1,273 research outputs found
Onsager-Manning-Oosawa condensation phenomenon and the effect of salt
Making use of results pertaining to Painleve III type equations, we revisit
the celebrated Onsager-Manning-Oosawa condensation phenomenon for charged stiff
linear polymers, in the mean-field approximation with salt. We obtain
analytically the associated critical line charge density, and show that it is
severely affected by finite salt effects, whereas previous results focused on
the no salt limit. In addition, we obtain explicit expressions for the
condensate thickness and the electric potential. The case of asymmetric
electrolytes is also briefly addressed.Comment: to appear in Phys. Rev. Let
Exact asymptotic expansions for the cylindrical Poisson-Boltzmann equation
The mathematical theory of integrable Painleve/Toda type systems sheds new
light on the behavior of solutions to the Poisson-Boltzmann equation for the
potential due to a long rod-like macroion. We investigate here the case of
symmetric electrolytes together with that of 1:2 and 2:1 salts. Short and large
scale features are analyzed, with a particular emphasis on the low salinity
regime. Analytical expansions are derived for several quantities relevant for
polyelectrolytes theory, such as the Manning radius. In addition, accurate and
practical expressions are worked out for the electrostatic potential, which
improve upon previous work and cover the full range of radial distances
Two-dimensional one-component plasma on a Flamm's paraboloid
We study the classical non-relativistic two-dimensional one-component plasma
at Coulomb coupling Gamma=2 on the Riemannian surface known as Flamm's
paraboloid which is obtained from the spatial part of the Schwarzschild metric.
At this special value of the coupling constant, the statistical mechanics of
the system are exactly solvable analytically. The Helmholtz free energy
asymptotic expansion for the large system has been found. The density of the
plasma, in the thermodynamic limit, has been carefully studied in various
situations
Optimization of MIL-178(Fe) and Pebax® 3533 loading in mixed matrix membranes for CO2 capture
Global warming is considered as a consequence of extensive use of fossil fuels. Post combustion CO2 capture is an interesting and alternative solution where mixed matrix membranes (MMMs) can be an exciting candidate. This research focuses on the optimization of MMM composition consisting of Pebax® 3533 as the polymer matrix and porous coordination polymer (PCP) MIL-178(Fe) as a filler for gas separation application. MIL-178(Fe) characterized with SEM, TEM and TGA were applied to compare bare polymer and MMM. Optimum composition of the MMM obtained was 5 wt.% MIL-178(Fe) in Pebax® 3533. Average thickness of the optimized dense MMM was 116 ± 8 µm. Such MMM showed CO2 permeability and CO2/N2 selectivity of 312 ± 5 Barrer and 25.0 ± 0.5, respectively, 12% and 25% improved regarding the bare membrane. Additionally, optimum MMM was applied for CO2/CH4 separation and successfully compared in terms of improved CO2 permeability and CO2/CH4 selectivity
Impact of cow's milk intake on exercise performance and recovery of muscle function: a systematic review
Dairy products are thought to improve recovery after both resistance and endurance exercises due to their nutritional proprieties. We systematically reviewed the effects of dairy product intake on exercise performance and recovery of muscle function in humans. A literature search was conducted in the MEDLINE (via PubMed) and Web of Science databases from their inception to 15th April 2018. The initial search retrieved 7708 articles, and a total of 11 studies were finally included after applying inclusion and exclusion criteria. All the selected studies were conducted with cow's milk. Whereas some studies found significant positive effect of cow's milk on exercise performance and recovery of muscle function, others did not find any effect. These controversies could be due to the heterogeneity of cow's milk ingestion (e.g., amount of cow's milk, timing of consuming the cow's milk), to the type of intervention, and to the large heterogeneity of outcomes measured. Limited studies exist examining the effects of cow's milk consumption and its influence on exercise performance and recovery of muscle function, therefore further studies are needed to draw more definitive conclusions.The study was supported by the Spanish Ministry of Education (FPU 13/04365 and 15/04059), by the Redes temáticas de investigaciĂłn cooperativa RETIC (Red SAMID RD16/0022), and by the University of Granada Plan Propio de Investigacion 2016 -Excellence actions: Unit of Excellence on Exercise and Health (UCEES) - and Plan Propio de InvestigaciĂłn 2018 - Programa Contratos-Puente, and the Junta de AndalucĂa, ConsejerĂa de Conocimiento, InvestigaciĂłn y Universidades (ERDF: ref. SOMM17/6107/UGR), and by the Interprofessional Dairy Organization (INLAC) of Spain
Sedimentation of binary mixtures of like- and oppositely charged colloids: the primitive model or effective pair potentials?
We study sedimentation equilibrium of low-salt suspensions of binary mixtures
of charged colloids, both by Monte Carlo simulations of an effective
colloids-only system and by Poisson-Boltzmann theory of a colloid-ion mixture.
We show that the theoretically predicted lifting and layering effect, which
involves the entropy of the screening ions and a spontaneous macroscopic
electric field [J. Zwanikken and R. van Roij, Europhys. Lett. {\bf 71}, 480
(2005)], can also be understood on the basis of an effective colloid-only
system with pairwise screened-Coulomb interactions. We consider, by theory and
by simulation, both repelling like-charged colloids and attracting oppositely
charged colloids, and we find a re-entrant lifting and layering phenomenon when
the charge ratio of the colloids varies from large positive through zero to
large negative values
On the fluid-fluid phase separation in charged-stabilized colloidal suspensions
We develop a thermodynamic description of particles held at a fixed surface
potential. This system is of particular interest in view of the continuing
controversy over the possibility of a fluid-fluid phase separation in aqueous
colloidal suspensions with monovalent counterions. The condition of fixed
surface potential allows in a natural way to account for the colloidal charge
renormalization. In a first approach, we assess the importance of the so called
``volume terms'', and find that in the absence of salt, charge renormalization
is sufficient to stabilize suspension against a fluid-fluid phase separation.
Presence of salt, on the other hand, is found to lead to an instability. A very
strong dependence on the approximations used, however, puts the reality of this
phase transition in a serious doubt. To further understand the nature of the
instability we next study a Jellium-like approximation, which does not lead to
a phase separation and produces a relatively accurate analytical equation of
state for a deionized suspensions of highly charged colloidal spheres. A
critical analysis of various theories of strongly asymmetric electrolytes is
presented to asses their reliability as compared to the Monte Carlo
simulations
Collective modes and correlations in one-component plasmas
The static and time-dependent potential and surface charge correlations in a
plasma with a boundary are computed for different shapes of the boundary. The
case of a spheroidal or spherical one-component plasma is studied in detail
because experimental results are available for such systems. Also, since there
is some knowlegde both experimental and theoretical about the electrostatic
collective modes of these plasmas, the time-dependent correlations are computed
using a method involving these modes.Comment: 20 pages, plain TeX, submitted to Phys. Rev.
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