Microphase separation, stress relaxation and creep behavior of polyurethane nanocomposites

The microphase separation of polyurethane (PU) nanocomposite was studied. The result suggests that the addition of clay leads to a decrease in the size of hard domain and an increase in the degree of microphase separation. The stress relaxation and creep behavior of blank PU and PU/clay nanocomposites were investigated. The relaxation time spectrum and retardant time spectrum were derived according to the generalized Maxwell model and Voigt model with a Tikhonov regularization method. The characteristic relaxation time was identified with the corresponding relaxation process. At a small strain, the relaxation was mainly attributed to uncoiling/disentangling of soft segment chain network in the soft phase, with a single characteristic relaxation time in the range of 5~100s. The increase in the hard segment content leads to a decrease in the relaxation time, and the addition of clay leads to an increase in the relaxation time. At large strains, the multi-peak relaxations occurred, and they were attributed to the breakup of interconnected hard domains and pull-out of soft segment chains from hard domains, together with the disentangling of soft segment chain network in the soft phase. The creep results are in consistent with that of the stress relaxation. The relaxation and creep behavior were related to microphase separation of polyurethane. This study suggested that the relaxation spectrum H(ï´) can be used to examine the complicated relaxation processes for a multi-phase and multi-component polymer system

Recent Isotopic Evidence for Elevated Vehicular NOx Emission to Atmospheric Nitrate Formation in Chinese Megacities

As the primary component of air pollution, nitrogen oxides (NOx = NO + NO2) are responsible for the formation of ozone and fine particle matter (PM2.5), which together pose a threat to the environment and human health worldwide. Coal combustion is assumed to be a prominent emitter of atmospheric NOx in urban environments on the basis of nitrogen isotopic constraints (δ15N), but recently detailed NOx emission inventories are inconsistent with the extant isotopic estimates. To resolve this disagreement, we compiled and dissected the previously reported δ15N compositions of particulate nitrate in Chinese megacities over recent winter seasons from 2013 to 2017. The results show that the δ15N value of nitrate (δ15N-NO3–) decreased from North China to South China in general (e.g., from +13.8 ± 5.0‰ in Beijing to +2.7 ± 2.5‰ in Chengdu), but little variation was observed in any given city during this period (e.g, from +11.5 ± 5.0‰ in 2018 to +13.8 ± 5.0‰ in 2014 in Beijing). More interestingly, the initial average δ15N-NOx values (from −5.8 to −2.4‰) compared well among all the urban cities studied here, derived from the corresponding δ15N-NO3– values by correcting for the nitrogen isotopic fractionation effects. These results point toward the importance of NOx emissions from vehicular exhaust to nitrate formation in urban areas, which is estimated to account for 67.4 ± 10.1% on the basis of a Bayesian mixing model. The estimate agreed with reported data of local detailed emission inventory models (e.g., multiresolution emission inventory for China). Our results highlight that strengthening vehicle emission standards would benefit NOx abatements and improve the urban air quality in the near future

FeCoP₂ Nanoparticles Embedded in a Hybrid Carbon Matrix as a High Performance Bifunctional Catalyst of the Advanced Zinc–Air Battery

The novel catalyst (FeCoP2-CNC) is constructed by inserting the bimetallic phosphide into a hybrid carbon substrate. The structures associated with the active sites are optimized by incorporating ultrafine cellulose fibers as a carbon source. The increased graphitic-N and metal-N species in the carbon matrix, with the enlarged specific surface area, improves the performance of catalyzing oxygen reduction reaction. The increased proportion of surface metal hydroxide active sites improves the performance of catalyzing oxygen evolution reaction. As a high performance bifunctional catalyst, the FeCoP2-CNC is applied to a rechargeable zinc–air battery and exhibits excellent performance in the battery. The solid-state zinc–air battery has achieved an excellent power density (76.9 mW cm–2) and can cycle over 45 h. The solid-state zinc–air batteries are integrated into 2 × 2 and 3 × 3 modules to power practical devices. This work provides efficient approaches to enhance the performance of bifunctional catalysts, promoting the application of zinc–air batteries

Extending the Cycle Lifetime of Solid-State Zinc-Air Batteries by Arranging Stable Zinc Species Channels

The solid-state zinc-air batteries have attracted extensive attention due to their high theoretical energy density, high safety, and the compact structure. In this work, a novel hydrogel solid-state electrolyte was developed that was equipped with an interpenetrating network of zinc polyacrylate (PAZn) and polyacrylamide (PAM). At the same time, a cyclodextrin derivative with sulfonate groups was introduced as an additive. From the design of anionic groups in the network, effective and stable channels for zinc species have been established. The unique structure of the additives regulates the uniform deposition of zinc. After using this solid-state electrolyte, the cycle lifetime of solid-state zinc-air batteries assembled have been significantly extended. The byproducts were greatly suppressed and generated the smooth zinc electrode surface after the charge–discharge cycling

Electrophilic Halospirocyclization of <i>N</i>‑Benzylacrylamides to Access 4‑Halomethyl-2-azaspiro[4.5]decanes

An electrophilic spirocyclization of N-benzylacrylamides with N-halosuccinimides (NXS) as the halogenating reagents has been developed. This reaction is carried out at room temperature under simple conditions without relying on metal reagents, photochemistry, or electrochemistry, providing a fast and efficient route to synthesize a wide variety of 4-halomethyl-2-azaspiro[4.5]decanes with satisfactory yields. The approach is further highlighted through gram-scale synthesis and diverse transformations of the spiro products

Probing the Interaction between Nitrogen Dopants and Edge Structures of Doped Graphene Catalysts for the Highly Efficient Oxygen Reduction Reaction

The N-doped carbon-based catalysts have emerged as potential alternatives to Pt-based catalysts for the oxygen reduction reaction (ORR). Understanding the delicate interplay between dopants and graphene structures at the atomic level is crucial to rational designing high-performance carbon-based catalysts. Herein, we deeply explore the role of the edge structure of graphene, N doping configuration, position, and content in modulating the 4e– and 2e– ORR mechanisms using density functional theory calculations and comprehensively evaluate the ORR activity by combining the active site density and theoretical overpotential. We find that graphene with zigzag and armchair edges (GZ‑A) has extra spin density and high ORR activity compared to graphene with only armchair edges (GA‑A). The N doping position is more important than N doping content in improving ORR activity in N-doped GZ‑A because only the proper N doping position, such as along the armchair edge, can increase the effective active sites by modulating the spin density. On the contrary, increasing N doping content is more efficient in boosting the ORR activity of N-doped GA‑A since high N doping content contributes to the increased spin density and active site density. On the whole, N-doped GZ‑A has a much higher turnover frequency (TOF) value than N-doped GA‑A, and the GZ‑A with pyridinic-N doping along the armchair edge exhibits the highest TOF value of 1.37 × 1012 (U = 1.23 V)/s–1

Additional file 1: of Transcriptome profiling reveals candidate flavonol-related genes of Tetrastigma hemsleyanum under cold stress

Length Hist Distribution of Trinity and Unigene in T. hemsleyanum transcriptome. There were 151,924 ‘Trinity’ genes and 106,275 unigenes, which ranged from 201 to 15,668 bp in length. The average length of unigenes was 676 bp. The N50 and N90 length was 1121 bp and 262 bp, respectively. (XLS 484 bytes

Additional file 1 of Astragalus polysaccharide restores insulin secretion impaired by lipopolysaccharides through the protein kinase B /mammalian target of rapamycin/glucose transporter 2 pathway

Supplementary Material 1: Supplementary Figures 1 and 2

sj-pdf-1-imr-10.1177_03000605221126382 - Supplemental material for Misplaced drainage tube inserted in the vein in a percutaneous nephrostomy: a case series

Supplemental material, sj-pdf-1-imr-10.1177_03000605221126382 for Misplaced drainage tube inserted in the vein in a percutaneous nephrostomy: a case series by Yuanming Song, Changyong Zhao, Zhongyi Zhang, Shun Zhan, Zuze Qiu and Daobing Li in Journal of International Medical Research</p

Additional file 2: of Transcriptome profiling reveals candidate flavonol-related genes of Tetrastigma hemsleyanum under cold stress

Unigenes Expression matrix data in T. hemsleyanum transcriptome. Differential gene expression levels under cold stress and functional classifications of all annotated unigenes in T. hemsleyanum transcriptome. (XLSX 25195 kb