Temperature-scaling behavior of the Hall conductivity for Hg-based superconducting thin films

The Hall conductivities of HgBa_{2}CaCu_{2}O_{6+\delta}and HgBa_{2}Ca_{2}Cu_{3}O_{8+\delta} thin films are investigated for a magnetic field parallel to the c axis. The mixed-state Hall conductivity for these compounds is well described by \sigma_{xy}=C_{1}/H+C_{2}+C_{3}H. The prefactor C_1 shows a temperature dependence of the form C_1 = A(1-t)^n near T_c, where t=T/T_c is the reduced temperature. Contrary to the previous results, C_2 also follows a temperature-scaling behavior similar to that of the coefficient C_1. The observed value of n = 1.8 - 2.3 is comparable to the previously observed values for YBa_{2}Cu_{3}O_{7-\delta} and La_{2-x}Sr_{x}CuO_{4}.Comment: 5 pages, 4 eps figure

Rap1 binding to the talin 1 F0 domain makes a minimal contribution to murine platelet GPIIb-IIIa activation

Activation of platelet glycoprotein IIb-IIIa (GPIIb-IIIa; integrin aIIbb3) leads to high-affinity fibrinogen binding and platelet aggregation during hemostasis. Whereas GTP-bound Rap1 GTPase promotes talin 1 binding to the b3 cytoplasmic domain to activate platelet GPIIb-IIIa, the Rap1 effector that regulates talin association with b3 in platelets is unknown. Rap1 binding to the talin 1 F0 subdomain was proposed to forge the talin 1–Rap1 link in platelets. Here, we report a talin 1 point mutant (R35E) that significantly reduces Rap1 affinity without a significant effect on its structure or expression. Talin 1 head domain (THD) (R35E) was of similar potency to wild-type THD in activating aIIbb3 in Chinese hamster ovary cells. Coexpression with activated Rap1b increased activation, and coexpression with Rap1GAP1 reduced activation caused by transfection of wild-type THD or THD(R35E). Furthermore, platelets from Tln1R35E/R35E mice showed similar GPIIb-IIIa activation to those from wild- type littermates in response to multiple agonists. Tln1R35E/R35E platelets exhibited slightly reduced platelet aggregation in response to low doses of agonists; however, there was not a significant hemostatic defect, as judged by tail bleeding times. Thus, the Rap1–talin 1 F0 interaction has little effect on platelet GPIIb-IIIa activation and hemostasis and cannot account for the dramatic effects of loss of Rap1 activity on these platelet functions

In-plane Hall effect in c-axis-oriented MgB2 thin films

We have measured the longitudinal resistivity and the Hall resistivity in the ab-plane of highly c-axis-oriented MgB2 thin films. In the normal state, the Hall coefficient (R_H) behaves as R_H ~ T with increasing temperature (T) up to 130 K and then deviates from that linear T-dependence at higher temperatures. The T^2 dependence of the cotangent of the Hall angle is only observed above 130 K. The mixed-state Hall effect reveals no sign anomaly over a wide range of current densities from 10^2 to 10^4 A/cm^2 and for magnetic fields up to 5 T.Comment: 5 pages including 5 figure

Anisotropy of oxygen tracer diffusion in YBa sub 2 Cu sub 3 O sub 7-. delta. single crystals

The crystal structure of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} strongly suggests that the diffusion of oxygen in this material will be highly anisotropic, with diffusion in the ab plane being much faster than diffusion parallel to the c axis, and this has been assumed in most analyses of diffusion in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}. The present data confirm this hypothesis; the diffusion coefficient in the ab plane is several orders of magnitude greater than the diffusion coefficient along the c axis. Some interesting artifacts of the measurement, due to this strong anisotropy, are also revealed. Oxygen exchange in polycrystalline samples of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} is discussed in terms of these results. 15 refs., 9 figs