Islands of stability of the d-wave order parameter in s-wave anisotropic superconductors

In this paper we find and present on diagrams in the coordinates of η=2t 1/t 0 (the ratio of the second and the first nearest neighbor hopping integrals) and n (the carrier concentration) the areas of stability for the superconducting spin-singlet s- and d-wave and the spin-triplet p-wave order parameters hatching out during the phase transition from the normal to the superconducting phase. The diagrams are obtained for an anisotropic two-dimensional superconducting system with a relatively wide partially-filled conduction band. We study a tight-binding model with an attractive nearest neighbor interaction with the amplitude V 1, and the on-site interaction (with the amplitude V 0) taken either as repulsive or attractive. The problem of the coexistence of the s-, p- and d-wave order parameters is addressed and solved for chosen values of the ratio V 0/V 1. A possible island of stability of the d-wave order parameter in the s-wave order parameter environment for a relatively strong on-site interaction is revealed. The triple points, around which the s-, d-, and p-wave order parameters coexist, are localized on diagrams. It is shown that results of the calculations performed for the two-dimensional tight-binding band model are dissimilar with some obtained within the BCS-type approximation. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 200874.20.Rp Pairing symmetries (other than s-wave), 74.62.Yb Other effects,

MDM2 promotes p21(waf1/cip1) proteasomal turnover independently of ubiquitylation

The CDK inhibitor p21(waf1/cip1) is degraded by a ubiquitin-independent proteolytic pathway. Here, we show that MDM2 mediates this degradation process. Overexpression of wild-type or ring finger-deleted, but not nuclear localization signal (NLS)-deleted, MDM2 decreased p21(waf1/cip1) levels without ubiquitylating this protein and affecting its mRNA level in p53(–/–) cells. This decrease was reversed by the proteasome inhibitors MG132 and lactacystin, by p19(arf), and by small interfering RNA (siRNA) against MDM2. p21(waf1/cip1) bound to MDM2 in vitro and in cells. The p21(waf1/cip1)-binding-defective mutant of MDM2 was unable to degrade p21(waf1/cip1). MDM2 shortened the half-life of both exogenous and endogenous p21(waf1/cip1) by 50% and led to the degradation of its lysine-free mutant. Consequently, MDM2 suppressed p21(waf1/cip1)-induced cell growth arrest of human p53(–/–) and p53(–/–)/Rb(–/–)cells. These results demonstrate that MDM2 directly inhibits p21(waf1/cip1) function by reducing p21(waf1/cip1) stability in a ubiquitin-independent fashion