Carboxymethylation of corn starch and characterization using asymmetrical flow field-flow fractionation coupled with multiangle light scattering

Asymmetrical flow field-flow fractionation (AsFlFFF) was coupled online with multiangle light scattering (MALS) to study the changes in the molecular weight and the size distribution of the corn starch during carboxymethylation. A corn starch was derivatized with sodium chloroacetate in alcoholic medium under alkaline condition to produce carboxymethyl starches (CMS) having various degrees of substitution (DS). The change in thermal characteristics and granule structure of the native corn starch and CMS were compared using Thermogravimetric analysis and scanning electron microscope. The ionic strength of the carrier liquid (water with 0.02% NaN₃) was optimized by adding 50 mM NaNO₃ to minimize the interactions among the starch molecules and between the starch molecules and the AsFlFFF membrane. A field-programmed AsFlFFF allowed determination of the molecular weight distribution (MWD) of starches within about 25 min. It was found that carboxymethylation of starch results in reduction in the molecular weight due to molecular degradation by the alkaline treatment. The weight-average molecular weight (M_w) was reduced down to about 4.4 × 10⁵ from about 7.2 × 10⁶ when DS was 0.14. It seems AsFlFFF coupled with MALS (AsFlFFF/MALS) is a useful tool for monitoring the changes taking place in the molecular weight and the size of starch during derivatization.     

Common fixed point theorems for self-mappings in Menger PM-spaces with nonlinear contractive condition

The purpose of this paper is to prove some common fixed point theorems for a pair of self-mappings defined on Menger PM-spaces with nonlinear contractive condition in the sense of Fang (Fuzzy Set Syst 267:86–99, 2015). Following Pant and Pant (Filomat (31)(11):3495–3499, 2017), we define semi R-commutativity for a pair of self-mappings for Menger PM-spaces. Using this notion and the notion of orbital continuity introduced by ?iri? (Publ Inst Math (12)(26):19–26, 1971), we obtain the main results. These results generalize some known results. Some examples and comments according to the preceding results are given.     

Effect of positional substitution of methyl group on the fluorescence properties of quinolinium ion

In the present study we have investigated the effect of methyl substitution at various positions on the spectral and decay behavior of some quinolinium ions. The spectra reveal marked differences when methyl group is present at 7th and 8th positions. The non-radiative deactivation is also considerably affected by the substituent position. The results are explained by considering the modulation (decrease as compared to the unsubstituted quinolinium) in nonradiative rate (intersystem crossing) due to substitution.     

Characterization and transport properties of 10BaO–xAg<Subscript>2</Subscript>O–(85-x)V<Subscript>2</Subscript>O<Subscript>5</Subscript>–5TeO<Subscript>2</Subscript> glass system

Silver-based quaternary glasses were prepared by splat quenching technique. X-ray diffraction and differential scanning calorimetry were done for confirming their amorphous nature. The conductivity of the glasses was measured in the frequency range from 1 Hz to 32 MHz from room temperature to 373 K. Conductivity data, which obeys the Arrhenius type behavior, shows minimum at 30 mol% Ag₂O, suggesting that the conductivity mechanisms are different above and below these two regions. The minimum in conductivity is accompanied by an inverse behavior of activation energy. Experimental data suggests that a polaron hopping mechanism operates in the electronically conducting domain of 20 ≤ × ≤ 30, and an interstitial pair mechanism operates in the ionically conducting domain of 35 ≤ × ≤ 55.     

New mutation schemes for differential evolution algorithm and their application to the optimization of directional over-current relay settings

Differential evolution is a novel evolutionary approach capable of handling non-differentiable, nonlinear and multimodal objective functions. It has been consistently ranked as one of the best search algorithm for solving global optimization problems in several case studies. In the present study we propose five new mutation schemes for the basic DE algorithm. The corresponding versions are termed as MDE1, MDE2, MDE3, MDE4 and MDE5. These new schemes make use of the absolute weighted difference between the two points and instead of using a fixed scaling factor F, use a scaling factor following the Laplace distribution. The performance of the proposed schemes is validated empirically on a suit of ten benchmark problems having box constraints. Numerical analysis of results shows that the proposed schemes improves the convergence rate of the DE algorithm and also maintains the quality of solution. Efficiency of the proposed schemes is further validated by applying it to a real life electrical engineering problem dealing with the optimization of directional over-current relay settings. It is a highly constrained nonlinear optimization problem. A constraint handling mechanism based on repair methods is used for handling the constraints. Once again the simulation results show the compatibility of the proposed schemes for solving the real life problem.     

Synthesis of conformationally diverse tetrathiacalix[4]arene(amido)crowns and tetrathiacalix[4]arene amides with pendant amine functions

A series of conformationally diverse novel tetrathiacalix[4]arene(amido)crowns and amides from tetrakis((ethoxycarbonyl)methoxy)p-tert-butyl tetrathiacalix[4]arene and its debutylated analog have been prepared by their reaction with diamines [H₂N(CH₂)_nNH₂; n=2,3,4, and 6] and polyamines. It has been determined that the length of the alkyl spacer in diamines is pivotal for the formation of either the tetrathiacalix[4]arene bis(amido)crowns or tetrathiacalix[4]arene amides with pendant amine functions. The synthesized compounds represent potential building blocks for achieving sophisticated molecular assemblies for molecular organization and recognition. Single crystal X-ray analysis of tetrathiacalix[4]arene bis(amido)crown 6a revealed that it has a 1,3-alternate conformation, which forms supramolecular complexes with chloroform.     

Nitrile ligands for controlled synthesis of alkynyl-ruthenium based homo and hetero bimetallic systems

Wire like mono- and poly-nuclear molecules based on alkynyl ruthenium complexes whose core unit is trans-[Ru(CC-R)(R′CN)(dppe)₂][PF₆] are readily formed in soft conditions. The electronic dual character of the metallic unit, donor through the acetylide moiety, acceptor versus the nitrile ligand is exemplified through electrochemical studies of a series of ethynylferrocene and cyanoferrocene derivatives. A single crystal X-ray diffraction analysis of the [(dppe)₂(PhCC)Ru(NC-C₆H₄-CN)Ru(CCPh)(dppe)₂][2PF₆] bimetallic complex 5 shows that the global structure of such complexes consists of wire type dimetallic units. With the availability of this versatile, direct, and simple route, a new class of extended rigid rod systems of nanometric size with multilevel electron transfers is readily accessed.     

Polymer micro-environmental effects on the fluorescence characteristics of 5-aminoquinoline and 3-aminoquinoline

In this paper we report the spectral and decay behavior of two probes viz. 5-aminoquinoline (5AQ) and 3-aminoquinoline (3AQ) in three different polymeric systems viz. poly methyl methacrylate (PMMA), polyvinyl alcohol (PVA) and cellulose acetate (CA). Absorption spectra are nearly identical for all the polymers but the emission shows larger shift in case of CA as compared to PMMA and PVA. The behavior is explained on the basis of higher hydrogen bond donating ability in case of CA because of the presence of cellulosic hydrogens. Observed multiexponential decays are explained on the basis of free as well as hydrogen-bonded species and also trapping in various excited state geometries of the matrix.