New superconducting phases in field-induced organic superconductor lambda-(BETS)2FeCl4

We derive the parallel upper critical field, Hc2, as a function of the temperature T in quasi-2D organic compound lambda-(BETS)2FeCl4, accounting for the formation of the nonuniform Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) state. To further check the 2D LOFF model, we propose to study the Hc2(T) curve at low T in tilted fields, where the vortex state is described by the high Landau level functions characterized by the index n. We predict a cascade of first-order transitions between vortex phases with different n, between phases with different types of the symmetry at given n and the change of the superconducting transition from the second order to the first order as FeCl4 ions are replaced partly by GaCl4 ions.     

C-axis Josephson plasma resonance observed in Tl(2)Ba(2)CaCu(2)O(8) superconducting thin films by use of terahertz time-domain spectroscopy

We have unambiguously observed the c -axis Josephson plasma resonance (JPR) in high-critical-temperature (T(c)) cuprate (Tl(2)Ba(2)CaCu(2)O(8)) superconducting thin films, employing terahertz time-domain spectroscopy in transmission as a function of temperature in zero magnetic field. These are believed to be the first measurements of the JPR temperature dependence of a high-T(c) material in transmission. With increasing temperature, the JPR shifts from 705 GHz at 10 K to ~170 GHz at 98 K, corresponding to an increase in c-axis penetration depth from 22.4+/-0.6mum to 94+/-9mum . The linewidth of the JPR peak increases with temperature, which indicates an increase in the quasi-particle scattering rate. We have probed the onset of the c -axis phase coherence to ~0.95T(c) . The JPR vanishes above T(c) as expected.     

Spectroscopic Analysis of Folate Binding to Thymidylate Synthase Active Site

The fluorescence properties of folate binding to thymidylate synthase (TS) were analyzed. Two antifolates with different binding modes to the TS active site were the ligands. Intrinsic tryptophan fluorescence was used to evaluate the binding of both antifolates to the wild-type TS and a mutant Escherichia coli TS (K48Q) that is impaired in folate binding. During titration of wild-type TS with PDDF, tryptophan fluorescence was quenched at 330 nm, which was accompanied by an increase in emission at 379 nm, suggesting an energy transfer process from a tryptophan in the TS active site to the folate analogue. Energy transfer was not observed with the mutant TS, as expected. Tryptophan emission is a very useful tool to test for substrate-like inhibitors with biological activity.     

Data Collection for the Sloan Digital Sky Survey—A Network-Flow Heuristic

This paper describes an NP-hard combinatorial optimization problem arising in the Sloan Digital Sky Survey and a practical approximation algorithm that has been implemented and will be used in the survey. The algorithm is based on network flow theory and Lagrangian relaxation.     

High current densities at 20T in long (20m) tapes of CVD-prepared Nb3Ge

Critical current densities J_c as a function of magnetic field have been measured on tapes of chemically vapor deposited (CVD) Nb₃Ge that are up to 20m long. Values of J_c exceed 5 × 10⁴ A/cm² at 20T. Such high critical current densities are encouraging for use of this material in producing a 20T superconducting magnet.