6,695 research outputs found
Conductivity and permittivity of dispersed systems with penetrable particle-host interphase
A model for the study of the effective quasistatic conductivity and
permittivity of dispersed systems with particle-host interphase, within which
many-particle polarization and correlation contributions are effectively
incorporated, is presented. The structure of the system's components, including
the interphase, is taken into account through modelling their low-frequency
complex permittivity profiles. The model describes, among other things, a
percolation-type behavior of the effective conductivity, accompanied by a
considerable increase in the real part of the effective complex permittivity.
The percolation threshold location is determined mainly by the thickness of the
interphase. The "double" percolation effect is predicted. The results are
contrasted with experiment.Comment: 10 pages, 10 figure
Probability of the resistive state formation caused by absorption of a single-photon in current-carrying superconducting nano-strips
We have studied supercurrent-assisted formation of the resistive state in
nano-structured Nb and NbN superconducting films after absorption of a single
photon. In amorphous narrow NbN strips the probability of the resistive state
formation has a pronounced spectral cut-off. The corresponding threshold photon
energy decreases with the bias current. Analysis of the experimental data in
the framework of the generalized hot-spot model suggests that the quantum yield
for near-infrared photons increases faster than the photon nergy. Relaxation of
the resistive state depends on the photon energy making the phenomenon feasible
for the development of energy resolving single-photon detectors.Comment: 9 pages, 9 figures, submitted to Eur. Phys. Journa
Graphene spin capacitor for magnetic field sensing
An analysis of a novel magnetic field sensor based on a graphene spin
capacitor is presented. The proposed device consists of graphene nanoribbons on
top of an insulator material connected to a ferromagnetic source/drain. The
time evolution of spin polarized electrons injected into the capacitor can be
used for an accurate determination at room temperature of external magnetic
fields. Assuming a spin relaxation time of 100 ns, magnetic fields on the order
of mOe may be detected at room temperature. The observational
accuracy of this device depends on the density of magnetic defects and spin
relaxation time that can be achieved.Comment: 6 pages, 3 figure
Symmetric Diblock Copolymers in Thin Films (I): Phase stability in Self-Consistent Field Calculations and Monte Carlo Simulations
We investigate the phase behavior of symmetric AB diblock copolymers confined
into a thin film. The film boundaries are parallel, impenetrable and attract
the A component of the diblock copolymer. Using a self-consistent field
technique [M.W. Matsen, J.Chem.Phys. {\bf 106}, 7781 (1997)], we study the
ordered phases as a function of incompatibility and film thickness in
the framework of the Gaussian chain model. For large film thickness and small
incompatibility, we find first order transitions between phases with different
number of lamellae which are parallel oriented to the film boundaries. At high
incompatibility or small film thickness, transitions between parallel oriented
and perpendicular oriented lamellae occur. We compare the self-consistent field
calculations to Monte Carlo simulations of the bond fluctuation model for chain
length N=32. In the simulations we quench several systems from to
and monitor the morphology into which the diblock copolymers
assemble. Three film thicknesses are investigated, corresponding to parallel
oriented lamellae with 2 and 4 interfaces and a perpendicular oriented
morphology. Good agreement between self-consistent field calculations and Monte
Carlo simulations is found.Comment: to appear in J.Chem.Phy
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