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Obesity is a progressive metabolic disease that begins with lipid metabolism disorders. Aromatic amino acids (AAAs), including tryptophan, phenylalanine, and tyrosine, have diverse biological activities as nutrients. However, the underlying mechanisms by which AAAs affect lipid metabolism are unclear.

The increase in circulating insulin levels is associated with the onset of type 2 diabetes (T2D), and the levels of branched-chain amino acids and aromatic amino acids (AAAs) are altered in T2D, but whether AAAs play a role in insulin secretion and signaling remains unclear.

The high specific strength and modulus of carbon fiber-reinforced poly-ether-ether-ketone composites (CF/PEEK) have made them particularly useful for structural applications. However, undesired defects are derived from the incompatibility between the thermoplastic matrix and the thermoset-based sizing agent at the CF/PEEK interface. This issue is further aggravated by three-dimensional (3D) printing fabrication for incomplete impregnation during the printing process. Herein, we introduce a thermoplastic-based sizing treatment into CF/PEEK prepreg filament preparation in order to reduce or eliminate the defects from the material and process sources of (3D) printing. We evaluate the influence of the sizing treatment on the impregnation and compatibility behavior of the CF/PEEK prepreg filaments. In comparison to the unsized CF/PEEK composites, the tensile strength of the polyether imide- and PEEK-sized CF composites increased by 47.6% and 54.0%, respectively. In combination with the thermoplastic-based sizing treatment and prepreg filament approach, 3D printing has the potential to create structural parts with favorable interfacial bonding.

Ammonium recovery from wastewater by gas-permeable membranes is promising but suffers from the tradeoff between membrane stability and permeability under harsh operating conditions. Chemical-resistant membranes display modest permeability due to the poor solubility and processibility; chemically active membranes are easier to be endowed with better permeability however hinder by instability. To resolve such a problem, we cleverly design a novel membrane configuration via one-step solution-electrospinning, with the chemical-active component (low-strength fluorine polymer) as the inner skeleton to construct interconnected porous structures and the chemical-resistant component (high-strength fluorine polymer) as the outer armor to serve as a protective layer. Due to the significantly enhanced mass transfer coefficient, the interconnected-porous armor-structured membrane exhibited much higher permeability for NH4+-N recovery, which was 1.4 and 5 times that of the traditional PTFE membrane and PP membrane, respectively. Through long-term intermittent and consecutive experiments, the reusability and durability of the armor-structured nanofibrous membrane were verified. When treating actual hoggery wastewater with complicated water quality, the armor-structured nanofibrous membrane also displayed robust stable performance with excellent antiwettability. The mechanisms of membrane formation, corrosion resistance, and mass transfer were discussed in detail.

Brine drained from desalination plants or obtained from underground is a valuable source of minerals. However, the presence of calcium ions in the brine makes its direct application uneconomical. Sodium carbonate can be used to selectively remove calcium ions from brine but is associated with drawbacks, including low calcium removal efficiency, slow settling of the precipitate, significant magnesium loss, and high reagent cost. In this study, the influence of the operating conditions on calcium removal was systematically evaluated. The experimental results revealed that temperature was the most important factor affecting calcium removal efficiency and calcium/magnesium selectivity. The optimum operating conditions were determined to include a reaction temperature of 85°C, an equimolar dosage of sodium carbonate, and a brine salinity of >56 g kg–1. These conditions afforded a calcium removal efficiency of up to 85.4% with a magnesium loss of <6.7%. A pilot plant with a capacity of 120 m3d–1, based on static mixing/reaction and membrane distillation, was operated continuously for the decalcification and concentration of brine obtained from a desalination plant. The integration of the developed decalcification method, a brine-concentrating technology and separation technology such as nanofiltration would provide an alternative technique for exploiting brine.

Urease is a highly efficient catalyst for the hydrolysis of urea with a rate approximately 10 14 times the rate of the noncatalyzed reaction. It has a long and distinguished history in the development of enzymology. In this work the properties of urease and its applications in biotechnology are reviewed, including urea content analysis in blood, urine, alcoholic beverages, natural water and environmental wastewaters; analysis of heavy metal content in natural waters, wastewaters and soil; determination of creatinine, arginine and IgG; urea removal from artificial kidney dialyzates, alcohol beverages and fertilizer wastewaters; wastewater reclamation for life support systems in space; pH control or shift for multi-enzyme reaction system; and urea hydrolysis as sources of ammonia or carbon dioxide in special cases. Future research trends are also outlined.

The kinetics of urea hydrolysis catalyzed by urease, mainly in the absence of buffers by use of the self-buffer effect of the products, was investigated. The effect of pH, temperature, and concentration of enzyme, substrate, product, salt ions, and buffers on the kinetic behavior of urease was examined. A kinetic model of a modified Michaelis-Menten form, incorporating substrate and product inhibition, pH dependence, and temperature effect, was developed to describe the reaction rate. Experimental data indicated that urease in a buffer-free solution was less susceptible to the inhibition of substrate product. The Michaelis constant keeps almost constant with the variation of pH and temperature, and increases with the addition of buffers and salts. The data also suggested that the noncompetitive pattern of the product inhibition, which is not significantly affected by temperature, increases gently with increasing pH. A Monod form rate expression was proposed to analyze the pH effect on the maximum rate. The proposed kinetic model was also examined by the long-time experiments in which pH, substrate, and product concentration varied obviously during the reaction course.

Hollow‐fiber membrane reactive extraction and facilitated supported liquid membrane processes for the separation of charged species are analyzed theoretically. A mathematical model incorporating laminar flow, Nemst‐Planck diffusion, buffer effect, ion strength, interfacial reaction kinetics and/or equilibria, diffusivity of species in the membrane phase, shell resistances, and shell concentration is deueloped and solued numerically. When the lumen mass‐transfer resistance is dominant, the predicted remoual rate of a single ion or the separation rate of a mixture of ions by a simplified model with Fickian diffusion deuiates greatly from the prediction with the present model. For instance, when the concentration of triualent ions in the feed decreases to half of its initial ualue, the membrane length calculated using Fickian diffusion is 75% higher than the length predicted by Nemst‐Planck diffusion. Thus, the Leueque equation based on Fick's law does not adequately describe the mass transfer of the charged species in the lumen feed. The effect of buffer ions and diffusiuity of species in the membrane phase on the mass transfer of the species is also discussed.

Hollow‐fiber membrane separation or reaction processes, with a nonlinear boundary condition at the lumen interface, are analyzed numerically. Sixteen different nonlinear boundaly conditions in the literature were simplified to four dimensionless boundary conditions, in which only two parameters are needed to incorporate the effect on mass transport of membrane and shell resistances, lumen inlet Concentration, shell concentration, phase and/or chemical equilibria, and interface reaction kinetics. The lumen mass‐transfer coefjicients were obtained by solving the continuity mass‐conservation equation with the corresponding boundary conditions. The calculated results demonstrate that the lumen mass‐transfer coefjicient is a function of lumen‐inlet concentration and shell concentration, as opposed to the case when a linear boundary condition occurs at the lumen interface. By using the empirical correlations of the lumen local mass‐transfer coefjicient, an ordina ry differential equation substituting a partial differential equation can be applied to obtain the lumen dimensionless mixed‐cup concentration with an absolute error of less than 0.005 in most cases, thus making it possible to design and evaluate the hollow‐fiber membrane separation or reaction processes.

Hollowfiber membrane processes with a constant external resistance having a constant or variable shell concentration resulting from an operational mode of cocurrent or countercurrent are studied. By solving numerically the continuity massconservation equation with the corresponding boundary conditions, the lumen laminar masstransfer coefficients for both cases are correlated. The correlations greatly improve the calculating accuracy of the overall masstransfer coefficient and can be used to obtain the lumen mixedcup concentration by an algebraic equation substituting the partial differential equation. A separation factor m is introduced to characterize the effect of the operational mode. Calculation results demonstrate that the lumen masstransfer coefficient is independent of the real lumen and shell concentrations, but it is greatly influenced by m. The countercurrent mode, compared to the cocurrent mode, provides not only a higher mean driving force, but a higher lumen masstransfer coefficient. This conclusion is novel and valid for the tubeshell heat or masstransfer processes and is supported by the experimental data in the literature and our gas membrane separation experiments.