34 research outputs found

    Scalable and Environmentally Friendly Synthesis of Hierarchical Magnetic Carbon Nanosheet Assemblies and Their Application in Water Treatment

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    Large-scale assembling of graphitic carbon nanosheets to a three-dimensional hierarchical structure is a great challenge. Herein we report a facile synthesis of hierarchical magnetic carbon nanosheet assemblies (MCNSAs) via an ambient-pressure chemical vapor deposition method. To explore the formation mechanism, the as-prepared MCNSAs as well as the intermediates of synthesis were extensively characterized. It was revealed that two different carbon deposition processes, i.e., the dissolution–precipitation process and graphitic defects triggered catalytic decomposition of methane, were involved in the formation of MCNSAs. The disclosed method is simple and environmentally friendly, which is favorable for large-scale production. The resulting MCNSAs possess large surface areas, bimodal pore structures, abundant defective sites, excellent chemical stability, and sufficient magnetism. Such features afford significant advantages for application in water cleaning. As a proof of concept, the sorption performance of MCNSAs is demonstrated by using Congo red and Pb<sup>2+</sup> as model pollutants. The characteristics of the sorption process including kinetics, isotherms, recovery, regeneration, and recycling are investigated. The results indicate that the MCNSAs are a promising sorbent for water cleaning

    Pinned Chemical Waves in the Presence of Stokes Flow

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    Excitable reaction–diffusion systems form a wealth of dissipative concentration patterns that exist not only in chemical systems but also control or disrupt biological functions. An important example are rotating spiral waves in the autocatalytic Belousov–Zhabotinsky reaction. We show that the viscosity of this system can be increased by the addition of the polymer xanthan gum. In the resulting system, we pin spiral waves to a thin glass rod and then reposition the vortex centers by a linear motion of the heterogeneity. The Stokes flow generated by this motion can be a weak perturbation to the wave pattern and follows a simple, analytical expression. Numerical simulations of a corresponding reaction–diffusion-flow model reproduce the experimental observations and show that the spatial extent of the flow field can vary widely around the characteristic wavelength of the spiral. We find that a sharp spatial decay of the flow pattern corresponds to our experimental observations, whereas more expansive flow fields surprisingly allow the repositioning of spiral tips at speeds faster than the wave velocity

    Pinned Chemical Waves in the Presence of Stokes Flow

    No full text
    Excitable reaction–diffusion systems form a wealth of dissipative concentration patterns that exist not only in chemical systems but also control or disrupt biological functions. An important example are rotating spiral waves in the autocatalytic Belousov–Zhabotinsky reaction. We show that the viscosity of this system can be increased by the addition of the polymer xanthan gum. In the resulting system, we pin spiral waves to a thin glass rod and then reposition the vortex centers by a linear motion of the heterogeneity. The Stokes flow generated by this motion can be a weak perturbation to the wave pattern and follows a simple, analytical expression. Numerical simulations of a corresponding reaction–diffusion-flow model reproduce the experimental observations and show that the spatial extent of the flow field can vary widely around the characteristic wavelength of the spiral. We find that a sharp spatial decay of the flow pattern corresponds to our experimental observations, whereas more expansive flow fields surprisingly allow the repositioning of spiral tips at speeds faster than the wave velocity

    Remaining useful life prediction for a catenary, utilizing Bayesian optimization of stacking

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    This article addresses the problem that the remaining useful life (RUL) prediction accuracy for a high-speed rail catenary is not accurate enough, leading to costly and time-consuming periodic planned and reactive maintenance costs. A new method for predicting the RUL of a catenary is proposed based on the Bayesian optimization stacking ensemble learning method. Taking the uplink and downlink catenary data of a high-speed railway line as an example, the preprocessed historical maintenance and maintenance data are input into the integrated prediction model of Bayesian hyperparameter optimization for training, and the root mean square error (RMSE) of the final optimized RUL prediction result is 0.068, with an R-square (R2) of 0.957, and a mean absolute error (MAE) of 0.053. The calculation example results show that the improved stacking ensemble algorithm improves the RMSE by 28.42%, 30.61% and 32.67% when compared with the extreme gradient boosting (XGBoost), support vector machine (SVM) and random forests (RF) algorithms, respectively. The improved accuracy prediction lays the foundation for targeted equipment maintenance and system maintenance performed before the catenary system fails, thus potentially saving both planned and reactive maintenance costs and time

    Synthesis and Catalytic Activity of Amino Acids and Metallopeptides with Catalytically Active Metallocyclic Side Chains

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    Two approaches to prepare amino acids with catalytically active organometallic side chains are presented. These methods are notable in that they provide access either free or N-protected compounds that are structurally analogous to naturally occurring amino acids. The N-protected organometallic amino acids are compatible with standard peptide coupling conditions and can be used to prepare catalytically active metallopeptides

    Synthesis of Ultrafine Pt Nanoparticles Stabilized by Pristine Graphene Nanosheets for Electro-oxidation of Methanol

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    In this study, the pristine graphene nanosheets (GNS) derived from chemical vapor deposition process were employed as catalyst support. In spite of the extremely hydrophobic GNS surface, ultrafine Pt nanoparticles (NPs) were successfully assembled on the GNS through a surfactant-free solution process. The evolution of Pt NPs in the GNS support was studied using transmission electron microscopy. It was found that the high-energy surface sites in the GNS, such as edges and defects, played a critical role on anchoring and stabilizing Pt nuclei, leading to the formation of Pt NPs on the GNS support. The concentration of the Pt precursor, i.e., H<sub>2</sub>PtCl<sub>6</sub> solution had significant effects on the morphology of Pt/GNS hybrids. The resulting Pt/GNS hybrids were examined as catalysts for methanol electro-oxidation. It was indicated that the electrochemical active surface area and catalytic activity of the Pt/GNS hybrids were highly dependent on Pt loadings. The superior activity of the catalysts with low Pt loadings was attributed to the presence of Pt subnanoclusters as well as the strong chemical interaction of Pt NPs with the GNS support

    Data_Sheet_1_Association between environmental chemicals co-exposure and peripheral blood immune-inflammatory indicators.docx

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    Chronic inflammation is closely related to chronic inflammatory diseases, autoimmune diseases and cancer. Few studies have evaluated the effects of exposure to multiple chemical combinations on immunoinflammatory related indicators and their possible molecular mechanisms. This study explored the effect of exposure to various chemicals on immune-inflammatory biomarkers and its molecular mechanism. Using data from 1,723 participants in the National Health and Nutrition Examination Survey (NHANES, 2011–2012), the aim was to determine the association between chemical mixtures and immunoinflammatory biomarkers [including White blood cell (Wbc), neutrophil (Neu), lymphocytes (Lym), and Neutrophil-to-lymphocyte ratio (NLR)] using linear regression model, weighted quantile sum regression (WQSR) model, and bayesian nuclear machine regression (BKMR) model. Meanwhile, functional enrichment analysis and protein–protein interaction network establishment were performed to explore the molecular mechanism of inflammation induced by high-weight chemicals. In the linear regression model established for each single chemical, the four immunoinflammatory biomarkers were positively correlated with polycyclic aromatic hydrocarbons (PAHs), negatively correlated with perfluoroalkyl substances (PFASs), and positively or negatively correlated with metallic and non-metallic elements. WQSR model showed that cadmium (Cd), perfluorooctane sulfonic acid (PFOS) and perfluorodecanoic acid (PFDE) had the highest weights. In BKMR analysis, the overall effect of chemical mixtures was significantly associated with Lym and showed an increasing trend. The hub genes in high-weight chemicals inflammation-related genes were interleukin-6 (IL6), tumor necrosis factor (TNF), and interleukin-1B (IL1B), etc. They were mainly enriched in inflammatory response, Cytokine-cytokine receptor interaction, Th17 cell differentiation and IL-17 signaling pathway. The above results show that exposure to environmental chemical cocktails primarily promotes an increase in Lym across the immune-inflammatory spectrum. The mechanism leading to the inflammatory response may be related to the activation of IL-6 amplifier by the co-exposure of environmental chemicals.</p

    Bacterial Cytological Profiling Reveals the Mechanism of Action of Anticancer Metal Complexes

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    Target identification and mechanistic studies of cytotoxic agents are challenging processes that are both time-consuming and costly. Here we describe an approach to mechanism of action studies for potential anticancer compounds by utilizing the simple prokaryotic system, <i>E. coli,</i> and we demonstrate its utility with the characterization of a ruthenium polypyridyl complex [Ru­(bpy)<sub>2</sub>dmbpy<sup>2+</sup>]. Expression of the photoconvertible fluorescent protein Dendra2 facilitated both high throughput studies and single-cell imaging. This allowed for simultaneous ratiometric analysis of inhibition of protein production and phenotypic investigations. The profile of protein production, filament size and population, and nucleoid morphology revealed important differences between inorganic agents that damage DNA vs more selective inhibitors of transcription and translation. Trace metal analysis demonstrated that DNA is the preferred nucleic acid target of the ruthenium complex, but further studies in human cancer cells revealed altered cell signaling pathways compared to the commonly administrated anticancer agent cisplatin. This study demonstrates <i>E. coli</i> can be used to rapidly distinguish between compounds with disparate mechanisms of action and also for more subtle distinctions within in studies in mammalian cells

    Energetics of Variable Hapticity of Carbocyclic Rings in Cyclopentadienylmetal Carbonyl Systems of the Second Row Transition Metals C<sub>5</sub>H<sub>5</sub>M(CO)<sub><i>n</i></sub>C<sub><i>m</i></sub>H<sub><i>m</i></sub> (M = Ru, Tc, Mo, Nb) Including Mechanistic Studies of Carbonyl Dissociation

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    Decarbonylation of the experimentally known CpRu­(CO)<sub>2</sub>(η<sup>1</sup>-C<sub>5</sub>H<sub>5</sub>), CpMo­(CO)<sub>2</sub>(η<sup>3</sup>-C<sub>7</sub>H<sub>7</sub>), and CpNb­(CO)<sub>2</sub>(η<sup>4</sup>-C<sub>8</sub>H<sub>8</sub>) (Cp = η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>), each with uncomplexed 1,3-butadiene units in the C<sub><i>n</i></sub>H<sub><i>n</i></sub> ring, as well as the related CpTc­(CO)<sub>2</sub>(η<sup>2</sup>-C<sub>6</sub>H<sub>6</sub>), to give the corresponding carbonyl-free derivatives CpM­(η<sup><i>n</i></sup>-C<sub><i>n</i></sub>H<sub><i>n</i></sub>) derivatives has been studied by density functional theory. For ruthenium, technetium, and molybdenum the coordinated C<sub><i>n</i></sub>H<sub><i>n</i></sub> ring of the intermediate monocarbonyl CpM­(CO)­(η<sup><i>n</i>–2</sup>-C<sub><i>n</i></sub>H<sub><i>n</i></sub>) contains an uncomplexed CC double bond and each decarbonylation step proceeds with a significant energy barrier represented by a higher energy transition state. However, decarbonylation of CpNb­(CO)<sub>2</sub>(η<sup>4</sup>-C<sub>8</sub>H<sub>8</sub>) to the monocarbonyl proceeds without an energy barrier, preserving the tetrahapto coordination of the C<sub>8</sub>H<sub>8</sub> ring to give CpNb­(CO)­(η<sup>4</sup>-C<sub>8</sub>H<sub>8</sub>) in which the niobium atom has only a 16-electron configuration. All of the monocarbonyl derivatives CpM­(CO)­(C<sub><i>n</i></sub>H<sub><i>n</i></sub>) are predicted to be strongly energetically disfavored with respect to disproportionation to give CpM­(CO)<sub>2</sub>(C<sub><i>n</i></sub>H<sub><i>n</i></sub>) + CpM­(C<sub><i>n</i></sub>H<sub><i>n</i></sub>). This allows us to understand the failure to date to synthesize any of the monocarbonyl derivatives

    Direct Measurement of Trafficking of the Cystic Fibrosis Transmembrane Conductance Regulator to the Cell Surface and Binding to a Chemical Chaperone

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    Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) result in the disease cystic fibrosis. Deletion of Phe508, the most prevalent mutation associated with this disease, disrupts trafficking of the protein. Small molecule correctors yield moderate improvements in the trafficking of ΔF508-CFTR to the plasma membrane. It is currently not known if correctors increase the level of trafficking through improved cargo loading of transport vesicles or through direct binding to CFTR. Real-time measurements of trafficking were utilized to identify the mechanistic details of chemical, biochemical, and thermal factors that impact CFTR correction, using the corrector molecule VX-809, a secondary mutation (I539T), and low-temperature conditions. Each individually improved trafficking of ΔF508-CFTR to approximately 10% of wild-type levels. The combination of VX-809 with either low temperature or the I539T mutation increased the amount of CFTR on the plasma membrane to nearly 40%, indicating synergistic activity. The number of vesicles reaching the surface was significantly altered; however, the amount of channel in each vesicle remained the same. Direct binding measurements of VX-809 in native membranes using backscattering interferometry indicate tight binding to CFTR, which occurred in a manner independent of mutation. The similar values obtained for all forms of the channel indicate that the binding site is not compromised or enhanced by these mutations
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