Electrical properties of Poly(ethylene glycol dimethacrylate-n-vinyl imidazole)/Single Walled Carbon Nanotubes/n-Si Schottky diodes formed by surface polymerization of Single Walled Carbon Nanotubes

In this paper we report the electrical characteristics of the Schottky diodes formed by surface polymerization of the Poly(ethylene glycol dimethacrylate-n-vinyl imidazole)/Single Walled Carbon Nanotubes on n-Si. The Single Walled Carbon Nanotubes were synthesized by CVD method. The main electrical properties of the Poly(ethylene glycol dimethacrylate-n-vinyl imidazole)/Single Walled Carbon Nanotubes/n-Si have been investigated through the barrier heights, the ideality factors and the impurity density distribution, by using current-voltage and reverse bias capacitance voltage characteristics. Electrical measurements were carried out at room temperature. Poly(ethylene glycol dimethacrylate-n-vinyl imidazole)/Single Walled Carbon Nanotubes/n-Si Schottky diode current-voltage characteristics display low reverse-bias leakage currents and average barrier heights of 0.61 ± 0.02 eV and 0.72 ± 0.02 eV obtained from both current-voltage and capacitance-voltage measurements at room temperature, respectively.     

The circuit realization of Mexican Hat wavelet function

A wavelet network circuit implementation for Mexican Hat mother wavelet has been proposed for nonlinear function approximation which can also be used for the realization of the algebraic nonlinear components. The Mexican Hat mother wavelet function has been implemented with discrete circuit components and it has been observed that the experimental waveform obtained from the realized circuit is approximately same as the Spice simulation of the original function. The circuit simulations of exemplar functions implemented in Spice are also given.     

Hydrogen-dependent denitrification in an alternating anoxic-aerobic SBR membrane bioreactor.

A novel hydrogenotrophic denitrification system, which consisted of a sequencing batch membrane bioreactor, was evaluated for simultaneous removal of nitrate and soluble microbial products (SMP) from a synthetic groundwater feed. A hollow fiber membrane diffuser was used for bubble-less diffusion of hydrogen into the bioreactor under anoxic condition followed by aerobic SMP removal and biomass filtration. During the anoxic period, the nitrate loading of 0.328 kg N m(-3) d(-1) was completely denitrified to below detectable levels. A denitrification rate of 0.8 kg N m(-3) d(-1) was obtained at steady state biomass concentrations of 1,162 mg I(-1). During the aerobic period when biomass filtration was performed, 81% of SMP produced within the anoxic phase was retained by the membrane, 9% was biologically removed, 5% was passed through the membrane and 5% was discharged during the wasting of mixed liquor. The aerobic cycle was instrumental as it allowed for effective biomass filtration via membrane scouring and assisted in further reduction of effluent organic matter.     

ION EXCHANGE PROPERTIES OF BiO(NO3) 0.5H2O TOWARDS FLUORIDE IONS

ABSTRACT

We studied the ion exchange behavior of the inorganic anion exchanger BiO(NO₃)0.5H₂O with regard to fluoride ions. The ion exchange reaction was rapid at pH 1, 6.6, and 12. The mechanisms of ion exchange reactions at pH 1 and pH 2-12 were studied in a solution with fluoride ions excess to BiO(NO₃)0.5H₂O. A mixture of the β-phase and an unknown phase was produced in the solution at pH 1. BiOF was produced at pH 2-12. Fluoride ions did not react at pH 13, due to the decomposition of BiO(NO₃) 0.5H₂O at pH 13 to yield Bi₂O₃ (major) and Bi₂O₂CO₃ (minor). The structure of the reaction products depended on the solution pH, mole ratios of BiO(NO₃)0.5H₂O to F’, and the reaction time. We observed that BiO(NO₃)0.5H₂O is capable of removing 99% of the fluoride ions from the solution at pH 1-12 under optimal conditions. The ion exchange reaction of BiO(NO₃)0.5H₂O with fluoride ions was studied under the co-existence of both Cl and Br^?at pH 1, 6.6, 12, and 13. The order of decreasing affinity was found to be (Br^?, Cl^?)> F^?. The reaction product was not a simple mixture of BiOCl, BiOBr, and bismuth oxide fluorides, but an unknown compound.     

Ethinylestradiol removal in a conventional and a simultaneous nitrification-denitrification membrane bioreactor

The removal of a synthetic estrogen 17α-ethinylestradiol (EE2) was investigated in submerged membrane bioreactors (MBRs) with simultaneous nitrification-denitrification (SND) and conventional nitrification. The influent EE2 concentration was 500 ng/L as EE2. Using a yeast estrogen screen test, the conventional-MBR (C-MBR) and SND MBR (SND-MBR) removed 57 and 58% of the estrogenic activity (EA) respectively; there was no significant difference in their removal efficiencies. Biodegradation was the dominant removal mechanism for both reactors with K(BIO) coefficients of 1.5 ± 0.6 and 1.6 ± 0.4 day(-1) for the C-MBR and the SND-MBR respectively. Sorption to solid particles removed approximately 1% of influent EA in each reactor; the particle partitioning coefficient, K(D), was calculated to be 0.21 ± 0.07 L/(g MLSS) for the C-MBR and 0.27 ± 0.1 L/(g MLSS) for the SND-MBR. These findings suggest that conditions favoring SND in MBRs have no significant impact on EA reduction.     

Production and characterization of poly(ethylene glycol dimethacrylate-styrene-glycidyl methacrylate) microbeads

Nonswellable and swellable poly(ethyleneglycol dimethacrylate)-based microbeads that could react directly with the biological molecules were produced by a suspension polymerization procedure. For this purpose, ethyleneglycol dimethacrylate (EGDMA) was copolymerized with glycidyl methacrylate (GMA) in an aqueous suspension medium. Benzoyl peroxide and poly(vinyl alcohol) were used as the initiator and the stabilizer, respectively. The copolymerization provided nonswellable, tranparent, and spherical copolymer microbeads in the size range of 100–300 μm. On the other hand, swellable copolymer microbeads in the aqueous medium were obtained by using toluene as a diluent in the same copolymerization recipe. In a separate group of polymerizations, styrene (St) monomer was also included within the monomer phase to regulate the hydrophobicity of resulting microbeads. Nonswellable and swellable poly-(EGDMA-St-GMA) microbeads were obtained by changing the type and concentration of the ingredients within the monomer phase. The effects of glycidyl methacrylate, styrene, and toluene concentrations on the microbead yield, the average size, and the swellability of microbeads were investigated. In the second part of the study, the interaction of produced microbeads with a selected enzyme (i.e., chymotrypsin) was investigated. The most stable chymotrypsin immobilization was achieved with the swellable poly(EGDMA)-based microbeads including styrene. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1319–1334, 1998     

Human serum albumin (HSA) adsorption with chitosan microspheres

In this study, chitosan microspheres were prepared and characterized for adsorption of human serum albumin (HSA) as affinity sorbent. The chitosan microspheres were obtained with a “suspension crosslinking technique” in the size range of 30–700 μm by using a crosslinker, i.e., glutaraldehyde. The chitosan microspheres used in HSA adsorption studies were having the average size of 170 ± 81 μm. Adsorption medium pH and the initial HSA concentration in the adsorption medium were changed as 4.0–7.0 and 0.5–2.0 mg HSA/mL, respectively, to investigate the HSA adsorption capacity of chitosan microspheres. Maximum HSA adsorption (i.e., 11.35 mg HSA/g chitosan microspheres) was obtained at pH 5.0 and 1.5 mg HSA/mL of the initial HSA concentration in the adsorption medium was obtained as the saturation value for HSA adsorption. A very common dye ligand, i.e., Cibacron Blue F3GA was attached to the chitosan microspheres to increase the HSA adsorption capacity. Actually, the HSA adsorption capacity was increased up to 15.35 mg HSA/g chitosan microspheres in the case of Cibacron Blue F3GA attached to chitosan microspheres used. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3035–3039, 2002     

Evolution equations for nonlinear waves in a tapered elastic tube filled with a viscous fluid

In this work, employing the reductive perturbation method and treating the arteries as a tapered, thin walled, long and circularly conical prestressed elastic tube, the propagation of weakly nonlinear waves is investigated in such a fluid-filled elastic tube. By considering the blood as an incompressible viscous fluid, depending on the viscosity and perturbation parameters we obtained various evolution equations as the extended Korteweg-de Vries (KdV), extended KdV Burgers and extended perturbed KdV equations. Progressive wave solutions to these evolution equations are obtained and it is observed that the wave speeds increase with the distance for negative tapering while they decrease for positive tapering.     

Effects of ochratoxin A on micronucleus frequency in human lymphocytes

Ochratoxin A (OTA), a nephrotoxic and carcinogenic mycotoxin, was investigated to examine its potency to induce micronuclei (MN) in cultured human lymphocytes. Lymphocyte cultures were treated for the last 48 h with OTA at concentrations of 25 microM, 10 microM, 1 microM, 100 nM, 10 nM, 1 nM, and 100 microM and absolute ethanol. At the highest concentration, OTA was found to induce MN in cytokinesis-blocked lymphocytes (p < 0.05). The 25 microM OTA concentration also led to a clear decrease in the percentage of binucleated cells, probably due to cytotoxicity. OTA at the other concentrations tested did not induce MN frequency. These results indicate that a high concentration of OTA is genotoxic in cultured human lymphocytes.