The effect of forward and backward scattering on the law of darkening for the Milne problem and the spherical albedo

A synthetic kernel is used to study the effect of forward and backward scattering on the law of darkening for the Milne problem and the spherical albedo.     

Radiation transport in plane-parallel media with non-uniform surface illumination

Fourier and other integral transform techniques are used to reduce the problem of radiation transport in plane-parallel media with non-uniform surface illumination to a convenient computational form, and theF _N method is used to provide a basis for approximate solutions.     

A point source in a finite sphere

Exact analysis and the F_N method are used to compute the radiation field due to a point source of radiation located at the center of a finite sphere.     

On computing the Chapman-Enskog functions for viscosity and heat transfer and the Burnett functions

Hermite cubic splines and collocation are used to solve, in an efficient and accurate way, the Chapman-Enskog equations for viscosity and heat transfer and to compute the Burnett functions required for Poiseuille-flow problems based on rigid-sphere collisions and the linearized Boltzmann equation.     

Particular solutions of the equation of transfer

Particular solutions corresponding to various forms for the inhomogeneous source term are established for the equation of transfer with Lth order anisotropic scattering.     

Molecular dynamics simulation of the formation, structure, and dynamics of small phospholipid vesicles

Here, we use coarse grained molecular dynamics (MD) simulations to study the spontaneous aggregation of dipalmitoylphosphatidylcholine (DPPC) lipids into small unilamellar vesicles. We show that the aggregation process occurs on a nanosecond time scale, with bicelles and cuplike vesicles formed at intermediate stages. Formation of hemifused vesicles is also observed at higher lipid concentration. With either 25% dipalmitoylphosphatidylethanolamine (DPPE) or lysoPC mixed into the system, the final stages of the aggregation process occur significantly faster. The structure of the spontaneously formed vesicles is analyzed in detail. Microsecond simulations of isolated vesicles reveal significant differences in the packing of the lipids between the inner and outer monolayers, and between PC, PE, and lysoPC. Due to the small size of the vesicles they remain almost perfectly spherical, undergoing very limited shape fluctuations or bilayer undulations. The lipid lateral diffusion rate is found to be faster in the outer than in the inner monolayer. The water permeability coefficient of the pure DPPC vesicles is of the order of 10(-)(3) cm s(-)(1), in agreement with experimental measurements.     

Application of mean field boundary potentials in simulations of lipid vesicles

A method is presented to enhance the efficiency of simulations of lipid vesicles. The method increases computational speed by eliminating water molecules that either surround the vesicle or reside in the interior of the vesicle, without altering the properties of the water at the membrane interface. Specifically, mean field force approximation (MFFA) boundary potentials are used to replace both the internal and external excess bulk solvent. In addition to reducing the cost of simulating preformed vesicles, the molding effect of the boundary potentials also enhances the formation and equilibration of vesicles from random solutions of lipid in water. Vesicles with diameters in the range from 20 to 60 nm were obtained on a nanosecond time scale, without any noticeable effect of the boundary potentials on their structure.