The active principle in a methanolic extract of the laboratory-grown cyanobacterium, Fischerella sp. isolated from Neem (Azadirachta indica) tree bark was active against Mycobacterium tuberculosis, Enterobacter aerogenes, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli as well as three multi-drug resistant E. coli strains in in vitro assays. Based on MS, UV, IR 1 H NMR analyses the active principle is proposed to be Hapalindole T having the empirical formula C 21 H 23 N 2 ClSO and a molecular weight of 386 with the melting point range 179-182 • C. The estimated production of Hapalindole T from the cyanobacterium is 1.25 mg g −1 lyophilized biomass. It is suggested that cyanobacteria colonizing specialized niches such as tree bark could be an antibacterial drug resource.

In this article, an analytical model is devised for analyzing time periodic electroosmotic flows through nanochannels within the continuum regime, without presuming the validity of the Boltzmann distribution of ionic charges. The charge density distributions are obtained from the conservation considerations of the individual ionic species and other thermochemical constraints and are subsequently utilized to derive the potential distribution within the electrical double layer (EDL). This, coupled with the Navier-Stokes equation, yields a closed-form expression of the time-dependent velocity field that is valid under overlapped EDL conditions. This expression is first validated in asymptotic limits of thin EDLs, for which closed form expressions have been benchmarked in the literature. Further analyses are carried out to bring out the influences of the frequency of the electrical field on the electroosmotic flow features in the presence of overlapped EDLs.

The present study was aimed at the isolation, purification and structural elucidation of an antibacterial entity/lead molecule from the Antarctic cyanobacterium Nostoc CCC 537. A methanolic extract of the cyanobacterium was bioassayed with Enterobacter aerogenes as a target. The extract was purified by TLC, and the most active band was subjected to HPLC. The fraction (retention time 15.7 min) designated as the active principle was antibacterial towards Gram positive Mycobacterium tuberculosis H37Rv, Staphylococcus aureus ATCC 25923, Gram negative Salmonella typhi MTCC 3216, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25992, Enterobacter aerogenes MTCC 2822 and multi-drug resistant strains of Escherichia coli GS 2003/01, 02, 03.

Pure and 1 at% gallium (Ga)-doped zinc oxide (ZnO) thin films have been prepared with a low-cost spin coating technique on quartz substrates and annealed at 500 °C in vacuum ∼10−3 mbar to create anion vacancies and generate charge carriers for photovoltaic application. Also, 0.5–1.5 at% extra zinc species were added in the precursor sol to investigate changes in film growth, morphology, optical absorption, electrical properties and photoluminescence. It is shown that 1 at% Ga–ZnO thin films with 0.5 at% extra zinc content after vacuum annealing for 60 min correspond to wurtzite-type hexagonal structure with (0001) preferred orientation, electrical resistivity of ∼9 × 10−3 Ω cm and optical transparency of ∼65–90% in the visible range. Evidence has been advanced for the presence of defect levels within bandgap such as zinc vacancy (VZn), zinc interstitial (Zni), oxygen vacancy (Vo) and oxygen interstitial (Oi). Further, variation in ZnO optical bandgap occurring with Ga doping and insertion of additional zinc species has been explained by invoking two competing phenomena, namely bandgap widening and renormalization, usually observed in semiconductors with increasing carrier concentration.

This paper reports a comparative study of an optical humidity sensor based on titania films fabricated by sol–gel and thermal evaporation methods. As semiconducting oxides are known for their n-type conduction because of the presence of oxygen vacancies, therefore they prove to be very good sensors for humidity. Sensing elements of the optical humidity sensor presented here consist of a rutile structured one-layered TiO2 thin film deposited on the base of an isosceles glass prism of thickness 1000 Å. This TiO2 film is porous and sensitive to humidity. The other sensing element consists of a film of the same material deposited by the thermal evaporation method on the base of a prism of the same thickness. Light from a He–Ne laser enters the prism from one of the isosceles faces of the prism and gets reflected from the glass–film interface, before emerging out from its other isosceles face. The emergent beam is collected through an optical fibre, which is connected to an optical power meter for measurement. Variations in the intensity of light caused by changes in humidity lying in the range of 5% RH to 95% RH have been recorded. A sensor fabricated by the thermal evaporation method shows better sensitivity than the sol–gel method. Scanning electron micrographs of both the films show that the film prepared by the thermal evaporation method is more porous and continuous than the film prepared by the sol–gel method, resulting in more sensitivity to humidity.