1,929 research outputs found

    Angular Correlations in Internal Pair Conversion of Aligned Heavy Nuclei

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    We calculate the spatial correlation of electrons and positrons emitted by internal pair conversion of Coulomb excited nuclei in heavy ion collisions. The alignment or polarization of the nucleus results in an anisotropic emission of the electron-positron pairs which is closely related to the anisotropic emission of γ\gamma-rays. However, the angular correlation in the case of internal pair conversion exhibits diverse patterns. This might be relevant when investigating atomic processes in heavy-ion collisions performed at the Coulomb barrier.Comment: 27 pages + 6 eps figures, uses revtex.sty and epsf.sty, tar-compressed and uuencoded with uufile

    Alternative N-Terminal Domains of PSD-95 and SAP97 Govern Activity-Dependent Regulation of Synaptic AMPA Receptor Function

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    SummaryPSD-95 and SAP97 are scaffolding proteins that have been implicated in regulating AMPA receptor incorporation and function at synapses. Gain- and loss-of-function approaches, however, have generated conflicting results. To minimize adaptations during development and potential dominant-negative effects of overexpression, we have combined silencing of endogenous PSD-95 in mature neurons with heterologous expression of specific SAP97 or PSD-95 isoforms. We find that both PSD-95 and SAP97 contain alternative N termini expressing either double cysteines that normally are palmitoylated (α-isoforms) or an L27 domain (β-isoforms). Whereas α-isoforms of PSD-95 and SAP97 influence AMPA receptor-mediated synaptic strength independent of activity, the effects of β-isoforms are regulated by activity in a CaMKII-dependent manner. Importantly, the synaptic effects of the β-isoforms are masked by the endogenous α-isoform of PSD-95. These results demonstrate that the different N termini of the predominant endogenous forms of PSD-95 (α-isoform) and SAP97 (β-isoform) govern their role in regulating synaptic function

    Intrinsic peculiarities of real material realizations of a spin-1/2 kagome lattice

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    Spin-1/2 magnets with kagome geometry, being for years a generic object of theoretical investigations, have few real material realizations. Recently, a DFT-based microscopic model for two such materials, kapellasite Cu3Zn(OH)6Cl2 and haydeeite Cu3Mg(OH)6Cl2, was presented [O. Janson, J. Richter and H. Rosner, arXiv:0806.1592]. Here, we focus on the intrinsic properties of real spin-1/2 kagome materials having influence on the magnetic ground state and the low-temperature excitations. We find that the values of exchange integrals are strongly dependent on O--H distance inside the hydroxyl groups, present in most spin-1/2 kagome compounds up to date. Besides the original kagome model, considering only the nearest neighbour exchange, we emphasize the crucial role of the exchange along the diagonals of the kagome lattice.Comment: 4 pages, 4 figures. A paper for the proceedings of the HFM 2008 conferenc
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