Transition metal spinel oxides have recently been predicted to create efficient transparent conducting oxides for optoelectronic devices. These compounds can be easily tuned by doping or defect to adapt their electronic or magnetic properties. However, their cation distribution is very complex and band structures are still subject to controversy. We propose a complete density functional theory investigation of fayalite (Fe2SiO4) spinel, using Generalized Gradient Approximation (GGA) and Local Density Approximation (LDA) in order to explain the electronic and structural properties of this material. A detailed study of their crystal structure and electronic structure is given and compared with experimental data. The lattice parameters calculated are in agreement with the lattice obtained experimentally. The band structure of Fe2SiO4 spinel without Coulomb parameter U shows that the bands close to Fermi energy appear to be a band metal, with four iron d-bands crossing the Fermi level, in spite of the fact that from the experiment it is found to be an insulator.
Natural products are purified organic compounds isolated from natural sources that are produced by the pathways of primary or secondary metabolism. 1 A large amount of archaeological evidence exists which indicates that humans were using medicinal plants during the Paleolithic period, approximately 60,000 years ago. Furthermore, animals such as non-human primates, monarch butterflies and sheep are also known to ingest medicinal plants to treat illness. 2 Indigofera pulchra (Willd) is an erect stiff, grey-pubescent softly wooded under-shrub that grows up to 1-1.5 m high. It is widely distributed from Senegal to Nigeria and over Eastern and central Africa from Ethiopia to Angola. 3 In ethno medicine, the leaves are used to treat infected wound, itching skin and as snake antidote; 3 as prophylactic against snake bite 4 and for the treatment of malaria and dysentery. 5,6
Dutsen dan Libya is a rock material used in traditional medicine for the treatment of a myriad of ailments like cold, fever, stomach disorder, diarrhea and Jaundice. To evaluate the scientific basis for the use of the rock, the antimicrobial activities of its water extract was studied against some common gram positive and gram negative bacteria and fungi. The antimicrobial activity of the aqueous extract was evaluated by determination of the diameter of zone of inhibition using the paper disk diffusion method. Results showed sensitivity to Pseudomonas aeruginosa, Streptococcus pyogenes, Staphylococcus aureus, Corynebacterium ulcerans, Klebsiella pneumoniae and Candida albicans. Bacillus subtilis, Salmonella typhi, Escherichia Coli and Neisseria gonorhoea were resistant. Studies on the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the rock-extract solution on the test organisms showed the lowest MIC at the dose level of 1.25mg/ml and MBC at the dose level of 2.50mg/ml respectively against Pseudomonas aeruginosa and Streptococcus pyogenes. The highest MIC (2.5 mg/ml) and MBC (5.00mg/ml) were exhibited against staphylococcus aureus, corynebacterium ulcerans, klebsiella pneumoniae and Candida albicans.
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