Comprehensive Mechanism for CO Electroreduction on Dual-Atom-Catalyst-Anchored N-Doped Graphene

Carbon neutrality has drawn increasing attention for realizing the carbon cyclization and reducing the greenhouse effect. Although the C1 products, such as CO, can be achieved with a high Faraday efficiency, the targeted production of C2 fuels as well as the mechanism have not been systematically investigated. In this work, we carry out a first-principles study to screen dual-atom catalysts (DACs) for producing C2 fuels through the electrocatalytic carbon monoxide reduction reaction (e-CORR). We find that methanol, ethanol and ethylene can be produced on both DAC−Co and DAC−Cu, while acetate can be achieved on DAC−Cu only. Importantly, methanol and ethylene are preferred on DAC−Co, while acetate and ethylene on DAC−Cu. Furthermore, we show that the explicit solvent can enhance the adsorption and influence the protonation steps, which subsequently affects the protonation and dimerization behavior as well as the performance and selectivity of e-CORR on DACs. We further demonstrate that the C−C coupling is easy to be formed and stabilized if the Integrated Crystal Orbital Hamilton Population (ICOHP) is low because of the low energy barrier. Our findings provide not only guidance on the design of novel catalysts for e-CORR, but an insightful understanding on the reduction mechanism.     

Divergent and Overlapping Roles for Selected Phytochemicals in the Regulation of Pathological Cardiac Hypertrophy

Plant-based foods, like fruits, vegetables, whole grains, legumes, nuts, seeds and other foodstuffs, have been deemed as heart healthy. The chemicals within these plant-based foods, i.e., phytochemicals, are credited with protecting the heart. However, the mechanistic actions of phytochemicals, which prevent clinical endpoints, such as pathological cardiac hypertrophy, are still being elucidated. We sought to characterize the overlapping and divergent mechanisms by which 18 selected phytochemicals prevent phenylephrine- and phorbol 12-myristate 13-acetate-mediated cardiomyocyte enlargement. Of the tested 18 compounds, six attenuated PE- and PMA-mediated enlargement of neonatal rat ventricular myocytes. Cell viability assays showed that apigenin, baicalein, berberine hydrochloride, emodin, luteolin and quercetin dihydrate did not reduce cell size through cytotoxicity. Four of the six phytochemicals, apigenin, baicalein, berberine hydrochloride and emodin, robustly inhibited stress-induced hypertrophy and were analyzed further against intracellular signaling and genome-wide changes in mRNA expression. The four phytochemicals differentially regulated mitogen-activated protein kinases and protein kinase D. RNA-sequencing further showed divergence in gene regulation, while pathway analysis demonstrated overlap in the regulation of inflammatory pathways. Combined, this study provided a comprehensive analysis of cardioprotective phytochemicals. These data highlight two defining observations: (1) that these compounds predominantly target divergent gene pathways within cardiac myocytes and (2) that regulation of overlapping signaling and gene pathways may be of particular importance for the anti-hypertrophic actions of these phytochemicals. Despite these new findings, future works investigating rodent models of heart failure are still needed to understand the roles for these compounds in the heart.     

Stability of ion triplets in ionic liquid/lithium salt solutions: Insights from implicit and explicit solvent models and molecular dynamics simulations

Binding energies of ion triplets formed in ionic liquids by Li⁺ with two anions have been studied using quantum‐chemical calculations with implicit and explicit solvent supplemented by molecular dynamics (MD) simulations. Explicit solvent approach confirms variation of solute‐ionic liquid interactions at distances up to 2 nm, resulting from structure of solvation shells induced by electric field of the solute. Binding energies computed in explicit solvent and from the polarizable continuum model approach differ largely, even in sign, but relative values generally agree between these two models. Stabilities of ion triplets obtained in quantum‐chemical calculations for some systems disagree with MD results; the discrepancy is attributed to the difference between static optimized geometries used in quantum chemical modeling and dynamic structures of triplets in MD simulations. © 2015 Wiley Periodicals, Inc.     

Epigenetic Genome Mining of an Endophytic Fungus Leads to the Pleiotropic Biosynthesis of Natural Products

The small‐molecule biosynthetic potential of most filamentous fungi has remained largely unexplored and represents an attractive source for the discovery of new compounds. Genome sequencing of Calcarisporium arbuscula, a mushroom‐endophytic fungus, revealed 68 core genes that are involved in natural product biosynthesis. This is in sharp contrast to the predominant production of the ATPase inhibitors aurovertin B and D in the wild‐type fungus. Inactivation of a histone H3 deacetylase led to pleiotropic activation and overexpression of more than 75 % of the biosynthetic genes. Sampling of the overproduced compounds led to the isolation of ten compounds of which four contained new structures, including the cyclic peptides arbumycin and arbumelin, the diterpenoid arbuscullic acid A, and the meroterpenoid arbuscullic acid B. Such epigenetic modifications therefore provide a rapid and global approach to mine the chemical diversity of endophytic fungi.     

Reconstitution of Biosynthetic Machinery for the Synthesis of the Highly Elaborated Indole Diterpene Penitrem

Penitrem A is one of the most elaborated members of the fungal indole diterpenes. Two separate penitrem gene clusters were identified using genomic and RNA sequencing data, and 13 out of 17 transformations in the penitrem biosynthesis were elucidated by heterologous reconstitution of the relevant genes. These reactions involve 1) a prenylation‐initiated cationic cyclization to install the bicyclo[3.2.0]heptane skeleton (PtmE), 2) a two‐step P450‐catalyzed oxidative processes forming the unique tricyclic penitrem skeleton (PtmK and PtmU), and 3) five sequential oxidative transformations (PtmKULNJ). Importantly, without conventional gene disruption, reconstitution of the biosynthetic machinery provided sufficient data to determine the pathway. It was thus demonstrated that the Aspergillus oryzae reconstitution system is a powerful method for studying the biosynthesis of complex natural products.     

Near-Wall Modification of an Explicit Algebraic Reynolds Stress Model Using Elliptic Blending

The elliptic blending approach is used in order to modify an Explicit Algebraic Reynolds Stress Model so as to reproduce the correct near wall behaviour of the turbulent stresses. The anisotropy stress tensor is expressed as a linear combination of tensor bases whose coefficients are sensitised to the non-local wall-blocking effect through the elliptic blending parameter γ. This parameter is obtained from a separate elliptic equation. The model does not use the distance from the wall thus it can be easily applied to complex geometries. It is validated against detailed DNS data for mean and turbulence quantities for the case of flow and heat transfer between parallel flat plates at three Reynolds numbers as well as against experimental data for the flow in a backward facing step at Re _H = 28,000. The comparison with DNS results or experiments is quite satisfactory and shows the validity of the approach.     

阻抗式和简单调压室甩荷时水位波动的显式计算方法

目前对调压室水位波动的研究主要有图解法和数值计算。尚未看到考虑阻力项后调压室水位波动随时间变化的显函数计算方法。本文从调压室的基本微分方程出发，采用泰勒级数展开式推导了阻抗式和简单式调压室甩荷时水位波动的显式计算方法。运用这种方法不仅可以计算调压室水位波动的过程，而且可以方便的计算调压室的最高涌浪和第二振幅。     

非协调四结点平面等参位移元新列式方法

本文导出一种等参协调元位移函数的新的表示方法,在此基础上建立起了构造等参非协调元的新方法。作为实例,构造出两个可以给出单刚显式的四结点平面非协调新单元。