In Zhang et al. (2007) and Zhang (2021) we constructed all single-peak traveling wave solutions of the Camassa–Holm equation including some explicit solutions. In general it is a challenge to ...construct exact multi-peak traveling wave solutions. As an example a periodic traveling wave (or wavetrain), a special type of spatiotemporal oscillation that is a periodic function of both space and time, plays a fundamental role in many mathematical equations such as shallow water wave equations. In this paper we will construct some new exact periodic traveling wave solutions of the Camassa–Holm equation.
The experiments were done to investigate the effect of soil pH and organic matter content on EDTA-extractable heavy metal contents in soils and heavy metal concentrations in rice straw and grains. ...EDTA-extractable Cr contents in soils and concentrations in rice tissues were negatively correlated with soil pH, but positively correlated with organic matter content. The combination of soil pH and organic matter content would produce the more precise regression models for estimation of EDTA-Cu, Pb and Zn contents in soils, demonstrating the distinct effect of the two factors on the availability of these heavy metals in soils. Soil pH greatly affected heavy metal concentrations in rice plants. Furthermore, inclusion of other soil properties in the stepwise regression analysis improved the regression models for predicting straw Fe and grain Zn concentrations, indicating that other soil properties should be taken into consideration for precise predicting of heavy metal concentrations in rice plants.
Soil pH and organic matter content significantly affect heavy metal availability and accumulation in rice plants.
•The feasibility of using geopolymer as the next-generation soil stabilizer has been confirmed by this experimental study.•The strength, stiffness, and ductility of the soil were improved after the ...stabilization with metakaolin based geopolymer.•The shrinkage of the soil was reduced after the stabilization with metakaolin based geopolymer.•The formation of geopolymer gel in the stabilized soil was confirmed by examining the SEM–EDX and XRD results.
In many civil engineering constructions, soft and weak soils are often stabilized with ordinary Portland cement (OPC) and lime. The production processes of traditional stabilizers are energy intensive and emit a large quantity of CO2. Geopolymer, with its high strength, low cost, low energy consumption and CO2 emissions during synthesis, offers a promising alternative to OPC. In this study, a lean clay was stabilized with metakaolin based geopolymer at different concentration (ranging from 3 to 15wt.% of unstabilized soil at its optimum water content) to examine the feasibility of geopolymer in stabilizing soils. Geopolymer stabilized soil specimens were characterized with compressive strength testing, volume measurements during curing, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The testing results indicated that with geopolymer concentrations, compressive strength, failure strain and Young’s modulus of the stabilized soil specimens increased, and shrinkage strains during curing decreased. The microstructural analyses confirmed the formation of geopolymer gels in the stabilized soil, and showed the soil tended to form more homogeneous and compact microstructures after stabilization. This study illustrated that metakaolin based geopolymer can be an effective soil stabilizer for clayey soils. Further studies on the long-term performance of geopolymer stabilized soils, the use of geopolymers synthesized from industrial wastes, and the financial and environmental cost of applying geopolymer in soil stabilization are worth being conducted.
HAK/KUP/KT (High-affinity K
transporters/K
uptake permeases/K
transporters) is the largest potassium transporter family in plants, and plays pivotal roles in K
uptake and transport, as well as biotic ...and abiotic stress responses. However, our understanding of the gene family in barley (Hordeum vulgare L.) is quite limited.
In the present study, we identified 27 barley HAK/KUP/KT genes (hereafter called HvHAKs) through a genome-wide analysis. These HvHAKs were unevenly distributed on seven chromosomes, and could be phylogenetically classified into four clusters. All HvHAK protein sequences possessed the conserved motifs and domains. However, the substantial difference existed among HAK members in cis-acting elements and tissue expression patterns. Wheat had the most orthologous genes to barley HAKs, followed by Brachypodium distachyon, rice and maize. In addition, six barley HAK genes were selected to investigate their expression profiling in response to three abiotic stresses by qRT-PCR, and their expression levels were all up-regulated under salt, hyperosmotic and potassium deficiency treatments.
Twenty seven HAK genes (HvHAKs) were identified in barley, and they differ in tissue expression patterns and responses to salt stress, drought stress and potassium deficiency.
► Se alleviated Cd-toxicity, reduced Cd content and O2−, H2O2, MDA in rice plants. ► Se counteracted Cd-induced alterations of antioxidant enzymes. ► Se suppressed Cd-induced increase in SOD, APX, ...but elevated depressed CAT activity. ► Se markedly increased H+-ATPase, Ca2+-ATPase activities in roots under Cd exposure.
Hydroponic experiments were performed to investigate physiological mechanisms of selenium (Se) mitigation of Cd toxicity in rice. Exogenous Se markedly reduced Cd concentration in leaves, roots, and stems. Addition or pretreatment of 3μM Se in 50μM Cd solution significantly addressed Cd-induced growth inhibition, recovered root cell viability, and dramatically depressed O2−, H2O2, and malondialdehyde (MDA) accumulation. Supplemental Se counteracted 50μM Cd-induced alterations of certain antioxidant enzymes, and uptake of nutrients, e.g. depressed Cd-induced increase in leaf and root superoxide dismutase (SOD) and leaf peroxidase (POD) activities, but elevated depressed catalase (CAT) activity; decreased Cd-induced high S and Cu concentrations in both leaves and roots. External Se counteracted the pattern of alterations in ATPase activities induced by Cd, e.g. significantly elevated the depressed root H+- and Ca2+-ATPase activities, but decreased the ascent root Na+K+-ATP activity. Results indicate that alleviated Cd toxicity by Se application is related to reduced Cd uptake and ROS accumulation, balanced nutrients, and increased H+- and Ca2+-ATPase activities in rice.
Wearable strain sensors with excellent stretchability and sensitivity have emerged as a very promising field which could be used for human motion detection and biomechanical systems, etc. ...Three-dimensional (3D) graphene foam (GF) has been reported before for high-performance strain sensors, however, some problems such as high cost preparation, low sensitivity, and stretchability still remain. In this paper, we report a highly stretchable and sensitive strain sensor based on 3D GF and polydimethylsiloxane (PDMS) composite. The GF is prepared by assembly process from graphene oxide via a facile and scalable method and possesses excellent mechanical property which facilitates the infiltration of PDMS prepolymer into the graphene framework. The as-prepared strain sensor can be stretched as high as 30% of its original length and the gauge factor of this sensor is as high as 98.66 under 5% of applied strain. Moreover, the strain sensor shows long-term stability in 200 cycles of stretching-relaxing. Implementation of the device for monitoring the bending of elbow and finger results in reproducibility and various responses in the form of resistance change. Thus, the developed strain sensors exhibit great application potential in fields of biomechanical systems and human-interactive applications.
Municipal amalgamation is one of the core policy tools for Chinese government intervention in urbanization. The city-county merger policy provides a valuable research object for examining whether ...government-led urban expansion improves the quality of public services. By using city panel data from 2003 to 2019, this paper examines the policy effects of city-county mergers on the quality of public services using the Propensity Score Matching-Difference-in-Differences (PSM-DID) model. The results indicate that, after controlling for other factors, city-county mergers have increased the quality of public services by 1.2%. A placebo test has validated the robustness of this positive effect. Through further tests, the paper finds that the policy has positively affected all three aspects of the quality of public services in China: education, health care, and transport infrastructure, with the greatest impact being on education. Using a case study of a city-county merger in the Fenghua District of Ningbo, this paper depicts the transmission mechanism and argues that the policy affects the quality of public services by providing institutional security (financial and administrative power) and promoting regional integration in the new city area.
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