950 resultados para Atmospheric tubes
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The effect of a radio-frequency driven, microscale non thermal atmospheric pressure plasma jet operated in helium with vol. 0.3% molecular oxygen gas admixture, on PC-3 prostate cancer cells has been investigated. The viability of cells exposed to the plasma was found to decrease with increasing plasma exposure time, with apoptosis through caspase and PARP cleavage being observed. High concentrations of nitrite and nitrate were detected in growth media exposed to the plasma and were found to increase in a time dependent manner post exposure. This indicates a slow release of reactive nitrogen species into the growth media, which is likely to influence cellular response to plasma exposure.
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Milling of plant and soil material in plastic tubes, such as microcentrifuge tubes, over-estimates carbon (C) and under-estimates nitrogen (N) concentrations due to the introduction of polypropylene into milled samples, as identified using Fourier-transform infra-red spectroscopy.
This study compares C and N concentrations of roots and soil milled in microcentrifuge tubes versus stainless steel containers, demonstrating that a longer milling time, greater milling intensity, smaller sample size and inclusion of abrasive sample material all increase polypropylene contamination from plastic tubes leading to overestimation of C concentrations by up to 8 % (0.08 g g(-1)).
Erroneous estimations of C and N, and other analytes, must be assumed after milling in plastic tubes and milling methods should be adapted to minimise such error.
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Evidence has accumulated of high temperature (> 4 MK) coronal emission in active region cores that corresponds to structures in equilibrium. Other studies have found evidence of evolving loops. We investigate the EUV intensity and temperature variations of short coronal loops observed in the core of NOAA Active Region 11250 on 13 July 2011. The loops, which run directly between the AR opposite polarities, are first detectable in the 94Å band of Fe XVIII, implying an effective temperature ~ 7 MK. The low temperature component of the 94 Å signal is modeled in terms of a linear superposition of the 193 Å and 171 Å signals in order to separate the hot component. After identifying the loops we have used contemporaneous HMI observations to identify the corresponding inter-moss regions, and we have investigated their time evolution in six AIA EUV channels. The results can be separated into two classes. Group 1 (94Å, 335Å, 211Å) is characterized by hotter temperatures (~2-7 MK), and Group 2 (193Å, 171Å, 131Å) by cooler temperatures (0.4 - 1.6 MK). For Group 1 the intensity peaks in the 94Å channel are followed by maxima in the 335 Å channel with a time lag of ~8 min, suggestive of a cooling pattern with an exponential decay. While the 211Å maxima follow those in the 335 Å channel, there is no systematic relation which would indicate a progressive cooling process through the lower temperatures, as has been observed in other investigations. In Group 2 the signals in the 171 and 131Å channels track each other closely, and lag behind the 193Å. In the inter-moss region of the loop the peak temperature and peak emission measure have opposite trends. The hot 94Å brightenings occur in the central part of the loops with maximum temperatures ~7 MK. Subsequently the loops appear to fill with plasma with an emission measure compatible with the 193 Å signal and temperature in the range ~ 1.5-2 MK. Although the exact details of the time evolution are still under investigation, these non static loops show high levels of intermittency in the 94Å signal (please see poster "Intermittent and Scale-Invariant Intensity Fluctuations in Hot Coronal Loops," by Lawrence et al. in this session).
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The emergence of multidrug-resistant pathogens within the clinical environment is presenting a mounting problem in hospitals worldwide. The 'ESKAPE' pathogens (Enterococcusfaecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.) have been highlighted as a group of causative organisms in a majority of nosocomial infections, presenting a serious health risk due to widespread antimicrobial resistance. The stagnating pipeline of new antibiotics requires alternative approaches to the control and treatment of nosocomial infections. Atmospheric pressure nonthermal plasma (APNTP) is attracting growing interest as an alternative infection control approach within the clinical setting. This study presents a comprehensive bactericidal assessment of an in-house-designed APNTP jet both against biofilms and planktonic bacteria of the ESKAPE pathogens. Standard plate counts and the XTT metabolic assay were used to evaluate the antibacterial effect of APNTP, with both methods demonstrating comparable eradication times. APNTP exhibited rapid antimicrobial activity against all of the ESKAPE pathogens in the planktonic mode of growth and provided efficient and complete eradication of ESKAPE pathogens in the biofilm mode of growth within 360 s, with the exception of A. baumannii where a >4log reduction in biofilm viability was observed. This demonstrates its effectiveness as a bactericidal treatment against these pathogens and further highlights its potential application in the clinical environment for the control of highly antimicrobial-resistant pathogens.
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In this work we demonstrate the synthesis of a TiO2/PEDOT:PSS nanocomposite material in aqueous solution through atmospheric pressure direct current (DC) plasma processing at room temperature. The dispersion of the TiO2 nanoparticles is enhanced after microplasma processing, and TiO2/polymer hybrid nanoparticles with a distinct core shell structure have been obtained. We have observed increased TiO2/PEDOT:PSS nanocomposite electrical conductivity due to microplasma processing. The improvement in nanocomposite properties is due to the enhanced dispersion and stability in liquid polymer of microplasma treated TiO2 nanoparticles. Both plasma induced surface charge and nanoparticle surface termination with specific plasma chemical species are thought to provide an enhanced barrier to nanoparticle agglomeration and promote nanoparticle-polymer bonding, which is expected to have a significant benefit in materials processing with inorganic nanoparticles for wide range of applications.
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This paper presents a novel strategy for the prevention of ventilator-associatedpneumonia that involves coating poly(vinyl chloride, PVC) endotracheal tubes (ET) withhydrogels that may be subsequently used to entrap nebulized antimicrobial solutions. Candidatehydrogels were prepared containing a range of ratios of hydroxyethyl methacrylate (HEMA) andmethacrylic acid (MAA) from 100:0 to 70:30 using free radical polymerization and, whenrequired, simultaneous attachment to PVC was performed. The mechanical properties, glasstransition temperatures, swelling kinetics, uptake of gentamicin from an aqueous medium, andgentamicin release were characterized. Increasing the MAA content of the hydrogels significantlydecreased the ultimate tensile strength, % elongation at break, Young’s modulus, and increasedthe glass transition temperature, the swelling ratio, and gentamicin uptake. Microbial(Staphylococcus aureus and Pseudomonas aeruginosa) adherence to control (drug-free) hydrogelswas observed; however, while adherence to gentamicin-containing p(HEMA) occurred, noadherence occurred to gentamicin-containing HEMA:MAA copolymers. Antimicrobialpersistence of gentamicin-containing hydrogels was examined by determining the zone ofinhibition against each microorganism on successive days. Hydrogel composition affected the observed antimicrobial persistence,with the hydrogel composed of 70:30 HEMA:MAA exhibiting >20 days persistence against S. aureus and P. aeruginosa,respectively. To simulate clinical use, the hydrogels (coated onto PVC) were first exposed to a nebulized solution of gentamicin(4 mL, 80 mg for 20 min), and then to nebulized bacteria (4 mL ca. 1 × 109 colony forming units mL−1, 30 min). Viable bacteriawere not observed on the gentamicin-treated p(HEMA: MAA) copolymers, whereas growth was observed on gentamicin-treatedp(HEMA). In light of the excellent antimicrobial activity and physicochemical properties, p(HEMA: MAA) copolymerscomposed of ratios of 80:20 or 70:30 HEMA: MAA were identified as potentially useful coatings of endotracheal tubes to be usedin conjunction with the clinical nebulization of gentamicin and designed for the prevention of ventilator-associated pneumonia
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The nature and kinetics of plasmid DNA damage after DNA exposure to a kHz-driven atmospheric pressure nonthermal plasma jet has been investigated. Both single-strand break (SSB) and double-strand break (DSB) processes are reported here. While SSB had a higher rate constant, DSB is recognized to be more significant in living systems, often resulting in loss of viability. In a helium-operated plasma jet, adding oxygen to the feed gas resulted in higher rates of DNA DSB, which increased linearly with increasing oxygen content, up to an optimum level of 0.75% oxygen, after which the DSB rate decreased slightly, indicating an essential role for reactive oxygen species in the rapid degradation of DNA.
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We study the magnetospheric structure and the ionospheric Joule Heating of planets orbiting M-dwarf stars in the habitable zone using a set of magnetohydrodynamic models. The stellar wind solution is used to drive a model for the planetary magnetosphere, which is coupled with a model for the planetary ionosphere. Our simulations reveal that the space environment around close-in habitable planets is extreme, and the stellar wind plasma conditions change from sub- to super-Alfvénic along the planetary orbit. As a result, the magnetospheric structure changes dramatically with a bow shock forming in the super-Alfvénic sectors, while no bow shock forms in the sub-Alfvénic sectors. The planets reside most of the time in the sub-Alfvénic sectors with poor atmospheric protection. A significant amount of Joule Heating is provided at the top of the atmosphere as a result of the intense stellar wind. For the steady-state solution, the heating is about 0.1%-3% of the total incoming stellar irradiation, and it is enhanced by 50% for the time-dependent case. The significant Joule Heating obtained here should be considered in models for the atmospheres of habitable planets in terms of the thickness of the atmosphere, the top-side temperature and density, the boundary conditions for the atmospheric pressure, and particle radiation and transport. Here we assume constant ionospheric Pedersen conductance similar to that of the Earth. The conductance could be greater due to the intense EUV radiation leading to smaller heating rates. We plan to quantify the ionospheric conductance in future study.
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Cold plasma is an emerging non-thermal processing technology that could be used for large scale leaf decontamination as an alternative to chlorine washing. In this study the effect of an atmospheric cold plasma apparatus (air DBD, 15 kV) on the safety, antioxidant activity and quality of radicchio (red chicory, Cichorium intybus L.) was investigated after 15 and 30 min of treatment (in afterglow at 70 mm from the discharge, at 22 °C and 60% of RH) and during storage. Escherichia coli O157:H7 inoculated on radicchio leaves was significantly reduced after 15 min cold plasma treatment (-1.35 log MPN/cm<sup>2</sup>). However, a 30 min plasma treatment was necessary to achieve a significant reduction of Listeria monocytogenes counts (-2.2 log CFU/cm<sup>2</sup>). Immediately after cold plasma treatment, no significant effects emerged in terms of antioxidant activity assessed by the ABTS and ORAC assay and external appearance of the radicchio leaves. Significant changes between treated and untreated radicchio leaves are quality defects based on the cold plasma treatment. Atmospheric cold plasma appears to be a promising processing technology for the decontamination of leafy vegetables although some criticalities, that emerged during storage, need to be considered in future studies.
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An evaluation of the global atmospheric energetics is presented in the framework of the basic decomposition into the zonal mean and eddy components, the zonal wavenumber decomposition, and the three-dimensional normal mode decomposition. An extension to the normal mode energetics formulation is also presented in the study, which enables the explicit evaluation of the conversion rate between available potential energy and kinetic energy along with their generation and dissipation rates, in both the zonal wavenumber and vertical mode domains. In addition, it has been proposed an extended energy cycle diagram describing the flow of energy among the zonal mean and eddy components, and also among the barotropic and baroclinic components. The energetics is first assessed for three reanalysis datasets and five state-ofthe- art climate models simulations representing the present climate conditions. It is performed a comparative analysis between the observationally based energetics and that based on the climate models' simulations. In order to appraise possible changes in the atmospheric energetics of a future climate scenario relative to that of the present climate conditions, the analysis is extended using the datasets simulated by the same five climate models for a future climate scenario experiment, as defined in the Special Report on Emissions Scenarios (SRES) of the Intergovernmental Panel on Climate Change (IPCC).
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Esta tese debruça-se sobre a biodiversidade de líquenes epífitos de pinhais dunares portugueses e sobre uso de líquenes como biomonitores de poluição atmosférica nesse habitat. A Mata Nacional das Dunas de Quiaios (Figueira da Foz) foi o ponto de partida dos estudos de biodiversidade efetuados nesta tese, mas alguns deles estenderam-se à maior parte da costa portuguesa. Como resultado, encontrou-se uma espécie nova para a ciência, Lecanora sorediomarginata Rodrigues, Terrón & Elix, epifítica sobre Pinus pinaster Aiton e P. pinea L, que se encontra distribuída na maior parte da costa. Esta espécie caracteriza-se morfologicamente por um talo crustáceo, de cor esbranquiçada a acinzentada ou esverdeada e que desenvolve sorálios a partir de pequenas verrugas marginais. Quimicamente caracteriza-se pela presença dos ácidos 3,5-dicloro-2'-O-metilnorestenospórico [maior], 3,5-dicloro-2 -O-metilanziaico [menor], 3,5-dicloro-2 -O-metilnordivaricático [menor], 5-cloro-2'-Ometilanziaico [traço] e úsnico [traço]; atranorina [menor] e cloroatranorina [menor]. É quimicamente semelhante a L. lividocinerea Bagl., com a qual apresenta afinidades filogenéticas com base na análise da sequência ITS do rDNA, e a L. sulphurella Hepp. Adicionalmente, espécies Chrysothrix flavovirens Tønsberg e Ochrolechia arborea (Kreyer) Almb, também se encontraram epifíticas sobre P. pinaster e P. pinea em vários pinhais ao longo da costa, representando novos registos para a flora liquénica portuguesa, bem como a espécie Lepraria elobata Tønsberg encontrada epifítica sobre P. pinaster apenas nas Dunas de Quiaios. Além disso, as espécies Hypotrachyna lividescens (Kurok.) Hale e H. pseudosinuosa (Asahina) Hale encontraram-se epifíticas sobre P. pinaster e outros forófitos nas Dunas de Quiaios, constituindo novos registos para a flora liquénica da Península Ibérica. Estes resultados põe em evidência a importância dos pinhais dunares como habitat para líquenes epífitos. Num estudo conduzido entre janeiro e julho de 2008 num pinhal dunar (Mata do Urso, Figueira da Foz), em cuja bordadura existe uma fábrica de celulose de papel, usaram-se transplantes de líquenes da espécie Flavoparmelia caperata (L.) Hale para avaliar a acumulação de trinta e três elementos putativamente emitidos por fábricas de papel e pasta de papel. A cinética da fluorescência da clorofila a foi estudada nos líquenes transplantados, através da análise dos parâmetros Fv/Fm, F0, Fm, qP, NPQ, PSII, e Exc, de forma a avaliar os efeitos decorrentes da acumulação de elementos na vitalidade dos líquenes. Pretendeu-se avaliar se a acumulação de elementos e a cinética da fluorescência da clorofila a variavam significativamente com o local e o tempo de exposição, tendo em consideração os resultados obtidos de transplantes colocados num local de referência (Dunas de Quiaios) durante o mesmo período de tempo. (Continua no verso) resumo A maior parte dos elementos — Al, B, Ba, Ca, Co, Cr, Cu, Fe, Hg, Li, Mg, Mn, Mo, Na, Ni, P, S, Sb, Sc, Sr, Ti e V — ocorreu em concentrações significativamente mais elevadas nos transplantes expostos a 500 m da fábrica. Cerca de metade dos elementos estudados — B, Ba, Cr, Fe, Hg, Mg, Mn, Mo, Na, P, Pb, S, Sb e V — encontraram-se em concentrações significativamente mais elevadas nos transplantes expostos durante 180 dias. O solo foi identificado como uma fonte parcial da maior parte dos elementos. Os parâmetros Fv/Fm, Fm, PSII e Exc variaram significativamente com o local e/ou com o tempo de exposição. Observou-se um decréscimo significativo nos parâmetros Fv/Fm e Fm nos transplantes expostos a 500 e 1000 da fábrica, e também naqueles expostos durante 135 e 180 dias. Observou-se também um decréscimo significativo nos parâmetros PSII e Exc expostos durante 180 dias. Estes parâmetros correlacionaram-se de forma negativa e significativa com a acumulação de elementos: Fv/Fm: B, Ba, Co, Fe, Hg, Mg, Mn, Mo, N, P, S, Sb e Zn; Fm: Ba, Co, Hg, Mn, Mo, N, P, S, Sb e Zn; PSII: N e P; Exc: Mn, N, P e S. Estudos acerca da diversidade liquénica efetuados nos mesmos locais onde os transplantes foram colocados no local impactado, revelaram um menor valor de diversidade liquénica a 500 m da fábrica, que foi também o único local onde se encontraram espécies nitrófilas, o que se poderá dever à deposição de amónia e/ou poeiras. À semelhança de outros estudos, este trabalho confirma que os líquenes podem ser usados com sucesso em estudos de biomonitorização, mesmo em locais florestados. Além disso, traz também informações adicionais sobre como a acumulação de elementos pode influenciar a cinética da fluorescência da clorofila a em líquenes.
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This paper presents an experimental investigation carried out on concrete filled fibre reinforced polymers (FRP) tubes, subjected to monotonic and cyclic loading. Two types of FRP materials were used: glass fibres and carbon fibres. Different failure modes and the effect of concrete fill, type of confinement materials, reinforcement ratio based on tube thickness and type of loading are examined. The study shows that external confinement of concrete by means of modern materials, such fibre reinforced polymers, can enhance its strength and ductility as well as result in large energy absorption capacity. This has important safety implications, especially in regions with seismic activity. A model that predicts the behaviour of confined concrete which takes into account the stiffness and effectiveness of different confinement materials is briefly introduced.
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Dissertação de mestrado, Biologia Marinha, Faculdade de Ciências e Tecnologia, Universidade do Algarve; Instituto Español de Oceanografia; 2015
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In this study, the diurnal atmospheric grass pollen concentration profile within the Danish city of Aarhus was shown to change in a systematic manner as the pollen season progressed. Although diurnal grass pollen profiles can differ greatly from day-to-day, it is common practice to establish the time of day when peak concentrations are most likely to occur using seasonally averaged diurnal profiles. Atmospheric pollen loads are highly dependent upon emissions, and different species of grass are known to flower and emit pollen at different times of the day and during different periods of the pollen season. Pollen concentrations are also influenced by meteorological factors – directly through those parameters that govern pollen dispersion and transport, and indirectly through the weather-driven flowering process. We found that three different profiles dominated the grass pollen season in Aarhus – a twin peak profile during the early season, a single evening profile during the middle of the season, and a single midday peak during the late season. Whilst this variation could not be explained by meteorological factors, no inconsistencies were found with the theory that it was driven by a succession of different grass species with different diurnal flowering patterns dominating atmospheric pollen loads as the season progressed. The potential for exposure was found to be significantly greater during the late-season period than during either the early- or mid-season periods.