For many regenerative electrochemical energy‐conversion systems, hybrid electrocatalysts comprising transition metal (TM) oxides and heteroatom‐doped (e.g., nitrogen‐doped) carbonaceous materials are ...promising bifunctional oxygen reduction reaction/oxygen evolution reaction electrocatalysts, whose enhanced electrocatalytic activities are attributed to the synergistic effect originated from the TM–N–C active sites. However, it is still ambiguous which configuration of nitrogen dopants, either pyridinic or pyrrolic N, when bonded to the TM in oxides, predominately contributes to the synergistic effect. Herein, an innovative strategy based on laser irradiation is described to controllably tune the relative concentrations of pyridinic and pyrrolic nitrogen dopants in the hybrid catalyst, i.e., NiCo2O4 NPs/N‐doped mesoporous graphene. Comparative studies reveal the dominant role of pyridinic‐NCo bonding, instead of pyrrolic‐N bonding, in synergistically promoting reversible oxygen electrocatalysis. Moreover, density functional theory calculations provide deep insights into the corresponding synergistic mechanism. The optimized hybrid, NiCo/NLG‐270, manifests outstanding reversible oxygen electrocatalytic activities, leading to an overpotential different ΔE among the lowest value for highly efficient bifunctional catalysts. In a practical reversible Zn–air battery, NiCo/NLG‐270 exhibits superior charge/discharge performance and long‐term durability compared to the noble metal electrocatalysts.
An innovative strategy based on laser irradiation is developed to selectively regulate relative contents of pyridinic and pyrrolic nitrogen in NiCo2O4/N‐graphene hybrids. Strong chemical bonding forms between nitrogen and cobalt, and pyridinic‐NCo bonds, instead of pyrrolic‐NCo bonds, are identified to predominantly contribute to synergistic catalysis, leading to substantially enhanced oxygen electrocatalytic activities, outperforming a combination of benchmark noble metal catalysts.
BACKGROUND From the end of December 2019, coronavirus disease 2019 (COVID-19) began to spread in central China. Social capital is a measure of social trust, belonging, and participation. This study ...aimed to investigate the effects of social capital on sleep quality and the mechanisms involved in people who self-isolated at home for 14 days in January 2020 during the COVID-19 epidemic in central China. MATERIAL AND METHODS Individuals (n=170) who self-isolated at home for 14 days in central China, completed self-reported questionnaires on the third day of isolation. Individual social capital was assessed using the Personal Social Capital Scale 16 (PSCI-16) questionnaire. Anxiety was assessed using the Self-Rating Anxiety Scale (SAS) questionnaire, stress was assessed using the Stanford Acute Stress Reaction (SASR) questionnaire, and sleep was assessed using the Pittsburgh Sleep Quality Index (PSQI) questionnaire. Path analysis was performed to evaluate the relationships between a dependent variable (social capital) and two or more independent variables, using Pearson's correlation analysis and structural equation modeling (SEM). RESULTS Low levels of social capital were associated with increased levels of anxiety and stress, but increased levels of social capital were positively associated with increased quality of sleep. Anxiety was associated with stress and reduced sleep quality, and the combination of anxiety and stress reduced the positive effects of social capital on sleep quality. CONCLUSIONS During a period of individual self-isolation during the COVID-19 virus epidemic in central China, increased social capital improved sleep quality by reducing anxiety and stress.
Pagoda[4]arene and i‑Pagoda[4]arene Han, Xiao-Ni; Han, Ying; Chen, Chuan-Feng
Journal of the American Chemical Society,
05/2020, Letnik:
142, Številka:
18
Journal Article
Recenzirano
A new type of macrocyclic arenes, named pagoda4arene (P4) and i-pagoda4arene (i-P4), were conveniently synthesized by the TFA-catalyzed one-pot condensation of 2,6-dimethoxylanthracene and ...paraformaldehyde in dichloromethane at room temperature. P4 and i- P4 showed unique square pagoda structures and fixed conformations in solution and also exhibited strong blue fluorescence. Moreover, P4 and i-P4 with deep and rich-electron cavities could not only encapsulate n-hexane and one or two dichloromethane molecules in the solid state but also showed strong binding abilities toward neutral dinitriles with different chain lengths and various nitrogen-containing heterocyclic salts to form 1:1 stable host–guest complexes in both solution and the solid state. In particular, it was also found that with the increase in the alkyl chain length of the dinitriles, the association constants for their complexes with both P4 and i-P4 were markedly increased from glutaronitrile to octanedinitrile as a result of the deep cavities of the macrocycles and multiple intermolecular interactions. Since P4 and i- P4 had stable planar chirality, their efficient resolutions were further achieved by HPLC with a chiral column. Interestingly, the two enantiomers showed mirror-imaged CD signals and excellent CPL properties, which could allow them to have potential applications in chiral luminescent materials.
A new class of chiral macrocyclic arene composed of three chiral 2,6‐dihydroxyltriptycene subunits bridged by methylene groups was designed and synthesized. Structural studies showed that the ...macrocyclic molecule adopts a hex‐nut‐like structure with a helical chiral cavity and highly fixed conformation. Efficient resolution was achieved through the introduction of chiral auxiliaries to give a couple of enantiopure macrocycles, which exhibited high enantioselectivity towards three pairs of chiral compounds containing a trimethylamino group.
Go nuts! A novel triptycene‐based chiral macrocyclic host with a hex‐nut‐like structure and highly fixed conformation was synthesized. Efficient resolution was achieved through the introduction of chiral auxiliaries to give a couple of enantiopure macrocycles, which exhibited highly enantioselective recognition of three pairs of chiral compounds containing a trimethylamino group.
Abstract
Supramolecular tessellation has gained increasing interest in supramolecular chemistry for its structural aesthetics and potential applications in optics, magnetics and catalysis. In this ...work, a new kind of supramolecular tessellations (STs) have been fabricated by the exo-wall interactions of pagoda4arene (P4). ST with rhombic tiling pattern was first constructed by P4 itself through favorable π···π interactions between anthracene units of adjacent P4. Notably, various highly ordered STs with different tiling patterns have been fabricated based on exo-wall charge transfer interactions between electron-rich P4 and electron-deficient guests including 1,4-dinitrobenzene, terephthalonitrile and tetrafluoroterephthalonitrile. Interestingly, solvent modulation and guest selection played a crucial role in controlling the molecular arrangements in the co-crystal superstructures. This work not only proves that P4 is an excellent macrocyclic building block for the fabrication of various STs, but also provides a new perspective and opportunity for the design and construction of supramolecular two-dimensional organic materials.
The first alkali‐metal vanadium iodate fluoride, CsVO2F(IO3), with a novel 3D anionic framework, has been rationally designed and hydrothermally synthesized. The 3D VO2F(IO3)− framework in ...CsVO2F(IO3) is built from 0D Λ‐shaped cis‐VO3F(IO3)24− polyanions via corner‐sharing of oxo anions and bridging of the iodate groups. CsVO2F(IO3) displays both a strong second‐harmonic generation (SHG) 1.1 times as strong as KTiOPO4 (KTP) under 2.05 μm laser radiation and high laser‐induced damage threshold (LIDT) of 107.9 MW cm−2. This work provides a new route to design SHG crystals with stable 3D anionic structures from low‐dimensional structural building units.
From zero to threero: CsVO2F(IO3) is the first example of a 3D VO2F(IO3)− anionic framework built from 0D Λ‐shaped cis‐VO3F(IO3)24− units. The system shows a strong second‐harmonic generation (SHG), 1.1 times as strong as KTiOPO4 under 2.05 μm laser radiation and a high laser‐induced damage threshold of 107.9 MW cm−2.
There exist about 3.7σ positive and 2.4σ negative deviations in the muon and electron anomalous magnetic moments (g−2). Also, some ratios for lepton universality in τ decays have almost 2σ deviations ...from the Standard Model. In this paper, we propose a lepton-specific inert two-Higgs-doublet model. After imposing all the relevant theoretical and experimental constraints, we show that these lepton anomalies can be explained simultaneously in many parameter spaces with m > 200 GeV and mA(mH±) > 500 GeV for appropriate Yukawa couplings between leptons and inert Higgs. The key point is that these Yukawa couplings for μ and τ/e have opposite sign.
Alginate oligosaccharides (AOS), products of alginate degradation by endotype alginate lyases, possess favorable biological activities and have broad applications. Although many have been reported, ...alginate lyases with homogeneous AOS products and secretory production by an engineered host are scarce. Herein, the alginate lyase AlyC7 from
sp. C42 was characterized as a trisaccharide-producing lyase exhibiting high activity and broad substrate specificity. With PelB as the signal peptide and 500 mM glycine as the additive, the extracellular production of AlyC7 in
reached 1122.8 U/mL after 27 h cultivation in Luria-Bertani medium. The yield of trisaccharides from sodium alginate degradation by the produced AlyC7 reached 758.6 mg/g, with a purity of 85.1%. The prepared AOS at 20 μg/mL increased the root length of lettuce, tomato, wheat, and maize by 27.5%, 25.7%, 9.7%, and 11.1%, respectively. This study establishes a robust foundation for the industrial and agricultural applications of AlyC7.
We present a concrete realization of the sound speed resonance (SSR) mechanism for primordial black hole (PBH) formation within a specific model of Dirac-Born-Infeld (DBI) inflation. We perform a ...perturbative approach to phenomenologically construct such a viable DBI inflation model that involves the nonoscillating stage and the oscillating stage, with a type of specific forms of the warp factor and the potential. We show that the continuous but nonsmooth conjunction of sound speed between two stages does not yield manifest effects on the phenomenology of SSR, and thus, our model gives rise to the same PBH mass spectrum as the original predictions of SSR. Additionally, we also demonstrate that the violation of adiabaticity of the Mukhanov-Sasaki equation does not affect the comoving curvature perturbation after Hubble crossing in the nonresonant region. Making use of observational data, we derive various cosmological constraints on the parameter space. Our analyses show that the predicted tensor-to-scalar ratio is typically small, while the amplitude of primordial non-Gaussianity can meet with cosmic microwave background bounds, and additionally, the consistency relation for single-field slow-roll inflation is softly violated in our case due to the small sound speed variations.
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