Existence and approximation of solutions for a class of nonlinear impulsive functional differential equations with anti-periodic boundary conditions

This paper describes the method of quasilinearization for first-order nonlinear impulsive functional differential equations with anti-periodic boundary conditions. A monotone iterative technique coupled with lower and upper solutions is employed to obtain sequences of approximate solutions converging monotonically and quadratically to the unique solution of the problem at hand.     

Metal ion-catalysed reduction of indolic imides,a facile β-carboline synthesis

A novel procedure for the synthesis of β-carbolines by metal catalysed reduction of imides with sodium borohydride is described.     

Biological and phytochemical studies on Capparis decidua (Forssk) Edgew from Cholistan desert

Abstract

The present work deals with the biological and phytochemical studies on Capparis decidua (Forssk) Edgew from Cholistan desert of Pakistan. Aerial and floral parts of C. decidua were collected and dried under shade. Powdered materials of each part of C. decidua were extracted with methanol separately, followed by phytochemical studies. Hexane fraction of aerial parts of the C. decidua obtained after solvent-solvent extraction was purified through repeated column chromatography by increasing order of polarity. Four compounds were purified and identified as simiarenol (1), lupeol (2), taraxerol (3) and β-sitosterol (4). Simiarenol and lupeol were isolated for the first time from genus Capparis. The structures of these compounds were established by comparing the spectroscopic data (¹H NMR, ¹³C NMR, IR, UV & Mass spectrometry) reported in literature. The structure of 1 was further confirmed by XRD analysis. Anti-bacterial activities of crude methanolic extracts were determined against 13 bacterial strains (MIC 250-1000?μg/mL). α-Glucosidase and urease inhibitory activities of pure compounds were also determined. Compounds 1, 2 and 4 showed α-glucosidase inhibition with IC₅₀ at 96.12?±?0.12, 65.28?±?0.13 and 128.14?±?0.17?μM, respectively.     

Installation of Kayzero-INAA standardization in the TNRC and its applications for trace elements determination in different materials

The paper focuses on the validation of the k ₀-method of instrumental neutron activation analysis (k ₀-INAA) in the Tajura Nuclear Research Center (TNRC) via the analysis of several certified reference materials. The selected reference materials were: SRM 1572 Citrus Leaves, SRM 1575 Pine Needles, IAEA-A11 Milk Powder, IAEA-V-10 Hay Powder, RM IAEA-Soil-7 and RM IAEA-SL-1 Lake Sediment. The method is based on the PC version Kayzero/Solcoi software package issued by DSM. All the samples, reference materials and monitors were irradiated in various positions of the Tajura reactor with different f and α. The parameters f and α (f — thermal/epithermal neutron flux ratio, α — parameter accounting for the non-ideality of the 1/E epithermal neutron fluence rate distribution) were determined using the bare triple monitor method. The results obtained for all the reference materials are in good agreement with the certified values.     

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of dextran and dextrin derivatives

Application of matrix-assisted laser desorption/ionization (MALDI) to the analysis of dextran and dextrin derivatives, specifically glucose saccharides, by time-of-flight (TOF) mass spectrometry has been reported. MALDI-TOF analysis was carried out on alpha-, beta- and gamma-cyclodextrin, two O-methylated-beta-cyclodextrins of differing degrees of substitution (DS) and dextrans (a linear glucose saccharide), as pure and doped solutions and as mixtures of two or more of these. Doping was carried out with trace amounts of inorganic salts. The purpose of the analysis of the cyclodextrins was to determine whether they would form inclusion complexes with the various cations added, or whether less specific cation addition/exchange was occurring either prior to desorption or in the gas phase.     

Non-trivial temperature effects on the cation exchange chromatography and chelation ion chromatography of metal ions

The effect of column temperature upon the retention of metal ions on sulfonated and mono-, di-, and amino-carboxylated cation exchange columns has been investigated. The retention of alkali, alkaline earth and transition metal ions on each of the above types of cation exchanger was studied over the temperature range 19-65 degrees C. A major difference between the behaviour of mono- and divalent metal ions was shown on each of the above stationary phases, with the monovalent alkali metals exhibiting clearly exothermic behaviour (a decrease in retention with increased temperature) under acidic eluent conditions and an apparent relationship between retention factor and the magnitude of the temperature effect. The effect of temperature upon alkaline earth metal ions was less defined, although strongly endothermic behaviour (increase in retention with temperature) could be seen on all stationary phases through correct choice of eluent. The transition metal ions studied showed endothermic behaviour on all four stationary phases, with the sulfonated column unexpectedly showing the largest increases in retention. The above behaviour can be partially explained through the dominance of the type of solute-stationary phase interaction governing retention. In several of the above columns, both ion-exchange and surface complexation interactions can occur, with the effects of temperature indicating which process dominates under specific eluent conditions.     

Synthesis of cicerfuran, an antifungal benzofuran, and some related analogues

Routes were investigated for the synthesis of cicerfuran, a hydroxylated benzofuran from wild chickpea implicated in resistance to Fusarium wilt, and some of its analogues. A novel method is described for the synthesis of oxygenated benzofurans by epoxidation and cyclisation of 2′-hydroxystilbenes. The stilbene intermediates required could be synthesised by palladium-catalysed coupling of styrenes with mono-oxygenated aryl halides but not with di-oxygenated aryl halides. Stilbenes corresponding to the latter were synthesised by Wittig reactions.     

Analytical performance of a high-pressure radio frequency-only quadrupole collision cell with an axial field applied by using conical rods

The effect on triple-quadrupole performance of applying an axial field, in an rf-only quadrupole collision cell operated at pressures sufficiently high that collisional focusing is operating, has been investigated. The advantages of such cells have been shown previously to include increased transmission and much improved resolution in fragment ion spectra relative to the performance of collision cells operating at lower gas pressures. The disadvantages of high-pressure collision cells all derive from the relatively long transit times for the ions, which can be long relative to characteristic times for scanning the first mass filter (precursor ion selector) or for switching its setting in multiple reaction monitoring (MRM) cycles. The present work describes experiments on a high-pressure cell in which an axial field is created through use of conical rather than cylindrical or hyperbolic rods. In addition, results of computations of the electric fields within such a cell, and of ion trajectories through it, are presented. It is shown that application of axial fields of the order of 0. 1 V/cm can remove all hysteresis effects associated with the long ion transit times, and thus provide excellent performance in quantitation work using MRM, as well as in other scan modes. Furthermore, the advantages of collisional focusing in quadrupole collision cells are shown to be unimpaired by these low axial fields.     

Flow Injection Spectrophotometric Determination of 2,4‐D Herbicide

2,4‐Dichlorophenoxy acetic acid herbicide is spectrophotometrically determined by diazotization method in a flow injection assembly. The method is based on base hydrolysis of herbicides. The hydrolyzed product 2,4‐dichlorophenol is reacted with diazotized sulfanilic acid. The absorbance of the resulting coloured product was measured at 480 nm. The calibration graph is linear over the range of 0.2–20 μgmL^?1, with a relative standard deviation of (RSD) of 7.2% and sample throughput of 90 samples h^?1. The % recovery for determination of 2,4‐dichlorophenoxy acetic acid was found to be 92.0–95.3%. The method is easy, simple and faster than the established chromatographic method. The method was applied for determination of 2,4‐dichlorophenoxy acetic acid herbicide in commercial formulations and for residue determination in fruits and food samples.