Improvement of Thermodynamic Phase Stability and High-Rate Capability of Li Layered Oxides.

The use of elemental doping in lithium cobalt oxide (LCO) cathode material at high cutoff voltage is a widely adopted technique in the field of rechargeable batteries to mitigate multiple unfavorable phase transitions. However, there is still a lack of fundamental understanding regarding the rationality of each doping element implemented in this method, specifically considering the various thermodynamic stability and phase transitions. Herein, we investigated the effect of Ti doping on an O2 phase LCO (LCTO) cathode material that exhibited enhanced rate performance. We suggest that the incorporation of Ti into an O2 phase LCO results in the mitigation of multiple-phase transitions and the improvement of phase stability, thereby yielding a high-rate-capable cathode material. Through a combination of experimental and computational calculations, we demonstrate that Ti doping improves the thermodynamic stability and kinetics of Li-ions during the cycling process.

Synthesis and biological evaluation of indane-based fluorescent probes for detection of amyloid-ß aggregates in Alzheimer's disease.

In this article, the development of fluorescent imaging probes for the detection of Alzheimer's disease (AD)-associated protein aggregates is described. Indane derivatives with a donor-π-acceptor (D-π-A) structure were designed and synthesized. The probes were evaluated for their ability to bind to ß-amyloid (Aß) protein aggregates, which are a key pathological hallmark of AD. The results showed that several probes exhibited significant changes in fluorescence intensity at wavelengths greater than 600 nm when they were bound to Aß aggregates compared to the Aß monomeric form. Among the tested probes, four D-π-A type indane derivatives showed promising binding selectivity to Aß aggregates over non-specific proteins such as bovine serum albumin (BSA). The molecular docking study showed that our compounds were appropriately located along the Aß fibril axis through the hydrophobic tunnel structure. Further analysis revealed that the most active compound having dimethylaminopyridyl group as an election donor and dicyano group as an electron acceptor could effectively stain Aß plaques in brain tissue samples from AD transgenic mice. These findings suggest that our indane-based compounds have the potential to serve as fluorescent probes for the detection and monitoring of Aß aggregation in AD.

Strong Anionic Repulsion for Fast Na Kinetics in P2-Type Layered Oxides.

An intriguing mechanism for enabling fast Na kinetics during oxygen redox (OR) is proposed to produce high-power-density cathodes for sodium-ion batteries (SIBs) based on the P2-type oxide models, Na2/3 [Mn6/9 Ni3/9 ]O2 (NMNO) and Na2/3 [Ti1/9 Mn5/9 Ni3/9 ]O2 (NTMNO) using the "potential pillar" effect. The critical structural parameter of NTMNO lowers the Na migration barrier in the desodiated state because the electrostatic repulsion of O(2p)O(2p) that occurs between transition metal layers is combined with the chemically stiff Ti4+ (3d)O(2p) bond to locally retain the strong repulsion effect. The NTMNO interlayer distance moderately decreases upon charging with oxygen oxidation, whereas that of NMNO decreases at a much faster rate, which can be explained by the dependence of OR activity on the coordination environment. Fundamental electrochemical experiments clearly indicate that the Ti doping of the bare material significantly improves its rate capability during OR, and detailed electrochemical and structural analyses show much faster Na kinetics for NTMNO than for NMNO. A systematic comparison of the two cathode oxides based on experiments and first-principles calculations establishes the "potential pillar" concept of not only improving the sluggish Na kinetics upon OR reaction but also harnessing the full potential of the anionic redox for high-power-density SIBs.

One-pot bifunctionalization of silica nanoparticles conjugated with bioorthogonal linkers: application in dual-modal imaging.

Covalent surface modification of silica nanoparticles (SNPs) offers great potential for the development of multimodal nanomaterials for biomedical applications. Herein, we report the synthesis of covalently conjugated bifunctional SNPs and their application to in vivo multimodal imaging. Bis(methallyl)silane 15 with cyclopropene and maleimide, designed as a stable bifunctional linker, was efficiently synthesized by traceless Staudiger ligation, and subsequently introduced onto the surface of monodispersed SNPs via Sc(OTf)3-catalyzed siloxane formation. The bifunctional linker-grafted SNP 20 underwent both thiol-conjugated addition and tetrazine cycloaddition in one pot. Finally, positron emission tomography/computed tomography and fluorescence imaging study of dual functional SNP [125I]28 labeled with NIR dye and 125I isotope showed a prolonged circulation in mice, which is conducive to the systemic delivery of therapeutics.

Determining Factors in Triggering Hysteretic Oxygen Capacities in Lithium-Excess Sodium Layered Oxides.

Oxygen redox (OR) reactions in sodium layered oxide cathodes have been studied intensively to harness their full potential in achieving high energy density for sodium-ion batteries (SIBs). However, OR triggers a large hysteretic voltage during discharge after the first charge process for OR-based oxides, and its intrinsic origin is unclear. Therefore, in this study, an in-depth reinvestigation on the fundamentals of the reaction mechanism in Na[Li1/3Mn2/3]O2 with a Mn/Li ratio (R) of 2 was performed to determine the factors that polarize the OR activity and to provide design rules leading to nonhysteretic oxygen capacity using first-principles calculations. Based on thermodynamic energies, the O2-/O22- and O2-/On- conditions reveal the monophasic (0.0 ≤ x ≤ 4/6) and biphasic (4/6 ≤ x ≤ 1.0) reactions in Na1-x[Li2/6Mn4/6]O2, but each stability at x = 5/6 is observed differently. The O-O bond population elucidates that the formation of an interlayer O-O dimer is a critical factor in triggering hysteretic oxygen capacity, whereas that in a mixed layer provides nonhysteretic oxygen capacity after the first charge. In addition, the migration of Li into the 4h site in the Na metallic layer contributes less to the occurrence of voltage hysteresis because of the suppression of the interlayer O-O dimer. These results are clearly elucidated using the combined-phase mixing enthalpies and chemical potentials during the biphasic reaction. To compare the Mn oxide with R = 2, Na1-x[Li1/6Mn5/6]O2 tuned with R = 5 was investigated using the same procedure, and all the impeding factors in restraining the nonhysteretic OR were not observed. Herein, we suggest two strategies based on three types of OR models: (i) exploiting the migration of Li ions for the suppression of the interlayer O-O dimer and (ii) modulating the Mn/Li ratio for controlling the OR participation, which provides an exciting direction for nonhysteretic oxygen capacities for SIBs and lithium-ion batteries.

Emotional Distress of the COVID-19 Cluster Infection on Health Care Workers Working at a National Hospital in Korea.

BACKGROUND: Frontline healthcare workers responding to coronavirus disease 2019 (COVID-19) inevitably face tremendous psychological burden. Thus, the present study aimed to identify the psychological impact and the factors contributing to the likely increase in emotional distress of healthcare workers. METHODS: The participants include a total of 99 healthcare workers at Bugok National Hospital. Psychometric scales were used to assess emotional distress (12-item General Health Questionnaire; GHQ-12), depression symptoms (Patient Health Questionnaire-9; PHQ-9), and post-traumatic stress disorder-related symptoms (Impact of Events Scale-Revised; IES-R). A supplementary questionnaire was administered to investigate the experience of healthcare workers exposed to COVID-19-infected patients. Based on the results of GHQ-12 survey, participants were categorized into two groups: distress and non-distress. All the assessed scores were compared between the two groups. A logistic regression model was constructed to identify factors associated with emotional distress. RESULTS: Emotional distress was reported by 45.3% (n = 45) of all participants. The emotionally distressed group was more likely to be female, manage close contacts, have higher scores on PHQ-9 and IES-R, feel increased professional risk, and report that proper infection control training was not provided. Female gender, managing close contacts, higher scores on PHQ-9, and a feeling that proper infection control training was not provided were associated with emotional distress in logistic regression. CONCLUSION: Frontline healthcare workers face tremendous psychological burden during the COVID-19 pandemic. Therefore, appropriate psychological interventions should be provided to the HCWs engaged in the management of COVID-19-infected patients.

Intrinsic Origin of Nonhysteretic Oxygen Capacity in Conventional Na-Excess Layered Oxides.

An intriguing redox chemistry via oxygen has emerged to achieve high-energy-density cathodes and has been intensively studied for practical use of anion-utilization oxides in A-ion batteries (A: Li or Na). However, in general, the oxygen redox disappears in the subsequent discharge with a large voltage hysteresis after the first charge process for A-excess layered oxides exhibiting anion redox. Unlike these hysteretic oxygen redox cathodes, the two Na-excess oxide models Na2IrO3 and Na2RuO3 unambiguously exhibit nonhysteretic oxygen capacities during the first cycle, with honeycomb-ordered superstructures. In this regard, the reaction mechanism in the two cathode models is elucidated to determine the origin of nonhysteretic oxygen capacities using first-principles calculations. First, the vacancy formation energies show that the thermodynamic instability in Na2IrO3 increases at a lower rate than that in Na2RuO3 upon charging. Second, considering that the strains of Ir-O and Ru-O bonding lengths are softened after the single-cation redox of Ru4+/Ru5+ and Ir4+/Ir5+, the contribution in the oxygen redox from x = 0.5 to 0.75 is larger in Na1-xRu0.5O1.5 than that in Na1-xIr0.5O1.5. Third, the charge variations indicate a dominant cation redox activity via Ir(5d)-O(2p) for x above 0.5 in Na1-xIr0.5O1.5. Its redox participation occurred with the oxygen redox, opposite to the behavior in Na1-xRu0.5O1.5. These three considerations imply that the chemical weakness of Ir(5d)-O(2p) leads to a more redox-active environment of Ir ions and reduces the oxygen redox activity, which triggers the nonhysteretic oxygen capacity during (de)intercalation. This provides a comprehensive guideline for design of reversible oxygen redox capacities in oxide cathodes for advanced A-ion batteries.

GadgetArm-Automatic Grasp Generation and Manipulation of 4-DOF Robot Arm for Arbitrary Objects Through Reinforcement Learning.

Automatic robot gripper system which involves the automated object recognition of work-in-process in production line is the key technology of the upcoming manufacturing facility achieving Industry 4.0. Automatic robot gripper enables the manufacturing system to be autonomous, self-recognized, and adaptable by using artificial intelligence of robot programming dealing with arbitrary shapes of work-in-processes. This paper specifically explores the chain of key technologies, such as 3D object recognition with CAD and point cloud data, reinforcement learning of robot arm, and customized 3D printed gripper, in order to enhance the intelligence of the robot controller system. And it also proposes the integration with 3D point cloud based object recognition and game-engine based reinforcement learning. The result of the prototype of the intelligent robot gripping system developed by the proposed method with a 4 degree-of-freedom robot arm is explained in this paper.

Uncovering the Structural Evolution in Na-Excess Layered Cathodes for Rational Use of an Anionic Redox Reaction.

A new paradigm based on an anionic O2-/On- redox reaction has been highlighted in high-energy density cathode materials for sodium-ion batteries, achieving a high voltage (∼4.2 V vs Na/Na+) with a large anionic capacity during the first charge process. The structural variations during (de)intercalation are closely correlated with stable cyclability. To determine the rational range of the anion-based redox reaction, the structural origins of Na1-xRu0.5O1.5 (0 ≤ x ≤ 1.0) were deduced from its vacancy (□)/Na atomic configurations, which trigger different interactions between the cations and anions. In the cation-based Ru4+/Ru5+ redox reaction, the □ solubility into fully sodiated Na2RuO3 predominantly depends on the crystallographic 4h site when 0.0 ≤ x ≤ 0.25, and the electrostatic repulsion of the linear O2--□-O2- configuration is accompanied by the increased volumetric strain. Further Na extraction (0.25 ≤ x ≤ 0.5) induces a compensation effect, leading to Na2/3[Na□Ru2/3]O2 with the □ formation of 2b and 2c sites, which drastically reduce the volumetric strain. In the O2-/On- anionic redox region (0.5 ≤ x ≤ 0.75), Na removal at the 4h site generates a repulsive force in O2--□-O2- that increases the interlayer distance. Finally, in the 0.75 ≤ x ≤ 1.0 region, the anionic O charges are unprotected by repulsive forces, and their consumption causes severe volumetric strain in Na1-xRu0.5O1.5. Coupling our mechanistic understanding of the structural origin with the □- and Na-site preferences and the electrostatic interaction between lattice O and vacancies in Na1-xRu0.5O1.5, we determined the rational range of the anionic redox reaction in layered cathode materials for rechargeable battery research.

Mechanism of histone lysine methyl transfer revealed by the structure of SET7/9-AdoMet.

The methylation of lysine residues of histones plays a pivotal role in the regulation of chromatin structure and gene expression. Here, we report two crystal structures of SET7/9, a histone methyltransferase (HMTase) that transfers methyl groups to Lys4 of histone H3, in complex with S-adenosyl-L-methionine (AdoMet) determined at 1.7 and 2.3 A resolution. The structures reveal an active site consisting of: (i) a binding pocket between the SET domain and a c-SET helix where an AdoMet molecule in an unusual conformation binds; (ii) a narrow substrate-specific channel that only unmethylated lysine residues can access; and (iii) a catalytic tyrosine residue. The methyl group of AdoMet is directed to the narrow channel where a substrate lysine enters from the opposite side. We demonstrate that SET7/9 can transfer two but not three methyl groups to unmodified Lys4 of H3 without substrate dissociation. The unusual features of the SET domain-containing HMTase discriminate between the un- and methylated lysine substrate, and the methylation sites for the histone H3 tail.