517 research outputs found
Competing interactions in two dimensional Coulomb systems: Surface charge heterogeneities in co-assembled cationic-anionic incompatible mixtures
A binary mixture of oppositely charged components confined to a plane such as
cationic and anionic lipid bilayers may exhibit local segregation. The relative
strength of the net short range interactions, which favors macroscopic
segregation, and the long range electrostatic interactions, which favors
mixing, determines the length scale of the finite size or microphase
segregation. The free energy of the system can be examined analytically in two
separate regimes, when considering small density fluctuations at high
temperatures, and when considering the periodic ordering of the system at low
temperatures (F. J. Solis and M. Olvera de la Cruz, J. Chem. Phys. 122, 054905
(2000)). A simple Molecular Dynamics simulation of oppositely charged monomers,
interacting with a short range Lennard Jones potential and confined to a two
dimensional plane, is examined at different strengths of short and long range
interactions. The system exhibits well-defined domains that can be
characterized by their periodic length-scale as well as the orientational
ordering of their interfaces. By adding salt, the ordering of the domains
disappears and the mixture macroscopically phase segregates in agreement with
analytical predictions.Comment: 8 pages, 5 figures, accepted for publication in J. Chem. Phys, Figure
1 include
Simulation of boron diffusion during low-temperature annealing of implanted silicon
Modeling of ion-implanted boron redistribution in silicon crystals during
low-temperature annealing with a small thermal budget has been carried out. It
was shown that formation of "tails"' in the low-concentration region of
impurity profiles occurs due to the long-range migration of boron interstitialsComment: 16 pages, 3 figure
Method of Laser Cross-correlation Optical Spectroscopy for Investigation of Dispersion Medium
In the paper, we suggest one of the possible schemes of a cross-correlation optical spectroscopicdevice for investigation of turbid colloidal solutions and suspensions. This devise is designed fordeterminationof the hydrodynamic radii of nanoparticles. The cross-correlation function is constructed for two signals of light intensity scattered on a cuvette with the investigated dispersion medium. The construction of crosscorrelation optical spectroscopicdevice makes it possible to detect single scattered light by suppressing multiple scattering. We carried out an analysis of literature containing theory of light scattering and results of applying cross-correlation method for investigation of solutions and suspensions. Based on the analytical review, the scheme of cross-correlation optical spectroscopicdevice was developed and constructed.
Keywords: specklefield, cross-correlation, optical spectroscopy, size distribution, dispersion mediu
Tunable coaxial cavity resonator for linear and nonlinear microwave characterization of superconducting wires
We discuss experimental results obtained using a tunable cylindrical coaxial
cavity constituted by an outer Cu cylinder and an inner Pb-BSCCO wire. We have
used this device for investigating the microwave response of the
superconducting wire, both in the linear and nonlinear regimes. In particular,
by tuning the different modes of the cavity to make them resonant at exactly
harmonic frequencies, we have detected the power emitted by the superconducting
inner wire at the second- and third-harmonic frequency of the driving field.
The results obtained in the nonlinear regime, whether for the microwave surface
impedance or the harmonic emission, are qualitatively accounted for considering
intergrain fluxon dynamics. The use of this kind of device can be of strong
interest to investigate and characterise wires of large dimensions to be used
for implementing superconducting-based microwave devices.Comment: 14 pages, 6 embedded figures, accepted for publication in Supercond.
Sci. Techno
Unusual features in the nonlinear microwave surface impedance of Y-Ba-Cu-O thin films
Striking features have been found in the nonlinear microwave (8 GHz) surface
impedance of high-quality YBaCuO thin films with comparable
low power characteristics [ and ]. The surface resistance is found to increase,
decrease, or remain independent of the microwave field (up to 60 mT)
at different temperatures and for different samples. However, the surface
reactance always follows the same functional form. Mechanisms which may
be responsible for the observed variations in and are briefly
discussed.Comment: 4 pages, 4 figure
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