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Selenium concentration of one spot urine sample cannot reflect selenium status during whole pregnancy. Studies on variations of urinary selenium concentration at different stages of pregnancy are limited. To assess variations of urinary selenium concentrations during three trimesters of pregnancy and to explore the influencing factors. This study included 2613 pregnant women from a birth cohort study (Wuhan, China) enrolled between October 2014 and October 2016. Selenium concentrations of urine samples collected at three trimesters were measured. We used a generalized linear mixed effects model to observe the changes in urinary selenium concentration during pregnancy and its influencing factors. The median value (range) of gestational weeks at urine sample collection was 11 (9−14), 24 (15−27), and 34 (28−41) respectively. Urine selenium concentration varied across trimesters (geometric mean: 16.34, 17.65 and 18.83 μg/g creatinine, respectively), with an upward trend (β = −0.145, 95%CI: −0.164, −0.126) (β = −0.066, 95%CI: −0.083, −0.048). The concentrations of urinary selenium increased with the increasing of educational level [ β (95%CI): ≤ 9 years = −0.105 (−0.163, −0.047); 10–12 years = −0.086(−0.126, −0.047); > 12 years = reference]. Pregnant women who rarely or only took multivitamins in the first trimester [ β (95% CI): rarely = −0.076 (−0.144, −0.007); only in the first three months of pregnancy = −0.104 (−0.170, −0.038); always = reference], or were not exposed to passive smoking during pregnancy（ β = −0.093 , 95% CI: − 0.173, − 0.014), or exercised three to four days per week for the first three months before delivery（ β = −0.074 , 95% CI: − 0.140, − 0.008) had lower urinary selenium concentrations. Pregnant women who took calcium supplements after the third month of pregnancy had higher urinary selenium levels（ β = 0.114, 95% CI: 0.059, 0.169). Urine selenium concentrations of pregnant women showed an upward trend across trimesters. Educational level, calcium or multivitamin supplementation, passive smoking, and physical exercise might impact urine selenium levels. [ABSTRACT FROM AUTHOR]

Water electrolysis is the most clean and high-efficiency technology for production of hydrogen, an ultimate clean energy in future. Highly efficient non-noble electrocatalysts for hydrogen evolution reaction (HER) are desirable for large scale production of hydrogen by water electrolysis. Especially, exposing as many active sites as possible is a vital way to improve activities of the catalysts. Herein, a series of new hydrangea like composite catalysts of ultrathin Mo 2 S 3 nanosheets assembled uprightly and interlacedly on N, S-dual-doped graphitic biocarbon spheres were facilely prepared. The unique structure endowed the catalysts highly exposed edge active sites and prominently high activities for HER. Especially, the optimized catalyst Mo 2 S 3 /NSCS-50 exhibited as low as 106 mV of overpotential at 10 mA/cm2 (denoted as ƞ 10). The catalyst also showed low Tafel slope of 53 mV/dec, low electron transfer resistance of 34 Ω and high stability evidenced by the result that the current density only attenuated 11.7% after 10 h i-t test. The catalyst has shown broad prospect for commercial application in water electrolysis. • New Mo 2 S 3 ultrathin nanosheets based catalysts have been fabricated for HER. • Mo 2 S 3 ultrathin nanosheets assembled uprightly and interlacedly on carbon spheres. • Hydrangea like composite catalysts were formed based on the above assembly. • The unique structure can provide plenty of exposed edge active sites. • The catalysts exhibited prominent activities and high stabilities for HER. [ABSTRACT FROM AUTHOR]

• A novel communication-efficient federated recommendation model is proposed. • A many-objective evolutionary method is used to achieve parameter reduction. • Recommended performances and communication cost are optimized simultaneously. The federated recommendation system (FedRS), which is the application of the recommendation system (RS) in federated learning, has been creatively developed as increasing attention has been paid to user privacy protection. However, traditional federated learning consumes excessive communication time and resource, which seriously limits the development of the FedRS. To reduce the communication cost and improve the recommendation performance of FedRS, an improved many-objective federated recommendation model with a novel parameter reduction strategy is proposed in this paper. The model aims to optimize the number of parameters shared between the server and client to improve communication efficiency in the federated process. Optimal parameter selection solutions can be obtained using the many-objective evolutionary algorithm (MaOEA), which can optimize the recommendation accuracy, novelty, diversity, and communication efficiency of FedRS simultaneously. Furthermore, the reference vector guided evolutionary algorithm (RVEA) was adopted to evaluate the proposed model. Experiments were performed on two famous recommendation datasets to examine the superiority of RVEA for the evaluation. The performance results indicated that the proposed model can not only provide accurate, diverse, and novel recommendations for the client, but can also realize efficient communication. [ABSTRACT FROM AUTHOR]

Highly efficient multifunctional earth-abundant elements based electrocatalysts are key important for development of clean energy transformation technologies, such as metal-air batteries, fuel cells and water electrolysis. Herein, composite catalysts of N-doped carbon wrapping Co x P hollow spheres have been successfully prepared by pyrolysis of precursors from self-assembly of cobalt salt, terephthalic acid and PVP followed by carbonization and phosphatization in the presence of sodium hypophosphite. The resulted composites showed high specific surface areas, pore volumes and nitrogen contents, especially more than 47% of pyridinic-N. The electrocatalytic activity tests showed that the optimized Co x P-NC-420 sample exhibited superior multifunctional performances and high stabilities for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) under alkaline conditions. A low overpotential of 125/273 mV (at 10 mA cm−2) and Tafel slope of 66/81 mV dec−1 was obtained for HER and OER, respectively. As for ORR, as high as 0.860 V of half-wave potential was obtained, which is even 36 mV higher than that of Pt/C (20%). The catalyst also exhibited high practical performances on water electrolysis and Zn−air battery. Only 1.61 V of cell voltage was needed to reach 10 mA cm−2 for water electrolysis, and 1.374 V of open-circuit potential and 52 mW cm−2 of power density were obtained for Zn−air battery, which was 16 mW cm−2 higher than that of Pt/C (20%). Moreover, a highly effcient self-driven water electrolyzer has been designed with Co x P-NC-420 as both anode and cathode catalyst, powered by two-series-connected Co x P-NC-420-based Zn–air batteries. This work provides a new strategy for fabrication of non-precious multifunctional electrocatalysts. [ABSTRACT FROM AUTHOR]