A device for X‐Ray elemental mapping using annular radioisotope source

An energy‐dispersive system is described for elemental mapping by X‐ray fluorescence spectrometry. The present study describes the design of an X‐ray fluorescence spectrometer and presents its performance in elemental mapping applications. The spectrometer is based on a new ring‐shaped collimator with a pinhole in the center of it and a ring‐shaped Am‐241 isotope mounted in the collimator as a source for excitation of X‐ray fluorescence. The photons were detected by high‐resolution Si (Li) detector coupled to a multi‐channel analyser and cooled by liquid nitrogen. In this study, we used two samples; one of them was made from pure elemental powders, and the second one was a piece of a stone and three types of maps were plotted. In the maps type one, the areas of the elements were shown with a single color. These maps only show the location of the elements in the sample. In the maps type two, the area of each element was shown with different colors because of the count (intensity) related to the area. In the third type of the maps for each element, depending on the elements' position on the sample, the counts were plotted in three dimensions. The areas with higher intensity have greater height, and areas with lower intensity have lower altitude. These two last types of maps provide information about the homogeneity or heterogeneity of the elemental distribution in the samples. The spectrometer can perform non‐destructive analyses of samples and objects in the air. Copyright © 2017 John Wiley & Sons, Ltd.     

Binding energy of the donor impurities in GaAs-Ga_(1-x)Al_xAs quantum well wires with Morse potential in the presence of electric and magnetic fields

The behavior of a donor in the GaAs–Ga_(1-x)Al_xAs quantum well wire represented by the Morse potential is examined within the framework of the effective-mass approximation. The donor binding energies are numerically calculated for with and without the electric and magnetic fields in order to show their influence on the binding energies. Moreover, how the donor binding energies change for the constant potential parameters(De, re, and a) as well as with the different values of the electric and magnetic field strengths is determined. It is found that the donor binding energy is highly dependent on the external electric and magnetic fields as well as parameters of the Morse potential.     

Disposable Amperometric Biosensor Based on Poly‐L‐lysine and Fe3O4 NPs‐chitosan Composite for the Detection of Tyramine in Cheese

An amperometric tyramine biosensor based on poly‐L‐lysine (PLL) and Fe₃O₄ nanoparticles (Fe₃O₄NP) modified screen printed carbon electrode (SPCE) was developed. PLL was formed on the SPCE by the electropolymerization of L‐lysine. Subsequently, Fe₃O₄NP suspension prepared in chitosan (CH) solution was casted onto the PLL/SPCE. Tyrosinase (Ty) enzyme was immobilized onto the modified Fe₃O₄?CH/PLL/SPCE and the electrode was coated with Nafion to fabricate the Ty/Fe₃O₄?CH/PLL/SPCE. Different techniques including scanning electron microscopy, chronoamperometry (i–t curve), cyclic voltammetry and electrochemical impedance spectroscopy were utilized to study the fabrication processes, electrochemical characteristics and performance parameters of the biosensor. The analytical performance of the tyramine biosensor was evaluated with respect to linear range, sensitivity, limit of detection, repeatability and reproducibility. The response of the biosensor to tyramine was linear between 4.9×10^?7–6.3×10^?5 M with a detection limit of 7.5×10^?8 M and sensitivity of 71.36 μA mM^?1 (595 μA mM^?1 cm^?2). The application of the developed biosensor for the determination of tyramine was successfully tested in cheese sample and mean analytical recovery of added tyramine in cheese extract was calculated as 101.2±2.1 %. The presented tyramine biosensor is a promising approach for tyramine analysis in real samples due to its high sensitivity, rapid response and easy fabrication.     

Modification of polydivinylbenzene microspheres by a hydrobromination/click-chemistry protocol and their protein-adsorption properties

Hydrophobic- and/or hydrophilic-polymer-grafted PDVB microspheres are synthesized by the combination of hydrobromination and click-chemistry processes. The modified-PDVB microspheres and the intermediates at various stages of synthesis are characterized using GPC, 1H NMR and FTIR spectroscopy and TGA analysis. Use of the microspheres as a support matrix for reversible protein immobilization via adsorption is investigated. The system parameters such as the adsorption conditions (i.e., enzyme concentration, medium pH) and desorption are studied and evaluated with regards to the biocatalytic activity and adsorption capacity.     

Self‐Assembly of 3,6‐Bis(4‐triazolyl)pyridazine Ligands with Copper(I) and Silver(I) Ions: Time‐Dependant 2D‐NOESY and Ultracentrifuge Measurements

Two 3,6‐bis(R‐1H‐1,2,3‐triazol‐4‐yl)pyridazines (R=mesityl, monodisperse (CH₂ CH₂O)₁₂CH₃) were synthesized by the copper(I)‐catalyzed azide–alkyne cycloaddition and self‐assembled with tetrakis(acetonitrile)copper(I) hexafluorophosphate and silver(I) hexafluoroantimonate in dichloromethane. The obtained copper(I) complexes were characterized in detail by time‐dependent 1D [¹H, ¹³C] and 2D [¹H‐NOESY] NMR spectroscopy, elemental analysis, high‐resolution ESI‐TOF mass spectrometry, and analytical ultracentrifugation. The latter characterization methods, as well as the comparison to analog 3,6‐di(2‐pyridyl)pyridazine (dppn) systems and their corresponding copper(I) and silver(I) complexes indicated that the herein described 3,6‐bis(1H‐1,2,3‐triazol‐4‐yl)pyridazine ligands form [2×2] supramolecular grids. However, in the case of the 3,6‐bis(1‐mesityl‐1H‐1,2,3‐triazol‐4‐yl)pyridazine ligand, the resultant red‐colored copper(I) complex turned out to be metastable in an acetone solution. This behavior in solution was studied by NMR spectroscopy, and it led to the conclusion that the copper(I) complex transforms irreversibly into at least one different metal complex species.     

In vitro evaluation of mucoadhesive vaginal tablets of antifungal drugs prepared with thiolated polymer and development of a new dissolution technique for vaginal formulations

The main objective of this work was to develop antifungal matrix tablet for vaginal applications using mucoadhesive thiolated polymer. Econazole nitrate (EN) and miconazole nitrate (MN) were used as antifungal drugs to prepare the vaginal tablet formulations. Thiolated poly(acrylic acid)-cysteine (PAA-Cys) conjugate was synthesized by the covalent attachment of L-cysteine to PAA with the formation of amide bonds between the primary amino group of L-cysteine and the carboxylic acid group of the polymer. Vaginal mucoadhesive matrix tablets were prepared by direct compression technique. The investigation focused on the influence of modified polymer on water uptake behavior, mucoadhesive property and release rate of drug. Thiolated polymer increased the water uptake ratio and mucoadhesive property of the formulations. A new simple dissolution technique was developed to simulate the vaginal environment for the evaluation of release behavior of vaginal tablets. In this technique, daily production amount and rate of the vaginal fluid was used without any rotational movement. The drug release was found to be slower from PAA-Cys compared to that from PAA formulations. The similarity study results confirmed that the difference in particle size of EN and MN did not affect their release profile. The release process was described by plotting the fraction released drug versus time and n fitting data to the simple exponential model: M(t)/M(∞)=kt(n). The release kinetics were determined as Super Case II for all the formulations prepared with PAA or PAA-Cys. According to these results the mucoadhesive vaginal tablet formulations prepared with PAA-Cys represent good example for delivery systems which prolong the residence time of drugs at the vaginal mucosal surface.     

N-picolinamides as ligands for Ullmann-type homocoupling reactions

The use of N-phenylpicolinamide (NPPA) as a ligand in Ullmann-type homocoupling reactions of aryl iodides and bromides in common solvents, such as DMF and MeCN has been successfully demonstrated at room temperature. In addition, this work provided the first example of the homocoupling of an aryl chloride at 82 °C, which is a relatively low temperature when compared to regular Ullmann reaction temperatures. Also, NPPA was successfully employed in base—and heat free Suzuki reactions, including electron rich and poor aryl halides with heteroarylboronic acids in moderate yields.     

Effect of Solvent Composition on Protonation Constants of Some Glycine Dipeptides

Stoichiometric protonation constants (log₁₀ K ₁ and log₁₀ K ₂) of some aliphatic dipeptides (Gly–Tyr, Gly–Phe, Gly–Val, Gly–Leu, Gly–Thr, Gly–Met and Gly–Pro) were determined potentiometrically in 20, 40, and 60 % (v/v) 1,4-dioxane–water and dimethyl sulfoxide–water mixtures at 25.0 (±0.1) °C with an ionic strength of 0.10 mol·L^?1 sodium chloride. The protonation constants were calculated with the computer program PKAS and selection of the best fit chemical models is based on the statistical parameters. The effects of solvent composition on these protonation constants are discussed to determine the factors which control these processes. It has been observed that, while the correlation between log₁₀ K ₁ and log₁₀ K ₂ with the percentages of dimethyl sulfoxide in the dimethyl sulfoxide–water mixtures are not linear, these values linearly increase as the concentration of 1,4-dioxane increases in the solvent mixtures.