A method is presented to tailor the lateral size of graphene oxide (GO) in the range of 10–100nm and simultaneously tailor its edge structure by oxidation with periodic acid in a one-pot process. The ...obtained GO nanosheets are photoluminescent and exhibit lateral size-dependent behavior. The emission wavelength could be tuned from 550 to 470nm by decreasing the lateral size. The fluorescence of GO nanosheets shows a sensitive and selective quenching effect to Fe3+ ions, allowing it to be used as a fluorescent probe to detect Fe3+ ions with a detection limit of 1ppm.
Abstract
An excellent magnetic multi-walled carbon nanotubes (MMWCNT) containing carboxyl material modified with ferroferric oxide (Fe3O4) nanoparticles was synthesized as the adsorbent for magnetic ...solid-phase extraction (MSPE) of five heavy metal ions (Pb2+, Cu2+, Co2+, Cd2+, Cr4+) in water samples followed by on-line inductively coupled plasma mass spectrometry (ICP-MS) detection. The characteristics of the adsorbent were analyzed using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and vibrating sample magnetometer (VSM). Some factors affecting extraction efficiency including pH of sample solution, the amount of adsorbent, extraction method and time, concentration and volume of desorption solvent, desorption time and evaluation of coexisting ions were optimized. Under the optimum conditions, good linearity (r ≥ 0.9951) was obtained within the range of 0.1–50.0 ng·mL−1. The limits of detection (LODs) and limits of quantification (LOQs) were 4.0–25.0 ng·L−1 and 15.0–80.0 ng·L−1, respectively. And satisfactory recoveries of five heavy metal ions ranged from 81.11% to 105.53% were acquired, and the relative standard deviations (RSDs) were no more than 6.05%. The MMWCNT synthesized had strong adsorption force for the five investigated heavy metal ions, respectively. Hence, the proposed method was so suitable and sensitive that it can be applied to the determination of trace analysis of heavy metals in water samples.
Growth of silver nanoparticles by the citrate reduction of silver nitrate under the range of pH from 5.7 to 11.1 was investigated systematically and quantitatively. Reduction of the silver precursor ...(Ag+) was promoted with increased pH, attributed to the higher activity of the citrate reductant under high pH value. Under high pH, the product was composed of both spherical and rod-like silver nanoparticles as a result of the fast reduction rate of the precursor. Under low pH, the product was mainly dominated by triangle or polygon silver nanoparticles due to the slow reduction rate of the precursor. The product that is dominated by spherical silver nanoparticles cannot be acquired by the one-step citrate reduction method in the range of pH investigated, indicating the poor balance between the nucleation and growth processes in the reactions. On the basis of the results of quantitative analyses, a stepwise reduction method, in which the nucleation and growth processes were carried out at high and low pH, respectively, was proposed for the syntheses of spherical silver nanoparticles.
Aligned steel fibers significantly enhance the flexural capacity of geopolymer composite. However, research on the flexural capacity of aligned steel fiber-reinforced geopolymer composite (ASFRGPC) ...is rare. Therefore, this study investigates the flexural capacity of the ASFRGPC beam. First, geopolymer beams with different fiber layer thicknesses were prepared and four-point bending tests were carried out. On this ground, simplified flexural capacity calculation models were established for full-section and partial-section ASFRGPC beams. Then, experimental data from full-section ASFRGPC were used to determine the stress block parameters α1 and β1. It turned out that the values of α1 ranged from 0.951 to 0.987 and those of β1 ranged from 0.804 to 0.841. By approximating the stress block parameters α1 and β1 as 1.0 and 0.8, the errors in the resulting flexural capacity and the depth of the compression zone are no more than 4.7% and 3.1%, respectively. Finally, experimental data from partial-section ASFRGPC were used to analyze the impact of fiber layer thickness on the flexural capacity. The results showed that as the thickness of the steel fiber layer increases, the flexural capacity initially increases until reaches a maximum and then decreases. Therefore, it indicates that there exists an optimum thickness for the steel fiber layer. It has also been found that the optimal thickness of the steel fiber layer is not a fixed value, which depends on the tensile strength of the ASFRGPC and the compressive strength of the geopolymer matrix.
A synergy of numerical simulation, ground-based measurement and satellite observation was applied to evaluate the impact of biomass burning originating from Southeast Asia (SE Asia) within the ...framework of NASA's 2006 Biomass burning Aerosols in Southeast Asia: Smoke Impact Assessment (BASE-ASIA). Biomass burning emissions in the spring of 2006 peaked in March–April when most intense biomass burning occurred in Myanmar, northern Thailand, Laos, and parts of Vietnam and Cambodia. Model performances were reasonably validated by comparing to both satellite and ground-based observations despite overestimation or underestimation occurring in specific regions due to high uncertainties of biomass burning emission. Chemical tracers of particulate K+, OC concentrations, and OC/EC ratios showed distinct regional characteristics, suggesting biomass burning and local emission dominated the aerosol chemistry. CMAQ modeled aerosol chemical components were underestimated at most circumstances and the converted AOD values from CMAQ were biased low at about a factor of 2, probably due to the underestimation of biomass emissions. Scenario simulation indicated that the impact of biomass burning to the downwind regions spread over a large area via the Asian spring monsoon, which included Southern China, South China Sea, and Taiwan Strait. Comparison of AERONET aerosol optical properties with simulation at multi-sites clearly demonstrated the biomass burning impact via long-range transport. In the source region, the contribution from biomass burning to AOD was estimated to be over 56%. While in the downwind regions, the contribution was still significant within the range of 26%–62%.
► We model biomass burning in Southeast Asia which has been rarely studied. ► Impact of biomass burning in both source and downwind regions are assessed. ► Contributions from biomass burning to aerosol are quantatively determined. ► Model evaluations suggest biomass burning emission inventory should be improved.
This study integrates data from regional model simulations, reanalysis data set, radiosonde observations, lidar measurements, and satellite products to evaluate the direct radiative forcing effect of ...biomass burning and dust over East Asia. During March and April, we find an overall cooling effect of the dust of −5 to −9 W/m2. Biomass burning aerosols from Peninsular Southeast Asia exhibit a warming effect of 5–10 W/m2 over the source area, lower than that over the downwind area of 10–20 W/m2 because of significantly higher cloud coverage in South China. Dust and biomass burning aerosols are found to cool the near surface layer (0–1 km) by −0.5 and −0.3 K, respectively, and warm the upper air (1–5 km) by +0.1 and +0.2 K, respectively. In Taipei, simultaneous presences of dust and biomass burning lead to cooling of near‐surface air by −1.5 K and warming of upper air by +1 K.
Plain Language Summary
Biomass burning and dust are the largest natural emission sources of atmospheric aerosol. However, no solid consensus exists regarding whether biomass burning or dust contributes to a net warming or cooling effect. This study integrates data from regional climate model simulations, reanalysis data, radiosonde observations, lidar measurements, and satellite products to evaluate the climate effects of biomass burning and dust at a regional scale over East Asia. We find prominent warming effects by biomass burning in Peninsular Southeast Asia, which is more significant over the downwind area in South China than over the emission source area. Dust exhibits cooling effects, with a few exceptions over areas covered by semipersistent snow or ice. We also reveal that under conditions in which both biomass burning and dust aerosols are present, they exhibit an overall slight warming effect.
Key Points
Peninsular Southeast Asia biomass burning shows larger warming effect (10‐20 W/m2) over downwind region than over the source area (5‐10 W/m2)
Dust shows a cooling effect of up to ‐9 W/m2 with a few exceptions along north and east edges of Tibet Plateau due to snow or ice cover
Dust and biomass burning cool the near surface air and warm the upper air, and their radiative efficiencies decrease during transport
Abstract
Background
Avian leukosis virus (ALV) is an infectious retrovirus, that mainly causes various forms of tumours, immunosuppression, a decreased egg production rate and slow weight gain in ...poultry. ALV consists of 11 subgroups, A–K, among which ALV-K is an emerging subgroup that has become prevalent in the past 10 years. Most ALV-K isolates showed weak replication ability and pathogenicity. In this study, the weak replication ability of ALV-K was explored from the perspective of the interaction between ALV-K gp85 and the Tva receptor.
Methods
Fourteen soluble recombinant ALV-A/K gp85 chimeric proteins were constructed by substituting the sequence difference regions (hr1, hr2 and vr3) of the ALV-A gp85 protein with the skeleton ALV-K gp85 protein for co-IP and competitive blocking tests.
Results
The binding capacity of ALV-K gp85 to Tva was significantly weaker than that of ALV-A gp85 (P < 0.05) and the key amino acid sites 199–205, 269, 319, 321 and 324 of ALV-K env contributed to the weaker replication capacity of ALV-K than ALV-A.
Conclusions
This is the first study to reveal the molecular factors of the weak replication ability of ALV-K from the perspective of the interaction of ALV-K gp85 to Tva, providing a basis for further elucidation of the infection mechanism of ALV-K.
Polylactide (PLA) is one of the most attractive biodegradable polymers owing to advantages such as high mechanical properties, biocompatibility and renewable raw material. However, wide applications ...of PLA are hindered by its inherent brittleness. In this work, glycidyl methacrylate (GMA)-functionalized core-shell starch-based nanoparticles (GMA-CSS) were prepared via soap-free emulsion polymerization and melt-blended with PLA. The combination of GMA and core-shell structure imparted the PLA with superior toughness. Specifically, with addition of 10 wt% GMA-CSS, the elongation at break of the PLA was improved to 449%, which was 63 times higher than that of neat PLA. Besides, the calculated toughness of PLA/GMA–CSS–10 blends was as high as 130.71 MJ/m3, which was 54 times higher than that of neat PLA. The toughening mechanism was revealed by TEM, SEM and DMA results. We envision this work establishes an efficient yet novel toughening strategy to prepare high-performance PLA and will promote the wide application in agriculture field of PLA.
•A novel GMA-functionalized core-shell starch-based nanoparticle (GMA-CSS) was prepared.•The toughness of PLA was increased significantly.•The interfacial strength of PLA/GMA-CSS was greatly improved.
A synthetic study including model, ground observation, sounding profiles, and satellite retrievals was applied to investigate the interannual variations of biomass burning from Peninsular Southeast ...Asia (PSEA) in terms of its emission, transport and impacts over the local and downwind areas. Study period ranged from 2006 to 2010 during March and April which was the PSEA biomass burning season. Analysis of geopotential height indicated that PSEA biomass burning plume was rapidly uplifted by the lee side trough over Yungui Plateau into free troposphere which favors the long-range transport down to East Asia (EA). Lightning data from NASA demonstrated deep convection was weak over PSEA during the burning season and it may only play a minor role for uplifting. Although PSEA biomass burning had large annual variation such as the emission in 2010 was 65% higher than that in 2008, its impact at near surface layer for CO, O3 and PM2.5 within 0–1 km height had less variability since most of the plume was uplifted into free troposphere. At lower part of free troposphere within 1 km–3 km however, impact of PSEA biomass burning at downwind areas showed consistent annual variations with the emission changes. Sounding observations demonstrated PSEA biomass burning may have almost no impact on the near surface layer O3 over Taiwan but contributed more than 30% of O3 at free troposphere within 1–6 km height during massive burning events. PSEA biomass burning also significantly affected aerosol optical depth (AOD) over EA, with the contributions ranged from 0.1 to 0.3 (25%–45% in total AOD) in 2008 to 0.2–0.6 (50%–70% in total AOD) in 2010. Our analysis indicated that although PSEA biomass burning may have relatively stable impact on air quality over EA from year to year, it will cause significant disturbance to the free troposphere over EA for both atmospheric chemistry and radiative forcing budget.
•Upper and lower limit of PSEA biomass burning impact and its interannual variation are examined.•Uplift of biomass burning is examined and lee side trough play major role instead of deep convection.•Biomass burning may have little impact in PBL but contribute 30% to free troposphere O3 at Taiwan.
Triangular silver nanoprisms were synthesized by stepwise reduction of silver nitrate with sodium borohydride (NaBH4) and trisodium citrate. In this approach, first small spherical silver ...nanoparticles were prepared by the rapid reduction of the precursor with NaBH4 at ice-bath temperature. After being heated to 70 °C, further reduction of the precursor contributed to the formation of additional small spherical silver nanoparticles attributed to the catalysis effect of the silver particles formed at the low temperature. The residual precursor after the formation of the small spherical silver nanoparticles is necessary to promote the dissolution of the small nanoparticles and their transformation into the triangular nanoprisms. After consumption of most of the precursor, the nanoprisms became more uniform in shape and size driven by the Ostwald ripening. The triangular nanoprisms prepared by such an approach are expected to be potentially useful in biolabeling since the citrate ligand on the nanoprism surface is ready to be replaced by biomolecules.
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