The mononuclear ruthenium(III)-2,3,5,6-tetrakis(2-pyridyl)pyrazine complex [Ru(bpy)(tppz)Cl][PF<Subscript>6</Subscript>]<Subscript>2</Subscript>: synthesis,crystal structure,electrochemical, and spectroelectrochemical studies

The mononuclear Ru(III) complex, [Ru(bpy)(tppz)Cl][PF₆]₂.acetylacetone, where tppz is 2,3,5,6-tetrakis(2-pyridyl)pyrazine and bpy is 2,2′-bipyridine, has been prepared and characterized by physicochemical and spectroscopic methods, cyclic voltammetry, and single crystal X-ray structure analysis. The coordination around the Ru(III) center is distorted octahedral, with bite angles of 80.70–161.83° for the chelating bpy and tppz ligands. The two pyridyl rings of the bpy ligand are nearly coplanar. UV–vis spectroelectrochemical studies of this complex in acetonitrile showed a reversible redox behavior evaluated by the maintenance of isosbestic points in the UV–vis spectrum for both forward reduction and reverse oxidation processes. Magnetic susceptibility data derived from paramagnetic NMR data revealed an effective magnetic moment of 1.79 BM at room temperature.     

Extreme values of elastic strain and energy in sine-Gordon multi-kink collisions

In our recent study the maximal values of kinetic and potential energy densities that can be achieved in the collisions of N slow kinks in the sine-Gordon model were calculated analytically (for N = 1, 2, and 3) and numerically (for 4 ≤ N ≤ 7). However, for many physical applications it is important to know not only the total potential energy density but also its two components (the on-site potential energy density and the elastic strain energy density) as well as the extreme values of the elastic strain, tensile (positive) and compressive (negative). In the present study we give (i) the two components of the potential energy density and (ii) the extreme values of elastic strain. Our results suggest that in multi-soliton collisions the main contribution to the potential energy density comes from the elastic strain, but not from the on-site potential. It is also found that tensile strain is usually larger than compressive strain in the core of multi-soliton collision.     

Scattering of the double sine-Gordon kinks

We study the scattering of kink and antikink of the double sine-Gordon model. There is a critical value of the initial velocity \(v_{{\mathrm {cr}}}\) of the colliding kinks, which separates different regimes of the collision. At \(v_{\mathrm {in}}>v_{\mathrm {cr}}\) we observe kinks reflection, while at \(v_{\mathrm {in}}<v_{\mathrm {cr}}\) their interaction is complicated with capture and escape windows. We obtain the dependence of \(v_{\mathrm {cr}}\) on the parameter of the model. This dependence possesses a series of local maxima, which has not been reported by other authors. At some initial velocities below the critical value we observe a new phenomenon – the escape of two oscillons in the final state. Besides that, at \(v_{\mathrm {in}}<v_{\mathrm {cr}}\) we found the initial kinks’ velocities at which the oscillons do not escape, and the final configuration looks like a bound state of two oscillons.     

Similarity solution of air and nanofluid impingement cooling of a cylindrical porous heat sink

Journal of Thermal Analysis and Calorimetry - In the present paper, a numerical study on flow and heat transfer of air/nanofluid impinging jet flow through a cylindrical porous heat sink has been...     

A poly(4-nitroaniline)/poly(vinyl alcohol) electrospun nanofiber as an efficient nanosorbent for solid phase microextraction of diazinon and chlorpyrifos from water and juice samples

4-Nitroaniline was electropolymerized in a weakly alkaline medium, and the resulting poly(4-nitroaniline) (P4-NA)) was used to fabricate - by electrospinning - a nanofiber consisting of P4-NA and poly(vinyl alcohol) (PVA). The PVA fraction was then dissolved in hot water and this causes the porosity of electrospun nanofiber to be largely enhanced. The resulting nanofiber was utilized as a sorbent for solid phase microextraction of the model organophosphorus pesticides diazinon and chloropyrifos from aqueous media. The extracted analytes were then analyzed by corona discharge ion mobility spectrometry (CD-IMS). Under the optimized conditions, the limits of detection (at S/N?=?3; for n?=?10) are 0.4 and 0.6 ng mL^?1 for diazinon and chloropyrifos, respectively. The relative standard deviations at the levels of 25, 50 and 100 ng mL^?1 (for n?=?3) ranged from 4.0–12.3% (both intra-day and inter-day). Eventually, the method was used to analyze different water samples, including spiked drinking water, sea water, lagoon water, and groundwater sample in the proximity of rice fields, and in two juice samples. Recoveries ranged between 82 and 102%.

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Graphical abstract An electrospun nanofiber consisting of highly porous poly(4-nitroaniline) was synthesized and used as a sorbent for solid phase microextraction of diazinon and chlorpyrifos from water and juice samples prior to quantitation by corona discharge ion mobility spectrometry.

     

CO2/H2 separation by facilitated transport membranes immobilized with aqueous single and mixed amine solutions: Experimental and modeling study

An experimental and theoretical analysis to separate CO₂ using facilitated transport membranes immobilized with different aqueous single and mixed amine solutions have been performed. The membranes containing monoethanolamine (MEA), diethanolamine (DEA), monoprotonated ethylenediamine (EDAH⁺) and piperazine (PZ), as well as aqueous blends of PZ with MEA, DEA or EDAH⁺ were considered. The aqueous solution of PZ showed the highest CO₂ permeation rate with respect to other single amine solutions. Therefore blends of PZ with MEA, DEA and EDAH⁺ increased the permeance of carbon dioxide through mixed amine membranes.     

Chitosan-Placental ECM Composite Thermos-Responsive Hydrogel as a Biomimetic Wound Dressing with Angiogenic Property

Attempts are being made to develop an ideal wound dressing with excellent biomechanical and biological properties. Here, a thermos-responsive hydrogel is fabricated using chitosan (CTS) with various concentrations (1%, 2.5%, and 5% w/v) of solubilized placental extracellular matrix (ECM) and 20% β-glycerophosphate to optimize a smart wound dressing hydrogel with improved biological behavior. The thermo-responsive CTS (TCTS) alone or loaded with ECMs (ECM-TCTS) demonstrate uniform morphology using SEM. TCTS and ECM1%-TCTS and ECM2.5%-TCTS show a gelation time of 5 min at 37 °C, while no gel formation is observed at 4 and 25 °C. ECM5%-TCTS forms gel at both 25 and 37 °C. The degradation and swelling ratios increase as the ECM content of the hydrogel increase. All the constructs show excellent biocompatibility in vitro and in vivo, however, the hydrogels with a higher concentration of ECM demonstrate better cell adhesion for fibroblast cells and induce expression of angiogenic factors (VEGF and VEGFR) from HUVEC. Only the ECM5%-TCTS has antibacterial activity against Acinetobacter baumannii ATCC 19606. The data obtained from the current study suggest the ECM2.5%-TCTS as an optimized smart biomimetic wound dressing with improved angiogenic properties now promises to proceed with pre-clinical and clinical investigations.     

Improving activity of anticancer oxalipalladium analog by the modification of oxalate group with isopentylglycine

In this article, we describe the influence of structure on biological behavior of amino acid-Pd complex and compare it with oxalipalladium. A new water-soluble oxalipalladium analog with formula of [Pd(DACH)(isopentylgly)](NO₃), where DACH is 1R,2R-diaminocyclohexane, has been synthesized and characterized by elemental analysis, conductivity measurements, IR, UV–Vis, and ¹H NMR spectroscopies. The interactions of oxalipalladium and its amino acid derivative with highly polymerized calf-thymus DNA have been extensively studied by spectroscopic methods. The high binding constants of oxalipalladium (0.38 × 10⁴ M^?1) and new amino acid-Pd complex (0.65 × 10⁴ M^?1) were determined using absorption measurements. Also circular dichroism (CD) studies show that Pd complex causes more disturbances on DNA structure rather than oxalipalladium. The experimental results proposed that [Pd(DACH)(isopentylgly)](NO₃) is bound to DNA by groove-binding mode as well as partially covalent interaction, while oxalate analog binds covalently to DNA after hydrolysis. Interaction of the two metal derivative complexes was studied by molecular docking simulation. The results showed that amino acid-Pd complex has higher negative docking energy and higher tendency for interaction with DNA, and exert more structural change on DNA. Finally, the anticancer and growth inhibitory activities of synthesized complexes were investigated against human colon cancer cell line of HCT116 after 24 h incubation time using MTT assay. Results show that the complex [Pd(DACH)(isopentylgly)](NO₃) showed enhanced anticancer and growth inhibitory activities against human colon can cell line HCT116.     

Synthesis and antibacterial study of 2-amino-4H-pyrans and pyrans annulated heterocycles catalyzed by sulfated polysaccharide-coated BaFe12O19 nanoparticles

Research on Chemical Intermediates - In this procedure, the synthesis of ecofriendly, magnetically retrievable BaFe12O19 was reported using a sulfated polysaccharide of&nbsp;algal origin, Irish...