Nanobiosensor design utilizing a periplasmic E. coli receptor protein immobilized within Au/polycarbonate nanopores

A new type of nanopore sensor design is reported for a reagent-less electrochemical biosensor with no analyte "tagging" by fluorescent molecules, nanoparticles, or other species. This sensor design involves immobilization within Au-coated nanopores of bacterial periplasmic binding proteins (bPBP), which undergo a wide-amplitude, hinge-twist motion upon ligand binding. Ligand binding thus triggers a reduction in the effective thickness of the immobilized protein film, which is detected as an increase in electrolyte conductivity (decrease in impedance) through the nanopores. This new sensor design is demonstrated for glucose detection using a cysteine-tagged mutant (GGR Q26C) of the galactose/glucose receptor (GGR) protein from the bPBP family. The GGR Q26C protein is immobilized onto Au nanoislands that are deposited within the pores of commercially available nanoporous polycarbonate membranes.     

Magnetic force microscopy of nano-size magnetic domain ordering in heavy ion irradiated fullerene films

In the present work, magnetic force microscopy is employed to investigate the magnetic ordering in ion irradiated fullerene films. It is observed that magnetic domain size is approximately 100-200 nm and magnetic signal is stronger at the domain boundaries. Magnetic signal arise in irradiated films is confirmed by magnetic measurements using a superconducting quantum interference device which increases with the ion fluence. The induced magnetism is possibly due to structural defects in the amorphous carbon phase formed by ion irradiation.     

Stimulated coherent Smith-Purcell radiation from a metallic grating

A relativistic electron beam with velocity ν_bz passing over a metallic grating, with deep periodic depressions of wavenumber k₀z, excites a slow wave (ω, k_z) via Cerenkov interaction, ω=(k_z+k₀)ν_b. The beam bunches induce currents in the fins of the grating that act as a phased radiating dipole array, thereby generating coherent radiation at a wavelength λ=(2π/k₀l)(c/ν_b-sin&thetas;) where l is an integer and &thetas; is the angle of emission measured from the normal of the grating. The current threshold for the instability and radiation power scaling with beam current are discussed     

3D MHD cross flow over an exponential stretching porous surface

The present study aims to investigate the effects of thermal‐diffusion and diffusion‐thermo onan magnetohydrodynamic convective flow of viscous fluids over an exponentially stretching sheet. Thermal radiation effects are also considered in the study. This analysis is carried out in three dimensions and a similarity transformation is adopted to get a set of ordinary differential equations from a set of partial differential equations. And the Fourth‐order Runge‐Kutta method and shooting technique along with the secant method are employed to find out an iterative solution. We also analyze here the influence of the variable magnetic field, nonuniform permeability and variable chemical reaction on the fluid flow. The impact of various pertinent parameters of interest has extensively been explored through graphs and tables. The major findings of the present study are that resistive Lorentz force diminishes the fluid velocity and uplifts the thermal as well as concentration fields. Inclusion of porous matrix improves the viscous drag force which in turn augments wall shear stresses and peters out the heat and mass transfer rates from the sheet. In addition, the thermal expansion coefficient has an inverse relation with temperature.     

Temperature-dependent barrier height in CdSe Schottky diode

This article reports the measurements of temperature-dependent barrier height (BH) of CdSe Schottky diodes. These diodes have been made by thermal evaporation technique on ITO glass and glass substrates at room temperature. The XRD measurements have been made and the average particle size has been calculated which comes out to be ~20 nm. The Au dots have been made for non-ohmic contacts. I–V characteristics have been measured at different temperatures (280–330 K). These characteristics obey the thermionic emission theory. The BH decreases and ideality factor increases with the increase in temperature. Richardson’s plot has been made and Richardson’s constant has been calculated which is less than the expected value. Capacitance measurements have been done at different frequencies and the interface states have been calculated. The results have been explained on the basis of BH inhomogeneities.     

Study of the distribution of ²²⁶Ra in ground water near the uranium industry of Jharkhand, India

Ground water is the principal source of drinking water in the rural areas of India. With the aim of determining, the contribution of (226)Ra to natural background radiation through drinking water exposure pathway near an operating uranium mining industry at Jaduguda, Jharkhand state of eastern India, the (226)Ra activity concentrations were measured in potable ground water. The water analysed, both tube well and well water, was collected in areas near the uranium industry and away. The (226)Ra concentration was measured by emanometric technique. The (226)Ra level in ground water was ranging between minimum detection limit of 3.5 mBq l(-1) and a maximum of 208 mBq l(-1). The analysis of variance reveals that there is insignificant statistical variation in the median (226)Ra concentration up to a distance of >10 km from the mining complex. Variation in concentration of (226)Ra in sources is attributed to the local geochemistry and environmental factors. The (226)Ra concentration was significantly elevated in natural artesian wells in the vicinity of uranium mineralised hill and it varies from 53.4 to 754 mBq l(-1). The WHO [Guidelines for Drinking Water Quality. Third Edition, Vol. 1, Recommendation (2004)] guideline value of 1000 mBq l(-1) has not been exceeded in any of the sources investigated.     

Non-toxicity of water soluble multi-walled carbon nanotube on Escherichia-coli colonies

Carboxylic acid functionalized water soluble carbon nanotube (wsCNT) shows no toxic effect against the growth of Escherichia-coli (E. coli), a gram-negative bacteria. Treatment up to 8 microg mL(-1) of wsCNT did not show any toxic effect on E. coli growth that was followed by using bacterial growth kinetics and Spread Plate Technique (SPT). The number of E-coli colonies counts with and without wsCNT showed nearly no change and the bacterial growth kinetics in both the cases showing no toxic effect of wsCNT on the growth of E. coli.     

Nanostructured membranes and electrodes with sulfonic acid functionalized carbon nanotubes

Herein we report the covalent functionalization of multiwall carbon nanotubes by grafting sulfanilic acid and their dispersion into sulfonated poly(ether ether ketone). The nanocomposites were explored as an option for tuning the proton and electron conductivity, swelling, water and alcohol permeability aiming at nanostructured membranes and electrodes for application in alcohol or hydrogen fuel cells and other electrochemical devices. The nanocomposites were extensively characterized, by studying their physicochemical and electrochemical properties. They were processed as self-supporting films with high mechanical stability, proton conductivity of 4.47 × 10⁻² S cm⁻¹ at 30 °C and 16.8 × 10⁻² S cm⁻¹ at 80 °C and 100% humidity level, electron conductivity much higher than for the plain polymer. The methanol permeability could be reduced to 1/20, keeping water permeability at reasonable values. The ratio of bound water also increases with increasing content of sulfonated filler, helping in keeping water in the polymer in conditions of low external humidity level.     

Effect of dye doping in poly(vinyl alcohol) waveguides

Dye-doped poly(vinyl alcohol) (PVA) waveguides have been fabricated and characterized. The waveguiding parameters of PVA film, for example the refractive index, thickness, birefringence, polarization conversion and propagation losses, were evaluated using the various concentration of dyes in polymeric solution. It has been shown that the dyes can affect the basic waveguiding parameters considerably. However, birefringence in PVA waveguides remains unaffected irrespective of any dyes and any concentration of dye used.