Cross-linked PMMA-based bifunctional amino derivatives

Journal of Thermal Analysis and Calorimetry - The main purpose of the present study is to investigate the role of 1,12-diaminododecane and 4,4′-diaminobiphenyl, as bifunctional amino...     

Monte Carlo simulations of a D-T neutron generator shielding for landmine detection

Shielding for a D–T sealed neutron generator has been designed using the MCNP5 Monte Carlo radiation transport code. The neutron generator will be used in field for the detection of explosives, landmines, drugs and other ‘threat’ materials. The optimization of the detection of buried objects was started by studying the signal-to-noise ratio for different geometric conditions.     

Design of a novel optical sensor for determination of trace amounts of copper by UV–visible spectrophotometry in real samples

A new optical chemical sensor is established for sensitive and selective spectrophotometric detection of copper based on the immobilization of 3‐(2‐methyl‐2,3‐dihydro‐1,3‐benzothiezol‐2‐yl)‐2H‐chromen‐2‐one on a triacetylcellulose membrane. Copper ions react with the immobilized ligand and cause an increase in the absorption of the membrane at 550 nm in universal buffer solution at pH = 6. The effects of pH, indicator concentration and reaction time on the immobilization of the ligand were studied. This optode exhibits a linear range of 7.0 × 10^?7 to 1 × 10^?4 mol l^?1 of copper ion concentration with a limit of detection of 3.0 × 10^?7 mol l^?1. The response time of the newly designed optode is within 3 min. The effect of different possible interfering species was investigated and it was found that the sensor has very good selectivity. The proposed sensor benefits from advantages such as low cost, high stability, low detection limit, fast response time, reproducibility, relatively long lifetime, and good selectivity for Cu²⁺ ion determination among a large number of alkali, alkaline earth, transition and heavy metal ions. The sensor can readily be regenerated with thiourea solution and its response is reversible and reproducible (relative standard deviation < 1.4%). The proposed optode was applied successfully for the determination of Cu(II) in various samples.     

Monitoring of L-Shape Bolted Joint Tightness Using Thermal Contact Resistance

In this paper, we describe the possible use of hermal contact resistance measured under ambient conditions as a non-destructive feature to monitor L-shape bolted joints. We demonstrate that thermal contact resistance can be correlated to the contact pressure of L-shape bolted joints and thus can be used to infer joint tightness. Five different torque levels of bolt tightness in an L-shape bolted joint were measured for contact pressure and thermal contact resistance using Fuji Prescale® pressure-sensitive film and a test setup in ambient conditions. Using probabilistic analysis, probability density functions (PDFs) and intervals developed from the PDFs, the contact pressure and thermal contact resistance were developed and correlated. By examining the intervals of the contact pressure and thermal contact resistance at each torque level, it was concluded that thermal contact resistance measured under ambient conditions can be used to describe bolted joint tightness.     

Radiation synthesis of acrylic acid onto poly(tetraflouroethylene-perflourovinyl ether) film: Chemical modifications and electrical conductivity

Graft-polymerization of acrylic acid (AAc) monomer onto poly(tetraflouroethylene-perflouro vinyl ether) (PFA) copolymer film was carried out using gamma irradiation technique to synthesize grafted copolymer film PFA-g-PAAc (PFA-COOH). The effect of the dose on the degree of grafting of AAc onto PFA film was investigated. The results showed that the degree of grafting increases with increasing the irradiation dose. The grafted [PFA-COOH] film was chemically modified by reaction with aniline to produce modified [PFA-CO-NH-ph] film, followed by sulphonation reaction to introduce sulfonic acid (SO₃H) groups to get other modified [PFA-CO-NH-ph-SO₃H] film. The chemical structures of the grafted and modified films were identified by FT-IR, XRD, and SEM. It is of particular interest to measure the electrical conductivity of grafted and modified membranes as a function of degree of grafting. It was found that the conductivity of the grafted films increases with increasing the degree of grafting, however a slightly increase in conductivity was observed in [PFA-CO-NH-ph-SO₃H] sample. The electrical conductivity property of the modified PFA membranes suggests their possible use for fuel cell applications.     

Synthesis and spectroscopic studies of stable aqueous dispersion of silver nanoparticles

A facile approach for the synthesis of stable aqueous dispersion of silver nanoparticles (AgNPs) using glucose as the reducing agent in water/micelles system, in which cetyltrimethylammonium bromide (CTAB) was used as capping agent (stabilizer) is described. The evolution of plasmon band of AgNPs was monitored under different conditions such as (a) concentration of sodium hydroxide, (b) concentration of glucose, (c) concentration of silver nitrate (d) concentration of CTAB, and (e) reaction time. AgNPs were characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), fluorescence spectroscopy and FT-IR spectroscopy. The results revealed an easy and viable strategy for obtaining stable aqueous dispersion of AgNPs with well controlled shape and size below 30 nm in diameter.     

Kinetics and mechanism of the oxidative decolorization of direct violet 31 in the presence of peroxodisulfate-silver(I) as a redox system

Transition Metal Chemistry - The redox decolorization of direct violet 31 [DV-31]? by Ag(I)/S2O82? under conditions similar to the Fenton process was studied kinetically in aqueous...