8,244 research outputs found
Steady States of Infinite-Size Dissipative Quantum Chains via Imaginary Time Evolution
Directly in the thermodynamic limit, we show how to combine imaginary and
real time evolution of tensor networks to efficiently and accurately find the
nonequilibrium steady states (NESS) of one-dimensional dissipative quantum
lattices governed by the Lindblad master equation. The imaginary time evolution
first bypasses any highly correlated portions of the real-time evolution
trajectory by directly converging to the weakly correlated subspace of the
NESS, after which real time evolution completes the convergence to the NESS
with high accuracy. We demonstrate the power of the method with the dissipative
transverse field quantum Ising chain. We show that a crossover of an order
parameter shown to be smooth in previous finite-size studies remains smooth in
the thermodynamic limit.Comment: 5+3 pages, 5 figures, 2 table
Dna2p Helicase/Nuclease Is a Tracking Protein, Like FEN1, for Flap Cleavage during Okazaki Fragment Maturation
During cellular DNA replication the lagging strand is generated as discontinuous segments called Okazaki fragments. Each contains an initiator RNA primer that is removed prior to joining of the strands. Primer removal in eukaryotes requires displacement of the primer into a flap that is cleaved off by flap endonuclease 1 (FEN1). FEN1 employs a unique tracking mechanism that requires the recognition of the free 5' terminus and then movement to the base of the flap for cleavage. Abnormally long flaps are coated by replication protein A (RPA), inhibiting FEN1 cleavage. A second nuclease, Dna2p, is needed to cleave an RPA-coated flap producing a short RPA-free flap, favored by FEN1. Here we show that Dna2p is also a tracking protein. Annealed primers or conjugated biotin-streptavidin complex block Dna2p entry and movement. Single-stranded binding protein-coated flaps inhibit Dna2p cleavage. Like FEN1, Dna2p can track over substrates with a non-Watson Crick base, such as a biotin, or a missing base within a chain. Unlike FEN1, Dna2p shows evidence of a "threading-like" mechanism that does not support tracking over a branched substrate. We propose that the two nucleases both track, Dna2p first and then FEN1, to remove initiator RNA via long flap intermediates
Efficiency of thin film photocells
We propose a new concept for the design of high-efficiency photocells based
on ultra-thin (submicron) semiconductor films of controlled thickness. Using a
microscopic model of a thin dielectric layer interacting with incident
electromagnetic radiation we evaluate the efficiency of conversion of solar
radiation into the electric power. We determine the optimal range of parameters
which maximize the efficiency of such photovoltaic element.Comment: 5 pages, 3 figure
Schwinger model on a half-line
We study the Schwinger model on a half-line in this paper. In particular, we
investigate the behavior of the chiral condensate near the edge of the line.
The effect of the chosen boundary condition is emphasized. The extension to the
finite temperature case is straightforward in our approach.Comment: 4 pages, no figure. Final version to be published on Phys. Rev.
Theory of non-Fermi liquid near a diagonal electronic nematic state on a square lattice
We study effects of Fermi surface fluctuations on a single-particle life time
near the diagonal electronic nematic phase on a two-dimensional square lattice.
It has been shown that there exists a quantum critical point (QCP) between the
diagonal nematic and isotropic phases. We study the longitudinal fluctuations
of the order parameter near the critical point, where the singular forward
scattering leads to a non-Fermi liquid behavior over the whole Fermi surface
except along the k_x- and k_y-directions. We will also discuss the temperature
and chemical potential dependence of the single-particle decay rate.Comment: 4 pages, 3 figures, revtex
Signature of Schwinger's pair creation rate via radiation generated in graphene by strong electric current
Electron - hole pairs are copuously created by an applied electric field near
the Dirac point in graphene or similar 2D electronic systems. It was shown
recently that for sufficiently large electric fields and ballistic times the
I-V characteristics become strongly nonlinear due to Schwinger's pair creation.
Since there is no energy gap the radiation from the pairs' annihilation is
enhanced. The spectrum of radiation is calculated. The angular and polarization
dependence of the emitted photons with respect to the graphene sheet is quite
distinctive. For very large currents the recombination rate becomes so large
that it leads to the second Ohmic regime due to radiation friction.Comment: 9 pages, 7 figure
Widespread dispersal and aging of organic carbon in shallow marginal seas
The occurrence of pre-aged organic carbon (OC) in continental margin surface sediments is a commonly observed phenomenon, yet the nature, sources, and causes of this aged OC remain largely undetermined for many continental shelf settings. Here we present the results of an extensive survey of the abundance and radiocarbon content of OC in surface sediments from the northern Chinese marginal seas. Pre-aged OC is associated with both coarser (>63 µm) and finer (<63 µm) sedimentary components; measurements on specific grain-size fractions reveal that it is especially prevalent within the 20–63 µm fraction of inner shelf sediments. We suggest that organic matter associated with this sortable silt fraction is subject to protracted entrainment in resuspension-deposition loops during which it ages, is modified, and is laterally dispersed, most likely via entrainment within benthic nepheloid layers. This finding highlights the complex dynamics and predepositional history of organic matter accumulating in continental shelf sediments, with implications for our understanding of carbon cycling on continental shelves, development of regional carbon budgets, and interpretation of sedimentary records
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