Acetaldehyde adsorption and catalytic decomposition on Pd(1 1 0) and the dissolution of carbon

The reaction of acetaldehyde with the Pd(1 1 0) surface has been studied using a molecular beam reactor, TPD and LEED. Below 270 K acetaldehyde sticks to the surface with a high initial probability (∼0.8), but no gas phase products evolve. When the reaction is run at >270 K, hydrogen evolves into the gas phase early in the reaction together with methane in a non-steady-state fashion, but above 300 K there is a very efficient steady-state catalytic reaction at the surface; this reaction is the decarbonylation of acetaldehyde to produce methane and carbon monoxide in the gas phase. This behaviour continues up to about 400 K. However, when acetaldehyde is dosed at 423 K, the reaction rate slowly evolves through a maximum to a very low catalytic rate. Upon carrying out reactor experiments at 473 K and above, the reaction mechanism changes to total dehydrogenation, and CO and H₂ are produced at high steady-state rate, not withstanding the fact that carbon is continually being deposited onto the surface. This carbon does not appear to affect the reaction, which takes place on a surface with a c(2 × 2)-C layer present, since the extra carbon is lost from the reaction zone by diffusion into the bulk of the crystal.     

On the correlation of a group of rankings with an external ordering relative to the internal concordance

A method is presented for comparing the strength of agreement of a group rankings with an external ordering to the corresponding measure of concordance within the group. While the procedure is not model dependent, we illustrate the characteristics of interest using an existing model for a nonnull distribution for a population of rankings. U-statistics and a jackknife with adjusted degrees of freedom are employed to set approximate confidence intervals on the contrast between the two measures of rank order agreement.     

Distributed feedback fiber laser pumped by multimode laser diodes

A distributed feedback fiber laser made of highly Er-Yb codoped phosphate glass fiber has been demonstrated experimentally. Efficient pump absorption allows for multimode pumping into the cladding of the active fiber. Output powers up to 160 mW have been achieved. The 35 mm long fiber laser device emits with >50 dB side mode suppression ratio.     

Multiscale cumulative residual distribution entropy and its applications on heart rate time series

Nonlinear Dynamics - Distribution entropy has been proved to reveal stability for short time series and to distinguish different classes of series by complexity. However, there still exists some...     

A sufficient condition for finite decidability

We prove that a varietyV which is locally finite, finitely generated, congruence permutable and of finite type, and whose subdirectly irreducible algebras are all either abelian or linear type 3 above the monolith is finitely decidable if and only if the theory of the finite abelian algebras inV is decidable.Presented by R. McKenzie.     

Volume Estimate Via Total Curvature in Hyperbolic Spaces

Let D Hⁿ(–k²) be a convex compact subset of the hyperbolicspace Hⁿ(–k²) with non-empty interior and smooth boundary.It is shown that the volume of D can be estimated by the totalcurvature of D. More precisely, , where K denotes the Gauss–Kronecker curvature of D andVol(S^n–1) denotes the Euclidean volume of the sphere.2000 Mathematics Subject Classification 53C21.     

An exact algorithm for solving the bilevel facility interdiction and fortification problem

We present an exact approach for solving the $r$-interdiction median problem with fortification. Our approach consists of solving a greedy heuristic and a set cover problem iteratively that guarantees to find an optimal solution upon termination. The greedy heuristic obtains a feasible solution to the problem, and the set cover problem is solved to verify optimality of the solution and to provide a direction for improvement if not optimal. We demonstrate the performance of the algorithm in a computational study.