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 $\phi$ 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 $\phi$), 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

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

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

On projective varieties with strictly nef tangent bundles

In this paper, we study smooth complex projective varieties $X$ such that some exterior power $\bigwedge^r T_X$ of the tangent bundle is strictly nef. We prove that such varieties are rationally connected. We also classify the following two cases. If $T_X$ is strictly nef, then $X$ isomorphic to the projective space $\mathrm{P}^n$. If $\bigwedge^2 T_X$ is strictly nef and if $X$ has dimension at least $3$, then $X$ is either isomorphic to $\mathrm{P}^n$ or a quadric $\mathrm{Q}^n$.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