Methodic aspects of XPS depth profiling for investigations of fuel cell components

The focus of this work is to obtain detailed information about the physical composition of the individual fuel cell components in order to optimize them and increase cell durability. An approach for the ex‐situ characterization of fuel cell components, such as gas diffusion media or catalyst layers is by using XPS. In this work, we address methodic aspects of depth profiling of direct methanol fuel cell components (microporous layers and catalyst layers) using adhesive tape peel‐off with subsequent XPS analysis. By using this approach, we have successfully demonstrated cross‐over of Ru ions and possibly Pt ions from the anodic catalyst to the cathodic catalyst layer and even to the microporous layer. Moreover, our experimental results allow determining where the dissolved catalyst ions redeposit within the membrane electrode assembly. Finally, our findings suggest that cross‐over of Pt and Ru ions, observed under different operation conditions, are uncoupled. Copyright © 2014 John Wiley & Sons, Ltd.     

Diferric oxo-bridged complexes of a polydentate aminopyridyl ligand: synthesis,structure and catalytic reactivity

The catalytic reactivity of a group of diferric oxo-bridged complexes (1–3) of a tetradentate ligand (bpmen = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-1,2-diaminoethane) toward alkane hydroxylation has been evaluated. Among the three complexes, the µ-oxo diiron(III) complex [Fe(bpmen)(µ-O)FeCl₃] (1) has been synthesized for the first time. The complex 1 has been characterized by spectroscopic analysis and X-ray crystallography. At room temperature, the µ-oxo diiron(III) complexes 1–3 have been found to be useful catalysts in hydroxylation of alkanes with m-chloroperbenzoic acid as oxidant. [Fe(bpmen)(µ-O)FeCl₃] (1) has been found to be the most active catalyst. Moreover, the catalytic ability of the complexes in the oxidation of alcohols to ketones with hydrogen peroxide at room temperature has also been investigated.     

Structural optimization of cyclic sulfonamide based novel HIV-1 protease inhibitors to picomolar affinities guided by X-ray crystallographic analysis

Synthesis and HIV-1 protease inhibitory activity of compound 5 based on the structure of a novel cyclic sulfonamide pharmacophore has been recently disclosed from our group. X-ray crystallographic structure of 5 when bound to the HIV-1 protease defined its binding mode. The importance of the geometry of the substitution at C4–Me (S configuration) was emphasized. In the present paper we wish to disclose the design of novel inhibitors 47 and 48 based on the X-ray structure of compound 5 bound to the HIV-1 protease, their synthesis and activity against HIV-1 protease. By making changes at the C4 position and the carbamate linkage the above compounds 47 and 48 were found to be approximately one hundred fold more active compared to 5 and their K_i values are in the picomolar range. An unusual observation regarding the activity and geometry was made with compounds 51 and 52. X-ray results demonstrate that 48 and 52 bind to the same binding pocket with simultaneous change in the conformation of the cyclic sulfonamide ring.     

Excitation function of (p, pn) reactions at high energy

A closed theoretical formula for the (p, pn) reaction cross section at high energies in light, medium and heavy nuclei has been derived, and a comparison of the calculated cross sections with the experimental datais made for ¹²C, ¹⁹F, ⁵⁴Fe, ⁵⁸Ni, ⁵⁹Co, ⁶⁴Zn, ⁶⁵Cu, ¹⁰⁰Mo, ¹²⁷I, ¹⁴²Ce, ¹⁸²Ta and ²³⁸U at incident energies above 50 MeV. Good agreement between experimental and calculated cross sections is obtained in the entire energy range considered. In deducing the formula a direct reaction with a pure knock-out mechanism has been assumed.     

Optical soliton perturbation with Raman scattering and saturable amplifiers

The method of multiple-scale perturbation is developed to study the propagation of solitons through an optical fiber described by the perturbed nonlinear Schrödinger's equation. We show that, by introducing a proper definition of the phase of the soliton, one can obtain the corrections to the pulse where the usual soliton perturbation approach fails. A comparison is made with results obtained by other methods as well as with numerical simulations.     

On semistable principal bundles over a complex projective manifold,II

Let (X, ω) be a compact connected Kähler manifold of complex dimension d and \({E_G\,\longrightarrow\,X}\) a holomorphic principal G–bundle, where G is a connected reductive linear algebraic group defined over \({\mathbb{C}}\). Let Z(G) denote the center of G. We prove that the following three statements are equivalent:

1. (1)
   There is a parabolic subgroup \({P\,\subset\,G}\) and a holomorphic reduction of structure group \({E_P\,\subset\,E_G}\) to P, such that the corresponding L(P)/Z(G)–bundle

   $E_{L(P)/Z(G)}\,:=\,E_P(L(P)/Z(G))\,\longrightarrow\,X$

   admits a unitary flat connection, where L(P) is the Levi quotient of P.
    
2. (2)
   The adjoint vector bundle ad(E _G ) is numerically flat.
    
3. (3)
   The principal G–bundle E _G is pseudostable, and

   $\int\limits_X c_2({\rm ad}(E_G))\omega^{d-2}\,=\,0.$
    

If X is a complex projective manifold, and ω represents a rational cohomology class, then the third statement is equivalent to the statement that E _G is semistable with c ₂(ad(E _G )) = 0.

     

The Torelli theorem for the moduli spaces of connections on a Riemann surface

Let (X,x₀) be any one-pointed compact connected Riemann surface of genus g, with g≥3. Fix two mutually coprime integers r>1 and d. Let M_X denote the moduli space parametrizing all logarithmic -connections, singular over x₀, on vector bundles over X of degree d. We prove that the isomorphism class of the variety M_X determines the Riemann surface X uniquely up to an isomorphism, although the biholomorphism class of M_X is known to be independent of the complex structure of X. The isomorphism class of the variety M_X is independent of the point x₀∈X. A similar result is proved for the moduli space parametrizing logarithmic -connections, singular over x₀, on vector bundles over X of degree d. The assumption r>1 is necessary for the moduli space of logarithmic -connections to determine the isomorphism class of X uniquely.     

Some moduli stacks of symplectic bundles on a curve are rational

Let C be a smooth projective curve of genus g?2 over a field k. Given a line bundle L on C, let Sympl2n,L be the moduli stack of vector bundles E of rank 2n on C endowed with a nowhere degenerate symplectic form up to scalars. We prove that this stack is birational to BGm×As for some s if deg(E)=n⋅deg(L) is odd and C admits a rational point P∈C(k) as well as a line bundle ξ of degree 0 with ξ⊗2?OC. It follows that the corresponding coarse moduli scheme of Ramanathan-stable symplectic bundles is rational in this case.     

Application of the Weisz Ring oven technique to the separation and identification of micro-quantities of some less familiar cations

Summary Use of the ring oven in separation and identification of mixtures of less familiar metal ions has been described. Separation of metal ions from the following mixtures has successfully been carried out: 1. UO₂(II) and Th(IV), 2. Th(IV) and Ce(IV), 3. Pd(II) and Au(III), 4. Pt(IV) and Au(III), 5. Ce(III) and Ce(IV), 6. UO₂(II), Th(IV) and Ti(IV), 7. Th(IV), Ti(IV) and Ce(IV), 8. Th(IV), Ce(IV) and Zr(IV), 9. Ti(IV), V(V) and Zr(IV), 10. Mo(VI), V(V) and W(VI) and 11. Be(II), Al(III) and Mg(II). In the case of binary mixtures, the separation was in the form of a central spot and a concentric ring; in ternary mixtures the metals were precipitated in a central spot and two concentric rings.

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Zusammenfassung Zur Trennung und Identifizierung folgender Gemische seltenerer Metallionen wurde der Ringofen mit Erfolg verwendet: 1. UO₂(II) und Th(IV), 2. Th(IV) und Ce(IV), 3. Pd(II) und Au(III), 4. Pt(IV) und Au(III), 5. Ce(III) und Ce(IV), 6. UO₂(II), Th(IV) und Ti(IV), 7. Th(IV), Ti(IV) und Ce(IV). 8. Th(IV), Ce(IV) und Zr(IV), 9. Ti(IV), V(V) und Zr(IV), 10. Mo(VI), V(V) und W(VI) und 11. Be(II), Al(III) und Mg(II). Bei binären Gemischen erfolgt die Trennung in einen zentralen Fleck und einen Ring, bei ternären Mischungen in einen Fleck und zwei konzentrische Ringe.

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Résumé On a décrit l'utilisation du four annulaire pour la séparation et l'identification de mélanges d'ions métalliques moins courants. On a effectué la séparation des ions métalliques à partir des mélanges suivants: 1. UO₂(II) et Th(IV), 2. Th(IV) et Ce(IV), 3. Pd(II) et Au(III), 4. Pt(IV) et Au(III), 5. Ce(III) et Ce(IV), 6. UO₂(II), Th(IV) et Ti(IV), 7. Th(IV), Ti(IV) et Ce(IV), 8. Th(IV), Ce(IV) et Zr(IV), 9. Ti(IV), V(V) et Zr(IV), 10. Mo(VI), V(V) et W(VI) et 11. Be(II), Al(III) et Mg(II). Dans le cas des mélanges binaires, la séparation se présentait sous forme d'une tache centrale et d'un anneau concentrique; chez les mélanges ternaires, les métaux étaient précipités en une tache centrale et deux anneaux concentriques.

     

Polymerization of N-vinylcarbazole by thionyl chloride

The polymerization of N-vinylcarbazole (NVC) initiated by SOCl₂ in benzene and nitrobenzene solvents was studied at 32°C. R_p is first order with respect to SOCl₂ concentration and also to NVC concentration up to a certain NVC concentration, after which it falls. Rate and the molecular weight increase with increasing dielectric constant of the medium. The rate and molecular weight are depressed by the addition of amines, thiophene, and water. The degree of polymerization is independent of SOCl₂ and NVC concentration. A conventional cationic mechanism has been suggested, and a suitable kinetic scheme has been proposed in conformity with the findings.