Evaporation waves in superheated dodecane

We have observed propagating adiabatic evaporation waves in superheated liquid dodecane, C_(12)H_(26). Experiments were performed with a rapid decompression apparatus at initial temperatures of 180–300°C. Saturated dodecane in a tube was suddenly depressurized by rupturing a diaphragm. Motion pictures and still photographic images, and pressure and temperature data were obtained during the evaporation event that followed depressurization. Usually, a front or wave of evaporation started at the liquid free surface and propagated into the undisturbed regions of the metastable liquid. The evaporation wave front moved with a steady mean velocity but the front itself was unstable and fluctuating in character. At low superheats, no waves were observed until a threshold superheat was exceeded. At moderate superheats, subsonic downstream states were observed. At higher superheats, the downstream flow was choked, corresponding to a Chapman–Jouguet condition. At the most extreme superheat tested, a vapour content of over 90% was estimated from the measured data, indicating a nearly complete evaporation wave. Our results are interpreted by modelling the evaporation wave as a discontinuity, or jump, between a superheated liquid state and a two-phase liquid–vapour downstream state. Reasonable agreement is found between the model and observations; however, there is a fundamental indeterminacy that prevents the prediction of the observed wave speeds

IRIS Observations of the Mg II h & k Lines During a Solar Flare

The bulk of the radiative output of a solar flare is emitted from the chromosphere, which produces enhancements in the optical and UV continuum, and in many lines, both optically thick and thin. We have, until very recently, lacked observations of two of the strongest of these lines: the Mg II h & k resonance lines. We present a detailed study of the response of these lines to a solar flare. The spatial and temporal behaviour of the integrated intensities, k/h line ratios, line of sight velocities, line widths and line asymmetries were investigated during an M class flare (SOL2014-02-13T01:40). Very intense, spatially localised energy input at the outer edge of the ribbon is observed, resulting in redshifts equivalent to velocities of ~15-26km/s, line broadenings, and a blue asymmetry in the most intense sources. The characteristic central reversal feature that is ubiquitous in quiet Sun observations is absent in flaring profiles, indicating that the source function increases with height during the flare. Despite the absence of the central reversal feature, the k/h line ratio indicates that the lines remain optically thick during the flare. Subordinate lines in the Mg II passband are observed to be in emission in flaring sources, brightening and cooling with similar timescales to the resonance lines. This work represents a first analysis of potential diagnostic information of the flaring atmosphere using these lines, and provides observations to which synthetic spectra from advanced radiative transfer codes can be compared.Comment: 12 pages, 14 figures, Accepted for publication in Astronomy and Astrophysic

Acinetobacter calcoaceticus plays a bridging function in drinking water biofilms

Intergeneric coaggregation of six drinking water autochthonous heterotrophic bacteria isolated from a model laboratory system were tested for their ability to coaggregate by a visual assay and by two microscopic techniques (epifluorescence and scanning electron microscopies). One isolate, identified as Acinetobacter calcoacticus, was found not only to autoaggregate, but also to coaggregate with four of the five other isolates (Burkholderia cepacia, Methylobacterium sp., Mycobacterium mucogenicum, Sphingomonas capsulata and Staphylococcus sp.) to different degrees as assessed by the visual assay, highlighting a possible bridging function in a biofilm consortium. In its absence, no coaggregation was found. Microscopic observations revealed a higher degree of interaction for all the aggregates than did the visual assay. Heat and protease reversed autoaggregation and coaggregation, suggesting that interactions were lectin-saccharide mediated. The increase/decrease in the level of extracellular proteins and polysaccharides produced during intergeneric bacteria association was not correlated with coaggregation occurrence, but probably with coaggregation strength. The bridging function of A. calcoaceticus was evidenced by multispecies biofilm studies through a strain exclusion process.Este trabalho investiga a co-agregação intergenérica de seis bactérias heterotróficas autóctones de água potável isoladas de um sistema laboratorial modelo, testando assim a sua capacidade de co-agregação através do ensaio visual e de duas técnicas microscópicas (microscopia de epifluorescência e microscopia electrónica de varrimento). Para o isolado identificado como Acinetobacter calcoaceticus, foi detectado através do ensaio visual que não só auto-agrega, mas também co-agrega, a diferentes intensidades, com quatro dos outros cinco isolados (Burkholderia cepacia, Methylobacterium sp., Mycobacterium mucogenicum, Sphingomonas capsulata and Staphylococcus sp.), realçando a possível função de ligação em biofilmes multi-espécie. Na sua ausência não foi detectada co-agregação. As observações microscópicas revelaram um maior grau de interacção para todos os agregados do que a detectada pelo ensaio visual. O tratamento com calor e protease reverteram a auto-agregação e a co-agregação, sugerindo que as interacções são mediadas por lectinas-açúcares. O aumento/diminuição no nível de proteínas e polissacarídeos extracelulares produzidos durante os fenómenos de co-agregação não estão relacionados com a sua ocorrência, mas provavelmente com a sua força de interacção. A função de ligação da A. calcoaceticus nos consórcios microbianos foi evidenciada pela formação de biofilmes multi-espécie, através de um processo de exclusão bacteriana.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/31661/2006, FRH/BPD/20582/200

A review of current and emergent biofilm control strategies

Microbial adhesion to surfaces and the consequent biofilm formation has been documented in many different environments. Biofilms constitute a protected mode of growth that allows microorganisms to survival in hostile environments, being their physiology and behavior significantly different from their planktonic counterparts. In dairy industry, biofilms may be a source of recalcitrant contaminations, causing food spoilage and are possible sources of public health problems such as outbreaks of foodborne pathogens. Biofilms are difficult to eradicate due to their resistant phenotype. However, conventional cleaning and disinfection regimens may also contribute to inefficient biofilm control and to the dissemination of resistance. Consequently, new control strategies are constantly emerging with main incidence in the use of biosolutions (enzymes, phages, interspecies interactions and antimicrobial molecules from microbial origin). The present review will focus on describing the mechanisms involved in biofilm formation and behavior, deleterious effects associated with their presence, and some of the current and emergent control strategies, providing new insight of concern for food industry.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/31661/200

Comparison of methods to assess biofilm disinfection and recovery by drinking water-isolated bacteria

Drinking water (DW) distribution systems are known to harbour biofilms even in the presence of disinfectants. DW biofilms are constituted by microbial communities adapted to low nutrient concentrations and high chlorine levels. Biofilm formation and resistance to disinfection have been recognized as important factors that contribute to the survival and persistence of microbial contamination in DW. The purpose of this work was the comparison of diverse methods to assess the disinfection of biofilms formed by six DW-isolated opportunistic bacteria (Acinetobacter calcoaceticus, Burkholderia cepacia, Methylobacterium sp., Mycobacterium mucogenicum, Sphingomonas capsulata and Staphylococcus sp.) by sodium hypochlorite (SHC). Single and multi-species biofilms (composed of combinations of 6 and 5 bacteria) were developed in 96- wells microtiter plates for 3 days, afterwards, were exposed to several independent SHC concentrations (0.1, 0.5, 1 and 10 mg/L) during 1 h. The potential of biofilms to recover was assessed 24 h after disinfection. The disinfection efficacy and recovery were assessed in terms of variation in: biofilm mass (crystal violet staining); metabolic activity (XTT staining); cultivability (CFUs) and viability (Live/Dead staining). The results indicated that biomass removal increased with increasing SHC concentration, but total biofilm mass removal was not achieved. The effects of SHC on the biofilm activity, cultivability and viability were also concentration dependent. Total biofilm inactivation was achieved only for A. calcoaceticus biofilms and for multi-species biofilms without A. calcoaceticus, when exposed to high SHC concentrations. Almost all multispecies biofilms were more resistant to removal and inactivation than the single biofilms. Methylobacterium sp. and A. calcoaceticus formed the most resistant and the most susceptible biofilms, respectively. On the other hand, biofilm combination with the six DW bacteria was the most resistant to SHC and combination without A. calcoaceticus was the least resistant, for all concentration tested. The several methods used to assess of biofilm activity (metabolic activity, cultivability and viability) provided comparable results. However the viability results provide the worst case scenario in terms of biofilm control analysis (higher number of viable cells for all the SHC concentrations tested). The recovery results demonstrated that only biofilms without A.calcoaceticus were not able to recover their biomass from the SHC treatments. Also, those biofilms had a decreased ability to recover their metabolic activity, cultivability and viability. Conversely, multi-species biofilms without Staphylococcus sp. had the highest ability to recover from disinfection. Biofilm mass and activity recovery were not correlated for all the biofilms tested. However, the data of biofilm recovery in terms of metabolic activity, cultivability and viability also provided comparable results

Drinking water biofilm monitoring by Propella™ and flow cell bioreactors under different operating conditions

Monitoring of biofilm subjected to different process conditions was performed using two distinct bioreactors, Propella™ and flow cell system. Biofilms were grown on polyvinyl chloride (PVC) and stainless steel (SS) coupons under laminar (Reynolds number of 2000) and turbulent (Reynolds number of 11000) flow. The parameters analyzed were culturable cells, using R2A, and total bacteria, which were assessed using a DNA-binding stain coupled with epifluorescence microscopy. The impact of the different operating conditions in the studied parameters was established after the biofilms reached the steady-state. It was found that the biofilm steady-state was achieved 3 d after the starting of operating conditions for turbulent flow and for both bioreactors and adhesion surfaces. Under laminar flow it was only achieved 6 d after. The number of total bacteria was invariably higher than the culturable cells. The number of total and culturable bacteria in turbulent flow-generated biofilms were similar in both bioreactors, regardless the adhesion surface tested. Under laminar flow, the Propella™ bioreactor allowed the formation of steady-state biofilms with a higher number of total and culturable bacteria than those from the flow cell system. Comparing the effect of the flow regime on biofilm accumulation, only turbulent flow-generated biofilms formed on the flow cell system had a higher amount of total and culturable bacteria than those formed under laminar flow. In terms of adhesion surface effect on steady-state biofilms, a higher number of total and culturable cells were found on PVC surfaces comparatively to SS when biofilms were formed using the flow cell system. Biofilm formation on PVC and SS was similar in the Propella™ system for both flow regimes.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/31661/200

Processing XML: a rewriting system approach

SIMÕES, Alberto ; CRUZ, Daniela da ; RAMALHO, José Carlos, ed. lit. – “XATA 2010 XML : associated technologies and applications, 8, Vila do Conde, 2010”. [S.l. : s.n.], 2010. ISBN 978-972-99166-9-4.Nowadays XML processing is performed using one of two approaches: using the SAX (Simple API for XML) or using the DOM (Document Ob ject Model). While these two approaches are adequate for most cases there are situations where other approaches can make the solution easier to write, read and, therefore, to maintain. This document presents a rewriting approach for XML documents processing, focusing the tasks of transforming XML documents (into other XML formats or other textual documents) and the task of rewriting other textual formats into XML dialects. These approaches were validated with some case studies, ranging from an XML authoring tool to a dictionary publishing mechanism

T2O - Recycling thesauri into a multilingual ontology

In this article we present T-2O - a workbench to assist the process of translating heterogeneous resources into ontologies, to enrich and add multilingual information, to help programming with them, and to support ontology publishing. T - 2O is an ontology algebra.(undefined

A textual rewriting system for NLP

In this document we describe the use of Text : Rewrite Rules in several tasks related to Speech