PreT 2 Objects in Topological Categories

In previous papers, two notions of pre-Hausdorff (PreT ₂) objects in a topological category were introduced and compared. The main objective of this paper is to show that the full subcategory of PreT ₂ objects is a topological category and all of T ₀, T ₁, and T ₂ objects in this topological category are equivalent. Furthermore, the characterizations of pre-Hausdorff objects in the categories of filter convergence spaces, (constant) local filter convergence spaces, and (constant) stack convergence spaces are given and as a consequence, it is shown that these categories are homotopically trivial.     

Intra-domain traffic engineering with shortest path routing protocols

Throughout the last decade, extensive deployment of popular intra-domain routing protocols such as open shortest path first and intermediate system–intermediate system, has drawn an ever increasing attention to Internet traffic engineering. This paper reviews optimization techniques that have been deployed for managing intra-domain routing in networks operated with shortest path routing protocols, and the state-of-the-art research that has been carried out in this direction.     

Amide-based tripodal receptors for selective anion recognition

The binding properties of ethylester derivative of p-tetraphenyl tetrahomodioxacalix[4]arenes (1) towards alkali, alkaline-earth, transition and heavy metal cations using UV-absorption spectrophotometry and ¹H-NMR spectroscopy are reported.     

The new dispirobino and dispiroansa spermine derivatives of cyclotriphosphazenes

In this study, the crystal structures of the dispiroansa spermine derivatives of cyclotriphosphazene are characterised for the first time. The reaction of spiro-, gem-disubstituted cyclotriphosphazene derivatives, N₃P₃Cl₄R₂ [R = NHPh, (HN(CH₂)₃NH)_0.5, (OCH₂C(CH₃)₂CH₂O)_0.5], (1–3), with spermine (4), in aprotic solvents such as CH₂Cl₂ results in a series of dispirobino spermine derivatives of cyclotriphosphazene (5a, 6a, 7), namely spermine bridged compounds. Whereas, in protic solvents such as CHCl₃ give, dispiroansa derivatives (8–10) namely tetracyclic cyclotriphosphazene. The new series of dispirobino and dispiroansa spermine derivatives of cyclotriphosphazene (5a, 6a, 7–10) have been characterised by elemental analysis, mass spectrometry, X-ray (for 5a, 8, 10) and ¹H, ³¹P NMR spectroscopies.     

Synthesis,spectroscopic and crystallographic characterization of the cobalt(III) ternary mixed-ligand complexes of N(4)-allyl/methyl thiosemicarbazones, <Emphasis Type="Italic">N,N,N</Emphasis>′<Emphasis Type="Italic">,N</Emphasis>′-tetramethylethylenediamine and azide

Mixed-ligand ternary cobalt(III) complexes consisting of N,N,N′,N′-tetramethylethylenediamine (tmen), R-salicylaldehyde-N(4)-allyl/methyl thiosemicarbazones (R=3-OMe (L^I/L^II) or H (L^III/L^IV) and azide, of general formula [CoL(tmen)(N₃)], were synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structure of [CoL^I(tmen)(N₃)] has a slightly distorted octahedral coordination geometry involving the O, N and S atoms of thiosemicarbazone.     

Immobilization of urease in poly(1-vinyl imidazole)/poly(acrylic acid) network

In this study, urease was immobilized in a polymer network obtained by complexation of poly(1-vinyl imidazole) (PVI) with poly(acrylic acid) (PAA). Preparation of the polymer network was monitored by FT-IR spectroscopy. Scanning electron microscopy (SEM) revealed that enzyme immobilization had a strong effect on film morphology. Proton conductivity of the PVI/PAA network was measured via impedance spectroscopy under humidified conditions. Values of the Michaelis-Menten constant (K _M) for immobilized urease were higher than for the free enzyme, indicating a decreased affinity of the enzyme to its substrate. The basic characteristics (pH_opt, pH_stability, T _opt, T _stability, reusability, and storage stability) of immobilized urease were determined. The results show that the PAA/PVI polymer network is suitable for enzyme immobilization.     

Rapid Hyperbranched Polythioether Synthesis Through Thiol-Michael Addition Reaction

In this study, two types of hyperbranched (HB) polythioether could readily be achieved in a short time at ambient temperature through a thiol-Michael addition reaction. Dimethyl acetylenedicarboxylate (DMADC) or methyl propiolate (A₂) and trimethylolpropane tris(3-mercaptopropionate) (B₃) monomers were reacted using an organobase 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as a catalyst in chloroform at room temperature to provide subsequent HB polythioethers. The effect of TBD concentration on the polymerization was studied for the DMDAC case monitoring the molecular weight evolution against time. HB polythioethers were characterized using spectroscopic (nuclear magnetic resonance) and chromatographic (gel permeation chromatography with refractive index and light-scattering detectors) techniques. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 824–830     

Existence of a global weak solution to Compressible Primitive Equations

In this Note, we show a global weak existence result for a two dimensional Compressible Primitive Equations for atmosphere dynamics modeling.