Castor oil-based hyperbranched polyurethanes as advanced surface coating materials

21st Century is treated as the century for highly branched macromolecules, because of their unique structural architecture and outstanding performance characteristics, in the field of polymer science. In the present study, castor oil-based two hyperbranched polyurethanes (HBPUs) were synthesized via A₂ + B₃ approach using castor oil or monoglyceride of the castor oil as the hydroxyl containing B₃ reactant and toluene diisocyanate (TDI) as an A₂ reactant along with 1,4-butane diol (BD) as the chain extender and poly(?-caprolactone) diol (PCL) as a macroglycol. The adopted ‘high dilution and slow addition’ technique offers hyperbranched polymers with high yield and good solubility in most of the polar aprotic solvents. Fourier transforms infra-red spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analyses confirmed the chemical structure of synthesized polymers, while wide angle X-ray diffraction (WXRD) and scanning electron microscope (SEM) resulted the insight of their physical structures. The degree of branching was calculated from ¹H NMR and found to be 0.57 for castor oil based hyperbranched polyurethane (CHBPU), while it was 0.8 for monoglyceride based hyperbranched polyurethane (MHBPU). The studies showed that MHBPU and CHBPU exhibited tensile strength 11 MPa and 7 MPa, elongation at break 695% and 791%, scratch hardness 5 kg and 4.5 kg, gloss 84 and 72, respectively. Thermal properties like thermo stability, melting point, enthalpy, degree of crystallinity and glass transition temperature (T_g); and chemical resistance in different chemical media were found to be almost equivalent for both the polyurethanes. The measurements of dielectric constant and lost factor indicated that both the HBPUs behave as dielectric materials. Thus the synthesized HBPUs have the potential to be used as advanced surface coating materials.     

Bioprocess Scale-up for Acetohydroxamic Acid Production by Hyperactive Acyltransferase of Immobilized Rhodococcus Pyridinivorans

Catalysis Letters - In this study, Rhodococcus pyridinivorans cells containing hyperactive acyltransferase was immobilized on various macromolecules based-polymeric matrices and used to improve...     

Antibacterial Activity of the Sponge Ircinia Ramosa: Importance of its Surface-Associated Bacteria

Variations in the antibacterial activity of the sponge Ircinia ramosa were evaluated during two collection periods (January and May) against vicinity fouling bacteria (VFB) and sponge surface-associated bacteria (SAB). The density of fouling bacteria in the water column, as well as epibacterial abundance on the sponge surface, was enumerated during both collections, and both increased in the warmer month of May. The extracts obtained from SAB were also tested for their role in antibacterial activity of the host. Sponge-associated bacteria are capable of producing antibacterial metabolites. The antibacterial activity that originated from polar fractions in the cooler month of January shifted towards the nonpolar fractions in May. Nonpolar fractions were more useful for the sponge when threatened with increased bacterial density. Thus, the chemical nature and production of antibacterial compounds produced by sponge or its associated bacteria appears to be governed by the environment. An inverse relationship was observed between the epibacterial abundance over the sponge surface in nature and the antibacterial activity displayed by the sponge extracts in laboratory bioassays. This investigation reveals the importance of collection period as well as the role of associated bacteria in the evaluation of antibacterial activity.     

Sequence,Chromatin and Evolution of Satellite DNA

Satellite DNA consists of abundant tandem repeats that play important roles in cellular processes, including chromosome segregation, genome organization and chromosome end protection. Most satellite DNA repeat units are either of nucleosomal length or 5–10 bp long and occupy centromeric, pericentromeric or telomeric regions. Due to high repetitiveness, satellite DNA sequences have largely been absent from genome assemblies. Although few conserved satellite-specific sequence motifs have been identified, DNA curvature, dyad symmetries and inverted repeats are features of various satellite DNAs in several organisms. Satellite DNA sequences are either embedded in highly compact gene-poor heterochromatin or specialized chromatin that is distinct from euchromatin. Nevertheless, some satellite DNAs are transcribed into non-coding RNAs that may play important roles in satellite DNA function. Intriguingly, satellite DNAs are among the most rapidly evolving genomic elements, such that a large fraction is species-specific in most organisms. Here we describe the different classes of satellite DNA sequences, their satellite-specific chromatin features, and how these features may contribute to satellite DNA biology and evolution. We also discuss how the evolution of functional satellite DNA classes may contribute to speciation in plants and animals.     

Detection of local community structures in complex dynamic networks with random walks

Identification of interaction patterns in complex networks via community structures has gathered a lot of attention in recent research studies. Local community structures provide a better measure to understand and visualise the nature of interaction when the global knowledge of networks is unknown. Recent research on local community structures, however, lacks the feature to adjust itself in the dynamic networks and heavily depends on the source vertex position. In this study the authors propose a novel approach to identify local communities based on iterative agglomeration and local optimisation. The proposed solution has two significant improvements: (i) in each iteration, agglomeration strengthens the local community measure by selecting the best possible set of vertices, and (ii) the proposed vertex and community rank criterion are suitable for the dynamic networks where the interactions among vertices may change over time. In order to evaluate the proposed algorithm, extensive experiments and benchmarking on computer generated networks as well as real-world social and biological networks have been conducted. The experiment results reflect that the proposed algorithm can identify local communities, irrespective of the source vertex position, with more than 92% accuracy in the synthetic as well as in the real-world networks.     

Dimensional analysis for planetary mixer: Mixing time and Reynolds numbers

Mixing time number is a convenient parameter to characterize mixing performance of stirred tanks. This dimensionless number is now well established for agitated vessels equipped with vertically and centrally mounted impeller for Newtonian as well as for non-Newtonian fluids. To our knowledge, there is more ambiguity concerning its definition for planetary mixers especially when they have dual motion (around two perpendicular axes) to achieve homogenization. In this study, dimensional analysis of mixing time and reliability of the modified Reynolds and mixing time numbers are proposed for such a planetary mixer particularly named as TRIAXE^® system. These two numbers are based on the maximum tip speed of mixer as the characteristic velocity. Modified dimensionless numbers are consistent with the definition of conventional Reynolds and mixing numbers (when only one revolving motion around the vertical axis of the mixing device occurs in the vessel).Mixing time experiments with TRIAXE^® mixer for highly viscous Newtonian fluids showed that the proposed modified Reynolds and mixing time numbers succeeded to obtain a unique mixing curve irrespective of the different speed ratio chosens. This agreement proves that the proposed modified dimensionless numbers can be well adapted for engineering purposes and they can be used to compare the mixing performance of planetary mixers.     

Influence of Liquid Phase Additives on Structural and Sintering Behaviour of Samarium Modified Lead Titanate Ceramics

The combination of metal oxides Bi₂O₃:Li₂O in a ratio 89:11 gives a eutectic with a melting point of ～680°C. Such a low melting point oxide combination creates a working liquid phase at a highly favorable temperature for use as a densification aid. A liquid—phase sintering aid incorporating Bi₂O₃ and Li₂O is presented which demonstrates not only a reduction in the required sintering temperature but also shows relatively higher ‘c/a’ ratio (tetragonality) of PbTiO₃ ceramics with no fragility of the samples. Detailed dilatometric investigations have been performed in order to study the dominant shrinkage mechanism in the present system. Besides acting as a liquid phase fluxing agent, Bi₂O₃/Li₂O also behave as Curie shifter, which decreases Curie temperature in lead titanate system. The Curie temperature has also been verified from the thermal expansion behavior of sintered specimens. The value of dielectric constant increases after poling which may be due to the dominance of 180° domain wall over 90°.     

Low temperature coefficient and low line sensitivity subthreshold curvature-compensated voltage reference

A high-order curvature-compensated subthreshold voltage reference is proposed in this paper. The proposed curvature-compensated voltage reference consists of two supply-independent first-order voltage references and a curvature compensation circuit. The supply-independent first-order voltage reference uses a negative feedback loop which improves the line sensitivity and eliminates the demand of operational amplifier, whereas the curvature compensation circuit provides high-order temperature-compensated output reference voltage. The proposed curvature-compensated voltage reference provides an output reference voltage of 118.54 mV with a temperature coefficient of 21.5 ppm/°C over a wide temperature range of −60°C to 120°C . The power supply rejection ratio and line sensitivity are observed as −68.64 dB (for the frequency range of 1 Hz to 100 Hz) and 0.035%/V (for the supply voltage varies from 0.85 V to 2.5 V), respectively. The values of output noise at the frequencies of 1 kHz and 10 kHz without using any capacitive filter are obtained as 179.13 nV/ √ Hz and 123.87 nV/ √ Hz , respectively.     

Combined economic and emission dispatch problems using biogeography-based optimization

In this work, biogeography-based optimization (BBO) is presented for solving different constrained economic load dispatch (ELD) problems combined with economic emission aspects in power system. Nonlinear characteristics of generators like valve point discontinuities, ramp rate limits and prohibited operating zones are considered in the problem. The simulation results show that the proposed BBO algorithm based solutions prove to be the best near-global optimal as compared to the solutions based on Newton–Raphson, Tabu search, genetic algorithm (GA), non-dominated sorting genetic algorithm (NSGA), fuzzy logic controlled genetic algorithm (FCGA), particle swarm optimization (PSO) and differential evolution (DE).