Threshold Switching of Ag or Cu in Dielectrics: Materials,Mechanism, and Applications

Threshold switches with Ag or Cu active metal species are volatile memristors (also termed diffusive memristors) featuring spontaneous rupture of conduction channels. The temporal dynamics of the conductance evolution is closely related to the electrochemical and diffusive dynamics of the active metals which could be modulated by electric field strength, biasing duration, temperature, and so on. Microscopic pictures by electron microscopy and quantitative thermodynamics modeling are examined to give insights into the underlying physics of the switching. Depending on the time scale of the relaxation process, such devices find a variety of novel applications in electronics, ranging from selector devices for memories to synaptic devices for neuromorphic computing.     

Statically optimal dynamic soft real-time semi-partitioned scheduling

Real-Time Systems - Semi-partitioned scheduling is an approach to multiprocessor real-time scheduling where most tasks are fixed to processors, while a small subset of tasks is allowed to migrate....     

Flexible,Graphene‐Coated Biocomposite for Highly Sensitive,Real‐Time Molecular Detection

Wearable biosensors hold significant potential for healthcare and environmental applications, and the development of flexible and biocompatible sensing platforms for high accuracy detection of physiological biomarkers remains an elusive goal. Herein, an ultrasensitive, flexible sensor is described that is based on a 3D hierarchical biocomposite comprised of hollow, natural pollen microcapsules that are coated with a conductive graphene layer. Modular assembly of the graphene‐coated microcapsules onto an ultrathin polyethylene terephthalate layer enables a highly flexible sensor configuration with tunable selectivity afforded by subsequent covalent immobilization of antibodies against target antigens. In a proof‐of‐concept example, the biosensor demonstrates ultrahigh sensitivity detection of prostate specific antigen (PSA) down to 1.7 × 10^?15m with real‐time feedback and superior performance over conventional 2D graphene‐coated sensors. Importantly, the device performance is consistently high across various bending conditions. Taken together, the results demonstrated in this work highlight the merits of employing lightweight biocomposites as modular building blocks for the design of flexible biosensors with highly responsive and sensitive molecular detection capabilities.     

Disgust sensitivity predicts intuitive disapproval of gays.

Two studies demonstrate that a dispositional proneness to disgust (“disgust sensitivity”) is associated with intuitive disapproval of gay people. Study 1 was based on previous research showing that people are more likely to describe a behavior as intentional when they see it as morally wrong (see Knobe, 2006, for a review). As predicted, the more disgust sensitive participants were, the more likely they were to describe an agent whose behavior had the side effect of causing gay men to kiss in public as having intentionally encouraged gay men to kiss publicly—even though most participants did not explicitly think it wrong to encourage gay men to kiss in public. No such effect occurred when subjects were asked about heterosexual kissing. Study 2 used the Implicit Association Test (IAT; Nosek, Banaji, & Greenwald, 2006) as a dependent measure. The more disgust sensitive participants were, the more they showed unfavorable automatic associations with gay people as opposed to heterosexuals. Two studies demonstrate that a dispositional proneness to disgust (“disgust sensitivity”) is associated with intuitive disapproval of gay people. Study 1 was based on previous research showing that people are more likely to describe a behavior as intentional when they see it as morally wrong (see Knobe, 2006, for a review). As predicted, the more disgust sensitive participants were, the more likely they were to describe an agent whose behavior had the side effect of causing gay men to kiss in public as having intentionally encouraged gay men to kiss publicly—even though most participants did not explicitly think it wrong to encourage gay men to kiss in public. No such effect occurred when subjects were asked about heterosexual kissing. Study 2 used the Implicit Association Test (IAT; Nosek, Banaji, & Greenwald, 2006) as a dependent measure. The more disgust sensitive participants were, the more they showed unfavorable automatic associations with gay people as opposed to heterosexuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lunar Dust Levitation

Observations of a lunar “horizon glow” by several Surveyor spacecraft on the lunar surface in the 1960s and detections of dust particle impacts by the Apollo 17 Lunar Ejecta and Meteoroid Experiment have been explained as the result of micron-sized charged particles lifting off the surface. The surface of the Moon is exposed to the solar wind and solar UV radiation causing photoemission, so it develops a surface charge and an electric field near the surface. Dust particles injected into this plasma from the lunar regolith, whether from human and mechanical activity or from meteoroid impacts or electrostatic forces, may be stably levitated above the surface and may undergo preferential deposition onto areas of the lunar surface (or equipment) with different electrical properties. This can lead to a net transport as well as contamination of sensitive equipment. This paper reports on new experimental measurements and numerical simulations of the plasma environment above the lunar surface and the related behavior of charged dust.     

EBSD-Based Microscopy: Resolution of Dislocation Density

Consideration is given to the resolution of dislocation density afforded by EBSD-based scanning electron microscopy. Comparison between the conventional Hough- and the emerging high-resolution cross-correlation-based approaches is made. It is illustrated that considerable care must be exercised in selecting a step size (Burger's circuit size) for experimental measurements. Important variables affecting this selection include the dislocation density and the physical size and density of dislocation dipole and multi-pole components of the structure. It is also illustrated that simulations can be useful to the interpretation of experimental recoveries.     

Electrospun Nanoparticle–Nanofiber Composites via a One‐Step Synthesis

A facile approach to synthesize and incorporate metal nanoparticles (NPs) into electrospun polymer nanofibers (NFs) wherein the electrospinning polymer acts as both a reducing agent for the metal salt precursor, as well as a protecting and templating agent for the ensuing NPs, is reported. Such a true one‐step process at ambient conditions and free of organic solvents is demonstrated using a system comprising AgNO₃ and poly(ethylene oxide) (PEO) at electrospinnable molecular weights of 600, 1000, or 2000 kDa. The PEO transforms Ag⁺ into AgNPs, a phenomenon that has not been previously possible at PEO molecular weights less than 20 kDa without the addition of a separate reducing agent and stabilizer or the application of heat. Results from X‐ray photoelectron spectroscopy and UV–Vis absorption spectrophotometry analyses support the formation of pseudo‐crown ethers in high molecular weight PEO as the mechanism in the development of NPs. The AgNPs reduce fiber diameter and enhance fiber quality (reduced beading) due to increased electrical conductivity. Interestingly, several of the NFs exhibit AgNP‐localized nanochain formation and protrusion from the NF surface that can be attributed to the combined effect of applied electrical field on the polymer and the differences between the electrical conductivity and polarizability of the polymer and metal NPs.     

Emission modeling of styrene from vinyl ester resins with low hazardous air pollutant contents

Styrene is a commonly used co-monomer in vinyl ester (VE) resins, which acts as a reactive diluent and is required in most liquid molding fabrication methods to reduce viscosity and improve overall resin performance. Resins containing low hazardous air pollutant contents have been developed to reduce the styrene emissions during composite fabrication. VE monomers with a bimodal molecular weight distribution have been used to effectively decrease the amount of styrene in the system while maintaining low resin viscosities. Fatty acid vinyl ester (FAVE) resins partially replace styrene with non-volatile fatty acid monomers to reduce styrene emissions. The emissions from bimodal and FAVE resins were measured as a function of time and various parameters, including styrene content, VE molecular weight, and fatty acid monomer content and chain length. The initial emission rate from VE resins is only dependent on styrene content for constant evaporation geometry. Furthermore, the evaporation rate constant was the same regardless of VE molecular weight, styrene content, or the use of co-reactive diluent (MFA monomers). The diffusivity was not dependent on the styrene content in the resin, but decreased linearly as the VE molecular weight increased because of a corresponding increase in the resin viscosity. The diffusivity also increased as the content of MFA increased because of a decrease in the resin viscosity with high MFA content at high emission time. Furthermore, the emission profiles were accurately modeled using a modified version of 1D diffusion through a planar sheet that accounts for the depth change as a function of styrene evaporation. Overall, the model predicted emission profiles similar to the experimentally measured profiles as a function of time for various styrene contents, VE molecular weights, and fatty acid monomer contents.     

Modeling efficiency and water balance in PEM fuel cell systems with liquid fuel processing and hydrogen membranes

Integrating PEM fuel cells effectively with liquid hydrocarbon reforming requires careful system analysis to assess trade-offs associated with H₂ production, purification, and overall water balance. To this end, a model of a PEM fuel cell system integrated with an autothermal reformer for liquid hydrocarbon fuels (modeled as C₁₂H₂₃) and with H₂ purification in a water–gas-shift/membrane reactor is developed to do iterative calculations for mass, species, and energy balances at a component and system level. The model evaluates system efficiency with parasitic loads (from compressors, pumps, and cooling fans), system water balance, and component operating temperatures/pressures. Model results for a 5-kW fuel cell generator show that with state-of-the-art PEM fuel cell polarization curves, thermal efficiencies >30% can be achieved when power densities are low enough for operating voltages >0.72 V per cell. Efficiency can be increased by operating the reformer at steam-to-carbon ratios as high as constraints related to stable reactor temperatures allow. Decreasing ambient temperature improves system water balance and increases efficiency through parasitic load reduction. The baseline configuration studied herein sustained water balance for ambient temperatures ≤35 °C at full power and ≤44 °C at half power with efficiencies approaching ∼27 and ∼30%, respectively.