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Are there temporal trends of sperm concentration (SC) and total sperm count (TSC) in Chinese healthy males from 1981 to 2019?

Our result indicated a temporal decrease in SC and TSC among 327 373 healthy Chinese men in the recent four decades.

A review of 61 papers reported a temporal decline in SC and TSC from 1938 to 1990. This trend was later confirmed by a systematic review of 185 published papers from 1981 to 2013. However, the majority of the included individuals were from western countries. In China, whether SC and TSC have declined remains controversial.

This systematic review of published articles used data extracted from Pubmed, Science Direct, Embase, China-National-Knowledge-Infrastructure (CNKI) and Wanfang Data to assess changes in SC and TSC in China from 1981 to 2019.

A total of 111 studies including 327 373 individuals who provided semen samples from 1981 to 2019 were extracted for the present analysis. Study selection and data extraction were performed by two independent researchers Science Funding of Shaanxi Province, Science Funding of Health Department, Shaanxi Province, Fundamental Research Funds for the Central University and the Project of Independent Innovative Experiment for Postgraduates in Medicine in Xi’an Jiaotong University. The authors have no conflicts of interests to declare.

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N/A.A chemical actuator was developed taking advantage of the internal microstructure of a plant stem. Stem xylems of Cucurbita moschata were chemically modified with a pH-responsive polymer to obtain an intelligent hydraulic valve. The chemical composition of the device was based mainly on biological scaffolds combined with a minimum content of a tailor-made synthetic copolymer. A pH-sensitive hydrogel composed of a copolymer of acrylic acid was grafted on the inner surface of stem microchannels, assessing the physicochemical properties and the response of the developed actuator under different pressure and pH conditions. Variation of average microcapillary diameter in response to pH stimuli was estimated using Poiseuille’s model. This microfluidic device demonstrated the pH-responsive properties and efficient control of flux, showing its open/close transition at pH 3.25 and mechanical stability until pressures of 1.75 meters of water column (mH2O). This actuator has adequate response to open/close cycling and relevance to be evaluated as a pH-response valve of aqueous systems. This kind of actuator is a research topic of high interest with potential application to technology demands.Solar-driven highly-efficient photocatalytic reduction of CO2 into value-added fuels has been regarded as a promising strategy to assuage the current global warming and energy crisis, but developing highly product-selective, long-term stable and low-cost photocatalysts for C2 production remains a grand challenge. Herein, we demonstrate that two-dimensional β- and δ-phase Cu2S monolayers are promising photocatalysts for the reduction of CO2 into C2H5OH. The calculated potential-limiting steps for the CO2 reduction reaction (CO2RR) are less than 0.50 eV, while those for the hydrogen evolution reaction are as high as 1.53 and 0.87 eV. Most strikingly, the C-C coupling only needs to overcome an ultra-low kinetic barrier of ∼0.30 eV, half of that on the Cu surface, indicating that they can boost the C2H5OH conversion efficiency greatly. Besides, these catalysts also exhibit satisfactory band edge positions and suitable visible light absorption, rendering them ideal for the visible light driven CO2RR. check details Our work not only provides a promising photocatalyst for achieving the efficient and selective CO2RR, but also brings new opportunities for advanced sustainable C2H5OH product.A new planar carbon allotrope named net-Y with periodic four-six-eight-membered carbon rings has been synthesized in this study. In this paper, the adsorption properties of CO and CO2 on the pristine net-Y and two Fe-doped net-Y surfaces were studied using first-principles calculations. Using adsorption energy, charge analysis, adsorption distance, deformation charge density and density of states, it can be found that the adsorption of CO and CO2 on the pristine net-Y surface appears as physisorption with weak interactions. Based on this, in order to enhance the adsorption strength of CO and CO2 on the surface of net-Y, Fe-doping is performed on net-Y. The calculation results after doping show that the doping of Fe atoms at different positions can significantly improve the adsorption strength of the two gas molecules. After CO and CO2 are adsorbed on the doped net-Y surface, the adsorption energy is greatly improved compared with the pristine adsorption energy, which makes the two gas molecules form a chemical bond with the substrate. Subsequently, the results of charge density and density of states further prove that the adsorption system shows chemisorption with strong interactions. Comparing doped and pristine adsorption, after Fe doping, the adsorption of CO and CO2 is stronger, which makes it possible to use this material effectively for the adsorption and removal of CO and CO2 gases.Correction for ‘Antiviral drug design based on the opening mechanism of spike glycoprotein in SARS-CoV-2’ by Ruichao Mao et al., Phys. Chem. Chem. Phys., 2021, DOI 10.1039/d1cp01045j.Soft elastomers with their ability to integrate strain-adaptive stiffening and coloration have recently received significant research attention for application in artificial muscle and active camouflage. However, there is a lack of theoretical understanding of their complex molecular dynamics and mechanochromic coupling/decoupling. In this study, a topological dynamics model is proposed to understand the anchoring-mediated topology signature of self-assembled elastomers. Based on the constrained molecular junction model, a free-energy function is firstly formulated to describe the working principles of strain-adaptive stiffening and coloration in the self-assembled elastomer. A coupled ternary “rock-paper-scissors” model is proposed to describe the topological dynamics of self-assembly, mechanochromic coupling and mechanoresponsive stiffening of the self-assembled elastomers, in which there are three fractal geometry components in the topology network. Finally, the proposed models are verified using the experimental results reported in the literature.