Attenuation Characteristics and Sensitivity Analysis for Coplanar Waveguide

The behaviour of attenuation losses in Coplanar waveguides (CPW) is studied for quasi-planar transmission lines with constant characteristic impedance (Z₀) and resistivity, having different geometry's. This behavior helps in making a suitable choice of the type of structure and its dimensional parameters depending upon the application. Minimization of loss for a chosen substrate thickness, conductivity and impedance is analyzed. Dispersion characteristics of CPW have been plotted for various metallization thicknesses. A sensitivity analysis for effective dielectric constant with respect to various dimensional parameters of CPW is presented.     

Development of biosensor for phenol detection using agarose–guar gum based laccases extracted from Pleurotus ostreatus

Laccases from Pleurotus ostreatus was extracted from the Shaken flask cultures of Pleurotus ostreatus grown at 25°C with continuous agitation (110 rpm.) in baffled 1000 mL Erlenmeyer flasks containing 200 mL medium. The basal GYP medium used for cultures contained 20 g glucose l^?1, 5 g yeast extract l^?1, 5 g peptone from casein l^?1, and 1 g MgSO₄.7H₂O l^?1. The pH was adjusted to 5.0 with H₃PO₄ before sterilization. The kinetics of oxidation reactions catalyzed by laccases was studied using 2,2′‐azino‐bis (3‐ethylbenzthiazoline‐6‐sulphonic acid). The laccases showed lower specific activity and higher activity in nonpolar organic solvents. A biosensor using laccases was constructed for the determination of phenol. The enzyme was extracted from Pleurotus ostreatus and entrapped in agarose–guar gum composite biopolymer matrix. Phenol was determined by direct reduction of biocatalytically liberated quinone species at ?0.1 V versus Ag/AgCl (3M KCl). The response was found to be linear and concentration dependent.It has a shelf life of more than 2 months when stored at 4°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of novel Al(III)-metallopolymer and its application as a non-volatile resistive memristive material

In this study, Al(III)-metallopolymer is synthesized with our previously reported ligand to understand the difference in the interaction of the reported ligand with transition metal ions (Fe(II) and Cr(II) ions) and smaller cationic radius main group metal ion. Al(III)-metallopolymer is thoroughly characterized by different analytical techniques to understand the structure–property relationship. Surface morphological analyses reveal the formation of long nano-fiber strands on the respective substrates. This polymer has shown reversible redox behavior, which is ligand centric as no d-orbitals are available on the central metal ion for the electron push-pull mechanism. Al(III)-metallopolymer is fluorescent active, and it is shown a reversible change in absorption spectrum on the application of the appropriate potential. This ligand-based redox-switching also generates a bistable state when a metal–insulator(thin film of polymer)-metal sandwich device is probed in between ±1 V, and it is stable in the ambient condition to sustain several flip-flop cycles without any degradation for 10³ s as observed from the experimental data. This work enlightens a new metallopolymer with a low value of SET-RESET voltage and a long retention time for the future memristive device, which can operate at very low voltage compared to conventional Si-based memory chips.     

Modulation of Transaminase Activity by Encapsulation in Temperature-Sensitive Poly(N-acryloyl glycinamide) Hydrogels

Smart hydrogels hold much potential for biocatalysis, not only for the immobilization of enzymes, but also for the control of enzyme activity. We investigated upper critical solution temperature-type poly N-acryloyl glycinamide (pNAGA) hydrogels as a smart matrix for the amine transaminase from Bacillus megaterium (BmTA). Physical entrapment of BmTA in pNAGA hydrogels results in high immobilization efficiency (>89 %) and high activity (97 %). The temperature-sensitiveness of pNAGA is preserved upon immobilization of BmTA and shows a gradual deswelling upon temperature reduction. While enzyme activity is mainly controlled by temperature, deactivation tended to be higher for immobilized BmTA (≈62–68 %) than for free BmTA (≈44 %), suggesting a deactivating effect due to deswelling of the pNAGA gel. Although the deactivation in response to hydrogel deswelling is not yet suitable for controlling enzyme activity sufficiently, it is nevertheless a good starting point for further optimization.     

Development of shelf stable pepper based appetizers by response surface methodology (RSM)

The paper deals with three pepper-based appetizers developed in the form of convenient beverage mixes. The optimization of ingredients in the formulations of spiced drink mix, spiced tomato mix and chakota soup mix was achieved using response surface methodology with statistical design software. The active ingredient pepper was 1.5 and 2.8/100 g as black pepper and 9/100 g as white pepper with total pungency (expressed as piperine, g/100 g) of 0.08, 0.155, 0.155 in spiced drink mix, chakota soup mix and spiced tomato mix, respectively. The appetizer mixes packed in paper/Al foil/ polythene (PFP) and polypropylene (PP) pouches were stored at ambient temperature as well as 37 °C. Periodic evaluation (2-months interval) revealed that spice drink mix and spiced tomato mix had a shelf life of 6 months, while it was 8 months for chakota soup mix packed in PFP pouches under ambient conditions (18-33 °C).     

Mechanism of charge recombination and IPCE in ZnO dye‐sensitized solar cells having I−/I and Br−/Br redox couple

The influence of intensity and wavelength variation on the solar cell parameters of two different ZnO‐based liquid state DSSCs named as Cell (A) ZnO/EosinY/LiI and Cell (B) ZnO/EosinY/LiBr was studied. It was found that V_oc and I_sc depend logarithmically and linearly on light flux, respectively, which indicates that light absorption and carrier diffusion do not limit the solar cell efficiency. The data was analyzed to ascertain the charge recombination mechanism between conduction band electrons and the electrolytes. The regeneration of dye due to I⁻/I₃ and Br⁻/Br redox couple was examined by studying the wavelength dependence of IPCE. An estimation of series and shunt resistance is made using two methods: (i) different illumination method (ii) single I–V curve, for the two cells in order to understand the role of the electrolyte in controlling the solar cell parameters. Copyright © 2010 John Wiley & Sons, Ltd.     

Hydration process and crack tendency of concrete based on resistivity and restrained shrinkage crack

Hydration process, crack potential and setting time of concrete grade C30, C40 and C50 were monitored by using a non-contact electrical resistivity apparatus, a novel plastic ring mould and penetration resistance methods, respectively. The results show the highest resistivity of C30 at the early stage until a point when C50 accelerated and overtook the others. It has been experimentally confirmed that the crossing point of C30 and C50 corresponds to the final setting time of C50. From resistivity derivative curve, four different stages were observed upon which the hydration process is classified; these are dissolution, induction, acceleration and deceleration periods. Consequently, restrained shrinkage crack and setting time results demonstrated that C50 set and cracked the earliest. The cracking time of all the samples occurred within a reasonable experimental period thus the novel plastic ring is a convenient method for predicting concrete’s crack potential. The highest inflection time (t _i) obtained from resistivity curve and the final setting time (t _f) were used with crack time (t _c) in coming up with mathematical models for the prediction of concrete’s cracking age for the range of concrete grade considered. Finally, an ANSYS numerical simulation supports the experimental findings in terms of the earliest crack age of C50 and the crack location.     

Single‐Molecule Imaging Reveals that Small Amyloid‐β1–42 Oligomers Interact with the Cellular Prion Protein (PrPC)

Oligomers of the amyloid‐β peptide (Aβ) play a central role in the pathogenesis of Alzheimer’s disease and have been suggested to induce neurotoxicity by binding to a plethora of cell‐surface receptors. However, the heterogeneous mixtures of oligomers of varying sizes and conformations formed by Aβ42 have obscured the nature of the oligomeric species that bind to a given receptor. Here, we have used single‐molecule imaging to characterize Aβ42 oligomers (oAβ42) and to confirm the controversial interaction of oAβ42 with the cellular prion protein (PrP^C) on live neuronal cells. Our results show that, at nanomolar concentrations, oAβ42 interacts with PrP^C and that the species bound to PrP^C are predominantly small oligomers (dimers and trimers). Single‐molecule biophysical studies can thus aid in deciphering the mechanisms that underlie receptor‐mediated oAβ‐induced neurotoxicity, and ultimately facilitate the discovery of novel inhibitors of these pathways.     

Filter‐Through Method of Making Highly Efficient Polymer‐Clay Nanocomposite Membranes

Electrospun filter with hierarchical pore structure and variable pore diameter is used for the first time in making a flexible, strong, and high gas‐barrier membrane. A versatile, technical, benign processing method for the fabrication of highly filled (>25 wt%) efficient gas‐barrier polymer membrane with perfectly aligned synthetic high‐aspect ratio layered silicate (clay) of variable and considerable thickness (up to 5 µm) is presented. This process combines advantageous features of an electrospun substrate like high porosity, variable pore size (typically <5 µm), thermoplasticity and of an aqueous suspension of a synthetic clay consisting of single 1 nm thick layers with a huge median lateral extension (>10 µm) in a layered structure. By simple and fast filtration, a gas‐barrier self‐assembled layer of variable and appropriate thickness is obtained on a mechanically stable thermoplastic electrospun filter support that subsequently can be laminated adhesively or via hot pressing, even in a multilayer structure, if required. The resulting composite membranes are flexible, strong, transparent, and show enhanced gas‐barrier properties.