Electron emissions in mesoscopic conductors are inherently correlated due to the Pauli exclusion principle. In this paper, we show that the correlation can be read from the electron emission rate. To ...demonstrate this, we concentrate on the electron emission in a single-channel quantum point contact (QPC). The emission can be driven by either a dc bias voltage or an unit-charged Lorentzian voltage pulse. In the case of dc bias voltage, the correlation is pronounced at both short and long times. The long-time correlation can be effectively suppressed by increasing the electron temperature and/or decreasing the transmission probability of the QPC. In contrast, the short-time correlation is much robust. As a consequence, the emission at high temperatures and/or low transmission probabilities can be treated as a Poisson process at long times, but follows a non-Poisson renewal statistics at short times. In the case of Lorentzian pulse, the correlation is much sensitive to the electron temperature. As the electron temperature increases, the electron emission evolves gradually from a non-renewal process at low temperatures to a time-dependent Poisson process at high temperatures.
The search for the QCD critical point in heavy-ion collision experiments requires dynamical simulations of the bulk evolution of QCD matter as well as of fluctuations. We consider two essential ...ingredients of such a simulation: a generic extension of hydrodynamics by a parametrically slow mode or modes (“Hydro+”) and a description of fluctuations out of equilibrium. By combining the two ingredients, we are able to describe the bulk evolution and the fluctuations within the same framework. Critical slowing-down means that equilibration of fluctuations could be as slow as hydrodynamic evolution, and thus fluctuations could significantly deviate from equilibrium near the critical point. We generalize hydrodynamics to partial-equilibrium conditions where the state of the system is characterized by the off-equilibrium magnitude of fluctuations in addition to the usual hydrodynamic variables-conserved densities. We find that the key element of the new formalism-the extended entropy taking into account the off-equilibrium fluctuations-is remarkably similar to the 2PI action in the quantum field theory. We show how the new Hydro+ formalism reproduces two major effects of critical fluctuations on the bulk evolution: the strong frequency dependence of the anomalously large bulk viscosity as well as the stiffening of the equation of state with an increasing frequency or wave number. While the agreement with known results confirms its validity, the fact that Hydro+ achieves this within a local and deterministic framework gives it significant advantages for dynamical simulations.
We introduce a general approach to extract the wave function of quasiparticles from the scattering matrix of a quantum conductor, which offers a unified way to study the features of quasiparticles ...from on-demand coherent electron sources with different configurations. We first show that the quasiparticles are particle-hole pairs in the Fermi sea, which can be indexed with the flow density . Both the excitation probability and the particle/hole components of the quasiparticles can be solely decided from the polar decomposition of the scattering matrix. By using such approach, we then investigate the quasiparticles from the electron sources based on a quantum point contact and a quantum dot (QD). We find that the quasiparticles from different electron sources have different features, which can be seen from the corresponding -dependence of the excitation probability and the particle/hole components. We further show that these features can also be characterized by the full counting statistics of the quasiparticles, which can be approximated by a binomial distribution with cumulant generating function . For the quantum-point-contact-based electron sources, both and are monotonically increasing functions of the driving strength. In contrast, for the quantum-dot-based electron sources, both and can exhibit oscillations, which can be attributed to the interplay between the charge excitation and charge relaxation processes in the QD.
Chiral kinetic theory Stephanov, M A; Yin, Y
Physical review letters,
10/2012, Letnik:
109, Številka:
16
Journal Article
Recenzirano
Odprti dostop
We derive the nonequilibrium kinetic equation describing the motion of chiral massless particles in the regime where it can be considered classically. We show that the Berry monopole which appears at ...the origin of the momentum space due to level crossing is responsible for the chiral magnetic and vortical effects.
Aims
To isolate a novel endophytic bacterium from Panax ginseng that could have excellent properties in converting ginsenoside Rb1 to ginsenoside Rg3.
Methods and Results
Based on a 16S rDNA gene ...sequence, the strain named GE 17‐7 was identified as Burkholderia sp. This strain has shown the highest activity in converting ginsenoside Rb1 to 20(S)‐ginsenoside Rg3. During the biotransformation of ginsenoside Rb1, the final metabolite was identified by nuclear magnetic resonance analysis and the transformation pathway of ginsenoside Rb1 was also identified by thin‐layer chromatography and high performance liquid chromatography analysis in this study.
Conclusions
We have successfully isolated a β‐glucosidase‐producing endophytic bacterium GE 17‐7 from P. ginseng. Ginsenoside Rg3 was produced by strain GE 17‐7 from ginsenoside Rb1 via ginsenoside Rd.
Significance and Impact of the Study
This is the first report of the conversion of major ginsenoside Rb1 into minor ginsenoside Rg3 by fermentation with Burkholderia sp. endophytic bacteria in P. ginseng. These results suggest a new preparation method for ginsenoside Rg3 using strain GE 17‐7 in the pharmaceutical industry.
We propose a scheme to manipulate the electron-hole excitation in the voltage pulse electron source, which can be realized by a voltage-driven Ohmic contact connecting to a quantum hall edge channel. ...It has been known that the electron-hole excitation can be suppressed via Lorentzian pulses, leading to noiseless electron current. We show that, instead of the Lorentzian pulses, driven via the voltage pulse with duration t0, the electron-hole excitation can be tuned so that the corresponding energy distribution of the emitted electrons follows the Fermi distribution with temperature , with TS being the electron temperature in the Ohmic contact. Such Fermi distribution can be established without introducing additional energy relaxation mechanism and can be detected via shot noise thermometry technique, making it helpful in the study of thermal transport and decoherence in mesoscopic system.
With the aggravation of environmental pollution and the energy crisis, it is particularly important to develop and design environment-friendly and efficient spontaneous enhanced visible-light-driven ...photocatalysts for water splitting. Herein novel type-II van der Waals (vdW) GaSe/CN and Ga2SSe/CN heterostructures are proposed through first-principles calculations. Their electronic properties and photocatalytic performance are theoretically analyzed. In particular, their appropriate band gap and band-edge position meet the requirements of the oxygen evolution reaction, and the reaction is thermodynamically feasible in most pH ranges. The unique band alignment of these heterostructured photocatalysts leads to high solar-to-hydrogen energy conversion efficiencies up to 15.11%, which has a good commercial application prospect. More excitingly, with the application of 2% biaxial strain, the smooth progress of the water-splitting reaction of the GaSe/CN and Ga2SSe/CN heterostructures can still be maintained, and the carrier mobility and optical absorption characteristics can be effectively improved. Consequently, these findings suggest that the GaSe/CN and Ga2SSe/CN vdW heterostructures have promising potentials as photocatalysts for water splitting. This work may provide a promising clue for the design of efficient and stable photocatalytic water-splitting catalysts under visible spectroscopy.
Abstract
Mitochondrial DNA (mtDNA) resides in a high ROS environment and suffers more mutations than its nuclear counterpart. Increasing evidence suggests that mtDNA mutations are not the results of ...direct oxidative damage, rather are caused, at least in part, by DNA replication errors. To understand how the mtDNA replicase, Pol γ, can give rise to elevated mutations, we studied the effect of oxidation of Pol γ on replication errors. Pol γ is a high fidelity polymerase with polymerase (pol) and proofreading exonuclease (exo) activities. We show that Pol γ exo domain is far more sensitive to oxidation than pol; under oxidative conditions, exonuclease activity therefore declines more rapidly than polymerase. The oxidized Pol γ becomes editing-deficient, displaying a 20-fold elevated mutations than the unoxidized enzyme. Mass spectrometry analysis reveals that Pol γ exo domain is a hotspot for oxidation. The oxidized exo residues increase the net negative charge around the active site that should reduce the affinity to mismatched primer/template DNA. Our results suggest that the oxidative stress induced high mutation frequency on mtDNA can be indirectly caused by oxidation of the mitochondrial replicase.
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