Modelling of poly(ethylene terephthalate) reactors. III. A semibatch prepolymerization process

A mathematical modelling of a semibatch prepolymerization process has been undertaken. Prepolymerization conducted at constant temperature and pressure and with a predetermined variation in temperature and pressure has been studied. Influence of DMT and TPA addition during prepolymerization has also been examined. The focus has been on investigation of the influence of processing and operational variables on productivity and side product formation, which controls product quality. The results of this investigation (which are applicable only up to DP ? to 30) are borne out by the limited experimental data available in the literature. Important pragmatic implications of the results of the work in terms of design and operation of prepolymerization reactors have been emphasized.     

Scandium ion doped yttrium oxide transparent ceramic from nitrate alanine microwave combustion synthesized nanopowders

One atomic percent Neodymium ion doped Yttrium oxide, with 25 at% scandium ion (Nd_0.02Sc_0.5Y_1.48O₃), was synthesized by nitrate alanine microwave gel combustion followed by calcinations at 1000 °C for 2 h. Phase purity of nanopowder was characterized by X-Ray Diffraction (XRD). Neodymium and scandium ion doping was confirmed by cell parameter calculation and Scanning Electron Microscope-Electron Dispersive X-ray (SEM-EDX) analysis. Particles with size range 25–35 nm with close to spherical shape were obtained as observed by Transmission Electron Microscopy (TEM). Powder on compaction followed by vacuum sintering at 1765 °C for 40 min led to the formation of ceramic with 76% transmission at 2500 nm compared to translucent ceramic obtained without scandium ion doping. This indicates formation of highly sinterable neodymium doped yttrium oxide nanopowders by nitrate alanine microwave gel combustion route with scandium ion additive. Further the absorption and emission bands of Nd_0.02Sc_0.5Y_1.48O₃ are inhomogeneously broadened and fluorescence lifetime is longer than Nd_0.02Y_1.98O₃.     

Low temperature synthesis of magnetite and maghemite nanoparticles

We report on the synthesis of iron oxide nanoparticles below 100 degrees C by a simple chemical protocol. The uniqueness of the method lies in the use of Ferrous ammonium sulphate (in conjugation with FeCl3) which helps maintain the stability of Fe2+ state in the reaction sequence thereby controlling the phase formation. Hexamine was added as the stabilizer. The nanoparticles synthesized at three different temperatures viz, 5 degrees, 27 degrees, and 95 degrees C are characterized by several techniques. Generally, when a mixture of Fe3+ and Fe2+ is added to sodium hydroxide, alpha-Fe2O3 (the anti-ferromagnetic phase) is formed after the dehydration process of the hydroxide. In our case however, the phases formed at all the three temperatures were found to be ferro (ferri) magnetic, implying modification of the formation chemistry due to the specifics of our method. The nanoparticles synthesized at the lowest temperature exhibit magnetite phase, while increase in growth temperature to 95 degrees C leads to the maghemite phase.     

Magnetite/CdTe magnetic-fluorescent composite nanosystem for magnetic separation and bio-imaging

A new synthesis protocol is described to obtain a CdTe decorated magnetite bifunctional nanosystem via dodecylamine (DDA) as cross linker. High resolution transmission electron microscopy (HRTEM), energy-dispersive x-ray spectroscopy (EDAX), vibrating sample magnetometry (VSM), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS) and fluorescence microscopy are used to characterize the constitution, size, composition and physical properties of these superparamagnetic-fluorescent nanoparticles. These CdTe decorated magnetite nanoparticles were then functionalized with anti-epidermal growth factor receptor (EGFR) antibody to specifically target cells expressing this receptor. The EGFR is a transmembrane glycoprotein and is expressed on tumor cells from different tissue origins including human leukemic cell line Molt-4 cells. The magnetite-CdTe composite nanosystem is shown to perform excellently for specific selection, magnetic separation and fluorescent detection of EGFR positive Molt-4 cells from a mixed population. Flow cytometry and confocal laser scanning microscopy results show that this composite nanosystem has great potential in antibody functionalized magnetic separation and imaging of cells using cell surface receptor antibody.     

A two-component modeling for free stream velocity in magnetohydrodynamic nanofluid flow with radiation and chemical reaction over a stretching cylinder

This analysis explores the influence of magnetohydrodynamic (MHD) nanofluid flow over a stretching cylinder with radiation effect in presence of chemically reactive species. The thermal radiation phenomenon is incorporated in the temperature equation. The mathematical modeling of the physical problem produces nonlinear set of partial differential equations corresponding to the momentum and energy equations that can be transformed into simultaneous system of ordinary differential equations with appropriate boundary conditions by applying similarity transformations. Shooting technique is used to solve the molded equations after adoption of Runge–Kutta–Fehlberg approach and ODE45 solver in MATLAB. A parametric analysis has been carried out to investigate the impacts of physical parameters that are considered in the current study. The attractive pattern studied the consequence of Brownian motion along with thermophoresis parameter. The outcomes of prominent fluid parameters, especially heat radiation, Lewis number, free stream velocity, chemical reaction, thermophoresis, and Brownian motion on the concentration, temperature, as well as velocity have been examined and are displayed through graphs and tables. The present study reveals that the temperature phenomenon enhances with an increase in radiation parameter, while nanoparticle concentration phenomenon reduces with an increase in chemical reaction parameter.