Autonomous system for rapid field quantification of Escherichia coli in surface waters.

AIMS: The purpose of this work is to present and evaluate the performance of a novel Automatic Lab-in-vial Escherichia coli Remote Tracking technology based on an automated real-time defined substrate approach, implemented in both portable and in situ instruments. METHODS AND RESULTS: We present the fresh water calibration procedure, and assess performance using side-by-side comparison with most probable number (MPN) approaches in terms of accuracy, reproducibility and capability to correctly generate early-warning alerts. Long-term data from an operational in situ deployment at a potential bathing site is presented as well. CONCLUSIONS: Automatic Lab-in-vial Escherichia coli Remote Tracking technology is shown to be an accurate and rapid bacterial quantification technology, capable of autonomous in situ measurements with metrological capabilities comparable to those of an approved laboratory using MPN microplate techniques. SIGNIFICANCE AND IMPACT OF THE STUDY: Rapid quantification of bacterial pollution is a requirement in water quality applications ranging from recreational water use, agriculture and aquaculture to drinking and wastewater treatment. The method and instruments presented in this work should enable fast and accurate bacterial concentration measurements to be performed in a portable or in situ manner, thus simplifying operational logistics, reducing time-to-result delays, and eliminating sample transportation constraints associated with traditional techniques.

Localized Fibrous Tumor of the Pleura An Unusual Cause of Severe Hypoglycaemia. Case Report.

Localized fibrous tumors of the pleura are rare. If there are symptomatic, the symptoms are based on hormone production or size. Complete resection offers the best results. However, recurrence is reported in a significant number of patients. Usually no oncologic treatment is necessary.

Bubble production mechanism in a microfluidic foam generator.

We present the design and characterization of a microfluidic bubble generator that has the potential of producing monodisperse bubbles in 256 production channels that can operate in parallel. For a single production channel we demonstrate a production rate of up to 4 kHz with a coefficient of variation of less than 1%. We observe a two-stage bubble production mechanism: initially the gas spreads onto a shallow terrace, and then overflows into a larger foam collection channel; pinning of the liquid-gas meniscus is observed at the terrace edge, the result being an asymmetric pinch-off. A semiempirical physical model predicts the scaling of bubble size with fluid viscosity and gas pressure from measurements of the pinned meniscus width.

Microemulsions as reaction media for the synthesis of Pt nanoparticles.

For the synthesis of Pt nanoparticles we used water-in-oil droplet microemulsions as templates. The focus was on the correlation between the size of the microemulsion droplets and that of the resulting Pt particles. To study this correlation in a systematic way, all particles were synthesized at the water emulsification failure boundaries where the microemulsion droplets are spherical and where their size can easily be tuned by the amount of added water. The metallic particles were synthesized by mixing two microemulsions one of which contains the metal salt H(2)PtCl(6) and the other the reducing agent NaBH(4). The size and structure of the microemulsion droplets was studied via small-angle X-ray scattering, while the Pt particles were characterized by high-resolution transmission electron microscopy in combination with energy-dispersive X-ray spectroscopy and selected area electron diffraction. The clear correlation between droplet and particle size was further supported by accompanying Monte Carlo simulations.

Microfluidic capillary separation and real-time spectroscopic analysis of specific components from multiphase mixtures.

We present a technique of phase separation suitable for microfluidic systems and demonstrate its efficient integration with a microfluidic optical cell for performing real-time spectrometric measurements on one specific phase from a mixture. We demonstrate that efficient and robust phase separation based on capillarity is possible within a microfluidic chip using either microfabricated capillary channels in polydimethylsiloxane (PDMS) or oil-wet fluoropolymer membranes, allowing for extraction of either the continuous or of the dispersed phases from a multiphase mixture. We analyze the dependence of phase separation efficiency on the operating parameters of the device and observe the presence of a hysteresis cycle during pressure sweeps above a water breakthrough pressure (P(b)); we also observe and analyze the reversibility of the oil-wet state of the membrane upon pressure reduction below a reset pressure (P(r) < P(b)). We test the capillary separation method extensively with several types of organic/water mixtures and emulsions and derive criteria for design and operation of a robust microfluidic capillary separator. As an example of monitoring application we describe the design and manufacturing of a microfluidic spectrometer cell optimized for fast response time, which was used to analyze the oil extracted from an oil/water emulsion using a capillary separator. The complete separator-sensor system is characterized in terms of response and cleanup times to instantaneous changes in the dye concentration of the phase of interest.

The antimicrobial reagent role on the degradation of model cellulose film.

The effect of the antimicrobial agent TMPAC (3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride) on the cellulase activity on model cellulose substrate was investigated by in situ-null ellipsometry. The cellulases used were extracted from Trichoderma viride and Aspergillus niger, and the model cellulose film was prepared by spin-coating silicon oxide wafers with cellulose solubilized in N-methylmorpholine-N-oxide/dimethyl sulfoxide solution. Upon enzyme addition to the previously equilibrated cellulose film, the initial enzyme adsorption on the substrate was followed by an overall decrease in film mass owing to enzymatic digestion of the cellulose. The loss of cellulose film mass was associated with a non-monotonously behavior of the cellulose film thickness. The activities of the two enzymes were different, a much higher degradation rate being observed for the Trichoderma viride cellulase. The degradation rate with this cellulase decreased significantly when the cellulose film was treated with the antimicrobial agent. The antimicrobial agent did not affect the cellulose degradation catalyzed by the Aspergillus niger cellulase. It was, hence, demonstrated for the first time that, depending on the cellulase type, the antimicrobial agent can inhibit enzymatic activity at the solid-liquid interface.

Structural transitions of encapsidated polyelectrolytes.

Conformations and structural transitions of polyelectrolytes strictly confined onto a spherical 2D surface have been investigated by scaling descriptions based on physical arguments concerning polyelectrolyte adsorption onto planar surface and liquid crystals as well as by Monte Carlo simulations using a bead-spring model with short-range and electrostatic repulsions. In case of the electrostatic screened regime, a disordered-ordered (spiral) transition at increasing persistence length of the chain was found. It was predicted that the transition occurred when the persistence length is comparable with the mean spacing between adjacent strands of the ordered chain. The presence of a non-screened electrostatic repulsion led to a more complex behavior with i) a re-entrant order-disorder transition and ii) a tennis ball texture as an additional smectic/nematic structure. The various competing structures given by the theory were recovered by the Monte Carlo simulations, which also indicated that the tennis ball texture was favored over the spiral structure by the long-range interactions for semi-flexible chains.

Two-dimensional melting transition observed in a block copolymer.

We report the observation of two-dimensional melting in a monolayer film of a sphere-forming diblock copolymer. By annealing in a well-controlled temperature gradient we obtain a complete record of the transition from a low-temperature hexatic phase to a high-temperature liquid in a single experiment. We investigate the temperature dependence of the orientational and translational correlation lengths, as well as of the topological defect density. All evidence suggests that the melting transition is first-order, but correlations in the liquid phase indicate the existence of an underlying second-order transition preempted by the first-order freezing.