Population Balance Modeling with Coupled Agglomeration and Disintegration Processes for TiO2 Nanoparticles Formation and Experimental Validation

Particle size distribution of nanoparticles plays an important role in modelling many scientific and engineering problems. In this article, we proposed a Finite Volume Method (FVM) to model TiO₂ nanoparticles formation using population balance equations (PBEs) by incorporating the simultaneous agglomeration and disintegration processes. The superposition of the PBEs for agglomeration and disintegration with different kernels leads to a system of partial-integro differential equations, which are numerically solved by using FVM. The precipitation of TiO₂ nanoparticles in the batch reactor is studied experimentally as well as by numerical simulations based on Austin and Diemer disintegration kernels and Shear agglomeration kernel. Finally, the capability of the precipitation model is evaluated and the experimental results on particle sizes are compared with the numerical results.

     

Monomers for preparation of amide linked RNA: synthesis of C3′-homologated nucleoside amino acids from d-xylose

Amides as neutral and hydrophobic internucleoside linkages in RNA are highly interesting modifications for RNA interference. However, testing amides in siRNAs is hampered by the shortage of efficient methods to synthesize the monomeric building blocks, the nucleoside amino acid equivalents. This paper reports an efficient synthesis of protected ribonucleoside 5′-amino 3′-carboxylic acids from d-xylose in 14 steps 7% overall yield. The key features that ensure efficiency and ease of operations are chemoselective reduction of the ester and minimization of protecting group manipulation.     

The cone phase of liquid crystals: Triangular lattice of double-tilt cylinders

We predict the existence of a new defect-lattice phase near the nematic-smectic-C(NC) transition. This tilt-analogue of the blue phase is a lattice of double-tilt cylinders which are disclination lines in the smectic layer normal as well as the c-field. We discuss the structure and stability of the cone phase. We suggest that many ‘nematics’ exhibiting short range layering and tilt order may in fact be in the molten cone phase, which is a line liquid.     

A phenomenological model for the undulating twist grain boundary-C* phase

We propose a simple phenomenological model which is able to account for the various twist grain boundary (TGB) phases, including the recently discovered undulating twist grain boundary-C* (UTGB_C*) phase. In the UTGB_C* phase, the smectic C* (SmC*)-like blocks and the grain boundaries separating them undulate to form a two-dimensional square lattice perpendicular to the TGB helix axis. We treat the grain boundaries separating adjacent smectic blocks as interfaces with an anisotropic interfacial tension. At moderate chiral strengths we find a TGB_A-TGB_C-SmC* sequence. As the chiral strength is increased this goes to the sequence TGB_A-UTGB_C*-SmC*. Such sequences have been observed experimentally.     

A phenomenological model for the undulating twist grain boundary-C* phase

We propose a simple phenomenological model which is able to account for the various twist grain boundary (TGB) phases, including the recently discovered undulating twist grain boundary-C* (UTGB_C*) phase. In the UTGB_C* phase, the smectic C* (SmC*)-like blocks and the grain boundaries separating them undulate to form a two-dimensional square lattice perpendicular to the TGB helix axis. We treat the grain boundaries separating adjacent smectic blocks as interfaces with an anisotropic interfacial tension. At moderate chiral strengths we find a TGB_A-TGB_C-SmC* sequence. As the chiral strength is increased this goes to the sequence TGB_A-UTGB_C*-SmC*. Such sequences have been observed experimentally.     

Escape configuration lattice near the nematic-isotropic transition: tilt analogue of blue phases

We predict the possible existence of a new phase of liquid crystals near the nematic-isotropic transition. This phase is an achiral, tilt analogue of the blue phase and is composed of a lattice of double-tilt, escape-configuration cylinders. We discuss the structure and the stability of this phase and provide an estimate of the lattice parameter.     

Rheology of active-particle suspensions

We study the interplay of activity, order, and flow through a set of coarse-grained equations governing the hydrodynamic velocity, concentration, and stress fields in a suspension of active, energy-dissipating particles. We make several predictions for the rheology of such systems, which can be tested on bacterial suspensions, cell extracts with motors and filaments, or artificial machines in a fluid. The phenomena of cytoplasmic streaming, elastotaxis, and active mechanosensing find natural explanations within our model.