Optical Emission and Raman Spectroscopy Studies of Reactivity of Low-Pressure Glow Discharges in Ar–O<Subscript>2</Subscript> and He–O<Subscript>2</Subscript> Gas Mixtures with Coked Catalysts

We demonstrate that low-pressure glow discharges in He–O₂ gas mixture are effective in removing carbonaceous surface layers from coked catalysts. These discharges contain a number of reactive species including O, O₃, and O₂*, and all these could contribute in the decoking process. However, an evolving understanding is that the O atoms in the discharge have a predominant role in this. A working hypothesis is that the O atoms react with the coke to form CO, CO₂ and other carbon complexes. Online measurements using emission spectra from O, H, and CO in the discharges are compared for the cases of He–O₂ and Ar–O₂ gas mixtures. Under the reported experimental conditions the estimated reactivity of the He–O₂ discharges is considerably higher compared with discharges in the Ar–O₂ gas mixture. Raman spectroscopy is used to confirm the removal of the coke from the surface of Pt/Alumina catalyst.     

An Optimal Diversification Network Model with Fixed-Solution Universe Subsets

This paper develops a generalized dynamic network model for portfolio investment diversification. The model considers the situation of the fixed solution subset corresponding to a fixed single-resource economic investment such as that found in many oil-producing nations. Quadratic side constraints on the variance of the resultant flow distribution are added to the model to accommodate uncertainty. The model has been tested using a prototype example. The results indicate that the risk associated with a single-resource investment can be reduced by determining optimal investment weights.     

Syntheses, characterization, biological activity and fluorescence properties of bis-(salicylaldehyde)-1,3-propylenediimine Schiff base ligand and its lanthanide complexes

Eight new lanthanide metal complexes [LnL(NO(3))(2)]NO(3) {Ln(III) = Nd, Dy, Sm, Pr, Gd, Tb, La and Er, L = bis-(salicyladehyde)-1,3-propylenediimine Schiff base ligand} were prepared. These complexes were characterized by elemental analysis, thermogravimetric analysis (TGA), molar conductivity measurements and spectral studies ((1)H NMR, FT-IR, UV-vis, and luminescence). The Schiff base ligand coordinates to Ln(III) ion in a tetra-dentate manner through the phenolic oxygen and azomethine nitrogen atoms. The coordination number of eight is achieved by involving two bi-dentate nitrate groups in the coordination sphere. Sm, Tb and Dy complexes exhibit the characteristic luminescence emissions of the central metal ions attributed to efficient energy transfer from the ligand to the metal center. Most of the complexes exhibit antibacterial activity against a number of pathogenic bacteria.     

Multiscaling analysis of a slowly varying anaerobic digestion model

We construct the slowly varying limiting state solutions to a nonlinear dynamical system for anaerobic digestion with Monod-based kinetics involving slowly varying model parameters arising from slow environmental variation. The advantage of these approximate solutions over numerical solutions is their applicability to a wide range of parameter values. We use these limiting state solutions to develop analytic approximations to the full nonlinear system by applying a multiscaling technique. The approximate solutions are shown to compare favorably with numerical solutions.     

On convergence of homotopy analysis method and its modification for fractional modified KdV equations

In this paper, the homotopy analysis method (HAM) and its modification (MHAM) are applied to solve the nonlinear time- and space-fractional modified Korteweg-de Vries (fmKdV). The fractional derivatives are described by Caputo’s sense. Approximate and exact analytical solutions of the fmKdV are obtained. The MHAM in particular overcomes the computing difficulty encountered in HAM. Convergence theorems for both the homogeneous and non-homogeneous cases are given. The results of applying this procedure to the studied cases show the high accuracy and efficiency of the approach.     

Recent developments in polyetherimide membrane for gas separation

Polyetherimide (PEI) is an extraordinary type of polyimide with excellent thermal and mechanical properties. The polymer is also gas permeable and is considered one of the best membranes for gas separation. Despite the high selectivity, PEI suffers from low permeability due to the trade‐off between phenomena in polymers. To overcome this limitation, fillers are added during the membrane preparation to create voids for better gas transport. In this paper, permeability and selectivity data of PEI membranes for the separation of oxygen, carbon dioxide, and helium are discussed. The paper also summarizes the reported studies for adding fillers to improve the membrane performance.     

Separation of organohalides from their microemulsions by the pervaporation technique: Application to the n-butyl bromide/SDS/n-butanol/water system

An n-butyl bromide/sodium dodecyl sulfate/n-butanol/water microemulsion system was chosen as a model of an organohalide-containing microemulsion. Two systems were prepared using the Bourayne method: a water-rich system and an n-butyl-bromide-rich system. The destabilization of this micro-organized system and the phase separation were investigated. This microemulsion, in which the oil phase in the feed is the lower layer, was successfully destabilized using the pervaporation technique with polydimethylsiloxane and poly(vinyl alcohol) membranes. In this way, different factors governing the separation process were investigated such as the mass transfer and the effect of time and operating temperature on the microemulsion destabilization.     

Assessment of Environmental Quantitative Variation of Diosgenin in Fenugreek Seeds via High-Performance Thin-Layer Chromatography Method

JPC – Journal of Planar Chromatography – Modern TLC - Fenugreek is one of the oldest medicinal plants known by mankind. The aim of this study is to evaluate the effect of environmental...     

Crystal structure of tetrakisdiphenylammonium hexadecachlorotetrabismuthate(III)

[(C₆H₅)₂NH₂]₄ ⁺[Bi₄Cl₁₆]^4– crystallizes in the triclinic space group witha=11.835(2),b=12.393(2),c=12.625(3)Å, =108.37(3), =108.69(3), =96.00(3)° andD _c=2.135 g cm^–3 forZ=1. The [Bi₄Cl₁₆]^4– anion is a centrosymmetric cluster of four distorted edge-sharing BiCl₆ octahedra. The ranges of the Bi–Cl bonds are 2.484(4)–2.606(3)Å for Bi–Cl(terminal), 2.691(3)–2.956(4)Å for Bi-Cl(µ₂), and 2.960(3)–3.120(4)Å for Bi-Cl(µ₃). The cations and anions are held in place by weak hydrogen bonds.     

Cover Picture: Nanomaterials for Fluorescence and Multimodal Bioimaging (Chem. Rec. 3/2023)

Bioconjugated nanomaterials replace molecular probes in bioanalysis and bioimaging in vitro and in vivo. Nanoparticles of silica, metals, semiconductors, polymers, and supramolecular systems, conjugated with contrast agents and drugs for image-guided (MRI, fluorescence, PET, Raman, SPECT, photodynamic, photothermal, and photoacoustic) therapy infiltrate into preclinical and clinical settings. Small bioactive molecules like peptides, proteins, or DNA conjugated to the surfaces of drugs or probes help us to interface them with cells and tissues. Nevertheless, the toxicity and pharmacokinetics of nanodrugs, nanoprobes, and their components become the clinical barriers, underscoring the significance of developing biocompatible next-generation drugs and contrast agents. This account provides state-of-the-art advancements in the preparation and biological applications of bioconjugated nanomaterials and their molecular, cell, and in vivo applications. It focuses on the preparation, bioimaging, and bioanalytical applications of monomodal and multimodal nanoprobes composed of quantum dots, quantum clusters, iron oxide nanoparticles, and a few rare earth metal ion complexes.