Superhydrophobic fabrics suggest tremendous potential in some emerging fields such as electronic skin, bioelectronic sensors and special clothing due to their excellent liquid repellency and ...self-cleaning properties. However, currently reported superhydrophobic materials are usually prepared using biologically toxic fluorinated compounds, which severely restricts their practical applications. Herein, we propose a two-step thiol-ene click reaction strategy to fabricate fluorine-free superhydrophobic cotton fibers (Fabric-SH-PB-SiO2). The 1,2-polybutadiene (1,2-PB) with flexible rubber molecular chains and low surface energy was coated by cotton fiber through thiol-ene click reaction. Subsequently, based on this reaction, the coated cotton fiber was used to establish chemical bonds with hydrophobic silica. The Fabric-SH-PB-SiO2 possesses a rich multi-level micro-nano structure that can form stable air layer on the surface of the fabric, which showed a high hydrophobic angle of 156° and exhibited some distinct advantages such as anti-fouling and self-cleaning characteristics, high buoyancy, and reduced drag. More remarkably, the Fabric-SH-PB-SiO2 could float on the water surface after carrying 34 times its weight. Compared with unmodified fabrics, the Fabric-SH-PB-SiO2 demonstrated a high drag reduction rate of up to 102 %, among the highest values for the reported hydrophobic materials. The strategy developed here provides insights towards fabricating high-buoyancy fluorine-free superhydrophobic cotton fibers.
The chitosan microparticles were prepared using the inverse phase emulsion dispersion method and modified with thiourea (TCS). TCS was characterized by scanning electron microscope (SEM), the Fourier ...transform infrared (FT-IR) spectra, sulfur elemental analysis, specific surface area and pore diameter. The effects of various parameters, such as pH, contact time, initial concentration and temperature, on the adsorption of Pt(IV) and Pd(II) by TCS were investigated. The results showed that the maximum adsorption capacity was found at pH 2.0 for both Pt(IV) and Pd(II). TCS can selectively adsorb Pt(IV) and Pd(II) from binary mixtures with Cu(II), Pb(II), Cd(II), Zn(II), Ca(II), and Mg(II). The adsorption reaction followed the pseudo-second-order kinetics, indicating the main adsorption mechanism of chemical adsorption. The isotherm adsorption equilibrium was well described by Langmuir isotherms with the maximum adsorption capacity of 129.9
mg/g for Pt(IV) and 112.4
mg/g for Pd(II). The adsorption capacity of both Pt(IV) and Pd(II) decreased with temperature increasing. The negative values of enthalpy (Δ
H°) and Gibbs free energy (Δ
G°) indicate that the adsorption process is exothermic and spontaneous in nature. The adsorbent was stable without loss of the adsorption capacity up to at least 5 cycles and the desorption efficiencies were above 95% when 0.5
M EDTA–0.5
M H
2SO
4 eluent was used. The results also showed that the preconcentration factor for Pt(IV) and Pd(II) was 196 and 172, respectively, and the recovery was found to be more than 97% for both precious metal ions.
Most terrestrial plants are able to form a root symbiosis with arbuscular mycorrhizal (AM) fungi for enhancing the assimilation of mineral nutrients. AM fungi are obligate symbionts that depend on ...host plants as their sole carbon source. Development of an AM association requires a continuous signal exchange between the two symbionts, which triggers coordinated differentiation of both partners, to enable their interaction within the root cells. The control of the AM symbiosis involves a finely-tuned process, and an increasing number of studies have pointed to a pivotal role of several phytohormones, such as strigolactones (SLs), gibberellic acids (GAs), and auxin, in the modulation of AM symbiosis, through the early recognition of events up to the final arbuscular formation. SLs are involved in the presymbiotic growth of the fungus, while auxin is required for both the early steps of fungal growth and the differentiation of arbuscules. GAs modulate arbuscule formation in a dose-dependent manner, via DELLA proteins, a group of GRAS transcription factors that negatively control the GA signaling. Here, we summarize the recent findings on the roles of these plant hormones in AM symbiosis, and also explore the current understanding of how the DELLA proteins act as central regulators to coordinate plant hormone signaling, to regulate the AM symbiosis.
Understanding the immiscible displacement mechanism in porous media is vital to enhancing the hydrocarbon resources in the oil and gas reservoir. Improving resource recovery requires quantitatively ...characterizing the effect of wettability heterogeneity on the immiscible displacement behaviors at the pore scale, which can be used to predict the displacement distribution of multiphase fluids and evaluate the optimal wettability strategy in porous media. The heterogeneity of fluid wettability in a natural rock makes it extremely hard to directly observe the fluid displacement behaviors in the reservoir rocks and quantify the sensitivity of preferential displacement path and displacement efficiency to wettability distribution. In this study, the phase-field model coupling wettability heterogeneity was established. The gas-water two-phase displacement process was simulated under various wettability distributions and injecting flux rates in a complex pore structure. The effect of wettability heterogeneity on immiscible displacement behavior was analyzed. The results indicated that wettability heterogeneity significantly affects the fluid displacement path and invasion patterns, while the injecting flux rate negatively influences the capillary–viscous crossover flow regime. The continuous wetting patches enhanced the preferential flow and hindered displacement, whereas the dalmatian wetting patches promoted a higher displacement efficiency. The results of the fractal dimensions and specific surface area also quantitatively show the effects of wettability distribution and heterogeneity on the complexity of the two-phase fluid distribution. The research provides the theoretical foundation and analysis approach for designing an optimal wettability strategy for injecting fluid into unconventional oil and gas reservoirs.
In this work, we examined the effects of various parameters, such as pH, contact time, initial concentration, and temperature, on the adsorption of Hg(II) by ethylenediamine-modified magnetic ...crosslinking chitosan microspheres (EMCR). EMCR had the diameter size range of 80–250
μm, average pore size of 826
nm, BET surface area of 68.6
m
2/g, and saturated magnetization of 15.4
emu/g. The maximum uptake of Hg(II) was recorded at pH 5. At pH 3, Hg(II) could be selectively separated from Cd(II), Pb(II), Zn(II), Cu(II), Ca(II), and Mg(II). Equilibrium data were fitted well with Langmuir isotherms with the maximum adsorption capacity of 2.69
mmol/g for Hg(II). Both kinetics and thermodynamic parameters of the adsorption process were obtained. The data indicated that adsorption process was exothermic spontaneous reaction and kinetically proceeded according to pseudo-second-order model. The metal ion-loaded EMCR were regenerated with an efficiency of more than 90% using 0.02–0.1
M thiourea.
It is well known that second phases act as micro-cathodes in the corrosion of traditional Mg alloys. However, the effect of second phases on the corrosion behavior of Mg-rare earth (RE) alloys is ...ambiguous in view of the second phases consisting of Mg and more active RE elements. The role of second phases in the corrosion of cast EW75 (Mg–5Y–7Gd–1Nd–0.5Zr) was studied by scanning electron microscopy (SEM) observations, Scanning Kelvin Probe Force Microscopy (SKPFM) analysis, immersion and electrochemical tests. It is found that the second phases in EW75 are more active than Mg matrix and preferentially dissolved at the initial corrosion stage. It indicates that the second phases act as micro-anodes, which are greatly different from the role of second phases in traditional Mg alloys.
Formula: see text state estimation is addressed for continuous-time neural networks in the paper. The norm-bounded uncertainties are considered in communication neural networks. For the considered ...neural networks with uncertainties, a reduced-order Formula: see text state estimator is designed, which makes that the error dynamics is exponentially stable and has weighted Formula: see text performance index by Lyapunov function method. Moreover, it is also given the devised method of the reduced-order Formula: see text state estimator. Then, considering that sampling the output y(t) of the neural network at every moment will result in waste of excess resources, the event-triggered sampling strategy is used to solve the oversampling problem. In addition, a devised method is also given for the event-triggered reduced-order Formula: see text state estimator. Finally, by the well-known Tunnel Diode Circuit example, it shows that a lower order state estimator can be designed under the premise of maintaining the same weighted Formula: see text performance index, and using the event-triggered sampling method can reduce the computational and time costs and save communication resources.
Abstract
To study and prevent the water hazards of deep coal mines roof in the Inner Mongolia–Shaanxi (IM–S) mining area, it is essential to correctly evaluate the water-richness distributions of ...water-bearing aquifers in roof. This paper puts forward a sediment control method for water-richness law and zoning in the roof aquifers of deep Jurassic coals. To determine the vertical distance of direct water-bearing aquifers, the height of fractured water-conducting zone was detected by an underground network parallel electrical method. The plane and lateral spatial distribution patterns of the water-bearing aquifers and the control of the water-richness distribution was analyzed with the sediment control method. An evaluation system that consisted of four indicators, i.e., sedimentary environmental impact index, interlayer ratio of sandstone and mudstone, sandstone thickness, geophysical water-richness anomaly index was constructed. Furthermore, an Analytic Hierarchy Process (AHP) was introduced to establish the comprehensive zoning map. Finally, through the example analysis of Muduchaideng coal mine, the zoning evaluation results of water-richness were verified by the mine inflow. The findings of this study provide scientific guidance for prevention and control of mine water hazards in the IM–S mining area.
PDF
