Rare examples of fluoride-based multiferroic materials in Mn-substituted BaMgF4 systems: experimental and theoretical studies

A series of Mn-substituted BaMgF(4) samples have been synthesized by a hydrothermal route. X-ray diffraction study reveals that the products are monophasic in nature. Scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS) studies were carried out to investigate the morphology and stoichiometry for these compounds. X-ray photoelectron spectroscoy (XPS) and electron spin resonance (ESR) studies were done to confirm the oxidation state of dopant ion. Room temperature ferromagnetism was observed on Mn substitution at the Mg site in BaMgF(4) samples. The saturation magnetization increases initially, shows a peaking effect, and then decreases with further increase in Mn concentration in BaMg(1-x)Mn(x)F(4) (0.0 ≤ x ≤ 0.15). However, ferroelectricity was found to decrease with an increase in Mn concentration in the series of investigated BaMg(1-x)Mn(x)F(4) (0.0 ≤ x ≤ 0.15) samples. First-principle calculations, using the projector augmented wave potentials on Mn-substituted BaMgF(4), confirmed the decrease in magnetic moment with an increase in Mn content beyond certain concentration. These samples exhibit very weak magnetocapacitive coupling, which can be attributed to the very small magnetic signal observed in these samples.     

Nature of intramolecular transannular interaction in group 13 atranes: a theoretical study

Ab initio molecular orbital (MO) calculations at the MP2/6-31+G* level coupled with quantum theory of atoms in molecules (QTAIM) analysis were carried out on group 13 atranes (M = B, Al, Ga) with special emphasis on the nature of the transannular M···N interaction present in these molecules. Substituents at the equatorial position were found to influence the extent of transannular interaction. Boratrane molecules were found to have the strongest M···N interaction and consequently have higher stabilization energies. QTAIM analysis revealed the presence of significant covalent character in the transannular M···N bonds which decreases down the group.     

Correlating SAXS analysis with LSPR behavior: poly(vinyl alcohol)-stabilized Ag nanoparticles

We explore the localized surface plasmon resonance (LSPR) behavior of aqueous sols of PVA-stabilized AgNPs synthesized in presence of glucose as a reducing agent. The in situ synthesis parameters are tuned by adding increasing amounts of NaOH, which causes interesting variations in pH, LSPR curve broadening, and the evolution of AgNPs embedded PVA cross-linked nanostructures. Small angle X-ray scattering (SAXS) analysis is used to investigate sol aggregate characteristics. In all samples, mass fractal aggregates of two radius of gyration are formed. Assuming spherical form, the SAXS nanoparticle size distribution predicts a range from 6 to 60 nm. However, only the fractal aggregate features closely correspond to the observed LSPR characteristics.     

Organogel-hydrogel transformation by simple removal or inclusion of N-Boc-protection

Development of organo- and hydrogelators is on the rise because of their extensive applications, from advanced materials to biomedicine. However, designing both types of gelator from a common structural scaffold is challenging, and becomes more significant if transformation between them can be achieved by a simple method. The present work reports the design and synthesis of both organo- and hydrogelators from amino acid/peptide-based amphiphilic precursors with a naphthyl group at the N terminus and a primary amine-containing hydrophilic ethyleneoxy unit at the C terminus. In alkaline medium, tert-butyloxycarbonyl (Boc) protection at the primary amine of the amphiphiles resulted in efficient organogelators (minimum-gelation concentration (MGC)=0.075-1.5% w/v). Interestingly, removal of the Boc protection from the ethyleneoxy unit, under acidic conditions, yielded amphiphiles capable of gelating water (MGC=0.9-3.0% w/v). Simple protection and deprotection chemistry was used to achieve transformation between the organogel and hydrogel by alteration of the pH. Combinations of different aliphatic and aromatic amino acids were investigated to discover their cumulative effect on the gelation properties. Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were employed to investigate the supramolecular morphology of the thermoreversible gels. Spectroscopic investigations (FTIR, photoluminescence, XRD) revealed that noncovalent interactions, such as hydrogen bonding, π-π stacking, and van der Waals interactions play a decisive role in self-assembled gelation.     

Scattering of water waves by a submerged thin vertical elastic plate

The problem of water wave scattering by a thin vertical elastic plate submerged in infinitely deep water is investigated here assuming linear theory. The boundary condition on the elastic plate is derived from the Bernoulli–Euler equation of motion satisfied by the plate. This is converted into the condition that the normal velocity of the plate is prescribed in terms of an integral involving the difference in velocity potentials (unknown) across the plate multiplied by an appropriate Green’s function. The reflection and transmission coefficients are obtained in terms of integrals involving combinations of the unknown velocity potential on the two sides of the plate and its normal derivative on the plate, which satisfy three simultaneous integral equations, solved numerically. These coefficients are computed numerically for various values of different parameters and are depicted graphically against the wave number for different situations. The energy identity relating these coefficients is also derived analytically by employing Green’s integral theorem. Results for a rigid plate are recovered when the parameters characterizing the elastic plate are chosen negligibly small.     

The Euler class group of a polynomial algebra with coefficients in a line bundle

Let $A$ be a commutative Noetherian ring and $P$ be a projective $A$ -module of rank $=(\text {dim}(A)-1)$ . An intriguing open question is to find the precise obstruction for $P$ to split as: $P\simeq Q\oplus A$ for some $A$ -module $Q$ . In this paper we settle this question when $A=R[T]$ for some ring $R$ containing the field of rationals and $P$ is a projective $A$ -module of rank $=\text {dim}(R)$ .     

Numerical simulation of Casson fluid flow through differently shaped arterial stenoses

The present investigation deals with a mathematical model of blood flow through an asymmetric (about its narrowest point) arterial constriction obtained from casting of a mildly stenosed artery. The flowing blood is represented as the suspension of all red cells (erythrocytes) in plasma assumed to be Casson fluid, while the arterial wall is considered to be rigid having differently shaped stenoses in its lumen arising from various types of abnormal growth or plaque formation. The governing equations of motion accompanied by the appropriate choice of the boundary conditions are solved numerically by Marker and Cell method in order to compute the physiologically significant quantities with desired degree of accuracy. The necessary checking for numerical stability has been incorporated in the algorithm for better precision of the results computed. The quantitative analyses have been carried out finally with the inclusion of the respective profiles of the flow field over the entire arterial segment as well. The key factors such as the wall shear stress, the pressure drop and the velocity profiles are exhibited graphically and examined thoroughly for qualitative insight into blood flow phenomena through arterial stenosis.     

Hausdorff and upper box dimension estimate of hyperbolic recurrent sets

In this paper, under the open set condition we have determined the lower and upper bounds of the Hausdorff dimensions and the upper box-counting dimensions of the limit sets of hyperbolic recurrent iterated function systems in terms of the unique zeros h and H of the two pressure functions. In addition, we have estimated the bounds of h, H-dimensional Hausdorff and packing measures. The result in this paper generalizes existing results about fractal dimensions of many other iterated function systems.     

One-Pot Green Synthesis of 3'-(2-Aminobenzimidazolyl)-2-Phenyl Spiro[4H-Benzopyran-4,2'-Thiazolidin]-4-Ones and Acylation Using Trifluoroacetic Anhydride

Abstract

An expeditious one-pot synthesis of a novel heterocyclic system, 3′-(2-aminobenzimidazolyl)-2-phenyl spiro[4H-benzopyran-4,2′-thiazolidin]-4-ones, has been accomplished by condensing substituted hydrazinobenzimidazole, flavanone, and mercaptoacetic acid by conventional heating in ethanol or toluene, and in an ionic liquid, viz., 1-butyl-3-methyl-imidazolium hexafluorophosphate. Excellent yields (85%–90%) and higher purity are obtained in the ionic-liquid-mediated synthesis as compared with the conventional procedure (55%–60%). Further, these compounds were acylated with trifluoroacetic anhydride. The structures of the compounds were confirmed by IR, ¹H NMR, ¹³C NMR, mass spectral data, and elemental analysis. The compounds, upon evaluation for their antibacterial, antifungal, and insecticidal activities, exhibited excellent results.

[Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: Table S1, S2, and S3]

GRAPHICAL ABSTRACT      

Spectroscopic Probe of the Distribution of Cationic Drug or Dye Between Anionic Polymers

Abstract

Knowledge of the distribution of a drug (or dye) between different biopolymers may be useful in understanding the mechanism of drug action. We have studied the distribution of drugs or dyes between different anionic polymers as model systems. Spectrophotometric and circular dichroism have been used as techniques to monitor the distribution of intercalating, partially intercalating, and nonintercalating cationic dyes or drugs between DNA and other anionic polymers. Both spectrophotometric and circular dichroic evidence indicates that the partially intercalating dye dimethylmethylene blue distributes itself between DNA and heparin with a preference for DNA. In the case of the intercalating drug actinomycin-D, DNA uses its intercalating ability to win heparin in competitive binding of the drug. The picture is somewhat different when pinacyanol (PCYN) chloride, a nonintercalating dye, is used as the ligand in the competitive binding of DNA and poly(styrene sulfonate) (PSS); DNA loses to PSS in competitive binding of this ligand. The equilibrium constant of the distribution of PCYN between DNA and PSS has been determined from a method developed here.