CFD multiphase modelling for evaluation of gas mixing in an anaerobic digester

Biogas production from municipal and industrial solid and liquid waste has captured the attention of engineers and managers both in the UK and globally due the substantial benefits for achieving environmental protection, energy generation and Green House Gas emission reductions. However, there are number of problems involved in scaling up experimental anaerobic digestion (AD) plants to field level plants. One such problem associated with AD is mixing, which is a vital component to segregate synthesized gas and biomass from digester liquid, to enhance homogeneity and to ensure adequate contact between bacteria and substrate in the AD. Such situations are well suited to Computational Fluid Dynamic (CFD) analysis, where models can be calibrated and validated using the pilot plant and can then be used to accurately simulate the performance of the large-scale reactors. The aim in this work has been to further understand and enhance the use of bubble mixing approaches to improve the performance of future bioreactors. A computational model has been developed to simulate the complex flows occurring in a digester. The paper discusses CFD simulations of a lab scale AD for evaluating mixing characteristics that provides understanding required for developing accurate simulations of mixing conditions in the large-scale systems with the reactor contents simulated for both Newtonian and non-Newtonian case

Complex free energy landscapes in biaxial nematics and role of repulsive interactions : A Wang - Landau study

General quadratic Hamiltonian models, describing interaction between crystal molecules (typically with $D_{2h}$ symmetry) take into account couplings between their uniaxial and biaxial tensors. While the attractive contributions arising from interactions between similar tensors of the participating molecules provide for eventual condensation of the respective orders at suitably low temperatures, the role of cross-coupling between unlike tensors is not fully appreciated. Our recent study with an advanced Monte Carlo technique (entropic sampling) showed clearly the increasing relevance of this cross term in determining the phase diagram, contravening in some regions of model parameter space, the predictions of mean field theory and standard Monte Carlo simulation results. In this context, we investigated the phase diagrams and the nature of the phases therein, on two trajectories in the parameter space: one is a line in the interior region of biaxial stability believed to be representative of the real systems, and the second is the extensively investigated parabolic path resulting from the London dispersion approximation. In both the cases, we find the destabilizing effect of increased cross-coupling interactions, which invariably result in the formation of local biaxial organizations inhomogeneously distributed. This manifests as a small, but unmistakable, contribution of biaxial order in the uniaxial phase.The free energy profiles computed in the present study as a function of the two dominant order parameters indicate complex landscapes, reflecting the difficulties in the ready realization of the biaxial phase in the laboratory.Comment: 23 pages, 12 figure

Religion and Devotional Ethics in Thiruvaenkadathanthathi

Anthathi literature can be said to be a genre that arose due to the Yaapu form in minor literature. It is said that in Tamil overall 238 Anthathi verses are found.  The Anthathi literature flourished and it helped in memorizing the devotional songs. So the period of Bhakti literature was the period when many Anthathis appeared. Among these, Thiruvaenkadathanthathi which was recited for the blessings of Thirumal, is a special one which is recited in the literary tradition. The purpose of this article is to examine the religious status and devotion recorded in this book

Electronics and Chemistry: Varying Single Molecule Junction Conductance Using Chemical Substituents

We measure the low bias conductance of a series of substituted benzene diamine molecules while breaking a gold point contact in a solution of the molecules. Transport through these substituted benzenes is by means of nonresonant tunneling or superexchange, with the molecular junction conductance depending on the alignment of the metal Fermi level to the closest molecular level. Electron-donating substituents, which drive the occupied molecular orbitals up, increase the junction conductance, while electron-withdrawing substituents have the opposite effect. Thus for the measured series, conductance varies inversely with the calculated ionization potential of the molecules. These results reveal that the occupied states are closest to the gold Fermi energy, indicating that the tunneling transport through these molecules is analogous to hole tunneling through an insulating film.Comment: 14 pages, 4 figure

Purification and characterization of a new cold active lipase, EnL A from Emericella nidulans NFCCI 3643

A mesophilic fungi producing an extracellular cold-active lipase was isolated from the soil samples of palm oil mill effluent dump sites, Pedavegi, West Godavari Dist, A.P. India and was identified as Emericella nidulans. The enzyme was purified by ammonium sulfate fractionation followed by hydrophobic interaction chromatography using phenyl sepharose. The enzyme was 35 fold pure compared to crude with a specific activity of 1494.51 U/mg. SDS PAGE analysis revealed that the protein is monomeric with a MW of ˜54 kDa and zymogram analysis showed that the purified protein was active. Characterization studies revealed that the temperature optimum was at 30°C and an optimum pH of 5. The Km and Vmax values were found to be 0.61 mM and 322.58 mM/min.mg, respectively. Sequencing of the purified protein by MALDI TOF-MS analysis followed by BLAST P analysis indicated that the protein is a putative secretary lipase from E. nidulans. Search of lipase engineering data base (LED) revealed that this protein belongs to a newly introduced super family of Candida antarctica lipase A like and to the homologous family of Aspergillus lipase like.Key words: Cold active lipase, Emericella nidulans, hydrophobic interaction chromatography, Candida antarctica lipase A like