Electronic Lieb lattice signatures embedded in two-dimensional polymers with square lattice

Exotic band features, such as Dirac cones and flat bands, arise directly from the lattice symmetry of materials. The Lieb lattice is one of the most intriguing topologies, because it possesses both Dirac cones and flat bands which intersect at the Fermi level. However, materials with Lieb lattice remain experimentally unreached. Here, we explore two-dimensional poly-mers (2DPs) derived from zinc-phthalocyanine (ZnPc) building blocks with a square lattice (sql) as potential electronic Lieb lattice materials. By systematically varying the linker lengths (ZnPc-xP), we found that some ZnPc-xP exhibit a characteristic Lieb lattice band structure. Interestingly though, fes bands are also observed in ZnPc-xP. The coexistence of fes and Lieb in sql 2DPs challenges the conventional perception of the structure-electronic structure relation. In addition, we show that manipula-tion of the Fermi level, achieved by electron removal or atom substitution, effectively preserves the unique characteristics of Lieb bands. Chern number calculations confirm the non-trivial nature of the Lieb Dirac bands. Our discoveries provide a fresh perspective on 2D polymers and redefine the search for Lieb lattice materials into a well-defined chemical synthesis task.Comment: 9 pages, 15 figure

Nitrogen Use Efficiency in Rice

Food security is a major global issue because of the growing population and decreasing land area. Rice (Oryza sativa L.) is the most important staple cereal crop in the world. Application of nitrogen (N) fertilizer has improved crop yield in the world during the past five decades but with considerable negative impacts on the environment. New solutions are therefore urgently needed to simultaneously increase yields while maintaining or preferably decreasing applied N to maximize the nitrogen use efficiency (NUE) of crops. Plant NUE is inherently complex with each step (including N uptake, translocation, assimilation, and remobilization) governed by multiple interacting genetic and environmental factors. Based on the current knowledge, we propose some possible approaches enhancing NUE, by molecular manipulation selecting candidate genes and agricultural integrated management practices for NUE improvement. Developing an integrated research program combining approaches, mainly based on whole-plant physiology, quantitative genetics, forward and reverse genetics, and agronomy approaches to improve NUE, is a major objective in the future

Sequentially reinforced additive coating for transparent and durable superhydrophobic glass

Now that there are various routes to prepare superhydrophobic surfaces for self-cleaning, anti-icing, liquid collecting, etc., attentions are moving toward low-cost upscaling of routes and increasing the reliability for actual applications. However, the required micro–nano structures for superhydrophobicity are light scattering and very vulnerable to abrasion. This intrinsically conflicts with the transparency and durability of superhydrophobic glass, which are the major barriers for its commercialization. In this study, we present a novel sequentially reinforced additive coating (SRAC) process to realize robust and transparent micro–nano structured film with tough intergranular sintering. A benign aqueous-based ink with poly(furfuryl alcohol) (PFA) and silica species is carefully designed and sprayed on glass to enable self-phase separation and morphology construction. The coatings reach the static contact angle (SCA) for water over 166° and withstand a 6H pencil scratching, the cross-cut test, and sand abrasion. Moreover, we also performed a 90 day outdoor performance test and the glass maintained superhydrophobicity with an SCA of 154°. These results provide a low-cost waterborne ink formula, and the high throughput and upscalable SRAC process could be a convenient technology for the fabrication of large area, robust superhydrophobic coatings

Quantum Dots-Based Immunochromatographic Strip for Rapid and Sensitive Detection of Acetamiprid in Agricultural Products

In this study, a rapid and sensitive immunochromatographic strip (ICS) assay, based on quantum dots (QDs), was developed for the qualitative and quantitative detection of acetamiprid in agricultural samples. Acetamiprid-ovalbumin conjugates (ACE-OVA) and goat anti-mouse IgG were sprayed onto a nitrocellulose membrane as a test and control line. Two kinds of anti-acetamiprid monoclonal antibodies (mAb) obtained in our lab were characterized by the ELISA and surface plasmon resonance assay. The competitive immunoassay was established using a QDs-mAb conjugate probe. The visual detection limit of acetamiprid for a qualitative threshold was set as 1 ng/mL to the naked eye. In the quantitative test, the fluorescence intensity was measured by a portable strip reader and a standard curve was obtained with a linear range from 0.098 to 25 ng/mL, and the half maximal inhibitory concentration of 1.12 ng/mL. The developed method showed no evident cross-reactivities with other neonicotinoid insecticides except for thiacloprid (36.68%). The accuracy and precision of the developed QDs-ICS were further evaluated. Results showed that the average recoveries ranged from 78.38 to 126.97% in agricultural samples. Moreover, to test blind tea samples, the QDs-ICS showed comparable reliability and a high correlation with ultra-performance liquid chromatography-tandem mass spectrometry. The whole sample detection could be accomplished within 1 h. In brief, our data clearly manifested that QDs-ICS was quite qualified for the rapid and sensitive screening of acetamiprid residues in an agricultural product analysis and paves the way to point-of-care testing for other analytes

Analytical Model for Load–Slip Relationship of Perfobond Shear Connector Based on Push-Out Test

In composite structures, the perfobond connector is an alternative type of shear connector which consists of a steel plate with a certain number of holes. The load–slip relationship is critical for structural analysis and numerical simulation of composite structures using perfobond connectors. In this study, push-out tests were conducted on 72 specimens to obtain the load–slip behaviors of perfobond connectors. Based on the test results, parametric study was performed to analyze the effects of changing the hole geometry, the concrete strength, the configuration of the rebar in hole, the dimensions of the perfobond rib, and the size of the concrete slab. Furthermore, the characteristics and physical meanings of the load–slip curves were analyzed, and the limits and conditions for theoretical expressions were derived. Finally, an analytical model was proposed to express the load–slip relationship of perfobond connectors covering a wide range of design variables

Experimental and Parametric Study on the Pull-Out Resistance of a Notched Perfobond Shear Connector

To ease the installation of perforating rebars through multi-holes, an alternative notched perfobond shear connector was proposed by cutting out the hole edge. This paper presents the test results of six pull-out specimens with conventional and notched perfobond shear connectors. The objective was to compare the failure modes and pull-out behaviors of perfobond shear connectors using circular holes and notched holes. Furthermore, the explicit finite element method was introduced and validated to generate parametric results for pull-out tests of notched perfobond shear connectors. A total of 33 parametric simulations were performed to further study the influences of several variables, including the hole diameter, the cut width, the perfobond thickness, the concrete strength, the diameter and strength of the rebar, and the strength of the structural steel. The experimental and numerical results were used to evaluate the previous equations for perfobond shear connectors. Finally, an alternative equation was proposed to estimate the pull-out resistance of notched perfobond shear connectors

Experimental and Numerical Study on Shear Resistance of Notched Perfobond Shear Connector

In steel and concrete composite bridges, it is difficult to perforate the reinforcing bars through the circular holes of conventional perfobond shear connectors with multi-ribs. To ease the installation of perforating rebars, an alternative notched perfobond shear connector was proposed by cutting out the edge of the circular hole. This paper presents the push-out test results of six specimens which were fabricated and loaded to failure. The main purpose was to compare the failure mode, shear capacity and slip behavior of perfobond shear connectors using circular holes and notched holes. Furthermore, 43 nonlinear finite element simulations were performed to further study the effects of several variables, including the hole diameter, the hole distance, the hole number, the cut width, the perfobond thickness, the concrete strength, the rebar diameter, the rebar strength, and the steel strength. The parametric results were generated to evaluate the shear capacity equations for perfobond shear connectors. Finally, an analytical model was developed to estimate the shear capacity of notched perfobond shear connectors

Effect of heat treatment on the preservation of

Heat treatment was used to extend the shelf life of postharvest Chaenomeles speciosa (Sweet) Nakai (C. speciosa), its effects on the quality and physiological properties of C. speciosa were studied. The results showed that heat treatment reduced the weight loss, inhibited the decline of titratable acids (TA), maintained a higher activity of peroxidase (POD) and catalase (CAT), compared to untreated C. speciosa. Treatment in hot water dipping at 50℃ for 2-4 min maintained the better quality of postharvest C. speciosa stored at 0℃ for 120 days, which indicated that heat treatment is an effective preservation technology to prolong the shelf life of C. speciosa

Compression Characteristics and Constitutive Model of Low-Exotherm Modified Polyurethane Grouting Materials

In permafrost regions, ordinary polyurethane grouting materials are not suitable for the repair and reinforcement of road engineering due to the release of a large amount of heat during the reaction process. In this study, the polyurethane grouting material is modified by changing the catalyst, blowing agent, and reaction scheme to reduce the heat released during the reaction. The stress-strain curves of low-exotherm polyurethane grouting material specimens possessing various densities are investigated by means of unconfined uniaxial compression experiments, and the stress-strain relationships and failure mode of low- and high-density specimens are analysed. The characteristics of three stages in the compression process of the materials, namely, the elasticity stage, platform stage, and densification stage, are studied. The compressive strength increases with the increase in density, and the brittle failure of materials with higher density is more obvious. From the microscopic point of view, combined with the experimental results, the constitutive model of low-exotherm modified polyurethane grouting material was established. The established model is in good agreement with the experimentally measured stress-strain curves and effectively predicted the stress-strain characteristics for a specimen possessing a different density