Gravimetric analysis of CO2 adsorption on activated carbon at various pressures and temperatures using piezoelectric microcantilevers

We investigated the adsorption and desorption of CO(2) on activated carbon using piezoelectric microcantilevers. After coating the free end of a cantilever with activated carbon, variations in the resonance frequency of the cantilever were measured as a function of CO(2) pressure, which is related to mass changes due to the adsorption or desorption of CO(2). The pressure-dependent viscous damping effects were compensated in the calculation of the CO(2) adsorption capacity of the activated carbon by comparing the frequency differences between the coated and uncoated cantilevers. The mass sensitivity of the piezoelectric cantilever was found to be better than 1 pg. The fractional coverage of CO(2) agreed with a Langmuir adsorption isotherm, indicating that a submonolayer of adsorbed CO(2) occurred on the surface of the activated carbon under the experimental conditions. The heat of adsorption was determined using the Clausius-Clapeyron relation and the fractional coverage of CO(2) at various temperatures and pressures.     

Properties and Dispersion of EPDM/Modified‐Organoclay Nanocomposites

Elastomers show improved properties when reinforced with nanoclay at low filler loadings, but dispersion of the clay is difficult in non‐polar polymers, such as ethylene propylene diene monomer (EPDM). In this work several compatibilization approaches were studied, including the addition of EPDM modified with maleic anhydride (EPDM‐g‐MA) and the use of organoclay modified with maleic anhydride‐grafted liquid vinyl polybutadiene (LVPB‐g‐MA). The use of LVPB‐g‐MA‐modified organoclay increased the degree of dispersion as measured by X‐ray diffraction, giving increased thermal stability and modulus, and decreased swelling. Flame resistance was poorer for the EPDM/LVPB‐g‐MA‐modified organoclay system compared to the unmodified EPDM/organoclay compound. The resistivity of the nanoclay‐filled composites was lower than the reference EPDM compound, but dielectric properties for the LVPB‐g‐MA modified organoclay were similar to the reference.

     

Substrate dependent self-organization of mesoporous cobalt oxide nanowires with remarkable pseudocapacitance

A scheme of current collector dependent self-organization of mesoporous cobalt oxide nanowires has been used to create unique supercapacitor electrodes, with each nanowire making direct contact with the current collector. The fabricated electrodes offer the desired properties of macroporosity to allow facile electrolyte flow, thereby reducing device resistance and nanoporosity with large surface area to allow faster reaction kinetics. Co(3)O(4) nanowires grown on carbon fiber paper collectors self-organize into a brush-like morphology with the nanowires completely surrounding the carbon microfiber cores. In comparison, Co(3)O(4) nanowires grown on planar graphitized carbon paper collectors self-organize into a flower-like morphology. In three electrode configuration, brush-like and flower-like morphologies exhibited specific capacitance values of 1525 and 1199 F/g, respectively, at a constant current density of 1 A/g. In two electrode configuration, the brush-like nanowire morphology resulted in a superior supercapacitor performance with high specific capacitances of 911 F/g at 0.25 A/g and 784 F/g at 40 A/g. In comparison, the flower-like morphology exhibited lower specific capacitance values of 620 F/g at 0.25 A/g and 423 F/g at 40 A/g. The Co(3)O(4) nanowires with brush-like morphology exhibited high values of specific power (71 kW/kg) and specific energy (81 Wh/kg). Maximum energy and power densities calculated for Co(3)O(4) nanowires with flower-like morphology were 55 Wh/kg and 37 kW/kg respectively. Both electrode designs exhibited excellent cycling stability by retaining ～91-94% of their maximum capacitance after 5000 cycles of continuous charge-discharge.     

Design of a slider-crank leg mechanism for mobile hopping robotic platforms

Legged locomotion has been widely researched due to its effectiveness in overcoming uneven terrains. Due to previous efforts there has been much progress in achieving dynamic gait stability and as the next step, mimicking the high speed and efficiency observed in animals has become a research interest. The main barrier in developing such a robotic platform is the limitation in the power efficiency of the actuator: the use of pneumatic actuators produce sufficient power but are heavy and big; electronic motors can be compact but are disadvantageous in producing sudden impact from stall which is required for high speed legged locomotion. As a new attempt in this paper we suggest a new leg design for a mobile robot which uses the slider-crank mechanism to convert the continuous motor rotation into piston motion which is used to impact the ground. We believe this new mechanism will have advantage over conventional leg mechanism designs using electronic motors since it uses the continuous motion of the motor instead of sudden rotation movements from stall state which is not ideal to draw out maximum working condition from an electronic motor. In order to control impact timing from the periodic motion of the piston a mechanical passive clutch trigger mechanism was developed. Dynamic analysis was performed to determine the optimal position for the mechanical switch position of the clutch trigger mechanism, and the results were verified through simulation and experiment. Development of a legged locomotion with two degrees of freedom, slider-crank mechanism for impact and additional actuation for swing motion, is proposed for future work.     

Modular Layer‐by‐Layer Assembly of Polyelectrolytes,Nanoparticles, and Molecular Catalysts into Solar‐to‐Chemical Energy Conversion Devices

The design and fabrication of solar‐to‐chemical energy conversion devices are enabled through interweaving multiple components with various morphologies and unique functions using a versatile layer‐by‐layer assembly method. Cationic and anionic polyelectrolytes are used as an electrostatic adhesive to assemble the following functional materials: plasmonic Ag nanoparticles for improved light harvesting, upconversion nanoparticles for utilization of near‐infrared light, and polyoxometalate water oxidation catalysts for enhanced catalytic activity. Polyelectrolytes also have an additional function of passivating the surface recombination centers of the underlying photoelectrode. These functional components are precisely assembled on a model photoanode (e.g., Fe₂O₃ and BiVO₄) in a desired order and various combinations without degradation of their intrinsic properties. As a result, the performance of water oxidation photoanodes is synergistically enhanced. This study can enable the design and fabrication of novel solar‐to‐chemical energy conversion devices.     

Novel CFTR Activator Cact-3 Ameliorates Ocular Surface Dysfunctions in Scopolamine-Induced Dry Eye Mice

Cystic fibrosis transmembrane conductance regulator (CFTR) is highly expressed on the ocular epithelium and plays a pivotal role in the fluid secretion driven by chloride transport. Dry eye disease is one of the most common diseases with limited therapeutic options. In this study, a high-throughput screening was performed to identify novel CFTR activators capable of inducing chloride secretion on the ocular surface. The screening of 50,000 small molecules revealed three novel CFTR activators. Among them, the most potent CFTR activator, Cact-3 (7-(3,4-dimethoxyphenyl)-N-(4-ethoxyphenyl)pyrazolo [1,5-α]pyrimidine-2-carboxamide), produced large and sustained Cl⁻ currents in WT-CFTR-expressing FRT cells with no alterations of ANO1 and hERG channel activity. The application of Cact-3 strongly activated CFTR in the ocular epithelia of mice and it also significantly increased CFTR-mediated Cl⁻ transport in a primary cultured human conjunctival epithelium. Cact-3 strongly stimulated tear secretion in normal mice. In addition, Cact-3 significantly reduced ocular surface damage and the expression of proinflammatory factors, including interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ in an experimental mouse model of dry eye disease. These results suggest that Cact-3, a novel CFTR activator, may be a potential development candidate for the treatment of dry eye disease.