Precious Metal Recovery from Fuel Cell MEA's (open access)

Precious Metal Recovery from Fuel Cell MEA's

In 2003, Engelhard Corporation received a DOE award to develop a cost-effective, environmentally friendly approach to recover Pt from fuel cell membrane electrode assemblies (MEA’s). The most important precious metal used in fuel cells is platinum, but ruthenium is also added to the anode electrocatalyst if CO is present in the hydrogen stream. As part of the project, a large number of measurements of Pt and Ru need to be made. A low-cost approach to measuring Pt is using the industry standard spectrophotometric measurement of Pt complexed with stannous chloride. The interference of Ru can be eliminated by reading the Pt absorbance at 450 nm. Spectrophotometric methods for measuring Ru, while reported in the literature, are not as robust. This paper will discuss the options for measuring Pt and Ru using the method of UV-VIS spectrophotometry
Date: April 25, 2004
Creator: Shore, Lawrence
System: The UNT Digital Library
Collinear Splitting, Parton Evolution and the Strange-Quark Asymmetry of the Nucleon in Nnlo Qcd. (open access)

Collinear Splitting, Parton Evolution and the Strange-Quark Asymmetry of the Nucleon in Nnlo Qcd.

We consider the collinear limit of QCD amplitudes at one-loop order, and their factorization properties directly in color space. These results apply to the multiple collinear limit of an arbitrary number of QCD partons, and are a basic ingredient in many higher-order computations. In particular, we discuss the triple collinear limit and its relation to flavor asymmetries in the QCD evolution of parton densities at three loops. As a phenomenological consequence of this new effect, and of the fact that the nucleon has non-vanishing quark valence densities, we study the perturbative generation of a strange-antistrange asymmetry s(x)-{bar s}(x) in the nucleon's sea.
Date: April 25, 2004
Creator: Rodrigo, G.; Catani, S.; de Florian, D. & Vogelsang, W.
System: The UNT Digital Library
Prospects for single-particle imaging at XFELs (open access)

Prospects for single-particle imaging at XFELs

X-ray free-electron lasers will produce pulses of x-rays that are 10 orders of magnitude brighter than today's undulator sources at synchrotrons. This may enable atomic resolution imaging of single macromolecules.
Date: April 25, 2004
Creator: Chapman, H N; Hau-Riege, S P; London, R A; Marchesini, S; Noy, A; Szoke, A et al.
System: The UNT Digital Library