Dielectric properties of solution-grown-undoped and acrylic-acid-doped ethyl cellulose

Dielectric capacities and losses were measured, in the temperature (50–170°C) and frequency (01–100 kHz range), for undoped and acrylic acid (AA) doped ethyl cellulose (EC) films (thickness about 20 μm) with progressive increase in the concentration of dopant in the polymer matrix. The variation of capacity with temperature is attributed to thermal expansion in the lower temperature region to the orientation of dipolar molecules in the neighbourhood of glass transition temperature (T _g) and random thermal motion of molecules aboveT _g. The dielectric losses exhibit a broad peak. Doping with AA is found to affect the magnitude and position of the peak. AA is found to have a two-fold action. Firstly, it enhances the chain mobility and secondly, it increases the dielectric loss by forming charge transfer complexes.     

Synthesis and characterization of catalysts produced from paper mill sludge: I. Determination of NOx removal capability

Characteristics and catalytic properties of a series of carbon-based catalysts (CBCs) produced from paper mill sludge were evaluated. The major processes involved in the production of the catalysts were chemical activation, impregnation, pyrolysis, and post pyrolysis rinsing. The porous structure, catalytic activity and thermostability of the catalysts were tailored during the production stage by introducing hetero-atoms (zinc chloride, and ferric nitrate) in the carbon structure. Characterization of the produced CBCs included determination of the surface area, pore size, and pore size distribution (PSD) from standard N₂-adsorption isotherm data. The extent of graphitization and the presence of metal crystals were identified from X-ray diffraction (XRD). The limit of the catalyst gasification was estimated from thermogravimetric analysis (TGA) conducted in an oxidized environment. The NO_x reduction capability of the produced catalysts was evaluated in the presence of carbon monoxide using a fixed bed reactor. The reaction temperature ranged from 300 to 500°C. It was shown that paper mill sludge is an excellent precursor for the production of CBCs with NO_x removal capability of 66–94%. The catalytic capability of the produced CBCs varied according to the method of production, catalyst surface properties (surface area, pore structure, PSD), metal composition and reaction temperature. The highest NO_x removal capacity was observed for the catalytic reactions carried out at 400°C. The mesoporous catalyst produced with a Zn:Fe molar ratio of 1:0.5 exhibited the maximum NO_x removal catalytic activity of 94%.     

Macroporous interpenetrating cryogel network of poly(acrylonitrile) and gelatin for biomedical applications

Cryogels are supermacroporous gel network formed by cryogelation of appropriate monomers or polymeric precursors at subzero temperature. The beneficial feature of this system is a unique combination of high porosity with adequate mechanical strength and osmotic stability, due to which they are being envisaged as potential scaffold material for various biomedical applications. One of the important aspect of cryogel is simple approach by which they can be synthesized and use of aqueous solvent for their synthesis which make them suitable for different biological applications. Various modifications of the cryogels have been sought which involves coupling of various ligands to its surfaces, grafting of polymer chain to cryogel surface or interpenetrating networks of two or more polymers to form a cryogel which provides diversity of its applications. In the following work we have synthesized full interpenetrating network of polyacrylonitrile (PAN)-gelatin with varied gelatin concentration. The PAN-gelatin cryogel interpenetrating network is macroporous in nature and has high percentage swelling equilibrium in the range of 862-1,200 with a flow rate greater than 10 ml/min, which characterizes the interconnectivity of pores and convective flow within the network. PAN-gelatin interpenetrating cryogel network has good mechanical stability as determined by Young's modulus which varies from 123 kPa to 819 kPa depending upon the polymer concentration. Moreover they are shown to be biocompatible and support cell growth within the scaffolds.     

Studies of Texture Gradients in the Localized Necking Band of AA5754 by EBSD and Microstructure-Based Finite Element Modeling

This work aims to understand the texture distribution in the localized necking band formed during uni-axial tension of AA5754 using an edge-constrained, plane strain post-necking FE model. The model domain is a long cross section of the band. Initial grain structure is mapped into the mesh from EBSD data using a modified Voroni-cell interpolation and considering pre-straining prior to localized necking. The material points in grains are assumed to exhibit isotropic elastoplastic behavior but have a relative strength in terms of Taylor factors which are updated by a Taylor-Bishop-Hill model. The predicted textures and gradients within the localized necking band correlate well with experimental measurements where large rigid body rotation and lattice spin are experienced due to geometric constraints and excessive deformation in the band.     

Adsorptive removal of Erythrosine dye onto activated low cost de-oiled mustard

The present paper is aimed to investigate and develop cheap adsorption methods for colour removal from wastewater using waste material de-oiled mustard as adsorbent. De-oiled mustard, a biosorbent, was successfully utilized for removing a water-soluble xanthene dye, Erythrosine from wastewater. Kinetic studies of adsorption of Erythrosine at de-oiled mustard were carried out at 30 degrees C, using aqueous solutions with 5 x 10(-5)M concentration of Erythrosine. The adsorption process followed a pseudo-first order model. The equilibrium process can be well described by both Freundlich and Langmuir models, at 30, 40 and 50 degrees C. Free energy of adsorption (DeltaG degrees ), enthalpy (DeltaH degrees ), and entropy (DeltaS degrees ) changes were calculated to predict the nature of adsorption. The estimated values for DeltaG degrees were -12.81 x 10(3) and -12.57 x 10(3) over activated carbon and activated de-oiled mustard at 203 K (30 degrees C), indicate toward a spontaneous process. The positive value for DeltaH degrees indicates that the adsorption of Erythrosine dye to de-oiled mustard is an endothermic process.     

Edematogenic and myotoxic activities of the duvernoy’s gland secretion of <i>Philodryas olfersii</i> from the north-east region of Argentina

Philodryas olfersii is found in South America, from Amazonas to Patagonia. It is important to characterize the venom of P. olfersii, who inhabits the North-East region of Argentina, since snake venoms are known to exhibit considerable variability in composition and biological activities. In this work, mice weighing 18-20 g (n = 4 for each experimental group) were used. For the edematogenic activity mice were injected s.c. in the right foot pad with 50 µl of solutions containing different amounts of venom, whereas the left foot pad was injected with 50 µl of PBS. Two hours after injection mice were killed by cervical dislocation and both feet were cut off and weighed individually. For the myotoxic activity mice were injected i.m. with 100 µl of solutions containing 40 µg of venom. Blood samples were extracted after 1, 3, 6, 8, 10, 12, 14, 16 and 24 h of venom injection to determinate serum CPK activity and mice were sacrificed at the same time intervals to obtain the inoculated gastrocnemius muscle. They were fixed with Bouin solution and stained with Hematoxylin-Eosin. Results showed that P. olfersii venom exhibits a high edematogenic activity (MED = 0.31 µg) and a moderate myotoxic activity. Myonecrosis reached its highest level after 12 h of venom injection as shown by plasmatic CPK levels (5,401 ± 330 IU/l) and microscopic assay. It demonstrates the potential toxicity of the venom of P. olfersii, who inhabits the North-East region of Argentina. It also reinforces the original warning concerning the potential danger of bites by colubrids.     

EVALUATION OF RHEOLOGICAL PROPERTIES OF MEDIUM FOR AFM PROCESS

Abrasive Flow Machining (AFM) is a new non-traditional machining process used to deburr, radius, polish, and remove recast layer of components used in a wide range of applications. Material removal in AFM takes place by flowing medium (i.e. carrier/or putty mixed with abrasive particles), across the surface to be machined. The medium is the key element in the process because of its ability to precisely abrade the selected areas along its flow path. From the literature review, it is found that there is a need to study how to evaluate rheological properties of the medium in general, and viscosity in particular. Viscosity of the medium has significant effects on the AFM process performance.

In the present work, effects of concentration and mesh size of abrasive particles, and temperature of medium on the medium viscosity have been studied. To determine the viscosity of the abrasive medium, a viscometer has been designed and fabricated based on the principle of capillary viscometry. Experiments have been conducted at different abrasive concentrations and mesh sizes, and medium temperatures. It is observed from the experiments that the viscosity of the medium increases with the abrasive concentration and decreases with the abrasive mesh size and medium temperature. Theoretical values obtained from mathematical model, and experimental results are compared. The results of viscosity are correlated with the process performance parameters, i.e. material removal and surface roughness. It is observed that there is an increase in material removal and decrease in surface roughness value as viscosity of the medium increases.     

Characterisation of molecular beam epitaxy-grown InGaAs multilayer structures using photoluminescence

Molecular beam epitaxy-grown InGaAs/GaAs multilayer structures were used to characterise for their indium composition, quantum well widths and energy levels in quantum wells employing low-temperature photoluminescence spectroscopy. The effect of surface segregation and thermal desorption of indium atoms in these structures which changes the intended square well and barrier profiles is demonstrated. These shape changes in the well and barrier must be taken into account to correctly predict the quantum well energy level positions and hence the indium composition and the quantum well width.     

Enhanced photoluminescence from free-standing microstructures fabricated on MBE grown PbSe–PbSrSe MQW structure

Fabrication of microrods from multi-quantum well (MQW) PbSe–PbSrSe structure grown in molecular beam epitaxy (MBE) followed by its morphological as well as optical characterizations are described. Pulsed PL intensity is increased by 64 times per unit surface area from a free-standing MQW microrod mounted on copper heat sink compared with the bulk sample. Enhancement in side emission power due to the higher optical confinement effect during pulsed photoluminescence (PL) from MQW semiconductor microtube inserted in hollow quartz optical fiber signifies that these microstructures are robust in nature and crucial contenders for portable mid-infrared optoelectronic devices to be used in the field of industrial trace-gas sensing.