A Membrane Sensor for Selective Determination of Bisacodyl in Tablets

A novel PVC membrane sensor for bisacodyl based on bisacodyl‐phosphotungstate ion pair complex was prepared. The influence of membrane composition (i.e. percent of PVC, plasticizer, and ion‐pair complex), pH of test solution and foreign cations on the electrode performance were investigated. The optimized membrane demonstrates Nernstian response (60.3 ± 2.1 mV per decade) for bisacodyl cations over a wide linear range from 8.0 × 10^?5 to 5.0 × 10^?3 M at 25 °C. The potentiometric response is independent from the pH of the solution in the pH range of 1.5–3.5. The proposed sensor has the advantages of easy preparation, good selectivity, fast response time, and small interferences from hydrogen ions. It was successfully used for determination of bisacodyl in tablets, and the results obtained with the electrode were in good agreement with the official chromatographic method.     

Methane Conversion to Hydrogen and Higher Hydrocarbons by Double Pulsed Glow Discharge

Pulsed atmospheric glow plasma, sustained by corona discharge, was utilized to convert methane. Analysis by gas chromatography showed that hydrogen and C₂-products are the main constituents of outlet mixture while C₂₊-products with small concentrations were also detected. The chemical energy efficiency turned out to be about 9% for the best result obtained by this type of reactor. It has been shown that more improvement of energy efficiency is possible by increasing the pulse repetition rate.     

Facile preparation of peracetates and per-3-bromobenzoates of alpha-mono- and disaccharides

A simple and convenient method for the preparation of fully acetylated and (3- bromo)benzoylated alpha-monosaccharides and disaccharides through vigorous mechanical mixing of solid reactants on a high speed shaker is described. Using this technique a variety of alpha-acylated sugars are prepared, including penta-O-acetyl-alpha-D-galactopyranose, penta-O- acetyl-alpha-D-glucopyranose, penta-O-acetyl-alpha-D-mannopyranose, octa-O-acetyl-alpha-lactose, penta-O-(3-bromo)benzoyl-alpha-D-galactopyranose, penta-O-(3-bromo)benzoyl-alpha-D-gluco- pyranose, penta-O-(3-bromo)benzoyl-alpha-D-mannopyranose, and octa-O-(3-bromo)benzoyl- alpha-lactose.     

Preparation of a novel stir bar coating based on montmorillonite doped polypyrrole/nylon-6 nanocomposite for sorptive extraction of organophosphorous pesticides in aqueous samples

In the present work, a novel nanocomposite (NC) was prepared by reinforcing montmorillonite (MMT) into polypyrrole-nylon-6 (PPy-N6) hybrid through in situ oxidative polymerisation of PPy in the MMT-N6 mixture. The prepared novel NC was deposited as a thin layer coating on the stir bar substrate by solvent exchange method. Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy were applied to characterise the prepared NCs. The prepared stir bar based on MMT/PPy/N6 NC was applied for sorptive extraction of some organophosphorous pesticides (OPPs) in river water samples with detection by gas chromatography-mass spectrometry (GC-MS). The effect of MMT doping level in the NC and also the effect of PPy hybridation with N6 on the coating extraction capability were studied. Central composite design was used to optimise and study the effects of influencing factors on the stir bar sorptive extraction efficiency such as salt content, pH, extraction time, desorption time, desorption solvent and its volume. The method optimisation step was performed using gas chromatography-flame ionisation detector, while the method validation was conducted using GC-MS. Limits of detection of the developed method are in the range of 0.05–0.3 μg L^?1 and the linear dynamic ranges are in the range of 0.3–1000 and 1–1000 μg L^?1, respectively. The intra-day precision (RSD %) of developed method with four replicates varied between 5.4 and 8.2% for distilled water spiked at 100 μg L^?1. The applicability of the developed method was examined by extraction and determination of OPP compounds in river water samples, indicating the relative recoveries in the range of 80.3–95.3%.     

Correlation of CO2 solubility in N-methyldiethanolamine + piperazine aqueous solutions using extended Debye–Hückel model

Solubility data of CO₂ in aqueous N-methyldiethanolamine (MDEA) solutions of concentration (2.52, 3.36, and 4.28) kmol/m³ were obtained at temperatures (313, 323, and 343) K and partial pressures ranging from about (30 to 5000) kPa. A thermodynamic model based on extended Debye–Hückel theory was applied to predict and correlate of CO₂ solubility in various aqueous amine solutions. The effect of piperazine (PZ) concentration on CO₂ loading in MDEA solutions was determined at PZ concentration (0.36, 0.86, and 1.36) kmol/m³. Using experimental data in various temperatures the interaction parameters of activity coefficient model for these systems were determined. The results show the model consistency with experimental and literature data and PZ is beneficial to the CO₂ loading. The comparison of results of this study with previous data work shows the wide range of CO₂ loading considered in this work and the better agreement of model with experimental data. The average absolute relative deviation percent (δ_AAD) for all data points were 8.11%.     

Tractor beam for fully immersed multiple objects: Long distance pulling,trapping, and rotation with a single optical set‐up

In this article, we have theoretically demonstrated the mechanism of an active tractor beam for multiple fully immersed objects with additional abilities to yielding stable long distance levitation, a controlled rotation and a desired 3D trapping. This is demonstrated with a single optical set‐up by using two coaxial, or even non‐coaxial, superimposed higher order monochromatic Bessel beams of reverse helical nature and different frequencies. The superimposed beams can possess periodic intensity variations both along and around the beam‐axis due to a difference in longitudinal wave‐numbers and beam orders, respectively. The difference in frequencies of the two laser beams makes the intensity pattern to move along and around the beam‐axis in a continuous way without manual ramping of phase, which allows for bidirectional movement of completely immersed multiple particles. The condition for increasing or decreasing the dimension of binding regions is also proposed here to manipulate multiple immersed objects of different sizes under dipole approximation.

     

用于甲烷水蒸气重整的镍基催化剂的失活和再生

The deactivation of nickel catalysts used in Arak and Razi petrochemical complexes followed by catalyst regeneration was evalu-ated. The characterization of the different structures was made by powder X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),transmission electron microscopy(TEM),and carbon & sulfur analyzer. The Ni particle size was estimated from XRD patterns and TEM graphs. The agglomeration of nickel particle and the poison by sulfur components were recognized as the main reasons in deactivation of Arak and Razi catalysts,respectively. The activity of the used catalysts before and after regeneration was measured on methane steam reforming at a CH4:H2O ratio of 1:3 at 850 oC. The regeneration processes for Arak and Razi samples were performed with CO2 as an oxidative atmosphere and steam as a regenerating agent,respectively. The results show that,(1) no residual sulfur components were on the regenerated Razi catalyst surface without changing the structure of the catalyst and the regenerated catalyst has gained 80% of its catalytic activity,and that(2) the nickel particle size of regenerated Arak specimen decreased remarkably as measured by Debye-Scherrer equation from XRD patterns. TEM images were in agreement with the XRD results and indicated a decrease in nickel particle size of regenerated catalyst. Additionally,in both regenerated catalysts all the coke on the surface of the support was eliminated after regeneration.     

Computer-Algebra Implementation of the Least-Squares Method on the Nonnegative Orthant

Maple procedures for solving the so-called NNLS (Nonnegative Least Squares) problem are described. The NNLS problem is to minimize