The analysis of the charge on a cylindrical dielectric particle in unipolar corona field

In this study, a nonlinear integro-differential equation is derived to express the charging kinetics of stationary and rotational cylindrical dielectric particle in unipolar corona field. An algorithm is developed to solve the derived equation numerically by using Euler method. The variation of charge on the dielectric cylindrical particle is presented and evaluated by considering the variable parameters of the particle, medium and field. Assessments of the numerical results demonstrate that the limit charge value on stationary cylindrical dielectric particle during the charging process in unipolar corona field is less in comparison with the rotational cylindrical particle in identical conditions. Also this is an important factor for electron–ion technology in the aspect of charging kinetic problems.     

Cholesterol effects on vesicle pools in chromaffin cells revealed by carbon-fiber microelectrode amperometry

Cell–cell communication is often achieved via granular exocytosis, as in neurons during synaptic transmission or neuroendocrine cells during blood hormone control. Owing to its critical role in membrane properties and SNARE function, cholesterol is expected to play an important role in the highly conserved process of exocytosis. In this work, membrane cholesterol concentration is systematically varied in primary culture mouse chromaffin cells, and the change in secretion behavior of distinct vesicle pools as well as pool recovery following stimulation is measured using carbon-fiber microelectrode amperometry. Amperometric traces obtained from activation of the younger readily releasable and slowly releasable pool (RRP/SRP) vesicles at depleted cholesterol levels showed fewer sustained fusion pore features (6.1 ± 1.1% of spikes compared with 11.2 ± 1.0% for control), revealing that cholesterol content influences fusion pore formation and stability during exocytosis. Moreover, subsequent stimulation of RRP/SRP vesicles showed that cellular cholesterol level influences both the quantal recovery and kinetics of the later release events. Finally, diverging effects of cholesterol on RRP and the older reserve pool vesicle release suggest two different mechanisms for the release of these two vesicular pools.     

Ligand exchange chromatography: a vital dimension for the reliable characterization of heterocycles in crude oils and refined products

In the present study, we established a statistical distribution pattern of indigenous sulfur, nitrogen, and oxygen species in Arabian Heavy crude oil and its distilled fractions: naphtha, gas oil, and vacuum gas oil (VGO) using chemical derivatization with methyl iodide and subsequent characterization by positive electrospray Fourier transform mass spectrometry. It was observed that sulfur species for naphtha and gas oil were accumulated at lower double bond equivalent values and at lower carbon numbers compared to VGO, whereas crude oil encompassed a complete range of the sulfur species detected in all distilled fractions. Moreover, the use of alumina column chromatography and ligand exchange chromatography (LEC) on a palladium-bonded silica stationary phase revealed additional structural features of sulfur heterocycles in terms of condensed and non-condensed thiophenes. During LEC separation, in addition to sulfur heterocycles, interesting results were obtained for oxygen-containing compounds. Ortho-substituted alkyl phenols were separated from meta- and para-substituted alkyl phenols on a palladium-bonded silica stationary phase.     

Effects of several different flux enhancing chemicals on filterability and fouling reduction of membrane bioreactor (MBR) mixed liquors

The main objective of this work was to determine the effectiveness of various chemicals on filterability and fouling reduction in MBR mixed liquors. Different lab-scale experiments were conducted with a total of 7 different additives (3 cationic polymers (MPL30, MPE50, KD452), a biopolymer (Chit), a starch (Sta), and 2 metal salts (FeCl₃, PACl)). Initially, batch shaker tests were performed for each additive to determine the optimum dosages in terms of soluble microbial products (SMP) removal. Then, short-term filtration trials and critical flux tests were performed. All tested additives were able to remove SMP, but at different extent; 33, 45, 51, 36, 38, 54, and 56% for MPL30, MPE50, KD452, FeCl₃, PACl, Chit, and Sta, respectively. The cationic polymer KD452 exhibited the best performance in terms of the extent of SMP removal and the required dosage. All tested cationic polymers, starch and chitosan significantly reduced fouling rates and increased permeability values. At their optimum dosages, the cationic polymers MPE50, MPL30 and KD452 provided 96, 80 and 74% reductions in fouling rates, respectively. The enhancements in critical flux achieved by MPL30, MPE50, KD452, FeCl₃, PACl, Chit, and Sta were 38, 46, 38, 14, 14, 0, and 22% in comparison with raw mixed liquor. Cationic polymers increased critical flux values to levels above 50 L m⁻² h⁻¹. SMP removal from MBR mixed liquors and further improvement in filtration performance and fouling control did not always correlate. Overall, based on the lab-scale tests conducted, cationic polymeric additives were found to be favorable over the other additives due to their steady and successful performance in fouling control. The performance of cationic polymers was independent of small variations in dosing, while for other additives over- or under-dosing showed detrimental effects on filterability.     

Performance evaluation of IDW,Kriging and multiquadric interpolation methods in producing noise mapping: A case study at the city of Isparta,Turkey

In order to produce an accurate noise map of a city or a region, it is necessary to make noise measurements at certain locations and these measurements must be modeled with the most suitable mathematical algorithm. A homogeneous and representative distribution of the noise measurement points is the first key factor in the production of sound noise maps. The second key element is the calculation of the noise values of gridding points based on noise measurement points according to the selected mathematical calculation method and the generation of maps according to these gridding points. In this study, a noise map of the Isparta city center and its periphery was produced using inverse distance weighted (IDW), Kriging and multiquadric interpolation methods with different parameters and four grid resolution. Then, the influence of parameter selection for each method was investigated in themself by taking into account grid resolution, namely 10 ∗ 10 m, 50 ∗ 50 m, 100 ∗ 100 m and 200 ∗ 200 m, and the performance of three method with 50 ∗ 50 m grid resolution were compared with each other. In addition, the noise mapping of the city of Isparta were produced by Kriging method with respect to maximum, average and minimum noise data and they were evaluated by considering the national environmental noise thresholds.     

Bioanalytical tools for single-cell study of exocytosis

Regulated exocytosis is a fundamental biological process used to deliver chemical messengers for cell-cell communication via membrane fusion and content secretion. A plethora of cell types employ this chemical-based communication to achieve crucial functions in many biological systems. Neurons in the brain and platelets in the circulatory system are representative examples utilizing exocytosis for neurotransmission and blood clotting. Single-cell studies of regulated exocytosis in the past several decades have greatly expanded our knowledge of this critical process, from vesicle/granule transport and docking at the early stages of exocytosis to membrane fusion and to eventual chemical messenger secretion. Herein, four main approaches that have been widely used to study single-cell exocytosis will be highlighted, including total internal reflection fluorescence microscopy, capillary electrophoresis, single-cell mass spectrometry, and microelectrochemistry. These techniques are arranged in the order following the route of a vesicle/granule destined for secretion. Within each section, the basic principles and experimental strategies are reviewed and representative examples are given revealing critical spatial, temporal, and chemical information of a secretory vesicle/granule at different stages of its lifetime. Lastly, an analytical chemist’s perspective on potential future developments in this exciting field is discussed.     

Development of a Novel Molecularly Imprinted Overoxidized Polypyrrole Electrode for the Determination of Sulfasalazine

A novel molecularly imprinted overoxidized polypyrrole electrode was produced for the determination of sulfasalazine (SSZ). The electrode was attained by electropolymerization of pyrrole onto a pencil graphite electrode by cyclic voltammetry. The SSZ was penetrated into the structure during the process. Differential pulse voltammetry was used to determine performance of imprinted (MIP) and non‐imprinted (NIP) electrodes. The linear range was attained in the range between 1.0 to 10.0 ppm of SSZ (R²=0.9993) with a detection limit of 0.265 ppm. The developed MIP electrode and analysis method are suitable for analysis of SSZ with reproducible response and precision in real samples.     

Effect of the nature of sulfur compounds on their reactivity in the oxidative desulfurization of hydrocarbon fuels with oxygen over a modified CuZnAlO catalyst

The reactivity of thiophene, dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT), which are the representatives of the main classes of sulfur compounds that are the constituents of diesel fractions, was studied in the course of their oxidative desulfurization with oxygen on a CuO/ZnO/Al₂O₃ catalyst modified with boron and molybdenum additives. At T ≥ 375°C, the reactivity increased in the order thiophene < DBT < 4,6-DMDBT. The degree of sulfur removal in the form of SO₂ from hydrocarbon fuel, which was simulated by a solution of 4,6-DMDBT in toluene, was 80%. Under the assumption of a first order reaction with respect to sulfur compound and oxygen, the apparent activation energies of the test processes were calculated. An attempt was made to reveal the role of the adsorption of sulfur compounds in the overall process of oxidative desulfurization with the use of X-ray diffraction analysis, X-ray photoelectron spectroscopy, and differential thermal and thermogravimetric analysis with the massspectrometric monitoring of gas phase composition.     

Influence of Solute–Solvent Interaction on Acid Strength of Some Substituted Phenols in Ethanol–Water Media

The solute–solvent interactions of some phenol derivatives were investigated potentiometrically in 0–60 % (v/v) ethanol–water mixtures. The acidity constants values were correlated with either macroscopic parameters such as molar fraction, permittivity and the solvating ability or microscopic parameters, such as the Kamlet–Taft solvatochromic parameters. Moreover, it is demonstrated that the pK _a values in any ethanol–water mixtures are linearly related to the pK _a values of the phenols in pure water. The slope and intercept parameters of the linear correlations are related with the mole fraction of ethanol. These equations permit accurate calculation of the pK _a values of the studied phenols at any ethanol–water composition.