Wavelet Transform for Real-Time Detection of Action Potentials in Neural Signals

We present a study on wavelet detection methods of neuronal action potentials (APs). Our final goal is to implement the selected algorithms on custom integrated electronics for on-line processing of neural signals; therefore we take real-time computing as a hard specification and silicon area as a price to pay. Using simulated neural signals including APs, we characterize an efficient wavelet method for AP extraction by evaluating its detection rate and its implementation cost. We compare software implementation for three methods: adaptive threshold, discrete wavelet transform (DWT), and stationary wavelet transform (SWT). We evaluate detection rate and implementation cost for detection functions dynamically comparing a signal with an adaptive threshold proportional to its SD, where the signal is the raw neural signal, respectively: (i) non-processed; (ii) processed by a DWT; (iii) processed by a SWT. We also use different mother wavelets and test different data formats to set an optimal compromise between accuracy and silicon cost. Detection accuracy is evaluated together with false negative and false positive detections. Simulation results show that for on-line AP detection implemented on a configurable digital integrated circuit, APs underneath the noise level can be detected using SWT with a well-selected mother wavelet, combined to an adaptive threshold

RHEOLOGICAL CHARACTERIZATION OF A CLAY FORMATION FROM DRIFTS EXCAVATION : ELASTIC AND ELASTOPLASTIC APPROACH

International audienceAn extensive scientific programme has been carried out by Andra (French Agency in charge of radioactive waste management) for investigating feasibility of High Level Activity Waste disposal in deep geological formation. An Underground Research Laboratory (URL) is currently being constructed in North-eastern France to assess the adequacy of a hard-clay argillite layer (Callovo-Oxfordian formation) situated between 420 m and 550 m of depth. Geotechnical measurements have been carried out during the shafts and drifts excavation and particularly upon the main level of the laboratory (-490 m). The drifts are “horseshoe section” type with about 17 m² in area mainly supported by metallic ribs and rock bolts. The digging has been performed with classical pneumatic hammer. Measurement sections have been instrumented very close to the front face using convergencemeters and radial extensometers. This paper presents a comparison between in situ measurements and numerical modelling. Elastic calculations are not in agreement with the measured deformations. An elastoplastic constitutive model considering damage and using Hoek & Brown criteria has been developed and implemented in the FLAC3D numerical code. Mechanical parameters came from lab tests performed on core samples. For the first meters, model provides consistent displacements. Beyond 4 meters, a time dependent convergence takes place and has to be integrated in the model to take into account creep and/or hydromechanical behaviour

Hydromechanical response to a mine by test experiment in a deep claystone

International audienceIn order to demonstrate the feasibility of radioactive waste repository in deep geological formation, an underground research laboratory is being constructed by Andra (French national radioactive waste management agency) in eastern France, in a Callovo-Oxfordian claystone. 15 boreholes were drilled from a drift at -447 m to install sensors around the shaft (6 m diameter) at depth -460 m to -474 m in order to record the hydromechanical behaviour of the claystone during a shaft sinking (drill and blast method). This paper is devoted to the analysis of the mechanical and hydromechanical behaviour observed during the shaft sinking. Analytical approach used herein allows to realistically evaluate the undrained response of the shaft neighboring with agreement with the in situ measurements. For the transient phase, prediction is qualitatively in accordance with measurement. In addition, deformation and displacement measurements are successfully compared to a simple 3D elastic calculation performed with the real face advancing. This emphasizes the quality of the data set which would be compared in the Modex-Rep European project with complex numerical modelling (poro-elasto-plasic-damage models, creep behaviour,...).En France, l'Andra (Agence Nationale de gestion des déchets radioactifs) est en charge des études pour la faisabilité d'un stockage de déchet radioactif haute activité à vie longue, dans une formation géologique profonde comme des argiles. Pour cela, l'Andra a construit le laboratoire de recherche souterrain de Meuse Haute Marne dans le Nord-Est de la France (à 300 km environs de Paris) dans une formation d'argilite du Callovo-Oxfordien qui se trouve entre 420 m et 550 m au niveau du puits principal. La première expérimentation géomécanique réalisée dans le laboratoire est un " mine by test " autour du puits principal (diamètre 6 m). A partir d'une galerie se trouvant à -445 m, 15 forages ont été réalisés pour installer des capteurs et mesurer le comportement hydromécanique de l'argilite entre -460 et -470 m lors du creusement du puits principal. Les évolutions des mesures in situ sont présentées et comparées avec la solution analytique poro-élastique du creusement d'un puits infini. Les mesures de déplacement sont comparées avec les résultats d'un calcul élastique en 3D. Ces analyses simples montrent la cohérence et la qualité des différentes mesures in situ qui serviront de données de référence dans le projet Européen ModexRep, où le creusement du puits est simulé avec des modèles 3D complexes (poro-elasto-endo-plasticité, fluage,...)

Méthodes et systèmes pour la détection adaptative et temps réel d'activité dans les signaux biologiques

L intéraction entre la biologie et l électronique est une discpline en pleine essort. De nom-breux systèmes électroniques tentent de s interconnecter avec des tissus ou des cellules vivantesa n de décoder l information biologique. Le Potentiel d action (PA) est au coeur de codagebiologique et par conséquent il est nécéssaire de pouvoir les repérer sur tout type de signal bio-logique. Par conséquent, nous étudions dans ce manuscrit la possibilité de concevoir un circuitélectronique couplé à un système de microélectrodes capable d e ectuer une acquisition, unedétection des PAs et un enregistrement des signaux biologiques. Que ce soit en milieu bruitéou non, nous considérons le taux de détection de PA et la contrainte de temps réel commedes notions primordiales et la consommation en silicium comme un prix à payer. Initialementdéveloppés pour l étude de signaux neuronaux et pancréatiques, ces systèmes conviennent par-faitement pour d autres type de cellules.Interaction between biology and electronic is in expansion. Many electronic systems aretrying to interconnect with tissues or living cells to decode biological information. The ActionPotential (AP) is the heart of biological coding and therefore it is necessary to be able to locateit from any type of biological signal. Therefore, we study in this manuscript the possibility ofdesigning an electronic circuit coupled to microelectrodes capable of acquisition, detection ofPAs and recording of biological signals. Whether or not in a noisy environment, we consider thedetection rate of PA and the real time-computing constraint as an hard speci cationand andsilicon area as a price to pay. Initially developed for the study of neural signals and pancreatic,these systems are ideal for other types of cells.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Bio-Inspired Controller on an FPGA Applied to Closed-Loop Diaphragmatic Stimulation

Cervical spinal cord injury can disrupt connections between the brain respiratory network and the respiratory muscles which can lead to partial or complete loss of ventilatory control and require ventilatory assistance. Unlike current open-loop technology, a closed-loop diaphragmatic pacing system could overcome the drawbacks of manual titration as well as respond to changing ventilation requirements. We present an original bio-inspired assistive technology for real-time ventilation assistance, implemented in a digital configurable Field Programmable Gate Array (FPGA). The bio-inspired controller, which is a spiking neural network (SNN) inspired by the medullary respiratory network, is as robust as a classic controller while having a flexible, low-power and low-cost hardware design. The system was simulated in MATLAB with FPGA-specific constraints and tested with a computational model of rat breathing; the model reproduced experimentally collected respiratory data in eupneic animals. The open-loop version of the bio-inspired controller was implemented on the FPGA. Electrical test bench characterizations confirmed the system functionality. Open and closed-loop paradigm simulations were simulated to test the FPGA system real-time behavior using the rat computational model. The closed-loop system monitors breathing and changes in respiratory demands to drive diaphragmatic stimulation. The simulated results inform future acute animal experiments and constitute the first step toward the development of a neuromorphic, adaptive, compact, low-power, implantable device. The bio-inspired hardware design optimizes the FPGA resource and time costs while harnessing the computational power of spike-based neuromorphic hardware. Its real-time feature makes it suitable for in vivo applications

Outcome of Poor-Grade Subarachnoid Hemorrhage as Determined by Biomarkers of Glucose Cerebral Metabolism

Purpose: The aim of this study was to determine if the measurement of blood biomarkers of glucose cerebral metabolism, performed with retrograde jugular catheter, could predict the outcome of poor-grade aneurysmal subarachnoid hemorrhage (aSAH) patients. Methods: This study was conducted in 68 poor-grade aSAH patients. A total of 4,024 blood samples obtained from jugular and radial catheters were analyzed for glucose, lactate, and oxygen content every 8h for 10±0.5days. Metabolic ratio (MR) and lactate-oxygen index (LOI) were obtained by ratios using arterio-jugular differences. Functional outcome was evaluated at 12months with the Glasgow Outcome Scale. Results: Outcome was unfavorable in 40 patients. In this group of patients, the MR was significantly lower (p<0.0001) and the LOI was significantly higher (p=0.0001) than in the group with favorable outcome. The MR cutoff value, below which the patients are likely to have an unfavorable outcome, was determined to be 3.35. More interestingly, the data obtained in this study demonstrated that the patients achieving an unfavorable outcome were distinguished from those with a favorable outcome by having at least three events of MR inferior to 3.35 (sensitivity=90%, specificity=82.1%). Moreover, in patients who developed cerebral vasospasm, we observed a significant decrease in the MR. Conclusion: Our data provide additional support to the view that the MR is a reliable marker for predicting the outcome of poor-grade aSAH patients. Prospective studies are needed to confirm its value in multimodal monitorin

Nueva esterasa tolerante a los solventes orgánicos aislada por metagenómica: ideas sobre la clasificación de las esterasas/lipasas

In order to isolate novel organic solvent-tolerant (OST) lipases, a metagenomic library was built using DNA derived from a temperate forest soil sample. A two-step activity-based screening allowed the isolation of a lipolytic clone active in the presence of organic solvents. Sequencing of the plasmid pRBest recovered from the positive clone revealed the presence of a putative lipase/esterase encoding gene. The deduced amino acid sequence (RBest1) contains the conserved lipolytic enzyme signature and is related to the previously described OST lipase from Lysinibacillus sphaericus 205y, which is the sole studied prokaryotic enzyme belonging to the 4.4 / hydrolase subgroup (abH04.04). Both in vivo and in vitro studies of the substrate specificity of RBest1, using triacylglycerols or nitrophenyl-esters, respectively, revealed that the enzyme is highly specific for butyrate (C4) compounds, behaving as an esterase rather than a lipase. The RBest1 esterase was purified and biochemically characterized. The optimal esterase activity was observed at pH 6.5 and at temperatures ranging from 38 to 45 °C. Enzymatic activity, determined by hydrolysis of p nitrophenyl esters, was found to be affected by the presence of different miscible and non-miscible organic solvents, and salts. Noteworthy, RBest1 remains significantly active at high ionic strength. These findings suggest that RBest1 possesses the ability of OST enzymes to molecular adaptation in the presence of organic compounds and resistance of halophilic proteins.Con el fin de aislar nuevas variantes de lipasas tolerantes a solventes orgánicos (OST), se construyó una librería metagenómica a partir de ADN obtenido de una muestra de suelo de bosque templado. A través de un monitoreo en dos etapas, basado en la detección de actividades, se aisló un clon con actividad lipolítica en presencia de solventes orgánicos. La secuenciación del plásmido pRBest recuperado del clon positivo reveló la presencia de un gen codificante de una hipotética lipasa/esterasa. La secuencia deducida de amino ácidos (RBest1) contiene los motivos conservados de enzimas lipolíticas y está relacionada con la lipasa OST previamente descrita de Lysinibacillus sphaericus 205y, que es la única enzima procariota estudiada perteneciente al subgrupo 4.4 de α/β hidrolasas (abH4.04). Estudios in vivo e in vitro sobre la especificidad de sustratos de RBest1, utilizando triacil-gliceroles o p-nitrofenil-ésteres, respectivamente, revelaron que la enzima es altamente específica para compuestos butíricos (C4 ), comportándose como una esterasa y no como una lipasa. La esterasa RBest1 fue purificada y caracterizada bioquímicamente. La actividad óptima de esterasa fue observada a pH 6,5 y las temperaturas óptimas fueron entre 38 y 45 °C. Se estableció que la actividad enzimática, determinada por hidrólisis de p-nitrofenil ésteres, es afectada en presencia de diferentes solventes orgánicos miscibles y no miscibles, y también sales. Notoriamente, RBest1 permanece significativamente activa a elevadas fuerzas iónicas. Estos hallazgos sugieren que RBest1 posee la capacidad de las enzimas OST de la adaptación molecular en presencia de compuestos orgánicos, así como la resistencia de las proteínas halófilasFil: Berlemont, Renaud. Universite de Liege; BélgicaFil: Spee, Olivier. Universite de Liege; BélgicaFil: Delsaute, Maud. Universite de Liege; BélgicaFil: Lara, Yannick. Universite de Liege; BélgicaFil: Schuldes, Jörg. Universitat of Gottingen; AlemaniaFil: Simon, Carola. Universitat of Gottingen; AlemaniaFil: Power, Pablo. Universite de Liege; Bélgica. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Daniel, Rolf. Universitat of Gottingen; AlemaniaFil: Galleni, Moreno. Universite de Liege; Bélgic

Novel organic solvent-tolerant esterase isolated by metagenomics: insights into the lipase/esterase classification

in order to isolate novel organic solvent-tolerant (oSt) lipases, a metagenomic library was built using dna derived from a temperate forest soil sample. a two-step activity-based screening allowed the isolation of a lipolytic clone active in the presence of organic solvents. Sequencing of the plasmid pRBest recovered from the positive clone revealed the presence of a putative lipase/esterase encoding gene. the deduced amino acid sequence (RBest1) contains the conserved lipolytic enzyme signature and is related to the previously described oSt lipase from Lysinibacillus sphaericus 205y, which is the sole studied prokaryotic enzyme belonging to the 4.4 a/b hydrolase subgroup (abh04.04). Both in vivo and in vitro studies of the substrate specificity of RBest1, using triacylglycerols or nitrophenyl-esters, respectively, revealed that the enzyme is highly specific for butyrate (c4) compounds, behaving as an esterase rather than a lipase. the RBest1 esterase was purified and biochemically characterized. the optimal esterase activity was observed at ph 6.5 and at temperatures ranging from 38 to 45 °c. enzymatic activity, determined by hydrolysis of p‐nitrophenyl esters, was found to be affected by the presence of different miscible and non-miscible organic solvents, and salts. noteworthy, RBest1 remains significantly active at high ionic strength. these findings suggest that RBest1 possesses the ability of oSt enzymes to molecular adaptation in the presence of organic compounds and resistance of halophilic proteins

Grid Analysis of Radiological Data

IGI-Global Medical Information Science Discoveries Research Award 2009International audienceGrid technologies and infrastructures can contribute to harnessing the full power of computer-aided image analysis into clinical research and practice. Given the volume of data, the sensitivity of medical information, and the joint complexity of medical datasets and computations expected in clinical practice, the challenge is to fill the gap between the grid middleware and the requirements of clinical applications. This chapter reports on the goals, achievements and lessons learned from the AGIR (Grid Analysis of Radiological Data) project. AGIR addresses this challenge through a combined approach. On one hand, leveraging the grid middleware through core grid medical services (data management, responsiveness, compression, and workflows) targets the requirements of medical data processing applications. On the other hand, grid-enabling a panel of applications ranging from algorithmic research to clinical use cases both exploits and drives the development of the services

Long-term follow-up after retrosternal ileocolic esophagoplasty in two cases of long-gap esophageal atresia: why it is still a valid option as a rescue strategy

IntroductionEsophageal replacement surgery in children is sometimes necessary for long-gap esophageal atresia. Ileocolic esophagoplasty in the retrosternal space can serve as a good alternative technique in case of hostile posterior mediastinum. We present two cases of successful ileocolic transposition performed at 6 months of age.MethodsEsophageal replacement was performed through a midline laparotomy incision associated with a left cervical approach. The ileocolic transplant was pediculized on the right superior colic artery after ligating the right colic and ileocolic vessels. A retrosternal tunnel was created, and the ileocolic transplant pulled through it to reach the cervical region. Proximally, esophageal-ileal anastomosis and, distally, colonic–gastric anastomosis were performed. Ileocolic continuity was repaired.ResultsThere were no early postoperative complications. In both cases, the patients presented oral feeding difficulties during the first 6 postoperative months. Thereafter, full oral feeding was achieved, and both patients were clinically asymptomatic during the following 18 and 20 years, respectively, with satisfactory oral radiological assessments, showing no redundancy or inappropriate growth of the graft and no anastomotic stricture. Currently, these patients do not complain of dysphagia, pathological reflux, or respiratory symptoms.ConclusionWhen native esophagus preservation in long-gap esophageal atresia is estimated unfeasible, ileocolic transposition in the retrosternal space might be considered a good and safe option, particularly in those difficult cases after multiple previous surgical attempts and mediastinitis. This technique is putatively associated with a beneficial anti-reflux effect, thanks to the presence of the ileocecal valve, in preventing cervical peptic esophagitis. Long-term follow-up confirms that the transposed colon in the retrosternal space did not suffer any abnormal modification in size and growth