28,202 research outputs found
Theory of DNA translocation through narrow ion channels and nanopores with charged walls
Translocation of a single stranded DNA through genetically engineered
-hemolysin channels with positively charged walls is studied. It is
predicted that transport properties of such channels are dramatically different
from neutral wild type -hemolysin channel. We assume that the wall
charges compensate the fraction of the bare charge of the DNA piece
residing in the channel. Our prediction are as follows (i) At small
concentration of salt the blocked ion current decreases with . (ii) The
effective charge of DNA piece, which is very small at (neutral
channel) grows with and at reaches . (iii) The rate of DNA
capture by the channel exponentially grows with . Our theory is also
applicable to translocation of a double stranded DNA in narrow solid state
nanopores with positively charged walls.Comment: 3 pages, 1 figur
A quantum model for the magnetic multi-valued recording
We have proposed a quantum model for the magnetic multi-valued recording in
this paper. The hysteresis loops of the two-dimensional systems with randomly
distributed magnetic atoms have been studied by the quantum theory developed
previously. The method has been proved to be exact in this case. We find that
the single-ion anisotropies and the densities of the magnetic atoms are mainly
responsible for the hysterisis loops. Only if the magnetic atoms contained by
the systems are of different (not uniform) anistropies and their density is
low, there may be more sharp steps in the hysteresis loops. Such materials can
be used as the recording media for the so-called magnetic multi-valued
recording. Our result explained the experimental results qualitativly.Comment: 10 pages containing one Table. Latex formatted. 5 figures: those who
are interested please contact the authors requiring the figures. Submitted to
J. Magn. Magn. Mater. . Email address: [email protected]
The Algorithmic Complexity of Bondage and Reinforcement Problems in bipartite graphs
Let be a graph. A subset is a dominating set if
every vertex not in is adjacent to a vertex in . The domination number
of , denoted by , is the smallest cardinality of a dominating set
of . The bondage number of a nonempty graph is the smallest number of
edges whose removal from results in a graph with domination number larger
than . The reinforcement number of is the smallest number of
edges whose addition to results in a graph with smaller domination number
than . In 2012, Hu and Xu proved that the decision problems for the
bondage, the total bondage, the reinforcement and the total reinforcement
numbers are all NP-hard in general graphs. In this paper, we improve these
results to bipartite graphs.Comment: 13 pages, 4 figures. arXiv admin note: substantial text overlap with
arXiv:1109.1657; and text overlap with arXiv:1204.4010 by other author
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