Dinitrosyl Iron Complex [K-18-crown-6-ether][(NO)2Fe(MePyrCO2)]: Intermediate for Capture and Reduction of Carbon Dioxide

Continued efforts are made for the utilization of CO₂ as a C₁ feedstock for regeneration of valuable chemicals and fuels. Mechanistic study of molecular (electro-/photo-)catalysts disclosed that initial step for CO₂ activation involves either nucleophilic insertion or direct reduction of CO₂. In this study, nucleophilic activation of CO₂ by complex [(NO)₂Fe(μ-^MePyr)₂Fe(NO)₂]²⁻ ( 2 , ^MePyr=3-methylpyrazolate) results in the formation of CO₂-captured complex [(NO)₂Fe(^MePyrCO₂)]⁻ ( 2-CO₂ , ^MePyrCO₂=3-methyl-pyrazole-1-carboxylate). Single-crystal structure, spectroscopic, reactivity, and computational study unravels 2-CO₂ as a unique intermediate for reductive transformation of CO₂ promoted by Ca²⁺. Moreover, sequential reaction of 2 with CO₂, Ca(OTf)₂, and KC₈ established a synthetic cycle, 2 → 2-CO₂ → [(NO)₂Fe(μ-^MePyr)₂Fe(NO)₂] ( 1 ) → 2 , for selective conversion of CO₂ into oxalate. Presumably, characterization of the unprecedented intermediate 2-CO₂ may open an avenue for systematic evaluation of the effects of alternative Lewis acids on reduction of CO₂.     

Bucillamine Inhibits UVB-Induced MAPK Activation and Apoptosis in Human HaCaT Keratinocytes and SKH-1 Hairless Mouse Skin

Ultraviolet B (UVB) radiation is known as a culprit in skin carcinogenesis. We have previously reported that bucillamine (N-[2-mercapto-2-methylpropionyl]-L-cysteine), a cysteine derivative with antioxidant and anti-inflammatory capacity, protects against UVB-induced p53 activation and inflammatory responses in mouse skin. Since MAPK signaling pathways regulate p53 expression and activation, here we determined bucillamine effect on UVB-mediated MAPK activation in vitro using human skin keratinocyte cell line HaCaT and in vivo using SKH-1 hairless mouse skin. A single low dose of UVB (30 mJ cm⁻²) resulted in increased JNK/MAPK phosphorylation and caspase-3 cleavage in HaCaT cells. However, JNK activation and casaspe-3 cleavage were inhibited by pretreatment of HaCaT cells with physiological doses of bucillamine (25 and 100 µm ). Consistent with these results, bucillamine pretreatment in mice (20 mg kg⁻¹) inhibited JNK/MAPK and ERK/MAPK activation in skin epidermal cells at 6–12 and 24 h, respectively, after UVB exposure. Moreover, bucillamine attenuated UVB-induced Ki-67-positive cells and cleaved caspase-3-positive cells in mouse skin. These findings demonstrate that bucillamine inhibits UVB-induced MAPK signaling, cell proliferation and apoptosis. Together with our previous report, we provide evidence that bucillamine has a photoprotective effect against UV exposure.     

Diverse excitations of two-component rogue waves for a nonautonomous coupled partially nonlocal nonlinear Schrödinger model under a parabolic potential

Nonlinear Dynamics - Vector similar structures for solutions with similar expressions of nonlinear models are paid attention in the previous literature. However, the demand of different localized...     

Module-Designed Carbon-Coated Separators for High-Loading,High-Sulfur-Utilization Cathodes in Lithium–Sulfur Batteries

Lithium–sulfur batteries have great potential as next-generation energy-storage devices because of their high theoretical charge-storage capacity and the low cost of the sulfur cathode. To accelerate the development of lithium–sulfur technology, it is necessary to address the intrinsic material and extrinsic technological challenges brought about by the insulating active solid-state materials and the soluble active liquid-state materials. Herein, we report a systematic investigation of module-designed carbon-coated separators, where the carbon coating layer on the polypropylene membrane decreases the irreversible loss of dissolved polysulfides and increases the reaction kinetics of the high-loading sulfur cathode. Eight different conductive carbon coatings were considered to investigate how the materials’ characteristics contribute to the lithium–sulfur cell’s cathode performance. The cell with a nonporous-carbon-coated separator delivered an optimized peak capacity of 1112 mA∙h g⁻¹ at a cycling rate of C/10 and retained a high reversible capacity of 710 mA∙h g⁻¹ after 200 cycles under lean-electrolyte conditions. Moreover, we demonstrate the practical high specific capacity of the cathode and its commercial potential, achieving high sulfur loading and content of 4.0 mg cm⁻² and 70 wt%, respectively, and attaining high areal and gravimetric capacities of 4.45 mA∙h cm⁻² and 778 mA∙h g⁻¹, respectively.     

Carbon Encapsulation of High Entropy Alloy Nanoparticles with Extraordinary Coercivity and Saturation at Room Temperature

Owing to their unique properties and technological potential, high entropy alloys (HEAs) have become the subject of great interest in the materials science community. HEAs consist of more than four principle elements in equimolar ratio so their configurational entropy is intrinsically greater than one-principle element based. The increasing surface energy and chemical tendency toward clustering of like atoms at low dimension, however, make production of HEA-nanoparticles (HEA-NPs) extremely difficult. A facile production of HEA-NPs inside carbon nanotubes and nanoparticles is demonstrated in this work. Electron microscopic and elemental analyses confirm encapsulated to be solution phase; some embrace carbides and form multidomains with chemical composition ranging from quaternary to quinary phase. Multidomains and nonmagnetic centers create hardening thus promoting coercivity significantly at room temperature. Alloying induces electron redistribution into high spin states, accounting for observed high saturation. Configurational entropy of encapsulated HEA-NPs lies on a range comparable with bulk.     

荧光光谱结合表面增强拉曼光谱法研究紫檀芪与人血清白蛋白相互作用

在模拟人体生理条件下,应用荧光光谱和表面增强拉曼光谱法研究了紫檀芪(PTE)与人血清白蛋白(HSA)之间相互作用机制.结果表明,HSA的荧光能被PTE静态猝灭,并伴随有非辐射能量转移作用,两者形成了1:1复合物,结合距离r=1.495 nm,结合常数KA=1.12×104(298 K)、4.07×104(304 K)和2.45×105 L/mol(310 K).表面增强拉曼光谱研究揭示,PTE分子通过甲氧基与HSA进行结合;热力学数据表明,二者间的作用主要为疏水作用;标记竞争实验指出PTE优先结合HSA的位点Ⅲ.三维荧光光谱、同步荧光光谱和表面增强拉曼光谱结果显示,与PTE作用后,HSA构象发生变化,导致色氨酸残基周围环境疏水性降低,但对PTE分子构象影响不大.     

Exploring the Origin of Maximum Entropy States Relevant to Resonant Modes in Modern Chladni Plates

The resonant modes generated from the modern Chladni experiment are systematically confirmed to intimately correspond to the maximum entropy states obtained from the inhomogeneous Helmholtz equation for the square and equilateral triangle plates. To investigate the origin of maximum entropy states, the inhomogeneous Helmholtz equation is modified to consider the point interaction coming from the driving oscillator. The coupling strength associated with the point interaction is characterized by a dimensionless factor α. The δ potential of the point interaction is numerically modelled by a truncated basis with an upper index N. The asymptotic behavior for the upper index N is thoroughly explored to verify that the coupling strength of α = 1.0 can make the theoretical resonant modes agree excellently with the maximum entropy states as N→∞. It is further authenticated that nearly the same resonant modes can be obtained by using a larger coupling strength α when a smaller upper index N is exploited in the calculation.     

ANiN(A=Li,Na,Mg,Ca)的结构、热力学、弹性和电子性质的第一性原理研究

三元过渡金属氮化物ANiN(A=Li,Na,Mg,Ca)是潜在的可充放电池的电极材料.物理性质,比如热稳定性、电子能隙以及弹性稳定性等,对于这些材料的电池应用都是非常重要的.本文使用第一原理方法,对比研究了 ANiN这些材料的结构、动力学、弹性和电子结构性质.对状态方程和声子谱的计算被用来确定体系的稳定结构.对最稳定结...     

Fabrication and transformation of dense SnO2 via laser ablation condensation

Dense SnO₂ nanocondensates with fluorite-type-related structures have been synthesized via severe heating-cooling under energetic Nd-YAG laser pulse irradiation of the Sn target in oxygen ambient. Transmission electron microscopic observations indicated that the fluorite type transformed in a martensitic manner into a baddeleyite-type structure with accompanied dislocations, twinning, commensurate shearing and shape change. The Pa3¯-modified fluorite-type structure was hardly observed possibly due to its transformation into α-PbO₂ type and then rutile-type structures in the dynamic process.