Study of Groundwater-Surface Water Interactions to Identify Potential Aquitard Breach Locations along the Wolf River, Tennessee

Inter-aquifer exchanges due to breaches in the confining clay layer can potentially contaminate the Memphis aquifer, as lesser-quality waters permeate from the unconfined aquifer. Losing river reaches could indicate breach locations, as these should depress water-table locally, resulting in downward vertical exchange fluxes (VEFs) along nearby streambeds. A spatial analysis of seepage meter measurements performed along the Wolf River identified three potentially losing sub-reaches, where VEFs were studied at a finer scale, using multiple point-scale methods. Results were mixed, displaying large spatial variability, possibly due to mismatches between the process and observation scales. Differential stream gaging was conducted to assess losses integrally over sub-reaches, confirming one losing location; however, comparing groundwater river stages suggested gaining conditions at this location. Pinpointing losing reaches using point-scale methods is difficult due to the disparity of scales. Effective methodologies are needed that comply with the scale of the problem

Molecular Dynamics Simulation of Dipalmitoylphosphatidylserine Bilayer with Na+ Counterions

AbstractWe performed a molecular dynamics simulation of dipalmitoylphosphatidylserine (DPPS) bilayer with Na+ counterions. We found that hydrogen bonding between the NH3+ group and the phosphate group leads to a reduction in the area per headgroup when compared to the area in dipalmitoylphosphatidylcholine bilayer. The Na+ ions bind to the oxygen in the carboxyl group of serine, thus giving rise to a dipolar bilayer similar to dipalmitoylphosphatidylethanolamine bilayer. The results of the simulation show that counterions play a crucial role in determining the structural and electrostatic properties of DPPS bilayer

Effect of shape anisotropy on transport in a 2-dimensional computational model: Numerical simulations showing experimental features observed in biomembranes

We propose a 2-d computational model-system comprising a mixture of spheres and the objects of some other shapes, interacting via the Lennard-Jones potential. We propose a reliable and efficient numerical algorithm to obtain void statistics. The void distribution, in turn, determines the selective permeability across the system and bears a remarkable similarity with features reported in certain biological experiments.Comment: 1 tex file, 2 sty files and 5 figures. To appear in Proc. of StatPhys conference held in Calcutta, Physica A 199

A model for within-group coalitionary aggression among males

Perhaps the most common form of cooperation among primates is the formation of coalitions. Competition among males within a group concerns a constant quantity of the limiting resource (fertilizations). Contest competition over fertilizations is known to produce payoffs that are distributed according to the priority-of-access model, and hence show an exponential decline in payoff with rank. We develop a model for rank-changing, within-group coalitions among primate males. For these coalitions to occur, they must be both profitable (i.e. improve fitness) for all coalition members and feasible (i.e. be able to beat the targets). We assume that the value of the coalition is the sum of the payoffs of the partners in their original ranks. We distinguish three basic coalition configurations, depending on the dominance ranks of the coalition partners relative to their target. We predict five basic coalition types. First, all-up, rank-changing coalitions targeting individuals ranking above all coalition partners; these are expected to involve coalition partners ranking just below their target, concern top rank, and be small, just two or three animals. Second, bridging, rank-changing coalitions, where higher-rankers support lower-rankers to rise to a rank below themselves; these are expected to be most common where a high-ranking male in a despotic system can support a low-ranking relative. Third, bridging non-rank-changing coalitions; these are expected to be common whenever high-ranking males have low-ranking close relatives. Fourth, non-rank-changing coalitions by high-rankers against lower-ranking targets; these are expected to serve to counteract or prevent the first type. Fifth, non-rank-changing, leveling coalitions, in which all partners rank below their target and which flatten the payoff distribution; these are expected to be large and mainly involve lower-ranking males. Bridging, rank-changing coalitions are expected in situations where contest is strong, all-up rank-changing coalitions where contest is intermediate, and leveling coalitions where contest is weak. We review the empirical patterns found among primates. The strong predictions of the model are confirmed by observational data on male-male coalitions in primate

N spike D-strings in AdS Space with mixed flux

We use Dirac-Born-Infeld action to study the spinning D-string in $AdS_3$ background in the presence of both NS-NS and RR fluxes. We compute the scaling relation between the energy (E) and spin (S) in the `long string limit'. The energy of these spiky string is found to be a function of spin with the leading logarithmic behaviour and the scaling relation appears to be independent of the amount of flux present. We further discuss folded D-string solutions in $AdS_3$ background with pure NS-NS and R-R fluxes.Comment: 27 pages, 12 figure