113 research outputs found

    How other Europeans assess the dangers of leaving the EU

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    Public support for the EU rose after the referendum, while Jean-Claude Juncker has painted a starry picture of the Union's prospects without Britain. In effect, writes Catherine E De Vries, the UK is a guinea pig for Eurosceptics on the rest of the continent. Consequently, national leaders have every incentive to make Brexit as arduous as possible for the UK. Parties like the AfD are watching

    Th<sub>3</sub>[Th<sub>6</sub>(OH)<sub>4</sub>O<sub>4</sub>(H<sub>2</sub>O)<sub>6</sub>](SO<sub>4</sub>)<sub>12</sub>(H<sub>2</sub>O)<sub>13</sub>: A Self-Assembled Microporous Open-Framework Thorium Sulfate

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    A neutral-framework thorium oxohydroxosulfate hydrate has been isolated from aqueous solution. This microporous structure, which self-assembles without a templating agent, is built from [Th<sub>6</sub>(OH)<sub>4</sub>O<sub>4</sub>(H<sub>2</sub>O)<sub>6</sub>]<sup>12+</sup> hexamers and thoriumĀ­(IV) monomers linked through bridging sulfates. Solution conditions were chosen to enable an active competition between sulfate and hydroxide for thorium coordination. Synthetic requirements are discussed for this rare example of a thoriumĀ­(IV) polynuclear complex containing mixed oxo-, hydroxo-, and sulfato-bridging moieties

    A robust seismic phase unwrapping method

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    Primary GO categorisation, KEGG and BIOCARTA pathway analyses (Target gene (cis, trans and co-expression) of lncRNAs were predicted based on differentially expressed mRNAs in IBDV-stimulated chicken DCs). (XLSX 335 kb

    Tailoring the Olefin Selectivity in Catalytic Oxidative Dehydrogenation of Light Alkane by the Isolation Strategy

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    Olefins are important building blocks that have been extensively used to produce diverse consumer products in petrochemical industry. Owing to the requirement of low-carbon-footprint processes and the increasing use of light alkanes sourced from shale gas, an environmentally friendly and economic route alternative to the state-of-the-art steam cracking of crude oil has been investigated for olefin production. The oxidative dehydrogenation (ODH) of alkanes to olefins has attracted wide attention due to the absence of thermodynamic limitations and coke formation. However, excessive oxidation of olefin is prone to occur in this process. Developing a suitable ODH catalyst with high performance, particularly with enhanced selectivity, is more and more urgent but still remains a challenge. In this Review, we talk about the representative currently developed isolation strategies to optimize the selectivity of olefins via the ODH process, particularly for the conversion of ethane to ethylene, which include the dispersion regulation of metal oxide, the isolation of metal and nonmetal sites, the construction of dual functional sites to isolate dehydrogenation and oxidation steps, and the adoption of selective oxygen species with the promotion of soft oxidants as reactants. Furthermore, the mechanistic aspects about the activation of ethane and the participation of oxygen species for tailoring the selectivity are then classified and discussed in detail. Finally, the perspectives and the emerging technologies for the ODH process are listed and evaluated

    Exploring Second-Order Nonlinear Optical Properties and Switching Ability of a Series of Dithienylethene-Containing, Cyclometalated Platinum Complexes: A Theoretical Investigation

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    The second-order nonlinear optical (NLO) properties of a series of dithienylethene- (DTE-) containing PtĀ­(II) complexes have been investigated by density functional theory calculations. The first hyperpolarizabilities Ī² of studied systems can be greatly enhanced by simple ligand substitutions. Because of the nature of DTE units, the Ī² values also can be varied by the use of lights in the studied systems. The highest Ī² difference between photoisomers can over 1000 Ɨ 10<sup>ā€“30</sup> esu, with the contrast around five times. Thus, the studied systems can act as effective photoswitchable second-order NLO materials. The time-dependent density functional theory calculations revealed that the charge transfer patterns of studied systems have special characters compared to other reported DTE-containing NLO switched chromogens, the DTE units mainly act as electron-donors in studied systems, and the variation of Ī² can be viewed as alternation of donor abilities of DTE units; thus, our work also proposed a new mechanism for designing photoswitched NLO multifunctional materials

    Influence of Countercation Hydration Enthalpies on the Formation of Molecular Complexes: A Thoriumā€“Nitrate Example

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    The influence of countercations (A<sup><i>n</i>+</sup>) in directing the composition of monomeric metalā€“ligand (ML) complexes that precipitate from solution are often overlooked despite the wide usage of A<sup><i>n</i>+</sup> in materials synthesis. Herein, we describe a correlation between the composition of ML complexes and A<sup>+</sup> hydration enthalpies found for two related series of thorium (Th)ā€“nitrate molecular compounds obtained by evaporating acidic aqueous Thā€“nitrate solutions in the presence of A<sup>+</sup> counterions. Analyses of their chemical composition and solid-state structures demonstrate that A<sup>+</sup> not only affects the overall solid-state packing of the Thā€“nitrato complexes but also influences the composition of the Thā€“nitrato monomeric anions themselves. Trends in composition and structure are found to correlate with A<sup>+</sup> hydration enthalpies, such that the A<sup>+</sup> with smaller hydration enthalpies associate with less hydrated and more anionic Thā€“nitrato complexes. This perspective, broader than the general assumption of size and charge as the dominant influence of A<sup><i>n</i>+</sup>, opens a new avenue for the design and synthesis of targeted metalā€“ligand complexes

    Identifying Size Effects of Pt as Single Atoms and Nanoparticles Supported on FeO<sub><i>x</i></sub> for the Water-Gas Shift Reaction

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    Identification of size effects at an atomic level is essential for designing high-performance metal-based catalysts. Here, the performance of a series of FeO<sub><i>x</i></sub>-supported Pt catalysts with Pt as nanoparticles (Pt-NP) or single atoms (Pt-SAC) are compared for the low-temperature water-gas shift (WGS) reaction. A variety of characterization methods such as adsorption microcalorimetry, H<sub>2</sub>-TPR, in situ DRIFTS, and transient analysis of product tests were used to demonstrate that Pt nanoparticles exhibit much higher adsorption strength of CO; the adsorbed CO reacts with the OH groups, which are generated from activated H<sub>2</sub>O, to form intermediate formates that subsequently decompose to produce CO<sub>2</sub> and H<sub>2</sub> simultaneously. On the other hand, Pt single atoms promote the formation of oxygen vacancies on FeO<sub><i>x</i></sub> which dissociate H<sub>2</sub>O to H<sub>2</sub> and adsorbed O that then combines with the weakly adsorbed CO on these Pt sites to produce CO<sub>2</sub>. The activation energy for the WGS reaction decreases with the downsizing of Pt species, and Pt-SAC possesses the lowest value of 33 kJ/mol. As a result, Pt-SAC exhibits 1 order of magnitude higher specific activity in comparison to Pt-NP. With a loading of only 0.05 wt % the Pt-SAC can achieve āˆ¼65% CO conversion at 300 Ā°C, representing one of the most active catalysts reported so far

    Thermochromism, the Alexandrite Effect, and Dynamic Jahnā€“Teller Distortions in Ho<sub>2</sub>Cu(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>

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    A 3dā€“4f heterobimetallic material with mixed anions, Ho<sub>2</sub>CuĀ­(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>, has been prepared under hydrothermal conditions. Ho<sub>2</sub>CuĀ­(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub> exhibits both thermochromism and the Alexandrite effect. Variable temperature single crystal X-ray diffraction and UVā€“visā€“NIR spectroscopy reveal that changes in the Cu<sup>II</sup> coordination geometry result in negative thermal expansion of axial Cuā€“O bonds that plays a role in the thermochromic transition of Ho<sub>2</sub>CuĀ­(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>. Magnetic studies reveal an effective magnetic moment of 14.97 Ī¼B. which has a good agreement with the calculated value of 15.09 Ī¼B

    Challenges in the Search for Magnetic Coupling in 3d/4f Materials: Syntheses, Structures, and Magnetic Properties of the Lanthanide Copper Heterobimetallic Compounds, RE<sub>2</sub>Cu(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>

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    Twelve new lanthanide copper heterobimetallic compounds, RE<sub>2</sub>CuĀ­(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub> (RE = Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), with two different structural topologies, have been prepared by hydrothermal treatment. Both structure types crystallize in the triclinic space group, <i>P</i>1Ģ…, but the unit cell parameters and structures are quite different. The earlier RE<sub>2</sub>CuĀ­(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub> (RE = Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm) share a common structural motif consisting of edge-sharing LnO<sub>8</sub> chains and [CuĀ­(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>]<sup>6ā€“</sup> units. The later lanthanide version (Yb and Lu) is composed of edge-sharing LnO<sub>7</sub> dimers bridged by similar [CuĀ­(TeO<sub>3</sub>)<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>]<sup>6ā€“</sup> units. The change in the structure type can be attributed to the decreasing ionic radii of the lanthanides. The compounds containing RE<sup>3+</sup> ions with diamagnetic ground states (Y<sup>3+</sup> and Eu<sup>3+</sup>) exhibit antiferromagnetic ordering at 12.5 K and 15 K, respectively, owing to the magnetic exchange between Cu<sup>2+</sup> moments. No magnetic phase transition was observed in all the other phases. The lack of magnetic ordering is attributed to the competing magnetic interactions caused by the presence of paramagnetic RE<sup>3+</sup> ions. The magnetism data suggests that substantial 3dā€“4f coupling only occurs in the Yb analogue

    Cuprous Iodide Pseudopolymorphs Based on Imidazole Ligand and Their Luminescence Thermochromism

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    Two cuprous iodide pseudopolymorphs, formulated as [(Cu<sub>4</sub>I<sub>4</sub>)Ā­(MBI)<sub>2</sub>]<sub>āˆž</sub> (MBI = 1,1ā€²-methylene-bisĀ­(imidazole)) with an irregular cubane-like Cu<sub>4</sub>I<sub>4</sub> cluster as tetrahedrally coordinated secondary building unit and imidazole derivative as bridging ligand, have been synthesized and characterized by single-crystal X-ray diffraction analysis. Both of two compounds only exhibited a single broad low-energy cluster-centered (<sup>3</sup>CC) triplet emission band between room temperature and 77 K. Of particular interest, these two Cu<sub>4</sub>I<sub>4</sub>-imidazole pseudopolymorphs still displayed thermochromic luminescence originating from a red shift of such tunable single cluster-centered triplet emission, being different from that observed in the previously reported Cu<sub>4</sub>I<sub>4</sub>-pyridine system by balancing temperature-dependent multiple emissions (high-energy and low-energy) derived from their energetically distinct triplet states
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