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This work investigated the effect of layered double hydroxides (LDHs) on the calcium leaching of cement pastes. The mass loss, porosity, leaching depth, compressive strength, and Vickers hardness were applied to evaluate the resistance to calcium leaching. Electrochemical impedance spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and mercury intrusion porosimetry were conducted to investigate changes of cement hydrates and microstructure in cement pastes. The results demonstrate that the resistance to calcium leaching improves with increasing the content of LDHs and calcined LDHs (C-LDHs), and C-LDHs perform better resistance than LDHs. It is due to the filling effect of LDHs and C-LDHs in cement pastes. Additionally, they promote cement hydration, increasing the content of cement hydrates. As a result, LDHs and C-LDHs decrease the porosity and refine the pore structure, increasing the resistance to calcium leaching. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to link scores of the Revised Child Anxiety and Depression Scale short version (RCADS-25) to the metric of the PROMIS pediatric item banks Anxiety and Depressive Symptoms in a general Dutch population sample. Methods: The RCADS-25 and PROMIS pediatric item banks Anxiety and Depressive Symptoms were administered online to 2,893 Dutch children and adolescents aged 8–18. Assumptions for linking methods were checked. Linking was achieved by using three item response theory (IRT) and two equipercentile methods. For each method, the observed PROMIS metric scores were compared to the ones predicted from the RCADS-25 subscale scores using correlations, mean and SD of differences, and RMSD. Results: The assumptions for IRT-based and equipercentile linking were met. The IRT-based method using separate calibration with Stocking-Lord constants was considered the optimal choice for linking both RCADS-25 subscales to the PROMIS metric. Based on this Stocking-Lord approach, we created item parameters for RCADS-25 items and two crosswalk tables. Conclusion: The RCADS-25 item parameters and crosswalk tables presented in this study are sufficiently valid. Researchers can use these products to translate the RCADS-25 anxiety and depression subscales scores to the PROMIS metric in order to ensure comparability with the previous research. [ABSTRACT FROM AUTHOR]

At present, the direct gold determination in geological samples by inductively coupled plasma mass spectrometry (ICP-MS) is still an arduous challenge due to both spectral and background interferences. It is very important and necessary to study the pretreatment processes; therefore, the polyurethane foam treatment and sample digestion methods are explored and compared here. The experimental results showed that the gold adsorption rate of treated foam was significantly improved as the impurities in the foam were cleaned up, and the potential difference of the liquid membrane was increased. Meanwhile, the combination of the foam enrichment and thiourea desorption achieved the selective adsorption and desorption of gold ions, eliminated the interference of coexisting ions, and perfected the detection limits. Compared with the traditional electric heating plate digestion method, microwave digestion, a closed digestion method, had the advantages of less sample and reagent dosage, short time consumption, high degree of automation, thorough digestion, good security, and environmental friendliness and met the requirements of green chemistry development. The proposed microwave digestion-foam enrichment-thiourea desorption-ICP-MS determination method was applied to the gold test in soil samples of the actual gold mining area. It has the great potential as a routine laboratory procedure. [ABSTRACT FROM AUTHOR]

Computational thinking (CT) is believed to be a critical factor to facilitate STEM learning, and a vital learning objective itself. Therefore, researchers are continuing to explore effective ways to improve and assess it. Makerspaces feature various hands-on activities, which can attract students with diverse interests from different backgrounds. If well designed, scaffolded maker activities have the potential to improve students' CT skills and STEM learning. In this study, we explore ways to improve and assess physics and engineering integrated CT skills through developing maker activities and assessments, which are applicable in both informal and formal educational settings. Our paper presents our work on improving and assessing CT in maker activities with two primary goals. First, it introduces the maker activities and instruments we developed to improve and assess CT that are integrated in physics and engineering learning. Second, it presents the students' CT skill and disposition change from pretest to posttest in two summer academies with CT enhanced maker activities, which was respectively led by after school educators and formal educators in a public library. [ABSTRACT FROM AUTHOR]

Background: Soil salinization is a major abiotic environmental stress factor threatening crop production throughout the world. Salt stress drastically affects the growth, development, and grain yield of rice (Oryza sativa L.), and the improvement of rice tolerance to salt stress is a desirable approach for meeting increasing food demand. Receptor-like cytoplasmic kinases (RLCKs) play essential roles in plant growth, development and responses to environmental stresses. However, little is known about their functions in salt stress. Previous reports have demonstrated that overexpression of an RLCK gene SALT TOLERANCE KINASE (STK) enhances salt tolerance in rice, and that STK may regulate the expression of GST (Glutathione S-transferase) genes. Results: The expression of STK was rapidly induced by ABA. STK was highest expressed in the stem at the heading stage. STK was localized at the plasma membrane. Overexpression of STK in rice increased tolerance to salt stress and oxidative stress by increasing ROS scavenging ability and ABA sensitivity. In contrast, CRISPR/Cas9-mediated knockout of STK increased the sensitivity of rice to salt stress and oxidative stress. Transcriptome sequencing analysis suggested that STK increased the expression of GST genes (LOC_Os03g17480, LOC_Os10g38140 and LOC_Os10g38710) under salt stress. Reverse transcription quantitative PCR (RT-qPCR) suggested that four stress-related genes may be regulated by STK including OsABAR1, Os3BGlu6, OSBZ8 and OsSIK1. Conclusions: These findings suggest that STK plays a positive regulatory role in salt stress tolerance by inducing antioxidant defense and associated with the ABA signaling pathway in rice. [ABSTRACT FROM AUTHOR]

Metal-free porous biochars are popularly utilized as catalysts for peroxydisulfate (PDS) activation. The enhancement effect of PDS activation of porous biochars fabricated by employing both hard template and alkali metal activating agent has not been explored completely. In addition, the role of the inherent carbon defect in PDS activation has not been clearly elucidated. Hence, a series of carbonaceous catalysts were fabricated using a sole template (KCl), a sole activating agent (Na2S2O3) or a combination of template and activating agent (KCl/Na2S2O3, KCl/KHCO3, KCl/NaHCO3, and KCl/Na2C2O4), to systematically investigate the effect of specific surface area (SSA) and intrinsic defect of porous biochar on its PDS activation ability. The biochar synthesized by KCl and Na2S2O3 (SK-C) exhibited the optimum degradation performance. The SK-C was found to possess an interconnected hollow cage with three-dimensional mesh structure showing the largest surface area, pore volume and C-sp3 edge defect content among all the catalysts, which explained its paramount catalytic ability. The SSA and C-sp3 content together can determine the catalytic performance in a quantitative relationship. The single electron transfer pathway from SDZ to inner-sphere bound SK-C/PDS* was the protagonist of pollutant oxidation. The degradation intermediates were detected and recognized and their toxicities were evaluated. This study for the first time comprehensively identified the synergistic effect between the SSA and inherent defects on improving the catalytic performance of biochar for PDS activation to removal contaminants. Highlights: Several porous biochars with various surface area and defect degree were fabricated. These catalysts were used for peroxydisulfate activation to degrade sulfadiazine. The catalyst made by employing Na2S2O3 and KCl exhibited the optimum performance. The surface area and C-sp3 together determined quantitatively the catalytic effect. The single electron transfer from organic to inner-sphere catalyst/peroxodisulfate* was dominant. [ABSTRACT FROM AUTHOR]

To fundamentally explore the correlation between crop nutritional quality and mineral elements, specific tests and accurate analysis were carried out on all organs and root soil of watermelon (Citrullus lanatus). The results showed that the distribution patterns of nitrogen and phosphorus at watermelon maturity were similar, and the average nitrogen and phosphorus contents were in the orders of leaf and seed > stem, peel, root > pulp > root soil, and peel > seed > root, stem, leaf > root soil > pulp, respectively. From the perspective of element geochemistry, biophile and lithophile elements had the strongest correlation with nitrogen and phosphorus, and watermelon did not antagonize soil nitrogen and phosphorus uptake. The prediction model of nitrogen translocation factor in watermelon organs to total acid was established by partial least squares with R2 = 0.81. Significantly, when the isometric log-ratio of nitrogen to phosphorus in watermelon leaves was 1.97 to 2.19, the watermelon pulp showed better quality with total acid > 0.5%, total sugar > 5% and soluble solids > 10%. Therefore, the characterization of nitrogen and phosphorus in watermelon leaves can serve as a non-destructive analysis to predict watermelon fruit quality. [ABSTRACT FROM AUTHOR]

Objectives: MTHFR C677T and A1298C have been associated with the risk of preeclampsia (PE), but with conflicting results. We performed this meta-analysis to derive a more precise estimation of the association between MTHFR polymorphisms and PE. Study design: An electronic search of PubMed and Chinese Biomedicine database was conducted to select studies for meta-analysis. 54 case controlled studies containing MTHFR C677T and A1298C gene polymorphisms were chosen, and odds ratio (OR) with confidence interval (CI) was used to assess the strength of this association. Result: These studies evaluated 7398 cases and 11230 controls for MTHFR C677T. The overall results suggested that MTHFR C677T was associated with the risk of PE. (T vs. C: OR = 1.157, 95 % CI: 1.057-1.266, p=0.002; TT+CT vs. CC: OR=1.165, 95 % CI : 1.049-1.293, P = 0.004; TT vs. CT + CC: OR = 1.371, 95 % CI: 1.153-1.63, p < 0.001). We also evaluated 1103 cases and 988 controls for MTHFR A1298C but could not demonstrate an increased risk of PE for this polymorphism ( p=0.667). A symmetric funnel plot, the Egger's test ( p = 0.819) suggested a lack of publication bias. Conclusion: This meta-analysis supports the idea that MTHFR C677T genotype is associated with increased risk for PE, especially in the case of Asians and Caucasians. [ABSTRACT FROM AUTHOR]

Human gut microbiota shows high inter-subject variations, but the actual spatial distribution and co-occurrence patterns of gut mucosa microbiota that occur within a healthy human instestinal tract remain poorly understood. In this study, we illustrated a model of this mucosa bacterial communities' biogeography, based on the largest data set so far, obtained via 454-pyrosequencing of bacterial 16S rDNAs associated with 77 matched biopsy tissue samples taken from terminal ileum, ileocecal valve, ascending colon, transverse colon, descending colon, sigmoid colon and rectum of 11 healthy adult subjects. Borrowing from macro-ecology, we used both Taylor's power law analysis and phylogeny-based beta-diversity metrics to uncover a highly heterogeneous distribution pattern of mucosa microbial inhabitants along the length of the intestinal tract. We then developed a spatial dispersion model with an R-squared value greater than 0.950 to map out the gut mucosa-associated flora's non-linear spatial distribution pattern for 51.60% of the 188 most abundant gut bacterial species. Furthermore, spatial co-occurring network analysis of mucosa microbial inhabitants together with occupancy (that is habitat generalists, specialists and opportunist) analyses implies that ecological relationships (both oppositional and symbiotic) between mucosa microbial inhabitants may be important contributors to the observed spatial heterogeneity of mucosa microbiota along the human intestine and may even potentially be associated with mutual cooperation within and functional stability of the gut ecosystem. [ABSTRACT FROM AUTHOR]

The original version of this article unfortunately contained mistakes. [ABSTRACT FROM AUTHOR]