Characterisation of different polymorphs of tris(8-hydroxyquinolinato)aluminium(III) using solid-state NMR and DFT calculations

Background  

Organic light emitting devices (OLED) are becoming important and characterisation of them, in terms of structure, charge distribution, and intermolecular interactions, is important. Tris(8-hydroxyquinolinato)-aluminium(III), known as Alq₃, an organomettalic complex has become a reference material of great importance in OLED. It is important to elucidate the structural details of Alq₃ in its various isomeric and solvated forms. Solid-state nuclear magnetic resonance (NMR) is a useful tool for this which can also complement the information obtained with X-ray diffraction studies.     

A solution of the DGLAP equation for gluon at low x

We obtain a solution of the DGLAP equation for the gluon at low x first by expanding the gluon in a Taylor series and then using the method of characteristics. We test its validity by comparing it with that of Glück, Reya and Vogt. The convergence criteria of the approximation used are also discussed. We also calculate εF ₂(x,Q)²/ε In Q ² using its approximate relations with the gluon distribution at low x. The predictions are then compared with the HERA data.     

The isothermal flash problem. Part II. Phase-split calculation

Algorithms for calculation of multiphase equilibrium at given temperature and pressure using a single Equation of State as the thermodynamic model are described. The use of stability analysis to generate initial estimates and of second order convergence methods lead to rapid solution even in the immediate vicinity of critical points.     

Effect of the wavelength dependence of the emissivity on inferred soot temperatures measured by spectrally resolved laser-induced incandescence

Flame-generated soot was heated using a pulsed laser, and temperatures of the irradiated soot were inferred by fitting the Planck function to spectrally resolved laser-induced incandescence with the temperature as an adjustable parameter. The effect of the wavelength dependence of the emissivity on the inferred temperatures of the irradiated soot was studied using selected expressions for the soot emissivity in the fit. Depending upon the choice of the functional form of the emissivity, the maximum temperature reached by the soot during the laser pulse was calculated to span a range of 341 K (3475–3816 K) at a 1064-nm laser fluence of 0.1 J/cm² and 456 K (4115–4571 K) at a 1064-nm laser fluence of 0.4 J/cm² with a 1σ standard deviation about the mean of ∼25 K. Comparison of the present results with temperature measurements from previous studies suggests that the emissivity may depend on flame conditions and that further investigation on the subject is needed. The use of two-color or spectrally resolved LII to infer the soot temperature during or after laser heating requires a careful characterization of the wavelength dependence of the emissivity. The spread in temperature leads to large uncertainties regarding the physico-chemical processes occurring at the surface of the soot during the laser heating.     

Physical properties from association models

Equation of state models with a ‘chemical’ contribution that accounts for association and solvation effects, are computationally intensive as they have to solve an internal chemical equilibrium calculation.

Frequently, only the final results of this internal calculation are used in the subsequent evaluation of physical properties from the model. As a consequence, a substantial amount of unneeded work is performed. We show here how the state function minimization in the chemical equilibrium calculation can be utilized to simplify the calculation of physical properties like pressure and chemical potentials and the derivatives of these properties with respect to temperature, volume and composition.     

Increased oxygen transfer in a yeast fermentation using a microbubble dispersion

A microbubble dispersion (MBD) was used to supply oxygen for aerobic fermentations in a standard 2 L stirred tank fermenter. The microbubble dispersion was formed using only surfactants produced naturally. Growth rates ofSaccharomyces cerevisiae cultures were found to be equal or greater with MBD sparging than with gas sparging. The oxygen transfer coefficent with MBD sparging was found to be 190/h and independent of impeller speed from 100–580 rpm. The oxygen transfer coefficient with air sparging rose from 55 to 132/h over the same range of impeller speeds. Power requirements for the fermenter systems were estimated.