Existence of minimizers for a class of quasi-convex functionals with non-standard growth

We study the lower semicontinuity properties of non-autonomous variational integrals whose energy densities satisfy general growth conditions. We apply these results to solve Dirichlet’s boundary value problems for such functionals. Received: June 14, 2000; in final form: November 25, 2000 Published online: December 19, 2001     

Distribution of the strength of acid sites in mildly steamed HZSM-5 studied by IR spectroscopy

Steaming resulted in modification of the distribution of acid strength of OH groups. The contribution of less acidic sites increased and new, very strongly acidic hydroxyls characterized by IR band at 3590 cm^-1 appeared.     

Reaktionshemmender Einflu? von Schwefel auf die Aufkohlung von Nickel in Methan-Wasserstoff-Gemischen

Summary The carburization of nickel in CH₄-H₂ and CH₄-H₂S-H₂ gas mixtures was studied in a flow apparatus at 1060–1280 K applying the resistance-relaxation technique. The reaction of nickel with CH₄ is found to be thermally activated with an activation energy of 128 kJ/mol. The ratecontrolling step is the separation of the first hydrogen atom from the CH₄-molecules impinging on the surface. Small H₂S-amounts, resulting in PH₂S/PH₂-ratios between 8 × 10^–9 and 9 × 10^–5 decrease the initial carburization rate by a factor of up to 100. The kinetic data are interpreted in terms of poisoning of active surface sites by adsorbed sulfur. From this analysis adsorption isotherms for sulfur are derived.