Effect of l-Histidine Substitution on Sol–Gel of Transition Metal Coordinated Poly Ethyleneimine: Synthesis and Biochemical Characterization

The study was aimed to investigate the effect of chemical modification of branched poly ethyleneimine (PEI) on chelation of transition metal ions (Me²⁺) including Zn²⁺, Cu²⁺ or Ni²⁺ and sol–gel conversion thereof. To modulate chelation property of PEI, imidazole moieties were introduced into the polymer backbone by carbodiimide chemistry at different molar ratios of fmoc-protected l-histidine. The synthesis was characterized by ¹H-NMR spectroscopy and size exclusion chromatography. Potentiometric titration of PEI/Me²⁺ aqueous dispersions showed formation of stable complexes at pH above 5 depending on the degree of l-histidine substitution. FT-IR spectroscopy showed the imidazole ring of l-histidine was involved in the coordination interactions between PEI and Me²⁺. Addition of Zn²⁺ to PEI solution induced sol–gel conversion at a critical molar ratio decreasing by a higher degree of l-histidine modification. The gelation process led to formation of stable globular nanostructures as confirmed by atomic force microscopy with projected mean diameters less than 200 nm. Cellular experiment showed that l-histidine substitution enhanced cyto-compatibility of PEI, moreover cytotoxicity decreased significantly upon coordination of Zn²⁺ with the polymers. Conclusively, the coordination complexes of Zn²⁺ and l-histidine substituted PEI could serve as a nano system for biomedical applications.     

Multi-level enhancement of structural behavior of bracing systems with coupling beams at floor level

Despite good rigidity, braced frames have weak nonlinear behavior and inadequate distribution of ductility in stories, which cause significant structural damage. In this research, a seismic resistant system called coupled concentrically braced frame (CCBF) is developed to enhance the performance of braced frames by coupling them with a beam. In this case, the coupling beams are the primary source for ductility of the system, and after their yielding in more severe earthquakes, the structure continues to benefit from the ductility of the braces as the secondary source; therefore, the system has two-level behavior caused by different probable seismic excitations. In this case, in addition to maintaining the stiffness of the two concentrically braced frames, the coupling beams resist against the movement of the braced frames, and as a result, the stiffness of the system is increased. Therefore, lighter elements can be used to resist lateral loads. Linear and nonlinear analyses of CCBF, and its comparison with other braced frames, indicate that participation of the coupling beams provides an adequate stiffness and ductility. These frames have more stable nonlinear behavior than conventional ones and continue their nonlinear behavior even after fracture of coupling beams in severe earthquakes.     

Micromachined plastic W-band bandpass filters

Results are presented for micromachined plastic waveguide bandpass iris filters for W-band applications using a cost-effective polymer micro hot embossing process in conjunction with metallic electroplating and sealing techniques. The prototype filter has an 8-μm thick electroplated gold layer on a polymeric WR-10 waveguide with a 5-cavity Chebyschev-type design. Measurement results show center frequency of 96.77 GHz with a bandwidth of 3.15%, a loaded quality factor 31.73 and an unloaded quality factor for a single cavity resonator is 1210.6, respectively. A minimum insertion loss of −1.22 dB and return loss of better than −9.3 dB have been measured over the entire passband.     

The effect of sequential coupling on radial displacement accuracy in electromagnetic inside-bead forming: simulation and experimental analysis using Maxwell and ABAQUS software

Electromagnetic forming (EMF) is a high strain rate forming technology which can effectively deform and shape high electrically conductive materials at room temperature. In this study, the electromagnetic and mechanical parts of the process simulated using Maxwell and ABAQUS software, respectively. To provide a link between the software, two approaches include ‘loose’ and ‘sequential’ coupling were applied. This paper is aimed to investigate how sequential coupling would affect radial displacement accuracy, as an indicator of tube final shape, at various discharge voltages. The results indicated a good agreement for the both approaches at lower discharge voltages with more accurate results for sequential coupling, but at high discharge voltages, there was a non-negligible overestimation of about 43% for the loose coupling reduced to only 8.2% difference by applying sequential coupling in the case studied. Therefore, in order to reach more accurate predictions, applying sequential coupling especially at higher discharge voltages is strongly recommended.     

Joint behavior and design procedure of a through plate connection for steel beam to hollow or concrete‐filled tubular columns

The through plate connection has a practical reliable configuration for fully restrained connections for a steel I‐beam to hollow or concrete‐filled tubular columns in seismic areas. Based on experimental programs of authors on interior planar moment connections via through plate technique, this paper presents the outcome of the studies focusing on the joint behavior and the shear transfer in the panel zone of through plate connection. Based on the conducted approved three full‐scale tests, the behavior of connection components and panel zone shear force were investigated accurately in order to provide useful information and key parameters to facilitate design calculations and proportioning the connection. The contribution of each component in the total shear capacity of the panel zone region was determined. Load transfer mechanisms were explained and by quantifying the portion of load transfer paths, the calculation approach was described for design purpose. The proposed design procedure was validated for a wide range of beam to column connections using finite element models. Verified numerical models were used to conduct parametric studies. The numerical results revealed that the proposed analysis method can predict well the induced demand in the connection components and also the design procedure is suitable and secure for all cases.     

Recent advances in core/shell bicomponent fibers and nanofibers: A review

There has been a steady progress in developing synthetic fibers in the past few years. Bicomponent fibers and nanofibers in a core/shell (C/S) configuration, including two dissimilar materials have presented unusual potential for use in many novel applications. These fibers can be produced using a variety of materials via different techniques i.e., coaxial melt spinning and electrospinning. In this review, we discuss the recent advances in C/S fibers and nanofibers’ production. The first part has been assigned to the bicomponent fibers manufacturing technology, while production and applications of C/S nanofibers have been described in the second part. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46265.     

Vacuum enhanced membrane distillation for trace contaminant removal of heavy metals from water by electrospun PVDF/TiO<Subscript>2</Subscript> hybrid membranes

Electrospun hybrid membranes were synthesized using electrospinning of Poly (vinylidenefluoride) - titanium tetraisopropoxide (PVDF-TTIP) sol. Asymmetric post-treatment of membrane conducted for deprotonation of titanate and making hydrophilic/hydrophobic dual characteristics. The membranes were characterized by various methods such as wettability, scanning electron microscopy, infrared spectroscopy, X-ray diffraction and liquid entry pressure tests. For evaluating the separation performance, these membranes were applied in the VMD process to treat water heavy metal contaminants. The effects of operating parameters such as flow rate, temperature and membrane properties as porosity, on contaminant removal and producing ultra-pure water have been studied.     

The removal of cationic dyes from aqueous solutions by adsorption onto pistachio hull waste

The efficacy of pistachio hull powder (PHP) prepared from agricultural waste was investigated in this study as a novel adsorbent for the elimination of dye molecules from contaminated streams. Removal of methylene blue (MB) as a cationic model dye by PHP from aqueous solution was studied under different experimental conditions. The selected parameters were solution pH (2–10), PHP dosage (0.5–3 g/L), MB concentrations (100–400 mg/L), contact time (1–70), and solution temperature (20–50 °C). The experimental results indicated that the maximum MB removal could be attained at a solution pH of 8. The dosage of PHP was also found to be an important variable influencing the MB removal percentage. The removal efficiency of MB improved from 94.6 to 99.7% at 70 min contact time when the MB concentration was decreased from 300 to 100 mg/L at a pH and PHP dosage of 8 and 1.5 g/L, respectively. The kinetic analysis showed that the pseudo-second-order model had the best fit to the experimental data. The Langmuir equation provided the best fit for the experimental data of the equilibrium adsorption of MB onto PHP at different temperatures. In addition, the maximum adsorption capacity increased from 389 to 602 mg/g when the temperature was increased from 20 to 50 °C. The thermodynamic evaluation of MB adsorption on PHP revealed that the adsorption phenomenon under the selected conditions was a spontaneous physical process. Accordingly, pistachio hull waste was shown to be a very efficient and low-cost adsorbent, and a promising alternative for eliminating dyes from industrial wastewaters.