Temperature tunability of topological phase transitions and edge states in two-dimensional acoustic topological insulators.

Topological insulators are characterized by exhibiting an internal insulating state but a surface conductor state, which makes them advantageous for applications in novel devices. However, for most given acoustic topological metamaterials, the operating frequency is relatively fixed and the effect of temperature on their topological properties is rarely considered. Therefore, a temperature-tunable acoustic topological insulator is constructed in this paper. The quadruple degenerate Dirac cone formed at Γ point can be opened by adjusting the temperature, causing topological band inversion between the doubly degenerate dipolar and quadrupole states, and achieving topological phase transition. The evolution of its topological state with temperature is numerically investigated and a novel topological acoustic waveguide is constructed. The switching effect of temperature on the waveguide device is verified by numerical simulation and experiment. Non-contact active modulation of edge states in the structure is achieved by temperature-controlled topological phases, exhibiting acoustic switching effects. This study can provide corresponding references for the intelligent control of acoustic topology in noise, vibration, and other aspects.

Genetic algorithm with skew mutation for heterogeneous resource-aware task offloading in edge-cloud computing.

Recent years, edge-cloud computing has attracted more and more attention due to benefits from the combination of edge and cloud computing. Task scheduling is still one of the major challenges for improving service quality and resource efficiency of edge-clouds. Though several researches have studied on the scheduling problem, there remains issues needed to be addressed for their applications, e.g., ignoring resource heterogeneity, focusing on only one kind of requests. Therefore, in this paper, we aim at providing a heterogeneity aware task scheduling algorithm to improve task completion rate and resource utilization for edge-clouds with deadline constraints. Due to NP-hardness of the scheduling problem, we exploit genetic algorithm (GA), one of the most representative and widely used meta-heuristic algorithms, to solve the problem considering task completion rate and resource utilization as major and minor optimization objectives, respectively. In our GA-based scheduling algorithm, a gene indicates which resource that its corresponding task is processed by. To improve the performance of GA, we propose to exploit a skew mutation operator where genes are associated to resource heterogeneity during the population evolution. We conduct extensive experiments to evaluate the performance of our algorithm, and results verify the performance superiority of our algorithm in task completion rate, compared with other thirteen classical and up-to-date scheduling algorithms.

Dual-functional pentamode metamaterial with water-like and topological transmission properties.

In this paper, a water-like pentamode metamaterial (PM) with a single metallic material is designed and the topological edge-state transmission properties of elastic waves in the PM are thoroughly investigated. Numerical results indicate that by introducing structural perturbation into PM, the Dirac point degeneracy atK-point can be opened and topological band inversion can be generated. Topological edge states are also obtained by organizing PM structural units, which are robust to defects such as bending and cavities. In addition, it also has the mimics water in acoustic properties over a wide frequency range, i.e. it exhibits transparency when surrounded by water. Therefore, it will have both good transmission efficiency and acoustic stealth performance when used as an underwater waveguide. The dual-functional PM proposed in this study provides theoretical guidance for designing underwater stealth acoustic waveguides.

Trihalomethane prediction model for water supply system based on machine learning and Log-linear regression.

Laboratory determination of trihalomethanes (THMs) is a very time-consuming task. Therefore, establishing a THMs model using easily obtainable water quality parameters would be very helpful. This study explored the modeling methods of the random forest regression (RFR) model, support vector regression (SVR) model, and Log-linear regression model to predict the concentration of total-trihalomethanes (T-THMs), bromodichloromethane (BDCM), and dibromochloromethane (DBCM), using nine water quality parameters as input variables. The models were developed and tested using a dataset of 175 samples collected from a water treatment plant. The results showed that the RFR model, with the optimal parameter combination, outperformed the Log-linear regression model in predicting the concentration of T-THMs (N25 = 82-88%, rp = 0.70-0.80), while the SVR model performed slightly better than the RFR model in predicting the concentration of BDCM (N25 = 85-98%, rp = 0.70-0.97). The RFR model exhibited superior performance compared to the other two models in predicting the concentration of T-THMs and DBCM. The study concludes that the RFR model is superior overall to the SVR model and Log-linear regression models and could be used to monitor THMs concentration in water supply systems.

[Distribution Characteristics and Risk Assessment of Accumulated Heavy Metals in Bioretention Systems].

Topsoil samples (0-10 cm) from four bioretention systems with different land-use types were collected, including parking lot, roadside, residential area, and industrial park systems. The accumulation contents of As, Hg, Cd, Cr, Pb, Cu, Ni, and Zn were analyzed and evaluated, as were the influencing factors, pollution level, potential ecological risk, and human health risk. The results showed that there were significant differences in the accumulated contents of eight heavy metals. The average ω(As), ω(Hg), ω(Cd), ω(Cr), ω(Pb), ω(Cu), ω(Ni), and ω(Zn) were 8.92, 0.25, 0.10, 31.56, 14.81, 21.27, 23.69, and 62.75 mg·kg-1, respectively, and the average contents of As and Hg were 1.26 and 5.21 times the soil background values, respectively. Correlation analysis showed that the contents of the eight heavy metals were positively correlated with soil organic matter, pH value (except Hg), and phosphorus content (except As). The results of the Nemerow Comprehensive Pollution Index and Hakanson Potential Ecological Index showed that the pollution level and ecological risk of the other seven heavy metals were relatively low, whereas the pollution level and ecological risk of Hg reached the level of severe pollution and strong ecological risk, respectively. Affected by Hg, the comprehensive pollution level and ecological risk were relatively high; thus, Hg was a potential threat to the soil environment. The non-carcinogenic risks of heavy metals in the four systems were acceptable, but the carcinogenic risks were all beyond 10-6 though lower than 10-4, which indicated that these four systems had a certain carcinogenic risk, in which As was the main risk factor. Among these four land-use types, the accumulated pollutant contents, pollution levels, ecological risk, and human health risk of parking lots and roadside bioretention systems were much higher than those of residential areas and industrial parks.

Introduction of N-containing moieties by ammonia plasma technique can substantially improve ciprofloxacin removal by biochar and the associated mechanisms: Spectroscopic and site energy distribution analysis.

A low-temperature plasma device was developed to introduce N-containing moieties into biochar type CS-300 to improve ciprofloxacin removal. The sorption capacity of ciprofloxacin by the treated biochars was 2.61-4.26 times that of CS-300, and the mechanisms were explained by X-ray photoelectron spectroscopy and site energy distribution analysis. The results showed that the π-π stacking mechanism dominated ciprofloxacin removal by biochars. Ammonia-plasma treatment introduced abundant amino and amide groups to CS-300. They increased the π electron density in the delocalized system in CS-300, thus enhancing ciprofloxacin removal by the π-π stacking mechanism. Plasma treatment also enhanced polar interactions between ciprofloxacin and CS-300 through hydrogen- and ionic bonding occurring at high-energy sites with energy over 10,000 J/mol, thereby increasing ciprofloxacin removal. The maximum removal efficiency of ciprofloxacin by the treated biochars reached 71.0-85.7% at pH 6, while that for CS-300 was only 31.6% and occurred at pH 4. This implied that plasma treatment not only greatly increased the maximum removal efficiency but also shifted the optimal pH from acidic to nearly-neutral condition. Our findings highlight that ammonia-plasma treatment is a promising technique to improve ciprofloxacin removal by biochars and the treated biochars have potential applications in its removal from water.

A mechanistic study on removal efficiency of four antibiotics by animal and plant origin precursors-derived biochars.

Extensive research has been performed on the utilization of biochar for pollutant removal via sorption. Additionally, the relationship between sorption strength of organic pollutants by organic matter and nanomaterials and their sorption site energy distribution has been studied. However, the linkage between removal efficiency of organic pollutants and the sorption site energy distribution on biochars is unknown. As a first attempt to address this knowledge gap, three biochars were derived from two plant-origin precursors (corn straw-CS; birch sawdust-BS) and one animal-origin precursor (meat and bone meal-MBM) at 500 °C (CS-500, BS-500, and MBM-500). In addition, two biochars were prepared with CS at 300 and 800 °C (CS-300 and CS-800) to examine the relationship between their site energy distribution and removal efficiency of antibiotics including sulfadiazine (SDZ), sulfamethoxazole (SMX), tetracycline (TC) and ciprofloxacin (CFX) by these materials. Our findings showed that the antibiotic-biochar interactions can be well interpreted with site energy distribution and XPS analysis results. Polar interactions between CS-300, CS-500, and CS-800 and SDZ and SMX occurring at the high-energy sites dominated their removal. However, TC and CFX removal by these biochars was driven by their polar interactions occurring at high-energy sites and π-π interactions at low-energy sites. The π-π stacking mechanism tended to dominate their removal with increasing charring temperature. Abundance of polar functionalities on CS-500, BS-500, and MBM-500 and TC removal efficiency of these materials consistently followed an order of MBM-500 > CS-500 > BS-500, highlighting importance of precursors for making biochars and polar interactions in its removal.

Research on Progress in Combined Remediation Technologies of Heavy Metal Polluted Sediment.

Heavy metals contaminated sediment has become a worldwide environmental issue due to its great harm to human and aquatic organisms. Thus, economical, effective, and environmentally-friendly remediation technologies are urgently needed. Among which, combined remediation technologies have attracted widespread attention for their unique advantages. This paper introduces combined remediation technologies based on physical-, chemical-, and bio-remediation of heavy metal polluted sediments. Firstly, the research progress in physical-chemical, bio-chemical, and inter-organismal (including plants, animals, microorganisms) remediation of heavy metal polluted sediments are summarized. Additionally, the paper analyzes the problems of the process of combined remediation of heavy metals in river sediments and outlooks the future development trends of remediation technologies. Overall, this review provides useful technology references for the control and treatment of heavy metal pollution in river sediments.

Plasma assisted-synthesis of magnetic TiO2/SiO2/Fe3O4-polyacrylic acid microsphere and its application for lead removal from water.

Hybrid microsphere of polyacrylic acid (PAA) grafted TiO2/SiO2/Fe3O4 (TSF-PAA) was synthesized via coating polyacrylic acid on the core-shell-shell TiO2/SiO2/Fe3O4 (TSF) structure with the aid of plasma technique. The synthesized microsphere was applied to remove Pb2+ from water. The state-of-the techniques including TEM, FTIP, TGA, and XPS were used to characterize the morphology and the surface functionalities of the microsphere and confirmed that PAA was successfully grafted on TSF surfaces and active functional groups were introduced. A combination of the BET, VSM, and XRD results showed that plasma treatment decreased surface area of TSF by 36%, whereas its magnetic property and crystalline structure were not significantly altered. Both the Pb2+-sorbed magnetic TSF and TSF-PAA can be separated with a magnet from the aqueous phase. The pH and dosage changes of the microspheres exerted an intense influence on their lead removal efficiency. Compared to TSF, the removal capacity of Pb2+ by TSF-PAA was considerably improved from 65% to 95%, attributable to the fact that PAA coating induced by plasma treatment additionally introduced carboxylic and hydroxyl groups to TSF. Their introduction greatly enhanced the interaction between Pb2+ and TSF-PAA relative to that with TSF, which had hydroxyl groups only as supported by XPS analysis.

Effective removal of heavy metals by nanosized hydrous zirconia composite hydrogel and adsorption behavior study.

A novel type of adsorbent, hydrous zirconium oxide (HZO) based on polymer hydrogel (HZO-P(TAA/HEA) hydrogel), was synthesized by irradiation polymerization and in situ precipitation methods to remove heavy metals from water efficiently. The composite hydrogel was characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), swelling kinetics, zeta potential, X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectra (FTIR), and X-ray photoelectron spectroscopy (XPS). The results indicated that HZO nanoparticles were stably loaded on the P(TAA/HEA) hydrogel, swelling properties, and thermal stability were also enhanced after the loading of HZO. Besides, the batch adsorption experiments revealed that adsorption time, pH, initial concentration of heavy metals, and coexisting ions influenced the adsorption process significantly. The adsorption capacities of HZO-P(TAA/HEA) hydrogel for Pb2+, Cu2+, Cd2+, and Ni2+ was 0.620 mmol g-1, 0.615 mmol g-1, 0.701 mmol g-1, and 0.700 mmol g-1, respectively. The adsorption isotherms fitted Langmuir equation well, and the adsorption kinetics followed second-order kinetics; it was manifested that the priority of competitive adsorption followed the order: Pb2+ > Cu2+ > Ni2+ > Cd2+. Furthermore, based on the analysis results of FTIR and XPS, the adsorption mechanism could mainly be the complexation between hydrous zirconia and heavy metals. The results indicate that nanocomposite HZO-P(TAA/HEA) hydrogel is a promising heavy metal adsorbent.

Compact flexible multifrequency splitter based on plasmonic graded metallic grating arc waveguide.

A compact flexible multifrequency splitter based on an arc waveguide constructed of plasmonic metallic grating structures with graded-height T-grooves is proposed and studied. The dispersion curves and cutoff frequencies of the plasmonic grating waveguides with different T-groove metallic grating heights are different. The guided spoof surface plasmonic polariton waves at different frequencies can be localized at dissimilar angles along the graded grating arc waveguide. The output flexibility at an arbitrary groove for different frequencies is realized by introducing an additional symmetrical T-groove structure as an output. The compact four-, seven-, and eight-output frequency splitters demonstrate its flexible multifrequency separation capability at different output angle locations, while the dimensional size of the frequency splitters is not increased. Measurement results at the microwave frequency display excellent agreement with numerical simulation results.

Rational drug design of indazole-based diarylurea derivatives as anticancer agents.

A series of novel indazole-based diarylurea derivatives targeting c-kit were designed by structure-based drug design. The derivatives were prepared, and their antiproliferative activities were evaluated against human colon cancer HCT-116 cell line and hepatocellular carcinoma PLC/PRF/5 cell line. The antiproliferative activities demonstrated that six of nine compounds exhibited comparable activities with sorafenib against HCT-116. The structure-activity relationship (SAR) analysis indicated that the indazole ring part tolerated different kinds of substituents, and the N position of the central pyridine ring played key roles in antiproliferative activity. The SAR and interaction mechanisms were further explored using molecular docking method. Compound 1i with N-(2-(pyrrolidin-1-yl)ethyl)-carboxamide possessed improved solubility, 596.1 ng/ml and best activities, IC50 at 1.0 µm against HCT-116, and 3.48 µm against PLC/PRF/5. It is a promising anticancer agent for further development.

Chiral Lewis acid catalyzed asymmetric cycloadditions of disubstituted ketenes for the synthesis of ß-lactones and δ-lactones.

Highly diastereo- and enantioselective [2 + 2]- and [4 + 2]-cycloadditions of disubstituted ketenes were realized by chiral Lewis acid catalysis. A series of arylalkylketenes underwent the reaction smoothly with isatins and ß,γ-unsaturated α-ketoesters, providing optically active ß-lactones and δ-lactones with vicinal chiral centers in excellent yields (up to 99%) and enantioselectivities (up to 99% ee), as well as exclusively high diastereoselectivities under 0.2-2 mol % catalyst loading.

Enantioselective synthesis of ß-pyrazole-substituted alcohols through an asymmetric ring-opening reaction of meso-epoxides.

An efficient and practical synthesis of optically pure ß-pyrazole-substituted alcohols was achieved by an asymmetric ring-opening reaction of meso-epoxides with pyrazole derivatives as the nucleophile. In the presence of 1 mol % of an N,N'-dioxide-Sc(OTf)(3) complex, excellent enantioselectivity and yields were obtained from meso-epoxides. The process could also be used for a mixture of cis- and trans-stilbene oxides. A proposed transition-state model is provided.

New electrophilic addition of α-diazoesters with ketones for enantioselective C-N bond formation.

α-Diazoesters were discovered to be good electrophiles in a catalytic asymmetric α-functionalization of ketones for the first time. This reaction also provided a direct and efficient method for C-N bond formation with excellent yields (up to 98%) and enantioselectivities (up to 99% ee) under mild conditions. The application of the electrophilicity of α-diazoesters opens up a novel way to access the diversity of diazo chemistry.

Catalytic asymmetric Roskamp reaction of alpha-alkyl-alpha-diazoesters with aromatic aldehydes: highly enantioselective synthesis of alpha-alkyl-beta-keto esters.

The first catalytic enantioselective Roskamp reaction of alpha-alkyl-alpha-diazoesters with aromatic aldehydes was realized using a simple chiral N,N'-dioxide-scandium(III) complex. Remarkably, with 0.05 mol % catalyst, the reaction was performed well over a series of substrates, giving the desired products chemoselectively in excellent yields (up to 99%) and enantioselectivities (up to 98% ee) under mild conditions. This protocol provides a promising method for the synthesis of chiral alpha-alkyl-beta-keto esters and 1,3-diols.

Asymmetric cyanation of activated olefins with ethyl cyanoformate catalyzed by a modular titanium catalyst.

Asymmetric cyanation of a class of easily available olefins with a favorable cyanide source ethyl cyanoformate (CNCOOEt) was realized by an interesting modular catalyst. High yields and ee values were obtained for a range of substrates under solvent-free and mild reaction conditions. The products obtained could be easily transformed to the enantioenriched useful intermediates 5, 6, and pharmaceutically important gamma-aminobutyric acid 7.