Bacterial Active Community Cycling in Response to Solar Radiation and Their Influence on Nutrient Changes in a High-Altitude Wetland

Indexación: Web of Science; Scopus.Microbial communities inhabiting high-altitude spring ecosystems are subjected to extreme changes in solar irradiance and temperature throughout the diel cycle. Here, using 16S rRNA gene tag pyrosequencing (cDNA) we determined the composition of actively transcribing bacteria from spring waters experimentally exposed through the day (morning, noon, and afternoon) to variable levels of solar radiation and light quality, and evaluated their influence on nutrient recycling. Solar irradiance, temperature, and changes in nutrient dynamics were associated with changes in the active bacterial community structure, predominantly by Cyanobacteria, Verrucomicrobia, Proteobacteria, and 35 other Phyla, including the recently described Candidate Phyla Radiation (e.g., Parcubacteria, Gracilibacteria, OP3, TM6, SR1). Diversity increased at noon, when the highest irradiances were measured (3.3-3.9 H', 1125 W m(-2)) compared to morning and afternoon (0.6-2.8 H'). This shift was associated with a decrease in the contribution to pyrolibraries by Cyanobacteria and an increase of Proteobacteria and other initially low frequently and rare bacteria phyla (< 0.5%) in the pyrolibraries. A potential increase in the activity of Cyanobacteria and other phototrophic groups, e.g., Rhodobacterales, was observed and associated with UVR, suggesting the presence of photo activated repair mechanisms to resist high levels of solar radiation. In addition, the percentage contribution of cyanobacterial sequences in the afternoon was similar to those recorded in the morning. The shifts in the contribution by Cyanobacteria also influenced the rate of change in nitrate, nitrite, and phosphate, highlighted by a high level of nitrate accumulation during hours of high radiation and temperature associated with nitrifying bacteria activity. We did not detect ammonia or nitrite oxidizing bacteria in situ, but both functional groups (Nitrosomona and Nitrospira) appeared mainly in pyrolibraries generated from dark incubations. In total, our results reveal that both the structure and the diversity of the active bacteria community was extremely dynamic through the day, and showed marked shifts in composition that influenced nutrient recycling, highlighting how abiotic variation affects potential ecosystem functioning.http://journal.frontiersin.org/article/10.3389/fmicb.2016.01823/ful

Rubidium and zirconium abundances in massive Galactic asymptotic giant branch stars revisited

Luminous Galactic OH/IR stars have been identified as massive (>4-5 M_s) AGB stars experiencing HBB and Li production. Their Rb abundances and [Rb/Zr] ratios derived from hydrostatic model atmospheres, are significantly higher than predictions from AGB nucleosynthesis models, posing a problem to our understanding of AGB evolution and nucleosynthesis. We report new Rb and Zr abundances in the full sample of massive Galactic AGB stars, previously studied with hydrostatic models, by using more realistic extended model atmospheres. We use a modified version of the spectral synthesis code Turbospectrum and consider the presence of a circumstellar envelope and radial wind. The Rb and Zr abundances are determined from the 7800 A Rb I resonant line and the 6474 A ZrO bandhead, respectively, and we explore the sensitivity of the derived abundances to variations of the stellar (Teff) and wind (M_loss, beta and vexp) parameters in the extended models. The Rb and Zr abundances derived from the best spectral fits are compared with the most recent AGB nucleosynthesis theoretical models. The new Rb abundances are much lower (even 1-2 dex) than those derived with the hydrostatic models, while the Zr abundances are similar. The Rb I line profile and Rb abundance are very sensitive to the M_loss rate but much less sensitive to variations of the wind velocity-law and the vexp(OH). We confirm the earlier preliminary results based on a smaller sample of massive O-rich AGB stars, that the use of extended atmosphere models can solve the discrepancy between the AGB nucleosynthesis theoretical models and the observations of Galactic massive AGB stars. The Rb abundances, however, are still strongly dependent of the M_loss, which is unknown in these AGB stars. Accurate M_loss rates in these massive Galactic AGB stars are needed in order to break the models degeneracy and get reliable Rb abundances in these stars.Comment: Accepted for publication in A&A, 14 pages, 12 figures, 4 table

Applications of Artificial Neural Network (ANN) method for performance prediction of the effect of a vertical 90° bend on an air-silicone oil flow

Knowledge of how the presence of a bend can change the flow patterns of a gas–liquid mixture is important for the design of multiphase flow systems, particularly to prevent burn-out and erosion–corrosion. Burn-out and erosion–corrosion both have serious implications for heat and mass transfer. The objective of this work therefore is to train an artificial neural network (ANN), a powerful interpolation technique, to predict the effect of a vertical 90o bend on an air–silicone oil mixture over a wide range of flow rates. Experimental data for training, validation, testing and final prediction were obtained using advanced instrumentation, wire mesh sensor (WMS) and high speed camera. The performance of the models were evaluated using the mean square error (MSE), average absolute relative error (MAE), Chi square test (X2) and cross correlation coefficients (R). The performance discriminator X2 for prediction of average void fraction is 2.57e-5 and that for probability density function (PDF) of void fraction MAE is 0.0028 for best performing models. The well trained ANN is then used to predict the effects of the two input parameters individually. The predicted results show that for the before the bend scenario, the most effective input parameter that reflects a change in flow pattern is the gas superficial velocity. On the other hand, the most unfavourable output parameter to measure after the bend is the average void fraction based on the fact that the flow near the bend is a developing one

Experimental study of the hydrodynamic behaviour of slug flow in a vertical riser

This paper presents an investigation of the hydrodynamics of slug flow in a vertical 67 mm internal diameter riser. The slug flow regime was generated using a multiphase air–silicone oil mixture over a range of gas (0.42<USG<1.35 m/s) and liquid (0.05<USL<0.38 m/s) superficial velocities. Electrical capacitance tomography (ECT) was used to determine: the velocities of the Taylor bubbles and liquid slugs, the slug frequencies, the lengths of Taylor bubbles and the liquid slugs, the void fractions within the Taylor bubbles and liquid slugs and the liquid film thicknesses. A differential pressure transducer was used to measure the pressure drops along the length of the riser. It was found that the translational velocity of a Taylor bubble (the structure velocity) was strongly dependent on the mixture superficial velocity. As the gas superficial velocity, was increased, the void fraction and the lengths of the liquid slugs and the Taylor bubbles were observed to increase. The increase in gas superficial velocity causes an increase in the frictional pressure drop within the pipe, whilst the total pressure drop (which is a sum of the hydrostatic and frictional pressure drop) along the length of the riser decreases. In addition, the frequencies of the liquid slugs were observed to increase as the liquid superficial velocity increases, but to be weakly dependant on the gas superficial velocity. The manual counting method for the determination of slug frequency was found to be in good agreement with the power spectral density (PSD) computed method

Effects of thermal expansion on moderately intense turbulence in premixed flames

This study aims at analytically and numerically exploring the influence of combustion-induced thermal expansion on turbulence in premixed flames. In the theoretical part, contributions of solenoidal and potential velocity fluctuations to the unclosed component of the advection term in the Reynolds-averaged Navier-Stokes equations are compared, and a new criterion for assessing the importance of the thermal expansion effects is introduced. The criterion highlights a ratio of the dilatation in the laminar flame to the large-scale gradient of root mean square (rms) velocity in the turbulent flame brush. To support the theoretical study, direct numerical simulation (DNS) data obtained earlier from two complex-chemistry, lean H2-air flames are analyzed. In line with the new criterion, even at sufficiently high Karlovitz numbers, the results show significant influence of combustion-induced potential velocity fluctuations on the second moments of the turbulent velocity upstream of and within the flame brush. In particular, the DNS data demonstrate that (i) potential and solenoidal rms velocities are comparable in the unburnt gas close to the leading edge of the flame brush and (ii) potential and solenoidal rms velocities conditioned to unburnt gas are comparable within the entire flame brush. Moreover, combustion-induced thermal expansion affects not only the potential velocity but even the solenoidal one. The latter effects manifest themselves in a negative correlation between solenoidal velocity fluctuations and dilatation or in the counter-gradient behavior of the solenoidal scalar flux. Finally, a turbulence-in-premixed-flame diagram is sketched to discuss the influence of combustion-induced thermal expansion on various ranges of turbulence spectrum

Insulin resistance and endometrial cancer risk: A systematic review and meta-analysis

Abstract Aim: It has been suggested that chronic hyperinsulinemia from insulin resistance is involved in the etiology of endometrial cancer (EC). We performed a systematic review and meta-analysis to assess whether insulin resistance is associated with the risk of EC. Methods: We searched PubMed-Medline, Embase, Scopus, and Web of Science for articles published from database inception through 30th September 2014. We included all observational studies evaluating components defining insulin resistance in women with and without EC. Quality of the included studies was assessed by NewcastleeOttawa scale. Randomeffects models and inverse variance method were used to meta-analyze the association between insulin resistance components and EC. Results: Twenty-five studies satisfied our inclusion criteria. Fasting insulin levels (13 studies, n Z 4088) were higher in women with EC (mean difference [MD] 33.94 pmol/L, 95% confi- dence interval [CI] 15.04e52.85, p Z 0.0004). No differences were seen in postmenopausal versus pre- and postmenopausal subgroup analysis. Similarly, non-fasting/fasting C-peptide levels (five studies, n Z 1938) were also higher in women with EC (MD 0.14 nmol/L, 95% CI 0.08e0.21, p < 0.00001). Homeostatic model assessment - insulin resistance (HOMA-IR) values (six studies, n Z 1859) in EC patients were significantly higher than in women without EC (MD 1.13, 95% CI 0.20e2.06, p Z 0.02). There was moderate-to-high heterogeneity among the included studies. Conclusion: Currently available epidemiologic evidence is suggestive of significantly higher risk of EC in women with high fasting insulin, non-fasting/fasting C-peptide and HOMAIR values.Revisión por pare

Comparison of experimental and Computational Fluid Dynamics (CFD) studies of slug flow in a vertical riser

This paper presents a comparison of the results obtained from experiments and CFD studies of slug flow in a vertical riser. A series of two experimental investigations were carried out on a 6 m vertical pipe with a 0.067 m internal diameter charged with an air–silicone oil mixture. For the first set of experiments, the riser was initially full of air, and then liquid and gas flows set to liquid and gas superficial velocities = 0.05 and 0.344 m/s, respectively, electrical capacitance tomography (ECT) and wire mesh sensor (WMS) transducers were employed. In the second one, the riser was initially full of (static) liquid, and then liquid and gas flows set to liquid and gas superficial velocities = 0.05 and 0.344 m/s, respectively, only ECT was used. A characterisation of the observed slug flow regimes was carried out. This includes the evaluation of the instantaneous distribution of the phases over the pipe cross-section, the Probability Density Function (PDF) of void fraction, time series of cross-sectional void fraction, Power Spectral Density (PSD), structure velocity of the Taylor bubble, lengths of the liquid slug and Taylor bubble and void fractions in the liquid slug and Taylor bubble. The simulation results were validated both qualitatively and quantitatively against experimental data. A reasonably good agreement was observed between the results of the experiment and CFD

Experimental study of the hydrodynamic behaviour of slug flow in a horizontal pipe

This paper investigates the unsteady hydrodynamic behaviour of slug flow occurring within an air–silicone oil mixture, within a horizontal 67 mm internal diameter pipe. A series of slug flow regime experiments were performed for a range of injected air superficial velocities (0.29–1.4 m s−1) and for liquid flows with superficial velocities of between 0.05–0.47 m s−1. A pair of Electrical Capacitance Tomography (ECT) probes was used to determine: the slug translational velocities of the elongated bubbles and liquid slugs, the slug frequencies, the lengths of elongated bubbles and the liquid slugs, the void fractions within the elongated bubbles and liquid slugs. The pressure drop experienced along the pipe was measured using a differential pressure transducer cell (DP cell). A comparative analysis of the current experimental data and that previously published experimental confirms good agreement

A non-separability measure for spatially disjoint vectorial fields

Vectorial forms of structured light that are non-separable in their spatial and polarisation degrees of freedom have become topical of late, with an extensive toolkit for their creation and control. In contrast, the toolkit for quantifying their non-separability, the inhomogeneity of the polarisation structure, is less developed and in some cases fails altogether. To overcome this, here we introduce a new measure for vectorial light, which we demonstrate both theoretically and experimentally. We consider the general case where the local polarisation homogeneity can vary spatially across the field, from scalar to vector, a condition that can arise naturally if the composite scalar fields are path separable during propagation, leading to spatially disjoint vectorial light. We show how the new measure correctly accounts for the local path-like separability of the individual scalar beams, which can have varying degrees of disjointness, even though the global vectorial field remains intact. Our work attempts to address a pressing issue in the analysis of such complex light fields, and raises important questions on spatial coherence in the context of vectorially polarised light