Higher-voltage operation is crucial to increase the energy density of rechargeable batteries. Here we explored the Cr 4+ /Cr 3+ redox couple in a polyanion framework for a high-voltage sodium battery cathode. An archetypal NASICON-phase Na 3 Cr 2 (PO 4 ) 3 exhibited a reversible redox activity at ca. 4.5 V versus Na/Na + , offering further scope for searching new high-voltage materials based on Cr 4+ /Cr 3+ redox couple.

Reversibility of an electrode reaction is important for energy-efficient rechargeable batteries with a long battery life. Additional oxygen-redox reactions have become an intensive area of research to achieve a larger specific capacity of the positive electrode materials. However, most oxygen-redox electrodes exhibit a large voltage hysteresis >0.5 V upon charge/discharge, and hence possess unacceptably poor energy efficiency. The hysteresis is thought to originate from the formation of peroxide-like O22− dimers during the oxygen-redox reaction. Therefore, avoiding O-O dimer formation is an essential challenge to overcome. Here, we focus on Na2-xMn3O7, which we recently identified to exhibit a large reversible oxygen-redox capacity with an extremely small polarization of 0.04 V. Using spectroscopic and magnetic measurements, the existence of stable O−• was identified in Na2-xMn3O7. Computations reveal that O−• is thermodynamically favorable over the peroxide-like O22− dimer as a result of hole stabilization through a (σ + π) multiorbital Mn-O bond.

Kinetic formation of the peroxo-like O22− dimer is identified as the origin of a voltage hysteresis in oxygen-redox battery electrodes.

Cellular senescence is a complex stress response characterized by permanent loss of proliferative capacity and is implicated in agerelated disorders. Although the transcriptional activity of p53 (encoded by TP53) is known to be vital for senescence induction, the downstream effector genes critical for senescence remain unsolved. Recently, we have identified the proline dehydrogenase gene (PRODH) to be upregulated specifically in senescent cells in a p53-dependent manner, and the functional relevance of this to senescence is yet to be defined. Here, we conducted functional analyses to explore the relationship between PRODH and the senescence program. We found that genetic and pharmacological inhibition of PRODH suppressed senescent phenotypes induced by DNA damage. Furthermore, ectopic expression of wild-type PRODH, but not enzymatically inactive forms, induced senescence associated with the increase in reactive oxygen species (ROS) and the accumulation of DNA damage. Treatment with N-acetyl-L-cysteine, a ROS scavenger, prevented senescence induced by PRODH overexpression. These results indicate that PRODH plays a causative role in DNA damage-induced senescence through the enzymatic generation of ROS.

NASICON-type Na2CrTi(PO4)3 offers a stable redox reaction of Cr4+/Cr3+ at 4.5 V vs. Na/Na+.

Conspectus Sustainable development cannot be achieved without substantial technological advancements. For instance, flexible electricity management requires smart power sourcing with advanced energy storage/conversion technologies. Remedies for abrupt power spikes/drops observed in renewable energy sources such as solar and wind require rapid load-leveling using high-power energy storage systems when they are integrated into a microgrid. Electrochemical energy storage devices efficiently convert electrical and chemical energy, which can potentially function as distributed power sources. Among these, lithium-ion batteries are a present de facto standard with their relatively high energy density and energy efficiencies that are based on topochemical intercalation chemistry, whereby guest lithium ions are (de)­intercalated reversibly with simultaneous redox reactions and minimal structural changes. However, their energy density, power density, life-cycle cost, calendar life, and safety remain unsatisfactory for widespread use. When the storage capacity is maximized, as a result of which a labile deep charge/discharge state is generated, to develop batteries with high energy density, subsequent irreversible phase transformations or chemical reactions occur in many cases. The combination of the reversible electrode reactions and the subsequent irreversible phase transformations sometimes causes a charge/discharge curve characterized by a large voltage hysteresis with 100% Coulombic efficiency. Because a large voltage hysteresis significantly degrades the energy efficiency, unveiling the reaction mechanism is of primary importance in mitigating energy loss. In this Account, we comprehensively discuss the distinct and reversible charge/discharge reactions, generalized by the term “square scheme”, which includes both thermodynamic and kinetic processes. The difficulties encountered in analyzing the square scheme are that both energy efficient and inefficient processes coexist and compete with each other, where the latter involves the time-dependent phenomenon. Here, we provide the theoretical models and analytical expressions for kinetic square-scheme electrodes under several electrochemical conditions, including galvanostatic charge/discharge, the galvanostatic intermittent titration technique (GITT), the potentiostatic intermittent titration technique (PITT), and constant-current/constant-voltage (CC–CV) charge/discharge. The validity of the analytical models was confirmed for two typical square-scheme electrodes: Na1–x Ti0.5Co0.5O2 and Na2–x Mn3O7. Na1–x Ti0.5Co0.5O2, which is a sodium-ion battery cathode material, undergoes phase transitions between high-spin and low-spin states after transition-metal oxidation/reduction, while Na2–x Mn3O7, which is a large-capacity oxygen-redox cathode material, exhibits O–O bond formation after oxide-ion oxidation and O–O bond cleavage after peroxide reduction, both of which trigger large voltage hysteresis. This Account emphasizes the importance of the quantitative analyses of the...

This study reveals a novel role of d-amino acid oxidase in promoting cellular senescence induced by genotoxic stresses via enzymatic generation of reactive oxygen species.

An infrared ray electronic video-endoscope with a laser diode light source was used to obtain information on the submucosal area. As contrast medium we employed indocyanine green, which has a light absorption peak in the infrared range. The wavelength of the laser diode was set to 810 nm as suggested by the results of the spectrophotometric study on the reflected light at fingertips after injection of ICG (3 mg/kg). Using this system we inspected the stomach under visible light and then continuously under infrared light before and after intravenous injection of ICG (2 mg/kg). A dendritic figure with fine ramifications emerged in the early stage after intravenous injection of indocyanine green, which was not seen under visible light. These features of the figure visualized by the infrared endoscope suggest that they have a close relationship with blood vessels and blood circulation beneath the mucosal surface. This infrared electronic endoscope system provides submucosal information more readily and at a lower cost than ever before, and also the infrared lighting method of this system could be applied to almost all available electronic endoscopes by modulating infrared cutting filters, so it could become a valuable clinical tool.