On the Proton Conductivity of Nafion-Faujasite Composite Membranes for Low Temperature Direct Methanol Fuel Cells.

Although zeolites are introduced to decrease methanol crossover of Nafion membranes for direct methanol fuel cells (DMFCs), little is known about the effect of their intrinsic properties and the interaction with the ionomer. In this work, Nafion-Faujasite composite membranes prepared by solution casting were characterized by extensive physicochemical and electrochemical techniques. Faujasite was found to undergo severe dealumination during the membrane activation, but its structure remained intact. The zeolite interacts with Nafion probably through hydrogen bonding between Si-OH and SO3H groups, which combined with the increase of the water uptake and the water mobility, and the addition of a less conductive phase (the zeolite) leads to an optimum proton conductivity between 0.98 and 2 wt% of zeolite. Hot pressing the membranes before their assembling with the electrodes enhanced the DMFC performance by reducing the methanol crossover and the serial resistance

Sulfonated polyether ether ketone-based composite membranes doped with a tungsten-based inorganic proton conductor for fuel cell applications

Sulfonated polyether ether ketone (SPEEK)-based composite membranes doped with hydrated tungsten oxide were prepared and studied for proton exchange membrane applications. Hydrated tungsten oxide (W O3 ·2 H2 O) was synthesized via acidic hydrolysis of sodium tungstate and its structure and physicochemical features were investigated by thermogravimetric analysis (TG), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). SPEEK/ W O3 ·2 H2 O composite membranes were prepared by mixing proper amounts of SPEEK and hydrated W O3 in dimethylacetamide as casting solvent. The composite membranes were characterized by XRD, TG-DTA, EIS, and water uptake measurements as a function of the oxide content in the membrane. In particular, XRD patterns as well as TG measurements indicated the existence of a coordinative interaction between the water molecules of tungsten oxide and the SPEEK sulfonic acid groups. This interaction lead to the enhancement of the membrane proton conductivity, as well as of their properties, from the point of view of heat resistance and water solubility. In fact, the addition of tungsten oxide resulted in higher proton conductivity, improved heat resistance, and lower water solubility. © 2006 The Electrochemical Society. All rights reserved

Redox-active coordination polymers as bifunctional electrolytes in slurry-based aqueous batteries at neutral pH

Highly water-dispersible, redox-active 1D coordination polymers (CPs) have been synthesized using low-cost precursors. These CPs, containing chloranilic acid as organic ligand and a transition element, such as Fe and Mn as a metal center, form long-term stable slurries containing up to 100 g/L solid particles in aqueous media (0.5 M NaCl, 1 mg carbon nanotubes). Voltammetry studies showed that the iron-based particulate slurries exhibited three different redox stages with no metal plating. However, the suspensions with manganese-based coordination polymers experienced a metal plating process in the same potential window range as for the iron-based CPs. Moreover, the particulate suspension of iron-CPs shown longer-term stability than their isostructural analogs based on manganese. The 1D Fe-CPs were used as catholyte and anolyte in a symmetrical cell with a low-cost size exclusion cellulose membrane acting as a separator. The cell experienced a reversible capacity value of 45 mAh/g (225 mAh/L) at a current density value of 20 mA/g for 50 cycles (~12 days) at neutral pH. This study opens the possibility of using inexpensive coordination polymers as single bifunctional electrolyte material in aqueous batteries and other sustainable energy storage-related systems

A neutral-pH aqueous redox flow battery based on sustainable organic electrolytes

Aqueous organic redox flow batteries (AORFBs) have gained increasing attention for large-scale storage due to the advantages of decoupled energy and power, safe and sustainable chemistry, and tunability of the redox-active species. Here, we report the development of a neutral-pH AORFB assembled with a highly water-soluble ferrocene 1,1-disulfonic disodium salt (DS−Fc) and two viologen derivatives, 1,1’-bis(3-sulfonatopropyl)-viologen (BSP−Vi) and Bis(3-trimethylammonium)propyl viologen tetrachloride (BTMAP−Vi). Synthesized electrolytes showed excellent redox potential, good diffusion coefficient, and a good transfer rate constant. In particular, BSP−Vi has a more negative redox potential (-0.4 V) than BTMAP−Vi (−0.3 V) and faster kinetics; therefore, it was selected to be assembled in an AORFB as anolyte, coupled with DS−Fc as catholyte.The resulting AORFB based on BTMAP−Vi/DS−Fc and BSP−Vi/DS−Fc redox couple had a high cell voltage (1.2 V and 1.3 V, respectively) and theoretical energy density (13 WhL−1 and 14 WhL−1 respectively) and was able to sustain 70 charge-discharge cycles with energy efficiency as high as 97 %

Total and functional parasite specific IgE responses in Plasmodium falciparum-infected patients exhibiting different clinical status

Blood samples were collected from controls and P. falciparum-infected patients before treatment on the day of hospitalization (day 0) in India and, in addition, on days 7 and 30 after treatment in Gabon. Total IgE levels were determined by ELISA and functional P. falciparum-specific IgE were estimated using a mast cell line RBL-2H3 transfected with a human Fcε RI α-chain that triggers degranulation upon human IgE cross-linking. Mann Whitney and Kruskall Wallis tests were used to compare groups and the Spearman test was used for correlations. Total IgE levels were confirmed to increase upon infection and differ with level of transmission and age but were not directly related to the disease phenotype. All studied groups exhibited functional parasite-specific IgEs able to induce mast cell degranulation in vitro in the presence of P. falciparum antigens. Plasma IgE levels correlated with those of IL-10 in uncomplicated malaria patients from Gabon. In Indian patients, plasma IFN-γ , TNF and IL-10 levels were significantly correlated with IgE concentrations in all groups

Using olive mill wastewate to improve performance in producing electricity from domestic wastewater by using single-chamber microbial fuel cell

Improving electricity generation from wastewater (DW) by using olive mill wastewater (OMW) was evaluated using single-chamber microbial fuel cells (MFC). Doing so single-chambers air cathode MFCs with platinum anode were fed with domestic wastewater (DW) alone and mixed with OMW at the ratio of 14:1 (w/w). MFCs fed with DW + OMW gave 0.38 V at 1 kO, while power density from polarization curve was of 124.6mW m 2. The process allowed a total reduction of TCOD and BOD5 of 60% and 69%, respectively, recovering the 29% of the coulombic efficiency. The maximum voltage obtained from MFC fed with DW + OMW was 2.9 times higher than that of cell fed with DW. DNA-fingerprinting showed high bacterial diversity for both experiments and the presence on anodes of exoelectrogenic bacteria, such as Geobacter spp. Electrodes selected peculiar consortia and, in particular, anodes of both experiments showed a similar specialization of microbial communities independently by feeding used

Growing drift-cyclotron modes in the hot solar atmosphere

Well-known analytical results dealing with ion cyclotron and drift waves and which follow from the kinetic theory are used and the dispersion equation, which describes coupled two modes, is solved numerically. The numerical results obtained by using the values for the plasma density, magnetic field and temperature applicable to the solar corona clearly show the coupling and the instability (growing) of the two modes. The coupling happens at very short wavelengths, that are of the order of the ion gyro radius, and for characteristic scale lengths of the equilibrium density that are altitude dependent and may become of the order of only a few meters. The demonstrated instability of the two coupled modes (driven by the equilibrium density gradient) is obtained by using a rigorous kinetic theory model and for realistic parameter values. The physical mechanism which is behind the coupling is simple and is expected to take place throughout the solar atmosphere and the solar wind which contain a variety of very elongated density structures of various sizes. The mode grows on account of the density gradient, it is essentially an ion mode, and its further dissipation should result in an increased ion heating

Impact of mosquito bites on asexual parasite density and gametocyte prevalence in asymptomatic chronic Plasmodium falciparum infections and correlation with IgE and IgG titers.

International audienceAn immunomodulatory role of arthropod saliva has been well documented, but evidence for an effect on Plasmodium sp. infectiousness remains controversial. Mosquito saliva may orient the immune response toward a Th2 profile, thereby priming a Th2 response against subsequent antigens, including Plasmodium. Orientation toward a Th1 versus a Th2 profile promotes IgG and IgE proliferation, respectively, where the former is crucial for the development of an efficient antiparasite immune response. Here we assessed the direct effect of mosquito bites on the density of Plasmodium falciparum asexual parasites and the prevalence of gametocytes in chronic, asymptomatic infections in a longitudinal cohort study of seasonal transmission. We additionally correlated these parasitological measures with IgE and IgG antiparasite and anti-salivary gland extract titers. The mosquito biting density was positively correlated with the asexual parasite density but not asexual parasite prevalence and was negatively correlated with gametocyte prevalence. Individual anti-salivary gland IgE titers were also negatively correlated with gametocyte carriage and were strongly positively correlated with antiparasite IgE titers, consistent with the hypothesis that mosquito bites predispose individuals to develop an IgE antiparasite response. We provide evidence that mosquito bites have an impact on asymptomatic infections and differentially so for the production of asexual and sexual parasites. An increased research focus on the immunological impact of mosquito bites during asymptomatic infections is warranted, to establish whether strategies targeting the immune response to saliva can reduce the duration of infection and the onward transmission of the parasite