Effect of metallic ions on dispersibility of fine diaspore

Dispersion experiments were conducted to study the influence of metallic cations on the dispersibility of diaspore. The reaction mechanisms were investigated based on the analysis of zeta （ξ） potential and calculations of solution chemistry and DLVO theory. The results show that the valence of cations, instead of the cation type, plays an important role in the dispersibility of diaspore The impact of multivalent metallic cations is greater than that of monovalent cations. In the presence of Ca^2＋ and Mg^2＋, the dispersion of diaspore doesn＇t change in the range of pH value below 10. However, Ca^2＋ and Mg^2＋ may induce strong coagulation of particles when pH value is higher than 10. The adsorption of species of calcium and magnesium ions on diaspore can cause the compression of electric double layer, the decrease of the absolute value of zeta potential and the repulsion force between diaspore particles. The new IEP （isoelectric point） appeared at pH value of 11 may attribute to the adsorption of Mg（OH）2（s）.

Improving the Dispersibility of Poly(urea-formaldehyde) Microcapsules for Self-Healing Coatings Using Preparation Process

Poly(urea-formaldehyde)(PUF)microcapsules were prepared by in-situ polymerization with four different pro-cesses in this paper.The chemical composition,surface morphology,particle size distribution,and thermal sta-bility were characterized by FTIR,SEM,particle size analyzer,and TGA,respectively.The results demonstrated that the agglomeration of the PUF microcapsules was related to the agglomeration of the emulsion particles caused by the changes of emulsion interface during the shell polymerization.Due to the slow deposition of the shell material,the PUF microcapsules with the core-shell structure prepared by the process with ammonium chloride as the last additive showed good dispersibility with an average diameter of 6.36μm,high core content of 71.3 wt%,and high yield of 61.3 wt%.The PUF microcapsules had good thermal stability below 216?C.The PUF microcapsules could be uniformly dispersed in the epoxy coating in a single form.The epoxy coating with 2 wt%PUF microcapsules showed good self-healing property,and the service life of the coating was about doubled.

A hydrophobic peptide fraction that enhances the water dispersibility of curcumin

The present study describes the complexation between curcumin(Cur) and a peptide mixture(Pep). Pep was prepared by enzymatic hydrolysis of casein and used as an excipient for poorly water-soluble Cur. An aqueous solution of Pep and an acetone solution of Cur were mixed and lyophilized to obtain a white-yellow powder of the peptide and Cur complex(CurPep). The water dispersibility of Cur was enhanced by the complexation with Pep. Pep was fractionated using ammonium sulfate precipitation and ultrafiltration to identify which peptides preferentially interact with Cur. Relatively hydrophobic peptides with high molecular weights(>5 k Da) were more effective in enhancing the water dispersibility of Cur than other fractions. Cur-Pep dispersed under acidic and neutral conditions, at which amphoteric Pep is positively or negatively charged. Cur-Pep exists as a hydrocolloid with particle size 160–330 nm in aqueous media.

Dispersibility, Shape and Magnetic Properties of Nano-Fe₃O₄Particles

Nano-Fe3O4 particles were prepared by a two-step microemulsion method, the influence of molar ratio of water to NP-5 (R), alkali concentration and temperature on dispersibility and shape of the nanoparticles were discussed. Magnetic studies were also carried out using VSM in this paper. It was found that the optimum preparation parameters are R = 6.0, alkali concentration = 2.5 mol.L–1, initial total iron concentration as 0.88 mol.L–1, and the temperature being 30°C, the prepared nano magnetite particles have uniform size and good dispersibility with a crystal structure belonging to cubicFe3O4 and lattice parameters of a = 8.273 ?. The results of magnetic studies show, magnetic properties of particles are influenced by dispersibility of nanoparticles which depends on size of clusters. The better dispersibility of nanoparticles leads to more ordered inner magnetic vector, and so the stronger magnetic behavior of nano-Fe3O4 particles.

Enhanced dispersibility and thermal stability of β-cyclodextrin functionalized graphene

A series of β-cyclodextrin （CDs） functionalized graphene nanohybrids have been successfully fabricated utilizing the classical covalent modification methods at different reaction temperatures. It is very interesting that although both CDs and graphene oxide （GO） could he easily decomposed, the effective combination of GO with CDs leads to significantly enhanced thermal stability of graphene derivatives （GO-CDs）. Moreover, the introduction of CDs could dramatically improve the dispersibility promotion of our products in both polar/protic and nonpolar/aprotic solvents, which will contribute to the preparation of polymer nanocomposites and increase of their thermal stability. The improved thermal degradation temperatures can be obtained for polyvinyl alcohol after filling with as little as 1 wt.% of the hybrid. The obtained products could be potentially used in heat-retardant or thermal-control materials.

One-step functionalization of graphene via Diels-Alder reaction for improvement of dispersibility

Good dispersibility of graphene in a medium or matrix is a critical issue in practical applications.In this work,graphene was functionalized using N-(4-hydroxyl phenyl)maleimide(4-HPM)via the Diels—Alder(DA)reaction by a one-step catalyst-free approach.The optimal reaction condition was found to be 90℃for 12 h using dimethytformamide(DMF)as the solvent.FTIR,Raman spectroscopy,XPS and EDS proved that 4-HPM moieties were successfully grafted onto the surface of graphene.UVvis and TGA confirmed that the grafting amount of 4-HPM was 3.75%-3.97%based on the mass of graphene.Functionalized graphene showed excellent dispersion stability when dispersed in common solvents such as ethanol,DMF,water,tetrahydrofuran and pxylene.Meanwhile,functionalized graphene also exhibited pH sensitivity in aqueous due to the phenolic hydroxyls from the 4-HPM moieties.As a result of good dispersion stability and pH sensitivity,compared with graphene,functionalized graphene had better adsorption capacity for methylene blue(MB)from aqueous solution.

Strong synergy between physical and chemical properties:Insight into optimization of atomically dispersed oxygen reduction catalysts

Atomically dispersed catalysts exhibit significant influence on facilitating the sluggish oxygen reduction reaction(ORR)kinetics with high atom economy,owing to remarkable attributes including nearly 100%atomic utilization and exceptional catalytic functionality.Furthermore,accurately controlling atomic physical properties including spin,charge,orbital,and lattice degrees of atomically dispersed catalysts can realize the optimized chemical properties including maximum atom utilization efficiency,homogenous active centers,and satisfactory catalytic performance,but remains elusive.Here,through physical and chemical insight,we review and systematically summarize the strategies to optimize atomically dispersed ORR catalysts including adjusting the atomic coordination environment,adjacent electronic orbital and site density,and the choice of dual-atom sites.Then the emphasis is on the fundamental understanding of the correlation between the physical property and the catalytic behavior for atomically dispersed catalysts.Finally,an overview of the existing challenges and prospects to illustrate the current obstacles and potential opportunities for the advancement of atomically dispersed catalysts in the realm of electrocatalytic reactions is offered.

Alkyl dimethyl betaine activates the low-temperature collection capacity of sodium oleate for scheelite

The impact of alkyl dimethyl betaine (ADB) on the collection capacity of sodium oleate (NaOl) at low temperatures was evaluated using flotation tests at various scales. The low-temperature synergistic mechanism of ADB and NaOl was explored by infrared spectroscopy, X-ray photoelectron spectroscopy, surface tension measurement, foam performance test, and flotation reagent size measurement.The flotation tests revealed that the collector mixed with octadecyl dimethyl betaine (ODB) and NaOl in a mass ratio of 4:96 exhibited the highest collection capacity. The combined collector could increase the scheelite recovery by 3.48% at low temperatures of 8–12℃. This is particularly relevant in the Luanchuan area, which has the largest scheelite concentrate output in China. The results confirmed that ODB enhanced the collection capability of NaOl by improving the dispersion and foaming performance. Betaine can be introduced as an additive to NaOl to improve the recovery of scheelite at low temperatures.

Oxygen‑Coordinated Single Mn Sites for Efficient Electrocatalytic Nitrate Reduction to Ammonia

Electrocatalytic nitrate reduction reaction has attracted increasing attention due to its goal of low carbon emission and environmental protection.Here,we report an efficient NitRR catalyst composed of single Mn sites with atomically dispersed oxygen(O)coordination on bacterial cellulose-converted graphitic carbon(Mn-O-C).Evidence of the atomically dispersed Mn-(O-C_(2))_(4)moieties embedding in the exposed basal plane of carbon surface is confirmed by X-ray absorption spectroscopy.As a result,the as-synthesized Mn-O-C catalyst exhibits superior NitRR activity with an NH_(3)yield rate(RNH_(3))of 1476.9±62.6μg h^(−1)cm^(−2)at−0.7 V(vs.reversible hydrogen electrode,RHE)and a faradaic efficiency(FE)of 89.0±3.8%at−0.5 V(vs.RHE)under ambient conditions.Further,when evaluated with a practical flow cell,Mn-O-C shows a high RNH_(3)of 3706.7±552.0μg h^(−1)cm^(−2)at a current density of 100 mA cm−2,2.5 times of that in the H cell.The in situ FT-IR and Raman spectroscopic studies combined with theoretical calculations indicate that the Mn-(O-C_(2))_(4)sites not only effectively inhibit the competitive hydrogen evolution reaction,but also greatly promote the adsorption and activation of nitrate(NO_(3)^(−)),thus boosting both the FE and selectivity of NH_(3)over Mn-(O-C_(2))_(4)sites.

Tunable dispersion relations manipulated by strain in skyrmion-based magnonic crystals

We theoretically investigate the propagation characteristics of spin waves in skyrmion-based magnonic crystals. It is found that the dispersion relation can be manipulated by strains through magneto-elastic coupling. Especially, the allowed bands and forbidden bands in dispersion relations shift to higher frequency with strain changing from compressive to tensile,while shifting to lower frequency with strain changing from tensile to compressive. We also confirm that the spin wave with specific frequency can pass the magnonic crystal or be blocked by tuning the strains. The result provides an advanced platform for studying the tunable skyrmion-based spin wave devices.

Pipeline thickness estimation using the dispersion of higher-order SH guided waves

Thickness measurement plays an important role in the monitoring of pipeline corrosion damage. However, the requirement for prior knowledge of the shear wave velocity in the pipeline material for popular ultrasonic thickness measurement limits its widespread application. This paper proposes a method that utilizes cylindrical shear horizontal(SH) guided waves to estimate pipeline thickness without prior knowledge of shear wave velocity. The inversion formulas are derived from the dispersion of higher-order modes with the high-frequency approximation. The waveform of the example problems is simulated using the real-axis integral method. The data points on the dispersion curves are processed in the frequency domain using the wave-number method. These extracted data are then substituted into the derived formulas. The results verify that employing higher-order SH guided waves for the evaluation of thickness and shear wave velocity yields less than1% error. This method can be applied to both metallic and non-metallic pipelines, thus opening new possibilities for health monitoring of pipeline structures.

Saturation Estimation with Complex Electrical Conductivity for Hydrate-Bearing Clayey Sediments:An Experimental Study

Clays have considerable influence on the electrical properties of hydrate-bearing sediments.It is desirable to understand the electrical properties of hydrate-bearing clayey sediments and to build hydrate saturation(S_(h))models for reservoir evaluation and monitoring.The electrical properties of tetrahydrofuran-hydrate-bearing sediments with montmorillonite are characterized by complex conductivity at frequencies from 0.01 Hz to 1 kHz.The effects of clay and Sh on the complex conductivity were analyzed.A decrease and increase in electrical conductance result from the clay-swelling-induced blockage and ion migration in the electrical double layer(EDL),respectively.The quadrature conductivity increases with the clay content up to 10%because of the increased surface site density of counterions in EDL.Both the in-phase conductivity and quadrature conductivity decrease consistently with increasing Sh from 0.50 to 0.90.Three sets of models for Sh evaluation were developed.The model based on the Simandoux equation outperforms Archie’s formula,with a root-mean-square error(E_(RMS))of 1.8%and 3.9%,respectively,highlighting the clay effects on the in-phase conductivity.The fre-quency effect correlations based on in-phase and quadrature conductivities exhibit inferior performance(E_(RMS)=11.6%and 13.2%,re-spectively)due to the challenge of choosing an appropriate pair of frequencies and intrinsic uncertainties from two measurements.The second-order Cole-Cole formula can be used to fit the complex-conductivity spectra.One pair of inverted Cole-Cole parameters,i.e.,characteristic time and chargeability,is employed to predict S_(h) with an E_(RMS) of 5.05%and 9.05%,respectively.

Mass-spring model for elastic wave propagation in multilayered van der Waals metamaterials

Multilayered van der Waals(vdW)materials have attracted increasing interest because of the manipulability of their superior optical,electrical,thermal,and mechanical properties.A mass-spring model(MSM)for elastic wave propagation in multilayered vdW metamaterials is reported in this paper.Molecular dynamics(MD)simulations are adopted to simulate the propagation of elastic waves in multilayered vdW metamaterials.The results show that the graphene/MoS_(2)metamaterials have an elastic wave bandgap in the terahertz range.The MSM for the multilayered vdW metamaterials is proposed,and the numerical simulation results show that this model can well describe the dispersion and transmission characteristics of the multilayered vdW metamaterials.The MSM can predict elastic wave transmission characteristics in multilayered vdW metamaterials stacked with different two-dimensional(2D)materials.The results presented in this paper offer theoretical help for the vibration reduction of multilayered vdW semiconductors.

Patterns and drivers of avian taxonomic and phylogenetic beta diversity in China vary across geographical backgrounds and dispersal abilities

Geographical background and dispersal ability may strongly influence assemblage dissimilarity;however,these aspects have generally been overlooked in previous large-scale beta diversity studies.Here,we examined whether the patterns and drivers of taxonomic beta diversity(TBD)and phylogenetic beta diversity(PBD)of breeding birds in China vary across(1)regions on both sides of the Hu Line,which demarcates China’s topographical,climatic,economic,and social patterns,and(2)species with different dispersal ability.TBD and PBD were calculated and partitioned into turnover and nestedness components using a moving window approach.Variables representing climate,habitat heterogeneity,and habitat quality were employed to evaluate the effects of environmental filtering.Spatial distance was considered to assess the impact of dispersal limitation.Variance partitioning analysis was applied to assess the relative roles of these variables.In general,the values of TBD and PBD were high in mountainous areas and were largely determined by environmental filtering.However,different dominant environmental filters on either side of the Hu Line led to divergent beta diversity patterns.Specifically,climate-driven species turnover and habitat heterogeneity-related species nestedness dominated the regions east and west of the line,respectively.Additionally,bird species with stronger dispersal ability were more susceptible to environmental filtering,resulting in more homogeneous assemblages.Our results indicated that regions with distinctive geographical backgrounds may present different ecological factors that lead to divergent assemblage dissimilarity patterns,and dispersal ability determines the response of assemblages to these ecological factors.Identifying a single universal explanation for the observed pattern without considering these aspects may lead to simplistic or incomplete conclusions.Consequently,a comprehensive understanding of large-scale beta diversity patterns and effective planning of conservation strategies necessitate the consideration of both geographical background and species dispersal ability.

A simple atomization approach enables monolayer dispersion of nano graphenes in cementitious composites with excellent strength gains

Carbon nano additives(CNAs)are critical to achieving the unique properties of functionalized composites,however,controlling the dispersion of CNAs in material matrix is always a challenging task.In this study,a simple atomization approach was successfully developed to promote the dispersion efficiency of graphene nanoplatelets(GNPs)in cement composites.This atomization approach can be integrated with the direct,indirect and combined ultrasonic stirrings in a homemade automatic stirring-atomization device.Mechanical and microstructure tests were performed on hardened cement pastes blended with GNPs in different stirring and mixing approaches.Results show that the direct ultrasonic stirrings enabled more homogeneous dispersions of GNP particles with a smaller size for a longer duration.The atomized droplets with the mean size of~100μm largely mitigated GNPs’agglomerations.Monolayer GNPs were observed in the cement matrix with the strength gain by up to 54%,and the total porosity decrease by 21%in 0.3 wt%GNPs dosage.The greatly enhanced dispersion efficiency of GNPs in cement also raised the cement hydration.This work provides an effective and manpower saving technique toward dispersing CNAs in engineering materials with great industrialization prospects.

Real-time data processing method for CO_(2) dispersion interferometer on EAST

A real-time data processing system is designed for the carbon dioxide dispersion interferometer(CO_(2)-DI)on EAST.The system utilizes the parallel and pipelining capabilities of an fieldprogrammable gate array(FPGA)to digitize and process the intensity of signals from the detector.Finally,the real-time electron density signals are exported through a digital-to-analog converter(DAC)module in the form of analog signals.The system has been successfully applied in the CO_(2)-DI system to provide low-latency electron density input to the plasma control system on EAST.Experimental results of the latest campaign with long-pulse discharges on EAST(2022–2023)demonstrate that the system can respond effectively in the case of rapid density changes,proving its reliability and accuracy for future electron density calculation.

THE PERSISTENCE OF SOLUTIONS IN A NONLOCAL PREDATOR-PREY SYSTEM WITH A SHIFTING HABITAT

In this paper,we mainly study the propagation properties of a nonlocal dispersal predator-prey system in a shifting environment.It is known that Choi et al.[J Differ Equ,2021,302:807-853]studied the persistence or extinction of the prey and of the predator separately in various moving frames.In particular,they achieved a complete picture in the local diffusion case.However,the question of the persistence of the prey and of the predator in some intermediate moving frames in the nonlocal diffusion case was left open in Choi et al.'s paper.By using some a prior estimates,the Arzelà-Ascoli theorem and a diagonal extraction process,we can extend and improve the main results of Choi et al.to achieve a complete picture in the nonlocal diffusion case.

Parkland trees on smallholder farms ameliorate soil physical-chemical properties in the semi-arid area of Tigray,Ethiopia

Proposed agroforestry options should begin with the species that farmers are most familiar with,which would be the native multipurpose trees that have evolved under smallholder farms and socioeconomic conditions.The African birch(Anogeissus leiocarpa(DC.)Guill.&Perr.)and pink jacaranda(Stereospermum kunthianum Cham.)trees are the dominant species in the agroforestry parkland system in the drylands of Tigray,Ethiopia.Smallholder farmers highly value these trees for their multifunctional uses including timber,firewood,charcoal,medicine,etc.These trees also could improve soil fertility.However,the amount of soil physical and chemical properties enhanced by the two species must be determined to maintain the sustainable conservation of the species in the parklands and to scale up to similar agroecological systems.Hence,we selected twelve isolated trees,six from each species that had similar dendrometric characteristics and were growing in similar environmental conditions.We divided the canopy cover of each tree into three radial distances:mid-canopy,canopy edge,and canopy gap(control).At each distance,we took soil samples from three different depths.We collected 216 soil samples(half disturbed and the other half undisturbed)from each canopy position and soil depth.Bulk density(BD),soil moisture content(SMC),soil organic carbon(SOC),total nitrogen(TN),available phosphorus(AP),available potassium(AK),p H,electrical conductivity(EC),and cation exchange capacity(CEC)were analysed.Results revealed that soil physical and chemical properties significantly improved except for soil texture and EC under both species,CEC under A.leiocarpus,and soil p H under S.kunthianum,all the studied soils were improved under both species canopy as compared with canopy gap.SMC,TN,AP,and AK under canopy of these trees were respectively 24.1%,11.1%,55.0%,and 9.3% higher than those soils under control.The two parkland agroforestry species significantly enhanced soil fertility near the canopy of topsoil through improving soil physical and chemical properties.These two species were recommended in the drylands with similar agro-ecological systems.

Discussion on“Dispersion characteristics of clayey soils containing waste rubber particles”[J Rock Mech Geotech Eng 15(2023)3050-3058]

We read with great interest the recent article by Erenson(2023)entitled“Dispersion characteristics of clayey soils containing waste rubber particles”.The author has studied the dispersion characteristics of clayey soils containing different percentages of waste rubber particles(WRPs)by performing several tests(viz.consistency limit,linear shrinkage limit,double hydrometer,crumb test and pinhole test)and scanning electron microscopy(SEM)analysis on five clayey(viz.Na-activated bentonite,refined ball clay,Ukrainian kaolin,Avanos kaolin and Afyon clay)samples containing 0%,5%,10%and 15%WRPs.It should be noted that Erenson(2023)has presented some interesting observations,but there are some serious issues that we want to share through this discussion and request the author of the original paper to address them to avoid their persistence in the scientific literature.

Overview of computation strategies on the dispersion analysis for explicit finite difference solution of acoustic wave equation

Finite-difference(FD)method is the most extensively employed numerical modeling technique.Nevertheless,when using the FD method to simulate the seismic wave propagation,the large spatial or temporal sampling interval can lead to dispersion errors and numerical instability.In the FD scheme,the key factor in determining both dispersion errors and stability is the selection of the FD weights.Thus,How to obtain appropriate FD weights to guarantee a stable numerical modeling process with minimum dispersion error is critical.The FD weights computation strategies can be classified into three types based on different computational ideologies,window function strategy,optimization strategy,and Taylor expansion strategy.In this paper,we provide a comprehensive overview of these three strategies by presenting their fundamental theories.We conduct a set of comparative analyses of their strengths and weaknesses through various analysis tests and numerical modelings.According to these comparisons,we provide two potential research directions of this field:Firstly,the development of a computational strategy for FD weights that enhances stability;Secondly,obtaining FD weights that exhibit a wide bandwidth while minimizing dispersion errors.