19 research outputs found

    Correlation between the deleterious effect of parasites on hosts and the relative growth rate (RGR) of host with parasite (a) and without parasite (b), parasitism response of RGR of hosts (c).

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    <p>Pearson correlation coefficient (<i>r</i>) and <i>p</i>-values are given and values in bold are statistically significant at <i>p</i><0.05.</p

    Means and standard errors of parasites biomass (a) and the deleterious effect of parasites (b) on exotic, invasive species and native, non-invasive species.

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    <p><i>F</i>-values and significance levels of one-way ANOVA represent the effect of the origin of the species (invasive or native) on the parasites biomass and the deleterious effect of parasites on hosts (<sup>***</sup><i>p</i><0.001;<sup>**</sup><i>p</i><0.01; <sup>*</sup><i>p</i><0.05).</p

    Rate-Limiting O–O Bond Formation Pathways for Water Oxidation on Hematite Photoanode

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    Photoelectrochemical (PEC) water oxidation has attracted heightened interest in solar fuel production. It is well accepted that water oxidation on hematite is mediated by surface trapped holes, characterized to be the high valent −FeO species. However, the mechanism of the subsequent rate-limiting O–O bond formation step is still a missing piece. Herein we investigate the reaction order of interfacial hole transfer by rate law analysis based on electrochemical impedance spectroscopy (EIS) measurement and probe the reaction intermediates by operando Fourier-transform infrared (FT-IR) spectroscopy. Distinct reaction orders of ∼1 and ∼2 were observed in near-neutral and highly alkaline environments, respectively. The unity rate law in near-neutral pH regions suggests a mechanism of water nucleophilic attack (WNA) to −FeO to form the O–O bond. Operando observation of a surface superoxide species that hydrogen bonded to the adjacent hydroxyl group by FT-IR further confirmed this pathway. In highly alkaline regions, coupling of adjacent surface trapped holes (I2M) becomes the dominant mechanism. While both are operable at intermediate pHs, mechanism switch from I2M to WNA induced by local pH decrease was observed at high photocurrent level. Our results highlight the significant impact of surface protonation on O–O bond formation pathways and oxygen evolution kinetics on hematite surfaces

    Trace-Level Potentiometric Detection in the Presence of a High Electrolyte Background

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    Polymeric membrane ion-selective electrodes (ISEs) have become attractive tools for trace-level environmental and biological measurements. However, applications of such ISEs are often limited to measurements with low levels of electrolyte background. This paper describes an asymmetric membrane rotating ISE configuration for trace-level potentiometric detection with a high-interfering background. The membrane electrode is conditioned in a solution of interfering ions (e.g., Na<sup>+</sup>) so that no primary ions exist in the ISE membrane, thus avoiding the ion-exchange effect induced by high levels of interfering ones in the sample. When the electrode is in contact with the primary ions, the interfering ions in the membrane surface can be partially displaced by the primary ions due to the favorable ion–ligand interaction with the ionophore in the membrane, thus causing a steady-state potential response. By using the asymmetric membrane with an ion exchanger loaded on the membrane surface, the diffusion of the primary ions from the organic boundary layer into the bulk of the membrane can be effectively blocked; on the other hand, rotation of the membrane electrode dramatically reduces the diffusion layer thickness of the aqueous phase and significantly promotes the mass transfer of the primary ions to the sample–membrane interface. The induced accumulation of the primary ions in the membrane boundary layer largely enhances the nonequilibrium potential response. By using copper as a model, the new concept offers a subnanomolar detection limit for potentiometric measurements of heavy metals with a high electrolyte background of 0.5 M NaCl

    miR-29b-Loaded Gold Nanoparticles Targeting to the Endoplasmic Reticulum for Synergistic Promotion of Osteogenic Differentiation

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    Precise control of stem cells, such as human bone marrow-derived mesenchymal stem cells (hMSCs), is critical for the development of effective cellular therapies for tissue engineering and regeneration medicine. Emerging evidence suggests that several miRNAs act as key regulators of diverse biological processes, including differentiation of various stem cells. In this study, we have described a delivery system for miR-29b using PEI-capped gold nanoparticles (AuNPs) to synergistically promote osteoblastic differentiation. The cell proliferation assay revealed that AuNPs and AuNPs/miR-29b exert negligible cytotoxicity to hMSCs and MC3T3-E1 cells. With the assistance of AuNPs as a delivery vector, miR-29b could efficiently enter the cytoplasm and regulate osteogenesis. AuNPs/miR-29b more effectively promoted osteoblast differentiation and mineralization through induced the expression of osteogenesis genes (RUNX2, OPN, OCN, ALP) for the long-term, compared to the widely used commercial transfection reagent, Lipofectamine. With no obvious cytotoxicity, PEI-capped AuNPs showed great potential as an adequate miRNA vector for osteogenesis differentiation. Interestingly, we observed loading of AuNPs as well as AuNPs/miR-29b into the lumen of the endoplasmic reticulum (ER). Our findings collectively suggest that AuNPs, together with miR-29b, exert a synergistic promotory effect on osteogenic differentiation of hMSCs and MC3T3-E1 cells

    Fabrication of 3D Porous Hierarchical NiMoS Flowerlike Architectures for Hydrodesulfurization Applications

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    Layered transition-metal sulfides such as MoS<sub>2</sub> often show a range of intriguing electronic, catalytic, and optical properties. Because of their high surface energy, layered materials generally tend to stack and prevent the exposure of additional edge sites. Here, we demonstrate a facile approach for the preparation of hierarchical NiMoS nanoflowers via SiO<sub>2</sub>-assisted hydrothermal synthesis. The structure and morphology of the nanomaterials are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopy analyses, revealing that different sizes of NiMoS nanoflowers assembled from various nanosheet thicknesses can be tuned by modifying the Si/Mo molar ratio. The key aspect of this strategy is to construct the three-dimensional nanostructures around the SiO<sub>2</sub> nanospheres while maintaining a flowerlike feature. The correlation between the nanosheet thickness, surface area, and total dispersion of the Mo atoms indicated that the large quantity and efficient accessibility of NiMoS active sites originating from the synergistically multiscale structure and atom-scale modulations between MoS<sub>2</sub> and Ni atoms are the determining factors for the observed impressive hydrodesulfurization performance and the stable recyclability of these materials

    Hydrogen-Bond Bridged Water Oxidation on {001} Surfaces of Anatase TiO<sub>2</sub>

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    To gain an atomic-level understanding of the relationship among the surface structure, the interfacial interaction, and the water oxidation activity on TiO<sub>2</sub>, we studied the adsorption of water and its photocatalytic oxidation on anatase TiO<sub>2</sub> with {101} and {001} exposed surfaces by in situ infrared spectroscopy, kinetic isotope effect studies, and density functional theory (DFT)-based molecular dynamics calculations. Our experimental results demonstrate that the oxidation reaction occurs exclusively on hydrogen-bonded water molecules (via surface hydroxyls) over {001} surface, whereas water molecules coordinated on the {101} surface, which are conventionally assigned to the reactive target for hole transfer, remain unchanged during the irradiation. The theoretical calculations reveal that the selective oxidation of water adsorbed on the {001} surfaces is primarily attributed to the formation of hydrogen bonds, which provides a channel to the rapid hole transfer and facilitates the O–H bond cleavage during water oxidation

    Photoinduced Stepwise Oxidative Activation of a Chromophore–Catalyst Assembly on TiO<sub>2</sub>

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    To probe light-induced redox equivalent separation and accumulation, we prepared ruthenium polypyridyl molecular assembly [(dcb)<sub>2</sub>Ru(bpy-Mebim<sub>2</sub>py)Ru(bpy)(OH<sub>2</sub>)]<sup>4+</sup> (Ru<sub>a</sub><sup>II</sup>–Ru<sub>b</sub><sup>II</sup>–OH<sub>2</sub>) with Ru<sub>a</sub> as light-harvesting chromophore and Ru<sub>b</sub> as water oxidation catalyst (dcb = 4,4′-dicarboxylic acid-2,2′-bipyridine; bpy-Mebim<sub>2</sub>py = 2,2′-(4-methyl-[2,2′:4′,4″-terpyridine]-2″,6″-diyl)bis(1-methyl-1H-benzo[<i>d</i>]imidazole); bpy = 2,2′-bipyridine). When bound to TiO<sub>2</sub> in nanoparticle films, it undergoes MLCT excitation, electron injection, and oxidation of the remote −Ru<sub>b</sub><sup>II</sup>–OH<sub>2</sub> site to give TiO<sub>2</sub>(e<sup>–</sup>)–Ru<sub>a</sub><sup>II</sup>–Ru<sub>b</sub><sup>III</sup>–OH<sub>2</sub><sup>3+</sup> as a redox-separated transient. The oxidized assembly, TiO<sub>2</sub>–Ru<sub>a</sub><sup>II</sup>–Ru<sub>b</sub><sup>III</sup>–OH<sub>2</sub><sup>3+</sup>, similarly undergoes excitation and electron injection to give TiO<sub>2</sub>(e<sup>–</sup>)–Ru<sub>a</sub><sup>II</sup>–Ru<sub>b</sub><sup>IV</sup>O<sup>2+</sup>, with Ru<sub>b</sub><sup>IV</sup>O<sup>2+</sup> a known water oxidation catalyst precursor. Injection efficiencies for both forms of the assembly are lower than those for [Ru(bpy)<sub>2</sub>(4,4′-(PO<sub>3</sub>H<sub>2</sub>)<sub>2</sub>bpy)]<sup>2+</sup> bound to TiO<sub>2</sub> (TiO<sub>2</sub>–Ru<sup>2+</sup>), whereas the rates of back electron transfer, TiO<sub>2</sub>(e<sup>–</sup>) → Ru<sub>b</sub><sup>III</sup>–OH<sub>2</sub><sup>3+</sup> and TiO<sub>2</sub>(e<sup>–</sup>) → Ru<sub>b</sub><sup>IV</sup>O<sup>2+</sup>, are significantly decreased compared with TiO<sub>2</sub>(e<sup>–</sup>) → Ru<sup>3+</sup> back electron transfer

    Self-Assembled Bilayers on Indium–Tin Oxide (SAB-ITO) Electrodes: A Design for Chromophore–Catalyst Photoanodes

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    A novel approach for creating assemblies on metal oxide surfaces via the addition of a catalyst overlayer on a chomophore monolayer derivatized surface is described. It is based on the sequential self-assembly of a chromophore, [Ru­(bpy)­(4,4′-(PO<sub>3</sub>H<sub>2</sub>bpy)<sub>2</sub>)]<sup>2+</sup>, and oxidation catalyst, [Ru­(bpy)­(P<sub>2</sub>Mebim<sub>2</sub>py)­OH<sub>2</sub>]<sup>2+</sup>, pair, resulting in a spatially separated chromophore–catalyst assembly
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