Quantity–intensity curves were used to evaluate the dynamics of soil potassium (K) at different soil depths under different K management. The equilibrium concentration ratio of K (CR0) increased with increasing K concentration. K fertilization and straw return increased soil K supplying capacity by increasing CR0, non-specific available K (-∆K0) and equilibrium K (CK0). The CR0 increase 107%, 392% and 577% at the 0–20 cm layer and 55%, 102% and 131% at the 20–40 cm layer, respectively, under K fertilization, straw return and the interaction of them. The CK0 and -∆K0 at the 0–20 cm layer significantly increased after K fertilization and straw return. The labile K varied from 0.11 to 0.19 cmol kg−1, contributed 85.3% to 107.6% of NH4OAc extracted K. Soil K potential buffering capacity showed significant differences in soil depths, while little difference was observed under different K management. Th e exchangeable K was meaningless for guiding K application when minimum exchangeable K took up 85.9% to 99.0% of equilibrium exchangeable K. Our results showed K fertilization and straw return was the optimal management to enhance soil K supplying capacity, especially at the 0–20 cm layer.Abbreviations N: nitrogen; P: phosphorus; K: potassium; RS: straw; Q/I: quantity/intensity; CR0: equilibrium concentration ratio of K; KL: labile K; non-specifically available K: -∆K0; PBCK: potential buffering capacity; EK0: equilibrium exchangeable K; CK0: equilibrium solution K; α: magnitude of conversion of added K to exchangeable pool; β: conversion of added K to non-exchangeable K pool; Emin: minimum exchangeable K.
Abstract The biomedical and surgical applications of hydrogels demand effective methods to adhere hydrogels to diverse substrates including living tissues. Here a mussel mimetic polyurethane as topological suture material for tough adhesion of hydrogels by introducing catechol moieties into polymer chains is presented. Solution of the stitching polyurethane can be injected onto the surface of a hydrogel, followed by diffusing spontaneously into the hydrogel, then get triggered by oxidant for in situ gelation. Oxidative cross‐linkage of catechol‐modified polyurethane after penetration into hydrogels or living tissues can establish enough covalently entangled networks to afford desired adhesion strength. The mussel mimetic polyurethane demonstrates excellent adhesion strength of hydrogels to versatile substrates including inorganics, polymers, and biomaterials, with no requirements for specific functional groups or chemical modification. The adhesion energy achieved by the topological stitching strategy can reach up to 350 J m −2 . Moreover, the stitching polymer shows potential for debonding under the catalysis of elastase. This work will possibly become a promising strategy candidate for adhesion in wet environments.
Abstract Facile functionalization of multilayer fullerenes (carbon nano‐onions, CNOs) was carried out by [2+1] cycloaddition of nitrenes. The products were further derivatized by using the “grafting from” strategy of in situ ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Using one‐step nitrene chemistry with high‐energy reagents, such as azidoethanol and azidoethyl 2‐bromo‐2‐methyl propanoate, in N ‐methyl‐2‐pyrrolidone at 160°C for 16 h, hydroxyl and bromide functionalities were introduced onto the surfaces of CNOs. These hydroxyl CNOs (CNO‐OH) and bromic CNOs (CNO‐Br) were extensively characterized by various techniques such as thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), Raman spectroscopy and X‐ray photo electron spectroscopy (XPS). TGA measurements indicated that the surface hydroxyl and bromide group density reached 1.49 and 0.49 mmol g −1 , respectively. The as‐functionalized CNOs showed much better solubility in solvents than pristine CNOs. The CNO‐OH were also observed to fluoresce at λ =453 nm in water. The CNO‐OH and CNO‐Br can be conveniently utilized as macroinitiators to conduct surface‐initiated in‐situ polymerizations. Poly( ε ‐caprolactone) (PCL, 45wt %) and polystyrene (PS, 60 wt%) were then grafted from surfaces of CNOs through the ROP of ε ‐caprolactone with the macroinitiator CNO‐OH and the ATRP of styrene with the macroinitiator CNO‐Br, respectively. The structures and morphology of the resulting products were characterized by 1 H NMR, scanning electron microscopy (SEM), TEM, and atomic force microscopy (AFM). The polymer functionalized CNOs have good solubility/dispersibility in common organic solvents. The facile and scalable functionalization approaches can pave the way for the comprehensive investigation of chemistry of CNOs and fabrication of novel CNO‐based nanomaterials and nanodevices.
OBJECTIVE: To investigate various methods for constructing soybean lecithin (SL)-based vesicles and evaluate the permeation-enhancing effect of SL-based vesicles on the penetration of insulin through buccal mucosa. METHODS: The ultrasonic method, high speed shear method and high pressure homogenization method were respectively used to prepare the SL-based vesicles, and the particle size of the vesicles was measured with photon correlation spectrometry (PCS). The penetration rate of insulin through porcine buccal mucosa was investigated with the Valia-Chien diffusion cells. RESULTS: The average particle sizes of 3 formulations of SL-based vesicles were 97.39, 85.60, and 100.60 nm when prepared by ultrasonic method, and were 58.7, 88.7, and 91.9 nm when prepared by high pressure homogenization method. Both vesicles presented good stability. However, the SL-based vesicles prepared by high speed shear method had larger average diameters and were found to be unstable. Transmission electron microscopy showed that SL-based vesicles had a spherical shape and the result accorded with PCS. The permeation flux of insulin of formulation 1 and control solution were 0.0024 and 0.0008 IU x ml(-1) x min(-1), respectively. The accumulative amount of formulation 1 at 180 min was (0.436 +/- 0.010 ) IU x ml(-1), which was 1.46 times higher than the control solution. CONCLUSIONS: The SL-based vesicles obtained using high pressure homogenization method are characterized by small particle size, narrow distribution, good stability, and powerful permeation-enhancing effect, which enables them to be good carriers for the buccal delivery of insulin.
Fe2AlB2 material was prepared through spark plasma sintering (SPS) by using Fe/Al/B mixed powder as the raw material. The effects of sintering temperature, holding time, and Al content on the phase composition and microstructure of the product were studied to obtain materials with high Fe2AlB2 content. Results showed that when the sintering temperature was increased to approximately 1000°C, SPS induced a thermal explosion reaction, resulting in the formation of a dense sintered sample with high Fe2AlB2 content. The sample contained a small amount of FeB and FeAl3 impurities. The synthesis of Fe2AlB2 could be promoted by optimizing holding time and increasing Al content in the raw materials. The most suitable process parameters for the synthesis of materials with high Fe2AlB2 content were 1000°C, no holding, and 2Fe/1.1Al/2B raw material. The Fe2AlB2 sample had good mechanical properties. Its Vickers hardness and bending strength were 10.5 GPa and 352 MPa, respectively. Given that the synthesized Fe2AlB2 material was unstable, continuously increasing the temperature or extending the holding time would cause it to decompose.
Abstract The exploration of cost‐effective and efficient catalysts for the transformation of CO 2 into chemicals at room temperature and low CO 2 pressure is a key challenge. Here, a green synthesis method of porous organic polymer was developed, which was obtained by the Scholl coupling reaction via polycondensation of 1,3,5‐triphenylbenzene and 1,10‐phenanthroline at room temperature. The polymer has a large surface area (1074 m 2 g −1 ) and exhibited excellent CO 2 capture of 77.26 cm 3 g −1 at 273.15 K and 1.00 bar. After loading cobalt acetate, an ultralow Co loading phenanthroline‐based porous organic polymer was obtained with very high catalytic efficiency in TOF of 263 h −1 for the fixation of CO 2 to cyclic carbonates at room temperature and atmospheric with free‐solvent, which is over six‐fold than that of a molecular analogue, 1,10‐phenanthroline‐Co(OAc) 2 . This work provided a facile, powerful, green, and efficient strategy for designing porous organic polymers as high‐efficient heterogeneous catalysts in the fixation of carbon dioxide.
Responsive membranes have been used to construct smart biomaterial interfaces. We report a novel approach to fabricate honeycomb films with a pattern of thermoresponsive polymer, namely poly(N-isopropylacrylamide). The approach was based on a combination of the breath figure method and reversible addition–fragmentation chain transfer. The hybrid film had morphological and chemical patterns resulting in varied wettability and morphology at various stages, as well as high thermo-responsiveness. Enhanced cell adhesion was observed at an incubation temperature of 37 °C, which is above its lower critical solution temperature (LCST). Furthermore, cells could be harvested at temperatures below the LCST without trypsin treatment. The non-invasive characteristics give this membrane potential as a substrate for cell sheet engineering.
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