Green synthesis and chemical characterization of silver nanoparticles obtained using Allium saralicum aqueous extract and survey of in vitro antioxidant,cytotoxic, antibacterial and antifungal properties

Allium saralicum R.M. Fritsch has been used in Iranian traditional medicine as a remedial supplement for microbial diseases. This paper reports the green synthesis, chemical characterization and antioxidant, cytotoxic, antibacterial and antifungal properties of silver nanoparticles obtained using aqueous extract of A. saralicum leaves. In this synthesis, no surfactants or stabilizers were used. For characterization, UV–visible spectroscopy, transmission electron microscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy and field emission scanning electron microscopy were used. 2,2‐Diphenyl‐1‐picrylhydrazyl was used in experiments to assess the antioxidant potential of the silver nanoparticles, which revealed an impressive prevention in comparison with butylated hydroxytoluene. The synthesized silver nanoparticles at low doses (1–250 μg dl^?1) did not show marked cytotoxic activity (against cervical cancer cells (Hela), breast cancer cells (MCF‐7) and human embryonic kidney cells (HEK‐293)). Agar diffusion tests were applied to determine the antibacterial and antifungal characteristics. Compared with all standard antimicrobials, the silver nanoparticles showed higher antibacterial and antifungal activities (p ≤ 0.01). Also, the silver nanoparticles inhibited the growth of all bacteria and fungi at concentrations of 31–250 μg ml^?1, and destroyed them at concentrations of 31–500 μg ml^?1 (p ≤ 0.01). Because the silver nanoparticles obtained using aqueous extract of A. saralicum leaves have antioxidant, non‐cytotoxic, antifungal and antibacterial potentials, they can be used as a medical supplement or drug.     

Reaction between alkyl isocyanides and 3-formylchromones in the presence of monocyclic unsaturated acyl compounds: Competition between Friedel-Crafts acylation and Diels-Alder cycloaddition

The highly reactive alkylaminofurochromenone intermediate, produced from the reaction between 3-formylchromones and alkyl isocyanides, was trapped by monocyclic unsaturated acyl compounds such as maleic anhydride or maleimide derivatives to yield new types of organic fluorophores 4-(alkylamino)-1H-furo[3,4-b]xanthene-1,3,10-triones or 4-(alkylamino)chromeno[2,3-f]isoindole-1,3,10(2H)-triones, which exhibited strong sky blue emission in solution. The reaction is very simple from an experimental point-of-view and allows the creation of a fused benzene ring with concomitant formation of three new C–C bonds in a single operation.     

On the Littlewood cyclotomic polynomials

In this article, we study the cyclotomic polynomials of degree N−1 with coefficients restricted to the set {+1,−1}. By a cyclotomic polynomial we mean any monic polynomial with integer coefficients and all roots of modulus 1. By a careful analysis of the effect of Graeffe's root squaring algorithm on cyclotomic polynomials, P. Borwein and K.K. Choi gave a complete characterization of all cyclotomic polynomials with odd coefficients. They also proved that a polynomial p(x) with coefficients ±1 of even degree N−1 is cyclotomic if and only if p(x)=±Φp₁(±x)Φp₂(±xp₁)?Φpr(±xp₁p₂?pr−1), where N=p₁p₂?pr and the pi are primes, not necessarily distinct. Here is the pth cyclotomic polynomial. Based on substantial computation, they also conjectured that this characterization also holds for polynomials of odd degree with ±1 coefficients. We consider the conjecture for odd degree here. Using Ramanujan's sums, we solve the problem for some special cases. We prove that the conjecture is true for polynomials of degree α²pβ−1 with odd prime p or separable polynomials of any odd degree.     

Direct electrical measurement of the conversion of metal acetates to metal sulfides by hydrogen sulfide

Copper acetate and related metal salt films react directly with hydrogen sulfide at room temperature to form metal sulfides, resulting in conductivity changes as large as 108. The observed changes in conductivity are related to the solubility product constant (Ksp) and the difference in conductivity between the metal salt and the resulting metal sulfide. A smaller Ksp indicates a more stable metal sulfide and, therefore, greater metal salt reactivity. Polyaniline nanofiber/metal salt composites were also examined and show metal sulfide conversion with changes in resistance up to 106. The direct electrical measurement of the conversion of metal salt to metal sulfide has the potential to be the basis of a new type of sensitive, thin-film chemical sensor.     

Simple adaptive output-feedback lag-synchronization of multiple time-delayed chaotic systems

In this letter, a simple adaptive output-feedback controller is designed for lag-synchronization of two multiple time-delayed chaotic systems in the presence of uncertainty, external disturbances, and input nonlinearity. Based on Lyapunov stability theorem and adaptive techniques, sufficient conditions for lag-synchronization of these two systems are achieved. To deal with the existence of unknown time-delays in the system dynamics, the novel Lyapunov-Krasovskii functionals are used. Finally, a numerical simulation is presented to show the effectiveness of the proposed chaos lag-synchronization scheme.     

A novel one-pot pseudo-five-component condensation reaction towards bifunctional diazepine-tetrazole containing compounds: synthesis of 1H-tetrazolyl-1H-1,4-diazepine-2,3-dicarbonitriles and 1H-tetrazolyl-benzo[b][1,4]diazepines

A novel and efficient method has been developed for the one-pot synthesis of bifunctional diazepine-tetrazole containing compounds. 1H-Tetrazolyl-1H-1,4-diazepine-2, 3-dicarbonitrile and 1H-tetrazolyl-benzo[b][1,4]diazepine derivatives were synthesized in good yields using 2,3-diaminomaleonitrile or an aromatic diamine, ketones, trimethylsilyl azide, and an isocyanide in the presence of p-toluenesulfonic acid as a catalyst in methanol at room temperature.     

Electrical and optical characteristics of porous silicon impregnated with LaF3 by a novel chemical bath technique

The structural, electrical and optical characteristics of porous silicon (PS) due to the impregnation of LaF₃ into PS by a novel chemical-bath deposition (CBD) technique have been investigated in this article. Without removing the PS from the anodization chamber the impregnation with LaF₃ has been done by reacting LaCl₃ with HF in the same chamber at room temperature. The impregnation of LaF₃ was confirmed by the SEM on the cross-section of the LaF₃/PS/Si system and EDX. The modification of PS surface by LaF₃ had direct influence on the electrical and optical properties of PS. Electrical properties of Ag/LaF₃/PS/p-Si/Ag structures were studied through the current-voltage (I-V) and capacitance-voltage (C-V) characteristics. Formation of metal-insulator-semiconductor (MIS) diode was evident whose forward current increased with annealing. A diode factor of about 2.4 has been obtained for the annealed heterostructure indicating a high density of trap states. The C⁻²-V curves of all samples showed negative flat band voltage of around −2 V confirming a large number of fixed positive charges in the LaF₃. The photoluminescence (PL) intensity of the LaF₃-impregnated PS showed aging for the as-deposited samples, but when annealed PS structure recovered the PL intensity. Experimental results show that the optimized chemical bath passivation process for the LaF₃ on porous silicon could enable the porous silicon to be an important material for photonic application.     

Phase proportioning in CuAlBe shape memory alloys during thermomechanical loadings using electric resistance variation

The microstructure of shape memory alloys changes with the thermomechanical history of the material. During thermomechanical loading, austenite, thermally-induced martensite or stress-induced martensite can be simultaneously present in the material. In applications integrating SMA parts, utilization conditions seriously affect the microstructure and can generate macroscopic strain or stress. Consequently, during thermomechanical loadings, it is important to be able to proportion the different phases and consequently to understand the kinetic transformation. This is very useful in the development of constitutive equations. This study shows, by a series of tests, that the proposed experimental method, based on the measurement of the variation of electric resistance of CuAlBe wires, permits to determine the volume fraction of the different phases present in the material (i.e., austenite, stress-induced martensite and thermally-induced martensite). The proposed method is applied to the most common thermomechanical behavior met in engineering applications of shape memory alloys: pseudoelasticity, pseudoplasticity, recovery-stress and stress-assisted two-way shape memory effect. The proportioning method based on a mixture law integrating the resistivity of pure phases present in the SMA is first performed on different two-phase mixture cases and then applied to a three phase mixture case.     

Nanostructured polyaniline sensors

The conjugated polymer polyaniline is a promising material for sensors, since its conductivity is highly sensitive to chemical vapors. Nanofibers of polyaniline are found to have superior performance relative to conventional materials due to their much greater exposed surface area. A template-free chemical synthesis is described that produces uniform polyaniline nanofibers with diameters below 100 nm. The interfacial polymerization can be readily scaled to make gram quantities. Resistive-type sensors made from undoped or doped polyaniline nanofibers outperform conventional polyaniline on exposure to acid or base vapors, respectively. The nanofibers show essentially no thickness dependence to their sensitivity.