Vibration analysis of nanorings using nonlocal continuum mechanics and shear deformable ring theory

In this article, we use shear deformable ring theory (SDRT) for the analysis of free in-plane vibration of nanorings based on nonlocal elasticity theory. The equations of motion of the nanoring are derived for the aforementioned problem by considering the small scale effect. Analytical solutions for the natural frequencies of the nanorings are presented. It is shown that the nonlocal effects play an important role in the vibration of nanorings and cannot be neglected. The effects of the small scale on the natural frequencies considering various parameters such as the radius of the nanoring, the thickness of the nanoring and mode numbers are investigated.     

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.     

Preparation of photocatalytic ZnO nanoparticles and application in photochemical degradation of betamethasone sodium phosphate using taguchi approach

In this study, ZnO nanoparticles were prepared by a sol-gel method for the first time. Taguchi method was used to identify the several factors that may affect degradation percentage of betamethasone sodium phosphate in wastewater in UV/K₂S₂O₈/nano-ZnO system. Our experimental design consisted of testing five factors, i.e., dosage of K₂S₂O₈, concentration of betamethasone sodium phosphate, amount of ZnO, irradiation time and initial pH. With four levels of each factor tested. It was found that, optimum parameters are irradiation time, 180 min; pH 9.0; betamethasone sodium phosphate, 30 mg/L; amount of ZnO, 13 mg; K₂S₂O₈, 1 mM. The percentage contribution of each factor was determined by the analysis of variance (ANOVA). The results showed that irradiation time; pH; amount of ZnO; drug concentration and dosage of K₂S₂O₈ contributed by 46.73, 28.56, 11.56, 6.70, and 6.44%, respectively. Finally, the kinetics process was studied and the photodegradation rate of betamethasone sodium phosphate was found to obey pseudo-first-order kinetics equation represented by the Langmuir-Hinshelwood model.     

Buckling analysis of variable thickness nanoplates using nonlocal continuum mechanics

This paper presents an investigation on the buckling characteristics of nanoscale rectangular plates under bi-axial compression considering non-uniformity in the thickness. Based on the nonlocal continuum mechanics, governing differential equations are derived. Numerical solutions for the buckling loads are obtained using the Galerkin method. The present study shows that the buckling behaviors of single-layered graphene sheets (SLGSs) are strongly sensitive to the nonlocal and non-uniform parameters. The influence of percentage change of thickness on the stability of SLGSs is more significant in the strip-type nonoplates (nanoribbons) than in the square-type nanoplates.     

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%.

Open image in new window

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.

     

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.     

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.     

Emergence of electromotive force in precession-less rigid motion of deformed domain wall

Recently it has been recognized that the electromotive force (emf) can be induced just bythe spin precession where the generation of the electromotive force has been considered asa real-space topological pumping effect. It has been shown that the amount of theelectromotive force is independent of the functionality of the localized moments. It wasalso demonstrated that the rigid domain wall (DW) motion cannot generate electromotiveforce in the system. Based on real-space topological pumping approach in the current studywe show that the electromotive force can be induced by rigid motion of a deformed DW. Wealso demonstrate that the generated electromotive force strongly depends on the DWbulging. Meanwhile results show that the DW bulging leads to generation of theelectromotive force both along the axis of the DW motion and normal to the direction ofmotion.     

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.