Journal of the Association of Arab Universities for Basic and Applied Sciences最新文献

Tafel extrapolation method has been employed to determine the corrosion resistance of super austenitic stainless steel (UNS S31254) in a CO₂-saturated acidizing oilfield environment. Green inhibitors (Tridax procumbens and Chromolaena odorata extracts) were employed for protection of the alloy in the environment. Over 90% inhibition efficiency was achieved at inhibition dosage of 100 ppm for one of the inhibitors. Results showed that both inhibitors are effective for protecting the alloy in the acidizing environment. The result of the adsorption isotherm showed that the adsorption of the extracts on the surface of UNS S31254 is a monolayer and consistent with the Langmuir isotherm.

A dense and mesoporous ceramic from locally sourced Nigerian clay under fracture-strength test were produced and the reliability analysis of the fractured strength was conducted using a three-parameter Weibull probability distribution. The samples were prepared by addition of starch (0–20wt%), pressed at 60 MPa and fired at 1300 °C. The as-received Nigerian clay, dense and porous ceramic were characterized using XRD, XRF, TGA/DTA, PSD, multi-point BET and FESEM. The fracture strength of the samples (33 each) was determined using a three-point bending test. The fracture strength data were analyzed using three-parameter Weibull probability distribution. From the characterization results, a mullite ceramic formed at a sintering temperature of 1300 °C. The threshold strength for the three-parameter Weibull provides the strength below which the dense and the porous ceramic will not fail. The Weibull moduli of the ceramics at different starch compositions show that failure modes in these materials are not identical. The Weibull modulus increases with increase in percentage starch from 0% to 15%. However, the value decreases with 20% starch addition. Reliability analysis provides a detailed interpretation and assessment of the fracture strength of the porous ceramics.

In this paper, we have studied the flow of incompressible fluids in a straight square duct through the porous medium. The couple stress fluid model and Jeffrey fluid model are considered separately to study the flow properties. The governing partial differential equations have been solved numerically using finite difference method in each case. In both the cases, the variation of different flow parameters on the fluid velocity is illustrated graphically and the numerical results for the volume flow rate have been presented through tables. It is observed that, the velocity and volume flow rate decrease with an increase in couple stress parameter and porosity parameter, while the velocity and volume flow rate increase with an increase in Jeffrey parameter and pressure gradient.

A convenient, one-pot, multi-component protocol for the preparation of 2-(1-(2-oxo-2H-chromen-3-yl)ethylidene)hydrazinecarbothioamide derivatives has been achieved. Here, firstly we have reported the synthesis of 3-acetyl-2H-chromen-2-one using starch sulfuric acid and cellulose sulfuric acid as biodegradable catalysts. Subsequently, we also carried out the reaction of isothiocynates, hydrazine hydrate and 3-acetyl-2H-chromen-2-one in the presence of catalytic amount of glacial acetic acid in refluxing ethanol to afford corresponding 2-(1-(2-oxo-2H-chromen-3-yl)ethylidene)hydrazinecarbothioamide derivatives in high to excellent yields. All synthesized compounds were screened for antimicrobial activity. All compounds were found to show good to excellent activity against Escherichia coli MTCC 443.

This study involves the adsorption of Crystal Violet (CV) dye adsorbed from solution on the pyrophyllite’s surface. The batch technique was used under a variety of conditions to produce quantitative adsorption, namely amount of adsorbent, dye concentration, contact time, pH solution and temperature. The maximum adsorption capacity of Crystal Violet on pyrophyllite was 9.58 mg/g for 10 mg/L of CV concentration, pH = 6.8 at a temperature 20 °C and 1 g/L of adsorbent. This study of adsorption kinetics was carried out within framework of three models: intraparticle diffusion, pseudo-first order and pseudo-second order. The experimental isotherm data were analyzed using Langmuir and Freundlich models. Different thermodynamic parameters have shown spontaneous reaction with endothermic nature (The estimated value for ΔG was −7.64 kJ/mol at 293 K). Various techniques for characterizing the adsorbent were applied including X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled by energy dispersive X-ray spectroscopy (EDX). In addition, the regenerated adsorbents technique was reused several times; this demonstrated an economical aspect of using pyrophyllite which underlines the re-use importance considering the material capacity to regenerate.

This paper proposes to evaluate the adaptability risk in money laundering using Bitmap Index-based Decision Tree (BIDT) technique. Initially, the Bitmap Index-based Decision Tree learning is used to induce the knowledge tree which helps to determine a company’s money laundering risk and improve scalability. A bitmap index in BIDT is used to effectively access large banking databases. In a BIDT bitmap index, account in a table is numbered in sequence with each key value, account number and a bitmap (array of bytes) used instead of a list of row ids. Subsequently, BIDT algorithm uses the “select” query performance to apply count and bit-wise logical operations on AND. Query result coincides exactly to build a decision tree and more precisely to evaluate the adaptability risk in the money laundering operation. For the root node, the main account of the decision tree, the population frequencies are obtained by simply counting the total number of “1” in the bitmaps constructed on the attribute to predict money laundering and evaluate the risk factor rate. The experiment is conducted on factors such as regulatory risk rate, false positive rate, and risk identification time.

This paper describes a simple, rapid, inexpensive method for the preparation of a new biosorbent based on the modification of miswak fibers by NaOH (AT-Miswak-F). The synthesized AT-Miswak-F sorbent was utilized as an efficient sorbent for the extraction and preconcentration of iron group metal ions from various water samples. In this study, it was found that Fe(III), Co(II) and Ni(II) ions were completely extracted (100%) at pH range of 3–7 and flow rate of 0.3–2.0 mL min⁻¹. Also, the sorption capacity of AT-Miswak-F for Fe(III), Co(II) and Ni(II) are 0.54, 0.24 and 0.15 mmol g⁻¹, respectively. Equilibrium was best described by Freundlich isotherm model (R² = 0.793) and the initial rate constants were 0.077, 0.054 and 0.035 mmol g⁻¹ min⁻¹, respectively. Under the optimized conditions, the method exhibited a detection limit of 1.4, 2.8 and 2.1 ng mL⁻¹ for Fe(III), Co(II) and Ni(II) ions in water samples with relative standard deviations of 2.6% (n = 4). The method was successfully applied for the determination of Fe(III), Co(II) and Ni(II) ions in sea, ground and contaminated water samples.

Systematic Evolution of Ligands by EXponential enrichment (SELEX) is the method to select the specific aptamer against a wide range of targets. For this process, the initial library usually has a length of random sequences from ∼25 and it reaches over 100 bases. The lengthy sequences have disadvantages such as difficult to prepare, less stable and expensive. It is wise to prefer shorter version of aptamer for a wide range of applications including drug delivery process. It is a common practice to shorten the full-length aptamer by mapping analyses and it is tedious. Here, we used a crawling method to shorten the aptamer by different sequential deletion of bases from both 5′ and 3′ ends, assisted by Mfold web server application. Two different kinds of aptamer with varied lengths (randomized region of 30 and 74 bases) were desired for this study, generated against Influenza A/Panama/2007/1999 (H3N2) and gD protein of Herpes Simplex Virus-1. It was found that shortening the aptamer length by crawling pattern is possible with the assistance of Mfold web server application. The obtained results resemble the shortened aptamer derived by mapping analyses. The proposed strategy is recommended to predict the shorter aptamer without involving any wet experimental section.

The purpose of this study is to investigate the unsteady magnetohydrodynamic three-dimensional flow induced by a stretching surface. An incompressible electrically conducting Eyring-Powell fluid fills the convectively heated stretching surface in the presence of nanoparticles. The effects of thermal radiation, viscous dissipation and Joule heating are accounted in heat transfer equation. The model used for the nanofluid includes the effects of Brownian motion and thermophoresis. The highly nonlinear partial differential equations are reduced to ordinary differential equations with the help of similarity method. The reduced complicated two-point boundary value problem is treated numerically using Runge–Kutta–Fehlberg 45 method with shooting technique. A comparison of the obtained numerical results with existing results in a limiting sense is also presented. At the end, the effects of influential parameters on velocity, temperature and nanoparticles concentration fields are also discussed comprehensively. Further, the physical quantities of engineering interest such as the Nusselt number and Sherwood number are also calculated.

This paper is devoted to study the boundedness, ultimate boundedness, and the asymptotic stability of solutions for a certain class of third-order nonlinear differential equations using Lyapunov’s second method. Our results improve and form a complement to some earlier results in the literature.