C. A. M. dos Santos

Extreme thermopower anisotropy and interchain transport in the quasi-one-dimensional metal Li0.9Mo6O17.

Thermopower and electrical resistivity measurements transverse to the conducting chains of the quasi-one-dimensional metal Li0.9Mo6O17 are reported in the temperature range 5≤T≤500  K. For T≥400  K the interchain transport is determined by thermal excitation of charge carriers from a valence band ∼0.14  eV below the Fermi level, giving rise to a large, p-type thermopower that coincides with a small, n-type thermopower along the chains. This dichotomy-semiconductorlike in one direction and metallic in a mutually perpendicular direction-gives rise to substantial transverse thermoelectric effects and a transverse thermoelectric figure of merit among the largest known for a single compound.

Giant Nernst Effect and Bipolarity in the Quasi-One-Dimensional Metal Li0.9Mo6O17

The Nernst coefficient for the quasi-one-dimensional metal, Li{0.9}Mo{6}O{17}, is found to be among the largest known for metals (ν≃500  μV/KT at T∼20  K), and is enhanced in a broad range of temperature by orders of magnitude over the value expected from Boltzmann theory for carrier diffusion. A comparatively small Seebeck coefficient implies that Li{0.9}Mo{6}O{17} is bipolar with large, partial Seebeck coefficients of opposite sign. A very large thermomagnetic figure of merit, ZT∼0.5, is found at high field in the range T≈35-50  K.

Profiles of phenolic compounds by FT-ICR MS and antioxidative and antiproliferative activities of Stryphnodendron obovatum Benth leaf extracts

Stryphnodendron obovatum Benth is a Brazilian Cerrado tree, which is rich in catechin derivatives, being therefore widely used in folk medicine. Its seeds, beans and bark have been used for various medicinal purposes, but few reports have tried to correlate their biological activity with their chemical composition. In this study, we have profiled the main phenolic constituents of S. obovatum leaf extracts by ultrahigh resolution mass spectrometry (FT-ICR MS), and tried to establish a correlation of metabolites and antioxidant and in vitro antiproliferative activities. In the methanolic extract flavonoid derivatives were detected and they presented the most promising scavenging activities for methanolic extracts (EC50 0.86 ± 0.01 μg mL−1), being slightly more active than Trolox (EC50 1.13 ± 0.09 μg mL−1). In the hydroethanolic extract, catechin derivatives as well as protocatechuic acid-glucoside were detected and found to be a little less active than the control (EC50 1.39 ± 0.01 μg mL−1). The best performance in terms of antiproliferative activity was found for the methanolic extract for renal cell lines (TGI 40.6 g mL−1).

Transport Properties of Granular High-TC Superconductors

We report on the application of the Resistively Shunted Junction (RSJ) model to granular high TC superconductors. Some derived predictions of the RSJ model are applied to a set of superconducting granular samples which can be considered as a network of Josephson junctions. The investigated samples belong to both holedoped Y1ixPrxBa2Cu3O7id (x = 0.0, 0.35, and 0.45) and the electron-doped Sm2ixCexCuO4id (x = 0:18) systems which display the so-called double resistive superconducting transition. We have performed several transport measurements in these compounds including temperature and magnetic field dependence of the electrical resistance, R(T; H), and I-V characteristics. Several aspects of the I-V characteristics were quantitatively well described by the RSJ model. The combined results strongly suggest that dissipation in granular superconducting samples is a natural consequence of the normal current flowing in parallel with the supercurrent current.