Determination of cadmium(II) ion by atomic absorption spectrometry after cloud point extraction

In this work, cloud point extraction (CPE) technique was developed for the separation and pre-concentration of Cd(II). CPE was used with lipophilic hexadentate (N₄O₂) Schiff base ligand, L_22pysa (1, C₂₄H₂₆N₄O₂). The methodology is based upon the formation of a Cd(II)/L complex soluble in a micellar phase the non-ionic surfactant Triton X-114. This complex is then extracted into the surfactant-rich phase above its cloud point temperature. Several important variables that affect the CPE were investigated and optimized. Under the optimum experimental conditions, the calibration graph was linear over the range 1?C100?ng?mL^?1 with a correlation coefficient of 0.9997. The detection limit obtained under optimum conditions was 0.44?ng?mL^?l. The proposed method was successfully applied to the determination of Cd(II) in rice and various water samples.     

N-Bromo Reagent Mediated Oxidation of Urazoles to Their Corresponding Triazolinediones under Mild and Heterogeneous Conditions

Various N-bromo reagents [HMTAB, DABCO-bromine, DPTBE, and TBCA] were used as effective oxidizing agents for the oxidation of urazoles and bisurazoles to their corresponding triazolinediones under mild and heterogeneous conditions at room temperature with good to excellent yields. Also the oxidation of some new 4-phenylurazole derivatives with these reagents is discussed.     

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.     

Solution and solid-state studies of a new supramolecular proton transfer salt and its VO<Subscript>2</Subscript> complex constructed with chelidamic acid and 3,4-diaminopyridine

The proton transfer compound (Hdap)(chelH)·2H₂O (1) and its related anionic complex (Hdap) [VO₂(chel)] (2), where chelH₂ = 4-hydroxypyridine-2,6-dicarboxylic acid (chelidamic acid) and dap = 3,4-diaminopyridine, were synthesized and characterized by elemental analysis, spectroscopy (IR, UV–Vis), thermal (TG/DTG) analysis and single-crystal X-ray diffraction. Compound 1 resulted from proton transfer between chelH₂ and dap in aqueous solution. In 1, two carboxylic acids of chelH₂ were deprotonated and the protons transferred to the nitrogen atoms of one chelidamate anion and one dap moiety. Compound 2 resulted from complexation of 1 and vanadyl sulfate. In the crystal structure of 2, the metal ion is five coordinated by one tridentate ligand (chel)^2? and two O^2? anions, with (Hdap)⁺ as a counter cation. In both structures, a complicated hydrogen-bonding network accompanied with π–π, C–O···π and C–H···π stacking interactions leads to formation of a 3D supramolecular network. In the following, solution studies have been performed by means of pH potentiometric titrations method as a power technique. This method was used for determination of protonation constants of chelH₂ and dap in their probable protonated forms and for calculation of equilibrium constants for the chelH₂–dap proton transfer system and the stoichiometry and stability constants of binary and ternary complexes of this system with VO²⁺ ion in aqueous solution. The stoichiometries of the most complex species in solution were compared with the corresponding crystalline complexes in the solid state.     

Fabrication of highly sensitive cysteine electrochemical sensor based on nanostructured compound and carbon nanotube modified electrode

This work describes the electrochemical behavior of copper(II)-bis[5-((4-ⁿ-decyloxyphenyl)azo)-N-(ⁿethanol)-salicylaldiminato]film immobilized on the surface of multiwall carbon nanotube glassy carbon electrode and its electrocatalytic activity toward the oxidation of L-cysteine. The surface structure and composition of the sensor was characterized by scanning electron microscopy. Electrocatalytic oxidation of L-cysteine on the surface of modified electrode was investigated with cyclic voltammetry, chronoamperometry and hydrodynamic amperometery methods and the results showed that the Cu-Schiff base film displays excellent electrochemical catalytic activities towards L-cysteine oxidation. The modified electrode indicated reproducible behavior and high level of stability during the electrochemical experiments.     

Decoupling of the Leading Order DGLAP Evolution Equation with Spin Dependent Structure Functions

We propose an analytical solution for DGLAP evolution equations with polarized splitting functions at the Leading Order (LO) approximation based on the Laplace transform method. It is shown that the DGLAP evolution equations can be decoupled completely into two second order differential equations which then are solved analytically by using the initial conditions \(\delta F^{\mathrm {S}}(x,Q^{2})=\mathcal {F}[\partial \delta F^{\mathrm {S}}_{0}(x), \delta F^{\mathrm {S}}_{0}(x)]\) and \({\delta G}(x,Q^{2})=\mathcal {G}[\partial \delta G_{0}(x), \delta G_{0}(x)]\). We used this method to obtain the polarized structure function of the proton as well as the polarized gluon distribution function inside the proton and compared the numerical results with experimental data of COMPASS, HERMES, and AAC’08 Collaborations. It was found that there is a good agreement between our predictions and the experiments.