Advanced capabilities in electrical recording are essential for the treatment of heart-rhythm diseases. The most advanced technologies use flexible integrated electronics; however, the penetration of biological fluids into the underlying electronics and any ensuing electrochemical reactions pose significant safety risks. Here, we show that an ultrathin, leakage-free, biocompatible dielectric layer can completely seal an underlying layer of flexible electronics while allowing for electrophysiological measurements through capacitive coupling between tissue and the electronics, and thus without the need for direct metal contact. The resulting current-leakage levels and operational lifetimes are, respectively, four orders of magnitude smaller and between two and three orders of magnitude longer than those of any other flexible-electronics technology. Systematic electrophysiological studies with normal, paced and arrhythmic conditions in Langendorff hearts highlight the capabilities of the capacitive-coupling approach. Our technology provides a realistic pathway towards the broad applicability of biocompatible, flexible electronic implants.
Guard cells of the orchid genus, Paphiopedilum have been reported to lack developed chloroplasts and detectable chlorophyll a autofluorescence. Paphiopedilum stomata lack a photosynthesis-dependent opening response but have a blue light-specific opening. The present study found that low fluence rate green and red light elicited stomatal opening in Paphiopedilum and this opening was reversed by far red light, indicating the presence of a phytochrome-mediated opening response. Phytochrome-dependent, red light-stimulated opening was largest under low fluence rates and decreased to near zero as fluence rate increased. A recently discovered green light reversibility of blue light-specific stomatal opening was used to probe the properties of the blue light response in Paphiopedilum stomata. Blue light-stimulated opening was completely reversed by green light in the presence of far red light. Red light enhanced the blue light response of Paphiopedilum guard cells when given as a pretreatment or together with blue light. Analysis of guard cell pigments showed that guard cells have small amounts of chlorophyll a and b, zeaxanthin, violaxanthin, antheraxanthin and lutein. Zeaxanthin content increased in response to blue light or ascorbate and declined in the dark or under illumination in the presence of dithiothreitol, indicating the presence of an active xanthophyll cycle. Thus Paphiopedilum stomata possess both a blue light-mediated opening response with characteristics similar to species with normal chloroplast development and a novel phytochrome-mediated opening response.
Hydroisomerization of linear paraffins to branched isomers is an important petrochemical process, which commonly uses a microporous zeolite catalyst supported with Pt metal nanoparticles. Although attempts were made in the past to find an alternative to costly Pt, replacement with low-cost metals was not successful for conventional bulk zeolites, due to the low metal dispersion resulting in poor catalytic performance. Here, we demonstrate that Ni can replace Pt when it is supported on zeolites with uniform mesopores. Ni-supported MFI-, *MRE-, and TON-type zeolites possessing mesopores showed the same or even better catalytic performance in comparison to that of Pt-supported conventional MFI, *MRE, and TON zeolites, respectively. The Ni-supported zeolites exhibited even better branched isomer yields, despite low Ni loading. This result is ascribed to the confinement or sandwiching effect of Ni nanoparticles by the mesopore walls in the zeolites, which stabilizes the highly dispersed Ni nanoparticles.
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