Optimization of combined Reverse Osmosis: thermal Zero Liquid Discharge system parameters for an Ammonia and Urea production complex

Journal of Thermal Analysis and Calorimetry - Zero liquid discharge (ZLD) has shown to be a promising technology to recycle water with good quality. The ZLD objective is to purify the water from...     

Self-motile colloidal particles: from directed propulsion to random walk

The motion of an artificial microscale swimmer that uses a chemical reaction catalyzed on its own surface to achieve autonomous propulsion is fully characterized experimentally. It is shown that at short times it has a substantial component of directed motion, with a velocity that depends on the concentration of fuel molecules. At longer times, the motion reverts to a random walk with a substantially enhanced diffusion coefficient. Our results suggest strategies for designing artificial chemotactic systems.     

Evolution of growth modes for polyelectrolyte bundles

Multivalent ions induce attractions between polyelectrolytes, but lead to finite-sized bundles rather than macroscopic phase separation. The kinetics of aggregation and bundle formation of actin is tracked using two different fluorescently labeled populations of F-actin. It is found that the growth mode of these bundles evolves with time and salt concentration, varying from an initial lateral growth to a longitudinal one at later stages. The results suggest that kinetics play a role in bundle growth, but not in the lateral size of bundles, which is constant for linear and branched topologies.     

Control of Stem‐Cell Behavior by Fine Tuning the Supramolecular Assemblies of Low‐Molecular‐Weight Gelators

Controlling the behavior of stem cells through the supramolecular architecture of the extracellular matrix remains an important challenge in the culture of stem cells. Herein, we report on a new generation of low‐molecular‐weight gelators (LMWG) for the culture of isolated stem cells. The bola‐amphiphile structures derived from nucleolipids feature unique rheological and biological properties suitable for tissue engineering applications. The bola‐amphiphile‐based hydrogel scaffold exhibits the following essential properties: it is nontoxic, easy to handle, injectable, and features a biocompatible rheology. The reported glycosyl‐nucleoside bola‐amphiphiles (GNBA) are the first examples of LMWG that allow the culture of isolated stem cells in a gel matrix. The results (TEM observations and rheology) suggest that the supramolecular organizations of the matrix play a role in the behavior of stem cells in 3D environments.     

Numerical evaluation of passive control of shock wave/boundary layer interaction on NACA0012 airfoil using jagged wall

Shock formation due to flow compressibility and its interaction with boundary layers has adverse effects on aerodynamic characteristics, such as drag increase and flow separation. The objective of this paper is to appraise the prac-ticability of weakening shock waves and, hence, reducing the wave drag in transonic flight regime using a two-dimensional jagged wall and thereby to gain an appropriate jagged wall shape for future empirical study. Different shapes of the jagged wall, including rectangular, circular, and triangular shapes, were employed. The numerical method was validated by experimental and numerical studies involving transonic flow over the NACA0012 airfoil, and the results presented here closely match previous experimental and numerical results. The impact of parameters, including shape and the length-to-spacing ratio of a jagged wall, was studied on aerodynamic forces and flow field. The results revealed that applying a jagged wall method on the upper surface of an airfoil changes the shock structure significantly and disinte-grates it, which in turn leads to a decrease in wave drag. It was also found that the maximum drag coefficient decrease of around 17%occurs with a triangular shape, while the max-imum increase in aerodynamic efficiency (lift-to-drag ratio) of around 10%happens with a rectangular shape at an angle of attack of 2.26?.     

Using S-statistic for investigating the effect of temperature on hydrodynamics of gas–solid fluidization

The influence of temperature on fluidization was investigated by a statistical chaotic attractor comparison test known as S-statistic. After calibration of the variables used in this method, the S-test was applied to the radioactive particle tracking (RPT) data obtained from a lab-scale fluidized bed. Experiments were performed with sand as fluidized particles and in temperatures from ambient up to 600 °C with superficial gas velocities of 0.29, 0.38 and 0.52 m/s. Considering the behavior of bubbles and comparing with frequency domain analysis, it was concluded that S-statistic is a reliable method for characterization of fluidization process behavior at different temperatures.     

CFD modeling of catalyst pellet for oxidative coupling of methane: Heat transfer and reaction

This study deals with the phenomena occuring at single-pellet catalyst scale for the oxidative coupling of methane where heat transfer plays an important role. Computational fluid dynamics (CFD) is used for obtaining detailed rate and temperature profiles through the porous catalytic pellet where reaction and diffusion compete. Intra-particle temperature and concentration gradients were taken into account by solving heat transfer coupled with continuity equations in the catalyst pellet. In heat transfer, the energy term due to highly exothermic reaction was considered. Two external programs were successfully implemented into the CFD-code as kinetic and heat of reaction terms. Simulation results showed that reaction was favored at the beginning for the pellet, followed by diffusion predomination. The results of CFD simulation indicate that temperature variation within the catalyst pellet is <2 K due to exothermic oxidation. The results showed further that exothermic oxidation reactions occurred prior to endothermic coupling reaction in the pellet.     

Determination of Trace Methyl Tert‐Butyl Ether in Water Samples Using Dispersive Liquid‐Liquid Microextraction Coupled with GC‐FID

A rapid and sensitive analytical method has been developed for trace analysis of methyl tert‐butyl ether (MTBE) in water samples using dispersive liquid‐liquid microextraction and gas chromatography with flame ionization detection. Factors relevant to the microextraction efficiency, such as the kind of extraction solvent, the disperser solvent and their volumes, the effect of salt, sample solution temperature and the extraction time were investigated and optimized. Under the optimal conditions the linear dynamic range of MTBE was from 0.2 to 25.0 μg L^?1 with a correlation coefficient of 0.9981 and a detection limit of 0.1 μg L^?1. The relative standard deviation (RSD%) was less than 5.1% (n = 3) and the recovery values were in the range of 97.8 ± 0.9%. Finally, the proposed method was successfully applied for the analysis of MTBE in aqueous samples.