CORAL REEF STUDIES. II. THE DEPTH OF CORAL REEFS IN RELATION TO THEIR OXYGEN CONSUMPTION AND THE PENETRATION OF LIGHT IN THE WATER

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CORAL REEF STUDIES. III. GEOMORPHOLOGICAL NOTES ON THE CORAL REEFS OF BATAVIA BAY

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CORAL REEF STUDIES . I. THE SYMBIOSIS BETWEEN DAMSELFISHES AND SEA ANEMONES IN BATAVIA BAY.

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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, $r$, their lengths (denoted by $2l_1$ and $2l_2$), and their relative orientations (indicated by $\theta$ and $\phi$). When the objects have the same length ($2l_1=2l_2=l$), for particular values of separations, i.e for $r\leq0.8 l$, two types of minimum are appeared in the interaction energy with respect to $\theta$. By employing the closed form formula and introducing a scaled temperature $t$, 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 $r<0.8 l$, 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