Trace analysis of high-purity iron by total reflection X-ray fluorescence spectrometry

Summary A combined procedure enabling simultaneous multielement analysis of trace impurities in high-purity iron is presented. After removal of the iron matrix by solvent extraction with methyl isobutyl ketone, the trace elements Ti, V, Cr, Mn, Ni, Cu, Pb and Bi are determined by means of total reflection X-ray fluorescence analysis. Detection limits are found in the range of 100 ng/g. The reliability of the method is verified by the analysis of commercial high-purity iron and by the comparison of analytical data obtained by ICP-AES.     

The relativistic fermi gas in a nonuniform velocity field

We review the relativistic Fermi gas in an inhomogeneous velocity field and calculate components of the current vector and the energy-momentum tensor in a comoving frame. We derive quantum corrections to the classical distribution function in the framework of the grand canonical ensemble.     

On the power series coefficients of certain quotients of Eisenstein series

In their last joint paper, Hardy and Ramanujan examined the coefficients of modular forms with a simple pole in a fundamental region. In particular, they focused on the reciprocal of the Eisenstein series . In letters written to Hardy from nursing homes, Ramanujan stated without proof several more results of this sort. The purpose of this paper is to prove most of these claims.

     

Atom transfer and single-adatom contacts

The point contact of a tunnel tip approaching towards Ag(111) and Cu(111) surfaces is investigated with a low temperature scanning tunneling microscope. A sharp jump to contact, random in nature, is observed in the conductance. After point contact, the tip-apex atom is transferred to the surface, indicating that a one-atom contact is formed during the approach. In sharp contrast, the conductance over single silver and copper adatoms exhibits a smooth and reproducible transition from tunneling to contact regime. Numerical simulations show that this is a consequence of the additional dipolar bonding between the adatom and the surface atoms.