From frequency dispersion to ohmic impedance: A new insight on the high-frequency impedance analysis of electrochemical systems

International audienceThe increasing use of impedance for the characterization of an electrified interface is accompanied by the development of accurate models to analyze the results. In the present work, the concept of ohmic impedance is revisited using both numerical simulations and experimental results. The Havriliak-Negami equation is shown to provide a good representation of the high-frequency dispersion or complex ohmic impedance associated with the disk electrode geometry. An excellent fit to simulated complex ohmic impedance was found for both capacitive electrodes and for electrodes characterized by constant-phase-element behavior. The use of the Havriliak-Negami equation to account for the complex ohmic impedance was shown to extend the useful frequency range for regression of physical models to the impedance response for three experimental systems: a gold electrode in a 0.1 M sodium sulfate solution, an aluminum electrode in a 0.01 M sodium sulfate solution, and pure iron in a 0.5 M sulfuric acid solution

A zwitterionic interpenetrating network for improving the blood compatibility of polypropylene membranes applied to leukodepletion

Although widely used in blood-contacting devices, polypropylene (PP) membranes are prone to biofouling by plasma proteins and blood cells. The present study explores the effect of a surface zwitterionization process on the improvement of the biofouling resistance of PP membranes for leukocyte reduction filters. The modification strategy consists in forming an interpenetrating network of poly(glycidyl methacrylate-co-sulfobetaine methacrylate) (poly(GMA-co-SBMA) around the fibers of coated PP membranes, using a cross-linking agent: ethylenediamine (EDA). It is shown that with EDA, a range of poly(GMA-co-SBMA) concentration (1–5 mg/mL) leads to a 0°-water contact angle and high hydration of the networks without affecting the intrinsic porous structure of the material. Besides, the related membranes show excellent resistance to biofouling by Escherichia coli, fibrinogen, leukocytes, erythrocytes, thrombocytes and cells from whole blood with reductions in adsorption of 97%, 86%, 90%, 95%, 97% and 91%, respectively, compared to unmodified PP. Used in whole blood filtration, it is demonstrated that in the best conditions (5 mg/mL copolymer, with EDA), leukocytes can be efficiently removed (>99.99%) without altering the erythrocytes concentration in the permeate, and that leukodepletion is more efficient than that measured with a commercial hydrophilic PP blood filter (about 50% retention). Physical retention of leukocytes is only efficient if the membrane material is anti-biofouling, and so, does not interact with other blood components able to trigger leukocyte attachment/deformation

Surface Zwitterionization of Expanded Poly(tetrafluoroethylene) via Dopamine-Assisted Consecutive Immersion Coating

Expanded polytetrafluoroethylene (ePTFE) is one of thematerials widely used in the biomedicalfield, yet its application is being limitedby adverse reactions such as thrombosis when it comes in contact with blood.Thus, a simple and robust way to modify ePTFE to be biologically inert issought after. Modification of ePTFE without high-energy pretreatment, such asimmersion coating, has been of interest to researchers for its straightforwardprocess and ease in scaling up. In this study, we utilized a two-step immersioncoating to zwitterionize ePTFE membranes. Thefirst coating consists of the co-deposition of polyethylenimine (PEI) and polydopamine (PDA) to produceamine groups in the surface of the ePTFE for further functionalization. Theseamine groups from PEI will be coupled with the epoxide group of thezwitterionic copolymer, poly(GMA-co-SBMA) (PGS), via a ring-openingreaction in the second coating. The coated ePTFE membranes were physicallyand chemically characterized to ensure that each step of the coating is successful. The membranes were also tested for theirthrombogenicity via quantification of the blood cells attached to it during contact with biological solutions. The coated membranesexhibited around 90% reduction in attachment with respect to the uncoated ePTFE for both Gram-positive and Gram-negativestrains of bacteria (Staphylococcus aureusandEscherichia coli). The coating was also able to resist blood cell attachment from humanwhole blood by 81.57% and resist red blood cell attachment from red blood cell concentrate by 93.4%. These ePTFE membranes,which are coated by a simple immersion coating, show significant enhancement of the biocompatibility of the membranes, whichshows promise for future use in biological devices

Dendritic excitation–inhibition balance shapes cerebellar output during motor behaviour

Feedforward excitatory and inhibitory circuits regulate cerebellar output, but how these circuits interact to shape the somatodendritic excitability of Purkinje cells during motor behaviour remains unresolved. Here we perform dendritic and somatic patch-clamp recordings in vivo combined with optogenetic silencing of interneurons to investigate how dendritic excitation and inhibition generates bidirectional (that is, increased or decreased) Purkinje cell output during self-paced locomotion. We find that granule cells generate a sustained depolarization of Purkinje cell dendrites during movement, which is counterbalanced by variable levels of feedforward inhibition from local interneurons. Subtle differences in the dendritic excitation–inhibition balance generate robust, bidirectional changes in simple spike (SSp) output. Disrupting this balance by selectively silencing molecular layer interneurons results in unidirectional firing rate changes, increased SSp regularity and disrupted locomotor behaviour. Our findings provide a mechanistic understanding of how feedforward excitatory and inhibitory circuits shape Purkinje cell output during motor behaviour

Proceedings of the 3rd Biennial Conference of the Society for Implementation Research Collaboration (SIRC) 2015: advancing efficient methodologies through community partnerships and team science

It is well documented that the majority of adults, children and families in need of evidence-based behavioral health interventionsi do not receive them [1, 2] and that few robust empirically supported methods for implementing evidence-based practices (EBPs) exist. The Society for Implementation Research Collaboration (SIRC) represents a burgeoning effort to advance the innovation and rigor of implementation research and is uniquely focused on bringing together researchers and stakeholders committed to evaluating the implementation of complex evidence-based behavioral health interventions. Through its diverse activities and membership, SIRC aims to foster the promise of implementation research to better serve the behavioral health needs of the population by identifying rigorous, relevant, and efficient strategies that successfully transfer scientific evidence to clinical knowledge for use in real world settings [3]. SIRC began as a National Institute of Mental Health (NIMH)-funded conference series in 2010 (previously titled the “Seattle Implementation Research Conference”; $150,000 USD for 3 conferences in 2011, 2013, and 2015) with the recognition that there were multiple researchers and stakeholdersi working in parallel on innovative implementation science projects in behavioral health, but that formal channels for communicating and collaborating with one another were relatively unavailable. There was a significant need for a forum within which implementation researchers and stakeholders could learn from one another, refine approaches to science and practice, and develop an implementation research agenda using common measures, methods, and research principles to improve both the frequency and quality with which behavioral health treatment implementation is evaluated. SIRC’s membership growth is a testament to this identified need with more than 1000 members from 2011 to the present.ii SIRC’s primary objectives are to: (1) foster communication and collaboration across diverse groups, including implementation researchers, intermediariesi, as well as community stakeholders (SIRC uses the term “EBP champions” for these groups) – and to do so across multiple career levels (e.g., students, early career faculty, established investigators); and (2) enhance and disseminate rigorous measures and methodologies for implementing EBPs and evaluating EBP implementation efforts. These objectives are well aligned with Glasgow and colleagues’ [4] five core tenets deemed critical for advancing implementation science: collaboration, efficiency and speed, rigor and relevance, improved capacity, and cumulative knowledge. SIRC advances these objectives and tenets through in-person conferences, which bring together multidisciplinary implementation researchers and those implementing evidence-based behavioral health interventions in the community to share their work and create professional connections and collaborations

Ultramicrotomy of resin embedded structures as a confirmatory method

This project examined semi-thin sections (<1um) of horseshoe crabs (Limulus polyphemus) and rat skeletal muscle cells (L6 cells) embedded in epoxy resin using ultramicrotomy. Muscle cells were exposed to electromagnetic forces during culture in a previous MQP (Brito and Aboyeji, 2000) and sectioned to observe the ultrastructure differences between the exposed and controls. Embedding media were Spurr's resin and Epon-Araldite. This project examines structures in horseshoe crab gill that appeared to be cells in mitosis or apoptosis, from previous microscopy

Pour qui votait-on ? roman gaulois... / Vincent Dizon,...

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L'héritier du calife : roman gai / Vincent Dizon,... ; illustrations de Guy Yemet...

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L'Achélaime, roman gai... Illustrations de Guy Yemet / Vincent Dizon,...

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