Electro-oxidation of CO on Pd black in phosphotungstic acid

Electro-oxidation of CO by Pd black in phosphotungstic acid (PWA) has been studied on porous gas-diffusion electrodes. Galvanostatic steady-state polarization data show that the reaction proceeds under strong activation control at low current densities. The current density at 0.5 V_NHE is found to be three times higher than that in a H₂SO₄ reference electrolyte. X-ray photoelectron spectroscopic data on various electrochemically tested electrodes show lower oxidized Pd species in PWA than in H₂SO₄. It is conjectured that an increase in the electron density around Pd sites is ameliorated by PWA in relation to H₂SO_4, with a consequent promoting effect of the heteropolyacid towards CO electro-oxidation. Received: 29 July 1998 / Accepted: 15 September 1998     

The Gibbs-Thompson relation within the gradient theory of phase transitions

This paper discusses the asymptotic behavior as 0+ of the chemical potentials associated with solutions of variational problems within the Van der Waals-Cahn-Hilliard theory of phase transitions in a fluid with free energy, per unit volume, given by ²¦¦²+ W(), where is the density. The main result is that is asymptotically equal to E/d+o(), with E the interfacial energy, per unit surface area, of the interface between phases, the (constant) sum of principal curvatures of the interface, and d the density jump across the interface. This result is in agreement with a formula conjectured by M. Gurtin and corresponds to the Gibbs-Thompson relation for surface tension, proved by G. Caginalp within the context of the phase field model of free boundaries arising from phase transitions.     

MICROEMULSIONS AND THEIR POTENTIAL APPLICATIONS IN DYEING PROCESSES

Among organized molecular assemblies, microemulsions, transparent, homogeneous, isotropic, thermodynamically stable systems, have been recently used in industrial domains close to the dyeing area. The evaluation of extending the microemulsion technique to dyeing processes is proposed reporting some encouraging results obtained by quantitative thermodynamic measurements and by traditional qualitative laboratory tests.     

Local existence for quasilinear parabolic systems under nonlinear boundary conditions

Summary We prove local solvability of quasilinear parabolic systems by means of classical techniques based upon a priori estimates, without assuming any growth condition.     

Thermal stability of substituted poly-xylylenes

The insertion of meta units in the chain of poly-p-xylylene decreases both the onset temperature of oxidative degradation and the rate of decomposition.Functionalization of the polymer with chlorine and sulphonic groups makes the chain more resistant to high temperature treatments, notwithstanding the low stability of the substituent groups.

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Zusammenfassung Die Einführung von Metaeinheiten in die Kette von Poly-p-xylen setzt sowohl die Einsetztemperatur des oxydativen Abbaues als auch die Zersetzungsgeschwindigkeit herab. Die Einführung von Chlor und Sulfogruppen erhöht trotz der geringen Stabilität der Substituenten die Temperaturbeständigkeit der Kette.

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A note on regular points for solutions of elliptic systems

A vector valued function u(x), solution of a quasilinear elliptic system cannot be too close to a straight line without being regular.     

On sequences of maps into <Emphasis Type="Italic">S</Emphasis><Superscript>1</Superscript> with equibounded <Emphasis Type="Italic">W</Emphasis><Superscript>1/2</Superscript> energies

In the last years there has been some interest in studying mappings in the fractional Sobolev space W^1/2(, S¹), see e.g., [4] [3] [15] [12] and the paper [5]. Motivated by these papers, we characterize here in the framework of Cartesian currents, see [9], the class of weak limits of sequences of smooth mappings with values into S¹ with equibounded W^1/2 energies.