No abstract

Metal-free bifunctional oxygen electrocatalysts are extremely critical to the advanced energy conversion devices, such as high energy metal-air batteries. Effective tuning of edge defects and electronic density on carbon materials via simple methods is especially attractive. In this work, a facile alkali activation method has been proposed to prepare carbon with large specific surface area and optimized porosity. In addition, subsequent nitrogen-doping leads to high pyridinic-N and graphitic-N contents and abundant edge defects, further enhancing electrochemical activities. Theoretical modeling via first-principles calculations has been conducted to correlate the electrocatalytic activities with their fundamental chemical structure of N doping and edge defect engineering. The metal-free product (NKCNPs-900) shows a high half-wave potential of 0.79 V (ORR). Furthermore, the assembled Zn-air batteries display excellent performance among carbon-based metal-free oxygen electrocatalysts, such as large peak power density up to 131.4 mW cm, energy density as high as 889.0 W h kg at 4.5 mA cm, and remarkable discharge-charge cycles up to 575 times. Preliminarily, the rechargeable nonaqueous Li-air batteries were also investigated. Therefore, our work provides a low-cost, metal-free, and high-performance bifunctional carbon-based electrocatalyst for metal-air batteries.

The objective of this study is to verify the anatomic correlate of the second (2nd) outer retina band in optical coherence tomography (OCT), and to demonstrate the potential of using intrinsic optical signal (IOS) imaging for concurrent optoretinography (ORG) of phototransduction activation and energy metabolism in stimulus activated retinal photoreceptors. A custom-designed OCT was employed for depth-resolved IOS imaging in mouse retina activated by a visible light flicker stimulation. The spatiotemporal properties of the IOS changes at the photoreceptor outer segment (OS) and inner segment (IS) were quantitatively evaluated. Rapid IOS change was observed at the OS almost right away, and the IOS at the IS was relatively slow. Comparative analysis indicates that the OS-IOS reflects transient OS deformation caused by the phototransduction activation, and IS-IOS might reflect the energy metabolism caused by mitochondria activation in retinal photoreceptors. The consistency of the distribution of the IS-IOS and the 2nd OCT band supports the IS ellipsoid (ISe), which has abundant mitochondria, as the signal source of the 2nd OCT band of the outer retina.

Leachate nutrients from the nursery of containerized tree seedlings result in risks of inefficient fertilization through nutrient loss and contamination of ground water. In the present study, seedlings of Buddhist pine (Podocarpus macrophyllus) and Japanese maple (Acer palmatum) were cultured in containers of three differing sizes under contrasting photoperiods of naturally 11 h per day and an extended one of 20 h per day. Controlled release fertilizer (CRF, 14-14-14) was used to feed seedlings with sufficient nutrients for 5 months from June to November 2014. At the end of experiment, seedlings from all types of containers were measured for height and root collar diameter, whilst leachates were collected to determine nutrient concentrations of available phosphorus (P), potassium (K), ammonium and nitrate nitrogen (N) therein. Growth of both seedling species increased with the volume of container, but only growth of Japanese maple seedlings responded to photoperiod. In spite, there was greater amount of nutrients leached from containers planted with Buddhist pine than with Japanese maple; nearly no nutrient in the leachate affected by photoperiod. A negative correlation was found between concentrations of leachate nutrients and seedling height growth in all container sizes. In conclusion, nutrient leaching is a nonignorable but predictable factor by seedling height growth during the intensive culture of slowly growing seedlings of ornamental trees under the extended photoperiod.

Chloroplasts convert solar energy into biologically useful forms of energy by performing photosynthesis. Although light and particular genes are known to promote chloroplast development, little is known about the mechanisms that regulate the tissue-specificity and cell-specificity of chloroplast biogenesis. Thus, the mechanisms that determine whether non-photosynthetic plastids rather than chloroplasts develop in petals remain largely unexplored. Although heat stress is known to inhibit photosynthesis, we do not know whether heat stress affects chloroplast biogenesis. Here, we report that heat stress up-regulates the expression of chlorophyll biosynthesisrelated genes and promotes chloroplasts biogenesis in petals overexpressing SOC1 (suppressor of overexpression of CO) and novel SOC1-like genes. We also found that these specific MADS-box transcription factors are present in most photosynthetic eukaryotes and that the expression of more than one homolog is observed in chloroplast-containing tissues. These findings not only provide novel insights into the tissue specificity of chloroplast biogenesis and a method for producing green petals but also are consistent with heat stress influencing chloroplast biogenesis in higher plants.