Downstream Effluent Research Articles

Differential Effects of Heated Perfusate on Morphology, Viability, and Dissemination of Staphylococcus epidermidis Biofilms.

The biofilm phenotype offers bacterial communities protection from environmental factors, as evidenced by its role in the viability, persistence, and virulence of cells under conditions in which flow is present, such as in riverbeds, industrial piping networks, and the human circulatory system. Here, we examined the hypothesis that temperature-an environmental factor that affects the growth of the Gram-positive bacterium Staphylococcus epidermidis-controls, through dual mechanisms, persistence of this bacterial strain in a shear environment characteristic of the human circulatory system. We demonstrated that temperature and antibiotics impact the surface-adhered biofilm and material disseminated downstream in different ways. Specifically, by means of three-dimensional (3D) confocal and scanning electron microscopy, an increase in surface-adhered biofilm heterogeneity was observed with increasing temperature. Additionally, we found a 4-log decrease in cell viability at the biofilm surface as the perfusate temperature was increased from 37°C to 50°C. Finally, the viability of cell-containing fragments that were disseminated from the substrate was assessed by downstream sampling, culture, and optical density measurement. We found that although temperature decreased the viability of the surface-adhered biofilm, the downstream material remained viable. And yet, in the presence of antibiotics, the growth of disseminated material was nearly completely inhibited, even though the addition of antibiotics had no significant impact on the viability of the surface-adhered biofilm. The mechanism involves both biofilm structural damage, as quantified by morphology of debrided material, and reduced cell viability, as quantified by assay of bacterial cells present in the surface-adherent biofilm and in the downstream effluent. The results potentially identify parameter ranges in which elevated temperature could augment current antibiotic treatment regimens.IMPORTANCE Bacterial biofilms are a leading cause of medical device infections. Staphylococcus epidermidis is commonly responsible for these types of infections. With increasing occurrences of antibacterial resistance, there has been a new push to explore treatment options that augment traditional antibiotic therapies. Here, we show how thermal treatment can be applied to both degrade bacterial biofilms on substrates and impede the proliferation of cells that detach from them. Understanding the response of both surface-adhered and dispersed bacterial cells under thermal stress conditions is a foundational step toward the development of an in situ treatment/remediation method for biofilm growth in medical devices; such an application could use oscillatory flow of heated fluid in a catheter as an adjuvant to antibiotic treatment. The work furthermore provides new insight into the viability of disseminated biofilm material.

Highly selective Si3N4/SiO2 etching using an NF3/N2/O2/H2 remote plasma. I. Plasma source and critical fluxes

Highly selective plasma etching of silicon nitride (Si3N4), while not etching silicon dioxide (SiO2), is a critical step in the fabrication of microelectronics devices. In many applications, this etching must be damage-free and isotropic, which then motivates the use of remote plasmas where the reactants interacting with the substrate are dominantly neutral species. In this paper and Paper II, mechanisms for highly selective Si3N4 etching in remote plasmas are discussed based on results from experiments and simulations. It has been shown experimentally that high Si3N4/SiO2 etch selectivity (≈380) can be achieved in the downstream effluent of an NF3/N2/O2/H2 plasma. The authors found that H2 plays a principal role in the reaction mechanism as Si3N4/SiO2 selectivity shows a sharp maximum as a function of the H2 flow rate. Based on this observation, and measured densities of F-atoms and H2 in the process chamber, a mechanism of selective Si3N4/SiO2 etching is proposed in which HF molecules in vibrationally excited states accelerate etching reactions. A reaction mechanism for NF3/N2/O2/H2 plasmas and its afterglow was developed to computationally determine the species densities and fluxes on the wafer level, validated by comparing with experimentally measured F-atom and H2 densities. The calculated species densities and fluxes were used as input to an analytical model of Si3N4 and SiO2 etching based on the results of quantum chemistry simulations. This paper presents experimental results (etching data and species densities), the reaction mechanism for NF3/N2/O2/H2 plasmas, and the results of simulations of gas phase chemistry. Quantum chemistry simulations of elementary etching reactions, description of the analytical model of Si3N4 and SiO2 etching, calculations of the etch rates, and Si3N4/SiO2 selectivity with this model are presented in Paper II.

Combined ethanol and methane production from switchgrass (Panicum virgatum L.) impregnated with lime prior to steam explosion

Pretreatments are crucial to achieve efficient conversion of lignocellulosic biomass to soluble sugars. In this light, switchgrass was subjected to 13 pretreatments including steam explosion alone (195 °C for 5, 10 and 15 min) and after impregnation with the following catalysts: Ca(OH)2 at low (0.4%) and high (0.7%) concentration; Ca(OH)2 at high concentration and higher temperature (205 °C for 5, 10 and 15 min); H2SO4 (0.2% at 195 °C for 10 min) as reference acid catalyst before steam explosion. Enzymatic hydrolysis was carried out to assess pretreatment efficiency in both solid and liquid fraction. Thereafter, in selected pretreatments the solid fraction was subjected to simultaneous saccharification and fermentation (SSF), while the liquid fraction underwent anaerobic digestion (AD). Lignin removal was lowest (12%) and highest (35%) with steam alone and 0.7% lime, respectively. In general, higher cellulose degradation and lower hemicellulose hydrolysis were observed in this study compared to others, depending on lower biomass hydration during steam explosion. Mild lime addition (0.4% at 195 °C) enhanced ethanol in SSF (+28% than steam alone), while H2SO4 boosted methane in AD (+110%). However, methane represented a lesser component in combined energy yield (ethanol, methane and energy content of residual solid). Mild lime addition was also shown less aggressive and secured more residual solid after SSF, resulting in higher energy yield per unit raw biomass. Decreased water consumption, avoidance of toxic compounds in downstream effluents, and post process recovery of Ca(OH)2 as CaCO3 represent further advantages of pretreatments involving mild lime addition before steam explosion.

Fast, downstream removal of photoresist using reactive oxygen species from the effluent of an atmospheric pressure plasma Jet

In the semiconductor industry the plasma removal of photoresist (PR) between processing steps (so-called plasma ashing) is a critical issue in enabling the creation of advanced wafer architectures associated with the next generation of devices. We investigated the feasibility of a novel atmospheric-pressure plasma jet (APPJ) to remove PR. Our device operates at atmospheric pressure, eliminating the need for low-pressure operation used in conventional plasma ashing. Also, our method uses the downstream effluent of the source, avoiding issues relating to ion bombardment, a known hinderance to atomic precision manufacturing. Two-photon absorption laser induced fluorescence (TALIF) measurements of the system has shown that the PR removal rate is directly correlated with the atomic oxygen flux to the surface. The maximum removal rates achieved were 10 μm min−1, a factor of 100 improvement over typical low-pressure methods, while the quality of the etch, as assessed by attenuated total reflection fourier transform infrared spectroscopy, was found to be equal to low-pressure standards.

Combined ethanol and methane production using steam pretreated sugarcane bagasse

Efficient energy production relies on complementary use of crop residues, to enhance the amount of energy obtained per unit biomass. In this frame, sugarcane bagasse (SB) was pretreated and the resulting slurry and liquid fraction served, respectively, for simultaneous saccharification and fermentation (SSF) at high solid concentration (15%), and anaerobic digestion (AD). More specifically, SB was subjected to twelve pretreatments to enhance fiber deconstruction and subsequent energy output: steam explosion alone (195°C for 5, 10 and 15min), after impregnation with 0.4% and 0.7% Ca(OH)2, and at 205°C for the same three times after 0.7% Ca(OH)2 addition. After pretreatment, enzymatic hydrolysis was carried out on washed solid fraction; glucose and xylose were determined on this fraction as well as residual liquid fraction. On this latter, inhibitors (acetic and formic acid, furfural and 5-hydroxymethylfurfural) were also determined. Based on high glucose yield in enzymatic hydrolysis, three pretreatments were selected for SSF of the slurry. The same pretreatments underwent AD of the liquid fraction. Inhibitors augmented at increasing time and temperature, although never achieved critical levels. Lignin removal (range, 17–38%) was enhanced by lime addition, whereas increasing temperature and time did not contribute to delignification. Glucose yield in washed solid fraction varied accordingly. SSF exhibited the highest ethanol yield with mild lime addition (60% of theoretical) vs. steam alone (53%). However, modest yields were generally evidenced (average, 55%) as a result of high viscosity, especially in the case of high lime dose in SSF at high solid concentration. Combined energy yield (ethanol, methane and solid residue) proved lime effectiveness as catalyst in steam explosion of SB, beside two intrinsic advantages: low water consumption in SSF at high solid concentration, and the possibility of lime removal from downstream effluents through carbonation.

Decontamination of106Ru and99Tc bearing effl uents by chemical treatment

ABSTRACT Ion exchange separation of 137Cs and 90Sr from alkaline intermediate level waste (ILW) generated at back-end of nuclear fuel cycle results in downstream effluent containing substantial amounts of 106Ru and 99Tc activity. Efforts were made to develop suitable chemical treatment based processes for decontamination of these effluents. Feasibility of using various metal sulphides alone or in combination was examined for simultaneous removal of 106Ru and 99Tc. Based on these studies, a formulation involving precipitation of CoS in conjunction with FeS has been proposed for effective decontamination of the effluent. Presence of dibutyl phosphate (DBP) in some of the streams of ILW interfered with decontamination of 106Ru. A process involving removal of DBP as Fe-DBP complex followed by CoS and FeS precipitation developed in this study was found to be effective in decontamination of the effluent containing gross beta activity of 5550 to 37 Bq ml−1. It is inferred that the process is promising for practi...

Evaluation of estrogenic disrupting potency in aquatic environments and urban wastewaters by combining chemical and biological analysis

We studied estrogenic disrupting potency in rivers and wastewaters in the Orge catchment area near Paris, using analytical and biological approaches simultaneously. The MELN test was applied to surface-water samples, urban storm run-off and wastewater-treatment plant (WWTP) effluent in parallel with analytical determinations of natural estrogens and synthetic estrogen (ethinylestradiol) using liquid chromatography and tandem mass spectrometry. We quantified estrone in all samples in the range 0.1–15.7 ng/L. We also quantified β-estradiol in all samples, but at a lower level (0.1–2.3 ng/L), but we never detected α-estradiol. We quantified ethinylestradiol only in WWTP effluent (0.2 ng/L); we measured estriol in WWTP effluent (12.1 ng/L) and downstream effluent (4.9 ng/L). The biological responses using the MELN test closely followed the chemical responses. Analytical quantification of estrogens appears to be a simple way to trace estrogenic disruption in surface waters of urban areas, as these hormones are mainly responsible for biological effects.

Corrosion Behavior of Stainless Steel and Aluminum in a Downstream Environment of CF 4 / O 2 Microwave Plasma

The corrosion characteristics of type 316 stainless steel, component metals of the steel (Fe, Cr, Ni, and Mo), and Al in the downstream effluent of a plasma have been examined as a function of temperature (25-300°C) and feed gas composition (0-30 vol % Type 316, Fe, and Ni showed weight gains due to the formation of surface reaction films, which consist predominantly of involatile metal fluorides and grow parabolically with exposure time. Pure Cr and Mo exhibited weight losses due to the formation of volatile metal fluorides or oxyfluorides. The corrosion rate of these metals increased with increasing temperature, while that of Al was less than the limit of detection at all temperatures examined. The corrosion rates of Cr and Mo increased with increasing content of the reactant gas and reached maxima at whereas those of type 316, Fe, and Ni were nearly independent of the content. At 300°C, films underwent etching in a similar manner as Cr metal, while NiO, and films transformed into involatile fluorides or oxyfluorides. Mass spectrometric analyses suggested that F atoms and molecules are dominant species responsible for corrosion in the downstream effluent. The phase stability diagrams estimated metal fluorides to be the thermodynamically favored reaction products on the metals exposed to the effluent. © 2002 The Electrochemical Society. All rights reserved.

Rheolytic Thrombectomy with Use of the AngioJet-F105 Catheter: Preclinical Evaluation of Safety

A preclinical evaluation of the safety of the AngioJet-F105 rheolytic thrombectomy catheter. The AngioJet-F105 catheter uses multiple retrograde high-speed fluid jets impinging on a primary aspiration lumen to create a hydrodynamic recirculation vortex that traps and fragments adjacent thrombus, with simultaneous evacuation of the resulting debris through the aspiration lumen. The effect of the AngioJet on treated vessels was evaluated in 10 canines. Vascular integrity on histopathologic examination and endothelial coverage on scanning electron microscopic study were examined in 15 vessel segments treated with the AngioJet-F105 catheter, compared with four vessel segments subjected to the Fogarty balloon maneuver, and 10 untreated vessel segments. The size distribution of particulate debris, upstream and downstream, after thrombectomy was determined in a flow-circuit model simulating the superficial femoral artery. Aliquots from the downstream effluent were then injected into the renal arteries of two healthy canines. The device caused only minimal focal endothelial denudation and no significant deep injury. No significant difference in endothelial coverage occurred in AngioJet-treated vessel segments compared to untreated control vessels (mean +/- standard deviation: 88.0% +/- 7.9% vs 89.7% +/- 11.6%, P = .77). Vessels treated with the Fogarty balloon pullback maneuver had significantly less residual endothelial coverage (58.0% +/- 8.0%, P < .03). Particulate microemboli in the effluent of the flow model accounted for 12% of the initial thrombus volume (0% > 100 microm, 99.83% < or = 10 microm). Histopathologic evaluation of the four renal beds injected with the resulting debris demonstrated no signs of necrosis. A moderate transient increase in plasma-free hemoglobin occurred, with a mild corresponding decrease in hematocrit. The AngioJet-F105 catheter resulted in only mild and focal injury to the treated vessels. The vast majority of resulting particulate debris consist of microscopic particles, without significant ischemic effect.

A specific detector for nitrogen and halogen compounds in TLC on coated quartz rods

AbstractA new detector has been developed for use with the Iatroscan TH‐10 TLC/FID instrument‐a “solid‐phase” chromatographic system (SPC). This new detection system contains a unique stage of detection that is called a flame thermionic ionization detector or FTID. The FTID evolved from a similar device that recently has been used in gas chromatography. The basic concept of an FTID is that organic sample compounds are first decomposed by combustion in an H2‐air flame. The FTID does not sense any of the ionization produced directly in the flame but, instead, re‐ionizes the combustion products by means of a unique thermionic transducer placed in the downstream effluent of the flame. The thermionic transducer ionizes specifically only those combustion products which are acidic or electronegative in chemical activity. In particular, organic samples containing nitrogen (N) or halogen atoms combust to products which are especially well detected with high sensitivity. Hence, the FTID adds to the Iatroscan a state‐of‐the‐art detection stage which produces large signals for nitrogen and halogen compounds and negligible signals for hydrocarbon compounds.