Simultaneous Trace Level Determination of Potentially Genotoxic Hydrazine,Methylhydrazine and Alkylamines in Pharmaceutical Substances by CE Using Indirect Photometric Detection

A simple, fast, and sensitive capillary electrophoretic method was developed for determining two genotoxic impurities hydrazine and methylhydrazine and eight alkyl amines at trace levels in pharmaceutical substances using indirect photometric detection. The method development involved a systematic screening of various cationic visualizing reagents and optimization of separation conditions to obtain the best resolution and sensitivities. The optimized method was validated for specificity, precision, linearity, and accuracy. Linear calibration curves (R > 0.99) were obtained for all analytes in the range LOQ–200 % of nominal concentrations. The developed CE method was effectively implemented for estimating hydrazine and alkylamines in several active pharmaceutical ingredients (APIs).

     

A study of the fractional‐order mathematical model of diabetes and its resulting complications

Diabetes is a worldwide problem that affects one of every 11 persons nowadays. The IDF Diabetes Atlas (Eighth edition, 2017) states that approximately 415 million people in the world are living with the disease and that this number will rise to 629 million by the year 2045. It is a very serious problem of the world. A major part of the world population is affected by this disease and its resulting complications. In this paper, we propose to investigate a fractional‐order model of diabetes and its resulting complications. The mathematical model's parameters define the population of diabetic patients and those who are diabetic with complications at a given time t. We have also discussed the existence, uniqueness, and stability of the fractional‐order model, which we consider here. We make use of the homotopy decomposition method (HDM) in order to solve the problem.     

Importance of weak interactions in developing 1,3-bis(4,6-dimethyl-1H-nicotinonitrile-1-yl)1,3-dioxy propane polymorphs

The structure of 1,3-bis(4,6-dimethyl-1H-nicotinonitrile-1-yl)1,3-dioxy propane polymorphs has been characterized by X-ray diffraction, FT-IR, 1H and 13C NMR spectroscopies. The influence of intra and intermolecular weak interactions is thoroughly studied in solid state using single crystal X-ray diffraction and FT-IR. These polymorphs belong to monoclinic space group 'P2(1/n)' and 'P2(1/c)'. These polymorphs have C-H?n (lone pair), hydrogen bonds, C-N?π, C-H?π and π?π intermolecular non-covalent interactions. These polymorphs are the result of weak interactions and solvent used in crystallization. The FT-IR spectra have been recorded in the solid phase and NMR has been recorded in solvent. The optimized geometry has been calculated by B3LYP methods using different basis sets. The FT-IR and NMR spectra of 1st polymorphs has been calculated at B3LYP/6-31G (d) level. The scaled theoretical wave number showed good agreement with the experimental values. These two polymorphs as well as other stereomers are studied by DFT calculations.     

Hydroxo‐Bridged Dimers of Oxo‐Centered Ruthenium(III) Triangle: Synthesis and Spectroscopic and Theoretical Investigations

The homometallic hexameric ruthenium cluster of the formula [Ru^III₆(μ₃‐O)₂(μ‐OH)₂((CH₃)₃CCO₂)₁₂(py)₂] ( 1 ) (py=pyridine) is solved by single‐crystal X‐ray diffraction. Magnetic susceptibility measurements performed on 1 suggest that the antiferromagnetic interaction between the Ru^III centers is dominant, and this is supported by theoretical studies. Theoretical calculations based on density functional methods yield eight different exchange interaction values for 1 : J₁=?737.6, J₂=+63.4, J₃=?187.6, J₄=+124.4, J₅=?376.4, J₆=?601.2, J₇=?657.0, and J₈=?800.6 cm^?1. Among all the computed J values, six are found to be antiferromagnetic. Four exchange values (J₁, J₆, J₇ and J₈) are computed to be extremely strong, with J₈, mediated through one μ‐hydroxo and a carboxylate bridge, being by far the largest exchange obtained for any transition‐metal cluster. The origin of these strong interactions is the orientation of the magnetic orbitals in the Ru^III centers, and the computed J values are rationalized by using molecular orbital and natural bond order analysis. Detailed NMR studies (¹H, ¹³C, HSQC, NOESY, and TOCSY) of 1 (in CDCl₃) confirm the existence of the solid‐state structure in solution. The observation of sharp NMR peaks and spin‐lattice time relaxation (T1 relaxation) experiments support the existence of strong intramolecular antiferromagnetic exchange interactions between the metal centers. A broad absorption peak around 600–1000 nm in the visible to near‐IR region is a characteristic signature of an intracluster charge‐transfer transition. Cyclic voltammetry experiments show that there are three reversible one‐electron redox couples at ?0.865, +0.186, and +1.159 V with respect to the Ag/AgCl reference electrode, which corresponds to two metal‐based one‐electron oxidations and one reduction process.     

Electroluminescence in the phosphor anthracene doped by 9-vinylanthracene

Electroluminescence has been excited in the phosphor anthracene doped by 9-vinylanthracene (10⁻⁴ mole %) at room temperature (300°K). Variation of light output with voltage is governed by the relationB=B ₀ exp [−(C/V ^1/2)] as in the case of inorganic phosphors. HereB ₀ andC are constants andV is the rms value of the voltage applied to the phosphor. Frequency dependence of the electroluminescence has also been studied at different voltages of the applied electric field.     

A composite semi-conservative scheme for hyperbolic conservation laws

In this work a first order accurate semi-conservative composite scheme is presented for hyperbolic conservation laws. The idea is to consider the non-conservative form of conservation law and utilize the explicit wave propagation direction to construct semi-conservative upwind scheme. This method captures the shock waves exactly with less numerical dissipation but generates unphysical rarefaction shocks in case of expansion waves with sonic points. It shows less dissipative nature of constructed scheme. In order to overcome it, we use the strategy of composite schemes. A very simple criteria based on wave speed direction is given to decide the iterations. The proposed method is applied to a variety of test problems and numerical results show accurate shock capturing and higher resolution for rarefaction fan.     

Preparation and characterization of narrow compositional distribution polyampholytes as potential biomaterials: Copolymers of N-(3-aminopropyl)methacrylamide hydrochloride (APM) and methacrylic acid (MAA)

This article describes the preparation and solution properties of a series of polyampholytes composed of N-(3-aminopropyl)methacrylamide hydrochloride (APM) and methacrylic acid (MAA). In particular, conditions were found where the copolymers could be formed with little or no drift in composition over the course of polymerization to quite high conversions. The compositional drift, common to many copolymerizations, was limited by adjusting the reactivity of MAA through control of its degree of ionization (i.e., pH). As revealed by potentiometric measurements and changes in ¹H NMR spectra, the solution pH drifted over the course of some polymerizations. This was ascribed to changes in the pK_a values of the ammonium and carboxylate groups upon incorporation in the copolymer. The pH drift led to a change in degree of MAA ionization, and hence the relative reactivities of APM and MAA, but this effect could be minimized by using a buffer. Precipitation, which occurred during some polymerizations, could be prevented, in some cases, by the addition of salt or an organic cosolvent. Even in cases where precipitation could not be prevented, it was found that the copolymer was still formed with minimal compositional drift. The solubility of the resulting polyampholytes in aqueous solution was found to depend on their composition, as well as pH, ionic strength and temperature. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 353–365     

Approximation of functions by (N,p) operator

The present paper deals with finding of constant occurring in the order of approximation of the function ofLipα(0<α<1) class by using (N, p) operator. Obviously the factor 1/(1−α) becomes large when α is close to 1. We have shown the role of this factor in the constant of approximation.     

Lattice thermal conductivity of nylone and polyethylen at low temperatures

Using Callaway's model, the phonon conductivity of Nylone and Polyethylen has been calculated in the temperature range 0.2–5°K and the dislocations are taken as the scaterers of phonon. Good agreement is found between the calculated values and the experimental values of the phonon conductivity.