Internal noise determines external stochastic resonance in visual perception

AbstractWe provide the first experimental evidence that the internal noise level determines whether external noise can enhance the detectability of a weak signal. We conduct a visual detection experiment in the absence and presence of visual noise. We define three indices of external stochastic resonance effects, consider the spread of the psychometric function without external noise as an internal noise level index, and find that the indices of external stochastic resonance effects negatively correlate with the internal noise level index. Our results suggest that external stochastic resonance depends not only on the external but also on the internal noise level

Temperature-Graduated Nickel-Silica Catalysts for Photothermal Steam Reforming of Methane

Photothermal steam reforming of methane (PTSRM) is a promising catalytic technology for converting stable methane and water into hydrogen utilizing solar energy. In the present study, the photothermal catalytic activity of silica-supported nickel (Ni/SiO₂) catalysts was investigated using a gas-flow reactor under concentrated visible/near-infrared light irradiation with various experimental parameters to obtain insight into factors affecting the activity and selectivity. In the thermal SRM at 773 K in the dark, the CH₄ conversion reached near-equilibrium with all four Ni/SiO₂ catalysts, while there was a significant difference in activity between the catalysts in the PTSRM reaction under light irradiation. These results indicate that PTSRM activity was affected by both thermodynamic and kinetic aspects. The conversion–selectivity relationship revealed that the product selectivity in PTSRM was different from the values in thermal SRM in the dark and calculated thermodynamic equilibrium. We proposed that concentrated light irradiation created the highest temperature zone in the centre of the reactor and the lower temperature zone downstream, and the consecutive water gas shift reaction and CO hydrogenation occurred in the lower temperature zone, thus resulting in the characteristic product selectivity. This study shows the potential of PTSRM systems with controllable selectivity by the temperature gradients formed under concentrated sunlight irradiation

Self-Assembled π-Conjugated Organic/Polymeric Microresonators and Microlasers

Optical microresonators are minute dielectric objects that are utilized as essential components in micrometer-scale light and laser sources, optical integrated circuits, micro-displays, chemo- and biosensors, and so forth. Particularly, microresonators made from organic and polymeric materials find unique applications owing to structural flexibility, color tunability, and functionality with a simple fabrication process, low cost and low energy consumption. In this Account, we highlight our recent progress on organic/polymeric microresonators made through precisely controlled self-assembly. The microstructures display novel optical functions such as circularly polarized luminescence emission, lasing, light energy harvest, optical gate operations, optical memories and authentications, and optical sensing for environmental changes and mechanical forces. Our methodology for the precise design and control of organic and polymeric microstructures will bridge between nanometer-scale supramolecular chemistry and bulk materials and will pave the way toward flexible optical and laser applications.</p