Study of COVID-19 epidemiological evolution in India with a multi-wave SIR model

Nonlinear Dynamics - The global pandemic due to the outbreak of COVID-19 ravages the whole world for more than two years in which all the countries are suffering a lot since December 2019. In this...     

The integrable Boussinesq equation and it’s breather,lump and soliton solutions

The fourth-order nonlinear Boussinesq water wave equation, which explains the propagation of long waves in shallow water, is explored in this article. We used the Lie symmetry approach to analyze the Lie symmetries and vector fields. Then, by using similarity variables, we obtained the symmetry reductions and soliton wave solutions. In addition, the Kudryashov method and its modification are used to explore the bright and singular solitons while the Hirota bilinear method is effectively used to obtain a form of breather and lump wave solutions. The physical explanation of the extracted solutions was shown with the free choice of different parameters by depicting some 2-D, 3-D, and their corresponding contour plots.

     

Calix[4]arene-based ditopic receptors for simultaneous recognition of fluoride and cobalt(II) ions

A series of calix[4]arene based ditopic receptors possessing bipyridyl and hydrazone units have been synthesized and evaluated for ionic recognition. It has been observed that the synthesized derivatives function as allosteric receptors for simultaneous recognition of Co²⁺and F^? ions through non-covalent interactions. Significant bathochromic shifts in the UV–visible spectrum with a profound colour change promise their use to engineer novel applications.     

A theoretical perspective on the accuracy of rotational resonance (R 2)-based distance measurements in solid-state NMR

The application of solid-state NMR methodology for bio-molecular structure determination requires the measurement of constraints in the form of ¹³C–¹³C and ¹³C–¹⁵N distances, torsion angles and, in some cases, correlation of the anisotropic interactions. Since the availability of structurally important constraints in the solid state is limited due to lack of sufficient spectral resolution, the accuracy of the measured constraints become vital in studies relating the three-dimensional structure of proteins to its biological functions. Consequently, the theoretical methods employed to quantify the experimental data become important. To accentuate this aspect, we re-examine analytical two-spin models currently employed in the estimation of ¹³C–¹³C distances based on the rotational resonance (R ²) phenomenon. Although the error bars for the estimated distances tend to be in the range 0.5–1.0 Å, R ² experiments are routinely employed in a variety of systems ranging from simple peptides to more complex amyloidogenic proteins. In this article we address this aspect by highlighting the systematic errors introduced by analytical models employing phenomenological damping terms to describe multi-spin effects. Specifically, the spin dynamics in R ² experiments is described using Floquet theory employing two different operator formalisms. The systematic errors introduced by the phenomenological damping terms and their limitations are elucidated in two analytical models and analysed by comparing the results with rigorous numerical simulations.     

Photoluminescence and atomic force microscopy studies on pre- and post-irradiated ruby with Fe3+ ion

Photoluminescence spectra measured for pristine ruby and its two irradiated samples with Fe³⁺ ion show R₁, R₂, N lines and a broad band. Decrease in intensities of these features is observed with irradiation of Fe³⁺ ion in ruby. Progressive structural changes and modifications on surface of irradiated rubies with Fe³⁺ ion have been observed by atomic force microscopy. Decrease in intensities is discussed in terms of pair formation.     

A Novel and Efficient One Pot Synthesis of 2,4‐Disubstituted Thiazoles and Oxazoles Using Phenyltrimethylammoniumtribromide in Ionic Liquid

A novel and efficient one‐pot procedure has been described for synthesis of 2,4‐disubstituted thiazoles and oxazoles from substituted ketones using phenyltrimethylammoniumtribromide as in situ brominating agent followed by reaction with thioamide/thiourea and amides/ureas, respectively in [bmim][BF₄] ionicliquid. The advantages of the procedure include avoiding the handling of lacrymetric compounds, hazardous and toxic organic solvents along with good to excellent yield of the products.     

Iodine-catalyzed three-component one-pot synthesis of naphthopyranopyrimidines under solvent-free conditions

Iodine is found to be a highly efficient catalyst for the three-component coupling (3CC) of aldehydes, β-naphthol, and 1,3-dimethylbarbituric acid under solvent-free conditions to afford the corresponding 8,10-dimethyl-12-aryl-12H-naphtho[1′,2′5,6]pyrano[2,3-d]pyrimidine-9,11-diones in good yields with high selectivity. The use of readily available iodine makes this method very simple, convenient, and cost-effective.     

Concurrent determination of olanzapine,risperidone and 9‐hydroxyrisperidone in human plasma by ultra performance liquid chromatography with diode array detection method: application to pharmacokinetic study

A simple and sensitive ultra‐performance liquid chromatography (UPLC) method has been developed and validated for simultaneous estimation of olanzapine (OLZ), risperidone (RIS) and 9‐hydroxyrisperidone (9‐OHRIS) in human plasma in vitro. The sample preparation was performed by simple liquid–liquid extraction technique. The analytes were chromatographed on a Waters Acquity H class UPLC system using isocratic mobile phase conditions at a flow rate of 0.3 mL/min and Acquity UPLC BEH shield RP₁₈ column maintained at 40°C. Quantification was performed on a photodiode array detector set at 277 nm and clozapine was used as internal standard (IS). OLZ, RIS, 9‐OHRIS and IS retention times were found to be 0.9, 1.4, .1.8 and 3.1 min, respectively, and the total run time was 4 min. The method was validated for selectivity, specificity, recovery, linearity, accuracy, precision and sample stability. The calibration curve was linear over the concentration range 1–100 ng/mL for OLZ, RIS and 9‐OHRIS. Intra‐ and inter‐day precisions for OLZ, RIS and 9‐OHRIS were found to be good with the coefficient of variation <6.96%, and the accuracy ranging from 97.55 to 105.41%, in human plasma. The validated UPLC method was successfully applied to the pharmacokinetic study of RIS and 9‐OHRIS in human plasma. Copyright © 2015 John Wiley & Sons, Ltd.