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Low-voltage stimulated denitrification performance of high-salinity wastewater using halotolerant microorganisms
No full textNitrate is a common contaminant in high-salinity wastewater, which has adverse effects on both the environment and human health. However, conventional biological treatment exhibits poor denitrification performance due to the high-salinity shock. In this study, an innovative approach using an electrostimulating microbial reactor (EMR) was explored to address this challenge. With a low-voltage input of 1.2 V, the EMR reached nitrate removal kinetic parameter (kNO3-N) of 0.0166–0.0808 h−1 under high-salinities (1.5 %-6.5 %), which was higher than that of the microbial reactor (MR) (0.0125–0.0478 h−1). The mechanisms analysis revealed that low-voltage significantly enhanced microbial salt-in strategy and promoted the secretion of extracellular polymeric substances. Halotolerant denitrification microorganisms (Pseudomonas and Nitratireductor) were also enriched in EMR. Moreover, the EMR achieved a NO3-N removal efficiency of 73.64 % in treating high-salinity wastewater (salinity 4.69 %) over 18-cycles, whereas the MR only reached 54.67 %. In summary, this study offers an innovative solution for denitrification of high-salinity wastewate
Coupling amino acid injection and slow depressurization with hydrate swapping exploitation: An effective strategy to enhance in-situ CO<sub>2</sub> storage in hydrate-bearing sediment
No full textNatural gas (mainly methane, CH4) hydrates are a prospective energy resource. CH4-CO2 hydrate swapping has the advantages of producing CH4 gas for clean energy recovery and simultaneously storing CO2 in-situ for carbon emission reduction. Depressurization is the most feasible strategy to recover CH4 from hydrate-bearing sediments. The combination of these two methods has been proved feasible to produce CH4-rich gas and store CO2-rich hydrate. However, the efficiencies of CH4 recovery and CO2 storage decrease significantly when the reservoir is depressurized to the points below CH4/CO2 mixed hydrate equilibrium pressure causing unwanted CO2-rich hydrate dissociation. In this work, amino acid injection (AAI) (L-tryptophan or L-methionine) was employed for CH4/CO2 mixed hydrate formation with enhanced CO2 storage, followed by slow depressurization in various controlled manners, i.e., multistep depressurization, constant-pressure depressurization or multistep constant-pressure depressurization (MCPD) to recover CH4 from the mixed hydrates. In-situ Raman and gas chromatograph (GC) were employed to confirm the compositions of mixed hydrates formed and mixed gases produced. The results showed that AAI decreased CO2 fraction from 30 mol% to 3.1–8.4 mol% in the residual gas, indicating the technique helped regaining reservoir pressure and kinetically promoting further hydrate formation. The pressure recovered by AAI compensated the performance discrepancy caused by different solutions injected. Raman spectra and GC results confirmed CO2-rich hydrate formation, and up to 91.3% CO2 was stored in the sediments. During mixed hydrate dissociation, slow depressurization maintained high CH4-rich gas production (CH4 fraction over 87.5 mol%), with 9.7–30.6% CH4-rich gas recovered and 5.8–17.9% water produced among various trials. The best performance of CO2 storage and CH4 recovery was achieved by AAI of 1000 ppm L-tryptophan at 33.2 bar and MCPD to 20.9 bar, showing a final CO2 storage efficiency of 82.3%, gas recovery percentage of 30.6% and gas/water production ratio of 37.9 STP m3/m3. These findings provided guidance to enhance CO2-rich hydrate storage and CH4-rich gas production by multiple AAI and slow depressurization at controlled depletion pressures after hydrate swapping
Towards a mechanistic model of oxidase deactivation in a bubble column
No full textDespite the many advantages of biocatalysis, enzyme stability remains an issue. This work investigates the long-term kinetic stability of a water-forming NAD(P)H-oxidase (NOX2), an enzyme of potential industrial interest for NAD(P)H regeneration, in a bubble column sparged with air, which enables reasonable oxygen transfer but without drastic enzyme deactivation. Experiments have been performed with the particular goal of explaining the observed two-stage deactivation trend. We show evidence supporting the hypothesis that the first stage is related to the adsorption of enzymes to the interface, followed by a subsequent deactivation stage at the interface.The characterization of NOX deactivation in the bubble column setup, complemented by additional’quiescent’ experiments, has enabled the development of a first principles model as the first step towards a complete mechanistic model of oxidase deactivation at gas–liquid interfaces
Onboard identification of stability parameters including nonlinear roll damping via phase-resolved wave estimation using measured ship responses
No full textAccurate estimation of the roll damping of a ship is important for reliable prediction of roll motions. In particular, characterization and prediction of parametric roll incidence and other events associated with large roll angles require detailed knowledge about the damping terms. In the present paper, an approach to identify the stability parameters, i.e. linear and nonlinear roll damping coefficients in conjunction with the natural roll frequency, based on onboard response measurements is proposed. The method starts by estimating the encountered wave profile using wave-induced response measurements other than roll, e.g., heave, pitch, and sway motions. The estimated wave profile is then fed into a physic-based nonlinear roll estimator, and then the stability parameters that best reproduce the measured roll motion are identified by optimization. In turn, in-situ identification can be achieved while simultaneously collecting the response measurements. A numerical investigation using synthetic response measurements is made first, then follows an experimental investigation using a scaled model ship. Good results have been obtained in both long-crested and short-crested irregular waves
Modelling thermophysical properties of mixtures of 2-hydroxyethyl ammonium-based ionic liquids + water, methanol, or ethanol with the electrolyte-Cubic Plus Association Equation of State
No full textThis work presents a theoretical study using the electrolyte Cubic-Plus-Association (e-CPA) equation of state combined with quantum chemistry computations, for modeling the density and speed of sound of mixtures containing 2-hydroxyethylammonium-based (2-HEA-based) ionic liquids (ILs) + water/methanol/ethanol over wide ranges of temperatures. The e-CPA ion parameters were estimated by a simultaneous fitting of densities and speed of sounds of pure ILs. Aiming to reduce the number of adjustable parameters, the ion parameters were obtained by COSMO (Conductor-like Screening Model) volume implemented in MOPAC2016 (Molecular Orbital PACkage) based on the geometry optimization of ion structures. The results show that the e-CPA can satisfactorily predict the density and speed of sound of 2-HEA-based ILs + solvents with an absolute average deviation lower than 3%. The addition of two extra binary interaction parameters (solvent-cation and solvent-anion) can further reduce the overall deviation by less than 1%. The sensitivity analysis revealed that only the speed of sound of the 2-HEA-based ILs + solvent mixture is affected by changes in ion radii and dipole moment
Multi-objective cooperative controller design for rapid state-of-charge balancing and flexible bus voltage regulation in shipboard DC microgrids
No full textIn this paper, a multi-objective cooperative (MOC) controller based on average consensus algorithm is designed to achieve rapid State-of-Charge (SoC) balancing, proportional load current sharing, and flexible DC bus voltage regulation for parallel battery storage units (BSUs) in shipboard DC microgrids. Different from the conventional secondary controllers, the designed MOC controller can simultaneously achieve the above three control objectives with a fully distributed manner without requiring multiple controllers, thereby effectively improving the system stability and reducing the communication burden. Furthermore, an optimized convergence factor is designed to accelerate SoC balancing, and pinning control is introduced to obtain flexible and accurate DC bus voltage regulation. The process of SoC balancing and current sharing analysis, SoC convergence performance analysis, large-signal stability analysis, and global steady-state analysis verifies the rationality and stability of the MOC controller. Finally, the Matlab/Simulink simulation and StarSim HIL experimental results demonstrate the effectiveness and robustness of the designed MOC controller in a shipboard DC microgrid under various testing scenarios.</p
Acid doped branched poly(biphenyl pyridine) membranes for high temperature proton exchange membrane fuel cells and vanadium redox flow batteries
No full textBoth high temperature proton exchange membrane fuel cell (HT-PEMFC) and vanadium redox flow battery (VRFB) are represented as two advanced energy conversion and energy storage devices. They have a same core component of the separator membrane, which still faces several intractable scientific and industrial issues. For HT-PEMFC, the increase in conductivity is normally as the expense of mechanical strength; while for VRFB, the improvement in proton transport always brings in serious vanadium ion crossover. Meanwhile, the membrane also should possess an excellent chemical stability towards the attack by radicals or high valence vanadium ions. The above questions can be well solved by the preparation of triphenylbenzene (TPB) branched poly(biphenyl-4-acetylpyridine) membranes (x%TPB-PBAP), which are synthesized by one-step Friedel-Crafts polymerization. Amounts of alkaline pyridine groups equip x%TPB-PBAP membranes with good phosphoric acid and sulfonic acid absorption capability, resulting in high proton conductivity in both HT-PEMFC and VRFB. Meanwhile, the construction of the branched structure, i.e. a kind of covalently crosslinked network, can improve the mechanical strength and chemical stability. Consequently, the 1.5 %TPB-PBAP membrane displays large potential in both HT-PEMFC and VRFB. A single H2-O2 cell based on the 1.5 %TPB-PBAP/263 %PA membrane shows a peak power density of 1010 mW cm−2 at 180 °C without any back pressure. Meanwhile, the VRFB based on above membrane also depicts better battery efficiencies and cycle durability than that with Nafion 212
In situ neutron diffraction study and electron microscopy analysis of microstructure and texture evolution during annealing of rolled CoCrFeNi alloy doped with 1 at.%C
No full textIn situ neutron diffraction studies of changes in the dislocation density, volume fraction of carbides, and crystallographic texture have been performed during annealing of a cold-rolled multi-principal element CoCrFeNi alloy doped with 1 at.%C. In addition, microstructures of the as-rolled and several annealed samples of this alloy have been investigated using electron microscopy-based techniques. It is found that cold rolling to a thickness reduction of 74% results in a brass-type rolling texture with a spread of orientations between the Goss and brass components and with a pronounced 〈111〉//ND fiber. The deformed microstructure is characterized by a high density of dislocations and shows large variations in deformation structures in regions of different crystallographic orientations. In particular, bundles of deformation twins and high frequencies of shear bands are observed in regions having orientations along the 〈111〉//ND fiber. Annealing at 700 °C–1000 °C leads to recovery and recrystallization, during which shear bands and regions of mixed orientations act as preferential nucleation sites for recrystallized grains. Precipitation of M23C6 particles also takes place during annealing. The particles retard boundary migration, thus slowing down recrystallization and restricting grain growth. The average size of recrystallized grains does not exceed 5 μm even after annealing at 1000 °C for 60 min. While rolling textures are retained in some annealed samples, other samples demonstrate distinct recrystallization textures with new texture components. The results obtained in this work are compared with the literature data for several carbon-doped face-centered cubic multi-principal element alloys and for a carbon-free CoCrFeNi alloy.
Fabrication and<i> in vitro in vivo</i> evaluation of small polymeric devices for oral drug delivery
No full textOral dosage forms are the preferred solution for systemic treatment and prevention of disease conditions. However, the gastrointestinal (GI) tract presents many obstacles for successful drug delivery, including pH variations, enzymes, peristalsis and continuously regenerating mucus barriers covering the inner surface. This challenges the oral delivery of drug compounds, which are sensitive to degradation in these conditions and/or present poor permeability across the epithelial barrier.Engineered ingestible devices have been exploited as carriers to overcome the challenges related to oral drug delivery. These polymeric devices could be classified based on their proximity to the GI epithelium for enhanced drug absorption. This includes mucus-embedding devices (via adhesive forces), mucus-penetrating devices (via mechanical forces) and GI auto-injectors. These approaches have shown promise for enhanced drug bioavailability due to their localized controlled drug release in close proximity to the epithelial barrier.In this PhD thesis, the potential of different devices based on mucus-embedding and mucus-penetrating strategies to improve drug absorption is assessed. Additionally, methodologies are investigated for the production of suitable devices in this subject, ensuring drug encapsulation and controlled release. Mucus-embedding devices, such as microcontainers, are polymeric devices with a compartment for drug-loading until targeted unidirectional drug release. To assess sequential co-delivery, dual-compartment microcontainers (DCMCs) made in SU-8 were developed, which could be relevant for co-presentation of therapeutics and excipients that promote the drug absorption. As a proof-of-concept, the respective compartments were loaded with two model drugs, furosemide and propranolol, and coated with the pH-sensitive polymers Eudragit® S100 (ES100) and Eudragit® L100 (EL100). With this delivery system, we obtained a sequential release of the two drugs in vitro, and a difference in the absorption profile in vivo, according to the respective compartments. Microcontainers are commonly produced in SU-8, which is a biocompatible material, but it is relevant to scale up the production in biodegradable materials. A few approaches have been proposed for this purpose, but they present limitations regarding shapes and materials. Therefore, a novel scalable approach based on ultrasonic spray coating and microcutting is presented. Microcontainers were successfully producted in polycaprolactone (PCL) and poly(lactic-co-glycolic acid) (PLGA). After loading, the cavities were spray coated with Kollicoat® Protect (KPRO) or EL100 for targeted immediate or enteric drug release, respectively, which was confirmed in vitro and in vivo. Additionally, an enhanced drug uptake was observed from microcontainers compared to a powder suspension after oral dosing to rats.Mucus-penetrating devices have shown a particular potential to enhance the absorption of poorly permeable drugs such as peptides, which often benefit from encapsulation to avoid acidic and enzymatic degradation. An example of these devices is self-unfolding foils (SUFs). SUFs consist of an array of microcontainers comprised in an elastic foil, which unfolds upon capsule disintegration in the GI tract. This allows intimate contact with the epithelium during drug release by the application of mechanical forces relying on the elastomeric properties of the foil material, polydimethylsiloxane (PDMS). To assess the drug encapsulation from SUFs in vitro, a model drug, paracetamol, was loaded and sealed with different pH-sensitive mixtures. Among all the coatings evaluated, Eudragit® EFL30D-55 (EFL) seemed the most suitable material in this respect. Finally, the impact of the distance between the device and the GI epithelium, and the incorporation of mucus-penetrating microneedles, on the drug permeation was assessed in vitro with biosimilar mucus (BM). It was observed that the proximity to the apical membrane enhanced the permeation of a model macromolecule. Nevertheless, the incorporation of mucus-penetrating microneedles s did not result in an improved effect.In conclusion, this thesis highlights the potential of mucus-embedding and mucus-penetrating devices as a future strategy in oral drug delivery. This could be useful for the delivery of drug compounds that currently present a low bioavailability and are commonly delivered by other routes such as injections. Especially, if the presented platforms are intended to achieve an increased proximity and retention time in the GI epithelium. Future studies should include further research in the formulations utilized as well as further understanding of the device-epithelium interactions. One example of potential new formulations could be small peptide molecules and potential co-presentation with different excipients enhancing their absorption and/or inhibit the enzymatic degradation
Molecular insights into the synergistic inhibition mechanisms of antifreeze protein and methanol on carbon dioxide hydrate growth
No full textThe formation of CO2 hydrates during CO2 transportation and deep-sea injection poses a significant risk of pipeline blockage. Combining kinetic (KHIs) and thermodynamic hydrate inhibitors (THIs) serves as a promising efficient and economical strategy to mitigate this issue, whose performance and microscopic mechanisms yet are still poorly understood. This study employs molecular dynamics simulations to explore the effects of the combination of winter flounder antifreeze protein (wf-AFP) as a KHI and methanol as a THI on CO2 hydrate growth. We find that methanol and wf-AFP exhibit an intriguing synergistic inhibition performance on hydrate growth. In the AFP-only system, AFP serves as a spatial hindrance near the hydrate growth interface. However, in the AFP + methanol system, AFP changes its position due to the attractive force of methanol. Part of the AFP fragment remains on the hydrate interface, while the rest surrounds the CO2 droplet. Methanol, in addition to disrupting the water structure, combines with AFP to act as a double barrier to CO2 dissolution into the aqueous solution, thereby significantly reducing the gas source for hydrate growth. These findings provide molecular-level insights into hydrate inhibition mechanisms and guide the design of efficient inhibitors for safe CO2 transportation and injection