505 research outputs found
Charge transfer via a two-strand superexchange bridge in DNA
Charge transfer in a DNA duplex chain is studied by constructing a system
with virtual electrodes connected at the ends of each DNA strand. The systeym
is described by the tight-binding model and its transport is analyzed by the
transfer matrix method. The very weak distance dependence in long
(G:C)(T:A)_M(G:C)_3 DNA chain observed in experiment [B. Giese, et al., Nature
412, 318 (2001)] is explained by a unistep two-strand superexchange bridge
without the need for the multi-step thermally-induced hopping mechanism or the
dephasing effect. The crossover number M_c of (T:A) base pairs, where crossover
between strong and weak distance dependence occurs, reflects the ratio of
intra- and inter-strand neighboring base-base couplings.Comment: accepted for publication in Phys. Rev. Let
Phoenix, 2009-01-22
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An Agent-Based Modelling Simulation Approach to Calculate Processing Delay of GEO Satellite Payload
The global coverage of broadband multimedia and
internet-based services in terrestrial-satellite networks demand
particular interests for satellite providers in order to enhance services
with low latencies and high signal quality to diverse users. In
particular, the delay of on-board processing is an inherent source
of latency in a satellite communication that sometimes is discarded
for the end-to-end delay of the satellite link. The frame work for this
paper includes modelling of an on-orbit satellite payload using an
agent model that can reproduce the properties of processing delays.
In essence, a comparison of different spatial interpolation methods is
carried out to evaluate physical data obtained by an GEO satellite
in order to define a discretization function for determining that
delay. Furthermore, the performance of the proposed agent and the
development of a delay discretization function are together validated
by simulating an hybrid satellite and terrestrial network. Simulation
results show high accuracy according to the characteristics of initial
data points of processing delay for Ku bands
A mesoscopic ring as a XNOR gate: An exact result
We describe XNOR gate response in a mesoscopic ring threaded by a magnetic
flux . The ring is attached symmetrically to two semi-infinite
one-dimensional metallic electrodes and two gate voltages, viz, and
, are applied in one arm of the ring which are treated as the inputs of
the XNOR gate. The calculations are based on the tight-binding model and the
Green's function method, which numerically compute the conductance-energy and
current-voltage characteristics as functions of the ring-to-electrode coupling
strength, magnetic flux and gate voltages. Our theoretical study shows that,
for a particular value of () (, the elementary
flux-quantum), a high output current (1) (in the logical sense) appears if both
the two inputs to the gate are the same, while if one but not both inputs are
high (1), a low output current (0) results. It clearly exhibits the XNOR gate
behavior and this aspect may be utilized in designing an electronic logic gate.Comment: 8 pages, 5 figure
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