1,917 research outputs found
CORAL REEF STUDIES. II. THE DEPTH OF CORAL REEFS IN RELATION TO THEIR OXYGEN CONSUMPTION AND THE PENETRATION OF LIGHT IN THE WATER
abstract not availabl
CORAL REEF STUDIES. III. GEOMORPHOLOGICAL NOTES ON THE CORAL REEFS OF BATAVIA BAY
abstract not availabl
CORAL REEF STUDIES . I. THE SYMBIOSIS BETWEEN DAMSELFISHES AND SEA ANEMONES IN BATAVIA BAY.
abstract not availableÂ
Non-monotonic density dependence of the diffusion of DNA fragments in low-salt suspensions
The high linear charge density of 20-base-pair oligomers of DNA is shown to
lead to a striking non-monotonic dependence of the long-time self-diffusion on
the concentration of the DNA in low-salt conditions. This generic non-monotonic
behavior results from both the strong coupling between the electrostatic and
solvent-mediated hydrodynamic interactions, and from the renormalization of
these electrostatic interactions at large separations, and specifically from
the dominance of the far-field hydrodynamic interactions caused by the strong
repulsion between the DNA fragments.Comment: 4 pages, 2 figures. Physical Review E, accepted on November 24, 200
Quenched Charge Disorder and Coulomb Interactions
We develop a general formalism to investigate the effect of quenched fixed
charge disorder on effective electrostatic interactions between charged
surfaces in a one-component (counterion-only) Coulomb fluid. Analytical results
are explicitly derived for two asymptotic and complementary cases: i)
mean-field or Poisson-Boltzmann limit (including Gaussian-fluctuations
correction), which is valid for small electrostatic coupling, and ii)
strong-coupling limit, where electrostatic correlations mediated by counterions
become significantly large as, for instance, realized in systems with
high-valency counterions. In the particular case of two apposed and ideally
polarizable planar surfaces with equal mean surface charge, we find that the
effect of the disorder is nil on the mean-field level and thus the plates
repel. In the strong-coupling limit, however, the effect of charge disorder
turns out to be additive in the free energy and leads to an enhanced long-range
attraction between the two surfaces. We show that the equilibrium inter-plate
distance between the surfaces decreases for elevated disorder strength (i.e.
for increasing mean-square deviation around the mean surface charge), and
eventually tends to zero, suggesting a disorder-driven collapse transition.Comment: 13 pages, 2 figure
Attraction between like-charged colloidal particles induced by a surface a density - functional analysis
We show that the first non-linear correction to the linearised
Poisson-Boltzman n (or DLVO) theory of effective pair interactions between
charge-stabilised, co lloidal particles near a charged wall leads to an
attractive component of entro pic origin. The position and depth of the
potential compare favourably with rec ent experimental measurementsComment: 12 pages including 2 figures. submitted to physical review letter
A closed form for the electrostatic interaction between two rod-like charged objects
We have calculated the electrostatic interaction between two rod-like charged
objects with arbitrary orientations in three dimensions. we obtained a closed
form formula expressing the interaction energy in terms of the separation
distance between the centers of the two rod-like objects, , their lengths
(denoted by and ), and their relative orientations (indicated by
and ). When the objects have the same length (),
for particular values of separations, i.e for , two types of
minimum are appeared in the interaction energy with respect to . By
employing the closed form formula and introducing a scaled temperature , we
have also studied the thermodynamic properties of a one dimensional system of
rod-like charged objects. For different separation distances, the dependence of
the specific heat of the system to the scaled temperature has been studied. It
is found that for , the specific heat has a maximum.Comment: 10 pages, 9 figures, 1 table, Accepted by J. Phys.: Condens. Matte
Liquid-liquid interfacial tension of electrolyte solutions
It is theoretically shown that the excess liquid-liquid interfacial tension
between two electrolyte solutions as a function of the ionic strength I behaves
asymptotically as O(- I^0.5) for small I and as O(+- I) for large I. The former
regime is dominated by the electrostatic potential due to an unequal
partitioning of ions between the two liquids whereas the latter regime is
related to a finite interfacial thickness. The crossover between the two
asymptotic regimes depends sensitively on material parameters suggesting that,
depending on the actual system under investigation, the experimentally
accessible range of ionic strengths can correspond to either the small or the
large ionic strength regime. In the limiting case of a liquid-gas surface where
ion partitioning is absent, the image chage interaction can dominate the
surface tension for small ionic strength I such that an Onsager-Samaras
limiting law O(- I ln(I)) is expected. The proposed picture is consistent with
more elaborate models and published measurements.Comment: Accepted for publication in Physical Review Letter
Nonlinear screening of charged macromolecules
We present several aspects of the screening of charged macromolecules in an
electrolyte. After a review of the basic mean field approach, based on the
linear Debye-Huckel theory, we consider the case of highly charged
macromolecules, where the linear approximation breaks down and the system is
described by full nonlinear Poisson-Boltzmann equation. Some analytical results
for this nonlinear equation give some interesting insight on physical phenomena
like the charge renormalization and the Manning counterion condensation
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