Immunocytochemical localization of the main intrinsic polypeptide (MIP) in ultrathin frozen sections of rat lens.

The in situ distribution of the 26-kdalton Main Intrinsic Polypeptide (MIP or MP 26), a putative gap junction protein in ocular lens fibers, was defined at the electron microscope level using indirect immunoferritin labeling of ultrathin frozen sections of rat lens. MIP was found distributed throughout the plasma membrane of the lens fiber cell, with no apparent distinction between junctional and nonjunctional membrane. MIP was not detectable in the basal or lateral plasma membrane of the lens epithelial cell, including the interepithelial cell gap junctions; nor was MIP detectable in the plasma membrane or gap junctions of the hepatocyte. Previous reports have indicated that the protein composition of the lens fiber cell junction differs from that of the hepatocyte gap junction. The evidence presented here suggests that the composition of the fiber cell junction and plasma membrane is also immunocytochemically distinct from that of its progenitor, the lens epithelial cell

Phase transition between d-wave and anisotropic s-wave gaps in high temperature oxides superconductors

We study models for superconductivity with two interactions: $V^>$ due to antiferromagnetic(AF) fluctuations and $V^<$ due to phonons, in a weak coupling approach to the high temperature superconductivity. The nature of the two interactions are considerably different; $V^>$ is positive and sharply peaked at ($\pm\pi$,$\pm\pi$) while $V^<$ is negative and peaked at ($0,0$) due to weak phonon screening. We numerically find (a) weak BCS attraction is enough to have high critical temperature if a van Hove anomaly is at work, (b) $V^>$ (AF) is important to give d-wave superconductivity, (c) the gap order parameter $\Delta({\bf k})$ is constant(s-wave) at extremely overdope region and it changes to anisotropic s-wave as doping is reduced, (d) there exists a first order phase transition between d-wave and anisotropic s-wave gaps. These results are qualitatively in agreement with preceding works; they should be modified in the strongly underdope region by the presence of antiferromagnetic fluctuations and ensuing AF pseudogap.Comment: 4 pages in RevTex (double column), 4 figure

Hall effect in the normal state of high Tc cuprates

We propose a model for explaining the dependence in temperature of the Hall effect of high Tc cuprates in the normal state in various materials. They all show common features: a decrease of the Hall coefficient RH with temperature and a universal law, when plotting RH(T)/RH(T0) versus T/T0, where T0 is defined from experimental results. This behaviour is explained by using the well known electronic band structure of the CuO2 plane, showing saddle points at the energies ES in the directions (0,+/-pi) and (+/-pi,0). We remark that in a magnetic field, for energies E>ES the carrier orbits are hole-like and for E<ES they are electron-like, giving opposite contributions to RH. We are abble to fit the experimental results for a wide range of hole doping, and to fit the universal curve. For us kb*T0 is simply EF-ES, where EF is the Fermi level varying with the doping.Comment: 7 pages, 11 figure

Momentum Dependence of the Single-Particle Self-Energy and Fluctuation Spectrum of Slightly Underdoped Bi_2 Sr_2 CaCu_2 O_{8+\delta} from High Resolution Laser ARPES

We deduce the normal state angle-resolved single-particle self-energy $\Sigma(\theta, \omega)$ and the Eliashberg function (i.e., the product of the fluctuation spectrum and its coupling to fermions) $\alpha^2 F(\theta,\omega)$ for the high temperature superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ from the ultra high resolution laser angle-resolved photoemission spectroscopy (ARPES). The self-energy $\Sigma(\theta, \omega)$ at energy $\omega$ along several cuts normal to the Fermi surface at the tilt angles $\theta$ with respect to the nodal direction in a slightly underdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ were extracted by fitting the ARPES momentum distribution curves. Then, using the extracted self-energy as the experimental input, the $\alpha^2 F(\theta,\omega)$ is deduced by inverting the Eliashberg equation employing the adaptive maximum entropy method. Our principal new result is that the Eliashberg function $\alpha^2F(\theta,\omega)$ collapse for all $\theta$ onto a single function of $\omega$ up to the upper cut-off energy despite the $\theta$ dependence of the self-energy. The in-plane momentum anisotropy is therefore predominantly due to the anisotropic band dispersion effects. The obtained Eliashberg function has a small peak at $\omega\approx0.05$ eV and flattens out above 0.1 eV up to the angle-dependent cut-off. It takes the intrinsic cut-off of about 0.4 eV or the energy of the bottom of the band with respect to the Fermi energy in the direction $\theta$, whichever is lower. The angle independence of the $\alpha^2 F(\theta,\omega)$ is consistent only with the fluctuation spectra which have the short correlation length on the scale the lattice constant. This implies among others that the antiferromagnetic fluctuations may not be underlying physics of the deduced fluctuation spectrum.Comment: 10 pages, 10 figures. Accepted at PR