New Magnesium Composite with Mg17Al12 Intermetallic Particles

Powder Metallurgy and Metal Ceramics - Although magnesium is one of the materials with the lowest density, its application is limited amongst other commercial materials due to insufficient...     

The detailed kinetics of the adsorption of hydrogen on polycrystalline copper studied by reactive frontal chromatography

The coverage-dependent sticking probabilities of molecular hydrogen on polycrystalline copper supported on alumina have been determined in the temperature range 213–273 K by analysis of the hydrogen frontal adsorption line shape. In this temperature range the initial sticking probabilities increase from 8× 10^–13 (213 K) to 1.3× 10^–10 (273 K). The overall activation energy to adsorption has been found to be 42 kJ mol^–1. The application of reactive frontal chromatography for the measurement of hydrogen sticking probabilities on copper is a novel variant of the N₂O reactive frontal chromatographic method, developed for the measurement of copper surface areas. Its use here shows that reactive frontal chromatography may be applied generally to any adsorbate/adsorbent system involving activated adsorption and low sticking probabilities.     

Thermo-physical performance of DGEBA/1,8-NDA/barium carbonate composite for coating applications

The toughening of epoxy resins by incorporating inorganic fillers is of great importance nowadays, due to their wide range of applications. The present work reports the results of the addition of barium carbonate into a polymeric matrix containing diglycidyl ether of bisphenol-A (DGEBA) epoxy resin using 1,8-naphthalene diamine (1,8-NDA) as hardener to produce a novel composite for industrial applications. Cure kinetics of the composite system was investigated by means of differential scanning calorimeter (DSC) in dynamic mode. Kinetics of the reaction was interpreted according to the two isoconversional methods of Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (OFW). Using non-isothermal conditions, average value of the cure reaction activation energy in the propagation step was determined to be 57 and 60.2 kJ/mol for the KAS and OFW models, respectively. DMTA and TGA measurements were used in order to assess the effectiveness of the filler amount (2 Phr) on the final mechanical and thermal properties of the produced composite. The results verified that the thermal stability of the composite could be improved with the incorporation of BaCO₃. Microstructural observations from images analysis of SEM micrographs revealed that the barium salt was dispersed into polymer matrix homogeneously.     

Antioxidant potential and antimicrobial activity of chitosan–inulin conjugates obtained through the Maillard reaction

Food Science and Biotechnology - Chitosan (1%) was glycated with inulin (0.5, 1, and 2%) via the Maillard reaction at various initial pH values (5, 5.5, and 6). Higher pHs led to a greater pH drop...     

Effects of Silica Nanoparticles Content on the Properties and Corrosion Behavior of Electroless Ni-Ba-B Alloy Coatings

The beneficial role of silica nanoparticles addition as reinforcing agent on the various properties of the novel developed Ni-Ba-B coating was highlighted. Barium was considered as third element to act as an inhibiting alloying element for anodic passivation purposes. The ternary Ni-Ba-B coatings in three different concentrations of silica nanoparticles (0.5, 1.0 and 2.0 g/L) were coated on St 37 steel substrate in the presence of sodium dodecyl sulfate (SDS). The effect of nanoparticles on morphology and structure was investigated by FE-SEM, XRD and AFM tests. The nodularity and surface roughness of the coating increased by the presence of SiO2 nanoparticles in the electroless bath. The nanocomposite coating has amorphous and crystalline phases and its XRD peak at 44.50 is slightly sharper than the composite coating. DSC thermogram showed two exothermic peaks demonstrating its phase transformations. The WCA value of coating was confirmed its hydrophilicity property. Results also confirmed that the existence of silica nanoparticles results in an increase in the microhardness and corrosion resistance which may be attributed to the distribution of silica nanoparticles into Ni-Ba-B matrix.     

Computer-assisted design and synthesis of a highly selective smart adsorbent for extraction of clonazepam from human serum

A computational approach was applied to screen functional monomers and polymerization solvents for rational design of molecular imprinted polymers (MIPs) as smart adsorbents for solid-phase extraction of clonazepam (CLO) form human serum. The comparison of the computed binding energies of the complexes formed between the template and functional monomers was conducted. The primary computational results were corrected by taking into calculation both the basis set superposition error (BSSE) and the effect of the polymerization solvent using the counterpoise (CP) correction and the polarizable continuum model, respectively. Based on the theoretical calculations, trifluoromethyl acrylic acid (TFMAA) and acrylonitrile (ACN) were found as the best and the worst functional monomers, correspondingly. To test the accuracy of the computational results, three MIPs were synthesized by different functional monomers and their Langmuir–Freundlich (LF) isotherms were studied. The experimental results obtained confirmed the computational results and indicated that the MIP synthesized using TFMAA had the highest affinity for CLO in human serum despite the presence of a vast spectrum of ions.     

Crosstalk bounded uncorrelated jitter (BUJ) for high-speed interconnects

Bounded uncorrelated jitter (BUJ), a subcomponent of total jitter, is commonly caused by crosstalk coupling from adjacent interconnects on printed circuit boards (PCB). However, the characteristics of BUJ are still not well understood. Neither a mathematical model of jitter, nor an algorithm to generate histograms for BUJ has been developed to this date. Such a model and algorithm would empower designers to predict BUJ to achieve total jitter budget without lengthy simulations and measurements. In this paper, we first review the characteristics of a crosstalk pulse induced by an aggressor signal on a quiet trace. Then, by applying the superposition principle, a jitter model to calculate the time difference between the distortion-free and the distorted edge crossings of the victim signal was developed. This model is also extended to calculate the worst case timing difference, BUJ/sub p-p/. In addition, an algorithm to generate the histogram distribution of BUJ is also developed. The developed algorithm has fast execution times of 10-20 s, compared to simulation and measurement times of 10-30 min.     

Highly sensitive amperometric sensor for micromolar detection of trichloroacetic acid based on multiwalled carbon nanotubes and Fe(II)–phtalocyanine modified glassy carbon electrode

A highly sensitive electrochemical sensor for the detection of trichloroacetic acid (TCA) is developed by subsequent immobilization of phthalocyanine (Pc) and Fe(II) onto multiwalled carbon nanotubes (MWCNTs) modified glassy carbon (GC) electrode. The GC/MWCNTs/Pc/Fe(II) electrode showed a pair of well-defined and nearly reversible redox couple correspondent to (Fe(III)Pc/Fe(II)Pc) with surface-confined characteristics. The surface coverage (Γ) and heterogeneous electron transfer rate constant (k_s) of immobilized Fe(II)–Pc were calculated as 1.26 × 10^? 10 mol cm^? 2 and 28.13 s^? 1, respectively. Excellent electrocatalytic activity of the proposed GC/MWCNTs/Pc/Fe(II) system toward TCA reduction has been indicated and the three consequent irreversible peaks for electroreduction of CCl₃COOH to CH₃COOH have been clearly seen. The observed chronoamperometric currents are linearly increased with the concentration of TCA at concentration range up to 20 mM. Detection limit and sensitivity of the modified electrode were 2.0 μM and 0.10 μA μM^? 1 cm^? 2, respectively. The applicability of the sensor for TCA detection in real samples was tested. The obtained results suggest that the proposed system can serve as a promising electrochemical platform for TCA detection.     

Application of equi-potential lines method for accurate definition of the deforming zone in the upper-bound analysis of forward extrusion problems

Prediction of the optimal pressure is one of the objectives in the die design for the extrusion process. In this study, the concept of Equi-Potential Lines (EPLs) was applied for an accurate definition of the deforming zone in the upper-bound solution of the extrusion process. To implement the concept for the extrusion process, the initial and final shapes were considered and two different potentials were assigned to these. Then, the EPLs were drawn between the two shapes while minimizing the work path from the initial billet to the desired final shape. Bilinear, cubic Bezier, and polynomial curves were used for the definition of the deforming zone. It was shown that the coefficients of cubic Bezier curve could be replaced by the values obtained from the EPLs method. Moreover, accurate 3D streamlines representing material flow path in the deforming zone were obtained from the present method. Finally, forming pressures in the extrusion process were computed using the proposed geometry. To show the effectiveness of the proposed method, the estimated values were compared with experimental results. It was shown that the proposed method had a remarkable agreement with the experimental results.     

Relationships among the A Genomes of Triticum L. Species as Evidenced by SSR Markers, in Iran

The relationships among 55 wheat accessions (47 accessions collected from Iran and eight accessions provided by the Institute of Plant Biology of the University of Zurich, Switzerland) belonging to eight species carrying A genome (Triticum monococcum L., T. boeoticum Boiss., T. urartu Tumanian ex Gandilyan, T. durum Desf., T. turgidum L., T. dicoccum Schrank ex Schübler, T. dicoccoides (Körn. ex Asch. & Graebner) Schweinf. and T. aestivum L.) were evaluated using 31 A genome specific microsatellite markers. A high level of polymorphism was observed among the accessions studied (PIC = 0.77). The highest gene diversity was revealed among T. durum genotypes, while the lowest genetic variation was found in T. dicoccoides accessions. The analysis of molecular variance (AMOVA) showed a significant genetic variance (75.56%) among these accessions, representing a high intra-specific genetic diversity within Triticum taxa in Iran. However, such a variance was not observed among their ploidy levels. Based on the genetic similarity analysis, the accessions collected from Iran were divided into two main groups: diploids and polyploids. The genetic similarity among the diploid and polyploid species was 0.85 and 0.89 respectively. There were no significant differences in A genome diversity from different geographic regions. Based on the genetic diversity analyses, we consider there is value in a greater sampling of each species in Iran to discover useful genes for breeding purposes.