Novel Prehospital Prediction Model of Large Vessel Occlusion Using Artificial Neural Network

Background: Identifying large vessel occlusion (LVO) patients in the prehospital triage stage to avoid unnecessary and costly delays is important but still challenging. We aim to develop an artificial neural network (ANN) algorithm to predict LVO using prehospital accessible data including demographics, National Institutes of Health Stroke Scale (NIHSS) items and vascular risk factors.Methods: Consecutive acute ischemic stroke patients who underwent CT angiography (CTA) or time of flight MR angiography (TOF-MRA) and received reperfusion therapy within 8 h from symptom onset were included. The diagnosis of LVO was defined as occlusion of the intracranial internal carotid artery (ICA), M1 and M2 segments of the middle cerebral artery (MCA) and basilar artery on CTA or TOF-MRA before treatment. Patients with and without LVO were randomly selected at a 1:1 ratio. The ANN model was developed using backpropagation algorithm, and 10-fold cross-validation was used to validate the model. The comparison of diagnostic parameters between the ANN model and previously established prehospital prediction scales were performed.Results: Finally, 300 LVO and 300 non-LVO patients were randomly selected for the training and validation of the ANN model. The mean Youden index, sensitivity, specificity and accuracy of the ANN model based on the 10-fold cross-validation analysis were 0.640, 0.807, 0.833 and 0.820, respectively. The area under the curve (AUC), Youden index and accuracy of the ANN model were all higher than other prehospital prediction scales.Conclusions: The ANN can be an effective tool for the recognition of LVO in the prehospital triage stage

Conveniently-Grasped Field Assessment Stroke Triage (CG-FAST): A Modified Scale to Detect Large Vessel Occlusion Stroke

Background and Purpose: Patients with large vessel occlusion stroke (LVOS) need to be rapidly identified and transferred to comprehensive stroke centers (CSC). However, previous pre-hospital strategy remains challenging. We aimed to develop a modified scale to better predict LVOS.Methods: We retrospectively reviewed our prospectively collected database for acute ischemic stroke (AIS) patients who underwent CT angiography (CTA) or time of flight MR angiography (TOF-MRA) and had a detailed National Institutes of Health Stroke Scale (NIHSS) score at admission. Large vessel occlusion (LVO) was defined as the complete occlusion of large vessels, including the intracranial internal carotid artery (ICA), M1, and M2 segments of the middle cerebral artery (MCA), and basilar artery (BA). The Conveniently-Grasped Field Assessment Stroke Triage (CG-FAST) scale consisted of Level of Consciousness (LOC) questions, Gaze deviation, Facial palsy, Arm weakness, and Speech changes. Receiver Operating Characteristic (ROC) analysis was used to obtain the Area Under the Curve (AUC) of CG-FAST and previously established pre-hospital prediction scales.Results: Finally, 1,355 patients were included in the analysis. LVOS was detected in 664 (49.0%) patients. The sensitivity, specificity, positive predictive value, and negative predictive value of CG-FAST were 0.617, 0.810, 0.785, and 0.692 respectively, at the optimal cutoff (≥4). The AUC, Youden index and accuracy of the CG-FAST scale (0.758, 0.428, and 0.728) were all higher than other pre-hospital prediction scales.Conclusions: CG-FAST scale could be an effective and simple scale for accurate identification of LVOS among AIS patients

NMR Relaxometry Study of the Interaction of Water with a Nafion Membrane under Acid, Sodium, and Potassium Forms. Evidence of Two Types of Bound Water

PMID: 23678859International audienceThrough 1H NMR relaxometry techniques (determination of the spin–lattice relaxation time as a function of the NMR measurement frequency), we have investigated, on a molecular scale, the water behavior in Nafion NRE 212 under acid, sodium, and potassium forms, the latter arising from different chemical treatments (with and without EDTA). Quantitatively, it turns out that (i) EDTA removes unwanted cations that may affect water mobility and (ii) the natural countercations (sodium and potassium) also affect water mobility according to their size. In order to go further, we have developed a new methodology that rests on the comparison between samples prepared with H2O and D2O. For the latter, residual protons allow us to exclusively access intermolecular contribution to proton relaxation and, thus, enable us to deduce the intramolecular contribution of proton relaxation in H2O. The analysis of this contribution reveals, for the first time, two types of bound water in Nafion

Transport of Ions and Solvent Through a Nafion Membrane Modified with Polypyrrole

The Nafion®117 membrane was modified chemically, using a conducting polymer pyrrole. The oxidants ferric chloride (PPy-Fe), hydrogen peroxide (PPy-O) and ammonium persulfate (PPy-S) were used to carry out the polymerization in the membrane both in aqueous and organic media. The Nafion® modified in the presence of the N-méthylformamide increases the transport of alkali and heavy metal cations and reduces considerably the transport of methanol both in diffusion and electro-osmosis. Therefore, the modified Nafion® membrane can be used successfully in electrodialysis of electrolyte solutions in both aqueous and hydro-organic media and may be regarded as a good material to use in Direct Methanol Fuel Cells

Impact of chemical treatments on the behavior of water in Nafion® NRE-212 by 1H NMR: Self-diffusion measurements and proton quantization

International audienceIn this article, we have studied by 1H NMR the behavior of water in Nafion under acid, sodium and potassium forms which arises from different chemical treatments with or without EDTA. Self-diffusion coefficients were measured by PGSTE (Pulsed Gradient STimulated Echo) whereas integration of the proton spectrum provides a quantitative information about water content. Examination of the self-diffusion coefficients of water in Nafion shows clearly that: (i) in the acid form, the use of a chelating agent does not affect translational diffusion of water, (ii) regardless of sample conditioning, water within Nafion in acid form diffuses more rapidly than in sodium and potassium forms, in particular at low water content (at λ = 3.4, D = 5.4 × 10−7 cm2 s−1 vs. 7.2 × 10−8 cm2 s−1), and (iii) for a given water amount, water diffusion is identical in sodium and potassium forms. Point (ii) is due to the presence of oxonium ions within Nafion in acid form, favoring both vehicle and Grotthuss mechanisms. It is also due to a higher number of protons available for diffusion (we find an average value of 1.19 in acid form vs. 0.91 in sodium form). Our results suggest in the case of Nafion in acid form that, at low water content, diffusion occurs by jumps between different sites. Moreover, plotting self-diffusion coefficients vs. relative humidity leads to a clear differentiation between sodium and potassium cations, related to their respective solvation number

Determination of transverse water concentration profile through MEA in a fuel cell, using Neutron Scattering

International audienceSmall angle neutron scattering experiments were performed on a Proton Exchange Membrane Fuel Cell in order to determine the transversal water concentration profile, within the polymer electrolyte. This is determined, for the first time, under the state of art operating conditions. From the scattering spectra, different concentration profiles were deduced and discussed in term of a competition between electro-osmosis and back-diffusion. For steady states, the balance between these driving forces is modified by the current density. It is also demonstrated that this equilibrium is laterally non-uniform in the fuel cell. This is especially pronounced between the gas inlets and outlets, in a co-flow geometry

Chemical Modification of Perfluorosulfo-nated Membranes with Pyrrole for Fuel Cell Application: Preparation, Characteri-sation and Methanol Transport

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Recent progress in the development of efficient biomass-based ORR electrocatalysts

Platinum is considered the reference catalyst in many electrochemical devices such as electrolyzers or fuel cells. Nevertheless, the large-scale commercialization of these Pt-based devices is limited by the prohibitive cost of platinum as well as its quantity and availability. Regardless of its price and scarcity, it is well known that the oxygen reduction reaction (ORR) with Pt in acidic media is slow compared to that in alkaline media. Due to the lower overpotentials in the latter case, the possibility of using Pt-free catalysts opens the door to new catalyst research. Among them, the development of carbon-based catalysts, either metal-free or with non-precious metals, from the conversion of biomass precursors by various synthetic processes has recently become a challenging goal, as biomass represents an eco-friendly source of carbon. The surface chemistry, textural properties and structure of carbonaceous materials make it complex to identify the origin of ORR catalytic activities. This review provides a critical discussion of the influence of the physicochemical and electrochemical properties of biomass-derived, carbon-based electrocatalysts for the ORR reported over the past decade.This study was partly supported by the French PIA project “Lorraine Université d’Excellence”, reference ANR-15-IDEX-04-LUE and the TALiSMAN project funded by ERDF (2019–000214). JQB thanks the Ministerio de Universidades, the European Union and the University of Alicante for the financial support of his Margarita Salas fellowship (MARSALAS21-21)

Kinetics of water sorption and desorption in Nafion membrane: influence of the interfacial mass transfer coefficient

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