mean sea level is strongly influenced by the Atlantic conditions, and thus suggests that the quality of the information in the lateral boundary conditions (LBCs) is crucial for the good modelling of Mediterranean sea level. We also found that the regional differences inside the basin, that are induced by circulation changes, are model-dependent and thus not affected by the LBCs. Finally, we argue that a correct configuration of LBCs in the Atlantic should be used for future Mediterranean simulations, which cover hindcast period, but also for scenarios

Recherche-action : qualite de l'eau et changement des pratiques agricoles

National audienc

Recherche-action : qualité de l'eau et changements des pratiques agricoles

[fre] La pollution est un phénomène complexe qui fait intervenir des mécanismes bio-technique, social et économique. Nous présentons ici une recherche-action (en cours) sur les pratiques agricoles et la qualité de l'eau. Les résultats, jusqu'ici obtenus, montrent que jusqu'à un certain seuil (qui dépend des systèmes de production), il est possible de limiter les effluents en changeant de pratiques. Les modèles de simulation sont utilisés comme des outils de communications entre les différents acteurs engagés dans cette recherche-action. En outre les modèles (à l'occasion de leur construction et de la présentation des résultats) permettent : un dialogue scientifique avec les collègues des autres disciplines, la précision et la hiérarchisation d'un certain nombre des questions. [eng] On farm research : water quality and agricultural practices. The creation of a linear program, paying particular attention to nitrates assessment as well as to nitrates leaching, according to type of soil, pluviometry, croping system and agricultural practices (first of all : organic manure management). The cost appears to be very high and rises sharply as the nitrates level reaches 10 mg/l. The model shows great sensitivity and allows for the calculation of cost per mg. It also shows the advantages of establishing croping systems and farming practices which release few effluents. Bearing in mind current knowledge and potential developments (compost, better nutrition for cows, technical itinerairies for clean or specified crops - rather than use the term organic - with a higher added value...), it seems possible to maintain and develop a highly efficient localised farming system able to control its effluents.

Subfemtomolar electrochemical detection of target DNA by catalytic enlargement of the hybridized gold nanoparticle labels

7 pagesInternational audienceAfter showing the failure of conventional gold-enhancement procedures to amplify the gold nanoparticle-based electrochemical transduction of DNA hybridization in polystyrene microwells, a new efficient protocol was developed and evaluated for the sensitive quantification of a 35 base-pair human cytomegalovirus nucleic acid target (tDNA). In this assay, the hybridization of the target adsorbed on the bottom of microwells with an oligonucleotide-modified Au nanoparticle detection probe (pDNA-Au) was monitored by the anodic stripping detection of the chemically oxidized gold label at a screen-printed microband electrode (SPMBE). Thanks to the combination of the sensitive AuIII determination at a SPMBE with the large number of AuIII released from each pDNA-Au, picomolar detection limits of tDNA can be achieved. Further enhancement of the hybridization signal based on the autocatalytic reductive deposition of ionic gold (AuIII) on the surface of the gold nanoparticle labels anchored on the hybrids was first envisaged by incubating the commonly used mixture of AuIII and hydroxylamine (NH2OH). However, due to a considerable nonspecific current response of poor reproducibility it was not possible to significantly improve the analytical performances of the method under these conditions. Complementary transmission electronic microscopy experiments indicated the loss of most of the grown gold labels during the post-enlargement rinsing step. To circumvent this drawback, a polymeric solute containing polyethyleneglycol and sodium chloride was introduced in the growth media to act as aggregating agent during the catalytic process and thus retain the enlarged labels on the bottom of the microwell. This strategy, which led to an efficient increase of the hybridization response, allowed detection of tDNA concentrations as low as 600 aM (i.e., 104 lower than without amplification) and thus offers great promise for ultrasensitive detection of other hybridization events

Gestion du parcellaire, drainage. Analyse d'une exploitation laitiere en Lorraine

International audienceUne enquete aupres d'un millier d'exploitations agricoles, un suivi journalier de 8 fermes et un modele de programmation d'une exploitation reelle ont permis d'identifier et de mesurer les principales contraintes de la production laitiere sur les exploitations employant une grande proportion de prairies. Les principales contraintes sont liees a la distribution spatiale des champs et au milieu physique. L'etude montre les solutions possibles. Dans le cadre de la recherche realisee par l'equipe pluridisciplinaire sur les systemes de production en Lorraine, on insiste sur les problemes lies au parcellaire et a l'exces d'eau qui genent tant les agriculteurs lorrains