2-Sulfoethylammonium trifluoromethanesulfonate as an Ionic Liquid for High Temperature PEM Fuel Cells

2-Sulfoethylammonium trifluoromethanesulfonate ([2-Sea+][TfO−]) represents a novel class of proton-conducting ionic liquids (PILs) based on aminoalkylsulfonic acids. The fundamental suitability of [2-Sea+][TfO−] for application as a protic electrolyte in high temperature PEM fuel cells (HT-PEFCs) was investigated up to a temperature of 130°C. A comparison was made against a state-of-the-art electrolyte, phosphoric acid. [2-Sea+][TfO−] is electrochemically and thermally stable up to 140°C. The specific conductivity of 95 wt% [2-Sea+][TfO−] aqueous solution at 130°C is ≈20 times lower compared to 95 wt% H3PO4. The strong coupling of ion transport and viscous flow suggests a vehicular ion (proton) transport in [2-Sea+][TfO−]. 95 wt% [2-Sea+][TfO−] shows superior kinetics in terms of oxygen reduction reaction (ORR) on polycrystalline Pt compared to 95 wt% H3PO4 at temperatures greater than 90°C in a fuel cell-applicable potential range. Double layer capacitances suggest a complex double layer structure, including adsorbed [2-Sea+][TfO−] and water, as well as intermediates of oxygen reduction and Pt oxidation. Potential and temperature-dependent ORR kinetics in the presence of 95 wt% [2-Sea+][TfO−] yield different Tafel slopes (b = 82–139 mV) and symmetry factors (β = 0.46–0.96), indicating changes in surface coverages of the adsorbed species and possibly also a change in the reaction mechanism

A Continuum Saltation Model for Sand Dunes

We derive a phenomenological continuum saltation model for aeolian sand transport that can serve as an efficient tool for geomorphological applications. The coupled differential equations for the average density and velocity of sand in the saltation layer reproduce both known equilibrium relations for the sand flux and the time evolution of the sand flux as predicted by microscopic saltation models. The three phenomenological parameters of the model are a reference height for the grain-air interaction, an effective restitution coefficient for the grain-bed interaction, and a multiplication factor characterizing the chain reaction caused by the impacts leading to a typical time or length scale of the saturation transients. We determine the values of these parameters by comparing our model with wind tunnel measurements. Our main interest are out of equilibrium situations where saturation transients are important, for instance at phase boundaries (ground/sand) or under unsteady wind conditions. We point out that saturation transients are indispensable for a proper description of sand flux over structured terrain, by applying the model to the windward side of an isolated dune, thereby resolving recently reported discrepancies between field measurements and theoretical predictions.Comment: 11 pages, 7 figure

Corridors of barchan dunes: stability and size selection

Barchans are crescentic dunes propagating on a solid ground. They form dune fields in the shape of elongated corridors in which the size and spacing between dunes are rather well selected. We show that even very realistic models for solitary dunes do not reproduce these corridors. Instead, two instabilities take place. First, barchans receive a sand flux at their back proportional to their width while the sand escapes only from their horns. Large dunes proportionally capture more than they loose sand, while the situation is reversed for small ones: therefore, solitary dunes cannot remain in a steady state. Second, the propagation speed of dunes decreases with the size of the dune: this leads -- through the collision process -- to a coarsening of barchan fields. We show that these phenomena are not specific to the model, but result from general and robust mechanisms. The length scales needed for these instabilities to develop are derived and discussed. They turn out to be much smaller than the dune field length. As a conclusion, there should exist further - yet unknown - mechanisms regulating and selecting the size of dunes.Comment: 13 pages, 13 figures. New version resubmitted to Phys. Rev. E. Pictures of better quality available on reques

Random phase approximation up to the melting point: Impact of anharmonicity and nonlocal many-body effects on the thermodynamics of Au

Application of the generalized gradient corrected functional within standard density-functional theory results in a dramatic failure for Au, leading to divergent thermodynamic properties well below the melting point. By combining the upsampled thermodynamic integration using Langevin dynamics technique with the random phase approximation, we show that inclusion of nonlocal many-body effects leads to a stabilization and to an excellent agreement with experiment. © Published by the American Physical Society

Efficacy and safety of trimodulin, a novel polyclonal antibody preparation, in patients with severe community-acquired pneumonia: a randomized, placebo-controlled, double-blind, multicenter, phase II trial (CIGMA study)

Purpose The CIGMA study investigated a novel human polyclonal antibody preparation (trimodulin) containing ~ 23% immunoglobulin (Ig) M, ~ 21% IgA, and ~ 56% IgG as add-on therapy for patients with severe community-acquired pneumonia (sCAP). Methods In this double-blind, phase II study (NCT01420744), 160 patients with sCAP requiring invasive mechanical ventilation were randomized (1:1) to trimodulin (42 mg IgM/kg/day) or placebo for five consecutive days. Primary endpoint was ventilator-free days (VFDs). Secondary endpoints included 28-day all-cause and pneumonia-related mortality. Safety and tolerability were monitored. Exploratory post hoc analyses were performed in subsets stratified by baseline C-reactive protein (CRP; ≥ 70 mg/L) and/or IgM (≤ 0.8 g/L). Results Overall, there was no statistically significant difference in VFDs between trimodulin (mean 11.0, median 11 [n = 81]) and placebo (mean 9.6; median 8 [n = 79]; p = 0.173). Twenty-eight-day all-cause mortality was 22.2% vs. 27.8%, respectively (p = 0.465). Time to discharge from intensive care unit and mean duration of hospitalization were comparable between groups. Adverse-event incidences were comparable. Post hoc subset analyses, which included the majority of patients (58–78%), showed significant reductions in all-cause mortality (trimodulin vs. placebo) in patients with high CRP, low IgM, and high CRP/low IgM at baseline. Conclusions No significant differences were found in VFDs and mortality between trimodulin and placebo groups. Post hoc analyses supported improved outcome regarding mortality with trimodulin in subsets of patients with elevated CRP, reduced IgM, or both. These findings warrant further investigation