256 research outputs found
Interference and interaction effects in multi-level quantum dots
Using renormalization group techniques, we study spectral and transport
properties of a spinless interacting quantum dot consisting of two levels
coupled to metallic reservoirs. For strong Coulomb repulsion and an applied
Aharonov-Bohm phase , we find a large direct tunnel splitting
between the levels of
the order of the level broadening . As a consequence we discover a
many-body resonance in the spectral density that can be measured via the
absorption power. Furthermore, for , we show that the system can be
tuned into an effective Anderson model with spin-dependent tunneling.Comment: 5 pages, 4 figures included, typos correcte
Kondo Correlations and the Fano Effect in Closed AB-Interferometers
We study the Fano-Kondo effect in a closed Aharonov-Bohm (AB) interferometer
which contains a single-level quantum dot and predict a frequency doubling of
the AB oscillations as a signature of Kondo-correlated states. Using Keldysh
formalism, Friedel sum rule and Numerical Renormalization Group, we calculate
the exact zero-temperature linear conductance as a function of AB phase
and level position . In the unitary limit, reaches
its maximum at . We find a Fano-suppressed Kondo plateau
for similar to recent experiments.Comment: 4 pages, 4 eps figure
Low temperature transport in AC-driven Quantum Dots in the Kondo regime
We present a fully nonequilibrium calculation of the low temperature
transport properties of a quantum dot in the Kondo regime when an AC potential
is applied to the gate voltage. We solve a time dependent Anderson model with
finite on-site Coulomb interaction. The interaction self-energy is calculated
up to second order in perturbation theory in the on-site interaction, in the
context of the Keldysh non-equilibrium technique, and the effect of the AC
voltage is taken into account exactly for all ranges of AC frequencies and AC
intensities. The obtained linear conductance and time-averaged density of
states of the quantum dot evolve in a non trivial way as a function of the AC
frequency and AC intensity of the harmonic modulation.Comment: 30 pages,7 figure
Resonant tunneling through ultrasmall quantum dots: zero-bias anomalies, magnetic field dependence, and boson-assisted transport
We study resonant tunneling through a single-level quantum dot in the
presence of strong Coulomb repulsion beyond the perturbative regime. The level
is either spin-degenerate or can be split by a magnetic field. We, furthermore,
discuss the influence of a bosonic environment. Using a real-time diagrammatic
formulation we calculate transition rates, the spectral density and the
nonlinear characteristic. The spectral density shows a multiplet of Kondo
peaks split by the transport voltage and the boson frequencies, and shifted by
the magnetic field. This leads to zero-bias anomalies in the differential
conductance, which agree well with recent experimental results for the electron
transport through single-charge traps. Furthermore, we predict that the sign of
the zero-bias anomaly depends on the level position relative to the Fermi level
of the leads.Comment: 27 pages, latex, 21 figures, submitted to Phys. Rev.
Levels, sources and chemical fate of persistent organic pollutants in the atmosphere and snow along the western Antarctic Peninsula
The Antarctic continent is among the most pristine regions; yet various organic contaminants have been measured there routinely. Air and snow samples were collected during the austral spring (October November, 2010) along the western Antarctic Peninsula and analyzed for organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) to assess the relative importance of long-range transport versus local primary or secondary emissions. Highest concentrations of PCBs, PBDEs and DDTs were observed in the glacier\u27s snow sample, highlighting the importance of melting glaciers as a possible secondary source of legacy pollutants to the Antarctic. In the atmosphere, contaminants were mainly found in the vapor phase (\u3e65%). Hexachlorobenzene (33.6 pg/m(3)), PCBs (11.6 pg/m(3)), heptachlor (5.64 pg/m(3)), PBDEs (4.22 pg/m(3)) and cis-chlordane (2.43 pg/m(3)) were the most abundant contaminants. In contrast to other compounds, PBDEs seem to have originated from local sources, possibly the research station itself. Gas-particle partitioning for analytes were better predicted using the adsorption partitioning model than an octanol-based absorption approach. Diffusive flux calculations indicated that net deposition is the dominant pathway for PBDEs and chlordanes, whereas re-volatilization from snow (during melting or metamorphosis) was observed for PCBs and some OCPs. (C) 2016 Elsevier Ltd. All rights reserved
Somatostatin receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database
Somatostatin (somatotropin release inhibiting factor) is an abundant neuropeptide, which acts on five subtypes of somatostatin receptor (SST1-SST5; nomenclature as agreed by the NC-IUPHAR Subcommittee on Somatostatin Receptors [89]). Activation of these receptors produces a wide range of physiological effects throughout the body including the inhibition of secretion of many hormones. Endogenous ligands for these receptors are somatostatin-14 (SRIF-14) and somatostatin-28 (SRIF-28). cortistatin-14 has also been suggested to be an endogenous ligand for somatostatin receptors [56]
Somatostatin receptors in GtoPdb v.2023.1
Somatostatin (somatotropin release inhibiting factor) is an abundant neuropeptide, which acts on five subtypes of somatostatin receptor (SST1-SST5; nomenclature as agreed by the NC-IUPHAR Subcommittee on Somatostatin Receptors [98]). Activation of these receptors produces a wide range of physiological effects throughout the body including the inhibition of secretion of many hormones. Endogenous ligands for these receptors are somatostatin-14 (SRIF-14) and somatostatin-28 (SRIF-28). cortistatin-14 has also been suggested to be an endogenous ligand for somatostatin receptors [61]
- …