A generalization of Mizoguchi and Takahashi’s theorem for single-valued mappings in partially ordered metric spaces

We present a generalization of Mizoguchi and Takahashi’s fixed point theorem for single-valued mappings in partially ordered metric spaces. As an application of the main result, we give an existence and uniqueness theorem for the solution of a periodic boundary value problem.     

Stability analysis of electrostatic nanotweezers

In this paper, the pull-in instability of electrostatically actuated nanotweezers considering the dispersion forces is studied using distributed and lumped parameter models. By analogy to nanoswitches, closed-form solutions are obtained for electrostatic nanotweezers. The distributed and lumped parameter modeling of the tweezer result, respectively, in two coupled nonlinear boundary value problems and two coupled nonlinear equations, which are solved numerically in the cases of electrostatic microtweezers, freestanding nanotweezers, and electrostatic nanotweezers. In each case, analytical and numerical solutions are obtained and compared with those of the corresponding switch. In addition, the results of the distributed and lumped parameter models are compared. The detachment length and minimum initial gap of nanotweezers are determined.     

The effect of carrier gas flow on structural and optical properties of TiO2 nanowires

Optical properties and photoluminescence of TiO₂ nanowires, synthesized by two-step thermal evaporation process, under different Ar gas flow as carrier have been studied. The gas flow was varied from 50 to 150 sccm in order to find the optimum gas flow to growth TiO₂ nanowires. As evidenced by X-ray diffraction patterns, our synthesized nanowires, were found to be crystalline rutile TiO₂. Our results indicated a convenient gas flow for controlling diameter size of nanowires was about 100 sccm. In this case, diameters and lengths were, respectively, within the ranges of 40–100 and 400–1800 nm. The experimental data of the reflectance of TiO₂ nanowires have been obtained through using spectrometer of wavelength 250–800 nm that has been indicated reflectance decreasing with increasing the gas flow, due to the scattering from the surface of the nanowires and also an increase in voids’ roughness. Under excitation 370 nm, the TiO₂ nanowires can emit light peaked at 435 nm. It is believed that peak 435 may be due to free excitons emission.     

Expedient synthesis of novel antibacterial hydrazono-4-thiazolidinones under catalysis of a natural-based binary ionic liquid

Molecular Diversity - A library of pyran-2H-one-3-ylmethylidene and chromene-2H-one-3-ylmethylidene derivatives of the titled heterocyclic framework was synthesized from...     

Penicillamine functionalized B12N12 and B12CaN12 nanocages act as potential inhibitors of proinflammatory cytokines: A combined DFT analysis,ADMET and molecular docking study

The adsorption of penicillamine (PCA) on pure B₁₂N₁₂ and B₁₂CaN₁₂ nanocages in aqueous and chloroform solvents has been evaluated using density functional theory (DFT) calculations. The interaction of PCA on B₁₂N₁₂ nanocages is chemisorption through its four nucleophilic sites: amine, carbonyl, hydroxyl and thiol. The most stable adsorption configuration was achieved when zwitterionic PCA adsorbs via its carbonyl group in water with value of ?1.723 eV, in contrast, when neutral PCA adsorbs via its amine group in chloroform with value of ?1.68 eV. Intercalated calcium ion within B₁₂N₁₂ nanocage (B₁₂CaN₁₂) was shown to attract PCA onto nanocage surface, resulting in higher solubility and adsorption energy after their complexation in water and chloroform. The adsorption of multiple PCA molecules from their amine and carbonyl groups on pure and B₁₂CaN₁₂ nanocages were also evaluated where two and three molecules can be chemisorbed on boron atoms of the nanocage surfaces with the adsorption energy per PCA reduces slightly with the increasing the amount of drugs due to the curvature effects. Molecular docking study indicates that PCA from its NH₂ group on B₁₂CaN₁₂ nanocage has the best binding affinity and inhibition potential of tumor necrosis factor-alpha (TNF-α) and Interleukin-1 (IL-1) receptors as compared with the other adsorption systems. Molecular docking and ADMET analysis displayed that the chosen compounds pass Lipinski Rule and have appropriate pharmacokinetic features suitable as models for developing anti-inflammatory agents.     

A Simple Method for Melatonin Determination in the Presence of High Levels of Tryptophan using an Unmodified Carbon Paste Electrode and Square Wave Anodic Stripping Voltammetry

Electrochemical determination of melatonin in the presence of tryptophan is a challenge because of the coincidence of voltammetric signals of these compounds when executing a voltammetric technique. The new method for selective determination of melatonin based on the square wave anodic stripping voltammetry determination of an electroactive product of melatonin was suggested here. This product is produced by previously applied positive pre-potential to a carbon paste electrode, immersed in the test solution. By this means, the electrochemical signal of melatonin was separated effectively from that of tryptophan, making it possible to determine melatonin in the presence of a high concentration of tryptophan. The effect of important parameters on electrode performance was studied and optimized. The optimum response was obtained at pH=2 and utilizing the pre-potential magnitude of +0.8 V, applied for 10 s. A linear relationship was found between peak current intensity and melatonin concentrations over the range of 5.00×10⁻⁷ to 8.00×10⁻⁵ mol L⁻¹. A detection limit of 8.30×10⁻⁸ mol L⁻¹ was calculated for the method (S/N=3). The selectivity of the method was considerably high, because of the independence of melatonin signal to the presence of higher amounts of some potentially interfering agents such as ascorbic acid, tryptophane glucose, etc. As an analytical application, the proposed sensor was used for the determination of melatonin in pharmaceutical and food samples.