Nonlinear Sigma Model Analysis of the AFM Phase Transition of the Kondo Lattice

We have studied the antiferromagnetic quantum phase transition of a 2D Kondo-Heisenberg square lattice using the non-linear sigma model. A renormalization group analysis of the competing Kondo -- RKKY interaction was carried out to 1-loop order in the $\epsilon$ expansion, and a new quantum critical point is found, dominated by Kondo fluctuations. In addition, the spin-wave velocity scales logarithmically near the new QCP, i.e breakdown of hydrodynamic behavior. The results allow us to propose a new phase diagram near the AFM fixed point of this 2D Kondo lattice model.Comment: 4 pages, 4 figure

The Suppression of Radiation Reaction and Laser Field Depletion in Laser-Electron beam interaction

The effects of radiation reaction (RR) have been studied extensively by using the ultraintense laser interacts with the counter-propagating relativistic electron. At the laser intensity at the order of $10^{23}$ W/cm$^2$, the effects of RR are significant in a few laser period for a relativistic electron. However, the laser at such intensity is tightly focused and the laser energy is usually assumed to be fixed. Then, the signal of RR and energy conservation cannot be guaranteed. To assess the effects of RR in a tightly focused laser pulse and the evolution of the laser energy, we simulate this interaction with a beam of $10^9$ electrons by means of Particle-in-Cell (PIC) method. We observed that the effects of RR are suppressed due to the ponderomotive force and accompanied by a non-negligible amount of laser field energy reduction. This is due to the ponderomotive force that prevents the electrons from approaching the center of the laser pulse and leads to the interaction at weaker field region. At the same time, the laser energy is absorbed through ponderomotive acceleration. Thus, the kinetic energy of the electron beam has to be carefully selected such that the effects of RR become obvious.Comment: 6 pages, 3 figure

Identification of an N-terminal glycogen synthase kinase 3 phosphorylation site which regulates the functional localisation of polycystin-2 in vivo and in vitro

PKD2 is mutated in 15% of patients with autosomal dominant polycystic kidney disease (ADPKD). Polycystin-2 (PC2), the PKD2 protein, is a nonselective Ca2 + -permeable cation channel which may function at the cell surface and ER. Nevertheless, the factors that regulate the dynamic translocation of PC2 between the ER and other compartments are not well understood. Constitutive phosphorylation of PC2 at a single C-terminal site (Ser812) has been previously reported. Since we were unable to abolish phospholabelling of PC2 in HEK293 cells by site-directed mutagenesis of Ser812 or all 5 predicted phosphorylation sites in the C-terminus, we hypothesised that PC2 could also be phosphorylated at the N-terminus. In this paper, we report the identification of a new phosphorylation site for PC2 within its N-terminal domain (Ser76) and demonstrate that this residue is phosphorylated by glycogen synthase kinase 3 (GSK-3). The consensus recognition sequence for GSK-3 (Ser76/Ser80) is evolutionarily conserved down to lower vertebrates. In the presence of specific GSK-3 inhibitors, the lateral plasma membrane pool of endogenous PC2 redistributes into an intracellular compartment in MDCK cells without a change in primary cilia localization. Finally, co-injection of wild-type but not a S76A/S80A mutant PKD2 capped mRNA could rescue the cystic phenotype induced by an antisense morpholino oligonucleotide to pkd2 in zebrafish pronephric kidney. We conclude that surface localization of PC2 is regulated by phosphorylation at a unique GSK-3 site in its N-terminal domain in vivo and in vitro. This site is functionally significant for the maintenance of normal glomerular and tubular morphology