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In the pharmaceutical field, analytical chemistry is evolving and one area that is experiencing enthusiasm is the design and implementation of solid contact ion-selective electrodes. We have developed two potentiometric sensors for the selective assay of a widely used drug diclofenac sodium. Diclofenac sodium was targeted in one of its most recommended dosage forms (Arthrotec® tablets) in the presence of misoprostol. A cost-effective copper printed circuit board as a substrate has been coated with a PVC sensing membrane to fabricate sensor I. Hydrophobic carbon nanotubes (CNTs) have been modified through in situ reduction of pentafluorophenyl diazonium using sodium borohydride. An interlayer of the modified CNTs was inserted as a transducer layer between the Cu substrate and the ion-sensing membrane in sensor II to enhance its electrochemical performance and stability. The microfabricated electrodes demonstrated encouraging outcomes upon the direct assay of diclofenac sodium in combination with misoprostol and other additives without sample preparation steps. The responses presented a linear Nernstian pattern in the range of 1.0 × 10−4 to 1.0 × 10−2 mol l−1 with a slope of −58.2 and −58.4 mV/decade for sensors I and II, consequently. Finally, the sustainability of the developed technique was assured using advanced green metrics. [ABSTRACT FROM AUTHOR]

We have explored a set of structurally related fluorinated and non-fluorinated organosilicon additives and quantified their rates of reaction with the superoxide radical anion O2•−. using rapid-scan cyclic voltammetry. Absolute reaction rate measurements in acetonitrile solvent show that O2•− reacts with the fluorinated OS compounds with bimolecular rate constants k BM more than 1000x larger than k BM for the reaction between O2•− and ethylene carbonate. We further identified the products of reaction of a model OS compound using multiple nuclear magnetic resonance (NMR) methods and with gas chromatography/mass spectroscopy. Chemical analysis measurements show that addition of potassium superoxide KO2 to a model fluorinated OS compound produces only one product. Our results indicate that that OS compounds improve battery performance by rapidly scavenging O2•− in a way that produces a stable product and reduces or eliminates the competing chemical pathways associated with carbonate breakdown. These results provide new insights into how chemical structure impacts critical chemical reactions and may guide the design of new additives that further improve battery safety and stability. [ABSTRACT FROM AUTHOR]

We report an easy electrochemical route for preparing a catechol derivative (di-ferulyl sesamol derivative, designated as CA-Fer) functionalized low-cost carbon black (CB) modified electrode in a neutral pH buffer solution. As synthesized precursor organic compound, CA-Fer has been electrochemically oxidized over the CB by potential cycling treatment in pH 7 PBS that leads to a high redox active CA-Fer-catechol derivative (CB@CA-Fer-Redox), which exhibited a well-defined and stable surface-confined redox response at Eo' = 0.150 V vs Ag/AgCl with a surface excess value = 50.46 nmol cm-2. Unlike the conventional redox active mediators, GCE/CB@CA-Fer-Redox modified electrode has failed to show any mediated oxidation/reduction response to various electro-active biochemicals and chemicals, viz., ascorbic acid, glucose, cysteine, caffeic acid, hydrazine, hydrogen peroxide, uric acid, dopamine, creatinine, urea, nitrite, sulfide and sulfate ions, depicting a clear advantage of using it as a voltammetric pH sensor for real-time applications. The modified electrode showed a linear voltammetric potential signal against pH in a window, 3-11, with a slope value of (∂Ep/∂pH) = -59 ± 3 mV pH-1. As an independent study, a CA-Fer-Redox modified three-in-one screen printed electrode was developed, and a sensitive voltammetric pH analysis of some chemical biochemical real sample systems were demonstrated. [ABSTRACT FROM AUTHOR]

In the process of molten salt electrolysis, the influence of the composition of the electrolyte on the current efficiency and electrolysis quality is a key issue that needs to be studied urgently. Thus, the interaction between tantalum ions and anions, coordination competition between chlorine ions and fluoride ions in the electrochemical metallurgy of tantalum metal are investigated in this paper. Their effects on the reduction mechanism of tantalum ions was also studied. Moreover, the chemical coordination mechanism of tantalum ions in the above molten salts were revealed through electrochemical tests and chemical analysis. By adding fluoride ions, the reduction step of tantalum ions is reduced from two-step to one-step, which simplifies the reduction process, avoids the current empty consumption caused by the disproportionation reaction of low-valent tantalum ions, and optimizes the particle size of the product. [ABSTRACT FROM AUTHOR]

Micromixers are widely used in lab-on-a-chip devices for analytical chemistry, bioengineering, and biomedicine to achieve rapid mixing and analysis of samples. However, the existing micromixers are mostly two-dimensional structures with low mixing efficiency. Even three-dimensional (3D) micromixers with complex structures have low mixing efficiency in the low Reynolds number range. In this paper, a 3D split-and-recombination (SAR) micromixer inspired by the horseshoe transform principle is proposed to further improve the mixing efficiency. There 3D SAR micromixers with different subchannel sizes were designed and tested in the Reynolds numbers range of 0.1â€"100. The optimal size of the micromixer was revealed through computational fluid dynamics simulations and experimental test results. A minimum mixing index of 91% is achieved in the range of Reynolds numbers from 0.1 to 100. Especially, for Re â©ľ 20, the mixing index is higher than 99%. The results obtained indicate that this 3D SAR micromixer with an asymmetric structure shows a satisfactory choice in the fluid mixing process of microfluidic systems, and has a potential application in the field of microchip-based biochemical analysis. [ABSTRACT FROM AUTHOR]

The aim of the present study was to prepare U-7 wt% Nb alloy by the direct oxide electrochemical reduction (DOER) method. The alloy was prepared from the mixed oxide precursors namely, UO2 and Nb2O5. When the precursors were sintered in a reducing atmosphere of Ar-8 vol% H2, Nb2O5 was converted into NbO2. Subsequently, the mixed oxide pellet (UO2-NbO2) was reduced by the lithium metal, electrochemically generated from a molten LiCl-1 wt% Li2O bath at 700°C. The electro-lithiothermic reduction was performed by constant current electrolysis mode with a mixed oxide pellet as the cathode and platinum as the anode. The reduction pathways of the individual oxides and the mixture were established using cyclic voltammetry and potentiostatic electrolysis techniques. The reduced alloy was characterized by XRD and SEM-EDS. These results confirmed the formation of U-Nb alloy. The composition of the alloy was determined by EDS, EDXRF and chemical analysis. [ABSTRACT FROM AUTHOR]

The double-layer expansion at the interfaces of charged electrodes when a concentrated salt solution (molar concentration Csalt) is replaced by a diluted solution (Cfresh), produces an increase of the cell voltage. Experiments and simulations were performed in order to study the effect of several variables on the obtained transient voltage, V(t), and the rising of voltage at equilibrium, Δφeq. Carbon electrodes were prepared and characterized by cyclic voltammetry, amperometry, and N2-adsorption isotherms. The experimental results and finite elements simulations show that the shape of V(t) is influenced by the diffusion coefficients of the ions. On the other hand, experiments and simulations indicate that Δφeq present a Nernstian-like dependence with the dilution coefficient, Cdil = Csalt/Cfresh, while is independent of the initial charge and charging time. Quantitative features are interpreted by proposing a partial blocking of the electrodes for the dilution process, associated to irreversible incorporation of solution into the porous, presenting a model to estimate the blocking degree. Finally, cycles of charging-dilution-work-concentration were performed, extracting energies in the order of 100 μJ cm−2, which are in agreement with the model equations as function of Csalt and Cfresh. [ABSTRACT FROM AUTHOR]

Plasmas interacting with liquid microdroplets are gaining momentum due to their ability to significantly enhance the reactivity transfer from the gas phase plasma to the liquid. This is, for example, critically important for efficiently decomposing organic pollutants in water. In this contribution, the role of â‹...OH as well as non-â‹...OH-driven chemistry initiated by the activation of small water microdroplets in a controlled environment by diffuse RF glow discharge in He with different gas admixtures (Ar, O2 and humidified He) at atmospheric pressure is quantified. The effect of short-lived radicals such as Oâ‹... and Hâ‹... atoms, singlet delta oxygen (O2(a 1Î"g)), O3 and metastable atoms of He and Ar, besides â‹...OH radicals, on the decomposition of formate dissolved in droplets was analyzed using detailed plasma diagnostics, droplet characterization and ex situ chemical analysis of the treated droplets. The formate decomposition increased with increasing droplet residence time in the plasma, with ∼70% decomposition occurring within ∼15 ms of the plasma treatment time. The formate oxidation in the droplets is shown to be limited by the gas phase â‹...OH flux at lower H2O concentrations with a significant enhancement in the formate decomposition at the lowest water concentration, attributed to eâˆ'/ion-induced reactions. However, the oxidation is diffusion limited in the liquid phase at higher gaseous â‹...OH concentrations. The formate decomposition in He/O2 plasma was similar, although with an order of magnitude higher Oâ‹... radical density than the â‹...OH density in the corresponding He/H2O plasma. Using a one-dimensional reactionâ€"diffusion model, we showed that O2(a 1Î"g) and O3 did not play a significant role and the decomposition was due to Oâ‹..., and possibly â‹...OH generated in the vapor containing droplet-plasma boundary layer. [ABSTRACT FROM AUTHOR]

The recently discovered Indus stellar stream exhibits a diverse chemical signature compared to what is found for most other streams due to the abundances of two outlier stars, Indus_0 and Indus_13. Indus_13 exhibits an extreme enhancement in rapid neutron-capture (r-)process elements with [Eu/Fe] = + 1.81. It thus provides direct evidence of the accreted nature of r-process-enhanced stars. In this paper we present a detailed chemical analysis of the neutron-capture elements in Indus_13, revealing the star to be slightly actinide poor. The other outlier, Indus_0, displays a globular cluster-like signature with high N, Na, and Al abundances, while the rest of the Indus stars show abundances compatible with a dwarf galaxy origin. Hence, Indus_0 provides the first chemical evidence of a fully disrupted dwarf containing a globular cluster. We use the chemical signature of the Indus stars to discuss the nature of the stream progenitor which was likely a chemically evolved system, with a mass somewhere in the range from Ursa Minor to Fornax. [ABSTRACT FROM AUTHOR]

Based on the second Gaia data release (DR2) and APOGEE (DR16) spectroscopic surveys, we define two kinds of star samples: high-velocity thick disk (HVTD) with vϕ > 90 km s−1 and metal-rich stellar halo (MRSH) with vϕ < 90 km s−1. Due to high-resolution spectra data from APOGEE (DR16), we can accurately analyze the element abundance distribution of HVTD and MRSH. These element abundances constitute a multidimensional data space, and we introduce an algorithm method for processing multidimensional data to give the result of dimensionality reduction clustering. According to chemical property analysis, we derive that some HVTD stars could originate from the thin disk and some MRSH stars could originate from dwarf galaxies, but those stars that have similar chemical abundance characteristics in both samples may form in situ. [ABSTRACT FROM AUTHOR]

Research on microfluidic chips is becoming more and more important in life sciences, medical testing, and chemical reactions. In the process of separating particles by dielectrophoresis (DEP), focusing of mixed particles is essential. The commonly used focusing method is sheath flow which dilutes the particle samples. However, it requires an additional injector which precludes development of an integrated system for chemical analysis and biological detection. In this paper, we propose a novel sheathless, shunt-focusing approach using microfilters (MFs) and interdigital electrodes to achieve particle capture and separation. By passing through a shrinking channel, most of the flowing small particles pass through the MFs, generating an artificial sheath flow in the channels to achieve focusing. Subsequently, interdigital electrodes provide DEP force to separate the particles. Separation efficiency was assessed by collecting polystyrene (20 μm diameter) from silica (4 μm diameter) at various flow rates. From the experimental results, the efficiency of capture reached 71%–86% and that of separation was over 98.6%. This chip is expected to be applied to the separation of circulating tumor cells in blood samples. [ABSTRACT FROM AUTHOR]

We study four lines of sight that probe the transition from diffuse molecular gas to molecular cloud material in Taurus. Measurements of atomic and molecular absorption are used to infer the distribution of species and the physical conditions toward stars behind the Taurus Molecular Cloud (TMC). New high-resolution spectra at visible and near-IR wavelengths of interstellar Ca ii , Ca i , K i , CH, CH+, C2, CN, and CO toward HD 28975 and HD 29647 are combined with data at visible wavelengths and published CO results from ultraviolet measurements for HD 27778 and HD 30122. Gas densities and temperatures are inferred from C2, CN, and CO excitation and CN chemistry. Our results for HD 29647 are noteworthy because the CO column density is 1018 cm−2 while C2 and CO excitation reveals a temperature of 10 K and a density of ∼1000 cm−3, more like conditions found in dark molecular clouds. Similar results arise from our chemical analysis for CN through reactions involving observations of CH, C2, and NH. Enhanced potassium depletion and a reduced CH/H2 column density ratio also suggest the presence of a dark cloud. The directions toward HD 27778 and HD 30122 probe molecule-rich diffuse clouds, which can be considered CO-dark gas, while the sight line toward HD 28975 represents an intermediate case. Maps of dust temperature help refine the description of the material along the four sight lines and provide an estimate of the distance between HD 29647 and a clump in the TMC. An appendix provides results for the direction toward HD 26571; this star also probes diffuse molecular gas. [ABSTRACT FROM AUTHOR]

Complex simulations (e.g. multi-dimensional fluid models) usually prevent the use of very large chemistry models. In this work, the important physicochemical processes in a volume-production high-current negative hydrogen ion source (HCNHIS) are identified for a pressure range of 1–100 Torr using a global model. The particle species include H2(υ = 0–14), H(n = 1–3), , , H+, H−, and electrons. The simulation results indicate that for the production of negative hydrogen ions through dissociative attachments, the high vibrational levels of hydrogen molecules are important at low pressures, and the ground state and low vibrational levels of hydrogen molecules play an increasingly important role with increasing pressure. The reactions involving the ground state, low vibrational levels, and neighboring levels of each level tend to dominate the production of vibrational levels and transitions between them in the volume-production HCNHIS. With increasing pressure, the electron energy dissipation shifts from dissociation of H2(υ = 0) and electron excitation of H2(υ = 0) through an indirect mechanism followed by radiative decay (the EV process) to electron excitation of H2(υ = 0) through a resonant mechanism (the eV process). A valuable subset of reactions provided by the simplified model is proposed in the investigated pressure range, which could be incorporated in more complex simulations. The results obtained with the simplified model under different simulation conditions are within an acceptable error margin of the results for the full model, which indicates that the robustness of the simplified model of chemical reactions is guaranteed to some extent. [ABSTRACT FROM AUTHOR]

Due to the lack of effective methods to determine the cause of thermal runaway of lithium-ion batteries (LIBs), many fires are wrongly classified as LIBs fires. In this paper, we conducted different types of LIBs experiments to study the stage of thermal runaway and the distribution of combustion products. Through experiments analysis, we discovered for the first time the characteristic elements associated with the cause of thermal runaway of LIBs in the solid combustion products. Under overcharge conditions, the aluminum element was detected for the combustion products. The main reason is that a large amount of metal oxides precipitated from electrode materials react with aluminum foil at high temperatures to form alumina (Al2O3). However, under heating conditions, the aluminum element was not detected because of the lack of sufficient conditions for thermite reactions. The conclusion was verified by multiple sets of repeated experiments. [ABSTRACT FROM AUTHOR]

A novel microfluidic device for efficient passive mixing is reported. A series of sharp corner structures designed on side wall of an arc microchannel was utilized to induce three-dimensional vortices, which strongly stretched and folded the interface and significantly increased the interfacial contact area between different fluids. Additionally, the sharp corner structure induced high radial velocity and reduced the diffusion length because of the restricted effect of the geometrical structure. Eventually, the fluid mixing was significantly enhanced, and a mixing efficiency from ∼87% to 92% was achieved at moderate Reynolds number (Re) from 3.0 to 24.2 (10 to 80 μl min−1). The influence of the sharp corner position on the mixing was also investigated by the experiment and the numerical simulation. With single-layer structure and high mixing efficiency, the present device has great potential in the mixing process in variety of lab-chip applications, such as clinic diagnosis and analytic chemistry. [ABSTRACT FROM AUTHOR]

We present elemental abundance results for HE 2148−2039 and HE 2155−2043 based on a detailed high-resolution spectroscopic analysis. The high-resolution Subaru/High Dispersion Spectrograph (HDS) spectra used for our analysis have a resolution of R ∼ 60,000. Although limited information based on photometry and low-resolution spectroscopy is available, we present for the first time an abundance analysis based on high-resolution spectra for both objects. Our analysis shows that the two objects are extremely metal-poor with [Fe/H] < −3. Among the neutron-capture elements, abundances of only Sr and Ba could be determined in our program stars. For both the objects [Ba/Fe] is found to be <0. While strontium is underabundant in HE 2148−2039 with [Sr/Fe] ∼ −2.02, Sr is near solar in HE 2155−2043. The locations of the program stars in the absolute carbon abundance, A(C) versus [Fe/H] diagram, show that HE 2148−2039 is a carbon-enhanced metal-poor (CEMP)-no Group II object and HE 2155−2043 is a CEMP-no Group III object. Observed [Sr/Ba] ratios are characteristics of a fast rotating massive star progenitor for HE 2155−2043 and a metal-poor asymptotic giant branch (AGB) star for HE 2148−2039. The estimated [Sc/Mn] as well as [C/Cr] ratios in HE 2155−2043 show that the surface chemical composition of this object is mono-enriched. The surface chemical composition of HE 2148−2039 is also found to be mono-enriched based on the [Mg/C] ratio. With respect to their locations in the [C/N] versus Teff diagram, HE 2148−2039 shows signatures of mixing, and HE 2155−2043 falls in the unmixed region of the [C/N] versus Teff plot. Kinematic analysis shows that both objects belong to the Galactic halo population. [ABSTRACT FROM AUTHOR]

Chemical redox reactions between redox shuttles and lithium-ion battery particles have applications in electrochemical systems including redox-mediated flow batteries, photo-assisted lithium-ion batteries, and lithium-ion battery overcharge protection. These previous studies, combined with interest in chemical redox of battery materials in general, has resulted in previous reports of the chemical oxidation and/or reduction of solid lithium-ion materials. However, in many of these reports, a single redox shuttle is the focus and/or the experimental conditions are relatively limited. Herein, a study of chemical redox for a series of redox shuttles reacted with a lithium-ion battery cathode material will be reported. Both oxidation and reduction of the solid material with redox shuttles as a function of time will be probed using ferrocene derivatives with different half-wave potentials. The progression of the chemical redox was tracked by using electrochemical analysis of the redox shuttles in a custom electrochemical cell, and rate constants for chemical redox were extracted from using two different models. This study provides evidence that redox shuttleparticle interactions play a role in the overall reaction rate, and more broadly support that this experimental method dependent on electrochemical analysis can be applied for comparison of redox shuttles reacting with solid electroactive materials. [ABSTRACT FROM AUTHOR]

The native fluorescence of biomolecules has been used in analytical chemistry to determine the concentration of an analyte. However, detecting biomolecules based on their intrinsic fluorescence at low concentration is challenging due to their small quantum yield and poor photon stability. Ultraviolet plasmonics have been reported to increase the photon yield and the photon stability of the native fluorescence of biomolecules such as DNA, peptides, and proteins. However, the experimentally reported count rate, or net enhancement factor, is small-with 80× for DNA and 14× for amino acids. Here we report native fluorescence enhancement of tryptophan on aluminum hole-arrays. By optimizing excitation geometry and the hole spacings, we are able to achieve a 47× net enhancement factor, the highest reported in the literature for tryptophan molecules. We conducted photobleaching experiments and observed a 2.3× reduction in the fast photon bleaching rate and 1.9× reduction in the slow photon bleaching rate on an aluminum hole-array with 300 nm periodicity compared to an aluminum thin film. The enhancement of the total photon yield reaches 58×, which is a result of the enhanced radiative rate. This study shows that periodic aluminum hole-arrays allow detection of tryptophan at concentration levels lower than previously reported, underpinning further research into label-free biosensing. [ABSTRACT FROM AUTHOR]

Using the calypso algorithm with first-principles calculations, we have predicted two orthorhombic Cmmm and Pmmm structures for YB3. The new structures are energetically much better than the previously proposed WB3-type, ReB3-type, FeB3-type, and TcP3-type structures. We find that the Cmmm phase transforms to the Pmmm phase at about 31 GPa. Subsequent calculations show that the Cmmm phase is mechanical and dynamical stable at ambient conditions. The analysis of the chemical bonding properties indicates that there are strong B–B bonds that make considerable contributions to its stability. [ABSTRACT FROM AUTHOR]

Thin films of Co-doped BaFe2As2 of similar thickness (~40 nm) were grown with different growth rates (0.4 Ĺ s−1 and 0.9 Ĺ s−1) by pulsed laser deposition on CaF2(001) substrates. Analytical transmission electron microscopy (TEM) was applied to analyze the microstructure and secondary phases. The formation of BaF2 and a high concentration of planar defects (mainly stacking faults) are observed for the sample grown at a low rate. A higher growth rate results in high-quality epitaxial films with only few antiphase boundaries. A higher Tc was measured for the sample grown at a low growth rate, which is attributed to the difference in strain state induced by the high concentration of defects. Large crystalline Fe precipitates are observed in both samples. Chemical analysis shows a pronounced O and slight F content at the planar defects which highlights the role of O in defect formation. Electron-beam-induced irradiation damage during TEM measurements is observed and discussed. [ABSTRACT FROM AUTHOR]

The stability of the weakly ionized plasma and the transition from a stable homogeneous discharge to unstable filaments play an important role in gas laser physics, plasma-assisted combustion, chemical reforming, and material synthesis. Theoretical stability analysis and thermal-chemical mode analysis were performed to understand the mechanism of plasma thermal-chemical instability by using a zero-dimensional plasma system with both simplified and detailed chemical kinetics of H2/O2/N2 mixtures. The plasma dynamic and kinetic models accounted for multiple physical mechanisms in the chemically-reactive weakly ionized plasma, including ionization, attachment/detachment, recombination, vibrational and electronic energy relaxation, convective and diffusive species/heat removal, Joule heating, and detailed chemical kinetics. An analytical criterion and the explosive mode species/temperature pointers were formulated while the representative active species were identified for different thermal-chemical modes. The results showed that in addition to the classical thermal-ionization mechanism, various chemical modes from chemical heat imbalance and elementary kinetics significantly modified the time dynamics and the stability of the weakly ionized plasma. The present analysis provides insights and guidance to control plasma instability using chemical kinetics. [ABSTRACT FROM AUTHOR]

3D analysis of an arsenic-doped silicon fin sample is performed in a transmission electron microscope (TEM). High angle annular dark-field scanning TEM (STEM-HAADF) and energy-dispersive x-ray spectroscopy (STEM-EDX) modes are used simultaneously to extract 3D complementary multi-resolution information about the sample. The small pixel size and angular step chosen for the STEM-HAADF acquisition yield reliable information about the sidewall roughness and the arsenic clusters' average volume. The chemical sensitivity of STEM-EDX tomography gives insights into the 3D conformality of the arsenic implantation and its depth distribution. Non-negative matrix factorization method is employed to identify the chemical phases present in the sample automatically. A total variation minimization algorithm, implemented in 3D, produces high-quality volumes from heavily undersampled datasets. The extension of this correlative approach to electron energy-loss spectroscopy STEM tomography and atom probe tomography is also discussed. [ABSTRACT FROM AUTHOR]

Unambiguous evidence is presented that the chloride ions play a dual role in the formation of a micrometre thick film of polymerized [Cu-Cl-MBI]n. This occurs when the copper is exposed to 3 wt.% NaCl solution containing 1 mM of mixture of inhibitors 2-mercaptobenzimidazole, MBI, and octylphosphonic acid, OPA, in the molar ratio MBI:OPA of 9:1. The chloride ions act simultaneously as a promoter of polymerized [Cu–MBI]n/[Cu–Cl–MBI]n film formation and a reactant that is incorporated in the film, as confirmed by time-of-flight secondary ion mass spectrometry. Also, formation of a Cu2O film under the Cu-inhibitor film was proven by focused ion beam microscopy, with chemical analysis being employed at the cross-section of the thick polymerized film. The Cu(I) oxide underlayer, together with the porous straw-like morphology of the [Cu–Cl–MBI]n overlayer, is believed to be responsible for the excellent corrosion protection of copper, even in a chloride environment without the reservoir of MBI+OPA. We also report a new insight into the mechanism of degradation of the Cu–MBI/Cu–Cl–MBI film that results in the formation of (MBI)2 dimers. The inhibitor layer, formed in NaCl solution and containing the synergistic combination of MBI and OPA, showed outstanding resistance to degradation. [ABSTRACT FROM AUTHOR]

Thin films of Co-doped BaFe2As2 of similar thickness (~40 nm) were grown with different growth rates (0.4 Ĺ s−1 and 0.9 Ĺ s−1) by pulsed laser deposition on CaF2(001) substrates. Analytical transmission electron microscopy (TEM) was applied to analyze the microstructure and secondary phases. The formation of BaF2 and a high concentration of planar defects (mainly stacking faults) are observed for the sample grown at a low rate. A higher growth rate results in high-quality epitaxial films with only few antiphase boundaries. A higher Tc was measured for the sample grown at a low growth rate, which is attributed to the difference in strain state induced by the high concentration of defects. Large crystalline Fe precipitates are observed in both samples. Chemical analysis shows a pronounced O and slight F content at the planar defects which highlights the role of O in defect formation. Electron-beam-induced irradiation damage during TEM measurements is observed and discussed. [ABSTRACT FROM AUTHOR]

Confidence and integrity are critical in the physical and chemical analyses of tissues and living cells. However, many of the probes targeting biological markers for confocal spectroscopy affect cells' molecular identity. Hence, we combined photonics with electrical analysis in an assisted laser impedance spectroscopy facility and applied it to characterize two breast cancer cell lines (BT-474 and MCF-7) and lymphocytes (as a normal control). The setup comprised a sample holder with a ∼15 000 cell capacity fitted with two isolated conducting electrodes arranged concentrically and connected to an impedance analyser with a 20 Hz–1 MHz sweeping frequency. Capacitive transconductance measurements showed bands at 3491, 3494 and 3470 Hz corresponding to the BT-474, MCF-7, and lymphocytes, respectively. Under photonic stimulation by a 532 nm laser, these dark reference bands shifted to 3518, 3566 and 3674 Hz, respectively, reflecting optical transitions favouring ionic transport in the cells. Based on the experimental Nyquist diagrams and taking into account the roughness nature of the cell membrane, a constant phase element (CPE) was introduced in the circuit. The CPE was explained through a fractional parameter, α, based on fractional calculus. Results showed that, under photonic stimulation, α is less than ˝, and the minimum change of series and membrane resistances are about 28.95% and 58.88%, respectively. [ABSTRACT FROM AUTHOR]

A simple and compact temperature sensor based on a Mach–Zehnder modal interferometer has been fabricated by bending a single-mode fiber into a balloon-like configuration. Three different fiber sections, fiber without stripping, fiber with a stripped-off protective coating and fiber with a polyvinyl alcohol (PVA) coating have been utilized, each with a small bending diameter of 1 cm that mimics a balloon-like shape. The PVA-coated segment sensor structure showed the highest sensitivity of ∼−1.492 nm °C−1, a fast response time of ∼2.78 ms and a good resolution of ∼3 × 10−4 °C, for the temperature range 30 °C–55°C, benefiting from the good thermo-optical properties of PVA. This sensor can potentially be used in various temperature monitoring processes such as food industries, chemical analysis, detection of molecular analysis and label-free biomedicine. [ABSTRACT FROM AUTHOR]

The radiation doses from natural radiation sources in Japan are reviewed using the latest knowledge. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and the Nuclear Safety Research Association report the annual effective doses from cosmic rays, terrestrial radiation, inhalation, and ingestion as natural sources. In this paper, the total annual effective dose from cosmic-ray exposure is evaluated as 0.29 mSv. The arithmetic mean of the annual effective dose from external exposure to terrestrial radiation is 0.33 mSv for the Japanese population using the data of nationwide surveys by the National Institute of Radiological Sciences. Previously in Japan, although three different groups have conducted nationwide indoor radon surveys using passive-type radon monitors, to date only the Japan Chemical Analysis Center (JCAC) has performed a nationwide radon survey using a unified method for radon measurements conducted indoor, outdoor, and in the workplace. Consequently, the JCAC results are used for the annual effective dose from radon and that for radon inhalation is estimated as 0.50 mSv using a current dose conversion factor. In this paper, UNSCEAR values are used for the mean indoor and outdoor thoron-progeny concentrations, and the annual effective dose from thoron is reported as 0.09 mSv. Thus, the annual effective dose from radon and thoron inhalation is 0.59 mSv. From a JCAC large-scale survey of foodstuffs, the committed effective dose from the main radionuclides in dietary intake is 0.99 mSv. Finally, the Japanese population dose from natural radiation is given as 2.2 mSv, which is similar to the reported global average of 2.4 mSv. [ABSTRACT FROM AUTHOR]

V2AlC is a typical ternary intermetallic compound and a precursor to synthesis 2D-MXenes V2C. This work used cheap metal oxides and carbon as simple starting materials to fabricate MAX phases carbide V2AlC by molten salt electrolysis, and the obtained product could be converted into 2D V2C by a chemical etching process easily. The obtained ultrafine V2AlC possess high purity and homogeneity, and the 2D V2C from the chemical etching presented a unique layered Nano-sheets structure. TEM and X-ray photoelectron spectroscopy were combined to analysis the micromorphology and the chemical bonding states. And the reaction mechanism has been investigated to explore the facile synthetic method of V2AlC and 2D V2C. [ABSTRACT FROM AUTHOR]

Methyl carbamate CH3OC(O)NH2 is an isomer of glycine. Quantum chemical analyses show that methyl carbamate is a more stable isomer than glycine. Because of this, there could be a higher chance for methyl carbamate to exist in the interstellar medium (ISM) as compared to glycine. Despite immense searches, until now glycine has not been detected in the ISM; therefore, it is worthwhile to search its isomer methyl carbamate. In this paper, we present the constraints of methyl carbamate formation under the interstellar conditions. Large complex organic molecules are favorably produced in hot-corino environments of low-mass protostars. We for the first time carried out astrochemical modeling focusing on the formation of methyl carbamate in physical conditions similar to hot-corino objects. Consequently, we examined ALMA archival data for existing spectral line observations toward hot corinos NGC 1333 IRAS 4A2 and IRAS 16293B. Within the common spectral range toward these sources, we found three features are possibly related to the spectral transitions of methyl carbamate and consequently estimate the upper limit of column densities. Results of chemical modeling are consistent with the observational upper limit of estimated column density/abundance toward the sources. This may hint the validation of the proposed formation mechanism. Future observations using a telescope like ngVLA may confirm the presence of MC toward the hot corinos. [ABSTRACT FROM AUTHOR]

We present a detailed abundance analysis of the three brightest member stars at the top of the giant branch of the ultrafaint dwarf (UFD) galaxy Grus II. All stars exhibit a higher than expected [Mg/Ca] ratio compared to metal-poor stars in other UFD galaxies and in the Milky Way (MW) halo. Nucleosynthesis in high-mass (20 M⊙) core-collapse supernovae has been shown to create this signature. The abundances of this small sample (three) stars suggests the chemical enrichment of Grus II could have occurred through substantial high-mass stellar evolution, and is consistent with the framework of a top-heavy initial mass function. However, with only three stars it cannot be ruled out that the abundance pattern is the result of a stochastic chemical enrichment at early times in the galaxy. The most metal-rich of the three stars also possesses a small enhancement in rapid neutron-capture (r-process) elements. The abundance pattern of the r-process elements in this star matches the scaled r-process pattern of the solar system and r-process enhanced stars in other dwarf galaxies and in the MW halo, hinting at a common origin for these elements across a range of environments. All current proposed astrophysical sites of r-process element production are associated with high-mass stars, thus the possible top-heavy initial mass function of Grus II would increase the likelihood of any of these events occurring. The time delay between the α and r-process element enrichment of the galaxy favors a neutron star merger as the origin of the r-process elements in Grus II. [ABSTRACT FROM AUTHOR]

The ratio of γ counting efficiencies is very important in trace element analysis carried out by prompt- and delayed-γ neutron activation based on k0 standardization. Although the effect of correlation between counting efficiencies is well known and methods have been developed and adopted in prompt-γ neutron activation analysis to correctly evaluate the uncertainty, proposals and applications in delayed-γ neutron activation analysis are still lacking. To fill the gap, we developed a new method based on the use of reference γ-sources to determine the detection efficiency ratio and its uncertainty by taking full account of correlations. A measurement model that differs to some extent from the classical k0 formulation widely used in delayed-γ neutron activation analysis is required. A detection system was characterized to test the suitability of the method in a double-counting position setup, where the standard is placed far from the detector end-cap and the sample is placed close to it. The present paper is a significant expansion of a relevant abstract presented at the 'Mathematical and Statistical Methods for Metrology' Workshop, Torino, Italy, 30–31 May 2019 (pp 27–28 in www.msmm2019.polito.it/programme). [ABSTRACT FROM AUTHOR]

We design Al-doped V2O3 (AlxV2O3) compounds as cathodes of aluminium battery. A citric acid-assisted simple solid-state synthesis is used to produce AlxV2O3 compounds by heating, at different temperature, a reaction mixture of NH4VO3, Al(NO3)3·9H2O and citric acid under Ar flow. Al-doping in-between layers and at lattice sites of V2O3 is confirmed by structural, vibrational and chemical analyses. The doped compounds obtained at 600 °C and 800 °C are confirmed as Al0.56V2O3 and Al0.53V2O3 corresponding to theoretical capacities 488 and 490 mAh g-1, respectively, for the extraction of doped Al by considering three electron transfer (Al/Al3+). The as-synthesized AlxV2O3 compounds are tested as cathodes in aluminium battery with 1.0 M AlCl3:[EMIM]Cl electrolyte. The electrodes of Al0.56V2O3 and Al0.53V2O3 exhibited the first charge capacity of 415 and 385 mAh g-1, respectively. The electrochemical extraction of doped Al is confirmed by comparisons with bare V2O3 control cathodes and post-cycling structural studies. The extraction of doped Al from AlxV2O3 indicates its promising use in high capacity cathode for Al-ion battery. [ABSTRACT FROM AUTHOR]

A holy grail in analytical chemistry is the specific quantification of a single entity, be that entity an atom, a molecule, a nanoparticle, a virus, or a circulating tumor cell. Analytical chemistry is entering an era where this sensitivity can be achieved. In these experiments, the limit of detection is 1, and the limit of quantitation is not only measured in units of concentration but units of time: the waiting time before positively identifying a single entity. Electrochemistry is front and center in single entity experiments with hundreds of publications per year detailing observations of various entities colliding with micro- and nano-electrodes. These types of experiments are referred to as ‘stochastic electrochemistry’ due to the stochastic nature of the collision of an entity with an electrode surface. If methods of detection can be made specific, simple, inexpensive, and robust, the techniques hold the promise of transforming diagnostics (i.e., the specific detection of a single cancerous cell in blood). This review will critically analyze the stochastic electrochemistry literature and focus on reports detailing methods to ensure the response at the electrode surface is specific to the colliding entity. The topic of specificity, and strategies to achieve it, are highlighted. [ABSTRACT FROM AUTHOR]

Redox targeting reactions between lithium-ion battery materials and redox shuttles have been proposed to design high energy density redox flow batteries. Designing these batteries would require a deeper understanding of the kinetics of redox targeting reactions and the phase transformation of the materials involved. In this study, the oxidation and reduction of lithium iron phosphate, LiFePO4, via chemical and electrochemical routes will be compared. Ultraviolet-visible spectroscopy was used as a technique to characterize the extent of chemical lithiation/delithiation during chemical redox of LiFePO4, while the electrochemical redox was characterized using battery coin cells. The kinetic parameters extracted using the Johnson-Mehl-Avrami-Erofeyev-Kolomogorov model suggested that chemical redox was slower than electrochemical redox within the experimental regimes. Calculated apparent activation energies suggested the limitations in the chemical redox rate were due to different processes than the electrochemical redox. In addition, asymmetry observed for oxidation and reduction of LiFePO4 materials will be discussed. As pairs of solid battery electroactive particles and soluble redox shuttles are designed, tools and analysis such as those in this study will be needed for interrogating and comparing electrochemical and chemical oxidation and reduction of the solid particles to understand and design these systems. [ABSTRACT FROM AUTHOR]

Stable long-term cycling and solid-electrolyte-interphase (SEI) formation are key challenges in the design of Si/graphite composites as Li-ion battery (LIB) anode materials. Typically, these long-term cycling properties are examined in flooded half-cell settings making use of a Li-metal counter electrode and a Si/graphite working electrode. This form factor has the advantage of offering an unlimited supply of Li-ions and electrolyte, thus isolating performance degradation to the passivation of the working electrode. However, halfcell studies are ineffective in revealing performance and degradation mechanisms of the Si/graphite composite in a more commercially realistic full cell setting. This paper outlines an operando acoustic technique that can offer insights on SEI formation and capacity degradation of Si/graphite composites in a full cell setting. Through a combination of electrochemical and chemical analyses, we show that increasing passivation of the silicon particles in the Si/graphite composite anode is correlated with an increase in the acoustic time-of-flight shift. We further show that temporary loss of the acoustic signal during the first cycle is associated with significant gassing of the cell. The operando acoustic technique outlined here is low-cost, simple to setup and has the potential for localized resolution, indicating usefulness in commercial-scale Si/graphite cell quality control and diagnosis. [ABSTRACT FROM AUTHOR]

Over the years, Electroanalysis has been widely applied to elucidate redox behavior of novel molecules. The selectivity and low cost are spotlight features in pharmacopeial methods of identification, that can be reached by voltammetric approaches. In this work, differential pulse voltammetric (DPV) profile and the slope of the linear regression obtained from calibration graphs along with the scan study are proposed as new perspective of identification assays. With the proposed methodology we were able to identify the similarities among DPV profile and the slopes obtained for each tablet. In addition, this new technology was successfully employed to identify the following chemicals: Paracetamol (PAR), Promethazine (PMZ), Diclofenac (DIC), Piroxicam (PRX), Indomethacin (IND) and Cyclobenzaprine (CBP) in pharmaceutical assays using Pencil Graphite Electrodes. Furthermore, our new methodology was effectively compared to Raman Spectroscopy for the analysis of the range of chemicals in the pharmaceutical assays. [ABSTRACT FROM AUTHOR]

Iron sulfide corrosion product layers commonly form on mild steel surfaces corroding in aqueous H2S environments. These porous layers present a barrier which may reduce the corrosion rate, however, their semi-conductive nature leads to an acceleration of corrosion via galvanic coupling, by increasing the cathodic surface area. The electrocatalytic properties of different iron sulfides, which are important in this process, were unknown. The current study looks at the cathodic reaction rates on the surfaces of geological pyrite, geological pyrrhotite, and mild steel in HCl, CO2 and H2S aqueous solutions at different pH. Results show that in solutions where H+ reduction dominates, pyrite has similar electroactivity as X65 steel, while pyrrhotite exhibits approximately one order of magnitude smaller current densities. An extra wave observed in the cathodic sweeps on pyrrhotite was due to conversion of pyrrhotite to troilite. In aqueous CO2 solutions, similar results were obtained, while in H2S aqueous environments, both pyrite and pyrrhotite showed similar electroactivity that was slightly lesser than that of X65 steel. [ABSTRACT FROM AUTHOR]