Surveillance of Aeromonas sobria and Aeromonas hydrophila from commercial food stuffs and environmental sources

In tropical countries like India, commercial food items are often contaminated by various food-borne pathogens. Present research work reports the surveillance of A. sobria and A. hydrophila from commercial food stuffs and environmental sources across Tamil Nadu and Kerala, India. Samples were aseptically collected throughout the year and processed for isolation and identification of A. sobria and A. hydrophila. Isolates of Aeromonas were characterized for arrays of biochemical and phenotypic traits and finally assayed for antibiotic susceptibility test. A total of 71 suspected Aeromonas strains were isolated from 154 commercial food and environmental samples. Upon biochemical characterization of these isolates, 56(79%) were identified as A. sobria and remaining 15(21%) isolates were A. hydrophila. Upon detailed biochemical and phenotypical investigation, distinguishable results were obtained on esculin hydrolysis, acid production from L- arabinose, amylolytic, lipolytic and nuclease activities. All the isolates were 100% resistance to ampicillin, carbenicillin, cephalothin and clindamycin; 100% sensitive to colistin and moderate to cefuroxime, chloramphenicol, nalidixic acid, neomycin and nitrofurantoin. The present research suggested that colistin could be useful for motile Aeromonas infection but there has also been prevalence of multi drug resistant strains of Aeromonads in the Sothern states of India. The results aided our efforts to prove the strong occurrences of A. sobria and A. hydrophila as food borne pathogens in human consumable foods than in the environmental samples.&nbsp

Fluorinated graphene oxide for enhanced S and X-band microwave absorption

Here we report the microwave absorbing properties of three graphene derivatives, namely, graphene oxide (GO), fluorinated GO (FGO, containing 5.6 at. % Fluorine (F)), and highly FGO (HFGO, containing 23 at. % F). FGO is known to be exhibiting improved electrochemical and electronic properties when compared to GO. Fluorination modifies the dielectric properties of GO and hence thought of as a good microwave absorber. The dielectric permittivities of GO, FGO, and HFGO were estimated in the S (2 GHz to 4 GHz) and X (8 GHz to 12 GHz) bands by employing cavity perturbation technique. For this, suspensions containing GO/FGO/HFGO were made in N-Methyl Pyrrolidone (NMP) and were subjected to cavity perturbation. The reflection loss was then estimated and it was found that −37 dB (at 3.2 GHz with 6.5 mm thickness) and −31 dB (at 2.8 GHz with 6 mm thickness) in the S band and a reflection loss of −18 dB (at 8.4 GHz with 2.5 mm thickness) and −10 dB (at 11 GHz with 2 mm thickness) in the X band were achieved for 0.01 wt. % of FGO and HFGO in NMP, respectively, suggesting that these materials can serve as efficient microwave absorbers even at low concentrations

A microwave absorber based on strontium ferrite–carbon black–nitrile rubber for S and X-band applications

Flexible and thin single layer microwave absorbers based on strontium ferrite–carbon black–nitrile rubber composites have been fabricated employing a specific recipe and their reflection loss characteristics were studied in the S (2–4 GHz) and X-bands (8–12 GHz). The incorporation of carbon black not only reinforces the rubber by improving the mechanical properties of the composite but also modifies the dielectric permittivity of the composite. Strontium ferrite when impregnated into a rubber matrix imparts the required magnetic permeability to the composite. The combination of strontium ferrite and carbon black can then be employed to tune the microwave absorption characteristics of the resulting composite. The complex dielectric permittivity and permeability were measured by employing a cavity perturbation technique. The microwave absorption characteristics of composites were modelled in that an electromagnetic wave incident normally on the metal terminated single layer absorber. The influence of filler volume fraction, frequency, absorber thickness on the bandwidth of absorption are discussed and correlatedCochin University of Science and TechnologyComposites Science and Technology 82 (2013) 69–7

On the microwave absorption of magnetic nanofluids based on barium hexaferrite in the S and X bands prepared by pulsed laser ablation in liquid

Magnetic nanofluids can be prepared by dispersing surfacted nanoparticles in an appropriate carrier medium. The microwave absorbing properties of a magnetic nanofluid based on barium hexaferrite (BAF) is promising since BAF is a good microwave absorber. Surfacted BAF particles prepared by Pulsed Laser Ablation in Liquid (PLAL) overcome agglomeration and are stable under normal conditions. The evaluation of parameters namely ε′, ε″, μ′ and μ″ (real and imaginary parts of permittivity and permeability) will aid in the determination of the microwave absorbing properties since these parameters can be employed to model the optimum thickness of the absorber for maximum absorption using surface impedance equations. Moreover, the fluid can be coated with the required thicknesses on a surface once these parameters are evaluated and modelled. A magnetic nanofluid based on BAF is synthesized using PLAL and its microwave absorbing properties are evaluated and presented here. It is found that they serve as good absorbers in the S and X bands

Magnetically tunable liquid dielectric with giant dielectric permittivity based on core-shell superparamagnetic iron oxide

by S. Vinayasree, , T. S. Nitha, Chandra Sekhar Tiwary, P. M. Ajayan, P. A. Joy and M. R. Anantharama