On the verge of Umdeutung in Minnesota: Van Vleck and the correspondence principle (Part One)

In October 1924, the Physical Review, a relatively minor journal at the time, published a remarkable two-part paper by John H. Van Vleck, working in virtual isolation at the University of Minnesota. Van Vleck combined advanced techniques of classical mechanics with Bohr's correspondence principle and Einstein's quantum theory of radiation to find quantum analogues of classical expressions for the emission, absorption, and dispersion of radiation. For modern readers Van Vleck's paper is much easier to follow than the famous paper by Kramers and Heisenberg on dispersion theory, which covers similar terrain and is widely credited to have led directly to Heisenberg's "Umdeutung" paper. This makes Van Vleck's paper extremely valuable for the reconstruction of the genesis of matrix mechanics. It also makes it tempting to ask why Van Vleck did not take the next step and develop matrix mechanics himself.Comment: 82 page

Speciation of organic selenium compounds using reversed-phase liquid chromatography and inductively coupled plasma mass spectrometry. 3. Application of sector field instrument with low and high mass resolution for selenium speciation in herring gull eggs

A HPLC procedure based on reversed phase chromatography with methanol as the eluent for the speciation of organic Se compounds has been developed to study the appearance of Se species in herring gull eggs collected from mud flats of the North Sea. The extraction of Se species by using hot water was limited to a recovery of 8% only. The multielement capability of ICP-MS was exploited to obtain elemental correlation, and for Se compounds (selenocystine, selenocystamine, selenomethionine, selenoethionine) were used as standards. Among these only the presence of selenocystamine was evident, and correlations of this fraction with Cu, As and S became obvious