Synthesis of Isoindolo[2,1‐a]quinazoline‐5,11‐dione Derivatives via the Reductive One‐Pot Reaction of N‐Substituted 2‐Nitrobenzamides and 2‐Formylbenzoic Acids

Various isoindolo[2,1‐a]quinazoline‐5,11‐dione derivatives 3 were synthesized in good yields by means of the reductive reaction of N‐substituted 2‐nitrobenzamides 1 and 2‐formylbenzoic acids 2 in the presence of SnCl₂?2 H₂O under reflux in EtOH (Scheme, Table). The procedure needed two steps, the reduction of the nitro group of the 2‐nitrobenzamide and ring closure by nucleophilic addition of the NH₂ group to both the formyl and carboxylic acid C?O groups.     

Stability treatments of wave system in ℜn with coupling controllers via energy functional and decomposition methods

In this paper, the stabilizability conditions of a system of wave equations, coupled in parallel with distributed springs and viscous dampers, are investigated via energy perturbation and decomposition methods for different wave propagation speeds.     

Determination of caffeine in black tea leaves by Fourier transform infrared spectrometry using multiple linear regression

A simple and fast analytical procedure was developed for the determination of caffeine in black tea leaves. The method is based on multiple linear regression treatment of Fourier transform infrared spectrometric data obtained in the wave number range 1800–1300 cm⁻¹ after extraction of caffeine in CHCl₃ from tea samples, wetted with an aqueous solution of NH₃ (0.1 M). The procedure requires no complex sample preparation. It provided a limit of detection of 0.035 mg/ml, a sampling frequency of 6 h⁻¹ and a coefficient of variation of 0.8% for five independent measurements of a tea sample with 3.68% w/w caffeine content. This procedure provides a drastic reduction in the consuming organic solvent for each sample compare to that of the reference chromatographic determination. The accuracy of technique is evaluated by comparing the obtained results with those of a reference HPLC technique. An average value of 3.60±0.07% w/w was obtained by HPLC for a powdered tea sample which is compromising when is compared to 3.68±0.03% (w/w) obtained by this FTIR technique.     

Analytical approximation of the gamma ray spectra from germanium detectors

Several functional forms for shape function are tested using data obtained by a Ge(Li) detector. A function built from a Gaussian, a step function and a symmetric or asymmetric tailing on a linear or polynomial background is needed. A new shape function is proposed and superior fit are obtained.     

Sakiadis flow of an upper-convected Maxwell fluid

The flow of an upper-convected Maxwell (UCM) fluid is studied theoretically above a rigid plate moving steadily in an otherwise quiescent fluid. It is assumed that the Reynolds number of the flow is high enough for boundary layer approximation to be valid. Assuming a laminar, two-dimensional flow above the plate, the concept of stream function coupled with the concept of similarity solution is utilized to reduce the governing equations into a single third-order ODE. It is concluded that the fluid's elasticity destroys similarity between velocity profiles; thus an attempt was made to find local similarity solutions. Three different methods will be used to solve the governing equation: (i) the perturbation method, (ii) the fourth-order Runge-Kutta method, and (iii) the finite-difference method. The velocity profiles obtained using the latter two methods are shown to be virtually the same at corresponding Deborah number. The velocity profiles obtained using perturbation method, in addition to being different from those of the other two methods, are dubious in that they imply some degree of reverse flow. The wall skin friction coefficient is predicted to decrease with an increase in the Deborah number for Sakiadis flow of a UCM fluid. This prediction is in direct contradiction with that reported in the literature for a second-grade fluid.     

Vibrational spectra and assignments using ab initio and density functional theory analysis on the structure of biotin

Density functional theory (DFT) and Hartree-Fock calculations were performed using the following models: HF/6-311G(d), B3LYP/6-311G(d), B3LYP/6-311+G(d) and B3PW91/6-311G(d) calculations were performed for biotin. It has been characterized by IR and X-ray. The calculated results show that the predicted geometry can well reproduce the structural parameters. Predicted vibrational frequencies have been assigned and compared with experimental IR spectra and they supported each other. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between Cp,m degrees, Sm degrees, Hm degrees and temperatures.     

Real-life application of a QCM-based e-nose: quantitative characterization of different plant-degradation processes

Continuous surveillance of composting processes would enable a feedback loop to be obtained for both analysis and process control. For this purpose, we designed e-noses based on a six-electrode quartz-crystal microbalance (QCM) array coated with affinity materials and molecularly imprinted polymers (MIP). They enable quantitative monitoring of volatile organic compounds (VOCs) emitted directly in a compost bin and are highly suitable tools for achieving on-line characterization of the degradation processes occurring. During grass and pine composting (duration 14 days and 40 days, respectively), we observed concentrations of up to 250 ppm of esters, 700 ppm of alcohols, 250 ppm of terpenes, and 90% relative humidity directly on-line with such a system and could validate the data off-line by GC-MS. The sensor also gave direct insight into the differences between the two composting batch types. Besides duration, during grass composting larger amounts of alcohols are emitted whereas relative amount of terpenes is twice as high for pine composting. Detailed correlation of the sensor and the GC-MS data allows approximate estimation of the sensitivity of the sensor materials towards analyte classes such as, e.g., aliphatic alcohols or terpenes. Figure Mass sensitive sensor arrays coated with different molecularly imprinted and affinity materials are a highly suitable tool for quantitatively monitoring solvent patterns during composting procedures on-line in a composter headspace. Dedicated to Professor Udo Brinker on the occasion of his 65th birthday.     

Template polymerization of aniline in presence of poly(acrylamide-<Emphasis Type="Italic">co</Emphasis>-maleic acid) for preparation of conductive polymers

In the present work new conductive nanostructures based on poly (acrylamide-co-maleic acid) (PAAMA) and polyaniline were prepared. The template polymerization of aniline was conducted in the aqueous solution of PAAMA with different ratios (w/w%) of aniline to polyacid. The prepared composite was characterized by FTIR and UV–Vis spectroscopy, SEM, electrical conductivity measurements and solubility tests.     

Response surface analysis for understanding the effects of synthesis parameters on the microstructure of hyperbranched polyesters

Synthesis parameters including the time of condensation reaction, the monomer-to-core ratio (2, 2-bis (hydroxymethyl) propionic acid) (pseudo-generation) and the type of catalyst were changed methodically to investigate their effects on the microstructure of resulting hyperbranched polyesters (HBPEs). Response surface methodology (RSM) was utilized to uncover the relationship between changing variables and the number of terminal hydroxyl groups of HBPSs by which the individual and interactive effects of the aforementioned synthesis parameters were explored. The degree of branching and molecular weight of the HBPEs were evaluated by titration of hydroxyl number and gel permeation chromatography, respectively. Fourier transform infrared spectroscopy and nuclear magnetic resonance analyses confirmed attachment of functional groups to the molecules. Interpretations based on RSM showed that increase of the number of the core molecules, which is equivalent To reduction of the pseudo-generation, narrows the molecular weight distribution of the prepared hyperbranched polyester; so that the lowest molecular weight distribution is obtained for the first pseudo-generation HBPEs with the monomer-to-core ratio of 3:1 and the average number of the terminal hydroxyl groups in between 6 and 8. The samples prepared by the sulfuric acid catalyst had the highest average number of terminal hydroxyl groups, at the same time narrowest molecular weight distribution.     

Magnetic solid-phase extraction to preconcentrate trace amounts of gold (III) using nickel ferrite magnetic nanoparticles

In this research, nickel ferrite (NiFe₂O₄) magnetic nanoparticles were synthesised by a simple method and applied as sorbent for magnetic solid-phase extraction of trace amounts of Au(III) from water samples. Detection in this technique was performed by flame atomic absorption spectrometry. The effects of sample pH, amount of sorbent, extraction time, desorption solvent and its volume on the extraction process were optimised. The effects of interfering ions on the recovery of the analyte were also evaluated in model solutions. The best results were obtained at pH 6.5 with 5 mL of eluent solution (0.1 mol L^?1 sodium thiosulphate) and an extraction time of 30 min. Under optimal conditions, the sorption capacity was 34.6 mg g^?1. Also, enhancement factor (for 100 mL of sample solution) was found to be 19.3. The calibration graph was linear in the range of 4.4–800.0 µg L^?1 gold concentration and the limit of detection was 1.32 µg L^?1. The relative standard deviation of the method (for n = 8) was 1.57%. The method was successfully applied to the extraction of Au(III) from water samples.