Combining lanthanum-modified bentonite and calcium peroxide to enhance phosphorus removal from lake sediments.

Lanthanum-modified bentonite (LMB) and calcium peroxide (CP) are known for their effective removal phosphorus (P) capacities. The present study aims to investigate the effects of the combined use of LMB and CP（LMB + CP）on the sediment P, dissolved organic matter (DOM) and iron (Fe) concentrations through a 90-day incubation experiment. The combined treatment showed strong removal effects on sediment P and DOM. Indeed, the SRP and DOM concentrations in the 0-10 cm sediment layer decreased following the combined application of LMB and CP by 40.67 and 28.95%, respectively, compared to those of the control group (CK). In contrast, the HCl-P in the 0-5 cm sediment layer increased following the combined treatment by 13.28%. In addition, compared with the single application of LMB, the LMB + CP treatment significantly reduced the soluble Fe (Ⅱ) in the sediment pore water and promoted the oxidation of Fe. Therefore, LMB + CP can enhance the removal of internal P from sediments. The DOM removal and Fe oxidation in sediment pore waters are beneficial for enhancing the adsorption of P by LMB. On the other hand, the single and combined applications of LMB and CP increased the richness of the sediment microbial communities while exhibiting slight effects on their diversity. According to the results of this study, the combined use of LMB and oxidizing materials represents a novel method for treating lakes with high internal phosphorus and DOM loads in sediments.

Investigation of the Stereochemical Mechanism of the Nucleophilic Substitution Reaction at Pentacoordinate Phosphorus of Spirophosphorane.

The stereochemical mechanism of the nucleophilic substitution reaction at pentacoordinate phosphorus (P-V) atom is rarely studied. Here, we report the Atherton-Todd-type reaction of pentacoordinate hydrospirophosphorane with phenolic compounds in detail. The stereochemical mechanism of nucleophilic substitution at P-V atom was proposed by 31P NMR tracing experiment, X-ray diffraction analysis, and density functional theory calculations. The first step of the Atherton-Todd-type reaction is the formation of halogenated spirophosphorane intermediate with retention of configuration at phosphorus definitely. The second step is a nucleophilic substitution reaction at P-V atom of halogenated spirophosphorane. When using CCl4 as a halogenating agent, the reaction of chlorinated spirophosphorane proceeds via SN2(P-V) mechanism, and the backside attack of P-Cl bond is the main pathway. For chlorinated spirophosphorane with ΔP configuration, the completely P-inverted product is normally obtained. As for chlorinated spirophosphorane with ΛP configuration, which has larger steric hindrance behind P-Cl bond, the proportion of P-retained products apparently increases and a pair of diastereoisomers is acquired. Furthermore, if CBr4 is used as a halogenating agent, the nucleophilic substitution reaction of brominated spirophosphorane may go through a SN1(P-V) mechanism to afford a pair of diastereoisomers.

Income and Technology as Drivers of Australian Healthcare Expenditures.

The roles of income and technology as the major determinants of aggregate healthcare expenditure (HEXP) continue to interest economists and health policy researchers. Concepts and measures of medical technologies remain complex; however, income (on the demand side) and technology (on the supply side) are important drivers of HEXP. This paper presents analysis of Australia's HEXP, using time-series econometrics modeling techniques applied to 1971-2011 annual aggregate data. Our work fills two important gaps in the literature. First, we model the determinants of Australia's HEXP using the latest and longest available data series. Second, this novel study investigates several alternative technology proxies (input and output measures), including economy-wide research and development expenditures, hospital research expenditures, mortality rate, and two technology indexes based on medical devices. We then apply the residual component method and the technology proxy approach to quantify the technology effects on HEXP. Our empirical results suggest that Australian aggregate healthcare is a normal good and a technical necessity with the income elasticity estimates ranging from 0.51 to 0.97, depending on the model. The estimated technology effects on HEXP falling in the 0.30-0.35 range and mimicking those in the literature using the US data, reinforce the global spread of healthcare technology. Copyright © 2016 John Wiley & Sons, Ltd.

NeighborNet: Learning Intra- and Inter-Image Pixel Neighbor Representation for Breast Lesion Segmentation.

Breast lesion segmentation from ultrasound images is essential in computer-aided breast cancer diagnosis. To alleviate the problems of blurry lesion boundaries and irregular morphologies, common practices combine CNN and attention to integrate global and local information. However, previous methods use two independent modules to extract global and local features separately, such feature-wise inflexible integration ignores the semantic gap between them, resulting in representation redundancy/insufficiency and undesirable restrictions in clinic practices. Moreover, medical images are highly similar to each other due to the imaging methods and human tissues, but the captured global information by transformer-based methods in the medical domain is limited within images, the semantic relations and common knowledge across images are largely ignored. To alleviate the above problems, in the neighbor view, this paper develops a pixel neighbor representation learning method (NeighborNet) to flexibly integrate global and local context within and across images for lesion morphology and boundary modeling. Concretely, we design two neighbor layers to investigate two properties (i.e., number and distribution) of neighbors. The neighbor number for each pixel is not fixed but determined by itself. The neighbor distribution is extended from one image to all images in the datasets. With the two properties, for each pixel at each feature level, the proposed NeighborNet can evolve into the transformer or degenerate into the CNN for adaptive context representation learning to cope with the irregular lesion morphologies and blurry boundaries. The state-of-the-art performances on three ultrasound datasets prove the effectiveness of the proposed NeighborNet.

Tungsten migration and transformation characteristics in lake sediments under changing habitats from algae to macrophytes.

Tungsten (W), a toxic and hazardous pollutant, poses substantial risks to both aquatic life and human health. However, the available understanding of the migration properties of W in lake sediments under various habitats is still limited. This study was designed to evaluate variations in the concentrations of soluble W, manganese (Mn), and iron (Fe) in the summer season by applying a high-resolution Peeper sampling device. According to the results, soluble W concentrations and release fluxes were higher in the pore water of sediments in algae-dominated lake areas than in areas dominated by aquatic plants. This result indicates that the competition for adsorption between algae-derived dissolved organic matter and W, as well as the reductive dissolution caused by dissolved organic matter on Fe (III)/Mn (IV) (hydroxyl) oxides, contributes to the release of W from lake sediments. W uptake by aquatic plants and in-situ formation of Fe (III)/Mn (IV) (hydroxyl) oxides might be the primary factor that controls W release from lake sediments. Aquatic plants can effectively control W release from sediments. The findings of this work provide a scientific basis for the effective control of W release from shallow lake sediments.

The combined effects of lanthanum-modified bentonite and Vallisneria spiralis on phosphorus, dissolved organic matter, and heavy metal(loid)s.

The use of lanthanum-modified bentonite (LMB) combined with Vallisneria spiralis (V∙s) (LMB + V∙s) is a common method for controlling internal phosphorus (P) release from sediments. However, the behaviors of iron (Fe) and manganese (Mn) under LMB + V∙s treatments, as well as the associated coupling effect on P, dissolved organic matter (DOM), and heavy metal(loid)s (HMs), require further investigations. Therefore, we used in this study a microelectrode system and high-resolution dialysis technology (HR-Peeper) to study the combined effects of LMB and V∙s on P, DOM, and HMs through a 66-day incubation experiment. The LMB + V∙s treatment increased the sediment DO concentration, promoting in-situ formations of Fe (III)/Mn (IV) oxyhydroxides, which, in turn, adsorbed P, soluble tungsten (W), DOM, and HMs. The increase in the concentrations of HCl-P, amorphous and poorly crystalline (oxyhydr) oxides-bound W, and oxidizable HMs forms demonstrated the capacity of the LMB + V∙s treatment to transform mobile P, W, and other HMs forms into more stable forms. The significant positive correlations between SRP, soluble W, UV254, and soluble Fe (II)/Mn, and the increased concentrations of the oxidizable HMs forms suggested the crucial role of the Fe/Mn redox in controlling the release of SRP, DOM, and HMs from sediments. The LMB + V∙s treatment resulted in SRP, W, and DOM removal rates of 74.49, 78.58, and 54.78 %, which were higher than those observed in the control group (without LMB and V∙s applications). On the other hand, the single and combined uses of LMB and V·s influenced the relative abundances of the sediment microbial communities without exhibiting effects on microbial diversity. This study demonstrated the key role of combined LMB and V∙s applications in controlling the release of P, W, DOM, and HMs in eutrophic lakes.

Cyanobacterial blooms increase the release of vanadium through iron reduction and dissolved organic matter complexation in the sediment of eutrophic lakes.

Vanadium (V), a hazardous environmental contaminant, can be highly toxic to aquatic or even human life. Nonetheless, knowledge of its redox geochemistry and mobility in sediments, especially those of eutrophic lakes, remains limited. In this study, we combined in situ high-resolution sampling and laboratory simulation experiments for monitoring soluble and labile V to reveal the mobilization mechanism of V in the sediment of Lake Taihu. The results showed that the concentration of soluble V (1.18-5.22 µg L-1) exceeded the long-term ecotoxicology limitation proposed by the government of the Netherlands. The highest value appeared in summer (July to September), with an average concentration of 3.87 µg L-1, which exceeded the short-term exposure limit. The remobilization of V in summer was caused by the combined effect of the reduction of Fe(hydr)oxides and dissolved organic matter (DOM) complexation, which accelerated the release of associated Fe-bound V and increased the solubility of DOM-V. Additionally, V showed high mobility in winter, owing to the species of V(Ⅲ)/V(Ⅳ) being oxidized to V(Ⅴ) with higher solubility. It is noteworthy that the elevated remobilization of V in sediments increases the risk of V release from sediments, which poses the threat of water V pollution in Lake Taihu.

Spatiotemporal characterization of vanadium at the sediment-water interface of a multi-ecological lake.

As an emerging environmentally harmful metal, vanadium (V) deserves significant research attention due to its hazardous concentrations in aquatic environments. However, the research on the characterization of V in sediment-water interface (SWI) remains limited. In this study, seasonal sampling was conducted in algal- and macrophyte-dominated zones via the method of in situ high-resolution diffusive gradients in thin films (DGT). The concentration of dissolved V in water in algal-dominated regions (12 sites) exceeded the long-term ecotoxicology limit of 1.2 µg⋅L-1. Seasonal variations of chemical speciation of V were observed in three ecological sites. DGT-labile V at the SWI exhibited two basic patterns associated with eutrophic status, one showing sharply decreasing gradients in the vicinity of the SWI and the other showing the absence of diffusion gradient. Positive correlations were observed between the water-dissolved V and the DGT-labile V, indicating DGT-labile V is a sensitive indicator for the release of V from sediment into water. Moreover, the mobility of V was influenced by the reduction of Fe(hydr)oxides and complexation with organic matter, in particular, during periods of algal blooms. It is suggested that V contamination at the SWI of algal-dominated zones deserves additional attention.