Generic crack patterns in rubber‐modified polymers under biaxial stress states

The damage mechanisms in three different systems, namely, acrylonitrile‐butadiene‐styrene, methacrylate‐butadiene‐styrene modified poly(vinyl chloride), and styrene‐butadiene‐styrene have been investigated. The damage was analyzed over a range of biaxial stress states with confocal microscopy and scanning electron microscopy. The macroscopic yield followed a linear behavior for all the systems in an octahedral shear stress versus mean stress plot, whereas popular models for this class of materials predicted a nonlinear response. Over a certain range of biaxial stress states, a damage pattern generic to all the systems was observed. The damage pattern consisted of an array of cracks propagating perpendicular to the direction of the maximum tensile principal stress and arranged itself in a more or less periodic fashion. There was also self‐similarity in the patterns at various length scales. Similar patterns have also occurred in several other polymeric systems. The interaction in the ensemble of cracks created seems to lead to stress reduction at the crack tips, thereby limiting the crack sizes. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2248–2256, 2003     

Classical methods in molecular scattering: a continuous quantization procedure

A simple improvement of the quasiclassical histogram approximation in molecular scattering is presented, based on a continuity ansatz that relates arbitrary classical actions and non-stationary quantum states. This procedure is applied to the case of collinear collisions in atom—harmonic oscillator systems and increases the accuracy of standard quasiclassical methods     

Lagrangian finite element analysis applied to viscous free surface fluid flow

A new Lagrangian finite element formulation is presented for time-dependent incompressible free surface fluid flow problems described by the Navier-Stokes equations. The partial differential equations describing the continuum motion of the fluid are discretized using a Galerkin procedure in conjunction with the finite element approximation. Triangular finite elements are used to represent the dependent variables of the problem. An effective time integration procedure is introduced and provides a viable computational method for solving problems with equality of representation of the pressure and velocity fields. Its success has been attributed to the strict enforcement of the continuity constraint at every stage of the iterative process. The capabilities of the analysis procedure and the computer programs are demonstrated through the solution of several problems in viscous free surface fluid flow. Comparisons of results are presented with previous theoretical, numerical and experimental results.     

On the calculation of force constants using isotopic frequencies by parametric method: Application to systems of (3×3) order

A method is proposed for the determination of angle parameters for ONF, ONCl and ONBr, utilising the isotopic frequencies of two isotopically substituted molecules. The force constants, Coriolis coupling constants, inertia defect, mean amplitudes of vibration and rotational distortion constants were also calculated and compared with literature values.     

Stochastic recursive inclusion in two timescales with an application to the Lagrangian dual problem

In this paper we present a framework to analyze the asymptotic behavior of two timescale stochastic approximation algorithms including those with set-valued mean fields. This paper builds on the works of Borkar and Perkins & Leslie. The framework presented herein is more general as compared to the synchronous two timescale framework of Perkins & Leslie, however the assumptions involved are easily verifiable. As an application, we use this framework to analyze the two timescale stochastic approximation algorithm corresponding to the Lagrangian dual problem in optimization theory.     

A double helix is the repeating unit in a luminescent calcium 5-aminoisophthalate supramolecular edifice with water-filled hexagonal channels

Calcium 5-aminoisophthalate {[Ca(AIP)(OH2)4](H2O)} proportional, variant (1), synthesized from Ca(OH)2 and H2AIP, exists as a double helix. Hydrogen-bonding interactions between metal-bound water molecules, carboxylate oxygen, and the -NH2 group result in the formation of a supramolecular assembly, where the double helices are connected to each other to form hexagonal channels filled with water molecules.     

Cored anion-exchange chromatography media for antibody flow-through purification

Agarose-based anion-exchangers (e.g. quaternary amine, Q) have been widely used in monoclonal antibody flow-through purification to remove trace levels of impurities. Such media are often packed in a large column and the operation is usually robust but with limited throughput due to the compressibility of agarose and consequentially low bed permeability. In order to address this limitation, cored Q beads consisting of a rigid core and a thin agarose gel coating were developed and evaluated for protein flow-through chromatography. Using laboratory-scale columns it was found that, the cored beads indeed provide significantly enhanced rigidity and flow permeability relative to conventional homogeneous agarose resins. Depending on the structure and size of the cored beads, the permeability was 2-4-fold higher than that of a commonly used commercial agarose resin. Good virus and host cell protein clearance was achieved with the cored Q beads even at increased flow velocities. In addition, the impermeable core allows for more efficient use of buffers without loss of useful capacity in polishing applications. Process analyses based upon the experimental data demonstrated that the enhanced permeability achieved with the cored beads can significantly improve process throughput and economics.     

Seeking tetrameric transition metal phosphonate with a D4R core and organising it into a 3-D supramolecular assembly

The first cubic zinc phosphonate [tBuPO(3)Zn(2-apy)](4) (1) whose core resembles the D4R SBU of zeolites, has been synthesised from a reaction between zinc acetate, tert-butylphosphonic acid and 2-aminopyridine at room temperature; the X-ray structure determination reveals that the molecules of , which crystallise in the tetragonal I4(1)/a space group with crystallographically imposed 4 symmetry, form a 3-D supramolecular assembly aided by N-H...O hydrogen bonding.