29 research outputs found

    Software for the frontiers of quantum chemistry:An overview of developments in the Q-Chem 5 package

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    This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange–correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods include novel variants of both coupled-cluster and configuration-interaction approaches along with methods based on the algebraic diagrammatic construction and variational reduced density-matrix methods. Methods highlighted in Q-Chem 5 include a suite of tools for modeling core-level spectroscopy, methods for describing metastable resonances, methods for computing vibronic spectra, the nuclear–electronic orbital method, and several different energy decomposition analysis techniques. High-performance capabilities including multithreaded parallelism and support for calculations on graphics processing units are described. Q-Chem boasts a community of well over 100 active academic developers, and the continuing evolution of the software is supported by an “open teamware” model and an increasingly modular design

    Effect of eNOS on Ischemic Postconditioning-Induced Autophagy against Ischemia/Reperfusion Injury in Mice

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    Autophagy is involved in the development of numerous illnesses, including ischemia/reperfusion (I/R). Endothelial nitric oxide synthase (eNOS) participates in the protective effects of ischemic postconditioning (IPostC). However, it remains unclear whether eNOS-mediated autophagy serves as a critical role in IPostC in the hearts of mice, in protecting against I/R injury. In the present study, the hearts of mice with left anterior descending coronary artery ligation were studied as I/R models. H9c2 cells underwent exposure to hypoxia/reoxygenation (H/R) and were examined as in vitro model. IPostC reduced mice myocardial infarct size and improved the structure of the heart. IPostC increased the formation of autophagosomes and increased the phosphorylation of eNOS and adenosine monophosphate-activated protein kinase (AMPK). Autophagy and eNOS inhibition suppressed the cardioprotective effects of IPostC. AMPK or eNOS inhibition abolished the improvement effect of IPostC on autophagy. AMPK inhibition decreased eNOS phosphorylation in the heart. Additionally, H9c2 cells suffering hypoxia were used as in vitro model. Autophagy or eNOS inhibition abolished the protective effects of hypoxic postconditioning (HPostC) against H/R injury. AMPK and eNOS inhibition/knockout decreased autophagic activity in the HPostC group. These results indicated that IPostC protects the heart against I/R injury, partially via promoting AMPK/eNOS-mediated autophagy

    Interactions between Graphene and Ionic Liquid Electrolyte in Supercapacitors

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    The graphene material prepared by the chemical reduction method usually has oxygenic functional groups in it and such functional groups often result in interactions between the graphene electrode and the electrolyte in supercapacitors. We have examined the existential form of interactions between graphene as the electrode and three kinds of ionic liquid, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (EMI-TFSI), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4), and 1-methyl-1-propylpiperidinium bis (trifluoromethyl sulfonyl) imide (MPPp-TFSI), as the electrolyte of a supercapacitor. Mass spectroscopy (MS) and Fourier transform infrared spectroscopy (FT-IR) analyses confirmed that the residual hydroxyl groups in graphene were transferred to EMI+ and TFSI lost oxygen atoms to graphene, while little reaction took place in BF4 or MPPp(+), during the process of charging. The chemical reactions are suggested to contribute to the device capacitance while it is also one of the reasons for the decreased electrochemical stability window. In this study the highest energy density achieved using the graphene electrode is 169 Wh kg (1) in MPPp-TFSI electrolyte charged to 4.4 V. (C) 2016 Elsevier Ltd. All rights reserved

    Ionic liquid modified graphene for supercapacitors with high rate capability

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    Ionic liquids (ILs) with large electrochemical windows up to 4 V have been employed as the electrolyte to boost the energy density of graphene-based supercapacitors. However, due to the larger molecular size, lower conductivity, and higher viscosity of the IL electrolyte, graphene-based supercapacitors in IL electrolyte usually exhibit low rate capability. To make graphene-based electrodes more compatible with the IL electrolyte, we functionalized chemically reduced graphene oxide with the same IL which is also used as the electrolyte. Electrochemical test results show that the relaxation time and charge transfer resistance at electrode-electrolyte interface for IL modified electrode is one third and one fourth of that for the pristine graphene electrode, respectively, indicating the improved compatibility between the IL modified electrode and the electrolyte. Furthermore, the capacitance retention of the IL modified electrode from current density of 0.5 to 20 A g(-1) is 85%, which is much higher than that of the pristine electrode (53%). (C) 2015 Elsevier Ltd. All rights reserved

    Formation of Halogenated Polyaromatic Compounds by Laccase Catalyzed Transformation of Halophenols

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    Laccases are a type of extracellular enzyme produced by fungi, bacteria, and plants. Laccase can catalyze one-electron oxidation of a variety of phenolic compounds using molecular oxygen as the electron acceptor. In this study, transformation of halophenols (XPs) in laccase-catalyzed oxidation processes was explored. We first examined the intrinsic reaction kinetics and found that the transformation of XPs appeared first order to the concentrations of both XPs and laccase. A numerical model was developed to describe the role of humic acid (HA) in this process. It was demonstrated that HA could reverse the oxidation of XPs by acting as the inner filtrator of XP radical intermediates formed upon reactions between the substrates and laccase. The extent of such reversion was proportional to HA concentration. MS analysis in combination with quantum chemistry computation suggested that coupling products were generated. XPs coupled to each via CC or COC pathways, generating hydroxyl polyhalogenated biphenyl ethers (OH-PCDEs) and hydroxyl polyhalogenated biphenyls, respectively. Many of these polyhalogenated products are known to be hazardous to the ecosystem and human health, but they are not synthetic chemicals. This study shed light on their genesis in the environmental media

    Solvent-Controlled Morphology of Zinc–Cobalt Bimetallic Sulfides for Supercapacitors

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    Bimetallic sulfides offer high theoretical specific capacitance and good stability as electrode materials due to their diverse redox reactions, larger specific surface areas, and better conductivity. The morphology of the electrode material is an important influencing factor for the electrochemical properties. Herein, a series of ZnCoS electrode materials with different morphologies were prepared by varying the solvent in the solvothermal reaction, and the effects of different microstructures on the electrochemical properties of ZnCoS were investigated. The ratio of water and ethanol in the solvent was controlled to modulate the microstructure of the as-prepared ZnCoS materials. XRD and XPS revealed the physical and chemical structure of the ZnCoS materials. SEM and TEM observations showed that the microstructure of ZnCoS transformed from one-dimensional wires to two-dimensional sheets with increasing amounts of ethanol. The maximum specific capacitance of the as-prepared ZnCoS materials is 6.22 F cm−2 at a current density of 5 mA cm−2, which is superior to that of most previously reported bimetallic sulfides. The enhanced electrochemical performance could be ascribed to its sheet-assembled spherical structure, which not only shortens the path of ion diffusion but also increases the contact between surface active sites and the electrolyte. Moreover, the spherical structure provides numerous void spaces for buffering the volume expansion and penetration of the electrolyte, which would be favorable for electrochemical reactions. Furthermore, the ZnCoS electrodes were coupled with activated carbon (AC) electrodes to build asymmetric supercapacitors (ASCs). The ASC device exhibits a maximum energy density of 0.124 mWh cm−2 under a power density of 2.1 mW cm−2. Moreover, even under a high-power density of 21 mW cm−2, the energy density can still reach 0.055 mWh cm−2
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