Relation between electric properties and water saturation for hematitic sandstone with frequency

This paper focuses on the effect of water saturation on A. C. electrical conductivity and dielectric constant of fully and partially saturated hematitic sandstone sample (Aswan area, Egypt). The saturation of the sample was changed from partial to full saturation. Complex resistivity measurements at room temperature (~16°C), were performed in the frequency range from 0.1 Hz to 100 KHz. Experimental electrical spectra indicate, generally, that the electrical conductivity and dielectric constant vary strongly with water saturations and frequency. The low frequency electrical conductivity and dielectric constant are mainly controlled by surface conduction and polarization of the electrical double layer. The behaviour of the electrical conductivity and dielectric constant, with increasing water content, were argued to the orientational polarization of bound water for very low saturations, displacement of the excess surface charges for relatively low saturations, and free exchange of excess ions in double layer with the bulk electrolyte and generation of transient diffusion potentials which lag behind the applied field for high saturations

Biological indicators, genetic polymorphism and expression in Aspergillus flavus under copper mediated stress

AbstractFungi are considered model organisms for studying stress response and metal adaptation for both biotechnological and environmental purposes. In a previous study, copper was added in concentrations 1 and 10mM to Aspergillus flavus to induce laccase production for bioremediation, but using high concentrations of copper resulted in laccase inhibition despite the increase in bioremediation. In this study, the same copper sulfate was added and some oxidative biomarkers and antioxidative defense enzymes were assessed for stressed cultures of both copper and gamma radiation which was used as a positive stress inducer. The increase in copper concentrations resulted in an increase in superoxide dismutase enzyme activity, lipid peroxidation and protein carbonylation. On the other hand, catalase was inhibited by the addition of both copper concentrations, but exposure to gamma radiation resulted in an increased copper production. Glutathione peroxidase showed variation under stress, while both reduced glutathione and mycelial growth decreased in copper amended cultures. There was an increase in total endogenous carbohydrates. The main location of copper at the end of the incubation period seemed to reside in the cytosolic fraction of the fungus as detected by atomic absorption spectrometry. Genetic polymorphism was evident in the presence of copper as detected by RAPD-PCR. The expression of both laccase and superoxide dismutase suggest that each has a specific role in bioremediation, depending on the added copper concentration

In Vitro Screening for Antimicrobial Activity of Some Medicinal Plant Seed Extracts

Phytochemical screening (saponins, tannins, steroids, alkaloids, flavonoids, phenols and glycosides) of four medicinal plant seeds (Jatropha curcas, Simmondsia chinensis (Jojoba), Moringa oleifera and Datura metel) extracted by aqueous, ethanol and Folch solvents, were examined for their antimicrobial activity against three types of plant pathogenic fungi namely; Botrytis cinerea, Fusarium oxysporum and Rhizoctonia solani, in addition to four types of bacteria, namely; Bacillus cereus, Staphylococcus aureus, Ralstonia solanacearum and Pesudomonas aeruginosa using disc diffusion paper. Results revealed that different concentrations of aqueous extracts were more effective against bacterial activity compared to fungal activity, except for D. metel aqueous extract which showed no antifungal effect and very weak effect on only two of the tested bacteria. B. cereus was more sensitive to J. curcas aqueous extract, while P. aeruginosa was more sensitive to S. chinensis and M. oleifera aqueous extracts. On the other hand, results showed that J. curcas and M. oleifera ethanol extracts were more effective on Staph. aureus growth, while S. chinensis and D. metel did not have any effect on any of the fungi or bacteria under study. The evaluation of the antifungal and antibacterial effect did not confirm the broad spectrum of S. chinensis Folch extract, while M. oleifera and D. metel were more effective on reducing R. solani growth. Also F. oxysporum was affected by J. curcas Folch extract only at high concentrations. These findings support that the traditional use of the plant extracts in the treatment of different infections caused by pathogenic microbes is valuable and should be taken in consideration

Modification of bacterial cell membrane to accelerate decolorization of textile wastewater effluent using microbial fuel cells: role of gamma radiation

The aim of the present work was to increase bacterial adhesion on anode via inducing membrane modifications to enhance textile wastewater treatment in Microbial Fuel Cell (MFC). Real textile wastewater was used in mediator-less MFCs for bacterial enrichment. The enriched bacteria were pre-treated by exposure to 1 KGy gamma radiation and were tested in MFC setup. Bacterial cell membrane permeability and cell membrane charges were measured using noninvasive dielectric spectroscopy measurements. The results show that pre-treatment using gamma radiation resulted in biofilm formation and increased cell permeability and exopolysaccharide production; this was reflected in both MFC performance (average voltage 554.67 mV) and decolorization (96.42%) as compared to 392.77 mV and 60.76% decolorization for non-treated cells. At the end of MFC operation, cytotoxicity test was performed for treated wastewater using a dermal cell line, the results obtained show a decrease in toxicity from 24.8 to 0 (v/v%) when cells were exposed to gamma radiation. Fourier-transform infrared (FTIR) spectroscopy showed an increase in exopolysaccharides in bacterial consortium exposed to increasing doses of gamma radiation suggesting that gamma radiation increased exopolysaccharide production, providing transient media for electron transfer and contributing to accelerating MFC performance. Modification of bacterial membrane prior to MFC operation can be considered highly effective as a pre-treatment tool that accelerates MFC performance

6S rRNA of a Bacillus isolate 16S rRNA characterization of a Bacillus isolate and its tolerance profile after subsequent subculturing

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