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Despite increasing evidence calculating the extent of COVID learning loss, few researchers have attempted to collect and examine the evidence through meta-analysis. To fill this gap, our meta-analysis seeks to explore the existing research regarding the effects of COVID on learning in reading and mathematics. Our findings illustrate that the learning loss was real and significant compared to previous school years. Applying our rigorous inclusion criteria informed by best evidence synthesis methodology, we identified 30 eligible studies. On average, meta-regression results showed that students lost 0.21 (p =.006) standard deviations of learning during the pandemic school closures. Moderator analysis further showed none of the group comparisons (i.e., subject, grade levels, country and test-type) are statistically significant. In the final section of this article, we provide recommendations for educational policymakers to address this challenge. • A meta-analysis of high-quality research examining COVID learning loss in K-12 education settings worldwide. • An analysis of 30 studies determined that on average, students lost 0.21 standard deviations of learning overall. • We provide policy recommendations to address COVID learning loss. [ABSTRACT FROM AUTHOR]

Dynamic cerebral perfusion computed tomography (DCP-CT) is an advanced imaging technique that helps in the clinical diagnosis of cerebrovascular diseases (CVDs). However, radiation dose deposition during repeated CT scans seriously limits its clinical application. Effective DCP-CT imaging method based on low-dose protocol is needed. A regularized least-squares method with high interpretability based on voxel-level time-attenuation curve (TAC) correction (VTC) is proposed in this study for low-dose DCP-CT image reconstruction. The theory of third-order Hermite interpolation (THI) is applied to voxel-level TAC correction during dynamic images reconstruction. The peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) are used to quantitatively evaluate the proposed method in terms of imaging accuracy and noise reduction, while hemodynamic maps, including cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transition time (MTT), are calculated to validate its ability to restore hemodynamic parameters. It is proven that the proposed VTC method for low-dose DCP-CT imaging has better performance than several state-of-the-art dynamic CT imaging methods. It can be expected that the VTC method can play an important role in the promotion of the clinical application of DCP-CT for the diagnosis of CVD. [ABSTRACT FROM AUTHOR]

Urbanization and industrialization have resulted in an excessive intensity of land use, structural imbalances, and regional ecological deterioration. To achieve sustainable development, it is essential to optimize different land use types and enhance the ecosystem service value (ESV). However, previous studies rarely combined the optimization of land use quantitative structure with the simulation of land use spatial layout under the background of maximizing economic and ecological benefits at the same time, and this kind of research was rarely applied to state-level new areas. On the premise of maximizing economic and ecological benefits, this study develops an improved optimization method that integrates the non-dominated sorting genetic algorithm II (NSGA-II) with the patch generating land use simulation (PLUS) model. The approach optimizes land use while predicting ESV for a state-level new area-Liangjiang New Area (LJNA). The model operation takes into full account ecological spatial constraints, including ecological protection red line, prime farmland, and urban development land use suitability. Results show that LJNA encountered the most substantial increase in built-up land (392.31 km2) due to farmland occupation, leading to a continuous decrease in ESV (443.6 million yuan) from 2000 to 2020. Optimization results for 2030 indicate that the main difference between different scenarios is the area of forest and built-up land. Under ecological protection priority scenario, ESV will increase in 2030 but built-up land should be confined within 620 km2. We present multiple land use scenarios based on decision makers' preferences, offering important implications for the balance and optimization of land resources under different policy priorities using coupled spatiotemporal simulation-quantitative allocation model. This study provides valuable references for future land use optimization research. • An improved multi-objective land use optimization method is developed. • The method integrates the non-dominated sorting genetic algorithm II with the patch generating land use simulation model. • The method optimizes land use while predicting ESV for the Liangjiang New Area, China. • The ecological spatial constraints are developed based on ecological protection red line, prime farmland, and urban development land use suitability. • Taking into account both ecological and economic benefit, four development scenarios are set up. [ABSTRACT FROM AUTHOR]

• We propose a co-planar optical power splitter based on cascaded hybrid-core vertical directional couplers, which serves to split arbitrary ratio power of arbitrary guide modes. • We fabricate the optical power splitter using micro-fabrication facilities. • Our fabricated chip demonstrates power splitting for the E 11 , E 21 and E 12 modes between two few-mode waveguides. • The experimental device shows that optical power splitting ranges can be larger than 11.0 dB, 12.1 dB and 11.3 dB for the E 11 , E 21 and E 12 modes, respectively, over the C + L band and beyond. • The proposed optical power splitter could be used in the mode division-multiplexing systems where power splitting for arbitrary guide modes in few-mode waveguide is required in the ultra-broadband wavelength range for mode manipulating, such as mode power distribution, mode dependent loss equalization and all-optical MIMO signal processes. We propose a co-planar optical power splitter based on cascaded hybrid-core vertical directional couplers, which serves to split arbitrary ratio power of arbitrary guide modes. We fabricate the optical power splitter using micro-fabrication facilities. Our fabricated chip demonstrates power splitting for the E 11 , E 21 and E 12 modes between two few-mode waveguides. The experimental device shows that optical power splitting ranges can be larger than 11.0 dB, 12.1 dB and 11.3 dB for the E 11 , E 21 and E 12 modes, respectively, over the C + L band and beyond. The proposed optical power splitter could be used in the mode division-multiplexing systems where power splitting for arbitrary guide modes in few-mode waveguide is required in the ultra-broadband wavelength range for mode manipulating, such as mode power distribution, mode dependent loss equalization and all-optical MIMO signal processes. [ABSTRACT FROM AUTHOR]

Zeolite-tailored bimetallic Pt-Sn catalysts have been shown to be effective for propane dehydrogenation (PDH). Here, we have successfully prepared and compared two Sn-Beta-supported bimetallic PtSn catalysts (Pt/Sn-Beta (DG) and Pt/Sn-Beta (DA)), in which the Sn-Beta zeolite was prepared by a dry-gel (DG) synthesis method involving in situ Sn incorporation or a post-synthesis method involving dealumination and Sn incorporation (DA), respectively. The as-prepared Pt/Sn-Beta (DG), possessing a less fraction of extra-framework Sn species comparing to Pt/Sn-Beta (DA), shows a superior performance in terms of activity (TOF, 1.8 s-1), selectivity (99.0%) and stability (7360 min) at 550 °C using 40 kPa propane and 60 kPa nitrogen gas, reflecting one of the highest PDH performances for bimetallic Pt-Sn catalysts under similar conditions. By a combination of the state-of-the-art electron microscopy-based techniques and advanced spectroscopy techniques, we found that the proper Pt-Sn nano-alloying in Pt/Sn-Beta (DG), rather than Sn coverage on Pt species in Pt/Sn-Beta (DA) owing to the migration of excess extraframework Sn species, is essential for providing an enhanced PDH performance, as the active Pt species could be well isolated, accessed and stablized in Pt/Sn-Beta (DG) by alloying. We demonstrate a process that constructs highly active Pt–Sn alloy nanoparticles on Sn-Beta zeolite with a high activity (TOF of 1.8 h−1), selectivity (99%) and stability (7360 min one-pass durability) for propane dehydrogenation. [Display omitted] • Sn-Beta zeolite from the dry-gel synthesis method was served as catalyst support. • Pt–Sn nanoalloy was formed via the interaction of Pt and Sn in Sn-Beta zeolite. • Pt/Sn-Beta shows a high activity and selectivity for propane dehydrogenation. • The excellent stability of Pt/Sn-Beta is benefited from the of Pt–Sn nanoalloy. [ABSTRACT FROM AUTHOR]

Abstract: Based upon a bench-top micro-CT system, propagation-based phase-contrast imaging has been investigated using insects and a thin plastic sheet. The system mainly includes a micro-focus source with focal spot size of 13–20μm and a cooled X-ray CCD detector with pixel size of 24μm. The edge-enhancement effect can be found clearly in the acquired images. With a 0.5mm thickness plastic edge phantom, the effects of X-ray tube voltage and imaging geometry on the phase-contrast imaging were investigated, and quantitative index, edge-enhancement index (EEI), were also calculated. In our study, an interesting phenomenon was observed that the phase-contrast effect becomes more pronounced as the tube voltage increases from 20kVp to 90kVp. Further investigation indicates that smaller focal spot size resulting from the reduction of tube current at higher tube voltage, has caused the unexpected phenomenon. Inferred from our results, phase-contrast effect is insensitive to the tube voltage in the range of 20–90kVp (widely used in medical diagnosis); however, it is sensitive to the focal spot size. In addition, for the investigation of the effect of imaging geometry, an optimal geometric magnification range of 2.5–4.5 is suggested to get a good phase-contrast imaging for a micro-CT system with source-to-detector distance of 720mm. [Copyright &y& Elsevier]