In situ one-step hydrothermal strategy for synthesis of Fe3O4@MIL-100(Fe) core-shell magnetic microspheres and used for adsorptive removal of MB dye from aqueous solution.
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A new route ...for Fe3O4@MIL-100(Fe) core-shells is proposed via in situ one-step hydrothermal strategy, in which Fe3O4 microspheres not only serve as magnetic cores but also provide Fe(III) for MIL-100(Fe) synthesis. The MIL-100(Fe) is uniformly grown as a shell on the surface of Fe3O4, and the shell thickness can be fine-tuned from 73.5 to 148nm by simply controlling the reaction time. Compared with Fe3O4, the surface area and pore volume of the Fe3O4@MIL-100(Fe) are significantly increased while the magnetism is barely affected. The application of Fe3O4@MIL-100(Fe) in adsorption was tested using several dyes as model analytes, and showed high adsorption capacity (221mgg−1) towards methylene blue (MB), which is based on electrostatic interactions and size filter effect. The MB adsorption isotherm follows Langmuir model and pseudo second-order kinetic model. Intra-particle diffusion model reveals that both film and pore diffusions are involved in the rate limiting steps. The adsorption is controlled by enthalpy change rather than entropy effect. ΔH, ΔS and ΔG values indicated that the adsorption process was spontaneous and exothermic. Simple synthesis procedure, immense magnetism, high adsorption capacity and excellent reusability of Fe3O4@MIL-100(Fe) make it an attractive candidate for application of MB removal from polluted environmental samples.
The quantitative correlation of the catalytic activity with the microscopic structure of heterogeneous catalysts is a major challenge for the field of catalysis science. It requests synergistic ...capabilities to tailor the structure with atomic scale precision and to control the catalytic reaction to proceed through well-defined pathways. Here we leverage on the controlled growth of MoS2 atomically thin films to demonstrate that the catalytic activity of MoS2 for the hydrogen evolution reaction decreases by a factor of ∼4.47 for the addition of every one more layer. Similar layer dependence is also found in edge-riched MoS2 pyramid platelets. This layer-dependent electrocatalysis can be correlated to the hopping of electrons in the vertical direction of MoS2 layers over an interlayer potential barrier. Our experimental results suggest the potential barrier to be 0.119 V, consistent with theoretical calculations. Different from the conventional wisdom, which states that the number of edge sites is important, our results suggest that increasing the hopping efficiency of electrons in the vertical direction is a key for the development of high-efficiency two-dimensional material catalysts.
Rechargeable aluminum-ion batteries (RAIBs) are regarded as the next generation of low-cost and high-capacity electrical energy storage systems. Compared to graphene-based cathodes, metal ...dichalcogenide cathodes can potentially provide RAIBs with higher capacities. However, metal dichalcogenides suffer from poor cycling performance, hindering the further development of high-capacity RAIBs. Thus, to further improve the performance of RAIBs, it is imperative to gain a deep understanding of the mechanisms behind the energy-storage and capacity-deterioration characteristics of these materials. In this work, we conducted detailed characterization to acquire a deep understanding of the energy storage mechanism of a CoSe2-based cathode. The characterization results revealed that energy storage involved incorporation of Al3+ into CoSe2 to generate AlmConSe2 (i.e., partial substitution of Co2+ by Al3+) and elemental Co, while capacity deterioration resulted from the dissolution of active cobalt species into the electrolyte and the pulverization of the CoSe2 phase. The understanding of the capacity-deterioration mechanism allowed us to design a two-step concept for a new type of RAIB composite cathode material. Thus, we employed a conductive wrapping layer of reduced graphene oxide (rGO) to protect CoSe2/carbon nanodice composites from cobalt dissolution and CoSe2 pulverization while also improving the conductivity of the materials. This novel design resulted in a CoSe2/carbon nanodice@rGO composite material with an outstanding cycling performance (after 500 cycles) of 143 mA h g−1 at 1000 mA g−1, which is one of the best performances for a metal-based RAIB cathode material reported to date. These findings are of great significance for the further development of high-capacity RAIBs.
In recent years, haze pollution has become one of the most critical environmental issues in Xi'an, China, with particular matter (PM) being one of the top pollutants. As an important fraction of PM, ...bioaerosols may have adverse effects on air quality and human health. In this study, to better understand the characteristics of such biological aerosols, airborne microbial samples were collected by using an Andersen six-stage sampler in Xi'an from October 8th to 22nd, 2014. The concentration, size distribution and genera of airborne viable bacteria and fungi were comparably investigated during the haze days and non-haze days. Correlations of bioaerosol levels with meteorological parameters and PM concentrations were also examined. The results showed that the daily average concentrations of airborne viable bacteria and fungi during the haze days, 1102.4–1736.5 and 1466.2–1703.9 CFU/m3, respectively, were not only much higher than those during the non-haze days, but also exceeded the recommended permissible limit values. Comparing to size distributions during the non-haze days, slightly different patterns for bacterial aerosols and similar single-peak distribution pattern for fungal aerosols were observed during the haze days. Moreover, more allergic and infectious genera (e.g. Neisseria, Aspergillus, and Paecilomyces) in bioaerosols were identified during the haze days than during non-haze days. The present results reveal that bioaerosols may have more significant effects on public health and urban air quality during the haze days than during non-haze days.
•On haze days, concentrations of viable bacteria and fungi were much higher than on non-haze days.•There was different size distribution for airborne bacteria between the haze and non-haze days.•For fungal aerosols, similar size distribution can be found between the haze and non-haze days.•Compared to the non-haze days, some more allergic and infectious genera can be found during the haze days.•More attention should be paid to the potential health risk related to bioaerosols during the haze days.
Proteinaceous matter is an important component of PM2.5, which can cause adverse health effects and also influence the air quality and climate change. However, there is little attention to high ...time-resolved variations and potential role of aerosol proteins during haze pollution periods. In this study, PM2.5 samples were first collected by a medium flow sampler in autumn and winter in Xi'an, China. Then three high time-resolved monitoring campaigns during haze pollution periods were conducted to determine the evolving characteristics of total protein concentration and explore the interactive relationship between protein and other chemical compositions. The results showed that the average protein concentration in PM2.5 in Xi'an (5.46 ± 3.32 μg m−3) was higher than those in most cities of China, and varied by seasons and air pollution conditions. In particular, the protein concentration in PM2.5 increased with the increase of air quality index (AQI). The continuous variations of aerosol proteins during the haze pollution periods further showed that PM2.5, atmospheric humidity and long-distance air mass transport exerted the significant impacts on the protein components in aerosols. Based on the present observation, it is suggested that aerosol proteins might affect the generation of secondary aerosols under haze weather conditions. The present results may provide a new possible insight into the variations and the role of aerosol proteinaceous matter during the formation and development of haze pollution.
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•The high time-resolved variations of proteins in PM2.5 during haze pollution events was examined.•Protein concentration in PM2.5 increased with the increase of air quality index (AQI).•PM2.5, RH and air transport contributed significantly to the variations in aerosol proteins.•Sources of proteins in PM2.5 were different on haze and non-haze days.•Aerosol proteins may affect the formation of secondary aerosols under haze pollution weather.
SUMMARY
Source time-reversal imaging (TRI) based on decoupled elastic wave equation can utilize vector P- and S-wave time differences and achieve high-precision source location in complex geological ...models. The imaging condition is critical for TRI. However, because of the orthogonally polarized properties of P and S waves, traditional vector dot product imaging condition directly applied to TRI will decrease the effective imaging values. In contrast, the energy current density vectors of P and S waves represent the propagation directions of the wavefields and are almost parallel. Their dot product can result in the maximum imaging energy. Based on this principle, we propose a P- and S-wave energy current density vectors dot product imaging condition (PSEDPIC), which uses the propagation direction information of P and S waves at the source point to suppress imaging artefacts generated by waves with inconsistent propagation directions. Numerical tests reveal that PSEDPIC can (1) reduce the image artefacts, (2) improve the imaging spatial resolution and (3) allow a shallower imaging region. In addition, if the numerical simulation algorithm used in TRI can reconstruct the seismic wavefield accurately in the presence of surface topography, the impact of an observation system with elevation differences on imaging can be eliminated automatically. For this reason, we use the curvilinear grid finite-difference method to directly reconstruct the wavefield in TRI to solve the problem of data elevation correction. The test results of 3-D synthetic and field data for microseismic monitoring demonstrate the effectiveness of the proposed method.
Layered topographies and geologies are known to have considerable effects on the spatially variable seismic motions scattered by a canyon in a layered half-space. In this study, based on a ...substructure replacement technique, a coupled finite element method and scaled boundary finite element method based on scaling splicing lines (hereafter referred to as coupled FEM/SBFEM) is developed for a scattering field analysis, considering the effect of the layered topographical characteristics. The near field is modelled using the finite element method (FEM), and the far field is modelled using an improved scaled boundary finite element method, which can model the radiation damping of a layered half-space precisely. In the modified version of SBFEM, a novel dimensionless frequency is proposed to facilitate obtaining the time-domain response efficiently using a fast Fourier transformation. Several examples are investigated to demonstrate the versatility and validity of the proposed method. Parametric studies are performed to investigate the characteristics of the ground motions of a trapezoidal canyon in a layered half-space in the frequency and time domains (where the ground motions significantly differ from those of a uniform half-space), and to investigate the effects on ground motions caused by the soil layer thickness, burial depth, and impedance ratio.
Frequent low visibility, haze pollution caused by heavy fine particulate matter (PM2.5) loading, has been entailing significant environmental issues and health risks in China since 2013. A ...substantial fraction of bioaerosols was observed in PM (1.5–15%) during haze periods with intensive pollution. However, systematic and consistent results of the variations of bioaerosol characteristics during haze pollution are lacking. The role of bioaerosols in air quality and interaction with environment conditions are not yet well characterized. The present article provides an overview of the state of bioaerosol research during haze episodes based on numerous recent studies over the past decade, focusing on concentration, size distribution, community structure, and influence factors. Examples of insightful results highlighted the characteristics of bioaerosols at different air pollution levels and their pollution effects. We summarize the influences of meteorological and environmental factors on the distribution of bioaerosols. Further studies on bioaerosols, applying standardized sampling and identification criteria and investigating the influence of mechanisms of environmental or pollution factors on bioaerosols as well as the sources of bioaerosols are proposed.
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•Understanding the spatial and temporal distribution and dynamic variations of bioaerosols.•Comparing the characteristics of bioaerosols on haze and non-haze days.•Investigating the influences of meteorological and environmental factors on bioaerosols.
This review emphatically discussed the characteristics of bioaerosols during haze episodes in China, as well as influence factors.
Aiming at oil extraction from a tight reservoir, the Jilin oil field was selected as the research object of this study. Based on the molecular structures of conventional long-chain alkyl anionic ...surfactants, a new temperature-resistant anionic/nonionic surfactant (C
P
E
C) was prepared by introducing polyoxyethylene and polyoxypropylene units into double-chain alcohols. The resulting structures were characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (
H-NMR), and electrospray ionization mass spectrometry (ESI-MS). Then, based on surface tension, interfacial tension, adsorption resistance, wettability, and emulsification performance tests, the performance of C
P
E
C was evaluated. The FT-IR, ESI-MS, and NMR spectra confirmed that C
P
E
C was successfully prepared. The critical micelle concentration (CMC) of C
P
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C in water was 2.9510 × 10
mol/L (the corresponding mass concentration is 0.26%), and the surface tension of the aqueous C
P
E
C solution at this concentration was 30.5728 mN/m. At 0.3% concentration, the contact angle of the C
P
E
C solution was 31.4°, which is 60.75% lower than the initial contact angle. Under high-temperature conditions, C
P
E
C can still reduce the oil-water interfacial tension to 10
mN/m, exhibiting good temperature resistance. At 110 °C, upon adsorption to oil sand, the C
P
E
C solution could reduce the oil-water interfacial tension to 0.0276 mN/m, and the interfacial tension can still reach the order of 10
mN/m, indicating that C
P
E
C has strong anti-adsorption capability. Additionally, it has good emulsifying performance; upon forming an emulsion with crude oil, the highest drainage rate was only 50%. The forced imbibition oil recovery of C
P
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C is 65.8%, which is 38.54, 24.22, and 27.25% higher than those of sodium dodecyl benzene sulfonate, alkyl polyoxyethylene ether carboxylate, and alkyl ether carboxylate, respectively.
Objective
To investigate the effects of repetitive transcranial magnetic stimulation (rTMS) on serum levels of brain-derived neurotrophic factor (BDNF), interleukin (IL)-1β, and tumor necrosis factor ...(TNF)-α in elderly patients with refractory depression.
Methods
A total of 58 elderly patients diagnosed with refractory depression between January 2015 and December 2016 were divided randomly into two groups: 29 patients who received rTMS and 29 controls without rTMS. Thirty healthy individuals were also enrolled and all received rTMS. Serum levels of BDNF, IL-1β, and TNF-α were measured before the study (0 days), and at 48 hours and 1, 2, 3, and 4 weeks after the first TMS treatment.
Results
BDNF levels gradually increased with treatment duration in the rTMS group and were significantly higher compared with the control group. In contrast, IL-1β and TNF-α levels gradually decreased and were significantly lower than in the control group. None of the serum factors were affected by rTMS in the healthy individuals. BDNF levels were negatively correlated and IL-1β and TNF-α levels were positively correlated with Hamilton Depression Rating Scale-24 scores.
Conclusion
These results suggest that rTMS may increase BDNF and decrease IL-1β and TNF-α serum levels in elderly patients with refractory depression.
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