11,794 research outputs found
Electronic Conduction in Short DNA Wires
A strict method is used to calculate the current-voltage characteristics of a
double-stranded DNA. A more reliable model considering the electrostatic
potential drop along an individual DNA molecular wire between the contacts is
considered and the corresponding Green's Function is obtained analytically
using Generating Function method, which avoids difficult numerical evaluations.
The obtained results indicate that the electrostatic drop along the wire always
increases the conductor beyond the threshold than without considering it, which
is in agreement with recent experiments. The present method can also be used to
calculate the current-voltage characteristics for other molecular wires of
arbitrary length.Comment: 9 pages, 2 figur
Elastic property of single double-stranded DNA molecules: Theoretical study and comparison with experiments
This paper aims at a comprehensive understanding on the novel elastic
property of double-stranded DNA (dsDNA) discovered very recently through
single-molecule manipulation techniques. A general elastic model for
double-stranded biopolymers is proposed and a new structural parameter called
the folding angle is introduced to characterize their deformations. The
mechanical property of long dsDNA molecules is then studied based on this
model, where the base-stacking interactions between DNA adjacent nucleotide
basepairs, the steric effects of basepairs, and the electrostatic interactions
along DNA backbones are taken into account. Quantitative results are obtained
by using path integral method, and excellent agreement between theory and the
observations reported by five major experimental groups are attained. The
strong intensity of the base-stacking interactions ensures the structural
stability of DNA, while the short-ranged nature of such interactions makes
externally-stimulated large structural fluctuations possible. The entropic
elasticity, highly extensibility, and supercoiling property of DNA are all
closely related to this account. The present work also suggests the possibility
that negative torque can induce structural transitions in highly extended DNA
from right-handed B-form to left-handed configurations similar with Z-form
configuration. Some formulae concerned with the application of path integral
method to polymeric systems are listed in the Appendix.Comment: 19 pages in latex format, including 7 EPS figures and 1 table.
Submitted to PR
Entropic Elasticity, Cooperative Extensibility and Supercoiling Property of DNA: A Unified Viewpoint
A unified model is constructed to study the recently observed DNA entropic
elasticity, cooperative extensibility, and supercoiling property. With the
introduction of a new structural parameter (the folding angle ), bending
deformations of sugar-phosphate backbones, steric effects of nucleotide
basepairs, and short-range basestacking interactions are considered. The
comprehensive agreement of theoretical results with experimental observations
on both torsionally relaxed and negatively supercoiled DNAs strongly indicates
that, basestacking interactions, although short-ranged in nature, dominate the
elasticity of DNA and hence are of vital biological significance.Comment: 4 pages in Latex format, with 3 EPS figures included. A typographic
mistake in Eq. (7) is corrected in this version. A slightly different version
of this paper will appear in PR
Maximum matching on random graphs
The maximum matching problem on random graphs is studied analytically by the
cavity method of statistical physics. When the average vertex degree \mth{c} is
larger than \mth{2.7183}, groups of max-matching patterns which differ greatly
from each other {\em gradually} emerge. An analytical expression for the
max-matching size is also obtained, which agrees well with computer
simulations. Discussion is made on this {\em continuous} glassy phase
transition and the absence of such a glassy phase in the related minimum vertex
covering problem.Comment: 7 pages with 2 eps figures included. Use EPL style. Submitted to
Europhysics Letter
Nonequilibrium work equalities in isolated quantum systems
We briefly introduce the quantum Jarzynski and Bochkov-Kuzovlev equalities in
isolated quantum Hamiltonian systems, which includes the origin of the
equalities, their derivations using a quantum Feynman-Kac formula, the quantum
Crooks equality, the evolution equations governing the characteristic functions
of the probability density functions for the quantum work, the recent
experimental verifications. Some results are given here first time. We
particularly emphasize the formally structural consistence between these
quantum equalities and their classical counterparts, which shall be useful in
understanding the existing equalities and pursuing new fluctuation relations in
other complex quantum systems.Comment: 1 figur
Optimal Transmit Antenna Selection Algorithm in Massive MIMOME Channels
This paper studies the transmit antenna selection in massive multiple-input
multiple-output (MIMO) system over wiretap channel. The transmitter, equipped
with a large-scale antenna array whose size is much larger than that of the
eavesdropper and legitimate receiver, selects a subset of antennas to transmit
messages. An branch-and-bound (BAB) search based algorithm for antenna
selection in independent and identical Rayleigh flat fading channel is proposed
to maximize the secrecy capacity between the transmitter and the legitimate
receiver when the transmit power is equally allocated into the active antennas.
Furthermore, the proposed algorithm is separately applied to two scenarios
which is based on whether the channel side information of the eavesdropper
(CSIE) is available. Simulation results show that the proposed algorithm has
the same performance as the exhaustive search under both scenarios but with
much lower complexity.Comment: This paper will be presented at IEEE Wireless Communications and
Networking Conference (WCNC), 201
Gigapixel microscopy using a flatbed scanner
Microscopy imaging systems with a very wide field-of-view (FOV) are highly
sought in biomedical applications. In this paper, we report a wide FOV
microscopy imaging system that uses a low-cost scanner and a
closed-circuit-television (CCTV) lens. We show that such an imaging system is
capable to capture a 10 mm * 7.5 mm FOV image with 0.77 micron resolution,
resulting in 0.54 gigapixels (109 pixels) across the entire image (26400 pixels
* 20400 pixels). The resolution and field curve of the proposed system were
characterized by imaging a USAF resolution target and a hole-array target. A
1.6 gigapixel microscopy image (0.54 gigapixel with 3 colors) of a pathology
slide was acquired by using such a system for application demonstration
Can pulling cause right- to left-handed structural transitions in negatively supercoiled DNA double-helix?
The folding angle distribution of stretched and negatively supercoiled DNA
double-helix is investigated based on a theoretical model we proposed earlier
[H. Zhou et al., Phys. Rev. Lett. 82, 4560 (1999)]. It is shown that pulling
can transit a negatively supercoiled DNA double-helix from the right-handed
B-form to a left-handed configuration which resembles DNA Z-form in some
important respects. The energetics of this possible transition is calculated
and the comparison with recent experimental observations are qualitatively
discussed.Comment: 3 pages. A new paragraph as well as two figures are added in the
revised paper. A new reference (Ref. 7) is include
On projective varieties with strictly nef tangent bundles
In this paper, we study smooth complex projective varieties such that
some exterior power of the tangent bundle is strictly nef. We
prove that such varieties are rationally connected. We also classify the
following two cases. If is strictly nef, then isomorphic to the
projective space . If is strictly nef and if
has dimension at least , then is either isomorphic to
or a quadric .Comment: This article supersedes arXiv:1609.06867. To appear in J. Math. Pures
App
Bell Rate Model with Dynamic Disorder: Model and Its Application in the Receptor-ligand Forced Dissociation Experiments
We extend the Bell forced dissociation rate model to take account into
dynamic disorder. The motivation of the present work is from the recent forced
dissociation experiments of the adhesive receptor-ligand complexes, in which
some complexes were found to increase their mean lifetimes (catch bonds) when
they are stretched by mechanical force, while the force increases beyond some
thresholds their lifetimes decrease (slip bonds). Different from our previous
model of force modulating dynamic disorder, in present work we allow that the
projection of force onto the direction from the bound to the transition state
of complex could be negative. Our quantitative description is based on a
one-dimension diffusion-assisted reaction model. We find that, although the
model can well describe the catch-slip transitions observed in the single bond
P-selctin glycoprotein ligand 1(PSGL-1)-P- and L-selectin forced dissociation
experiments, it might be physically unacceptable because the model predicts a
slip-catch bond transitions when the conformational diffusion coefficient tends
to zero.Comment: 9 pages, 6 figure
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