A current-driven six-channel potentiostat for rapid performance characterization of microbial electrolysis cells

Knowledge of the performance of microbial electrolysis cells under a wide range of operating conditions is crucial to achieve high production efficiencies. Characterizing this performance in an experiment, however, is challenging due to either the long measurement times of steady-state procedures or the transient errors of dynamic procedures. Moreover, wide parallelization of the measurements is not feasible due to the high measurement equipment cost per channel. Hence, to speedup this characterization and to facilitate low-cost, yet widely parallel measurements, this paper presents a novel rapid polarization curve measurement procedure with a dynamic measurement resolution that runs on a custom six-channel potentiostat with a current-driven topology. As case study, the procedure is used to rapidly assess the impact of altering pH values on a microbial electrolysis cell that produces H-2. A $\times 2$ - $\times 12$ speedup could be obtained in comparison with the state-of-the-art, depending on the characterization resolution (16-128 levels). On top of this speedup, measurements can be parallelized up to $6\times$ on the presented, affordable-42-per-channel-potentiostat

A 64-channel, 1.1-pA-accurate on-chip potentiostat for parallel electrochemical monitoring

Electrochemical monitoring is crucial for both industrial applications, such as microbial electrolysis and corrosion monitoring as well as consumer applications such as personal health monitoring. Yet, state-of-the-art integrated potentiostat monitoring devices have few parallel channels with limited flexibility due to their channel architecture. This work presents a novel, widely scalable channel architecture using a switch capacitor based Howland current pump and a digital potential controller. An integrated, 64-channel CMOS potentiostat array has been fabricated. Each individual channel has a dynamic current range of 120dB with 1.1pA precision with up to 100kHz bandwidth. The on-chip working electrodes are post-processed with gold to ensure (bio)electrochemical compatibility

A tourism development model based on sustainable tourism the Seychelles : a unique archipelago in the tropics

The archipelago of the Seychelles in the tropics (Africa) is one example of a tourist destination which directs its tourism policy to a development model based on a concept of sustainable tourism, that is quality tourism. It consists in reviewing and increasing the quality of tourism services and restricting the quantitative capacity, mainly of the tourist accommodation, taking into account the host population, the economy and the environment. Although imbedded in the history of policy, it was principally a reaction to the pressure on the environment due to the tourism and economic development of the Seychelles. This paper will analyse the tourism development of the Seychelles. It examines the presents strenghts, weaknesses, opportunities and threats of tourism in the Seychelles and gives recommendations for a better appraisal of sustainable tourism.peer-reviewe

An affordable multichannel potentiostat with 128 individual stimulation and sensing channels

(Bio)electrochemical reactions are a promising, environmentally friendly alternative for many chemical processes. These processes, however, are known to be slow in time, to be strongly dependent on the environment and to vary between different samples. This necessitates research on studying optimal operating conditions of the (bio)electrochemical cells. Yet, current experiments have to rely on slow, sequential tests. To overcome these, this work proposes a potentiostat with 128 parallel channels to speed up research experiments. The 128-channel potentiostat makes extensive use of time-sharing and is implemented with PCB technology resulting in a cost-per-channel of only 5$, 4x lower than the state-of-the-art (SotA) and an area-per-channel of ≈ 93 mm 2 , 5x lower than the SotA. Realtime digital compensation of each individual channel is used to obtain a channel-to-channel mismatch below 1%. A cyclic voltametry experiment on all channels simultaneously illustrates the low channel-to-channel mismatch. A chronoamperometry experiment with 128 different potential steps in parallel illustrates the 128x experiment speedup

Processus de binding actif en mémoire de travail préservé chez des adultes autistes sans déficience intellectuelle

Le trouble du spectre autistique est une condition neuro-développementale qui se caractérise par une altération de diverses fonctions cognitives, dont la mémoire de travail. La mémoire de travail (MdT) est une fonction exécutive essentielle puisqu’elle permet de garder activées des informations suffisamment longtemps en mémoire afin d’accomplir une tâche. Ce déficit pourrait être dû à une diminution de l’activité préfrontale et une communication diminuée entre les régions frontales et pariétales. En MdT, le concept de binding, peu étudié mais de grande importance, se définit comme étant la capacité à faire des associations entre les informations. Deux formes de binding coexistent, l’une étant une forme automatique de binding, se faisant à l’insu de l’individu, et la seconde une forme contrôlée, pour laquelle un effort conscient de la part de l’individu, afin de créer le lien entre les informations, est requis. L’objectif de l'étude est d’étudier les mécanismes cérébraux sous-tendant ces deux formes de binding, avec une attention plus particulière pour le binding actif. L’hypothèse comportementale est que les adultes présentant un trouble autistique sans déficience intellectuelle démontreront une atteinte spécifique du binding actif, comparativement à une atteinte moindre du binding passif. Ceci se traduira sur le plan cérébral par une perturbation de la connectivité préfronto-hippocampique, mais une activité préservée de l’hippocampe durant la tâche de binding actif comparativement à la tâche de binding passif. Enfin, la littérature évaluant les anomalies structurelles et anatomiques dans l’autisme rapportent un élargissement du volume de l’hippocampe, du CPF et du lobe pariétal droit ainsi qu’une diminution du volume du lobe pariétal gauche, toutes trois faisant partie du réseau neuronal responsable de la MdT. Ces différences structurelles pourraient avoir un impact sur les performances en binding des individus autistes. L’hypothèse concernant les analyses anatomiques prédit donc que les participants TSA présenteront un volume de matière grise du CPF et du lobe pariétal droit plus important que les individus NT, ainsi qu’un volume du lobe pariétal gauche diminué. Les performances en binding actif seront corrélées aux différences volumétriques comparativement aux performances de binding passif. Dix-huits participants TSA ainsi que dix-huits participants contrôles ont effectué une tâche dans une machine IRM. La tâche consiste en la présentation de mots et d’ellipses (indiquant la position spatiale) de couleur, à mémoriser. Deux conditions sont présentées, la première visant à étudier le binding passif, la seconde étudie le concept de binding actif. Les résultats suggèrent que les deux formes de binding sont préservées dans l’autisme. Au niveau cérébral pour le binding actif, lors de la phase de maintien en MdT, les participants TSA ont présenté une activation plus faible dans le gyrus frontal inférieur droit, ainsi qu’une activation plus importante dans la région pariétal et frontale, au niveau du gyrus post-central pariétal droit et du gyrus frontal précentral droit. Ces résultats semblent indiquer une utilisation différentes entre les deux groupes des ressources cérébrales. Au niveau anatomique, un volume de matière grise plus important chez les participants TSA a été retrouvé dans la région limbique, temporale, occipitale, frontale, cingulaire et pariétale.Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by socio-communicative deficits, as well as restrictive interests and repetitive behaviors. Alterations in executive functions, including in working memory (WM), can also be found throughout the spectrum. WM is a temporary storage system allowing active conservation of information for a short period of time. The ability to associate different information together in WM, referred to as binding, is crucial for episodic memory and learning processes. There are two types of binding. Passive binding occurs when the association between two pieces of information is made unconsciously and automatically. Active binding requires a conscious effort to associate two pieces of information. These two types of binding rely on different neural substrates; passive binding is based on the functioning of the hippocampus, while active binding is based on the communication between the hippocampus and prefrontal cortex. Some studies have suggested impairments in WM tasks requiring intentional organisation of information in ASD. Other studies also suggested preserved capabilities in the passive form of binding in ASD. The objective of this project is to investigate the neural substrates underlying the two forms of binding in high functionning autistic adults, with more attention to the active form, using functional magnetic resonance imaging (fMRI). The study included 18 ASD participants and 18 controls (CT). All participants performed a WM task in an MRI scanner. The task consisted in the memorization of the association between three words and three spatial positions (defined by ellipses). At the behavioral level, both groups have a similar level of performance, which suggest that the active binding is preserved in autism. ASD participants showed higher levels of activation in the right frontal lobe (precentral gyrus), and in the right parietal lobe (postcentral gyrus) during the maintenance phase. They also showed lower levels of activation in the right inferior frontal gyrus. This difference of levels of activation could mean that the two groups use their cerebral resources differently. At the anatomic level, ASD participants showed lower volume of grey matter in the limbic, temporal, occipital, frontal, occipital, frontal, cingulate and parietal regions

Successive parabolic interpolation as extremum seeking control for microbial fuel & electrolysis cells

Microbial Fuel Cell (MFC) power production and Microbial Electrolysis Cell (MEC) organic production depend strongly on their dynamic environment conditions, like inlet substrate concentration, temperature, etc. This work presents a discrete extremum seeking controller to quickly tune the MFC and MEC electrical settings in order to achieve maximum performance irrespective of these dynamic environment conditions using the successive parabolic interpolation iteration scheme. The controller converges in about 3.5 days within 5% of the cell's maximum performance and in about 5.4 days within 1% for an established MFC model. The proposed discrete parabola controller converges 3x faster than the state-of-the-art controllers without requiring a time-consuming calibration procedure. Equally fast convergence speed is achieved on a MEC model

A four-quadrant switched capacitor DC-DC convertor enabling power-efficient lab-grade potentiostats

This paper presents a low-power potentiostat based on a four-quadrant switched capacitor DC-DC convertor for use in lab applications. The gearbox convertor achieves a compliance voltage of ±2.5V. Through the use of frequency scaling, the convertor features output currents in the range of 1µA to 1mA, outclassing other state-of-the-art power efficient potentiostats. A hysteretic control loop and a seperate hysteretic comparator allow the potentiostat to be used for both voltammetric and ampere-metric experiments. Simulations demonstrate a peak efficiency of 87%, and a competitive overall efficiency. The system is designed and simulated in a 0.35µm process