137 research outputs found

    Physiologically Based Pharmacokinetic Model for Inorganic and Methylmercury in a Marine Fish

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    A physiologically based pharmacokinetic (PBPK) model was developed to simulate the uptake, distribution, and elimination of inorganic mercury [HgĀ­(II)] and methylmercury (MeHg) in a marine fish, <i>Terapon jarbua</i>. In this model, fish were schematized as a six-compartment model by assuming that blood was the medium linking the exchange between the different compartments. The transfer rates between blood and other compartments were determined during a period of 10-day dietary HgĀ­(II) or MeHg exposure, followed by a 30-day depuration. For both Hg species, the exchange rates between liver and blood were high, indicating that liver served as a ā€œtransferring stationā€ in the distribution. Their accumulation in the kidney was relatively constant and low. The carcass (mainly muscle) represented a large sink for both HgĀ­(II) and MeHg with the highest input rate constants and relatively lower output rate constants. Significant differences were observed in the rate constants between the two Hg species, suggesting great variations in their exchange and transportation routes. Modeling simulation for the first time demonstrated that the gill was the most important route in HgĀ­(II) elimination in marine fish, with a rate constant of 0.90 d<sup>ā€“1</sup>. A long time frame is needed to study the exact rate of MeHg elimination in marine fish. This study showed that the PBPK modeling provided critical information for the uptake, distribution and elimination of HgĀ­(II) and MeHg in the fish body, especially in elucidating the role of each compartment

    In Vivo Mercury Demethylation in a Marine Fish (<i>Acanthopagrus schlegeli</i>)

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    Mercury (Hg) in fish has attracted public attention for decades, and methylmercury (MeHg) is the predominant form in fish. However, the in vivo MeHg demethylation and its influence on Hg level in fish have not been well-addressed. The present study investigated the in vivo demethylation process in a marine fish (black seabream, <i>Acanthopagrus schlegeli</i>) under dietary MeHg exposure and depuration and quantified the biotransformation and interorgan transportation of MeHg by developing a physiologically based pharmacokinetic (PBPK) model. After exposure, we observed a 2-fold increase of the whole-body inorganic Hg (IHg), indicating the existence of an in vivo demethylation process. The results strongly suggested that the intestine played a predominant role in MeHg demethylation with a significant rate (6.6 Ā± 1.7 day<sup>ā€“1</sup>) during exposure, whereas the hepatic demethylation appeared to be an extremely slow (0.011 Ā± 0.001 day<sup>ā€“1</sup>) process and could hardly affect the whole-fish Hg level. Moreover, demethylation in the intestine served as an important pathway for MeHg detoxification. Our study also pointed out that in vivo MeHg demethylation could influence Hg level and speciation in fish although food is the major pathway for Hg accumulation. Enhancing in vivo MeHg biotransformation (especially in the intestine) could be a potential key solution in minimizing Hg contamination in fish. The related factors involved in intestinal demethylation deserve more attention in the future

    Inorganic Nanostructures with Sizes down to 1 nm: A Macromolecule Analogue

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    Ultrathin nanostructures exhibit many interesting properties which are absent or less-pronounced in traditional nanomaterials of larger sizes. In this work, we report the synthesis of ultrathin nanowires and nanoribbons of rare earth hydroxides and demonstrate some new phenomena caused by their atomic-level lateral size (1 nm), including ligand-induced gelation, self-assembly framework, and conformational diversity. These features are typically, although not exclusively, found in polymer solutions. The properties of the inorganic backbone and the emerging polymeric characteristics combined prove to be very promising in the design of new hybrid materials

    Self-Adjustable Crystalline Inorganic Nanocoils

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    Biomacromolecules such as proteins, although extremely complex in microstructure, can crystallize into macro-sized crystals after self-adjusting their shapes, based on which the structure of biology is built. Inorganic nanowires/nanoribbons with a similar one-dimensional topology but much simpler structures can hardly be as flexible as macromolecules when constructing superlattice structures because of their inherent rigidity. Here we report the synthesis of crystalline indium sulfide nanoribbon-based nanocoils that are formed by spontaneous self-coiling of ultrathin nanoribbons. The nanostructures are flexible and appear as relatively random coils because of their ultrathin ribbon structures (āˆ¼0.9 nm in thickness) with high aspect ratios. Moreover, the nanocoils can self-adjust their shapes and assemble into two-dimensional superlattices and three-dimensional supercrystals in solution. The ultrathin nanocoils are expected to bring new insights into the use of flexible nanocrystals as building blocks for constructing superstructures

    Anion-Exchange-Driven Disassembly of a SiO<sub>2</sub>/CTAB Composite Mesophase: the Formation of Hollow Mesoporous Silica Spheres

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    Silica-based surfactant/inorganic composite mesophases have been extremely studied. In this work, we developed a mild method to realize the room-temperature disassembly of a SiO<sub>2</sub>/cetyltrimethylammonium bromide (CTAB) mesophase in a neutral medium. Using KMnO<sub>4</sub> as a typical etching agent, SiO<sub>2</sub>/CTAB mesophase spheres were partially disassembled into normal or rattle-type hollow structures. The disassembly of the SiO<sub>2</sub>/CTAB spheres was supposed to be driven by anion exchange between permanganate and silicate ions. This unique method makes possible the selective etching of a SiO<sub>2</sub>/CTAB mesophase over a SiO<sub>2</sub> phase

    Versatile Inorganic Subnanometer Nanowire Adhesive

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    Adhesives are applied extensively in daily life and industries, and people have developed numerous commercial polymeric adhesives. However, in most cases, these adhesives work on dry surfaces in air and form permanent bonds with the substrates, limiting the applications of adhesives. Inspired by the innate adhesive functions of some animals, such as geckos, spiders, mussels, and clingfish, scientists have developed various adhesive compositions and structures to meet various conditions. Here, we show a versatile subnanometer nanowire (SNW) adhesive with high strength and great reversibility, which could be prepared at a large scale through a facile room-temperature reaction. The SNW adhesive contacts the substrates at multiple sites due to the ultrahigh flexibility, and meanwhile, the multilevel interactions among the SNWs endow them with strong cohesion, so they exhibit good adhesive performance. This adhesive is applicable to various substrates, such as metals, polymers, and glass, and not only possesses good stability at room temperature in air but also is suitable for underwater environments and ultralow temperatures. Moreover, this adhesive could be easily recycled and removed from the substrates without any residue and damage. The SNW adhesive not only inspires the design of hierarchical adhesive structures with new contact modes but also has potential for practical applications

    Versatile Inorganic Subnanometer Nanowire Adhesive

    No full text
    Adhesives are applied extensively in daily life and industries, and people have developed numerous commercial polymeric adhesives. However, in most cases, these adhesives work on dry surfaces in air and form permanent bonds with the substrates, limiting the applications of adhesives. Inspired by the innate adhesive functions of some animals, such as geckos, spiders, mussels, and clingfish, scientists have developed various adhesive compositions and structures to meet various conditions. Here, we show a versatile subnanometer nanowire (SNW) adhesive with high strength and great reversibility, which could be prepared at a large scale through a facile room-temperature reaction. The SNW adhesive contacts the substrates at multiple sites due to the ultrahigh flexibility, and meanwhile, the multilevel interactions among the SNWs endow them with strong cohesion, so they exhibit good adhesive performance. This adhesive is applicable to various substrates, such as metals, polymers, and glass, and not only possesses good stability at room temperature in air but also is suitable for underwater environments and ultralow temperatures. Moreover, this adhesive could be easily recycled and removed from the substrates without any residue and damage. The SNW adhesive not only inspires the design of hierarchical adhesive structures with new contact modes but also has potential for practical applications

    Surface Confinement Etching and Polarization Matter: A New Approach To Prepare Ultrathin PtAgCo Nanosheets for Hydrogen-Evolution Reactions

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    One of the important objectives in fuel-cell technology is to improve the activity and reduce the loading of Pt for hydrogen-evolution electrocatalysis. Here, an oxidative etching strategy of stacking faults is developed to prepare PtĀ­AgCo nanosheets by element-specific anisotropic growth. Sophisticated use of defects in crystal growth allows tailoring the morphology and interfacial polarization to improve catalytic performance of nanosheets for the hydrogen-evolution reaction. Systematic studies reveal that the presence of the stacking faults may be the knob for the formation of nanosheets. In particular, the chemical composition of nanosheets is potentially the key for altering the hydrogen-evolution reaction. As a result, the PtĀ­AgCo-II ultrathin nanosheets possess useful HER properties, achieving a current density up to 705 mA cm<sup>ā€“2</sup> at a potential of āˆ’400 mV

    The starting page of the simulation software.

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    <p>The starting page of the simulation software.</p
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