Tensor interaction constraints from beta decay recoil spin asymmetry of trapped atoms

We have measured the angular distribution of recoiling daughter nuclei emitted from the Gamow-Teller $\beta$ decay of spin-polarized $^{80}$Rb. The asymmetry of this distribution vanishes to lowest order in the Standard Model (SM) in pure Gamow-Teller decays, producing an observable very sensitive to new interactions. We measure the non-SM contribution to the asymmetry to be $A_{T}$= 0.015 $\pm$ 0.029 (stat) $\pm$ 0.019 (syst), consistent with the SM prediction. We constrain higher-order SM corrections using the measured momentum dependence of the asymmetry, and their remaining uncertainty dominates the systematic error. Future progress in determining the weak magnetism term theoretically or experimentally would reduce the final errors. We describe the resulting constraints on fundamental 4-Fermi tensor interactions.Comment: 11 pages, 13 figures; v2 published in Phys. Rev. C, with referee clarifications and figures improved for black-and-whit

Ambient particulate matter induces oxidative DNA damage in lung epithelial cells

Although epidemiological studies have established a correlation between pm10 levels and acute cardiovascular and respiratory complications, hardly any data is available on possible chronic effects such as cancer. The purpose of this study was to investigate the production of free radicals by ambient particulate matter (tsp) and to link these data to oxidative dna damage in lung epithelial cells. In line with previous findings on pm10, supercoiled plasmid dna was depleted by tsp as well as tsp supernatant (p <.001), and this effect was reduced in the presence of mannitol (5 mm). Using electron spin resonance (esr) and the spin trap dimethyl-1-pyrroline n-oxide (dmpo) we were able to show that hydroxyl radicals (oh) are formed from both tsp and tsp supernatant. The dmpo-oh signal was completely abrogated when tsp was preincubated with deferoxamine (5 mm), showing the importance of iron and other soluble metals in this process. Atomic absorption spectroscopy (aas) analysis of the tsp supernatant showed the presence of soluble fe, v,and ni (respectively 253.0, 14.7, and 76.0 mug/g insoluble tsp). To investigate the biological significance of oh formation by tsp,8-hydroxydeoxyguanosine (8-oxodg) was measured in a rat type ii cell line by immunocytochemistry. The formation of this hydroxyl-radical-specific dna adduct was increased twofold (p <.01) after incubation with tsp supernatants, and this effect was inhibited by deferoxamine (p <.01). In summary, our results provide direct evidence that ambient particulate matter generates hydroxyl radicals in acellular systems. Furthermore, we showed that these particulates induce the hydroxyl-radical-specific dna lesion 8-oxodg in lung target cells via an iron-mediated mechanism

Double Ionization of Helium by Electron-Impact in the Impulsive Regime

Abstract: The dynamics of helium double ionization by 2 keV electron impact has been investigated experimentally and theoretically at large momentum transfer of |q| = 2 a.u. Fully resolved fivefold differential cross sections (FDCS) are presented for symmetric and asymmetric energy sharing between the two ejected electrons at excess energies from 10 eV to 40 eV, and for the coplanar as well as the out-of-plane scattering geometries. Experimentally, a multielectron -recoil-ion coincidence technique has been applied and a large part of the final-state momentum-space has been mapped. The presently employed theoretical model treats the interaction between the two slow ejected electrons nonperturbatively using the convergent close coupling (CCC) method, whereas the projectile-target interaction is described in the first Born approximation. The experimental and theoretical FDCS agree well in shape. The cross section is dominated by two pairs of strong peaks. From this pattern it can be concluded that the two-step 1 mechanism which is due to interelectron interaction after a single ionizing collision is the dominant ionisation process for the present kinematics.