Low-Resistance Monovalent-Selective Cation Exchange Membranes for Energy-Efficient Ion Separations

The desalination of brackish water provides water to tens of millions of people around the world, but current technologies deplete much needed nutrients from the water, which is detrimental to both public health and agriculture. A selective method for brackish water desalination, which retains the needed nutrients, is electrodialysis (ED) using monovalent-selective cation exchange membranes (MVS-CEMs). However, due to the trade-off between membrane selectivity and resistance, most MVS-CEMs demonstrate either high transport resistance or low selectivity, which increase energy consumption and hinder the use of such membranes for brackish water desalination by ED. Here, we used molecular layer deposition (MLD) to uniformly coat CEMs with ultrathin layers of alucone. The positive surface charge of the alucone instills monovalent selectivity in the CEM. Using MLD enabled us to precisely control and minimize the selective layer thickness, while the flexibility and nanoporosity of the alucone prevent cracking and delamination. Under conditions simulating brackish water desalination, this compound provides monovalent selectivity with negligible added resistance—the smallest reported resistance for a monovalent-selective layer, to date—thereby alleviating the selectivity–resistance trade-off. Addressing the water–energy nexus, we show that using these membranes in ED will cut at least half of the energy required for selective brackish water desalination with current MVS-CEMs. </div

Combined experimental and theoretical study on the blast response of arching masonry walls

This paper studies the nonlinear dynamic response of arching masonry walls to blast load. The methodology combines laboratory blast testing and nonlinear dynamic modeling of arching one-way masonry walls and their response to blast load. The paper aims at enhancing the understanding of the dynamic and nonlinear physical response of the structural system. The experimental phase focuses on a one-way arching masonry wall tested in a blast simulator. The test is designed to explore global and local measures of the response of such walls. New experimental data that contributes to the understanding of the blast response and for validating theoretical and numerical models is presented. The theoretical phase develops a nonlinear, dynamic, continuous beam-type model that considers the deformability of the mortar joints and the masonry units. The model combines inertial effects with geometrical and material nonlinearities and uses the finite element method for the numerical solution. The model is examined and evaluated against the experimental benchmark, and then it is used to explore the impact of the boundary conditions and the blast intensity on the dynamic response. The combined investigation highlights, explores, and quantifies the unique aspects of the complex dynamic response of such walls to blast loading

Optogenetic Control of Human Induced Pluripotent Stem Cell‐Derived Cardiac Tissue Models

Background Optogenetics, using light‐sensitive proteins, emerged as a unique experimental paradigm to modulate cardiac excitability. We aimed to develop high‐resolution optogenetic approaches to modulate electrical activity in 2‐ and 3‐dimensional cardiac tissue models derived from human induced pluripotent stem cell (hiPSC)‐derived cardiomyocytes. Methods and Results To establish light‐controllable cardiac tissue models, opsin‐carrying HEK293 cells, expressing the light‐sensitive cationic‐channel CoChR, were mixed with hiPSC‐cardiomyocytes to generate 2‐dimensional hiPSC‐derived cardiac cell‐sheets or 3‐dimensional engineered heart tissues. Complex illumination patterns were designed with a high‐resolution digital micro‐mirror device. Optical mapping and force measurements were used to evaluate the tissues' electromechanical properties. The ability to optogenetically pace and shape the tissue's conduction properties was demonstrated by using single or multiple illumination stimulation sites, complex illumination patterns, or diffuse illumination. This allowed to establish in vitro models for optogenetic‐based cardiac resynchronization therapy, where the electrical activation could be synchronized (hiPSC‐derived cardiac cell‐sheets and engineered heart tissue models) and contractile properties improved (engineered heart tissues). Next, reentrant activity (rotors) was induced in the hiPSC‐derived cardiac cell‐sheets and engineered heart tissue models through optogenetics programmed‐ or cross‐field stimulations. Diffuse illumination protocols were then used to terminate arrhythmias, demonstrating the potential to study optogenetics cardioversion mechanisms and to identify optimal illumination parameters for arrhythmia termination. Conclusions By combining optogenetics and hiPSC technologies, light‐controllable human cardiac tissue models could be established, in which tissue excitability can be modulated in a functional, reversible, and localized manner. This approach may bring a unique value for physiological/pathophysiological studies, for disease modeling, and for developing optogenetic‐based cardiac pacing, resynchronization, and defibrillation approaches