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

A series of new organosilicon(IV) complexes have general formulae R₃SiL and RSiLOEt with Schiff bases (R = Me and Ph). The Schiff bases (LH) have been derived from the condensation of (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone with semicarbazide, thiosemicarbazide, and phenylthiosemicarbazide, respectively. The compounds have been characterized by the elemental analysis, molar conductance, and spectral (UV, IR, ¹H, ¹³C, and ²⁹Si NMR) studies. These studies showed that the ligands coordinate with the silicon atom in a tridentate manner through phenolic oxygen, azomethine nitrogen and thiolic sulfur. Further applying experimental spectroscopic techniques, theoretical data calculated using density functional theory by B3LYP/6.31+g(d,p) has also been used for structural determination. The resulting complexes have been proposed to have trigonal bipyramidal and distorted octahedral geometries. Few representative Schiff base and their silicon complexes have been screened for their in vitro antibacterial activity against Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration (MIC) of selected compounds was determined. The screening results show that organosilicon(IV) complexes have better antibacterial activity than the free ligands.

The spline collocation method is a competent and highly effective mathematical tool for constructing the approximate solutions of boundary value problems arising in science, engineering and mathematical physics. In this paper, a quintic polynomial spline collocation method is employed for a class of fractional boundary value problems (FBVPs). The FBVPs are expressed in terms of Caputo’s fractional derivative in this approach. The consistency relations are derived in order to compute the approximate solutions of FBVPs. Finally, numerical results are given, which demonstrate the effectiveness of the numerical scheme.

The nonlocal symmetries for the special $K\left(m\text{,}n\right)$ equation, which is called KdV-type $K\left(3\text{,}2\right)$ equation, are obtained by means of the truncated Painlevé method. The nonlocal symmetries can be localized to the Lie point symmetries by introducing auxiliary dependent variables and the corresponding finite symmetry transformations are computed directly. The KdV-type $K\left(3\text{,}2\right)$ equation is also proved to be consistent tanh expansion solvable. New exact interaction excitations such as soliton–cnoidal wave solutions are given out analytically and graphically.

In this article, the existence of a unique solution of Fredholm–Volterra integral equation of the second kind is guaranteed. The Fredholm integral term is assumed in position with bad kernel, while the Volterra integral term is considered in time with continuous kernel. Under certain conditions and new discussions, the bad kernel will tend to a logarithmic kernel. Then, using Chebyshev polynomial, a main theorem of spectral relationships of Fredholm integral equation of the first kind with logarithmic kernel multiplying by a smooth kernel is stated and used to obtain numerically the Fredholm–Volterra integral equation of the second kind. Finally, numerical results are obtained and the error, in each case, is computed.

The corrosion inhibition efficiency of 2-amino-4-(2,4-dihydroxyphenyl) quinoline-3-carbonitrile (ADQC) on SAE 1006 steel has been investigated using electrochemical (EIS and Polarization), surface (SEM, EDX and AFM) and quantum chemical calculation methods. Results showed that inhibition efficiency increases with increasing ADQC concentration and maximum value of 96.12% was obtained at 25 mg/L concentration. EIS results showed the ADQC inhibits SAE 1006 steel corrosion becoming the adsorbate at metal/electrolyte interfaces. Polarization study showed that ADQC acts as cathodic type inhibitor. SEM, EDX and AFM finding supported the adsorption of ADQC on the mild steel surface. The quantum chemical calculations provide good insight about the adsorption and inhibition mechanism of ADQC. The experimental and quantum chemical calculation results were in good agreement.

In this paper, we practiced relatively new, analytical method known as the variational homotopy perturbation method for solving Klein–Gordon and sine-Gordon equations. To present the present method’s effectiveness many examples are given. In this study, we compare numerical results with the exact solutions, the Adomian decomposition method (ADM), the variational iteration method (VIM), homotopy perturbation method (HPM), modified Adomian decomposition method (MADM), and differential transform method (DTM). The results reveal that the VHPM is very effective.

This study presents the development of a novel maximum-power point-tracking (MPPT) method based on an input shaping scheme controller. The proposed method that changes the initial input response into a shapeable MPPT algorithm is designed based on an exponential input function. This type of input function is selected because of its capability to stabilize the system at the end of the simulation time and remain at the same condition at the final response time. A comparison of the system with the proposed method and the system with traditional perturb and observe (PnO) method is also provided. Results show that the system with the proposed method produces higher output power than the system with PnO method; the difference is approximately 15.45%. Results reveal that the exponential function input shaper allows the overall output system to exhibit satisfactory behavior and can efficiently track the maximum output power.

In this paper, a class of non-linear vector differential equations of third order with delay is considered. The stability, boundedness and ultimately boundedness of solutions are studied. The technique of proofs involves defining an appropriate Lyapunov functional. The obtained results include and improve the results in the literature.

This study was designed to investigate the awareness regarding global warming among the College of Science students at University of Bahrain. A total of 143 science students were examined using a questionnaire that covered three aspects of global warming including causes, impacts, and solutions. The study included 51, 28, 40 and 24 students from the departments of biology, chemistry, mathematics, and physics respectively. The results have shown that 55 ± 10.18% of all students examined answered the questions correctly of which 51 ± 10.28% were in the first year, while 60 ± 7.4% were in their fourth year indicating a direct positive impact of university education. A significant dependence (p ⩽ 0.05) was recorded between first and fourth year students’ answers. The results have shown that fourth year biology students were the most knowledgeable, a fact that can be attributed to their academic curriculum. Therefore, the study has recommended integrating environmental concepts into the university curriculum for all students irrespective of their academic specialization in order to increase the environmental awareness.

The study investigated adsorption, leaching potential, and phytotoxicity of alachlor, bromacil, and diuron on melon, Molokhia, and wheat in Gaza strip. Plant height was used to estimate growth inhibition (phytotoxicity). Growth inhibition data were regressed versus concentrations of corresponding herbicide to estimate EC₅₀ value. The lowest EC₅₀ value indicates the highest phytotoxicity. Adsorption results indicated that alachlor, bromacil and diuron have different shapes. Leaching potentials indicated that alachlor totally disappeared from the top 5 cm and accumulated at a deeper depth whereas bromacil and diuron accumulated in the top 8 cm of soil layer with a decreasing intensity at deeper depth. Phytotoxicity tests showed that diuron has the lowest EC₅₀ values on melon (1.64) and Molokhia (0.15) whereas bromacil has the lowest one on wheat (0.08), values are in (mg/kg soil). Results of binary mixtures showed that the mixture contained alachlor and diuron was the most toxic to melon, whereas mixture contained alachlor and bromacil was the most toxic to Molokhia and wheat. Tertiary mixture (alachlor + bromacil + diuron) was more toxic on Molokhia than melon and wheat, EC₅₀ values were 3.02, 32.174, and 633.9 TU/kg soil on Molokhia, melon, and wheat respectively. An interesting outcome of the study is that Molokhia was the most sensitive plant and binary mixtures showed synergistic phytotoxicity.