Charge pumping in a quantum wire driven by a series of local time-periodic potentials

We develop a method to calculate electronic transport properties through a mesoscopic scattering region in the presence of a series of time-periodic potentials. Using the method, the quantum charge pumping driven by time-periodic potentials is studied. Jumps in the pumped current are observed at the peak positions of the Wigner delay time. Our main results in both the weak pumping and strong pumping regimes are consistent with experimental results. More interestingly, we also observed the nonzero pumping at the phase difference phi=0 and addressed its relevance to the experimental result.Comment: 5 page

Carbon nanotube-based quantum pump in the presence of superconducting lead

Parametric electron pump through superconductor-carbon-nanotube based molecular devices was investigated. It is found that a dc current, which is assisted by resonant Andreev reflection, can be pumped out from such molecular device by a cyclic variation of two gate voltages near the nanotube. The pumped current can be either positive or negative under different system parameters. Due to the Andreev reflection, the pumped current has the double peak structure around the resonant point. The ratio of pumped current of N-SWNT-S system to that of N-SWNT-N system (I^{NS}/I^N) is found to approach four in the weak pumping regime near the resonance when there is exactly one resonant level at Fermi energy inside the energy gap. Numerical results confirm that in the weak pumping regime the pumped current is proportional to the square of the pumping amplitude V_p, but in the strong pumping regime the pumped current has the linear relation with V_p. Our numerical results also predict that pumped current can be obtained more easily by using zigzag tube than by using armchair tube

Update on the Combined Analysis of Muon Measurements from Nine Air Shower Experiments

Over the last two decades, various experiments have measured muon densities in extensive air showers over several orders of magnitude in primary energy. While some experiments observed differences in the muon densities between simulated and experimentally measured air showers, others reported no discrepancies. We will present an update of the meta-analysis of muon measurements from nine air shower experiments, covering shower energies between a few PeV and tens of EeV and muon threshold energies from a few 100 MeV to about 10GeV. In order to compare measurements from different experiments, their energy scale was cross-calibrated and the experimental data has been compared using a universal reference scale based on air shower simulations. Above 10 PeV, we find a muon excess with respect to simulations for all hadronic interaction models, which is increasing with shower energy. For EPOS-LHC and QGSJet-II.04 the significance of the slope of the increase is analyzed in detail under different assumptions of the individual experimental uncertainties

Pterin interactions with distinct reductase activities of NO synthase.

Besides oxidizing L-arginine, neuronal NO synthase (NOS) NADPH-dependently reduces various electron acceptors, including cytochrome c and tetrazolium salts. The latter NADPH diaphorase reaction is used as a NOS-specific histochemical stain. Both reductase activities have been utilized to analyse electron transfer mechanisms within NOS. Basal L-arginine turnover by homodimeric NOS is enhanced by exogenous tetrahydrobiopterin, and the intra-subunit electron flow may include intermediate trihydrobiopterin. In the present work we have investigated the possible role of the tetrahydrobiopterin binding site of NOS in its reductase activities by examining the effects of anti-pterin type (PHS) NOS inhibitors. Although the type I anti-pterin, PHS-32, which does not affect basal dimeric NOS activity, also had no effect on either reductase activity, the type II anti-pterin, PHS-72, which inhibits basal NOS activity, inhibited both reductase activities and the NADPH diaphorase histochemical stain. Pterin-free NOS monomers catalysed both cytochrome c and tetrazolium salt reduction. Our data suggest that both NOS reductase activities are independent of tetrahydrobiopterin. However, occupation of an exosite near the pterin site in NOS by type II anti-pterins may interfere with the electron flow within the active centre, suggesting that steric perturbation of the pterin binding pocket or reductase interaction contribute to the mechanism of inhibition by this class of NOS inhibitors