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Strategies for recovery and recycling of nutrients from municipal sewage treatment effluent and hydrothermal liquefaction wastewaters for the growth of the microalga Scenedesmus sp. AMDD
No full textDeveloping reliable processes for recycling nutrients obtained from hydrothermal liquefaction of algae could improve the sustainability and scalability of algae based biofuels. In this study, hydrothermal liquefaction (HTL) wastewater was obtained from continuous liquefaction experiments in plug flow reactor and two strategies were evaluated to recycle both phosphorous and nitrogen for the growth of Scenedesmus sp. AMDD. The first strategy involved using HTL wastewater as a source of nitrogen while minimizing the algae growth inhibitors present in wastewater using hydrothermal gasification and activated carbon adsorption. The second strategy focused on recovering nitrogen as ammonia and phosphorous as struvite from HTL wastewater and recycling only the nutrients thereby decoupling the HTL wastewater and most inhibitors from nutrient recycle process. Water samples obtained from these two strategies were analyzed using various techniques (elemental analysis, gas chromatography, and hydrogen NMR) and potential growth inhibitors were identified as nitrogen containing heteroaromatics. The second approach relied solely on activated carbon treatment to remove these heteroaromatics. Although comparable growth rates were obtained using the first approach after strong dilution, algae growth and biomass yields obtained using the latter approach was much more robust as indicated by less variability, similar rates and biomass yields as compared to the synthetic medium. Apparent nitrogen and phosphorous removal rates for this case were\u202f>\u202f99% and 68\u202f\ub1\u202f5.7%, respectively. This approach of decoupling nitrogen and phosphorous nutrients from HTL water offers a flexible, reliable, and scalable process for recycling nutrients without the inhibitors in HTL water and an important step towards the commercial production of algae for biofuels.Peer reviewed: YesNRC publication: Ye
Feasibility of a microalgal wastewater treatment for the removal of nutrients under non-sterile conditions and carbon limitation
No full textMicroalgal treatment of municipal wastewater has been discussed as a novel strategy for the removal of excess nutrients and metals. Additionally, a number of products can be obtained from the resulting microalgal biomass, including energy products that can be utilized within the treatment plant. However, the effectiveness of these microalgal systems can be significantly affected by the natural biota, which could consequently impact the quality of the wastewater effluent. This study evaluated the performance of two microalgal species in the removal of nutrients from non\u2010sterile, highly concentrated synthetic wastewater. The results showed that monocultures of Scenedesmus sp. AMDD and Chlorella sorokiniana could remove up to 60\u2009% NH4+, and 44 and 35\u2009% PO43\u2010, respectively, in a semi\u2010continuous cultivation mode without negatively affecting effluent quality.Peer reviewed: YesNRC publication: Ye
Roles of cytosolic glutamine synthetases in arabidopsis development and stress responses
No full textGlutamine (Gln) has as a central role in nitrogen (N) and carbon (C) metabolism. It is synthesized during assimilation of ammonium by cytosolic and plastidial glutamine synthetases (GS; EC 6.1.1.3). Arabidopsis thaliana has five cytosolic GS (GS1) encoding genes designated as GLN1;1\u2013GLN1;5 and one plastidial GS (GS2) gene. In this report that concerns cytosolic GS, we show by analyzing single, double and triple mutants that single genes were dispensable for growth under laboratory conditions. However, loss of two or three GS1 isoforms impacted plant form, function and the capacity to tolerate abiotic stresses. The loss of GLN1;1, GLN1;2 and GLN1;3 resulted in a significant reduction of vegetative growth and seed size. In addition, we infer that GLN1;4 is essential for pollen viability but only in the absence of GLN1;1 and GLN1;3. Transcript profiling revealed that expression of GLN1;1, GLN1;2, GLN1;3 and GLN1;4 was repressed by salinity and cold stresses. Among all single gln1 mutants, growth of gln1;1 seedlings showed an enhanced sensitivity to the GS inhibitor phosphinothricin (PPT), as well as to cold and salinity treatments, suggesting a non-redundant role for GLN1;1. Furthermore, the increased sensitivity of gln1;1 mutants to methyl viologen was associated with an accelerated accumulation of reactive oxygen species (ROS) in the thylakoid of chloroplasts. Our data demonstrate, for the first time, an involvement of the cytosolic GS1 in modulating ROS homeostasis in chloroplasts. Collectively, the current study establishes a link between cytosolic Gln production and plant development, ROS production and stress tolerance.Peer reviewed: YesNRC publication: Ye
Application of direct analysis in real time to the study of chemical vapor generation mechanisms: identification of intermediate hydrolysis products of amine-boranes
No full textIn order to elucidate controversial results emerging in chemical vapor generation (CVG) for trace element determination, we conducted a series of experiments devoted to the identification of intermediates formed by acid hydrolysis of amine-boranes. For the first time, direct analysis in real time coupled with high-resolution mass spectrometry (DART-Orbitrap) was applied for detection of this class of compounds. Mass spectra of both solid amine-boranes and their aqueous solutions (pH ~\u20098, no hydrolysis) were acquired for understanding their ionization pathway. Mass spectra of aqueous solutions of t-BuNH2\ub7BH3 and Me2NH\ub7BH3 were acquired under conditions that are employed in CVG (0.017\u20134.0 mol L 121 HCl, 0.167\u20130.2 mol L 121 borane reagent). The results disclose a reactivity driven by pH of amine-boranes undergoing hydrolysis. At low acidity, the hydrolysis proceeds according to the currently accepted displacement mechanisms (i.e., R3N\ub7BH3 + H3O+ \u2192 R3NH+ + H2OBH3). At higher acidity, N-tert-butyl, cyclotriborazane, and bis(dimethylamino)boronium were identified, for the first time, during the hydrolysis of t-BuNH2\ub7BH3 and Me2NH\ub7BH3, respectively. Formation of these intermediates was ascribed to a hydrolysis pathway starting with the ionization of the amine-borane, (i.e., R3N\ub7BH3 + H3O+ \u2192 [(H2O)R3NBH2] + + H2). The new evidence explains the anomalous behavior observed in CVG by amine-borane derivatization, and updates the currently accepted mechanisms for the acid hydrolysis of amine-boranes.Peer reviewed: YesNRC publication: Ye
Identification of a \u3b1\u2010helical molten globule intermediate and structural characterization of \u3b2\u2010cardiotoxin, an all \u3b2\u2010sheet protein isolated from the venom of Ophiophagus hannah(king cobra)
No full text\u3b2\u2010Cardiotoxin is a novel member of the snake venom three\u2010finger toxin (3FTX) family. This is the first exogenous protein to antagonize \u3b2\u2010adrenergic receptors and thereby causing reduction in heart rates (bradycardia) when administered into animals, unlike the conventional cardiotoxins as reported earlier. 3FTXs are stable all \u3b2\u2010sheet peptides with 60\u201380 amino acid residues. Here, we describe the three\u2010dimensional crystal structure of \u3b2\u2010cardiotoxin together with the identification of a molten globule intermediate in the unfolding pathway of this protein. In spite of the overall structural similarity of this protein with conventional cardiotoxins, there are notable differences observed at the loop region and in the charge distribution on the surface, which are known to be critical for cytolytic activity of cardiotoxins. The molten globule intermediate state present in the thermal unfolding pathway of \u3b2\u2010cardiotoxin was however not observed during the chemical denaturation of the protein. Interestingly, circular dichroism (CD) and NMR studies revealed the presence of \u3b1\u2010helical secondary structure in the molten globule intermediate. These results point to substantial conformational plasticity of \u3b2\u2010cardiotoxin, which might aid the protein in responding to the sometimes conflicting demands of structure, stability, and function during its biological lifetime.Peer reviewed: YesNRC publication: Ye
Characterizing the properties of nearby molecular filaments observed with Herschel
No full textContext. Molecular filaments have received special attention recently thanks to new observational results on their properties. In particular, our early analysis of filament properties from Herschel imaging data in three nearby molecular clouds revealed a narrow distribution of median inner widths centered at a characteristic value of about 0.1 pc. Aims. Here, we extend and complement our initial study with a detailed analysis of the filamentary structures identified with Herschel in eight nearby molecular clouds (at distances <500 pc). Our main goal is to establish statistical distributions of median properties averaged along the filament crests and to compare the results with our earlier work based on a smaller number of filaments. Aims. We use the column density (NH2) maps derived from Herschel data and the DisPerSE algorithm to trace a network of individual filaments in each cloud. We analyze the density structure along and across the main filament axes in detail. We build synthetic maps of filamentary clouds to assess the completeness limit of our extracted filament sample and validate our measurements of the filament properties. These tests also help us to select the best choice of parameters to be used for tracing filaments with DisPerSE and fitting their radial column density profiles. Methods. Our analysis yields an extended sample of 1310 filamentary structures and a selected sample of 599 filaments with aspect ratios larger than 3 and column density contrasts larger than 0.3. We show that our selected sample of filaments is more than 95% complete for column density contrasts larger than 1, with only ~ 5% spurious detections. On average, more than 15% of the total gas mass in the clouds, and more than 80% of the dense gas mass (at NH2 > 7
7 10 21 cm -2 ), is found to be in the form of filaments. Analysis of the radial column density profiles of the 599 filaments in the selected sample indicates a narrow distribution of crest-averaged inner widths, with a median value of 0.10 pc and an interquartile range of 0.07 pc. In contrast, the extracted filaments span wide ranges in length, central column density, column density contrast, and mass per unit length. The characteristic filament width is well resolved by Herschel observations, and a median value of ~0.1 pc is consistently found using three distinct estimates based on (1) a direct measurement of the width at half power after background subtraction, as well as (2) Gaussian and (3) Plummer fits. The existence of a characteristic filament width is further supported by the presence of a tight correlation between mass per unit length and central column density for the observed filaments. Results. Our detailed analysis of a large filament sample confirms our earlier result that nearby molecular filaments share a common mean inner width of ~0.1 pc, with typical variations along and on either side of the filament crests of about \ub1 0.06 pc around the mean value. This observational result sets strong constraints on possible models for the formation and evolution of filaments in molecular clouds. It also provides important hints on the initial conditions of star formation.Peer reviewed: YesNRC publication: Ye
Contribution of active iron uptake to Acinetobacter baumannii pathogenicity
No full textAcinetobacter baumannii is an important nosocomial pathogen. Mechanisms that allow A. baumannii to cause human infection are still poorly understood. Iron is an essential nutrient for bacterial growth in vivo, and the multiplicity of iron uptake systems in A. baumannii suggests that iron acquisition contributes to the ability of A. baumannii to cause infection. In Gram-negative bacteria, active transport of ferrisiderophores and heme relies on the conserved TonB-ExbB-ExbD energy-transducing complex, while active uptake of ferrous iron is mediated by the Feo system. The A. baumannii genome invariably contains three tonB genes (tonB1, tonB2, and tonB3), whose role in iron uptake is poorly understood. Here, we generated A. baumannii mutants with knockout mutations in the feo and/or tonB gene. We report that tonB3 is essential for A. baumannii growth under iron-limiting conditions, whereas tonB1, tonB2, and feoB appear to be dispensable for ferric iron uptake. tonB3 deletion resulted in reduced intracellular iron content despite siderophore overproduction, supporting a key role of TonB3 in iron uptake. In contrast to the case for tonB1 and tonB2, the promoters of tonB3 and feo contain functional Fur boxes and are upregulated in iron-poor media. Both TonB3 and Feo systems are required for growth in complement-free human serum and contribute to resistance to the bactericidal activity of normal human serum, but only TonB3 appears to be essential for virulence in insect and mouse models of infection. Our findings highlight a central role of the TonB3 system for A. baumannii pathogenicity. Hence, TonB3 represents a promising target for novel antibacterial therapies and for the generation of attenuated vaccine strains.Peer reviewed: YesNRC publication: Ye
EuroGames16: evaluating change detection in online conversation
No full textWe introduce the challenging task of detecting changes from an online conversation. Our goal is to detect significant changes in, for example, sentiment or topic in a stream of messages that are part of an ongoing conversation. Our approach relies on first applying linguistic preprocessing or collecting simple statistics on the messages in the conversation in order to build a time series. Change point detection algorithms are then applied to identify the location of significant changes in the distribution of the underlying time series. We present a collection of sport events on which we can evaluate the performance of our change detection method. Our experiments, using several change point detection algorithms and several types of time series, show that it is possible to detect salient changes in an on-line conversation with relatively high accuracy.Peer reviewed: YesNRC publication: Ye
Plastic fuel tank design optimization using BlowView software
No full textThe aim of this work is to show both the latest developments and capabilities of BlowDesign, the design optimization package of the BlowView1 software, to improve the extrusion blow molding process for the manufacturing of multilayer plastic fuel tanks (PFT). The design optimization scheme in BlowDesign for the manufacturing of blow moulded multilayer fuel tanks uses two main consecutive optimization steps: die shaping geometry and processing conditions optimization. The die shaping optimization consists of manipulating the geometry of the bushing-mandrel shape in order to distribute the material uniformly around the inflated part using static flexible deformable ring (SFDR) die technology. The process optimization consists of manipulating design variables such as the extrusion flow rate, extrusion time, pre-blow pressure and the die gap programming profile (programming points) to minimize the part thickness variance around the desired thickness distribution or to minimize the part weight subject to a minimum thickness constraint. The client performance requirement criteria could be achieved using one of the following die technologies: vertical wall distribution system (VWDS), partial wall distribution system (PWDS) or die slide motion (DSM). In this work, the proposed optimization approach will be investigated on a specific Jerry Can and PFT. During the former optimization, a barrier layer thickness optimization is performed simultaneously to minimize the hydrocarbon permeation through the PFT wall to satisfy the daily emission imposed by government regulation. This numerical optimization is shown to be an excellent tool to cost effectively improve the design while satisfying the process constraints.Peer reviewed: NoNRC publication: Ye
Proceedings of the Third Meeting on Climatic Data and Loads and Flood-Resistant Buildings
No full textPeer reviewed: NoNRC publication: Ye