Ab initio data-analytics study of carbon-dioxide activation on semiconductor oxide surfaces

The excessive emissions of carbon dioxide (CO$_2$) into the atmosphere threaten to shift the CO$_2$ cycle planet-wide and induce unpredictable climate changes. Using artificial intelligence (AI) trained on high-throughput first principles based data for a broad family of oxides, we develop a strategy for a rational design of catalytic materials for converting CO$_2$ to fuels and other useful chemicals. We demonstrate that an electron transfer to the $\pi^*$-antibonding orbital of the adsorbed molecule and the associated bending of the initially linear molecule, previously proposed as the indicator of activation, are insufficient to account for the good catalytic performance of experimentally characterized oxide surfaces. Instead, our AI model identifies the common feature of these surfaces in the binding of a molecular O atom to a surface cation, which results in a strong elongation and therefore weakening of one molecular C-O bond. This finding suggests using the C-O bond elongation as an indicator of CO$_2$ activation. Based on these findings, we propose a set of new promising oxide-based catalysts for CO$_2$ conversion, and a recipe to find more

Combining vibrotactile feedback with volitional myoelectric control for robotic transtibial prostheses

In recent years, the development of myoelectric control for robotic lower-limb prostheses makes it possible for amputee users to volitionally control prosthetic joints. However, the human-centered control loop is not closed due to the lack of sufficient feedback of prosthetic joint movement, and it may result in poor control performance. In this research, we propose a vibrotactile stimulation system to provide the feedback of ankle joint position, and validate the necessity of combining it with volitional myoelectric control to achieve improved control performance. The stimulation system is wearable and consists of six vibrators. Three of the vibrators are placed on the anterior side of the thigh and the other three on the posterior side of the thigh. To explore the potential of applying the proposed vibrotactile feedback system for prosthetic ankle control, eight able-bodied subjects and two transtibial amputee subjects (TT1 and TT2) were recruited in this research, and several experiments were designed to investigate subjects' sensitivities to discrete and continuous vibration stimulations applied on the thigh. Then, we proposed a stimulation controller to produce different stimulation patterns according to current ankle angle. Amputee subjects were asked to control a virtual ankle displayed on the computer screen to reach different target ankle angles with a myoelectric controller, and control performances under different feedback conditions were compared. Experimental results indicated that subjects were more sensitive to stimulation position changes (identification accuracies were 96.39pm0.86%, 91.11% and 93.89% for able-bodied subjects, TT1 and TT2, respectively) than stimulation amplitude changes (identification accuracies were 89.89pm2.40%, 87.04% and 85.19% for able-bodied subjects, TT1 and TT2, respectively). Response times of able-bodied subjects, TT1 and TT2 to stimulation pattern changes were 0.47pm0.02s, 0.53s and 0.48s, respectively. Furthermore, for both TT1 and TT2, the absolute error of virtual ankle control reduced by about 50% with the addition of vibrotactile feedback. These results suggest that it is promising to apply the vibrotactile feedback system for the control of robotic transtibial prostheses

Theoretical study of the crystal plane effect and ion-pair active center for C-H bond activation by Co3O4 nanocrystals

Methane has attracted extensive interest in recent years due to its potential application as a replacement of oil and a feedstock for valuable chemicals. Due to the large C-H bond energy, the conversion of methane into useful products has been a challenge. In the present study, density functional theory (DFT) calculations were performed to study the activation of the C-H bond of methane on the (001) and (011) planes of Co3O4, which showed that CH4 activation on Co3O4 nanocrystals was fairly easy with only small energy barriers (less than 1.1 eV). Surface Co-O ion pairs are the active site for C-H bond activation, where the two ions provide a synergistic effect for the activation of the strong C-H bond and yield surface Co-CH3 and O-H species. The Co3O4(011) surface is shown to be more reactive for C-H bond activation than the Co3O4(001) surface, which is consistent with previous experimental results. Our results suggest that methane oxidation on Co3O4 nanocrystals has strong crystal plane effect and structure sensitivity and the ion-pair active center plays a significant role in activating the strong C-H bond. (C) 2014, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved

P53 Contributes to Cisplatin Induced Renal Oxidative Damage via Regulating P66shc and MnSOD

Background/Aims: Cisplatin is widely used to treat malignancies. However, its major limitation is the development of dose-dependent nephrotoxicity. The precise mechanisms of cisplatin-induced kidney damage remain unclear. Previous study demonstrated the central role of mitochondrial ROS (mtROS) in the pathogenesis of cisplatin nephrotoxicity. The purpose of this study was to explore the mechanism of mtROS regulation in cisplatin nephrotoxicity. Methods: p53, MnSOD and p66shc were detected at mRNA and protein levels by qPCR and western blot in HK2 cells. mtROS levels were determined by DCFDA and MitoSOX staining. Cell viability and cell apoptosis were accessed by CCK-8 assay, TUNEL assay and flow cytometry, respectivesly. siRNAs were used to knock down p53 and p66shc expression and subsequent changes were observed. In vivo assays using a mouse model of cisplatin-induced acute kidney injury were used to validate the in vitro results. Results: In HK2 cells, cisplatin exposure decreased the MnSOD and increased the expression of p53 and p66shc. MnTBAP, a MnSOD mimic, blocked cisplatin-induced the generation of mtROS and cell injury. P66shc and p53 siRNAs rendered renal cells resistant to cisplatin-induced mtROS production and cell death. Furthermore, knockdown of p53 restored MnSOD and inhibiting p66shc. Consistent with these results, we revealed that p53 inhibitor reduced cisplatin-induced oxidative stress and apoptosis by regulating MnSOD and p66shc in the kidney of cisplatin-treated mice. Conclusion: Our study identifies activation of p53 signalling as a potential strategy for reducing the nephrotoxicity associated with cisplatin treatments and, as a result, broadens the therapeutic window of this chemotherapeutic agent

Mitochondrial Fission Is Required for Angiotensin II-Induced Cardiomyocyte Apoptosis Mediated by a Sirt1-p53 Signaling Pathway

Hypertension-induced cardiac apoptosis is a major contributor to early-stage heart-failure. Our previous studies have found that p53-mediated mitochondrial fission is involved in aldosterone-induced podocyte apoptosis. However, it is not clear that whether p53-induced mitochondrial fission is critical for hypertensive Angiotensin II (AngII)-induced cardiomyocyte apoptosis. In this study, we found that inhibition of the mitochondrial fission protein Drp1 (dynamin-related protein 1) by Mdivi-1 prevented cardiomyocyte apoptosis and cardiac remodeling in SHRs. In vitro we found that treatment of cultured neonatal rat cardiomyocytes with AngII induced Drp1 expression, mitochondrial fission, and apoptosis. Knockdown of Drp1 inhibited AngII-induced mitochondrial fission and cardiomyocyte apoptosis. Furthermore, AngII induced p53 acetylation. Knockdown of p53 inhibited AngII-induced Drp1 expression, mitochondrial fission, and cardiomyocyte apoptosis. Besides, we found that Sirt1 was able to reverse AngII-induced p53 acetylation and its binding to the Drp1 promoter, which subsequently inhibited mitochondrial fission and eventually attenuated cardiomyocyte apoptosis. Collectively, these results suggest that AngII degrades Sirt1 to increase p53 acetylation, which induces Drp1 expression and eventually results in cardiomyocyte apoptosis. Sirt1/p53/Drp1dependent mitochondrial fission may be a valuable therapeutic target for hypertension induced heart failure

Synergistic effect of Ru-N₄ sites and Cu-N₃ sites in carbon nitride for highly selective photocatalytic reduction of CO₂ to methane

Developing single-atom photocatalysts for selective conversion of CO2 to valuable fuel is of great attraction but remains challenging. In this work, ruthenium and copper single atoms are for the first time simultaneously incorporated into polymeric carbon nitride (PCN) through a simple preassembly-coprecipitation-pyrolysis process. The obtained PCN-RuCu sample exhibited much higher selectivity (95%) for CH4 production than the individual Ru or Cu decorated PCN during photocatalytic CO2 reduction under visible-light irradiation. The atomically dispersed Ru-N4 and Cu-N3 moieties were confirmed by spherical aberration-corrected electron microscopy and extended X-ray absorption fine structure spectroscopy. Density function theory (DFT) calculations revealed that the co-existence of Ru-N4 sites and Cu-N3 sites can effectively tune the electronic structure of PCN, making the Ru sites account for photogenerated electron-hole pairs and the Cu sites for CO2 hydrogenation. Moreover, the synergetic effect between Ru and Cu single atoms significantly promotes the consecutive hydrogenation processes of *CO species towards CH4 production. Our studies provide a new understanding of the mechanism for photocatalytic reduction of CO2 to CH4, and pave a new way to design photocatalysts for the selective production of solar fuels.Ministry of Education (MOE)Submitted/Accepted versionThis work was supported by the Ministry of Education, Singapore, under AcRF-Tier2 (MOE2018-T2-1-017) and AcRF-Tier1 (MOE2019-T1- 002-012, RG102/19). The authors also thank the support from NTU seed funding for Solar Fuels Laboratory. LH thanks for the financial support from Shenzhen Clean Energy Research Institute (CERI-KY-2019-003). Y. G.W and J.W.C were financially supported by NSFC No. 22022504 of China, Guangdong “Pearl River” Talent Plan (No. 2019QN01L353), Shenzhen Science and Technology Plan (No. JCYJ20210324103608023) and Guangdong Provincial Key Laboratory of Catalysis (No. 2020B121201002)

Electronic structure engineering to boost oxygen reduction activity by controlling the coordination of the central metal

Adjusting the electronic structure of the active center is a highly effective strategy for improving the performance of catalysts. Herein, we report an atomically dispersed catalyst (FeCl1N4/CNS), which realized for the first time a great improvement of the ORR by controlling the electronic structure of the central metal with a coordinated chlorine. The half-wave potential of FeCl1N4/CNS is E1/2 = 0.921 V, which is the highest among the reported values for non-precious metal electrocatalysts and far exceeds that of FeN4/CN and commercial Pt/C in alkaline solution. Besides an exceptionally high kinetic current density (Jk) of 41.11 mA cm−2 at 0.85 V, it also has a good methanol tolerance and outstanding stability. Experiments and DFT demonstrated that the near-range interaction with chlorine and the long-range interaction with sulfur of Fe modulated the electronic structure of the active site, thus resulting in a great improvement of the ORR in alkaline media. The present findings could open new avenues for the design of superior electrocatalysts

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<p>Hypertension-induced cardiac apoptosis is a major contributor to early-stage heart-failure. Our previous studies have found that p53-mediated mitochondrial fission is involved in aldosterone-induced podocyte apoptosis. However, it is not clear that whether p53-induced mitochondrial fission is critical for hypertensive Angiotensin II (AngII)-induced cardiomyocyte apoptosis. In this study, we found that inhibition of the mitochondrial fission protein Drp1 (dynamin-related protein 1) by Mdivi-1 prevented cardiomyocyte apoptosis and cardiac remodeling in SHRs. In vitro we found that treatment of cultured neonatal rat cardiomyocytes with AngII induced Drp1 expression, mitochondrial fission, and apoptosis. Knockdown of Drp1 inhibited AngII-induced mitochondrial fission and cardiomyocyte apoptosis. Furthermore, AngII induced p53 acetylation. Knockdown of p53 inhibited AngII-induced Drp1 expression, mitochondrial fission, and cardiomyocyte apoptosis. Besides, we found that Sirt1 was able to reverse AngII-induced p53 acetylation and its binding to the Drp1 promoter, which subsequently inhibited mitochondrial fission and eventually attenuated cardiomyocyte apoptosis. Collectively, these results suggest that AngII degrades Sirt1 to increase p53 acetylation, which induces Drp1 expression and eventually results in cardiomyocyte apoptosis. Sirt1/p53/Drp1dependent mitochondrial fission may be a valuable therapeutic target for hypertension induced heart failure.</p