A general route via formamide condensation to prepare atomically dispersed metal-nitrogen-carbon electrocatalysts for energy technologies

Single-atom electrocatalysts (SAECs) have gained tremendous attention due to their unique active sites and strong metal–substrate interactions. However, the current synthesis of SAECs mostly relies on costly precursors and rigid synthetic conditions and often results in very low content of single-site metal atoms. Herein, we report an efficient synthesis method to prepare metal–nitrogen–carbon SAECs based on formamide condensation and carbonization, featuring a cost-effective general methodology for the mass production of SAECs with high loading of atomically dispersed metal sites. The products with metal inclusion were termed as formamide-converted metal–nitrogen–carbon (shortened as f-MNC) materials. Seven types of single-metallic f-MNC (Fe, Co, Ni, Mn, Zn, Mo and Ir), two bi-metallic (ZnFe and ZnCo) and one tri-metallic (ZnFeCo) SAECs were synthesized to demonstrate the generality of the methodology developed. Remarkably, these f-MNC SAECs can be coated onto various supports with an ultrathin layer as pyrolysis-free electrocatalysts, among which the carbon nanotube-supported f-FeNC and f-NiNC SAECs showed high performance for the O2 reduction reaction (ORR) and the CO2 reduction reaction (CO2RR), respectively. Furthermore, the pyrolysis products of supported f-MNC can still render isolated metallic sites with excellent activity, as exemplified by the bi-metallic f-FeCoNC SAEC, which exhibited outstanding ORR performance in both alkaline and acid electrolytes by delivering ∼70 and ∼20 mV higher half-wave potentials than that of commercial 20 wt% Pt/C, respectively. This work offers a feasible approach to design and manufacture SAECs with tuneable atomic metal components and high density of single-site metal loading, and thus may accelerate the deployment of SAECs for various energy technology applications

Task effect on L2 rhythm production by Cantonese learners of Portuguese

ABSTRACT This study examines L2 Portuguese speech produced by eight native Cantonese speakers from Macao, China. The aims of this study are to investigate (1) whether the speech rhythm in L2 Portuguese is more source-like (more similar to Cantonese) or more target-like (more similar to Portuguese), and (2) whether L2 speech rhythm differs across three different tasks: a reading task, a retelling task, and an interpreting task. Seven rhythm metrics, i.e., %V, ΔC, ΔV, VarcoC, VarcoV, rPVI_C, and nPVI_V, were adopted for comparison and investigation. The results showed that L2 Portuguese rhythm produced by Cantonese speakers differed from L1 Portuguese speakers’ rhythm. R-deletion and vowel epenthesis were the reasons for the variabilities and instabilities of L2 Portuguese production by Cantonese learners, as they affect the duration and the number of vowel intervals and consonantal intervals. Moreover, in Cantonese learners’ L2 Portuguese production, the semi-spontaneous tasks (retelling and interpreting) presented a significant difference from the reading task. The driving force for such a difference was the cognitive load behind the tasks.</div

Comparison of different pretreatment methods on phosphorus release and recovery as struvite from excess sludge

Recovering phosphorus (P) from excess sludge of wastewater treatment plants (WWTPs) has attracted considerable attention. An efficient P release method is undoubtedly critical for a satisfactory recovery performance. In this study, the effectiveness of three sludge pretreatment methods, i.e. anaerobic digestion (AD), EDTA-anaerobic digestion (EA) and ultrasound combined with EA (U-EA), on P release and struvite recovery from excess sludge was investigated. The results showed that different pretreatment methods resulted in the different characteristics of P release and recovery. For P release, the highest P release rate (57.14% of sludge total phosphorus, TP) was achieved by U-EA pretreatment, followed by EA and AD. Furthermore, U-EA was beneficial for sludge disintegration and reduction, by which the mixed liquor suspended solids (MLVSS) reduction rate reached 42.00% at a specific energy of 110,000 kJ/kg TS. For the P recovery (in the form of struvite), there was only a little difference in the optimal conditions and P recovery rate (89.29–94.49% of TP in the supernatant). AD pretreatment was beneficial for the purity of products and achieved the highest struvite purity (85.14%), followed by EA (80.95%) and U-EA (77.56%). In summary, the highest recovery rate of TP from excess sludge (53.50% of sludge TP) and struvite yield (26.10 mg/gSS) was obtained by U-EA.</p

Efficacy of fractional carbon dioxide laser therapy for burn scars: a meta-analysis

Background: The present study evaluates the effectiveness of fractional carbon dioxide (CO2) laser for the treatment of burn scars. Method: Literature search was conducted in electronic databases and studies were selected by following pre-determined eligibility criteria. Random effect meta-analyses were performed to achieve the effect size of the changes (mean difference (MD) between post-treatment and pretreatment values) in selected scar assessment scale scores and other important outcome measures. Results: 14 studies were included. Treatment of burn scars with fractional CO2 laser significantly improved Vancouver Scar Scale (MD −3.01 [95% confidence interval (CI) −3.79, −2.22]; p ˂ .00001), Patient and Observer Scar Assessment Scale (POSAS)– Patient (MD −14.38 [95% CI −17.62, −11.13]; p ˂ .00001, POSAS – Observer (MD −8.81 [9% CI −11.60, −6.02]; p ˂ .00001 and Scar Assessment Scale (MD 1.64 [95% CI 0.49, 2.78]; p = .005) scores especially with regards to pigmentation, vascularity, pliability, and height of scar. Pain and pruritis also improved with this treatment. Scar thickness measured with ultrasonography decreased non-significantly (MD −0.48 [95% CI −1.04, 0.09]; p = .1) whereas cutometer measures, R0 (scar firmness) and R2 (scar elasticity) did not change meaningfully. Conclusion: Fractional CO2 laser therapy is a valuable tool for the treatment of burn scars which has potential for reducing scar severity.</p

Self-tapping screws as reinforcement on single-dowel connections with artificial cracks

Self-tapping screws have the potential to reinforce timber elements. However, their application is restricted due to a lack of design guidance. Compared with fully threaded screws, partially threaded screws with a shorter thread length have less drive-in torque, enabling easier installation. This study showed that partially threaded screws are as effective as fully threaded screws in enhancing the mechanical properties of single-dowel timber connections with artificial cracks. A total of 120 embedment tests were conducted, using screws with two thread lengths (33% and 100%) on single-dowel connections. The connections were also prepared with three different widths of artificial crack to represent splitting of the wood due to moisture variation. The results showed that the screws with 33% thread length were as effective as screws with 100% thread length at reinforcing the connections when the crack width was 1.5?mm or 4.5?mm. However, for a crack width of 6?mm, the embedment strength of the connections reinforced with screws with a 33% thread length was significantly lower (about 15.7%) than the connections reinforced with screws with a 100% thread length. This research demonstrates the potential of using self-tapping screws with a partial thread to reinforce existing timber elements with cracks.</p

The Lewis Base-Catalyzed Silylation of AlcoholsA Mechanistic Analysis

Reaction rates for the base-catalyzed silylation of primary, secondary, and tertiary alcohols depend strongly on the choice of solvent and catalyst. The reactions are significantly faster in Lewis basic solvents such as dimethylformamide (DMF) compared with those in chloroform or dichloromethane (DCM). In DMF as the solvent, the reaction half-lives for the conversion of structurally similar primary, secondary, and tertiary alcohols vary in the ratio 404345:20232:1. The effects of added Lewis base catalysts such as 4-<i>N</i>,<i>N</i>-dimethylaminopyridine (DMAP) or 4-pyrrolidinopyridine (PPY) are much larger in apolar solvents than in DMF. The presence of an auxiliary base such as triethylamine is required in order to drive the reaction to full conversion

Aluminated Derivatives of Porous Magadiite Heterostructures for Acid-Catalyzed <i>tert</i>-Butylation of Catechol

Novel porous magadiite/Al-magadiite heterostructures (PMH/PAMH) and aluminated derivatives of PMH (<i>x</i>Al-PMH, <i>x</i> = Al/Si in feeding) were fabricated upon two-dimensional interlayer cosurfactant-directing TEOS hydrolysis–condensation–polymerization from synthetic Na-magadiite/Na-[Al]­magadiite and postgrafting of Al into the interlayer silica framework of PMH from NaAlO₂ precursor, respectively. Characterization studies indicate that PMH and PAMH possess high surface area (SA), high thermal stability, and unique supermicro–mesoporous structure upon effective assembly of interlayer mesostructured silica and clay layers but weak Lewis acidity. The <i>x</i>Al-PMH (<i>x</i> = 0.2, 0.4) samples show successful incorporation of Al into interlayer mesostructure of PMH mainly in tetra-coordinated form, leading to greatly increased Lewis acidity and newly created Brønsted acidity together with well-kept layered supermicro-mesoporous porosity and reduced SA (>280 m²/g) while 0.6Al-PMH shows collapsed layers. 0.4Al-PMH exhibits the highest liquid-phase Friedel–Crafts <i>tert</i>-butylation activity of catechol with 93.4% conversion and 80.4% 4-<i>tert</i>-butylcatechol selectivity due to the strongest synergy between the surface acidity and supermicro–mesostructure

Additional file 7 of Establishment and validation of a predictive model of preeclampsia based on transcriptional signatures of 43 genes in decidua basalis and peripheral blood

Additional file 7: Data 6. The raw clinical data of GSE8530

Additional file 3 of Establishment and validation of a predictive model of preeclampsia based on transcriptional signatures of 43 genes in decidua basalis and peripheral blood

Additional file 3: Data 2. MEblue Go term

Additional file 6 of Establishment and validation of a predictive model of preeclampsia based on transcriptional signatures of 43 genes in decidua basalis and peripheral blood

Additional file 6: Data 5. The raw clinical data of GSE8620