Polyoxometalate (POM)-layered double hydroxides (LDH) composite materials: design and catalytic applications

Layered double hydroxides (LDHs) are an important large class of two-dimensional (2D) anionic lamellar materials that possess flexible modular structure, facile exchangeability of inter-lamellar guest anions and uniform distribution of metal cations in the layer. Owing to the modular accessible gallery and unique inter-lamellar chemical environment, polyoxometalates (POMs) intercalated with LDHs has shown a vast array of physical properties with applications in environment, energy, catalysis, etc. Here we describe how polyoxometalate clusters can be used as building components for the construction of systems with important catalytic properties. This review article mainly focuses on the discussion of new synthetic approaches developed recently that allow the incorporation of the element of design in the construction of a fundamentally new class of materials with pre-defined functionalities in catalytic applications. Introducing the element of design and taking control over the finally observed functionality we demonstrate the unique opportunity for engineering materials with modular properties for specific catalytic applications

Rational design of a polyoxometalate intercalated layered double hydroxide: highly efficient catalytic epoxidation of allylic alcohols under mild and solvent-free conditions

Intercalation catalysts, owing to their modular and accessible gallery and unique interlamellar chemical environment, have shown wide application in various catalytic reactions. However, the poor mass transfer between the active components of the intercalated catalysts and organic substrates is one of the challenges that limit their further application. Herein, we have developed a novel heterogeneous catalyst by intercalating the polyoxometalate (POM) of Na9LaW10O36⋅32 H2O (LaW10) into layered double hydroxides (LDHs), which have been covalently modified with ionic liquids (ILs). The intercalation catalyst demonstrates high activity and selectivity for the epoxidation of various allylic alcohols in the presence of H2O2. For example, trans-2-hexen-1-ol undergoes up to 96 % conversion and 99 % epoxide selectivity at 25 °C in 2.5 h. To the best of our knowledge, the Mg3Al−ILs−C8−LaW10 composite material constitutes one of the most efficient heterogeneous catalysts for the epoxidation of allylic alcohols (including the hydrophobic allylic alcohols with long alkyl chains) reported so far

Characterization and Correction of the Scattering Background Produced by Dust on the Objective Lens of the Lijiang 10-cm Coronagraph

Scattered light from the objective lens, directly exposed to the intense sunlight, is a dominant source of stray light in internally occulted coronagraphs. The variable stray light, such as the scatter from dust on the objective lens, can produce varying scattering backgrounds in coronal images, significantly impacting image quality and data analysis. Using data acquired by the Lijiang 10-cm Coronagraph, the quantitative relationship between the distribution of dust on the objective lens and the resulting scattering backgrounds background is analyzed. Two empirical models for the scattering background are derived, and used to correct the raw coronal data. The second model, which depends on three parameters and performs better, shows that the scattering-background distribution varies with angle, weakens with increasing height, and enhances with increasing dust level on the objective lens. Moreover, we find that the dust on the center of the objective lens can contribute more significantly to the scattering background than on the edge. This study not only quantitatively confirms the significant impact of the stray light produced by dust on the objective lens of the coronagraph, but also corrects the coronal data with this stray light for the first time. Correcting for dust-scattered light is crucial for the high-precision calibration of ground-based coronagraph data, enabling a more accurate analysis of coronal structures. Furthermore, our model is envisioned to support the provision of reliable observational data for future routine coronal magnetic-field measurements using ground-based coronagraphs.Comment: 18 pages, 14 figrue

Analysis of bacterial and fungal community structure in replant strawberry rhizosphere soil with denaturing gradient gel electrophoresis

High quality DNA is the basis of analyzing bacterial and fungal community structure in replant strawberry rhizosphere soil with the method of denaturing gradient gel electrophoresis (DGGE). DNA of soil  microorganisms was extracted from the rhizosphere soil of strawberries planted in different replanted  years (0, two, six and seven), respectively, and crude DNA was purified after extraction. Three methods  were established to evaluate the effects of cetyl trimethylammonium bromide (CTAB),  polyvinylpolypyrolidone (PVPP), proteinase K and bacteriolytic enzymes on DNA extraction. DNA  fragments above 23 kb in size were isolated well by method 1 (1% CTAB, proteinase K, no PVPP, no  bacteriolytic enzyme) and method 3 (no CTAB, no proteinase K, 3% PVPP, bacteriolytic enzyme). Method 3 got the best yields 43.06 ìg/g, and A260/A280 and A260/A230 were 1.1623 and 0.8135, respectively,  which could ensure the veracity of subsequent DGGE analysis. Method 2 (3% CTAB, no proteinase K, no PVPP, no bacteriolytic enzyme) could not extract enough DNA to do the next PCR-DGGE analysis.  F341/R534 and FR1/FF390 primers were used to amplify the 16S rDNA V3 region of bacteria and 18S rDNA of fungi, and the expected fragments of 230 bp 16S rDNA V3 region and 390 bp 18S rDNA were amplified. The results of DGGE analysis showed that there were common and specific bacterial and fungal  communities in different replant soils of strawberry. There were 84 and 54% similarity of bacterial and  fungal communities between different replant soils. The numbers of both bacterial and fungal communities increased in the replant strawberry soil, they were positively correlated with the replant years. As the  number of replant years increased from two to seven years, while the ratio of bacteria/fungi was  decreased from 2.29 to 1.46 in the rhizosphere soils planted with strawberries.Key words: Rhizosphere soil, bacterial community, fungal community, replant strawberry, fruiting fields

The Development and Validation of an EFL Learner Attitude Scale for Phonetic Symbol Learning in A Chinese University Context

Research has established that learner attitude significantly impacts the outcomes of learning English as a foreign language (EFL). However, previous studies have rarely considered a validated attitude scale for English phonetic symbol learning (EPSL). This study aims to develop and validate a scale to measure students\u27 attitudes toward EPSL by integrating findings from learning attitude research in education and psychology. The results demonstrate that the attitude scale can predict attitudes towards EPSL in the context of a Chinese university and has good reliability and validity (KMO=0.892, α=0.749). Pedagogical suggestions are made to help students develop a more positive attitude toward EPSL

Constraint Mechanism of Environmental Regulation on Carbon Emission of Heavy Industry in Chengdu-Chongqing Region of China

Regional differences and development heterogeneity lead to an unbalanced distribution of heavy industry in Chengdu-Chongqing region of China. Under the background of low-carbon development, clarifying the constraint mechanism of environmental regulations on carbon emissions of heavy industry becomes more important to solve prominent problems of resources and the environment. In this work, literature analysis, comparative analysis and statistical induction are carried out to illustrate a constraint mechanism of environmental regulation on carbon emission. Based on literature reports and government yearbook data, the impacts of environmental regulations on carbon emissions of heavy industry in Chengdu-Chongqing region are studied. Analysis and demonstration are carried out from four dimensions: corporate identity, technological progress, policy constraints, and government supervision. The predicament of environmental regulation affecting heavy industry carbon emission reduction is expounded and puts forward reasonable policy suggestions. The research results can enrich the theory of environmental regulation, and provide policy suggestions for optimizing the green transformation of heavy industry

Identification and analysis of the stigma and embryo sac-preferential/specific genes in rice pistils

The secretion-related genes. (XLS 40 kb

Layered double hydroxide anchored ionic liquids as amphiphilic heterogeneous catalysts for the Knoevenagel condensation reaction

In recent years, great attention has been dedicated to the development of heterogeneous base catalysts providing a green and sustainable process in benign aqueous media. Herein, the ionic liquid modified layered double hydroxide (LDH) based catalysts of LDH-IL-Cn (n = 4, 8, 12) were prepared by adopting an exfoliation/assembly strategy, in which the ionic liquids (ILs) were covalently anchored onto the surface of LDH layers. The resulting LDH-IL-Cn were characterized by FT-IR, solid-state 13C NMR, 29Si CP/MAS NMR, 27Al-MAS NMR, XRD, TG-DTA, BET, XPS, SEM, CO2-TPD, contact angle experiments, etc. The catalytic performance of LDH-IL-C12 for the Knoevenagel condensation of a variety of aldehydes with ethyl cyanoacetate/malononitrile in H2O at room temperature showed excellent yields and selectivities. Moreover, the base catalyst of LDH-IL-C12 can be easily recycled and reused for at least 5 times without the decrease of its catalytic efficiency. The scaled-up experiments revealed that the catalyst retained its efficiency and robustness