On a solvable system of p difference equations of higher order

Periodica Mathematica Hungarica - In this paper we present the well-defined solution of the following system of higher-order rational difference equations: $$begin{aligned}...     

Photocatalytic Degradation of Oxytetracycline in Aqueous Solutions with TiO2 in Suspension and Prediction by Artificial Neural Networks

In this study, the photocatalytic degradation of oxytetracycline (OTC) in aqueous solutions has been studied under different conditions such as initial pollutant concentrations, amount of catalyst, and pH of the solution. Experimental results showed that photocatalysis was clearly the predominant process in the pollutant degradation, since OTC adsorption on the catalyst and photolysis are negligible. The optimal TiO₂ concentration for OTC degradation was found to be 1.0 g/L. The apparent rate constant decreased, and the initial degradation rate increased with increasing initial OTC concentration with the other parameters kept unchanged. Subsequently, data obtained from photocatalytic degradation were used for training the artificial neural networks (ANN). The Levenberg–Marquardt algorithm, log sigmoid function in the hidden layer, and the linear activation function in the output layer were used. The optimized ANN structure was four neurons at the input layer, eighteen neurons at the hidden layer, and one neuron at the output layer. The application of 18 hidden neurons allowed to obtain the best values for R² and the mean squared error, 0.99751 and 7.504e–04, respectively, showing the relevance of the training, and hence the network can be used for final prediction of photocatalytic degradation of OTC with suspended TiO₂.     

Electrochemical performance of catalyst couples M/stainless steel 430 (M: Ni,Co, and Cu) for the hydrogen production in KOH electrolyte

Journal of Solid State Electrochemistry - In this work, three catalysts (nickel, cobalt, copper) are electrochemically deposited on stainless steel substrates AISI 430 and their performances as...     

Thin‐layer chromatography‐bioautographic method for the detection of arginase inhibitors

Arginase represents a promising therapeutic target for various pathologies including inflammatory, cardiovascular, and parasitic diseases or cancers. In the current work, we report, for the first time, about the development of a thin‐layer chromatography‐based bioautography which can be used to rapidly detect arginase inhibitors in complex matrices such as plant extracts. The assay is based on the detection of urea produced by arginase using the coloring reagent α‐isonitrosopropiophenone, resulting in the formation of a pink background on thin‐layer chromatography plates. The assay conditions were optimized in order to provide sufficient contrast between the pink colored thin‐layer chromatography plate and the clearer zones generated by the presence of arginase inhibitors. Different parameters were tested, such as incubation time and temperature, atmospheric conditions, as well as substrate and enzyme concentrations. This technique makes it possible to detect 0.1 μg of a known arginase inhibitor, N^ω‐hydroxy‐nor‐Arginine, after it has been spotted, either pure or mixed with a Myrtus communis methanolic fruit extract, and the plate has been developed in an appropriate solvent. The newly developed method was used to reveal the presence of an inhibitor in hempseed cakes (Cannabis sativa L.).     

Potassium Fluoride on Alumina: One-Pot Synthesis of N-Allyl Trichloroacetamides by Cascade Condensation-Sigmatropic Rearrangement

Allyl alcohols adsorbed on Al₂O₃-KF at room temperature reacted with trichloroacetonitrile and gave rearranged trichloroacetamides at room temperature, in one pot reaction.     

EDXRF analysis of suspended particulate matter (SPM) from residential and industrial areas in Cairo,Egypt

Due to the remarkable increasing of the mass concentrations of suspended particulate matter (SPM) as an air pollution indicator in Greater Cairo‐Egypt, regular sampling during autumn 2014 and winter 2014/2015 seasons has been performed from industrial and residential areas. It was found that the average mass concentrations of the SPM collected from residential and industrial areas are equal to 531 ± 198 and 912 ± 230 μg/m³, respectively. These quantities are much higher than the maximum allowance level, especially for the industrial area. By utilizing three secondary targets, energy dispersive x‐ray fluorescence working under vacuum environment was used for elemental analysis of 19 elements namely; Na, Al, Si, S, Cl, K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, Pb, Se, Br, Rb, and Sr. The present optimized selective excitation energy dispersive x‐ray fluorescence analysis has considerably enhanced the analytical range with respect to our previous similar studies, including low Z elements such as Na, Al, S, and Cl and attaining lower detection limits in the range of ng/m³. Remarkable high elemental concentrations were determined for most of the detected elements from the industrial area samples, strongly indicating the influence of the industrial and anthropogenic activities. The average percentages of the mass concentration of the detected inorganic elements account only for 3.2% and 10.5% of the total mass concentration collected from the residential and industrial areas, respectively, thus directly indicating that the content of organic pollutants in SPM is the dominant contribution.     

Lead speciation of PM2.5 collected from Greater Cairo,Egypt and Zarqa,Jordan: An energy dispersive X-ray fluorescence and X-ray absorption near edge structure study

Fine aerosol particles with an aerodynamic diameter equal or less than 2.5 μm (PM_2.5) have been collected from two sites (residential and industrial) in Greater Cairo, Egypt and one site in Zarqa, Jordan. Based on the elemental quantitative analysis of PM_2.5 using energy dispersive X-ray fluorescence with Mo secondary target, Pb concentrations increased remarkably during winter season regardless of the sampling location. Moreover, it reached the maximum concentration at the industrial location of Greater Cairo, Egypt, and it equals 415 ± 485 ng/m³. The remarkable high standard deviation is due to the significant variation of Pb concentration from time to time during that winter season. Depending on the energy dispersive X-ray fluorescence results, specific PM_2.5 samples that have the highest concentration of Pb (two samples/location) have been selected for the X-ray absorption near edge structure measurements to estimate the oxidation state of Pb species. The X-ray absorption near edge structure measurements including 13 Pb references have been carried out at Pb-L₃ absorption edge (13.039 keV) using fluorescence mode. It was shown that PM_2.5 contains divalent and tetravalent lead in both industrial site in Greater Cairo, Egypt and urban site of Zarqa, Jordan although that of a residential area of Greater Cairo-Egypt is almost divalent lead.     

Existence Results on the Second-Order Nonconvex Sweeping Processes with Perturbations

We prove several existence theorems for second-order differential inclusions of the form , when K and F are two convex or nonconvex set-valued mappings taking their values in a Hilbert space.     

Bare Histidine–Serine Models: Implication and Impact of Hydrogen Bonding on Nucleophilicity

A new family of 2‐hydroxyalk(en/yn)ylimidazoles has been evaluated as serine–histidine bare dyad models for the ring‐opening reaction of L ‐lacOCA, a cyclic O‐carboxyanhydride. These models were selected to unravel the implication of intramolecular hydrogen bonding and to substantiate its influence on the nucleophilicity of the alcohol moiety, as it is suspected to occur in enzyme active sites. Although designed to exclusively facilitate the preliminary step of proton transfer during the studied ring‐opening reaction, these minimalistic models depicted a measureable increase in reactivity relative to the isolated fragments. A couple of reliable experimental and theoretical methods have been developed to readily monitor the strength of the intramolecular hydrogen bond in dilute solution. Results show that the folded conformers are the most nucleophilic species because of the intramolecular hydrogen bond.