Precise determination of lithium isotopes in seawater using MC-ICP-MS

Li (lithium) isotope analysis using MC-ICP-MS is a very powerful tracer measurement method. This is widely used for identification of Li isotopes in many fields of study. This useful method, however, has an effect on the natural Li isotope background. This is impacted by the instrument matrix. In this study, we show that the MC-ICP-MS condition is characterized by both a low baseline background and a high-sensitivity distance at Ar plasma condition. In addition, the Li isotope ratio was measured by the use of experimental conditions that were superior to both the general plasma condition and those used in other studies. The samples were subjected to both acid leaching and a cation exchange resin (Bio-Rad AG 50 W-X8 200–400 mesh) modified for seawater samples. The isotope variations were corrected using the bracket method, the measured Li isotope ratio of sample, and the mean ratios of the L-SVEC standard (NIST L-SVEC Li₂CO₃) measured before and after the sample run. The isotope variation was presented as the deviation (per mil) of the measured ratio from that of the recommended value.     

A facile synthesis of simple alkaloids—synthesis of 2,3-polymethylene-4(3H)-quinazolinones and related alkaloids

An efficient procedure for preparation of the simple alkaloids, 2,3-polymethylene-4(3H)-quinazolinones, luotonin A, tryptanthrin, and rutaecarpine has been established by the reaction of lactam-HCl salts with POCl₃ followed by cyclization with methyl anthranilate.     

Optimal poroelastic layer sequencing for sound transmission loss maximization by topology optimization method

Optimal layer sequencing of a multilayered acoustical foam is solved to maximize its sound transmission loss. A foam consisting of air and poroelastic layers can be optimized when a limited amount of a poroelastic material is allowed. By formulating the sound transmission loss maximization problem as a one-dimensional topology optimization problem, optimal layer sequencing and thickness were systematically found for several single and ranges of frequencies. For optimization, the transmission losses of air and poroelastic layers were calculated by the transfer matrix derived from Biot's theory. By interpolating five intrinsic parameters among several poroelastic material parameters, distinct air-poroelastic layer distributions were obtained; no filtering or postprocessing was necessary. The optimized foam layouts by the proposed method were shown to differ depending on the frequency bands of interest.     

Antibacterial behaviour of quaternized poly(vinyl chloride)-g-poly(4-vinyl pyridine) graft copolymers

Amphiphilic graft copolymers consisting of poly(vinyl chloride)(PVC) main chains and poly(4-vinyl pyridine)(P4VP) side chains were synthesized via atom transfer radical polymerization(ATRP) using direct initiation of chlorine atoms. The successful synthesis of PVC-g-P4 VP graft copolymers was confirmed by Fourier transform infrared spectroscopy(FTIR) and proton nuclear magnetic resonance(1H-NMR). Transmission electron microscope(TEM) and small angle X-ray scattering(SAXS) analysis showed that PVC-g-P4 VP exhibited microphase-separated, ordered structure with 37.6 nm of domain spacing, which was not observed in neat PVC. For antibacterial applications, the tertiary nitrogen atoms of PVC-gP4 VP was quaternized using 1-bromohexane, as confirmed by FTIR measurements. Bacteria including Escherichia coli(E. coli), Staphylococcus aureus(S. aureus), Bacillus cereus(B. cereus), and Pseudomonas aeruginosa(P. aeruginosa) were completely killed in 24 h on the quaternized PVC-g-P4VP(46% grafting) surface, indicating its excellent antibacterial behavior while it showed to be cytotoxic to mammalian cell.     

Effect of addition of 1-butyl-3-methylimidazolium thiocyanate on conductivity of Na-containing polymer electrolyte

Research in the environmentally friendly energy field has grown rapidly due to severe problems such as global warming and climate change. Sodium-ion technology is one of the most promising alternatives to lithium-ion batteries. Use of ionic liquids containing thiocyanate anion has been considered because of their low cost, low viscosity, and nonhazardous nature. In this work, polyethylene oxide (PEO)–sodium perchlorate (NaClO₄) samples containing different amounts of 1-butyl-3-methylimidazolium thiocyanate ionic liquid were prepared by a solution casting method. Addition of the ionic liquid to the PEO–NaClO₄ electrolyte further increased the ionic conductivity. The electrolyte containing 30 wt% ionic liquid exhibited the maximum ionic conductivity of ~5.0 × 10^?4 S/cm at room temperature. Fourier-transform infrared (FT-IR) spectroscopy revealed the interaction between the polymer chain and salt ion complexes for various sodium salt contents. Differential scanning calorimetry (DSC) demonstrated that the crystallinity was reduced by addition of 1-butyl-3-methylimidazolium thiocyanate ionic liquid.     

Aggregation of ranked votes considering different relative gaps between rank positions

This paper considers ranked voting systems to determine the rank order of candidates who compete for a limited number of positions. We show that the preferential voting problems based on the data envelopment analysis (DEA) (Wang et al, 2007) can be solved using the extreme points of constraints on rank position importance incorporated in the formulation. This is basically due to the fact that the so-called inverse positive property of the constraints makes it possible to easily find their extreme points. Further, we emphasize that this finding is not restricted to Wang et al’s two linear models, but is also applicable to other DEA-based preferential voting problems, which include the constraints accounting for different relative gaps between rank positions.     

α,β-Unsaturated acyl cyanide synthesis via triethylamine catalyzed redox cyanation

Stereoselective redox cyanation of alkynyl aldehydes was explored, furnishing (E)-α,β-unsaturated acyl cyanides. This reaction was catalyzed by mild TEA base, as a dual role of Lewis base and Brönsted base. TMSCN treated with TEA was an effective reagent for generating umpolung intermediates from alkynyl aldehydes, and this nucleophilic intermediate can be protonated by equimolar amount of EtOH, promoting the efficient conversion into α,β-unsaturated acyl cyanides. The synthesized acyl cyanides were successfully applied as the synthetic precursors in the iron-catalyzed arylation reactions.