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[en] In light of a recent experiment indicating an anomalously large enhancement of the M3 moment in ³⁹K we examine in detail the possible mechanisms usually at play in the renormalization of magnetic moments. These include meson exchange currents, core polarization, and Δ excitations. We conclude that none of the nuclear structure mechanisms presently known are able to account for any enhancement of the M3 moment and suggest the need for a reevaluation of the experimental analysis

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[en] We discover several magnetic Feshbach resonances in collisions of ultracold ³⁹K atoms, by studying atom losses and molecule formation. Accurate determination of the magnetic-field resonance locations allows us to optimize a quantum collision model for potassium isotopes. We employ the model to predict the magnetic-field dependence of scattering lengths and of near-threshold molecular levels. Our findings will be useful to plan future experiments on ultracold ³⁹K atoms and molecules

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[en] Growth rates and total population of E. coli were reduced fourfold when natural KCl (/sup N/KCl) in the medium was replaced by ³⁹KCl from a particular source. A prolonged lag period was noted in cultures containing either /sup N/KCl or ³⁹KCl when inoculated with bacteria adapted to ³⁹KCl. These changes were not due to endogenous radiation because these differences were not observed when (a) the KCl concentrations were reduced from 50 to 5 mM and (b) the ³⁹KCl from the prime source was replaced with ³⁹KCl from a second source; also the addition of ⁴⁰KCl to ³⁹KCl did not improve growth. These results suggest that the ³⁹KCl from the primary source contained an unidentified inhibitor that is not readily detected by physical and chemical analyses. 8 references, 3 figures, 2 tables

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