Identification of tenuazonic acid as a novel type of natural photosystem II inhibitor binding in QB-site of Chlamydomonas reinhardtii

AbstractTenuazonic acid (TeA) is a natural phytotoxin produced by Alternaria alternata, the causal agent of brown leaf spot disease of Eupatorium adenophorum. Results from chlorophyll fluorescence revealed TeA can block electron flow from QA to QB at photosystem II acceptor side. Based on studies with D1-mutants of Chlamydomonas reinhardtii, the No. 256 amino acid plays a key role in TeA binding to the QB-niche. The results of competitive replacement with [14C]atrazine combined with JIP-test and D1-mutant showed that TeA should be considered as a new type of photosystem II inhibitor because it has a different binding behavior within QB-niche from other known photosystem II inhibitors. Bioassay of TeA and its analogues indicated 3-acyl-5-alkyltetramic and even tetramic acid compounds may represent a new structural framework for photosynthetic inhibitors

Molten salt derived Mo2AlB2 with excellent HER catalytic performance

Mo2AlB2 is a lamellar transition metal boride that is prepared by selectively etching the MoAlB MAB phase precursor. Most methods for synthesizing Mo2AlB2 require the use of strong acids or bases and a long reaction time. In this study, we present a Lewis acid molten salt method for synthesizing the lamellar structured Mo2AlB2 by selectively etching a layer of aluminium atoms from the MoAlB precursor. The synthesized Mo2AlB2 shows excellent catalytic activity for hydrogen evolution reaction under alkaline conditions, with long-term stability, and a low overpotential of 145 mV and Tafel slope of 76 mV dec−1 at 10 mA cm−2

Educational Process Mining for Discovering Students\u27 Problem-Solving Ability in Computer Programming Education

Educational process mining is now a promising method to provide decision-support information for the teaching-learning process via finding useful educational guidance from the event logs recorded in the learning management system. Existing studies mainly focus on mining students\u27 problem-solving skills or behavior patterns and intervening in students\u27 learning processes according to this information in the late course. However, educators often expect to improve the learning outcome in a proactive manner through dynamically designing instructional strategies prior to a course that are more appropriate to students\u27 average ability. Therefore, in this article, we propose a two-stage problem-solving ability modeling approach to obtain students\u27 ability in different learning stages, including the pre-problem-solving ability model and the post-problem-solving ability model. The models are trained with Gradient Boosting Decision Tree (GBDT) on the historical event logs of the prerequisite course and the target course, respectively. With the premodel, we establish the students\u27 pre-problem-solving ability profiles that reflect their average knowledge level before starting a course. Then, the instructional design is dynamically chosen according to the profiles. After a course completes, the post-problem-solving ability profiles are generated by the postmodel to analyze the learning outcome and prompt the learning feedback, in order to complete the closed-loop teaching process. We study the modeling of coding ability in computer programming education to show our teaching strategy. The experimental results show that the generalizable problem-solving ability models yield high classification precision, while most students\u27 abilities have been significantly improved by the proposed approach at the end of the course

Reunderstanding the reaction mechanism of aqueous Zn–Mn batteries with sulfate electrolytes: role of the zinc sulfate hydroxide

Rechargeable aqueous Zn-Mn batteries have garnered extensive attention for next-generation high-safety energy storage. However, the charge-storage chemistry of Zn-Mn batteries remains controversial. Prevailing mechanisms include conversion reaction and cation (de)intercalation in mild acid or neutral electrolytes, and a MnO2 /Mn2+ dissolution-deposition reaction in strong acidic electrolytes. Herein, a Zn4 SO4 ·(OH)6 ·xH2 O (ZSH)-assisted deposition-dissolution model is proposed to elucidate the reaction mechanism and capacity origin in Zn-Mn batteries based on mild acidic sulfate electrolytes. In this new model, the reversible capacity originates from a reversible conversion reaction between ZSH and Znx MnO(OH)2 nanosheets in which the MnO2 initiates the formation of ZSH but contributes negligibly to the apparent capacity. The role of ZSH in this new model is confirmed by a series of operando characterizations and by constructing Zn batteries using other cathode materials (including ZSH, ZnO, MgO, and CaO). This research may refresh the understanding of the most promising Zn-Mn batteries and guide the design of high-capacity aqueous Zn batteries.Ministry of Education (MOE)Submitted/Accepted versionThis work was financially supported by the National Natural Science Foundation of China (21972111, 22179109), Natural Science Foundation of Chongqing (cstc2018jcyjAX0714), and Venture & Innovation Support Program for Chongqing Overseas Returnees (cx2019073), Chongqing Engineering Research Center for Micro-Nano Biomedical Materials and Devices, and Chongqing Key Laboratory for Advanced Materials and Technologies. H.J.F. thanks the financial support from Singapore Ministry of Education by Tier 1 grant (RG 85/20)

Ultrafast Synthesis of Metal-Layered Hydroxides in a Dozen Seconds for High-Performance Aqueous Zn (Micro-) Battery

Abstract Efficient synthesis of transition metal hydroxides on conductive substrate is essential for enhancing their merits in industrialization of energy storage field. However, most of the synthetic routes at present mainly rely on traditional bottom-up method, which involves tedious steps, time-consuming treatments, or additional alkaline media, and is unfavorable for high-efficiency production. Herein, we present a facile, ultrafast and general avenue to synthesize transition metal hydroxides on carbon substrate within 13 s by Joule-heating method. With high reaction kinetics caused by the instantaneous high temperature, seven kinds of transition metal-layered hydroxides (TM-LDHs) are formed on carbon cloth. Therein, the fastest synthesis rate reaches ~ 0.46 cm2 s−1. Density functional theory calculations further demonstrate the nucleation energy barriers and potential mechanism for the formation of metal-based hydroxides on carbon substrates. This efficient approach avoids the use of extra agents, multiple steps, and long production time and endows the LDHs@carbon cloth with outstanding flexibility and machinability, showing practical advantages in both common and micro-zinc ion-based energy storage devices. To prove its utility, as a cathode in rechargeable aqueous alkaline Zn (micro-) battery, the NiCo LDH@carbon cloth exhibits a high energy density, superior to most transition metal LDH materials reported so far

A compact aqueous K-ion Micro-battery by a Self-shrinkage assembly strategy

Micro-batteries are promising power sources to drive miniaturized or portable electronic devices due to their higher energy density than micro-supercapacitors. Current micro-batteries still suffer from relatively large footprint and unsatisfactory areal electrochemical performance caused by loose electrode structure. Here, we develop a compact aqueous K-ion micro-battery through the self-shrinking of reduced graphene oxide hydrogel to realize small footprint and high areal capacity at the same time. With a volume of as small as 0.00381 cm(-3), this micro-battery delivers the highest areal capacity (5.1 mAh cm(-2)) and energy density (4.78 mWh cm(-2)) among all reported micro-batteries. Meanwhile, this micro-battery can be prepared into different shapes and attached onto a range of animals (ants, crabs and butterflies, etc.) for wide applications

Fixture-free omnidirectional prestretching fabrication and integration of crumpled in-plane micro-supercapacitors

Multidimensional folded structures with elasticity could provide spatial charge storage capability and shape adaptability for micro-supercapacitors (MSCs). Here, highly crumpled in-plane MSCs with superior conformality are fabricated in situ and integrated by a fixture- free omnidirectional elastic contraction strategy. Using carbon nanotube microelectrodes, a single crumpled MSC holds an ultrahigh volumetric capacitance of 9.3 F cm(-3), and its total areal capacitance is 45 times greater than the initial state. Experimental and theoretical simulation methods indicate that strain-induced improvements of adsorption energy and conductance for crumpled microelectrodes are responsible for the prominent enhancement of electrochemical performance. With outstanding morphological randomicity, the integrated devices can serve as smart coatings in moving robots, withstanding extreme mechanical deformations. Notably, integration on a spherical surface is possible by using a spherical mask, in which a small area of the microdevice array (3.9 cm(2)) can produce a high output voltage of 100 V