The Einstein relation in nanostructured materials: simplified theory and suggestion for experimental determination

An attempt is made to study the Einstein relation for the diffusivity–mobility ratio (DMR) in quantum wells (QWs) and quantum well wires (QWWs) of tetragonal compounds on the basis of a newly formulated electron energy spectrum taking into account the combined influences of the anisotropies in effective electron mass, the spin–orbit splitting, and the presence of crystal field splitting, respectively. The results for quantum-confined III–V compounds form a special case of our generalized analysis. The DMR has also been studied for QWs and QWWs of II–VI and IV–VI materials. Taking QWs and QWWs of CdGeAs₂, InAs, CdS and PbSe as examples, it was found that the DMR increases with increasing carrier statistics and decreasing film thickness respectively in various oscillatory manners emphasizing the influence of dimensional quantizations and the energy band constants in different cases. An experimental method of determining the DMR in nanostructures with arbitrary dispersion laws has also been suggested and the present simplified analysis is in agreement with the suggested relationship. The well-known results for nanostructures with parabolic energy bands have also been obtained as special cases from this generalized analysis under certain limiting conditions.     

Prevalence,characterization, and genetic diversity of Listeria monocytogenes isolated from foods of animal origin in North East India

Listeria monocytogenes is a pathogenic microorganism infects man mostly through food. A total of 1615 samples of foods of animal origin and water were collected from retail meat shops of North-Eastern India and processed. Sixty-three (3.9%) samples were positive for L. monocytogenes. Animal origin foods showing the highest prevalence was chevon (9.8%) followed by beef (8.9%), chicken (8.5%), pork (2.8%) and milk (1.8%). The prevalence rate in water from retail meat shops was 10%. Recovered L. monocytogenes were distributed into 3 serogroups, of which 74.6% fit in to 1/2a, 3a serogroup, 17.5% to 1/2b, 3b and 7.9 % to 4b, 4d, 4e serogroups. Thirty-five isolates out of 63 possessed all the tested four virulence genes. RAPD- and ERIC -PCR based analyses jointly revealed a discriminative genetic profile for the L. monocytogenes. On the whole, the occurrence of L. monocytogenes in foods of animal origin of North Eastern India displays public health hazard.     

Alginate–chitosan composite hydrogel film with macrovoids in the inner layer for biomedical applications

Making of a layered composite using two biopolymer gels with regularly aligned voids in the inner layer is described in this article. Calcium alginate constituted the inner layer, within which voids of 500 μm diameter were embedded in monolayer or in multiple layers using a fluidic device for bubbling. The chitosan without any additional crosslinker was used to form the outer layer. The layered structure enabled compartmentalization of drug hold-up, and differential release rates. These aspects were reviewed using bovine serum albumin and vitamin B₁₂ as model solutes. The presence of voids at the inner layer of alginate increased the uptake, raising the level of absorptivity to more than 4000%. The composite film could hold two solutes at a time. The one, held inside the alginate layer started releasing only after 1 h of dipping in the release media. The adhesive strength between layers and the response of the composite film to compressive deformation are studied here. The effect of single or multiple layers of voids in the inner layer is reviewed. The slowing of degradation rate due to chitosan-encapsulation is experimentally determined. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47599.     

Prediction of creep curve of HP40Nb steel using artificial neural network

Neural Computing and Applications - Simulation of creep curves using data obtained from a limited number of short-time creep tests is helpful for predicting the long-time creep life of materials by...     

Studies on the dehydration kinetics and rehydration of YAG precursor powder in the hydroxyhydrogel form

YAG precursor powder was prepared in the hydroxyhydrogel form. Dehydration kinetic study and rehydration experiment was carried out to know the behavior of water molecules and hydroxide bonds present in the hydroxyhydrogel network structure with temperature. Rate constants and activation energies for dehydration and dehydroxylation were evaluated by static thermogravimetry. Percent rehydration was determined at different heat treatment temperatures. The results obtained were explained, correlated to establish the thermal stability of hydroxyhydrogel network structure and finally supported by the FTIR analysis.     

A moment-method characterization of V-Koch fractal dipole antennas

This article compares input impedances and radiation characteristics of half wavelength Koch fractal V–electric dipoles having included angles 60°, 90° and 120°. The study considers three structures. In the 1st structure the Koch arms open into the V-region, in 2nd structure they open away from the V-region and in the third structure, one arm opens into and the other away from the V-region. A first iteration, structure 1 of V-Koch electric dipole antenna with included angle of 120° was fabricated and the experimental return loss was in good agreement with simulation. At their first resonances the antennas’ gain and input resistance decrease with decrease in included angles, an observation synonymous to Euclidian electric dipoles. In terms of gain, the first structure is found to give better performance than the other two. For this structure, the pattern distortion at the second resonance was also less compared to the other structures.     

Intergranular Critical Current Density in Polycrystalline (Bi-Pb)-2223 High Temperature Superconductor by ac Susceptibility Measurements

The field dependence of real () and imaginary () component of ac susceptibility of superconductors within the critical state model can conveniently be used for evaluating the critical current when field amplitude is larger than the penetration field. A method to analyze the real () and imaginary () component of fundamental ac susceptibility with the objective of extracting the temperature dependence of critical current density J _c(T) is reported. The procedure makes use of the ac susceptibility data of two polycrystalline (Bi-Pb)-2223 samples measured with different excitation amplitudes below and close to the critical temperature. The temperature dependence of J _c is extracted using the isothermal scan over and data. Results obtained from this procedure are found to be in fair agreement with J _c(T) calculated from traditional loss-maximum data.