Water management strategies for PGM-free catalyst layers for polymer electrolyte fuel cells

Platinum group metal–free (PGM-free) catalysts are promising candidates to catalyze the oxygen reduction reaction in polymer electrolyte fuel cells (PEFCs). Because of their low activity, larger loadings are used resulting in thicker catalyst layers. Transport, particularly water management, thereby becomes a more prominent performance factor. Currently, very few works attempted to understand water management in PGM-free catalyst layers, mainly because of other challenges that had to be overcome first, such as enhancing their activity and durability. The field has also been active in a hypothesis discussion of micropores flooding that led to the belief that poor stability of the PEFC performance is linked to active sites flooding within the micropores. We present here an overview of recent advances in understanding water management in the PGM-free catalyst layer for oxygen reduction reaction in PEFCs and provide an opinion on design guidance in optimizing catalyst layers to avoid flooding.     

Impact of Deuteration and Temperature on Furan Ring Dynamics

Despite significant progress in conformational analysis of cyclic molecules, the number of computational studies is still limited while most of that available in the literature data have been obtained long time ago with outdated methods. In present research, we have studied temperature driven conformational changes of the furan ring at three different temperatures. Additionally, the effect of deuteration on the ring dynamics is discussed; in addition, the aromaticity indices following the Bird and HOMA schemes are computed along all trajectories. Our ab initio molecular dynamic simulations revealed that deuteration has changed the furan ring dynamics and the obvious consequences; in addition, the shape and size of molecule are expected to be different.     

Determination of SLES in Personal Care Products by Colloid Titration with Light Reflection Measurements

The method of colloid titration with poly(diallyldimethylammonium) chloride has been improved to detect the endpoint with an off-vessel light reflectance sensor. The digital color sensor used measures light reflectance by means of light guides, with no immersion into the reaction solution. In such a method, the optical signal is free of disturbances caused by sticky flocs in the solution. The improved automatic titration set was applied for the determination of sodium laureth sulfate (SLES) in industrial batches and commercial personal care products. The sample color and opacity do not disturb the SLES quantification. When the SLES content lies in the range from 5% to 9%, the optimal sample weight is from 6 g to 3 g.     

Dynamics of a thermoelastic von Kármán plate in a subsonic gas flow

We discuss the problem of non-linear oscillations of a clamped thermoelastic plate in a subsonic gas flow. The dynamics of the plate is described by von Kármán system in the presence of thermal effects. No mechanical damping is assumed. To describe the influence of the gas flow we apply the linearized theory of potential flows. Our main result states that each weak solution of the problem considered tends to the set of the stationary points of the problem. A similar problem was considered in [27], but with rotational inertia accounted for, i.e. with the additional term −αΔu_tt,α > 0, and the same result on stabilization was obtained. There was introduced the decomposition of the solution such that the one term tends to zero and the other is compact in special (“local energy”) topology. This decomposition enables us to prove the main result. But the case of rotational inertia neglected (α = 0) appears more difficult. Low a priori smoothness of u_t in the case α = 0 prevents us to construct such a decomposition. In order to prove additional smoothness of u_t we use analyticity of the corresponding thermoelastic semigroup proved in [25]. The isothermal variant of this problem with additional mechanical damping term −εΔu_t , ε > 0 was considered in [13] and stabilization to the set of stationary solutions to the problem was proved. The problem, considered in the present work can also be regarded as an extension of the result of [18] to the case when gas occupies an unbounded domain.     

Properties of an organosilicon nanophase generated in a poly(amide imide) matrix by the sol‐gel technique

Poly(amide imide) (PAI) nanocomposites prepared by the in situ generation of crosslinked organosilicon nanophase (ON) through the sol‐gel process were characterized by wide‐angle and small‐angle X‐ray diffraction, thermogravimetric analysis, dynamic mechanical analysis and kinetics of water uptake. It was concluded that the polymer nanocomposite (PNC) were likely to possess a complex morphology on the nanoscale characterized by co‐existence of two mixed nanophases of different compositions. At low methyl triethoxysilane (MTS) contents the fractal‐like organization of paracrystalline nano‐domains of PAI chain fragments is destroyed by the randomly distributed ON particles, whereas on the increase of MTS content the spatial correlations between ON particles become stronger, giving rise to their own fractal‐like structure. The higher values of small‐angle X‐ray scattering (SAXS) invariant, apparent water diffusivity and limiting water uptake for the PNC compared to the pristine PAI were assumed to reflect the loose inner structures of PAI‐rich and ON‐rich nanophases, respectively. Copyright © 2005 John Wiley & Sons, Ltd.     

En route to osmium analogues of KP1019: synthesis, structure, spectroscopic properties and antiproliferative activity of trans-[Os(IV)Cl4(Hazole)2

By controlled Anderson type rearrangement reactions complexes of the general formula trans-[Os(IV)Cl(4)(Hazole)(2)], where Hazole = 1H-pyrazole, 2H-indazole, 1H-imidazole, and 1H-benzimidazole, have been synthesized. Note that 2H-indazole tautomer stabilization in trans-[Os(IV)Cl(4)(2H-indazole)(2)] is unprecedented in coordination chemistry of indazole. The metal ion in these compounds possesses the same coordination environment as ruthenium(III) in (H(2)ind)[Ru(III)Cl(4)(Hind)(2)], where Hind = 1H-indazole, (KP1019), an investigational anticancer drug in phase I clinical trials. These osmium(IV) complexes are appropriate precursors for the synthesis of osmium(III) analogues of KP1019. In addition the formation of an adduct of trans-[Os(IV)Cl(4)(Hpz)(2)] with cucurbit[7]uril is described. The compounds have been comprehensively characterized by elemental analysis, EI and ESI mass spectrometry, spectroscopy (IR, UV-vis, 1D and 2D NMR), cyclic voltammetry, and X-ray crystallography. Their antiproliferative acitivity in the human cancer cell lines CH1 (ovarian carcinoma), A549 (nonsmall cell lung carcinoma), and SW480 (colon carcinoma) is reported.     

Conjugation of organoruthenium(II) 3-(1H-benzimidazol-2-yl)pyrazolo[3,4-b]pyridines and indolo[3,2-d]benzazepines to recombinant human serum albumin: a strategy to enhance cytotoxicity in cancer cells

Following our strategy of coupling cyclin-dependent kinase (Cdk) inhibitors with organometallic moieties to improve their physicochemical properties and bioavailability, five organoruthenium complexes (1c-5c) of the general formula [RuCl(η(6)-arene)(L)]Cl have been synthesized in which the arene is 4-formylphenoxyacetyl-η(6)-benzylamide and L is a Cdk inhibitor [3-(1H-benzimidazol-2-yl)-1H-pyrazolo[3,4-b]pyridines (L1-L3) and indolo[3,2-d]benzazepines (L4 and L5)]. All of the compounds were characterized by spectroscopic and analytical methods. Upon prolonged standing (2-3 months) at room temperature, the dimethyl sulfoxide (DMSO) solutions of 1c and 2c(-HCl) afforded residues, which after recrystallization from EtOH and EtOH/H(2)O, respectively, were shown by X-ray diffraction to be cis,cis-[Ru(II)Cl(2)(DMSO)(2)(L1)]·H(2)O and mer-[Ru(II)Cl(DMSO)(3)(L2-H)]·H(2)O. Compound 5c, with a coordinated amidine unit, undergoes E/Z isomerization in solution. The antiproliferative activities and effects on the cell cycle of the new compounds were evaluated. Complexes 1c-5c are moderately cytotoxic to cancer cells (CH1, SW480, A549, A2780, and A2780cisR cell lines). Therefore, in order to improve their antiproliferative effects, as well as their drug targeting and delivery to cancer cells, 1c-5c were conjugated to recombinant human serum albumin, potentially exploiting the so-called "enhanced permeability and retention" effect that results in the accumulation of macromolecules in tumors. Notably, a marked increase in cytotoxicity of the albumin conjugates was observed in all cases.     

Critical homoclinic orbits lead to snap-back repellers

When nondegenerate homoclinic orbits to an expanding fixed point of a map f:X→X,X⊆Rⁿ, exist, the point is called a snap-back repeller. It is known that the relevance of a snap-back repeller (in its original definition) is due to the fact that it implies the existence of an invariant set on which the map is chaotic. However, when does the first homoclinic orbit appear? When can other homoclinic explosions, i.e., appearance of infinitely many new homoclinic orbits, occur? As noticed by many authors, these problems are still open. In this work we characterize these bifurcations, for any kind of map, smooth or piecewise smooth, continuous or discontinuous, defined in a bounded or unbounded closed set. We define a noncritical homoclinic orbit and a homoclinic orbit of an expanding fixed point is structurally stable iff it is noncritical. That is, only critical homoclinic orbits are responsible for the homoclinic explosions. The possible kinds of critical homoclinic orbits will be also investigated, as well as their dynamic role.     

Synthesis and structural characterisation of gallium and indium fluoroalkoxide ‘ate’ complexes

The treatment of InCl₃ with MOCH(CF₃)₂ (M = Li, Na, K) in a 1:6 stoichiometry, followed by recrystallisation results in the formation of the bimetallic “ate” complexes [Na₃In(OCH(CF₃)₂)₆(THF)₃] (2) and [Li₃In(OCH(CF₃)₂)₆(THF)₃] (5) from hexane, and [K₃In(OCH(CF₃)₂)₆]_n (4) from a THF and toluene mixture. If a 1:3 stoichiometry is used chloride containing compounds [Na₂InCl(OCH(CF₃)₂)₄(THF)₄] (1) and [KInCl₂ (OCH(CF₃)₂)₂(THF)₃]_n · THF (3) are obtained on recrystallisation from hexane. Treatment of GaCl₃ with 6 equivalents of LiOC(CH₃)₂CF₃ gives [LiGa(OC(CH₃)₂CF₃)₄(THF)₂] (6) on recrystallisation from hexane. The protolysis reaction between In(N(SiMe₃)₂)₃, formed in situ from (Me₃Si)₂NH, ⁿBuLi and Incl₃, and HOCH(CH₃)CF₃ results in isolation of [LiIn(OCH(CH₃)CF₃)₃Bu]₂ (7) from hexane. The structures of 2, 4, and 5 all contain the tetranuclear core InO₆M₃. Compounds 1 and 3 have residual chloride; 1 is a trinuclear species with two THF ligands per Na, while 3 is a linear polymer. Compound 6 has a GaO₂Li four-membered parallelogram at its core. Complex 7 has a tetranuclear In₂O₆Li₂ core and an unexpected ⁿBu group on the In atoms. The coordination spheres of the alkali metals in 1-6 include solvated THF while 1-5 display additional close M?F interactions.