Output feedback stabilization of nonlinear dual-rate sampled-data systems via an approximate discrete-time model

The problem of output feedback stabilization of nonlinear sampled-data control systems is considered under the low measurement rate constraint. A dual-rate control scheme is proposed that utilizes a numerical integration scheme to approximately predict the missing output values between measured output samples. It is shown that if an observer-based output feedback controller that semiglobally practically asymptotically (SPA) stabilizes the single-rate sampled-data plant model is given, then the SPA stability property will be preserved for the closed-loop dual-rate sampled-data system, on the basis of the proposed dual-rate control scheme under standard assumptions. A numerical example is given to illustrate the design method

Amoebicidal efficacy of a novel multi-purpose disinfecting solution: First findings

Free-living amoebae of the genus Acanthamoeba can cause a sight-threatening corneal infection, Acanthamoeba keratitis, mostly in contact lens wearers. The use of ineffective contact lens disinfecting solutions is one of the most important risk factors for this infection. This study concerns a new multi-purpose contact lens disinfecting solution, OPTI-FREE (R) PureMoist (R), tested for its efficacy against Acanthamoeba trophozoites and cysts by using the most probable number technique for amoebic enumeration. Acanthamoeba castellanii ATCC 50373 and an environmental strain of Acanthamoeba genotype T4 isolated from tap water in Istanbul were used during the experiments. OPTI-FREE (R) PureMoist (R) achieved total kill (more than a 3-log reduction) of trophozoites of both strains before the manufacturer-recommended disinfection time (6 h). In contrast, this solution had limited cysticidal activity against the ATCC strain but more against the environmental strain, with log reductions of 0.75 and 2.20, respectively, after 6 h of exposure. (C) 2014 Elsevier Inc. All rights reserved

Occurrence of Aerobic and Anaerobic Bacteria in the Consumer End of a Water Distribution System

In this study, mixed species biofilm formation including sulphate-reducing bacteria (SRB) on polypropylene surface and bacteriology of network water were investigated in a model water distribution system during a nine-month period. Water and biofilm samples were analyzed for the enumeration of aerobic heterotrophic bacteria (AHB), anaerobic heterotrophic bacteria (ANHB) and SRB. The number of live/dead bacteria was also analyzed by epifluorescence microscopy. In addition, extracellular polysaccharide substances (EPS) extraction, carbohydrate analysis and scanning electron microscope observation were performed. A biofilm with heterogeneous structure formed on the polypropylene surface of the model water distribution system. Live/dead staining data indicated that biofilm matured in the first month. It was observed that especially AHB entered into a viable but not culturable state because of the temperature decrease. It was also noted that temperature is an important environmental factor especially for planktonic SRB. The quantity of carbohydrate significantly decreased according to the temperature

Acanthamoeba and other free-living amoebae in bat guano, an extreme habitat

Several representatives of the so-called free-living amoebae (FLA) are of medical relevance, not only as facultative pathogens but also as vehicles for pathogenic bacteria. Some FLA can survive and even grow under extreme environmental conditions. Bat guano is an exceptional habitat, the conditions becoming gradually more extreme with aging. In the current study, samples of bat guano of different ages from five caves in Slovenia were screened for the presence of FLA. FLA were isolated from almost all guano samples, including guano with a pH of 3.5. Only the two samples that had been drawn from > 20-year-old guano were negative for FLA. Generally, FLA diversity correlated to high concentrations of cultivable bacteria (similar to 10(8) CFU/g) and fungi (similar to 10(5) CFU/g). Interestingly, the absence of FLA in seasoned guanos was mirrored by the presence of dictyostelid slime moulds. The isolated amoebae were identified as belonging to the genera Acanthamoeba, Copromyxa, Naegleria, Sappinia, Tetramitus, Thecamoeba, Vahlkampfia, Vannella and Vermamoeba. To the best of our knowledge, this is the first study on the diversity of FLA in guano

EVALUATION OF ANTIBACTERIAL ACTIVITY OF SOME PLANT METHANOLIC EXTRACTS

The purpose of our study is to evaluate antibacterial acitivity of the methanolic extracts of 14 medicinal plants 8 of which are endemic species to Anatolia using the Disc diffusion assay. By disk diffusion assay, the antibacterial activity of plant extracts was evaluated by using the noncytotoxic concentrations for Vero cell line determined by MTT assay. The methanolic extracts were evaluated for antibacterial activity against 9 standart strains (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Bacillus subtilis ATCC 6633, Klebsiella pneumoniae ATCC 4352, Staphylococcus aureus ATCC 25923, Staphylococcus marcescens ATCC 13880, Escherichia faecalis ATTC 29212, Staphylococcus enteretidis ATCC 13076 and Proteus mirabilis ATCC 14153) and 11 environmental strains (S.aureus F1, F2, F3, Serratia marcescens F4, F5, F6, F7, P. aeruginosa F8, F9, P. spp. and Salmonella spp.). It was found that three plant extracts from the 14 plants studied had antibacterial activity. Olea europaea L. plant inhibited the growth of Staphylococcus aureus F1 environmental strain, Cotinus coggygria plant inhibited the growth of Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Enterococcus faecalis, Salmonella enteretidis, Proteus mirabilis standard strains and Staphylococcus aureus F1, Staphylococcus aureus F2, Staphylococcus aureus F3 environmental strains and Rosa damascena plant inhibited the growth of Staphylococcus aureus F3 environmental strain