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11.
Small angle X‐ray scattering (SAXS) and wide angle X‐ray diffraction (WAXD) were adopted to investigate the formation and development of high order structure within polyacrylonitrile (PAN) precursor during coagulation. The scattering signal came from the microvoids and long period structure was separated reasonably by the analog computation method of decomposition of the one‐dimensional profile. Based on the established methodology, the statistic parameters of long period structure, such as length of the long period structure, crystalline region and amorphous region, were obtained by the analysis of correlation function. The results indicated that during the coagulation, the length of long period of the nascent coagulated fiber was 56.1 nm (meridional direction) and 35.6 nm (equatorial direction), respectively. The evolution of the long period during the coagulation was also discussed by combining WAXD data. With the processing of coagulation, the long period was decreased since the crystallinity increased. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
12.
The structures of the O‐glycosyltransferase LanGT2 and the engineered, C? C bond‐forming variant LanGT2S8Ac show how the replacement of a single loop can change the functionality of the enzyme. Crystal structures of the enzymes in complex with a nonhydrolyzable nucleotide‐sugar analogue revealed that there is a conformational transition to create the binding sites for the aglycon substrate. This induced‐fit transition was explored by molecular docking experiments with various aglycon substrates.  相似文献   
13.
An oil-soluble antioxidant, alkylated diphenylamine (ADPA), was prepared by alkylation of diphenylamine. The influence of ADPA on the thermal-oxidative stability of poly-α-olefin (PAO8) was evaluated by thermogravimetry (TG). For comparison, the thermal-oxidative stability of PAO8 with zinc dialkyl dithiophosphate (ZDDP) was also investigated. Activation energy (Ea)of the corresponding thermal-oxidative degradation process was evaluated by the Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods. To demonstrate the reliability of the kinetic study, the antioxidant performance of ADPA and ZDDP in PAO8 was also studied by the pressure drop (PDT) and accelerated oxidation (AOT) tests. The results indicate that ADPA has better antioxidant ability than ZDDP in increasing the Ea value and enhancing the oxidative stability of PAO8. Good correlation between the applied test methods was established.  相似文献   
14.
The density of the LiF-Li2CO3 melts system was measured using the Archimedean method. Using the quadratic regression orthogonal design with two factors, a regression equation for the density of LiF-Li2CO3 melts was obtained in which the concentration of LiF and temperature were considered. The results indicated that the density of the LiF-Li2CO3 melts decreased with either increasing the concentration of LiF or increasing temperature; a linear relation was observed between density and temperature. In addition, the influences of NaF, KF, NaCl, and KCl additives on the densities of the given systems were studied. The addition of NaF and KF increased the density of the melts, whereas NaCl and KCl resulted in an initial increase and subsequent decrease with an increasing additive concentration. The density attained a maximum at NaCl and KCl mass fraction of approximately 15%.  相似文献   
15.
With the calorimetric (adsorption heat versus coverage) curve also measured together with the adsorption isotherm, the simultaneous use of both curves showed that there were two phases of adsorption in the adsorption of methanol, dimethyl ether, ethene and propane in SAPO-34. The dual-site Langmuir equation gave good fits to the adsorption data to support the interpretation that a second (type 2) adsorption phase occurred in the high-pressure region in addition to a first (type 1) adsorption phase on the acid sites at lower pressures. Adsorption experiments and calculations using binary gas mixtures showed that due to the existence of two types of adsorption, the multicomponent Langmuir isotherm equation (Langmuir competitive adsorption model) calculated incorrect surface concentrations when the concentrations were high. In contrast, the ideal adsorbed solution theory (IAST) calculated correct surface concentrations in the adsorption of mixtures.  相似文献   
16.
Solar water splitting provides a clean and renewable approach to produce hydrogen energy. In recent years, single‐crystal semiconductors such as Si and InP with narrow band gaps have demonstrated excellent performance to drive the half reactions of water splitting through visible light due to their suitable band gaps and low bulk recombination. This Minireview describes recent research advances that successfully overcome the primary obstacles in using these semiconductors as photoelectrodes, including photocorrosion, sluggish reaction kinetics, low photovoltage, and unfavorable planar substrate surface. Surface modification strategies, such as surface protection, cocatalyst loading, surface energetics tuning, and surface texturization are highlighted as the solutions.  相似文献   
17.
The dispersion into water of nanocapsules bearing a highly hydrophobic fluorinated internal lining yielded encapsulated air nanobubbles. These bubbles, like their micrometer‐sized counterparts (microbubbles), effectively reflected ultrasound. More importantly, the nanobubbles survived under ultrasonication 100‐times longer than a commercial microbubble sample that is currently in clinical use. We justify this unprecedented stability theoretically. These nanobubbles, owing to their small size and potential ability to permeate the capillary networks of tissues, may expand the applications of microbubbles in diagnostic ultrasonography and find new applications in ultrasound‐regulated drug delivery.  相似文献   
18.
We report a facile and green method for the fabrication of new type of electrocatalysts based on MnO2 nanoparticles incorporated on MgAl LDH P-type semiconductive channel and explore its practical applications as high-performance electrode materials for electrochemical biosensor. A series of MgAl layered doubled hydroxide (LDH) nanohybrids with fixed Mg/Al (M2+/M3+ atomic ratio of 3) and varied amount of MnCl2.4H2O are fabricated by a facile co-precipitation method. This approach demonstrates the combination of distinct properties including excellent intercalation features of LDH for entrapping nanoparticles and high loading of MnO2 nanoparticles in the host layers of LDH. Among all samples, Mn5–MgAl with 0.04% loaded manganese has a good crystalline morphology. A well-dispersed MnO2 nanoparticles encapsulated into the host matrix of hydrotalcite exhibit enhanced electrocatalytic activity towards the reduction of H2O2 as well as excellent stability, selectivity and reproducibility due to synergistic effect of good catalytic ability of MnO2 and conductive MgAl LDH. Glass carbon electrode (GCE) modified with Mn5–MgAl possesses a wide linear range of 0.05–78 mM, lowest detection limit 5 μM (S/N = 3) and detection sensitivity of 0.9352 μAmM−1. This outstanding performance enables it to be used for real-time tracking of H2O2 secreted by live HeLa cells. This work may provide new insight in clinical diagnosis, on-site environmental analysis and point of care testing devices.  相似文献   
19.
20.
Herein, a manganese‐catalyzed nucleophilic addition of inert C(sp2) H bonds to aldehydes and nitriles is disclosed by virtue of a dual activation strategy. The reactions feature mild reaction conditions, excellent regio‐ and stereoselectivity, and a wide substrate scope, which includes both aromatic and olefinic C H bonds, as well as a large variety of aldehydes and nitriles. Moreover, mechanistic studies shed light on possible catalytic cycles.  相似文献   
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