28,397 research outputs found
Effect of particle polydispersity on the irreversible adsorption of fine particles on patterned substrates
We performed extensive Monte Carlo simulations of the irreversible adsorption
of polydispersed disks inside the cells of a patterned substrate. The model
captures relevant features of the irreversible adsorption of spherical
colloidal particles on patterned substrates. The pattern consists of (equal)
square cells, where adsorption can take place, centered at the vertices of a
square lattice. Two independent, dimensionless parameters are required to
control the geometry of the pattern, namely, the cell size and cell-cell
distance, measured in terms of the average particle diameter. However, to
describe the phase diagram, two additional dimensionless parameters, the
minimum and maximum particle radii are also required. We find that the
transition between any two adjacent regions of the phase diagram solely depends
on the largest and smallest particle sizes, but not on the shape of the
distribution function of the radii. We consider size dispersions up-to 20% of
the average radius using a physically motivated truncated Gaussian-size
distribution, and focus on the regime where adsorbing particles do not interact
with those previously adsorbed on neighboring cells to characterize the jammed
state structure. The study generalizes previous exact relations on monodisperse
particles to account for size dispersion. Due to the presence of the pattern,
the coverage shows a non-monotonic dependence on the cell size. The pattern
also affects the radius of adsorbed particles, where one observes preferential
adsorption of smaller radii particularly at high polydispersity.Comment: 9 pages, 5 figure
Caracterização geoambiental de áreas antropizadas no MunicÃpio de ItaboraÃ, Rio de Janeiro.
bitstream/CNPS/11855/1/bp162000itaborai.pdfEquipe técnica: CirÃaca Arcangela F. de Santana do Carmo, Sergio Gomes Tôsto, Sebastião Barreiros Calderano, Hélio Monteiro Penha, Braz Calderano Filho, Waldir de Carvalho Júnior, Washington de Oliveira Barreto, José Lopes de Paula, AluÃsio Granato de Andrade
Clustering, Angular Size and Dark Energy
The influence of dark matter inhomogeneities on the angular size-redshift
test is investigated for a large class of flat cosmological models driven by
dark energy plus a cold dark matter component (XCDM model). The results are
presented in two steps. First, the mass inhomogeneities are modeled by a
generalized Zeldovich-Kantowski-Dyer-Roeder (ZKDR) distance which is
characterized by a smoothness parameter and a power index ,
and, second, we provide a statistical analysis to angular size data for a large
sample of milliarcsecond compact radio sources. As a general result, we have
found that the parameter is totally unconstrained by this sample of
angular diameter data.Comment: 9 pages, 7 figures, accepted in Physical Review
On the 2D Dirac oscillator in the presence of vector and scalar potentials in the cosmic string spacetime in the context of spin and pseudospin symmetries
The Dirac equation with both scalar and vector couplings describing the
dynamics of a two-dimensional Dirac oscillator in the cosmic string spacetime
is considered. We derive the Dirac-Pauli equation and solve it in the limit of
the spin and the pseudo-spin symmetries. We analyze the presence of cylindrical
symmetric scalar potentials which allows us to provide analytic solutions for
the resultant field equation. By using an appropriate ansatz, we find that the
radial equation is a biconfluent Heun-like differential equation. The solution
of this equation provides us with more than one expression for the energy
eigenvalues of the oscillator. We investigate these energies and find that
there is a quantum condition between them. We study this condition in detail
and find that it requires the fixation of one of the physical parameters
involved in the problem. Expressions for the energy of the oscillator are
obtained for some values of the quantum number . Some particular cases which
lead to known physical systems are also addressed.Comment: 15 pages, 8 figures, matches published versio
Exact Lyapunov Exponent for Infinite Products of Random Matrices
In this work, we give a rigorous explicit formula for the Lyapunov exponent
for some binary infinite products of random real matrices. All
these products are constructed using only two types of matrices, and ,
which are chosen according to a stochastic process. The matrix is singular,
namely its determinant is zero. This formula is derived by using a particular
decomposition for the matrix , which allows us to write the Lyapunov
exponent as a sum of convergent series. Finally, we show with an example that
the Lyapunov exponent is a discontinuous function of the given parameter.Comment: 1 pages, CPT-93/P.2974,late
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