Developments in gene therapy have led to a need for new and more efficient transfection vectors. So far, the use of viruses has received major attention. During the recent years, however, cationic liposomes have emerged as a potential rival for viruses and have several advantages, e.g. nonimmunogenity, low toxicity and a capability to carry larger amounts of DNA. Yet, the properties of cationic...

Brownian dynamics ~BD! simulations of a linear freely jointed bead–rod polymer chain with excluded volume ~EV! interaction have been performed under elongational flow with and without the use of fluctuating hydrodynamic interactions ~HI!. The dependence of the chain size, shape and intrinsic elongational viscosity on the elongational rate «̇ are reported. A sharp coil–stretch transition is obser...

Filament stretching experiments are used to follow the evolution in the flow-induced birefringence (FIB) and the tensile force in polymeric fluid threads undergoing uniaxial elongation. The tests are performed with several monodisperse polystyrene solutions spanning concentrations from 0.025 to 12 wt.%, and the measurements are used to investigate the extent of hysteresis in the polymeric stres...

We analyse the structure of a single polymer tethered to a solid surface undergoing a Couette flow. We study the problem using molecular dynamics (MD) and hybrid MD-continuum simulations, wherein the polymer and the surrounding solvent are treated via standard MD, and the solvent flow farther away from the polymer is solved by continuum fluid dynamics (CFD). The polymer represents a freely join...

We design and analyze up to third order accurate discontinuous Galerkin (DG) methods satisfying a strict maximum principle for Fokker–Planck equations. A procedure is established to identify an effective test set in each computational cell to ensure the desired bounds of numerical averages during time evolution. This is achievable by taking advantage of the two parameters in the numerical flux ...

A 37-kb DNA fragment containing five fengycin synthetase genes, including fenC, fenD, fenE, fenA, and fenB, was cloned and sequenced. Among these genes, fenC encodes a fengycin synthetase 2,560 amino acids long with an estimated molecular mass of 287 kDa. This protein contains two amino acid activation modules, FenC1 and FenC2, which activate L-glutamic acid and L-ornithine, respectively. Prime...

We present a new finite-difference formulation to update the conformation tensor in dumbbell models (e.g., Oldroyd-B, FENE-P, Giesekus) that guarantees positive eigenvalues of the tensor (i.e., the tensor remains positive definite) and prevents over-extension for finite-extensible models. The formulation is a generalization of the second-order, central difference scheme developed by Kurganov an...

The dynamics of drop formation and pinch-off have been investigated for a series of low viscosity elastic fluids possessing similar shear viscosities, but differing substantially in elastic properties. On initial approach to the pinch region, the viscoelastic fluids all exhibit the same global necking behaviour that is observed for a Newtonian fluid of equivalent shear viscosity. For these low ...

We examine a heterogeneous alternating-direction method for the approximate solution of the FENE Fokker–Planck equation from polymer fluid dynamics and we use this method to solve a coupled (macro-micro) Navier–Stokes–Fokker–Planck system for dilute polymeric fluids. In this context the Fokker–Planck equation is posed on a high-dimensional domain and is therefore challenging from a computationa...