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[Display omitted] • GQD-DDT and GQD-MPA was synthesized using novel hydrothermal protocol. • GQD-DDT and GQD-MPA was used for the identification of cations using colorimetric and spectrophotometric assay. • GQD-DDT and GQD-MPA have well activity for ion sensing in aqueous solution. This study describes the synthesis of various types of thiolated-graphene quantum dots (GQDs) for the simultaneous multi-sensing of heavy metal ions using one-droplet microfluidic paper-based analytical devices (OD- µ PADs). For the first time, functionalized GQDs were synthesized and stabilized on the surface of hydrophobic fiber-glass with simple manufacturing and assembly strategy towards colorimetric chemosensing of ions including iron, copper, cobalt, mercury, chrome, manganese, and nickel. For this purpose, GQDs are functionalized by various organic species including cysteamine, decanethiol, and mercaptopropionic acid (MPA) towards specific electrostatic interaction with metal ions of Fe (II), Cu (II), Co(II), Hg (II), Mn (II), and Ni (II). Therefore, an innovative GQDs-based miniaturized chemo-system was proposed for the environmental analysis. Additionally, the results were confirmed using fluorescence spectrometry as an optical detection method. Finally, this simple and efficient colorimetric platform was used for facile metal ions detection in human urine models, and environmental fluids, which can provide a commercial device for sensing contaminants by non-professional users in biomedical/environmental mixture. As an economical technique, this platform presents a "mix-and-sense" system without dye (as a side substance) or chemical treatments. The low instrumental requirements, the color uniformity, and the disposability of OD- μ PADs approve the commercial application of the engineered ion-chemosensor. [ABSTRACT FROM AUTHOR]

Cationized birch xylan was prepared and its use as a papermaking chemical was evaluated. The focus was on studying the effects of cationized birch xylan on the wet and dry strength of fine paper. The results of the laboratory experiments show that the addition of 3 percent of cationized birch xylan to birch kraft pulp improved the initial wet strength of the web by 30 percent compared to base stock at a solids content of 55%. Furthermore, the tensile stiffness of the wet web increased by approximately a third and the dry tensile strength improved by 26%, while the dry elastic modulus was not changed. The improvements in the strength properties were clear when compared to the base stock, but not as high as achieved with conventionally used cationized starch. The difference between the xylan and starch is most likely due to the shorter polymer chain length of the cationized xylan. [ABSTRACT FROM AUTHOR]

Highlights: [•] Improvement of the direct quantification with analytical pyrolysis. [•] Optimization of the chromatographic parameters after pyrolysis of cationic starch. [•] Quantification of cationic starches in cellulose matrixes. [•] Validation of the cationic starch quantification in paper samples. [ABSTRACT FROM AUTHOR]

Accumulation of interfacial space charge in oil-paper interface is a critical issue in insulation diagnostics of transformers. This interfacial charge mainly accumulates due to the conductivity difference of oil and paper. Accumulation of interfacial charge leads to localized field enhancement, which further leads to partial discharges and acceleration in the aging of insulation. Therefore, from the point of view of transformer insulation diagnostics, assessment of interfacial charge is very important. However, it is not easy to estimate interfacial space charge behavior from the transformer diagnostics methods currently in use. In case of Polarization-Depolarization Current (PDC) measurement, a well known method for transformer condition monitoring, the effect of interfacial charge is reflected in the non-linearity of current response during polarization and de-polarization. During de-polarization process, a part of the interfacial charge accumulated during polarization period is absorbed by the electrodes producing a current, which is difficult to separate using conventional linear dielectric theory. In this paper, an attempt has been made to separate this current component from de-polarization current through considering charge de-trapping mechanism. Terming this current component as de-trapping current, its relationship with other parameters of transformer insulation is discussed. The developed methodology has been applied on several practical transformers. It was observed that the time constant of de-trapping current is related to the paper conductivity, oil conductivity, dissipation factor and age of the insulation. [ABSTRACT FROM PUBLISHER]

Abstract: This study examines and quantifies the effect of cationic polyacrylamide (CPAM) dissolution kinetics and charge density on the adsorption and aggregation state of gold nanoparticles (AuNPs) on paper and the resulting Surface Enhanced Raman Scattering (SERS) performance. Dissolution kinetics of CPAM of different charge density was studied by monitoring their viscosity and hydrodynamic diameter over regular intervals of time. It was found that the degree of dissolution of CPAM greatly affected the surface coverage and aggregation of AuNPs on the CPAM pre-adsorbed paper substrate and their SERS reproducibility. CPAM of higher charge density dissolves faster and produced a more uniform aggregation and higher surface coverage of AuNPs on paper for a higher and more reproducible Raman EF. Understanding the CPAM dissolution process enables the optimization of SERS performance of the AuNPs-paper as a bio-diagnostic platform. [Copyright &y& Elsevier]

Abstract: This study examines and quantifies the effect of cationic polyelectrolyte adsorption on paper on the aggregation and retention of gold nanoparticles (AuNPs) to optimize their Surface Enhanced Raman Scattering (SERS) enhancement factor and sensitivity. Aggregation of metallic nanoparticles is known as a key factor for intense SERS enhancement. Paper substrates were treated with aqueous solutions of cationic polyacrylamide (CPAM) varying in concentration, charge density, and molecular weight to control the AuNPs’ aggregate size distribution and surface coverage on paper. The Raman Enhancement Factor of AuNPs-CPAM paper was almost an order of magnitude greater than for the untreated AuNPs paper. The high loading and uniform distribution of AuNPs aggregates on CPAM pre-treated paper contributed toward the excellent SERS reproducibility, sensitivity, and high enhancement factor. This configuration of AuNP on paper was favoured by treating the substrate with CPAM solutions of higher concentrations, higher charge density, and greater molecular weight. [Copyright &y& Elsevier]

It is important to study the steel corrosion inhibition behavior in complex chloride salt environments. This paper uses the fact that calcined layered double hydroxides (CLDHs) have a certain memory effect, which means that it can reabsorb water and anions and partially restore the lamellar structure under certain conditions. This work investigated the influence of cation types on the steel corrosion inhibition behavior of CLDH in saturated calcium hydroxide solution using equilibrium isotherms of Cl− uptake, the electrochemical method, X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and scanning electron microscopy (SEM) techniques. The results show that the corrosion inhibition of the CLDH is affected by the cation types in the following order: Ca2+>Mg2+>K+≈Na+·Na+ and K+ increase the pH of the solution and decrease the corrosion inhibition of CLDH. The addition of Mg2+ can promote the reconstruction of Mg-Al-Zn-Cl hydrotalcite. The addition of Ca2+ can promote the formation of new Ca-Al layered double hydroxide (Ca-Al-LDH) and improve the corrosion inhibition. [ABSTRACT FROM AUTHOR]

A new approach for the chemical modification of the surface of paper based on the application of colloidal mixtures containing cationic starch and polyoxometalates on uncoated base paper is presented. Polyoxometalates with the Keggin-type structure and physical properties similar to those presented by coating pigments, namely H3PW12O40∙23H2O, H4SiW12O40∙24H2O, and K7PW11O39∙9H2O, have been used in order to improve the quality of inkjet printing. The analysis of the different samples by FTIRATR spectroscopy showed the presence of the polyoxometalates (and the cationic starch) on the top surface of the paper. In addition, the determination of surface energy parameters, namely the polar component (σsp) and the dispersive component (σsd) of the surface energy, by contact angle measurements revealed that, for the new samples, the polar component level was much higher than that of the uncoated base paper. The quality of inkjet printing, evaluated by parameters such as the gamut area and the optical density, was considerably improved by these surface treatments. [ABSTRACT FROM AUTHOR]

Abstract: Large numbers of soil samples are routinely analyzed using methylene blue (MB) titration to determine clay content. Although, the MB filter paper spot test titration is simple, it is labor-intensive, subjective, and leaves no record for subsequent re-examination. Preliminary thermometric monitoring of the titration indicated a switch from endothermic to exothermic reaction during titration. We examined this nearly universal property of physicochemical processes as a potential replacement method to automate the MB clay titration, making use of literature data. We translated the isothermal enthalipmetric titration of montmorillonite using MB by Rytwo and Ruiz-Hitzky to an adiabatic thermometric titration (2003). The plot of temperature versus titrant volume gave two intersecting linear segments dependent on the titrated percentage of the clay''s cation exchange capacity (CEC). The MB filter paper spot test endpoint reflects the first excess MB that persists in the solid suspension, which also happens to be a function of the clay''s CEC. The spot test endpoint is correlated to the thermometric indicator point and, for montmorillonite, the two are related by an exact factor of two. Although this factor will naturally be dependent on the clay minerals in the samples, the analyses show that the thermometric indicator titration method is a viable replacement for the spot test. The proposed automation is commonplace as it is practiced with other types of titrations. [Copyright &y& Elsevier]

The results of applying heterogeneous chemiluminescent analysis for determination of micro-components are generalized, and the possibility of using this method for determination of toxic anions in waters is demonstrated. Anions undergo conversion beforehand, which causes formation of new analytical forms, i.e., derivates being active in chemiluminescent reactions with luminol. If volatile products are generated as analytical forms, they undergo gas extraction from the matrix with detection using a chemiluminescent indicator in the carrier gas stream at the interface gas-liquid (aqueous solution of luminol). Thus, the techniques for determination of Cl, Br, I, ClO, BrO, IO, NO, NO, S, CrO, AsO, Cl and chloramines are developed. The detection limit (DL) is 0.5-5.0 μg/l, and the analysis time is 2-9 min. In another case, products of conversion are sorbed from the solution on a solid sorbent, and detection is carried out by a luminol solution on the solid surface. A series of heteropoly acids (phosphorus, arsenic, silicon, and germanium) and their ion associates with cation surfactants, along with other large anions, are determined in the form of sorbable ion associates. The DL is 0.02-0.7 μg/l, and the analysis time is 30 min. The advantages of application of heterogeneous chemiluminescent analysis over analysis in homogeneous media are indicated, and the prospects for development of the theoretical bases and field of application are demonstrated. [ABSTRACT FROM AUTHOR]

This article was written to serve as an introduction to this issue of the Canadian Journal of Chemistry that honors the contributions to chemistry of Professor D.R. Arnold. It summarizes the observations reported in a communication that appeared in the Journal of the American Chemical Society 30 years ago in June 1973. This historically important communication laid the foundation for his program on the photochemical generation and reactivity of radical ions in solution and also served as a guide for a developing area of interest of many other research groups. [ABSTRACT FROM AUTHOR]

White light solid-state lighting applications still face significant challenges due to insufficient efficient and stable red light emitting materials. Therefore, a series of orange-red fluorescent materials, CaLu 2-x Mg 2 Si 3 O 12 :xCe3+ (CLMS:xCe3+; x = 0.02, 0.04, 0.06, 0.08, 0.10, 0.12) were prepared in this paper. Luminescence spectra testing revealed that the optimal concentration of Ce3+ ions in the crystal lattice is x = 0.04. At 460 nm excitation, the emission wavelength is approximately 592 nm. To enhance the thermal stability and luminescence performance of CLMS:Ce3+, the CaLu 1.96-y Me y Mg 2 Si 3 O 12 :0.04Ce3+ (Me = Sr, Ba; y = 0, 0.02, 0.05, 0.10, 0.15, 0.20) fluorescent materials were successfully prepared. It was found that phosphor's fluorescence intensity was enhanced after the introduction of Sr2+ or Ba2+ ions. Meanwhile, the phosphors were tested for thermal stability, and the emission intensities of CLMS:0.04Ce3+, CLMS:0.04Ce3+,0.10Sr2+, and CLMS:0.04Ce3+,0.05Ba2+ phosphors decreased to 77.60%, 85.53%, and 87.63% at 423 K, respectively. This proves that Sr2+ and Ba2+ ions have a positive effect on the thermal stability performance of CLMS:0.04Ce3+ phosphor. Testing of the w-LED devices, the CCT was reduced. The CRI was improved to 80.4 and 81.6 and luminescence efficiency was improved to 107.71 lm/W and 115.04 lm/W after Sr2+ or Ba2+ ions were introduced. In summary, this study demonstrates that CaLu 2-x-y Me y Mg 2 Si 3 O 12 :xCe3+ (Me = Sr, Ba) is an auspicious fluorescent material with high thermal stability, which is potentially informative for the field of white-light illumination. [ABSTRACT FROM AUTHOR]

White light solid-state lighting applications still face significant challenges due to insufficient efficient and stable red light emitting materials. Therefore, a series of orange-red fluorescent materials, CaLu 2-x Mg 2 Si 3 O 12 :xCe3+ (CLMS:xCe3+; x = 0.02, 0.04, 0.06, 0.08, 0.10, 0.12) were prepared in this paper. Luminescence spectra testing revealed that the optimal concentration of Ce3+ ions in the crystal lattice is x = 0.04. At 460 nm excitation, the emission wavelength is approximately 592 nm. To enhance the thermal stability and luminescence performance of CLMS:Ce3+, the CaLu 1.96-y Me y Mg 2 Si 3 O 12 :0.04Ce3+ (Me = Sr, Ba; y = 0, 0.02, 0.05, 0.10, 0.15, 0.20) fluorescent materials were successfully prepared. It was found that phosphor's fluorescence intensity was enhanced after the introduction of Sr2+ or Ba2+ ions. Meanwhile, the phosphors were tested for thermal stability, and the emission intensities of CLMS:0.04Ce3+, CLMS:0.04Ce3+,0.10Sr2+, and CLMS:0.04Ce3+,0.05Ba2+ phosphors decreased to 77.60%, 85.53%, and 87.63% at 423 K, respectively. This proves that Sr2+ and Ba2+ ions have a positive effect on the thermal stability performance of CLMS:0.04Ce3+ phosphor. Testing of the w-LED devices, the CCT was reduced. The CRI was improved to 80.4 and 81.6 and luminescence efficiency was improved to 107.71 lm/W and 115.04 lm/W after Sr2+ or Ba2+ ions were introduced. In summary, this study demonstrates that CaLu 2-x-y Me y Mg 2 Si 3 O 12 :xCe3+ (Me = Sr, Ba) is an auspicious fluorescent material with high thermal stability, which is potentially informative for the field of white-light illumination. [ABSTRACT FROM AUTHOR]

In the past 20 years, perovskite-related research has attracted wide attention. The related research into two-dimensional/quasi-two-dimensional perovskite has propelled the research of perovskite materials to a new height. To improve the properties of quasi-2D perovskite, improve the stability of materials, and achieve specific functions, using different types, volumes, and lengths of organic spacers is an essential method. In this paper, quasi-2D perovskites with EDA (ethylene diammonium), PDA (1,3-propanediammonium), and BDA (1,4-butanediammonium) (m = 2–4) as organic spacers were prepared, and the effects of different organic spacers on the 2D perovskite were investigated. The results show that the length of the organic spacer significantly impacts the perovskite's properties. A shorter organic spacer can effectively reduce the quantum confinement and dielectric confinement in perovskite. It should be noted that if the organic spacer is too short, the stability of the quasi-2D perovskite will be greatly reduced. [ABSTRACT FROM AUTHOR]

1-octadecanol is known to be a highly effective agglomerating agent for laser toner ink. However, the office waste paper used in the actual production often contains various types of inks. The effect of the offset ink and types of surfactants with different charge characteristics were studied relative to the agglomeration of the laser toner ink under neutral pulping conditions. It was found that the addition of a small amount of the offset ink printed waste paper was beneficial for the agglomeration of the laser toner ink. The optimal percentage of addition is 12.5% to 25%. The offset printed ink had a positive charge of 0.001±0.0005 mEq/g when the offset ink was treated by 70°C water at neutral conditions. Addition of a proper amount of cationic surfactant was beneficial to improve the agglomeration at any ratio of the mixed laser printed and offset waste papers. When the percentage of offset waste paper was less than 50%, the addition of anionic surfactant and nonionic surfactant was harmful for agglomeration, and there was no significant effect at higher offset content. [ABSTRACT FROM AUTHOR]

The Cairns-distributed electrons and positive ions in a plasma made up of a negative dust fluid are taken into account to examine the presence of arbitrary amplitude dust-acoustic solitons. It has previously been noted that nonthermal ions and thermal electrons generate both compressive and rarefactive solitons. In this paper, we noticed that nonthermal electrons together with nonthermal ions are responsible for producing the rarefactive solitons. It is found that the Sagdeev potential strongly depends on plasma parameters, such as nonthermal index α and Mach number, which, in turn, influence the Sagdeev potential and solitons significantly. We also found that the critical match number and height of soliton increase with the nonthermal parameter α. We further note that the Sagdeev potential as a function of potential φ becomes more negative and the amplitude of the soliton also enhances as the value of Mach number rises. It is concluded that the model presented here based on nonthermal ions and electrons in a negative dust fluid provides a worthy interpretation for electrostatic solitons observed in space plasmas. [ABSTRACT FROM AUTHOR]

Paper-capillary spray modified on the basis of paper spray ionization in order to facilitate the combination with portable mass spectrometry is an ambient ionization technique, which can be uesd to detect compounds rapidly without the restriction of location and environment. Paper-capillary spray and ambient ionization portable mass spectrometry in positive ion mode were used to collect mass spectrum information of 40 kinds of cathinones controlled in China. The ［M+H］+ peak of MS1, the characteristic fragment ions of MS2 and MS2_DDA mode and their relative abundance ratio were analyzed. The obtained mass spectrum information was used to establish a database for the rapid screening of 40 cathinones. It was found that C—N cleavage at the α site existed in all the cathinones through the study of their fragmentation characteristics. Whether the highest ion peak was ［M—H2O+H］+ fragment peak could infer the existence of secondary and tertiary amine structures. A series of characteristic peaks of m/z 98+CnH2n would exist when the N was substituted by pyrrolidinyl. The characteristic ion of ［M+H］+ lost 48 u or that of non ［M+H］+ lost 30 u would exist when the benzene ring was substituted by methylenedioxy. The fragmentation characteristics were studied to design and establish a complete analysis strategy for the unknown cathinones. The strategy could be applied in the following three aspects. 1) To judge whether they are cathinones; 2) To judge whether they are 40 kinds of cathinones in the database; 3) To infer the characteristic structure of cathinones outside the scope of the database. The strategy was successfully used for the structural identification of 10 analytes, which included the common categories of drugs controlled in China. No interference or misjudgment was found, and the database could be used normally. The structures inferred by the analysis strategy were consistent with the actual structure, and the isomers involved would also be distinguished because of their different fragment ions, indicating that this scheme was feasible. This method only needs simple sample loading operation and integrated small mass spectrometer, and is not limited by location and environment. In the investigation of such drug cases, this method can carry out rapid screening and timely feedback, which plays an important role in the rapid and accurate crackdown on the crime of cathinones and it is expected to be a new way to study and judge the crime of cathinones. [ABSTRACT FROM AUTHOR]

Plasma jet normally operates in a regime of positive or negative streamers. Different propagating behaviors have been investigated for positive streamers. However, there are few studies on negative streamers. In this paper, a two-dimensional fluid model is used to simulate the behavior of a negative streamer encountered with a cloud of positive ions. Simulation results indicate that the negative streamer behaves like a free streamer when the ion cloud has a low charge density. After initiation near the needle tip, the streamer propagates along the axis, passes through the ion cloud, and finally reaches the anode vicinity along a straight line. When the streamer reaches the ion cloud, its head radius (R0) is investigated as a function of parameters, including the voltage amplitude and the gap width, as well as the charge density, axial position, and spatial size of the ion cloud. At a given moment, electric field strength and electron density near the streamer head increase with increasing charge density of the ion cloud. In the case of a high charge-density ion cloud, after a primary streamer propagates some distance along the axis, a positive secondary streamer, and a negative secondary streamer start to propagate from the cloud to the cathode and the anode, respectively. [ABSTRACT FROM AUTHOR]

Supercapacitors have a wide range of applications in high-technology fields. The desolvation of organic electrolyte cations affects the capacity size and conductivity of supercapacitors. However, few relevant studies have been published in this field. In this experiment, the adsorption behavior of porous carbon was simulated with first-principles calculations using a graphene bilayer with a layer spacing of 4–10 Å as a hydroxyl-flat pore model. The reaction energies of quaternary ammonium cations, acetonitrile, and quaternary ammonium cationic complexes were calculated in a graphene bilayer with different interlayer spacings, and the desolvation behavior of TEA+ and SBP+ ions was described. The critical size for the complete desolvation of [TEA(AN)]+ was 4.7 Å, and the partial desolvation size ranged from 4.7 to 4.8 Å. The critical size for the complete desolvation of [SBP(AN)]+ was 5.2 Å, and the partial desolvation size ranged from 5.2 to 5.5 Å. As the ionic radius of the quaternary ammonium cation decreased, the desolvation size showed a positive trend. A density of states (DOS) analysis of the desolvated quaternary ammonium cations embedded in the hydroxyl-flat pore structure showed that the conductivity of the hydroxyl-flat pore was enhanced after gaining electrons. The results of this paper provide some help in selecting organic electrolytes to improve the capacity and conductivity of supercapacitors. [ABSTRACT FROM AUTHOR]

Broadband cyan-emitting phosphors with strong absorption between 300 and 400 nm are ideal replacements for traditional blue and green phosphors used in commercial light-emitting diodes (LEDs). In this paper, a series of K 1-x AlSiO 4 : xCe3+(x = 0.02–0.06) broadband cyan phosphors were prepared using the traditional high-temperature solid state method and the cation un-equivalent substitution strategy. It was found that the KAlSiO 4 matrix has a monoclinic structure with high symmetry. The experimental and theoretical optical band gaps of the host were 5.6 eV and 4.86 eV, respectively. After doping with Ce3+, strong absorption was observed in the near ultraviolet region. The optimum Ce3+ doping concentration in the host was 0.04 as indicated by the strongest observed emission intensity. The full width at half maximum of the emission spectra of the series of samples are all greater than 120 nm and covered the blue and green wavelength ranges (370–600 nm). The luminous intensity of the K 0 · 96 AlSiO 4 : 0.04Ce3+phosphor at 150 °C was 91.1% of that at room temperature, and the Gaussian peak of the emission spectrum slightly broadened. These results were also combination with theoretical DFT calculations. It was found that the phosphor had very good thermal stability and rigidity. The phosphor was also mixed with a commercial red phosphor, interfaced with a UV chip and packaged into an LED. This LED was characterized and had a color rendering index greater than 90 across a broad range of drive currents. This work highlights the utility of the fabricated phosphor as means of simplifying white-light LED fabrication. [ABSTRACT FROM AUTHOR]

• The mechanism of organic electrode weakening self-discharge effect of dual-ion battery was explored. • The performance of metal-free dual-ion batteries in different ionic liquid electrolytes was investigated. • The method of reducing the dissolution of organic electrode in ionic liquid electrolyte was discussed. The strong self-discharge reaction is one of the key factors limiting the practical use of dual-ion batteries, which leads to low coulombic efficiency and discharge capacity loss. It is of great significance to effectively reduce the self-discharge effect through redox reactions between organic electrodes and electrolytes. Herein, a dual-ion battery study that uses 1,4,5,8-naphthalenetetracarboxylic dianhydride as the anode and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide as the electrolyte is conducted. Due to the introduction of organic materials, the storage mechanism of cations on the anode is changed, which weakens the self-discharge effect. The battery shows a low self-discharge rate of 6.12% h−1 and a high discharge capacity of 114 mAh g−1. The voltage declines by only 0.14 V after resting for 15 h due to the strong redox reaction between Pyr 14 + cations and the C O groups of NTCDA. Meanwhile, a double-layer filter paper system with small porosity is used to improve the cycle performance of the battery. [ABSTRACT FROM AUTHOR]

The ancient porcelain is the treasure of Chinese civilization. In this paper, multiple surface analysis tools were applied to characterize the attractive silvery bright spots on the glaze of black-glazed tea bowl fragment. The raindrop-shaped silver flecks covering the surface were symbols of North China oil spots. High-resolution time of flight-secondary ion mass spectrometry（TOF-SIMS） data confirmed the main component of the oil spot was iron oxide. Positive ions were Fe+（m/z 55.93）, FeO+（m/z 71.93）, Fe2O+（m/z 127.86）, and negative ions were FeO-（m/z 71.93）, FeO-2（m/z 87.92）. A series of peaks were detected by micro-Raman spectroscopy, such as 230, 294, 412, 502, 611, 1 337 cm-1. This suggested existence of hematite（α-Fe2O3） in the spot. Secondary ion imaging of TOF-SIMS indicated the oil spots（～120 μm） was formed by self-organization and dispersion of hundreds hexagonal hematite crystal（～2-10 μm）. Hematite was spatially complementary to alkaline calcareous glaze that contains silicon, aluminum, calcium, and sodium. TOF-SIMS depth profiling of the spot suggested a more than 5 μm continuous hematite layer on the glaze of black-glazed tea bowl. The main mineral of α-Fe2O3 crystals was hematite, which was ochre usually. Specular hematite, a subspecies of hematite with silver or black color, was believed to play critical role in the formation of the oil spot. With the optical microscope observations, we believed that the silvery material on the surface of the oil spots should be a thin layer of specular hematite and the lower ochre layer was hematite. In fact, the oil spot appeared silvery-white and reflective when viewed from 15° to 165°, while it appeared ochre when the angles of gaze was not greater than 15° from the glazed surface of the specimen. The extraordinary visual property of color changing with different angle of gaze formed the charm of Song dynasty oil spot tea bowls. With these results, a hypothesis for the formation of the North China oil spots was enlightened. The molten phase of Fe-rich soy-black glaze gradually formed micron-sized hematite particulates at sealed kiln of high temperature（1 250 ℃）. When the kiln was unsealed, the hot porcelain was exposed to cold air immediately. A thin layer of specular hematite was generated on top of hematite particulates. [ABSTRACT FROM AUTHOR]

An elaborate account of groundwater quality estimation for irrigation in Katthiwada area Alirajpur district Madhya Pradesh is presented in this paper. The selected 20 groundwater samples from open-dug wells have been subjected to chemical analysis by standard techniques of graphic representation in tabular form. The analysis of dug wells samples for determination of Physicochemical parameters indicates that all groundwater samples are colourless, odourless, and tasteless with pH (7.0 -8.7), Electrical conductivity (238-1555), Total dissolved solids (450 -1180) mg/l. The chemical parameters involve the determination of the ionic concentration of cations - Calcium (0.89 to 3.04 mg/l), Magnesium (0.49 to 3.12 mg/l), potassium (0.01 to 0.13 mg/l) and sodium (0.95 to 10.35 mg/l) and anion - nitrate (0.56 to 1.45), Hco3 (1.19 to 3.85 mg/l), chloride (0.31 to 5.10) and sulphate (0.02 to 2.68 mg/l). The quality of groundwater for irrigational purposes depends on different chemical parameters such as sodium persent; Kelley's Ratio, Sodium Adsorption Ratio, Residual Sodium Carbonate, and Magnesium-Hazard. U. S. Salinity diagram shows that 19 samples belong to the C2 S1 type (medium salinity - low sodium water), 1 sample represents to C3 S1 type (high salinity - low sodium water) and 1 sample falls into C3 S2. Wilcox diagram shows that 16 samples of the groundwater fall under the excellent to good category, and 4 samples represent the good to permissible categories. The groundwater of the Katthiwada area is suitable for irrigation use. [ABSTRACT FROM AUTHOR]

Red‐emitting color‐convertors have attracted considerable attention for promising applications in solid‐state lighting (SSL) to improve color rendition. However, the current nitride and fluoride phosphor powders have encountered several challenges, such as high cost, narrow emission bands, and insufficient stability during operation, which limit the development of high‐power full‐spectrum SSL. In this study, thermally robust Gd3(Al,Ga)5O12:Mn (GAGG:Mn) solid‐solution ceramics (SSCs) with dual wavelength red‐emission bands were prepared via an oxygen solid‐state sintering reaction. The doped Mn ions occupied octahedral Al3+ and Ga3+ sites to generate Mn4+ luminescent centers with pronounced deep‐red emissions peaking at 698 nm (2E → 4A2), and Mn2+ luminescent centers with broad red emissions at 628 nm (4T1 → 6A1). Because the cationic radius matching effect induced the regulation of valence state of Mn, the photoluminescence of the GAGG:Mn SSCs can be tailored by the substitution of Al3+ with Ga3+. Moreover, the Mn3+ also existed in the GAGG lattice host, and their concentration decreased with increasing Ga3+ contents owing to the mismatch of ionic radius between Mn3+ and Ga3+ ions. With the optimization of Al/Ga ratio and concentration of Mn ions, a broad emission band ranging from 550 to 800 nm (bandwidth = 250 nm) was achieved from Gd3Al3Ga2O12:0.3%Mn SSCs upon 465‐nm excitation. Moreover, the GAGG:Mn SSC has over 17‐fold enhanced thermal conductivity compared with the corresponding phosphor powder. This paper opens a door of regulating the valence state of luminescence centers with cation substitution and the application of oxide red‐emitting color‐convertors. [ABSTRACT FROM AUTHOR]

The presence of reactive hydrogen-silyl (SiH) bonds in oligomethylhydridesiloxanes provides their widespread use in the building, paper, textile, and rubber industries. Low-molecular fractions of methylhydridesiloxanes, both cyclic and linear, adversely affect the operational properties of oligomer-based materials. The main goal of the present study is detection and identification of these fractions in a 136-157M commercial product, as well as in the co-oligomers synthesized from it. The method of gas chromatography–mass spectrometry has been used in the study. First, it has been proved that an increase in the temperature of the column and evaporator from 60 to 300°C does not change the composition of the low-molecular fractions. Consequently, there is no depolymerization processes related to the formation of low-molecular compounds during the analysis. To perform a qualitative analysis, the components of low-molecular fraction have been separated on a capillary column and then identified using a mass detector with an ion trap. It is shown that electron ionization triggers fragmentation of molecules and the formation of positively charged ions. As for methylhydridesiloxanes, cations with a molecular weight of [M – 15]+ arising from the rupture of the carbon-silyl bond are formed first. When such a rupture occurs in cyclosiloxanes with a total number of units of more than four, further dissociation processes can occur with the detachment of the neutral fragment (methylsilane) and the formation of bicyclosiloxane cations. Since the set of positive ions is individual for each of the components and depends on , a component-wise description of the entire low-molecular fraction becomes possible with a high degree of reliability. It is shown that, for the commercial sample under consideration, it can be described by two homologous series: cyclic , where m ≥ 4, and linear siloxanes , where n ≥ 1. [ABSTRACT FROM AUTHOR]

To quantitatively describe the kind of interaction between ion and solvent, it is convenient to use the concept of negative or positive solvation. We have established earlier that diffusion displacement distance ( d ¯ ) of an ion correlates with its solvation type. The ion is solvated positively if the average d ¯ value exceeds the crystallographic (structural) radius of an ion r i ; otherwise, ion solvation is negative. In this paper, we have estimated the length, time and velocity of ion diffusion displacement (hop) for singly charged ions Li + , Na + , K + , Rb + , Cs + , Me 4 N + , Et 4 N + , Bu 4 N + , F - , Cl - , Br - , BPh 4 - over the temperature range from 273.15 K to 473.15 K and for ions Pr 4 N + , I - , NO 3 - , ClO 4 - at 298.15 K in ethylene glycol. The fact of the negative solvation of almost all ions studied (except Li + , Na + , F - ) in ethylene glycol has been established for the first time. It has been shown that Me 4 N + ion has turned out solvated solvophilically in EG as well as in water while ions Et 4 N + , Bu 4 N + , and BPh 4 - appeared to be solvated solvophobically. We have estimated the temperature of transition T tr (from negative to positive ion solvation) for K + and Rb + ions. It physically corresponds to the absence of solvation of the ion ( d ¯ = r i ). [ABSTRACT FROM AUTHOR]

The tip size of metal protrusions is an important factor affecting corona discharge, since it influences the electric filed, the ionization range and strength around the protrusion defect. Most existing studies on the influence of protrusion tip size on corona discharge are implemented by experimental methods. However, these studies are difficult to obtain the microphysical process of charged particles, which is related to the generation of current pulses and electromagnetic (EM) waves. In this paper, a hydrodynamic simulation model is proposed to study the effect of protrusion tip size on the microphysical process and current pulses of negative corona discharge. A mapping relationship between microscopic behaviors of charged particles and current pulses is established by this simulation method. Based on the comparison of microphysical quantities, the effect of defect tip size on the detailed parameters of current pulses is clearly explained. It shows that with the increase of tip size under a constant voltage, all the five parameters of current pluses increase. The rising time is related to the effective ionization coefficient, while the falling time is dependent on the velocities of positive and negative ions. The experiment and simulation results coincide in current waveforms and all five parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chromogenic sensor for selective estimation of aqueous ferric ions was developed. • The chromogenic paper strip was prepared via doping tannic onto filter paper. • A visible color shift from white to purple was observed in the presence of Fe(III). • A concentration range of 10–190 ppm was monitored a detection limit of Fe(III). • The current sensor is a simple and practical tool for real-time detection of Fe(III). Investigation of chromogenic sensor which can selectively estimate ferric cations in aqueous environment with prospect to produce portable platforms is currently proposed. Herein, the chromogenic sensor (Tannic Acid@Filter Paper; TA@FP) was prepared via doping of tannic acid within filter paper to afford the excellent selectivity for ferric cations over various examined metal ions. The designed chromogenic sensor was applied for estimating ferric ions via turn-on detection, while, it could acquire a marked visible color shifting from white to purple hue depending on the total content of Fe (III) ions in the aqueous medium. Complete characterization of the designed sensor before and after its exploitation in estimation of ferric cations was systematically performed via different spectral and microscopic analyses. The functionalized TA@FP was quite sensitive for quantitative estimation of ferric ions with wide scaling linear concentration range of 10–190 ppm. Maximum sensitivity of the exploited platform was observed at very low concentration (10 ppm) rather than the higher concentrations. The correlation coefficient (R2 = 0.99) was closer to unity. The prepared chromogenic sensor could be described as a simple and practical sensing tool for real-time quantitative and qualitative assessment of Fe (III) cations. [ABSTRACT FROM AUTHOR]

The paper deals with the gas-phase formation of nanoparticles that is a fundamental process responsible for the condensed matter in the Universe, which also attracts attention due to its involvement in the particle synthesis for various nanotechnology applications. Previously reported results on MgO nano-oxides formed by Mg combustion showed a unique phenomenon coined "the condensation stagnation" that is the occurrence of critical clusters with suppressed growth. Here we focus on the effect of an external ionizer on this condensation growth stagnation. We show that the condensation stagnation occurring in the Mg particle flame subjected to a positive ion flux is similar to that in the unaffected flame. In contrast, applying negative charging significantly influences the state of stagnation of the system, i.e., no critical clusters are observed in the products sampled from the flame. The discovered critical behavior of the state of stagnation is explained in terms of the heat transfer between the condensed MgO nanoparticles and the surrounding gas, which efficiency depends on the sign of the nanoparticle charge. This dependence of the heat transfer efficiency on the nanoparticle charge is a new fundamental effect that should become the basis for accurate modeling in two-phase high-temperature systems. [ABSTRACT FROM AUTHOR]

In this paper, the corona discharge process of the bar-plate gap at −1 kV DC voltage is simulated using a two-dimensional axisymmetric plasma module. We analyze the variation of air negative corona discharge current, and the distribution morphology of microparticles in different discharge stages in detail. The significance of plasma chemical reactions at some typical time and the distribution characteristics of heavy particles are investigated according to reaction rates. Results show that, in the current rising stage, the collision ionization reactions (e.g., R1 and R2) and electron adsorption reaction (e.g., R3) play a major role, which lead to the increase in charged particles and the formation of an electron avalanche. In the current drop stage, all reaction rates decreased, except for collision ionization and electron attachment, partial charge transfer reactions (e.g., R8, R10, R11, and R14), and composite reactions (e.g., R16, R17, and R18), which come into play and gradually reduce the number of charged ions in the gap. In the current stabilizing stage, the main chemical reactions are composite reactions (e.g., R16 and R17), then the corona discharge ends. For the heavy particle distribution, O2+ and O4+ are the main positive ions, O2− is the most abundant negative ions, and the neutral particles are mainly O. [ABSTRACT FROM AUTHOR]

Due to their good dielectric properties and low global warming potential, C4F7N–CO2 and C4F7N–N2 mixtures have shown promising potential to replace SF6 in high voltage gas insulated equipment. However, during manufacturing, installation, and transportation of power equipment, burs and metal particles can be inevitably left inside, and they can cause corona discharge. Fundamental investigation of the corona discharge mechanism is essential to monitor partial discharge signals in environmentally friendly power equipment. This paper applies the fluid model to investigate the discharge mechanism of C4F7N–CO2 and C4F7N–N2 mixtures in negative point-plane corona discharge. A 2D axisymmetric model combines the drift-diffusion equations for electrons, positive ions, and negative ions and Poisson's equation to study the process of dynamics. The gas is a mixture of C4F7N (5%, 7%, or 13%) and CO2 or N2 (95%, 93%, or 87%). The rise time of the first discharge pulse in C4F7N–CO2 and C4F7N–N2 mixtures is about 0.1 ns. The interval time between the first and the second pulse in the 5% C4F7N–95%CO2 mixture is about 1.5 times longer than that in the 5% C4F7N–95% N2 mixture. When the C4F7N content is 7% and 13%, the interval time between the first and second pulses in C4F7N–CO2 mixtures is about 2 and 3 times longer than those in C4F7N–N2 mixtures, respectively. The suppression regions in C4F7N–CO2 mixtures are larger than those in corresponding C4F7N–N2 mixtures. The total number of electrons, positive ions, and negative ions in C4F7N–CO2 mixtures is higher than that in C4F7N–N2 mixtures, while the reduced electric field in C4F7N–CO2 mixtures is smaller than that in C4F7N–N2 mixtures. [ABSTRACT FROM AUTHOR]

This paper describes the construction of the Periodic Tables for cations of all elements with charges + 1, + 2, + 3 and anions with charge − 1. The Table for cations+1 differs significantly from other newly constructed Tables and from known Tables, as the d- and f-blocks are inserted into s-block and split it up for two parts. Importantly, a new type of 3d- and 4f-shell contractions has been discovered. The manifestations of secondary periodicity in case of anions is absent or opposite to the manifestations observed for atoms and cations. For kainosymmetric anions, the ionization energies are lowered, which contradicts the theoretical assumptions and experimental data supporting the classical concept of kainosymmetry. Simple formulas are proposed for quantitative description of the manifestations of internal periodicity and kainosymmetry. The regularities of change in these manifestations depending on the charge and the position of ions or atoms in the Periodic Table are established. In the 6th period, the bifurcation in the properties characteristic of the internal periodicity does not occur at usual position, i.e. in the middle of the row from the block of the Periodic Table (p3–p4), but takes place earlier, along with the transition of the electronic configurations p2–p3. In other words, the place of transition from "early" to "late" elements changes. [ABSTRACT FROM AUTHOR]

In this paper cation arrangement in two samples of aluminoceladonite, emerald-green and dark-green were studied by Mössbauer, Raman and X-ray photoelectron spectroscopies. The X-ray photoelectron spectroscopy (XPS) spectra obtained in the region of the Si2p, Al2p, Fe2p, K2p, and O1s core levels provided information, for the first time highlighting a route to identify the position of Si, Al, K, and Fe cations in a structure of layered silicates. The XPS analysis showed the presence of Al in tetrahedral and octahedral coordination while the K2p line indicated the possibility of K+ substitution by other cations in interlayer sites. Mössbauer spectroscopy provided information about crystal chemistry with respect to the local electronic and geometric environment around the Fe atom and to distortions of the polyhedra. It turned out that iron was located mostly in the cis-octahedra position wherein about 75% of iron appeared in the form of Fe3+. The most preferred cation combinations around Fe corresponded to 3Fe3+ ions and MgFe2+Fe3+/2MgFe3+. Raman spectroscopy illustrated aluminium substitution in silicon and iron positions wherein the concentration of the aluminium determined the degree of structural distortion within the layered system. These isomorphic substitutions implied a typical band arrangement in the hydroxyl region, which has not been observed in celadonites so far. [ABSTRACT FROM AUTHOR]

This paper explores the head-on collision between two-counter propagating positron acoustic solitons and double layers (DLs) in an unmagnetized collisionless plasma having mobile cold positrons fluid, immobile positive ions and ( r , q )-distributed hot positrons, and hot electrons. By employing the extended Poincaré–Lighthill–Kuo method, the coupled Korteweg–de Vries (KdV), modified KdV (mKdV) and Gardner equations are derived to archive this goal. The effect of dimensionless parameters on the propagation characteristics of interacting KdV solitons (KdVSs), mKdV solitons (mKdVSs), Gardner solitons (GSs) and DLs are examined in detail by considering the limiting cases of ( r , q )-distribution. It is noted that the interaction of GSs and DLs are reported for the first time. The outcomes might be comprehended and beneficial not only in space and astrophysical environments but also in laboratory studies. [ABSTRACT FROM AUTHOR]

Some hearing, vestibular, and vision disorders are imputable to voltage-gated Ca2+ channels of the sensory cells. These channels convey a large Ca2+ influx despite extracellular Na+ being 70-fold more concentrated than Ca2+; such high selectivity is lost in low Ca2+, and Na+ can permeate. Since the permeation properties and molecular identity of sensory Ca2+ channels are debated, in this paper, we examine the Na+ current flowing through the L- and R-type Ca2+ channels of labyrinth hair cells. Ion currents and cytosolic free Ca2+ concentrations were simultaneously monitored in whole-cell recording synchronous to fast fluorescence imaging. L-type and R-type channels were present with different densities at selected sites. In 10 nM Ca2+, the activation and deactivation time constants of the L-type Na+ current were accelerated and its maximal amplitude increased by 6-fold compared to physiological Ca2+. The deactivation of the R-type Na+ current was not accelerated, and its current amplitude increased by 2.3-fold in low Ca2+; moreover, it was partially blocked by nifedipine in a voltage- and time-dependent manner. In conclusion, L channel gating is affected by the ion species permeating the channel, and its selectivity filter binds Ca2+ more strongly than that of R channel; furthermore, external Ca2+ prevents nifedipine from perturbing the R selectivity filter. [ABSTRACT FROM AUTHOR]

• During the transportation and diffusion of cations, a stable solvated layer can be formed to prevent the charge exchange between the cation and the charged surface of nano SiO 2 particle. • When the concentration of salt solution is increased and the valence of cations is increased, the hydrogen bond is easier to break through the solvation layer to gather on the surface of nano SiO 2 particles. • When the cations transport to the position of 7 Å away from the surface of nano-SiO 2 particles, the short-range force begins to affect the movement of cations. When the cations transport to the position of 2 ∼ 3 Å away from the surface of nano-SiO 2 particles, the charge exchange occurs and the cations continue to oscillate. Nano-SiO 2 solution has great potential for application in the field of oil and gas exploration and development. However, its application is restricted due to the aggregation of nano-SiO 2 in stratum water. This paper studies the process of interaction between nano-SiO 2 particles and salt solutions by using the molecular dynamics simulation experiments, including the characteristics of transportation and diffusion of cations around the nano SiO 2 , the effect of cations on the recombination and destruction of hydrogen bonds, the interaction energy between cations and nano SiO 2. The main results are as follows. During the transportation and diffusion of cations in the solution, the hydrogen bonds of water molecules are broken, so that the hydrogen bonds can be rearranged, and a stable solvated layer can be formed. In the solvated layer, the repulsive force of solvation can prevent the charge exchange between cation and the charged surface of nano SiO 2 particle. Compared with the monovalent salt solution, more divalent cations can break through the solvation layer to generate the charge exchange on the surface of nano-SiO 2 particle. More divalent cations can conduct small amplitude oscillation movement near the surface of nano-SiO 2 particle due to the strong electrostatic effect. When the concentration of salt solution is increased (3000 mg/L → 7000 mg/L) and the valence of cations is increased (monovalent → bivalent), the hydrogen bond is easier to break through the solvation layer to gather on the surface of nano SiO 2 particles, which is unfavorable to the stability of nano SiO 2 particles. When the cations transport to the position of 7 Å away from the surface of nano-SiO 2 particles, the short-range force (including hydrogen bond force, van der Waals force, and electrostatic force) begins to affect the movement of cations. When the cations transport to the position of 2 ∼ 3 Å away from the surface of nano-SiO 2 particles, the charge exchange occurs between cations and the surface of nano SiO 2 particle, so that the local energy is increased and the cation continues to oscillate. In summary, with the increasing of concentration of salt solution and the valence state, more cations can break through the solvation layer to be adsorbed on the surface of nano SiO 2 particle, showing that the ability of transportation and diffusion of cations is weakened, the interaction energy between nano SiO 2 particle and salt solution molecules is enhanced. The electrostatic force is the main force to destroy the stability of nano SiO 2 particle. The conclusions can provide a certain theoretical basis for the efficient application of nano-SiO 2 materials in the field of oil and gas exploration and development and other interrelated industry. [ABSTRACT FROM AUTHOR]

The experimental data reported in this paper suggest that titanium(IV) oxyhydroxyphosphate-based ion-exchange materials are potentially attractive for extraction of heavy metal cations from solutions. We have studied the time-dependent ion exchange activity of titanium phosphates for Zn2+, Co2+, and Ni2+ cations in relation to the liquid : solid ratio, temperature, and equilibrium pH of the cation exchange process. The results demonstrate that the selectivity of an ion exchanger for metal cations is determined by the ionic radii of the metals. Conditions for effective use of titanium phosphate materials for extraction of Zn2+, Co2+, and Ni2+ cations from solutions (liquid : solid ratio, temperature, and pH) have been optimized experimentally. [ABSTRACT FROM AUTHOR]

The results reported in this paper suggest that titanium(IV) oxyhydroxyphosphates can be used for sorption extraction of valuable metal cations from solutions, followed by desorption and concentration of the metal cations and simultaneous regeneration of the titanium phosphate material for further use. Conditions for effective desorption processes (desorbing agent concentration and desorption time) have been studied and optimized. The sorption/desorption process effectiveness in the case of multistep use of the sorbent has been shown to decline as a result of steric hindrances associated with its dehydration. As the sorption properties of the sorbent degrade, it can be used for extraction of trace amounts of highly toxic metal cations and then buried. [ABSTRACT FROM AUTHOR]

Negative corona discharge can deflect in transverse airflow in pin-to-plane electrodes at atmospheric pressure. In this paper, we investigate the mechanism of Trichel pulse discharge deflection in transverse airflow and give a further understanding of the dynamic process of the deflection through experiments and simulations. In experiments, we quantitatively record the deflection angle by processing the discharge images, and they show that a larger airflow speed will lead to a larger deflection angle. In simulations, the discharge deflection angle is calculated through a 2D fluid model. Besides, the periodic fluctuation of the deflection angle with Trichel pulses is revealed, and this phenomenon can be explained by the alternative dominant effect of airflow or ionization on the net production of positive ions in the vicinity of the tip. When the effect of airflow is dominant, more positive ions will generate away from the center of the tip, which will lead to an increase in the deflection angle. On the other hand, when the effect of ionization prevails, more positive ions will generate near the center because the electric field here is stronger, and the deflection angle will decrease. In addition, if these two effects balance, the deflection angle will reach its maximum or minimum value. [ABSTRACT FROM AUTHOR]

This paper demonstrates the feasibility of using titanium(IV) oxyhydroxyphosphate-based materials for sorption extraction of heavy metal cations from solutions. We have determined Pb2+ and Cd2+ sorption characteristics of ion exchangers, examined the kinetics of Pb2+ and Cd2+ sorption on the titanium phosphate materials, and assessed the effect of ionic radius on the affinity of the sorption matrices for metal cations. Conditions for effective use of the ion exchange materials for extracting Pb2+ and Cd2+ cations from solutions (liquid : solid ratio and pH) have been optimized experimentally. [ABSTRACT FROM AUTHOR]

Ternary metal oxide compounds, such as Ti-Nb and Nb-W oxides, have renewed research interest in energy storage materials because these oxides contain multivalent metal ions that may be able to control the ion transport in solid lithium batteries. One of these oxides is Ti2Nb10O29, which is composed of metal–oxygen octahedra connected through corner-sharing and edge-sharing to form "block structures". In the early 1970s Von Dreele and Cheetham proposed a metal-atoms ordering in this oxide crystal using Rietveld refined neutron powder diffraction method. Most recent studies on these oxides, however, have not considered cation ordering in evaluating the battery electrode materials. In this paper, by utilizing the latest scanning transmission electron microscopy combined with energy dispersive X-ray spectroscopy imaging technology, the cation chemical ordering in those oxide crystals was directly revealed at atomic resolution. [ABSTRACT FROM AUTHOR]

The paper delivers an analyzing and discussion of the experimental results for the effect of lanthanum substitution on the structural behavior for compounds (Bi2Ba2CaCu2-XLaXO8+δ) with variation concentrations from 0 up to 0.2 with a fraction of 0.05. Specimens prepared by solid-state reaction. We investigate the structural properties, studying the lanthanum substitution instead of lead using the resulting properties of XRD. The sintering process was done below the melting point of any one of the component materials. The optimum sintering temperature was equal to 850 °C for 72 h to produce an active powder with higher densities and reduced the distance between the grains. (FWHM) results were calculated using X-ray information. The crystallite size D was estimated by Scherer and Williamson-Hall equations, where the results showed that the crystallite size (57.029-63.281 nm) and (56.395-65.948 nm) respectively, besides, the degree of crystallinity (41.64-63.79%) correlation with concentrations of lanthanum substitution. Through the outcome values, the results of the three methods are observed close to each other and this indicates that these methods are compatible with the compound and that the partial replacement occurs a noticeable change in the size of the crystallite as well as in the degree of crystallinity. [ABSTRACT FROM AUTHOR]

• Critical roles of A, B-site cations, and oxygen vacancies are revealed in Bi 0.15 Sr 0.85 Co 1− x Fe x O 3−δ perovskites. • BiSC 0.8 Fe 0.2 shows excellent OER activity and marvelous durability in 0.1 M KOH. • A link between bulk properties and OER activity has been established. • The highly A-site deficient surface layer also plays a critical role in OER. Development of perovskite-type electrocatalysts with high activity, excellent durability and affordable cost provides a promising solution to promote commercialization of clean energy technologies. Here we prepared Bi 0.15 Sr 0.85 Co 1− x Fe x O 3−δ (x = 0.2, 0.4, 0.6, 0.8, 1) perovskites by the conventional solid-state reaction route, and investigated their OER electrocatalytic activity and durability in 0.1 M KOH solution to reveal the critical role of A, B-site cations and oxygen vacancies. Results show the OER activity decreases with increasing x. The optimum composition, BiSC 0.8 F 0.2 , presents impressive electrocatalytic performances with low overpotential (330 mV on rotation disk electrode, and 283 mV on carbon paper electrode at 10 mA/cm2) and excellent long-time durability showing a small increase in the overpotential of 17 mV in 167.5 h. Comprehensive analysis and discussion on the bulk and surface properties reveal the critical role of A, B-site cations and oxygen vacancies on OER, and interrelations of Co2+ fraction, oxygen non-stoichiometry and the OER overpotential have been established. Most importantly, a highly A-site deficient surface layer is found on the as-synthesized perovskite, which facilitate OER by exposing more active B-site cations. This work not only reports a promising OER electrocatalyst with high activity and superior durability, but also provides perspectives on relational design for highly efficient and stable perovskite electrocatalysts for OER using solid-state reaction method. [ABSTRACT FROM AUTHOR]

In this paper we introduce the error-functions for one-sided and double-sided Taylor's approximations of real analytic functions. We illustrate the appli- cation of error-functions in the process of generalization of one trigonometric inequality. [ABSTRACT FROM AUTHOR]

Rare earth substituted yttrium iron garnets (Re:YIG) are an important class of magnetic ceramics which can be widely used in microwave-related, magnetic and magneto-optic devices. For this reason, this paper investigates the structural behavior and magnetic performance of the Eu, Ce-YIG garnet by the traditional ceramic technique. Oxide powders with stoichiometric ratios were blended to achieve the chemical composition (Y 2.75-x Ce 0.25 Eu x Fe 5 O 12 where x = 0, 0.15, 0.25 and 0.35). The mixed powder was calcined at 1000 °C for 20 h in the air condition, sintered at 1350 °C for 14 h and then the sample became denser at 1420 °C for 6 h in the air. The XRD results showed that the Eu3+ ion is effective in solubilizing the Ce3+ ion and that the lowest amount of required Eu to dissolve the 0.25 Ce is about 0.25 in the structure. The XPS data confirmed that the Fe2+ and Ce4+ cations are not present in the structure. Moreover, the substituted garnet with 0.25 Ce and 0.25 Eu increased saturation magnetization by about 21% compared to the pure YIG. The magnetic coercivity increases from 16.41 Oe for the pure YIG to 25.52 for the Y 2.75 Ce 0.25 Fe 5 O 12 and then decreases with the Eu substitution. [ABSTRACT FROM AUTHOR]

In this paper we consider the Euler-Poisson system (describing a plasma consisting of positive ions with a negligible temperature and massless electrons in thermodynamical equilibrium) on the Sobolev spaces Hs(R3), s > 5/2. Using a geometric approach we show that for any time T > 0 the corresponding solution map, (ρ0, u0) 7! (ρ(T), u(T)), is nowhere locally uniformly continuous. On the other hand it turns out that the trajectories of the ions are analytic curves in R3. [ABSTRACT FROM AUTHOR]

This paper presents the basic physical and numerical principles of a fluid model of the negative ions source. The model gives self-consistent two-dimensional description of the source, including the neutral gas flow, plasma chemistry, RF coupling in the source driver and plasma transport through the magnetic filter. The different particle species (electrons, the three types of the positive ions: H + , H 2 + , H 3 + , negative ions H − and the neutral species: hydrogen atoms H and molecules H 2) are described by separate continuity equations and the electron temperature is governed by the electron energy balance equation. The particle fluxes are found from momentum equations neglecting the inertia terms (drift-diffusion approximation). The electrostatic coupling between electrons and ions is described by the Poisson equation. The paper focuses on details of the RF model and on the initial code developments to simulate the currents in the source induced by the RF currents flowing in the feeding coils. In our approach, the RF electrical field is split in a plasma part plus another one in vacuum, E = E p + E V , which simplifies the boundary conditions for E p while E V is obtained from a theoretical formulation for the field generated by a current loop, which results in a fast and flexible numerical algorithm providing converged solution for the RF field after a few iterations, even for the cases with high conductivity of the plasma. The numerical method is based on finite volume approximation and 9-point discretization is used to account on anisotropy due to magnetic field. The semi implicit numerical solver allows for large time steps (> 1000 × explicit time step) producing steady-state solution in a reasonable time (few hours for a typical mesh). The RF model has been successfully coupled to the fluid equations of the source and self-consistent solutions are analyzed in order to see the influence of the driver parameters and RF model assumptions (e.g. stochastic conductivity, induced magnetic field) on the heating efficiency and the plasma dynamics. It has been found that without magnetic field the plasma dynamics in the SPIDER source is almost independent on the details of the RF coupling model. • 2D fluid model of negative ion source is presented, including RF coupling. • Without magnetic field, results are almost independent on details of the RF model. • With magnetic field, the RF coupling model strongly affects the plasma dynamics. [ABSTRACT FROM AUTHOR]

This paper develops a theoretical model for formation of multilayers in the magnetized electronegative plasma at the edge of plasma ion source. The impacts of positive ion temperature and collisions are studied and quantified by obtaining the structure of the plasma sheath. By adding the negative ions into the discharge, the solutions of Poisson's equation become oscillatory. A finite temperature for the positive ions and also the collisions results in a change in the behavior of such oscillatory solutions. Here, it is assumed that the collision frequency depends on the positive ions velocity and thermal positive ions flow is adiabatic. The spatial distribution of the species density, electric potential, and positive ion velocity is calculated for different values of positive ion temperature and negative ion concentration for two limiting cases where the collision frequency either is constant or depends linearly on velocity. In addition, the influence of the plasma parameters such as negative ion density and temperature and positive ion temperature is investigated on the space charge and positive ion flux as well as parameter space region. It is also shown that the presence of the negative ion into the plasma ion source influences the extracted positive ion flux and increases the positive ions intensity. [ABSTRACT FROM AUTHOR]

Propagation of nonlinear and supernonlinear positron-acoustic periodic waves is examined in an electron-positron-ion plasma composed of static positive ions, mobile cold positrons, and q-nonextensive electrons and hot positrons. Employing the phase plane theory of planar dynamical systems, all qualitatively different phase portraits that include nonlinear positron-acoustic homoclinic orbit, nonlinear positron-acoustic periodic orbit, supernonlinear positron-acoustic homoclinic orbit, and supernonlinear positron-acoustic periodic orbit are demonstrated subjected to the parameters q, μ1, μ 2, σ1, σ 2, and V. The nonlinear and supernonlinear positron-acoustic periodic wave solutions are reported for different situations through numerical computations. It is observed that the nonextensive parameter (q) acts as a controlling parameter in the dynamic motion of nonlinear and supernonlinear positron-acoustic periodic waves. The dynamic motions for the positron-acoustic traveling waves with the influence of an extrinsic periodic force are investigated through distinct qualitative approaches, such as phase portrait analysis, sensitivity analysis, time series analysis, and Poincaré section. The results of this paper may be applicable in understanding nonlinear, supernonlinear positron-acoustic periodic waves, and their chaotic motion in space plasma environments. [ABSTRACT FROM AUTHOR]