Peracetic acid‐enhanced photocatalytic and sonophotocatalytic inactivation of E. coli in aqueous suspensions

BACKGROUND: Although chlorination is an effective and widely employed method of water disinfection, it suffers serious drawbacks such as the formation of toxic chlorinated by‐products. Therefore, other disinfection technologies have been researched and developed, including advanced oxidation. RESULTS: The efficacy of heterogeneous photocatalysis and sonophotocatalysis induced by UV‐A irradiation and low frequency (24–80 kHz) ultrasound irradiation in the presence of TiO₂ as the photocatalyst and peracetic acid (PAA) as an additional disinfectant to inactivate E. coli in sterile water was evaluated. PAA‐assisted UV‐A/TiO₂ photocatalysis generally leads to nearly complete E. coli inactivation in 10–20 min of contact time with the extent of inactivation depending on the photocatalyst type and loading (in the range 100–500 mg L^?1) and PAA concentration (in the range 0.5–2 mg L^?1). The simultaneous application of ultrasound and UV‐A irradiation in the presence of TiO₂ and PAA prompted further E. coli inactivation. CONCLUSIONS: The proposed advanced disinfection technology offers complete E. coli inactivation at short treatment times and low PAA doses. Copyright © 2010 Society of Chemical Industry     

Atomically Thin Mica Flakes and Their Application as Ultrathin Insulating Substrates for Graphene

By mechanical exfoliation, it is possible to deposit atomically thin mica flakes down to single‐monolayer thickness on SiO₂/Si wafers. The optical contrast of these mica flakes on top of a SiO₂/Si substrate depends on their thickness, the illumination wavelength, and the SiO₂ substrate thickness, and can be quantitatively accounted for by a Fresnel‐law‐based model. The preparation of atomically thin insulating crystalline sheets will enable the fabrication of ultrathin, defect‐free insulating substrates, dielectric barriers, or planar electron‐tunneling junctions. Additionally, it is shown that few‐layer graphene flakes can be deposited on top of a previously transferred mica flake. Our transfer method relies on viscoelastic stamps, as used for soft lithography. A Raman spectroscopy study shows that such an all‐dry deposition technique yields cleaner and higher‐quality flakes than conventional wet‐transfer procedures based on lithographic resists.     

Dependability analysis of semi-Markov systems

This paper presents a dependability analysis (Availability-Reliability-Maintainability, Mean times) for semi-Markov systems with finite state space, by a new method, based on algebraic calculus within a convolution algebra. This method permits us to obtain, by simple matrix calculus, closed form solutions of transition probabilities and dependability measures. It is a quite general method that does not need the semi-Markov kernel to be absolutely continuous. Thus we obtain, as an example, the classical availability formulae modelled by an alternating renewal process, by a simple algebraic calculus without probabilistic argument. A detailed application of the method is given.     

Microbiological quality of tomatoes and peppers produced under the good agricultural practices protocol AGRO 2-1 & 2-2 in Crete, Greece

The efficiency of the good agricultural practices (GAP) protocol AGRO 2-1 & 2-2, in advancing microbiological-quality of tomatoes and peppers, was studied in greenhouses at Ierapetra, Crete, Greece. The 240 tested vegetables-samples, produced under AGRO 2-1 & 2-2, showed satisfactory quality: Listeria monocytogenes absent per 25 g; Escherichia coli < 20 Colony Forming Units per gram (CFU/g); total coliforms 4.37–4.68 log CFU/g; aerobic plate counts 5.78–5.92 log CFU/g. Based on actual results and practices evaluation, we conclude that AGRO 2-1 & 2-2 can reduce microbial hazards for consumers and furthermore can establish practices in compliance to basic Euro-Retailer-Produce GAP (EUREPGAP) requirements.     

Evaluation of a multifunctional indicator for the electroanalytical determination of nitrite

The derivatisation of phloroglucinol by acidified nitrite has been investigated as a means through which the latter can be quantified within freshwater and saline samples. The resulting nitroso derivative is shown to provide a number of options through which an electroanalytical signal can be obtained. Three distinct species can be electrochemically addressed and their respective sensitivities and practical implementations have been evaluated. The technology has been successfully transferred from bulk electrode formats to a disposable screen-printed electrode platform that is more amenable to field analysis. The analytical viability of the resulting assay system has been critically assessed and validated through the determination of endogenous nitrite within lake water and through recovery experiments in seawater.     

Parlay‐based service provision in circuit‐ and packet‐switched telecommunications networks

The spectrum of potential value added services over Internet telephony is wide, but the current service provision solutions are inadequate or proprietary. The nature of Internet differs significantly from that of circuit switched network, however, VoIP architectures can capitalize service control architectures in the PSTN world. We describe such an architecture based on the intelligent network and the Parlay, employing distributed objects and mobile agents as enabling technologies. This architecture has been implemented in the PSTN and the Internet and it has provided a framework for service provisioning, augmenting the space of supported services. Copyright © 2004 John Wiley & Sons, Ltd.     

Strong buffering characteristics and swelling behavior of cationic copolymers

The swelling behavior of crosslinked cationic copolymers of 2-hydroxyethyl methacrylate with (3-methacryloylamino propyl) trimethylammonium chloride was investigated in various buffered solutions as a function of ionic strength and pH. The equilibrium degree of swelling increased as the pH decreased or as the cationic group-containing comonomer in the polymer increased. The water transport in such copolymers was controlled by a non-Fickian mechanism. These results can be used in the development of physiologically sensitive controlled drug delivery systems. © 1994 John Wiley & Sons, Inc.     

Self- and mutual-diffusion coefficients in the dodecane/polystyrene system

The self-diffusion coefficient of dodecane in cross-linked polystyrene was measured using pulsed gradient spin echo nuclear magnetic resonance (PGSE–NMR) spectroscopy. The concentration and temperature dependence of the diffusion coefficient was analyzed by the Fujita and Vrentas–Duda models. Parameters describing the Fujita model were determined from fitting of diffusion data to the PVT behavior of the system. Parameters describing the Vrentas–Duda model were determined from the analysis of the viscosity of dodecane, the viscoelastic relaxation properties, and the glass transition temperature of polystyrene as well as from the diffusion coefficient of the system, measured from independent experiments. Both the Fujita and Vrentas–Duda models described well the concentration and temperature dependence of the diffusion coefficient. Mutual diffusion coefficients were determined from these results. © 1994 John Wiley & Sons, Inc.     

Changes in the catechin and epicatechin content of grape seeds on storage under different water activity (aw) conditions

Storage effect on antioxidant content and capacity of grape seeds under different a_w conditions (a_w 0.33; 0.53; 0.75/50 days, 25 °C) was examined. Total phenol content (determined by the Folin–Ciocalteu method) decreased during storage though changes were trivial for samples stored at 33% or 53% RH. High level of humidity (75%) accelerated degradation and resulted in a ∼50% reduction of total phenol content. Minor loss of the DPPH radical scavenging activity (%RSA) of the extracts was observed. Catechin and epicatechin content monitored by RP-HPLC was reduced during storage, particularly at 75% RH. Epicatechin content proved to be less sensitive to water activity conditions than catechin content. Results of various in vitro assays (Folin–Ciocalteu, FRAP, DPPH, ABTS, CBA, ORAC and copper induced liposome oxidation) did not support difference in terms of resistance to oxidation. Based on the continuous release of gallic acid, our finding was related to hydrolytic reactions. Control of a_w of grape seeds can be of practical importance for the wine industry.