1,228 research outputs found
Two-component plasma in a gravitational field: Thermodynamics
We revisit the model of the two-component plasma in a gravitational field,
which mimics charged colloidal suspensions. We concentrate on the computation
of the grand potential of the system. Also, a special sum rule for this model
is presented.Comment: 7 pages, LaTeX2
Screening of charged spheroidal colloidal particles
We study the effective screened electrostatic potential created by a
spheroidal colloidal particle immersed in an electrolyte, within the mean field
approximation, using Poisson--Botzmann equation in its linear and nonlinear
forms, and also beyond the mean field by means of Monte Carlo computer
simulation. The anisotropic shape of the particle has a strong effect on the
screened potential, even at large distances (compared to the Debye length) from
it. To quantify this anisotropy effect, we focus our study on the dependence of
the potential on the position of the observation point with respect with the
orientation of the spheroidal particle. For several different boundary
conditions (constant potential, or constant surface charge) we find that, at
large distance, the potential is higher in the direction of the large axis of
the spheroidal particle
Non-linear screening of spherical and cylindrical colloids: the case of 1:2 and 2:1 electrolytes
From a multiple scale analysis, we find an analytic solution of spherical and
cylindrical Poisson-Boltzmann theory for both a 1:2 (monovalent co-ions,
divalent counter-ions) and a 2:1 (reversed situation) electrolyte. Our approach
consists in an expansion in powers of rescaled curvature , where
is the colloidal radius and the Debye length of the electrolytic
solution. A systematic comparison with the full numerical solution of the
problem shows that for cylinders and spheres, our results are accurate as soon
as . We also report an unusual overshooting effect where the
colloidal effective charge is larger than the bare one.Comment: 9 pages, 11 figure
A Generalization of the Stillinger-Lovett Sum Rules for the Two-Dimensional Jellium
In the equilibrium statistical mechanics of classical Coulomb fluids, the
long-range tail of the Coulomb potential gives rise to the Stillinger-Lovett
sum rules for the charge correlation functions. For the jellium model of mobile
particles of charge immersed in a neutralizing background, the fixing of
one of the -charges induces a screening cloud of the charge density whose
zeroth and second moments are determined just by the Stillinger-Lovett sum
rules. In this paper, we generalize these sum rules to the screening cloud
induced around a pointlike guest charge immersed in the bulk interior of
the 2D jellium with the coupling constant ( is the
inverse temperature), in the whole region of the thermodynamic stability of the
guest charge . The derivation is based on a mapping technique of
the 2D jellium at the coupling = (even positive integer) onto a
discrete 1D anticommuting-field theory; we assume that the final results remain
valid for all real values of corresponding to the fluid regime. The
generalized sum rules reproduce for arbitrary coupling the standard
Z=1 and the trivial Z=0 results. They are also checked in the Debye-H\"uckel
limit and at the free-fermion point . The generalized
second-moment sum rule provides some exact information about possible sign
oscillations of the induced charge density in space.Comment: 16 page
Globalization and formal sector migration in Brazil
Summary. â Comprehensive linked employerâemployee data allow us to study the relationship between domestic formal sector migration in Brazil and globalization. Considerable worker flows in the formal labor market during 1997â2001 are directed toward lower income
regionsâthe reverse flows of those often posited for informal labor markets. Estimation of the workerâs multi-choice migration problem shows that previously unobserved employer covariates are significant predictors associated with migration flows. These results support the idea that globalization acts on internal migration through job stability at exporting establishments and employment opportunities at locations with a concentration of foreign owned establishments. A 1% increase in exporter employment predicts a 0.3% reduced probability of migration. A 1% increase in the concentration of foreign owned establishments at potential destinations is
associated with a 0.2% increase in the migration rate.
ïżœ 2010 Elsevier Ltd. All rights reserve
The Ideal Conductor Limit
This paper compares two methods of statistical mechanics used to study a
classical Coulomb system S near an ideal conductor C. The first method consists
in neglecting the thermal fluctuations in the conductor C and constrains the
electric potential to be constant on it. In the second method the conductor C
is considered as a conducting Coulomb system the charge correlation length of
which goes to zero. It has been noticed in the past, in particular cases, that
the two methods yield the same results for the particle densities and
correlations in S. It is shown that this is true in general for the quantities
which depend only on the degrees of freedom of S, but that some other
quantities, especially the electric potential correlations and the stress
tensor, are different in the two approaches. In spite of this the two methods
give the same electric forces exerted on S.Comment: 19 pages, plain TeX. Submited to J. Phys. A: Math. Ge
Using the heart rate variability for classifying patients with and without chronic heart failure and periodic breathing
Assessment of the dynamic interactions between cardiovascular signals can provide valuable information that improves the understanding of cardiovascular control. Heart rate variability (HRV) analysis is known to provide information about the autonomic heart rate modulation mechanism. Using the HRV signal, we aimed to obtain parameters for classifying patients with and without chronic heart failure (CHF), and with periodic breathing (PB), non-periodic breathing (nPB), and Cheyne-Stokes respiration (CSR) patterns. An electrocardiogram (ECG) and a respiratory flow signal were recorded in 36 elderly patients: 18 patients with CHF and 18 patients without CHF. According to the clinical criteria, the patients were classified into the follow groups: 19 patients with nPB pattern, 7 with PB pattern, 4 with Cheyne-Stokes respiration (CSR), and 6 non-classified patients (problems with respiratory signal). From the HRV signal, parameters in the time and frequency domain were calculated. Frequency domain parameters were the most discriminant in comparisons of patients with and without CHF: PTOT, PLF and fpHF. For the comparison of the nPB vs CSR patients groups, the best parameters were RMSSD and SDSD. Therefore, the parameters appear to be suitable for enhanced diagnosis of decompensated CHF patients and the possibility of developed periodic breathing and a CSR pattern
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