31,672 research outputs found
Adsorption of Self-Assembled Rigid Rods on Two-Dimensional Lattices
Monte Carlo (MC) simulations have been carried out to study the adsorption on
square and triangular lattices of particles with two bonding sites that, by
decreasing temperature or increasing density, polymerize reversibly into chains
with a discrete number of allowed directions and, at the same time, undergo a
continuous isotropic-nematic (IN) transition. The process has been monitored by
following the behavior of the adsorption isotherms for different values of
lateral interaction energy/temperature. The numerical data were compared with
mean-field analytical predictions and exact functions for noninteracting and 1D
systems. The obtained results revealed the existence of three adsorption
regimes in temperature. (1) At high temperatures, above the critical one
characterizing the IN transition at full coverage Tc(\theta=1), the particles
are distributed at random on the surface and the adlayer behaves as a
noninteracting 2D system. (2) At very low temperatures, the asymmetric monomers
adsorb forming chains over almost the entire range of coverage, and the
adsorption process behaves as a 1D problem. (3) In the intermediate regime, the
system exhibits a mixed regime and the filling of the lattice proceeds
according to two different processes. In the first stage, the monomers adsorb
isotropically on the lattice until the IN transition occurs in the system and,
from this point, particles adsorb forming chains so that the adlayer behaves as
a 1D fluid. The two adsorption processes are present in the adsorption
isotherms, and a marked singularity can be observed that separates both
regimes. Thus, the adsorption isotherms appear as sensitive quantities with
respect to the IN phase transition, allowing us (i) to reproduce the phase
diagram of the system for square lattices and (ii) to obtain an accurate
determination of the phase diagram for triangular lattices.Comment: Langmuir, 201
Zero-field magnetization reversal of two-body Stoner particles with dipolar interaction
Nanomagnetism has recently attracted explosive attention, in particular,
because of the enormous potential applications in information industry, e.g.
new harddisk technology, race-track memory[1], and logic devices[2]. Recent
technological advances[3] allow for the fabrication of single-domain magnetic
nanoparticles (Stoner particles), whose magnetization dynamics have been
extensively studied, both experimentally and theoretically, involving magnetic
fields[4-9] and/or by spin-polarized currents[10-20]. From an industrial point
of view, important issues include lowering the critical switching field ,
and achieving short reversal times. Here we predict a new technological
perspective: can be dramatically lowered (including ) by
appropriately engineering the dipole-dipole interaction (DDI) in a system of
two synchronized Stoner particles. Here, in a modified Stoner-Wohlfarth (SW)
limit, both of the above goals can be achieved. The experimental feasibility of
realizing our proposal is illustrated on the example of cobalt nanoparticles.Comment: 5 pages, 4 figure
One-Loop Electroweak Corrections to the Muon Anomalous Magnetic Moment Using the Pinch Technique
The definition of the physical properties of particles in perturbative gauge
theories must satisfy gauge invariance as a requisite. The Pinch Technique
provides a framework to define the electromagnetic form factors and the
electromagnetic static properties of fundamental particles in a consistent and
gauge-invariant form. We apply a simple prescription derived in this formalism
to check the calculation of the gauge-invariant one-loop bosonic electroweak
corrections to the muon anomalous magnetic moment.Comment: 6 pages and 1 eps figur
A probabilistic model for crystal growth applied to protein deposition at the microscale
A probabilistic discrete model for 2D protein crystal growth is presented.
This model takes into account the available space and can describe growing
processes of different nature due to the versatility of its parameters which
gives the model great flexibility. The accuracy of the simulation is tested
against a real protein (SbpA) crystallization experiment showing high agreement
between the proposed model and the actual images of the nucleation process.
Finally, it is also discussed how the regularity of the interface (i.e. the
curve that separates the crystal from the substrate) affects to the evolution
of the simulation.Comment: 13 pages, 12 figure
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