Size exclusion (radio) chromatography of aqueous humic acid solutions with cesium and strontium

The high-performance size-exclusion chromatography (HPSEC) and radiochromatography (HPSERC) was used for the identification of radiocesium and radiostrontium interaction with humic acid. It was found that the behavior of humic acid on size-exclusion chromatography is sensitive to the salt concentration and pH of the mobile phase. At lower ionic strength and in acidic region of pH, the Aldrich humic acid exhibited three main fraction within the ranges >760 kDa, 25–100 kDa and <5 kDa. Radiocesium was found in the low-molecular fractions (<1 kDa) of humic acids but radiostrontium interacts preferably with the fractions of humic acid of molecular weight within the range 2–5 kDa.     

UCN production in superfluid helium

Ultra-cold neutrons (UCN) are produced in superfluid helium by single- and multi-phonon excitation. The UCN production rate density R _II via multiphonons can be larger than that by one-phonon excitation R _I being due to the dependence of the incident neutron spectral flux density dφ/dλ on the wavelength λ. Received: 28 March 2002 / Accepted: 19 December 2002 / Published online: 11 March 2003 RID="a" ID="a"e-mail: wschott@e18.physik.tu-muenchen.de RID="b" ID="b"On leave of absence from PNPI, Gatchina, Russia Communicated by T. Walcher     

Quenching of triplet excitions by trapped holes in crystalline pyrene

The rate of quenching of triplet excitions by trapped holes in crystalline pyrene has been measured as a function of hole concentration. The rate constant is γ=4.5×10^?11 cm³ sec^?1 within 50%, not far below that of a diffusion limited process. The quenching by free holes is not observed in the experimental conditions used.     

Silicium-Komplexe. VI. Oxalato-silicate und Oxalato-germanate

Silicon complexes. VI. Oxalatosilicates and oxalatogermanates By reaction of SiCl₄(GeCl₄) or diaryldichloro silanes (germanes) with Ag₂C₂O₄ and quartary ammonium or phosphonium iodides, compounds of the following formulas were prepared: These products are resistant towards hydrolysis and were characterized by IR-spectra, conductivity and thermal decomposition. The compounds resulting from reaction of monoorganitrichloro silanes nearly correspond to the formula and are extremely sensitive towards hydrolysis.     

Silane. XII. Alkalische Solvolyse von substituierten Benzylsilanen

Alcaline solvolysis of substituted phenyl and benzyl silanes listed in “Inhaltsübersicht” is compared. The inductive transfer coefficient of the CH₂ group is fixed.