Spectroscopic indications of polaronic carriers in the quasi-one-dimensional conductor (TaSe4)2I.

Angle-resolved photoemission (ARPES) on the quasi-one-dimensional conductor (TaSe4)2I shows a hidden Fermi-surface crossing in its metallic state and the opening of a Peierls gap at low temperatures. The underlying quasiparticles have vanishing spectral weight and extremely short coherence lengths. They are interpreted as polarons in the strong-coupling adiabatic limit, and almost all their ARPES weight is incoherent. These observations suggest a scenario where the long-standing contradictions between ARPES and other experiments on Peierls materials could be resolved.

Phase diagram of an asymmetric spin ladder.

We investigate an asymmetric zigzag spin ladder with different exchange integrals on both legs using bosonization and renormalization group approaches. When the leg exchange integrals and frustration both are sufficiently small, renormalization group analysis shows that the Heisenberg critical point flows to an intermediate-coupling fixed point with gapless excitations and a vanishing spin velocity. When they are large, a spin gap opens and a dimer liquid is realized. Here, we find a continuous manifold of Hamiltonians with dimer product ground states, interpolating between the Majumdar-Ghosh and sawtooth spin-chain model.

Electronic structure of solids with competing periodic potentials.

When electrons are subject to a potential with two incommensurate periods, translational invariance is lost, and no periodic band structure is expected. However, model calculations based on nearly free one-dimensional electrons and experimental results from high-resolution photoemission spectroscopy on a quasi-one-dimensional material do show dispersing band states with signatures of both periodicities. Apparent band structures are generated by the nonuniform distribution of electronic spectral weight over the complex eigenvalue spectrum.

Dynamical properties of the one-dimensional band insulator (NbSe4)3I

Optical and photoemission experiments reveal unexpected spectral signatures of one-dimensional band insulators. In the model compound (NbSe (4))3I the optical conductivity decays as a power law sigma(1)(omega) approximately omega(-4.25) above a sharp gap edge. Photoemission observes both the valence and a shadow band, produced by a commensurate superstructure. We identify an optical and photoemission band gap consistent with other measurements but much smaller than the energy scale defined by the dispersion of the band peak in the photoemission spectra.

Blood coagulation factors in the elderly.

To investigate causes of the age-dependent increase of thromboembolic events, plasma coagulation parameters were determined in healthy elderly blood donors in comparison with young, and elderly diseased blood donors. Partial thromboplastin and thrombin clotting times were slightly shortened, whereas prothrombin and reptilase clotting times were unaltered. Plasma concentration of clotting factors like F I, VII, VIII: C, X, HMW-kininogen and prekallikrein were increased, whereas the coagulation inhibitor antithrombin III was decreased. Concerning fibrinolysis, plasminogen and alpha-2-antiplasmin were not affected by age, but plasminogen activators in the euglobulin fraction were lower. This shift in the pattern of coagulation factors favors enhanced fibrin formation and delayed fibrinolysis in the elderly. Higher intermediary products demonstrate that activation of coagulation and fibrinolysis happen more often in elderly healthy people. Together with blood stasis and vessel wall damage, this shift of the hemostatic balance contributes to a higher incidence of thromboembolic disorders in the aged.