Synthesis of pyrido[3′,2′:4,5]thieno[2,3-e][1,2,4]triazolo[4,3-a]pyrimidin-5(4H)-one derivatives

Some new pyrido[3′,2′:4,5]thieno[2,3-e]-[1,2,4]triazolo[4,3-a] pyrimidin-5(4H)-ones were prepared through heterocyclization of ethyl 3-aminothieno[2,3-b]pyridine-2-carboxylate with phenyl or ethyl isothiocyanate followed by nucleophilic displacement with hydrazine, and finally cyclocondensation with orthoesters. Correspondence: Abolghasem Davoodnia, Department of Chemistry, School of Sciences, Islamic Azad University, Mashhad Branch, Mashhad 91735-413, Iran.     

Synthesis of pyrazolo[4,3-<Emphasis Type="Italic">e</Emphasis>][1,2,4]triazolo[4,3-<Emphasis Type="Italic">c</Emphasis>]pyrimidines

Starting from 1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-ones, a synthesis pathway to the tricyclic pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines is described. Reaction of 1,5-dihydro-4H-pyrazolo[3,4-d] pyrimidin-4-ones with phosphoryl chloride afforded the corresponding 4-chloro-1H-pyrazolo[3,4-d]pyrimidines. Treatment of these compounds with hydrazine hydrate at reflux temperature gave the hydrazino derivatives, which were subsequently cyclized to the titled compounds on heating with orthoesters in ethanol. Correspondence: Abolghasem Davoodnia, Department of Chemistry, School of Sciences, Islamic Azad University, Mashhad Branch, Mashhad 91735-413, Iran.     

The effects of freestream turbulence on the drag coefficient of a sphere

The effects of freestream turbulence intensity and integral length scale as freestream turbulent parameters on the drag coefficient of a sphere were experimentally investigated in a closed circuit wind tunnel. The Reynolds number, Re = Ud/ν, was varied from 2.2 × 10⁴ to 8 × 10⁴ by using spheres with diameter d of 20, 51 and 102 mm in addition to altering the freestream velocity, U. The freestream turbulence intensity Tu and flow integral length scale Λ were manipulated by the utilization of orifice perforated plates. The proper combination of orifice perforated plate hole diameter, sphere size, and sphere location along the center line of the wind tunnel enabled the independent alterations of turbulence intensity and relative integral length scale (Λ/d) from 1.8% to 10.7% and from 0.1 to 2.6, respectively, at each studied Reynolds number. Results show that over the range of conditions studied, the drag always decreases with increasing Tu and, the critical Reynolds number at which the drag coefficient is dramatically reduced is decreased by increasing Tu. Most interestingly, the drag at any particular Re and Tu may be significantly lowered by reducing Λ/d; this is particularly the case at high Re and Tu.     

Direct Electrochemistry and Electrocatalytic Properties of Hemoglobin Immobilized on Carbon Nanotubes Ionic Liquid Electrode

Hemoglobin (Hb) was directly immobilized on a multiwalled carbon nanotubes ionic liquid electrode by immersing this electrode in a solution consisting of Hb and 1‐octyl‐pyridinium chloride as an ionic liquid. The immobilized Hb displayed a pair of well‐defined cyclic voltammetric peaks with a formal potential of ?0.187 V in acetate buffer solution, pH 5.0. This modified electrode exhibits fast response, a long linearity range, a low detection limit, high stability and excellent sensitivity through hydrogen peroxide detection with a detection limit (3σ) of 3.18 µM. The electrode was also used for electrocatalysis and voltammetric determination of oxygen and trichloroacetic acid.     

In vitro and in vivo evaluation of cytotoxicity,antioxidant, antibacterial,antifungal, and cutaneous wound healing properties of gold nanoparticles produced via a green chemistry synthesis using Gundelia tournefortii L. as a capping and reducing agent

The exploitation of various plant materials for the biosynthesis of nanoparticles is considered a green technology because it does not involve any harmful chemicals. The aim of the experiment was chemical characterization and evaluation of cytotoxicity, antioxidant, antibacterial, antifungal, and cutaneous wound healing activities of gold nanoparticles using aqueous extract of Gundelia tournefortii L. leaves (AuNPs@GT). These nanoparticles were characterized by fourier transformed infrared spectroscopy (FT‐IR), field emission scanning electron microscopy (FE‐SEM), energy dispersive X‐ray spectroscopy (EDS), and UV–visible spectroscopy. DPPH free radical scavenging test was done to assess the antioxidant properties, which indicated similar antioxidant potentials for AuNPs@GT and butylated hydroxytoluene. Agar diffusion tests were applied to determine the antibacterial and antifungal characteristics. Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), and Minimum Fungicidal Concentration (MFC) were specified by macro‐broth dilution assay. AuNPs@GT indicated higher antibacterial and antifungal effects than all standard antibiotics (p ≤ 0.01). Also, AuNPs@GT inhibited the growth of all bacteria and fungi and removed them at 2‐4 mg/mL concentrations (p ≤ 0.01). In vivo experiment, after creating the cutaneous wound, the rats were randomly divided into six groups: untreated control, treatment with Eucerin basal ointment, treatment with 3% tetracycline ointment, treatment with 0.2% HAuCl₄ ointment, treatment with 0.2% G. tournefortii ointment, and treatment with 0.2% AuNPs@GT ointment. These groups were treated for 10 days. For histopathological and biochemical analysis of the healing trend, a 3 × 3 cm section was prepared from all dermal thicknesses at day 10. Use of AuNPs@GT ointment in the treatment groups substantially reduced (p ≤ 0.01) the wound area, total cells, neutrophil, and lymphocyte and remarkably raised (p ≤ 0.01) the wound contracture, hydroxyl proline, hexosamine, hexuronic acid, fibrocyte, fibroblast, and fibrocytes/fibroblast rate compared to other groups. The synthesized AuNPs@GT had great cell viability dose‐dependently (Investigating the effect of the plant on HUVEC cell line) and revealed this method was nontoxic. The results showed that the leave aqueous extract of G. tournefortii is very good bioreductant in the synthesis of gold nanoparticles for treatment of bacterial, fungal, and skin diseases.     

One-pot synthesis of 2-amino-3-cyano-4-arylsubstituted tetrahydrobenzo[<Emphasis Type="Italic">b</Emphasis>]pyrans catalysed by silica gel-supported polyphosphoric acid (PPA-SiO<Subscript>2</Subscript>) as an efficient and reusable catalyst

A convenient method for the synthesis of tetrahydrobenzo[b]pyrans by a one-pot three-component cyclocondensation of dimedone, aryl aldehydes, and malononitrile in water using silica gel-supported polyphosphoric acid (PPA-SiO₂) as an efficient and reusable catalyst is described. The present methodology offers several advantages, such as a simple procedure with ease of handling, short reaction time, high yields, and the absence of any volatile and hazardous organic solvents.     

A Modified and Green Procedure for the Synthesis of β-Amido Ketones Using a BrΦnsted-Acidic Ionic Liquid as Novel and Reusable Catalyst

A green and improved method for the synthesis of β‐amido ketones through one‐pot multi‐component reaction of an enolizable ketone, aryl aldehyde, acetonitrile or benzonitrile in the presence of trimethylsilyl chloride using 3‐methyl‐1‐(4‐sulfonic acid)butylimidazolium hydrogen sulfate [(CH₂)₄SO₃HMIM][HSO₄], a Br?nsted‐acidic ionic liquid, as an effective and recyclable catalyst is described. The present methodology offers several advantages such as simple procedure with an easy work‐up, relatively short reaction time, and good to excellent yields.     

Synthesis and Performance of High Efficiency Cosurfactants: 2. Commercial Variants

Commercially viable cosurfactant species of enhanced surface activity were used to formulate middle phase microemulsions. These cosurfactants were made from butanol, with randomly added equal weights of ethoxylate (EO) and propoxylate (PO) groups, to give a wide variation in molecular weight. It was found that cosurfactant requirements for microemulsion formation with the highest molecular weight compound studied was reduced more than an order of magnitude when compared to 2-butanol.     

New thermally stable condensation polymers containing central ketal moieties derived from malonaldehydetetramethyl acetal and dihydroxyaromatic compounds

Abstract

A number of new condensation polymers with acetal units in the main chain and having linear and ladder-form structure and high thermal stability were synthesized by solution polycondensation of dihydroxyaromatic compounds with malonaldehydetetramethyl acetal as a reactive protected 1,3-dicarbonyl compound. Optimal conditions for polycondensation were obtained via study of the model compounds. In order to obtain high molecular weight polymers, general investigations on the influence of reaction conditions, such as monomer concentration and reaction temperature were carried out. All polymers were obtained in high yields and moderate inherent viscosity ranging from 0.25 to 0.41?dL/g. The proposed chemical structures of condensation polymers were confirmed by ¹H-NMR, ¹³C-NMR, FTIR spectroscopies, TGA, and DSC. Thermal analysis indicated that these polymers are stable up to 360?°C, and a 10% weight loss (T₁₀) were recorded on the TG curves in the temperature range of 381–411?°C in nitrogen atmosphere, indicating their good thermal stability.     

Nonlinear dynamic response of axially moving,stretched viscoelastic strings

The dynamical response of axially moving, partially supported, stretched viscoelastic belts is investigated analytically in this paper. The Kelvin–Voigt viscoelastic material model is considered and material, not partial, time derivative is employed in the viscoelastic constitutive relation. The string is considered as a three part system: one part resting on a nonlinear foundation and two that are free to vibrate. The tension in the belt span is assumed to vary periodically over a mean value (as it occurs in real mechanisms), and the corresponding equation of motion is derived by applying Newton’s second law of motion for an infinitesimal element of the string. The method of multiple scales is applied to the governing equation of motion, and nonlinear natural frequencies and complex eigenfunctions of the system are obtained analytically. Regarding the resonance case, the limit-cycle of response is formulated analytically. Finally, the effects of system parameters such as axial speed, excitation characteristics, viscousity and foundation modulus on the dynamical response, natural frequencies and bifurcation points of system are presented.