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In this study, asymmetric Al2O3-SiO2 Janus nanoparticles with a dumbbell-like structure were synthesized by a facile chemical process in the aqueous phase. Prior to synthesis, Al2O3 nanoparticles in hydrosol were amino-modified using 3-aminopropyl triethoxysilane (KH550) and then carboxyl acid-functionalized using a ring-opening reaction of the amine functions with succinic anhydride, imparting unique anionic properties to the Al2O3 end. SiO2 nanoparticles were rendered hydrophobic through modification with hexamethyldisilazane (HMDS) and further functionalized with 3-chloropropyl triethoxysilane (KH230). The two nanoparticle hydrosols were then mixed, and the asymmetric Al2O3-SiO2 Janus nanoparticles were synthesized via the reaction between the –NH2 and −CH2Cl groups. The prepared Janus nanoparticles were primarily characterized by dynamic light scattering (DLS), Zeta potential (ZP), and transmission electron microscopy (TEM). The results indicated that about 90% of the modified Al2O3 and SiO2 nanoparticles were covalently coupled in a one-to-one manner to form the dominant dumbbell-like structure. These Janus nanoparticles exhibit amphiphilic properties, making them highly promising surfactants for emulsifying oil–water mixtures. [ABSTRACT FROM AUTHOR]

Trace regression has received a lot of attention due to its ability to account for matrix-type covariates, including panel data, images, and genomic microarrays as special cases. However, most of its existing research focuses on the case of mean regression. In this paper, we consider the expectile trace regression, which can provide a more diversified picture of the regression relationship at different expectiles, via the low-rank and group sparsity regularization. The upper bound for the statistical rate of convergence of the regularized estimator is established under some mild conditions. Some simulations, as well as a real data example, are also provided to illustrate the finite sample performance of the developed expectile trace regression. [ABSTRACT FROM AUTHOR]

Small area estimation is a method for prediction involving subpopulation of interest. A standard measure of uncertainty for the prediction is the mean squared prediction error (MSPE). Various predictors and MSPE estimators have been proposed based on different principles over past decades. Despite various existing studies on performance of individual MSPE estimators, a comprehensive comparison of different MSPE estimators in terms of finite sample performance, especially for several recently proposed MSPE estimators, has not been documented. To this end, we carry out a study that systematically compare the existing MSPE estimators regarding their finite sample performance and computational speed. Performance of prediction intervals is also considered, which involves both the predictor and the associated MSPE estimator. The study covers two main types of small area models, namely, the area-level (Fay-Herriot) model and the unit-level (nested-error regression) model. Illustrative examples are provided. [ABSTRACT FROM AUTHOR]

Dumbbell-like SiO2 nanoparticles were synthesized by a simple chemical process in aqueous phase. Prior to the preparation, 3-aminopropyl triethoxysilane (KH550) and 3-chloropropyl triethoxysilane (KH230) were used as modifiers for the surface modification of SiO2 nanoparticles in SiO2 hydrosol. By mixing the SiO2 hydrosol modified by KH550 and KH230, respectively, the dumbbell-like SiO2 nanoparticles were obtained via the reaction between the –NH2 and –CH2Cl groups on the surface of the two SiO2 nanoparticles. The dumbbell-like SiO2 nanoparticles were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS). The results showed that the modified SiO2 nanoparticles are covalently coupled in a one-to-one manner. Detailed DLS analysis indicated that about 90% of the single nanoparticles were involved in the coupling reaction and formed new dumbbell-like SiO2 nanoparticles when the ratio of the two kinds of surface modified SiO2 was 1:1. Furthermore, the dumbbell-like SiO2 nanoparticles can be deployed as particle emulsifiers for stabilizing oil-water model systems during emulsification. Highlights: Asymmetric SiO2 nanoparticles with dumbbell-like structure has been successfully synthesized in a one-to-one coupling manner in aqueous phase. About 90% of the single SiO2 nanoparticles were transformed into new dumbbell-like SiO2 nanoparticles in the 1:1 hybrid system. The asymmetric dumbbell-like SiO2 nanoparticles can be used as stabilizers in oil-water system. [ABSTRACT FROM AUTHOR]

The prospect of carbon sequestration in soils of karst areas remains unclear. The study on migration and transformation of dissolved organic matter (DOM) in limestone soil under the high calcium environment of karst regions has seldom been reported. This study conducted soil column experiments on two surface soils (H1 and S2) and two subsurface soils (H2 and S2) from two limestone soil profiles in the karst region of southwest China and investigated their DOM leaching behaviours under different Ca2+ concentration levels. The results showed that the DOM leaching process can be described by the Elovich equation, including a rapid DOM release stage and the relatively stable DOM release stage. When the Ca2+ concentration of eluent increases from 0 to 2.5 mmol L−1, the percentage of dissolved organic carbon (DOC) loss in H1, H2, S1, and S2 soils decreased from 66.3% to 58.8%, from 76.2% to 72.4%, from 73.0% to 68.8%, and from 52.5% to 46.6%, respectively, and the apparent molecular weight of leached DOM increases, the aromaticity of leach DOM and the contribution of humic‐like components decrease. The results further show that the influence of Ca2+ on easily leaching DOM is stronger than that on the stable DOM, indicating that high Ca2+ runoff can enrich high aromaticity and high molecular weight soil organic matter (SOM) in the limestone soil during the leaching process. This research is helpful to understand the migration and fate of SOM in limestone soils and provides theoretical support for increasing soil carbon sinks in karst areas. [ABSTRACT FROM AUTHOR]