Morphology Development in Polymer Fibers undergoing Solvent/Non-solvent Exchange

Summary: The solvent/non-solvent interchange across the fiber surface affects the morphology of the fiber in various ways. In this paper, simulations have been performed to elucidate the diverse morphologies obtained during spinning of polymer fibers under the presence of a non-solvent. The proposed model deals with a ternary system derived from Cahn-Hilliard equation, alternatively known as Time Dependent Ginzburg Landau-TDGL model B equation, involving the spatio-temporal evolution of concentration order parameter. Depending on the coexistence region of the ternary phase diagram, various fiber morphologies including concentric bands, internal microfibrillar structures, and porous structures were discerned. It may be inferred that the formation of the aforementioned diverse morphologies is a direct consequence of the initial conditions of the starting mixtures in a manner governed by the relative rates of solvent/non-solvent exchange and the dynamics of phase separation.     

Crystal-liquid crystal binary phase diagrams

We propose a new theoretical scheme for the binary phase diagrams of crystal-liquid crystal mixtures by a combination of a phase field model of solidification, the Flory-Huggins theory for liquid-liquid mixing and Maier-Saupe-McMillan (FH-MSM) model for nematic and smectic liquid crystal orderings. The phase field theory describes the crystal phase transition of anisotropic organic crystal and/or side chain liquid crystalline polymer crystals while the FH-MSM model explains isotropic, nematic and smectic-A phase transitions. Self-consistent calculations reveal several possible phase diagram topologies of the binary crystal-liquid crystal mixtures. The calculated phase diagrams were found to accord well to the reported experimental results.     

AC susceptibility study in the single-phase Bi-2223 system

We have found that the composition, Bi_1.2Pb_0.33Sr_1.54Ca_2.06Cu₃O_y which is comparatively poorer in Bi and Sr with respect to 2:2:2:3, a single-phase 110 K superconductor can be obtained. Such polycrystalline samples have been synthesized by two different methods. The synthesized samples have been characterized by their X-ray diffraction patterns and temperature dependence of DC electrical resistivity and AC susceptibility down to 20 K have been carried out. The samples have been identified as having single phase with a sharp transition. The results of their AC susceptibility have been analysed using Clems critical state model. The effective volume fraction of the grains and the temperature dependence of the intergranular current density have been estimated.     

An automated simultaneous measurement of thickness and wave velocity by ultrasound

The measurement of wave velocity in a sample requires an accurate determination of the sample thickness at the points of interrogation. The theory of an automated technique is presented. In its application, the thickness of the sample is first calculated by the knowledge of the wave velocity in the immersion fluid. This thickness is then used to calculate the wave velocity in the sample. The results of the application of the technique to isotropic and anisotropic materials are presented.     

Harnessing the Effect of pH on Lipid Production in Batch Cultures of <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis> SKY7

The objective of this research was to investigate the kinetics of lipid production by Yarrowia lipolytica SKY7 in the crude glycerol-supplemented media with and without the control of pH. Lipid and citric acid production were improved with the pH control condition. There was no significant difference observed in the biomass concentration with or without the pH control. In the pH-controlled experiments, the biomass and lipid concentration reached 18 and 7.78 g/L, (45.5% w/w), respectively, with lipid yield (Yp/s) of 0.179 g/g at 60 h of fermentation. The lipid production was directly correlated with growth and the process was defined as growth associated. After 60 h of fermentation, the lipid degradation was noticed in the pH-controlled reactor whereas it occurred after 84 h in the pH-uncontrolled reactor. Apart from lipid, citric acid was produced as the major extracellular product in both fermentations but the much lower concentration in uncontrolled pH. Based on the experimental results, it is evident that controlling the pH will enhance the lipid production by 15% compared to pH-uncontrolled fermentation.     

Nondestructive evaluation of helicopter rotor blades using guided Lamb modes

This paper presents an application for turning and direct modes in a complex composite laminate structure. The propagation and interaction of turning modes and fundamental Lamb modes are investigated in the skin, spar and web sections of a helicopter rotor blade. Finite element models were used to understand the various mode conversions at geometric discontinuities such as web-spar joints. Experimental investigation was carried out with the help of air coupled ultrasonic transducers. The turning and direct modes were confirmed with the help of particle displacements and velocities. Experimental B-Scans were performed on damaged and undamaged samples for qualitative and quantitative assessment of the structure. A strong correlation between the numerical and experimental results was observed and reported.     

Cu-mediated 1,3-dipolar cycloaddition of azomethine ylides with dipolarophiles: a faster access to spirooxindoles of potential pharmacological interest

CuI facilitated three-component reaction of isatin derivatives, l-proline and terminal alkynes containing an amide or ester functional group. The multi-component reaction (MCR) afforded a faster and practical synthesis of spirooxindole derivatives. A range of novel spirooxindoles were synthesized by using this straightforward and one-pot efficient methodology. A representative compound showed significant inhibition of PDE4B enzyme in vitro and good interactions with this protein in silico.     

Synthesis and Characterization of Cardo Polysulfonates of 1,1′-Bis(4-Hydroxy Phenyl)Cyclohexane with 1,3-Benzene and 2,4-Toluene Disulfonyl Chlorides

Abstract

Cardo polysulfonates (PSBCB and PSBCT) of 1,1′-bis(4-hydroxy phenyl)cyclohexane with benzene-1,3 and toluene-2,4-disulfonyl chlorides have been synthesized by interfacial polycondensation of 1,1′-bis(4-hydroxy phenyl)cyclohexane (0.005 mol) with benzene-1,3/toluene-2,4-disulfonyl chlorides (0.005 mol) using water-chloroform (4:1, v/v) as interphase, alkali (0.015 mol) as acid acceptor, and cetyl trimethyl ammonium bromide (0.125 g) as emulsifier at 0°C for 3 hours. The structures of the polymers were supported by IR and NMR spectral data. The PSBCT was fractionated into several fractions by using 1,2-dichloroethane as solvent and n-butanol as precipitant. The fractions were characterized by GPC and viscometry in different solvents at four different temperatures. Viscosity studies showed that the PSBCT is flexible in solutions and has a specific solvent effect. PSBCB and PSBCT have good biological activity against E. coli and S. citrus organisms, and they possess excellent hydrolytic stability toward acids and alkalis.