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As-vacancies (V_As) in La-1111-systems, which are nominally non-magnetic defects, are shown to create in their vicinity by symmetry ferromagnetically oriented local magnetic moments due to the strong, covalent bonds with neighboring Fe atoms that they break. From microscopic theory in terms of an appropriately modified Anderson-Wolff model, we find that the moment formation results in a substantially enhanced paramagnetic susceptibility in both the normal and superconducting (SC) state. Despite the V_As act as magnetic scatterers, they do not deteriorate SC properties which can even be improved by V_As by suppressing a competing or coexisting commensurate spin density wave or its remnant fluctuations. Due to the induced local magnetic moments an s_++-scenario in related systems is unlikely., Comment: 7 pages, 4 Figures

We describe in this short review the influence of discrete symmetries in complex quantum dots on the Kondo co-tunneling through these nano-objects. These discrete symmetries stem from the geometrical structure of the tunneling devices (e.g spatial symmetry of multivalley quantum dot in a tunneling contact with leads). They affect the dynamical symmetry of spin multiplets characterizing the ground state and excitations in quantum dots with definite electron number occupation. The influence of external electric and magnetic fields on these symmetries is examined, and analogies with the physics of quantum tunneling through molecular complexes are discussed., Comment: Short review (22 pages) prepared for "Encyclopedia of Complexity" (Springer, 2008)