One‐Pot Synthesis of New 1,5‐Disubstituted Tetrazoles Bearing 2,2‐Bis(trimethylsilyl)ethenyl Groups via The Ugi Four‐Component Condensation Reaction Catalyzed by MgBr2·2Et2O

A simple one‐pot Ugi four‐component condensation reaction has been developed for the synthesis of tetrazoles bearing 2,2‐bis(trimethylsilyl)ethenyl groups from the synthesized 4‐[2,2‐bis(trimethylsilyl) ethenyl]benzaldehyde ( 1 ), various amines, isocyanides, and trimethylsilylazide at room temperature, without solvent, and in the presence of catalytic amounts of MgBr₂·2Et₂O as catalyst.     

Using an Inhibitor to Prevent Plasticizer Migration from Polyurethane Matrix to EPDM Based Substrate

The loss of adhesion between the propellant and insulator is one of the most important problems in solid propellant motors due to migration of plasticizer to interface of propellant and insulator. In this work, the polyurethane (PU) binder containing DOP plasticizer was used as a polymeric matrix and β-cyclodextrin (β-CD) was applied as inhibitor agent to prevent plasticizer migration from the PU matrix into the ethylene propylene diene monomer (EPDM) substrate. To increase the compatibility of β-CD and PU matrix, a derivative of β-CD has been synthesized using toluene diisocyanate (β-CD-TDI). The synthesized derivative was characterized by MALDI-MS and FTIR-ATR analyses. FTIR-ATR results confirmed the formation of bonding between β-CD and the polymeric network while the MALDIMS results showed that the synthesized derivative contained two β-CD and 7 TDI molecules bonded to β-CD. Investigation of the mechanical properties of PU modified by β-CD-TDI showed a decrease in tensile strength and an increase in elongation at break with increasing β-CD-TDI content. DMTA results showed a decrement in crosslinking density by increasing the β-CD-TDI content. Also, to investigate plasticizer migration, extraction of the DOP plasticizer from samples was performed using dichloromethane solvent and its concentration was measured by gas chromatography. The results of migration evaluation after four months showed that using β-CD as an inhibitor agent in the PU binder could prevent the migration of plasticizer to EPDM substrate.     

Rattle-type Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SnO<Subscript>2</Subscript> core-shell nanoparticles for dispersive solid-phase extraction of mercury ions

The synthesis of rattle-type nanostructured Fe₃O₄@SnO₂ is described along with their application to dispersive solid-phase extraction of trace amounts of mercury(II) ions prior to their determination by continuous-flow cold vapor atomic absorption spectrometry. The voids present in rattle-type structures make the material an effective substrate for adsorption of Hg(II), and also warrant high loading capacity. The unique morphology, large specific surface, magnetism property and the synergistic effect of magnetic cores and SnO₂ shells render these magnetic nanorattles an attractive candidate for solid-phase extraction of heavy metal ions.The sorbent was characterized by transmission electron microscopy, scanning electron microscopy, FTIR, energy-dispersive X-ray spectroscopy and by the Brunnauer-Emmett-Teller technique. The effects of pH value, adsorption time, amount of sorbent, volume of sample solutions, concentration and volume of eluent on extraction efficiencies were evaluated. The calibration plot is linear in the 0.1 to 40 μg·L^?1 concentration range, and the preconcentration factor is 49. The detection limit is 28 ng·L^?1. The sorbent was applied to the analysis of (spiked) river and sea water samples. Recoveries ranged from 97.2 to 100.5%.

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Graphical abstract A yolk-shell structure based on a Fe₃O₄ core and SnO₂ shell was developed as an efficient MSPE sorbent. A middle silica layer was etched by alkaline solution. The resulting sorbent was utilized for preconcentration of mercury ions from aqueous media.

     

A Simple Colorimetric Au-on-Au Tip Sensor with a New Functional Nucleic Acid Probe for Food-borne Pathogen Salmonella typhimurium

An Au-on-Au tip sensor is developed for the detection of Salmonella typhimurium (Salmonella), using a new synthetic nucleic acid probe (NAP) as a linker for the immobilization of a DNA-conjugated Au nanoparticle (AuNP) onto a DNA-attached thin Au layer inside a pipette tip. In the presence of Salmonella, RNase H2 from Salmonella (STH2) cleaves the NAP and the freed DNA-conjugated AuNP can be visually detected by a paper strip. This portable biosensor does not require any electronic, electrochemical or optical equipment. It delivers a detection limit of 3.2×10³ CFU mL⁻¹ for Salmonella in 1 h without cell-culturing or signal amplification and does not show cross-reactivity with several control bacteria. Further, the sensor reliably detects Salmonella spiked in food samples, such as ground beef and chicken, milk, and eggs. The sensor can be reused and is stable at ambient temperature, showing its potential as a point-of-need device for the prevention of food poisoning by Salmonella.     

Synthesis of a new magnetic nano-island titania photocatalyst and investigation of its photocatalytic activity

In this study, a new magnetic nano-island titania photocatalyst (Fe₃O₄@SiO₂·TiO₂) was designed and fabricated. Precipitation, sol-gel, and hydrothermal methods were utilized to synthesize the magnetite, silica shell, and titania islands, respectively. Characterization of the synthesized catalyst was carried out by XRD, EDS, FTIR, SEM, TEM, and VSM analysis. The TEM analysis revealed that the overall size of the catalyst is about 490 nm, and titania island on the magnetic core was about 50 nm. VSM analysis showed that the photocatalyst has a fantastic paramagnetic property with magnetic saturation of 52 emu g^?1. Furthermore, photocatalytic activity of the synthesized catalyst was evaluated in the removal of p-nitrophenol as a typical pollutant of nitro-aromatic compounds such that its degradation and mineralization efficiency were obtained at 82 and 45% after 100 and 200 min of the process, respectively, using 100 ppm of the photocatalyst in pH = 6.5.     

Improvement in Adhesion between Ethylene–Propylene–Diene Terpolymer (EPDM)-based Elastomer and Polyurethane Coating Using Epoxy–Polysulfide Copolymer As Adhesion Promoter

Epoxy–polysulfide copolymer as an adhesion promoter was added to ethylene–propylene–diene terpolymer and the effect of maleation of terpolymer with maleic anhydride on its adhesion to polyurethane coating was studied. The results show that using epoxy-polysulfide copolymer as the adhesion promoter cause a significant improvement in adhesion of terpolymer to polyurethane coating. The contact angle of the water reduced from 88° for the unmodified terpolymer to 65° for the maleated terpolymer containing 10 phr of epoxy–polysulfide copolymer. Peel strength was also increased from 0.2 N/mm for the unmodified terpolymer to 1.12 N/mm for the above-mentioned modified elastomer. Effect of the composition of the polymer blends on the loss tangent and storage modulus was studied to evaluate phase separation and crosslink density. The improvement of adhesion to polyurethane occurred without phase separation, which was further confirmed by the results of the mechanical and morphological investigations.     

Surface and bulk modification of ethylene-propylene-diene terpolymer elastomer: Adhesion to polyurethane and mechanical properties

Effect of adding millable polyurethane as adhesion promoter to the ethylene-propylene-diene terpolymer as well as to the terpolymer modified by grafting of maleic anhydride on the adhesion between the terpolymer and polyurethane coating was studied. The results of peel test and water contact angle measurements showed that surface and bulk modification of terpolymer cause a significant improvement in its adhesion properties. The effect of the composition of the polymer blends on the loss tangent was studied to evaluate the extent of polymer compatibility and damping characteristics. Results demonstrated that modification of terpolymer with maleic anhydride can improve its compatibility with polyurethane, which was further confirmed by the results of the mechanical and morphological study.     

Robust control of wheel slip in anti-lock brake system of automobiles

In this paper, performances of two model-free control systems including Fuzzy Logic Control (FLC) and Neural Predictive Control (NPC) on tracking performance of wheel-slip in Anti-lock Braking System (ABS) are compared. As an accurate and control oriented model, a half vehicle model is developed to generate extensive simulation data of the braking system. Brake system identification is preformed through a Perceptron neural networks model of brake system which is trained with offline data by Gradient Descent Back Propagation (GDBP) algorithm. In order to reduce the time cost of the calculations and improving the robustness of closed loop control system, an online Perceptron neural network adaptively generates the optimum control actions. By a comparative simulation analysis it is shown that the NPC system has a better tracking performance, shorter stopping time and distance than the FLC controllers. The robustness of the proposed control systems are evaluated under ±25 % uncertainty. It is shown that the NPC system is more robust against both exogenous disturbances and modeling uncertainties than the FLC system.