Removing 65 Years of Approximation in Rotating Ring Disk Electrode Theory with Physics-Informed Neural Networks.

The rotating Ring Disk Electrode (RRDE), since its introduction in 1959 by Frumkin and Nekrasov, has become indispensable with diverse applications in electrochemistry, catalysis, and material science. The collection efficiency (N) is an important parameter extracted from the ring and disk currents of the RRDE, providing valuable information about reaction mechanism, kinetics, and pathways. The theoretical prediction of N is a challenging task: requiring solution of the complete convective diffusion mass transport equation with complex velocity profiles. Previous efforts, including by Albery and Bruckenstein who developed the most widely used analytical equations, heavily relied on approximations by removing radial diffusion and using approximate velocity profiles. 65 years after the introduction of RRDE, we employ a physics-informed neural network to solve the complete convective diffusion mass transport equation, to reveal the formerly neglected edge effects and velocity corrections on N, and to provide a guideline where conventional approximation is applicable.

An evolutionary continuum from nucleated dwarf galaxies to star clusters.

Systematic studies1-4 have revealed hundreds of ultra-compact dwarf galaxies (UCDs5) in the nearby Universe. With half-light radii rh of approximately 10-100 parsecs and stellar masses M* ≈ 106-108 solar masses, UCDs are among the densest known stellar systems6. Although similar in appearance to massive globular clusters7, the detection of extended stellar envelopes4,8,9, complex star formation histories10, elevated mass-to-light ratio11,12 and supermassive black holes13-16 suggest that some UCDs are remnant nuclear star clusters17 of tidally stripped dwarf galaxies18,19, or even ancient compact galaxies20. However, only a few objects have been found in the transient stage of tidal stripping21,22, and this assumed evolutionary path19 has never been fully traced by observations. Here we show that 106 galaxies in the Virgo cluster have morphologies that are intermediate between normal, nucleated dwarf galaxies and single-component UCDs, revealing a continuum that fully maps this morphological transition and fills the 'size gap' between star clusters and galaxies. Their spatial distribution and redder colour are also consistent with stripped satellite galaxies on their first few pericentric passages around massive galaxies23. The 'ultra-diffuse' tidal features around several of these galaxies directly show how UCDs are forming through tidal stripping and that this evolutionary path can include an early phase as a nucleated ultra-diffuse galaxy24,25. These UCDs represent substantial visible fossil remnants of ancient dwarf galaxies in galaxy clusters, and more low-mass remnants probably remain to be found.

Effect of aeration/micro-aeration on lignocellulosic decomposition, maturity and seedling phytotoxicity during full-scale biogas residues composting.

With the accelerated construction of biogas plants, the amount of biogas residues are expanding. Composting has been widely implemented to deal with biogas residues. Aeration regulation is the main factor affecting the post-composting treatment of biogas residues as high-quality fertilizer or soil amendment. Therefore, this study aimed to investigate the impact of different aeration regulations on full-scale biogas residues compost maturity by controlling oxygen concentration under micro-aeration and aeration conditions. Results showed that micro-aerobic extended the thermophilic stage of 17 days at above 55 ℃ and facilitated the mineralization process of organic nitrogen into nitrate nitrogen to retain higher N nutrition levels compared to aerobic treatment. For biogas residues with high moisture, aeration should be regulated at different full-scale composting stages. Total organic carbon (TOC), NH4+-N, NO3--N, total potassium (TK), total phosphorus (TP) and the germination index (GI) could be used to evaluate stabilization, fertilizer efficiency and phytotoxicity of compost with frequent monitoring times. However, seedling growth trials were still necessary in full-scale composting plants when changing of composting process or biogas residues feedstock.

The greenhouse gas emission potential and phytotoxicity of biogas slurry in static storage under different temperatures.

With the booming development of biogas industry to treat organic waste in China, the by-product of biogas slurry was accompanied with a huge amount. Static storage process of biogas slurry was normally operated under different seasons before application to land which would cause nutrition decomposition and greenhouse gas emission. Thus, the aim of this study was to investigate the nutrition decomposition, greenhouse gas emission (CH4 and N2O), and phytotoxicity of biogas slurry under different static temperatures, furthermore to illuminate the network among them and functional microorganism. According to the results, higher temperature at 30 °C contributed to fast and complete degradation of COD. In addition, more quantity of NH4+ conversion and NO3- formation appeared at 30 °C. These factors resulted in relatively less crop toxicity together. CH4 was the dominant greenhouse gas emission than N2O and was highest in 30 °C treatment with total emission of 273.7 L/(m3·d) and greenhouse gas emission of 20.01 kg CO2e (carbon dioxide equivalent). Lower temperature was conductive to N reservation and reduction of greenhouse gas emission, but making against with stabilization of organic matter and crop safety. At the same dilution times (≤3) of biogas slurry with deionized water, higher temperature at 30 °C could reduce 30 days of storage time, but 10 °C was still unsafe for crop. Structural equation model was further illustrated the positive effect of temperature on NO3-, CH4, GI, and N2O and negative on COD and NH4+. These results could help to monitor the environmental risk, evaluate the maturity, guide the irrigation scheme, and regulate the static storage condition of biogas slurry under different seasons.