Fuel cell rejuvenation of hygrothermally aged Nafion

International audienceNafion ® membranes stored for long periods at 80 °C under elevated relative humidity up to 95%RH exhibit large modifications of their properties attributed to the sulfonic acid end-group condensation into sulfonic anhydrides. The present study is devoted to the membrane property rejuvenation, namely the hydrolysis of the sulfonic anhydrides under different experimental conditions. Aged membranes were exposed to pure water and to acid solutions or vapors in order to check the reversibility of the condensation reaction. Indeed, the hydrolysis process is slow in pure water and limited while it is fast and complete in the presence of acid or base. The native polymer chemical structure and the main membrane properties (mechanical properties, hydrophilicity, etc.) are completely restored. No evidence of hygrothermal aging was observed after fuel cell operation and it is shown that a membrane previously aged under ex situ conditions can be completely rejuvenated when operated in fuel cell

Fuel cell rejuvenation of hygrothermally aged Nafion

Nafion ® membranes stored for long periods at 80 °C under elevated relative humidity up to 95%RH exhibit large modifications of their properties attributed to the sulfonic acid end-group condensation into sulfonic anhydrides. The present study is devoted to the membrane property rejuvenation, namely the hydrolysis of the sulfonic anhydrides under different experimental conditions. Aged membranes were exposed to pure water and to acid solutions or vapors in order to check the reversibility of the condensation reaction. Indeed, the hydrolysis process is slow in pure water and limited while it is fast and complete in the presence of acid or base. The native polymer chemical structure and the main membrane properties (mechanical properties, hydrophilicity, etc.) are completely restored. No evidence of hygrothermal aging was observed after fuel cell operation and it is shown that a membrane previously aged under ex situ conditions can be completely rejuvenated when operated in fuel cell

Case-Control Cohort Study of Patients' Perceptions of Disability in Mastocytosis

BACKGROUND: Indolent forms of mastocytosis account for more than 90% of all cases, but the types and type and severity of symptoms and their impact on the quality of life have not been well studied. We therefore performed a case-control cohort study to examine self-reported disability and impact of symptoms on the quality of life in patients with mastocytosis. METHODOLOGY/PRINCIPAL FINDINGS: In 2004, 363 mastocytosis patients and 90 controls in France were asked to rate to their overall disability (OPA score) and the severity of 38 individual symptoms. The latter was used to calculate a composite score (AFIRMM score). Of the 363 respondents, 262 were part of an ongoing pathophysiological study so that the following data were available: World Health Organization classification, standard measures of physical and psychological disability, existence of the D816V KIT mutation, and serum tryptase level. The mean OPA and AFIRMM scores and the standard measures of disability indicated that most mastocytosis patients suffer from disabilities due to the disease. Surprisingly, the patient's measurable and perceived disabilities did not differ according to disease classification or presence or absence of the D816V KIT mutation or an elevated (> or = 20 ng/mL) serum tryptase level. Also, 32 of the 38 AFIRMM symptoms were more common in patients than controls, but there were not substantial differences according to disease classification, presence of the D816V mutation, or the serum tryptase level. CONCLUSIONS: On the basis of these results and for the purposes of treatment, we propose that mastocytosis be first classified as aggressive or indolent and that indolent mastocytosis then be categorized according to the severity of patients' perceived symptoms and their impact on the quality of life. In addition, it appears that mastocytosis patients suffer from more symptoms and greater disability than previously thought, that mastocytosis may therefore be under-diagnosed, and that the symptoms of the indolent forms of mastocytosis might be due more to systemic release of mediators than mast cell burden

Phenotypic and genotypic characteristics of mastocytosis according to the age of onset.

International audienceAdult's mastocytosis is usually associated with persistent systemic involvement and c-kit 816 mutation, while pediatrics disease is mostly limited to the skin and often resolves spontaneously. We prospectively included 142 adult patients with histologically proven mastocytosis. We compared phenotypic and genotypic features of adults patients whose disease started during childhood (Group 1, n = 28) with those of patients whose disease started at adult's age (Group 2, n = 114). Genotypic analysis was performed on skin biopsy by sequencing of c-kit exons 17 and 8 to 13. According to WHO classification, the percentage of systemic disease was similar (75 vs. 73%) in 2 groups. C-kit 816 mutation was found in 42% and 77% of patients in groups 1 and 2, respectively (p<0.001). 816 c-kit mutation was associated with systemic mastocytosis in group 2 (87% of patients with systemic mastocytosis vs. 45% with cutaneous mastocytosis, p = 0.0001). Other c-kit activating mutations were found in 23% of patients with mastocytosis' onset before the age of 5, 0% between 6 and 15 years and 2% at adults' age (p<0.001). In conclusion, pathogenesis of mastocytosis significantly differs according to the age of disease's onset. Our data may have major therapeutic relevance when considering c-kit-targeted therapy

Minimum Information about a Biosynthetic Gene cluster

A wide variety of enzymatic pathways that produce specialized metabolites in bacteria, fungi and plants are known to be encoded in biosynthetic gene clusters. Information about these clusters, pathways and metabolites is currently dispersed throughout the literature, making it difficult to exploit. To facilitate consistent and systematic deposition and retrieval of data on biosynthetic gene clusters, we propose the Minimum Information about a Biosynthetic Gene cluster (MIBiG) data standard.Chemistry and Chemical Biolog

Off-design operation of a PEM fuel cell stack integrated into a m-CHP system with membrane reformer

A micro-CHP system, rated at 5 kWel, based on a membrane reformer and a PEMFC is studied. The identification of the operative conditions of the PEMFC is crucial for a good integration with the membrane reformer: the hydrogen separated in the membrane reactor, after cooling, directly feeds the FC [1]. In principle, Pd-based membranes can produce high-purity hydrogen (target= 99.99%, i.e. selectivity=104). However, the selectivity may decrease, in particular when thin Pd-membranes on ceramic support are adopted, and determine low-purity hydrogen (e.g. 99.9% with 100ppm CO, i.e. selectivity=102). A methanator is therefore added along the hydrogen cooling line to prevent CO-poisoning of the FC anodes. The quality of hydrogen affects the cell voltage and the overall system performances, therefore FC control strategies must be investigated. Build-up of inert and poisoning species in the hydrogen recirculation loop can be limited by venting a fraction of the anodic off-gas, whose amount can be optimized. Efficiency losses are estimated around one percentage point for each decrement of the order of magnitude of the selectivity. Deviations from the nominal operation occur during transients, at part-load or in case of faults of the Pd-membranes. These circumstances are investigated by simulating the FCs subsystem that includes the stack, the air and hydrogen blowers and the air humidifier. A dynamic, 1D (along the channels) model of PEMFC has been developed to simulate mixed co/counter flow between anode and cathode streams, which characterize the flow field of large-surface cells. The poisoning effect of CO on Pt-Ru catalyst is also modeled [2]. An experimental campaign on an 8-cells stack (cell area 220 cm2) was performed to characterize the FC operation with reformate gas. The impact of fuel composition, containing up to 20% of inert gases (N2, CO2, CH4) and CO up to 40 ppm, and operative conditions (pressure and humidity) was analyzed on the overall stack performance as well as on the current density distribution along the cell surface. Experimental data constituted a valuable source for the validation of the model

Development of exacerbated load cycles as AST for PEMFC stacks and validation by in-situ and ex-situ characterizations

International audienceProton Exchange Membrane Fuel Cell (PEMFC) technologies are considered as a promising and clean energy supply for both transportation and stationary applications. State of art components present performance enabling integration of stacks in actual systems and vehicles. However, durability still needs to be improved as well as overall system cost still needs to be reduced to enable large scale competitive deployment. Assessment of components and stacks durability is thus essential from early stage of development until implementation into systems. To this end, the intention of the European project ID-FAST was to support the development of accelerated stress tests (AST) for automotive application to be validated first on single cells and then on specific stack designs. The methodology selected was to consider as a starting point the performance losses and degradation phenomena induced by ageing tests following a load profile and operating conditions representative of real drive cycles [1]. Next step was to define modified load cycles enabling to exacerbate the degradation and voltage losses induced, while keeping same mechanisms involved thus allowing to reach similar level of performance after a shorter ageing period and less cycles applied

Development of exacerbated load cycles as AST for PEMFC stacks and validation by in-situ and ex-situ characterizations

International audienceProton Exchange Membrane Fuel Cell (PEMFC) technologies are considered as a promising and clean energy supply for both transportation and stationary applications. State of art components present performance enabling integration of stacks in actual systems and vehicles. However, durability still needs to be improved as well as overall system cost still needs to be reduced to enable large scale competitive deployment. Assessment of components and stacks durability is thus essential from early stage of development until implementation into systems. To this end, the intention of the European project ID-FAST was to support the development of accelerated stress tests (AST) for automotive application to be validated first on single cells and then on specific stack designs. The methodology selected was to consider as a starting point the performance losses and degradation phenomena induced by ageing tests following a load profile and operating conditions representative of real drive cycles [1]. Next step was to define modified load cycles enabling to exacerbate the degradation and voltage losses induced, while keeping same mechanisms involved thus allowing to reach similar level of performance after a shorter ageing period and less cycles applied