10,240 research outputs found
Optimal Capacity of the Blume-Emery-Griffiths perceptron
A Blume-Emery-Griffiths perceptron model is introduced and its optimal
capacity is calculated within the replica-symmetric Gardner approach, as a
function of the pattern activity and the imbedding stability parameter. The
stability of the replica-symmetric approximation is studied via the analogue of
the Almeida-Thouless line. A comparison is made with other three-state
perceptrons.Comment: 10 pages, 8 figure
Fragility, Stokes-Einstein violation, and correlated local excitations in a coarse-grained model of an ionic liquid
Dynamics of a coarse-grained model for the room-temperature ionic liquid,
1-ethyl-3-methylimidazolium hexafluorophosphate, couched in the united-atom
site representation are studied via molecular dynamics simulations. The
dynamically heterogeneous behavior of the model resembles that of fragile
supercooled liquids. At or close to room temperature, the model ionic liquid
exhibits slow dynamics, characterized by nonexponential structural relaxation
and subdiffusive behavior. The structural relaxation time, closely related to
the viscosity, shows a super-Arrhenius behavior. Local excitations, defined as
displacement of an ion exceeding a threshold distance, are found to be mainly
responsible for structural relaxation in the alternating structure of cations
and anions. As the temperature is lowered, excitations become progressively
more correlated. This results in the decoupling of exchange and persistence
times, reflecting a violation of the Stokes-Einstein relation.Comment: Published on the Phys. Chem. Chem. Phys. websit
Metabolomic systems biology of trypanosomes
Metabolomics analysis, which aims at the systematic identification and quantification of all metabolites in biological systems, is emerging as a powerful new tool to identify biomarkers of disease, report on cellular responses to environmental perturbation, and to identify the targets of drugs. Here we discuss recent developments in metabolomic analysis, from the perspective of trypanosome research, highlighting remaining challenges and the most promising areas for future research
Theory of electronic properties and quantum spin blockade in a gated linear triple quantum dot with one electron spin each
We present a theory of electronic properties and the spin blockade phenomena
in a gated linear triple quantum dot. Quadruple points where four different
charge configurations are on resonance, particularly involving (1,1,1)
configuration, are considered. In the symmetric case, the central dot is biased
to higher energy and a single electron tunnels through the device when (1,1,1)
configuration is resonant with (1,0,1),(2,0,1),(1,0,2) configurations. The
electronic properties of a triple quantum dot are described by a Hubbard model
containing two orbitals in the two unbiased dots and a single orbital in the
biased dot. The transport through the triple quantum dot molecule involves both
singly and doubly occupied configurations and necessitates the description of
the (1,1,1) configuration beyond the Heisenberg model. Exact eigenstates of the
triple quantum dot molecule with up to three electrons are used to compute
current assuming weak coupling to the leads and non-equilibrium occupation of
quantum molecule states obtained from the rate equation. The intra-molecular
relaxation processes due to acoustic phonons and cotunneling with the leads are
included, and are shown to play a crucial role in the spin blockade effect. We
find a quantum interference-based spin blockade phenomenon at low source-drain
bias and a distinct spin blockade due to a trap state at higher bias. We also
show that, for an asymmetric quadruple point with
(0,1,1),(1,1,1,),(0,2,1),(0,1,2) configurations on resonance, the spin blockade
is analogous to the spin blockade in a double quantum dot
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