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Radionuclides, such as strontium (Sr), are hazardous radioactive isotopes commonly found in nuclear waste, posing serious environmental and health risks due to their long half-lives and ability to bioaccumulate. Inspired by the electronic modification effect, this study theoretically predicts that doping can significantly enhance the adsorptive performance of MXenes for radionuclides. Specifically, we employed comprehensive first-principles simulations to investigate the impact of nitrogen (N) doping on the adsorption behavior of Ti2CT2 (T = O, F, OH) MXenes for Sr ions, focusing on surface N doping and C-site N doping as effective strategies to improve adsorption. The results confirmed that both types of N doping are beneficial for the adsorption performance of Ti2CT2, and the adsorption strengths of Ti2CT2 with surface N doping are significantly enhanced. This was analyzed and attributed to the ability of N doping to enhance the charge transfer between the Ti2CT2 surface and Sr ions, thus enhancing the adsorption properties. By elucidating the N doping mechanisms, this study is expected to provide theoretical guidance for the design of high-performance MXene materials in radionuclides remediation applications. [ABSTRACT FROM AUTHOR]

2D lamellar membranes (2DLMs) are used for efficient desalination and nanofiltration. However, weak interactions between adjacent stacked nanosheets result in susceptibility to swelling that limits practical applicability. Inspired by the super adhesion of multi-point suction cups on octopus tentacles, a 2DLM is constructed from Ti3 C2 Tx MXene supported by the macrocyclic "multi-point" molecule cucurbit[5]uril (CB5) and demonstrated for nanofiltration of methyl blue (MB) and enrichment of uranyl carbonate. Experimental results and density functional theory calculations indicate that CB5 rivets to the surface of the nanoflakes through strong stable interactions between its multiple binding sites and surface hydroxyl functional groups on MXene nanosheets. This novel 2DLM exhibits excellent nanofiltration performance (69 L m-2 h-1 bar-1 permeance with 93.6% rejection for MB) and can be recycled at least 30 times without significant degradation. The 2DLM exhibits excellent swelling resistance at high salinity, with a demonstration of selective enrichment of uranyl carbonate from artificial water and natural seawater. The results provide a new strategy for constructing highly stable 2DLMs with interlayer spacing controllable from sub-nano to nanometer scales, for size-selective sieving of molecules and ions, high-efficiency nanofiltration, and other applications.

We have systematically investigated the solution and aggregation behaviors of yttrium (Y) on symmetrically inclined tungsten (W) grain boundary (GB) Σ 5 (310)/[001] by first-principles simulation. It is found that the most stable site for Y is located on the GB plane, and the solution energy of the Y substitutional site increases with increasing the distance from the GB plane. The charge redistribution of Y atoms is positively correlated with the solution energy, i.e., the deviation of the electrons of Y atoms is beneficial to its solution in the W–GB system. Further, the segregation of multiple Y atoms in the W–GB is clearly observed, where the Y atoms preferentially occupy the GB plane substitutional sites. The alloying Y atoms at the GB plane sites can effectively strengthen the GB when the concentration is less than 3.367%. The stronger binding energy of W–Y than the binding energy of W–W in the GB region is the main factor for the strengthening of the GB. [ABSTRACT FROM AUTHOR]

Purpose: To assess eye axial length (AL), spherical equivalent (SE), astigmatic power, distance unaided visual acuity (UCVA), and their relationship in 7- and 8-year-old pupils in Kunming, Southern China. Methods: Grade I and grade II pupils underwent measurement of AL, UCVA, and refraction. The associations of AL with SE, UCVA and astigmatic power were studied. Results: Two hundred ninety one pupils enrolled with 50.2% girls. AL was 22.71 ± 0.61 mm in children with emmetropia (UCVA > 0.8, –0.50 < SE < +0.50D and astigmatism < 0.50D), it was 23.46 ± 2.42 mm in children with mild myopia (–1 ≤ SE < –0.50D and astigmatism < 0.50D), it was 23.96 ± 1.16 mm in children with myopia (SE < –1D and astigmatism < 0.50D), and it was 22.20 ± 1.16 mm in children with astigmatism (astigmatism ≥ 0.50D). AL was highly related to SE (r = 0.572, P <.0001) with the formula AL = 22.45–0.59*SE. Conclusion: In these 7- to 8-year old pupils, average AL was 22.88 ± 0.09 mm and average SE was –0.75 ± 0.13D. Astigmatic eyes demonstrated relative shorter AL while severe myopic eyes had the longest AL, although both had worse UCVA. One mm extra axial length corresponded to –1.69D extra myopia for 7- and 8-year-old pupils in Southern China. [ABSTRACT FROM AUTHOR]

Introduction: To explore the prevalence of visual impairment due to uncorrected ametropia from primary students in multi-ethnic regions of Yunnan (Southern China). Methods: Primary school students of 7 ~ 12 years old from 5 multi-ethnic regions were screened. Cycloplegic refraction and subjective trial lens visual acuity were measured in all children with distance unaided visual acuity < 20/20. Gender, ages, ethnics, and regions were assessed with analysis of difference and Odds Ratio (OR) respectively, by statistics software R. Results: Of all 24296 children, the incidence rate for visual impairment from ametropia was 19.18% (myopia accounted for 94.31%) for 7 ~ 12 years old in Yunnan primary schools in a multi-ethnic region. Myopia prevalence differed significantly among gender, ages, ethnics, and regions (P =.0003, P <.00001, P <.00001, P <.00001, respectively). Girls were more prone to have myopia (OR = 1.19, 95%, CI = 1.11–1.27) than boys; the risk of myopia increased with age: 9–10 years OR = 2.6 (95% CI = 2.62–3.2), 11–12 years OR = 6.6 (95% CI = 6–7.26). Three ethnic minorities surveyed were less prone to myopia than Han: Dai OR = 0.62 (95% CI = 0.47–0.8) Hani OR = 0.56 (95%CI = 0.41–0.76) Buyi OR = 0.50 (95% CI = 0.4–0.62). Conclusions: Myopia, not corrected by glasses, was the most frequent cause of visual impairment in Yunnan primary schools, in a muli-ethnic region. Boys, young children and certain ethnic minorities were less prone to myopia. [ABSTRACT FROM AUTHOR]