32,151 research outputs found
Modeling the thermal evolution of enzyme-created bubbles in DNA
The formation of bubbles in nucleic acids (NAs) are fundamental in many
biological processes such as DNA replication, recombination, telomeres
formation, nucleotide excision repair, as well as RNA transcription and
splicing. These precesses are carried out by assembled complexes with enzymes
that separate selected regions of NAs. Within the frame of a nonlinear dynamics
approach we model the structure of the DNA duplex by a nonlinear network of
coupled oscillators. We show that in fact from certain local structural
distortions there originate oscillating localized patterns, that is radial and
torsional breathers, which are associated with localized H-bond deformations,
being reminiscent of the replication bubble. We further study the temperature
dependence of these oscillating bubbles. To this aim the underlying nonlinear
oscillator network of the DNA duplex is brought in contact with a heat bath
using the Nos-Hoover-method. Special attention is paid to the
stability of the oscillating bubbles under the imposed thermal perturbations.
It is demonstrated that the radial and torsional breathers, sustain the impact
of thermal perturbations even at temperatures as high as room temperature.
Generally, for nonzero temperature the H-bond breathers move coherently along
the double chain whereas at T=0 standing radial and torsional breathers result.Comment: 19 pages, 7 figure
Renormalisation group determination of the order of the DNA denaturation transition
We report on the nature of the thermal denaturation transition of homogeneous
DNA as determined from a renormalisation group analysis of the
Peyrard-Bishop-Dauxois model. Our approach is based on an analogy with the
phenomenon of critical wetting that goes further than previous qualitative
comparisons, and shows that the transition is continuous for the average
base-pair separation. However, since the range of universal critical behaviour
appears to be very narrow, numerically observed denaturation transitions may
look first-order, as it has been reported in the literature.Comment: 6 pages; no figures; to appear in Europhysics Letter
Discovery of a new radio galaxy within the error box of the unidentified gamma-ray source 3EG J1735-1500
We report the discovery of a new radio galaxy within the location error box
of the gamma-ray source 3EG J1735-1500. The galaxy is a double-sided jet source
forming a large angle with the line of sight. Optical observations reveal a V ~
18 magnitude galaxy at the position of the radio core. Although the association
with the EGRET source is not confirmed at the present stage, because there is a
competing, alternative gamma-ray candidate within the location error contours
which is also studied here, the case deserves further attention. The new radio
galaxy can be used to test the recently proposed possibility of gamma-ray
emitting radio galaxies beyond the already known case of Centaurus A.Comment: 12 pages, 3 figures. Accepted for publication in Ap
Determining the dimensionality of bipartite orbital-angular-momentum entanglement using multi-sector phase masks
The Shannon dimensionality of orbital-angular-momentum (OAM) entanglement produced in spontaneous parametric down-conversion can be probed by using multi-sector phase analysers [1]. We demonstrate a spatial light modulator-based implementation of these analysers, and use it to measure a Schmidt number of about 50
Hybrid Architecture for Engineering Magnonic Quantum Networks
We show theoretically that a network of superconducting loops and magnetic
particles can be used to implement magnonic crystals with tunable magnonic band
structures. In our approach, the loops mediate interactions between the
particles and allow magnetic excitations to tunnel over long distances. As a
result, different arrangements of loops and particles allow one to engineer the
band structure for the magnonic excitations. Furthermore, we show how magnons
in such crystals can serve as a quantum bus for long-distance magnetic coupling
of spin qubits. The qubits are coupled to the magnets in the network by their
local magnetic-dipole interaction and provide an integrated way to measure the
state of the magnonic quantum network.Comment: Manuscript: 4 pages, 3 figures. Supplemental Material: 9 pages, 4
figures. V2: Published version in PRA: 14 pages + 8 figures. Substantial
rearrangement of the content of the previous versio
Dynamics of Entanglement Transfer Through Multipartite Dissipative Systems
We study the dynamics of entanglement transfer in a system composed of two
initially correlated three-level atoms, each located in a cavity interacting
with its own reservoir. Instead of tracing out reservoir modes to describe the
dynamics using the master equation approach, we consider explicitly the
dynamics of the reservoirs. In this situation, we show that the entanglement is
completely transferred from atoms to reservoirs. Although the cavities mediate
this entanglement transfer, we show that under certain conditions, no
entanglement is found in cavities throughout the dynamics. Considering the
entanglement dynamics of interacting and non-interacting bipartite subsystems,
we found time windows where the entanglement can only flow through interacting
subsystems, depending on the system parameters.Comment: 8 pages, 11 figures, publishe in Physical Review
Characterization of high-dimensional entangled systems via mutually unbiased measurements
Mutually unbiased bases (MUBs) play a key role in many protocols in quantum
science, such as quantum key distribution. However, defining MUBs for arbitrary
high-dimensional systems is theoretically difficult, and measurements in such
bases can be hard to implement. We show experimentally that efficient quantum
state reconstruction of a high-dimensional multi-partite quantum system can be
performed by considering only the MUBs of the individual parts. The state
spaces of the individual subsystems are always smaller than the state space of
the composite system. Thus, the benefit of this method is that MUBs need to be
defined for the small Hilbert spaces of the subsystems rather than for the
large space of the overall system. This becomes especially relevant where the
definition or measurement of MUBs for the overall system is challenging. We
illustrate this approach by implementing measurements for a high-dimensional
system consisting of two photons entangled in the orbital angular momentum
(OAM) degree of freedom, and we reconstruct the state of this system for
dimensions of the individual photons from d=2 to 5.Comment: 8 page
- …