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In this study, MgAl-V2O74- LDHs/(poly(ethyleneimine)(PEI)/MXene)n composite films were synthesized via (i) in-situ hydrothermal growth of Mg-Al layered double hydroxides (LDHs) on AZ31 alloy followed by vanadate intercalation reactions, and (ii) the as-prepared MgAl-V2O74- LDHs film was covered by layer-by-layer assembly using (PEI/MXene)n, where n=5, 10, and 20. Film characterization revealed that the outer layers (PEI/MXene) were assembled on the surface by electrostatic interaction and provided a good coverage of LDHs nanosheets. But, microcracks appeared gradually on the surface and destroyed the film integrity with increasing number of PEI/MXene layers. The corrosion tests indicated that the MgAl-V2O74- LDHs/(PEI/MXene)10 composite films provided a better corrosion protection ability than that of n=5 and 20. The outer layers (PEI/MXene) had a corrosion inhibition protective effect on MgAl-V2O74- LDHs film. This work opened a new perspective of the MXene materials for anticorrosion application via a layer-by-layer assembly method.

A novel sandwich-like structure material was exploited for the fabrication of an effective corrosion resistance system. An environmentally friendly composite material was synthesized by installing 8-hydroxyquinoline (8-HQ) on the surface of graphene oxide (GO). In order to prevent leakage of corrosion inhibitor 8-HQ, GO/8-HQ was modified by polydopamine (PDA), denoted as GO/8-HQ/PDA. A sandwich-like structure (GO/8-HQ/PDA) enables long-term stable storage of corrosion inhibitor in the protective matrix. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were utilized to verify the sandwich-like structure of GO/8-HQ/PDA. The electrochemical tests in a 3.5 wt% NaCl solution showed that the addition of well-dispersed GO/8-HQ/PDA into epoxy system (GO/8-HQ/PDA-EP) remarkably improved corrosion protection of AZ31b magnesium alloy compared with pure epoxy (EP) coating. The sandwich structure protects the activity and structural integrity of the corrosion inhibitor (8-HQ). The corrosion inhibitor (8-HQ) of the GO/8-HQ/PDA sandwich structure cuts off the ion exchange between the metal alloy and the electrolyte solution, which hinders the electrochemical corrosion of the metal. A possible corrosion resistance mechanism of GO/8-HQ/PDA is fully discussed. This study provides feasibilities for the immobilization of corrosion inhibitors on the metal surface.

Incorporating visible light into sulfide oxidation is an emerging desirable strategy to produce versatile sulfoxides. We introduce the design and synthesis of multilayered wrinkled C3N4 nanosheets and demonstrate their unprecedented sulfide oxidation activity. Due to the wrinkled surfaces with a large SBET (208.6 m2g−1), wrinkled C3N4 nanosheets exhibit a sensitive optical response, facilitating the electron photoexcition. Layer structure confinement enables robust e−-h+ interactions and valid photoexcited excitons formation, allowing rapid 1O2 reactive species production. Integrating the sensitive optical response with robust e−-h+ interactions, photoexcited electrons and excitons are jointly produced, giving large yields of ⋅O2− and 1O2 reactive species that are conductive to O2− and 1O2 cocatalysis with an activity that is up to 33-fold that of bulk C3N4. In the cocatalysis mechanism, both O2− and 1O2, can produce peroxysulfoxide intermediates, resulting in target sulfoxides. This is the first report on sulfide oxidation via O2− and 1O2 cocatalysis and a promising study on catalyst exploitation for high-efficiency and high-selectivity production process.

Constructing the film with a green corrosion inhibitor is the key to metal corrosion protection. This study reports an environmentally friendly graphene oxide (GO) and carboxymethyl cellulose (CMC) composite films (CMC@GO) with enhanced corrosion protection performance. The CMC@GO composite film was grown on AZ31 magnesium alloy by the layer-by-layer (LbL) assembly method. Fourier transform infrared (FT-IR) spectroscopy and the solid-state NMR Spectrometer reveal the successful modification of CMC on the surface of GO nanosheets. The chemical states and the surface morphology of the CMC@GO composite film were obtained from X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The electrochemical measurements and equivalent circuit fitting results demonstrate that the film containing GO composites has higher corrosion resistance than the film of undoped GO. The CMC@GO composite film exerted the corrosion inhibition effect of GO, owing to the synergistic protective effect of GO and CMC.

This study aimed to compare the occlusal morphology and fracture behavior of lithium disilicate ceramic dental crowns on 12 human participants' premolar #45 designed by a knowledge-based AI (CEREC, biogeneric individual function, BI) and different human personnel (experienced technician, TD, and trained dental students, AD) using CAD software. Digital datasets of crown design were best-fit aligned with the original teeth to evaluate profile and volume discrepancies of the occlusal morphology, and difference in the functional cuspal angle. Milled and sintered lithium disilicate crowns were resin-luted to 3D-printed dental casts and were subjected to axial load-to-fracture test. The fracture loads and failure modes were recorded and examined. Repeated measures ANOVA with LSD post-hoc test, Kruskal-Wallis test, Pearson's correlation coefficient, paired t-test, and chi-square exact test were used for statistical analyses (α = 0.05). BI-generated crowns showed the highest occlusal profile discrepancy (0.3677 ± 0.0388 mm), whereas human-CAD designed crowns showed higher conformity to the original teeth (0.3254 ± 0.0515 mm for TD, 0.3571 ± 0.0820 for AD; z-difference method; p 0.001). Cusp angle values were significantly different in all groups except BI and TD (54.76 ± 3.81° for the original teeth, 70.84 ± 4.31° for BI, 67.45 ± 5.30° for TD, and 62.30 ± 7.92° for AD; p 0.001). Although all three groups of crown designs could achieve clinically acceptable fracture resistance (1556.09 ± 525.68 N for BI, 1486.00 ± 520.08 N for TD, 1425.77 ± 433.34 for AD; p = 0.505) such that no significant difference in fracture strength was found, most crowns presented catastrophic bulk fracture that was not clinically restorable because of the substrate fracture. Group BI had a significantly higher percentage of restorable substrate damage than TD (p = 0.014) and AD (p 0.001). In conclusion, in designing lithium disilicate dental crown, CAD design with human may be better than knowledge-based AI.

During the COVID-19 lockdown, ambient ozone levels are widely reported to show much smaller decreases or even dramatical increases under substantially reduced precursor NOx levels, yet changes in ambient precursor volatile organic compounds (VOCs) have been scarcely reported during the COVID-19 lockdown, which is an opportunity to examine the impacts of dramatically changing anthropogenic emissions on ambient VOC levels in megacities where ozone formation is largely VOC-limited. In this study, ambient VOCs were monitored online at an urban site in Guangzhou in the Pearl River Delta region before, during, and after the COVID-19 lockdown. The average total mixing ratios of VOCs became 19.1% lower during the lockdown than before, and those of alkanes, alkenes and aromatics decreased by 19.0%, 24.8% and 38.2%, respectively. The levels of light alkanes (C6) decreased by only 13.0%, while those of higher alkanes (C ≥ 6) decreased by 67.8% during the lockdown. Disappeared peak VOC levels in morning rush hours and the drop in toluene to benzene ratios during the lockdown suggested significant reductions in vehicle exhaust and industrial solvent emissions. Source apportioning by positive matrix factorization model revealed that reductions in industrial emissions, diesel exhaust (on-road diesel vehicles and off-road diesel engines) and gasoline-related emissions could account for 48.9%, 42.2% and 8.8%, respectively, of the decreased VOC levels during the lockdown. Moreover, the reduction in industrial emissions could explain 56.0% and 70.0% of the reductions in ambient levels of reactive alkenes and aromatics, respectively. An average increase in O

Worldwide, non-alcoholic fatty liver disease (NAFLD) is a common chronic liver disease closely associated with obesity, diabetes and other metabolic diseases. Shenling Baizhu powder (SLBZP), a formulation of a variety of natural medicinal plants, has hepatoprotective properties and clinical efficacy in treating non-infectious intestinal disease. SLBZP has improved NAFLD symptoms; however, its mechanism of action is unknown.We established an NAFLD model in rats given a high-fat diet (HFD), administered different interventions and measured serum biochemical indices and inflammatory factors. Liver tissues were stained with hematoxylin and eosin (HE) and oil red O, and colon tissues were analyzed by immunohistochemistry. The expression profiles of liver TLR4 pathway related protein was confirmed by western blotting. Changes in intestinal microbiota composition were analyzed using a 16S rDNA sequencing technique.Of note, SLBZP effectively reduced body weight in HFD-fed rats (p 0.05). Serum biochemical analysis indicated that SLBZP decreased the serum level of total cholesterol (TC) and improved liver function. Additionally, SLBZP decreased the serum level of endotoxin, tumor necrosis factor α (TNF-α), interleukin-1β (IL-β) (p 0.05), and decreased the expression of TLR4 pathway related protein. Pathological examination showed that SLBZP alleviates hepatic steatosis and repairs colon mucosa. Microbiome analysis revealed that SLBZP improved the abundance of intestinal microbiota. In taxonomy-based analysis, compared with control rats, SLBZP-treated rats showed obvious changes in intestinal microbiota composition. Moreover, SLBZP increased the relative abundance of short-chain fatty acid (SCFA)-producing bacteria, including Bifidobacterium and Anaerostipes.Taken together, these results suggest that the effects of SLBZP against NAFLD may be related to the increased abundance of beneficial gut microbiota and decreased levels of LPS in the portal vein.

The paper compares HydroChina’s involvement in Adama Wind Farm in Ethiopia as a case of South-South technology transfer to that of Vergnet, a French firm involved in the construction and financing of Ashegoda Wind Farm, as a case of North-South technology transfer. The impact of technology transfer is evaluated along four dimensions: capital goods and equipment, direct skill transfer, indirect skill transfer, and knowledge and expertise. In recent years, rise of south-south technology transfer led by Chinese-financed overseas renewable energy projects in developing countries has rekindled debate on motivations and impacts of China’s increasing engagements. However, the literature on impact of technology transfer in renewable energy is scarce and non-comparative in nature. This paper aims to fill in the gap. Through interviews with key stakeholders and detailed analysis of the negotiation and construction processes in both projects, the research shows although HydroChina shared a higher level of knowledge and expertise to local engineers and university scholars during the construction phase, Vergnet formed stronger long-term skill transfer linkages with local university students and employed a larger share of local workers than HydroChina. It is crucial to note the research presented here shows that host government, rather than donor country, has considerable capacity and can play a vital role in negotiating and maximizing technology transfer. In fact, the host government’s expectations and demands contributed to the variations in technology transfer patterns. The paper concludes with a discussion of potential opportunities and challenges, and policy recommendations to facilitate international technology transfer.

Carbonyls play a vital role in atmospheric photochemistry. Vehicle emission is among most important primary emission sources of carbonyls in urban areas, yet knowledge is quite scarce about real-world emissions of carbonyls with the changing on-road vehicle fleets. In this study, emissions of carbonyls were characterized based on tests in a busy urban tunnel in south China. Emission factor (EF) of carbonyls was measured to be 9.89 ± 0.65 mg km−1 on average, in which formaldehyde alone shared 53.1% with an EF of 5.25 ± 0.35 mg km−1, followed by acetaldehyde with an EF of 1.47 ± 0.13 mg km−1. Glyoxal and methylglyoxal showed identical EFs of 0.18 ± 0.02 mg km−1. Multiple linear regression retrieved total carbonyl EFs of 5.68, 47.71 and 35.09 mg km−1 and ozone formation potentials (OFPs) of 38.4, 329.3, and 242.4 mg km−1 for gasoline, diesel and liquefied petroleum gas vehicles (LPGVs), respectively. The unexpectedly high carbonyl emissions from LPGVs were largely attributed to the lack of after-treatment systems or the inefficiency of the after-treatment systems. Among vehicle-emitted non-methane hydrocarbons and carbonyls, carbonyls could contribute ~20% of the total OFPs while they only accounted for 7.1% of the total mass.

Yttrium-doped Mg-Al layered double hydroxide films (MgAlY-LDHs) were firstly fabricated by a hydrothermal method on anodized AZ31 and Mg-Y alloys. The structure, morphology, and composition of MgAlY-LDHs were characterized by X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), X-ray fluorescence spectrometry (XRF), backscattered electron spectrometer (BSE), field-emission scanning electronic microscope (FE-SEM), energy dispersive spectrometry (EDS) and glow discharge optical emission spectroscopy (GDOES), respectively. The electrochemical behavior was investigated using polarization curves, electrochemical impedance spectroscopy (EIS), and immersion tests. The results indicated that the Y ions can be successfully intercalated in the MgAl-LDH lamella by isomorphous replacement, which can enhance corrosion protective performance and possess the self-healing ability of coatings. Furthermore, the in-situ growth of ternary LDHs film on high-strength Mg-rare earth (RE) alloys demonstrated the considerable potential of anti-corrosion protection for industrial application. The schematic representation of the growth mechanism and electrochemical behavior of MgAlY-LDHs nanosheet was put forward finally.

This study demonstrated a dye-sensitized TiO 2 -polyoxometalate system (denoted TiO 2 -(PW 12 -TH) 8 , where PW 12 = PW 12 O 40 3− and TH = thionine) for selective oxidation of alcohols under visible light. The results showed that various substituted alcohols were transformed into their corresponding aldehydes with high selectivity. Due to more efficient electrons transfer, large surface area, and enhanced visible light absorption, the photocatalytic activity of TiO 2 -(PW 12 -TH) 8 was superior to any other dye-sensitized system reported to date. The response in the photocurrent-time curves over several on/off cycles of intermittent irradiation showed good reproducibility. The photocurrent response of TiO 2 -(PW 12 -TH) 8 was much higher than that of TiO 2 /TH (physical mixture of TiO 2 and TH), SiO 2 -(PW 12 -TH) 8 or P25-(PW 12 -TH) 8 (P25 = Degussa P25), attributed to the more efficient transfer and longer lifetime of photoexcited electrons. This photocatalytic process confirmed that efficient electron transfer during photocatalytic oxidation plays a vital role in determining the reaction conversion and obtaining good selectivity. Electron paramagnetic resonance (EPR) spectra and radical scavenging experiments proved that superoxide radicals and electrons were the main reactive species in the proposed system, the absence of hydroxyl radicals and holes is demonstrated to be the key of high reaction selectivity.

The preparation of excellent anti-corrosion coatings is necessary for practical large-scale applications. In this study, a micro-arc oxidation (MAO) coating was prepared on the AZ31 magnesium alloy in advance. Then, on the basis of the MAO coating, the graphene oxide (GO)/MgAl-layered double hydroxide (MgAl-LDH) composite was prepared by hydrothermal chemical transformation in pure GO solution with the mixed oxide of aluminum and magnesium in the MAO coating as the endogenous cation, without introducing any kind of salts. The chemical states, structural composition and morphology of the GO/LDH-MAO coating were confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The potentiodynamic polarization revealed that 0.1 GO/LDH-MAO coating (3.89 × 10−9 A/cm2) is more resistant to corrosion than MAO coating (9.89 × 10−6 A/cm2) in 3.5 wt% NaCl solution. The organic combination of Mg Al LDH and GO can obviously enhance the corrosion protection ability of the coating. This research explored in detail the possible corrosion protection mechanisms regarding GO/LDH-MAO coatings, which supplied the feasibility for enhancing the anti-corrosion performance of MAO coating.

MXenes, a novel two-dimensional (2D) material of Ti3C2, present wide applications in energy-related fields. However, a mass of sedimentary multilayer Ti3C2 was discarded and non-recyclable due to incomplete exfoliation in the preparation of single layer Ti3C2. In this work, a composite structure, mixing MXenes/magnesium aluminum-layered double hydroxides (MXenes/MgAl-LDHs) with Y(OH)3, was synthesized in-situ as a smart coating on Mg alloy AZ31 via (i) exfoliating those multilayer Ti3C2 to few-layer MXenes (FLMs), and (ii) adding Y(NO3)3 to FLMs solution for a one-step hydrothermal treatment. Results show the electronegative mainboard of MXenes can effectively absorb cations in the reaction solution, and promote growth of MgAl-LDHs and Y(OH)3 on its surface. Moreover, MgAl-LDHs being the intermediate connector facilitate growth of MXenes upon the surface of Mg alloy AZ31. The corrosion tests indicated that the composite coating modified with yttrium had an excellent anticorrosion performance (Ecorr = −0.36 VSCE, Icorr = 9.12 × 10−9 A cm−2) and self-healing ability. Further, the formation and corrosion mechanism of composite coatings were finally proposed.

The unique porous characteristic of metal-organic frameworks (MOFs) has been attracting significant attention for gas storage, catalysis and drug delivery. However, the studies regarding loading inhibitors into MOFs for metallic anti-corrosion applications are scarcely reported. Herein, a strategy based on encapsulating corrosion inhibitors into MOFs matrix has been developed, and their corrosion process and mechanism have been fully studied. Specifically, an environmentally friendly green corrosion inhibitor, zinc gluconate (ZnG), was selected as a metal resource for the preparation of ZIF-8 and then inherently intercalated into the porous ZIF-8. Various characterizations were carried out to confirm that zinc gluconate was successfully loaded into the ZIF-8 matrix. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves show the evidence that the prepared ZnG@ZIF-8/EP coatings display good metallic anti-corrosion performances. The probably protecting mechanism of ZnG@ZIF/EP coatings for magnesium alloy surface was thoroughly discussed.

The Chinese wind power industry has experienced a period of rapid development for the past 10 years, but the utilization hours of wind power equipment started to drop abruptly since 2011, and the curtailment problem has become worse year by year. Throughout the year of 2012, Chinese wind power sector lost about 20 million MWh in electricity from wind curtailment. For regions that experienced the most serious curtailment problems in China, the percentage of wind power installation and consumption have been relatively low compared to other countries. Although previous studies have so far proposed many explanations, the main characteristics and most critical factors of the curtailment problems are not very clear. To fill this gap, we have performed a detailed study on the wind power curtailment problem from the perspective of the whole of China by analyzing a large amount of wind power curtailment data and the characteristics of wind power curtailment in China have been addressed from temporal-spatial perspective. According to the characteristics and curtailment data, we propose that the curtailment is rooted in unreasonable power source structure and long chain power grid network structure. Based on the above two reasons, this study has proposed further improvement measures in terms of the power source structure, consumption structure, the grid structure. Relative market and policy suggestions are proposed to provide guidance for the further development of wind power.

Statement of problem Although newly developed photoinitiators can make up for the limitations of camphorquinone, their absorption spectra are different. However, little attention has been paid to the compatibility of available wavelength spectra of light-polymerization units (LPUs) and photoinitiators within resin cements. Purpose The purpose of this in vitro study was to evaluate the effect of monowave and polywave light-emitting diode (LED) units on the adhesion of dual-polymerizing self-adhesive resin cements to monolithic zirconia. Material and methods Monowave LPUs and polywave LPUs were chosen to polymerize 2 dual-polymerizing self-adhesive resin cements. Ninety-six zirconia disks were randomly divided into 4 groups as different combinations of LPUs and resin cements, namely ES-U200, BS-U200, ES-SC, and BS-SC. Resin cements were adhered to zirconia disks, and the microshear bond strength (μSBS) test was conducted after 24 hours of H2O storage (24 h) and 10 000 thermocycles (10k/TC). Failure modes were examined by stereomicroscopy and scanning electron microscopy (SEM). The degree of conversion (DC) was tested both immediately and 24 hours later. In statistical analyses, 2-way ANOVA and the Tukey honestly significant difference post hoc test were performed for μSBS and DC results, and chi-square test was performed for failure mode analysis (α=.05 for all tests). Results The 2-way ANOVA demonstrated that different combinations of LPUs and resin cements, as well as different artificial aging levels, significantly influenced microshear bond strength values (P Conclusions Within the limitation of this in vitro study, the emission spectra of LED units significantly influenced the bond strengths, DC, and failure mode of dual-polymerizing self-adhesive resin cements to zirconia at both immediate and artificial aging levels. The LPU should provide light energy to match the absorption wavelengths of photoinitiators in the resin cements.