Electrochemical performance of novel Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> glass-ceramic nanocomposites as electrodes for energy storage devices

The novel Li₃V₂(PO₄)₃ glass-ceramic nanocomposites were synthesized and investigated as electrodes for energy storage devices. They were fabricated by heat treatment (HT) of 37.5Li₂O–25V₂O₅–37.5P₂O₅?mol% glass at 450 °C for different times in the air. XRD, SEM, and electrochemical methods were used to study the effect of HT time on the nanostructure and electrochemical performance for Li₃V₂(PO₄)₃ glass-ceramic nanocomposites electrodes. XRD patterns showed forming Li₃V₂(PO₄)₃ NASICON type with monoclinic structure. The crystalline sizes were found to be in the range of 32–56 nm. SEM morphologies exhibited non-uniform grains and changed with variation of HT time. The electrochemical performance of Li₃V₂(PO₄)₃ glass-ceramic nanocomposites was investigated by using galvanostatic charge/discharge methods, cyclic voltammetry, and electrochemical impedance spectroscopy in 1 M H₂SO₄ aqueous electrolyte. The glass-ceramic nanocomposites annealed for 4 h, which had a lower crystalline size, exhibited the best electrochemical performance with a specific capacity of 116.4 F g^?1 at 0.5 A g^?1. Small crystalline size supported the lithium ion mobility in the electrode by decreasing the ion diffusion pathway. Therefore, the Li₃V₂(PO₄)₃ glass-ceramic nanocomposites can be promising candidates for large-scale industrial applications in high-performance energy storage devices.     

Quantification of terbutaline in pharmaceutical formulation and human serum by adsorptive stripping voltammetry at a glassy carbon electrode

The electrochemical oxidative behavior of terbutaline at the glassy carbon electrode was studied in a series of the Britton-Robinson buffer of pH 2--11. Cyclic and square-wave voltammograms of terbutaline at the pH values 相似文献   

Synthesis,structural and ferroelectric properties of barium titanate based glass-ceramic nano-composites

Novel glass-ceramic nano-composites based on BaTiO₃–V₂O₅–Bi₂O₃ glasses were prepared via heat-treatment at crystallization temperature (T_cr). The nanostructural and ferroelectric properties were investigated by differential scanning calorimeter (DSC), transmission electron microscope (TEM), X-ray diffraction (XRD) and dielectric measurements, respectively. It was shown by XRD and TEM studies that appropriate heat-treatment glasses can turn into glass-ceramic nano-composites consisting of crystallites smaller than 30 nm embedded in the glassy matrix. The observed dielectric constant of heat‐treated samples, showed average broad peak around 324 K. The average Curie temperature (T_c) observed around 324 K in the present system. This observation of these glass-ceramic nano-composites can be utilized to control T_c by proper adjustment of BaTiO₃ content. This result, therefore, supports dipolar orientation and phase transition in the glass-ceramic samples dispersed with nanocrystalline BaTiO₃. Such a feature can be used for industrial applications where the shape of the application article is a necessary requirement such as integrated capacitor.     

Aqueous Urea Solution Promoted Resolution of Five-Component Mixture of Amino Acids on Silica TLC Plates

JPC – Journal of Planar Chromatography – Modern TLC - A thin-layer chromatographic system comprising of silica gel as stationary phase and 1.0% aqueous urea solution as mobile phase (pH...     

Stripping voltammetric determination of silymarin in formulations and human blood utilizing bare and modified carbon paste electrodes

Silymarin is one of the most powerful natural substances that have the ability to protect and rebuild the liver cells damaged by alcohol and other toxic substances. Silymarin showed two irreversible anodic peaks in buffered solutions (pH 2.5-8.0) at either the bare carbon paste electrode or the montmorillonite-Ca modified carbon paste one. These two peaks have been attributed to oxidation of the two phenolic OH groups at positions C-20 and C-7 of silymarin molecule. A square-wave adsorptive anodic stripping voltammetry method was optimized for determination of silymarin utilizing the bare and the modified carbon paste electrodes. The method was fully validated and successfully applied for the determination of silymarin in commercial formulations and human serum without prior extraction utilizing both carbon paste electrodes. Limits of quantitation of 1 × 10⁻⁷ and 7 × 10⁻⁹ mol L⁻¹ silymarin have been achieved in bulk form or in formulations while 2 × 10⁻⁷ and 8 × 10⁻⁹ mol L⁻¹ silymarin were achieved in spiked human serum utilizing the bare carbon paste electrode and the modified one, respectively. The two electrodes exhibited excellent selectivity towards silymarin even in the presence of 10²to 10³-fold excess of its co-formulated drugs, common excipients, and common metal ions. The pharmacokinetic parameters of silymarin in plasma of healthy human volunteers were estimated following the administration of a single oral dose of 120 mg silymarin utilizing the modified carbon paste electrode. The estimated pharmacokinetic parameters were favorably compared with those reported in literature.     

Synthesis, structural and transport properties of Li-doped molybdenum and vanadium oxide nanocrystalline films

The aim of this study was to determine an influence of lithium excess in nanocrystalline xLi₂O–(80 − x)V₂O₅–20MoO₃, nH₂O (0 ≤ x ≤ 15 mol.%) on their transport and structural properties. The obtained nanorods have width of 8–24 nm with lengths up to 200 nm. The density of the samples decreases with increasing Li content. The electrical conductivity shows that all samples are semiconductor and decreases with increasing Li content. From the best fits, reasonable values of various small polaron hopping parameters were obtained. The density of state N(E _F ) values were evaluated and found to vary from 2.76 to 11.14 × 10²¹ eV⁻¹ cm⁻³. The values of optical phonon frequency (ν _o ) were obtained to be 1.36–1.61 × 10¹³ Hz. The electrical conduction at T > θ_D/2 was due to non-adiabatic SPH.     

Synthèse de l'oxo-7 7H cyclohepta[b] pyridine et de quelques dérivés

This communication describes the synthesis of 7-one (7H) cyclohepta[b]pyridine and some derivatives (6,8-dimethyl; 8-methyl; 8-ethyl….). These compounds have been obtained by condensation of ketones with 2,3-diformylpyridine.     

Sur quelques récents résultats dans la théorie des surfaces algébriques

Sans résumé     

The effect of topical anesthesia on vocal fold motion

The objective of this study was to determine if topical anesthesia to the larynx and pharynx affects vocal fold motion during dynamic voice evaluation with transnasal flexible endoscopy. Transnasal dynamic laryngeal examinations of 10 patients with no voice complaints were evaluated by five blinded fellowship-trained laryngologists. Each patient was examined before and after application of topical anesthetic. Reviewers rated briskness of right and left vocal fold movement and longitudinal tension on a visual analogue scale. Statistical comparisons were made between individual subject scores before and after anesthetic application. Inter-rater reliability was also assessed. No statistical difference was observed between subject scores before and after anesthetic application. Average intraclass correlation coefficients were 0.643 and 0.591 for pre- and postanesthesia scores, respectively. Application of topical anesthesia to the larynx and pharynx does not affect vocal fold motion.